Matsepo Ramaboli
Postdoctoral Research Fellow; Stellenbosch University
Dr Matsepo Ramaboli holds a PhD in life sciences through the prestigious Fulbright scholarship from the University of South Carolina, USA. She has been the first registered postdoctoral fellow in the newly created African Microbiome Institute (AMI) at Stellenbosch University, where she has immersed herself in the ground breaking rural and urban studies that seek to assess geographic patterns in diet, the microbiome and risk of non-communicable diseases, working and collaborating with various world-renowned scientists constituting the AMI Research Consortium. She is keen to present the results of the ongoing pilot study in national and international meetings.
Abstract
Colon cancer is one of the westernized diseases, or non-communicable diseases (NCDs) common in the USA and Europe, rare in Africa. Until recently, indigenous southern Africans had the lowest risk for colon cancer (<5:100,000 compared to ~60:100,000). However, there is grave concern that with the massive population shift from rural to urban environments and westernization of their diets, NCDs are becoming more common in Africa. We have previously shown that westernization is associated with an increase in dietary fat and a reduction in plant fiber consumption. Here we investigate whether the increase in colon cancer is associated with an increase in colonic microbial metabolites related to fat consumption and associated with carcinogenesis, namely secondary bile acids, and a reduction in metabolites related to fiber fermentation, associated with suppression of neoplasia, notably the short-chain fatty acid (SCFA), butyrate.
Methods: Healthy middle aged volunteers were recruited from urban and rural Xhosas living in Khayelitsha and the Eastern Cape, respectively, as well as the rural Zimbabwean Mashonas. A fecal sample was collected from each participant for analysis. Quantitation of targeted fecal SCFA and bile acids was performed using gas chromatography techniques; functional microbial genes were quantitated using quantitative Polymerase Chain Reaction (qPCR), specifically: baiCD, the functional microbial gene for secondary bile acid synthesis, and bcoA, microbial butyryl CoA:acetate-CoA transferase, responsible for butyrate synthesis. Dietary information was collected using Food Frequency questionnaire and linked to local food composition tables. Unpaired Student’s t-test of significance was performed.
esults: Comparison of the various regions showed a trend of increasing bile acid levels, baiCD gene copies, and dietary fat amounts with changing region from more rural to more urban, although total energy consumption was slightly lower for Eastern Cape relative to Zimbabwe. Butyrate did not show such any correlation.
Conclusions: These results provide evidence that the recent increase on colon cancer with urbanization in South Africa is associated with an increase in dietary fat consumption and the microbial production of secondary bile acids, which have well recognized tumorigenic properties. Surprisingly, the “protective” fiber fermentation metabolites did not decrease with urbanization.