Single-cell transcriptomic profiling of human pancreatic islets reveals genes responsive to glucose exposure over 24 h.

AIMS/HYPOTHESIS: Disruption of pancreatic islet function and glucose homeostasis can lead to the development of sustained hyperglycaemia, beta cell glucotoxicity and subsequently type 2 diabetes. In this study, we explored the effects of in vitro hyperglycaemic conditions on human pancreatic islet gene expression across 24 h in six pancreatic cell types: alpha; beta; gamma; delta; ductal; and acinar. We hypothesised that genes associated with hyperglycaemic conditions may be relevant to the onset and progression of diabetes. METHODS: We exposed human pancreatic islets from two donors to low (2.8 mmol/l) and high (15.0 mmol/l) glucose concentrations over 24 h in vitro. To assess the transcriptome, we performed single-cell RNA-seq (scRNA-seq) at seven time points. We modelled time as both a discrete and continuous variable to determine momentary and longitudinal changes in transcription associated with islet time in culture or glucose exposure. Additionally, we integrated genomic features and genetic summary statistics to nominate candidate effector genes. For three of these genes, we functionally characterised the effect on insulin production and secretion using CRISPR interference to knock down gene expression in EndoC-ßH1 cells, followed by a glucose-stimulated insulin secretion assay. RESULTS: In the discrete time models, we identified 1344 genes associated with time and 668 genes associated with glucose exposure across all cell types and time points. In the continuous time models, we identified 1311 genes associated with time, 345 genes associated with glucose exposure and 418 genes associated with interaction effects between time and glucose across all cell types. By integrating these expression profiles with summary statistics from genetic association studies, we identified 2449 candidate effector genes for type 2 diabetes, HbA1c, random blood glucose and fasting blood glucose. Of these candidate effector genes, we showed that three (ERO1B, HNRNPA2B1 and RHOBTB3) exhibited an effect on glucose-stimulated insulin production and secretion in EndoC-ßH1 cells. CONCLUSIONS/INTERPRETATION: The findings of our study provide an in-depth characterisation of the 24 h transcriptomic response of human pancreatic islets to glucose exposure at a single-cell resolution. By integrating differentially expressed genes with genetic signals for type 2 diabetes and glucose-related traits, we provide insights into the molecular mechanisms underlying glucose homeostasis. Finally, we provide functional evidence to support the role of three candidate effector genes in insulin secretion and production. DATA AVAILABILITY: The scRNA-seq data from the 24 h glucose exposure experiment performed in this study are available in the database of Genotypes and Phenotypes (dbGap; https://www.ncbi.nlm.nih.gov/gap/ ) with accession no. phs001188.v3.p1. Study metadata and summary statistics for the differential expression, gene set enrichment and candidate effector gene prediction analyses are available in the Zenodo data repository ( https://zenodo.org/ ) under accession number 11123248. The code used in this study is publicly available at https://github.com/CollinsLabBioComp/publication-islet_glucose_timecourse .

Imeglimin: the New Kid on the Block.

PURPOSE OF REVIEW: This review aims to collect all the data regarding imeglimin and present it as one of the options for managing diabetes. RECENT FINDINGS: It is a new drug that has recently been approved as an oral anti-diabetic drug, either as monotherapy or in combination with other oral antidiabetic drugs including insulin, with modest HbA1c reduction, and a fairly safe profile. Imeglimin was first approved in 2021 in Japan and China and is available in India from October 2022. Imeglimin is the first compound in a new class of oral anti-diabetic medications known as "glimins" that include a tetrahydrotriazine ring. Glimins act by amplifying glucose-stimulated insulin secretion (GSIS) and preserving ß-cell mass, leading to augmented insulin secretion. Furthermore, It also intensifies insulin action by inhibiting of hepatic glucose output and recovery of altered insulin signalling in both hepatocytes (liver) and myocytes (skeletal muscle). This is a unique mode of action than has been demonstrated to be distinct from other classes of drugs, as it targets both insulin secretion and insulin resistance by correcting the mitochondrial dysfunction. Imeglimin has been studied in various phase III trials which have equivocally shown it to be effective in lowering glucose levels and improving pancreatic function and its recommended dose set at 1000 mg bid.

RASSF1A disrupts the NOTCH signaling axis via SNURF/RNF4-mediated ubiquitination of HES1.

RASSF1A promoter methylation has been correlated with tumor dedifferentiation and aggressive oncogenic behavior. Nevertheless, the underlying mechanism of RASSF1A-dependent tumor dedifferentiation remains elusive. Here, we show that RASSF1A directly uncouples the NOTCH-HES1 axis, a key suppressor of differentiation. Interestingly, the crosstalk of RASSF1A with HES1 occurs independently from the signaling route connecting RASSF1A with the Hippo pathway. At the molecular level, we demonstrate that RASSF1A acts as a scaffold essential for the SUMO-targeted E3 ligase SNURF/RNF4 to target HES1 for degradation. The reciprocal relationship between RASSF1A and HES1 is evident across a wide range of human tumors, highlighting the clinical significance of the identified pathway. We show that HES1 upregulation in a RASSF1A-depleted environment renders cells non-responsive to the downstream effects of γ-secretase inhibitors (GSIs) which restrict signaling at the level of the NOTCH receptor. Taken together, we report a mechanism through which RASSF1A exerts autonomous regulation of the critical Notch effector HES1, thus classifying RASSF1A expression as an integral determinant of the clinical effectiveness of Notch inhibitors.

Comparative Analysis of Orthosteric and Allosteric GLP-1R Agonists' Effects on Insulin Secretion from Healthy, Diabetic, and Recovered INS-1E Pancreatic Beta Cells.

Despite the availability of different treatments for type 2 diabetes (T2D), post-diagnosis complications remain prevalent; therefore, more effective treatments are desired. Glucagon-like peptide (GLP)-1-based drugs are currently used for T2D treatment. They act as orthosteric agonists for the GLP-1 receptor (GLP-1R). In this study, we analyzed in vitro how the GLP-1R orthosteric and allosteric agonists augment glucose-stimulated insulin secretion (GSIS) and intracellular cAMP production (GSICP) in INS-1E pancreatic beta cells under healthy, diabetic, and recovered states. The findings from this study suggest that allosteric agonists have a longer duration of action than orthosteric agonists. They also suggest that the GLP-1R agonists do not deplete intracellular insulin, indicating they can be a sustainable and safe treatment option for T2D. Importantly, this study demonstrates that the GLP-1R agonists variably augment GSIS through GSICP in healthy, diabetic, and recovered INS-1E cells. Furthermore, we find that INS-1E cells respond differentially to the GLP-1R agonists depending on both glucose concentration during and before treatment and/or whether the cells have been previously exposed to these drugs. In conclusion, the findings described in this manuscript will be useful in determining in vitro how pancreatic beta cells respond to T2D drug treatments in healthy, diabetic, and recovered states.

Short-chain fatty acids: possible regulators of insulin secretion.

The benefits of gut microbiota-derived short-chain fatty acids (SCFAs) towards health and metabolism have been emerging since the past decade. Extensive studies have been carried out to understand the mechanisms responsible in initiating the functionalities of these SCFAs towards body tissues, which greatly involves the SCFA-specific receptors free fatty acid receptor 2 (FFAR2) and free fatty acid receptor 3 (FFAR3). This review intends to discuss the potential of SCFAs particularly in regulating insulin secretion in pancreatic ß-cells, by explaining the production of SCFAs in the gut, the fate of each SCFAs after their production, involvement of FFAR2 and FFAR3 signalling mechanisms and their impacts on insulin secretion. Increased secretion of insulin after SCFAs treatments were reported in many studies, but contradicting evidence also exist in several other studies. Hence, no clear consensus was achieved in determining the true potential of SCFA in regulating insulin secretion. In this review, we explore how such differences were possible and hopefully be able to shed some perspectives in understanding SCFAs-signalling behaviour and preferences.

Glucose-mediated insulin secretion is improved in FHL2-deficient mice and elevated FHL2 expression in humans is associated with type 2 diabetes.

AIMS/HYPOTHESIS: The general population is ageing, involving an enhanced incidence of chronic diseases such as type 2 diabetes. With ageing, DNA methylation of FHL2 increases, as well as expression of the four and a half LIM domains 2 (FHL2) protein in human pancreatic islets. We hypothesised that FHL2 is actively involved in glucose metabolism. METHODS: Publicly available microarray datasets from human pancreatic islets were analysed for FHL2 expression. In FHL2-deficient mice, we studied glucose clearance and insulin secretion. Gene expression analysis and glucose-stimulated insulin secretion (GSIS) were determined in isolated murine FHL2-deficient islets to evaluate insulin-secretory capacity. Moreover, knockdown and overexpression of FHL2 were accomplished in MIN6 cells to delineate the underlying mechanism of FHL2 function. RESULTS: Transcriptomics of human pancreatic islets revealed that individuals with elevated levels of HbA1c displayed increased FHL2 expression, which correlated negatively with insulin secretion pathways. In line with this observation, FHL2-deficient mice cleared glucose more efficiently than wild-type littermates through increased plasma insulin levels. Insulin sensitivity was comparable between these genotypes. Interestingly, pancreatic islets isolated from FHL2-deficient mice secreted more insulin in GSIS assays than wild-type mouse islets even though insulin content and islet size was similar. To support this observation, we demonstrated increased expression of the transcription factor crucial in insulin secretion, MAF BZIP transcription factor A (MafA), higher expression of GLUT2 and reduced expression of the adverse factor c-Jun in FHL2-deficient islets. The underlying mechanism of FHL2 was further delineated in MIN6 cells. FHL2-knockdown led to enhanced activation of forkhead box protein O1 (FOXO1) and its downstream genes such as Mafa and Pdx1 (encoding pancreatic and duodenal homeobox 1), as well as increased glucose uptake. On the other hand, FHL2 overexpression in MIN6 cells blocked GSIS, increased the formation of reactive oxygen species and increased c-Jun activity. CONCLUSIONS/INTERPRETATION: Our data demonstrate that FHL2 deficiency improves insulin secretion from beta cells and improves glucose tolerance in mice. Given that FHL2 expression in humans increases with age and that high expression levels of FHL2 are associated with beta cell dysfunction, we propose that enhanced FHL2 expression in elderly individuals contributes to glucose intolerance and the development of type 2 diabetes. DATA AVAILABILITY: The human islet microarray datasets used are publicly available and can be found on https://www.ncbi.nlm.nih.gov/geo/ .

The multifaceted role of ATF4 in regulating glucose-stimulated insulin secretion.

Stress-inducible transcription factor ATF4 is essential for survival and identity of ß-cell during stress conditions. However, the physiological role of ATF4 in ß-cell function is not yet completely understood. To understand the role of ATF4 in glucose-stimulated insulin secretion (GSIS), ß-cell-specific Atf4 knockout (ßAtf4KO) mice were phenotypically characterized. Insulin secretion and mechanistic analyses were performed using islets from control Atf4f/f and ßAtf4KO mice to assess key regulators for triggering and amplifying signals for GSIS. ßAtf4KO mice displayed glucose intolerance due to reduced insulin secretion. Moreover, ßAtf4KO islets exhibited a decrease in both the insulin content and first-phase insulin secretion. The analysis of ßAtf4KO islets showed that ATF4 is required for insulin production and glucose-stimulated ATP and cAMP production. The results demonstrate that ATF4 contributes to the multifaceted regulatory process in GSIS even under stress-free conditions.

High bicarbonate concentration increases glucose-induced insulin secretion in pancreatic ß-cells.

Low serum bicarbonate is closely related to type 2 diabetes mellitus. However, the precise role of bicarbonate on glucose homeostasis and insulin secretion remains unknown. In this study, we investigated the effects of bicarbonate concentration on pancreatic ß-cells. It was observed that the high bicarbonate concentration of the cell culture medium significantly increased the glucose-induced insulin secretion (GSIS) levels in mouse islets, MIN6, and the INS-1E ß cells. MIN6 cells presented an impaired GSIS; the cells produced a lower bicarbonate concentration when co-cultured with Capan-1 than when with CFPAC-1. NBCe1, a major bicarbonate transporter was observed to block the increasing insulin secretions, which were promoted by a high concentration of bicarbonate. In addition, higher extracellular bicarbonate concentration significantly increased the intracellular cAMP level, pHi, and calcium concentration with a 16.7 mM of glucose stimulation. Further study demonstrated that a low concentration of extracellular bicarbonate significantly impaired the functioning of pancreatic ß cells by reducing coupling Ca2+ influx, whose process may be modulated by NBCe1. Taken together, our results conclude that bicarbonate may serve as a novel target in diabetes prevention-related research.

ß-cell mitochondria in diabetes mellitus: a missing puzzle piece in the generation of hPSC-derived pancreatic ß-cells?

Diabetes mellitus (DM), currently affecting 463 million people worldwide is a chronic disease characterized by impaired glucose metabolism resulting from the loss or dysfunction of pancreatic ß-cells with the former preponderating in type 1 diabetes (T1DM) and the latter in type 2 diabetes (T2DM). Because impaired insulin secretion due to dysfunction or loss of pancreatic ß-cells underlies different types of diabetes, research has focused its effort towards the generation of pancreatic ß-cells from human pluripotent stem cell (hPSC) as a potential source of cells to compensate for insulin deficiency. However, many protocols developed to differentiate hPSCs into insulin-expressing ß-cells in vitro have generated hPSC-derived ß-cells with either immature phenotype such as impaired glucose-stimulated insulin secretion (GSIS) or a weaker response to GSIS than cadaveric islets. In pancreatic ß-cells, mitochondria play a central role in coupling glucose metabolism to insulin exocytosis, thereby ensuring refined control of GSIS. Defects in ß-cell mitochondrial metabolism and function impair this metabolic coupling. In the present review, we highlight the role of mitochondria in metabolism secretion coupling in the ß-cells and summarize the evidence accumulated for the implication of mitochondria in ß-cell dysfunction in DM and consequently, how targeting mitochondria function might be a new and interesting strategy to further perfect the differentiation protocol for generation of mature and functional hPSC-derived ß-cells with GSIS profile similar to human cadaveric islets for drug screening or potentially for cell therapy.

Screening for suicide risk among older adults: assessing preliminary psychometric properties of the Brief Geriatric Suicide Ideation Scale (BGSIS) and the GSIS-Screen.

OBJECTIVES: To initially assess psychometric properties of two abbreviated versions of the Geriatric Suicide Ideation Scale (GSIS): a 10-item Brief Geriatric Suicide Ideation Scale (BGSIS), and a 5-item Geriatric Suicide Ideation Scale-Screen (GSIS-Screen). METHODS: A series of psychometric analyses was conducted, assessing the internal consistency, test-retest reliability, construct and predictive validity of the abbreviated GSIS scales. This was done by selecting-out GSIS items from a combined dataset of studies on suicide ideation in older adults: 1) The GSIS scale development study (n = 107); 2) A clinical trial of Interpersonal Psychotherapy (IPT) modified for suicidal older adults(n = 25); 3) A longitudinal study of risk and resiliency to suicide ideation in community-residing older adults (n = 173). RESULTS: Overall findings demonstrated strong internal consistency, test-retest reliability, concurrent and predictive validity for the BGSIS and GSIS-Screen with older adults across community, clinical, and residential settings. CONCLUSION: Study findings support the use of the abbreviated GSIS scales when conducting research on suicide risk identification among older adults. Future research is recommended testing these scales prospectively in public health, residential, and clinical settings, in research and healthcare delivery contexts.

Distinct biological activities of isomers from several families of branched fatty acid esters of hydroxy fatty acids (FAHFAs).

Branched fatty acid esters of hydroxy fatty acids (FAHFAs) are endogenous lipids with antidiabetic and anti-inflammatory effects. Each FAHFA family consists of esters with different acyl chains and multiple isomers with branch points at different carbons. Some FAHFAs, including palmitic acid hydroxy stearic acids (PAHSAs), improve insulin sensitivity and glucose tolerance in mice by enhancing glucose-stimulated insulin secretion (GSIS), insulin-stimulated glucose transport, and insulin action to suppress hepatic glucose production and reducing adipose tissue inflammation. However, little is known about the biological effects of other FAHFAs. Here, we investigated whether PAHSAs, oleic acid hydroxy stearic acid, palmitoleic acid hydroxy stearic acid, and stearic acid hydroxy stearic acid potentiate GSIS in ß-cells and human islets, insulin-stimulated glucose uptake in adipocytes, and anti-inflammatory effects in immune cells. We also investigated whether they activate G protein-coupled receptor 40, which mediates the effects of PAHSAs on insulin secretion and sensitivity in vivo. We show that many FAHFAs potentiate GSIS, activate G protein-coupled receptor 40, and attenuate LPS-induced chemokine and cytokine expression and secretion and phagocytosis in immune cells. However, fewer FAHFAs augment insulin-stimulated glucose uptake in adipocytes. S-9-PAHSA, but not R-9-PAHSA, potentiated GSIS and glucose uptake, while both stereoisomers had anti-inflammatory effects. FAHFAs containing unsaturated acyl chains with higher branching from the carboxylate head group are more likely to potentiate GSIS, whereas FAHFAs with lower branching are more likely to be anti-inflammatory. This study provides insight into the specificity of the biological actions of different FAHFAs and could lead to the development of FAHFAs to treat metabolic and immune-mediated diseases.

Protein Kinases Signaling in Pancreatic Beta-cells Death and Type 2 Diabetes.

Type 2 diabetes (T2D) is a worldwide serious public health problem. Insulin resistance and ß-cell failure are the two major components of T2D pathology. In addition to defective endoplasmic reticulum (ER) stress signaling due to glucolipotoxicity, ß-cell dysfunction or ß-cell death initiates the deleterious vicious cycle observed in T2D. Although the primary cause is still unknown, overnutrition that contributes to the induction of the state of low-grade inflammation, and the activation of various protein kinases-related metabolic pathways are main factors leading to T2D. In this chapter following subjects, which have critical checkpoints regarding ß-cell fate and protein kinases pathways are discussed; hyperglycemia-induced ß-cell failure, chronic accumulation of unfolded protein in ß-cells, the effect of intracellular reactive oxygen species (ROS) signaling to insulin secretion, excessive saturated free fatty acid-induced ß-cell apoptosis, mitophagy dysfunction, proinflammatory responses and insulin resistance, and the reprogramming of ß-cell for differentiation or dedifferentiation in T2D. There is much debate about selecting proposed therapeutic strategies to maintain or enhance optimal ß-cell viability for adequate insulin secretion in T2D. However, in order to achieve an effective solution in the treatment of T2D, more intensive clinical trials are required on newer therapeutic options based on protein kinases signaling pathways.

ß Cell GHS-R Regulates Insulin Secretion and Sensitivity.

Growth hormone secretagogue receptor (GHS-R) is widely known to regulate food intake and adiposity, but its role in glucose homeostasis is unclear. In this study, we investigated the expression of GHS-R in mouse pancreatic islets and its role in glycemic regulation. We used Ghsr-IRES-tauGFP mice, with Green Fluorescent Protein (GFP) as a surrogate for GHS-R, to demonstrate the GFP co-localization with insulin and glucagon expression in pancreatic islets, confirming GHS-R expression in ß and α cells. We then generated ß-cell-specific GHSR-deleted mice with MIP-Cre/ERT and validated that GHS-R suppression was restricted to the pancreatic islets. MIP-Cre/ERT;Ghsrf/f mice showed normal energy homeostasis with similar body weight, body composition, and indirect calorimetry profile. Interestingly, MIP-Cre/ERT;Ghsrf/f mice exhibited an impressive phenotype in glucose homeostasis. Compared to controls, MIP-Cre/ERT;Ghsrf/f mice showed lower fasting blood glucose and insulin; reduced first-phase insulin secretion during a glucose tolerance test (GTT) and glucose-stimulated insulin secretion (GSIS) test in vivo. The isolated pancreatic islets of MIP-Cre/ERT;Ghsrf/f mice also showed reduced insulin secretion during GSIS ex vivo. Further, MIP-Cre/ERT;Ghsrf/f mice exhibited improved insulin sensitivity during insulin tolerance tests (ITT). Overall, our results confirmed GHS-R expression in pancreatic ß and α cells; GHS-R cell-autonomously regulated GSIS and modulated systemic insulin sensitivity. In conclusion, ß cell GHS-R was an important regulator of glucose homeostasis, and GHS-R antagonists may have therapeutic potential for Type 2 Diabetes.

Control of TRPM3 Ion Channels by Protein Kinase CK2-Mediated Phosphorylation in Pancreatic ß-Cells of the Line INS-1.

In pancreatic ß-cells of the line INS-1, glucose uptake and metabolism induce the openings of Ca2+-permeable TRPM3 channels that contribute to the elevation of the intracellular Ca2+ concentration and the fusion of insulin granules with the plasma membrane. Conversely, glucose-induced Ca2+ signals and insulin release are reduced by the activity of the serine/threonine kinase CK2. Therefore, we hypothesized that TRPM3 channels might be regulated by CK2 phosphorylation. We used recombinant TRPM3α2 proteins, native TRPM3 proteins from INS-1 ß-cells, and TRPM3-derived oligopeptides to analyze and localize CK2-dependent phosphorylation of TRPM3 channels. The functional consequences of CK2 phosphorylation upon TRPM3-mediated Ca2+ entry were investigated in Fura-2 Ca2+-imaging experiments. Recombinant TRPM3α2 channels expressed in HEK293 cells displayed enhanced Ca2+ entry in the presence of the CK2 inhibitor CX-4945 and their activity was strongly reduced after CK2 overexpression. TRPM3α2 channels were phosphorylated by CK2 in vitro at serine residue 1172. Accordingly, a TRPM3α2 S1172A mutant displayed enhanced Ca2+ entry. The TRPM3-mediated Ca2+ entry in INS-1 ß-cells was also strongly increased in the presence of CX-4945 and reduced after overexpression of CK2. Our study shows that CK2-mediated phosphorylation controls TRPM3 channel activity in INS-1 ß-cells.

A novel gene in early childhood diabetes: EDEM2 silencing decreases SLC2A2 and PXD1 expression, leading to impaired insulin secretion.

Monogenic diabetes is a rare type of diabetes resulting from mutations in a single gene. To date, most cases remain genetically unexplained, posing a challenge for accurate diabetes treatment, which leads to on a molecular diagnosis. Therefore, a trio exome scan was performed in a lean, nonsyndromic Caucasian girl with diabetes onset at 2½ years who was negative for autoantibodies. The lean father had diabetes from age 11 years. A novel heterozygous mutation in EDEM2, c.1271G > A; p.Arg424His, was found in the proband and father. Downregulation of Edem2 in rat RIN-m ß-cells resulted in a decrease in insulin genes Ins1 to 67.9% (p = 0.006) and Ins2 to 16.8% (p < 0.001) and reduced insulin secretion by 60.4% (p = 0.0003). Real-time PCR revealed a major disruption of endocrine pancreas-specific genes, including Glut2 and Pxd1, with mRNA suppression to 54% (p < 0.001) and 85.7% (p = 0.01), respectively. No other expression changes related to stress or apoptotic genes were observed. Extended clinical follow-up involving ten family members showed that two healthy individuals carried the same mutation with no sign of diabetes in the clinical screen except for a slight increase in IA-2 antibody in one of them, suggesting incomplete penetrance. In conclusion, we describe EDEM2 as a likely/potential novel diabetes gene, in which inhibition in vitro reduces the expression of ß-cell genes involved in the glucose-stimulated insulin secretion (GSIS) pathway, leading to an overall suppression of insulin secretion but not apoptosis.

Phospholipase C-ß1 potentiates glucose-stimulated insulin secretion.

PLC-ß exerts biologic influences through GPCR. GPCRs are involved in regulating glucose-stimulated insulin secretion (GSIS). Previous studies have suggested that PLC-ßs might play an important role in pancreatic ß cells. However, because of a lack of the specific inhibitors of PLC-ß isozymes and appropriate genetic models, the in vivo function of specific PLC-ß isozymes in pancreatic ß cells and their physiologic relevance in the regulation of insulin secretion have not been studied so far. The present study showed that PLC-ß1 was crucial for ß-cell function by generation of each PLC-ß conditional knockout mouse. Mice lacking PLC-ß1 in ß cells exhibited a marked defect in GSIS, leading to glucose intolerance. In ex vivo studies, the secreted insulin level and Ca2+ response in Plcb1f/f; pancreas/duodenum homeobox protein 1 (Pdx1)-Cre recombinase-estrogen receptor T2 (CreERt2) islets was lower than those in the Plcb1f/f islets under the high-glucose condition. PLC-ß1 led to potentiate insulin secretion via stimulation of particular Gq-protein-coupled receptors. Plcb1f/f; Pdx1-CreERt2 mice fed a high-fat diet developed more severe glucose intolerance because of a defect in insulin secretion. The present study identified PLC-ß1 as an important molecule that regulates ß cell insulin secretion and can be considered a candidate for therapeutic intervention in diabetes mellitus.-Hwang, H.-J., Yang, Y. R., Kim, H. Y., Choi, Y., Park, K.-S., Lee, H., Ma, J. S., Yamamoto, M., Kim, J., Chae, Y. C., Choi, J. H., Cocco, L., Berggren, P.-O., Jang, H.-J., Suh, P.-G. Phospholipase Cß1 potentiates glucose-stimulated insulin secretion.

Controversial Roles of Gut Microbiota-Derived Short-Chain Fatty Acids (SCFAs) on Pancreatic ß-Cell Growth and Insulin Secretion.

In the past 15 years, gut microbiota emerged as a crucial player in health and disease. Enormous progress was made in the analysis of its composition, even in the discovery of novel species. It is time to go beyond mere microbiota-disease associations and, instead, provide more causal analyses. A key mechanism of metabolic regulation by the gut microbiota is through the production of short-chain fatty acids (SCFAs). Acting as supplemental nutrients and specific ligands of two G-protein-coupled receptors (GPCRs), they target the intestines, brain, liver, and adipose tissue, and they regulate appetite, energy expenditure, adiposity, and glucose production. With accumulating but sometimes conflicting research results, key questions emerged. Do SCFAs regulate pancreatic islets directly? What is the effect of ß-cell-specific receptor deletions? What are the mechanisms used by SCFAs to regulate ß-cell proliferation, survival, and secretion? The receptors FFA2/3 are normally expressed on pancreatic ß-cells. Deficiency in FFA2 may have caused glucose intolerance and ß-cell deficiency in mice. However, this was contrasted by a double-receptor knockout. Even more controversial are the effects of SCFAs on insulin secretion; there might be no direct effect at all. Unable to draw clear conclusions, this review reveals some of the recent controversies.

A Psychometric Assessment of the Suicidal Behaviors Questionnaire (SBQ-5) and Geriatric Suicide Ideation Scale-Screen (GSIS-screen) in Middle-Aged and Older Men.

Objectives. To investigate the psychometric properties of the five-item Suicidal Behaviors Questionnaire (SBQ-5) and the Geriatric Suicide Ideation Scale-Screen (GSIS-Screen, submitted) among community-residing middle-aged and older men.Methods. The SBQ-5 and GSIS-Screen were administered to 93 men, 55 years or older, who participated in an eligibility assessment (Time 1) for an upstream psychological intervention study to prevent the onset of suicide ideation among men struggling to transition to retirement. Eligible participants later completed the full GSIS and measures of depression and hopelessness at a pre-group assessment (Time 2).Results. The SBQ-5 was positively associated with the GSIS-Screen at the eligibility assessment. Internal consistency for both measures was low but acceptable. Time 1 scores on both screens predicted suicide ideation at Time 2, controlling for the intervening time lag and for baseline cognitive and physical functioning. Only the GSIS-Screen uniquely predicted future depression and hopelessness ratings.Conclusions. The SBQ-5 and the GSIS-Screen have acceptable psychometric properties among middle-aged and older community-residing men; the GSIS-Screen is more closely associated with later-life suicide risk factors.Clinical Implications. Brief screening tools may be of use in effectively identifying suicide ideation in community-residing middle-aged and older men.

Determinants of Suicide-related Ideation in Late Life Depression: Associations with Perceived Stress.

Objectives: Perceived stress is emerging as a potential contributing factor in suicide-related ideation in older adults. We hypothesized higher levels of perceived stress would be associated with increased self-reported suicidal ideation independent of depressive symptom severity.Methods: This study used data from community-dwelling older adults aged ≥65 with a current diagnosis of major depression. Eligible participants completed measures of depression symptom severity (Hamilton Depression Rating Scale-17 item), current suicidal ideation (Geriatric Suicide Ideation Scale), and perceived stress (Perceived Stress Scale).Results: Participants were 225 older adults with a mean age of 71.4 (SD = 5.6). Sixty-five percent of the sample was female. Fifteen percent of the variance in suicidal ideation was accounted for by lower education (p = .03), male sex (p = .03) and higher current perceived stress (p < .001). Specifically, stress accounted for 12% of the variance.Conclusions: Perceived stress is an important avenue to increase identification of individuals with a higher risk of suicide-related ideation among older adults with a current diagnosis of major depression.Clinical Implications: Screening for perceived stress may allow for improved screening and prevention of suicidal activity in depressed older adults.

miR-17-92 and miR-106b-25 clusters regulate beta cell mitotic checkpoint and insulin secretion in mice.

AIMS/HYPOTHESIS: Adult beta cells in the pancreas are the sole source of insulin in the body. Beta cell loss or increased demand for insulin impose metabolic challenges because adult beta cells are generally quiescent and infrequently re-enter the cell division cycle. The aim of this study is to test the hypothesis that a family of proto-oncogene microRNAs that includes miR-17-92 and miR-106b-25 clusters regulates beta cell proliferation or function in the adult endocrine pancreas. METHODS: To elucidate the role of miR-17-92 and miR-106b-25 clusters in beta cells, we used a conditional miR-17-92/miR-106b-25 knockout mouse model. We employed metabolic assays in vivo and ex vivo, together with advanced microscopy of pancreatic sections, bioinformatics, mass spectrometry and next generation sequencing, to examine potential targets of miR-17-92/miR-106b-25, by which they might regulate beta cell proliferation and function. RESULTS: We demonstrate that miR-17-92/miR-106b-25 regulate the adult beta cell mitotic checkpoint and that miR-17-92/miR-106b-25 deficiency results in reduction in beta cell mass in vivo. Furthermore, we reveal a critical role for miR-17-92/miR-106b-25 in glucose homeostasis and in controlling insulin secretion. We identify protein kinase A as a new relevant molecular pathway downstream of miR-17-92/miR-106b-25 in control of adult beta cell division and glucose homeostasis. CONCLUSIONS/INTERPRETATION: The study contributes to the understanding of proto-oncogene miRNAs in the normal, untransformed endocrine pancreas and illustrates new genetic means for regulation of beta cell mitosis and function by non-coding RNAs. DATA AVAILABILITY: Sequencing data that support the findings of this study have been deposited in GEO with the accession code GSE126516.