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Aims/hypothesis: Genetic studies show coupling of genes affecting beta cell function to type 1 diabetes, but hitherto no studies on whether beta cell dysfunction could precede insulitis and clinical onset of type 1 diabetes are available.Methods: We used 40-day-old BioBreeding (BB) DRLyp/Lyp rats (a model of spontaneous autoimmune type 1 diabetes) and diabetes-resistant DRLyp/+ and DR+/+ littermates (controls) to investigate beta cell function in vivo, and insulin and glucagon secretion in vitro. Beta cell mass was assessed by optical projection tomography (OPT) and morphometry. Additionally, measurements of intra-islet blood flow were performed using microsphere injections. We also assessed immune cell infiltration, cytokine expression in islets (by immunohistochemistry and qPCR), as well as islet Glut2 expression and ATP/ADP ratio to determine effects on glucose uptake and metabolism in beta cells.Results: DRLyp/Lyp rats were normoglycaemic and without traces of immune cell infiltrates. However, IVGTTs revealed a significant decrease in the acute insulin response to glucose compared with control rats (1685.3 ± 121.3 vs 633.3 ± 148.7; p < 0.0001). In agreement, insulin secretion was severely perturbed in isolated islets, and both first- and second-phase insulin release were lowered compared with control rats, while glucagon secretion was similar in both groups. Interestingly, after 5-7 days of culture of islets from DRLyp/Lyp rats in normal media, glucose-stimulated insulin secretion (GSIS) was improved; although, a significant decrease in GSIS was still evident compared with islets from control rats at this time (7393.9 ± 1593.7 vs 4416.8 ± 1230.5 pg islet−1 h−1; p < 0.0001). Compared with controls, OPT of whole pancreas from DRLyp/Lyp rats revealed significant reductions in medium (4.1 × 109 ± 9.5 × 107 vs 3.8 × 109 ± 5.8 × 107 μm3; p = 0.044) and small sized islets (1.6 × 109 ± 5.1 × 107 vs 1.4 × 109 ± 4.5 × 107 μm3; p = 0.035). Finally, we found lower intra-islet blood perfusion in vivo (113.1 ± 16.8 vs 76.9 ± 11.8 μl min−1 [g pancreas]−1; p = 0.023) and alterations in the beta cell ATP/ADP ratio in DRLyp/Lyp rats vs control rats.Conclusions/interpretation: The present study identifies a deterioration of beta cell function and mass, and intra-islet blood flow that precedes insulitis and diabetes development in animals prone to autoimmune type 1 diabetes. These underlying changes in islet function may be previously unrecognised factors of importance in type 1 diabetes development. [ABSTRACT FROM AUTHOR]

Glycogen metabolism in β-cells may affect downstream metabolic pathways controlling insulin release. We examined glycogen metabolism in human islets and in the rodent-derived INS-1 832/13 β-cells and found them to express the same isoforms of key enzymes required for glycogen metabolism. Our findings indicate that glycogenesis is insulin-independent but influenced by extracellular glucose concentrations. Levels of glycogen synthase decrease with increasing glucose concentrations, paralleling accumulation of glycogen. We did not find cAMP-elicited glycogenolysis and insulin secretion to be causally related. In conclusion, our results reveal regulated glycogen metabolism in human islets and insulin-secreting cells. Whether glycogen metabolism affects insulin secretion under physiological conditions remains to be determined. [ABSTRACT FROM AUTHOR]

In an earlier study, infection of human pancreatic islets with epidemic strains of echovirus (E4, E16, E30), with proven but differently ability to induce islet autoimmunity, resulted either in a severe damage (i.e., E16 and E30) or proceeded without visible changes in infected islets (i.e., E4). In this study, the ability of these strains to replicate in beta cells and the consequence of such an infection for beta cell lysis and beta cell function was studied in the pancreatic beta cell lines INS-1, MIN6, and NIT-1. The strains of E16 and E30 did replicate in INS1, MIN6, and NIT1 cells and resulted in a pronounced cytopathic effect within 3 days following infection. By contrast, E4 replicated in all examined insulinoma cells with no apparent cell destruction. The insulin release in response to high glucose stimulation was hampered in all infected cells ( P < 0.05) when no evidence of cytolysis was present; however, the adverse effect of E16 and E30 on insulin secretion appeared to be higher than that of the E4 strain. The differential effects of echovirus infection on cell lysis, and beta cell function in the rodent insulinoma INS1, MIN6, and NIT 1 cells reflect those previously obtained in primary human islets and support the notion that the insulin-producing beta cells can harbor a non-cytopathic viral infection. J. Med. Virol. 88:971-978, 2016. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: The G-coupled 5-hydroxytryptamine 2B (5-HT) receptor is known to regulate the proliferation of islet beta cells during pregnancy. However, the role of serotonin in the control of insulin release is still controversial. The aim of the present study was to explore the role of the 5-HT receptor in the regulation of insulin secretion in mouse and human islets, as well as in clonal INS-1(832/13) cells. Methods: Expression of HTR2B mRNA and 5-HT protein was examined with quantitative real-time PCR, RNA sequencing and immunohistochemistry. α-Methyl serotonin maleate salt (AMS), a serotonin receptor agonist, was employed for robust 5-HT receptor activation. Htr2b was silenced with small interfering RNA in INS-1(832/13) cells. Insulin secretion, Ca response and oxygen consumption rate were determined. Results: Immunohistochemistry revealed that 5-HT is expressed in human and mouse islet beta cells. Activation of 5-HT receptors by AMS enhanced glucose-stimulated insulin secretion (GSIS) in human and mouse islets as well as in INS-1(832/13) cells. Silencing Htr2b in INS-1(832/13) cells led to a 30% reduction in GSIS. 5-HT receptor activation produced robust, regular and sustained Ca oscillations in mouse islets with an increase in both peak distance (period) and time in the active phase as compared with control. Enhanced insulin secretion and Ca changes induced by AMS coincided with an increase in oxygen consumption in INS-1(832/13) cells. Conclusions/interpretation: Activation of 5-HT receptors stimulates GSIS in beta cells by triggering downstream changes in cellular Ca flux that enhance mitochondrial metabolism. Our findings suggest that serotonin and the 5-HT receptor stimulate insulin release. [ABSTRACT FROM AUTHOR]

Background: A novel coronavirus, SARS-CoV-2 (known as COVID-19), spread rapidly around the world, affecting all and creating an ongoing global pandemic. Across the United States, Latinx and Indigenous populations have been disproportionately affected by COVID-19 cases and death rates. An examination of the perceptions and beliefs about the spread of the virus, COVID-19 testing, and vaccination amongst racial-ethnic minority groups, specifically Latinx and Indigenous Latin American immigrant communities, is needed to alleviate the widespread disparity in new cases and deaths.Methods: This study was carried out from August 2020 to January 2021 and used community-based participatory research to engage community partners and build the capacity of community health workers (i.e., promotores de salud) and pre-medical and medical students in conducting qualitative research. The objective of the study was to examine the structural and social determinants of health on perceptions of the coronavirus, its spread, and decisions around COVID-19 testing and vaccination. Data collection included ethnography involving observations in public settings and focus groups with members of Latinx and Indigenous Mexican farm-working communities in the Eastern Coachella Valley, located in the Inland Southern California desert region. A total of seven focus groups, six in Spanish and one in Purépecha, with a total of 55 participants were conducted. Topics covered include perceptions of the coronavirus and its spread, as well as COVID-19 testing and vaccination.Results: Using theme identification techniques, the findings identify structural and social factors that underly perceptions held by Latinx and Indigenous Mexican immigrants about the virus and COVID-19, which, in turn, shape attitudes and behaviors related to COVID-19 testing and vaccination. Common themes that emerged across focus groups include misinformation, lack of trust in institutions, and insecurity around employment and residency.Conclusions: This immigrant population is structurally vulnerable to historical and present-day inequalities that put them at increased risk of COVID-19 exposure, morbidity, and mortality. Study findings indicate a significant need for interventions that decrease structural vulnerabilities by addressing issues of (dis)trust in government and public health among this population. [ABSTRACT FROM AUTHOR]