Studies implicating sodium-glucose cotransporter 2 (SGLT2) inhibitors in glucagon secretion by pancreatic α-cells reported controversial results. We hypothesized that interindividual heterogeneity in ...SGLT2 expression and regulation may affect glucagon secretion by human α-cells in response to SGLT2 inhibitors. An unbiased RNA-sequencing analysis of 207 donors revealed an unprecedented level of heterogeneity of
expression. To determine heterogeneity of SGLT2 expression at the protein level, the anti-SGLT2 antibody was first rigorously evaluated for specificity, followed by Western blot and immunofluorescence analysis on islets from 10 and 12 donors, respectively. The results revealed a high interdonor variability of SGLT2 protein expression. Quantitative analysis of 665 human islets showed a significant SGLT2 protein colocalization with glucagon but not with insulin or somatostatin. Moreover, glucagon secretion by islets from 31 donors at low glucose (1 mmol/L) was also heterogeneous and correlated with dapagliflozin-induced glucagon secretion at 6 mmol/L glucose. Intriguingly, islets from three donors did not secrete glucagon in response to either 1 mmol/L glucose or dapagliflozin, indicating a functional impairment of the islets of these donors to glucose sensing and SGLT2 inhibition. Collectively, these data suggest that heterogeneous expression of SGLT2 protein and variability in glucagon secretory responses contribute to interindividual differences in response to SGLT2 inhibitors.
Elevated plasma concentration of the pro-atherogenic oxidized low density lipoprotein cholesterol (LDL) triggers adverse effects in pancreatic beta-cells and is associated with type 2 diabetes. Here, ...we investigated whether the endoplasmic reticulum (ER) stress is a key player coupling oxidative stress to beta-cell dysfunction and death elicited by human oxidized LDL. We found that human oxidized LDL activates ER stress as evidenced by the activation of the inositol requiring 1α, and the elevated expression of both DDIT3 (also called CHOP) and DNAJC3 (also called P58IPK) ER stress markers in isolated human islets and the mouse insulin secreting MIN6 cells. Silencing of Chop and inhibition of ER stress markers by the chemical chaperone phenyl butyric acid (PBA) prevented cell death caused by oxidized LDL. Finally, we found that oxidative stress accounts for activation of ER stress markers induced by oxidized LDL. Induction of Chop/CHOP and p58IPK/P58IPK by oxidized LDL was mimicked by hydrogen peroxide and was blocked by co-treatment with the N-acetylcystein antioxidant. As a conclusion, the harmful effects of oxidized LDL in beta-cells requires ER stress activation in a manner that involves oxidative stress. This mechanism may account for impaired beta-cell function in diabetes and can be reversed by antioxidant treatment.
Cancer cells integrate multiple biosynthetic demands to drive unrestricted proliferation. How these cellular processes crosstalk to fuel cancer cell growth is still not fully understood. Here, we ...uncover the mechanisms by which the transcription factor Carbohydrate responsive element binding protein (ChREBP) functions as an oncogene during hepatocellular carcinoma (HCC) development. Mechanistically, ChREBP triggers the expression of the PI3K regulatory subunit p85α, to sustain the activity of the pro-oncogenic PI3K/AKT signaling pathway in HCC. In parallel, increased ChREBP activity reroutes glucose and glutamine metabolic fluxes into fatty acid and nucleic acid synthesis to support PI3K/AKT-mediated HCC growth. Thus, HCC cells have a ChREBP-driven circuitry that ensures balanced coordination between PI3K/AKT signaling and appropriate cell anabolism to support HCC development. Finally, pharmacological inhibition of ChREBP by SBI-993 significantly suppresses in vivo HCC tumor growth. Overall, we show that targeting ChREBP with specific inhibitors provides an attractive therapeutic window for HCC treatment.
Maturity-onset diabetes of the young (MODY) represents an autosomal dominant genetic form of diabetes, coined by Tattersall and Fajans in 1974 as having one or more variations in a single gene 1, 2. ...MODY is initially characterised by fasting hyperglycaemia, often diagnosed in children or young adults 2, 3. Currently, MODY accounts for 1–5% of all individuals with diabetes 4, and at least 14 distinct subtypes have been reported to date 5, 6. Heterozygous mutations in the gene encoding hepatocyte nuclear factor 1-alpha (HNF1A) cause the most common form of monogenic diabetes, known as HNF1A-MODY 7. This form of MODY is highly prevalent in populations with European ancestry (>70%) and is more frequent than previously thought. Approximately 95% of individuals with HNF1A-MODY are misdiagnosed as either type 1 diabetes or type 2 diabetes, thus revealing a lack of physician awareness and/or access to genetic testing 8. Early diagnosis is critical since HNF1A-MODY affects 50% of children born to a mutation carrier, and penetrance is often above 90%, such that three or more generations are usually affected 9.
In islet transplantation (ITx), primary graft function (PGF) or beta cell function measured early after last infusion is closely associated with long term clinical outcomes. We investigated the ...association between PGF and 5 year insulin independence rate in ITx and pancreas transplantation (PTx) recipients. This retrospective multicenter study included type 1 diabetes patients who underwent ITx in Lille and PTx in Nantes from 2000 to 2022. PGF was assessed using the validated Beta2-score and compared to normoglycemic control subjects. Subsequently, the 5 year insulin independence rates, as predicted by a validated PGF-based model, were compared to the actual rates observed in ITx and PTx patients. The study enrolled 39 ITx (23 ITA, 16 IAK), 209 PTx recipients (23 PTA, 14 PAK, 172 SPK), and 56 normoglycemic controls. MeanSD PGF was lower after ITx (ITA 22.35.2, IAK 24.86.4, than after PTx (PTA 38.915.3, PAK 36.89.0, SPK 38.710.5), and lower than mean beta-cell function measured in normoglycemic control: 36.64.3. The insulin independence rates observed at 5 years after PTA and PAK aligned with PGF predictions, and was higher after SPK. Our results indicate a similar relation between PGF and 5 year insulin independence in ITx and solitary PTx, shedding new light on long-term transplantation outcomes.
Using 13C6 glucose labeling coupled to gas chromatography-mass spectrometry and 2D 1H-13C heteronuclear single quantum coherence NMR spectroscopy, we have obtained a comparative high-resolution map ...of glucose fate underpinning β cell function. In both mouse and human islets, the contribution of glucose to the tricarboxylic acid (TCA) cycle is similar. Pyruvate fueling of the TCA cycle is primarily mediated by the activity of pyruvate dehydrogenase, with lower flux through pyruvate carboxylase. While the conversion of pyruvate to lactate by lactate dehydrogenase (LDH) can be detected in islets of both species, lactate accumulation is 6-fold higher in human islets. Human islets express LDH, with low-moderate LDHA expression and β cell-specific LDHB expression. LDHB inhibition amplifies LDHA-dependent lactate generation in mouse and human β cells and increases basal insulin release. Lastly, cis-instrument Mendelian randomization shows that low LDHB expression levels correlate with elevated fasting insulin in humans. Thus, LDHB limits lactate generation in β cells to maintain appropriate insulin release.
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•Human and rodent islets generate lactate following glucose stimulation•β cells specifically express LDHB, which acts to limit lactate generation•LDHB inhibition leads to inappropriate insulin release at low glucose•LHDB cis-EQTLs associate with fasting glucose in humans
Cuozzo et al. show that glucose-stimulated rodent and human islets generate lactate. Transcriptomic, imaging, and Mendelian randomization analyses reveal that LDHB restrains β cell lactate production and contributes to basal/fasting insulin release. LDHB expression and thus regulated lactate generation might reflect a key mechanism underlying β cell metabolism and function.
Active sodium-glucose transporters play a role to glucose homeostasis and represent novels targets for the management of type 2 diabetes (T2D). Sodium-glucose cotransporter 1 (SGLT1) is essential for ...intestinal glucose absorption from the lumen into enterocytes, whereas glucose reabsorption by the kidney is mainly mediated by sodium-glucose cotransporter 2 (SGLT2). SGLT2 inhibitors were developed to occlude SGLT2 glucose reabsorption pathway and cause glycosuria, thereby reducing plasma glucose concentrations. This new class of antidiabetic drugs has been shown to be effective in reducing cardiovascular morbidity and mortality in patients with T2D. Initial clinical studies also suggest that SGLT1 inhibition increases glucagon-like peptide 1 (GLP-1) secretion and decreases postchallenge blood glucose excursion, resulting in a dose-dependent improvement of glucose control. In parallel, we recently identified a previously unknown effect of bile diversion in gastric bypass on sodium glucose transport and postprandial glucose homeostasis, through the modulation of intestinal trafficking of endogenous sodium. This mechanism is consistent with available clinical evidence, and opens up new perspectives in metabolic surgery. More generally, the modulation of intestinal sodium-glucose cotransport appears to be a promising avenue to prevent or treat T2D.
Thioredoxin interacting protein (TxNIP), which strongly responds to glucose, has emerged as a central mediator of glucotoxicity in pancreatic β cells. TxNIP is a scaffold protein interacting with ...target proteins to inhibit or stimulate their activity. Recent studies reported that high glucose stimulates the interaction of TxNIP with the inflammasome protein NLRP3 (NLR family, pyrin domain containing 3) to increase interleukin-1 β (IL1β) secretion by pancreatic β cells. To better understand the regulation of TxNIP by glucose in pancreatic β cells, we investigated the implication of O-linked β-N-acetylglucosamine (O-GlcNAcylation) in regulating TxNIP at the posttranslational level. O-GlcNAcylation of proteins is controlled by two enzymes: the O-GlcNAc transferase (OGT), which transfers a monosaccharide to serine/threonine residues on target proteins, and the O-GlcNAcase (OGA), which removes it. Our study shows that TxNIP is subjected to O-GlcNAcylation in response to high glucose concentrations in β cell lines. Modification of the O-GlcNAcylation pathway through manipulation of OGT or OGA expression or activity significantly modulates TxNIP O-GlcNAcylation in INS1 832/13 cells. Interestingly, expression and O-GlcNAcylation of TxNIP appeared to be increased in islets of diabetic rodents. At the mechanistic level, the induction of the O-GlcNAcylation pathway in human and rat islets promotes inflammasome activation as evidenced by enhanced cleaved IL1β. Overexpression of OGT in HEK293 or INS1 832/13 cells stimulates TxNIP and NLRP3 interaction, while reducing TxNIP O-GlcNAcylation through OGA overexpression destabilizes this interaction. Altogether, our study reveals that O-GlcNAcylation represents an important regulatory mechanism for TxNIP activity in β cells.
Aberrant hepatic glucose production contributes to the development of hyperglycemia and is a hallmark of type 2 diabetes. In a recent study, we showed that the transcription factor E2F1, a component ...of the cell cycle machinery, contributes to hepatic steatosis through the transcriptional regulation of key lipogenic enzymes. Here, we investigate if E2F1 contributes to hyperglycemia by regulating hepatic gluconeogenesis.
We use different genetic models to investigate if E2F1 regulates gluconeogenesis in primary hepatocytes and in vivo. We study the impact of depleting E2F1 or inhibiting E2F1 activity in diabetic mouse models to evaluate if this transcription factor contributes to hyperglycemia during insulin resistance. We analyze E2F1 mRNA levels in the livers of human diabetic patients to assess the relevance of E2F1 in human pathophysiology.
Lack of E2F1 impaired gluconeogenesis in primary hepatocytes. Conversely, E2F1 overexpression increased glucose production in hepatocytes and in mice. Several genetic models showed that the canonical CDK4-RB1-E2F1 pathway is directly involved in this regulation. E2F1 mRNA levels were increased in the livers from human diabetic patients and correlated with the expression of the gluconeogenic enzyme Pck1. Genetic invalidation or pharmacological inhibition of E2F1 improved glucose homeostasis in diabetic mouse models.
Our study unveils that the transcription factor E2F1 contributes to mammalian glucose homeostasis by directly controlling hepatic gluconeogenesis. Together with our previous finding that E2F1 promotes hepatic steatosis, the data presented here show that E2F1 contributes to both hyperlipidemia and hyperglycemia in diabetes, suggesting that specifically targeting E2F1 in the liver could be an interesting strategy for therapies against type 2 diabetes.
•Genetic manipulation of the CDK4-RB1-E2F1 pathway in hepatocytes results in changes in gluconeogenic gene expression and glucose production.•Overexpression of E2F1 promotes gluconeogenesis in primary hepatocytes and in liver.•E2F1 mRNA levels are increased in the livers of diabetic patients and correlate with PCK1 gene expression.•Genetic depletion and pharmacological inhibition of E2F1 reduces hyperglycemia in diabetic mice.
Pancreatic islet transplantation offers a promising biotherapy for the treatment of type 1 diabetes, but this procedure has met significant challenges over the years. One such challenge is to address ...why primary graft function still remains inconsistent after islet transplantation. Several variables have been shown to affect graft function, but the impact of procedure-related complications on primary and long-term graft functions has not yet been explored.
Twenty-six patients with established type 1 diabetes were included in this study. Each patient had two to three intraportal islet infusions to obtain 10,000 islet equivalent (IEQ)/kg in body weight, equaling a total of 68 islet infusions. Islet transplantation consisted of three sequential fresh islet infusions within 3 months. Islet infusions were performed surgically or under ultrasound guidance, depending on patient morphology, availability of the radiology suite, and patient medical history. Prospective assessment of adverse events was recorded and graded using "Common Terminology Criteria for adverse events in Trials of Adult Pancreatic Islet Transplantation."
There were no deaths or patients dropouts. Early complications occurred in nine of 68 procedures. β score 1 month after the last graft and optimal graft function (β score ≥7) rate were significantly lower in cases of procedure-related complications (P = 0.02, P = 0.03). Procedure-related complications negatively impacted graft function (P = 0.009) and was an independent predictive factor of long-term graft survival (P = 0.033) in multivariate analysis.
Complications occurring during radiologic or surgical intraportal islet transplantation significantly impair primary graft function and graft survival regardless of their severity.
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