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β-cell function in black South African women: Exploratory associations with insulin clearance, visceral and ectopic fat

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Melony C. Fortuin-De Smidt, Amy E. Mendham, Jon Hauksson, Ali Alhamud, Darko Stefanovski, Olah Hakim, Jeroen Swart, Louise M. Goff, Steven E. Kahn, Tommy Olsson, Julia H. Goedecke

Original languageEnglish
Pages (from-to)550-560
Number of pages11
JournalEndocrine Connections
Volume10
Issue number5
DOIs
PublishedMay 2021

Bibliographical note

Funding Information: This study was funded by the National Research Foundation of South Africa (NRF), Competitive Programme for Rated Researchers (Grant no: 93577), the NRF/STINT Sweden/South Africa Research Collaboration Programme (UID: 106784), the South African Medical Research Council (SAMRC). M F is a recipient of SAMRC, through its Division of Research Capacity Development, Clinician Researcher Development PhD Scholarship Programme. The content hereof is the sole responsibility of the authors and does not necessarily represent the official views of the SAMRC. S K is supported in part by the United States Department of Veterans Affairs.The authors thank Nandipha Sinyanya, Ntombekhaya Zoneleni, Keitumetse Smouse and Hendriena Victor for their valuable contribution towards the study. Funding Information: This study was funded by the National Research Foundation of South Africa (NRF), Competitive Programme for Rated Researchers (Grant no: 93577), the NRF/STINT Sweden/South Africa Research Collaboration Programme (UID: 106784), the South African Medical Research Council (SAMRC). M F is a recipient of SAMRC, through its Division of Research Capacity Development, Clinician Researcher Development PhD Scholarship Programme. The content hereof is the sole responsibility of the authors and does not necessarily represent the official views of the SAMRC. S K is supported in part by the United States Department of Veterans A 贀airs. Publisher Copyright: © 2021 The authors Published by Bioscientifica Ltd. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

King's Authors

Abstract

The role of ectopic fat, insulin secretion and clearance in the preservation of β-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 (SI), 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 SI, 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.

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