Effect of exercise training on insulin sensitivity, hyperinsulinemia and ectopic fat in black South African women: a randomized controlled trial

Melony C Fortuin-de Smidt, Amy E Mendham, Jon Hauksson, Olah Hakim, Darko Stefanovski, Louise Clamp, Lindokuhle Phiri, Jeroen Swart, Louise M Goff, Lisa K Micklesfield, Steven E Kahn, Tommy Olsson, Julia H Goedecke

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Abstract

Objective: We investigated the effects of a 12-week exercise intervention on insulin sensitivity (SI) and hyperinsulinemia and associated changes in regional and ectopic fat.

Research design and methods: Healthy, black South African women with obesity (mean age 23 ± 3.5 years) and of isiXhosa ancestry were randomised into a 12-week aerobic and resistance exercise training group (n = 23) and a no exercise group (control, n = 22). Pre and post-intervention testing included assessment of SI, insulin response to glucose (AIRg), insulin secretion rate (ISR), hepatic insulin extraction (FEL) and disposition index (DI) (AIRg × SI) (frequently sampled i.v. glucose tolerance test); fat mass and regional adiposity (dual-energy X-ray absorptiometry); hepatic, pancreatic and skeletal muscle fat content and abdominal s.c. and visceral adipose tissue volumes (MRI).

Results: Exercise training increased VO2peak (mean ± s.d.: 24.9 ± 2.42 to 27.6 ± 3.39 mL/kg/min, P < 0.001), SI (2.0 (1.2-2.8) to 2.2 (1.5-3.7) (mU/l)-1 min-1, P = 0.005) and DI (median (interquartile range): 6.1 (3.6-7.1) to 6.5 (5.6-9.2) × 103 arbitrary units, P = 0.028), and decreased gynoid fat mass (18.5 ± 1.7 to 18.2 ± 1.6%, P < 0.001) and body weight (84.1 ± 8.7 to 83.3 ± .9.7 kg, P = 0.038). None of these changes were observed in the control group, but body weight increased (P = 0.030). AIRg, ISR and FEL, VAT, SAT and ectopic fat were unaltered after exercise training. The increase in SI and DI were not associated with changes in regional or ectopic fat.

Conclusion: Exercise training increased SI independent from changes in hyperinsulinemia and ectopic fat, suggesting that ectopic fat might not be a principal determinant of insulin resistance in this cohort.

Original languageEnglish
Pages (from-to)51-61
Number of pages11
JournalEuropean Journal of Endocrinology
Volume183
Issue number1
DOIs
Publication statusPublished - 1 Jul 2020

Keywords

  • Adipose Tissue/metabolism
  • Adiposity
  • Adult
  • Blood Glucose
  • Exercise Therapy/methods
  • Female
  • Humans
  • Hyperinsulinism/complications
  • Insulin Resistance
  • Obesity/complications
  • South Africa
  • Treatment Outcome
  • Young Adult

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