Effect of macaroni pasta prepared from modified unripe banana flour and turmeric extract on gut microbiota, serum lipid profile, and insulin sensitivity in wistar rats

Abstract

Metabolic syndrome is a cluster of interrelated metabolic disorders that increase the risk of developing type 2 diabetes and cardiovascular diseases. One of the nutritional interventions for metabolic syndrome is the dietary supplementation of resistant starch (RS), which is not digested and absorbed in the small intestine but is fermented by microorganisms in the large intestine, thus helps improving gut microbiota. A number of meta-analysis have confirm the beneficial effects of RS on glycemic control and lipid profile. Unripe banana is considered the RS-richest non-processed food and studies have suggested that consumption of unripe bananas confers beneficial effects for human health. However, unripe banana is not consumed directly due to its hardness and high astringency and when cooked its native RS is rendered digestible, In this study we have developed macaroni pasta from chemically modified unripe banana flour (RS4), which did not lose their indigestibility after being cooked. The macaroni pasta was also developed in the turmeric supplemented form (0.15% (w/w), a medicinal plant well known for its glucose and lipid lowering effects. Both types of macaroni were cooked and given to Wistar rats (n=7 per group) at a daily dose of 4g/kg body weight in comparison to the commercial wheat macaroni for 6 weeks in order to investigate their effects on gut microbiota, serum lipid profile, and insulin sensitivity. The treatment No significant physiological differences between groups were observed except rats that consumed banana RS4 macaroni had significantly smaller stomachs (p<0.05, Kruskal Wallis test). Profiles of liver function tests, renal function tests and insulin sensitivity tests were not significantly different between groups. Interestingly, Wistar rats receiving modified banana RS4 macaroni or banana RS4 macaroni with turmeric extract showed a significantly lower serum triglyceride levels (p<0.05, Kruskal Wallis test) and a trend of lower fasting blood glucose, total cholesterol and LDL-cholesterol, although it was not statistically significance. Analysis of gut microbiota analysis by PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) of bacterial 16S rRNA V3 region encoding gene demonstrated a significant increase of Shannon diversity index (p<0.05, Wilcoxon signed Rank test) in rats given banana RS4 macaroni supplemented with turmeric extract, which was consistent with the results from the sequencing-based method. Further analysis of the 16S rRNA encoding gene sequencing results demonstrated that addition of turmeric extract to banana RS4 macaroni significantly increased the relative abundance of Lachnospiraceae, Erysipelotrichaceae and Clostridiaceae. Although the contribution of these bacteria to animal's health is not fully understood, the finding that low dose of turmeric extract could significantly increase their relative abundance indicates the possibility of these bacteria in mediating health beneficial effects of turmeric. Nevertheless, further investigation in rats with metabolic syndrome may be needed to demonstrate a more prominent effect. In conclusion, this study has demonstrated that consumption of banana RS4 macaroni confers health benefits towards healthy rats consuming a regular diet and the addition of turmeric extract can significantly alter gut microbiota of the experimental animals.