Changes In Leptin Concentrations Research Articles

The Beneficial Effects of Nordic Walking Training Combined with Time-Restricted Eating 14/24 in Women with Abnormal Body Composition Depend on the Application Period.

The aim of the study was to assess the impact of two lengths of Nordic walking (NW) training interventions combined with time-restricted eating (TRE) on improving body-composition parameters, lipid profiles, and levels of selected adipokines in women with elevated body mass. Overweight and obese women (n = 55, age: 21-85) were recruited. Four groups were selected: 6 weeks (SG6, n = 13) and 12 weeks intervention (SG12, n = 13); and two control groups: CON6 (n = 13) and CON12 (n = 13). The training sessions took place three times a week (60 min each) and were conducted outdoors under the supervision of a professional coach. The training intensity was determined individually. The extended NW program combined with TRE induced a significant weight reduction in SG12 by 1.96 kg (p = 0.010) and fat tissue by 1.64 kg (p = 0.05). The proposed interventions did not affect LBM, TBW [kg], VFA, and lipid profile. The LDL/HDL ratio changed with a small size effect. The leptin concentration differed between groups (p = 0.006), but not over time. For resistin, the differentiating factor was time (p = 0.019), with lower results observed after the intervention. The change in leptin concentration was negatively correlated with its baseline concentration (p = 0.025). Extended to 12 weeks, this intervention allows for an improvement in body composition. Neither 6 nor 12 weeks of training and fasting affected the lipoprotein profile. It is, therefore, indicated to recommend prolonged training protocols and to inform patients that beneficial effects will be seen only after prolonged use of training and time-restricted eating.

Effects of coffee supplementation on homocysteine and leptin levels: a systematic review and meta-analysis of clinical trials.

It has been reported that the consumption of antioxidant foods and beverages may benefit the development of cardiovascular risk factors. However, the impact of coffee consumption on some of these factors, such as homocysteine and leptin is controversial. Some clinical trials have suggested that coffee administration increases plasma total homocysteine levels, while others have found no significant changes in leptin concentrations. This study aimed to assess the effects of coffee supplementation on homocysteine and leptin concentrations in a meta-analysis of clinical trials. PubMed, Web of Science, Scopus, ClinicalTrials.gov, and Google Scholar databases were searched from inception to September 29, 2021. A fixed-effects model and the generic inverse variance weighting method were used for meta-analysis. The meta-analysis demonstrated that coffee administration significantly increases homocysteine levels (WMD: 0.55 µmol/L, 95% CI: 0.17, 0.93, p = 0.005, I2 = 0%) but has no significant changes in leptin concentrations (WMD: 1.34 ng/mL, 95% CI: -0.78, 3.45, p = 0.21, I2 = 0%). Additionally, the sensitivity analysis was robust for both homocysteine and leptin levels. The results of the present meta-analysis revealed that coffee supplementation raises serum homocysteine concentrations but has no effect on circulating leptin levels.

The role of leptin in monitoring training loads during rowing: a systematic review

Objective: In competitive sports, too small or too large loads lead to poor sports results. Situation of overload are particularly dangerous to the body, which may lead to overtraining. In this work, the literature on the possibility of assessing training loads with the use of leptin concentration measurement in men and women practicing rowing was analysed. Materials and methods: A systematic review was performed using the Scopus, Pubmed and Google Scholar databases between 1995-2020. After an initial analysis of 56 articles and taking the analysed topics into account, 25 articles were included in this review. As part of the review, data for 75 rowers were analysed. The usefulness of leptin - a hormone produced by adipose tissue - as a marker of training loads in several sports disciplines, with particular emphasis on rowing, was evaluated. Within this context, the role of leptin may be to control these loads due to its relatively high sensitivity in response to increases in training intensity or volume. The presented general characteristics of rowing and the physiological basis of exercise are the background for considerations on the possibility of using leptin as a burden marker in this discipline. Results: Due to the fact that the concentration of leptin correlates with the content of adipose tissue and BMI (Body Mass Index), its changes may inform about training loads directly related to the amount of energy expenditure. A review of the literature from the last 25 years, i.e. from the moment when this hormone was discovered, allowed to formulate the thesis that leptin may be a marker of training loads, however, determining its concentration makes sense when the same factors that may affect its secretion are taken into account each time. Conclusions: Training in rowing, that involves high training loads, causes significant changes in blood leptin levels. Training periods with high exercise load, associated with a significant increase in energy expenditure, lead to a decrease in resting leptin concentration, while periods with less load increase it. The main factor determining changes in leptin concentration during training is the amount of energy expenditure, which in the case of rowing involving very large muscle groups, is very high. Although the amount of energy expenditure in training, leading to a decrease in leptin concentration is difficult to determine, the energy expenditure cannot be less than 800 kcal in a single training unit.

Early Post-Transplant Leptin Concentration Changes in Kidney Transplant Recipients.

Background and Objectives: Kidney transplant recipients represent a unique population with metabolic abnormalities, altered nutritional and immune status, as well as an imbalanced regulation of adipocytokine metabolism. Leptin is a hormonally active protein mainly produced by fat tissue that modulates appetite, satiety, and influences growth, energy, and bone metabolism. There has been great interest in the role of this hormone in chronic kidney disease-related protein energy wasting; thus, a positive leptin correlation with body mass index and fat mass was confirmed. This study was designed to determine the association of pre and post-kidney transplant leptin concentration with nutritional status and body composition. Materials and Methods: We studied 65 kidney transplant recipients. Nutritional status was evaluated before kidney transplantation and 6 months later using three different malnutrition screening tools (Subjective Global Assessment Scale (SGA), Malnutrition Inflammation Score (MIS), and Geriatric Nutritional Risk Index (GNRI)), anthropometric measurements, and body composition (bioelectrical impedance analysis (BIA)). Demographic profile, serum leptin levels, and other biochemical nutritional markers were collected. Statistical analysis was performed with R software. Results: Median age of the studied patients was 45 years, 42% were females, and 12% had diabetes. Leptin change was associated with body weight (p < 0.001), waist circumference (p < 0.001), fat mass (p < 0.001) and body fat percentage (p < 0.001), decrease in parathyroid hormone (PTH) (p < 0.001) transferrin (p < 0.001), diabetes mellitus (p = 0.010), and residual renal function (p = 0.039), but not dependent on dialysis vintage, estimated glomerular filtration rate (eGFR), or delayed graft function at any time during the study. After adjustment for age and sex, body mass index (BMI) (p < 0.001), fat mass (p < 0.001), and body fat percentage (p < 0.001) were independent variables significantly associated with post-transplant leptin change. Lower leptin values were found both before and after kidney transplantation in the SGA B group. GNRI as a nutritional status tool was strongly positively related to changes in leptin within the 6-month follow-up period. Conclusions: Kidney transplant recipients experience change in leptin concentration mainly due to an increase in fat mass and loss of muscle mass. GNRI score as compared to SGA or MIS score identifies patients in whom leptin concentration is increasing alongside an accumulation of fat and decreasing muscle mass. Leptin concentration evaluation in combination with BIA, handgrip strength measurement, and GNRI assessment are tools of importance in defining nutrition status in the early post-kidney transplant period.

Neonatal and Adolescent Adipocytokines as Predictors of Adiposity and Cardiometabolic Risk in Adolescence.

This study aimed to examine associations of changes in leptin and adiponectin concentrations from birth to age 12 years with adolescent adiposity and cardiometabolic risk in the Health Outcomes and Measures of Environment (HOME) Study, a prospective birth cohort (Cincinnati, Ohio; N = 166). Adiposity and cardiometabolic risk factors were assessed at age 12 years using anthropometry, dual-energy x-ray absorptiometry, and fasting serum biomarkers. Cardiometabolic risk scores were calculated by summing age- and sex- standardized z scores for individual cardiometabolic risk factors. Most serum adipocytokine concentrations at birth were not associated with adiposity or cardiometabolic risk outcomes. Leptin and adiponectin concentrations at age 12 years were associated with all outcomes in the expected direction. Adolescents with increasing (β: 4.2; 95% CI: 3.2 to 5.2) and stable (β: 2.2; 95% CI: 1.2 to 3.2) leptin concentrations from birth to age 12 years had higher cardiometabolic risk scores than adolescents with decreasing concentrations (reference group). Adolescents with increasing (e.g., fat mass index = β: -1.04; 95% CI: -1.27 to -0.80) and stable (β: 0.66; 95% CI: -0.92 to -0.40) adiponectin/leptin ratios had more favorable adiposity outcomes than adolescents with decreasing ratios. In this cohort, changes in leptin concentrations and adiponectin/leptin ratios over childhood were associated with adiposity and cardiometabolic risk scores, indicating that adipocytokine concentrations are potential biomarkers for predicting excess adiposity and cardiometabolic risk in adolescence.

Hunger hormone and sleep responses to the built-in blue-light filter on an electronic device: a pilot study.

The aim of the current study was to investigate the effect of the blue-light filtering 'Night Shift' function on the Apple iPad at night and leptin production, perceived hunger levels and markers of sleep quality and quantity in healthy young adults. In a randomised, crossover design, 13 young adults (6 male/7 female) performed three experimental trials. Two of the interventions included one hour of night-time electronic device use; reading on an iPad ~30 cm from eyes, either with (iPad+NS) or without (iPad) the 'Night Shift' blue-light filtering feature turned on. The control trial involved reading a hard-copy book for one hour (CON). Leptin and perceived hunger and tiredness levels were assessed at various time points for the three experimental conditions. Objective sleep indices (actigraphy) and subjective ratings of sleep were recorded. There were no significant interactions for any of the measured variables (p > 0.05). Small to moderate effect sizes were found for perceived sleep quality, with CON (7.3 ± 1.7) having the highest value when compared to iPad+NS (6.6 ± 1.8, d = 0.29) and iPad (5.6 ± 2.3, d = 0.66). Moderate effects were associated with iPad+NS when compared to iPad (d = 0.77) and for iPad compared to CON (d = 0.90) for pre-post change in leptin concentration. Use of electronic devices at night may result in moderate suppression of leptin levels and impaired sleep quality, with negligible differences associated with whether or not the 'Night Shift' feature is turned on.

Gender-specific change in leptin concentrations during long-term CPAP therapy

PurposeNasal continuous positive airway pressure (CPAP) alleviates sleepiness in patients with obstructive sleep apnoea syndrome (OSAS), but part of OSAS patients keep gaining weight. Leptin and insulin-like growth factor-1 (IGF-1) interact with energy balance, and CPAP therapy has been suggested to influence these endocrine factors. We hypothesised that leptin would decrease during long-term CPAP therapy, and weight gain would associate with OSAS severity, lower CPAP adherence, lower IGF-1, and leptin concentrations.MethodsConsecutive patients (n = 223) referred to sleep study with suspected OSAS were enrolled. Patients underwent cardiorespiratory polygraphy at baseline. Questionnaires were completed, and blood samples were drawn both at baseline and after 3 years. A total of 149 (67%; M 65, F 84) patients completed the follow-up. Plasma samples were available from 114 patients, 109 of which with CPAP adherence data (49 CPAP users, 60 non-users).ResultsAt baseline, the CPAP users were more obese and had more severe OSAS than the non-users. Leptin concentrations did not differ. After follow-up, leptin concentrations were higher in CPAP users (30.2 ng/ml vs. 16.8 ng/ml; p = 0.001). In regression analysis, increase in leptin concentrations was independent of age, baseline body mass index (BMI), or the change in BMI. Leptin concentrations increased among females (− 8.9 vs. 12.7 ng/ml; p < 0.001); whereas in men, CPAP did not have an effect, if not opposed the natural decrease in leptin observed in men not using CPAP. Change in IGF-1 levels did not differ.ConclusionsOur results suggest increase in leptin concentrations during long-term CPAP therapy among females.

Dysregulation of a long noncoding RNA reduces leptin leading to a leptin-responsive form of obesity.

Quantitative changes in leptin concentration lead to alterations in food intake and body weight, but the regulatory mechanisms that control leptin gene expression are poorly understood. Here we report that fat-specific and quantitative leptin expression is controlled by redundant cis elements and trans factors interacting with the proximal promoter together with a long noncoding RNA (lncOb). Diet-induced obese mice lacking lncOb show increased fat mass with reduced plasma leptin levels and lose weight after leptin treatment, whereas control mice do not. Consistent with this finding, large-scale genetic studies of humans reveal a significant association of single-nucleotide polymorphisms (SNPs) in the region of human lncOb with lower plasma leptin levels and obesity. These results show that reduced leptin gene expression can lead to a hypoleptinemic, leptin-responsive form of obesity and provide a framework for elucidating the pathogenic mechanism in the subset of obese patients with low endogenous leptin levels.

Legume consumption increase adiponectin concentrations among type 2 diabetic patients: A randomized crossover clinical trial

Background and objectiveThis randomized crossover clinical trial investigated the effects of substituting legumes for meat consumption in the therapeutic lifestyle change (TLC) diet on leptin and adiponectin concentrations among type 2 diabetic patients. Material and methodsThirty-one type 2 diabetic patients (24 women, age: 58.1±6.0 years) were randomly assigned to groups designated to consume a legume-free TLC diet or a legume-based TLC diet for 8 weeks. Both diets were similar except for the replacement of two servings of red meat with legumes 3 days per week in the legume-based TLC group. Leptin and adiponectin concentrations were measured at baseline and after the 8-week intervention. ResultsThe legume-based TLC diet significantly increased adiponectin concentrations in comparison with the legume-free TLC diet. There was no significant change in leptin concentrations after both intervention diets. ConclusionsLegumes increased serum adiponectin concentrations in type 2 diabetic patients.Registration number: IRCT201202251640N7.

Legume consumption increase adiponectin concentrations among type 2 diabetic patients: A randomized crossover clinical trial

Background and objectiveThis randomized crossover clinical trial investigated the effects of substituting legumes for meat consumption in the therapeutic lifestyle change (TLC) diet on leptin and adiponectin concentrations among type 2 diabetic patients. Material and methodsThirty-one type 2 diabetic patients (24 women, age: 58.1±6.0 years) were randomly assigned to groups designated to consume a legume-free TLC diet or a legume-based TLC diet for 8 weeks. Both diets were similar except for the replacement of two servings of red meat with legumes 3 days per week in the legume-based TLC group. Leptin and adiponectin concentrations were measured at baseline and after the 8-week intervention. ResultsThe legume-based TLC diet significantly increased adiponectin concentrations in comparison with the legume-free TLC diet. There was no significant change in leptin concentrations after both intervention diets. ConclusionsLegumes increased serum adiponectin concentrations in type 2 diabetic patients.Registration number: IRCT201202251640N7.

Circadian leptin concentration changes in critically ill heart failure patients.

Physiologically, leptin concentration is controlled by circadian rhythm. However, in critically ill patients, circadian rhythm is disrupted. Thus we hypothesized that circadian leptin concentration changes are not preserved in critically ill patients. Ten consecutive critically ill heart failure patients with the clinical indication for mechanical ventilation and sedation were included into our study. Plasma leptin concentration was measured every 4 h during the first day (0-24 h) and during the third day (48-72 h) after admission. During the first day, there were significant leptin concentration changes (ANOVA, p<0.05), characterized by an increase in concentration by 44 % (16-58 %); p=0.02 around noon (10 am-2 pm) and then a decrease in concentration by 7 % (1-27 %); p=0.04 in the morning (2 am-6 am). In contrast, there was no significant change in leptin concentration during the third day after admission (ANOVA, p=0.79). Based on our preliminary results, we concluded that in critically ill heart failure patients, the circadian rhythm of plasma leptin concentration seems to be preserved during the first but not during the third day after admission.

Leptin Function and Regulation.

We summarize the biological impact of leptin signaling as well as the molecular and cellular characteristics of leptin action. Our focus is principally in the central nervous system and we describe the properties of the neuronal networks that are mediators of leptin's effects on ingestive behavior, energy balance, and the reproductive system. The molecular targets of leptin's effects are also responsible for the attenuation and termination of the intracellular signal transduction pathway for leptin, providing a clear understanding of the mechanisms leading to leptin resistance or insensitivity. Using the tools of comparative biology, we explore the potential functions of leptin in fish and birds. Based on the highly variable expression of leptin in multiple tissues, a clear lack of expression of leptin in adipocytes in numerous species of fish and birds and an absence of changes of leptin concentrations in blood that are correlated with changes in nutritional status, it is clear that leptin is unlikely to function as a signal for triglyceride stores in nonmammalian species. This comparative survey serves to highlight the unique function of leptin in mammalian biology as a modulator of energy balance, sexual development, and fertility. © 2018 American Physiological Society. Compr Physiol 8:351-369, 2018.

Bariatric Surgery-Induced Lower Angiopoietin-Like 2 Protein Is Associated With Improved Cardiometabolic Profile

BackgroundPlasma angiopoietin-like 2 (Angptl2), a proinflammatory protein, has been associated with obesity and diabetes. Whether weight loss induced by bariatric surgery and associated improvement of the cardiometabolic risk profile influence circulating Angptl2 levels is unknown. We tested whether biliopancreatic diversion with duodenal switch (BPD-DS) surgery alters plasma Angptl2 concentrations. MethodsSeverely obese patients (n = 73; body mass index: 49.8 ± 7.1) underwent BPD-DS. Plasma levels of Angptl2 and metabolic biomarkers were obtained acutely (days 1 and 5) and at 6 and 12 months after surgery, and compared with results in an age- and sex-matched control group (n = 33) remaining on the waiting list. ResultsPreoperative Angptl2 levels were high (median: 12.3 ng/mL) and correlated with metabolic and anthropometric parameters. A significant (P < 0.01) increase in Angptl2 levels, fasting glucose, insulin, and interleukin-6 levels was observed acutely postoperatively (day 1) followed by a progressive decline from day 5. Besides weight loss, Angptl2 levels were decreased at the 12-month follow-up (11.5 ± 4.7 vs 14.0 ± 4.0 ng/mL, P < 0.0001), but not at the 6-month time point. Long-term changes in plasma Angptl2 levels showed significant positive correlations with changes in fasting glucose, insulin resistance, and tumour necrosis factor-α levels, and negative correlation with changes in leptin concentration (P < 0.05). No significant correlation was observed between changes in anthropometric parameters and Angptl2. ConclusionsPlasma Angptl2 levels decreased after BPD-DS in severely obese patients; no changes occurred in control participants. Lowered circulating levels of the inflammatory factor Angptl2 because of BPD-DS were closely related to favourable changes in glucose-insulin homeostasis and inflammatory profiles.

Extrauterine growth and adipocytokines in appropriate-for-gestational-age preterm infants.

Extra-uterine growth retardation in preterm infants is associated with an increased risk for cardiometabolic diseases later in life. Adipocytokines are also associated with the development of cardiometabolic diseases. We examined the relationship between extra-uterine growth and serum concentrations of adipocytokines and metabolic hormones in preterm infants. Serum concentrations of leptin, adiponectin, insulin, IL-6, TNF-α, C-peptide, GIP, GLP-1 and glucagon were measured in 38 appropriate-for-gestational-age preterm infants at birth, and at 33 and 38 weeks of postmenstrual age using a Bio-Plex 200TM suspension array system. Serum concentrations of leptin were not correlated with body weight at any time point. However, serum concentrations of adiponectin were correlated with body weight at all time points. Serum concentrations of IL-6 were decreased from birth to 33 and 38 weeks. Serum concentrations of TNF-α were not changed. Serum concentrations of C-peptide, GIP and glucagon increased from birth to 33 weeks, and decreased from 33 to 38 weeks. Serum concentrations of insulin and GLP-1 were not changed. Changes in serum concentrations of leptin and adiponectin showed unique profiles, thereby suggesting maldevelopment of white adipose tissue. This may affect the future development of adipose tissue and lead to increased risk for cardio-metabolic disorders. This article is protected by copyright. All rights reserved.

Leptin and energy restriction induced adaptation in energy expenditure

BackgroundDiet-induced weight loss is accompanied by adaptive thermogenesis, i.e. a disproportional reduction of resting energy expenditure (REE) a decrease in physical activity and increased movement economy. ObjectiveTo determine if energy restriction induced adaptive thermogenesis and adaptations in physical activity are related to changes in leptin concentrations. MethodsEighty-two healthy subjects (23 men, 59 women), mean±SD age 41±8years and BMI 31.9±3.0kg/m2, followed a very low energy diet for 8weeks with measurements before and after the diet. Leptin concentrations were determined from fasting blood plasma. Body composition was assessed with a three-compartment model based on body weight, total body water (deuterium dilution) and body volume (BodPod). REE was measured (REEm) with a ventilated hood and predicted (REEp) from measured body composition. Adaptive thermogenesis was calculated as REEm/REEp. Parameters for the amount of physical activity were total energy expenditure expressed as a multiple of REEm (PAL), activity-induced energy expenditure divided by body weight (AEE/kg) and activity counts measured by a tri-axial accelerometer. Movement economy was calculated as AEE/kg (MJ/kg/d) divided by activity counts (Mcounts/d). ResultsSubjects lost on average 10.7±4.1% body weight (P<0.001). Leptin decreased from 26.9±14.3 before to 13.9±11.3μg/l after the diet (P<0.001). REEm/REEp after the diet (0.963±0.08) was related to changes in leptin levels (R2=0.06; P<0.05). There was no significant correlation between changes in leptin concentrations and changes in amount of physical activity. Movement economy changed from 0.036±0.011J/kg/count to 0.028±0.010J/kg/count and was correlated to the changes in leptin concentrations (R2=0.07; P<0.05). ConclusionDuring energy restriction, the decrease in leptin explains part of the variation in adaptive thermogenesis. Changes in leptin are not related to the amount of physical activity but could partly explain the increased movement economy.

Is there a role for leptin in the reduction of depression symptoms during weight loss therapy in obese adolescent girls and boys?

Several studies have sought to clarify the association between adolescent obesity and psychological distress. Recently, a biological link between leptin resistance and depression has been proposed. The aim of the present study was to examine changes in leptin concentrations as a potential predictor of reduced depression symptoms in obese adolescents during long-term interdisciplinary weight loss therapy. Seventy-five obese adolescents (age: 16.28±2.37 years; BMI: 35.65±4.64kg/m2) engaged in a long-term interdisciplinary therapy for weight loss. They were evaluated at baseline and after 1 year of treatment for body composition, serum analyses and depression symptomatology. After therapy, body mass BMI, fat mass (% and kg), waist circumference, visceral, subcutaneous and visceral/subcutaneous fat and depression symptoms decreased and lean mass (%) increased significantly. There was an improvement in inflammatory profiles with a significant reduction in leptin and increase in adiponectin. Regression analyses showed that decreased leptin predicted amelioration in depression symptoms independent of age, gender and changes in visceral fat, body mass, fat mass (%) and leptin/adiponectin ratio. These associations appear stronger in girls than boys. The attenuation of hyperleptinemia appears to play an important role in the association between weight loss and depression, particularly in obese girls.

Roux-en-Y gastric bypass decreases pro-inflammatory and thrombotic biomarkers in individuals with extreme obesity.

The low-grade inflammatory state in obesity leads to insulin resistance and endothelial dysfunction, which promote cardiovascular diseases in individuals with obesity. The purpose of this study was to evaluate the early effects of weight loss achieved through bariatric surgery on the inflammatory and prothrombotic states. This study also aimed to identify the role of hyperleptinemia on the prothrombotic state. The sample was composed of 41 extremely obese who underwent Roux-en-Y gastric bypass (RYGB). Anthropometric and clinical data, and biochemical markers of inflammation were collected prior to surgery and 6 months post-RYGB. It was found that plasminogen activator inhibitor-1 (PAI-1) concentrations were higher among extremely obese individuals with hyperleptinemia than in those without hyperleptinemia (p < 0.01).In relation to the baseline, post-surgery body mass index (BMI) was reduced by 12.9 kg/m(2), corresponding to 63.50 % of excess weight loss. Additionally, waist circumference was found to decrease significantly from 126.2 to 101.4 cm. Plasma total cholesterol (p < 0.01), LDL cholesterol (p = 0.02), triglycerides (p < 0.01), and glucose (p = 0.01) were also found to decrease. Pro-inflammatory biomarkers were observed to decrease: PAI-1 by 55.9 ± 6.0 % (p < 0.01), C-reactive protein (CRP) by 18.8 ± 3.4 % (p < 0.01), intercellular adhesion molecule-1 (ICAM-1) by 89.9 ± 5.7 % (p < 0.01), leptin by 27.9 ± 3.2 % (p < 0.01), and resistin by 69.3 ± 5.8 % (p < 0.01). Additionally, significant decreases of tumor necrosis factor alpha (TNF-α) and leptin/adiponectin ratio were observed. Anti-inflammatory cytokines adiponectin and interleukin-10 (IL-10) were significantly increased (170.7 ± 82.5 %, p < 0.01; 122.7 ± 55.1 %, p = 0.02). CRP levels were predictive of ICAM-1 (p = 0.04), and changes in leptin concentrations were associated with decreased PAI-1 levels (p = 0.03). We observed that individuals with obesity that have hyperleptinemia have higher circulating PAI-1 levels, which could indicate increased risk for cardiovascular disease. The biomarkers of inflammation and thrombosis measured in this study decreased after RYGB, suggesting that the surgery may be effective in reducing pro-inflammatory and thrombotic risk in individuals with extreme obesity.

Serum leptin profiles, food intake, and body weight in melatonin-implanted Syrian hamsters (Mesocricetus auratus) exposed to long and short photoperiods

We have shown that circadian changes in leptin concentrations are inversely linked to circulating melatonin levels in the Syrian hamster. The present study aimed to assess the effects of subcutaneous melatonin implants under different photoperiodic conditions: did the implants affect serum leptin levels, body weight, food consumption, and/or testicular weight? Male hamsters were exposed to long and short photoperiods for 10 weeks and received subcutaneous melatonin implants (1 mg in 24 mg beeswax) every 2 weeks. Blood samples were collected every week at midday (1200 hours) or midnight (0000 hours) to assess leptin and melatonin concentrations. Testes were measured to calculate weight. Body weight and food intake were determined every week. Melatonin implants blocked the testicular regression produced by short photoperiods. No differences in body weight were observed among any of the groups. Food consumption increased only with the melatonin implant in the short photoperiod. Serum leptin levels in both photoperiods remained constant. Differences were apparent between noon and night leptin profiles. Noon leptin levels were high (16-18 ng/mL) compared to night leptin levels (8-11 ng/mL) in untreated controls. On the other hand, serum leptin concentrations declined in melatonin-implanted hamsters in both photoperiods. The effects of melatonin on leptin hormone profiles are very pronounced, and melatonin seems to have both physiologically and pharmacologically suppressive effects on leptin production by direct or indirect mechanisms.

A Meta-Analysis of Reference Values of Leptin Concentration in Healthy Postmenopausal Women

ObjectiveThere are numerous reports about the leptin concentration (LC) in postmenopausal women (PW). Changes in LC can elicit different clinical outcomes. We systematically analyzed the LC in PW.MethodsA search was conducted in original English-language studies published from 1994 to October 2012 in the following databases: Medline (78), Cochrane Center (123) Embase (505), Biological abstracts (108), Cochrane (53) and Science Finder Scholar (0). A meta-analysis was undertaken on the correction coefficient (r) between the serum LC and body mass index (BMI) for healthy PW across studies containing a dataset and sample size. Pre-analytical and analytical variations were examined. Pre-analytical variables included fasting status (FS) and sampling timing. Analytical variation comprised assay methodology, LC in those undertaking hormone replacement therapy (HRT) and those not having HRT as well as LC change according to age.ResultsTwenty-seven studies met the inclusion criteria. Eighteen studies detected LC in the morning in a FS, 15 studies denoted the r between leptin and the BMI. A combined r was counted for the 15 studies (r = 0.51 [95% confidence interval (CI), 0.46–0.54], P = 0.025), and if sampling collection was in the FSat morning, a combined r was form 10 studies (r = 0.54 [95% CI, 0.45–0.54], P = 0.299) and heterogeneity was diminished. LC did not change between HRT users and non-users in 7 studies. Five studies analyzed changes in LC according to age.ConclusionBased on all studies that investigated both LC and BMI, LC was positively correlated with the BMI. No studies established reference ranges according to the Clinical and Laboratory Standards Institute (CLSI) in healthy PW, and there was a wide variation in LC values. These differences suggest that caution should be used in the interpretation and comparison between studies.

Leptin exacerbates collagen‐induced arthritis via enhancement of Th17 cell response

To determine the role of leptin in modulating Th17 cell response and joint inflammation in mice with collagen-induced arthritis (CIA). Leptin receptor expression on T cells was examined by polymerase chain reaction (PCR) analysis, immunofluorescence microscopy, and flow cytometry. Effects of leptin on Th17 cell differentiation and proliferation were evaluated by quantitative PCR, carboxyfluorescein diacetate succinimidyl ester proliferation assay, and flow cytometry. Dynamic changes in leptin concentrations in the joint tissue and synovial fluid of mice with CIA were determined by immunohistochemistry analysis and enzyme-linked immunosorbent assay (ELISA). Arthritis symptoms and joint pathology in mice with CIA were assessed after injection of leptin into the knee joint. Th1 and Th17 cell populations in the spleen, draining lymph nodes, and joint tissue were analyzed by flow cytometry and enzyme-linked immunospot assay. Interleukin-17 messenger RNA and protein levels in the joint tissue were measured by PCR analysis and ELISA. In culture, leptin treatment significantly increased Th17 cell generation from naive CD4+ T cells. During CIA development, markedly elevated levels of leptin were detected in the joint tissue and synovial fluid. Moreover, injection of leptin into the knee joint of collagen-immunized mice resulted in an early onset of arthritis and substantially increased the severity of clinical symptoms, accompanied by more pronounced synovial hyperplasia and joint damage. Further examination by immunofluorescence microscopy confirmed the presence of significantly increased numbers of Th17 cells in the joint tissue and draining lymph nodes of leptin-treated mice with CIA. The results of this study identify a previously undescribed function of leptin in enhancing Th17 cell response and exacerbating joint inflammation in mice with CIA.