Differences in Fecal Gut Microbiota, Short-Chain Fatty Acids and Bile Acids Link Colorectal Cancer Risk to Dietary Changes Associated with Urbanization Among Zimbabweans

Abstract

The incidence of colorectal cancer (CRC) is gradually rising in sub-Saharan Africa.This may be due to dietary changes associated with urbanisation, which may induce tumour-promoting gut microbiota composition and function. We compared faecal microbiota composition and activity in 10 rural and 10 urban Zimbabweans for evidence of a differential CRC risk. Dietary intake was assessed by a food frequency questionnaire. Faecal microbiota composition, metabolomic profile, functional microbial genes were analysed, and bile acids and short chain fatty acids quantified.Animal protein intake was higher among urban volunteers, but carbohydrate and fibre intake were similar. Bacteria related to Blautia obeum, Streptococcus bovis and Subdoligranulum variable were higher in urban residents, whereas bacteria related to Oscillospira guillermondii and Sporobacter termitidis were higher in rural volunteers. Faecal levels of primary bile acids, cholic acid and chenodeoxycholic acid (p<0.05), and secondary bile acids, deoxycholic acid (p<0.05) and ursodeoxycholic acid (p<0.001) were higher in urban residents. Faecal levels of acetate and propionate, but not butyrate, were higher in urban residents. The gut microbiota composition and activity among rural and urban Zimbabweans retain significant homogeneity (possibly due to retention of dietary fibre), but urban residents have subtle changes, which may indicate a higher CRC risk.

Gut Microbiota Profiling in Patients With HER2-Negative Metastatic Breast Cancer Receiving Metronomic Chemotherapy of Capecitabine Compared to Those Under Conventional Dosage

“…Although no previous study investigated the predictive value of the gut microbiota for drug resistance monitoring and prognostic evaluation in breast cancer, some evidence on these two types of microbes showed the similar predictive tendency in the association with gastrointestinal tumors. Blautia obeum was one of the gut microbes involved in the transformation of carcinogen heterocyclic amines, and the reduced abundance of the taxa may increase heterocyclic amine-induced colorectal cancer risk (44). Slaxkia in the human gut was reported by several studies to be involved in the onset of colorectal cancer, which may be used as a microbial biomarker in colorectal cancer for prevention, diagnosis, prognosis, and/or therapeutics (45,46).…”

Identification of crucial genes and pathways associated with colorectal cancer by bioinformatics analysis

“…By 2030, 2.2 million new cases and 1.1 million cases of mortality are predicted to occur, a situation that is responsible for the rising global burden of CRC (23). Although numerous studies have reported that unhealthy dietary habits, environmental changes and genetic aberrancies may be the primary causes of CRC, the precise molecular events orchestrating CRC initiation and progression remain elusive (24,25). In the present study, bioinformatics methods were used to identify the crucial genes and pathways associated with CRC.…”

Diet and the Human Gut Microbiome: An International Review

“…However, the role of the gut microbiome in the rising incidences of colorectal cancer (CRC) in countries undergoing dietary and lifestyle transitions, typical of sub-Saharan Africa, is just unfolding. The age-standardized incidence of CRC per 100,000 has been traditionally < 5 [40], but, despite variations between African countries, larger incidences of > 10 have been reported in some countries [41]. In Zimbabwe, an observational study was recently undertaken to assess the link between CRC risk and dietary changes from traditional to Western during urbanization [41].…”

“…The age-standardized incidence of CRC per 100,000 has been traditionally < 5 [40], but, despite variations between African countries, larger incidences of > 10 have been reported in some countries [41]. In Zimbabwe, an observational study was recently undertaken to assess the link between CRC risk and dietary changes from traditional to Western during urbanization [41]. Owing to retention of fiber intake in the urban population, the levels of butyrate and butyrogenic bacteria were similar between rural and urban participants, yet the levels of bile acids indicative of high-fat diet were higher among urban participants.…”