Applications | Food and Nutrition: Starch Metabolism in Relation to Colon Cancer and Obesity
Tracing starch digestion
Introduction
Relating microbial species to physiological processes like resistant starch fermentation in complex ecosystems as the colon, is a major task in nutritional sciences in the context of health and disease (Egert et al., 2018; Herrmann et al., 2018). The occurrence of colon cancer is an important cause of death in the western society and increasing in both man and women. Starch metabolites are thought to play an essential role in the prevention of colon cancer and obesity (Venema et al., 2010). The potential beneficial effects of dietary starch probably depend on its digestion and fermentation characteristics (Conlon & Bird, 2015). Part of the starch, the resistant starch (RS), escapes from digestion and is fermented in the large intestine into short chain fatty acids (SCFA’s) like acetate, propionate, and butyrate. A high rate of SCFA production, especially butyrate, is associated with health promoting activities in the colon. RS may cause these prebiotic effects in the colon by stimulating the growth of specific probiotic bacteria like Bacteroides sp. (Fig. 1). Besides the RS fraction as an important regulator of digestion, simultaneous uptake of dietary fat also affects starch digestibility (Azzout-Marniche et al., 2019) and is therefore important for obesity research.
Figure 1. Bacteroides sp, a (probiotic) bacterium in human intestines (https://alchetron.com).
Stable Isotope Solution: 13C-labelled starches
One of the problems when investigating the effects of prebiotics like RS is how to follow the dynamics of its metabolites e.g. in the blood plasma and to distinguish these from other internal or external sources. The use of uniformly labelled dietary 13C-starch enables tracing of metabolites and linking SCFA production to bacterial species, either in vivo or in vitro systems like TIM-2 (TNO gastro-Intestinal Models). It also facilitates tracing the digestibility of starch in lowly and highly digestible-starch diets or low-fat, high-starch diets to investigate the development of obesitas.
Results from publications with IsoLife’s 13C Starch
Binsl et al. (2010) found in experiments using TIM-2 that fermentation of U-13C starch resulted in the production of SCFA’s with the following composition 35% acetate, 12% propionate, and 53% butyrate. This was confirmed by Herrmann et al. (2018) who accurately measured digestion and fermentation characteristics for the first time in vivo in mice, also showing that the predominantly produced SCFA was butyrate. Species responsible for the production of SCFA’s were found in the genus Bacteroides and genera affiliated with Prevotellaceae, Ruminococcaceae, and Clostridiales (Kovatcheva-Datchary et al., 2009; Herrmann et al., 2017, 2018).
In a study by Fernández-Calleja et al. (2019) to measure effects of lowly and highly digestible-starch diets (LDD vs HDD), an oral 13C-labelled starch bolus was given to mice and total 13C hepatic enrichment was determined immediately before and 4 h after administration of the bolus. In both male and female mice, hydrogen production was increased by the LDD. Only in females, starch-derived glucose oxidation in response to the starch bolus were higher in LDD versus HDD mice. Azzout-Marniche et al. (2019) reported large differences in adiposity (fat mass/body weight) gain between ‘sensitive’ and ‘resistant’ rats that were fed a low-fat, high-starch diet. Experiments with 13C-labelled dietary starch revealed that “sensitive” rats showed a larger increase in whole body glucose oxidation and a decrease in lipid oxidation. These results show that changes in starch digestibility impacts glucose metabolism and fat accumulation and may have important implications for the development of obesity.
References
Azzout-Marniche D, C Chaumontet, J Piedcoq, N Khodorova, G Fromentin, D Tomé, C Gaudichon, PC Even. 2019.
High pancreatic amylase expression promotes adiposity in obesity-prone carbohydrate-sensitive rats.
The Journal of Nutrition 149: 270–279.
Binsl TW, AA de Graaf, K Venema, J Heringa, A Maathuis, P de Waard, JHGM van Beek. 2010.
Measuring non-steady-state metabolic fluxes in starch-converting faecal microbiota in vitro.
Beneficial Microbes 1: 391-405.
Conlon M.A. and A.R. Bird. 2015. The impact of diet and lifestyle on gut microbiota and human health. Nutrients 7: 17-44.
The impact of diet and lifestyle on gut microbiota and human health.
Nutrients 7: 17-44.
Fernández-Calleja JMS, LMS Bouwman, HJM Swarts, A Oosting, J Keijer, EM van Schothorst. 2019.
Extended indirect calorimetry with isotopic CO2 sensors for prolonged and continuous quantification of exogenous vs. total substrate oxidation in mice.
NATURE – Scientific Reports 9: 11507.
Herrmann E, W Young, V Reichert-Grimm, S Weis, CU Riedel, D Rosendale, H Stoklosinski, M Hunt, M Egert. 2018.
In vivo assessment of resistant starch degradation by the caecal microbiota of mice using RNA-based Stable Isotope Probing—A proof-of-principle study.
Nutrients 10: 179; doi:10.3390/nu10020179.
Herrmann E, W Young, D Rosendale, R Conrad, CU Riedel, M Egert. 2017.
Determination of resistant starch assimilating bacteria in fecal samples of mice by in vitro RNA-based Stable Isotope Probing.
Frontiers in Microbiology 8: 1331.
Kovatcheva-Datchary P, M Egbert, A Maathuis, M Rajilic-Stojanovic, AA de Graaf, H Smidt, WM de Vos, K Venema. 2009 (Award winning publication).
Linking phylogenetic identities of bacteria to starch fermentation in an in vitro model of the large intestine by RNA-based stable isotope probing.
Environmental Microbiology 11: 914-926.
Venema K, AA de Graaf, AJH Maathuis, P Kovatcheva-Datchary, H Smidt. 2010.
Fermentation in the large intestine unravelled using 13C-labelled substrates: implications for obesity and gut health.
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