Chronic administration of DSP-7238, a novel, potent, specific and substrate-selective DPP IV inhibitor, improves glycaemic control and beta-cell damage in diabetic mice.

AIMS: The purpose of this study is to assess the in vitro enzyme inhibition profile of DSP-7238, a novel non-cyanopyrrolidine dipeptidyl peptidase (DPP) IV inhibitor and to evaluate the acute and chronic effects of this compound on glucose metabolism in two different mouse models of type 2 diabetes. METHODS: The in vitro enzyme inhibition profile of DSP-7238 was assessed using plasma and recombinant enzymes including DPP IV, DPP II, DPP8, DPP9 and fibroblast activation protein alpha (FAPalpha) with fluorogenic substrates. The inhibition type was evaluated based on the Lineweaver-Burk plot. Substrate selectivity of DSP-7238 and comparator DPP IV inhibitors (vildagliptin, sitagliptin, saxagliptin and linagliptin) was evaluated by mass spectrometry based on the changes in molecular weight of peptide substrates caused by release of N-terminal dipeptides. In the in vivo experiments, high-fat diet-induced obese (DIO) mice were subjected to oral glucose tolerance test (OGTT) following a single oral administration of DSP-7238. To assess the chronic effects of DSP-7238 on glycaemic control and pancreatic beta-cell damage, DSP-7238 was administered for 11 weeks to mice made diabetic by a combination of high-fat diet (HFD) and a low-dose of streptozotocin (STZ). After the dosing period, HbA1c was measured and pancreatic damage was evaluated by biological and histological analyses. RESULTS: DSP-7238 and sitagliptin both competitively inhibited recombinant human DPP IV (rhDPP IV) with K(i) values of 0.60 and 2.1 nM respectively. Neither vildagliptin nor saxagliptin exhibited competitive inhibition of rhDPP IV. DSP-7238 did not inhibit DPP IV-related enzymes including DPP8, DPP9, DPP II and FAPalpha, whereas vildagliptin and saxagliptin showed inhibition of DPP8 and DPP9. Inhibition of glucagon-like peptide-1 (GLP-1) degradation by DSP-7238 was apparently more potent than its inhibition of chemokine (C-X-C motif) ligand 10 (IP-10) or chemokine (C-X-C motif) ligand 12 (SDF-1alpha) degradation. In contrast, vildagliptin and saxagliptin showed similar degree of inhibition of degradation for all the substrates tested. Compared to treatment with the vehicle, single oral administration of DSP-7238 dose-dependently decreased plasma DPP IV activity and improved glucose tolerance in DIO mice. In addition, DSP-7238 significantly decreased HbA1c and ameliorated pancreatic damage following 11 weeks of chronic treatment in HFD/STZ mice. CONCLUSIONS: We have shown in this study that DSP-7238 is a potent DPP IV inhibitor that has high specificity for DPP IV and substrate selectivity against GLP-1. We have also found that chronic treatment with DSP-7238 improves glycaemic control and ameliorates beta-cell damage in a mouse model with impaired insulin sensitivity and secretion. These findings indicate that DSP-7238 may be a new therapeutic agent for the treatment of type 2 diabetes.

Brain-derived neurotrophic factor enhances glucose utilization in peripheral tissues of diabetic mice.

AIMS: Repetitive subcutaneous or intracerebroventricular administration of brain-derived neurotrophic factor (BDNF) ameliorates glucose metabolism and enhances energy expenditure in obese diabetic C57BL/KsJ-db/db mice. To explore the mechanism of action through which BDNF regulates glucose metabolism, we examined the effects of BDNF on glucose utilization and norepinephrine (NE) content in peripheral tissues of diabetic mice. METHODS: [(14)C]2-deoxyglucose ([(14)C]2-DG) uptake into peripheral tissues was analysed after intravenous injection of [(14)C]2-DG in db/db and normal C57BL/6 mice, and [(14)C]2-DG uptake and NE content in peripheral tissues were analysed after subcutaneous administration of BDNF (20 mg/kg) to male db/db and normal mice for 8 days. RESULTS: [(14)C]2-DG uptake in the diaphragm, heart, gastrocnemius, soleus and interscapular brown adipose tissue (BAT) of db/db mice was significantly lower than in normal mice. Repetitive administration of BDNF to db/db mice for 8 days enhanced [(14)C]2-DG uptake in the diaphragm, heart, soleus, BAT and liver. The NE content in heart, skeletal muscle, interscapular BAT and liver of db/db mice given BDNF was high compared with db/db mice given vehicle, whereas no significant change in NE content in peripheral tissues was observed in normal mice given BDNF and those given vehicle. BDNF did not affect [(14)C]2-DG uptake or NE content in the white adipose tissue of db/db mice. CONCLUSIONS: These data indicate that BDNF ameliorates glucose metabolism by enhancement of glucose utilization in muscle and BAT, with this effect caused by modulation of the central and peripheral nervous systems.

Brain-derived neurotrophic factor regulates energy expenditure through the central nervous system in obese diabetic mice.

It has been previously demonstrated that brain-derived neurotrophic factor (BDNF) regulates glucose metabolism and energy expenditure in rodent diabetic models such as C57BL/KsJ-lepr(db)/lepr(db) (db/db) mice. Central administration of BDNF has been found to reduce blood glucose in db/db mice, suggesting that BDNF acts through the central nervous system. In the present study we have expanded these investigations to explore the effect of central administration of BDNF on energy metabolism. Intracerebroventricular administration of BDNF lowered blood glucose and increased pancreatic insulin content of db/db mice compared with vehicle-treated pellet pair-fed db/db mice. While body temperatures of the pellet pair-fed db/db mice given vehicle were reduced because of restricted food supply in this pair-feeding condition, BDNF treatment remarkably alleviated the reduction of body temperature suggesting the enhancement of thermogenesis. BDNF enhanced norepinephrine turnover and increased uncoupling protein-1 mRNA expression in the interscapular brown adipose tissue. Our evidence indicates that BDNF activates the sympathetic nervous system via the central nervous system and regulates energy expenditure in obese diabetic animals.

Acute effects of brain-derived neurotrophic factor on energy expenditure in obese diabetic mice.

OBJECTIVE: We recently demonstrated that chronic treatment with brain-derived neurotrophic factor (BDNF) regulates energy expenditure in obese diabetic C57BL/KsJ-db/db mice. In this study, we investigated the acute effects of BDNF on energy expenditure. DESIGN: After BDNF was singly administered to male db/db mice (aged 10-12 weeks), their body temperature and whole body glucose oxidation were measured. Their norepinephrine (NE) turnover and uncoupling protein (UCP) 1 expression in interscapular brown adipose tissue (BAT) were also analyzed. RESULTS: Even though the body temperatures of hyperphagic db/db mice dropped remarkably in a 24 h period after food deprivation, only a single subcutaneous administration of BDNF significantly prevented the reduction of body temperature. BDNF was also observed to have similar efficacy in cold exposure experiments at 15 degrees C. Respiratory excretion of (14)CO(2) after intravenous injection of D-[(14)C(U)]-glucose was significantly increased by BDNF administration, indicating that BDNF increases whole-body glucose oxidation. BDNF administered intracerebroventricularly was also able to prevent the reduction of body temperature of db/db mice. To clarify the BDNF action mechanism we examined NE turnover in BAT. Four hours after a single administration, BDNF reduced NE content in the presence of the tyrosine hydroxylase inhibitor, alpha-methyl-P-tyrosine methyl ester, indicating enhanced NE turnover in BAT. BDNF also increased the expression of the UCP1 mRNA and protein in BAT. CONCLUSION: These data indicate that BDNF rapidly regulates energy metabolism in obese diabetic animals, partly through activating the sympathetic nervous system and inducing UCP1 gene expression in BAT.

Brain-derived neurotrophic factor ameliorates lipid metabolism in diabetic mice.

AIM: It has been reported previously that brain-derived neurotrophic factor (BDNF) regulates blood glucose metabolism in rodent obese diabetic models such as C57BL/KsJ-leprdb/leprdb (db/db) mice. BDNF further regulates energy expenditure, possibly through the central and autonomous nervous systems. In this study, we evaluated the effect of BDNF on both lipid and glucose metabolisms to clarify its action mechanism. METHODS: To control the energy intake, we used a pellet pair-feeding apparatus to synchronize food intake precisely between BDNF-treated and vehicle-treated db/db mice. BDNF (50 mg/kg/week) was subcutaneously injected to male db/db mice twice weekly for 3 weeks, and blood glucose, serum biochemical lipid parameters and tissue weights were measured. Liver triglyceride contents were measured and liver sections were histologically analysed. RESULTS: Twice weekly BDNF treatment for 3 weeks significantly lowered blood glucose compared with pellet pair-fed, vehicle-treated db/db mice (294 +/- 109 vs. 529 +/- 91 mg/dL). Serum non-esterified free fatty acid (726 +/- 72 vs. 999 +/- 220 microEq/l), total cholesterol (125 +/- 8 vs. 151 +/- 23 mg/dL) and phospholipid levels (215 +/- 13 vs. 257 +/- 36 mg/dL) of the BDNF-treated db/db mice decreased significantly. Liver weights (1.51 +/- 0.11 vs. 2.05 +/- 0.11 g), liver triglyceride contents (17.5 +/- 1.4 vs. 26.1 +/- 2.1 mg/g) and fatty liver in histological appearance were reduced with BDNF treatment. There were no significant differences in body weights and white adipose tissue weights between the two groups. CONCLUSIONS: Taken together with the accelerating effect of BDNF on energy metabolism, these findings indicate that BDNF improves glucose and lipid metabolism in obese diabetic animals without enlarging liver or adipose tissues.