Ectopic fat deposition in populations of black African ancestry: A systematic review and meta-analysis

Louise M Goff,Martin B Whyte,Daniel J Cuthbertson,Graham J Kemp,Reuben M Reed,Sarah J Nevitt

doi:10.1007/s00592-021-01797-5

Louise M Goff, Martin B Whyte + Show 4 more

Open Access

https://doi.org/10.1007/s00592-021-01797-5

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Abstract

AimsIn populations of black African ancestry (BA), a paradox exists whereby lower visceral adipose tissue is found despite their high risk for type 2 diabetes (T2D). This systematic review investigates ethnic differences in other ectopic fat depots (intrahepatic lipid: IHL; intramyocellular lipid: IMCL and intrapancreatic lipid; IPL) to help contextualise their potential contribution to T2D risk.MethodsA systematic literature search was performed in December 2020 to identify studies reporting at least one ectopic fat comparison between BA and one/more other ethnicity. For IHL, a meta-analysis was carried out with studies considered comparable based on the method of measurement.ResultsTwenty-eight studies were included (IHL: n = 20; IMCL: n = 8; IPL: n = 4). Meta-analysis of 11 studies investigating IHL revealed that it was lower in BA populations vs pooled ethnic comparators (MD −1.35%, 95% CI −1.55 to −1.16, I2 = 85%, P < 0.00001), white European ancestry (MD −0.94%, 95% CI −1.17 to -0.70, I2 = 79%, P < 0.00001), Hispanic ancestry (MD −2.06%, 95% CI −2.49 to −1.63, I2 = 81%, P < 0.00001) and South Asian ancestry comparators (MD −1.92%, 95% CI −3.26 to −0.57, I2 = 78%, P = 0.005). However, heterogeneity was high in all analyses. Most studies found no significant differences in IMCL between BA and WE. Few studies investigated IPL, however, indicated that IPL is lower in BA compared to WE and HIS.ConclusionThe discordance between ectopic fat and greater risk for T2D in BA populations raises questions around its contribution to T2D pathophysiology in BA.

Highlights

In the UK, type 2 diabetes (T2D) is 2–5 times more prevalent in ethnic minorities than in the general population [1], with diagnosis typically occurring 10–12 years earlier [2], and at a lower body mass index (BMI) [3]
Our metaanalysis provides evidence that black African ancestry (BA) populations have lower intrahepatic lipid (IHL) compared to other ethnic groups, in both sexes, across all ages and BMI categories and independent of glycaemic status
For intrapancreatic lipid (IPL), there were a notable lack of studies; those included suggest there may be lower IPL in BA compared to both white European ancestry (WE) and HIS populations

Summary

Introduction

In the UK, type 2 diabetes (T2D) is 2–5 times more prevalent in ethnic minorities than in the general population [1], with diagnosis typically occurring 10–12 years earlier [2], and at a lower body mass index (BMI) [3]. Despite their greater risk, the pathophysiology of T2D in populations of black African ancestry (BA) remains poorly understood. Current theories of T2D pathogenesis postulate that ectopic fat deposition and subsequent lipotoxicity play a central role [6, 7].

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