GLP-1 preserves β cell function via improvement on islet insulin signaling in high fat diet feeding mice

The role of gut-islet axis in pancreatic islet function and glucose homeostasis

The gastrointestinal tract plays a vital role in the occurrence and treatment of metabolic diseases. Recent studies have convincingly demonstrated a bidirectional axis of communication between the gut and islets, enabling the gut to influence glucose metabolism and energy homeostasis in animals strongly. The 'gut-islet axis' is an essential endocrine signal axis that regulates islet function through the dialogue between intestinal microecology and endocrine metabolism. The discovery of glucagon-like peptide-1 (GLP-1), gastric inhibitory peptide (GIP) and other gut hormones has initially set up a bridge between gut and islet cells. However, the influence of other factors remains largely unknown, such as the homeostasis of the gut microbiota and the integrity of the gut barrier. Although gut microbiota primarily resides and affect intestinal function, they also affect extra-intestinal organs by absorbing and transferring metabolites derived from microorganisms. As a result of this transfer, islets may be continuously exposed to gut-derived metabolites and components. Changes in the composition of gut microbiota can damage the intestinal barrier function to varying degrees, resulting in increased intestinal permeability to bacteria and their derivatives. All these changes contribute to the severe disturbance of critical metabolic pathways in peripheral tissues and organs. In this review, we have outlined the different gut-islet axis signalling mechanisms associated with metabolism and summarized the latest progress in the complex signalling molecules of the gut and gut microbiota. In addition, we will discuss the impact of the gut renin-angiotensin system (RAS) on the various components of the gut-islet axis that regulate energy and glucose homeostasis. This work also indicates that therapeutic approaches aiming to restore gut microbial homeostasis, such as probiotics and faecal microbiota transplantation (FMT), have shown great potential in improving treatment outcomes, enhancing patient prognosis and slowing down disease progression. Future research should further uncover the molecular links between the gut-islet axis and the gut microbiota and explore individualized microbial treatment strategies, which will provide an innovative perspective and approach for the diagnosis and treatment of metabolic diseases.

Evaluation of the Effect of Dietary Manganese on the Intestinal Digestive Function, Antioxidant Response, and Muscle Quality in Coho Salmon

Manganese (Mn) is a nutritional element required for fish growth and physiology functions. In this study, we examined the effect of Mn on the intestinal digestive function, antioxidant response, and muscle quality in coho salmon (Oncorhynchus kisutch). Nine hundred salmons with initial weight approximately 0.35 g were fed with six isoproteic and isoenergetic diets formulated to contain 2.4, 8.5, 14.8, 19.8, 24.6, and 33.7 mg/kg Mn for 84 days. The result showed that the activity of trypsin and lipase was elevated, whereas α-amylase activity was not affected by various Mn diets in intestine. Dietary Mn elevated the activity of Mn-superoxide dismutase (Mn-SOD), total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-PX), and catalase (CAT), but had no influence on copper/zinc-superoxide dismutase (Cu/Zn-SOD) in intestine. Dietary Mn at 8.5, 14.8, 19.8, 24.6, and 33.7 mg/kg enhanced the gene expression level of protein kinase B (Akt) and mammalian target of rapamycin (mTOR). In addition, the accumulation of Mn in muscle was enhanced with increasing levels of dietary Mn. Dietary Mn elevated the content of sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca), but the content of iron (Fe) and Zn was decreased by dietary Mn in the salmon muscle. The content of fatty acids and amino acids was enhanced by various levels of dietary Mn in muscle. Moreover, a significant quadratic effect was observed on the texture of salmon muscle. The dietary Mn requirement was 16.9-25.7 mg/kg Mn to acquire the highest value of muscle texture using the quadratic regression model. The diets at 14.8 and 19.8 mg/kg Mn had a higher score of sensory evaluation for raw muscle. Our result showed that dietary Mn affected the intestinal digestion function and antioxidant response, which may further result in the change of muscle quality in coho salmon. The result will provide reference for detecting the effect of dietary micronutrients on the muscle quality of salmons.

Outer Membrane Vesicles Released from Garlic Exosome-like Nanoparticles (GaELNs) Train Gut Bacteria that Reverses Type 2 Diabetes via the Gut-Brain Axis

Gut microbiota function has numerous effects on humans and the diet humans consume has emerged as a pivotal determinant of gut microbiota function. Here, a new concept that gut microbiota can be trained by diet-derived exosome-like nanoparticles (ELNs) to release healthy outer membrane vesicles (OMVs) is introduced. Specifically, OMVs released from garlic ELN (GaELNs) trained human gut Akkermansia muciniphila (A. muciniphila) can reverse high-fat diet-induced type 2 diabetes (T2DM) in mice. Oral administration of OMVs released from GaELNs trained A. muciniphila can traffick to the brain where they are taken up by microglial cells, resulting in inhibition of high-fat diet-induced brain inflammation. GaELNs treatment increases the levels of OMV Amuc-1100, P9, and phosphatidylcholines. Increasing the levels of Amuc-1100 and P9 leads to increasing the GLP-1 plasma level. Increasing the levels of phosphatidylcholines is required for inhibition of cGas and STING-mediated inflammation and GLP-1R crosstalk with the insulin pathway that leads to increasing expression of Insulin Receptor Substrate (IRS1 and IRS2) on OMV targeted cells. These findings reveal a molecular mechanism whereby OMVs from plant nanoparticle-trained gut bacteria regulate genes expressed in the brain, and have implications for the treatment of brain dysfunction caused by a metabolic syndrome.

GLP-1/GLP-1RAs: New Options for the Drug Treatment of NAFLD

Non-alcoholic fatty liver disease (NAFLD) has recently emerged as a global public health concern. Currently, the cornerstone of NAFLD treatment is lifestyle modification and, if necessary, weight loss. However, compliance is a challenge, and this approach alone may not be sufficient to halt and treat the more serious disease development, so medication is urgently needed. Nevertheless, no medicines are approved to treat NAFLD. Glucagon-like peptide-1 (GLP-1) is an enteropeptide hormone that inhibits glucagon synthesis, promotes insulin secretion, and delays gastric emptying. GLP-1 has been found in recent studies to be beneficial for the management of NAFLD, and the marketed GLP-1 agonist drugs have different degrees of effectiveness for NAFLD while lowering blood glucose. In this article, we review GLP-1 and its physiological roles, the pathogenesis of NAFLD, the correlation between NAFLD and GLP-1 signaling, and potential strategies for GLP-1 treatment of NAFLD.

A purified fraction of polysaccharides from the fruits of Lycium barbarum L. improves glucose homeostasis and intestinal barrier function in high-fat diet-fed mice

High-fat diet (HFD) consumption can induce intestinal barrier dysfunction and disrupt glucose metabolism. Our previous studies have demonstrated that polysaccharides obtained from the fruits of Lycium barbarum L. (LBPs) could suppress acute experimental diabetes as well as colitis in mice. In the present study, the modulating effects of a purified fraction of LBPs, named LBPs-4, on glucose homeostasis and intestinal barrier function in mice fed with a HFD were investigated. Our results indicated that the oral administration of LBP-4 (200 mg per kg per day) improved hyperglycemia, glucose intolerance, insulin resistance and islet β-cell hyperplasia in HFD-fed mice. Moreover, LBPs-4 intervention enhanced the intestinal barrier integrity by increasing the expression levels of zonula occludens 1 and claudin-1 and the number of goblet cells in the colon. LBPs-4 also modulated the composition of gut microbiota by increasing the relative abundances of butyrate producer Allobaculum and acetate producer Romboutsia. The results of fecal transplantation experiments, transferring of microbiota from LBPs-4-fed donor mice to HFD-fed recipient mice, validated the cause-effect relationship between LBPs-4-evoked changes in the gut microbiota and improvement of glucose homeostasis and intestinal barrier function. Collectively, these findings suggested that LBPs-4 might be developed as promising prebiotics to improve glucose metabolism and gut health.

Pathogenetic Pathways in Nonalcoholic Fatty Liver Disease: An Incomplete Jigsaw Puzzle

Nonalcoholic fatty liver disease (NAFLD)-a condition of excess fat accumulation in hepatocytes associated with metabolic dysfunction-has surpassed viral hepatitis to become the most prevalent chronic liver disease worldwide. As of now, only modestly effective pharmacological therapies for NAFLD exist. The uncomplete understanding of the pathophysiology underlying the heterogeneous disease spectrum known as NAFLD remains one of the major obstacles to the development of novel therapeutic approaches. This review compiles current knowledge on the principal signaling pathways and pathogenic mechanisms involved in NAFLD, which are analyzed in relation to its main pathological hallmarks (ie, hepatic steatosis, steatohepatitis, and liver fibrosis).

Effect of the m6ARNA gene on the prognosis of thyroid cancer, immune infiltration, and promising immunotherapy

BACKGROUND

Accumulating evidence suggests that N6-methyladenosine (m6A) RNA methylation plays an important role in tumor proliferation and growth. However, its effect on the clinical prognosis, immune infiltration, and immunotherapy response of thyroid cancer patients has not been investigated in detail.

METHODS

Clinical data and RNA expression profiles of thyroid cancer were extracted from the Cancer Genome Atlas-thyroid carcinoma (TCGA-THCA) and preprocessed for consensus clustering. The risk model was constructed based on differentially expressed genes (DEGs) using Least Absolute Shrinkage and Selection Operator (LASSO) and Cox regression analyses. The associations between risk score and clinical traits, immune infiltration, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Set Enrichment Analysis (GSEA), immune infiltration, and immunotherapy were assessed. Immunohistochemistry was used to substantiate the clinical traits of our samples.

RESULTS

Gene expression analysis showed that 17 genes, except YHTDF2, had significant differences (vs healthy control, P<0.001). Consensus clustering yielded 2 clusters according to their clinical features and estimated a poorer prognosis for Cluster 1 (P=0.03). The heatmap between the 2 clusters showed differences in T (P<0.01), N (P<0.001) and stage (P<0.01). Based on univariate Cox and LASSO regression, a risk model consisting of three high-risk genes (KIAA1429, RBM15, FTO) was established, and the expression difference between normal and tumor tissues of three genes was confirmed by immunohistochemical results of our clinical tissues. KEGG and GSEA analyses showed that the risk DEGs were related mainly to proteolysis, immune response, and cancer pathways. The levels of immune infiltration in the high- and low-risk groups were different mainly in iDCs (P<0.05), NK cells (P<0.05), and type-INF-II (P<0.001). Immunotherapy analysis yielded 30 drugs associated with the expression of each gene and 20 drugs associated with the risk score.

CONCLUSIONS

Our risk model can act as an independent marker for thyroid cancer and provides promising immunotherapy targets for its treatment.

Neuroprotective effects of glucagon-like peptide-1 (GLP-1) analogues in epilepsy and associated comorbidities

Epilepsy is a common neurological condition induced by losing equilibrium of different pathway as well as neurotransmitters that affects over 50 million people globally. Furthermore, long-term administration of anti-seizure medications has been associated with psychological adverse effects. Also, epilepsy has been related to an increased prevalence of obesity and called type 2 diabetes mellitus. On the other hand, GLP-1 receptors are located throughout the brain, including the hippocampus, which have been associated to majority of neurological conditions, such as epilepsy and psychiatric disorders. Moreover, the impact of different GLP-1 analogues on diverse neurotransmitter systems and associated cellular and molecular pathways as a potential therapeutic target for epilepsy and associated comorbidities has piqued curiosity. In this regard, the anticonvulsant effects of GLP-1 analogues have been investigated in various animal models and promising results such as anticonvulsants as well as cognitive improvements have been observed. For instance, GLP-1 analogues like liraglutide in addition to their possible anticonvulsant benefits, could be utilized to alleviate mental cognitive problems caused by both epilepsy and anti-seizure medication side effects. In this review and growing protective function of GLP-1 in epilepsy induced by disturbed neurotransmitter pathways and the probable mechanisms of action of GLP-1 analogues as well as the GLP-1 receptor in these effects have been discussed.

Exenatide improves hepatocyte insulin resistance induced by different regional adipose tissue

Obesity is resulted from energy surplus and is characterized by abnormal adipose tissue accumulation and/or distribution. Adipokines secreted by different regional adipose tissue can induce changes in key proteins of the insulin signaling pathway in hepatocytes and result in impaired hepatic glucose metabolism. This study aimed to investigate whether exenatide affects key proteins of IRS2/PI3K/Akt2 signaling pathway in hepatocytes altered by the different regional fat depots. Six non-obese patients without endocrine diseases were selected as the research subjects. Their subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT)were co-cultured with HepG2 cells in the transwell chamber. In the presence or absence of exenatide, adipokines content in the supernatant of each experimental group was detected by ELISA. In addition, HepG2 cells in each co-culture group with and without insulin were collected, and the expression of key proteins IRS2, p-IRS2(S731), PI3K-p85, Akt2, and p-Akt2(S473) was detected by western blotting (WB). The results showed that the adipokines IL-8, MCP-1, VEGF, and sTNFR2 in the supernatant of HepG2 cells induced by different regional adipose tissue were significantly higher than those in the HepG2 group, and VAT released more adipokines than SAT. Furthermore, these adipokines were significantly inhibited by exenatide. Importantly, the different regional fat depot affects the IRS2/PI3K/Akt2 insulin signaling pathway of hepatocytes. Exenatide can up-regulate the expression of hepatocyte proteins IRS2, PI3K-p85, p-Akt2(S731) inhibited by adipose tissue, and down-regulate the expression of hepatocyte proteins p-IRS2(S731) promoted by adipose tissue. The effect of VAT on the expression of these key proteins in hepatocytes is more significant than that of SAT. But there was no statistical difference in the expression of Akt2 protein among each experimental group, suggesting that exenatide has no influence on the expression of Akt2 protein in hepatocytes. In conclusion, exenatide may improve hepatic insulin resistance (IR) by inhibiting adipokines and regulating the expression of key proteins in the IRS2/PI3K/Akt2 pathway.

Potential new therapeutic target for Alzheimer's disease: Glucagon-like peptide-1

Increasing evidence shows a close relationship between Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM). Recently, glucagon-like peptide-1 (GLP-1), a gut incretin hormone, has become a well-established treatment for T2DM and is likely to be involved in treating cognitive impairment. In this mini review, the similarities between AD and T2DM are summarised with the main focus on GLP-1-based therapeutics in AD.

Mechanisms of Beta-Cell Apoptosis in Type 2 Diabetes-Prone Situations and Potential Protection by GLP-1-Based Therapies

Type 2 diabetes (T2D) is characterized by chronic hyperglycemia secondary to the decline of functional beta-cells and is usually accompanied by a reduced sensitivity to insulin. Whereas altered beta-cell function plays a key role in T2D onset, a decreased beta-cell mass was also reported to contribute to the pathophysiology of this metabolic disease. The decreased beta-cell mass in T2D is, at least in part, attributed to beta-cell apoptosis that is triggered by diabetogenic situations such as amyloid deposits, lipotoxicity and glucotoxicity. In this review, we discussed the molecular mechanisms involved in pancreatic beta-cell apoptosis under such diabetes-prone situations. Finally, we considered the molecular signaling pathways recruited by glucagon-like peptide-1-based therapies to potentially protect beta-cells from death under diabetogenic situations.