Abdominal adipose tissue cytokine gene expression: relationship to obesity and metabolic risk factors

Relationship between CT anthropometric measurements, adipokines and abdominal aortic calcification

BACKGROUND

Visceral obesity and aortic calcification are both associated with cardiovascular events. The purpose of this study was to examine if visceral obesity was associated with the severity of abdominal aortic calcification.

METHODS

One hundred and forty eight patients with peripheral artery disease were assessed by CT angiography. The severity of infrarenal abdominal aortic calcification was measured using a validated technique. The size of the visceral and subcutaneous compartments was estimated from anthropometric measurements made from the same CT. Calcification and anthropometric measurements were compared with Spearman's correlation and multiple logistic regression (adjusting for age, gender, hypertension, diabetes, smoking and cholesterol).

RESULTS

The relative size of the visceral compartment estimated from CT diameter ratios was correlated with abdominal aortic calcification severity, r=0.27, p=0.001 and independently associated with calcification allowing for other cardiovascular risk factors (OR 6.63, 95% CI 1.90-23.14). The relative size of the visceral compartment was associated with serum osteoprotegerin levels, suggesting a possible mechanism underlying the detrimental influence of visceral adiposity.

CONCLUSION

The association of visceral adiposity and arterial calcification suggests one mechanism, which may contribute to the detrimental effects of central obesity.

The effect of dietary carbohydrate on genes for fatty acid synthase and inflammatory cytokines in adipose tissues from lean and obese subjects

BACKGROUND

Hepatic de novo lipogenesis (DNL) is markedly stimulated in humans by low-fat diets enriched in simple sugars. However, the dietary responsiveness of the key enzyme controlling DNL in human adipose tissue, fatty acid synthase (FAS), is uncertain.

HYPOTHESIS

Adipose tissue mRNA for FAS is increased in lean and obese subjects when hepatic DNL is elevated by a eucaloric, low-fat, high-sugar diet.

DESIGN

Twelve lean and seven obese volunteers were given two eucaloric diets (10% vs. 30% fat; 75% vs. 55% carbohydrate; sugar/starch 60/40) each for 2 weeks by a random-order cross-over design. FAS mRNA in abdominal and gluteal adipose tissues was compared to hepatic DNL measured in serum by isotopic and nonisotopic methods. Adipose tissue mRNA for tumor necrosis factor-alpha and IL-6, which are inflammatory cytokines that modulate DNL, was also assayed.

RESULTS

The low-fat high-sugar diet induced a 4-fold increase in maximum hepatic DNL (P<.001) but only a 1.3-fold increase in adipose tissue FAS mRNA (P=.029) and no change in cytokine mRNA. There was a borderline significant positive correlation between changes in FAS mRNA and hepatic DNL (P=.039). Compared to lean subjects, obese subjects had lower levels of FAS mRNA and higher levels of cytokine mRNA (P<.001).

CONCLUSIONS

The results suggest that key elements of human adipose tissue DNL are less responsive to dietary carbohydrate than is hepatic DNL and may be regulated by diet-independent factors. Irrespective of diet, there is reduced expression of the FAS gene and increased expression of cytokine genes in adipose tissues of obese subjects.

Subcutaneous and omental fat expression of adiponectin and leptin in women with polycystic ovary syndrome

OBJECTIVE

To assess message expression of adiponectin and leptin in visceral and SC fat in women with polycystic ovary syndrome (PCOS) and in control women.

DESIGN

Prospective clinical trial.

SETTING

Academic medical centers in Mexico City, Mexico and New York, New York.

PATIENT(S)

Women with PCOS and control women.

INTERVENTION(S)

Surgical biopsies of visceral (omental) and subcutaneous (SC) adipose tissue, fasting blood samples, and ultrasound measurements of visceral and SC fat.

MAIN OUTCOME MEASURE(S)

Messenger RNA assessment of adiponectin and leptin in adipose tissue samples; serum measurements of adiponectin, leptin, glucose, insulin, and hormone levels; measurements of fat quantity by ultrasound. Correlative analyses as well as comparisons between women with PCOS and control women were performed.

RESULT(S)

Confirming previous data, women with PCOS had more insulin resistance, similar serum leptin, but lower serum adiponectin compared with control women. When control women were divided into quartiles by body mass index (BMI), messenger RNA expression of leptin and adiponectin decreased with increasing BMI. Adiponectin and leptin expression was significantly lower in women with PCOS; in weight-matched patients and control women, leptin and adiponectin expression was statistically significantly lower in SC tissue, and adiponectin expression was statistically significantly lower in omental tissue in women with PCOS. In control women, there was greater expression in SC tissue compared with in visceral tissue. There were significant negative correlations between visceral and SC fat mass by both ultrasound as well as adiponectin and leptin expression in women with PCOS. Serum adiponectin correlated statistically significantly with visceral adiponectin expression (r = 0.64) in women with PCOS, and there was a statistically significant correlation between SC adiponectin expression and the Quantitative Insulin-Sensitivity Check Index as a marker of insulin resistance (r = 0.43).

CONCLUSION(S)

Adipocytokine expression in fat tissue appears to be down-regulated by an increased fat mass; this is particularly evident in the case of adiponectin expression in women with PCOS. It is probable that insulin resistance is a factor that may contribute, in part, to these findings.

The role of periadventitial fat in atherosclerosis

CONTEXT

It has become increasingly evident that adipose tissue is a multifunctional organ that produces and secretes multiple paracrine and endocrine factors. Research into obesity, insulin resistance, and diabetes has identified a proinflammatory state associated with obesity. Substantial differences between subcutaneous and omental fat have been noted, including the fact that omental fat produces relatively more inflammatory cytokines. Periadventitial fat, as a specific adipose tissue subset, has been overlooked in the field of atherosclerosis despite its potential diagnostic and therapeutic implications.

OBJECTIVE

To review (1) evidence for the role of adventitial and periadventitial fat in vessel remodeling after injury, (2) the relationship between adventitial inflammation and atherosclerosis, (3) the association between periadventitial fat and plaque inflammation, and (4) the diagnostic and therapeutic implications of these roles and relationships for the progression of atherosclerosis.

DATA SOURCES

We present new data showing greater uptake of iron, administered in the form of superparamagnetic iron oxide, in the periadventitial fat of atherosclerotic mice than in control mice. In addition, macrophage density in the periadventitial fat of lipid-rich plaques is increased compared with fibrocalcific plaques.

CONCLUSIONS

There is a striking paucity of data on the relationship between the periadventitial fat of coronary arteries and atherosclerosis. Greater insight into this relationship might be instrumental in making strides into the pathophysiology, diagnosis, and treatment of coronary artery disease.

Biomarkers of obesity and subsequent cardiovascular events

Obesity is a major risk factor for cardiovascular diseases, but the mechanisms for increased cardiovascular risk in obesity are still unclear. Inflammation and increased oxidative stress are two potential mechanisms proposed to play a major role in the morbidity associated with obesity. Studies that investigate these mechanisms rely on biomarkers, but validated biomarkers for obesity-related cardiovascular outcomes are lacking. By finding optimal biomarkers, diagnostic criteria for cardiovascular diseases can be refined in the obese beyond "traditional" risk factors to identify early pathologic processes. The objective of this review is to identify potential early biomarkers resulting from obesity and associated with cardiovascular disease. Studies were initially identified through the search engine PubMed by using the keywords "obesity" and "biomarker." Subsequently, combinations of the keywords "obesity," "biomarker," "cardiovascular risk," "adipose tissue," "adipokine," "adipocytokine," and "oxidative stress" were used. The SOURCE database and Online Mendelian Inheritance in Man (OMIM) were used to obtain more information on the biomarkers. Results of the searches yielded a large number of potential biomarkers that occur in obesity and which either correlate with traditional cardiovascular risk factors or predict subsequent cardiovascular events. Several biomarkers are promising regarding their biologic properties, but they require further validation in humans.

Interleukin-6, C-reactive protein and biochemical parameters during prolonged intermittent fasting

BACKGROUND

It is well known that nutritional habits, sleeping patterns and meal frequency have profound effects on maintaining human health. Ramadan is a religious month for Islam, during which Muslims do not eat and drink during the daylight hours. The duration of restricted food and beverage intake is approximately 12 h/day for 1 month, which makes Ramadan a model of prolonged intermittent fasting.

METHODS

In order to evaluate the effects of long-lasting modifications of food intake on inflammatory markers and biochemical parameters 40 healthy volunteers of normal weight [20 females aged between 20 and 38 years, 20 males aged between 23 and 39 years, body mass index (BMI) <25 kg/m(2)] who fasted during Ramadan and another 28 healthy age- and BMI-matched volunteers (14 males, 14 females) who did not fast participated in the study. Venous blood samples were taken 1 week before Ramadan, during the last week of Ramadan and 3 weeks after Ramadan. Serum interleukin-6 (IL-6), C-reactive protein (CRP), homocysteine, vitamin B(12), folate, total cholesterol (TC), triglycerides, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) levels were measured.

RESULTS

No significant changes were observed in serum total cholesterol, triglycerides and LDL levels. TC/HDL ratio (HDL risk factor) was decreased during and after Ramadan in both genders in the fasting group while there were no changes in the nonfasting group. IL-6 (p < 0.001), CRP (p < 0.001) and homocysteine (p < 0.01) levels were significantly low during Ramadan in the fasting subjects of both genders when compared to basal values (1 week before Ramadan).

CONCLUSION

Our results demonstrate that prolonged intermittent fasting in a model like Ramadan has some positive effects on the inflammatory status of the body and on the risk factors for cardiovascular diseases such as homocysteine, CRP and TC/HDL ratio.

Adiponectin gene expression and adipocyte NF-kappaB transcriptional activity in elderly overweight and obese women: inter-relationships with fat distribution, hs-CRP, leptin and insulin resistance

OBJECTIVE

The regulatory processes that modulate adiponectin production and the mechanisms involved in nuclear factor kB (NF-kB) transcriptional activity in human adipocytes are not yet fully known. The aim of our study was to evaluate the inter-relationships between body fat, fat distribution, systemic inflammation, insulin resistance, leptin and the serum and subcutaneous adipose tissue gene expression levels of tumor necrosis factor-alpha (TNF-alpha), adiponectin and the inhibitor kappa B-alpha (IkB-alpha), in subjects with a wide range of body mass index (BMI). We also wanted to determine which of these variables was most closely related to adiponectin gene expression and adipocyte NF-kB transcriptional power.

METHODS

A total of 27 women aged between 50 and 80 years, with BMI ranging from 22.1 to 53.3 kg/m(2), were studied. In all subjects BMI, waist circumference, body composition by dual X-ray absorptometry, triglycerides, cholesterol, high-density lipoprotein cholesterol (HDL-Ch), glucose, insulin, homeostasis model assessment of insulin resistance (HOMA), high-sensitive C-reactive protein (hs-CRP), serum adiponectin, leptin and TNF-alpha were evaluated. Subcutaneous adipose tissue biopsies were taken from the abdomen of all subjects and the mRNA levels of adiponectin, TNF-alpha and IkB-alpha were determined.

RESULTS

BMI and waist circumference were associated positively with leptin, HOMA, and hs-CRP, and negatively with HDL-Ch; waist was also associated with adiponectin and IkB-alpha mRNA. HOMA was negatively associated with serum adiponectin and adiponectin mRNA. Hs-CRP was negatively associated with IkB-alpha mRNA, and was positively associated with HOMA. Step-down multiple regression analysis was performed to determine the joint effects of BMI, waist circumference, triglycerides, HDL-Ch, HOMA, hs-CRP, leptin, serum and TNF-alpha mRNA on adiponectin gene expression: waist circumference and leptin were both included in the best fitting regression equation for predicting adiponectin gene expression (R(2)=0.403, P=0.006). Stepwise multiple regression analysis was performed, considering IkB-alpha mRNA as a dependent variable and BMI, waist, HDL-Ch, HOMA, hs-CRP and adiponectin mRNA as independent variables. Adiponectin mRNA was the only variable to enter the regression (R(2)=0.406, P<0.001).

CONCLUSION

Our results suggest that abdominal adiposity and leptin are independent predictors of adiponectin gene expression and that in human adipocytes, adiponectin gene expression is strongly related to IkB-alpha mRNA.

Distribuição centrípeta da gordura corporal, sobrepeso e aptidão cardiorrespiratória: associação com sensibilidade insulínica e alterações metabólicas

O objetivo do presente estudo foi investigar associações entre a distribuição centrípeta da gordura corporal e lipídios-lipoproteínas séricos, pressão arterial e índice Homa-IR de resistência insulínica, mediante ajuste estatístico de indicadores quanto ao sobrepeso e à aptidão cardiorrespiratória. Foram analisados 89 voluntários (44 homens e 45 mulheres). A distribuição centrípeta da gordura foi analisada através de circunferência da cintura (CC) e o sobrepeso pelo índice de massa corporal (IMC). A aptidão cardiorrespiratória foi acompanhada pelo VO2máx estimado por teste de caminhada. Após ajuste pelos valores de IMC verificamos coeficientes de correlação significativos entre CC e níveis de pressão arterial e ApoB em homens, e entre CC e índice Homa-IR e triglicerídios em mulheres. Após ajuste pelos valores de VO2máx observamos correlações significativas entre CC e ApoB e índice Homa-IR em homens, e entre CC e índice Homa-IR em mulheres. Conclui-se que, dependendo do sexo, a quantidade e a distribuição da gordura corporal podem apresentar ações distintas na resistência insulínica e nas disfunções associadas. A aptidão cardiorrespiratória per se parece não contribuir na minimização da associação entre a distribuição centrípeta da gordura e o índice Homa-IR; porém, apresenta considerável impacto na associação entre a distribuição centrípeta da gordura e o metabolismo lipídico e os níveis de pressão arterial, sobretudo nos homens.

Effect of calorie restriction with or without exercise on insulin sensitivity, beta-cell function, fat cell size, and ectopic lipid in overweight subjects

OBJECTIVE

The purpose of this article was to determine the relationships among total body fat, visceral adipose tissue (VAT), fat cell size (FCS), ectopic fat deposition in liver (intrahepatic lipid [IHL]) and muscle (intramyocellular lipid [IMCL]), and insulin sensitivity index (S(i)) in healthy overweight, glucose-tolerant subjects and the effects of calorie restriction by diet alone or in conjunction with exercise on these variables.

RESEARCH DESIGN AND METHODS

Forty-eight overweight volunteers were randomly assigned to four groups: control (100% of energy requirements), 25% calorie restriction (CR), 12.5% calorie restriction +12.5% energy expenditure through structured exercise (CREX), or 15% weight loss by a low-calorie diet followed by weight maintenance for 6 months (LCD). Weight, percent body fat, VAT, IMCL, IHL, FCS, and S(i) were assessed at baseline and month 6.

RESULTS

At baseline, FCS was related to VAT and IHL (P < 0.05) but not to IMCL. FCS was also the strongest determinant of S(i) (P < 0.01). Weight loss at month 6 was 1 +/- 1% (control, mean +/- SE), 10 +/- 1% (CR), 10 +/- 1% (CREX), and 14 +/- 1% (LCD). VAT, FCS, percent body fat, and IHL were reduced in the three intervention groups (P < 0.01), but IMCL was unchanged. S(i) was increased at month 6 (P = 0.05) in the CREX (37 +/- 18%) and LCD (70 +/- 34%) groups (P < 0.05) and tended to increase in the CR group (40 +/- 20%, P = 0.08). Together the improvements in S(i) were related to loss in weight, fat mass, and VAT, but not IHL, IMCL, or FCS.

CONCLUSIONS

Large adipocytes lead to lipid deposition in visceral and hepatic tissues, promoting insulin resistance. Calorie restriction by diet alone or with exercise reverses this trend.

Therapy Insight: managing cardiovascular risk in patients with rheumatoid arthritis

Chronic low-grade inflammation was recognized during the past decade as an important risk factor for the development of atherosclerosis and, more recently, for the development of heart failure. Patients with rheumatoid arthritis (RA) are at increased risk of morbidity and mortality from ischemic cardiovascular events and heart failure. Epidemiologic and clinical studies indicate that RA is an independent risk factor for cardiovascular disease, which suggests that chronic exposure to high levels of inflammatory mediators contributes to this enhanced risk. The relative contribution of conventional risk factors to the acceleration of cardiovascular disease does not seem to be increased in patients with RA compared with control populations. Nonetheless, some preclinical laboratory measures of risk factors (e.g. insulin sensitivity) are adversely modulated in the context of the highly inflammatory rheumatoid microenvironment. Discerning the net effect of RA therapies on cardiovascular disease is also challenging because, theoretically, their biologic effects could either promote or attenuate atherosclerosis and ventricular dysfunction; however, available data suggest a beneficial effect on cardiovascular morbidity and mortality in patients with RA. This review provides an overview of the potential influence of RA and its treatment on the development and progression of cardiovascular disease, and outlines some preliminary recommendations for prevention and management of this complication in patients with RA.

Effects of etanercept in patients with the metabolic syndrome

BACKGROUND

Adipose-derived cytokines, including tumor necrosis factor alpha, may contribute to the inflammation that occurs in the metabolic syndrome. We investigated the effects of inhibition of tumor necrosis factor alpha with etanercept in patients with the metabolic syndrome.

METHODS

Fifty-six subjects with the metabolic syndrome were randomized to administration of either etanercept or identical placebo, 50 mg subcutaneously once a week for 4 weeks. The C-reactive protein level was the primary end point. Effects on other inflammatory markers (including fibrinogen, interleukin 6, and adiponectin), insulin sensitivity, lipid levels, and body composition were also determined.

RESULTS

Baseline characteristics were similar between the groups. Two subjects dropped out of each group, and etanercept was well tolerated throughout the study. The C-reactive protein levels decreased significantly in the treated compared with the placebo group (-2.4 +/- 0.4 vs 0.5 +/- 0.7 mg/L; P<.001). Adiponectin levels rose significantly in the etanercept group compared with the placebo group (0.8 +/- 0.4 vs -0.3 +/- 0.3 microg/mL; P = .03). Fibrinogen levels decreased (-68 +/- 16 vs -2 +/- 31 mg/dL [-2.0 +/- 0.47 vs -0.06 +/- 0.91 micromol/L]; P = .04) and interleukin 6 levels tended to decrease (-1.2 +/- 0.8 vs 0.5 +/- 0.5 ng/L; P = .07) in the etanercept-treated subjects compared with placebo, respectively. No changes occurred in body composition parameters or insulin sensitivity, but high-density lipoprotein levels tended to decrease in the etanercept group (-1 +/- 1 vs 2 +/- 1 mg/dL [-0.03 +/- 0.03 vs 0.05 +/- 0.03 mmol/L]; P = .06) compared with the placebo group.

CONCLUSIONS

Etanercept reduces C-reactive protein levels and tends to improve other inflammatory cardiovascular risk indexes in patients with the metabolic syndrome. Etanercept may interrupt the inflammatory cascade that occurs with abdominal obesity. Further, longer-term studies are needed to determine the effects of tumor necrosis factor alpha inhibition on cardiovascular disease in patients with the metabolic syndrome.

MCH-/- mice are resistant to aging-associated increases in body weight and insulin resistance

Ablation of the hypothalamic peptide, melanin-concentrating hormone (MCH), leads to a lean phenotype and resistance to diet-induced obesity. Observation of MCH(-/-) mice at older ages suggested that these effects persist in mice >1 year old. Leanness secondary to caloric restriction is known to be associated with improved glucose tolerance as well as an overall increase in life span. Because the MCH(-/-) model represents leanness secondary to increased energy expenditure rather than caloric restriction, we were interested in determining whether this model of leanness would be associated with beneficial metabolic effects at older ages. To assess the effects of MCH ablation over a more prolonged period, we monitored male and female MCH(-/-) mice up to 19 months. The lean phenotype of MCH(-/-) mice persisted over the duration of the study. At 19 months, MCH(-/-) male and female mice weighed 23.4 and 30.8% less than their wild-type counterparts, a result of reduced fat mass in MCH(-/-) mice. Aged MCH(-/-) mice exhibited better glucose tolerance and were more insulin sensitive compared with wild-type controls. Aging-associated decreases in locomotor activity were also attenuated in MCH(-/-) mice. We also evaluated two molecules implicated in the pathophysiology of aging, p53 and silent inflammatory regulator 2 (Sir2). We found that expression of the tumor suppressor protein p53 was higher in MCH(-/-) mice at 9 and 19 months of age. In contrast, expression of Sir2 was unchanged. In aggregate, these findings suggest that MCH ablation improves the long-term outcome for several indicators of the aging process.

Social relationships, sleep quality, and interleukin-6 in aging women

This study examined the interplay of social engagement, sleep quality, and plasma levels of interleukin-6 (IL-6) in a sample of aging women (n = 74, aged 61-90, M age = 73.4). Social engagement was assessed by questionnaire, sleep was assessed by using the NightCap in-home sleep monitoring system and the Pittsburgh Sleep Quality Index, and blood samples were obtained for analysis of plasma levels of IL-6. Regarding subjective assessment, poorer sleep (higher scores on the Pittsburgh Sleep Quality Index) was associated with lower positive social relations scores. Multivariate regression analyses showed that lower levels of plasma IL-6 were predicted by greater sleep efficiency (P < 0.001), measured objectively and by more positive social relations (P < 0.05). A significant interaction showed that women with the highest IL-6 levels were those with both poor sleep efficiency and poor social relations (P < 0.05). However, those with low sleep efficiency but compensating good relationships as well as women with poor relationships but compensating high sleep efficiency had IL-6 levels comparable to those with the protective influences of both good social ties and good sleep.

Pharmacogenomics and cardiovascular drugs: need for integrated biological system with phenotypes and proteomic markers

Personalized medicine is based on a better knowledge of biological variability, considering the important part due to genetics. When trying to identify involved genes and their products in differential cardiovascular drug responses, a five-step strategy is to be followed: 1) Pharmacokinetic-related genes and phenotypes (2) Pharmacodynamic targets, genes and products (3) Cardiovascular diseases and risks depending on specific or large metabolic cycles (4) Physiological variations of previously identified genes and proteins (5) Environment influences on them. After summarizing the most well-known genes involved in drug metabolism, we will take as example of drugs, the statins, considered as very important drugs from a Public-Health standpoint, but also for economical reasons. These drugs respond differently in human depending on multiple polymorphisms. We will give examples with common ApoE polymorphisms influencing the hypolipemic effects of statins. These drugs also have pleiotropic effects and decrease inflammatory markers. This illustrates the need to separate clinical diseases phenotypes in specific metabolic pathways, which could propose other classifications, of diseases and related genes. Hypertension is also a good example of clinical phenotype which should be followed after various therapeutic approaches by genes polymorphisms and proteins markers. Gene products are under clear environmental expression variations such as age, body mass index and obesity, alcohol, tobacco and dietary interventions which are the first therapeutical actions taken in cardiovascular diseases. But at each of the five steps, within a pharmacoproteomic strategy, we also need to use available information from peptides, proteins and metabolites, which usually are the gene products. A profiling approach, i.e., dealing with genomics, but now also with proteomics, is to be used. In conclusion, the profiling, as well as the large amount of data, will more than before render necessary an organized interpretation of DNA, RNA as well as proteins variations, both at individual and population level.