Association of fat mass profile with natriuretic peptide receptor alpha in subcutaneous adipose tissue of medication-free healthy men: A cross-sectional study

Background: Atrial natriuretic peptide increases lipolysis in human adipocytes by binding to natriuretic peptide receptor-A (NPRA). The aim of the current study was to examine the associations of NPRA mRNA of subcutaneous adipose tissue with fat mass, fat-free mass, body mass index (BMI) and arterial blood pressure in medication-free healthy men. Method: Thirty-two volunteers [age (years): 36.06±7.36, BMI: 27.60±4.63 (kg/m2)] underwent assessments of body height/weight, % fat mass, fat-free mass (kg), blood pressure, and a subcutaneous adipose tissue biopsy via a surgical technique. Results: We found that NPRA mRNA was negatively associated with % fat mass (r=-0.40, R2=0.16, p=0.03) and BMI (r=-0.45, R2=0.20, p=0.01). Cohen’s f2 effect size analyses showed a small effect size between NPRA mRNA and BMI (f2=0.25). One-way analysis of variance with Bonferroni post-hoc tests showed a tendency for mean differences of NPRA mRNA across BMI categories (p=0.06). This was confirmed by Cohen’s d effect size analyses revealing a large effect size of NPRA mRNA between obese individuals (BMI≥30 kg/m2) and either normal weight (BMI=19-25 kg/m2; d=0.94) or overweight (BMI=25-30 kg/m2; d=1.12) individuals. Conclusions: NPRA mRNA is negatively associated with % fat mass and BMI in medication-free healthy men, suggesting a possible role of NPRA in the control of fat mass accumulatio

Assessment of the relationship between macronutrient intake and browning of white fat in adult males

Research conducted in rodents and humans present conflicting results on the relationship between caloric intake and the browning of subcutaneous white adipose tissue (scWAT). For example, exercise combined with caloric restriction did not change browning indices measured from human scWAT samples. In another study, caloric restriction in mice resulted in the browning of both scWAT and visceral white adipose tissue. Few investigators, however, have examined the relationship between differences in macronutrient intake and browning processes of human scWAT.Published versio

Thermogenic capacity of human white-fat: the actual picture

Presented at the 9th Greek Conference of Biochemistry and Physiology of Exercise, Thessaloniki, Greece, 18–20 October 2019Cold exposure and exercise may increase thermogenic capacity of white adipose tissue (WAT), which could subsequently enhance energy expenditure and body weight loss. We aimed to identify possible alterations in uncoupling protein 1 (UCP1)—the main biomarker of thermogenic activation—in human WAT due to both cold exposure and exercise, as well as the link between environmental temperature and thermogenic capacity of human WAT. MATERIAL & METHOD: We conducted four human experimental studies and two systematic reviews and meta-analyses—PROSPERO registration CRD42019120116, CRD42019120213. RESULTS: UCP1 mRNA was higher in winter than in summer [t(30) = 2.232, p = 0.03] in human WAT and our meta-analysis showed a main effect of cold exposure on human UCP1 mRNA [standard mean difference (Std-md) = 1.81, confidence interval (CI) = 0.50–3.13, p = 0.007]. However, UCP1 mRNA/protein expressions displayed no associations with %fat mass or BMI (p > 0.05, Cohen’s f2 < 0.20). Both a 2-hour cooling and a non-cooling protocol preceding the positron emission tomography/computed tomography (PET/CT) measurements revealed no association between environmental temperature and standardised uptake value (SUVmax) of human WAT, as well as no mean differences in SUVmax-WAT-activity between winter and summer. An 8-week exercise program had no effect on UCP1 of human WAT or on body composition. Our meta-analysis also revealed: (a) no effect of chronic exercise on human UCP1 mRNA, (b) a main effect of chronic exercise on UCP1 protein concentrations (Std-md = 0.59, CI = 0.03–1.16, p = 0.04) and UCP1 mRNA (Std-md = 1.76, CI = 0.48–3.04, p = 0.007) in WAT of normal diet animals, c) a main effect of chronic exercise on UCP1 mRNA (Std-md = 2.94, CI = 0.24–5.65, p = 0.03) and UCP1 protein concentrations (Std-md = 2.06, CI = 0.07–4.05, p = 0.04) of high-fat diet animals. CONCLUSIONS: Cold exposure represents a main stimulus for increased thermogenic capacity in human white adipocytes; however, this may have no impact on body weight loss. Chronic exercise may represent no major stimulus for UCP1 induced in human white adipocytes, while in animals it increases UCP1 gene independently of their diet. Therefore, evidence from animal studies regarding UCP1 gene activation in white adipocytes may not be applicable in humans. Finally, the identification of human WAT thermogenic capacity via PET/CT examination may be optimal with both a cooling and a non-cooling protocol.Published onlin

Dihydrotestosterone, and Not Testosterone, Enhances the LPS-Induced Inflammatory Cytokine Gene Expression in Human Adipocytes

Background: The development of obesity-related complications lies in the low-grade inflammatory state consequent to adipocyte dysfunction. The direct involvement of sex hormones in adipose tissue inflammation has been previously suggested, but the evidence is scarce. In this study, we evaluated the effects of sex steroids on the in-vitroexpression of inflammatory mediators in human-derived adipocytes before and after lipopolysaccharide (LPS) exposure. Methods: Human adipocytes were differentiated from the vascular stromal fraction of adipose tissue samples of subjects undergoing abdominoplasty. We evaluated MCP-1, IL-1β, IL-6, and TNF-α gene expression in the presence of the main sex steroids, testosterone (T), and 17β-estradiol (E). Furthermore, we analyzed the effects of adipocytes exposure to the non-aromatizable androgen dihydrotestosterone (DHT), together with the effects of adipocytes pre-incubation with the aromatase inhibitor anastrozole alone (A), and in combination with T (A/T) before incubation with LPS. Results: DHT, but not T, significantly enhanced the LPSinduction of MCP-1, IL-1β, IL-6, and TNF-α. Intriguingly, the exposure of adipocytes with A/T dramatically increased the LPS-induced expression of all considered inflammatory cytokines, even more than a hundred-fold. Conclusions: DHT and A/T dramatically enhance LPS-induced inflammatory cytokine expression in human-derived adipocytes. These results confirm the involvement of sex hormones in adipose tissue inflammation, suggesting a specific role for non-aromatizable androgens as the amplificatory sex hormones of the inflammatory response

Insulin and body weight but not hyperandrogenism seem involved in seasonal serum 25-OH-vitamin D3 levels in subjects affected by PCOS

PCOS patients were frequently characterized by lower plasma vitamin D levels. The mechanisms involved in this dysfunction remains still debated, therefore we evaluated the role of androgen, insulin and body weight on the serum VitD levels in women with or without PCOS. Eighty one patients 18\u201342 yrs old were studied into \u201cSUMMER\u201d and \u201cWINTER\u201d seasonal period: thirty seven PCOS, seventeen no-ovarian hyperandrogenic (noPCOS), twelve functional hypothalamic amenorrhea (FHA) and finally fifteen healthy (Con). Patients were further divided into: lean (L), obese (O), normo- (nINS) and hyperinsulinemic (hINS). All hormonal and metabolic parameters were measured at 1-7 days of the menstrual cycle. Our results show that VitD levels were lower in PCOS and in noPCOS than in FHA and Con, in particular in (O) and (hINS) PCOSs. Both in summer and in winter, PCOSs had basal VitD levels significantly lower than FHA and Con, whereas they were similar to noPCOS. Yet, LhINS and OPCOS had VitD levels lower than Con and noPCOS. VitD levels were comparable in LnINS PCOS and Con. In conclusion, PCOSs had levels of VitD lower than controls. Weight and hyperinsulinemia had a significant influence on these values. Finally, over 70% of our healthy patients had VitD deficiency

Infrared thermography for indirect assessment of activation of brown adipose tissue in lean and obese male subjects

Brown adipose tissue (BAT) plays a key role in adaptive thermogenesis in mammals, and it has recently been considered as an attractive therapeutic target for tackling human obesity by increasing energy expenditure. Thermal imaging using infrared thermography (IRT) has emerged as a potential safe, rapid and inexpensive technique for detecting BAT in humans. However, little attention has been given to the reliability of this method in obese subjects. To this end, we evaluated the capacity of IRT to detect activated supraclavicular (SCV) BAT in 14 lean and 16 mildly obese young adults after acute cold exposure. Using IRT we measured the temperature of the skin overlying the SCV and sternal areas at baseline and after acute cold stimulation. Additionally, energy expenditure was measured by indirect calorimetry and body composition was estimated using bioelectrical impedance analysis. Energy expenditure and SCV skin temperature significantly increased in lean subjects upon cold exposure, while no significant changes were detected in the obese group. Furthermore, cold-induced variations in SCV skin temperature of obese subjects showed a negative correlation with body mass index. This study suggests that in lean individuals BAT is a rapidly activated thermogenic tissue possibly involved in the regulation of energy balance, and can be indirectly assessed using IRT. In obese subjects, BAT seems less prone to be activated by cold exposure, with the degree of adiposity representing a limiting factor for the indirect detection of BAT activation by measuring the skin temperature overlying BAT

Insulin receptor and glucose transporters mRNA expression throughout the menstrual cycle in human endometrium: a physiological and cyclical condition of tissue insulin resistance.

The expression of insulin receptor (IR), together with that of glucose transporters 1 and 4 (GLUT1-4) and of Insulin Growth Factor-I and -II (IGF-I,-II) in the endometrium of healthy and young women in both phases of menstrual cycle was assessed. Sixteen out of 20 healthy and normal menstruating volunteers were studied. Endometrial samplings were performed in every subject, twice in the same cycle, during the follicular and luteal phase respectively. The mRNA expression of IR, GLUT1-4, IGF-I and -II were evaluated by real-time quantitative RT-PCR and immunostaining reactions. Our results indicate that IR, GLUT1-4, IGF-I and -II mRNAs were expressed in both phases of the endometrial cycle: GLUT4 and IGF-I mRNA expression were significantly higher in the follicular phase and localized at the epithelial and stromal cell level, respectively, whereas IR, GLUT1 and IGF-II mRNA expression were mostly present in the secretory phase and mainly localized at the stromal level. An inverse tendency of IR and GLUT4 mRNA expression was respectively observed from follicular to luteal phase. In conclusion our data suggest that IR, glucose transporters and IGFs are significantly and differently expressed at the endometrial level throughout the menstrual cycle and that human endometrium cyclically undergoes through a transitory condition from normal to an insulin-resistance state

A Novel Loss of Function Melanocortin-4-Receptor Mutation (MC4R-F313Sfs*29) in Morbid Obesity

CONTEXT: Melanocortin receptor-4 (MC4R) gene mutations are associated with early-onset severe obesity and the identification of potential pathological variants is crucial for the clinical management of patients with obesity.OBJECTIVE: To explore whether and how a novel heterozygous MC4R variant (MC4R-F313Sfs*29), identified in a young boy (BMI 38.8kg/m 2) during a mutation analysis conducted in a cohort of patients with obesity, plays a determinant pathophysiological role in the obesity development.DESIGN SETTING AND PATIENTS: The genetic screening was carried out in a total of 209 unrelated patients with obesity (BMI\u202f 65\u202f35\u202fkg/m 2). Structural and functional characterization of the F313Sfs*29-mutated MC4R was performed using computational approaches and in vitro, using HEK293 cells transfected with genetically-encoded biosensors for cAMP and Ca 2+.RESULTS: The F313Sfs*29 was the only variant identified. In vitro experiments showed that HEK293 cells transfected with the mutated form of MC4R did not increase intracellular cAMP or Ca 2+ levels after the stimulation with a specific agonist in comparison with HEK293 cells transfected with the wild type form of MC4R ( 06R/R0= -90%\ub18%; p<0,001). In silico modelling showed that the F313Sfs*29 mutation causes a major reorganization cytosolic domain of the MC4R, thus reducing the affinity of the putative GalphaS binding site.CONCLUSIONS: The newly discovered F313Sfs*29 variant of MC4R may be involved in the impairment of alpha-MSH-induced cAMP and Ca 2+ signaling, blunting intracellular G protein mediated signal transduction. This alteration might have led to the dysregulation of satiety signaling, resulting in hyperphagia and early onset of obesity

Changes in muscle myostatin expression in obese subjects after weight loss

Myostatin is a member of transforming growth factor-beta superfamily that plays an important inhibitory role during muscle development; in fact mutations of myostatin gene result in a hypermuscular phenotype. Moreover myostatin-deficient mice have a significant reduction in fat depots and a depression of adipogenesis. Little is known about myostatin function in muscle growth regulation in humans and in particular during caloric restriction. In the present work we quantified by real-time RT-PCR myostatin expression in muscle biopsies of a group of morbidly obese patients before and after weight loss obtained by biliopancreatic diversion (BPD). The patients reduced body weight by 38.9%, mostly due to fat-mass loss, showing also a significant reduction in the 24-hour EE as assessed by the respiratory chamber. Myostatin mRNA levels result clearly decreased after weight loss, suggesting a role in counteracting the progressive decline of muscle mass after BPD. Myostatin may provide therefore another mechanistic explanation for the control of energy partitioning between protein and fat, working against muscle wasting. Our data suggest that myostatin might represent an important regulator of skeletal muscle size also in conditions of food restriction in obese subjects