Calprotectin — A Novel Marker of Obesity

Background

The two inflammatory molecules, S100A8 and S100A9, form a heterodimer, calprotectin. Plasma calprotectin levels are elevated in various inflammatory disorders. We hypothesized that plasma calprotectin levels would be increased in subjects with low-grade systemic inflammation i.e. either obese subjects or subjects with type 2 diabetes.

Methodology/Principal Findings

Plasma calprotectin and skeletal muscle S100A8 mRNA levels were measured in a cohort consisting of 199 subjects divided into four groups depending on presence or absence of type 2 diabetes (T2D), and presence or absence of obesity. There was a significant interaction between obesity and T2D (p = 0.012). Plasma calprotectin was increased in obese relative to non-obese controls (p<0.0001), whereas it did not differ between obese and non-obese patients with T2D (p = 0.62). S100A8 mRNA levels in skeletal muscle were not influenced by obesity or T2D. Multivariate regression analysis (adjusting for age, sex, smoking and HOMA2-IR) showed plasma calprotectin to be strongly associated with BMI, even when further adjusted for fitness, CRP, TNF-α or neutrophil number.

Conclusions/Significance

Plasma calprotectin is a marker of obesity in individuals without type 2 diabetes.     

Is Predisposition to NAFLD and Obesity Communicable?

A forthcoming article in Nature reveals that inflammasome deficiency disturbs gut microbiota and predisposes to diet-induced obesity and liver disease. The aberrant microbiota and its consequences could be transferred by cohousing mutant and wild-type mice, suggesting that some aspects of metabolic syndrome can be communicable (Henao-Mejia et?al., 2012).     

Medical Students’ Attitudes towards Overweight and Obesity

Objective

Studies from the USA have identified medical students as a major source of stigmatizing attitudes towards overweight and obese individuals. As data from Europe is scarce, medical students’ attitudes were investigated at the University of Leipzig in Leipzig, Germany.

Design

Cross-sectional survey containing an experimental manipulation consisting of a pair of vignettes depicting an obese and a normal weight 42-year-old woman, respectively. Vignettes were followed by the Fat Phobia Scale (FPS), a semantic differential assessing weight related attitudes. In case of the overweight vignette a panel of questions on causal attribution for the overweight preceded administration of the FPS.

Subjects

671 medical students were enrolled at the University of Leipzig from May to June 2011.

Results

The overweight vignette was rated significantly more negative than the normal weight vignette (mean FPS score 3.65±0.45 versus 2.54±0.38, p<0.001). A higher proportion of students had negative attitudes towards the overweight as compared to the normal weight individual (98.9% versus 53.7%, p<0.001). A “positive energy balance” was perceived as the most relevant cause for the overweight, followed by “negligent personality trait”, “societal and social environment” and “biomedical causes”. Attributing a “positive energy balance” or “negligent personality trait” as relevant cause for the overweight was positively associated with negative attitudes.

Conclusion

The results of this study confirm and complement findings from other countries, mainly the USA, and indicate that weight bias in the health care setting may be a global issue. Stigmatizing attitudes towards overweight and obesity are prevalent among a sample of medical students at the University of Leipzig. Negative attitudes arise on the basis of holding the individual accountable for the excess weight. They call for bringing the topic of overweight and obesity more into the focus of the medical curriculum and for enhancing medical students’ awareness of the complex aetiology of this health condition.     

What Is the Economic Case for Treating Obesity?

From both societal and payer perspectives, the economic effect of obesity in the United States is substantial, estimated at approximately 6% of our national health expenditure and cost of care in a major health maintenance organization. The number of physician visits related to obesity has increased 88% in a 6-year period. The morbidity cost (lost productivity) and functional capability of the patient with obesity is increasing rapidly (50% increase in lost productivity, 36% increase in restricted activity, and 28% increase in number of bed-days). Cost savings of treating obesity are comparable to those of treating other chronic diseases such as coronary heart disease and diabetes. Most studies indicate that most of the direct health care costs of obesity are from type 2 diabetes, coronary heart disease and hypertension. To date, however, there have been no published reports of the cost effectiveness of the medical management of obesity treatment. In conclusion, the cost of obesity is comparable to that of other chronic diseases, yet it receives disproportionately less attention. Cost effectiveness studies need to be initiated promptly.     

Is Obesity a Risk Factor for Vaccine Non-Responsiveness?

Understanding the link between vaccine immunogenicity and efficacy is currently a major focus in HIV research. Consequently, recent developments in the HIV-1 vaccine field have led to a closer look at immune responses to known efficacious vaccines. We undertook a study to explore clinical predictors of vaccine efficacy following recombinant hepatitis B (rHBV) vaccination in a cohort of HIV-uninfected, hepatitis B virus naïve women living in a peri-urban setting in Cape Town. Our aim was to define host biological risk factors associated with lack of vaccine uptake. We found a significant association (p=0.009) between body mass index (BMI) and lack of vaccine-specific IgG titre (<10mIU/mL). Obese individuals (BMI ≥ 30kg/m²) were significantly more likely to be non-responders following 2 rHBV vaccine doses (Adjusted Odds Ratio of 8.75; p=0.043). There was no observed association between vaccine responses and age, method of contraception or time from vaccination to antibody measurement. These data suggest that obesity-associated factors interfere with vaccine immunogenicity and possible efficacy.     

Obesity and hypertension: two epidemics or one?

The association between obesity and hypertension is well documented, although the exact nature of this relation remains unclear. Sympathetic nervous and renin-angiotensin-aldosterone system activation appear to play an important role in the sodium and water retention, rightward shift in the pressure-natriuresis, and blood pressure elevation observed in obese individuals. Visceral obesity and the ectopic deposition of adipose tissue may be important in the activation of these systems and in the target organ damage that ensues. Weight loss is critical in the effective management of obesity hypertension and the accompanying target organ damage, although recidivism rates are high. However, prevention of weight gain should be the major priority for combating hypertension and its consequences in the future. The present review will provide an overview of our understanding of the etiology, pathophysiology, and treatment of obesity hypertension. Our focus is on the state of knowledge in humans. The potential role of abdominal obesity is considered throughout our review. We refer to relevant animal literature for supportive evidence and where little or no data in humans are available.     

Genetics of Obesity: What have we Learned?

Candidate gene and genome-wide association studies have led to the discovery of nine loci involved in Mendelian forms of obesity and 58 loci contributing to polygenic obesity. These loci explain a small fraction of the heritability for obesity and many genes remain to be discovered. However, efforts in obesity gene identification greatly modified our understanding of this disorder. In this review, we propose an overlook of major lessons learned from 15 years of research in the field of genetics and obesity. We comment on the existence of the genetic continuum between monogenic and polygenic forms of obesity that pinpoints the role of genes involved in the central regulation of food intake and genetic predisposition to obesity. We explain how the identification of novel obesity predisposing genes has clarified unsuspected biological pathways involved in the control of energy balance that have helped to understand past human history and to explore causality in epidemiology. We provide evidence that obesity predisposing genes interact with the environment and influence the response to treatment relevant to disease prediction.     

Lifelong Obesity in a Polygenic Mouse Model Prevents Age- and Diet-Induced Glucose Intolerance– Obesity Is No Road to Late-Onset Diabetes in Mice

Aims/Hypothesis

Visceral obesity holds a central position in the concept of the metabolic syndrome characterized by glucose intolerance in humans. However, until now it is unclear if obesity by itself is responsible for the development of glucose intolerance.

Methods

We have used a novel polygenic mouse model characterized by genetically fixed obesity (DU6) and addressed age- and high fat diet-dependent glucose tolerance.

Results

Phenotype selection over 146 generations increased body weight by about 2.7-fold in male 12-week DU6 mice (P<0.0001) if compared to unselected controls (Fzt:DU). Absolute epididymal fat mass was particularly responsive to weight selection and increased by more than 5-fold (P<0.0001) in male DU6 mice. At an age of 6 weeks DU6 mice consumed about twice as much food if compared to unselected controls (P<0.001). Absolute food consumption was higher at all time points measured in DU6 mice than in Fzt:DU mice. Between 6 and 12 weeks of age, absolute food intake was reduced by 15% in DU6 mice (P<0.001) but not in Fzt:DU mice. In both mouse lines feeding of the high fat diet elevated body mass if compared to the control diet (P<0.05). In contrast to controls, DU6 mice did not display high fat diet-induced increases of epididymal and renal fat. Control mice progressively developed glucose intolerance with advancing age and even more in response to the high fat diet. In contrast, obese DU6 mice did neither develop a glucose intolerant phenotype with progressive age nor when challenged with a high fat diet.

Conclusions/Interpretation

Our results from a polygenic mouse model demonstrate that genetically pre-determined and life-long obesity is no precondition of glucose intolerance later in life.     

Childhood Obesity: Do Parents Recognize This Health Risk?

Objective: This study examined parents’ understanding of excess weight as a health risk, knowledge of healthy eating habits, and recognition of obesity in their children. Research Methods and Procedures: An anonymous questionnaire was distributed during well‐care visits involving children 4 to 8 years of age at a pediatric faculty practice. Parents indicated their level of concern about excess weight and other familiar health risks using a four‐point Likert scale, answered multiple‐choice questions concerning healthy eating patterns, and communicated their perceptions about their child's weight using a visual analog scale. A parent's perception was considered “accurate” if it deviated from the child's growth chart percentile by <30 points. Results: Of the 83 parents surveyed, 23% (19/83) had overweight children (≥95th percentile of age‐ and gender‐specific BMI growth charts). These parents did not differ from other parents in their level of concern about excess weight as a health risk or in their knowledge of healthy eating patterns, but the two groups of parents did differ in the accuracy of their perceptions about their children's weight. Only 10.5% of parents of overweight children (2/19) perceived their child's weight accurately compared with 59.4% of other parents (38/64; p < 0.001). Parents of overweight children invariably underestimated their children's weight. The median difference between their perception and the growth chart percentile was ?45 points. Discussion: Given that most parents of overweight children fail to recognize that their child has a weight problem, pediatricians should develop strategies to help these parents correct their misperceptions.     

Obesity and post-prandial lipid metabolism. Feast or famine?

Both in Western countries and in third world countries there is an increasing incidence of obesity. Obesity per se or insulin resistance associated with obesity may increase cardiovascular risk factors including dyslipidemia, hypertension and Type 2 diabetes. Over the past decade the understanding has increased of specific mediators in the hypothalamus that are involved in regulating food intake and body weight. In obese humans fasting plasma lipids can be normal but postprandial lipid metabolism is abnormal with an accumulation of triglyceride-rich remnant lipoproteins. In viscerally obese men chylomicron remnant catabolism was markedly decreased when compared with lean individuals. The decreased clearance of chylomicron remnants in viscerally obese subjects may be explained by competition between chylomicron remnants and the increased hepatic production of VLDL for clearance by low density lipoprotein receptors. Increased food intake in rodent models of obesity was shown to be associated with a delay in the catabolism of remnant lipoprotein particles. Prevention of hyperphagia was found to correct the impairment in the metabolism of remnant lipoproteins. Under fasting and food restricted conditions the improvement of remnant metabolism was associated with an increased oxidation of remnant lipids as determined by a novel stable isotope breath test. Anti-obesity and lipid lowering drugs have been used for the treatment of obesity. Inhibitors of cholesterol synthesis inhibitors (statins) have been shown to be effective in treating dyslipidemia. Inhibition of cholesterol synthesis with Atorvastatin was shown to improve chylomicron metabolism by increasing chylomicron remnant catabolism in obese subjects as assessed by the newly developed stable isotope breath test.     

Obesity and melanoma: could fat be fueling malignancy?

Over the last decade, it has become increasingly clear that adipose tissue, and particularly adipocytes, contributes to tumor progression. Obesity, an ever‐increasing worldwide phenomenon, exacerbates this effect. The influence of obesity on melanoma remains poorly studied, although recent data do underline an association between the two diseases in both humans and murine models. Herein, we review the impact of obesity on melanoma incidence and progression and discuss the underlying mechanisms known to be involved. Adipose tissue favors the proliferation and aggressiveness of melanoma cells through a direct dialog, mediated by soluble factors and by exosomes, and through remodeling of the tumor microenvironment. This knowledge could, in the future, help to design new personalized therapeutic options for obese melanoma patients.     

Economics and Obesity: Costing the Problem or Evaluating Solutions?

There is no doubt that obesity is a major public health problem. However, what is the contribution of economics to solving it? In this report, we make the case that the role of economics is not in measuring the economic burden of obesity, through so‐called cost‐of‐illness studies. Such studies merely confirm that obesity is a serious societal issue; adding a monetary figure to this does not add much. The economic foundations of such estimates can also be questioned, thus lessening their policy relevance. The real value of economics in the arena of obesity care is in evaluating, through formal economic evaluation, the use of our scarce health care resources in different strategies to prevent and treat obesity.     

Obesity Impairs γδ T Cell Homeostasis and Antiviral Function in Humans

Obese patients are susceptible to increased morbidity and mortality associated with infectious diseases such as influenza A virus. γδ T cells and memory αβ T cells play key roles in reducing viral load by rapidly producing IFN-γ and lysing infected cells. In this article we analyze the impact of obesity on T lymphocyte antiviral immunity. Obese donors exhibit a reduction in γδ T cells in the peripheral blood. The severity of obesity negatively correlates with the number of γδ T cells. The remaining γδ T cells have a skewed maturation similar to that observed in aged populations. This skewed γδ T cell population exhibits a blunted antiviral IFN-γ response. Full γδ T cell function can be restored by potent stimulation with 1-Hydroxy-2-methyl-buten-4yl 4-diphosphate (HDMAPP), suggesting that γδ T cells retain the ability to produce IFN-γ. Additionally, γδ T cells from obese donors have reduced levels of IL-2Rα. IL-2 is able to restore γδ T cell antiviral cytokine production, which suggests that γδ T cells lack key T cell specific growth factor signals. These studies make the novel finding that the γδ T cell antiviral immune response to influenza is compromised by obesity. This has important implications for the development of therapeutic strategies to improve vaccination and antiviral responses in obese patients.     

Multiple Serotonin Receptors: Opportunities for New Treatments for Obesity?

Recent progress in the molecular pharmacology of 5-HT receptors and the development of selective ligands for various 5-HT receptor subtypes has advanced our understanding of the role of 5-HT mechanisms in the control of food intake and body weight The most intensively investigated 5-HT receptor subtypes have been the 5-HT_1A receptor, the 5-HT_1B receptor andthe5-HT_2C receptor. The overall pattern of results to date suggests that selective 5-HT_2C agonists may be novel anorectic drugs and prove useful in the treatment of obesity. However, a number of issues remain unresolved, particularly regarding potential side-effects, as the 5-HT_2C receptor agonist mCPP has been reported to induce anxiety and nausea in humans, actions that would clearly limit its therapeutic utility. In addition, the possible role of recently cloned 5-HT receptor subtypes such as 5-ht₅,5-ht₆ and 5-ht₇ remains unexplored and the development of selective ligands for these sites has the potential to lead to new treatments for obesity .