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The diagnosis of insulinoma in perinatal women can be difficult, as hypoglycemic symptoms may be masked by pregnancy‐associated insulin resistance. In addition, when multiple insulinomas are observed, it is necessary to consider the possibility not only of MEN1, but also of insulinomatosis.

BackgroundRecent data from clinical trial suggest that antibody cocktail therapy, a combination of the monoclonal antibodies casirivimab and imdevimab, has been shown to rapidly reduce the viral load and markedly decrease the risk of hospitalization or death among high-risk patients with coronavirus disease 2019 (Covid-19). However, it remains unclear how effective in a real-life clinical setting the therapy is.MethodsWe retrospectively analyzed mild to moderate Covid-19 patients with one or more high-risk factors for severe disease who consecutively underwent the antibody cocktail therapy of the disease in our institute in June 2021 through early September 2021, compared to those with high-risk factors who were isolated in non-medical facilities consecutively during the same period, thereby being not given the antibody cocktail therapy there. The key outcome was the percentage of patients with Covid-19-related deterioration which needed additional medical interventions, such as oxygen support or other antiviral therapies.ResultsData from 55 patients with initially receiving antibody cocktail therapy and 53 patients with isolation into non-medical facilities are analyzed. 22 (41.5 %) of 53 patients with isolation facilities were finally hospitalized to receive medical interventions. On the other hand, 13 (23.6 %) of 55 patients with antibody cocktail therapy in our hospital subsequently underwent further medical interventions because of the progression. In multivariate analysis with variables of age, BMI, and high-risk factors, the antibody cocktail therapy significantly reduced 70 % in the need for further medical interventions compared to the initial isolation in the non-medical facilities (odds ratio=0.30, 95%CI [0.10-0.87], p=0.027). Furthermore, patients with 96% or above of SPO2 were significantly more favorable for the therapy than those with 95% or below of SPO2.ConclusionThe treatment of antibody cocktail was closely linked to reduction in the need for further medical interventions. The result indicates that the antibody cocktail therapy is associated with reducing the strain on hospitals, which is related to the improvement of medical management for public health care in Covid-19 pandemic era.

We investigated whether overnutrition during pregnancy were associated with the changes in gene expressions, oxygen metabolism, and vascular and hepatic parenchymal remodeling in fetal livers at mid gestational days E14.5 of dams fed a control diet (CD group) or a high-fat diet (HFD group) during pregnancy. Synchrotron-based phase-contrast micro-CT demonstrated embryos of HFD group showed hepatomegaly accompanied with the same size umbilical vein and less portal branching, which might result in liver hypoxia. Correspondingly, fetal livers of HFD group increased the expression of HIF-1alpha. To identify genes and pathways targeted by maternal overnutrition in fetal livers, we assayed mRNA levels with microarray. We identified 430 differentially expressed genes (DEGs) including 146 upregulated- and 284 downregulated genes in fetal livers of HFD group compared with those of CD group. The up-regulated DEGs were significantly enriched in DNA alkylation, bile secretion, and the down-regulated DEGs mainly enriched in neuronal system, cell maturation. Among upregulated DEGs, a cancer/testis antigen HORMAD1 was induced by hypoxia up to 30-fold compared with that in normoxia in primary mouse hepatocytes (PMH), and the genetic inhibition of HIF-1alpha by siRNAs abolished the stimulatory effect of hypoxia on Hormad1 expression. In addition, we found three putative hypoxia response elements within the mouse Hormad1gene. Interestingly, the tumor suppressor WW domain-containing oxidoreductase (WWOX), which inhibits the activity of HIF-1alpha, were remarkably decreased in hypoxia in PMH. Finally, HORMAD1 protein was upregulated in fetal livers and NASH-based HCC in offspring of HFD group at 15 weeks old. Our results suggest that WWOX-HIF-1alpha-HORMAD1 pathway might be involved in the development of NAFLD in offspring of obese and/or diabetic pregnant woman, and be an important therapeutic target of NASH/HCC. Disclosure T. Takiyama: None. Y. Takiyama: Other Relationship; Self; Gilead Sciences, Inc., Research Support; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Mochida Pharmaceutical Co., Ltd., Roche Diabetes Care, Taisho Pharmaceutical Co., Ltd. R. Bessho: None. H. Kitsunai: None. Y. Takeda: None. H. Sakagami: None. T. Sera: None. M. Nakamura: None. S. Horike: None. Y. Nishikawa: None.

Background Recent data from clinical trial suggest that antibody cocktail therapy, a combination of the monoclonal antibodies casirivimab and imdevimab, has been shown to rapidly reduce the viral load and markedly decrease the risk of hospitalization or death among high-risk patients with coronavirus disease 2019 (Covid-19). However, it remains unclear how effective in a real-life clinical setting the therapy is. Methods We retrospectively analyzed mild to moderate Covid-19 patients with one or more high-risk factors for severe disease who consecutively underwent the antibody cocktail therapy of the disease in our institute in June 2021 through early September 2021, compared to those with high-risk factors who were isolated in non-medical facilities consecutively during the same period, thereby being not given the antibody cocktail therapy there. The key outcome was the percentage of patients with Covid-19-related deterioration which needed additional medical interventions, such as oxygen support or other antiviral therapies. Results Data from 55 patients with initially receiving antibody cocktail therapy and 53 patients with isolation into non-medical facilities are analyzed. 22 (41.5 %) of 53 patients with isolation facilities were finally hospitalized to receive medical interventions. On the other hand, 13 (23.6 %) of 55 patients with antibody cocktail therapy in our hospital subsequently underwent further medical interventions because of the progression. In multivariate analysis with variables of age, BMI, and high-risk factors, the antibody cocktail therapy significantly reduced 70 % in the need for further medical interventions compared to the initial isolation in the non-medical facilities (odds ratio=0.30, 95%CI [0.10-0.87], p=0.027). Furthermore, patients with 96% or above of SPO2 were significantly more favorable for the therapy than those with 95% or below of SPO2. Conclusion The treatment of antibody cocktail was closely linked to reduction in the need for further medical interventions. The result indicates that the antibody cocktail therapy is associated with reducing the strain on hospitals, which is related to the improvement of medical management for public health care in Covid-19 pandemic era.

The short‐form glucose‐dependent insulinotropic polypeptide (GIP) (1–30) is released from islet alpha cells and promotes insulin secretion in a paracrine manner in vitro. However, it is not well elucidated how GIP (1–30) is involved in glucose metabolism in vivo, since a specific assay system for GIP (1–30) has not yet been established. We first developed a sandwich enzyme‐linked immunosorbent assay (ELISA) specific for GIP (1–30) by combining a novel antibody specific to the GIP (1–30) C terminus with the common antibody against GIP N terminus. Then, we explored cross‐reactivities with incretins and glucagon‐related peptides in this ELISA. GIP (1–30) amide, but not GIP (1–42), GLP‐1, or glucagon increased absorbance in a dose‐dependent manner. We next measured plasma GIP (1–30) concentrations in nondiabetic participants (ND) during a 75‐g oral glucose tolerance test or cookie meal test (carbohydrates 75 g, lipids 28.5 g, proteins 8.5 g). Both glucose and cookie load increased GIP (1–30) concentrations in ND, but the increases were much lower than those of GIP (1–42). Furthermore, the DPP‐4 inhibitor significantly increased GIP (1–30) concentrations similarly to GIP (1–42) in ND. In conclusion, we for the first time developed an ELISA specific for GIP (1–30) and revealed its secretion in ND., For the first time, we established a novel ELISA specific for GIP (1–30). GIP (1–30) secretion is promoted by oral glucose and mix meal load in nondiabetics. DPP‐4 inhibitors increased peripheral blood GIP (1–30) levels.

BackgroundGlucagon stimulation test (GST) is often employed to assess the insulin reserve of the pancreatic beta cells in diabetic subjects. The clinical significance of the increment of plasma glucose (Δglucose) by exogenous glucagon during GST has not been elucidated. We investigated the relationship between Δglucose and clinical parameters including the liver and renal function in type 2 diabetic subjects, since we hypothesized that Δglucose is associated with the liver and renal function reflecting the capacity for gluconeogenesis in the organs.MethodsA total of 209 subjects with type 2 diabetes who underwent GST during admission were included in this cross-sectional study. We defined the difference between plasma glucose at fasting and 6 min after intravenous injection of 1 mg glucagon as Δglucose. We assessed correlations between Δglucose and clinical parameters such as diabetic duration, BMI, HbA1c, beta cell function, serum free fatty acids (FFA) which is known to stimulate gluconeogenesis, liver function, the indices of liver function, renal function, and urinary albumin excretion (UAE).ResultsIn correlation analysis, Δglucose positively correlated to FFA and estimated glomerular filtration rate (eGFR), but inversely to serum creatinine and cystatin C, although Δglucose showed no correlation with both liver function and the indices of residual liver function. Multiple regression analysis revealed that Δglucose was an independent determinant for the eGFR after 1 year, equally BMI, HbA1c, serum lipids, and UAE, which are known as the predictors for the development of chronic kidney disease.ConclusionOur results suggest that Δglucose during GST might be related to gluconeogenesis in the kidney and could be the determinant of future renal function in type 2 diabetes.

Previous studies have demonstrated intrarenal hypoxia in patients with diabetes. Hypoxia-inducible factor (HIF)-1 plays an important role in hypoxia-induced tubulointerstitial fibrosis. Recent clinical trials have confirmed the renoprotective action of SGLT2 inhibitors in diabetic nephropathy. We explored the effects of an SGLT2 inhibitor, luseogliflozin on HIF-1α expression in human renal proximal tubular epithelial cells (HRPTECs). Luseogliflozin significantly inhibited hypoxia-induced HIF-1α protein expression in HRPTECs. In addition, luseogliflozin inhibited hypoxia-induced the expression of the HIF-1α target genes PAI-1, VEGF, GLUT1, HK2 and PKM. Although luseogliflozin increased phosphorylated-AMP-activated protein kinase α (p-AMPKα) levels, the AMPK activator AICAR did not changed hypoxia-induced HIF-1α expression. Luseogliflozin suppressed the oxygen consumption rate in HRPTECs, and subsequently decreased hypoxia-sensitive dye, pimonidazole staining under hypoxia, suggesting that luseogliflozin promoted the degradation of HIF-1α protein by redistribution of intracellular oxygen. To confirm the inhibitory effect of luseogliflozin on hypoxia-induced HIF-1α protein in vivo, we treated male diabetic db/db mice with luseogliflozin for 8 to 16 weeks. Luseogliflozin attenuated cortical tubular HIF-1α expression, tubular injury and interstitial fibronectin in db/db mice. Together, luseogliflozin inhibits hypoxia-induced HIF-1α accumulation by suppressing mitochondrial oxygen consumption. The SGLT2 inhibitors may protect diabetic kidneys by therapeutically targeting HIF-1α protein.

Objective Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) possess multiple bioactive isoforms that are rendered non-insulinotropic by the enzyme dipeptidyl peptidase-4 (DPP-4). Recently, some ELISA kits have been developed to specifically measure “active” GIP and GLP-1, but it is unclear if these kits can accurately quantify all bioactive forms. Therefore, it remains uncertain to what extent treatment with a DPP-4 inhibitor boosts levels of biologically active GIP and GLP-1. Thus, we evaluated our novel receptor-mediated incretin bioassays in comparison to commercially available ELISA kits using plasma samples from healthy subjects before and after DPP-4 inhibitor administration. Methods We utilized cell lines stably co-transfected with human GIP or GLP-1 receptors and a cAMP-inducible luciferase expression construct for the bioassays and commercially available ELISA kits. Assays were tested with synthetic GIP and GLP-1 receptor agonists and plasma samples collected from subjects during a 75 g oral glucose tolerance test (OGTT) performed before or following 3-day administration of a DPP-4 inhibitor. Results A GIP isoform GIP(1–30)NH2 increased luciferase activity similarly to GIP(1–42) in the GIP bioassay but was not detectable by either a total or active GIP ELISA kit. During an OGTT, total GIP levels measured by ELISA rapidly increased from 0 min to 15 min, subsequently reaching a peak of 59.2 ± 8.3 pmol/l at 120 min. In contrast, active GIP levels measured by the bioassay peaked at 15 min (43.4 ± 6.4 pmol/l) and then progressively diminished at all subsequent time points. Strikingly, at 15 min, active GIP levels as determined by the bioassay reached levels approximately 20-fold higher after the DPP-4 inhibitor treatment, while total and active GIP levels determined by ELISA were increased just 1.5 and 2.1-fold, respectively. In the absence of DPP-4 inhibition, total GLP-1 levels measured by ELISA gradually increased up to 90 min, reaching 23.5 ± 2.4 pmol/l, and active GLP-1 levels determined by the bioassay did not show any apparent peak. Following administration of a DPP-4 inhibitor there was an observable peak of active GLP-1 levels as determined by the bioassay at 15 min after oral glucose load, reaching 11.0 ± 0.62 pmol/l, 1.4-fold greater than levels obtained without DPP-4 inhibitor treatment. In contrast, total GLP-1 levels determined by ELISA were decreased after DPP-4 inhibitor treatment. Conclusion Our results using bioassays indicate that there is a greater increase in plasma levels of bioactive GIP than GLP-1 in subjects treated with DPP-4 inhibitors, which may be unappreciated using conventional ELISAs., Highlights • Receptor-mediated bioassays were used to measure GIP and GLP-1 in humans. • The GIP bioassay, but not two ELISAs, detected both GIP(1–42) and GIP(1–30)NH2. • Active GIP levels were increased more than GLP-1 after DPP-4 inhibitor treatment.

We previously reported that the short-form gastric inhibitory polypeptide (GIP) 1-30 is released from islet alpha cells and promotes insulin secretion in a paracrine manner in vitro. However, the role played by GIP 1-30 in glucose metabolism in vivo remains unclear. We developed an enzyme-linked immunosorbent assay (ELISA) specific for GIP 1-30 and measured GIP 1-30 secretion in nondiabetic subjects (ND, n = 8) and patients with type 2 diabetes (T2D, n = 9). We developed a sandwich ELISA by combining a novel antibody to the GIP C-terminus with the N-terminal anti-GIP 1-42 antibody that is already available. We explored cross-reactivities with incretins and glucagon-related peptides. We next subjected ND and T2D subjects to the cookie meal test (CMT: carbohydrates 75 g, lipids 28.5 g, proteins 8.5 g) and measured GIP 1-30 blood levels. Absorbance increased in a dose-dependent manner on addition of the GIP 1-30 amide but not GIP 1-42, GLP-1, or glucagon. Post-CMT loading, GIP 1-30 concentrations increased in both ND and T2D subjects; however, in ND subjects, the increases were much lower than those of GIP 1-42 (GIP 1-30, before loading: 1.4 ± 0.5 pmol/L, after: 1.9 ± 0.6 pmol/L; GIP 1-42, before: 8.2 ± 0.1 pmol/L, after: 204.0 ± 35.2 pmol/L, P In conclusion, we developed a novel ELISA that is highly specific for GIP 1-30, the secretion of which was promoted by a mixed meal to a blood level lower than that of GIP 1-42. As is also true of the incretins, GIP 1-30 levels increased upon administration of DPP-4 inhibitor; GIP 1-30 secretion may differ between ND and T2D subjects. Disclosure Y. Takeda: None. Y. Fujita: None. T. Yanagimachi: None. N. Maruyama: Employee; Self; Immuno-Biological Laboratoties Co.,Ltd. R. Bessho: None. H. Sakagami: None. M. Haneda: None. T. Ota: None. Funding Japan Society for the Promotion of Science

Background Recent large-scale clinical studies demonstrate that sodium-glucose cotransporter 2 (SGLT2) inhibitors protect the diabetic kidney. However, clinical and animal studies have not shown the changes of the total glomeruli in the whole kidney treated with SGLT2 inhibitors. Methods We performed computed tomography (CT) imaging on mice using synchrotron radiation to investigate the impact of luseogliflozin, a SGLT2 inhibitor, on the number and volume of glomeruli in the whole kidney. Findings We did not observe a significant difference in the total glomerular number (Nglom) among mice. Luseogliflozin redistributed the number of glomeruli in different regions, accompanied by the normalization of diabetes-augmented renal volume (Vkidney). Diabetic db/db mice had a larger glomerular volume in the mid-cortex than did control db/m mice, and luseogliflozin increased the glomerular volume in all renal cortical zones of the whole kidney in db/db mice. According to the multivariate regression analysis, hemoglobin A1c level was the most relevant determinant of Vkidney, not Nglom or mean glomerular volume (Vglom), indicating that hyperglycemia induced renal (tubular) hypertrophy, but not glomerular enlargement. Luseogliflozin increased hypoxia in the juxtamedullary region, sustained upregulated renal renin expression and plasma renin activity, and failed to decrease albuminuria by downregulating megalin in db/db mice. Interpretation Based on our findings, SGLT2 inhibitors may alter glomerular distribution and size in addition to their glucose-lowering effects, presumably by affecting oxygen metabolism and humoral factors. Fund Funding for this research was provided by The Japan Society for the Promotion of Science , the Japan Diabetes Foundation, and Asahikawa Medical University .

To investigate the impact of diabetes and luseogliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor on the numbers and volumes of glomeruli in the whole kidneys, we performed CT imaging of diabetic db/db mice using synchrotron radiation at SPring-8. We found that there was no significant difference in the total glomerular number among mice. Diabetic mice had significantly larger glomerular volume in the mid-cortex compared to lean control db/m mice. Luseogliflozin reduced whole kidney volume, but not the glomerular hypertrophy in db/db mice. Luseogliflozin also decreased mesangial expansion and tubular damage in db/db mice. Luseogliflozin augmented hypoxia of S3 segment of proximal tubules in the juxtamedullary region and macula densa, as well as the number of intracellular vesicles in juxtaglomerular cells, and sustained upregulated renal renin expression in db/db mice. Luseogliflozin ameliorated hyperglycemia, glomerular and tubular injury, but not albuminuria. Db/db mice decreased the expression of renal megalin protein compared with that in db/m mice. Luseogliflozin-treated db/db mice also reduced the expression of megalin, accompanied with decreased reabsorbing urinary albumin as endocytotic ligand of megalin. In conclusion, our results suggest that oxygen metabolism and/or humoral factors more than blood glucose levels might determine the glomerular number and volume in diabetic kidney. Funding: This work was partially supported by a grant from the Japan Society for the Promotion of Science (JSPS KAKENHI grant no. 15K09372 to Y.T.), and by a Research Grant from the Japan Diabetes Foundation and Asahikawa Medical University (Research grant for Innovative Research in Life Science). Conflicts of Interests: Y.T. was also supported by several foundational grants, including grants from MSD, K.K., Eli Lilly and Company, Sanofi K.K., Takeda Pharmaceutical Co. and Taisho Pharmaceutical Co. No other potential conflicts of interest relevant to this article were reported. Ethical Approval Statement: These experiments were performed with the approval of the SPring-8 Proposal Review Committee (2012B1772, 2013A1655, 2013B1739).

SummaryMEN1-associated pancreatic neuroendocrine tumors (pNETs) may potentially express distinct hormones, but the mechanism has not been elucidated. Transcription factors such as MafA and Pdx1 have been identified to lead to beta cell differentiation, while Arx and Brn4 to alpha cell differentiation in developing pancreas. We hypothesized those transcription factors are important to produce specific hormones in pNETs, similarly to developing pancreas, and examined the expression of transcription factors in a case of MEN1 who showed immunohistological coexistence of several hormone-producing pNETs including insulinoma. A 70-year-old woman was found to manifest hypoglycemia with non-suppressed insulinemia and hypercalcemia with elevated PTH level. She was diagnosed as MEN1 based on the manifestation of primary hyperparathyroidism, pituitary adenoma and insulinoma, with genetic variation of MEN1 gene. She had pylorus-preserving pancreaticoduodenectomy because CT scan and SACI test indicated that insulinoma was localized in the head of the pancreas. Histopathological finding was MEN1-associated NET, G1. Interestingly, immunohistological examination of the resected pancreas revealed that two insulinomas, a glucagon-positive NET and a multiple hormone-positive NET coexisted. Hence, we examined the expression of transcription factors immunohistochemically to elucidate the role of the transcription factors in MEN1-associated hormone-producing pNETs. We observed homogeneous expressions of MafA and Pdx1 in insulinomas and Arx in glucagon-positive NET, respectively. Moreover, multiple hormone-positive NETs expressed several transcription factors heterogeneously. Collectively, our results suggested that transcription factors could play important roles in the production of specific hormones in MEN1-associated pNETs, similar to islet differentiation.Learning points:To date, it has been shown that different hormone-producing tumors coexist in MEN1-associated pNETs; however, the underlying mechanism of the hormone production in MEN1-associated pNETs has not been well elucidated.Although this case presented symptomatic hypoglycemia, several hormone-producing pNETs other than insulinoma also coexisted in the pancreas.Immunohistochemical analysis showed MafA and Pdx1 expressions distinctly in insulinoma, and Arx expression particularly in a glucagon-positive NET, while a multiple hormone-positive NET expressed MafA, Pdx1 and Arx.Collectively, clinicians should consider that several hormone-producing pNETs may coexist in a MEN1 case and examine both endocrinological and histopathological analysis of pNETs, regardless of whether symptoms related to the excess of hormones are observed or not.

Defects in glucose uptake by the skeletal muscle cause diseases linked to metabolic disturbance such as type 2 diabetes. The molecular mechanism determining glucose disposal in the skeletal muscle in response to cellular stimuli including insulin, however, remains largely unknown. The hypoxia-inducible factor-1α (HIF-1α) is a transcription factor operating in the cellular adaptive response to hypoxic conditions. Recent studies have uncovered pleiotropic actions of HIF-1α in the homeostatic response to various cellular stimuli, including insulin under normoxic conditions. Thus we hypothesized HIF-1α is involved in the regulation of glucose metabolism stimulated by insulin in the skeletal muscle. To this end, we generated C2C12myocytes in which HIF-1α is knocked down by short-hairpin RNA and examined the intracellular signaling cascade and glucose uptake subsequent to insulin stimulation. Knockdown of HIF-1α expression in the skeletal muscle cells resulted in abrogation of insulin-stimulated glucose uptake associated with impaired mobilization of glucose transporter 4 (GLUT4) to the plasma membrane. Such defect seemed to be caused by reduced phosphorylation of the protein kinase B substrate of 160 kDa (AS160). AS160 phosphorylation and GLUT4 translocation by AMP-activated protein kinase activation were abrogated as well. In addition, expression of the constitutively active mutant of HIF-1α (CA-HIF-1α) or upregulation of endogenous HIF-1α in C2C12cells shows AS160 phosphorylation comparable to the insulin-stimulated level even in the absence of insulin. Accordingly GLUT4 translocation was increased in the cells expressing CA-HIF1α. Taken together, HIF-1α is a determinant for GLUT4-mediated glucose uptake in the skeletal muscle cells thus as a possible target to alleviate impaired glucose metabolism in, e.g., type 2 diabetes.

Persistent high concentration of glucose causes cellular stress and damage in diabetes via derangement of gene expressions. We previously reported high glucose activates hypoxia‐inducible factor‐1α and downstream gene expression in mesangial cells, leading to an extracellular matrix expansion in the glomeruli. A glucose‐responsive transcription factor carbohydrate response element‐binding protein (ChREBP) is a key mediator for such perturbation of gene regulation. To provide insight into glucose‐mediated gene regulation in mesangial cells, we performed chromatin immunoprecipitation followed by DNA microarray analysis and identified platelet‐derived growth factor‐C (PDGF‐C) as a novel target gene of ChREBP. In streptozotocin‐induced diabetic mice, glomerular cells showed a significant increase in PDGF‐C expression; the ratio of PDGF‐C‐positive cells to the total number glomerular cells demonstrated more than threefold increase when compared with control animals. In cultured human mesangial cells, high glucose enhanced expression of PDGF‐C protein by 1.9‐fold. Knock‐down of ChREBP abrogated this induction response. Upregulated PDGF‐C contributed to the production of type IV and type VI collagen, possibly via an autocrine mechanism. Interestingly, urinary PDGF‐C levels in diabetic model mice were significantly elevated in a fashion similar to urinary albumin. Taken together, we hypothesize that a high glucose‐mediated induction of PDGF‐C via ChREBP in mesangial cells contributes to the development of glomerular mesangial expansion in diabetes, which may provide a platform for novel predictive and therapeutic strategies for diabetic nephropathy.

High glucose evokes a variety of signals in mesangial cells that alter cellular functions responsible for the development of diabetic glomerulopathy. The hypoxia-inducible factor-1alpha (HIF-1alpha) regulates cellular homeostasis under hypoxic conditions, but it also has pleiotropic effects in response to cellular stresses at normoxia. Here we determined whether HIF-1alpha has a role in the regulation of mesangial cells in hyperglycemia. In the streptozotocin-induced diabetic mouse model, glomerular mesangial cells had a significant increase in HIF-1alpha expression in the nucleus. In cultured mesangial cells, high glucose enhanced the expression of HIF-1alpha and its target genes known to be involved in the development of diabetic glomerulopathy. A glucose-responsive carbohydrate response element binding protein (ChREBP) was found to have a critical role in the transcriptional upregulation of HIF-1alpha and downstream gene expression in mesangial cells exposed to high glucose. Knockdown of HIF-1alpha or ChREBP in mesangial cells abrogated the high glucose-mediated perturbation of gene expression. Our results show that ChREBP and HIF-1alpha mediate gene regulation in mesangial cells. Further studies will be needed to find out whether these findings are relevant to the development of the diabetic nephropathy.

Incretins stimulate insulin secretion in a glucose-dependent manner but also promote pancreatic beta cell protection. Dipeptidyl peptidase-4 (DPP-4) inhibitors are a new glucose-lowering treatment that blocks incretin degradation by DPP-4. We assessed whether DPP-4 inhibition suppresses the progression to hyperglycaemia in a low-dose streptozotocin (STZ)-induced diabetic mouse model, and then investigated how DPP-4 inhibition affects islet function and morphology.The DPP-4 inhibitor, des-fluoro-sitagliptin (SITA), was administered to mice during and after STZ injections, and in some mice also before STZ.In control mice, STZ resulted in hyperglycaemia associated with impaired insulin secretion and excess glucagon secretion. In SITA-treated STZ mice, these metabolic abnormalities were improved, particularly when SITA administration was initiated before STZ injections. We observed beta cell loss and dramatic alpha cell expansion associated with decreased insulin content and increased glucagon content after STZ administration. In SITA-treated mice, islet architecture and insulin content were preserved, and no significant increase in glucagon content was observed. After STZ exposure, beta cell apoptosis increased before hyperglycaemia, and SITA treatment reduced the number of apoptotic beta cells. Interestingly, alpha cell proliferation was observed in non-treated mice after STZ injection, but the proliferation was not observed in SITA-treated mice.Our results suggest that the ability of DPP-4 inhibition to suppress the progression to STZ-induced hyperglycaemia involves both alleviation of beta cell death and alpha cell proliferation.