Adiponectin: action, regulation and association to insulin sensitivity

Inhibitors of cannabinoid receptors and glucose metabolism

PURPOSE OF REVIEW

Abdominal obesity is closely related to type 2 diabetes and overactivity of the endocannabinoid system. The present review aims at evaluating the role of endocannabinoid system in glucose dysregulation and the effects of cannabinoid 1 receptor blockade on glucose metabolism in both animal models and overweight/obese humans, especially with type 2 diabetes.

RECENT FINDINGS

Cannabinoid 1 receptors have been identified not only in the brain, but also in the adipose tissue, the gut, the liver, the skeletal muscle and even the pancreas, all organs playing a key role in glucose metabolism and type 2 diabetes. Rimonabant, the first selective cannabinoid 1 receptor blocker in clinical use, has been shown to reduce body weight, waist circumference, glycated haemoglobin, triglycerides, insulin resistance index, and to increase HDL cholesterol and adiponectin concentrations in patients with type 2 diabetes, confirming data on nondiabetic overweight/obese patients. Almost half of the metabolic changes, including glycated haemoglobin reduction, could not be explained by weight loss, in agreement with direct peripheral effects.

SUMMARY

Cannabinoid 1 blockade reduces food intake and body weight and improves metabolic regulation beyond just weight loss. Because of its positive effect on glucose metabolism, rimonabant deserves consideration in the treatment of overweight/obese patients with type 2 diabetes.

Epidermal growth factor and parathyroid hormone-related peptide mRNA in the mammary gland and their concentrations in milk: effects of postpartum hypoxia in lactating rats

The physiological adaptations of the neonatal rat to hypoxia from birth include changes in gastrointestinal function and intermediary metabolism. We hypothesized that the hypoxic lactating dam would exhibit alterations in mammary gland function leading to changes in the concentration of milk peptides that are important in neonatal gastrointestinal development. The present study assessed the effects of chronic hypoxia on peptides produced by the mammary glands and present in milk. Chronic hypoxia decreased the concentration of epidermal growth factor (EGF) in expressed milk and pup stomach contents and decreased maternal mammary gland EGF mRNA. The concentration of parathyroid hormone-related protein (PTHrp) was unchanged in milk and decreased in pup stomach contents; however, mammary PTHLH mRNA was increased by hypoxia. There was a significant increase in adiponectin concentrations in milk from hypoxic dams. Chronic hypoxia decreased maternal body weight, and pair feeding normoxic dams an amount of food equivalent to hypoxic dam food intake decreased body weight to an equivalent degree. Decreased food intake did not affect the expression of EGF, PTHLH, or LEP mRNA in mammary tissue. The results indicated that chronic hypoxia modulated mammary function independently of hypoxia-induced decreases in maternal food intake. Decreased EGF and increased adiponectin concentrations in milk from hypoxic dams likely affect the development of neonatal intestinal function.

Effects of soy protein and isoflavones on insulin resistance and adiponectin in male monkeys

Isoflavones may influence insulin action by means of their well-known receptor-mediated estrogenic activity. However, isoflavones also bind to peroxisome proliferator-activated receptors (PPARs) that are strongly associated with insulin action. Soy protein with its isoflavones has previously been shown to improve glycemic control in diabetic postmenopausal women and to improve insulin sensitivity in ovariectomized monkeys. The purpose of the current report was to extend our studies of dietary soy protein to male monkeys and determine effects of the soy isoflavones on insulin resistance. Two studies are reported here. Study one involved 91 male monkeys consuming 3 diets differing only by the source of protein (casein-lactalbumin, soy protein with a low isoflavone concentration, or soy protein with a high isoflavone concentration). Intravenous glucose tolerance tests were done, and plasma adiponectin and lipoprotein concentrations were determined after 25 months of study. Samples of visceral fat were obtained at 31 months for assessment of adiponectin and PPARgamma expression. The second study involved 8 monkeys in a Latin-square design that compared the effects of diets with casein/lactalbumin, soy protein with a high isoflavone concentration, or soy protein that was alcohol-washed to deplete the isoflavones. After 8 weeks of treatment, insulin sensitivity and plasma lipoproteins were assessed. At 10 weeks, a biopsy of the skeletal muscle was performed for determination of insulin receptor, PPARalpha, and PPARgamma content. The major findings were that consumption of isoflavone-containing soy protein dose-dependently increased insulin responses to the glucose challenge and decreased plasma adiponectin, whereas isoflavone-depleted soy protein decreased body weight and had no effect on plasma adiponectin concentrations. Muscle PPARalpha and gamma expression was also increased with the isoflavone-depleted soy relative to either casein or soy protein containing the isoflavones. Further studies are needed to determine the mechanisms involved in these effects of a high-soy isoflavone diet and to optimize dietary isoflavone content for maximal health benefits in male subjects.

Insulin, adiponectin, IGFBP-1 levels and body composition in small for gestational age born non-obese children during prepubertal ages

BACKGROUND

Being small for gestational age (SGA) at birth and postnatal growth pattern may have an impact on insulin resistance and body composition in later life. Adiponectin is a strong determinant of insulin sensitivity.

OBJECTIVE

The aim of this study was to evaluate insulin resistance and adiponectin levels in SGA born children with catch-up growth (CUG) in the absence of obesity in prepubertal ages and relations with body composition and insulin-like growth factor binding protein (IGFBP)-1.

METHODS

Twenty-four (15F, 9M) SGA born children with CUG but without obesity were evaluated at age 6.3 +/- 0.5 years with respect to glucose, insulin, IGFBP-1, leptin and adiponectin levels, and body composition by dual-energy X-ray absorptiometry (DEXA). Their data were compared to that of 62 (27F, 35M) appropriate for gestational age (AGA) children.

RESULTS

SGA and AGA children had similar height standard deviation score (SDS) corrected for parental height and body mass index (BMI) SDS. Homeostasis model for insulin resistance (HOMA-IR) was significantly high in SGA (0.7 +/- 0.6) than in AGA children (0.4 +/- 0.2) (P = 0.029). There were no significant differences in leptin, IGFBP-1, adiponectin, and total and truncal fat between SGA and AGA children. However, being born SGA and having higher BMI in the upper half for the distribution in the sample, although within normal ranges, was associated with lower adiponectin levels (estimated means of log adiponectin levels 3.8 +/- 0.3 vs. 4.4 +/- 0.1 microg/ml, P = 0.040).

CONCLUSIONS

SGA children with CUG and with no obesity have higher insulin levels compared to AGA children. Both SGA birth and recent size seem to have an effect on serum adiponectin levels in childhood.

HIV-associated lipodystrophy: a review of underlying mechanisms and therapeutic options

Lipodystrophy (LD) is a common adverse effect of HIV treatment with highly active antiretroviral therapy, which comprises morphological and metabolic changes. The underlying mechanisms for LD are thought to be due to mitochondrial toxicity and insulin resistance, which results from derangements in levels of adipose tissue-derived proteins (adipocytokines) that are actively involved in energy homeostasis. Several management strategies for combating this syndrome are available, but they all have limitations. They include: switching from thymidine analogues to tenofovir or abacavir in lipoatrophy, or switching from protease inhibitors associated with hyperlipidaemia to a protease-sparing option; injection into the face with either biodegradable fillers such as poly-L-lactic acid and hyaluronic acid (a temporary measure requiring re-treatment) or permanent fillers such as bio-alcamid (with the risk of foreign body reaction or granuloma formation); and structured treatment interruption with the risk of loss of virological control and disease progression. There is therefore a need to explore alternative therapeutic options. Some new approaches including adipocytokines, uridine supplementation, glitazones, growth hormone (or growth hormone-releasing hormone analogues), metformin and statins (used alone or in combination) merit further investigation.

Adiponectin: an intriguing hormone for paediatricians

Adiponectin, a protein hormone produced by adipocytes, is also found in breast milk, which in turn is implicated in childhood obesity prevention. Although a biological role for adiponectin has not been firmly established, clinical and experimental research indicates that it regulates lipid and glucose metabolism, affects foetal development, and exerts anti-inflammatory and antiatherogenic effects.

CONCLUSION

This review demonstrates an emerging interest of paediatric research on adiponectin. A better understanding of adiponectin's bioactivity might clarify whether breast milk indeed prevents childhood obesity.

In vivo endothelial gene regulation in diabetes

Background

An authentic survey of the transcript-level response of the diabetic endothelium in vivo is key to understanding diabetic cardiovascular complications such as accelerated atherosclerosis and endothelial dysfunction.

Methods

We used streptozotocin to induce a model of type I diabetes in transgenic mice that express green fluorescent protein under the control of an endothelial-specific promoter (Tie2-GFP) allowing rapid isolation of aortic endothelium. Three weeks after treatment, endothelial cells were isolated from animals with blood glucose > 350 mg/dl. Aortae from the root to the renal bifurcation were rapidly processed by mincing and proteolytic digestion followed by fluorescent activated cell sorting to yield endothelial cell populations of >95% purity. RNA was isolated from >50,000 endothelial cells and subjected to oligo dT amplification prior to transcriptional analysis on microarrays displaying long oligonucleotides representing 32,000 murine transcripts. Five regulated transcripts were selected for analysis by real-time PCR.

Results

Within replicate microarray experiments, 19 transcripts were apparently dysregulated by at least 70% within diabetic mice. Up-regulation of glycam1, slc36a2, ces3, adipsin and adiponectin was confirmed by real-time PCR.

Conclusion

By comprehensively examining cellular gene responses in vivo in a whole animal model of type I diabetes, we have identified novel regulation of key endothelial transcripts that likely contribute to the metabolic and pro-inflammatory responses that accompany diabetes.

Seven-year efficacy of a lopinavir/ritonavir-based regimen in antiretroviral-naïve HIV-1-infected patients

OBJECTIVE

Evaluate efficacy and tolerability of lopinavir/ritonavir (LPV/r) plus stavudine and lamivudine long term in antiretroviral-naïve patients.

DESIGN

Open-label follow-up of prospective, randomized, multicenter trial.

METHOD

Antiretroviral-naïve HIV-infected subjects (N = 00) received of 3 doses of LPV/r plus stavudine and lamivudine for 48 weeks then received LPV/r soft-gel capsules 400/00 mg plus stavudine and lamivudine. After 6 years, subjects replaced stavudine with tenofovir.

RESULTS

At 7 years, by intent-to-treat analysis, 61 % had plasma HIV-RNA <400 copies/mL and 59% had < 50 copies/mL. Thirty-nine subjects discontinued treatment due to adverse events (n = 6), personal/other reasons (0), loss to follow-up (9), and noncompliance (4). Among 28 subjects qualifying for drug resistance testing, no protease inhibitor or stavudine resistance was observed and 4 showed lamivudine resistance. Most common drug-related moderate or severe adverse events were diarrhea (28%), nausea (6%), and abdominal pain (11 %). Subjects who received stavudine (median 6.6 years) and switched to tenofovir demonstrated significant improvements in total cholesterol (p = .009), triglycerides (p = .023), apolipoprotein C-III (p < .001 ), adiponectin (p = .008), fasting insulin (p = .04), and leptin (p = .03).

CONCLUSION

LPV/r-based therapy demonstrated sustained efficacy with no protease inhibitor or stavudine resistance through 7 years in antiretroviral-naïve patients. Switching from stavudine to tenofovir resulted in significant improvements in multiple metabolic parameters.

Overweight Latino children and adolescents have marked endothelial dysfunction and subclinical vascular inflammation in association with excess body fat and insulin resistance

OBJECTIVE

We measured plasma markers of endothelial dysfunction, vascular inflammation, and pro-coagulation in obese Hispanic/Latino children and adolescents with normal glucose tolerance and determined their relationship to body composition and indexes of glucose and lipid metabolism.

RESEARCH DESIGN AND METHODS

A total of 38 lean or obese Hispanic children and adolescents (10-18 years of age) were selected. The overweight group (n = 21) had a BMI >85th percentile for their age and sex, and the lean group (n = 17) had a BMI between the 25th and 50th percentiles. Studies included an oral glucose tolerance test, measurements of plasma glucose and lipids, several markers of endothelial function and inflammation, and determination of body composition by dual X-ray absorptiometry.

RESULTS

The obese group had higher systolic blood pressure and plasma triglycerides and was more insulin resistant than the lean group. The obese group also had higher plasma soluble intercellular adhesion molecule (259.5 +/- 60.0 vs. 223.2 +/- 47.5 ng/ml, P = 0.047), tumor necrosis factor-alpha (2.57 +/- 1.1 vs. 1.74 +/- 0.6 pg/ml, P = 0.008), high-sensitivity C-reactive protein (2.0 vs. 0.13 mg/l, P < 0.0001), plasminogen-activated inhibitor-1 (47.0 +/- 35.7 vs. 12.0 +/- 5.2 ng/ml, P < 0.0001), tissue plasminogen activator (6.1 +/- 1.9 vs. 4.1 +/- 0.8 ng/ml, P = 0.001), and white blood cell count (6.9 vs. 5.3 x 10(3), P = 0.031) and lower levels of adiponectin (8.7 +/- 3.3 vs. 12.6 +/- 5.2 microg/ml, P = 0.022). No significant differences were observed for soluble vascular cell adhesion molecule or interleukin-6.

CONCLUSIONS

Overweight Hispanic children and adolescents with normal glucose tolerance exhibit increased plasma markers of endothelial dysfunction and subclinical inflammation in association with obesity and insulin resistance. These abnormalities may predispose them to the development of type 2 diabetes and cardiovascular disease.

The importance of treating cardiometabolic risk factors in patients with type 2 diabetes

Cardiometabolic risk factors are the combined vascular and metabolic components of risk that may lead to a cardiovascular event. There are numerous such factors. Underlying the concept of cardiometabolic risk is an association with excess visceral fat, leading to the dysregulation of the adipokines, the signalling proteins derived from adipose tissue. Changes in the levels of the adipokines - tumour necrosis factor-alpha, cholesteryl ester transfer protein and adiponectin, for example - can lead to alterations in insulin sensitivity and high-density lipoprotein cholesterol metabolism. At present, specific cardiometabolic risk factors are commonly managed on an individual basis. We are now moving from the era of single risk factor intervention, however, to multiple risk factor intervention in people at high cardiovascular risk, with the additional possibility of using new drug classes to target the underlying cardiometabolic problems more effectively.

Peroxisome Proliferator-Activated Receptor-γ–Mediated Effects in the Vasculature

Peroxisome proliferator-activated receptor (PPAR)-γ is a nuclear receptor and transcription factor in the steroid superfamily. PPAR-γ agonists, the thiazolidinediones, are clinically used to treat type 2 diabetes. In addition to its function in adipogenesis and increasing insulin sensitivity, PPAR-γ also plays critical roles in the vasculature. In vascular endothelial cells, PPAR-γ activation inhibits endothelial inflammation by suppressing inflammatory gene expression and therefore improves endothelial dysfunction. In vascular smooth muscle cells, PPAR-γ activation inhibits proliferation and migration and promotes apoptosis. In macrophages, PPAR-γ activation suppresses inflammation by regulating gene expression and increases cholesterol uptake and efflux. A recurring theme in many cell types is the modulation of the innate immunity system particularly through altering the activity of the nuclear factor κB. This system is likely to be even more prominent in modulating disease in vascular cells. The effects of PPAR-γ in the vascular cells translate into the beneficial function of this transcription factor in vascular disorders, including hypertension and atherosclerosis. Both human genetic studies and animal studies using transgenic mice have demonstrated the importance of PPAR-γ in these disorders. However, recent clinical studies have raised significant concerns about the cardiovascular side effects of thiazolidinediones, particularly rosiglitazone. Weighing the potential benefit and harm of PPAR-γ activation and exploring the functional mechanisms may provide a balanced view on the clinical use of these compounds and new approaches to the future therapeutics of vascular disorders associated with diabetes.

Type 2 diabetes: Gaining insight into the disease process using proteomics

The incidence of diabetes mellitus is growing rapidly, with an increasing disease related morbidity and mortality. This is caused by macro- and microvascular complications, as a consequence of the often late diagnosis of type 2 diabetes (T2D), but especially by the difficulties to control glucose homeostasis due to the progressive nature of the disease. T2D is moreover a dual disease, with components of beta-cell failure and components of insulin resistance in peripheral organs, such as liver, fat, and muscle. Understanding the pathogenesis of the disease by gaining insight into the molecular pathways involved in both phenomena is one of the major assets of proteomic approaches. Moreover, proteomics and peptidomics may provide us with robust biomarkers for beta-cell failure, insulin resistance in pheripheral organs, but also for the development of diabetic complications. This review focuses on the knowledge gained by use of proteomic and peptidomic techniques in the study of the pathophysiology of T2D and in the attempts to discover new therapeutic targets.

Distribution of adipose tissue: quantification and relationship with hepatic steatosis and vascular profiles of type 2 diabetic patients with metabolic syndrome

AIM

As the distribution of fat is increasingly related to cardiovascular events, we examined whether or not abdominal-fat quantification using magnetic resonance imaging (MRI) software is reliable, and whether or not it is related to clinical markers of fat distribution as well as to metabolic and vascular status.

METHODS

We recorded the anthropometric measurements of 34 obese type 2 diabetic patients with metabolic syndrome. The patients were enrolled to evaluate their abdominal (visceral and subcutaneous) adipose tissue by single-slice L3-L4 MRI. Manual and automated analyses were compared. The relationships between anthropometric measurements, biological markers and intima-media thickness of the common carotid artery were also assessed.

RESULTS

We validated the automated software to quantify abdominal-fat deposition with MRI compared with manual measurements (r2=0.95). The waist-to-hip-circumference ratio (WHR) was the only clinical parameter that correlated with the proportion and quantity of visceral and subcutaneous abdominal-adipose tissue evaluated by MRI (r=0.60). In addition, fat repartition as evaluated by WHR was related to hepatic steatosis parameters (ferritin and ALAT) and to intima-media thickness, whereas simple waist circumference was not a determinant in these obese patients. We also showed that the adiponectin-to-leptin ratio was related to adipose tissue distribution.

CONCLUSION

Distribution of abdominal fat, as evaluated by MRI, can be reflected by clinical determination of the WHR. Differences in regional accumulations of abdominal fat may be specifically related to variations in the risks of steatosis and vascular rigidity among obese type 2 diabetic patients.

Increased maternal nutrition increases leptin expression in perirenal and subcutaneous adipose tissue in the postnatal lamb

The present study tested the hypothesis that exposure to an increased level of maternal nutrition before birth results in altered expression of adipogenic, lipogenic, and adipokine genes in adipose tissue in early postnatal life. Pregnant ewes were fed either at or approximately 50% above maintenance energy requirements during late pregnancy, and quantitative RT-PCR was used to measure peroxisome proliferator-activated receptor (PPAR)-gamma, lipoprotein lipase (LPL), glycerol-3-phosphate-dehydrogenase (G3PDH), adiponectin, and leptin mRNA expression in perirenal (PAT) and sc adipose tissue (SCAT) in the offspring on postnatal d 30. Relative SCAT mass was higher in lambs of well-fed ewes (40.0 +/- 4.0 vs. 22.8 +/- 3.3 g/kg, P < 0.05) and was directly related to plasma insulin in the first 24 h after birth and to G3PDH and LPL expression. The expression of leptin mRNA in both the SCAT and PAT depots was higher (P < 0.05) in lambs of well-fed ewes. PPARgamma adiponectin, LPL, and G3PDH mRNA expression were not, however, different between well-fed and control groups in either depot. Relative PPARgamma expression in SCAT was directly related to plasma insulin concentrations in the first 24 h after birth (r(2) = 0.23; P < 0.05), and G3PDH and LPL expressions were also positively correlated with PPARgamma expression (r(2) = 0.27; P < 0.05). We have demonstrated that exposure to increased prenatal nutrition increases leptin expression at 1 month of age in both PAT and SCAT. The results of this study provide evidence that the nutritional environment before and immediately after birth can influence the development of adipose tissue in early postnatal life.

Cannabinoid-1 receptor antagonists in type-2 diabetes

Type-2 diabetes is closely related to abdominal obesity and is generally associated with other cardiometabolic risk factors, resulting in a risk of major cardiovascular disease. Several animal and human observations suggest that the endocannabinoid system is over-active in the presence of abdominal obesity and/or diabetes. Both central and peripheral endocannabinoid actions, via the activation of CB1 receptors, promote weight gain and associated metabolic changes. Rimonabant, the first selective CB(1) receptor blocker in clinical use, has been shown to reduce body weight, waist circumference, triglycerides, blood pressure, insulin resistance index and C-reactive protein levels, and to increase high-density lipoprotein (HDL) cholesterol and adiponectin concentrations in both non-diabetic and diabetic overweight/obese patients. In addition, a 0.5-0.7% reduction in HbA1c levels was observed in metformin- or sulphonylurea-treated patients with type-2 diabetes and in drug-naïve diabetic patients. Almost half of the metabolic changes, including HbA1c reduction, could not be explained by weight loss, suggesting that there are direct peripheral effects. Rimonabant was generally well-tolerated, and the safety profile was similar in diabetic and non-diabetic patients, with a higher incidence of depressed mood disorders, nausea and dizziness. In conclusion, the potential role of rimonabant in overweight/obese patients with type-2 diabetes and at high risk of cardiovascular disease deserves much consideration.

Metabolic syndrome: treatment of hypertensive patients

Metabolic syndrome (MetSyndr), a constellation of abnormalities [obesity, glucose intolerance, insulin resistance (IR), dyslipidemia (low HDL-cholesterol, high LDL-cholesterol and triglycerides (TG)], and elevated blood pressure (BP)], increases the risk of cardiovascular (CV) disease and premature death. From 10% to 30% of the adult population in industrialized countries has MetSyndr, which effectively predicts the development of type 2 diabetes mellitus (T2D) and CV disease. Because of the complex etiology of MetSyndr, a multi-targeted, integrated therapeutic approach is required to simultaneously treat high BP, obesity, lipid disorders and T2D (if present), to fully protect CV, cerebrovascular and renal systems. If lifestyle modification (weight control, diet, exercise, smoking cessation, moderation of alcohol intake) is ineffective, pharmaco-theraphy should be added to treat simultaneously the lipid- and non-lipid CV risk factors. Patients with HTN and MetSyndr should be started on angiotensin-converting enzyme (ACE) inhibitors, unless contraindicated. The ACE inhibitors and angiotensin receptor blockers (ARBs) reduce the odds of developing new onset T2D and also decrease albuminuria. The ACE inhibitors provide cardioprotective and renoprotective benefits beyond their effect on BP; they also improve IR. The ARBs are renoprotective in addition to being cardioprotective. Long-acting calcium channel blockers are also recommended in hypertensive patients with MetSyndr; these drugs also improve IR. Thiazides (at low doses) and selected ss-blockers can be given to patients with HTN and MetSyndr. Celiprolol in combination with diuretics has a favorable effect on glucose tolerance and IR in patients with HTN and MetSyndr, and spironolactone added to ACE inhibitor or ARB therapy provides additional reno- and CV protective benefits in patients with diabetic nephropathy. Carvedilol, a ss-blocker with vasodilating properties, added to ACE inhibitor or ARB therapy, is effective in preventing worsening of microalbuminuria in patients with HTN and MetSyndr; it also improves IR and glycemic control. Most patients eventually require two or more antihypertensive drugs to reach BP goal. It is recommended that therapy in patients whose BP is more than 20/10 mm Hg above target at diagnosis be initiated with a combination of antihypertensive drugs, administered either as individual drugs or as fixed-dose formulations. Treatment with fixed-dose combinations, such as irbesartan + hydrochlorothiazide provides good BP control in more than two-thirds of hypertensive patients with MetSyndr. Lipid and BP targets are reached in a high percent of patients with HTN and CV disease treated with a combination of amlodipine + atorvastatin. In conclusion, hypertensive patients with the MetSyndr be treated aggressively for each component of the syndrome to provide CV, cerebrovascular and renal protection.

CB1 receptors: emerging evidence for central and peripheral mechanisms that regulate energy balance, metabolism, and cardiovascular health

Insulin resistance, dyslipidaemia and obesity are the major cardiometabolic risk factors contributing to the development of type 2 diabetes and cardiovascular disease (CVD). Owing to the increasing prevalence of obesity, type 2 diabetes, and CVD, new and effective pharmacologic therapies are urgently needed. In this regard, the endogenous cannabinoid system (ECS), a neuromodulatory system involved in the regulation of various aspects of energy balance and eating behaviour through central and peripheral mechanisms, may present the potential to meet this need. In the central nervous system (CNS), cannabinoid type 1 (CB1) receptors and their respective ligands, the endocannabinoids, have a significant role in the modulation of food intake and motivation to consume palatable food. CB1 receptors have also been found in organs involved in the regulation of metabolic homeostasis, such as liver, white adipose tissue, muscle and pancreas. Dysregulation of the ECS has been associated with the development of dyslipidaemia, glucose intolerance, and obesity, and CB1 receptor blockade may have a role in ameliorating these metabolic abnormalities. Thus, pharmacologic options targeting the ECS may provide a novel, effective approach to the prevention and management of CVD, type 2 diabetes and obesity.

Correlates of serum C-reactive protein (CRP)--no association with sleep duration or sleep disordered breathing

STUDY OBJECTIVES

Increasing evidence suggests that alterations in sleep duration are associated with cardiovascular disease (CVD) and mortality. Additionally, sleep disordered breathing (SDB), which is associated with disturbed nighttime sleep and hypoxemia, may be an independent risk factor for CVD. The inflammatory marker, C-reactive protein (CRP), is an important predictor of CVD. We investigated potential associations between circulating CRP, sleep duration, and SDB.

DESIGN

Cross-sectional Study.

POPULATION

Participants were 907 adults from the Wisconsin Sleep Cohort Study (WSCS).

MEASUREMENTS AND RESULTS

CRP was measured after overnight polysomnography. The relationships between CRP and sleep parameters were evaluated using multiple linear regression with and without controlling for age, sex, and body mass index (BMI) and other potential confounders. CRP was found to be higher for women and had a strong positive correlation with age and BMI. CRP showed a significant positive association with current smoking, waist-hip ratio (WHR), LDL-cholesterol, triglycerides, leptin, and insulin, independent of age, sex, and BMI. Significant independent negative associations for CRP were observed with HDL-cholesterol (HDL), insulin sensitivity (quantitative insulin sensitivity check index [QUICKI]), and hours of exercise. There was a significant positive association between CRP levels and the apnea-hypopnea index (AHI, the measure of SDB), but these relationships were not significant after adjustment for age, sex, and BMI. No significant association between CRP levels and measures of sleep duration (polysomnographic and self-reported) were found.

CONCLUSION

There was no significant association between CRP levels and sleep duration. The lack of an independent association between CRP levels and SDB suggests that the reported relationship between these 2 variables may be primarily driven by their association with obesity.

A new approach to the study of diet and risk of type 2 diabetes

Type 2 diabetes mellitus (T2DM) is a polygenetic disorder resulting from interaction of both hereditary and environmental factors. Diet is an important environmental factor in the development of T2DM. However, there existed inconsistent conclusions among previous studies. The validity of a study of associations between diet and diabetes depends on the method used in the study. Associations between individual nutrients/foods and T2DM have been explored even till today, but the controversy is still unsolved due to the limitations of the study methods such as interactions among nutrients. Emergence of analyses on dietary patterns and diabetes shows its popularity in the studies of associations of dietary patterns with T2DM, but only a few articles have been published. In this review, dietary-pattern-related studies since 1990 were identified by searching through Medline and PubMed in order to analyze methods used in the studies of diabetes. A dietary pattern approach was introduced as an alternative complementary way used to test associations of diet with risk of T2DM and the advantages of the studies of T2DM using this new approach are also explored. It is concluded that the dietary pattern approach shows its advantages over that using individual nutrients or foods in studies on associations between the diet and diabetes, but its reproducibility and validity for such effects, however, need to be further verified in different ethnic population-based on diverse eating habits. The long-term effects of a beneficial dietary pattern on T2DM also require clarifying in future studies.

Risks of CHD identified by different criteria of metabolic syndrome and related changes of adipocytokines in elderly postmenopausal women

The objective of this study was to assess the capacity of different criteria of metabolic syndrome (MetS) to identify risks of coronary heart diseases (CHDs) and related changes of adipocytokines in postmenopausal women. A cross-sectional study was carried out in 225 community-dwelling, elderly postmenopausal Chinese women (age, 66.77+/-5.09 years) without hormone replacement therapy (HRT). Baseline data such as blood pressure, body mass index (BMI), serum lipid profiles, and fasting glucose were analyzed, and insulin sensitivity was estimated via the homeostasis model assessment for insulin resistance. Serum tumor necrosis factor alpha (TNFalpha), interleukin-6 (IL-6), and adiponectin were measured simultaneously. The prevalence of MetS identified by the Third Report of the National Cholesterol Education Programme Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults, the International Diabetes Federation (IDF), the Chinese Diabetes Society (CDS), and the Japanese Society of Internal Medicine (JPN) were 27.31%, 37.34%, 23.29%, and 13.65%, respectively. No significant differences of baseline data were found among different MetS groups, except for a significant higher waist circumference in the JPN-MetS group as compared with other MetS groups. The prevalence of confirmed CHD in the four MetS groups were 26.2%, 18.6%, 26.9%, and 32%, respectively. Odds ratios for CHD were 1.905 (95% CI=1.273-2.851), 1.208 (95% CI=0.778-1.876), 1.997 (95% CI=1.238-3.221), and 2.336 (95% CI=1.119-4.876), respectively. The JPN-MetS group had higher levels of TNFalpha and IL-6, whereas the CDS-MetS group correlated better with lower adiponectin levels. The IDF definition for MetS is the most sensitive one with regard to metabolic disorders, whereas JPN and CDS definitions correlate better with CHD and changes of adipocytokines among the four criteria studied.

Adipocytes, myofibers, and cytokine biology: new horizons in the regulation of growth and body composition

Muscle growth in meat animals is a complex process governed by integrated signals emanating from multiple endocrine and immune cells. A generalized phenomenon among meat animal industries is that animals commonly fail to meet their genetic potential for growth in commercial production settings. Therefore, understanding the impact of stress and disease on muscle growth is essential to improving production efficiency. The adipocyte in particular seems to be well positioned as an interface between energy status and immune function, and may thus influence nutrient partitioning and growth through a combination of signals that influence fat metabolism, glucose uptake, and insulin sensitivity. Adipocytes and myofibers are active participants in the innate immune response, and as such, produce a number of metabolic regulators, including leptin, adiponectin, and proinflammatory cytokines. Specifically, adipocytes and muscle cells respond directly to bacterial lipopolysaccharide (LPS) by producing interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNFalpha). However, adipocytes are also the predominant source of the antiinflammatory hormone adiponectin, which regulates the nuclear factor kappa-B transcription factor. The ability to recognize antigens and produce regulatory molecules strategically positions adipocytes and myofibers to regulate growth locally, and to reciprocally regulate metabolism peripherally.

Endothelial activation markers and their key regulators after restrictive bariatric surgery

OBJECTIVE

Increased plasma levels of endothelial activation markers in obese subjects reflect the positive association between cardiovascular diseases and obesity. The pro-inflammatory state associated with obesity is thought to play a major role in endothelial cell activation in severely obese individuals. Previous studies demonstrated that long-term weight loss after bariatric surgery is accompanied by a decreased proinflammatory state. However, little is known about the long-term effects of bariatric surgery on endothelial cell activation.

RESEARCH METHODS AND PROCEDURES

Plasma levels of soluble intercellular adhesion molecule-1 (sICAM-1), soluble endothelial selectin (sE-selectin), and soluble vascular cell adhesion molecule-1 (sVCAM-1), all markers of endothelial cell activation, and of their regulators adiponectin and resistin were measured at different time-points postoperatively in 26 consecutive patients who underwent restrictive surgery, with a follow-up of 2 years.

RESULTS

During the first 6 months after bariatric surgery, sE-selectin levels decreased. Despite substantial weight loss, sICAM-1 and sVCAM-1 plasma levels did not decrease significantly. After 24 months, sICAM-1 levels were significantly decreased, whereas sE-selectin levels were further decreased. However, sVCAM-1 levels remained elevated. Adiponectin levels did not change significantly during the first 6 months after bariatric surgery, whereas resistin levels increased. After 24 months, adiponectin levels were similar to normal-weight controls, but resistin levels remained high.

DISCUSSION

Reductions in plasma levels of different markers of endothelial activation after bariatric surgery show different temporal patterns, suggesting that distinct mechanisms are involved in their regulation. Although not all endothelial activation markers normalize after bariatric surgery, our findings suggest that bariatric surgery can reduce endothelial activation in the long term.

New predictors of the metabolic syndrome in children--role of adipocytokines

There is ample discussion of the relevance of the metabolic syndrome, the definition criteria, and predictive power. Nevertheless, along with the increasing prevalence of childhood obesity, the prevalence of the metabolic syndrome in obese children is reported at 30%, irrespective of the definition applied. Because children are otherwise relatively free of co-morbidities, they constitute an interesting population in which to study the sequence of events of obesity-related pathology. The adipocytokines appear to be important in this respect. Leptin was initially suggested as a promising "antiobesity" hormone. New concepts indicate that, in humans, leptin and its soluble receptor may be more important in states of energy deficiency rather than a predictor of the metabolic syndrome. Adiponectin, on the other hand, is not only related to obesity and insulin resistance, but appears to be the strongest predictor for metabolic syndrome, even in children. In newborns and infants, both adipocytokines occur in high concentrations, even though this cannot completely explain the increased risk for ensuing metabolic disease later in life. Finally, low-grade systemic inflammation may underlie the clustering of metabolic risk factors, but their role in children remains to be specified. Overall factors from the adipose tissue may constitute not only markers but also mediators of metabolic sequelae of obesity.

The impact of insulin resistance, serum adipocytokines and visceral obesity on steatosis and fibrosis in patients with chronic hepatitis C

AIMS

To assess whether host metabolic factors influence the degree of hepatic steatosis and fibrosis in patients infected with hepatitis C virus, and to evaluate the impact of anti-viral therapy on insulin resistance and serum levels of adipocytokines.

METHODS

Clinical and biochemical features, anthropometrical characteristics, and levels of fasting insulin, leptin, adiponectin and resistin were measured in 'naïve' patients with chronic hepatitis C, before, during and after therapy with Peg-Interferon-alpha 2a plus Ribavirin.

RESULTS

Forty-eight patients were included (M/F 28/20; mean age 50.0 +/- 12.6 years; 62.5% genotype-1). Body mass index was 26.4 +/- 4.0 kg/m(2), and visceral obesity was present in 24 patients. At multivariate analysis (RR; 95% CI), steatosis was associated to older age (1.08; 1-1.18), necroinflammatory activity (17.67; 1.6-194.46), and raised insulin levels (1.39; 1.1-1.77). Fibrosis was related to necroinflammatory activity (25.73; 2.54-261.11), and steatosis (6.47; 1.09-38.29). Sustained viral response was achieved by 62.5% of patients and was associated with younger age (0.92; 0.85-0.99), genotype non-1 (10.61; 1.52-73.76) and absence of visceral obesity (13.78; 2.36-80.29). At the end of follow-up, insulin and the homeostasis model assessment for insulin resistance were reduced and adiponectin increased when compared with baseline, all unrelated to the outcome of treatment.

CONCLUSIONS

Visceral obesity correlates with the degree of steatosis and fibrosis, and it negatively affects treatment response. Significant changes of insulin resistance and adipocytokines occur under treatment, irrespective of virological outcome.

48-h glucose infusion in humans: effect on hormonal responses, hunger and food intake

Experimentally-induced hyperglycemia by prolonged glucose infusion allows investigation of the effects of sustained stimulation of the pancreatic beta-cell on insulin secretion and sensitivity. Hormonal responses to a meal following prolonged glucose infusions have not been investigated. To determine if a 48-h glucose infusion alters hormonal responses to a test meal as well as food intake and hunger in normal weight individuals, 16 subjects (8 men, 8 women, age 18-30 years, mean BMI=21.7+/-1.6 kg/m2) were infused for 48 h with either saline (50 ml/h) or 15% glucose (200 mg/m2/min). Subjects ingested a 600 kcal mixed nutrient meal 3 h after infusion termination. Blood samples were taken during the 48 h and for 4 h following food ingestion. The 48-h glucose infusion elicited a metabolic profile of a glucose intolerant obese subjects, with increased plasma glucose, insulin and leptin (all P<0.01) and increased HOMA-IR (P<0.001). During meal ingestion, early insulin secretion was increased (P<0.05) but post-prandial glucose (P<0.01) and insulin (P<0.01) excursions were lower following the glucose infusion. Post-prandial plasma triglyceride concentrations were increased after glucose compared with saline. Food intake and hunger ratings were not different between the two conditions. Plasma leptin levels were inversely correlated with hunger (P<0.03) in both conditions and with food intake (P<0.003) during the glucose condition only. Thus, a 48-h glucose infusion does not impair post-prandial hormonal responses, alter food intake or hunger in normal weight subjects. The glucose-induced increases in plasma leptin result in a stronger inverse relationship between plasma leptin and hunger as well as food intake. These data are the first to demonstrate a relationship between leptin and hunger in normal weight, non-calorically restricted human subjects.

The endocannabinoid system: body weight and metabolic regulation

The endocannabinoid system elicits multiple physiologic functions that are not fully understood. Antagonism of cannabinoid type 1 (CB(1)) receptors has been the only successful new pharmacologic treatment approach in Phase III studies in obesity in the last 8 years. Whereas antagonism of (CB(1)) receptors acutely reduces food intake, the long-term effects on weight reduction and metabolic regulation appear to be mediated by stimulation of energy expenditure and by peripheral effects related to liver, skeletal muscle, adipose tissue, and pancreas physiology. For example, in the liver, lipogenic enzymes and fatty acid synthesis are upregulated by endocannabinoids, and in adipose tissue, antagonism of (CB(1)) receptors increases secretion of adiponectin. Some studies suggest that endocannabinoid formation is increased in obesity, perhaps because endocannabinoid degradation is decreased. Although many questions remain unanswered at present, the emerging concept of endocannabinoids as metabolic regulators helps to explain the success of rimonabant (SR141716), an antagonist of (CB(1)) receptors, currently in Phase III studies.

Decreased plasma adiponectin is associated with insulin resistance and HDL cholesterol in overweight subjects

The purpose of this study was to investigate plasma adiponectin concentration and its relation with metabolic parameters in overweight and normal weight subjects. The study was carried out in 46 overweight subjects (20 male, 26 female; mean age 39.4 +/- 10.2 years) and 48 (19 male, 29 female; mean age 36.1 +/- 10.6 years) sex- and age-matched normal weight subjects. Anthropometric measurements were recorded and adiponectin, glucose, insulin, lipid profile, total homocysteine (tHcy) and fibrinogen levels were measured. The insulin resistance index was assessed by homeostasis model assessment for insulin resistance (HOMA-IR). Plasma mean adiponectin concentrations of the overweight subjects were significantly lower than those of normal weight subjects (15.0 +/- 4.2 vs 17.3 +/- 5.6 ng/ml) (P<0.05). In overweight subjects, adiponectin levels negatively correlated with body weight (r = -0.35, P<0.001), body mass index (BMI) (r = -0.28, P<0.006), systolic blood pressure (r = -0.21, P<0.04), fasting insulin (r = -0.19, P<0.01) and HOMA-IR (r = -0.20, P<0.01) and positively with high-density lipoprotein cholesterol (HDL-C) (r = 0.27, P<0.009). Overweight subjects with low HDL-C levels had significantly decreased plasma adiponectin levels compared to those with high HDL-C levels (P<0.05). Multiple regression analysis revealed that BMI, HOMA-IR and HDL-C explained 12%, 20% and 15% variance of the adiponectin concentrations. These findings may suggest that circulating adiponectin is associated with insulin resistance and HDL-C levels independent from BMI in overweight subjects.

Increases in adiponectin predict improved liver, but not peripheral, insulin sensitivity in severely obese women during weight loss

Obesity-related glucose intolerance is a function of hepatic (homeostatic model assessment-insulin resistance [HOMA-IR]) and peripheral insulin resistance (S(i)) and beta-cell dysfunction. We determined relationships between changes in these measures, visceral (VAT) and subcutaneous (SAT) adipose tissue, and systemic adipocytokine biomarkers 1 and 6 months after surgical weight loss. HOMA-IR decreased significantly (-50%) from baseline by 1 month and decreased further (-67%) by 6 months, and S(i) was improved by 6 months (2.3-fold) weight loss. Plasma concentrations of leptin decreased and adiponectin increased significantly by 1 month, and decreases in interleukin-6, C-reactive protein (CRP), and tumor necrosis factor-alpha were observed at 6 months of weight loss. Longitudinal decreases in CRP (r = -0.53, P < 0.05) were associated with increases in S(i), and decreases in HOMA-IR were related to increases in adiponectin (r = -0.37, P < 0.05). Decreases in VAT were more strongly related to increases in adiponectin and decreases in CRP than were changes in general adiposity or SAT. Thus, in severely obese women, specific loss of VAT leads to acute improvements in hepatic insulin sensitivity mediated by increases in adiponectin and in peripheral insulin sensitivity mediated by decreases in CRP.

Serum adiponectin and leptin levels and insulin resistance in children born large for gestational age are affected by the degree of overweight

OBJECTIVE

Children born large for gestational age (LGA) are prone to develop insulin resistance later in life. One factor that affects insulin sensitivity is the hormone adiponectin. The aim of this study was to determine whether being LGA has an impact on serum adiponectin and leptin levels and insulin resistance parameters during childhood, taking into account the severity of overweight.

STUDY DESIGN

Serum levels of adiponectin, leptin, fasting glucose and insulin, homeostasis model assessment insulin resistance index (HOMA-IR), and anthropometric indices were evaluated in groups of non-obese children aged 6.5-8 years, born appropriate for gestational age (AGA, n = 40) or LGA (n = 41), matched for age, gender, height, weight and body mass index. The LGA group was divided in two subgroups according to the degree of overweight: (a) LGA with birthweight 90th-97th percentile (n = 25); and (b) LGA with birthweight > 97th percentile (n = 16).

RESULTS

LGA children had a higher mean serum adiponectin level than AGA children: 17.0 +/- 9 vs. 11.1 +/- 5 (microg/ml) (P < 0.01). LGA children had also higher insulin 6.2 +/- 2.8 vs. 4.8 +/- 2.4 (microU/ml) (P < 0.05) and HOMA-IR 1.32 +/- 0.66 vs. 1.02 +/- 0.55 (P < 0.01) than AGA children. Children born LGA > 97th percentile had a significantly higher mean serum leptin level than both AGA and LGA 90th-97th percentile children (17 +/- 13, 9.6 +/- 9.5, 7.8 +/- 7.9 ng/ml, respectively, P < 0.05), and more severely affected insulin resistance indices than LGA 90th-97th percentile children. In the regression analysis, birthweight was found to be an independent predictor of adiponectin serum levels.

CONCLUSION

Prepubertal LGA-born children had a higher mean serum adiponectin levels than matched AGA controls despite the fact that they were more insulin resistant. The degree of excess in utero weight gain appears to influence the metabolic profile in LGA-born prepubertal children. Further studies are needed to delineate the role of adiponectin in the risk of development of insulin resistance in children born LGA.

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.

Role of dietary soy protein in obesity

Soy protein is an important component of soybeans and provides an abundant source of dietary protein. Among the dietary proteins, soy protein is considered a complete protein in that it contains ample amounts of all the essential amino acids plus several other macronutrients with a nutritional value roughly equivalent to that of animal protein of high biological value. Soy protein is unique among the plant-based proteins because it is associated with isoflavones, a group of compounds with a variety of biological properties that may potentially benefit human health. An increasing body of literature suggests that soy protein and its isoflavones may have a beneficial role in obesity. Several nutritional intervention studies in animals and humans indicate that consumption of soy protein reduces body weight and fat mass in addition to lowering plasma cholesterol and triglycerides. In animal models of obesity, soy protein ingestion limits or reduces body fat accumulation and improves insulin resistance, the hallmark of human obesity. In obese humans, dietary soy protein also reduces body weight and body fat mass in addition to reducing plasma lipids. Several potential mechanisms whereby soy protein may improve insulin resistance and lower body fat and blood lipids are discussed and include a wide spectrum of biochemical and molecular activities that favorably affect fatty acid metabolism and cholesterol homeostasis. The biologic actions of certain constituents of soy protein, particularly conglycinin, soyasaponins, phospholipids, and isoflavones, that relate to obesity are also discussed. In addition, the potential of soy protein in causing food allergy in humans is briefly discussed.

Associations of adiponectin with metabolic and vascular risk parameters in the British Regional Heart Study reveal stronger links to insulin resistance-related than to coronory heart disease risk-related parameters

BACKGROUND AND AIM

Adiponectin is considered by many to be part of the 'common soil' linking type 2 diabetes and coronary heart disease (CHD). We examined the relationship between adiponectin and insulin resistance, metabolic, inflammatory and haemostatic risk factors and hepatic function.

METHODS AND RESULTS

The study was carried out in 3640 non-diabetic men aged 60-79 years drawn from general practices in 24 British towns and who were not on warfarin. Adiponectin was associated with waist circumference (inversely), alcohol intake (positively) and physical activity (nonlinearly); no association was seen with cigarette smoking, prevalent CHD or stroke. After adjustment for these factors, adiponectin was significantly inversely associated with insulin resistance, triglyceride, C-reactive protein (but not interleukin 6), tissue plasminogen activator and alanine aminotransferase and positively associated with high-density lipoprotein cholesterol (HDL-cholesterol) and Factor VIII, factors associated with diabetes. No association was seen with cholesterol, smoking, systolic blood pressure or coagulation factors. Risk of the metabolic syndrome decreased significantly with increasing adiponectin.

CONCLUSION

Adiponectin is inversely associated with factors strongly associated with the development of diabetes. Limited associations with the established major risk factors for CHD suggest adiponectin may be a stronger marker of risk for diabetes than for CHD.

Metabolic syndrome pathophysiology: the role of adipose tissue

Several pathophysiological explanations for the metabolic syndrome have been proposed involving insulin resistance, chronic inflammation and ectopic fat accumulation following adipose tissue saturation. However, current concepts create several paradoxes, including limited cardiovascular risk reduction with intensive glucose control in diabetics, therapies that result in weight gain (PPAR agonists), and presence of some of the metabolic traits among some lipodystrophies. We propose the functional failure of an organ, in this case, the adipose tissue as a model to interpret its manifestations and to reconcile some of the apparent paradox. A cornerstone of this model is the failure of the adipose tissue to buffer postprandial lipids. In addition, homeostatic feedback loops guide physiological and pathological adipose tissue activities. Fat turnover is determined by a complex equilibrium in which insulin is a main factor but not the only one. Chronically inadequate energy balance may be a key factor, stressing the system. In this situation, an adipose tissue functional failure occurs resulting in changes in systemic energy delivery, impaired glucose consumption and activation of self-regulatory mechanisms that extend their influence to whole body homeostasis system. These include changes in adipokines secretion and vascular effects. The functional capacity of the adipose tissue varies among subjects explaining the incomplete overlapping among the metabolic syndrome and obesity. Variations at multiple gene loci will be partially responsible for these interindividual differences. Two of those candidate genes, the adiponectin (APM1) and the perilipin (PLIN) genes, are discussed in more detail.

Deficiency of adiponectin receptor 2 reduces diet-induced insulin resistance but promotes type 2 diabetes

Adiponectin/adiponectin receptors (AdipoR) are involved in energy homeostasis and inflammatory pathways. To investigate the role of AdipoR2 in metabolic control, we studied the lipid and glucose metabolic phenotypes in AdipoR2-deficient mice. AdipoR2 deletion diminished high-fat diet-induced dyslipidemia and insulin resistance yet deteriorated glucose homeostasis as high-fat feeding continued, which resulted from the failure of pancreatic beta-cells to adequately compensate for the moderate insulin resistance. A defect in the AdipoR2 gene may represent a mechanism underlying the etiology of certain subgroups of type 2 diabetic patients who eventually develop overt diabetes, whereas other obese patients do not.

[New insight into the treatment of aortic stenosis]

Aortic valve stenosis (AS) is the most frequent heart disease after coronary artery disease and arterial hypertension and it is associated with a high incidence of adverse outcomes. Historically, calcific AS has been considered as "degenerative" because it was thought to be the result from aging and "wear and tear" of the aortic valve. However, this perception has changed over the years with the publication of several studies showing that the calcific AS shares many histological similarities with atherosclerosis, thus suggesting that this disease could eventually be modified by lifestyle or pharmacological therapies. Furthermore, recent data support the notion that AS is not an isolated disease uniquely limited to the valve. Indeed, AS is frequently associated with abnormalities of the systemic arterial system, and in particular with reduced arterial compliance, which may have important consequences on the pathophysiology and clinical outcome of this disease. Hence, the assessment of AS severity as well as its therapeutic management should be conducted with the use of a comprehensive evaluation that includes not only the aortic valve but also the systemic arterial system and the left ventricle, since these 3 entities are tightly intricated on both the pathophysiological and hemodynamic standpoints.

Plasma adiponectin levels and endometrial cancer risk in pre- and postmenopausal women

BACKGROUND

Adiponectin, an adipocytokine secreted by adipose tissue, is decreased in obesity, insulin resistance, type 2 diabetes, and polycystic ovary syndrome, all of which are well-established risk factors for endometrial cancer.

METHODS

We conducted a case-control study nested within the European Prospective Investigation into Cancer and Nutrition to examine the relation between prediagnostic plasma adiponectin levels and endometrial cancer risk. Among pre- and postmenopausal women who were not currently using exogenous hormones, 284 women developed incident endometrial cancer during an average of 5.1 yr of follow-up. Using risk set sampling, 548 control subjects were selected, matched on center, age, menopausal status, phase of menstrual cycle, time of blood draw, and fasting status. Conditional logistic regression models were used to estimate relative risks and 95% confidence intervals.

RESULTS

Adiponectin levels were inversely associated with endometrial cancer risk [body mass index-adjusted relative risk for the top vs. bottom quartile = 0.56 (95% confidence interval 0.36-0.86), P(trend) = 0.006]. There was evidence of a stronger inverse association among obese women than among nonobese women (P(heterogeneity) = 0.03). The inverse association also appeared stronger for women who were postmenopausal or perimenopausal than premenopausal at baseline, but this was not statistically significantly heterogeneous (P(heterogeneity) = 0.51). The association remained statistically significant after separate adjustment for other obesity-related physiological risk factors such as C-peptide, IGF binding protein-1, IGF binding protein-2, SHBG, estrone, or free testosterone but only marginally statistically significant after simultaneous adjustment for these factors.

CONCLUSIONS

High circulating adiponectin levels are associated with reduced endometrial cancer risk, largely independent of other obesity-related risk factors.

The adipocyte-myocyte axis in insulin resistance

Insulin resistance in skeletal muscle is linked to an elevated adipose tissue mass, as is found in obesity, but can also be observed in lipodystrophy, in which adipose tissue is greatly reduced. Adipose tissue releases endocrine and metabolic mediators and is actively involved in crosstalk with skeletal muscle, a process that precedes and underlies the development of insulin resistance in muscles. Adipokines including tumor necrosis factor alpha, interleukin-6, leptin and adiponectin influence insulin signaling in skeletal muscle. Free fatty acids, their metabolites and ectopic fat in muscle also contribute to insulin resistance. Recent research indicates inflammation, endoplasmic reticulum stress and oxidative stress could be underlying mechanisms at the center of the development of insulin resistance. Insights into the role of macrophages in adipose tissue add to the complicated interplay between adipose tissue and skeletal muscle.

Hypoadiponectinemia and circulating angiogenic factors in overweight patients complicated with pre-eclampsia

OBJECTIVE

Obesity is a risk factor for pre-eclampsia, and adiponectin is an important adipocyte-derived hormone that might protect the endothelium. Recent reports have underlined importance of circulating angiogenic factors for pathophysiology of pre-eclampsia. Here we examined whether adiponectin in conjunction with angiogenic factors plays some roles in the pathophysiology of pre-eclampsia.

STUDY DESIGN

We measured serum concentrations of adiponectin and angiogenic factors, vascular endothelial growth factor, placental growth factor, and the soluble vascular endothelial growth factor receptors, soluble fms-like tyrosine Kinase 1 (sFlt-1) and soluble fetal liver kinase 1 (sFlk-1), in women with pre-eclampsia and healthy pregnant women. We also investigated the differences of these factors in overweight and normal-weight patients with pre-eclampsia.

RESULTS

Significant correlations were found among the circulating adiponectin and angiogenic factors placental growth factor (R = 0.772, P = .0012) and sFlt-1 (R = 0.787, P = .0005); while, no correlation was found between adiponectin and sFlk-1 (R = 0.3, P = .3434) in patients with pre-eclampsia. Overweight patients with pre-eclampsia showed significantly lower adiponectin levels and a mild imbalance of circulating angiogenic factors, compared with normal-weight patients with pre-eclampsia.

CONCLUSION

Overweight women with pre-eclampsia appeared to have lower levels of adiponectin and sFlt1 and higher levels of placental growth factor than women with pre-eclampsia who were of normal weight. These results suggest that hypoadiponectinemia might be involved in the pathophysiology of overweight patients with pre-eclampsia.

Effective treatment of hypertension by AT(1) receptor antagonism: the past and future of telmisartan

Lowering blood pressure is the most effective treatment method to ensure a reduction in the total risk for cardiovascular morbidity and mortality. The renin-angiotensin system plays an important role in volume homeostasis and blood pressure regulation and is a target for several groups of pharmaceutical agents. Angiotensin II receptor blockers represent the newest class of antihypertensive compounds. They prevent the binding of angiotensin II to the subtype 1 receptor (AT(1)), which is believed to mediate most of the physiological actions relevant to the regulation of blood pressure. Telmisartan, a widely used AT(1) receptor antagonist, is a highly selective compound with high potency, a long duration of action and a tolerability profile similar to placebo. Numerous randomized clinical trials and community-based studies have demonstrated that oral telmisartan and combinations of telmisartan with hydrochlorothiazide are at least as effective in lowering blood pressure as all other hypertensive medications. This has been demonstrated in different populations of adult patients with mild-to-moderate essential hypertension, including patients with coexisting Type 2 diabetes, metabolic syndrome or renal impairment. Several large-scale, long-term, clinical endpoint studies are in progress to assess the beneficial effects of telmisartan on hypertension-related end-organ damage in patients at high risk of renal, cardiac and vascular damage whose blood pressure is well controlled. The most recent data from clinical trials and latest research regarding telmisartan will be reviewed in this article.

Interrelations between fat distribution, muscle lipid content, adipocytokines, and insulin resistance: effect of moderate weight loss in older women

BACKGROUND

Interrelations between fat distribution, muscle lipid infiltration, adipocytokines, insulin resistance, and moderate weight loss have not been investigated in obese older subjects.

OBJECTIVE

The objective was to evaluate relations between fat distribution, muscle lipid content, adipocytokines, and insulin resistance in older women and the effects of moderate weight loss.

DESIGN

In 35 healthy women aged 58-83 y, body mass index, waist circumference, sagittal abdominal diameter (SAD), and body composition measured by dual-energy X-ray absorptiometry were evaluated. A midthigh single computed tomography scan was performed to determine subcutaneous adipose tissue (AT), intermuscular AT (IAT), muscular tissue, and muscle lipid infiltration, evaluated as low-density lean tissue. Metabolic variables, insulin resistance measured by homeostasis model assessment, adiponectin, leptin, and high-sensitivity C-reactive protein were measured in all subjects and after weight loss in a subgroup of 15 obese women.

RESULTS

Waist circumference and SAD were positively correlated with leptin and insulin resistance and negatively correlated with adiponectin. Adiponectin was associated negatively with insulin resistance and positively with HDL cholesterol, whereas leptin was positively associated with insulin resistance and triacylglycerols. Midthigh subcutaneous AT was associated with insulin resistance and leptin, whereas IAT was associated with triacylglycerols. Stepwise regression with insulin resistance as the dependent variable and body mass index, SAD, triacylglycerols, HDL cholesterol, adiponectin, leptin, high-sensitivity C-reactive protein, and midthigh subcutaneous AT as independent variables showed that SAD entered the regression first (R(2) = 0.492) followed by adiponectin (R(2) = 0.63). After moderate weight loss, midthigh subcutaneous AT, IAT, low-density lean tissue, leptin, and insulin resistance decreased significantly; no significant changes in adiponectin were observed.

CONCLUSIONS

Fat distribution indexes and adiponectin are independently associated with insulin resistance. Even in older women, moderate weight loss improves body fat distribution, muscle lipid infiltration, and insulin resistance. Moderate weight loss results in a significant decrease in leptin but no changes in adiponectin.

Relationships of physical activity with metabolic syndrome features and low-grade inflammation in adolescents

AIMS/HYPOTHESIS

Physical activity has beneficial effects on symptoms of the metabolic syndrome and low-grade inflammation in adults. These associations have rarely been studied in adolescents. Moreover, it has not been established whether they depend on adiposity, fat localisation and adipokines.

SUBJECTS, MATERIALS AND METHODS

We used cross-sectional data of 640 12-year-old adolescents participating in the Intervention Centred on Adolescents' Physical Activity and Sedentary Behaviour Study (ICAPS). Weight, height, body fat mass and WHR were measured. Metabolic syndrome components, two inflammatory markers (IL-6 and C-reactive protein), plasma leptin, adiponectin and soluble TNF-alpha receptor 1 (sTNF-alpha R1) were determined. Insulin resistance was estimated by homeostasis model assessment (HOMA) and energy expenditure due to organised leisure-time physical activity (PAE) assessed by questionnaire.

RESULTS

The metabolic syndrome was present in 5.8% of the adolescents. After adjustment for sex, sexual maturity and socio-economic status, a beneficial relationship between PAE and all metabolic syndrome features was found, but only the associations with HOMA and IL-6 were independent of body fat mass and WHR. Adjusted means from the lowest to the highest tertile of PAE were 1.99, 1.80 and 1.78 for HOMA (p=0.04), and 0.88, 0.69 and 0.70 pg/ml for IL-6 (p=0.02). PAE was inversely associated with leptin, independently of body fat mass and WHR (p<10(-2)), but not with adiponectin or sTNF-alpha R1. Further adjustment for adipokines did not change the relationships of PAE with HOMA and IL-6.

CONCLUSIONS/INTERPRETATION

In adolescents, physical activity is inversely related to HOMA and IL-6, independently of adiposity and fat localisation. These relationships are not accounted for by adipokines.

Role of insulin, adipocyte hormones, and nutrient-sensing pathways in regulating fuel metabolism and energy homeostasis: a nutritional perspective of diabetes, obesity, and cancer

Traditionally, nutrients such as glucose and amino acids have been viewed as substrates for the generation of high-energy molecules and as precursors for the biosynthesis of macromolecules. However, it is now apparent that nutrients also function as signaling molecules in functionally diverse signal transduction pathways. Glucose and amino acids trigger signaling cascades that regulate various aspects of fuel and energy metabolism and control the growth, proliferation, and survival of cells. Here, we provide a functional and regulatory overview of three well-established nutrient signaling pathways-the hexosamine signaling pathway, the mTOR (mammalian target of rapamycin) signaling pathway, and the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway. Nutrient signaling pathways are interconnected, coupled to insulin signaling, and linked to the release of metabolic hormones from adipose tissue. Thus, nutrient signaling pathways do not function in isolation. Rather, they appear to serve as components of a larger "metabolic regulatory network" that controls fuel and energy metabolism (at the cell, tissue, and whole-body levels) and links nutrient availability with cell growth and proliferation. Understanding the diverse roles of nutrients and delineating nutrient signaling pathways should facilitate drug discovery research and the search for novel therapeutic compounds to prevent and treat various human diseases such as diabetes, obesity, and cancer.

The glucose clamp reveals an association between adiponectin gene polymorphisms and insulin sensitivity in obese subjects

Results concerning the association of adiponectin gene polymorphisms (single-nucleotide polymorphisms, SNPs) with obesity, type 2 diabetes (T2DM), metabolic disorders and insulin resistance have not lead to definite conclusions. The aim of our study was to investigate a possible association between the -11391G>A and -11377C>G SNPs of adiponectin gene and measure of insulin sensitivity evaluated by the hyperinsulinemic-euglycemic clamp in a group of 'uncomplicated' obese subjects (with no associated comorbidities) (n=99, mean age 35 years) with a history of obesity lasting at least 10 years. The study of uncomplicated obese subjects, free of possible confounding factors that could interfere with insulin sensitivity, such as pharmacological treatment, provides a good model to assess insulin sensitivity per se. We observed that subjects homozygous for the G allele at locus -11391 had lower M (mg/kg min)/fat-free mass (FFM) index and adiponectin levels compared to subjects with GA+AA genotypes (P=0.002 and P=0.03, respectively) and subjects carrying the -11377G variant had lower M (mg/kg min)/FFM index and adiponectin levels compared to noncarriers (P=0.003 and P=0.03, respectively). Our results imply that the two promoter SNPs, -11391G>A and -11377C>G, of the adiponectin gene are associated with a reduced insulin sensitivity evaluated by hyperinsulinemic-euglycemic clamp in obese subjects.

Pharmacological targeting of adipocytes/fat metabolism for treatment of obesity and diabetes

Obesity is now recognized as a rapidly increasing worldwide threat to health, largely as a result of causing diabetes. Thus, considerable efforts are underway in the pharmaceutical industry to find drugs to treat this condition. Target validation in various academic and industrial laboratories has revealed a number of potential molecular targets in fat cells or adipocytes. By definition, obesity is too much fat, and we here review efforts to treat obesity and, by proxy, diabetes by modulating the metabolic state of adipocytes.

Body fat at birth and cord blood levels of insulin, adiponectin, leptin, and insulin-like growth factor-I in small-for-gestational-age infants

BACKGROUND

Low birthweight has been associated with an increased risk of obesity, insulin resistance, and diabetes in adulthood. The aim of this study was to evaluate IGF-I, adiponectin, insulin levels, and body fat in small-for-gestational-age (SGA) infants at birth.

METHODS

We performed a transverse comparative study in SGA and appropriate-for-gestational-age (AGA) infants. The study was conducted at the Hospital of Gynecology and Obstetrics in Leon, Mexico. Weight, length, and percent of body fat were evaluated during the first 48 h of birth. Glucose, insulin, leptin, adiponectin, and IGF-I levels in cord blood were measured.

RESULTS

We studied 100 infants (50 SGA and 50 AGA). A history of diabetes in a second-degree relative was higher in SGA infants than in AGA infants (48.0 vs. 30.0%, respectively; p = 0.03). Glucose, adiponectin, insulin and IGF-I levels were similar between the groups. Leptin levels and percentage of body fat were lower in SGA than AGA (15.3 vs. 23.4 ng/mL; p = 0.003, 11.1 vs. 12.7%; p <0.001, respectively). Logistic regression analysis showed that length, percentage of body fat, and leptin levels were positively associated with birthweight. However, leptin levels were not independent of percentage of body fat.

CONCLUSIONS

Low body fat and leptin levels, but no evidence of increased metabolic risk at birth, were found in SGA infants.

Metabolic Syndrome Negatively Influences Disease Progression and Prognosis in Aortic Stenosis

OBJECTIVES

This study sought to examine the association between the metabolic syndrome (MS) and the progression of aortic stenosis (AS).

BACKGROUND

It has been suggested that aortic valve sclerosis and its progression to AS are caused by an atherosclerotic process. Metabolic syndrome is associated with a higher risk of vascular atherosclerosis. Thus, we hypothesized that the atherogenic features of MS could negatively influence disease progression and prognosis in patients with AS.

METHODS

We retrospectively analyzed the data of 105 consecutive patients (age 69 +/- 12 years, 64 men) with at least moderate AS. Of these patients, 40 (38%) had MS identified according to the modified clinical criteria proposed by the National Cholesterol Education Program-Adult Treatment Panel III. The hemodynamic progression of AS was assessed by the measurement of the annualized decrease in valve area during the follow-up period of the study, which averaged 28 +/- 13 months. Event-free survival was defined as the absence of death or aortic valve replacement during follow-up.

RESULTS

The hemodynamic progression of the stenosis was twice as fast (-0.14 +/- 0.13 cm2/year vs. -0.08 +/- 0.08 cm2/year, p = 0.008) and the three-year event-free survival was markedly lower (44 +/- 8% vs. 69 +/- 6%, p = 0.002) among patients with MS. In multivariate analysis, MS was found to be a strong independent predictor of both stenosis progression (p = 0.006) and event-free survival (odds ratio 3.85, 95% CI 1.96 to 7.58, p < 0.001).

CONCLUSIONS

The present study is the first to report that MS is associated with a faster disease progression and worse outcome in patients with AS. Such findings open new avenues of research and provide a strong impetus for the elaboration of additional prospective studies focusing on this association.

Effects of eicosapentaenoic acid (EPA) on adiponectin gene expression and secretion in primary cultured rat adipocytes

Adiponectin, a hormone produced by adipocytes, is involved in glucose metabolism and insulin sensitivity. The production of this adipokine is impaired in obesity and insulin resistance. Eicosapentaenoic acid (EPA) is a dietary n-3 polyunsaturated fatty acid that improves insulin sensitivity in several models of obesity and diabetes, which has been suggested to be related to adiponectin induction. An increase in adiponectin production has been also associated with an up-regulation of the transcriptional factor PPARgamma. The aim of this trial was to evaluate the direct effects of EPA on adiponectin gene expression and protein secretion in isolated rat adipocytes as well as to explore the potential mechanisms involved. A comparative study with troglitazone, a PPARgamma agonist, was also performed. For these purposes, primary rat adipocytes were cultured with EPA (100 and 200 microM) and with troglitazone (10 microM) for 96 hours. Both EPA and troglitazone improved glucose utilization by adipocytes. As expected, troglitazone enhanced adiponectin secretion and increased PPARgamma gene expression. However, EPA significantly decreased adiponectin gene expression and protein secretion and reduced PPARy mRNA levels, suggesting that the inhibition of adiponectin by EPA is likely to be secondary to the down-regulation of this adipogenic transcription factor. Moreover, these results suggest that other mechanisms different from the direct stimulation of adiponectin by the fatty acid are underlying the insulin-sensitizing properties observed after EPA treatment in vivo.