The Journal of clinical endocrinology and metabolism
-
J. Clin. Endocrinol. Metab. · Dec 2003
Local androgen inactivation in abdominal visceral adipose tissue.
We examined the expression and activity of two enzymes from the aldoketoreductase (AKR) family 1C, namely type 5 17beta-hydroxysteroid dehydrogenase (17beta-HSD-5, AKR1C3) and type 3 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD-3, AKR1C2) in female sc and omental adipose tissue and in preadipocyte primary cultures. 17beta-HSD-5 preferentially synthesizes testosterone from the inactive adrenal precursor androstenedione, whereas 3alpha-HSD-3 inactivates dihydrotestosterone. mRNAs of both enzymes were detected in adipose tissue from the omental and sc compartments. Real-time PCR quantification indicated a 3-fold higher 3alpha-HSD-3 expression compared with 17beta-HSD-5, and the expression of both enzymes tended to be higher in the sc vs. the omental depot. Accordingly, dose-response and time-course experiments performed in preadipocyte primary cultures indicated that 3alpha-HSD activity was higher than 17beta-HSD activity (13-fold maximum velocity difference). ⋯ Moreover, omental adipose tissue 3alpha-HSD activity was positively and significantly associated with CT-measured visceral adipose tissue (r = 0.43; P < 0.02) and omental adipocyte diameter (r = 0.42; P < 0.02). These results indicate that local androgen inactivation is a predominant reaction in female abdominal adipose tissue, with the greatest conversion rates observed in the presence of abdominal visceral obesity. Increased androgen inactivation in omental adipose tissue of abdominally obese women may impact locally on the regulation of adipocyte metabolism.
-
J. Clin. Endocrinol. Metab. · Jul 2003
Comparative StudyHomeostasis model assessment of insulin resistance, quantitative insulin sensitivity check index, and oral glucose insulin sensitivity index in nonobese, nondiabetic subjects with high-normal blood pressure.
To investigate the relationships between high-normal blood pressure (BP) and insulin resistance, we examined insulin sensitivity in 306 nonobese and nondiabetic Japanese subjects with various BP categories (optimal BP, normal BP, high-normal BP, and hypertension). Insulin sensitivity was measured from fasting plasma glucose and insulin values and those during a 75-g oral glucose tolerance test by five formulas: the homeostasis model assessment of insulin resistance (HOMA-R), the quantitative insulin sensitivity check index (QUICKI), the oral glucose insulin sensitivity (OGIS) index, and two insulin sensitivity indexes (ISI-composite and ISI-stumvoll). The HOMA-R was significantly higher, and the QUICKI was significantly lower in subjects with hypertension than in subjects with optimal BP. ⋯ The ISI-stumvoll was significantly lower in subjects with high-normal BP or hypertension than in subjects with optimal BP. The OGIS index, ISI-composite, and ISI-stumvoll significantly decreased with increasing severity of BP status among the normotensive groups (optimal BP, normal BP, and high-normal BP). These findings indicate that insulin resistance is present even in the high-normal BP categories of nonobese and nondiabetic Japanese individuals.
-
J. Clin. Endocrinol. Metab. · Jun 2003
Incretin secretion in relation to meal size and body weight in healthy subjects and people with type 1 and type 2 diabetes mellitus.
Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are incretin hormones secreted in response to meal ingestion, thereby enhancing postprandial insulin secretion. Therefore, an attenuated incretin response could contribute to the impaired insulin responses in patients with diabetes mellitus. The aim of the present investigation was to investigate incretin secretion, in obesity and type 1 and type 2 diabetes mellitus, and its dependence on the magnitude of the meal stimulus. ⋯ Incremental GLP-1 responses were normal in type 1 diabetic patients. Increased fasting concentrations of GIP and an early enhanced postprandial GIP response were seen in obese, compared with lean healthy subjects, whereas GLP-1 responses were the same in the two groups. beta-cell sensitivity to glucose, evaluated as the slope of insulin secretion rates vs. plasma glucose concentration, tended to increase in both type 2 diabetic patients (29%, P = 0.19) and obese healthy subjects (22% P = 0.04) during the large meal, compared with the small meal, perhaps reflecting the increased incretin response. We conclude: 1) that a decreased GLP-1 secretion may contribute to impaired insulin secretion in type 2 diabetes mellitus, whereas GIP and GLP-1 secretion is normal in type 1 diabetic patients; and 2) that it is possible to modulate the beta-cell sensitivity to glucose in obese healthy subjects, and possibly also in type 2 diabetic patients, by giving them a large meal, compared with a small meal.
-
J. Clin. Endocrinol. Metab. · Jun 2003
Randomized Controlled Trial Clinical TrialBeyond adrenal and ovarian androgen generation: Increased peripheral 5 alpha-reductase activity in women with polycystic ovary syndrome.
Hyperandrogenism, a main clinical feature of polycystic ovary syndrome (PCOS), is thought to result from enhanced ovarian and adrenal androgen generation. To investigate the contribution of peripheral steroidogenesis, we used an oral challenge with dehydroepiandrosterone (DHEA) and analyzed its downstream conversion toward androgens in eight women with PCOS (age, 20-32 yr; body mass index, 20-41 kg/m(2)) and eight healthy women matched for age and body mass index. They underwent frequent serum sampling and urine collection for 8 h on three occasions: at baseline, and after 4 d of dexamethasone (Dex; 4 x 0.5 mg/d), followed by ingestion of 100 mg DHEA or placebo. ⋯ PCOS women also had significantly higher baseline excretion of 5 alpha-reduced glucocorticoid (P < 0.01) and mineralocorticoid metabolites (P < 0.05). Taken together, these data indicate enhanced peripheral 5 alpha-reductase activity in PCOS. Thus, not only ovary and adrenal, but also liver and peripheral target tissues, significantly contribute to steroid alterations in PCOS.
-
J. Clin. Endocrinol. Metab. · Jun 2003
Obesity, regional fat distribution, and syndrome X in obese black versus white adolescents: race differential in diabetogenic and atherogenic risk factors.
The incidence of type 2 diabetes mellitus in children is increasing with the increasing prevalence of obesity, particularly in African-American children. We hypothesized that African-American obese adolescents are more insulin resistant than their white peers, but have lower insulin secretion, thus increasing their risk of type 2 diabetes mellitus. The present study investigated insulin sensitivity and secretion, visceral adiposity (VAT), and cardiovascular disease (CVD) risk profile in black obese adolescents (BOA) vs. white obese adolescents (WOA). ⋯ In conclusion, a given level of body mass index confers different metabolic risks for WOA vs. BOA. Although differences in fat patterning may help explain the more atherogenic risk profile in whites, the cause of the more diabetogenic insulin sensitivity/secretion profile in blacks remains unknown and needs to be investigated further.