Abstract

The gut microbiota has been recognized as an essential organ that affects human health and disease. Dysbiosis of the gut microbiota is probably the basis of many health challenges especially non-communicable diseases (NCDs) such as colon cancer, obesity, and diabetes. We hypothesized that the appearance of NCDs is a consequence of the progressive diminution in the consumption of fibre-rich foods with suppression if saccharolytic fermentation and the production of short chain fatty acids (SCFA), butyrate which has profound anti-inflammatory and anti- neoplastic properties, and the increase in fat and colonic secondary bile acids (BA) which are pro-neoplastic.

Healthy males and females were enrolled in this study from urban Western Cape (40-62y) and rural Eastern Cape (43-76y), South Africa. Fecal samples were collected from each participant for analyses; targeted fecal SCFA and BA; total microbial DNA was extracted for microbiota analysis using 16S rRNA amplicon sequencing. In addition, we targeted functional microbial genes involved in butyrate, butyryl CoA:acetate-CoA transferase (bcoA) and secondary bile acid (BaiCD) synthesis using real time PCR. Dietary information was collected using food frequency questionnaires and linked to food composition tables designed by the South African Medical Research Council (SAMRC).

Surprisingly, median dietary fibre intakes of the rural participants (26g/d) were significantly lower than in the urban participants (38g/d) (p = 0.043). However, food quantities consumed by urban participants was significantly higher in calories, fat, and meat (p<0.05). Targeted genes, bcoA and baiCD were not significantly different. Only decoxycholic-acid (DCA) was significant (p < 0.05) in targeted SFCA and BA. Correlation analysis indicated that total dietary fibre, cholesterol, total fat, total protein and energy were significantly negatively correlated to Peptostreptococcaceae and Selenomonadaceae while total sugar and carbohydrate were positively correlated. Total dietary fibre was positively correlated to Muribaculaceae, BMI (>35Kg/m2) was positively correlated to Peptostreptococcaceae and negatively correlated to Selenomonadaeae. Peptostreptococcaceae has previously been reported to be abundant in the guts of colorectal cancer patients, while Muribaculaceae has also been reported to be strongly correlated with propionate which has a significant role in inducing epithelial cell apoptosis in cancer patients.

These results suggest that the increasing incidence of NCDs in urbanised South Africans is more related to an increase in the consumption of high-fat, high calorie foods that a reduction of fibre-rich foods. This likely explains the remarkably high incidence of obesity in urban African women (>40%) and raises the concern that there are 17 cancers now strongly associated with obesity.

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