NF-κB activity during pancreas development regulates adult β-cell mass by modulating neonatal β-cell proliferation and apoptosis

Vitamin D supplementation could enhance the effectiveness of glibenclamide in treating type 2 diabetes by improving the function of pancreatic β-cells through the NF-κB pathway

PURPOSE

The high morbidity and mortality associated with type 2 diabetes mellitus (T2DM) pose a significant global health challenge, necessitating the development of more efficient anti-diabetic drugs with fewer side effects. This study investigated the intervention of vitamin D3 combined with glibenclamide in rats with T2DM to elucidate its effects on pancreatic β-cells through the NF-κB pathway.

METHODS

Twenty-four healthy male Sprague-Dawley (SD) rats were randomly assigned to four groups: the control group (CG), the model group (MG), the glibenclamide group (GG), and the glibenclamide + vitamin D3 group (GDG). After inducing the T2DM model using high-fat and high-sugar diet and intraperitoneal injection of streptozotocin, the rats in the GG group were administered glibenclamide orally (0.6 mg/kg/day), while those in the GDG group received both glibenclamide (0.6 mg/kg/day) and vitamin D3 (500 IU/kg/day) in corn oil for a duration of 8 weeks. Biochemical indices were measured, and histopathological changes in pancreatic tissue and islet β cells were observed using hematoxylin and eosin staining. The expression of pancreatic nuclear factor κB (NF-κB), islet β-cells, and inflammatory cytokines were assessed using the TUNEL method and PCR.

RESULTS

According to the data from this current study, the GDG group showed significant positive differences in plasma biochemical indices, as well as in the expression of β cells, NF-κB p65, TNF-α, IL-1β, INF-γ, and Fas, compared to the GG and CG groups (P < 0.05).

CONCLUSION

The results suggest that vitamin D has beneficial effects on T2DM by improving the functions of islet β cells through inhibition of the NF-κB signaling pathway. Therefore, it is suggested that vitamin D supplementation, when used alongside antidiabetic drugs, may more effectively prevent and treat T2DM.

Multi-omic human pancreatic islet endoplasmic reticulum and cytokine stress response mapping provides type 2 diabetes genetic insights

Endoplasmic reticulum (ER) and inflammatory stress responses contribute to islet dysfunction in type 2 diabetes (T2D). Comprehensive genomic understanding of these human islet stress responses and whether T2D-associated genetic variants modulate them is lacking. Here, comparative transcriptome and epigenome analyses of human islets exposed ex vivo to these stressors revealed 30% of expressed genes and 14% of islet cis-regulatory elements (CREs) as stress responsive, modulated largely in an ER- or cytokine-specific fashion. T2D variants overlapped 86 stress-responsive CREs, including 21 induced by ER stress. We linked the rs6917676-T T2D risk allele to increased islet ER-stress-responsive CRE accessibility and allele-specific β cell nuclear factor binding. MAP3K5, the ER-stress-responsive putative rs6917676 T2D effector gene, promoted stress-induced β cell apoptosis. Supporting its pro-diabetogenic role, MAP3K5 expression correlated inversely with human islet β cell abundance and was elevated in T2D β cells. This study provides genome-wide insights into human islet stress responses and context-specific T2D variant effects.

Unraveling the interplay: exploring signaling pathways in pancreatic cancer in the context of pancreatic embryogenesis

Pancreatic cancer continues to be a deadly disease because of its delayed diagnosis and aggressive tumor biology. Oncogenes and risk factors are being reported to influence the signaling pathways involved in pancreatic embryogenesis leading to pancreatic cancer genesis. Although studies using rodent models have yielded insightful information, the scarcity of human pancreatic tissue has made it difficult to comprehend how the human pancreas develops. Transcription factors like IPF1/PDX1, HLXB9, PBX1, MEIS, Islet-1, and signaling pathways, including Hedgehog, TGF-β, and Notch, are directing pancreatic organogenesis. Any derangements in the above pathways may lead to pancreatic cancer. TP53: and CDKN2A are tumor suppressor genes, and the mutations in TP53 and somatic loss of CDKN2A are the drivers of pancreatic cancer. This review clarifies the complex signaling mechanism involved in pancreatic cancer, the same signaling pathways in pancreas development, the current therapeutic approach targeting signaling molecules, and the mechanism of action of risk factors in promoting pancreatic cancer.

GIP_HUMAN [22-51] Peptide Encoded by the Glucose-Dependent Insulinotropic Polypeptide (GIP) Gene Suppresses Insulin Expression and Secretion in INS-1E Cells and Rat Pancreatic Islets

GIP_HUMAN [22-51] is a recently discovered peptide that shares the same precursor molecule with glucose-dependent insulinotropic polypeptide (GIP). In vivo, chronic infusion of GIP_HUMAN [22-51] in ApoE-/- mice enhanced the development of aortic atherosclerotic lesions and upregulated inflammatory and proatherogenic proteins. In the present study, we evaluate the effects of GIP_HUMAN [22-51] on insulin mRNA expression and secretion in insulin-producing INS-1E cells and isolated rat pancreatic islets. Furthermore, we characterize the influence of GIP_HUMAN [22-51] on cell proliferation and death and on Nf-kB nuclear translocation. Rat insulin-producing INS-1E cells and pancreatic islets, isolated from male Wistar rats, were used in this study. Gene expression was evaluated using real-time PCR. Cell proliferation was studied using a BrdU incorporation assay. Cell death was quantified by evaluating histone-complexed DNA fragments. Insulin secretion was determined using an ELISA test. Nf-kB nuclear translocation was detected using immunofluorescence. GIP_HUMAN [22-51] suppressed insulin (Ins1 and Ins2) in INS-1E cells and pancreatic islets. Moreover, GIP_HUMAN [22-51] promoted the translocation of NF-κB from cytoplasm to the nucleus. In the presence of a pharmacological inhibitor of NF-κB, GIP_HUMAN [22-51] was unable to suppress Ins2 mRNA expression. Moreover, GIP_HUMAN [22-51] downregulated insulin secretion at low (2.8 mmol/L) but not high (16.7 mmol/L) glucose concentration. By contrast, GIP_HUMAN [22-51] failed to affect cell proliferation and apoptosis. We conclude that GIP_HUMAN [22-51] suppresses insulin expression and secretion in pancreatic β cells without affecting β cell proliferation or apoptosis. Notably, the effects of GIP_HUMAN [22-51] on insulin secretion are glucose-dependent.

NF-κB-inducing kinase (NIK) is activated in pancreatic β-cells but does not contribute to the development of diabetes

The transcription factor nuclear factor-κB (NF-κB) has a key role in the pathogenesis of diabetes and its complications. Although activation of the canonical NF-κB pathway in β-cells is generally deleterious, little is known about the role of the non-canonical NF-κB signalling and its main regulator, the NF-κB-inducing kinase (NIK), on pancreatic β-cell survival and function. Previous studies based on models of NIK overexpression in pancreatic islet cells showed that NIK induced either spontaneous β-cell death due to islet inflammation or glucose intolerance during diet-induced obesity (DIO) in mice. Therefore, NIK has been proposed as a potential target for diabetes therapy. However, no clear studies showed whether inhibition of NIK improves diabetes development. Here we show that genetic silencing of NIK in pancreatic β-cells neither modifies diabetes incidence nor inflammatory responses in a mouse model of immune-mediated diabetes. Moreover, NIK silencing in DIO mice did not influence body weight gain, nor glucose metabolism. In vitro studies corroborated the in vivo findings in terms of β-cell survival, function, and downstream gene regulation. Taken together, our data suggest that NIK activation is dispensable for the development of diabetes.

Insm1, Neurod1, and Pax6 promote murine pancreatic endocrine cell development through overlapping yet distinct RNA transcription and splicing programs

Insm1, Neurod1, and Pax6 are essential for the formation and function of pancreatic endocrine cells. Here, we report comparative immunohistochemical, transcriptomic, functional enrichment, and RNA splicing analyses of these genes using gene knock-out mice. Quantitative immunohistochemical analysis confirmed that elimination of each of these three factors variably impairs the proliferation, survival, and differentiation of endocrine cells. Transcriptomic analysis revealed that each factor contributes uniquely to the transcriptome although their effects were overlapping. Functional enrichment analysis revealed that genes downregulated by the elimination of Insm1, Neurod1, and Pax6 are commonly involved in mRNA metabolism, chromatin organization, secretion, and cell cycle regulation, and upregulated genes are associated with protein degradation, autophagy, and apoptotic process. Elimination of Insm1, Neurod1, and Pax6 impaired expression of many RNA-binding proteins thereby altering RNA splicing events, including for Syt14 and Snap25, two genes required for insulin secretion. All three factors are necessary for normal splicing of Syt14, and both Insm1 and Pax6 are necessary for the processing of Snap25. Collectively, these data provide new insights into how Insm1, Neurod1, and Pax6 contribute to the formation of functional pancreatic endocrine cells.