New technique brings us closer to HIV, Hepatitis C vaccines

Plans for a new type of DNA vaccine to protect against the deadly HIV and Hepatitis C viruses have taken an important step forward, with University of Adelaide researchers applying for a patent based on groundbreaking new research.
Professor Eric Gowans from the University's Discipline of Surgery, based at the Basil Hetzel Institute at the Queen Elizabeth Hospital, has submitted a patent application for what he describes as a relatively simple but effective technique to stimulate the body's immune system response, thereby helping to deliver the vaccine.
While pre-clinical research into this vaccination technique is still underway, he's now searching for a commercial partner to help take it to the next stage.
Professor Gowans' work has focused on utilizing the so-called "accessory" or "messenger" cells in the immune system, called dendritic cells, to activate an immune response. These are a type of white blood cell that play a key role during infection and vaccination.
"There's been a lot of work done in the past to target the dendritic cells, but this has never been effective until now," Professor Gowans says. "What we've done is incredibly simple, but often the simple things are the best approach. We're not targeting the dendritic cells directly - instead, we've found an indirect way of getting them to do what we want."
Professor Gowans and his team have achieved this by including a protein that causes a small amount of cell death at the point of vaccination.
"The dead cells are important because they set off danger signals to the body's immune response. This results in inflammation, and the dendritic cells become activated. Those cells then create an environment in which the vaccination can be successful," Professor Gowans says.
Using a micro-needle device provided by United States company FluGen Inc., the researchers can puncture the skin to a depth of 1.5mm, delivering the vaccination directly into the skin. "We chose the skin instead of the muscle tissue, which is more common for DNA vaccines, because the skin has a high concentration of dendritic cells," Professor Gowans says.
Because the technique has the potential to translate to other, more common viruses in addition to the devastating HIV and Hepatitis C, the project attracted seed funding from The Hospital Research Foundation, and additional funding from the National Health and Medical Research Council (NHMRC).
The research is still in the pre-clinical phase, with a patient study due next year. "This technique has worked much better than I anticipated," Professor Gowans says. "We're now ready for a commercial partner to help us take this to the next phase, and we're in discussions with some potential partners at the moment."
Professor Gowans will present some of his work at the forthcoming 5th Australasian Vaccines & Immunotherapeutics Development Meeting (AVID2014), 7-9 May in Melbourne, Australia. Last month he was an invited speaker at the 23rd Australian Conference on Microscopy and Microanalysis (ACMM23) in Adelaide. A paper about this work has already been published recently in Immunology & Cell Biology.

Journal Reference:

1. Tessa Gargett, Branka Grubor-Bauk, Tamsin J Garrod, Wenbo Yu, Darren Miller, Lee Major, Steve Wesselingh, Andreas Suhrbier, Eric J Gowans. Induction of antigen-positive cell death by the expression of Perforin, but not DTa, from a DNA vaccine enhances the immune response. Immunology and Cell Biology, 2013; DOI: 10.1038/icb.2013.93

Malaria parasite transmission to mosquitos: Protein discovered as essential

In blue are Plasmodium falciparum malaria parasites in the sexual, gametocyte stage of development. In red are uninfected red blood cells.Credit: Manuel Llinás lab, Penn State University

Two teams have independently discovered that a single regulatory protein acts as the master genetic switch that triggers the development of male and female sexual forms (termed gametocytes) of the malaria parasite, solving a long-standing mystery in parasite biology with important implications for human health. The protein, AP2-G, is necessary for activating a set of genes that initiate the development of gametocytes -- the only forms that are infectious to mosquitos. The research also gives important clues for identifying the underlying mechanisms that control this developmental fate, determining whether or not a malaria parasite will be able to transmit the disease.

Even today, there is still a risk that malaria could be reintroduced into the United States and Europe, where malaria was largely eliminated by the 1950s. However, nearly half of the world's population -- 3.3 billion people -- currently live in 106 countries and territories that are at risk of malaria transmission, according to the U. S. Centers for Disease Control and Prevention. The World Health Organization estimates that there were 207 million cases of malaria and 627,000 deaths worldwide in 2012. Approximately 77 percent of those killed were children under the age of 5.

Malaria is caused by single-celled Plasmodium parasites. To survive and reproduce, these parasites have a rather complex lifecycle that involves three major stages. First, after a person is bitten by a parasite-carrying mosquito there is an initial infection in the liver, followed by the long-lasting red blood cell stage where the clinical symptoms of the malaria disease occur, and finally the mosquito stage, which is required to transmit the parasites to other people. All three stages are essential for the parasite to fully complete its developmental lifecycle. Surprisingly, the major blood stage form of the parasite that causes the terrible cycles of intense fevers associated with malaria in humans cannot be transmitted to mosquitos. For mosquito transmission to occur, the sexual form gametocytes, which are structurally distinct and have a very different program of gene and protein expression, have to form continually in the blood on a 2-day cycle. However, malaria parasites produce only a small number of sexual parasites per cycle -- a double-edged strategy for the parasite that, on the plus side, ensures its survival during dry seasons when mosquitos are rare, but on the down side also represents a potentially vulnerable chokepoint. How parasites "decide" to produce sexual stages has been a mystery that has puzzled malaria researchers for years.

"Exciting opportunities now lie ahead for finding an effective way to break the chain of malaria transmission by preventing the malaria parasite from completing its full lifecycle," said Manuel Llinás, an associate professor of biochemistry and molecular biology at Penn State University. 

Both manuscripts detail the role of the same AP2-G transcriptional regulator with remarkably similar findings -- despite the different groups' having worked with two highly diverged malaria parasites: Plasmodium falciparum, which causes the most severe form of human malaria and Plasmodium berghei, a commonly used model parasite infecting rodents.

"This sexual-stage bottleneck is an enticing target for interventions to prevent this comparatively small, yet critical number of sexual parasites from forming. If the sexual forms of the parasite never develop in an infected person's blood, then none will get into the mosquito's gut, and the mosquito will not be able to infect anyone else with malaria." Llinás said.

The study led by Llinás was initiated by experiments from Alfred Cortés' group at the Barcelona Centre for International Health Research, in which individual human malaria parasite clones from a single strain were found to have varying levels of the transcriptional regulator AP2-G, which mirrored varying levels of sexual stage (gametocyte) production. "The results were surprising because we found huge differences in the number of sexual-stage parasites produced by the different cell lines," Llinás said. One cell line produced ten times more than any of the others, most produced very few, and some produced none at all. Further experiments went on to show that the actual level of sexual-stage parasites produced by each parasite clone matched the proportion of individual cells specifically producing the AP2-G protein. "Our results perfectly correlate the expression of the ap2-g gene with the number of sexual-stage malaria parasites formed." Llinás said.

Because all these parasites share the identical DNA, or genetic makeup, yet the descendants of the individual cells produce significantly different numbers of sexual-stage parasites, Llinás said "we suspect that something outside the genes -- something other than a mutation in the DNA sequence -- is controlling the development of sexual-stage parasites." The research suggests that this phenomenon is not encoded directly in the parasite's DNA, but rather in other "epigenetic" differences between the parasites. In fact, Llinás said, "previous work has identified that a strong, repressing, epigenetic histone modification is present at the ap2-g gene and a few other locations in the malaria parasite genome." Cortés added: "For many years we have known that malaria parasites use epigenetic mechanisms to evade immune responses from the human host. Now we know that epigenetic mechanisms also regulate many other important processes in malaria parasite biology, including sexual differentiation."

When scientists discover a protein such as AP2-G that regulates a biological process, the typical next question is: and what other protein controls this regulator? "A beautiful aspect of our findings is that we don't need an upstream regulator for AP2-G. Instead, AP2-G can be activated by epigenetic mechanisms providing a plausible explanation for how low-level sexual conversion is triggered," says Cortés.

In what was originally a separate line of investigation, David Baker and Taane Clark and colleagues at the London School of Hygiene & Tropical Medicine and the Wellcome Trust Sanger Institute analyzed the whole-genome sequences of two P. falciparum laboratory strains that they knew were unable to produce gametocytes. Remarkably, they found that the only mutated, non-functional gene common to both strains was the ap2-g gene. David Baker said that "for more than 20 years my lab has been interested in identifying a malaria parasite gene underlying the switch to sexual development and finally the ap2-g locus, under epigenetic control, has come to light."

In the parallel study by the Waters and Billker groups, rodent malaria parasites that eventually lost their ability to produce sexual-stage parasites were selected over the course of a year in the laboratory (where the mosquito stage is not required). Using next-generation sequencing to identify the underlying mutations causing these effects, the groups found that the only common suspect was again the ap2-g gene -- the gene that codes for producing the AP2-G protein.

To confirm these observations, both studies disabled the ap2-g gene by cutting it out of the genome to remove its function from the parasite and the manipulated parasites indeed lost the ability to generate sexual-stage parasites. Furthermore, the parasites regained the ability to make gametocytes when the mutated gene in the selected rodent malaria parasites was repaired through gene therapy. Combined with other experiments, the results showed that sexual-stage malaria parasites are produced only when the AP2-G protein is in good working order. "Our research has demonstrated unequivocally that the AP2-G transcription-factor protein is essential for flipping the switch that initiates the transformation of malaria parasites in the blood from the asexual stage to the critical sexual stage of their life cycle," Llinás said.

The researchers agree these discoveries are exciting for the future of malaria research. Cells that make AP2-G enter sexual development, something that the groups are now able to control experimentally. "This opens the way to develop assays to screen for effective drugs that could disable commitment to sexual development and prevent transmission," comments Waters.

Billker adds "the discovery of AP2-G now gives us a new starting point to work out how the complex life cycle of malaria parasites is regulated by proteins within the parasite cells. It may even enable us to control parasite development in the laboratory."

The new ability to culture lots of sexual-stage malaria parasites will boost efforts to develop a sexual-stage vaccine that would help an infected person mount an immune response to prevent their malaria parasites from being transmitted to a mosquito -- effectively ending the life cycle for that person's batch of malaria parasites. "With the help of the next-generation technologies that we and other malaria researchers now are using, we are optimistic about more discoveries for malaria control that could occur soon -- even during the next 5 years," Llinás said.

Journal References:

1. Abhinav Sinha, Katie R. Hughes, Katarzyna K. Modrzynska, Thomas D. Otto, Claudia Pfander, Nicholas J. Dickens, Agnieszka A. Religa, Ellen Bushell, Anne L. Graham, Rachael Cameron, Bjorn F. C. Kafsack, April E. Williams, Manuel Llinás, Matthew Berriman, Oliver Billker, Andrew P. Waters. A cascade of DNA-binding proteins for sexual commitment and development in Plasmodium. Nature, 2014; DOI: 10.1038/nature12970
2. Björn F. C. Kafsack, Núria Rovira-Graells, Taane G. Clark, Cristina Bancells, Valerie M. Crowley, Susana G. Campino, April E. Williams, Laura G. Drought, Dominic P. Kwiatkowski, David A. Baker, Alfred Cortés, Manuel Llinás. A transcriptional switch underlies commitment to sexual development in malaria parasites. Nature, 2014; DOI: 10.1038/nature12920

Female fertility: What's testosterone got to do with it? Research shows male hormones may enhance IVF therapy

Several fertility clinics across the country are beginning to administer testosterone, either through a patch or a gel on the skin, to increase the number of eggs produced by certain women undergoing in vitro fertilization (IVF). Women are also purchasing the over-the-counter supplement DHEA, which is converted by the body into testosterone, to boost their chances of pregnancy with IVF.
A few clinical trials support the use of testosterone given through the skin, while others have shown no benefit of DHEA -- also used in attempts to slow aging and enhance muscle mass -- in increasing pregnancy and birth rates in women who don't respond well to IVF therapy. Lacking a large and convincing body of data on the topic, the jury is still out as to whether male hormones such as testosterone improve female fertility.
A new study suggests that male hormones, also called androgens, help drive the development of follicles -- structures that contain and ultimately release an egg that can be fertilized by a man's sperm. Published in the Proceedings of the National Academy of Sciences, the research also details how male hormones boost the production of follicles in mice. Authors believe the study provides potential biological targets to enhance fertility in women with diminished ovarian reserve, who produce few or no follicles in response to IVF drugs designed to boost follicle development.
"There is a raging debate in the reproductive endocrinology field about what male hormones are doing in female fertility," said Stephen R. Hammes, M.D., Ph.D.,senior study author and professor of Endocrinology at the University of Rochester School of Medicine and Dentistry. "Our study doesn't solve the controversy, but, along with some earlier seminal studies from other groups, it does tell us that we can't dismiss male hormones. They might actually be doing something useful."
Using multiple animal models and cell experiments, Hammes and lead study author Aritro Sen, Ph.D., research assistant professor of Endocrinology at the medical school found that male hormones promote follicle development in two ways. First, they prevent follicles from dying at an early stage. They do this by ramping up a molecule that stops cells from self destructing, a process called apoptosis. Hammes and Sen speculate that if a woman doesn't have enough androgens (male hormones), more of her follicles may be dying and fewer progressing to a mature stage when they produce and release an egg.
Second, androgens make ovarian cells more sensitive to follicle-stimulating hormone or FSH, which promotes follicle growth. They do this by creating more FSH receptors -- molecules on the surface of ovarian cells that jumpstart the follicle making process in response to the hormone.
"Androgens are increasing follicle growth and ensuring follicles don't die -- exactly what you want when providing fertility treatment," noted Hammes, who is also the chief of the Division of Endocrinology and Metabolism at UR Medicine's Strong Memorial Hospital.
When the team administered small doses of androgens to mice that were taking the equivalent of medications given to women undergoing IVF therapy, they developed more mature, egg-containing follicles than mice that didn't receive androgens. The androgen-treated female mice also released larger numbers of eggs with ovulation. IVF drugs are designed to do just that, enhance ovulation -- the production and discharge of an egg or eggs from the ovary. Unfortunately, these drugs aren't always effective in women with diminished ovarian reserve.
Kathleen M. Hoeger, M.D., M.P.H., director of UR Medicine's Strong Fertility Center, estimates that around 20 percent of the patients her team treats have diminished ovarian reserve, meaning they produce fewer follicles than estimated based on their age. Women who are 40 years or older are most likely to have diminished ovarian reserve, but it can appear in younger women as well.
"This information is important because it provides theoretical support for administering androgens to some women undergoing IVF, a practice that our fertility clinic and many others across the country have started in recent years," said Hoeger, who is also a professor of Obstetrics and Gynecology at the School of Medicine and Dentistry. "If these data are confirmed in clinical trials, we could propose that raising low levels of androgens in a woman with diminished ovarian reserve might increase her ability to produce more and better eggs for fertilization."
Hammes says the study calls for further clinical trials to determine whether androgens can have a positive effect on fertility when given at the right doses. And, by better understanding the biological pathways that are important for follicle development, scientists may be able to target these pathways with drugs or other interventions to improve IVF success rates.

Journal Reference:

1. A. Sen, H. Prizant, A. Light, A. Biswas, E. Hayes, H.-J. Lee, D. Barad, N. Gleicher, S. R. Hammes. Androgens regulate ovarian follicular development by increasing follicle stimulating hormone receptor and microRNA-125b expression. Proceedings of the National Academy of Sciences, 2014; 111 (8): 3008 DOI: 10.1073/pnas.1318978111

Cholesterol transporter structure decoded

Credit: Łukasz Jaremko, Mariusz Jaremko, Markus Zweckstetter / DZNE, Max Planck Institute for Biophysical Chemistry and UMG

The cholesterol transporter TSPO in the outer mitochondrial membrane serves as a docking site for important diagnostic markers and for a number of drugs such as diazepam.

The word "cholesterol" is directly linked in most people's minds with high-fat foods, worrying blood test results, and cardiovascular diseases. However, despite its bad reputation, cholesterol is essential to our wellbeing: It stabilizes cell membranes and is a raw material for the production of different hormones in the cell's power plants -- the mitochondria. Now, for the first time, scientists in Göttingen have solved the high-resolution structure of the molecular transporter TSPO, which introduces cholesterol into mitochondria. This protein also serves as a docking site for diagnostic markers and different drugs, such as Valium. The detailed knowledge of its three-dimensional shape and function opens up new diagnostic and therapeutic perspectives.

Not only are mitochondria the most important energy supplier in living cells. They also produce steroid hormones such as testosterone and oestradiol, which control many processes in the body. The raw material for the production of steroid hormones is cholesterol, which must first be transported into mitochondria across two membranes. This difficult task is carried out by a molecular transport protein named TSPO in the outer mitochondrial membrane. Using nuclear magnetic resonance spectroscopy, two teams working with the Göttingen-based scientists Markus Zweckstetter and Stefan Becker have now shown the complex three-dimensional structure of the protein "at work" in atomic detail.

The researchers achieved this methodical breakthrough by applying an ingenious trick: In their experiments, they coupled the transporter to an important diagnostic marker called PK11195; it was this complex that first gave the scientists analyzable results. In fact, the TSPO structure delivers more than just clues about how cholesterol is transported into the mitochondria. "We now also have a much better understanding of how TSPO recognizes and binds to diagnostic markers and drugs," explains Markus Zweckstetter, head of research groups at the German Center for Neurodegenerative Diseases (DZNE), at the Max Planck Institute for Biophysical Chemistry, and at the Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB) at the University Medical Center of Göttingen (UMG).

TSPO has long been successfully used in diagnostics and treatment of a number of diseases. "When the brain is injured or inflamed, its cells produce more TSPO. This fact is used in the diagnosis of neurodegenerative diseases such as Parkinson's and Alzheimer's," explains Stefan Becker, a protein chemist and Max Planck researcher who works next door to Zweckstetter.

Physicians also use radioactively tagged molecules such as PK11195 to visualize inflamed areas of the brain. A detailed understanding of how TSPO binds to such markers opens up novel paths for diagnostic imaging and could constitute an important step along the way to early detection of such diseases and inflammations.

TSPO also binds several medicinal drugs such as diazepam, also known by the trade name of Valium. Not only is diazepam a widely prescribed sedative; it is also used in the treatment of anxiety and epileptic seizures. The Göttingen researchers hope that detailed information about the transporter's structure will help to develop new TSPO-binding drugs.

Journal Reference:

1.  ukasz Jaremko, M. Jaremko, K. Giller, S. Becker, M. Zweckstetter. Structure of the Mitochondrial Translocator Protein in Complex with a Diagnostic Ligand. Science, 2014; 343 (6177): 1363 DOI: 10.1126/science.1248725

Remnant Lipoproteins and Atherosclerotic Disease

The function of serum lipoproteins is to deliver hydrophobic lipids (triglycerides) and sterols (cholesterol, cholesterol esters) to systemic tissues within an aqueous phase (plasma). Phospholipids, apoproteins, and cholesterol comprise the surface coat of lipoproteins, while triglycerides and cholesterol esters are concentrated in the core of these particles. The triglycerides are hydrolyzed and consumed as oxidizable substrate by such tissues as skeletal muscle and myocardium while the cholesterol can be used to modulate cell membrane fluidity and serve as a substrate for steroid hormone biosynthesis, among other functions. Lipoproteins are highly specialized and are separated according to density. Low-density lipoprotein cholesterol (LDL-C) is highly atherogenic and is a defined target of therapy for reducing risk of cardiovascular (CV) events by specialty societies around the world.^1-3 Treatment targets and thresholds for non-high-density lipoprotein cholesterol (non-HDL-C defined as total cholesterol minus HDL-C) were also defined by these societies. The latter is particularly noteworthy since non-HDL-C has been shown to be a stronger predictor of risk in the secondary prevention setting⁴ than LDL-C and encompasses the cholesterol in all atherogenic lipoprotein fractions, including remnant particles, very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and lipoprotein(a) [Lp(a)].

Chylomicrons and VLDLs are receiving much more intense scrutiny for their roles in atherogenesis. Chylomicrons are formed in jejunal enterocytes. A nascent chylomicron particle is comprised of apoB48 (a truncated version of apoB100, the principal apoprotein constituent of the hepatically derived lipoproteins VLDL, IDL, and LDL), phospholipid (PL), cholesterol ester (CE), and triglyceride (TG). Chylomicrons are responsible for delivering lipid derived from dietary and biliary sources to the liver. They are secreted into the perimesenteric lymphatics and enter the central circulation through the thoracic duct. Along the way, HDL particles transfer a variety of apoproteins (E, CI, CII, CIII) to these nascent chylomicrons. Apo CII is an activator of the enzyme lipoprotein lipase (LL). LL hydrolyzes triglycerides within the core of chylomicrons, thereby releasing free fatty acids, a readily oxidizable source of energy. As the triglycerides are progressively stripped away, chylomicron remnants (CR) are formed which constitute incompletely digested chylomicrons. Under normal physiological conditions, these CR are taken up into the space of Disse (the subendothelial space in hepatic sinusoids). If the remnant particle does not already contain apoE, it can take up apoE secreted by hepatocytes. The CRs are cleared by hepatocytes after binding via apoE to either heparin sulfate glycosaminoglycans or the LDL receptor-related protein. The hepatocytes then break down the CRs into their constituent lipids. Some of the lipid so released can then be repackaged into nascent VLDL particles and then secreted into the central circulation. Once in the circulation, HDL particles can transfer apoproteins to the VLDL particle surface which promotes lipolysis (apo CII) and clearance (apoE). Under normal circumstances the VLDL is progressively lipolyzed to form progressively smaller VLDLs (VLDL1, then VLDL2, then VLDL3), IDL, and then LDL.

Under normal physiological conditions lipoprotein production, metabolism, and clearance are efficient processes. However, given the high prevalence of atherosclerotic disease throughout the world, derangements in lipids and lipoproteins are epidemic. Among the most important metabolic derangements giving rise to impaired metabolism and clearance of chylomicrons and VLDLs are obesity, insulin resistance/metabolic syndrome, and diabetes mellitus (DM).^5,6 Insulin resistance (IR) induces a broad variety of disturbances in lipid metabolism.⁷ As adipocytes become insulin resistant, insulin can no longer appropriately inhibit hormone sensitive lipase (HSL), which leads to constitutive release of free fatty acid (FFA) from intracellular triglycerides stores. The FFAs are taken up into hepatocytes via the portal circulation and can then undergo any of four fates: (1) be taken up into the mitochondrial matrix and undergo beta-oxidation; (2) be reassimilated into triglyceride and secreted in VLDL particles; (3) be shunted toward gluconeogenesis and worsen the hyperglycemia of IR; and (4) undergo deposition as triglyceride leading to hepatic steatosis. In the setting of IR, insulin has reduced capacity to inhibit the hepatic secretion of VLDLs in the fed state. In addition, in patients with IR, apo CII is less available and apo CIII (an inhibitor of LL) production is increased. As the amount of secreted VLDL particles increases, LL activity is reduced and VLDL remnants and IDL accumulate with less formation of LDL. In an effort to offload triglyceride from remnant lipoproteins (VLDL 2+3 and IDL; RLPs), cholesterol ester transfer protein is activated which catalyzes a 1:1 stoichiometric exchange of triglyceride out of remnants lipoproteins in exchange for cholesterol ester from HDL and LDL particles.⁸ As the HDL and LDL particles become progressively more enriched with triglyceride, they become better substrates for lipolysis by hepatic lipase. This leads to HDL catabolism and a reduction in circulating levels of HDL-C and an increase in small, dense LDL particles, the so-called atherogenic dyslipidemia: low HDL-C, large number of LDL particles, and hypertriglyceridemia characterized by significant elevations in circulating RLPs.

Serum lipids are measured typically after an 8-12 hour fasting. In Western societies, during routine daily living, the majority of people are persistently post-prandial. In fact, meals tend to be consumed before the lipids and lipoproteins from the preceding meal are fully metabolized and cleared from the circulation. Consequently, we are exposed to much higher levels of RLPs and in a more persistent manner than what is suggested by the results of studies using fasting lipid samples. This would be especially true of patients afflicted with IR or established DM. As found in adults, RLPs are elevated in obese children and adolescents.⁹

Whether triglycerides constitute an independent risk factor for atherosclerotic cardiovascular disease (ASCVD) is controversial. A number of investigations suggest that they are, though much depends on covariate adjustment.^10-13 The suggestion that RLPs contribute to atherogenesis was first made by Zilversmit in 1979.¹⁴ Remnants correlate significantly with risk for CV events. In the Framingham Offspring Study, serum levels of RLPs correlate with risk for CV events in women with established coronary artery disease (CAD).¹⁵ Similarly in the Honolulu Heart Study, serum levels of RLPs were significantly associated with risk for CV events among men of Asian descent.¹⁶ In the ACCORD trial, RLPs correlated with CV events among diabetic women in a postprandial substudy.¹⁷ Remnant levels correlate with risk for acute CV events in Japanese patients with established coronary artery disease (CAD),¹⁸ carotid intima media thickness,¹⁹ carotid plaque macrophage density,²⁰ ischemic stroke,²¹ endothelial dysfunction²², and can be extracted from atherosclerotic plaque.²³ Among patients with Fredrickson type III dyslipoproteinemia (familial dysbetalipoproteinemia; due to defective apoE), serum remnants are increased leading to the development of xanthomas and elevated risk for CV events.²⁴ More recently, we have demonstrated that increased serum levels of RLPs (defined as sum of VLDL3+IDL) are highly associated with risk for CV events in both the Framingham Heart Study, the Jackson Heart Study, and a meta-analysis performed of both cohorts (HR 1.23; 95% CI 1.06-1.42, p=0.006).²⁵ There was no heterogeneity between cohorts. Thus, RLPs are similarly correlated with CV events in both Caucasians and African Americans.

The RLPs are larger than LDL particles and it has been assumed that their penetration into arterial walls would be limited from biophysical considerations alone. However, both apoB100 and apoB48 can be extracted from atherosclerotic plaque.²⁶ During atherogenesis, LDL particles are oxidatively modified. Oxidation by-products contained within the LDL then induce the expression of scavenging receptors (SR-A, CD-36) on the surface of macrophages to initiate lipid uptake and the formation of macrophage-derived foam cells. The latter step can apparently be bypassed with RLPs.²⁷ RLPs that transcytose into the subendothelial space can egress from the vessel wall via the vasa vasora. However, if the vessel is inflamed and an atherogenic milieu is established, there is increased intercellular matrix material deposited in the subendothelial space, which can trap RLPs. The RLPs do not require oxidative modification in order to be scavenged by macrophages because the macrophages recognize apoE on the surface of these lipoproteins, triggering lipoprotein uptake. Hence, it is biologically plausible that RLPs are in fact atherogenic.

The statins do not impact RLP formation and clearance to a significant degree. The fibrates and high-dose omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acids, i.e., the fish oils) both reduce VLDL secretion and promote the conversion of VLDL to LDL by activating LL.²⁸ Aerobic exercise, weight loss, and smoking cessation all correlate with reductions in RLPs because each of these lifestyle interventions reduces IR. In patients with elevated RLP levels, it is important to reduce intake of saturated fats and increase use of monounsaturated and polyunsaturated fats.

In an indirect way, RLPs were treated under the rubric of non-HDL-C by the Third Adult Treatment Panel.¹ However, treatment thresholds and targets for LDL-C and non-HDL-C have been eliminated and replaced by a risk benefit model of care, wherein the intensity of statin therapy is determined by 10 year projected risk.²⁹ The guidelines in Europe and Canada will not be changed in response to the ACC/AHA blood cholesterol treatment guideline. Consequently, there will be disparities in the degree to which RLPs are lowered and how they will (at least indirectly) be targeted for treatment. It is clear that considerable research needs to be done in establishing optimal therapeutic approaches for managing mixed dyslipidemias which include elevations in RLPs. Additional clinical trials will have to be designed that specifically enroll patients with elevated triglycerides and RLPs to help better ascertain the impact of specific therapies CV endpoints. This will make for an important and fascinating new chapter in cardiovascular medicine.

References

0.  
1. Executive Summary of The Third Report of The National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, And Treatment of High Blood Cholesterol In Adults (Adult Treatment Panel III). JAMA 2001;285:2486-97.
2. Reiner Z, Catapano AL, De Backer G, Graham I, Taskinen MR, Wiklund O, Agewall S, Alegria E, Chapman MJ, Durrington P, Erdine S, Halcox J, Hobbs R, Kjekshus J, Filardi PP, Riccardi G, Storey RF, Wood D. ESC/EAS Guidelines for the management of dyslipidaemias: the Task Force for the management of dyslipidaemias of the European Society of Cardiology (ESC) and the European Atherosclerosis Society (EAS). Eur Heart J 2011;32:1769-818.
3. Genest J, McPherson R, Frohlich J, Anderson T, Campbell N, Carpentier A, Couture P, Dufour R, Fodor G, Francis GA, Grover S, Gupta M, Hegele RA, Lau DC, Leiter L, Lewis GF, Lonn E, Mancini GB, Ng D, Pearson GJ, Sniderman A, Stone JA, Ur E. 2009 Canadian Cardiovascular Society/Canadian guidelines for the diagnosis and treatment of dyslipidemia and prevention of cardiovascular disease in the adult - 2009 recommendations. Can J Cardiol 2009;25:567-79.
4. Boekholdt SM, Arsenault BJ, Mora S, Pedersen TR, LaRosa JC, Nestel PJ, Simes RJ, Durrington P, Hitman GA, Welch KM, DeMicco DA, Zwinderman AH, Clearfield MB, Downs JR, Tonkin AM, Colhoun HM, Gotto AM, Jr., Ridker PM, Kastelein JJ. Association of LDL cholesterol, non-HDL cholesterol, and apolipoprotein B levels with risk of cardiovascular events among patients treated with statins: a meta-analysis. JAMA 2012;307:1302-9.
5. Grundy SM, Cleeman JI, Daniels SR, Donato KA, Eckel RH, Franklin BA, Gordon DJ, Krauss RM, Savage PJ, Smith SC, Jr., Spertus JA, Costa F. Diagnosis and management of the metabolic syndrome: an American Heart Association/National Heart, Lung, and Blood Institute Scientific Statement. Circulation 2005;112:2735-52.
6. Grundy SM. Metabolic syndrome: connecting and reconciling cardiovascular and diabetes worlds. J Am Coll Cardiol 2006;47:1093-100.
7. Bays HE, Toth PP, Kris-Etherton PM, Abate N, Aronne LJ, Brown WV, Gonzalez-Campoy JM, Jones SR, Kumar R, La Forge R, Samuel VT. Obesity, adiposity, and dyslipidemia: a consensus statement from the National Lipid Association. J Clin Lipidol 2013;7:304-83.
8. Toth PP, Barter PJ, Rosenson RS, Boden WE, Chapman MJ, Cuchel M, D'Agostino RB, Sr., Davidson MH, Davidson WS, Heinecke JW, Karas RH, Kontush A, Krauss RM, Miller M, Rader DJ. High-density lipoproteins: a consensus statement from the National Lipid Association. J Clin Lipidol 2013;7:484-525.
9. Choi YJ, Jo YE, Kim YK, Ahn SM, Jung SH, Kim HJ, Chung YS, Lee KW, Kim DJ. High plasma concentration of remnant lipoprotein cholesterol in obese children and adolescents. Diabetes Care 2006;29:2305-10.
10. Castelli WP. Epidemiology of triglycerides: a view from Framingham. Am J Cardiol 1992;70:3H-9H.
11. Miller M, Cannon CP, Murphy SA, Qin J, Ray KK, Braunwald E. Impact of triglyceride levels beyond low-density lipoprotein cholesterol after acute coronary syndrome in the PROVE IT-TIMI 22 trial. J Am Coll Cardiol 2008;51:724-30.
12. Miller M, Stone NJ, Ballantyne C, Bittner V, Criqui MH, Ginsberg HN, Goldberg AC, Howard WJ, Jacobson MS, Kris-Etherton PM, Lennie TA, Levi M, Mazzone T, Pennathur S, American Heart Association Clinical Lipidology T, Prevention Committee of the Council on Nutrition PA, Metabolism, Council on Arteriosclerosis T, Vascular B, Council on Cardiovascular N, Council on the Kidney in Cardiovascular D. Triglycerides and cardiovascular disease: a scientific statement from the American Heart Association. Circulation 2011;123:2292-333.
13. Chapman MJ, Ginsberg HN, Amarenco P, Andreotti F, Boren J, Catapano AL, Descamps OS, Fisher E, Kovanen PT, Kuivenhoven JA, Lesnik P, Masana L, Nordestgaard BG, Ray KK, Reiner Z, Taskinen MR, Tokgozoglu L, Tybjaerg-Hansen A, Watts GF. Triglyceride-rich lipoproteins and high-density lipoprotein cholesterol in patients at high risk of cardiovascular disease: evidence and guidance for management. Eur Heart J 2011;32:1345-61.
14. Zilversmit DB. Atherogenesis: a postprandial phenomenon. Circulation 1979;60:473-85.
15. McNamara JR, Shah PK, Nakajima K, Cupples LA, Wilson PW, Ordovas JM, Schaefer EJ. Remnant-like particle (RLP) cholesterol is an independent cardiovascular disease risk factor in women: results from the Framingham Heart Study. Atherosclerosis 2001;154:229-36.
16. Imke C, Rodriguez BL, Grove JS, McNamara JR, Waslien C, Katz AR, Willcox B, Yano K, Curb JD. Are remnant-like particles independent predictors of coronary heart disease incidence? The Honolulu Heart study. Arterioscler Thromb Vasc Biol 2005;25:1718-22.
17. Ginsberg HN, Elam MB, Lovato LC, Crouse JR, 3rd, Leiter LA, Linz P, Friedewald WT, Buse JB, Gerstein HC, Probstfield J, Grimm RH, Ismail-Beigi F, Bigger JT, Goff DC, Jr., Cushman WC, Simons-Morton DG, Byington RP. Effects of combination lipid therapy in type 2 diabetes mellitus. N Engl J Med 2010;362:1563-74.
18. Kugiyama K, Doi H, Takazoe K, Kawano H, Soejima H, Mizuno Y, Tsunoda R, Sakamoto T, Nakano T, Nakajima K, Ogawa H, Sugiyama S, Yoshimura M, Yasue H. Remnant lipoprotein levels in fasting serum predict coronary events in patients with coronary artery disease. Circulation 1999;99:2858-60.
19. Karpe F, Boquist S, Tang R, Bond GM, de Faire U, Hamsten A. Remnant lipoproteins are related to intima-media thickness of the carotid artery independently of LDL cholesterol and plasma triglycerides. J Lipid Res 2001;42:17-21.
20. Zambon A, Puato M, Faggin E, Grego F, Rattazzi M, Pauletto P. Lipoprotein remnants and dense LDL are associated with features of unstable carotid plaque: a flag for non-HDL-C. Atherosclerosis 2013;230:106-9.
21. Kim JY, Park JH, Jeong SW, Schellingerhout D, Park JE, Lee DK, Choi WJ, Chae SL, Kim DE. High levels of remnant lipoprotein cholesterol is a risk factor for large artery atherosclerotic stroke. J Clin Neurol 2011;7:203-9.
22. Maggi FM, Raselli S, Grigore L, Redaelli L, Fantappie S, Catapano AL. Lipoprotein remnants and endothelial dysfunction in the postprandial phase. J Clin Endocrinol Metab 2004;89:2946-50.
23. Rapp JH, Lespine A, Hamilton RL, Colyvas N, Chaumeton AH, Tweedie-Hardman J, Kotite L, Kunitake ST, Havel RJ, Kane JP. Triglyceride-rich lipoproteins isolated by selected-affinity anti-apolipoprotein B immunosorption from human atherosclerotic plaque. Arterioscler Thromb 1994;14:1767-74.
24. Vermeer BJ, Frants RR, Havekes LM. Familial dysbetalipoproteinemia: a genetically heterogenous disease caused by mutations of the ligand apolipoprotein E. J Invest Dermatol 1992;98(6 Suppl):57S-60S.
25. Toth PP, Massaro J, Jones S, Griswold M, Lirette S, Martin S, Joshi P, D'Agostino R. Abstract 14026: Remnant Lipoprotein Cholesterol Fractions and Risk for Cardiovascular Events in the Jackson Heart and Framingham Offspring Studies: A Meta-Analysis. Circulation 2013;128(22 Supplement):A14026.
26. Proctor SD, Mamo JC. Intimal retention of cholesterol derived from apolipoprotein B100- and apolipoprotein B48-containing lipoproteins in carotid arteries of Watanabe heritable hyperlipidemic rabbits. Arterioscler Thromb Vasc Biol 2003;23:1595-600.
27. Fujioka Y, Ishikawa Y. Remnant lipoproteins as strong key particles to atherogenesis. J Atheroscler Thromb 2009;16:145-54.
28. Toth PP, Dayspring TD, Pokrywka GS. Drug therapy for hypertriglyceridemia: fibrates and omega-3 fatty acids. Curr Atheroscler Rep 2009;11:71-9.
29. Stone NJ, Robinson J, Lichtenstein AH, Merz CN, Blum CB, Eckel RH, Goldberg AC, Gordon D, Levy D, Lloyd-Jones DM, McBride P, Schwartz JS, Shero ST, Smith SC, Jr., Watson K, Wilson PW. 2013 ACC/AHA Guideline on the Treatment of Blood Cholesterol to Reduce Atherosclerotic Cardiovascular Risk in Adults: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol 2013; [Epub Ahead of Print].

Major 'third-hand smoke' compound causes DNA damage and potentially cancer

Leftover cigarette smoke that clings to walls and furniture is a smelly nuisance, but now research suggests that it could pose a far more serious threat, especially to young children who put toys and other smoke-affected items into their mouths. Scientists reported today that one compound from this "third-hand smoke," which forms when second-hand smoke reacts with indoor air, damages DNA and sticks to it in a way that could potentially cause cancer.

Their talk was one of more than 10,000 presentations at the 247th National Meeting & Exposition of the American Chemical Society (ACS) in Dallas this week.

Bo Hang, Ph.D., who presented the research, said that although the idea of third-hand smoke made its debut in research circles just a few years ago in 2009, evidence already strongly suggests it could threaten human health.

"The best argument for instituting a ban on smoking indoors is actually third-hand smoke," said Hang, a scientist at Lawrence Berkeley National Laboratory (LBNL).

Researchers have found that many of the more than 4,000 compounds in second-hand smoke, which wafts through the air as a cigarette is smoked, can linger indoors long after a cigarette is stubbed out. Based on studies led by Hugo Destaillats, also at LBNL, these substances can go on to react with indoor pollutants such as ozone and nitrous acid, creating brand-new compounds, some of which may be carcinogenic.

One of those compounds goes by the acronym NNA. Hang's research has shown that NNA, a tobacco-specific nitrosamine, locks onto DNA to form a bulky adduct (a piece of DNA bound to a cancer-causing chemical), as well as other adducts, in lab test tubes. Other large compounds that attach to DNA tend to cause genetic mutations. NNA also breaks the DNA about as often as a related compound called NNK, which is a well-studied byproduct of nicotine and a known potent carcinogen. This kind of DNA damage can lead to uncontrolled cell growth and the formation of cancerous tumors.

Just as it took years to establish the cancer-causing effects of first-hand smoke that is inhaled as a person breathes in directly from the cigarette, making the connection between third-hand smoke or NNA and cancer could take a long time, Hang said. But early research into its nature, exposure and health effects is compelling enough that a research consortium dedicated to investigating third-hand smoke was formed in California in 2010. That consortium helped fund Hang's work on NNA-induced DNA damage, which he said could eventually be used as biomarkers to identify people who have been exposed to third-hand smoke.

The biggest potential health risk is for babies and toddlers, he noted. As they crawl and put their hands or toys in their mouths, they could touch, swallow or inhale compounds from third-hand smoke. Their small size and early developmental stage make them more vulnerable than adults to the effects of environmental hazards.

Although many public places prohibit smoking, Hang noted that people can still smoke in most rental apartments and private residences -- and smoking remains a huge public health issue. In 2011, nearly 44 million American adults reported smoking cigarettes, which ranks as the leading cause of preventable death in this country. And 34 million people smoke every day, according to data from the Centers for Disease Control & Prevention.

So far, the best way to get rid of third-hand smoke is by removing affected items, such as sofas and carpeting, as well as sealing and repainting walls, and sometimes even replacing contaminated wallboard, he explained. Replacing furniture can be pricey, but Hang said vacuuming and washing clothes, curtains and bedding can also help.

Hang's research was funded by the Tobacco-Related Disease Research Program, which is administered by the University of California.

source: American Chemical Society (ACS)

WHEN IS CHRONIC KIDNEY DISEASE SCREENING NECESSARY?

Introduction

Chronic kidney disease (CKD) is common and often asymptomatic at the time of diagnosis. Yet CKD is associated with substantial increases in the risk for cardiovascular (CV) events and overall mortality. These facts suggest the potential value of population-based screening for CKD.

However, the US Preventive Services Task Force (USPSTF)^[1] and American College of Physicians (ACP)^[2] have not recommended broad screening for CKD, citing a lack of evidence that screening improves important outcomes. The American Society of Nephrologists (ASN)^[3] retorts that all adults should undergo periodic screening for CKD.

Who is right? The current review examines the science behind these recommendations and offers a solution for the busy primary care clinician.

Background

Your next clinic patient is new to your practice. She is a 50-year-old woman who has been experiencing headaches and dizziness. She also told your medical assistant that she has chest pain on occasion during exercise. You complete a thorough evaluation with a history and physical examination for these problems but, thankfully, find no red flags.

You are about to discuss treatment options when she stops you. "Oh!" she says, "I'm so happy that you're taking the time to listen to me. I haven't been to the doctor in ages, but now that preventive care is covered by insurance, I wanted you to order 'the sampler.' Ha ha! No, but really, can you refer me for everything that I need? I promise to get it done!"

A well-performed study of over 46,000 outpatient primary care visits found that the average visit lasts approximately 20 minutes.^[4] The research also demonstrated that the average number of clinical items addressed in these encounters was 7, with a temporal trend toward a reduced amount of time devoted to each issue between 1997 and 2005. The case described above provides an example of the competing agendas that change and change again during an ordinary clinic visit.

What does it take to navigate these complexities? First, it requires a patient-centered approach. A systematic review and meta-analysis found that physicians trained in empathic care with an emphasis on communication were able to change their practice habits, even after a brief intervention.^[5] However, only more complex programs were found to be reliably effective in improving patient health behaviors and satisfaction. The mixed results of this body of research reconfirm how challenging these outcomes are.

But good communication and people skills are not enough. Good primary care physicians know their science and are able to inform patients with understandable and pertinent data to practice shared decision-making. This includes an understanding of current guidelines for preventive care. If we as primary care physicians cannot provide evidence-based preventive care, who will?

So, let's summarize the arguments for and against screening everyone for CKD.

The Evidence for Screening

Medical conditions need to fulfill certain criteria in order to be recommended for screening.^[6] They need to be detectable at an asymptomatic stage, and there must be an adequate screening test available. The screened condition must be amenable to an available intervention after screening that improves the chances of healthy outcomes, and the cost of this process should be acceptable to society.

There is no doubt that CKD fulfills at least some of these criteria. CKD is common and frequently undiagnosed, although the precise prevalence of undiagnosed CKD varies substantially with the population studied and the methods used to diagnose CKD. In a study of nearly 25,000 adults with at least 2 measurements of their estimated glomerular filtration rate (eGFR), the prevalence of CKD was 28.2%.^[7] Only 26.5% of patients with evidence of CKD had an established clinical diagnosis of kidney disease. Studies conducted in India and Iceland found rates of CKD among community-dwelling adults that ranged between 4% and 13%, and the prevalence of proteinuria was 0.9%-2.4%.^[8,9]

CKD is not only common, but it is also associated with profound health risks. A retrospective analysis of data from over 1 million adults found that compared with adults with an eGFR of 60 mL/min/1.72 m² of body surface area or more, the adjusted hazard ratios for both mortality and CV events increased linearly as eGFR declined (Table).

Table. Mortality HR With Declining eGFR^[10]

eGFR (mL/min/1.72 m2)	Mortality HR	CV Event HR
45-59	1.2	1.4
30-44	1.8	2.0
15-29	3.2	2.8
< 15	5.9	3.4

CV = cardiovascular; eGFR = estimated glomerular filtration rate; HR = hazard ratio

A meta-analysis published in 2010 confirmed the positive association between eGFR and the risk for death, and also found a linear trend toward a higher risk for death as the degree of albuminuria increased.^[11] Albuminuria and eGFR were independent variables associated with a higher risk for death in this study.

The Evidence Against Screening

Nonetheless, the USPSTF and ACP have failed to endorse routine screening for CKD among asymptomatic adults without substantial risk factors, such as diabetes or hypertension.^[1,2] The principal argument against screening for CKD is the lack of randomized trials comparing outcomes in screened vs nonscreened adults. But both venerable organizations describe other specific problems with generalized screening for CKD.

The USPSTF acknowledges the lack of a unified definition of CKD and the variability of testing results. For example, intraindividual variability for urinary albumin testing may be as high as 50%. Moreover, the USPSTF casts doubt on whether the discovery and treatment of CKD among asymptomatic adults improves clinical outcomes. Specifically, they cite a lack of studies regarding early treatment of CKD among persons without diabetes or hypertension. The USPSTF could not find a precise estimation of harms associated with CKD screening, although they imply that some patients would suffer false-positive diagnoses and adverse events associated with treatment.

The ACP argument follows these same lines, but provides more of a focus on the treatment of CKD. Angiotensin-converting enzyme inhibitors (ACEIs) can retard the progression of CKD to end-stage renal disease (ESRD). However, there is no evidence that ACEIs afford this same benefit to patients with isolated impaired GFR or albuminuria, and ACEIs have a weak, if any, effect on the risk for mortality among patients with CKD.

Angiotensin II receptor blockers (ARBs) similarly can reduce the risk for ESRD among patients with CKD. However, they are unproven among CKD patients without hypertension or diabetes, and ARBs are not associated with a CV or mortality benefit among patients with CKD alone. In contrast, statins also do not have an effect on the risk for ESRD among patients with CKD and dyslipidemia, but they are associated with improved CV and overall mortality outcomes.

The ACP also goes beyond a recommendation against the universal screening of adults for CKD. They recommend against testing for urinary protein among patients treated with an ACEI or an ARB, even among patients with diabetes. In their rationale for this recommendation, they cite a lack of evidence of the benefits of monitoring proteinuria.

The ASN Response

The USPSTF recommendations finding insufficient evidence to support universal screening for CKD were released in 2012. The more robust ACP recommendations specifically advocating against routine screening were published in December 2013. In between the release of these documents, the ASN released the contrarian viewpoint that all patients should be screened for kidney disease.^[3]

The ASN acknowledges the ACP's position, but argues that the identification of patients with CKD can help to prevent episodes of acute kidney injury mediated by nephrotoxic drugs or radiographic contrast agents. The ASN also underscores the critical role for hypertension and diabetes in promoting CKD, but they provide nowhere near the degree of evidence delivered by the USPSTF and ACP.

The Bottom Line for Primary Care

The ASN has a good point regarding the possibility of iatrogenic kidney injury among adults with unrecognized CKD. However, given the ubiquity of screening laboratory work for patients in the hospital and clinics, the risk for these injuries should be minimized with routine conscientious practice.^[12]

In trying to reconcile these disparate recommendations, it is helpful to remember that all 3 guidelines discuss the relationship among hypertension, diabetes, and CKD. The vast majority of cases of CKD are related to diabetes and hypertension. However, between 1988 and 1994, the prevalence of undiagnosed diabetes among US adults was estimated to be 2.7%.^[13] This level remained stable through 2002 but was twice as high among non-Hispanic black adults and Mexican-American adults compared with non-Hispanic white adults.^[14] It is not only adults who might have unrecognized diabetes. Among adolescents, the rate of undiagnosed diabetes has been found to be 0.12%.^[15]

Hypertension may similarly be underdiagnosed. Data from the National Health and Nutrition Examination Survey found that the overall prevalence of hypertension among US adults between 1999 to 2004 was 28.9%, and disease was undiagnosed in 28.2% of these patients.^[16] Another study demonstrated that the prevalence of CKD among individuals with undiagnosed hypertension was 22.0%, which was nearly twice the rate of adults with normal blood pressure.^[17]

It is clear that we must do a better job in identifying individuals with chronic high blood pressure and diabetes. Rather than using precious time to chase the unproven practice of generalized screening for CKD, doesn't it make more sense to focus on screening for the disease states that promote CKD, as well as other critical outcomes, such as CV disease and mortality? Discover the hypertension or diabetes, and the CKD will often reveal itself. Moreover, physicians can feel confident that renoprotective therapy in the context of hypertension and diabetes is effective, whereas this is a matter of debate among patients with CKD discovered on screening alone.

We cannot minimize the danger of CKD. But we also need to use the evidence to guide us in our best practice. We should focus on the risk factors for CKD and leave generalized screening possibly to another day in the future.

Clinical Pearls

• CKD may have a prevalence rate as high as 28% among US adults. Most of these individuals have no symptoms and have no formal diagnosis of CKD.

• CKD is independently associated with higher risks for CV disease and mortality.

• There are no adequate randomized trials on which to judge the value of universal screening of adults for CKD.

• The ACP and USPSTF cite this lack of evidence in their failure to endorse screening for CKD.

• The ASN disagrees with these recommendations and instead advocates routine periodic screening for CKD among adults.

• Given the close association between hypertension and diabetes and the risk for CKD, as well as the paucity of evidence that treatment of CKD in the absence of these comorbid conditions improves outcomes substantially, it makes sense for clinicians to focus on the identification and treatment of hypertension and diabetes instead of CKD.

References

1. Moyer VA; US Preventive Services Task Force. Screening for chronic kidney disease: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2012;157:567-570. Abstract
2. Qaseem A, Hopkins RH, Sweet DE, Starkey M, Shekelle P; Clinical Guidelines Committee of the American College of Physicians. Screening, monitoring, and treatment of stage 1 to 3 chronic kidney disease: a clinical practice guideline from the Clinical Guidelines Committee of the American College of Physicians. Ann Intern Med. 2013;159:835-847.
3. American Society of Nephrology. ASN emphasizes need for early detection of kidney disease, a silent killer. October 22, 2013. http://www.asn-online.org/news/2013/ASN_COMM_ACP_Screening_Response_102213_R12.pdf Accessed February 19, 2014.
4. Abbo ED, Zhang Q, Zelder M, Huang ES. The increasing number of clinical items addressed during the time of adult primary care visits. J Gen Intern Med. 2008;23:2058-2065. Abstract
5. Dwamena F, Holmes-Rovner M, Gaulden CM, et al. Interventions for providers to promote a patient-centred approach in clinical consultations. Cochrane Database Syst Rev. 2012;CD003267.
6. Wilson JM, Jungner G. Principles and Practice of Screening for Disease. Geneva: World Health Organization; 1968.
7. Ryan TP, Sloand JA, Winters PC, Corsetti JP, Fisher SG. Chronic kidney disease prevalence and rate of diagnosis. Am J Med. 2007;120:981-986. Abstract
8. Singh NP, Ingle GK, Saini VK, et al. Prevalence of low glomerular filtration rate, proteinuria, and associated risk factors in North India using Cockcroft-Gault and Modification of Diet in Renal Disease equation: an observational, cross-sectional study. BMC Nephrol. 2009;10:4.
9. Viktorsdottir O, Palsson R, Andresdottir MB, Aspelund T, Gudnason V, Indridason OS. Prevalence of chronic kidney disease based on estimated glomerular filtration rate and proteinuria in Icelandic adults. Nephrol Dial Tranplant. 2005;20:1799-1807.
10. Go AS, Chertow GM, Fan D, McCulloch CE, Hsu CY. Chronic kidney disease and the risks of death, cardiovascular events, and hospitalization. N Engl J Med. 2004;351:1296-1305. Abstract
11. Chronic Kidney Disease Prognosis Consortium, Masushita K, van der Velde M, et al. Association of estimated glomerular filtration rate and albuminuria with all-cause and cardiovascular mortality in general population cohorts: a collaborative meta-analysis. Lancet. 2010;375:2073-2081. Abstract
12. Morcos SK. Prevention of contrast media nephrotoxicity -- the story so far. Clin Radiol. 2004;59:381-389. Abstract
13. Harris MI, Flegal KM, Cowie CC, et al. Prevalence of diabetes, impaired fasting glucose, and impaired glucose tolerance in U.S. adults. The Third National Health and Nutrition Examination Survey, 1988-1994. Diabetes Care. 1998;21:518-524. Abstract
14. Cowie CC, Rust KF, Byrd-Holt DD, et al. Prevalence of diabetes and impaired fasting glucose in adults in the U.S. population: National Health And Nutrition Examination Survey 1999-2002. Diabetes Care. 2006;29:1263-1268. Abstract
15. Demmer RT, Zuk AM, Rosenbaum M, Desvarieux M. Prevalence of diagnosed and undiagnosed type 2 diabetes mellitus among US adolescents: results from the continuous NHANES, 1999-2010. Am J Epidemiol. 2013;178:1106-1113. Abstract
16. Cutler JA, Sorlie PD, Wolz M, Thom T, Fields LE, Roccella EJ. Trends in hypertension prevalence, awareness, treatment, and control rates in United States adults between 1988-1994 and 1999-2004. Hypertension. 2008;52:818-827. Abstract
17. Crews DC, Plantinga LC, Miller ER 3rd, et al; Centers for Disease Control and Prevention Chronic Kidney Disease Surveillance Team. Prevalence of chronic kidney disease in persons with undiagnosed or prehypertension in the United States. Hypertension. 2010;55:1102-1119. Abstract

 

Medscape Family Medicine © 2014  WebMD, LLC

Fructosamine, Glycated Albumin Viable Alternatives to HbA1c in Certain Settings

New research shows that fructosamine and glycated albumin not only are strongly associated with incident diabetes and diabetes-related microvascular disease, but also have prognostic value comparable to HbA1c (Lancet 2014; http://dx.doi.org/10.1016/S2213-8587(13)70199-2). The findings suggest that these two analytes might be useful complements to HbA1c in clinical practice, especially when HbA1c testing is not available, or when HbA1c results might be considered unreliable.

Fructosamine and glycated albumin are markers of short-term, 2–4 week glycemic control, but neither are used routinely in clinical practice. On the other hand, HbA1c, a measure of long-term glucose exposure in the blood, has been the primary test used to manage diabetes, and in 2010, also was recommended as a diagnostic test for the disease. However, HbA1c has some limitations, including assay interferences such as hemoglobin variants, and other conditions like hemolytic anemia and pregnancy that can affect validity of HbA1c results.

The authors measured fructosamine and glycated albumin from 11,348 non-diabetics and 958 diabetics, as part of the Atherosclerosis Risk in Communities (ARIC) studies. All ARIC participants included in the analysis had undergone ARIC’s second clinical examination between 1990 and 1992 as well as visit three, when retinal photographs were taken. The outcomes of interest were relationships between fructosamine and glycated albumin with risk of incident diabetes, retinopathy, and risk of incident chronic kidney disease (CKD) during 2 decades of follow up.

The researchers found that hazard ratios for incident diabetes were 4.96 and 6.17, respectively, for fructosamine and glycated albumin above the 95th percentile. Fructosamine and glycated albumin also were strongly associated with retinopathy. Fructosamine and glycated albumin predicted incident CKD almost as well as HbA1c, although the reverse was true when it came to predicting incident diabetes.

The authors used a standard commercial assay to measure fructosamine, but employed a novel enzymatic method for glycated albumin. Both showed “excellent” performance, with coefficients of variation ≤3%. However, they also have limitations, including being affected by alterations in serum protein turnover, and by certain conditions, including liver disease, hyperuricemia, and thyroid dysfunction.

Based on their findings, the authors suggested that fructosamine and glycated albumin testing might be particularly useful when short-term measurement of glycemic control is important, such as for monitoring changed treatment regimens.

source: www.aacc.org

Fructose not responsible for increase in non-alcoholic fatty liver disease, research shows

Non-alcoholic fatty liver disease is the most common chronic liver disease in developed countries, affecting up to 30 per cent of their populations.

Since the disease is closely linked to obesity and Type 2 diabetes, there's a growing debate in the medical community about whether diet plays a role in its development, specifically the consumption of fructose.

The possible link to non-alcoholic fatty liver disease has become the main criticism against fructose among those who believe there is something unique about the fructose molecule or the way it is metabolized and blame it for the obesity epidemic.

A meta-analysis of all available human trials published in the European Journal of Clinical Nutrition says fructose in and of itself is not to blame for the increase in non-alcoholic fatty liver disease.

But excess consumption of calories can contribute to the disease, regardless of whether those calories came from fructose or other carbohydrates, said the lead author, Dr. John Sievenpiper, a researcher in the Clinical Nutrition and Risk Factor Modification Centre of St. Michael's Hospital.

"The one thing fructose is supposed to do above all else is give you fatty liver disease, which some say is a starting point for metabolic syndrome--a term used to describe a group of conditions that puts people at higher risk of developing Type 2 diabetes, heart disease and other heart-related problems--and Type 2 diabetes itself," Dr. Sievenpiper said.

"But we found it behaves no differently than glucose or refined starches. It is only when you consume excess calories in the form of fructose that you see a signal for harm but no more harm than if you consume excess calories as glucose."

Fructose, which is naturally found in fruit, vegetables and honey, is a simple sugar that together with glucose forms sucrose, the basis of table sugar. It is also found in sucrose and high-fructose corn syrup, the two most common sweeteners in commercially prepared foods.

Non-alcoholic fatty liver disease is one cause of a fatty liver, occurring when fat is deposited in the liver. Unlike alcoholic liver disease, it is not due to excessive alcohol use.

Previous research by Dr. Sievenpiper has found that fructose by itself does not cause weight gain and does not itself have any impact on an emerging marker for the risk of cardiovascular disease known as postprandial triglycerides when it is substituted for other carbohydrates. It is when fructose is overconsumed providing excess calories that you see the adverse effects on health, but no more than when other carbohydrates are overconsumed.

A study he published in the February issue of Current Opinion in Lipidology also found no benefit in replacing fructose with glucose in commercially prepared foods. That research again showed that that when portion sizes and calories are the same, fructose does not cause any more harm than glucose.

"The debate over the role of fructose in obesity, fatty liver and other metabolic diseases has distracted us from the issue of overconsumption," Dr. Sievenpiper said. "Our data should serve to remind people that the excess calories, whether they are from fructose or other sources, are the issue."

Journal Reference:

1. S Chiu, J L Sievenpiper, R J de Souza, A I Cozma, A Mirrahimi, A J Carleton, V Ha, M Di Buono, A L Jenkins, L A Leiter, T M S Wolever, A C Don-Wauchope, J Beyene, C W C Kendall, D J A Jenkins. Effect of fructose on markers of non-alcoholic fatty liver disease (NAFLD): a systematic review and meta-analysis of controlled feeding trials. European Journal of Clinical Nutrition, 2014; DOI: 10.1038/ejcn.2014.8

source: www.sciencedaily.com

Circulating Cardiac Troponin T Exhibits a Diurnal Rhythm

Study Question:

What are the within-day, diurnal, and between-week biological variations of cardiac troponin T (cTnT) in subjects with increased odds to require hospital examination for chest pain?

Methods:

Two studies were conducted to assess biological cTnT variation, and investigate the presence of a diurnal rhythm of cTnT. Study 1 comprised 23 male subjects with type 2 diabetes, without acute cardiovascular disease. Serial venous blood samples were drawn over an 11-hour period (08:30-19:30 hours). In study 2, the presence of a diurnal cTnT rhythm was investigated by hourly sampling of seven subjects from study 1 over 25 hours.

Results:

In study 1, the investigators observed a gradual decrease in cTnT concentrations during the day (24 ± 2%). This decrease was present in all participants and most prominent in subjects with the highest baseline cTnT values (Pearson’s R 0.93). Diurnal variation of cTnT, as assessed in study 2, was characterized by peak concentrations during morning hours (08:30 hours,17.1 ± 2.9 ng/L), gradually decreasing values during daytime (20:30 hours,11.9 ± 1.6 ng/L), and rising concentrations during nighttime (08:30 hours next day,16.9 ± 2.8 ng/L).

Conclusions:

The authors concluded that a diurnal cTnT rhythm substantiates the recommendation that all dynamic changes of cTnT should be interpreted in relation to the clinical presentation.

Perspective:

The current study suggests that circulating cTnT exhibits a diurnal rhythm, characterized by peak concentrations during morning hours, gradually decreasing concentrations throughout the daytime, and rising concentrations during nighttime. This diurnal oscillation is a general phenomenon, but is most prominent in subjects with the highest cTnT values. The presence of a diurnal rhythm has implications for epidemiological studies, and underscores the importance of interpreting all dynamic changes of cTnT in the context of the clinical presentation. 

 

Authors:	Klinkenberg LJ, van Dijk JW, Tan FE, van Loon LJ, van Dieijen-Visser MP, Meex SJ.
Citation:	J Am Coll Cardiol 2014;Feb 26:[Epub ahead of print].