Although both insulin and glucagon are intimately involved in the regulation of glucose homeostasis, the intrinsic control of glucagon secretion, including the biogenesis and exocytosis of glucagon-containing granules, is far less understood compared with that of insulin. As Brefeldin A-inhibited guanine nucleotide exchange protein 3 (BIG3) is a negative regulator of insulin-granule biogenesis and insulin secretion, we investigated whether BIG3 plays any role in alpha-cells and glucagon secretion. We examined the expression of BIG3 in islet cells by immuno-fluorescence and confocal microscopy, and measured glucagon production and secretion in BIG3-depleted and wild-type mice, islets and cells. BIG3 is highly expressed in pancreatic alpha-cells in addition to beta-cells, but is absent in delta-cells. Depletion of BIG3 in alpha-cells leads to elevated glucagon production and secretion. Consistently, BIG3-knockout (BKO) mice display increased glucagon release under hypoglycemic conditions. Together with our previous studies, the current data reveal a conserved role for BIG3 in regulating alpha- and beta-cell functions. We propose that BIG3 negatively regulates hormone production at the secretory granule biogenesis stage and that such regulatory mechanism may be used in secretory pathways of other endocrine cells.

Mounting evidences have indicated that RNA N⁶-methyladenosine (m⁶A) modification played important roles in tumor formation and growth. However, it is rarely reported that m⁶A modifications are involved in the immune regulation and tumor microenvironment (TME) formation. In this study, we aimed to investigate the correlation between m⁶A modifications and TME regulation of colon adenocarcinoma (COAD) by bioinformatic analysis. NMF algorithm was applied to carry out consensus molecular subtype analysis on 36 selected m⁶A regulators regarding methylation modification, to identify m⁶A modification patterns and characteristics of m⁶A related genes in colon adenocarcinoma (COAD). Further, the relative infiltration levels of different immune cell subsets were quantified by ssGSEA and CIBERSORT algorithms, and a m⁶Sig scoring scheme was constructed to predict the prognosis and evaluate the response to immunotherapy in the patients with COAD. Among 579 COAD samples, we identified three different m⁶A modification patterns which were related to different biological pathways and clinical outcomes. Then, a scoring scheme termed "m⁶Sig score" was developed based on m⁶A-related characteristic genes, and was utilized to score patients with COAD into groups. We found that COAD patients with lower m⁶Sig scores exhibited prolonged survival and potentiated immune infiltration, which were associated with higher tumor mutation load, lower PD-L1 expression, and higher mutation rates of SMG (such as TTN and KRAS). Moreover, analysis regarding evaluation of immune response revealed that the patients with lower m⁶Sig scores had higher Immunophenoscore. Collectively, our study provided in depth insight into the interactions between m⁶A modification and regulation of TME. In addition, the quantitative evaluation of m⁶A modification patterns in our results may have implications in further immunotherapy for individual COAD patients.

Objective: The cardiometabolic index (CMI) serves as a comprehensive indicator of metabolic risk. Recent findings indicate a potential association between CMI and the likelihood of diabetes onset. The objective of this research is to explore the correlation between initial CMI values and the occurrence of newly diagnosed diabetes mellitus in individuals aged 45 years and above in China. Methods: In this research, data were sourced from the China Health and Retirement Longitudinal Study (CHARLS). To evaluate the association between baseline CMI and the incidence of newly diagnosed diabetes, multivariate logistic regression models were employed, with adjustments made for various potential confounding factors. Additionally, stratified analyses evaluated subgroup variations, and mediation analysis explored pathways through which CMI influences diabetes risk. Results: A cohort of 4,944 participants was followed, with 786 diagnosed with new‐onset diabetes. The occurrence of diabetes escalated with increasing CMI quartiles, with Q4 showing a 141% increased risk (OR 2.41, 95% CI, 1.94–3.02) in unadjusted models. This association remained significant after adjustment. Stratified analyses found that dyslipidemia modified the CMI–diabetes association. CMI, age, BMI, HbA1c, and hypertension were identified as independent predictors of new‐onset diabetes. Mediation analysis revealed that HbA1c mediated 9.70% of the CMI–diabetes relationship. Conclusion: In summary, our research establishes a connection between increased levels of CMI and the onset of diabetes, suggesting its potential as a predictive tool. The findings highlight CMI’s role in assessing diabetes risk and call for targeted interventions. Future research should validate these associations and explore underlying mechanisms for better prevention strategies.

Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid, plays an important role in regulating glucose metabolism. The aim of this study was to investigate the effect of DHA on insulin secretion and the underlying ion channel mechanism in rat pancreatic β-cells. The insulin secretion results illustrated that DHA promoted insulin secretion in a glucose-dependent manner. Calcium-imaging analysis indicated that DHA elevated intracellular Ca²⁺ concentration. Using the patch-clamp technique, we found that DHA prolonged the action potential duration (APD) and significantly inhibited voltage-dependent K⁺ (K_V) channels, but did not act directly on voltage-gated Ca²⁺ channels. Furthermore, our data demonstrate that the insulinotropic effect of DHA was mediated by G protein-coupled receptor 40 (GPR40) as well as the adenylyl cyclase (AC)/cyclic adenosine monophosphate (cAMP)/phospholipase-C (PLC) signaling pathway. Together, these findings illustrate that K_V channels play a vital role in DHA-augmented insulin secretion through a mechanism whereby DHA blocks K_V channels via GPR40 and the AC/cAMP/PLC signaling pathway in rat pancreatic β-cells.

PDF file - 790K, S Table 1. Primary and secondary antibodies used in immunostaining and Western Blotting experiments S Table 2. Antibodies used for immunoprecipitation experiments S Table 3. Primers used in real time RT-PCR and PCR of the ChIP experiments S Figure 1: The expression pattern of Sirt1 and beta-catenin changes in Caerulein induced pancreatitis. S Figure 2: The expression pattern of Sirt1 and beta-catenin, but not Dbc1, changes in pancreatic duct ligation. S Figure 3: In an in vitro ADM model, Sirt1 undergoes transient changes in subcellular localisation without changes in expression levels. S Figure 4: Deletion of functional Sirt1 in Pdx1-Cre;Sirt1ex4lox/lox pancreas impacts on acinar cell differentiation during ADM. S Figure 5: Acinar cell differentiation is not altered during ADM in Sirt1 transgenic (SirtTg) pancreas. S Figure 6: Nicotinamide represses ADM of human cells in culture. S Figure 7: Sirt1 co-localizes and interacts with beta-Catenin in acinar cells. S Figure 8: Nicotinamide increases beta-catenin/Wnt signaling in ADM cultures. S Figure 9: Dbc1 expression is decreased in PDAC but not in chronic pancreatitis.