Studies have shown ethnic differences in body fat distribution, characterised by greater peripheral and less central fat accumulation in black compared to white South African (SA) women. As sex hormones play an important role in body fat distribution, our study aimed to determine whether differences in body fat distribution between black and white SA women were associated with subcutaneous adipose tissue (SAT) expression of oestrogen receptors (ERA and ERB) and aromatase (CYP19A1). Body fat distribution (DXA and CT) and ERA, ERB and CYP19A1 expression in abdominal and gluteal SAT were measured in 26 black and 22 white SA women. Abdominal SAT ERA and ERB did not differ by ethnicity or BMI. Gluteal ERA was higher (1.08 ± 0.06 vs 0.99 ± 0.05, P < 0.001) and ERB was lower (0.99 ± 0.06 vs 1.10 ± 0.07, P < 0.001) in black vs white SA women. CYP19A1 increased with obesity in all depots (P < 0.001). In both black and white SA women, gluteal ERA was associated with lower central fat mass (FM) and greater gynoid FM (P < 0.05), while the inverse association was shown for CYP19A1 in all depots (P < 0.01). In conclusion, ethnic differences in gluteal ERA expression were associated with differences in body fat distribution previously reported between black and white SA women.

Circulating glucocorticoids are associated with metabolic syndrome and related cardiometabolic risk factors in non-Africans. This study investigated these associations in Africans, whose metabolic phenotype reportedly differs from Europeans. Adiposity, blood pressure, glycaemia, insulin resistance, and lipid profile, were measured in 316 African men and 788 African women living in Soweto, Johannesburg. The 2009 harmonized criteria were used to define metabolic syndrome. Serum glucocorticoids were measured using liquid chromatography-mass spectrometry. Cortisol was associated with greater odds presenting with metabolic syndrome (odds ratio (95% CI) =1.50 (1.04, 2.17) and higher systolic (beta coefficient, β (95% CI) =0.04 (0.01, 0.08)) and diastolic (0.05 (0.02, 0.09)) blood pressure, but higher HDL (0.10 (0.02, 0.19)) and lower LDL (−0.14 (−0.24, −0.03)) cholesterol concentrations, in the combined sample of men and women. In contrast, corticosterone was only associated with higher insulin sensitivity (Matsuda index; 0.22 (0.03, 0.41)), but this was not independent of BMI. Sex-specific associations were observed, such that both cortisol and corticosterone were associated with higher fasting glucose (standardized β (95% CI): 0.24 (0.12, 0.36) for cortisol and 0.12 (0.01, 0.23) for corticosterone) and HbA1c (0.13 (0.01, 0.25) for cortisol and 0.12 (0.01, 0.24) for corticosterone) in men only, but lower HbA1c (0.10 (−0.20, −0.01) for cortisol and −0.09 (−0.18, −0.03) for corticosterone) in women only. Our study reports for the first time that associations between circulating glucocorticoid concentrations and key cardiometabolic risk factors exhibit both glucocorticoid- and sex-specificity in Africans.

The role of ectopic fat, insulin secretion and clearance in the preservation ofβ-cell function in black African women with obesity who typically present with hyperinsulinaemia is not clear. We aim to examine the associations between disposition index (DI, an estimate of β-cell function), insulin secretion and clearance and ectopic fat deposition. This is a cross-sectional study of 43 black South African women (age 20–35 years) with obesity (BMI 30–40 kg/m²) and without type 2 diabetes that measured the following: DI, insulin sensitivity (S_I), acute insulin response (AIRg), insulin secretion rate (ISR), hepatic insulin extraction and peripheral insulin clearance (frequently sampled i.v. glucose tolerance test); pancreatic and hepatic fat, visceral adipose tissue (VAT) and abdominal s.c. adipose tissue (aSAT) volume (MRI), intra-myocellular (IMCL) and extra-myocellular fat content (EMCL) (magnetic resonance spectroscopy). DI correlated positively with peripheral insulin clearance (β 55.80, P = 0.002). Higher DI was associated with lower VAT, pancreatic fat and soleus fat, but VAT explained most of the variance in DI (32%). Additionally, higher first phase ISR (P = 0.033) and lower hepatic insulin extraction (P = 0.022) were associated with lower VAT, independent from S_I, rather than with ectopic fat. In conclusion, peripheral insulin clearance emerged as an important correlate of DI_. However, VAT was the main determinant of a lower DI above ectopic fat depots. Importantly, VAT, but not ectopic fat, is associated with both lower insulin secretion and higher hepatic insulin extraction. Prevention of VAT accumulation in young black African women should, therefore, be an important target for beta cell preservation.