Relationship between obesity, inflammation and insulin resistance: new concepts

White adipose tissue is the main site of energy storage, but it is now recognized as an active participant in regulating physiologic and pathologic processes including immunity and inflammation. It has an endocrine function by secreting at least two main hormones, leptin and adiponectin. It can secrete other products, named adipokines, including cytokines and chemokines, involved in inflammation process. The release of adipokines by either adipocytes or adipose tissue infiltrated macrophages lead to a chronic sub-inflammatory state that could play a central role in cardiovascular complications linked to obesity and insulin resistance, a risk factor to develop type-2 diabetes.     

Relationship between insulin and somatotropin in obesity.

The authors have estimated a correlation between the total insulin areas after glucose loading and total somatotropin areas during insulin-induced hypoglycaemia in 30 patients with obesity, as well as in a selected group of 16 patients with simple (essential) obesity. A significant negative correlation was found in both investigated groups. A new hypothesis assuming hyposecretion of somatotropin in obese subjects as a result of hyperinsulinaemia and subsequent increased somatomedin generation is suggested.     

Relationship between host abundance and parasite distribution: inferring regulating mechanisms from census data

1. We studied the effect of host abundance on parasite abundance and prevalence using data on 57 associations of fleas (Siphonaptera) and their mammalian hosts from Slovakia. 2. We assumed that flea-induced host mortality could be inferred from the relationship between flea aggregation and flea abundance, whereas host-induced flea mortality could be inferred from the relationship between flea abundance or aggregation and host abundance. 3. Relationships between flea abundance or prevalence and host abundance were either negative (in 23 flea-host associations) or absent (in 34 flea-host associations). Negative relationships between flea abundance and host abundance were always accompanied by negative relationships between flea prevalence and host abundance. 4. The link between flea abundance/prevalence and host abundance was evaluated as the coefficient of determination of the respective regressions. Across flea-host associations, this link decreased with an increase in the degree of flea aggregation (measured as a parameter b of Taylor's power law). 5. Mean crowding of fleas decreased with an increase of host abundance in eight flea-host associations, being asymptotic in four of them. On the other hand, mean crowding of fleas increased with an increase in flea abundance in 49 flea-host associations, being asymptotic in 15 of them. 6. Results of this study suggest that different flea-host associations are governed by different regulating mechanisms, but different regulation mechanisms may act simultaneously within the same flea-host associations.     

Systematic underestimation of association between serum cholesterol concentration and ischaemic heart disease in observational studies: data from the BUPA study.

OBJECTIVE--To estimate the size of the association between serum concentration of low density lipoprotein cholesterol and mortality from ischaemic heart disease. DESIGN--Prospective study of total serum cholesterol concentration and mortality from ischaemic heart disease in 21,515 men (538 deaths) and study of total cholesterol concentration measured on two occasions an average of three years apart in 5696 men in whom low density lipoprotein cholesterol concentration was also measured on the second occasion. SUBJECTS--Men who attended the medical centre of the British United Provident Association (BUPA) in London between 1975 and 1982. MAIN OUTCOME MEASURE--The difference in mortality from ischaemic heart disease for a 0.6 mmol/l difference in concentration of low density lipoprotein cholesterol after adjustment for, firstly, regression dilution bias, which arises from the random fluctuation of serum cholesterol concentration in people over time, and, secondly, the surrogate dilution effect, which arises because differences in total cholesterol concentration between people reflect smaller differences in low density lipoprotein cholesterol concentration. RESULTS--The observed difference in mortality from ischaemic heart disease associated with a difference of 0.6 mmol/l in total serum cholesterol concentration was 17% but increased to 24% after correction for the regression dilution bias and to 27% (95% confidence interval 21% to 33%) after adjustment for both sources of underestimation, which provides an estimate of the difference in mortality for a true difference of 0.6 mmol/l in low density lipoprotein cholesterol concentration. The association was greater at younger ages. The estimated decrease in mortality from all causes was 6% before and 10% (1% to 17%) after adjustment for the two sources of underestimation. There was no excess mortality from any cause associated with low cholesterol concentration. CONCLUSIONS--The association between serum cholesterol concentration and ischaemic heart disease is materially stronger than directly inferred from prospective studies. This has important implications for the health benefit of achieving low cholesterol concentrations.     

Visceral obesity and the heart

Obesity and particularly its deleterious form, visceral adiposity, has reached a high prevalence in the industrialized world owing to the lack of exercise and the widely available energy-dense diet. As a consequence, cardiovascular diseases and metabolic disorders are afflicting an unprecedented number of individuals at a world-wide scale. Over the last decades, investigations have established firm links between visceral obesity and the development of cardiovascular diseases. Moreover, studies in the field of lipid partitioning have demonstrated that inadequacy of homeostatic mechanism ensuring adequate handling of energy surplus is associated with accumulation of visceral fat and lipid overload of internal organs, which are participating to the development of heart diseases. Visceral obesity and its metabolic consequences often referred to as the metabolic syndrome is associated with the production of an atherosclerosis prone milieu. In this review, clinical implications of visceral obesity on the development of cardiovascular disorders are reviewed along with important mechanisms participating to the development of these disorders. Implications and failure of lipid partitioning and some of the potential pathways mediating development of heart diseases are also covered in view of recent development of therapeutic options.     

The relationship between measures of obesity and incident heart failure: The multi‐ethnic study of atherosclerosis

Objective : To evaluate the strength of association of body mass index (BMI) and waist circumference (WC) with incident heart failure (HF), exploring our associations by ethnicity and age. Design and Methods : 6,809 participants, aged 45‐84 years old, without clinical cardiovascular disease (2000–2002), from the Multi‐Ethnic Study of Atherosclerosis were included. Cox‐Proportional hazards models were used to examine associations of BMI and WC with incident HF. The predictive abilities of BMI and WC were compared using receiver operating characteristic curves. Results : Over a median follow‐up of 7.6 years, there were 176 cases. BMI and WC were associated with incident HF in men (1.33 [1.10‐1.61] and 1.38 [1.18‐1.62], respectively] and women (1.70 [1.33‐2.17] and 1.64 [1.29‐2.08], respectively). These associations became non‐significant after adjusting for obesity‐related conditions (hypertension, dysglycemia, hypercholesterolemia, left ventricular hypertrophy, kidney disease, and inflammation). The associations of BMI and WC did not vary significantly by ethnicity or age‐group, but were inverse in Hispanic men. The area under the curve for BMI and WC was 0.749 and 0.750, respectively, in men and 0.782 and 0.777, respectively, in women. Conclusions : The association between obesity and incident HF is largely mediated by obesity‐related conditions. BMI and WC have similar predictive abilities for incident HF.     

Association between HSV1 seropositivity and obesity: data from the National Health and Nutritional Examination Survey, 2007-2008

Background

Herpes simplex virus (HSV) is among the most common sexually transmitted pathogens in the United States and worldwide. HSV has a high incidence of undetected cases. In addition, there is no treatment, and there is a lack of knowledge why disparities among populations exist. Research studies suggest that fat tissue may participate in body''s immune responses, and the impact of obesity on susceptibility to HSV1 infection is not clear. The purpose of this study was to examine whether obesity is a risk factor for HSV1 infection using a large sample from the general population.

Methods/Principal Findings

This cross-sectional study used data from the National Health and Examination and Nutritional Examination Survey (NHANES) from 2007–2008. Variables, gender, age, race/ethnicity, marital status, education, poverty level, and diabetes represented potential confounders and were included in analyses. The two-tailed Pearson''s chi square, student''s t test, and a multiple logistic regression analysis were applied to evaluate associations using a significance value of p≤0.05. Adjusted odds ratios with 95% confidence interval represented the degree of these associations. The prevalence of HSV1 infection in US population between 20 and 49 years old was 60.3% (n = 1,536). In this study, having a BMI classified as the obese group (BMI 30–39.9) was significantly associated with HSV1 infection before [unadjusted OR = 1.74 (95% CI 1.20–2.51), p = 0.006] and after controlling for socio-demographic factors [adjusted OR = 1.50 (95%CI 1.06–2.13)], p = 0.026]. This association was stronger than three already established risk factors of age, female gender, and poverty level.

Conclusions/Significance

This study provides evidence that obesity may play a role in the susceptibility to HSV1 infection. Findings from this study suggest that obesity should be considered when designing preventive measures for HSV1 infection. These results may also explain why some people acquire HSV1 infections and some do not. Further, these findings may justify an increased emphasis on the control and prevention of HSV1 transmission and other pathogens in overweight and obese populations.     

The association between household socioeconomic position and prevalent tuberculosis in Zambia: a case-control study

Background

Although historically tuberculosis (TB) has been associated with poverty, few analytical studies from developing countries have tried to: 1. assess the relative impact of poverty on TB after the emergence of HIV; 2. explore the causal mechanism underlying this association; and 3. estimate how many cases of TB could be prevented by improving household socioeconomic position (SEP).

Methods and Findings

We undertook a case-control study nested within a population-based TB and HIV prevalence survey conducted in 2005–2006 in two Zambian communities. Cases were defined as persons (15+ years of age) culture positive for M. tuberculosis. Controls were randomly drawn from the TB-free participants enrolled in the prevalence survey. We developed a composite index of household SEP combining variables accounting for four different domains of household SEP. The analysis of the mediation pathway between household SEP and TB was driven by a pre-defined conceptual framework. Adjusted Population Attributable Fractions (aPAF) were estimated.Prevalent TB was significantly associated with lower household SEP [aOR = 6.2, 95%CI: 2.0–19.2 and aOR = 3.4, 95%CI: 1.8–7.6 respectively for low and medium household SEP compared to high]. Other risk factors for prevalent TB included having a diet poor in proteins [aOR = 3.1, 95%CI: 1.1–8.7], being HIV positive [aOR = 3.1, 95%CI: 1.7–5.8], not BCG vaccinated [aOR = 7.7, 95%CI: 2.8–20.8], and having a history of migration [aOR = 5.2, 95%CI: 2.7–10.2]. These associations were not confounded by household SEP. The association between household SEP and TB appeared to be mediated by inadequate consumption of protein food. Approximately the same proportion of cases could be attributed to this variable and HIV infection (aPAF = 42% and 36%, respectively).

Conclusions

While the fight against HIV remains central for TB control, interventions addressing low household SEP and, especially food availability, may contribute to strengthen our control efforts.     

Relationship between algae and environment: an Early Cretaceous case study, Trascău Mountains, Romania

The relationship between algae and depositional environment was studied in a limestone succession of Berriasian–Valanginian age. Several depositional environments were recorded from shallow subtidal to intertidal and supratidal, with salinity ranging from normal marine to fresh and/or supersaline water. The algal assemblages consist mainly of dasycladaleans, rivulariacean-type cyanobacteria and charophytes. Nipponophycus (Bryopsydales) and Lithocodium-Bacinella (microproblematicum), occur at some levels. Dasycladaleans are associated with subtidal, sometimes restricted (“lagoonal”) environments, while rivulariacean-like cyanobacteria and charophytes characterise intertidal-supratidal and fresh and/or supersaline environments, respectively. Among the dasycladaleans, Salpingoporella annulata is often related to restricted environments where it forms monospecific assemblages. Large dasycladaleans, such as Selliporella neocomiensis, Macroporella praturloni and Pseudocymopolia jurassica are found in subtidal high-energy deposits (bioclastic grainstones). The relationship between environment and algae, characteristic for each depositional unit, can be used to interpret the relative sea-level variations.     

Adult obesity: Panel study from native Amazonians

This paper examines three morphological indicators measuring obesity among a native Amazonian population of foragers-farmers in Bolivia (Tsimane’) and estimates the associations between them and standard covariates of obesity (e.g., socioeconomic status [SES]). We collected annual data from 350 non-pregnant women and 385 men ≥20 years of age from all 311 households in 13 villages during five consecutive years (2002–2006). We used three indicators to measure obesity: body-mass index (BMI), waist circumference (WC), and body fat using bioelectrical impedance analysis (BF-BIA). We ran separate individual random-effect panel multiple regressions for women and men with wealth, acculturation, health, and household food availability as key covariates, and controlled for village and year fixed effects and village × year interaction effects. Although BMI increases by a statistically significant annual growth rate of 0.64% among women and 0.37% among men over the five years, the increase does not yield significant biological meanings. Neither do we find consistent and biologically meaningful covariates associated with adult obesity.     

森林城市景观格局与热环境的关系——以龙泉市为例

景观格局分异特征在相当程度上影响着城市热环境.本研究以国家森林城市龙泉市为对象,通过地温反演和空间分析反映9类景观温度特征,运用景观格局分析方法从1～3.5 km 6个尺度探索格局指数与热环境的相关性.结果表明: 龙泉市高温区及次高温区主要分布于东北至西南一带,以城乡居民地为主,低温区和次低温区主要分布于西北、东南区域,以公益林为主;对海拔700 m以下区域各景观类型地表温度的统计发现,针叶林地、阔叶林地、针阔混交林地、竹林地、水域的地温均值相对较低,灌木林地、其他林地、耕地、建设用地的地温均值相对较高;对景观格局与热环境的分析发现,类型水平格局指数较景观水平格局指数更具实际意义,建设用地与热环境的相关系数可达0.835,针叶林地、阔叶林地、针阔混交林地、水域次之,在-0.5～-0.4,不同林地类型的降温效果在空间尺度上的表达不同,阔叶林地、针阔混交林地更利于在大尺度上降温;林地的面积和蓄积量越大,越易出现地表温度低值.     

Gender, obesity and repeated elevation of C-reactive protein: data from the CARDIA cohort

C-reactive Protein (CRP) measurements above 10 mg/L have been conventionally treated as acute inflammation and excluded from epidemiologic studies of chronic inflammation. However, recent evidence suggest that such CRP elevations can be seen even with chronic inflammation. The authors assessed 3,300 participants in The Coronary Artery Risk Development in Young Adults study, who had two or more CRP measurements between 1992/3 and 2005/6 to a) investigate characteristics associated with repeated CRP elevation above 10 mg/L; b) identify subgroups at high risk of repeated elevation; and c) investigate the effect of different CRP thresholds on the probability of an elevation being one-time rather than repeated. 225 participants (6.8%) had one-time and 103 (3.1%) had repeated CRP elevation above 10 mg/L. Repeated elevation was associated with obesity, female gender, low income, and sex hormone use. The probability of an elevation above 10 mg/L being one-time rather than repeated was lowest (51%) in women with body mass index above 31 kg/m(2), compared to 82% in others. These findings suggest that CRP elevations above 10 mg/L in obese women are likely to be from chronic rather than acute inflammation, and that CRP thresholds above 10 mg/L may be warranted to distinguish acute from chronic inflammation in obese women.     

Apelin 在心血管疾病中的研究进展

Apelin是APJ(angiotensin II protein J)的一个配体,是一种重要的生理调节肽。Apelin-APJ系统在心血管系统存在广泛的作用,参与高血压、冠心病、心力衰竭及心房纤颤等多种疾病的病理生理过程,本文就apelin的生物学特性及与多种心血管疾病的关系作一综述。     

The genetics of obesity in Mexican Americans: the evidence from genome scanning efforts in the San Antonio family heart study

Recent estimates indicate that approximately 18% of the population in the United States can be considered obese (defined as a body mass index [BMI] > or = 30), and this rate is even higher among ethnic populations such as Mexican Americans. This figure becomes very significant given the strong evidence for obesity as a major risk factor for a variety of chronic diseases including type 2 diabetes mellitus and coronary heart disease. The search for genes involved in the expression of obesity has been one of the focal points of the San Antonio Family Heart Study (SAFHS), a large, family-based study to examine the genetics of risk for atherosclerosis in Mexican Americans. To date, our genome scanning effort has reported two quantitative trait loci (QTLs) with pronounced effects on the expression of a variety of obesity--related phenotypes (e.g., leptin levels, fat mass, and BMI) located on chromosomes 2 and 8. We are currently working to further refine these signals and to identify the genes and allelic variants involved. Here, we summarize the latest results from our ongoing efforts to identify obesity genes in the San Antonio Family Heart Study.     

Relationship between oxidative stress and mitochondrial function in the post-conditioned heart

The pathways activated by post-conditioning may converge on the mitochondria, in particular on the mitochondrial permeability transition pore. We sought to characterize the inhibition status of the mitochondrial permeability transition early after the post-conditioning maneuver and before long reperfusion was established. We observed that post-conditioning maneuvers applied to isolated rat hearts, after a prolonged ischemia and before reperfusion, promoted cardiac mechanical function recovery and maintained mitochondrial integrity. These effects were evaluated by mitochondrial swelling, calcium transport, and NAD⁺ content measurements; the improvements were established before restoring a long lasting reperfusion period. Mitochondrial integrity was associated with a diminution in oxidative stress, since carbonylation of proteins was prevented and aconitase activity was preserved in the post-conditioned hearts, implying that ROS might mediate mitochondrial dysfunction and mPTP opening. In addition, we found that cytochrome release was significantly abolished in the post-conditioned heart, in contrast with conventionally reperfused hearts.