中度限食对肥胖小鼠胰岛β细胞分泌功能的影响

Effects of moderate calorie restriction on islet β-cell secretory dysfunction in obese mice

目的明确中度限食干预能否从形态和功能上逆转肥胖对胰岛β细胞的损伤。方法 4周龄雄性C57BL/6小鼠喂以高脂饮食8周,建立饮食诱导的肥胖模型,随后进行3周的高脂转普食(HF→NC组)或在此基础上40%限食干预(HF→NCCR组),同时设高脂对照组(H FAL组)和普食对照组(NC AL组),每组20只。实验终点取胰腺组织行胰岛素免疫组化染色,定量β细胞面积,并行腹腔葡萄糖耐量试验及胰岛素耐量试验,评估早时相和第二时相胰岛素分泌及胰岛素敏感性。同时,分离小鼠胰岛,行静态葡萄糖刺激的胰岛素分泌实验及胞浆胰岛素含量测定。结果实验终点HFAL组表现为显著肥胖、β细胞面积增加、糖耐量受损、早时相胰岛素分泌趋向降低及胰岛素抵抗,同时离体胰岛实验显示胞浆胰岛素含量增加,但胰岛素分泌缺陷:基础胰岛素分泌升高了30.6%,而16.7mmol/L高糖刺激下的胰岛素分泌降低了52.1%。HF→NC组小鼠的糖耐量恢复正常,体质量有所降低但未正常,早时相胰岛素分泌及离体胰岛高糖刺激的胰岛素分泌较HFAL组并无改善。经过3周的限食干预,HF→NCCR组体质量、β细胞面积、糖耐量、早时相胰岛素分泌、胰岛素敏感性及离体胰岛基础和高糖刺激下的胰岛素分泌均恢复正常。结论中度(40%)限食干预至体质量正常,可逆转饮食诱导肥胖小鼠的胰岛β细胞分泌功能紊乱,重建葡萄糖稳态。

Objective To investigate whether modest calorie restriction (CR) could reverse islet β-cell morphology and function disorder induced by obesity. Methods Male C57BL/6 mice were fed high fat diet (HF) for 8 weeks to create an diet-induced obese (DIO) model. Then they were divided into four groups: NC AL (normal chow, ad libitum), HF AL, HF→ NC (HF switching to NC) and HF→NC CR (40% CR). There were 20 mice in each group. These treatments continued for 3 weeks. At the end of the experiment, pancreas tissues were removed for insulin immunohistochemistry staining, to quantify β-cell area. Meanwhile, introperitoneal glucose tolerance test and insulin tolerance test were performed to evaluate early-phase insulin secretion, second-phase insulin secretion and insulin sensitivity. In addition, islets were isolated, the static glucose-stimulated insulin secretion and insulin content were measured in isolated islets. Results At the end of the experiment, HF AL mice showed significant obesity, increased β- cell area, impaired glucose intolerance, decreased tendency in early-phase insulin secretion and insulin resistance. At the same time, theinvitroisolated islet experiment displayed the increased insulin content and defective insulin secretion. The basal insulin secretion increased by 30.6%, while insulin secretion decreased by 52.1% under the condition of 16.7 mmol/L glucose stimulation. In the HF→NC group, after 3 weeks of intervention, the glucose tolerance returned to normal, body weights decreased. The early phase insulin secretion and insulin secretion stimulated by the high glucose in isolated islets of mice were not improved in HF NC group compared with those in HF AL group. After 3 weeks of dietary restriction intervention, body weights, beta cell area, glucose tolerance, early phase insulin secretion, insulin sensitivity, the basal insulin secretion and high glucose-stimulated insulin secretioninvitroreturned to normal in HF→NC CR group. Conclusion The moderate (40%) calorie restriction to normal body weight can reverse the defective insulin secretion and normalize glucose tolerance in DIO mice.