Replication of association study between type 2 diabetes mellitus and IGF2BP2 in Han Chinese population.

BACKGROUND: The association between IGF2BP2 and type 2 diabetes mellitus (T2DM) has been repeatedly confirmed among different ethnic populations. However, in several genome-wide association studies (GWAS) from the Chinese Han population, the gene IGF2BP2 has not been replicated. The results of relevant studies for the association between IGF2BP2 and T2DM showed controversy in Chinese Han population. It is necessary to systematically evaluate the contribution of common variants in IGF2BP2 to T2DM in Chinese Han population. METHODS: Two single-nucleotide polymorphisms (SNPs, rs4402960 and rs1470579) in IGF2BP2 were genotyped in Chinese Han population (3807 controls/4531 T2DM cases) by Illumina GoldenGate Indexing assay. The association between SNPs and T2DM was evaluated by multiple Logistic Regression analysis. A meta-analysis was used to estimate the effects of IGF2BP2 in 20854 Chinese Han individuals. RESULTS: rs1470579 and rs4402960 were confirmed to have strong association with T2DM in the Chinese Han population (rs1470579 P = 1.80×10(-7), OR (95% CI) = 1.22 (1.14-1.32), rs4402960 P = 7.46×10(-9), OR (95% CI) = 1.26 (1.17-1.37), respectively). Moreover, 11 studies for rs4402960 were included in the meta-analysis and 7 studies for rs1470579. The meta-analysis also showed the association between T2DM and IGF2BP2 (rs1470579 OR of 1.15 (95% CI = 1.10-1.19), P < 0.0001 under an additive model and rs4402960 OR of 1.14 (95% CI = 1.10-1.18), P < 0.0001 under an additive model). CONCLUSION: IGF2BP2 was strongly associated with the risk of T2DM in Chinese Han population.

[Analysis of medication with hypertension by different glucose tolerance status].

OBJECTIVE: To analyze the combination of hypertension and the use of antihypertensive drugs by different glucose tolerance status. METHODS: Matched case-control design was used to sample the subjects from the population for the prevalence of diabetes mellitus and metabolism syndrome from 2007 to 2008. There were 3 groups including normal glucose tolerance (NGT, n = 2124), impaired glucose regulation (IGR, n = 2162) and diabetes (DM, n = 2470). The matched factors were location, age and gender. All subjects were interviewed to describe the hypertension and antihypertensive drugs of these conditions. RESULTS: After adjusting for age, gender and location, the combination of hypertension in IGR and DM groups was higher than NGT (28.3%, 40.2% and 19.9%) and OR was 1.29 (1.08 - 1.53) and 1.99 (1.67 - 2.37) respectively. The percent of treatment, prescription compliance and the surveillance of hypertension in total subjects were 48.6%, 79.3% and 62.5%. And no difference was observed among 3 groups. The proportion of calcium channel blocker of DM groups was higher than NGT group. The uses of angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II receptor blocker (ARB) showed no difference among 3 groups. CONCLUSIONS: The combination of hypertension is higher in IGR and DM groups than that in NGT group. And the treatment rate of hypertension remains low. ACEI and ARB are under-utilized in IGR and DM groups.

[Ageing related changes of insulin secretion and insulin sensitivity among normal glucose tolerance individuals in China].

OBJECTIVE: To explore the aging-related changes of insulin secretion and insulin sensitivity among normal glucose tolerance (NGT) individuals in China. METHODS: A total of 34 293 individuals were recruited. All of them were described as NGT by 75 g oral glucose tolerance test (75 g OGTT) according to the diagnostic criterion of WHO, 1999. HOMA-ß, ΔI(30)/ΔG(30), InsAuc30/GluAuc30, InsAuc120/GluAuc120 were calculated to estimate insulin secretion; HOMA-IR and Matsuda index measured to estimate insulin sensitivity; Disposition index: DI(30) and DI(120) were used to estimate ß-cell function. RESULTS: HOMA-ß, ΔI(30)/ΔG(30), InsAuc30/GluAuc30 and InsAuc120/GluAuc120 were all lower in the elder group then the younger group (P trend < 0.05). The mean HOMA-ß dropped from 192 ± 16 (20 - 29 years) to 115 ± 7 (70 or elder) among men and from 162 ± 8 (20 - 29 years) to 120 ± 12 (70 or elder) among women. The mean ΔI(30)/ΔG(30) dropped from 20.0 ± 2.0 (20 - 29 years) to 8.6 ± 0.6 (70 or elder) among men and from 22.4 ± 1.6 (20 - 29 years) to 12.5 ± 1.7 (70 or elder) among women. The above index were negatively correlated with age in univariate linear regression (P < 0.05), the results among men and overall still existed after adjusted for BMI and waist circumference in multivariate linear regression, while the relation between HOMA-ß and age disappeared among women. Matsuda Index was positively correlated with age (ß = 0.02, P = 0.001) and HOMA-IR were negatively correlated with age (ß = -0.01, P = 0.001) among men even after adjusted for BMI and waist circumference and the above correlation between Matsuda Index/HOMA-IR and ageing was not significant until adjusted for BMI and waist circumference in multivariate linear regression. Among women HOMA-IR (ß = -0.01, P = 0.000), Matsuda index (ß = 0.03, P = 0.000). DI(30) and DI(120) were negatively correlated with age in both univariate and multivariate linear regression. CONCLUSIONS: The basal, postchallenge insulin secretion and postchallenge islet compensatory function decreases with ageing, while insulin sensitivity does not deteriorate with ageing and its related change of body composition and weight gain.

[The protection of islet ß-cells in db/db mice by combination pioglitazone and glucagon like peptide-1 treatment].

OBJECTIVES: To evaluate the effect of combination of liraglutide, a glucagon-like peptide-1 analogue and pioglitazone, an insulin sensitizer, on diabetic db/db mice. METHODS: Thirty-five 8-week old male db/db mice were divided into control group (n = 8), pioglitazone group (n = 9), liraglutide group (n = 9) and combined therapeutic group (n = 9), which was given normal saline 0.1 ml, 2/d, pioglitazone 24 mg×kg(-1)×d(-1) (feed contained 0.02% pioglitazone) + normal saline 0.1 ml, 2/d, liraglutide 300 mg/kg, 2/d, and pioglitazone 20 mg×kg(-1)×d(-1) (feed contained 0.02% pioglitazone) + liraglutide 300 mg/kg, 2/d, respectively. Liraglutide were given at 8:00 and 16:00 via subcutaneous injection after having been diluted with sterilized normal saline. Effect on glucose, lipid metabolism and islet ß-cell preservation were assessed after 4 weeks. Oneway ANOVA was adopted for statistical analysis. RESULTS: Combination therapy displayed promising anti-hyperglycemic [glycosylated hemoglobin A1c: (4.5 ± 0.6)% vs. (7.3 ± 0.4)%, P < 0.001]. Glucose tolerance were improved assessed by area under curve (AUC) of glucose by intraperitoneal glucose tolerance test (IPGTT) [(1814 ± 91) mmol×min×L(-1) vs. (4042 ± 183) mmol×min×L(-1), P < 0.001]; insulin release response to glucose were also preserved as AUC of insulin by IPGTT was higher [(1639 ± 372) µg×min×L(-1) vs.(834 ± 201) µg×min×L(-1)]. Combination therapy also reduced circulated free fatty acids and TG [(202.0 ± 20.4) µmol/L vs. (272.5 ± 21.7) µmol/L, (0.81 ± 0.28) mmol/L vs. (1.35 ± 0.21) mmol/L], and increased plasma adiponectin [(16.7 ± 2.0) mg/L vs. (10.2 ± 1.8) mg/L]. All P value < 0.05. Islet immunohistochemistry showed that combination therapy significantly increased insulin positive area were [(59.5 ± 1.5)% vs. (22.4 ± 1.5)%] and ratio of Brdu positive ß-cells was three folds than vehicle-treated mice [(2.4 ± 0.5)% vs. (0.8 ± 0.3)%], both greater than each single treatment. Combined therapy significantly improved islet ß cell/α cell distribution, which led to islet recovery. CONCLUSIONS: Combined therapy improves glucose and lipid metabolism, preserves islet ß-cell function and stimulates ß-cell proliferation, greater than either liraglutide or pioglitazone treatment alone.

[Effects of fenofibrate on the expression of peroxisome proliferator-activated-gamma coactivator-1α in skeletal muscle of rats infused with intralipid].

OBJECTIVE: To observe the effects of fenofibrate on the expression of peroxisome proliferator-activated (PPAR)-gamma coactivator-1α (PGC-1α) in skeletal muscle of rats with insulin resistance (IR) induced by elevated plasma free fatty acid (FFA) levels. METHODS: Male Sprague-Dawley (SD) rats were randomly divided into three groups: control group (Con, infused with saline), lipid infusion group (FFA) and fenofibrate treatment plus lipid infusion group (F-FFA). Plasma glucose, insulin and FFA were measured. Glucose infusion rate (GIR) was used to evaluate the insulin sensitivity by euglycemic-hyperinsulinemic clamp. The gene expression of PGC-1α in skeletal muscle was determined by real-time polymerase chain reaction (PCR). RESULTS: Compared with the control group, the levels of plasma FFA and insulin were elevated significantly in rats infused with lipid, but they decreased significantly in rats pretreated with fenofibrate then infused with lipid [FFA, Con: 0.46 (0.08 - 0.72) mmol/L, FFA: 1.45(0.87-1.70) mmol/L, F-FFA: 0.54 (0.06 - 0.84) mmol/L, all P < 0.01; Insulin, Con: (6.56 ± 0.78) µIU/ml, FFA: (10.54 ± 0.86) µIU/ml, F-FFA: (6.69 ± 0.84) µIU/ml, all P < 0.01]. In addition, the plasma glucose levels did not change markedly after lipid infusion; GIR was significantly reduced by 55.6% in lipid infusion group, but fenofibrate-pretreatment increased glucose infusion rate (GIR) [Con: (25.13 ± 2.10) mg×kg(-1)×min(-1), FFA: (10.16 ± 0.75) mg×kg(-1)×min(-1), F-FFA: (21.72 ± 2.89) mg×kg(-1)×min(-1), all P < 0.01]; the mRNA expression of PGC-1α decreased by about 71% in lipid infusion group but fenofibrate increased the gene expression by about 150% as compared with FFA group (all P < 0.01). CONCLUSION: The elevation of plasma FFA levels may induce IR, and it also decreases the mRNA expression of PGC-1α in skeletal muscle. And fenofibrate pretreatment reverses these changes.

Role and mechanism of uncoupling protein 2 on the fatty acid-induced dysfunction of pancreatic alpha cells in vitro.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Sequence of fat partitioning and its relationship with whole body insulin resistance.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

[Relationship between oxidative stress and beta cell lipoapoptosis in rats].

OBJECTIVE: 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. METHODS: 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. RESULT: 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). CONCLUSION: The frequency of beta cell apoptosis in high-fat feeding rats is affected by oxidative stress, which results in increasing UCP2 gene expression.

[Relationship between islet beta cell dysfunction and gene expression of uncoupling protein-2 and possible mechanism thereof].

OBJECTIVE: To study the effects of high fat diet on the functions of islet beta cells and the role of uncoupling protein-2 (UCP2) therein and possible mechanism. METHODS: Forty SD rats were randomly divided into two equal groups: high-fat-(HF) diet group, fed with HF diet for 20 weeks, and normal diet control (NC) group, fed with normal diet. At the end of the twentieth week blood samples were collected from the heart to determine the serum fasting blood glucose (FBG) and fasting insulin (FINS), and plasma nitrotyrosine, malondialdehyde (MDA), and glutamylcysteinylglycine (GSH), indicators of oxidative stress. Glucose infusion rate (GIR) was measured using euglycemic hyperinsulinemic clamp test to evaluate the peripheral insulin resistance. Pancreatic islets were isolated and collected. Islet perfusion was conducted to evaluate the insulin secretion in the islet beta cells. Real-time PCR was used to detect the expression of insulin receptor substrate-1 (IRS-1), IRS-2, and uncoupling protein 2 (UCP2) genes in the islet. Immunohistochemistry was used to detect the protein expression of IRS-1 and IRS-2. RESULTS: (1) The concentrations of plasma nitrotyrosine and MDA of the HF group were both significantly higher than those of the NC group (both P < 0.05). However, the plasma GSH of the HF group was significantly lower than that of the NC group (P < 0.01). (2) The blood glucose of both groups became stable since 60 min after the experiment and the GIR of the HF group was (5.25 +/- 1.2) mg x min(-1) x kg(-1), significantly lower r than that of the NC group [(13.6 +/- 1l.7) mg x min(-1) x kg(-1), P < 0.01). (3) The peak of glucose-stimulated insulin secretion (GSIS) of the HF group was significantly lower than that of the NC group; and the GSIS peak increase In comparison with the NC group. (4) In comparison with the NC group, the mRNA expression levels of IRS-1 and IRS-2 genes of the HF group were significantly lower, by 42.3% and 28.1% respectively (both P < 0.05), and the expression of UCP2 was significantly higher, by 32.5% (P < 0.05). (5) Compared with the NC group, the protein expression levels of IRS-1 and IRS-2 in the islets of the HF group were lower, by 26.3% and 11.2% respectively, however not significantly (both P > 0.05). (6) There was a significantly negative correlation between the UCP2 and IRS-1/IRS-2 gene expression in islet beta cells in the HF group (r = -0.621 and r = -0.436, both P < 0.05). CONCLUSION: High-fat-diet impairs the expression of insulin signal transduction molecules and the function of islet beta cells that may be correlated with overexpression of UCP2. The basic insulin secretion of HF group was significantly higher than that of the NC group; but the glucose-stimulated insulin secretion (GSIS) peak decreased in comparison with the NC group. Compared with the NC group, the protein expression levels of IRS-1 and IRS-2 in the islets of the HF group were lower, by 26.3% (P < 0.05) and 11.2% (P > 0.05) respectively.

[Effects of fenofibrate on gene expression of carnitine palmitoyltransferase 1 in liver and skeletal muscle and its influence on insulin sensitivity].

OBJECTIVE: To study the effects of fenofibrate (FF), a peroxisome proliferator activated receptor (PPAR) alpha activator, on the expression of carnitine palmitoyltransferase 1 (CPT-1) mRNA in liver and muscle and its influence on insulin sensitivity. METHODS: Thirty-two normal 8 week-old male SD rats were randomly divided into 3 groups: normal control group, fed with normal food for 3 weeks (NC group, n = 10), high fat diet group, fed with high fat food (HF group, n = 10), and high fat diet supplemented with FF group, fed with high fat food and given with gastric perfusion of FF (50 mg x kg(-1) x d(-1)) (FF group, n = 12). Fast serum triglyceride (TG) level was tested by automatic biochemical analyzer after 8-10 h fasting. Euglycemic-hyperinsulinemic clamp method was used to calculate the glucose infusion rate (GIR) so as to evaluate the insulin sensitivity. By the end of experiment the rats were killed with their internal organs taken out. The triglyceride (TG) contents of liver and skeletal muscle were measured using Folch method. Real-time PCR was used to detect the mRNA expression. of CPT-1 in the liver and skeletal muscles. RESULTS: As compared with the NC group, the TG levels of serum, liver, and skeletal muscle of the HF group were higher than those of the NC group by 0.45-fold, 2.14-fold, and 10.64-fold respectively. The GIR of the HF group was (6.2 +/- 0.8) mg x kg(-1) x min(-1), significantly lower than that of the NC group (15.8 +/- 2.1) mg x kg(-1) x min(-1), (P < 0.01), and that of the P < 0.01. The CPT-1 mRNA expression in liver of the HF group was not significantly different from that of the NC group (P > 0.05); the expression of CPT-1 mRNA in skeletal muscle of the HF group was lower than that of the NC group by 71% (P < 0.01). The CPT-1 mRNA expression in liver and skeletal muscle of the FF group were significantly higher than those of the HF group by 1.00 and 1.05 times respectively (both P < 05). The GIR was negatively correlated with the levels in the liver (r = -0.87, P < 0.01) and in the skeletal muscle (r = -0.78, P < 0.01). CONCLUSION: Fenofibrate promotes the oxygenation of fatty acids by up-regulating the CPT-1 mRNA expression in the liver and skeletal muscles, thus improving the insulin sensitivity.

[The mechanism of and relationship between lipid metabolism genes expression and insulin resistance in high fat-fed mice].

OBJECTIVE: To observe the relationship between changes of genes expression related to lipid metabolism and insulin resistance induced by high fat diet in SD rats. METHODS: Normal 8-week old male SD rats were randomly divided into 3 groups. They were fed with normal chow (NC, n = 10), high fat diet (HF, n = 10) and high fat diet supplemented with pioglitazone 15 mg x kg(-1) x d(-1) (HP, n = 12). The TG content of liver and skeletal muscle of the rats was measured. Glucose infusion rate (GIR) was used to evaluate the insulin sensitivity by using euglycemic-hyperinsulinemic clamp method. Genes expression was investigated using real-time PCR method. RESULTS: After high fat feeding for 20 weeks, the serum TG, the content of TG in the liver and skeletal muscle of the rats in the HF group increased 0.45, 2.28 and 9.31 fold respectively as compared with those in the NC group. The change of TG content in the liver and skeletal muscle was associated with the reduction of GIR [(6.16 +/- 0.75) mg x kg(-1) x min(-1) vs (15.82 +/- 2.10) mg x kg(-1).min(-1) (P < 0.01)]. As compared with the NC group, the expression of hormone-sensitive lipase (HSL) and fatty-acid synthase (FAS) gene in the HF group was enhanced by 28.2% and 21.3%, respectively (P < 0.05). In addition, the expression of acetyl-CoA carboxylase1 (ACC1) mRNA in the liver increased 48.3% (P < 0.05), increased 101.1% (P < 0.01) and carnitine palmitoyltransferase 1 (CPT-1) decreased 71.0% (P < 0.01) in the skeletal muscle in the rats of HF group. As compared with those in the HF group, GIR increased 1.54 fold in the HP group and on the contrary, serum TG, liver TG and muscle TG decreased about 66%, 64.5% and 59.6% respectively in the HP group (P < 0.05). Accordingly, the expression of FAS and HSL in the adipose tissue and the expression of ACC1 in the liver were reduced (P < 0.05) and the expression of CPT-1 was enhanced and ACC2 was reduced in the muscle (P < 0.01) in the HP group. CONCLUSIONS: The changing expression of genes related to lipid metabolism may play a role in the accumulation of lipids in non-adipose tissue and the induction of insulin resistance in rats fed with high fat diet.

[The relationship between islet alpha cell insulin resistance and inflammatory pathway activation and its mechanism].

OBJECTIVE: To study the changes of inflammatory path molecules in the islet alpha cells in high-fat-diet fed plus beta cell-deleted rat models and the effects of pioglitazone intervention. METHODS: Forty five normal male SD rats, 8 week old, were randomly divided into 3 groups, i.e., a normal diet group (NC), a high fat diet fed group (HF), and a high fat diet fed and pioglitazone treated group (HP, pioglitazone 15 mg kg(-1) d(-1)). At the end of twenty weeks of feeding, fasting serum insulin (FIns), glucagon, free fatty acid (FFA) and high sensitive C reactive protein (hsCRP) were determined. Glucose infusion rate (GIR) was measured by using euglycemic hyperinsulinemia clamp to evaluate the peripheral insulin resistance. The contents of glucagon in perfusion medium during islet cell perfusion was measured with RIA. At the same time, beta cell-deleted rat models were established by injecting large dose streptozocin (100 mg/kg) in 8 rats in each of the three groups, i.e., HF-B group, P-B group and NC-B group. Five days later, the rats were sacrificed and the pancreatic islets were isolated and collected. The expression of NF-kappaB and inhibitor kappaBalpha (IkappaBalpha) gene in the islets was detected with real-time PCR. RESULTS: (1) GIR was decreased significantly in HF group as compared with NC group (P < 0.01). The concentrations of serum FIns, glucagon, FFA and hsCRP in HF group were higher than those in NC group. Pioglitazone intervention could reverse these effects. (2) 16.7 mmol/L glucose could inhibit the glucagon secretion by the islet alpha cells of the NC group rats, but not of the HF group rats. Pioglitazone intervention could reverse these effects. (3) The gene expression of NF-kappaB was significantly increased by 20.5% in the HF-B group than in the NC-B group (P < 0.01). In contrast, the expression of IkappaBalpha was significantly decreased by 24.3% (P < 0.01). The expression of NF-kappaB and IkappaBalpha mRNAs in HP-B group, when compared with that of HF-B group, was improved 78.3% and 58.8%, respectively. CONCLUSIONS: High-fat-diet feeding induces islet alpha cell insulin resistance and activates the mRNA expression of inflammatory path molecules in beta cell-deleted rat models and it may relate with the increased plasma FFA concentration. Pioglitazone intervention can reverse these effects.

[Effect of lipid infusion on the function of islet beta cells and gene expression of insulin signal transduction system].

OBJECTIVE: To study the changes and mechanism of the function of islet beta cells and insulin signal transduction molecules after lipid infusion. METHODS: Twenty five SD rats were randomly divided into 2 groups, FFA group and NS group. Catheters were implanted under pentobarbital anesthesia in the right atrium via the jugular vein and the left carotid artery. A technique for a 48 h infusion in unrestrained rats was used for triglyceride and heparin or saline infusion. The infusion period started on day 2 after surgery. After 48 h infusion, we determined fasting serum insulin (Ins), free fat acid (FFA) in the blood. The glucose infusion rate (GIR) was measured by hyperinsulinemia euglycemic clamp to evaluate the peripheral insulin resistance. The ivgtt and islet cell perifusion was conducted to evaluate the function of islet beta cells. The rats in the two groups were sacrificed, and the pancreatic islets were isolated and collected. The expressions of insulin receptor substrate-1(IRS-1), insulin receptor substrate-2 (IRS-2) glucose transporter-2 (Glut-2) gene in islets and IRS-1, IRS-2 in muscle were detected by real-time PCR. RESULTS: (1) The serum FFA and insulin concentrations of blood in FFA group were higher than in NS group (P<0.05). (2) The GIR was decreased significantly in FFA group compared with that in NS group (P<0.05). (3) The glucose stimulated insulin secretion increased in the FFA group. (4) The gene expression of IRS-1 in muscle was significantly decreased by 87.7% in FFA group, and the expression of IRS-2 was decreased by 50.7% (all P<0.05). The gene expression of IRS-1 in islets was significantly increased by 29.3% (P<0.05), and the expressions of IRS-2, Glut-2 were increased by 345.1% and 536.4% respectively, in FFA group (all P<0.01). CONCLUSION: Lipid infusion in short time increased the secretion of insulin and impaired expression of insulin signal transduction molecules in muscle but it also increased the expression of insulin signal transduction molecules in islet beta cells.

[Study on the distribution and risk factors of hypertension among children: a cohort study].

OBJECTIVE: To explore the association between hypertension and the tendency of change among children,so as to lay a foundation for the prevention and control of hypertension. METHODS: Based on findings from the prevalence survey that carried out in September 1999 in Daqing of Heilongjiang province. New admission children were selected as subjects to conduct a five-year cohort study. All the subjects were interviewed with questionnaires and their blood specimens were collected for biochemical analysis. All data were analyzed using SPSS 10.0 software. Results The prevalence of hypertension among 447 children was found 2.01% at the baseline study but increased to 5.37% in the fifth year. During a five year period, the systolic pressure level among children increased from (100.65 +/- 11.62)mmHg (1 mm Hg = 0.133 kPa) to (106.67 +/- 9.29) mm Hg,while the diastolic pressure level was from (66.27 +/- 11.31) mm Hg to (70.28 +/- 7.98) mm Hg and showed significant difference between boys and girls. There were association between hypertension and family history, body mass index (BMI), triglyceride, insulin, insulin resistance index while insulin sensitivity index and family history, BMI and insulin sensitivity index appeared to be the important factors. Children under this study were divided to 'with family history or without' and then every group was divided to 'with over weight-obesity or normal'. Obesity and insulin sensitivity seemed the key risk factors on hypertension. Descent of insulin sensitivity was an independent risk factor. CONCLUSION: The level of blood tension among children in Daqing city was higher than that from the national data. The present study confirmed that over-weight,obesity, heredity and insulin resistance were the risk factors of hypertension while insulin resistance was related to hypertension. The interaction of these risk factors was independent or correlated to each other.

[Relationship between hepatic insulin resistance and the expression of genes involved in hepatic glucose output].

OBJECTIVE: To study the relationship between hepatic insulin resistance induced by high fat diet and the expression of genes involving hepatic glucose output. METHODS: Normal 8-week-old male SD rats were randomly divided into two groups, i.e, normal chow group (NC, n = 10) and high fat diet group (HF, n = 10). They were fed for 28 weeks. Body weight and fasting blood glucose (FBG) were measured. At the end of the experiment, the rats were sacrificed and their fasting insulin (INS) and triglycerides (TG) were measured. Hepatic insulin sensitivity was measured by tissue uptake of 3H-2-deoxyglucose and the content of hepatic glycogen was measured using the anthrone method. Gene expression was investigated by using the semi-quantitative RT-PCR method. RESULTS: As compared with NC group, CF group rats developed visceral obesity which was accompanied by higher plasma TG. FBG in CF group increased starting from the 18th week (NC 4.77+/-63 mmol/L vs HF 5.45+/-87 mmol/L, P < 0.05). The rate of uptake of 3H-2-deoxyglucose in livers decreased by 51% in the HF group. The content of hepatic glycogen increased by 92.4% (P < 0.01). The level of phosphoenolpyruvate carboxykinase (PEPCK) and PGC-1a mRNA increased by 41.5% and 30.8%, respectively (P < 0.05). CONCLUSION: A high fat diet induced expressions of PGC-1a and PEPCK. It suggests that gluconeogenesis may play a role in the increase of hepatic glucose output and FBG.

[The expression of insulin signal transduction molecules and islet alpha cell insulin resistance].

OBJECTIVE: To study the changes of insulin signal transduction molecules in islet alpha cells in high-fat-diet plus beta cell-deleting rat models and its underlying mechanism. METHODS: Thirty SD rats were randomly divided into 2 equal groups and fed with high-fat-diet (HF group) or normal diet (normal control group, NC group) respectively. At the end of twenty-week feeding, the fasting serum insulin (Ins), glucagon (Glc), free fatty acid (FFA), and triglyceride (TG were measured. The glucose infusion rate (GIR) was measured by using euglycemic hyperinsulinemia clamp to evaluate the peripheral insulin resistance. At the same time, large dose streptozocin (100 mg/kg) was injected so as to establish beta cell-deleting rat models, i.e., HF-B group (n = 8) and NC-B group (n = 8). Five days later, the rats of the HF-B and NC-B subgroups were sacrificed, and the pancreatic islets were isolated and collected. The expression of Glc, insulin receptor substrate-1 (IRS-1), IRS-2, and phosphatidylinositol-3-kinase (PI3K) gene in the islets were detected by RT-PCR. RESULTS: (1) The serum FFA, insulin and Glc concentrations of the HF group were 508 (394 - 622) micromol/L, 23.7 (14.0 - 33.4) mIU/L, and 345 (298.6 - 391.4) pg/ml respectively, all significantly higher than those of the NC group [325 (240 - 410) micromol/L, 11.5 (3.6 - 19.4) mIU/L, 256 (226.4 - 285.6) pg/ml; respectively, all P < 0.05]. The GIR of the HF group was 5.25 mgxmin(-1)xkg(-1) +/- 1.2 mgxmin(-1)xkg(-1), significantly lower than that of the NC group (13.6 mgxmin(-1)xkg(-1) +/- 1.7 mgxmin(-1)xkg(-1), P < 0.01)). (2) The gene expression of Glc of the HF-B subgroup was significantly higher than that of the NC-B subgroup by 34.2% +/- 2.1%. In contrast, the expression of IRS-2, and PI3K of the HF-B subgroup was significantly lower than that of the NC-B subgroup by 28.5% +/- 1.8% and 21.3% +/- 1.6% respectively (both P < 0.01). (3) The plasma FFA concentration was asignificantly negatively correlated with GIR (r = -0.675, P < 0.05) and IRS-2 gene expression in islet alpha cells (r = -0.458, P < 0.05) in the HF-B group. CONCLUSION: High-fat-diet feeding plus beta cell-deleting rat model shows an impaired expression of insulin signal transduction molecules in islet alpha cells which may relate with the increased plasma FFA concentration.

[Relationship between adipose phosphoenolpyruvate carboxykinase and occurrence and reversion of insulin resistance].

OBJECTIVE: To investigate the relationship between the expression of phosphoenolpyruvate carboxykinase (PEPCK) gene and insulin resistance induced by high-fat diet and the effect of rosiglitazone, a thiazolidinedione drug. METHODS: Sixty-three normal 8-week-old male SD rats were randomly divided into 2 groups: short-term group, n = 33, to be fed for 8 weeks and re-divide into 3 equal subgroups: standard chow diet subgroup (NC subgroup fed with standard chow diet), high-fat diet subgroup (HF subgroup, to be fed with lard), and high-fat diet with rosiglitazone subgroup (HF + rosiglitazone subgroup); and long-term group, n = 30, to be fed for 28 weeks, and re-divided into 3 corresponding 3 subgroups: By the end of experiment, serum samples were collected to examine the blood glucose (BG), triglyceride (TG) and free fatty acid (FFA). At the end of the experiment the rats were killed and the visceral adipose tissue was taken out to be weighed, and the liver, muscle, and epididymis were isolated. Glucose infusion rate (GIR) methods and tissue uptake of (3)H-2-deoxyglucose were used to short-and long-term groups evaluate the insulin sensitivity. PEPCK gene expression was investigated to detect the expression of PEPCK mRNA by using semi-quantitative RT-PCR method. RESULTS: In the short-term group, the serum FFA and TG of the HF + rosiglitazone subgroup were lower by 24.5% and 54.0% respectively compared with those the HF subgroup (both P < 0.01). In the long-term group, the serum TG of the HF subgroup was higher by 32.4% in comparison with that of the NC subgroup (P < 0.05), and the serum FFA and TG of the HF + rosiglitazone subgroup were lower by 49.5% and 23.0% respectively compared with those of the HF subgroup (both P < 0.0). In the short-term group the GIR of the HF subgroup was lower by 51.25% in comparison with that of the NC subgroup (P < 0.01). And the GIR of the HF + rosiglitazone subgroup was higher by 149.6% than that of the HF group (P < 0.01). In the long-term group, the rate of uptake of (3)H-2-deoxyglucose in liver, muscle and adipose tissue of the HF subgroup were lower by 42.0%, 36.7%, and 48.1% respectively than those of the HF subgroup (all P < 0.01), and the rate of uptake of 3H-2-deoxyglucose in liver, muscle and adipose tissue of the HF + rosiglitazone subgroup were higher by 39.6%, 66.3%, and 66.7% respectively than those of the HF subgroup (all P < 0.01). In the short-term group the adipose PEPCK mRNA expression of the HF subgroup was 89% +/- 13% that of the NC subgroup; and the adipose PEPCK mRNA expression of the HF + rosiglitazone subgroup was 154% +/- 28% that of the NC subgroup, and was higher by 65.4% than that the HF subgroup (P < 0.05). In the long-term group, the adipose PEPCK mRNA expression of the HF + rosiglitazone subgroup was 144% +/- 17% that of the NC subgroup (P < 0.05), and was higher by 43.3% than that of the HF subgroup (P < 0.05). CONCLUSION: Thiazolidinedione drug increases the re-esterification of fatty acids and reduces circulating FFA, and induces the expression of adipose PEPCK which is accompanied by reduction of FFA, thus improving insulin resistance.

[The effect of high fat feeding and rosiglitazone intervention on pancreatic alpha cell in rats].

OBJECTIVE: To observe the effect of high-fat diet and rosiglitazone intervention on the function of pancreatic alpha cell of SD rats. METHODS: 36 normal male SD rats, 8-week old, were randomly divided into 3 groups i.e., a normal chow group (CC, n = 12), an isocaloric high-fat diet group (CF, n = 12), and a rosiglitazone-treated group (Ro, n = 12, rosiglitazone 3 mg.kg(-1).d(-1) and isocaloric high fat diet). Triglyceride (TG) was measured every 4 weeks after feeding for 6 weeks. After 28 weeks, the secretion of insulin and glucagon (Gg) was assessed with intravenous glucose tolerance test (IVGTT) at 0, 3, 5, and 10 minutes. (3)H-2-deoxyglucose ((3)H-2-DG) uptake by tissues was measured to evaluate the insulin sensitivity. RESULTS: The ratio of intra-abdominal fat mass and body weight was higher in the rats of CF and Ro group than that in the rats of CC group. At the first 10 min of IVGTT, the Gg level was higher in the CF group than that in CC group [(119.3 +/- 12.4, 82.3 +/- 6.4, 72.2 +/- 5.8, 68.2 +/- 9.1) ng/L vs (96.8 +/- 9.1, 67.6 +/- 5.9, 57.9 +/- 5.3, 55.3 +/- 6.9) ng/L, P < 0.05] and Ro group [(78.4 +/- 6.0, 59.4 +/- 4.0, 49.9 +/- 6.2, 40.9 +/- 6.0) ng/L, P < 0.01], the level was even lower in the latter group than in CC group (P < 0.01). There was no difference of insulin level among the 3 groups. By using quantitative image analysis, the integrated A (area x A) of alpha cells was significantly higher in the CF group and Ro group as compared with that in the CC group (1661 +/- 130 and 1532 +/- 132 vs 1188 +/- 104, P < 0.05). In contrast, there was no difference among the 3 groups in the integrated A of beta cells. CONCLUSIONS: High-fat feeding induces insulin resistance in rats, which is associated with pancreatic alpha cell proliferation and abnormal Gg secretion.

[Electrical impedance spectroscopy method for measuring cold hardiness of plants].

Electrical impedance spectroscopy (EIS) is a method for measuring cold hardiness of plants. It has been widely used in the fields of agriculture, forestry and horticulture. In this paper the following aspects were introduced and discussed: (1) physical and physiological factors of impedance measurements in plants, (2) suitable models for measuring EIS, and (3) method for assessing cold hardiness by means of EIS. In traditional EIS analysis, after completion of the artificially controlled freezing tests, the extracellular resistance (r(e)) is the best parameter for determining cold hardiness of plants. It has been reported recently that cold hardiness might be determined just after sampling using EIS analysis without a controlled freezing test. The relaxation time (tau(1)) is the most suitable parameter: in the rapid hardening phase, differences in the hardening patterns of various provenances of Scots pine (Pinus sylvestris L.) could be distinguished by the relaxation time with an accuracy of +/-2 degrees C without a controlled freezing test.

[Effects of rosiglitazone and metformin on insulin resistance in high-fat diet rats].

OBJECTIVE: To observe the effects of rosiglitazone and metformin in rats on insulin resistance induced by high-fat diet. METHODS: Normal 8-week old male SD rats were divided into four groups. They were normal chow group (NC, n = 11), high-fat diet (HF, n = 11), metformin-treated (HF + Met, n = 11) and rosiglitazone-treated group (HF + Ros, n = 11). Rosiglitazone 3 mg x kg(-1) x d(-1) and metformin 300 mg x kg(-1) x d(-1) were given orally to HF + Ros and HF + Met group, respectively. After feeding for 8 weeks, serum insulin, adiponectin, glucose (BG), triglyceride (TG) and free fatty acid (FFA) were measured in all the rats. Insulin sensitivity was measured with glucose infusion rate (GIR) and determined by using euglycemic-hyperinsulinemic clamp method. RESULTS: High-fat diet induced obesity in SD rats after feeding for 8 weeks. High-fat diet decreased adiponectin level by 43.7% (P < 0.01) and GIR by 51.3% (P < 0.01) as compared with the NC group. Metformin decreased body weight by 8.4% (P < 0.01) and TG level by 40.5% (P < 0.01). Metformin significantly increased GIR by 58.9% (P < 0.01) when compared with the HF group. Rosiglitazone caused an apparent reduction of FFA (-25.3%, P < 0.05) and TG level (-54.0%, P < 0.01). At the same time, rosiglitazone increased adiponectin by 60% (P < 0.01), and improved insulin sensitivity by 149.6% (P < 0.01) as compared with the HF group. CONCLUSIONS: (1) High-fat diet induces insulin resistance in SD rats; this was associated with an increase in visceral fat and a decrease in the level of adiponectin; (2) Metformin treatment improved insulin sensitivity accompanied by a decrease in body weight and TG level; (3) Rosiglitazone treatment ameliorates IR in a greater extent and is accompanied by a reduction of FFA, TG and an increase of adiponectin levels.