An inverse correlation between serum leptin levels and hemoglobin A1c in patients with non-insulin dependent diabetes mellitus

Expression of leptin mRNA as non-invasive biomarker in type 2 diabetes mellitus

CONTEXT

Leptin, an adipocyte-derived signalling molecule that plays important role in the regulation of energy balance, body weight and glucose metabolism.

OBJECTIVE

To evaluate leptin mRNA expression as a predictive biomarker in type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

To detect the expression patterns of leptin mRNA, a quantitative real-time polymerase chain reaction was performed on samples collected from 71 T2DM patients and 32 non-diabetic controls. The receiver operating characteristic curve (ROC) was utilised to assess the discriminatory power of leptin mRNA.

RESULTS

Leptin mRNA levels were reduced significantly in diabetic patients compared with non-diabetic controls (P ≤ .0001). The ROC curve analysis showed a significant association between leptin mRNA levels and T2DM (P ≤ .0001), with a high area under the ROC curve (AUC) of 0.95 (95% CI: 0.89-0.98). The analysis also showed that fasting blood glucose and glycosylated haemoglobin had high AUC values of 0.88 and 0.97 with (95% CI: 0.80-0.93 and 0.92-0.99), respectively.

CONCLUSION

This study shows that the reduced leptin mRNA expression level is significantly associated with T2DM and could be used as a predictive and diagnostic biomarker for T2DM.

Adiponectin, Leptin, and Leptin Receptor in Obese Patients with Type 2 Diabetes Treated with Insulin Detemir

The aim of the present study is to quantitatively assess the expression of selected regulatory molecules, such as leptin, leptin receptor, and adiponectin in the blood of obese patients with type 2 diabetes both before treatment and after six months of pharmacological therapy with the long-lasting insulin analogue, insulin detemir. A significant decrease in the analysed regulatory molecules, i.e., leptin receptor and adiponectin, was found in blood plasma of the patients with untreated type 2 diabetes. These changes were accompanied by an increase in plasma leptin concentrations. Insulin treatment resulted in the normalization of plasma leptin receptor and adiponectin concentrations. The circulating leptin level did not change following anti-diabetic therapy with insulin detemir. Gender was a significant factor modifying the circulating level of all the analysed regulatory active compounds. Bioinformatic analysis was performed using Matlab with the Signal Processing Toolbox. The conducted discriminant analysis revealed that the leptin receptor, Δw(19), and adiponectin, Δw(21), were the parameters undergoing the most significant quantitative changes during the six-month therapy with insulin detemir. The conducted examinations indicated the contribution of adipocytokines—the biologically-active mediators of systemic metabolism, such as leptin and adiponectin in the pathomechanism of disorders being the basis for obesity which leads to development of insulin resistance, which, in turn, results in the occurrence of type 2 diabetes.

Expression of Leptin and Visfatin in Gingival Tissues of Chronic Periodontitis With and Without Type 2 Diabetes Mellitus: A Study Using Enzyme-Linked Immunosorbent Assay and Real-Time Polymerase Chain Reaction

BACKGROUND

The aim of this study is to investigate the protein and gene expression of leptin and visfatin in gingival tissue from patients with chronic periodontitis (CP), patients with CP and type 2 diabetes mellitus (T2DM), and healthy individuals.

METHODS

The study includes 50 individuals: 10 healthy individuals, 20 patients with CP, and 20 patients with CP and T2DM. Plaque index, gingival index, probing depth, and clinical attachment loss were measured, and gingival biopsies were obtained. Leptin and visfatin protein expression in gingival tissues was determined using enzyme-linked immunosorbent assay, and messenger RNA (mRNA) expression was measured via real-time polymerase chain reaction.

RESULTS

The highest leptin mRNA and protein expression was observed in the control group and was significantly (P ≤0.05) different from the CP and CP+T2DM groups. Gingival tissues from patients with CP and T2DM had a significant increase in visfatin and a decrease in leptin gene and protein expression (P <0.05) compared with both controls and patients with CP.

CONCLUSION

Expression of leptin and visfatin in the gingival tissues suggests a possible role for these adipokines in the pathogenesis of CP and T2DM.

Insulin resistance and adipokine levels correlate with early atherosclerosis - a study in prediabetic patients

Cardiovascular risk of prediabetes is still subject to controversies. We analyzed the associations between insulin resistance, adipokines and incipient atherosclerosis estimated by intima-media thickness (IMT) in a cross-sectional study on 122 prediabetic subjects without clinical signs of atherosclerotic disease. Homeostasis model assessment of insulin resistance (HOMA-IR, calculated as fasting insulin × fasting plasma glucose / 22.5), adiponectin, leptin, leptin-to-adiponectin ratio, carotid and femoral IMT were evaluated. We also assessed other parameters related to insulin resistance and adipokines (HbA_1c, anthropometric and lipid parameters), as they may also influence atherosclerosis. Carotid IMT was correlated to adiponectin and leptin-to-adiponectin ratio (all p < 0.05), but not with HOMA-IR or leptin, while femoral IMT showed no relationship with these factors. After adjusting for leptin, leptin-to-adiponectin ratio, triglycerides, HDL-cholesterol, cholesterol-to-HDL ratio, triglycerides-to-HDL ratio and HbA_1c, IMT values became correlated with HOMA-IR. Adjustment for HOMA-IR induced the appearance of new correlations between adipokines and both IMT values. In conclusion, insulin resistance and adipokines seem related to IMT in prediabetic subjects without clinical signs of arterial obstruction.

Dietary milled flaxseed and flaxseed oil improve N-3 fatty acid status and do not affect glycemic control in individuals with well-controlled type 2 diabetes

OBJECTIVE

To determine the effects of dietary consumption of milled flaxseed or flaxseed oil on glycemic control, n-3 fatty acid status, anthropometrics, and adipokines in individuals with type 2 diabetes.

DESIGN

Thirty-four participants were randomized into a parallel, controlled trial.

SUBJECTS

The participants were adults with type 2 diabetes (age 52.4 +/- 1.5 years, body mass index 32.4 +/- 1.0 kg/m(2), n = 17 men and 17 women).

INTERVENTIONS

Participants consumed a selection of bakery products containing no flax (control group [CTL], n = 9), milled flaxseed (FXS, n = 13; 32 g/d), or flaxseed oil (FXO, n = 12; 13 g/d) daily for 12 weeks. The FXS and FXO groups received equivalent amounts of alpha-linolenic acid (ALA; 7.4 g/day).

MEASURES OF OUTCOME

The primary outcome measures were fasting plasma hemoglobin A(1c), glucose, insulin, and phospholipid fatty acid composition. The secondary outcome measures were fasting circulating leptin and adiponectin, as well as body weight, body mass index, and waist circumference. Dietary intake assessment and calculations for homeostasis model assessment for insulin resistance and quantified insulin sensitivity check were also completed.

RESULTS

The FXS and FXO groups had increases in plasma phospholipid n-3 fatty acids (ALA, eicosapentaenoic acid [EPA], or decosapentaenoic acid [DPA], but not docosahexaenoic acid), and the FXO group had more EPA and DPA in plasma phospholipids compared to the FXS group. All groups had similar caloric intakes; however, the CTL group experienced a 4% weight gain compared to baseline (p < 0.05), while both flax groups had constant body weights during the study period. All other parameters, including glycemic control, were unchanged by dietary treatment.

CONCLUSIONS

Milled FXS and FXO intake does not affect glycemic control in adults with well-controlled type 2 diabetes. Possible prevention of weight gain by flax consumption warrants further investigation.

Neurobehavioral deficits in db/db diabetic mice

Recent clinical studies indicate neurobehavioral disturbances in type-2 diabetics. However, there is paucity of preclinical research to support this concept. The validity of db/db mouse as an animal model to study type-2 diabetes and related complications is known. The present study was designed to investigate comprehensively the db/db mouse behavior as preclinical evidence of type-2 diabetes related major neurobehavioral complications. We tested juvenile (5-6weeks) and adult (10-11weeks) db/db mice for behavioral depression in forced swim test (FST), psychosis-like symptoms using pre-pulse inhibition (PPI) test, anxiety behavior employing elevated plus maze (EPM) test, locomotor behavior and thigmotaxis using open field test and working memory deficits in Y-maze test. Both juvenile and adult group db/db mice displayed behavioral despair with increased immobility time in FST. There was an age-dependent progression of psychosis-like symptoms with disrupted PPI in adult db/db mice. In the EPM test, db/db mice were less anxious as observed by increased percent open arms time and entries. They were also hypo-locomotive as evident by a decrease in their basic and fine movements. There was no impairment of working memory in the Y-maze test in db/db mice. This is the first report of depression, psychosis-like symptoms and anxiolytic behavior of db/db mouse strain. It is tempting to speculate that this mouse strain can serve as useful preclinical model to study type-2 diabetes related neurobehavioral complications.

Inflammatory markers are increased in youth with type 1 diabetes: the SEARCH Case-Control study

CONTEXT

Increased inflammation may contribute to type 1 diabetes (T1D) complications.

OBJECTIVE

The objective of the study was to investigate the association of inflammation with obesity, hyperglycemia and dyslipidemia in youth with T1D.

DESIGN

This was a cross-sectional study of youth with and without T1D.

SETTING

The study was conducted in Colorado and South Carolina.

PATIENTS

SEARCH Case-Control participants with T1D [n = 553, mean age 15 yr (range 10-22), median duration 2.7 yr] and without diabetes [n = 215, mean age 15 yr (range 10-22)].

INTERVENTION

This was an observational study.

MAIN OUTCOME MEASURES

IL-6, high-sensitivity C-reactive protein (hsCRP), fibrinogen, and leptin were measured.

RESULTS

Inflammatory markers were evaluated by diabetes status, quartiles of glycated hemoglobin, and obesity using multiple linear regression analyses, adjusted for age, sex, study site, race/ethnicity, T1D duration, body mass index, and pubertal status. Compared with controls, youth with T1D had higher IL-6 and fibrinogen levels at all levels of glycemia and obesity, and hsCRP levels were significantly higher in youth with T1D in the top three quartiles of glycated hemoglobin (> or = 7.2%) and among normal-weight subjects. Leptin was lower in youth with poor glycemic control. Higher hsCRP and fibrinogen were correlated with higher total and LDL cholesterol, and apolipoprotein B in youth with T1D, whereas higher fibrinogen was correlated with higher LDL and apolipoprotein B in controls.

CONCLUSIONS

T1D is characterized by excess inflammation, independent of adiposity and glycemic control. Even T1D youth in good glycemic control had higher levels of IL-6 and fibrinogen than controls. Elevated inflammatory markers were associated with an atherogenic lipid profile, which may contribute to accelerated atherosclerosis in youth with T1D.

Abnormal glucose tolerance is associated with diminished postload change in leptin levels in women

BACKGROUND

It is generally accepted that the metabolic effects of leptin are diminished in the obese due to leptin resistance. Hormone resistance may develop if diurnal (including meal-related) changes in hormone levels are disrupted. We sought to describe leptin changes after a 75 g oral glucose tolerance test (OGTT) in women with a prior diagnosis of gestational diabetes mellitus (a high risk group for the metabolic syndrome) compared to that in healthy controls.

METHODS

In 2000 a retrospective cohort study was performed on women who had been diagnosed with gestational diabetes mellitus (WHO criteria 1985, n = 57) between 1996 and 1998 and on a healthy control female group (n = 36) all of whom had had a prior pregnancy without any diagnosis of diabetes. All the women underwent a standard 75 g OGTT. Serum leptin was measured by radioimmunoassay before and 90 min after the OGTT.

RESULTS

Using multilevel models of change, fasting leptin levels were shown to be associated with body mass index; 10.1% (95% CI 8.1-12.1%) increase per 1 kg/m(2) increase in body mass index), homeostasis model assessment insulin sensitivity; 0.4% (95% CI 0.2-0.7%) decrease per 1% increase in insulin sensitivity); abnormal glucose tolerance (24% decrease, 95% CI 8-37%); and smoking (31% decrease, 95% CI 16-44%). Postload (90 min) leptin levels decreased significantly in women with normal glucose tolerance by 13% (95% CI 8-18%), while no significant change in postload leptin level was apparent in women with abnormal glucose tolerance (3% increase, 95% CI -4% to 29%).

CONCLUSIONS

Disturbed leptin changes were found following an OGTT in women with abnormal glucose tolerance that might be either a cause or a consequence of leptin resistance.

Novel factors as therapeutic targets to treat diabetes. Focus on leptin and ghrelin

BACKGROUND

Obesity is the major cause of type 2 diabetes. In the mid 1990s interest in adipose tissue was revived by the discovery of leptin. The association of obesity and diabetes emphasizes their shared physiopathological features. At the end of the 1990s, ghrelin, a potent gastric orexigenic factor, was found to be involved in obesity. Leptin and ghrelin have opposite actions in several tissues including the regulation of feeding in the brain.

OBJECTIVE/METHODS

To survey the role of leptin and ghrelin in glucose metabolism. We summarize the current state of research and discuss the roles of ghrelin and leptin in glucose homeostases and the potential application of drugs targeting leptin and ghrelin signalling to prevent and treat diabetes.

RESULTS/CONCLUSIONS

A pressing challenge is to determine how leptin, ghrelin and other adipokines or gastric factors are involved in metabolic disorders. Answering these questions will require the development of new pharmacological tools that target specific adipokine systems. Hopefully, new therapeutic targets will be identified.

A high glycemic meal suppresses the postprandial leptin response in normal healthy adults

BACKGROUND/AIMS

To evaluate the metabolic effects of meals with varying glycemic index (GI).

METHODS

We measured the glucose, insulin and leptin responses to two contrasting breakfast cereals in a group of 10 young healthy volunteers. Meals were provided on two separate occasions in random order after a 12-hour overnight fast, and consisted of 50 g of available carbohydrate from either Corn Flakes (Kellogg's), or Fiber One (General Mills). Blood samples were obtained at rest, and 30, 60, 90 and 120 min after eating. The GI was calculated from the glucose response to the test meal normalized against a 50 g oral glucose load.

RESULTS

The GI for Corn Flakes was 125 +/- 17 units and 49 +/- 8 units for Fiber One(R). These meals were classified as high GI and low GI, respectively, and were significantly different from each other (p < 0.0003). The area under the insulin response curve (AUC) following the low glycemic meal was significantly attenuated compared to the high glycemic meal (14,064 +/- 2,694 vs. 6,828 +/- 1,182 pmol/l.min, p < 0.02). The leptin AUC revealed that circulating leptin was suppressed by the high glycemic meal compared to the low (3.1 +/- 1.5 vs. 9.6 +/- 3.6 ng/ml.min, p < 0.04).

CONCLUSIONS

Lower insulin and higher leptin suggests that low glycemic meals promote a postprandial metabolic milieu that is favorable for reduced food consumption; this may be advantageous in the control of obesity and related disorders including insulin resistance and type 2 diabetes.

Adiponectin and leptin: potential tools in the differential diagnosis of pediatric diabetes?

The incidence of type 1 and type 2 diabetes mellitus in the pediatric population has increased over the past decade. The practitioner is often faced with the challenge of differentiating between type 1 and type 2 diabetes at the time of initial diagnosis because of the overlap of clinical and laboratory characteristics between these two entities. Adipokines are proteins secreted by the adipose tissue. Leptin and adiponectin are two adipokines that have been extensively studied in vitro, in animal studies, and in human subjects with type 1 and type 2 diabetes. Leptin and adiponectin play a significant role in the regulation of lipid and carbohydrate metabolism. Adiponectin increases insulin sensitivity in both the liver and skeletal muscle. Leptin decreases appetite, increases energy expenditure, suppresses insulin synthesis and secretion and increases insulin sensitivity. Changes in the secretion or sensitivity to leptin and adiponectin may contribute to the development of type 1 and type 2 diabetes. Adiponectin is higher in adult and pediatric patients with type 1 diabetes compared to those with type 2 diabetes. Data regarding leptin levels are contradictory. Most studies report decreased serum leptin at the time of diagnosis in type 1 diabetes compared to type 2 diabetes subjects and non-diabetic controls. This paper will review basic research and clinical evidence supporting the role of adiponectin and leptin in the development of type 1 and type 2 diabetes and discuss their potential use as tools in the differential diagnosis of pediatric diabetes.

Antihyperglycemic and antioxidant properties of caffeic acid in db/db mice

This study investigated the blood glucose-lowering effect and antioxidant capacity of caffeic acid in C57BL/KsJ-db/db mice. Caffeic acid induced a significant reduction of the blood glucose and glycosylated hemoglobin levels than the control group. The plasma insulin, C-peptide, and leptin levels in caffeic acid group were significantly higher than those of the control group, whereas the plasma glucagon level was lower. Increased plasma insulin by caffeic acid was attributable to an antidegenerative effect on the islets. Caffeic acid also markedly increased glucokinase activity and its mRNA expression and glycogen content and simultaneously lowered glucose-6-phosphatase and phosphoenolpyruvate carboxykinase activities and their respective mRNA expressions, accompanied by a reduction in the glucose transporter 2 expression in the liver. In contrast to the hepatic glucose transporter 2, adipocyte glucose transporter 4 expression was greater than the control group. In addition, caffeic acid significantly increased superoxide dismutase, catalase, and glutathione peroxidase activities and their respective mRNA levels, while lowering the hydrogen peroxide and thiobarbituric acid reactive substances levels in the erythrocyte and liver of db/db mice. These results indicate that caffeic acid exhibits a significant potential as an antidiabetic agent by suppressing a progression of type 2 diabetic states that is suggested by an attenuation of hepatic glucose output and enhancement of adipocyte glucose uptake, insulin secretion, and antioxidant capacity.

Rethinking leptin and insulin action: Therapeutic opportunities for diabetes

Leptin is an adipocyte-derived hormone that primarily acts in the hypothalamus and plays a key role in the regulation of food intake, body weight, energy expenditure and neuroendocrine function. Leptin has direct peripheral effects on several tissues, and it may be independently involved in insulin secretion and action besides its effects on body weight regulation. Basal plasma leptin and insulin concentrations correlate with each other. Insulin and glucose appear to increase leptin secretion. In turn, leptin increases peripheral insulin sensitivity while decreasing insulin secretion from pancreatic beta cells. Leptin increases skeletal muscle glucose uptake and oxidation, and suppresses hepatic glucose output. Effects of leptin on lipid metabolism might reduce lipotoxicity and therefore contribute to the improvement of hepatic, skeletal and whole body insulin sensitivity. Leptin is the first adipokine used in the treatment of hypoleptinemic clinical disorders. Although leptin therapy has limited success in common obesity, it has impressive effects in congenital leptin deficiency, lipoatrophic diabetes and syndromes of severe insulin resistance. Leptin has been reported to ameliorate hyperinsulinemia and diabetes in the clinical setting of congenital leptin deficiency. It also improves hyperglycemia, insulin resistance, hyperinsulinemia, dyslipidemia and hepatic steatosis in lipoatrophic diabetes. These promising results warrant clinical trials to test the hypothesis that leptin alone or with classical antidiabetic agents may potentially be beneficial in the treatment of hypoleptinemic non-obese individuals with glucose intolerance and diabetes. This review summarizes the clinical applications of leptin, particularly emphasizing the effects of leptin on glucose homeostasis.

The hypoglycemic effects of hesperidin and naringin are partly mediated by hepatic glucose-regulating enzymes in C57BL/KsJ-db/db mice

Dietary antioxidant compounds such as bioflavonoids may offer some protection against the early stage of diabetes mellitus and the development of complications. We investigated the effect of citrus bioflavonoids on blood glucose level, hepatic glucose-regulating enzymes activities, hepatic glycogen concentration, and plasma insulin levels, and assessed the relations between plasma leptin and body weight, blood glucose, and plasma insulin. Male C57BL/KsJ-db/db mice (db/db mice, 5 wk old), an animal model for type 2 diabetes, were fed a nonpurified diet for 2 wk and then were fed an AIN-76 control diet or the control diet supplemented with hesperidin (0.2 g/kg diet) or naringin (0.2 g/kg diet). Hesperidin and naringin supplementation significantly reduced blood glucose compared with the control group. Hepatic glucokinase activity and glycogen concentration were both significantly elevated in the hesperidin- and the naringin-supplemented groups compared with the control group. Naringin also markedly lowered the activity of hepatic glucose-6-phosphatase and phosphoenolpyruvate carboxykinase compared with the control group. Plasma insulin, C-peptide, and leptin levels in the db/db mice from the 2 bioflavonoid-supplemented groups were significantly higher than those of the control group. Furthermore, plasma leptin was positively correlated with plasma insulin level (r = 0.578, P < 0.01) and body weight (r = 0.541, P < 0.05), and was inversely correlated with the blood glucose level (r = -0.46, P < 0.05). The current results suggest that hesperidin and naringin both play important roles in preventing the progression of hyperglycemia, partly by increasing hepatic glycolysis and glycogen concentration and/or by lowering hepatic gluconeogenesis.

Increased maternal plasma leptin in early pregnancy and risk of gestational diabetes mellitus

OBJECTIVE

Emerging evidence suggests that leptin, an adipocyte-derived hormone, may have independent direct effects on both insulin secretion and action, in addition to its well documented effects on appetite and energy expenditure. Some, but not all, previously published studies suggest that maternal leptin concentrations may be increased in pregnancies complicated by gestational diabetes mellitus (GDM). We examined the association between plasma leptin concentration and GDM risk.

METHODS

Women were recruited before 16 weeks of gestation and were followed up until delivery. Maternal plasma leptin concentrations (collected at 13 weeks of gestation) were measured by using immunoassay. We used generalized linear models to estimate relative risks and 95% confidence intervals.

RESULTS

GDM developed in 5.7% of the cohort (47 of 823). Elevated leptin concentrations were positively associated with GDM risk (P for trend <.001). After adjusting for maternal prepregnancy adiposity and other confounders, women with leptin concentrations of 31.0 ng/mL or higher experienced a 4.7-fold increased risk of GDM (95% confidence interval 1.2, 18.0) as compared with women who had concentrations of 14.3 ng/mL or lower. We noted a strong linear component of trend in risk of GDM with increasing maternal plasma leptin concentration. Each 10-ng/mL increase in the leptin concentration was associated with a 20% increase in GDM risk (relative risk 1.2; 95% confidence interval 1.0, 1.3).

CONCLUSIONS

Hyperleptinemia, independent of maternal adiposity, in early pregnancy appears to be predictive of an increased risk of GDM later in pregnancy. Additional larger prospective cohort studies are needed to confirm and more precisely assess the etiologic importance of hyperleptinemia in pregnancy.

LEVEL OF EVIDENCE

II-2

Does leptin link sleep loss and breathing disturbances with major public diseases?

Leptin is best known as a regulator of energy homeostasis, but it also interacts with sleep and breathing. Leptin secretion increases at night and decreases during the day. The circadian secretory profile of leptin is determined both by the hypothalamic circadian pacemaker and sleep-wake cycle. Leptin is also a powerful respiratory stimulant. Serum leptin levels are higher in obstructive sleep apnoea syndrome but lower during extended sleep deprivation in healthy subjects or in narcolepsy. Abnormalities in serum leptin concentrations have recently been linked with deleterious effects on weight control, cardiovascular health and glucose regulation. Since sleep curtailment and sleep-disordered breathing are epidemics of the modern society, better understanding of leptin pathophysiology could open new perspectives to pathophysiology of major public diseases, including obesity and metabolic syndrome.

Leptin: obesity, diabetes and other peripheral effects--a review

There is an increasing epidemic of obesity in the Western and developing world that has not spared children and, hence, is of great concern. Obesity presents numerous physiological and psychosocial problems for the child. Childhood obesity not only increases the risk of obesity in adulthood, it is associated with type 2 diabetes mellitus; is the leading cause of pediatric hypertension; increases the risk of coronary heart disease; and increases stress on the weight-bearing joints. Social and psychological problems are also significant consequences of obesity in children, with lowering of self-esteem and its effects on relationships with peers. Obesity is clearly associated with increased levels of the recently discovered hormone, leptin. Leptin, secreted from adipocytes, is involved in the regulation of food intake, energy expenditure, and energy balance in humans. This review focuses on the hormone, leptin, in an effort to document some of its many local and systemic effects on the body and, specifically, its potential role in obesity-induced diabetes.

Leptin: metabolic control and regulation

Leptin, a protein released from adipose tissue, is being recognized to play an integral role in endocrine regulation of metabolism. While it is clearly evident that leptin is decreased during caloric restriction, the response of leptin to other types of stress has been plagued by conflicting data. With hypoglycemia stress, the literature may conflict because experimentally hypoglycemia is induced with infusion of insulin, an endocrine factor that can increase leptin levels. With exercise, leptin's response may depend on duration and intensity of exercise. While it has been clearly shown that the sympathetic nervous system (SNS) inhibits leptin secretion in a variety of experimental modes, the hypothalamic-pituitary-adrenal (HPA) axis may stimulate leptin secretion. This creates a paradox of leptin regulation during stress since both systems are activated with stress. If the SNS inhibition overrides the HPA axis' activation of leptin secretion, leptin's role during stress may be to allow a shifting of fuel consumption towards carbohydrate utilization. In type 1 diabetes mellitus, autonomic dysfunction may prevent the fall in leptin during stress. Although obesity is associated with type 2 diabetes mellitus, patients may have decreased leptin levels, especially when glucose is poorly controlled. This may contribute to further obesity and worsening of the disease. The purpose of this review to is critically analyze the literature regarding the impact of different types of stress on leptin secretion, the function of leptin during stress, and the role of leptin in the pathophysiology of diabetes.

The effects of metformin and diet on plasma testosterone and leptin levels in obese men

OBJECTIVE

The aim of this study was to investigate the effects of combined hypocaloric diet and metformin on circulating testosterone and leptin levels in obese men with or without type 2 diabetes.

RESEARCH METHODS AND PROCEDURES

Twenty obese men with type 2 diabetes (mean body mass index [BMI]: 35.5 +/- 1.1 kg/m(2)) and 20 nondiabetic obese men were enrolled in the study. We measured serum follicle-stimulating hormone, luteinizing hormone (LH), total testosterone (TT), free testosterone (FT), sex-hormone-binding globulin (SHBG), dehydroepiandrosterone sulfate (DHEAS), and plasma leptin levels before and 3 months after metformin treatment. Both groups were placed on a hypocaloric diet and 850 mg of metformin taken orally twice daily for 3 months.

RESULTS

Metformin and hypocaloric diets led to decreases in BMI and waist and hip circumferences in both groups. A significant decrease in TT levels in the diabetic group and FT levels in the control group was found, whereas follicle-stimulating hormone, LH, and DHEAS levels were not changed significantly. A significant increase in SHBG levels was observed in the control group but not in the patient group. Leptin levels also decreased after treatment in both groups. Decreased testosterone levels were not correlated to changes in waist and hip circumference, waist-to-hip ratio, BMI, and levels of fasting blood glucose, leptin, SHBG, or DHEAS in the diabetic group. However, a decrease in FT was correlated to changes in the levels of SHBG (r = -0.71, p = 0.001) and LH (r = 0.80, p = 0.001) but not to other parameters.

DISCUSSION

We conclude that metformin treatment combined with a hypocaloric diet leads to reduced FT levels in obese nondiabetic men and to reduced TT levels in obese men with type 2 diabetes. Increased SHBG levels may account for the decrease in FT levels in the former group.

Relationship of leptin level with metabolic disorders and hypertension in Japanese type 2 diabetes mellitus patients

Leptin is considered to play an important role in the regulation of body weight and metabolism in obese individuals. However, the relationship of leptin with metabolic disorders or vascular complications in type 2 diabetic patients has yet to be elucidated. In this study, we investigated the association of leptin levels with clinical parameters (glycemic control, lipid levels, abdominal fat distribution) and investigated the leptin levels of diabetic patients with and without vascular complications in Japanese diabetic patients. In male and female patients, leptin levels were significantly associated with body mass index (BMI), percent body fat, insulin level, triglyceride (TG) level, total abdominal fat area (TFA), visceral fat area (VFS), and subcutaneous fat area (SFA). Only in male patients, leptin levels were inversely correlated with HDL-cholesterol, fasting plasma glucose (FPG), and HbA(1C). Leptin levels in male and female patients with hypertension were higher than in those without hypertension. Leptin levels of both males and females with angiopathy were not statistically different from those without angiopathy. In conclusion, leptin is involved in various metabolic disorders and hypertension, and we speculate that it may not be strongly associated with vascular complications in Japanese diabetic individuals.