Omental and subcutaneous adipose tissue steroid levels in obese men
ABSTRACT We examined plasma and fat tissue sex steroid levels in a sample of 28 men aged 24.8-62.2 years (average BMI value of 46.3 +/- 12.7 kg/m(2)). Abdominal adipose tissue biopsies were obtained during general or obesity surgery. Omental and subcutaneous adipose tissue steroid levels were measured by gas chromatography and chemical ionization mass spectrometry after appropriate extraction procedures. BMI and waist circumference were negatively correlated with plasma testosterone (r = -0.49 and -0.50, respectively, p < 0.01) and dihydrotestosterone (r = -0.58 and -0.56, respectively, p < 0.01), and positively associated with estrone levels (r = 0.64 and 0.62, respectively, p < 0.001). Regional differences in adipose tissue steroid levels were observed for dihydrotestosterone (p < 0.005), androstenedione (p < 0.0001) and dehydroepiandrosterone levels (p < 0.05), which were all significantly more concentrated in omental versus subcutaneous fat. Positive significant associations were found between circulating level of a steroid and its concentration in omental and subcutaneous adipose tissue, for estrone (r = 0.72 and 0.57, respectively, p < 0.01), testosterone (r = 0.66 and 0.58, respectively, p < 0.01) and dihydrotestosterone (r = 0.58 and 0.45, respectively, p < 0.05). Positive correlations were observed between plasma dehydroepiandrosterone-sulfate and omental (r = 0.56, p < 0.01) as well as subcutaneous adipose tissue dehydroepiandrosterone level (r = 0.38, p = 0.05). Positive significant associations were found between omental adipocyte responsiveness to positive lipolytic stimuli (isoproterenol, dibutyryl cyclic AMP and forskolin) and plasma or omental fat tissue androgen levels. In conclusion, although plasma androgen or estrogen levels are strong correlates of adipose tissue steroid content both in the omental and subcutaneous fat depots, regional differences may be observed. Androgen concentration differences in omental versus subcutaneous adipose tissue suggest a depot-specific impact of these hormones on adipocyte function and metabolism.
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ABSTRACT: MicroRNAs (miRNAs) are class of molecular regulators found to participate in numerous biological processes, such as adipogenesis and obesity in mammals. To determine the roles of miRNAs involved in castration-induced body fatness, we investigated the different miRNA expression patterns in subcutaneous adipose tissue between intact and castrated male pigs. Our results showed that castration led to decrease serum testosterone but increase serum Leptin levels (P < 0.01). Moreover, castration also increased adipocyte size, body fat content and backfat thickness in male pigs (P < 0.01). Meanwhile, miRNA expression profiles in adipose tissue were changed by castration, and 18 miRNAs were considered as the differentially expressed candidates between intact and castrated male pigs. Furthermore, functional analysis indicated that the differential expressed miRNAs and their target genes are involved in the regulation of fatty acid metabolism. In brief, our present study provides a comprehensive view on how miRNAs works in subcutaneous adipose tissue with castration. These results suggested that miRNAs might play an important role in the castration-induced fat deposition in male pigs.Journal of applied genetics 01/2014; 55(2). DOI:10.1007/s13353-014-0194-0 · 1.90 Impact Factor
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ABSTRACT: The metabolic syndrome is a cluster of metabolic disorders characterized by insulin resistance and hyperinsulinaemia, and its presence can increase the risk of cardiovascular disease significantly. The metabolic syndrome is associated with increased circulating androgen levels in women, which may originate from the ovaries and adrenal glands. Adipocytes are also able to synthesise steroid hormones, and this output has been hypothesised to increase with elevated insulin plasma concentrations. However, the contribution of the adipocytes to the circulating androgen levels in women with metabolic syndrome is limited and the effects of insulin are not fully understood. The aim of this study was to investigate the presence of steroid precursors and synthetic enzymes in human adipocyte biopsies as markers of possible adipocyte androgen synthesis. We examined pre and mature adipocytes taken from tissue biopsies of abdominal subcutaneous adipose tissue of participating women from the Department of Obstetrics and Gynaecology, of the Royal Derby Hospital. The results showed the potential for localised adipocyte androgen synthesis through the presence of the androgen precursor progesterone, as well as the steroid-converting enzyme 17α-hydroxylase. Furthermore, we found the controlled secretion of androstenedione in vitro and that insulin treatment caused levels to increase. Continued examination of a localised source of androgen production is therefore of clinical relevance due to its influence on adipocyte metabolism, its negative impact on female steroidogenic homeostasis, and the possible aggravation this may have when associated to obesity and obesity related metabolic abnormalities such as hyperinsulinaemia.01/2014; 1:254–263. DOI:10.1016/j.ymgmr.2014.05.002
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ABSTRACT: Dihydrotestosterone (DHT) originates via irreversible reduction of testosterone by catalytic activity of 5alpha-reductase enzyme and it is demonstratively the most effective androgen. Androgens influence adipose tissue in men either directly by stimulation of the androgen receptor or indirectly, after aromatization, by acting at the estrogen receptor. DHT as a non-aromatizable androgen could be responsible for a male type fat distribution. The theory of non-aromatizable androgens as a potential cause of a male type obesity development has been studied intensively. However, physiological levels of DHT inhibit growth of mature adipocytes. In animal models, substitution of DHT in males after gonadectomy has a positive effect on body composition as a testosterone therapy. Thus, DHT within physiological range positively influences body composition. However, there are pathological conditions with an abundance of DHT, e.g. androgenic alopecia and benign prostatic hyperplasia. These diseases are considered as risk factors for development of metabolic syndrome or atherosclerosis. In obese people, DHT metabolism in adipose tissue is altered. Local abundance of non-aromatizable androgen has a negative effect on adipose tissue and it could be involved in pathogenesis of metabolic and cardiovascular diseases. Increased DHT levels, compared to physiological levels, have negative effect on development of cardiovascular diseases. Difference between the effect of physiological and increased level brings about certain paradox.Physiological research / Academia Scientiarum Bohemoslovaca 11/2010; 60(2):253-61. · 1.49 Impact Factor