Wheat Alkylresorcinols Modulate Glucose Homeostasis through Improving GLP-1 Secretion in High-Fat-Diet-Induced Obese Mice

Grain bound polyphenols: Molecular interactions, release characteristics, and regulation mechanisms of postprandial hyperglycemia

Frequent postprandial hyperglycemia causes many chronic diseases. Grain polyphenols are widely recognized as natural active ingredients with high potential to treat chronic diseases due to their excellent postprandial hyperglycemic regulating effects. However, previous studies on polyphenols in grains mainly focused on the functional properties of free polyphenols and the extraction and physicochemical properties of bound polyphenols, ignoring the functional properties of bound polyphenols. Comprehensively understanding the binding properties of grain bound polyphenols (GBPs) and their mechanisms in regulating blood glucose levels is essential for developing and applying grain resources. This review summarizes the molecular interactions between GBPs and grain components and their effects on release characteristics and bioavailability at various stages. Meanwhile, the review focuses on elucidating the regulatory mechanism of post-release GBPs on postprandial hyperglycemia levels, incorporating insights from molecular docking, the gastrointestinal-brain axis, and gut flora. GBPs slow food digestion by occupying the active site of digestive enzymes and altering the secondary structure of enzymes and the hydrophobic environment of amino acid residues to inhibit enzyme activity. They modulate intestinal epithelial transport proteins (SGLT1, GLUT2, and GLUT4) to limit glucose absorption and increase glucose consumption. They also stimulate the release of short-term satiety hormones (CKK, GLP-1, and PYY) through the gastrointestinal-brain axis to decrease post-meal food intake. Furthermore, they optimize gut microbiota composition, promoting short-chain fatty acid production and bile acid metabolism. Therefore, developing functional foods with glucose-modulating properties based on GBPs is crucial for obesity prevention, diabetes management, and low-GI food development.

Olivetol's Effects on Metabolic State and Gut Microbiota Functionality in Mouse Models of Alimentary Obesity, Diabetes Mellitus Type 1 and 2, and Hypercholesterolemia

BACKGROUND

Disorders of glucose and lipid metabolism, such as obesity, diabetes mellitus, or hypercholesterolemia, can cause serious complications, reduce quality of life, and lead to increased premature mortality. Olivetol, a natural compound, could be proposed as a promising therapeutic agent for preventing, treating, or alleviating metabolic complications of such pathological conditions.

METHODS

In this study, the researchers conducted a broad parallel investigation of olivetol's effects on metabolic state and gut microbiota functionality in mouse models of alimentary obesity, diabetes mellitus type 1 and 2, and hypercholesterolemia.

RESULTS

According to the results of the study, olivetol caused a lowering of body weight in C57Bl6 mice fed a high-fat diet and in ldlr(-/-) mice, decreased serum glucose levels in db/db mice, improved lipid metabolism in ldlr(-/-) mice, and prevented inflammatory infiltration of the pancreas and loss of insulin secretion in NOD mice. In addition, olivetol affected the composition and functional activity of gut microbiota communities, inducing an expansion of probiotic species such as Akkermansia muciniphila and Bacteroides acidifaciens and depleting the representation of pathobionts such as Prevotella, although olivetol supplementation did not influence the diversity or richness of the communities.

CONCLUSIONS

These results suggest that olivetol is a promising therapeutic agent for preventing, treating, or alleviating the metabolic complications of obesity, diabetes mellitus type 1 and 2, and hypercholesterolemia; however, more investigations are required in order to attain a full understanding of its physiological effects.

Role of FFAR3 in ketone body regulated glucagon-like peptide 1 secretion

Background

Roux-en-Y gastric bypass (RYGB) is an effective treatment for obesity, resulting in long-term weight loss and rapid remission of type 2 diabetes mellitus. Improved glucagon-like peptide 1 (GLP-1) levels is one factor that contributes to the positive effects. Prior to RYGB, GLP-1 response is blunted which can be attributed to intestinal ketogenesis. Intestinal produced ketone bodies inhibit GLP-1 secretion in enteroendocrine cells via an unidentified G-protein coupled receptors (GPCRs). A possible class of GPCRs through which ketone bodies may reach are the free fatty acid receptors (FFARs) located at the basolateral membrane of enteroendocrine cells.

Aim

To evaluate FFAR3 expression in enteroendocrine cells of the small intestine under different circumstances, such as diet and bariatric surgery, as well as explore the link between ketone bodies and GLP-1 secretion.

Materials and methods

FFAR3 and enteroendocrine cell expression was analyzed using Western blot and immunohistochemistry in biopsies from healthy volunteers, obese patients undergoing RYGB and mice. GLUTag cells were used to study GLP-1 secretion and FFAR3 signaling pathways.

Results

The expression of FFAR3 is markedly influenced by diet, especially high fat diet, which increased FFAR3 protein expression. Lack of substrate such as free fatty acids in the alimentary limb after RYGB, downregulate FFAR3 expression. The number of enteroendocrine cells was affected by diet in the normal weight individuals but not in the subjects with obesity. In GLUTag cells, we show that the ketone bodies exert its blocking effect on GLP-1 secretion via the FFAR3, and the Gαi/o signaling pathway.

Conclusion

Our findings that ketone bodies via FFAR3 inhibits GLP-1 secretion bring important insight into the pathophysiology of T2D. This highlights the role of FFAR3 as a possible target for future anti-diabetic drugs and treatments.

Supplementation of a High-Fat Diet with Pentadecylresorcinol Increases the Representation of Akkermansia muciniphila in the Mouse Small and Large Intestines and May Protect against Complications Caused by Imbalanced Nutrition

Imbalanced nutrition, such as a high-fat/high-carbohydrate diet, is associated with negative effects on human health. The composition and metabolic activity of the human gut microbiota are closely related to the type of diet and have been shown to change significantly in response to changes in food content and food supplement administration. Alkylresorcinols (ARs) are lipophilic molecules that have been found to improve lipid metabolism and glycemic control and decrease systemic inflammation. Furthermore, alkylresorcinol intake is associated with changes in intestinal microbiota metabolic activity. However, the exact mechanism through which alkylresorcinols modulate microbiota activity and host metabolism has not been determined. In this study, alterations in the small intestinal microbiota (SIM) and the large intestinal microbiota (LIM) were investigated in mice fed a high-fat diet with or without pentadecylresorcinol (C15) supplementation. High-throughput sequencing was applied for jejunal and colonic microbiota analysis. The results revealed that C15 supplementation in combination with a high-fat diet could decrease blood glucose levels. High-throughput sequencing analysis indicated that C15 intake significantly increased (p < 0.0001) the abundance of the probiotic bacteria Akkermansia muciniphila and Bifidobacterium pseudolongum in both the small and large intestines and increased the alpha diversity of LIM (p < 0.05), but not SIM. The preliminary results suggested that one of the mechanisms of the protective effects of alkylresorcinol on a high-fat diet is the modulation of the content of SIM and LIM and metabolic activity to increase the probiotic bacteria that alleviate unhealthy metabolic changes in the host.

Nutrition at the Intersection between Gut Microbiota Eubiosis and Effective Management of Type 2 Diabetes

Nutrition is one of the most influential environmental factors in both taxonomical shifts in gut microbiota as well as in the development of type 2 diabetes mellitus (T2DM). Emerging evidence has shown that the effects of nutrition on both these parameters is not mutually exclusive and that changes in gut microbiota and related metabolites such as short-chain fatty acids (SCFAs) and branched-chain amino acids (BCAAs) may influence systemic inflammation and signaling pathways that contribute to pathophysiological processes associated with T2DM. With this background, our review highlights the effects of macronutrients, carbohydrates, proteins, and lipids, as well as micronutrients, vitamins, and minerals, on T2DM, specifically through their alterations in gut microbiota and the metabolites they produce. Additionally, we describe the influences of common food groups, which incorporate varying combinations of these macronutrients and micronutrients, on both microbiota and metabolic parameters in the context of diabetes mellitus. Overall, nutrition is one of the first line modifiable therapies in the management of T2DM and a better understanding of the mechanisms by which gut microbiota influence its pathophysiology provides opportunities for optimizing dietary interventions.