Lean Men Research Articles

Prolyl Carboxypeptidase Activity Is Present in Human Adipose Tissue and Is Elevated in Serum of Obese Men with Type 2 Diabetes

Prolyl carboxypeptidase (PRCP) is involved in metabolic disorders by hydrolyzing anorexigenic peptides. A link between serum PRCP activity and obesity has been reported, but its origin/source is still unclear. Previously proven correlations between human serum PRCP activity and the amount of adipose tissue may suggest that adipose tissue is an important source of circulating PRCP. We investigated PRCP activity in visceral, subcutaneous adipose tissue (VAT and SCAT), skeletal muscle tissue and serum of lean and obese men with or without type 2 diabetes (T2D). Correlations between PRCP activity, metabolic and biochemical parameters and immune cell populations were assessed. PRCP activity was the highest in VAT, compared to SCAT, and was very low in skeletal muscle tissue in the overall group. Serum PRCP activity was significantly higher in T2-diabetic obese men, compared to lean and obese non-diabetic men, and was positively correlated with glycemic control. A positive correlation was observed between serum PRCP activity and VAT immune cell populations, which might indicate that circulating PRCP activity is deriving rather from the immune fraction than from adipocytes. In conclusion, PRCP activity was observed in human adipose tissue for the first time and serum PRCP activity is correlated with T2D in obese men.

Leptin increases hepatic triglyceride export via a vagal mechanism in humans

Recombinant human leptin (metreleptin) reduces hepatic lipid content in patients with lipodystrophy and overweight patients with non-alcoholic fatty liver disease and relative hypoleptinemia independent of its anorexic action. In rodents, leptin signaling in the brain increases very-low-density lipoprotein triglyceride (VLDL-TG) secretion and reduces hepatic lipid content via the vagus nerve. In this randomized, placebo-controlled crossover trial (EudraCT Nr. 2017-003014-22), we tested whether a comparable mechanism regulates hepatic lipid metabolism in humans. A single metreleptin injection stimulated hepatic VLDL-TG secretion (primary outcome) and reduced hepatic lipid content in fasted, lean men (n= 13, age range 20-38 years) but failed to do so in metabolically healthy liver transplant recipients (n= 9, age range 26-62 years) who represent a model for hepatic denervation. In an independent cohort of lean men (n= 10, age range 23-31 years), vagal stimulation by modified sham feeding replicated the effects of metreleptin on VLDL-TG secretion. Therefore, we propose that leptin has anti-steatotic properties that are independent of food intake by stimulating hepatic VLDL-TG export via a brain-vagus-liver axis.

Do Sugar-Sweetened Beverages Increase Fasting FGF21 Irrespective of the Type of Added Sugar? A Secondary Exploratory Analysis of a Randomized Controlled Trial.

Human fibroblast growth factor 21 (FGF21) is a multifaceted metabolic regulator considered to control sugar intake and to exert beneficial effects on glucose and lipid metabolism. Elevated serum FGF21 levels are associated with metabolic syndrome, suggesting a state of FGF21 resistance. Further, given the evidence of a hepatic ChREBP and FGF21 signaling axis, it can be assumed that SSBs containing fructose would possibly increase FGF21 concentrations. We investigated the effects of sugar-sweetened beverage (SSB) consumption on fasting FGF21 levels in healthy, lean men, discriminating the effects of glucose, fructose, and their disaccharide sucrose by secondary data analysis from a randomized controlled trial. Seven weeks of daily SSB consumption resulted in increased fasting FGF21 in healthy, lean men, irrespective of the sugar type. Medians of ΔFGF21 between post-SSB intervention values (week 7) and no-intervention period values (IQR) in pg/mL were: glucose 17.4 (0.4–45.8), fructose 22.9 (−8.6–35.1), and sucrose 13.7 (2.2–46.1). In contrast, this change in FGF21 concentration was only 6.3 (−20.1–26.9) pg/mL in the control group. The lack of a fructose-specific effect on FGF21 concentrations is contrary to our assumption. It is concluded that SSB intake may impact FGF21 concentrations and could contribute to the increased FGF21 concentrations observed in subjects suffering from metabolic syndrome that is possibly associated with decreased FGF21 responsiveness.

Water intake, thirst, and copeptin responses to two dehydrating stimuli in lean men and men with obesity.

Physiological systems responsible for water homeostasis and energy metabolism are interconnected. This study hypothesized altered responses to dehydration including thirst, ad libitum water intake, and copeptin in men with obesity. Forty-two men (22 lean and 20 with obesity) were stimulated by a 2-hour hypertonic saline infusion and a 24-hour water deprivation. In each dehydrating condition, thirst, ad libitum water intake after dehydration, and urinary and hormonal responses including copeptin were assessed. After each dehydration condition, ad libitum water intake was similar between both groups (p > 0.05); however, those with obesity reported feeling less thirsty (p < 0.05) and had decreased copeptin response and higher urinary sodium concentrations when stressed (p < 0.05). Angiotensin II, aldosterone, atrial and brain natriuretic peptides, and apelin concentrations did not differ by adiposity group and did not explain the different thirst or copeptin responses in men with obesity. However, leptin was associated with copeptin response in lean individuals during the hypertonic saline infusion (p < 0.05), but the relationship was diminished in those with obesity. Diminished thirst and copeptin responses are part of the obesity phenotype and may be influenced by leptin. Adiposity may impact pathways regulating thirst and vasopressin release, warranting further investigation.

A randomized diet-induced weight-loss intervention reduces plasma complement C3: Possible implication for endothelial dysfunction.

ObjectiveComplement C3 and other components of the alternative pathway are higher in individuals with obesity. Moreover, C3 has been identified as a risk factor for cardiovascular disease. This study investigated whether, and how, a weight‐loss intervention reduced plasma C3, activated C3 (C3a), and factor D and explored potential biological effects of such a reduction.MethodsThe study measured plasma C3, C3a, and factor D by ELISA and measured visceral adipose tissue, subcutaneous adipose tissue, and intrahepatic lipid by magnetic resonance imaging in lean men (n = 25) and men with abdominal obesity (n = 52). The men with obesity were randomized to habitual diet or an 8‐week dietary weight‐loss intervention.ResultsThe intervention significantly reduced C3 (−0.15 g/L [95% CI: −0.23 to −0.07]), but not C3a or factor D. The C3 reduction was mainly explained by reduction in visceral adipose tissue but not subcutaneous adipose tissue or intrahepatic lipid. This reduction in C3 explained a part of the weight‐loss‐induced improvement of markers of endothelial dysfunction, particularly the reduction in soluble endothelial selectin and soluble intercellular adhesion molecule.ConclusionsDiet‐induced weight loss in men with abdominal obesity could be a way to lower plasma C3 and thereby improve endothelial dysfunction. C3 reduction may be part of the mechanism via which diet‐induced weight loss could ameliorate the risk of cardiovascular disease in men with abdominal obesity.

Sex-specific modulation of circulating growth differentiation factor-15 in patients with type 2 diabetes and/or obesity.

ObjectiveGrowth differentiation factor-15 (GDF15), a key metabolic regulator, is associated with obesity and diabetes in which sex-specific differences have been reported. Thus, we assessed whether GDF15 could be dependent on sex in diabetes and/or obesity groups.MethodsWe measured serum GDF15 levels by ELISA in eight lean women and men (n = 16), eight women and eight men having obesity (n = 16), eight women and eight men with type 2 diabetes (T2D, n = 16), and seven women and nine men with both diabetes and obesity (n = 16). Estimation of the difference in the means of each group was performed by two-way ANOVA. The interdependence of the different variates was addressed by multivariate analysis. Correlations between GDF15 levels and HOMA-IR, HbA1c, triglycerides, HDL, and LDL were explored by linear regression.ResultsBeing a woman and having obesity alone or in combination with diabetes decreased GDF15 serum levels (β = −0.47, CI = −0.95, 0.00, P = 0.052; β = −0.45, CI = −0.94, 0.05, P= 0.075). Diabetes independently of metformin treatment and obesity were not predictive of low GDF15 levels (β = 0.10, CI = −0.36, 0.57, P = 0.7). Correlation analysis showed that HOMA-IR (r = 0.45, P = 0.008) and triglycerides (r = 0.41, P = 0.017) were positively correlated and HDL (r = −0.48, P = 0.005) was negatively correlated with GDF15 levels in men.Conclusions/interpretationGDF15 level was significantly different between men and women, as well as between the groups. Sex and group interaction revealed that being a woman and having obesity alone or in combination with diabetes decreased GDF15 levels.

SKIN MICROVASCULAR FLOWMOTION IS UNALTERED IN ABDOMINALLY OBESE MEN

Objective: Abdominal obesity represents a systemic metabolic pathology, being related to the development of insulin resistance and cardiovascular diseases. Microvascular dysfunction is multifactorial and alters, among other things, insulin-mediated glucose disposal. We have previously shown that insulin-mediated microvascular recruitment in skeletal muscle is impaired in obese men and that weight loss can reverse this impairment. Our objective was to examine whether impairment of insulin-mediated microvascular function and subsequent reversal by weight loss can be detected in skin as well using flowmotion analyses. Design and method: Twenty-five lean and 53 abdominally obese men (waist circumference 102–110 cm; aged18–65 yrs.; no cardiovascular diseases or type 2 diabetes) were recruited. Following baseline measurements, the obese men were randomized to either an 8-week program of low calorie diet (LCD), or usual diet (control). Skin flowmotion was measured by laser-doppler flowmetry and Fourier analyses resulted in the contribution of five frequency domains: endothelial, 0.01–0.02 Hz; neurogenic, 0.02–0.06 Hz; myogenic, 0.06–0.15 Hz; respiratory, 0.15–0.40 Hz and cardiac, 0.40–1.60 Hz. Flowmotion was measured before and during a hyperinsulinaemic euglycaemic clamp. Results: Baseline flowmotion was not different between lean and obese men. In both lean and obese men, hyperinsulinaemia induced a similar increase in total flowmotion (lean: 6.5% (1.5, 11.5); obese: 3.6% (0.6, 6.6); p = 0.309 vs lean) and the endothelial domain (lean: 12.3% (1.7, 22.9); obese: 8.6% (2.5, 14.7); p = 0.538 vs lean), and a decrease in the neurogenic domain (lean: -14.2% (-24.8, -3.7); obese: -4.6% (-13, 3.8); p = 0.149 vs lean). The LCD intervention did not statistically significantly affect flowmotion. Conclusions: In contrast to insulin-mediated microvascular recruitment in skeletal muscle, skin microvascular flowmotion is unaltered in abdominally obese men versus lean. In addition, a weight loss intervention in the obese men did not affect skin microvascular flowmotion. These findings indicate that the sensitivity of the microvasculature to systemic mediators may differ between tissues.

Skeletal muscle mass to visceral fat area ratio as a predictor of NAFLD in lean and overweight men and women with effect modification by sex.

The effect of sarcopenic visceral obesity on the risk of nonalcoholic fatty liver disease (NAFLD) is uncertain. We investigated (a) whether the skeletal muscle mass to visceral fat area ratio (SV ratio), as a measure of sarcopenic visceral obesity, is a risk factor for NAFLD; and (b) whether the SV ratio adds to conventional adiposity measures to improve prediction of incident NAFLD. Adults without NAFLD (n = 151,017) were followed up for a median of 3.7 years. Hepatic steatosis was measured using ultrasonography, and liver fibrosis scores were estimated using the Fibrosis‐4 index (FIB‐4) and the NAFLD Fibrosis Score (NFS). Cox proportional hazards models were used to determine sex‐specific adjusted hazard ratios (aHRs) (95% confidence intervals [CIs]). The incremental predictive performance was assessed using the area under the receiver operating characteristic curve, net reclassification improvement, and integrated discrimination improvement. Multivariable aHRs (95% CIs) for incident NAFLD comparing the lowest versus the highest quintile of SV ratio were 3.77 (3.56–3.99) for men and 11.69 (10.46–13.06) for women (p–interaction by sex < 0.001). For incident NAFLD with intermediate/high FIB‐4, aHRs were 2.83 (2.19–3.64) for men and 7.96 (3.85–16.44) for women (similar results were obtained for NFS). Associations remained significant even after adjustment for body mass index, waist circumference, and time‐varying covariates. These associations were also more pronounced in nonobese than obese participants (p–interaction < 0.001). The addition of SV ratio to conventional adiposity measures modestly improved risk prediction for incident NAFLD. SV ratio was inversely associated with risk of developing NAFLD, with effect modification by sex and obesity. Conclusion: Low SV ratio is a complementary index to conventional adiposity measures in the evaluation of NAFLD risk.

Beta2 -agonist increases skeletal muscle interleukin 6 production and release in response to resistance exercise in men.

ObjectiveSeveral tissues produce and release interleukin‐6 (IL‐6) in response to beta2‐adrenergic stimulation with selective agonists (beta2‐agonists). Moreover, exercise stimulates muscle IL‐6 production, but whether beta2‐agonists regulate skeletal muscle production and release of IL‐6 in humans in association with exercise remains to be clarified. Thus, we investigated leg IL‐6 release in response to beta2‐agonist salbutamol in lean young men at rest and in recovery from resistance exercise.DesignThe study employed a randomized controlled crossover design, where 12 men ingested either salbutamol (16 mg) or placebo for 4 days, followed by the last dose (24 mg) administered 1½ h before exercise. Arterial and femoral venous plasma IL‐6 as well as femoral artery blood flow was measured before and ½–5 h in recovery from quadriceps muscle resistance exercise. Furthermore, vastus lateralis muscle biopsies were collected ½ and 5 h after exercise for determination of mRNA levels of IL‐6 and Tumor Necrosis Factor (TNF)‐α.ResultsAverage leg IL‐6 release was 1.7‐fold higher (p = 0.01) for salbutamol than placebo, being 138 ± 76 and 79 ± 66 pg min−1 (mean ± SD) for salbutamol and placebo, respectively, but IL‐6 release was not significantly different between treatments within specific sampling points at rest and after exercise. Muscle IL‐6 mRNA was 1.5‐ and 1.7‐fold higher (p = 0.001) for salbutamol than placebo ½ and 5 h after exercise, respectively, whereas no significant treatment differences were observed for TNF‐α mRNA.ConclusionsBeta2‐adrenergic stimulation with high doses of the selective beta2‐agonist salbutamol, preceeded by 4 consecutive daily doses, induces transcription of IL‐6 in skeletal muscle in response to resistance exercise, and increases muscle IL‐6 release in lean individuals.

A higher energy-adjusted Dietary Inflammatory Index is positively associated with total and visceral body fat in young male adults.

The energy-adjusted Dietary Inflammatory Index (E-DII™) has been associated with a high body mass index and markers of chronic diseases. Also, pro-inflammatory diets with a high E-DII have been positively associated with metabolic disturbances such as glucose intolerance and type II diabetes mellitus. However, it is unclear whether E-DII scores are positively associated with body fat percentage and visceral fat per se. This cross-sectional study aimed to evaluate whether the E-DII is associated with body fat content and metabolic health indicators in lean and obese young men. The present study was conducted on 59 participants, without comorbidities, not using tobacco, medication and nutritional supplements. Dietary data were obtained by 3-day food records to calculate E-DII scores based on 28 food parameters. Body composition was assessed by dual X-ray absorptiometry (DXA). Blood samples were taken to measure fasting glucose, insulin, triacylglycerols, total cholesterol, and low- and high-density lipoprotein cholesterol. An oral glucose tolerance test also was performed. Associations were determined by mixed-effects linear regression. E-DII scores ranged from -3.48 to +3.10. Energy intake was similar across E-DII tertiles. After adjusting for covariates, the highest E-DII tertile was associated with increased body fat, visceral adipose tissue and waist circumference. There was no association between E-DII scores and glycaemic parameters. In young participants, a dietary pattern with a higher E-DII (i.e., pro-inflammatory) score was associated with high body fat and markers of central adiposity assessed by DXA, regardless of body mass.

Identifying weight management clusters and examining differences in eating behaviour and psychological traits: An exploratory study

Previous research has suggested differences in psychological traits and eating behaviours between groups of individuals with varying weight management profiles, for example, differences between individuals who have maintained weight loss compared to those who have not. However, no study has looked at differences in traits across a sample with a broad range of characteristics including variations in bodyweight and its management. Across two studies, we identified and validated weight management profiles using a clustering approach and examined trait differences across groups. Data were collected using online questionnaires (Study 1: secondary data analysis; Study 2: primary data analysis allowing for cluster validation). Cluster analysis was implemented with BMI, diet history, weight suppression (difference between highest and current weight) as primary grouping variables, and age and gender as covariates. Differences in psychological and eating behaviour traits (e.g., restraint) were explored across clusters. In study 1, 423 participants (27.21 ± 9.90 years) were grouped into 5 clusters: ‘lean men’, ‘lean young women’, ‘lean middle-aged women’, ‘successful’ and ‘unsuccessful dieters’. The cluster structure was broadly replicated with two additional groups identified (‘lean women without dieting’ and ‘very successful dieters’) in study 2 with 368 participants (34.41 ± 13.63 years). In both studies, unsuccessful dieters had higher restrained and emotional eating scores than lean individuals, and in study 1, they also had higher food addiction scores than successful dieters. Individuals could be grouped in terms of their weight management profiles and differences in psychological and eating behaviour traits were evident across these groups. Considering the differences in traits between the clusters may further improve the effectiveness and adherence of weight management advice.

Thermogenic responses to different clamped skin temperatures in cold-exposed men and women.

Despite many decades of research examining thermoregulatory responses under varying cold stresses in humans, very little is known about the variability in metabolic heat production and shivering activity. Here, we used a novel closed-loop mean skin temperature clamping technique with a liquid-conditioned suit to isolate the effects of mean skin temperature on the subjective evaluation of thermal sensation, heat production, shivering responses, and oxidative fuel selection in young, lean, and healthy men (n = 12) and women (n = 12). Our results showed a skin temperature-dependent increase in metabolic heat production (5.2 ± 1.2 kJ/min, 5.9 ± 1.5 kJ/min, and 7.0 ± 1.8 kJ/min with skin temperature maintained at 31 ± 0.1°C, 29 ± 0.2°C, and 27 ± 0.1°C, respectively; P < 0.0001) and shivering intensity in both men and women [0.6 ± 0.1% maximal voluntary contraction (MVC), 1.1 ± 0.4% MVC, and 2.5 ± 0.7% MVC, respectively; P < 0.0001], including sex-dependent differences in heat production at all three temperatures (P < 0.005). Even when controlling for lean body mass and fat mass, sex differences persisted (P = 0.048 and P = 0.004, respectively), whereas controlling for differences in body surface area eliminated these differences. Interestingly, there were no sex differences in the cold-induced change in thermogenesis. Despite clamping skin temperature, there was tremendous variability in the rate of heat production and shivering intensity. Collectively this data suggests that many of the interindividual differences in thermogenesis and shivering may be explained by differences in morphology and body composition.

Body Composition and Serum Concentration of Thyroid Hormones in Euthyroid Men and Women from General Population.

Body composition, especially an increased amount of fat mass and decreased lean body mass, is connected with metabolic complications. Thyroid hormones can influence body composition pattern. To date, scarce data defining the relationships between thyroid hormones and parameters of body composition using dual-energy X-ray absorptiometry (DXA), especially in cohort studies, are available. Therefore, the aim of the present study was to investigate the relationships among serum concentrations of (thyroid-stimulating hormone (TSH), thyroid hormones, and distribution of fat tissue assessed using the DXA method in a euthyroid cohort from the Białystok PLUS study. We examined 582 euthyroid subjects who were divided into lean (body mass index (BMI) < 25 kg/m2) and overweight/obese (BMI ≥ 25 kg/m2) (84 lean men, 182 overweight/obese men, 160 lean women, and 156 overweight/obese women). Serum concentrations of TSH, free T3 (fT3), and free T4 (fT4) were assessed, and DXA was performed. We observed lower serum levels of fT4 (p = 0.03) and higher serum levels of fT3 (p = 0.04) in overweight/obese vs. lean men, whereas serum levels of TSH did not differ between these groups (p = 0.38). In lean men, we only observed a relationship between serum levels of TSH and visceral adipose tissue (VAT) (r = −0.24, p = 0.02). In overweight/obese men, we found that serum levels of fT3 were positively connected with total fat mass (r = 0.16, p = 0.02), android fat mass (r = 0.15, p = 0.03), and gynoid fat mass (r = 0.17, p = 0.01), but not with VAT (r = 0.03, p = 0.63). We did not observe differences in serum levels of TSH, fT3, and fT4 between lean and overweight/obese women. Additionally, we did not notice relationships between serum levels of thyroid hormones and fat in different regions estimated by DXA in lean and overweight/obese women (all p > 0.05). We concluded that the serum concentration of TSH is connected with VAT in lean men, whereas, in overweight/obese men, higher fT3 is connected with an increased fat amount. These associations are absent in women.

Ethnic and sex differences in hepatic lipid content and related cardiometabolic parameters in lean individuals.

BackgroundNonalcoholic fatty liver affects 25% to 30% of the US and European populations; is associated with insulin resistance (IR), type 2 diabetes, and increased cardiovascular risk; and is defined by hepatic triglyceride (HTG) content greater than 5.56%. However, it is unknown whether HTG content less than 5.56% is associated with cardiometabolic risk factors and whether there are ethnic (Asian Indian, AI, versus non-AI) and/or sex differences in these parameters in lean individuals.MethodsWe prospectively recruited 2331 individuals and measured HTG, using 1H magnetic resonance spectroscopy, and plasma concentrations of triglycerides, total cholesterol, LDL-cholesterol, HDL-cholesterol, and uric acid. Insulin sensitivity was assessed using Homeostatic Model Assessment of Insulin Resistance and the Matsuda Insulin Sensitivity Index.ResultsThe 95th percentile for HTG in lean non-AI individuals was 1.85%. Plasma insulin, triglycerides, total cholesterol, LDL-cholesterol, and uric acid concentrations were increased and HDL-cholesterol was decreased in individuals with HTG content > 1.85% and ≤ 5.56% compared with those individuals with HTG content ≤ 1.85%, and these altered parameters were associated with increased IR. Mean HTG was lower in lean non-AI women compared with lean non-AI men, whereas lean AI men and women had a 40% to 100% increase in HTG when compared with non-AI men and women, which was associated with increased cardiometabolic risk factors.ConclusionWe found that the 95th percentile of HTG in lean non-AI individuals was 1.85% and that HTG concentrations above this threshold were associated with IR and cardiovascular risk factors. Premenopausal women were protected from these changes whereas young, lean AI men and women manifested increased HTG content and associated cardiometabolic risk factors.FundingGrants from the United States Department of Health and Human Resources (NIH/National Institute of Diabetes and Digestive and Kidney Diseases): R01 DK113984, P30 DK45735, U24 DK59635, and UL1 RR024139; and the Novo Nordisk Foundation (NNF18CC0034900).

Effects of Diet-Induced Weight Loss on Plasma Markers for Cholesterol Absorption and Synthesis: Secondary Analysis of a Randomized Trial in Abdominally Obese Men.

Cross-sectional studies have shown that obesity is associated with lower intestinal cholesterol absorption and higher endogenous cholesterol synthesis. These metabolic characteristics have also been observed in patients with type 2 diabetes, metabolic syndrome, steatosis or cholestasis. The number of intervention studies evaluating the effect of weight loss on these metabolic characteristics is, however, limited, while the role of the different fat compartments has not been studied into detail. In a randomized trial, abdominally obese men (N = 54) followed a 6-week very low caloric (VLCD) diet, followed by a 2 week weight-maintenance period. Non-cholesterol sterols were measured at baseline and after 8 weeks, and compared to levels in lean participants (N = 25). After weight loss, total cholesterol (TC)-standardized cholestanol levels increased by 0.18 µmol/mmol (p < 0.001), while those of campesterol and lathosterol decreased by 0.25 µmol/mmol (p < 0.05) and 0.39 µmol/mmol (p < 0.001), respectively. Moreover, after weight loss, TC-standardized lathosterol and cholestanol levels were comparable to those of lean men. Increases in TC-standardized cholestanol after weight loss were significantly associated with changes in waist circumference (p < 0.01), weight (p < 0.001), BMI (p < 0.001) and visceral fat (p < 0.01), but not with subcutaneous and intrahepatic lipids. In addition, cross-sectional analysis showed that visceral fat fully mediated the association between BMI and TC-standardized cholestanol levels. Intrahepatic lipid content was a partial mediator for the association between BMI and TC-standardized lathosterol levels. In conclusion, diet-induced weight loss decreased cholesterol synthesis and increased cholesterol absorption. The increase in TC-standardized cholestanol levels was not only related to weight loss, but also to a decrease in visceral fat volume. Whether these metabolic changes ameliorate other metabolic risk factors needs further study.

Leptin Effects on Leydig Stem Cell Differentiation are Specific to Patients BMI

ABSTRACT Introduction Adult Leydig cells in the testes are essential for testosterone production. The growth and differentiation of Leydig cells could be affected by paracrine factors released by testicular microenvironment (TME) (Sertoli and peritubular myoid cells). In our recent study, we demonstrated that Leptin, a paracrine factor secreted by TME, is critical for Leydig stem cells (LSCs) differentiation and subsequent testosterone production via its interaction with Leptin receptor on LSCs, followed by downstream regulation of desert hedgehog (DHH) signaling. Although it is well-known that obesity adversely affects male fertility and testosterone production, the endogenous effects of Leptin on Leydig stem cell differentiation and transcription factors genes (TFs) binding to leptin receptor (LEPR) and the mechanism that are specific to patient's BMI (normal, obese and lean men) are understudied. Additionally, the underlying mechanism behind the differential effects of Leptin (if any) is unknown. Therefore, In the present study, we evaluated the impacts and mechanism of Leptin as a paracrine factor on LSC differentiation in patients with different BMI's. Objective To uncover the mechanism of Leptin as a paracrine factor on LSC differentiation in patients with different BMI's. Methods A total of 13 men with testicular failure that were subcategorized as obese (BMI &amp;gt;35), normal (BMI 25-30), and lean (BMI &amp;lt;25) underwent testis biopsies. Using an IRB approved protocol, about 10mg of testicular tissue from each of these men were processed for LSC isolation, culture and characterization. After characterization using Flow cytometry and Immunostaining, cells were treated for dose dependent (0, 1, 10 ng/mL respectively) and time dependent (24, 48, 72, and 96 hours) effects of Leptin in the presence or absence of testicular microenvironment. To validate the effects of leptin on DHH, - LSCs were treated with Leptin in the presence of DHH agonists (SAG) and antagonists (Vismodigib). For the functional studies, UCSC genome browser was used to identify the TFs binding the LEPR promoter. The list of TFs was subjected for Enrichr for enrichment analysis. To evaluate the effects of shortlisted TFs on leptin-LEPR, qPCR and western blotting were performed. Furthermore, to validate the specificity of interaction between Leptin-Leptin receptor on LSC differentiation, sorted LSCs were exposed to siRNA against LEPR in the presence of increased dose of Leptin, followed by evaluating the percentage shift in LSCs to ALCs. After treatment, qPCR, western blot and flow cytometry analysis were performed to evaluate the effects of treatment with respective to the BMI levels. RNA sequencing analysis was performed on cells extracted from men with different BMI's, treated with 0, 0.25, 1 and 10ng/ml Leptin to study the signatures specific effects of leptin with respect to patients BMI. For statistical analysis GraphPad Prism (GraphPad Software) were used. All data were presented as the means ± SEM. The statistical significance between two groups were estimated by unpaired two-tailed t test. Results Results showed that a strong relationship exists between BMI and leptin levels. Immunostaining, flow cytometry and RNA sequencing results showed that in the men with normal BMI, in the presence of low doses of leptin, there was a shift of the testicular cell population towards adult Leydig cells (increased population of cells staining positive for 3BHSD, LHR) and increased DHH signaling (GLI and SMO). On the contrary, at higher concentrations, the positive effects of leptin on cells from men with normal BMI were neutralized. Furthermore, in cells from lean patients, leptin treatment had a consistent, linear and positive impact on LSC differentiation markers and DHH signaling. Moreover, in cells from obese patients, leptin had a consistent, linear and negative impact on LSC differentiation and markers of DHH signaling. Enrichment analysis identified 50 TFs, of which SOX2, SOX8 and SOX9 were enriched for abnormal pituitary function and therefore for hypothalamic pituitary gonadal axis. The role of these TFs on LSC differentiation remained under-explored. RNA sequencing data from cells exposed to different concentrations of Leptin showed an inducing effect of Leptin on SOX2, SOX8 Sox9 respectively. Consequently, with increasing leptin doses SOX2, SOX8 Sox9 protein and expression has been upregulated. Mechanistically, Leptin-LEPR-TFs induced DHH signaling regulates LSCs differentiation in a different manner which is specific to patient's BMI. Conclusions Our results demonstrate the influence, BMI has on Leptin induced LSC differentiation. These findings suggest the future potential use of Leptin as a personalized therapy for inducing LSC differentiation and overcoming low Testosterone levels. Further studies are necessary to identify potential therapeutic effects of leptin treatment in improving fertility in the setting of leptin resistance and obesity. Financial Support: Supported by the American Urological Association Research Scholar Award to H.A. J.M.H. is supported by NIH grants 1R01 HL137355, 1R01 HL107110, 1R01 HL134558, 5R01 CA136387, 5UM1 HL113460 and Soffer Family Foundation. Disclosure No

Circumference-Based Predictions of Body Fat Revisited: Preliminary Results From a US Marine Corps Body Composition Survey.

Purpose: Body composition assessment methods are dependent on their underlying principles, and assumptions of each method may be affected by age and sex. This study compared an abdominal circumference-focused method of percent body fat estimation (AC %BF) to a criterion method of dual-energy x-ray absorptiometry (DXA), and a comparative assessment with bioelectrical impedance (BIA), in younger (≤30 years) and older (>age 30 years) physically fit (meeting/exceeding annual US Marine Corps fitness testing requirements) men and women. Methods: Fit healthy US Marines (430 men, 179 women; 18–57 years) were assessed for body composition by DXA (iDXA, GE Lunar), anthropometry, and BIA (Quantum IV, RJL Systems). Results: Compared to DXA %BF, male AC %BF underestimated for both ≤30 and >30 years age groups (bias, -2.6 ± 3.7 and -2.5 ± 3.7%); while female AC %BF overestimated for both ≤30 and >30 years age groups (2.3 ± 4.3 and 1.3 ± 4.8%). On an individual basis, lean men and women were overestimated and higher %BF individuals were underestimated. Predictions from BIA were more accurate and reflected less relationship to adiposity for each age and sex group (males: ≤30, 0.4 ± 3.2, >30 years, -0.5 ± 3.5; women: ≤30, 1.4 ± 3.1, >30 years, 0.0 ± 3.3). Total body water (hydration) and bone mineral content (BMC) as a proportion of fat-free mass (FFM) remained consistent across the age range; however, women had a higher proportion of %BMC/FFM than men. Older men and women (>age 30 years) were larger and carried more fat but had similar FFM compared to younger men and women. Conclusion: The AC %BF provides a field expedient method for the US Marine Corps to classify individuals for obesity prevention, but does not provide research-grade quantitative body composition data.

Aerobic Fitness Is Associated with Cerebral μ-Opioid Receptor Activation in Healthy Humans.

Central μ-opioid receptors (MORs) modulate affective responses to physical exercise. Individuals with higher aerobic fitness report greater exercise-induced mood improvements than those with lower fitness, but the link between cardiorespiratory fitness and the MOR system remains unresolved. Here we tested whether maximal oxygen uptake (V̇O2peak) and physical activity level are associated with cerebral MOR availability and whether these phenotypes predict endogenous opioid release after a session of exercise. We studied 64 healthy lean men who performed a maximal incremental cycling test for V̇O2peak determination, completed a questionnaire assessing moderate-to-vigorous physical activity (MVPA; in minutes per week), and underwent positron emission tomography with [11C]carfentanil, a specific radioligand for MOR. A subset of 24 subjects underwent additional positron emission tomography scan also after a 1-h session of moderate-intensity exercise and 12 of them also after a bout of high-intensity interval training. Higher self-reported MVPA level predicted greater opioid release after high-intensity interval training, and both V̇O2peak and MVPA level were associated with a larger decrease in cerebral MOR binding after aerobic exercise in the ventral striatum, orbitofrontal cortex, and insula. That is, more trained individuals showed greater opioid release acutely after exercise in brain regions especially relevant for reward and cognitive processing. Fitness was not associated with MOR availability. We conclude that regular exercise training and higher aerobic fitness may induce neuroadaptation within the MOR system, which might contribute to improved emotional and behavioral responses associated with long-term exercise.

Effects of intraduodenal infusion of lauric acid and L-tryptophan, alone and combined, on glucoregulatory hormones, gastric emptying and glycaemia in healthy men

Background and aimIn healthy men, intraduodenal administration of the fatty acid, lauric acid (‘C12’) and the amino acid, L-tryptophan (‘TRP’), at loads that individually do not affect energy intake, reduce energy intake substantially when combined. C12 and TRP may also stimulate cholecystokinin and glucagon-like peptide-1 (GLP-1), which both slow gastric emptying, a key determinant of postprandial blood glucose. Accordingly, combination of C12 and TRP has the potential to reduce post-meal glycaemia more than either nutrient alone. MethodsTwelve healthy, lean men (age (mean ± SD): 28 ± 7 years) received, on 4 separate occasions, 45-min intraduodenal infusions of C12 (0.3 kcal/min), TRP (0.1 kcal/min), C12 + TRP (0.4 kcal/min), or 0.9% saline (control), in a randomised, double-blind fashion. 30 min after commencement of the infusion a mixed-nutrient drink was consumed and gastric emptying measured (13C breath-test) for 3 h. Blood samples were obtained at baseline, in response to treatments alone, and for 2 h post-drink for measurements of plasma glucose, cholecystokinin, GLP-1, C-peptide, insulin and glucagon. ‘Early’ (first 30 min) and ‘overall’ glycaemic and hormone responses were evaluated. ResultsC12 + TRP and C12 delayed the rise in, but did not affect the overall glycaemic response to the drink, compared with control and TRP (all P < 0.05). C12 + TRP slowed gastric emptying compared with control and TRP (both P < 0.005), and C12 non-significantly slowed gastric emptying compared with control (P = 0.090). C12 + TRP and C12 delayed the rise in C-peptide and insulin, and also stimulated CCK and glucagon, compared with control and TRP (all P < 0.05). Only C12 + TRP stimulated early and overall GLP-1 compared with control (P < 0.05). ConclusionsIn healthy men, C12 + TRP and C12, in the loads administered, had comparable effects to delay the rise in glucose following a nutrient drink, probably primarily by slowing of gastric emptying, as a result of CCK and GLP-1 stimulation, while TRP had no effect.

Metabolic Risk Factors in Young Men With Healthy Body Fat But Different Level of Physical Activity.

The study was performed to evaluate metabolic risk in young lean individuals characterized by different physical activity. A total of 194 students (93 active with 5–7 h weekly physical activity and 101 inactive) were accepted for the study. The following percentages of body fat were accepted as characteristic for lean men: 14% to 17% in active and 18% to 24% in inactive participants. Circulating glucose, insulin, triacylglycerols (TG), total cholesterol (TC), and high-dendity lipoprotein (HDL)-cholesterol (HDL-C) were assayed. Daily intake of energy and macronutrients was briefly assessed from 24 h food records collected over 4 days preceding blood collection. Insulin and TG differed with respect to physical activity and was lower by 37.5% and 12.5%, respectively, in active versus inactive participants. In active students with upper quartile of body fat percentage, the only significant difference was found between circulating insulin (by 28%, p < .04). In inactive participants with upper quartile of body fat, significant differences were found between levels of insulin and TG (by 25% and by 37.5%, respectively). Diet composition did not differ with respect to the percentage of energy derived from protein, fat, and carbohydrates. An inverse association between insulin level and the percentage of body fat seems to be physiological one because it has been noted in both active and inactive individuals. On the contrary, elevation in circulating TG found exclusively in inactive subjects seems to be secondary to the changes in adiposity and circulating insulin and is followed by tendency to higher levels of TC.