Serum leptin concentration and insulin sensitivity in men with abdominal obesity

Fasting plasma leptin level is a surrogate measure of insulin sensitivity

CONTEXT

Published studies indicate marked variability in plasma leptin levels among persons with similar body mass index (BMI). We tested the hypothesis that such variations in leptin levels reflect differences in insulin sensitivity.

SUBJECTS AND METHODS

Using euglycemic clamp, we assessed insulin sensitivity (ISI) in 57 nondiabetic adults (36 women, 21 men), whose BMI ranged from 20 to 78 kg/m2. We identified 38 age-matched subjects, stratified by fasting leptin (normal, <15 ng/ml vs. high, >or=15 ng/ml) and BMI (nonobese, <27 kg/m2 vs. overweight/obese, BMI>or=27 kg/m2) and compared ISI across the four strata.

RESULTS

Fasting leptin levels correlated with ISI (r=-0.66 in men and -0.60 in women). In a multivariate regression model, leptin emerged as a strong predictor of ISI (r=-0.41, P=0.0002) after controlling for adiposity, whereas insulin weakened as a predictor (r=-0.32, P=0.0116). From regression plots of ISI vs. BMI and leptin, a BMI greater than 27 kg/m2 and a leptin level greater than 15 ng/dl strongly predicted decreased ISI. A fasting leptin cutoff of 15 ng/ml for detection of insulin sensitivity has a sensitivity of 72.7%, specificity of 56.3%, and positive predictive value of 69.6%. Overweight/obese subjects with fasting leptin less than 15 ng/ml were 100% more insulin sensitive than control subjects with leptin greater than 15 ng/ml.

CONCLUSIONS

Insulin sensitivity explains about 40% of the variance in fasting leptin levels. Thus, fasting plasma leptin levels probably serve as an endogenous response to ambient insulin resistance and may provide a surrogate measure of insulin action.

Pegylated leptin antagonist is a potent orexigenic agent: preparation and mechanism of activity

Leptin, a pleiotropic adipokine, is a central regulator of appetite and weight and a key immunomodulatory protein. Although inborn leptin deficiency causes weight gain, it is unclear whether induced leptin deficiency in adult wild-type animals would be orexigenic. Previous work with a potent competitive leptin antagonist did not induce a true metabolic state of leptin deficiency in mice because of a short circulating half-life. In this study, we increased the half-life of the leptin antagonist by pegylation, which resulted in significantly increased bioavailability and retaining of antagonistic activity. Mice administered the pegylated antagonist showed a rapid and dramatic increase in food intake with weight gain. Resulting fat was confined to the mesenteric region with no accumulation in the liver. Serum cholesterol, triglyceride, and hepatic aminotransferases remained unaffected. Weight changes were reversible on cessation of leptin antagonist treatment. The mechanism of severe central leptin deficiency was found to be primarily caused by blockade of transport of circulating leptin across the blood-brain barrier with antagonisms at the arcuate nucleus playing a more minor role. Altogether we introduce a novel compound that induces central and peripheral leptin deficiency. This compound should be useful in exploring the involvement of leptin in metabolic and immune processes and could serve as a therapeutic for the treatment of cachexia.

Cardiovascular metabolic syndrome - an interplay of, obesity, inflammation, diabetes and coronary heart disease

Cardiovascular disease is currently one of the biggest causes of morbidity and mortality facing humanity. Such a paradigm shift of disease pattern over the last century has only worsened due to the alarming global prevalence of obesity and type 2 diabetes. In recent years there is increasing focus on inflammation as one of the key players in the patho-physiology of these disorders. In addition to these overt risk factors new research is unraveling the significance of a constellation of early metabolic abnormalities that include weight gain, insulin resistance, prehypertension and a specific pattern of dyslipidaemia. There exists a complex interrelationship of these various metabolic disorders and their effect on cardiovascular system. Simplified explanation can be that inflammation increases insulin resistance, which in turn leads to obesity while perpetuating diabetes, high blood pressure, prothrombotic state and dyslipidaemia. While inflammation and insulin resistance have direct adverse effects on cardiac muscle, these metabolic abnormalities as a whole cause causes cardiovascular complications; warranting a multi pronged therapeutic and preventive approach for the 'Cardiovascular Metabolic Syndrome' as an entity.

Leptin levels in obese women with and without type 2 diabetes mellitus

INTRODUCTION

The role of leptin has been more clear in the endocrinology area after the discovery of its secretion from the adipose tissue. The aim of the study is to investigate the leptin levels in obese women in whom type 2 diabetes mellitus were present or absent.

MATERIALS AND METHODS

Thirty-five obese women with type 2 diabetes mellitus (group 1) and 34 obese women without type 2 diabetes mellitus (group 2) were enrolled in the study. In both groups the body mass index (BMI), waist circumference, and waist-to-hip ratio were measured. Leptin, HbA1c, creatinine and the lipid profile were assessed.

RESULTS

Leptin was found to be statistically significantly lower in group 1 than in group 2 (40.22 +/- 17.77 ng/ml versus 50.12 +/- 15.51 ng/ml, respectively; p = 0.019). It was well correlated with BMI in group 1 (r = 0.60, p = 0.0001). In group 1 also, correlation of leptin was moderate with creatinine and high-density lipoprotein-cholesterol (r = 0.36, p = 0.037 versus r = 0.37, p = 0.027, respectively), whereas triglyceride had a negative correlation (r = -0.34, p = 0.046). In group 2, the only significant correlation with leptin was BMI (r = 0.41, p = 0.02). Leptin was also significantly lower in 17 subjects with poorly controlled diabetes mellitus than in 18 well-controlled diabetics (33.54 +/- 15.82 ng/ml versus 44.61 +/- 17.54 ng/ml, respectively; p = 0.038).

CONCLUSION

Since leptin is lower in obese women with diabetes than without diabetes and additionally it is even lower in the poorly controlled diabetes subgroup, we think that further studies a rerequired to make clear the issue for lower leptin levels, whether it is a reason or an outcome.

Leptin levels in obese women with and without type 2 diabetes mellitus

INTRODUCTION: The role of leptin has been more clear in the endocrinology area after the discovery of its secretion from the adipose tissue. The aim of the study is to investigate the leptin levels in obese women in whom type 2 diabetes mellitus were present or absent. MATERIALS AND METHODS: Thirty-five obese women with type 2 diabetes mellitus (group 1) and 34 obese women without type 2 diabetes mellitus (group 2) were enrolled in the study. In both groups the body mass index (BMI), waist circumference, and waist-to-hip ratio were measured. Leptin, HbA1c, creatinine and the lipid profile were assessed. RESULTS: Leptin was found to be statistically significantly lower in group 1 than in group 2 (40.22 +/- 17.77 ng/ml versus 50.12 +/- 15.51 ng/ml, respectively; p = 0.019). It was well correlated with BMI in group 1 (r = 0.60, p = 0.0001). In group 1 also, correlation of leptin was moderate with creatinine and high-density lipoprotein-cholesterol (r = 0.36, p = 0.037 versus r = 0.37, p = 0.027, respectively), whereas triglyceride had a negative correlation (r = -0.34, p = 0.046). In group 2, the only significant correlation with leptin was BMI (r = 0.41, p = 0.02). Leptin was also significantly lower in 17 subjects with poorly controlled diabetes mellitus than in 18 well-controlled diabetics (33.54 +/- 15.82 ng/ml versus 44.61 +/- 17.54 ng/ml, respectively; p = 0.038). CONCLUSION: Since leptin is lower in obese women with diabetes than without diabetes and additionally it is even lower in the poorly controlled diabetes subgroup, we think that further studies a rerequired to make clear the issue for lower leptin levels, whether it is a reason or an outcome.

Effect of central and peripheral body fat distribution on sympathetic and baroreflex function in obese normotensives

BACKGROUND

Previous studies have shown that obesity is characterized by a sympathetic overactivity coupled with an insulin resistance state and a baroreflex impairment. The present study was set out to compare the effects of peripheral versus central obesity on sympathetic, metabolic and reflex function.

METHODS

In 36 lean subjects (age 35.8 +/- 1.4 years, mean +/- SEM), 20 subjects with peripheral obesity (PO) and 26 subjects with central obesity (CO), all age-matched and with normal blood pressure values, we measured beat-to-beat arterial blood pressure (Finapres), heart rate (HR, ECG), homeostasis model assessment (HOMA) index, plasma norepinephrine (NE, high-performance liquid chromatography) and postganglionic muscle sympathetic nerve traffic (MSNA, microneurography) at rest and during baroreceptor stimulation and deactivation induced by stepwise intravenous infusions of phenylephrine and nitroprusside, respectively.

RESULTS

Both HOMA index, NE and MSNA values were significantly increased (P < 0.01) in obese as compared with lean individuals. Subjects with CO displayed MSNA and HOMA values significantly greater than those found in individuals with PO (65.4 +/- 2.0 versus 47.9 +/- 1.9 bs/100hb and 2.85 +/- 0.10 versus 2.43 +/- 0.11 a.u., respectively, P < 0.05 for both). Both in male and female subjects with CO or PO, MSNA, HOMA index and waist-to-hip ratio were significantly related to each other. Baroreceptor-HR and -MSNA control was significantly (P < 0.01) impaired in obese as compared with lean subjects, the degree of impairment being similar in CO and PO.

CONCLUSIONS

These data suggest that CO is characterized by a sympathetic activation greater for magnitude than that detectable in PO. This appears not to be related to gender or to baroreflex mechanisms but rather to metabolic factors, i.e. to the greater insulin resistance characterizing CO.

Serum leptin levels in premature pubarche and prepubertal girls with and without obesity

Leptin can be regarded as a marker of the nutritional status of the body. This study was performed to determine the correlation of leptin levels with insulin (I) and androgens in girls with premature pubarche (PP) and prepubertal controls (C) with (OB) or without (nOB) obesity. We studied 25 girls with PP and 14 C; girls were dived into two subgroups according to body mass index (BMI): OB (18 PP and 8 C) and nOB (7 PP and 6 C). Obesity was defined as BMI >95th percentile for chronological age. Serum levels of leptin, I, glucose (G), DHEAS, testosterone, androstenedione (A), cortisol, SHBG, IGFBP-1 and lipid profile were measured. The fasting G to I ratio (FGIR) was calculated and FGIR <7 was considered as suggestive of I resistance (IR). Data were analyzed comparing PP vs C and OB vs nOB. Serum DHEAS (0.60 +/- 0.45 vs 0.18 +/- 0.22 microg/ml) and A (895.5 +/- 420.4 vs 457.0 +/- 352.1 pg/ml) levels were significantly higher in PP than C. Other hormonal and metabolic parameters were similar. Serum leptin (30.8 +/- 18.3 vs 8.1 +/- 5.9 ng/ml), A (841.8 +/- 471.1 vs 522.5 +/- 317.2 pg/ml), DHEAS (0.53 +/- 0.44 vs 0.31 +/- 0.39 microg/ml), G (88.4 +/- 8.8 vs 80.2 +/- 8.1 mg/dl), I (13.5 +/- 7.7 vs 5.1 +/- 3.7 microU/ml) and total cholesterol (TC) (180.5 +/- 30.9 vs 161.8 +/- 29.5 mg/dl) levels were greater in the OB than in the nOB group. IR was observed in 10 girls with OB and in one with nOB. Leptin was correlated with BMI (r = 0.83), SHBG (r = -0.44), IGFBP-1 (r = -0.47), I (r = 0.37), A (r = 0.48) and TC (r = 0.36), but in multiple regression analysis only with BMI (r2 = 0.72, p < 0.001). Girls with PP and prepubertal OB girls showed elevated leptin levels independent of I and androgen levels. Girls with OB had a greater degree of hyperandrogenism and IR. As obesity, IR and hyperandrogenism are common findings in polycystic ovary syndrome (PCOS), which is more prevalent in young women with a history of PP, a role of leptin in PCOS can be suggested. In addition, girls with PP could be considered a population at risk for plurimetabolic syndrome.

Case-control study of anthropometric measures and prostate cancer risk

A population-based case-control study of 988 stage T2 or greater prostate cancer cases and 1063 controls was conducted in Alberta from November 1997 to December 2000 to examine the influence of anthropometric risk factors on the risk of prostate cancer using several different measures. An in-person interview was conducted, and all anthropometric measurements were taken using standardized methods. Respondents also recalled their body weight at each decade from age 20 to the referent year. Several anthropometric variables were derived, and unconditional logistic regression analyses were performed. The multivariable odds ratios, when comparing the highest to the lowest quartile were: for body mass index, OR = 1.12 (95% CI 0.85-1.47); for waist-hip ratio, OR = 1.07 (0.83-1.38); for height, OR = 0.78 (0.60-1.02); for weight, OR = 0.91 (0.70-1.18); for weight gain since age 20, OR = 0.91 (0.70-1.19); and for difference between minimum and maximum adult weight, OR = 0.89 (0.69-1.16). Our study provides evidence for no association between any measures of anthropometry including several derived measures of changes in weight over lifetime and prostate cancer risk.

Clinical and pathophysiological consequences of abdominal adiposity and abdominal adipose tissue depots

OBJECTIVES

To highlight the clinical and metabolic correlates of abdominal obesity and various abdominal adipose tissue depots.

METHODS

We researched the topic using the search terms abdominal obesity, central obesity, visceral obesity, regional obesity, and subcutaneous adipose tissue from MEDLINE (National Library of Medicine, Bethesda, MD), PubMed (National Library of Medicine, Bethesda, MD), Current Contents (Institute for Scientific Information, Thomson Scientific, Philadelphia, PA), and using manual search for the cited references.

RESULTS

Abdominal obesity contributes significantly to the metabolic perturbations and cardiovascular risk in human beings. Abdominal adipose tissue depots (intraabdominal and subcutaneous [deep subcutaneous, posterior subcutaneous]) are metabolically active and appear to be important for the pathogenesis of insulin resistance, dyslipidemia, glucose intolerance, hypertension, hypercoagulable state, and cardiovascular risk. Adipocyte anatomy (size), physiology (growth, catecholamine sensitivity, lipolysis, insulin action), and biochemistry (leptin, plasminogen activator inhibitor-1, cytokines, renin-angiotensin system) are reported to be relatively site-specific, highlighting unique roles of regional adipose tissue depots.

CONCLUSIONS

Several physiological and metabolic parameters are site-specific in abdominal adipose tissue. The epidemiological, clinical, and prognostic significance and relative importance of the regional adipose tissue depots, however, remain to be ascertained.

Type 2 diabetes, cardiovascular risk, and the link to insulin resistance

BACKGROUND

Patients with type 2 diabetes mellitus frequently have coexistent dyslipidemia, hypertension, and obesity, and are at risk for microvascular and macrovascular disease complications such as myocardial infarction, stroke, retinopathy, and microalbuminuria. To optimize cardiovascular health outcomes for patients with type 2 diabetes, strategies to reduce the risks of microvascular and macrovascular disease are needed in clinical practice.

OBJECTIVE

This article provides an overview of the cardiovascular risk profile of patients with type 2 diabetes and discusses the cardiovascular consequences of use of the thiazolidinediones (insulin-sensitizing agents) in the treatment of type 2 diabetes.

METHODS

A literature search of MEDLINE/PubMed was performed to identify relevant articles published from 1966 to April 2003. Search terms used were diabetes, cardiovascular disease, atherosclerosis, dyslipidemia, obesity, hypertension, blood pressure, hyperglycemia, inflammation, C-reactive protein, fibrinolysis, plasminogen activator inhibitor type-1, microalbuminuria, thiazolidinediones, safety, hepatotoxicity, and edema. Bibliographies within the identified articles were also evaluated for additional relevant articles and information.

RESULTS

Recommendations for cardiovascular risk reduction through preventive and therapeutic strategies that target the symptoms of insulin resistance may reduce the microvascular and macrovascular sequelae of diabetes and ameliorate the impact of other components of the metabolic syndrome, including hypertension, hyperglycemia, and obesity. In this regard, thiazolidinediones are promising therapies.

CONCLUSIONS

Early data suggest that, in addition to reducing hyperglycemia, pioglitazone and rosiglitazone effect changes in the dyslipidemic profile, hemodynamics, vascular inflammation, and endothelial functioning of patients with type 2 diabetes. Additional research is needed to further distinguish the cardiovascular benefits of these drugs.

Insulin-leptin-visceral fat relation during weight loss

INTRODUCTION

The relation between insulin-leptin-visceral fat axis during weight loss has not been studied previously.

AIMS

To evaluate the insulin, leptin, and abdominal adiposity relation during weight loss in patients with upper body obesity.

METHODOLOGY

Twenty volunteers (7 men, 13 women) with mean age 50.6+/-6.3 (SD) and upper body obesity (weight 105.4+/-12.3 kg, BMI 35.9+/-2.5 kg/m2) were recruited. Participants were enrolled in a one-arm clinical study using a calorie-deficient diet and an escalating dose regimen of sibutramine, starting with 5 mg daily and increasing in 5-mg increments to 20 mg per day. Body weight, insulin, leptin, glucose, lipids, abdominal computed tomography (CT), and total body electrical conductance (TOBEC) were measured serially at weeks 0, 4, 8, 12, and 24.

RESULTS

Eighteen patients completed the 6-month study: one man and one woman discontinued because of adverse events. With diet and sibutramine, body weight was significantly and continuously reduced throughout the 6-month study. There was a 16.0% (p = 0.0001) reduction in body weight (p < 0.001) and 22.5% (p = 0.0001) decrease in total body fat mass. Abdominal CT scans showed a 28.3% (p = 0.0001) reduction in total abdominal fat, a 26.0% (p = 0.0001) reduction in subcutaneous fat (p < 0.001), and a 31.0% (p = 0.0003) reduction in visceral fat (p < 0.001). There was a 32.0% (p = 0.0008) reduction in leptin levels and 37.9% (p = 0.0001) reduction in insulin levels between baseline and week 4, but no further significant reduction in leptin and insulin levels was observed for the duration of the study. There was a significant correlation between insulin and leptin concentrations throughout the study (p = 0.0001). Leptin was presented as a function of insulin measured at the same time. Significant associations between visceral abdominal fat, subcutaneous fat, and leptin were also observed.

CONCLUSION

In this study, we found that leptin and insulin were related in weight loss. The data suggest that insulin may act as a strong regulator of leptin secretion during weight loss and that circulating leptin levels can be predicted by insulin level. Using sibutramine in conjunction with hypocaloric diet reduced body weight and decreased fat mass significantly. Visceral and subcutaneous abdominal fat depots were shown to decrease. Whether sibutramine exerts any selective reduction of visceral abdominal fat as opposed to total body fat mass will require further clinical investigation.

Maternal endotoxemia results in obesity and insulin resistance in adult male offspring

Events in utero appear to be important factors contributing to the development of somatic disorders at adult age. The aim of this study was to examine whether maternal immune challenge would be followed at adult age by metabolic and endocrine abnormalities in the offspring. Pregnant rats were given injections of either endotoxin (Escherichia coli lipopolysaccharide; 0.79 mg/kg, ip) or vehicle on days 8, 10, and 12 of gestation. Adult male offspring to lipopolysaccharide-exposed dams were heavier than controls (P < 0.05) and showed increased adipose tissue weights (P < 0.05), elevated food intake (P < 0.05), and increased circulating leptin (P < 0.01). The effect of insulin on glucose uptake was reduced, as measured by an euglycemic hyperinsulinemic clamp technique (P < 0.05). Serum levels of 17beta-estradiol and progesterone were elevated (P < 0.01 and P < 0.05, respectively). Baseline levels of corticosterone were normal, but the corticosterone response to stress was attenuated (P < 0.05), and hippocampal glucocorticoid receptor protein was up-regulated (P < 0.05). Female offspring were uninfluenced, except for increased testosterone levels (P < 0.05), increased baseline corticosterone levels (P < 0.05), and enlargement of heart and adrenals (P < 0.05). The results indicate that maternal endotoxemia leads to obesity, insulin resistance, and high serum levels of leptin in the adult male offspring. This study reports a novel animal model of obesity with features of the metabolic syndrome.

Leptin--much more than a satiety signal

Much attention has focused on the effects of leptin as a central satiety agent. There is now a significant amount of evidence that leptin is active in the periphery. This review focuses on the ability of leptin to modify insulin sensitivity, tissue metabolism, stress responses, and reproductive function. Leptin's effect on several of these systems is mediated via the hypothalamic-pituitary axis. Therefore, although in vitro studies provide evidence for direct effects on specific tissues and metabolic pathways, it is essential to consider the interactions between leptin and other regulatory factors in vivo. Little is known about the regulation of peripheral receptor expression or the production of binding proteins. Both of these factors determine the bioactivity of circulating leptin and have the potential to induce a peripheral resistance to leptin, similar to the central "leptin resistance" observed in obese subjects. Future research will clarify which of the endocrine and metabolic actions of peripheral leptin are of physiological relevance and which should be considered a pharmacological manipulation.

Metabolic complications of obesity. Pathophysiologic considerations

Given a specific research interest in human fatty acid metabolism, this article focuses primarily on the evidence surrounding the hypothesis that dysregulation of the fuel release function of fat cells (lipolysis) is an important contributing factor to the health hazards of obesity.

Daily hunger sensation and body compartments: II. Their relationships in obese patients

Hunger sensation (HS) is a signal whose levels change during the 24-h day. The daily mean level of HS was correlated with the human body compartments, as investigated by bioelectrical impedance analysis, to detect the relationship between the orectic perception and both the free fat mass (FFM) and the fat body mass (FBM) in 22 clinically healthy subjects (CHS) (2 M, 20 W, BMI: 18.5-24.0 kg/m2) and 48 obese patients (OP) (4 M, 44 W, BMI: 25.2-54.7 kg/m2). In CHS, the daily mean level of HS correlated positively with the FFM and negatively with the FBM. These correlations were not present in OP. This lack of relationships between HS and the body compartments where energy is maximally consumed (i.e., the FFM) and maximally stored (i.e., the FBM) indicates that the orectic response to energy expenditure and the orectic inhibition to fat accumulation are feedback mechanisms which are impaired in obesity.