Ethnic differences in hepatic and systemic insulin sensitivity and their associated determinants in obese black and white South African women

Diabetologia. 2015 Nov;58(11):2647-52. doi: 10.1007/s00125-015-3720-7. Epub 2015 Aug 1.

Abstract

Aims/hypothesis: There is evidence to suggest that ectopic fat deposition in liver and skeletal muscle may differ between black and white women resulting in organ-specific differences in insulin sensitivity. Accordingly, the aim of the study was to examine ethnic differences in hepatic and peripheral insulin sensitivity, and the association with hepatic and skeletal muscle lipid content, and skeletal muscle gene expression.

Methods: In a cross-sectional study including 30 obese premenopausal black and white women, body composition (dual energy x-ray absorptiometry), liver fat and skeletal muscle (soleus and tibialis anterior) fat accumulation (proton-magnetic resonance spectroscopy), skeletal muscle gene expression, insulin sensitivity (two-step isotope labelled, hyperinsulinaemic-euglycaemic clamp with 10 mU m(-2) min(-1) and 40 mU m(-2) min(-1) insulin infusions), and serum adipokines were measured.

Results: We found that, although whole-body insulin sensitivity was not different, obese white women presented with lower hepatic insulin sensitivity than black women (% suppression of endogenous glucose production [% supp EGP], median [interquartile range (IQR)]: 17 [5-51] vs 56 [29-100] %, p = 0.002). While liver fat tended to be lower (p = 0.065) and skeletal muscle fat deposition tended to be higher (p = 0.074) in black compared with white women, associations with insulin sensitivity were only observed in black women (% supp EGP vs liver fat: r = -0.57, p < 0.05 and % supp EGP vs soleus fat: r = -0.56, p < 0.05).

Conclusions/interpretation: These findings may suggest that black women are more sensitive to the effects of ectopic lipid deposition than white women.

Keywords: Black African; Ectopic fat; Ethnicity; Euglycaemic–hyperinsulinaemic clamp; Hepatic insulin sensitivity; Liver fat; Peripheral insulin sensitivity; Skeletal muscle lipid.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adipose Tissue / metabolism
  • Adiposity / ethnology
  • Adult
  • African Continental Ancestry Group*
  • Cross-Sectional Studies
  • European Continental Ancestry Group*
  • Female
  • Humans
  • Insulin Resistance / ethnology*
  • Liver / metabolism*
  • Middle Aged
  • Muscle, Skeletal / metabolism
  • Obesity / ethnology*
  • Obesity / metabolism
  • Premenopause
  • South Africa