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

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.

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Lean mass appears to be more strongly associated with bone health than fat mass in urban black South African women

The journal of nutrition health & aging ◽

10.1007/s12603-015-0492-1 ◽

2015 ◽

Vol 19 (6) ◽

pp. 628-636 ◽

Cited By ~ 12

Author(s):

O. F. Sotunde ◽

H. S. Kruger ◽

H. H. Wright ◽

L. Havemann-Nel ◽

I. M. Kruger ◽

...

Keyword(s):

South African ◽

Fat Mass ◽

Lean Mass ◽

Bone Health ◽

African Women ◽

Black South African ◽

South African Women

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An Exercise Intervention to Unravel the Mechanisms Underlying Insulin Resistance in a Cohort of Black South African Women: Protocol for a Randomized Controlled Trial and Baseline Characteristics of Participants (Preprint)

10.2196/preprints.9098 ◽

2017 ◽

Author(s):

Julia H Goedecke ◽

Amy E Mendham ◽

Louise Clamp ◽

Pamela A Nono Nankam ◽

Melony C Fortuin-de Smidt ◽

...

Keyword(s):

Physical Activity ◽

Insulin Resistance ◽

Insulin Sensitivity ◽

South African ◽

Exercise Intervention ◽

African Women ◽

Control Group ◽

Intravenous Glucose ◽

Black South African ◽

Causal Pathways

BACKGROUND The pathogenesis of type 2 diabetes (T2D) in black African women is complex and differs from that in their white counterparts. However, earlier studies have been cross-sectional and provide little insight into the causal pathways. Exercise training is consistently used as a model to examine the mechanisms underlying insulin resistance and risk for T2D. OBJECTIVE The objective of the study was to examine the mechanisms underlying the changes in insulin sensitivity and secretion in response to a 12-week exercise intervention in obese black South African (SA) women. METHODS A total of 45 obese (body mass index, BMI: 30-40 kg/m2) black SA women were randomized into a control (n=22) or experimental (exercise; n=23) group. The exercise group completed 12 weeks of supervised combined aerobic and resistance training (40-60 min, 4 days/week), while the control group maintained their typical physical activity patterns, and both groups were requested not to change their dietary patterns. Before and following the 12-week intervention period, insulin sensitivity and secretion (frequently sampled intravenous glucose tolerance test) and its primary and secondary determinants were measured. Dietary intake, sleep quality and quantity, physical activity, and sedentary behaviors were measured every 4 weeks. RESULTS The final sample included 20 exercise and 15 control participants. Baseline sociodemographics, cardiorespiratory fitness, anthropometry, cardiometabolic risk factors, physical activity, and diet did not differ between the groups (P>.05). CONCLUSIONS The study describes a research protocol for an exercise intervention to understand the mechanisms underlying insulin sensitivity and secretion in obese black SA women and aims to identify causal pathways underlying the high prevalence of insulin resistance and risk for T2D in black SA women, targeting specific areas for therapeutic intervention. CLINICALTRIAL Pan African Clinical Trial Registry PACTR201711002789113; http://www.pactr.org/ATMWeb/ appmanager/atm/atmregistry?_nfpb=true&_pageLabel=portals_app_atmregistry_portal_page_13 (Archived by WebCite at http://www.webcitation.org/6xLEFqKr0)

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HDL Subclass Distribution Shifts with Increasing Central Adiposity

Journal of Obesity ◽

10.1155/2019/2107178 ◽

2019 ◽

Vol 2019 ◽

pp. 1-6 ◽

Cited By ~ 3

Author(s):

Nicholas J. Woudberg ◽

Sandrine Lecour ◽

Julia H. Goedecke

Keyword(s):

South African ◽

Body Fat ◽

Fat Mass ◽

Fat Distribution ◽

Body Fat Distribution ◽

African Women ◽

Black South African ◽

Percentage Decrease ◽

South African Women

Although cross-sectional studies have shown that obesity is associated with lower concentrations of large high-density lipoprotein (HDL) subclasses, it is unknown if changes in HDL subclasses are related to changes in body fat and its distribution over time. We therefore assessed changes in HDL subclass distribution over a 5.5-year free-living follow-up period in 24 black South African women. At baseline and follow-up, body composition and body fat distribution were measured using anthropometry, dual X-ray absorptiometry, and computerized tomography. HDL subclass distribution was quantified using Lipoprint®. Over the 5.5-year follow-up period, body fat (+17.3 ± 4.5 kg,p<0.05) and trunk fat mass (+7.4 ± 1.9%, % fat mass, FM,p<0.05) increased, while leg fat mass (−2.53 ± 0.56%, % FM,p<0.001) and the distribution of large (−6.43 ± 2.12%,p<0.05) HDL subclasses decreased. A percentage decrease in large HDL subclasses was associated with a percentage increase in central fat mass (visceral adipose tissue (VAT) area,p<0.05) and a percentage decrease in peripheral fat mass (leg fat mass). These preliminary findings suggest that a relative redistribution of body fat from the periphery to the abdominal region were associated with a decrease HDL subclass size in black South African women and provide a novel link between body fat distribution and lipidology in this population.

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Insulin Response in Relation to Insulin Sensitivity: An appropriate -cell response in black South African women

Diabetes Care ◽

10.2337/dc08-2048 ◽

2009 ◽

Vol 32 (5) ◽

pp. 860-865 ◽

Cited By ~ 52

Author(s):

J. H. Goedecke ◽

J. A. Dave ◽

M. V. Faulenbach ◽

K. M. Utzschneider ◽

E. V. Lambert ◽

...

Keyword(s):

Insulin Sensitivity ◽

South African ◽

Cell Response ◽

Insulin Response ◽

African Women ◽

Black South African ◽

South African Women

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Insulin Response in Relation to Insulin Sensitivity: An Appropriate -Cell Response in Black South African Women: Response to Goedecke et al.

Diabetes Care ◽

10.2337/dc09-1077 ◽

2009 ◽

Vol 32 (10) ◽

pp. e123-e123 ◽

Cited By ~ 1

Author(s):

B. I. Joffe ◽

L. A. Distiller

Keyword(s):

Insulin Sensitivity ◽

South African ◽

Cell Response ◽

Insulin Response ◽

African Women ◽

Black South African ◽

South African Women

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β-cell function in black South African women: Associations with insulin clearance and ectopic fat

10.21203/rs.3.rs-35455/v2 ◽

2020 ◽

Author(s):

Melony Cathlin Fortuin-de Smidt ◽

Amy E Mendham ◽

Jon Hauksson ◽

Ali Alhamud ◽

Darko Stefanovski ◽

...

Keyword(s):

Insulin Secretion ◽

South African ◽

Cell Function ◽

Insulin Clearance ◽

African Women ◽

Ectopic Fat ◽

Black South African ◽

Β Cell Function ◽

Hepatic Insulin Extraction ◽

South African Women

Abstract Background: 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 hyperinsulinemia 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.Methods: 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 intravenous glucose tolerance test); pancreatic and hepatic fat, visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue (aSAT) volume (magnetic resonance imaging), intramyocellular (IMCL) and extramyocellular fat content (EMCL) (magnetic resonance spectroscopy). Results: DI correlated positively with peripheral insulin clearance before (β 55.80, p=0.002) and after adjusting for hepatic insulin extraction. 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) associated with lower VAT, independent from SI, rather than with ectopic fat. Conclusion: Peripheral insulin clearance emerged as an important correlate of DI, independent from hepatic insulin extraction. However, VAT was the main determinant of a lower DI above ectopic fat depots. Importantly, VAT, but not ectopic fat, was associated with both lower insulin secretion and higher hepatic insulin extraction, independent from SI, and may provide a novel explanation of these findings in black South African women with obesity.

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β -Cell Function in Black South African Women: Associations With Insulin Clearance And Ectopic Fat

10.21203/rs.3.rs-35455/v1 ◽

2020 ◽

Author(s):

Melony Cathlin Fortuin-de Smidt ◽

Amy E Mendham ◽

Jon Hauksson ◽

Ali Alhamud ◽

Darko Stefanovski ◽

...

Keyword(s):

Insulin Secretion ◽

South African ◽

Cell Function ◽

Insulin Clearance ◽

African Women ◽

Ectopic Fat ◽

Black South African ◽

Β Cell Function ◽

Hepatic Insulin Extraction ◽

South African Women

Abstract Background: The role of ectopic fat, insulin secretion and clearance in the preservation of β-cell function in obese, black African women who typically present with hyperinsulinemia is not clear. We aim to examine the associations between disposition index (DI, a measure of β-cell function), insulin secretion and clearance and ectopic fat deposition. Methods: This is a cross-sectional study of 43 obese (BMI 30-40 kg/m2) black South African ( women (age 20-35 years) 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 intravenous glucose tolerance test); pancreatic and hepatic fat, visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue (SAT) volume (magnetic resonance imaging), intramyocellular (IMCL) and extramyocellular fat content (EMCL) (magnetic resonance spectroscopy). DI correlated positively with peripheral insulin clearance before (β 55.80, p=0.002) and after adjusting for hepatic insulin extraction. 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) associated with lower VAT, independent from SI, rather than with ectopic fat. Conclusion: Peripheral insulin clearance emerged as an important determinant of DI, independent from hepatic insulin extraction. However, VAT was the main determinant of a lower DI above ectopic fat depots. Importantly, VAT, but not ectopic fat, was associated with both lower insulin secretion and higher hepatic insulin extraction, independent from SI, and may provide a novel explanation of these findings in obese black South African women.

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