Sequence of fat partitioning and its relationship with whole body insulin resistance / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Currently it is unclear whether lipid accumulation occurs in a particular sequence and its relationship with whole body insulin resistance (IR). This study aimed to answer this question.</p><p><b>METHODS</b>Male Sprague-Dawley (SD) rats were fed on a normal or a high-fat diet for 20 weeks. Serum triglycerides (TG), serum free fatty acids (FFA), fasting plasma glucose (FPG), and liver and skeletal muscle TG were measured. The glucose infusion rate (GIR) and mRNA levels of acetyl-CoA carboxylase (ACC) and carnitine palmitoyltransferase-1 (CPT-1) in the liver and skeletal muscle were determined at different stages.</p><p><b>RESULTS</b>Compared with rats fed on the normal diet, serum FFA was not significantly increased in rats fed on the high-fat diet until 20 weeks. In contrast, liver TG was significantly increased by the high-fat diet by four weeks (20-fold; P < 0.01), and remained elevated until the end of the study. However, skeletal muscle TG was not significantly increased by the high-fat diet until 20 weeks (10.6-fold; P < 0.01), and neither was the FPG. The GIR was significantly reduced (1.6-fold; P < 0.01) by the high-fat diet after 8 weeks. The mRNA levels of ACC gradually increased over time and CPT-1 decreased over time, in both the liver and skeletal muscle in rats fed the high-fat diet.</p><p><b>CONCLUSIONS</b>Lipid accumulation in the liver occurs earlier than lipid accumulation in the skeletal muscle. Fatty liver may be one of the early markers of whole body IR. Changes in the gene expression levels of ACC and CPT-1 may have important roles in the process of IR development.</p>

Role and mechanism of uncoupling protein 2 on the fatty acid-induced dysfunction of pancreatic alpha cells in vitro / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Uncoupling protein (UCP) 2 is related to the dysfunction of beta cells induced by fatty acids. However, whether UCP2 has similar effects on alpha cell is still not clear. This study aimed to investigate the effects of UCP2 and its possible mechanisms in lipotoxicity-induced dysfunction of pancreatic alpha cells.</p><p><b>METHODS</b>The alpha TC1-6 cells were used in this study to evaluate the effects of palmitate and/or UCP2 inhibit factors on the glucagon secretory function, glucagon content, the glucagon mRNA level and the nitrotyrosine level in the supernatant. Meantime, the expression levels of UCP2 and peroxisome proliferator-activated receptor-γ coactivator-1 alpha (PGC-1 alpha) were measured by real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blotting. Furthermore, the possible relationship between UCP2 and insulin signal transduction pathway was analyzed.</p><p><b>RESULTS</b>Palmitate stimulated alpha cell glucagon secretion and the expression of UCP2 and PGC-1 alpha, which could be partially decreased by the inhibition of UCP2. Palmitate increased nitrotyrosine level and suppressed insulin signal transduction pathway in alpha cells. Inhibition of UCP2 influenced the effects of free fatty acid on alpha cells and may relate to glucagon secretion.</p><p><b>CONCLUSION</b>UCP2 played an important role on alpha cell dysfunction induced by free fatty acid in vitro, which may be related to its effects on oxidative stress and insulin signal transduction pathway.</p>

Relationship between oxidative stress and beta cell lipoapoptosis in rats / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the effect of beta cell lipoapoptosis after long term high-fat feeding in rats, and to investigate the relationship between oxidative stress, gene expression and beta cell lipoapoptosis.</p><p><b>METHODS</b>Forty-one SD male rats were randomly divided into 2 groups: high-fat diet group (HF group) and control group (NC group). At the end of 28 weeks, the levels of malondialdehyde (MDA) and glutamylcysteinylglycine (GSH) in plasma and pancreatic tissue,the early-phase insulin secretion in beta cells, the beta cell apoptosis (TUNEL technology) and the uncoupling protein 2 (UCP2) gene expression in islets were measured.</p><p><b>RESULT</b>The concentrations of MDA both in plasma and pancreatic tissue were higher in HF group than those in NC group.In contrast, The contents of GSH both in plasma and pancreatic tissue were lower in HF group. Insulin secretion response to glucose load was significantly decreased in HF group (3.0 fold Compared with 5.7 fold, P<0.01). Blood glucose levels at 3 min, 5 min and 10 min during IVGTT were significantly higher in HF group than those in NC group (P<0.05). The frequency of beta cell apoptosis was increased by 40.0% in HF group (P<0.01). The gene expression of UCP2 in islets was increased by 22.4% in HF group (P<0.01).</p><p><b>CONCLUSION</b>The frequency of beta cell apoptosis in high-fat feeding rats is affected by oxidative stress, which results in increasing UCP2 gene expression.</p>

The sequence of fat deposit and its relationship with insulin resistance / 中华内分泌代谢杂志

Objective To observe the sequence of fat deposit and its relationship with insulin resistance in SD rats fed by high fat diet.Methods Normal 8-week-old male SD rats were randomly divided into normal chow (NC,n=40)and high fat diet(HF,n=40)groups.Triglyceride(TG)in serum,liver and muscle were measured;glucose infusion rate(GIR)and the mRNA level of genes related to lipid metabolism in liver and muscle were determined in different stages.GIR was detected by eugiyeemic-hyperinsulinemic clamp for evaluating the insulin sensitivity.Gene expression was determined by real-time PCR.Results(1)As compared with NC group,serum TG was not increased after high fat feeding for4 and 8 weeks,it began to increase after 12 weeks [0.52(0.15-1.00) mmol/L vs O.31(0.09-0.53)retool/L, P0.05)in skeletal muscle.After 8 weeks,the expression of ACC1 in liver in HF group was increased by 20.6%,CPT-1 was decreased by 27.1%(P