1. Unique Organization of Extracellular Amylases into Amylosomes in the Resistant Starch-Utilizing Human Colonic Firmicutes Bacterium Ruminococcus bromii.
Recent evidence indicates that certain human colonic bacteria play keystone roles in degrading nondigestible substrates, with the dominant but little-studied species Ruminococcus bromii displaying an exceptional ability to degrade dietary resistant starches (i.e., dietary starches that escape digestion by host enzymes in the upper gastrointestinal tract because of protection provided by other polymers, particle structure, retrogradation, or chemical cross-linking). In this report, we reveal the unique organization of the amylolytic enzyme system of R. bromii that involves cohesin-dockerin interactions between component proteins. While dockerins and cohesins are fundamental to the organization of cellulosomal enzyme systems of cellulolytic ruminococci, their contribution to organization of amylases has not previously been recognized and may help to explain the starch-degrading abilities of R. bromii.
2. Resistant starches for the management of metabolic diseases.
PURPOSE OF REVIEW:
Recent clinical trials and animal studies indicate that resistant starches may be beneficial therapeutic tools for the management of metabolic diseases. The purpose of this review is to summarize these findings and discuss the established and proposed mechanisms by which resistant starches exert their benefits. We also examine open questions regarding how resistant starches improve metabolism and propose future research directions for the field.
Data from both humans and animal models clearly support a role for resistant starches in improving a variety of metabolic features; however, discrepancies do exist regarding specific effects. Concomitant improvements in both insulin levels and body fat depots are often reported in rodents fed resistant starches, whereas resistant starch feeding in humans improves insulin sensitivity without having a major impact on fat mass. These differences could be explained by the coexistence of several mechanisms (both gut microbiota-dependent and gut microbiota-independent) underpinning the metabolic benefits of resistant starches.
Together, the studies presented in this review offer new insights into the potential pathways by which resistant starches enhance metabolic health, including modulation of the gut microbiota, gut peptides, circulating inflammatory mediators, innate immune cells, and the bile acid cycle.
3. Improving healthspan via changes in gut microbiota and fermentation.
Dietary resistant starch impact on intestinal microbiome and improving healthspan is the topic of this review. In the elderly population, dietary fiber intake is lower than recommended. Dietary resistant starch as a source of fiber produces a profound change in gut microbiota and fermentation in animal models of aging. Dietary resistant starch has the potential for improving healthspan in the elderly through multiple mechanisms as follows: (1) enhancing gut microbiota profile and production of short-chain fatty acids, (2) improving gut barrier function, (3) increasing gut peptides that are important in glucose homeostasis and lipid metabolism, and (4) mimicking many of the effects of caloric restriction including upregulation of genes involved in xenobiotic metabolism.
4. Influences of exogenous probiotics and tea polyphenols on the production of three acids during the simulated colonic fermentation of maize resistant starch.
In the present study, influences of nine probiotics and tea polyphenols on the production of acetic, butyric, and lactic acid from simulated colonic fermentation of maize resistant starch (RS) were investigated. RS was fermented by fecal extracts of healthy adults at 12 g L(-1) and 37 °C for 18-48 h in the presence and absence of exogenous probiotics and tea polyphenols. The added probiotics increased acetic and butyric acid production by 25-216 %. Eubacterium faecalis, Lactobacillus acidophilus, L. casei, and L. helveticus increased lactic acid production by 7-58 %; however, other probiotics decreased lactic acid production. Tea polyphenols facilitated lactic acid production but inhibited acetic and butyric acid production clearly. More importantly, the added probiotics weakened the inhibitory effects of tea polyphenols on the two acids, enhancing acetic and butyric acid production by 152-641 and 825-1,777 %, respectively. It is concluded that both probiotics and tea polyphenols have different impacts on the production of acetic, butyric and lactic acid during the colonic fermentation of RS. The impacts of other probiotics and food components on the colonic fermentation of RS and other dietary fibers should be investigated in future study to clarify their possible interactions.
5. The Glycemic Potential of White and Red Rice Affected by Oil Type and Time of Addition.
Limited research exists on how different oil types and time of addition affect starch digestibility of rice. This study aimed to assess the starch digestibility of white and red rice prepared with 2 oil types: vegetable oil (unsaturated fat) and ghee (clarified butter, saturated fat) added at 3 different time points during the cooking process ("before": frying raw rice in oil before boiling, "during": adding oil during boiling, and "after": stir-frying cooked rice in oil). Red rice produced a slower digestion rate than white rice. White rice digestibility was not affected by oil type, but was affected by addition time of oil. Adding oil "after" (stir-frying) to white or red rice resulted in higher slowly digestible starch. Red rice cooked using ghee showed the lowest amount of glucose release during in vitro digestion. The addition of ghee "during" (that is boiling with ghee) or "before" (that is frying rice raw with ghee then boiling) cooking showed potential for attenuating the postprandial glycemic response and increasing resistant starch content. This is the first report to show healthier ways of preparing rice. White rice with oil added "after" (stir-fried) may provide a source of sustained glucose and stabilize blood glucose levels. Boiling red rice with ghee or cooking red rice with ghee pilaf-style may provide beneficial effects on postprandial blood glucose and insulin concentrations, and improve colonic health. The encouraging results of the present study justify extending it to an in vivo investigation to conclusively determine the effect of time of addition of fat when rice is cooked on blood glucose homeostasis.
I'll leave my thoughts on these for the comments...what do you guys think?