The global prevalence of type 2 diabetes (T2D) is increasing rapidly [1]. T2D in ethnic minority groups in Europe is of particular interest as they have experienced rapidly changing environments and are disproportionally affected by T2D[2].
One of the largest ethnic minority populations in Europe are sub-Saharan Africans. We need to pin-point the environmental and health-behaviour factors associated with T2D in order to target interventions. Nevertheless, it is still unclear what factors are driving T2D in sub-Saharan African populations. Whilst epidemiological studies have looked at risk factors such as overweight, physical activity, smoking and education level, [4, 5] it is possible that health related behaviours not only affect T2D directly, but mediate their effect through epigenetics. Few have studied epigenetics in sub-Saharan Africans to date.
Epigenetics are heritable alterations to the genome that do not affect the DNA sequence. The most studied epigenetic mechanism is DNA methylation. An important characteristic of DNA methylation, as opposed to genetic variation, is that it can be affected by environmental and health-related behaviour factors and subsequently impact disease. Studies have shown a wide variety of health-related behaviour factors to affect DNA methylation, such as smoking[7], diet [8, 9], and physical activity[10]. If we can identify what socio-environmental and health-related behaviour factors, for example intake of a type of fatty acids, most significantly impact epigenetics and thereby increase T2D risk, we will not only learn what factors to target, but also how these factors biologically affect T2D. Epigenetics therefore has high potential as a novel approach to identify health-related behaviour factors most impacting T2D. This novel approach may be key in targeting interventions to curb the T2D epidemic in Africa.
The multi-centre RODAM study among Ghanaians, one of the largest sub-Saharan African groups in Europe, found a high burden of T2D among Ghanaian men and women living in Amsterdam (12.8: men, 9.9%: women), Berlin (15.3%, 10.2%) and London (10.4%, 8.9%)[3]. Worryingly, this study showed that the prevalence of T2D in urban Ghana was already at similarly high levels as among Ghanaian migrants in Europe (10.3%, 9.2%).
Our recently published analyses, the first epigenome-wide association study on adiposity in sub-Saharan Africans, revealed novel loci associated with adiposity that are potentially unique to sub-Saharan Africans[6]. This highlights epigenetics as a potential contributing factor to unexplained ethnic differences in health. Replication analyses are needed to confirm these findings as well as longitudinal studies to study causal effects. Fortunately, a follow-up to the RODAM study, pros-RODAM, will commence in 2018. Given the limited number of studies on epigenetics in Sub-Saharan Africans, major effort is needed to stimulate more studies to facilitate replication studies and meta-analyses in future.
References
[1] International Diabetes Federation (IDF). IDF Diabetes Atlas, 7th ed. Brussels, Belgium: International Diabetes Federation; 2015.[2] Meeks KAC, et al., Disparities in type 2 diabetes prevalence among ethnic minority groups resident in Europe: a systematic review and meta-analysis, Internal and emergency medicine 2016;11:327-40.
[3] Agyemang C, et al., Obesity and type 2 diabetes in sub-Saharan Africans – Is the burden in today’s Africa similar to African migrants in Europe? The RODAM study, BMC medicine 2016;14:166.
[4] Meeks KAC, et al., Prevalence of type 2 diabetes and its association with measures of body composition among African residents in the Netherlands–The HELIUS study, Diabetes research and clinical practice 2015;110:137-46.
[5] Agyemang C, et al., Brief Report: Diabetes Prevalence in Populations of South Asian Indian and African Origins: A Comparison of England and The Netherlands, Epidemiology 2011:563-7.
[6] Meeks KAC, et al., An epigenome-wide association study in whole blood of measures of adiposity among Ghanaians: the RODAM study, Clinical epigenetics 2017;9:103.
[7] Zeilinger S, et al., Tobacco smoking leads to extensive genome-wide changes in DNA methylation, PloS one 2013;8:e63812.
[8] Arpón A, et al., Adherence to Mediterranean diet is associated with methylation changes in inflammation-related genes in peripheral blood cells, Journal of physiology and biochemistry 2016;73:445-55.
[9] Greenlee H, et al., Long-term Diet and Biomarker Changes after a Short-term Intervention among Hispanic Breast Cancer Survivors: The ¡Cocinar Para Su Salud! Randomized Controlled Trial, Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology 2016;25:1491-502.
[10] Rönn T, et al., A six months exercise intervention influences the genome-wide DNA methylation pattern in human adipose tissue, PLoS genetics 2013;9:e1003572.
Leave a Reply