Dipeptidyl peptidase-4 inhibitor and sodium-glucose cotransporter 2 inhibitor additively ameliorate hepatic steatosis through different mechanisms of action in high-fat diet-fed mice.

AIM: Dipeptidyl peptidase-4 (DPP-4) inhibitors suppress the inactivation of incretin hormones and lower blood glucose levels by inhibiting DPP-4 function. Sodium-glucose cotransporter 2 (SGLT2) inhibitors lower blood glucose levels in an insulin-independent manner by inhibiting renal reabsorption of glucose. DPP-4 and SGLT2 inhibitors each have the potential to improve hepatic steatosis; however, their combined effects remain unclear. In this study, we examined the effects of the combination of these drugs on hepatic steatosis using high-fat diet-fed mice. METHOD: C57BL/6J male mice were fed a 60% high-fat diet for 2 months to induce hepatic steatosis. Mice were divided into four groups (control; DPP-4 inhibitor anagliptin; SGLT2 inhibitor luseogliflozin; anagliptin and luseogliflozin combination), and the effects of each drug and their combination on hepatic steatosis after a 4-week intervention were evaluated. RESULTS: There were no differences in blood glucose levels among the four groups. Anagliptin suppresses inflammation- and chemokine-related gene expression. It also improved macrophage fractionation in the liver. Luseogliflozin reduced body weight, hepatic gluconeogenesis and blood glucose levels in the oral glucose tolerance test. The combination treatment improved hepatic steatosis without interfering with the effects of anagliptin and luseogliflozin, respectively, and fat content and inflammatory gene expression in the liver were significantly improved in the combination group compared with the other groups. CONCLUSION: The combination therapy with the DPP-4 inhibitor anagliptin and the SGLT2 inhibitor luseogliflozin inhibits fat deposition in the liver via anti-inflammatory effects during the early phase of diet-induced liver steatosis.

Protective effects of imeglimin on the development of atherosclerosis in ApoE KO mice treated with STZ.

BACKGROUND: Imeglimin is a new anti-diabetic drug which promotes insulin secretion from pancreatic ß-cells and reduces insulin resistance in insulin target tissues. However, there have been no reports examining the possible anti-atherosclerotic effects of imeglimin. In this study, we investigated the possible anti-atherosclerotic effects of imeglimin using atherosclerosis model ApoE KO mice treated with streptozotocin (STZ). METHODS: ApoE KO mice were divided into three groups: the first group was a normoglycemic group without injecting STZ (non-DM group, n = 10). In the second group, mice were injected with STZ and treated with 0.5% carboxymethyl cellulose (CMC) (control group, n = 12). In the third group, mice were injected with STZ and treated with imeglimin (200 mg/kg, twice daily oral gavage, n = 12). We observed the mice in the three groups from 10 to 18 weeks of age. Plaque formation in aortic arch and expression levels of various vascular factors in abdominal aorta were evaluated for each group. RESULTS: Imeglimin showed favorable effects on the development of plaque formation in the aortic arch in STZ-induced hyperglycemic ApoE KO mice which was independent of glycemic and lipid control. Migration and proliferation of vascular smooth muscle cells and infiltration of macrophage were observed in atherosclerotic lesions in STZ-induced hyperglycemic ApoE KO mice, however, which were markedly reduced by imeglimin treatment. In addition, imeglimin reduced oxidative stress, inflammation and inflammasome in hyperglycemic ApoE KO mice. Expression levels of macrophage makers were also significantly reduced by imeglimin treatment. CONCLUSIONS: Imeglimin exerts favorable effects on the development of plaque formation and progression of atherosclerosis.

Imeglimin exerts favorable effects on pancreatic ß-cells by improving morphology in mitochondria and increasing the number of insulin granules.

Imeglimin is a new anti-diabetic drug commercialized in Japan (Twymeeg®) and has been drawing much attention in diabetes research area as well as in clinical practice. In this study, we evaluated the effect of imeglimin on pancreatic ß-cells. First, single-dose administration of imeglimin enhanced insulin secretion from ß-cells and decreased blood glucose levels in type 2 diabetic db/db mice. In addition, single-dose administration of imeglimin significantly augmented insulin secretion in response to glucose from islets isolated from non-diabetic db/m mice. Second, during an oral glucose tolerance test 4-week chronic treatment with imeglimin enhanced insulin secretion and ameliorated glycemic control in diabetic db/db mice. Furthermore, the examination with electron microscope image showed that imeglimin exerted favorable effects on morphology in ß-cell mitochondria and substantially increased the number of insulin granules in type 2 diabetic db/db and KK-Ay mice. Finally, imeglimin reduced the percentage of apoptotic ß-cell death which was accompanied by reduced expression levels of various genes related to apoptosis and inflammation in ß-cells. Taken together, imeglimin directly enhances insulin secretion in response to glucose from ß-cells, increases the number of insulin granules, exerts favorable effects on morphology in ß-cell mitochondria, and reduces apoptotic ß-cell death in type 2 diabetic mice, which finally leads to amelioration of glycemic control.

Early combination therapy of empagliflozin and linagliptin exerts beneficial effects on pancreatic ß cells in diabetic db/db mice.

Effects of combination therapy of dipeptidyl peptidase-4 (DPP-4) inhibitor and sodium-glucose co-transporter 2 (SGLT2) inhibitor on ß-cells are still unclear, although combination agent of these two drugs has become common in clinical practice. Therefore, we aimed to elucidate the effects of DPP-4 inhibitor and/or SGLT2 inhibitor on ß-cell mass and function and compared their effects between in an early and advanced phase of diabetes. We used 7-week-old db/db mice as an early phase and 16-week-old mice as an advanced phase and treated them for 2 weeks with oral administration of linagliptin, empagliflozin, linagliptin + empagliflozin (L + E group), and 0.5% carboxymethylcellulose (Cont group). Blood glucose levels in Empa and L + E group were significantly lower than Cont group after treatment. In addition, ß-cell mass in L + E group was significantly larger than Cont group only in an early phase, accompanied by increased Ki67-positive ß-cell ratio. In isolated islets, mRNA expression levels of insulin and its transcription factors were all significantly higher only in L + E group in an early phase. Furthermore, mRNA expression levels related to ß-cell differentiation and proliferation were significantly increased only in L + E group in an early phase. In conclusion, combination of DPP-4 inhibitor and SGLT2 inhibitor exerts more beneficial effects on ß-cell mass and function, especially in an early phase of diabetes rather than an advanced phase.

Protective effects of the SGLT2 inhibitor luseogliflozin on pancreatic ß-cells in db/db mice: The earlier and longer, the better.

AIMS: We compared the protective effects of sodium glucose co-transporter (SGLT) 2 inhibitor luseogliflozin on pancreatic ß-cells between early and advanced stages of diabetes and between short- and long-term use. MATERIALS AND METHODS: Diabetic db/db mice were treated with luseogliflozin for 2 weeks in an early stage of diabetes (7-9 weeks of age) and an advanced stage of diabetes (16-18 weeks) for a longer period of time (7-18 weeks). We performed various morphological analyses of pancreatic islets and examined gene expression profiles in islets after such treatment. RESULTS: In diabetic db/db mice, insulin biosynthesis and secretion were markedly increased by luseogliflozin in an early stage of diabetes but not in an advanced stage. In addition, ß-cell mass was preserved by luseogliflozin only in an early stage. Furthermore, when db/db mice were treated with luseogliflozin for a longer period of time, starting from an early stage, ß-cell function and mass were markedly preserved even after a longer period of time compared to untreated db/db mice. CONCLUSION: Luseogliflozin exerts more protective effects in an early stage of diabetes compared to an advanced stage, and longer-term use of luseogliflozin exerts more beneficial effects on pancreatic ß-cells compared to short-term use.

Decreased glucagon-like peptide 1 receptor expression in endothelial and smooth muscle cells in diabetic db/db mice: TCF7L2 is a possible regulator of the vascular glucagon-like peptide 1 receptor.

AIMS: Incretin signalling is known to prevent the development of arteriosclerosis by relaxation response in endothelial cells via the glucagon-like peptide 1 receptor. It remains unclear, however, whether vascular glucagon-like peptide 1 receptor expression is altered under some conditions. The aim of this study is to examine whether vascular glucagon-like peptide 1 receptor expression is altered by diabetic state as reported in pancreatic ß-cells. METHODS: We used 18-week-old male diabetic db/db mice and control db/m mice. Excised thoracic artery was specifically collected, and vascular endothelial cells were cultured. We compared the glucagon-like peptide 1 receptor expression levels between the db/db and db/m mice. RESULTS: Metabolic parameters were significantly worse in db/db mice. The glucagon-like peptide 1 receptor and transcription factor 7-like 2 expression levels in endothelial and smooth muscle cells were significantly lower in db/db mice. Furthermore, siRNA to transcription factor 7-like 2 decreased the transcription factor 7-like 2 levels and such reduction of the transcription factor 7-like 2 resulted in the downregulation of the glucagon-like peptide 1 receptor expressions in cultured vascular endothelial cells. CONCLUSION: The glucagon-like peptide 1 receptor expression level was significantly lower under diabetic condition which was accompanied by the reduction of the transcription factor 7-like 2 expression level. Furthermore, the transcription factor 7-like 2 is a possible regulator of the glucagon-like peptide 1 receptor expression in artery as reported in ß-cells.