Chen Lulu

Regulation of insulin secretion and expression of SUR1 gene by chronic exposure to free fatty acids in rat pancreatic β cells

SummaryTo study the effects of free fatty acids on insulin secretion and expression of SUR1 gene in rat pancreatic B cellsin vitro, and to explore the molecular mechanisms in lipotoxicity inducing insulin secretion dysfunction, pancreatic islet cells were isolated and digested from male SD rats. Purified islets were incubated with either 0.25 mmol/L palmitate or 0.125 mmol/L oleate for 48 hin vitro. Then islets were stimulated with either 5.6 mmol/L or 16.7 mmol/L glucose for 1 h. Insulin release was measured by using radioimmunoassay, and the expression of SUR1 gene mRNA was quantified by reserve transcription-polymerase chain reaction (RT-PCR). The islets exposed to both palmitate and oleate for 48 h showed an increased basal and a decreased glucose-indused insulin release as compared with control islets. Palmitate increased basal insulin secretion by 110 % (P<0.01), decreased glucose stimulated insulin secretion by 43% (P<0.01); while oleate increased basal insulin secretion by 80% (P<0.01) and decreased glucose stimulated insulin secretion by 32% (P<0.05). RT-PCR showed that oleate significantly suppressed SUR1 gene expression by 64% (P<0.01) as compared with the control group, while palmitate group manifested a light decrease of 15% (P>0.05) of SUR1 gene expression. Our results suggested that chronic exposure to free fatty acids of pancreatic β cells inhibited glucose stimulated insulin secretion. Regulation of SUR1 gene expression may be involved in such effects, which may also be one of the molecular mechanisms in lipotoxocity inducing β cells secretion dysfunction.

Efficacy and safety of risedronate sodium in treatment of postmenopausal osteoporosis

SummaryTo evaluate the efficacy and safety of risedronate sodium in treatment of postmenopausal osteoporosis, one-year randomized, double blind clinical trial was performed among 54 women with postmenopausal osteoporosis. The changes were compared in bone mineral density (BMD), bone metabolism markers and adverse events after 12 months oral administration of risedronate sodium. BMD was measured by dual energy X-ray absorptionmetry (DEXA) and bone turnover marker was detected. The results showed that there was a significant increase in BMD of the lumbar spine (3.29%±1.18%, 4.51%±1.64% respectively) after 6 and 12 months in the risedronate treatment group versus placebo control group (−0.62%±0.24%, 0.48%±0.18% respectively). Bone turnover was decreased to a stable nadir over 6 and 12 months for resorption markers [N-telopeptide (NTx),P<0.05] and over 12 months for formation marker (ALP,P<0.05; BGP,P<0.05). The safety profile of risedronate sodium was similar to that of placebo. There were no trends toward increased frequency of any adverse experience except for gastrointestinal symptoms (7.1%), rash (7.1%) and hematuria (3.6%), which were usually mild, transient, and resolved with continued treatment. It was concluded that risedronate was an efficacious and safe drug in treatment of postmenopausal osteoporosis.

Effects of insulin treatment on intracellular lipid metabolism in liver of diabetic rats.

SummaryThe effects and the mechanism of insulin treatment on intracellular lipid metabolism in liver of diabetic rats were evaluated. Type 2 diabetic rats were induced by injecting the streptozotocin (25 mg/kg) and fat rich food. According to the results of oral glucose tolerance test (OGTT) and glucose-induced insulin secretion test (IRT), the rats were divided into two groups; untreated group (UT) and insulin-treated group (IT). Normal rats (NC) served as controls. The treatment with either Humulin N (4–6 U/kg every day), or saline lasted for 4 weeks. Body weight, OGTT, IRT, blood lipids, intracellular lipids in liver, hepatic fatty acid oxidation and the activity of fatty acid synthase (FAS) were detected. The change of liver histology was observed. The insulin sensitivity index (ISI) was applied to assess the status of insulin resistance. The results showed that as compared with NC group, the plasma and hepatic intracellular Triglyceride (TG), total cholesterol (TC) and free fatty acids (FFAs) were increased significantly in UT group (P<0.05), and lipid droplets could be seen dispersedly in the liver specimens, the hepatic fatty acid oxidation was increased markedly (P<0.05), while the fatty acid synthase activity decreased (P<0.05). Insulin treatment resulted in a further accumulation of lipids in liver by 55.7%, 19.87% and 22.2% increase in TG, TC, FFAs respectively. The size of hepatocytes was enlarged and the cells were filled with fat drops. Plasma lipids showed little decrease and still significantly higher than those in NC group after the insulin treatment. Meanwhile, insulin treatment was companied by 20% decrease in the rate of fatty acid oxidation and 31% increase in hepatic FAS activity compared to UT group. It was concluded that treatment with insulin on type 2 diabetic rat increases hepatic intracellular lipid accumulation by inhibiting hepatic fatty acid oxidation and activating FAS.