Vitamin A influences the incretin hormone profiles by activating the retinoic acid receptor β

BACKGROUND

This study aimed to investigate the impact of Vitamin A (VA) on intestinal glucose metabolic phenotypes.

METHODS

Male C57BL/6 mice were randomized assigned to a VA-normal diet (VAN) or a VA-deficient diet (VAD) for 12 weeks. After12 weeks, the VAD mice were given 30 IU/g/d retinol for 10 days and VAN diet (VADN) for 10 weeks. By using glucose tolerance tests, immunofluorescence staining, quantitative polymerase chain reaction, siRNA transduction, and enzyme-linked immunosorbent assay, the glucose metabolic phenotypes as well as secretory function and intracellular hormone changes of STC-1 were assessed.

RESULTS

VAD mice showed a decrease of glucose-stimulated insulin secretion and a loss of intestinal glucagon-like peptide-1 (GLP-1) expression. Through reintroducing dietary VA to VAD mice, the intestinal VA levels, GLP-1 expression and normal glucose can be restored. The incubation with retinol increased VA signaling factors expression within STC-1 cells, especially retinoic acid receptor β (RARβ). The activation of RARβ restored intracellular incretin hormone synthesis and secretory function.

CONCLUSIONS

VA deficiency leads to an imbalance of intestinal glucose metabolic phenotypes through a mechanism involving RARβ signaling pathway, suggesting a new method to achieve the treatment for VAD induced glucose metabolism impairment.

Fermented foods: Harnessing their potential to modulate the microbiota-gut-brain axis for mental health

Over the past two decades, whole food supplementation strategies have been leveraged to target mental health. In addition, there has been increasing attention on the ability of gut microbes, so called psychobiotics, to positively impact behaviour though the microbiota-gut-brain axis. Fermented foods offer themselves as a combined whole food microbiota modulating intervention. Indeed, they contain potentially beneficial microbes, microbial metabolites and other bioactives, which are being harnessed to target the microbiota-gut-brain axis for positive benefits. This review highlights the diverse nature of fermented foods in terms of the raw materials used and type of fermentation employed, and summarises their potential to shape composition of the gut microbiota, the gut to brain communication pathways including the immune system and, ultimately, modulate the microbiota-gut-brain axis. Throughout, we identify knowledge gaps and challenges faced in designing human studies for investigating the mental health-promoting potential of individual fermented foods or components thereof. Importantly, we also suggest solutions that can advance understanding of the therapeutic merit of fermented foods to modulate the microbiota-gut-brain axis.

Dairy products and constituents: a review of their effects on obesity and related metabolic diseases

Obesity has become a global public health problem that seriously affects the quality of life. As an important part of human diet, dairy products contain a large number of nutrients that are essential for maintaining human health, such as proteins, peptides, lipids, vitamins, and minerals. A growing number of epidemiological investigations provide strong evidence on dairy interventions for weight loss in overweight/obese populations. Therefore, this paper outlines the relationship between the consumption of different dairy products and obesity and related metabolic diseases. In addition, we dive into the mechanisms related to the regulation of glucose and lipid metabolism by functional components in dairy products and the interaction with gut microbes. Lastly, the role of dairy products on obesity of children and adolescents is revisited. We conclude that whole dairy products exert more beneficial effect than single milk constituent on alleviating obesity and that dairy matrix has important implications for metabolic health.

Association of dairy consumption patterns with the incidence of type 2 diabetes: Findings from Alberta's Tomorrow Project

BACKGROUND AND AIMS

We aimed to extract dairy consumption patterns of men and women from a population-based cohort and then assess the association of each consumption pattern with incident T2D risk.

METHODS AND RESULTS

This prospective study was conducted within the framework of Alberta's Tomorrow Project (ATP), in which 8615 men and 15,016 women provided information on dietary intake by completing a food-frequency questionnaire at baseline, and then were followed up over time to determine the incidence of T2D via questionnaires. Principal Component Analysis (PCA) was used to extract dairy consumption patterns (DCPs). The association between each extracted pattern and T2D incidence was estimated using multivariable logistic regression models.The incidence of T2D among men and women was 3.8 and 3.2%, respectively, and the mean duration of follow-up was 5.2 years. Three major DCPs were identified. After controlling for potential confounders, the OR for risk of T2D in men in the highest compared with those in the lowest quartile of the DCP3 (whole milk, regular cheese, and non-fat milk as a beverage and in cereal) was 0.64 (95%CI: 0.47 to 0.88, P-trend=0.001), whereas it was not significant for women. DCP1 and DCP2 were not associated with incident T2D in men or women.

CONCLUSION

Adherence to a DCP characterized by higher consumption of whole milk, regular cheese, and non-fat milk was associated with decreased risk of incident T2D only in men. Our results support current evidence that a combination of different dairy products, regardless of their fat content, might be favorable for health maintenance, at least in men.

Digestion and Absorption of Milk Phospholipids in Newborns and Adults

Milk polar lipids provide choline, ethanolamine, and polyunsaturated fatty acids, which are needed for the growth and plasticity of the tissues in a suckling child. They may also inhibit cholesterol absorption by interacting with cholesterol during micelle formation. They may also have beneficial luminal, mucosal, and metabolic effects in both the neonate and the adult. The milk fat globule membrane contains large proportions of sphingomyelin (SM), phosphatidylcholine (PC), and phosphatidylethanolamine (PE), and some phosphatidylserine (PS), phosphatidylinositol (PI), and glycosphingolipids. Large-scale technical procedures are available for the enrichment of milk fat globule membrane (MFGM) in milk replacement formulations and food additives. Pancreatic phospholipase A2 (PLA2) and mucosal phospholipase B digest glycero-phospholipids in the adult. In the neonate, where these enzymes may be poorly expressed, pancreatic lipase-related protein 2 probably has a more important role. Mucosal alkaline SM-ase and ceramidase catalyze the digestion of SM in both the neonate and the adult. In the mucosa, the sphingosine is converted into sphingosine-1-phosphate, which is both an intermediate in the conversion to palmitic acid and a signaling molecule. This reaction sequence also generates ethanolamine. Here, we summarize the pathways by which digestion and absorption may be linked to the biological effects of milk polar lipids. In addition to the inhibition of cholesterol absorption and the generation of lipid signals in the gut, the utilization of absorbed choline and ethanolamine for mucosal and hepatic phospholipid synthesis and the acylation of absorbed lyso-PC with polyunsaturated fatty acids to chylomicron and mucosal phospholipids are important.

Dipeptidyl peptidase-4 and GLP-1 interplay in STC-1 and GLUTag cell lines

Glucagon like peptide-1 (GLP-1) is an incretin hormone, secreted from L-cells of distal ileum and colon in response to nutrient ingestion in human. GLP-1 plays a major role in gut motility, appetite regulation, and insulin secretion. Dipeptidyl peptidase-4 (DPP4), a serine peptidase, cleaves N-terminal dipeptides of GLP-1, rendering it inactive and responsible for its short half-life. DPP4 is widely expressed in numerous tissues in a membrane bound or soluble form. The enteroendocrine cell lines STC-1 and GLUTag are extensively used as models for in vitro studies, however, the basic parallel characterization between these cell lines is still missing. Previously, we demonstrated that these cell lines exhibit different responses to α-linolenic acid (αLA)-induced GLP-1 secretion. Therefore, we examined the basal and stimulated GLP-1 and DPP4 secretion between the two cell lines. GPR120 and GPR40 are known to bind long chain fatty acids. We found that STC-1 cells secreted significantly more basal and αLA-induced GLP-1 than GLUTag cells. In addition, STC-1 secreted DPP4 and expressed higher amounts of DPP4 and GPR120 than GLUTag cells, while GLUTag cells expressed higher GPR40 protein levels than STC-1 cells. Interestingly, the secreted soluble DPP4 did not change the active GLP-1 concentrations in the buffer group, and only 5.5 % of GLP-1 was degraded in the αLA stimulated group. These results suggested that STC-1 cells have a higher potential to secrete GLP-1 and DPP4 than GLUTag cells, and the membrane bound DPP4 may play a more significant role in the inactivation of GLP-1 secretion.