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)

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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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

JMIR Research Protocols ◽

10.2196/resprot.9098 ◽

2018 ◽

Vol 7 (4) ◽

pp. e75 ◽

Cited By ~ 11

Author(s):

Julia H Goedecke ◽

Amy E Mendham ◽

Louise Clamp ◽

Pamela A Nono Nankam ◽

Melony C Fortuin-de Smidt ◽

...

Keyword(s):

Insulin Resistance ◽

Randomized Controlled Trial ◽

South African ◽

Exercise Intervention ◽

Controlled Trial ◽

African Women ◽

Black South African ◽

Randomized Controlled ◽

Baseline Characteristics ◽

South African Women

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

Acta Endocrinologica ◽

10.1530/eje-19-0957 ◽

2020 ◽

Vol 183 (1) ◽

pp. 51-61 ◽

Cited By ~ 2

Author(s):

Melony C Fortuin-de Smidt ◽

Amy E Mendham ◽

Jon Hauksson ◽

Olah Hakim ◽

Darko Stefanovski ◽

...

Keyword(s):

Body Weight ◽

Insulin Sensitivity ◽

Exercise Training ◽

South African ◽

Fat Mass ◽

African Women ◽

Control Group ◽

Ectopic Fat ◽

Black South African ◽

South African Women

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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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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The Influence of Objectively Measured Physical Activity During Pregnancy on Maternal and Birth Outcomes in Urban Black South African Women

Maternal and Child Health Journal ◽

10.1007/s10995-018-2504-3 ◽

2018 ◽

Vol 22 (8) ◽

pp. 1190-1199 ◽

Cited By ~ 4

Author(s):

Estelle D. Watson ◽

Søren Brage ◽

Tom White ◽

Kate Westgate ◽

Shane A. Norris ◽

...

Keyword(s):

Physical Activity ◽

South African ◽

Birth Outcomes ◽

African Women ◽

Black South African ◽

South African Women ◽

Objectively Measured ◽

Objectively Measured Physical Activity

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“Just because you’re pregnant, doesn’t mean you’re sick!” A qualitative study of beliefs regarding physical activity in black South African women

BMC Pregnancy and Childbirth ◽

10.1186/s12884-016-0963-3 ◽

2016 ◽

Vol 16 (1) ◽

Cited By ~ 12

Author(s):

Estelle D. Watson ◽

Shane A. Norris ◽

Catherine E. Draper ◽

Rachel A. Jones ◽

Mireille N. M. van Poppel ◽

...

Keyword(s):

Physical Activity ◽

Qualitative Study ◽

South African ◽

African Women ◽

Black South African ◽

South African Women

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Are South African Mothers Moving? Patterns and Correlates of Physical Activity and Sedentary Behavior in Pregnant Black South African Women

Journal of Physical Activity and Health ◽

10.1123/jpah.2016-0388 ◽

2017 ◽

Vol 14 (5) ◽

pp. 329-335 ◽

Cited By ~ 7

Author(s):

Estelle D. Watson ◽

Mireille N. M. Van Poppel ◽

Rachel A. Jones ◽

Shane A Norris ◽

Lisa K. Micklesfield

Keyword(s):

Physical Activity ◽

Pregnant Women ◽

South African ◽

African Women ◽

Activity Levels ◽

Second Trimester ◽

Recreational Physical Activity ◽

Third Trimester ◽

Black South African ◽

South African Women

Background:Although physical activity during pregnancy may be beneficial, the prenatal period is a vulnerable time for decreasing physical activity levels and increasing sedentary time.Methods:This longitudinal cohort study measured physical activity using the Global Physical Activity Questionnaire (GPAQ) in singleton, pregnant women in the second (14–18 wk gestation; n = 332) and third trimester (29–33 wk; n = 256).Results:There was a significant decrease in total MVPA (MET mins/wk) between the second and third trimester (P = .01). The majority of physical activity time was spent in walking for transport (80%), and less than 2% in recreational activities. In both trimesters, being married was inversely associated with walking for transport (second trimester: β = –0.12 95% CI = –0.31 to –0.02, third trimester: β = –0.17 95% CI = –0.47 to –0.07) and owning a car was positively associated with recreational physical activity (second trimester: β = 0.16 95% CI = 0.02 to 0.32, third trimester: β = 0.17 95% CI = 0.04 to 0.27). The women spent an average of 5 hours per day sitting.Conclusions:The low and declining levels of physical activity during pregnancy in this population are a concern. Interventions that include lifestyle education and provision of accessible recreational physical activity programs for pregnant women are needed.

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