Segment of rat chromosome 20 regulates diet-induced augmentations in adiposity,glucose intolerance,and blood pressure

Previous linkage and association studies have suggested that a region of human chromosome 6 containing the tumor necrosis factor (TNF)-alpha gene is involved in the pathogenesis of obesity and obesity-associated hypertension. The aim of the present investigation was to establish whether a segment of rat chromosome 20 (RNO20), which also contains the TNF-alpha gene, determines diet-induced changes in adiposity and blood pressure (BP). The results showed that a transfer of the RNO20 segment from the normotensive Brown Norway (BN) rat onto the background of the spontaneously hypertensive rat (SHR) is associated with a significantly greater increase in adiposity, glucose intolerance, circulating leptin levels, and BP during 12-week, high-fat-diet feeding. In contrast, the transfer is not associated with significant changes in these variables during 12-week, normal-diet feeding. In addition, sequencing of the TNF-alpha gene revealed differences between SHR and BN in the 5'- and 3'-regulatory regions of the gene. Subsequent analyses of TNF-alpha gene expression in fat, muscle, and liver, however, did not provide support for the functional involvement of these differences. In summary, the investigated RNO20 segment contains 1 or more gene variants that affect adiposity, glucose tolerance, serum leptin levels, and BP, but only when the animals are exposed to a particular environment, ie, high-fat-diet feeding. Further studies are needed to identify genes mediating these effects. Considering current changes in our lifestyle involving an increased calorie and fat intake, we believe that gene-environment interactions, such as those described here, play an important role in the current epidemic of obesity and obesity-associated hypertension.     

Overexpression of Rad in muscle worsens diet-induced insulin resistance and glucose intolerance and lowers plasma triglyceride level

Rad is a low molecular weight GTPase that is overexpressed in skeletal muscle of some patients with type 2 diabetes mellitus and/or obesity. Overexpression of Rad in adipocytes and muscle cells in culture results in diminished insulin-stimulated glucose uptake. To further elucidate the potential role of Rad in vivo, we have generated transgenic (tg) mice that overexpress Rad in muscle using the muscle creatine kinase (MCK) promoter-enhancer. Rad tg mice have a 6- to 12-fold increase in Rad expression in muscle as compared to wild-type littermates. Rad tg mice grow normally and have normal glucose tolerance and insulin sensitivity, but have reduced plasma triglyceride levels. On a high-fat diet, Rad tg mice develop more severe glucose intolerance than the wild-type mice; this is due to increased insulin resistance in muscle, as exemplified by a rightward shift in the dose-response curve for insulin stimulated 2-deoxyglucose uptake. There is also a unexpected further reduction of the plasma triglyceride levels that is associated with increased levels of lipoprotein lipase in the Rad tg mice. These results demonstrate a potential synergistic interaction between increased expression of Rad and high-fat diet in creation of insulin resistance and altered lipid metabolism present in type 2 diabetes.     

Elevated IgG levels against specific bacterial antigens in obese patients with diabetes and in mice with diet-induced obesity and glucose intolerance

High fat diets increase the risk for insulin resistance by promoting inflammation. The cause of inflammation is unclear, but germfree mouse studies have implicated commensal gut bacteria. We tested whether diet-induced obesity, diabetes, and inflammation are associated with anti-bacterial IgG. Blood from lean and obese healthy volunteers or obese patients with diabetes were analyzed by ELISA for IgG against extracts of potentially pathogenic and pro-biotic strains of Escherichia coli (LF-82 and Nissle), Bacteroides thetaiotaomicron, and Lactobacillus acidophilus, and for circulating tumor necrosis factor α (TNFα). C57Bl/6 mice were fed low- or high-fat diets (10% or 60% kcal from fat) for 10 weeks and tested for anti-bacterial IgG, bodyweight, fasting glucose, and inflammation. Obese diabetic patients had significantly more IgG against extracts of E. coli LF-82 compared with lean controls, whereas IgG against extracts of the other bacteria was unchanged. Circulating TNFα was elevated and correlated with IgG against the LF-82 extract. Mice fed high-fat diets had increased fasting glucose levels, elevated TNFα and neutrophils, and significantly more IgG against the LF-82 extracts. Diabetes in obesity is characterized by increased IgG against specific bacterial antigens. Specific commensal bacteria may mediate inflammatory effects of high-fat diets.     

Development of cookie test for the simultaneous determination of glucose intolerance, hyperinsulinemia, insulin resistance and postprandial dyslipidemia

A new cookie test was developed for the simultaneous evaluation of multiple risk factors such as glucose intolerance, hyperinsulinemia, insulin resistance and postprandial dyslipidemia. The cookie consisting of 75 g carbohydrate and 25 g fat is ingested and the blood samples are obtained at 0, 1 and 2 hours later. When the two carbohydrate sources, liquid glucose and test cookie, were compared as a glucose load within 3 months, the 2 hr plasma glucose levels were not statistically different, proposing the use of the same criteria at 2 hour glucose level for the diagnosis of diabetes and impaired glucose tolerance (IGT) in subjects without exocrine pancreatic dysfunction. In addition, hyperinsulinemia, insulin resistance (AUC insulin, and/or AUC insulin X AUC glucose), and postprandial hyperlipidemia (DeltaTG, Triglyceride; DeltaRLP, remnant like particles) have been simultaneously uncovered. Reactive hypoglycemia with adverse epigastric discomfort was observed in 26.3% of the control subjects with liquid glucose, while it was observed in only 1 case (5.3%) without any symptom with cookie tests. In fact, one reactive hypoglycemia out of 5 with liquid glucose turned out to be IGT with cookie test. In 64 subjects with lifestyle-related diseases, cookie test revealed hyperinsulinemia and insulin resistance in 56% respectively, postprandial hyperlipidemia in 39%, diabetes and IGT in 22-23% of each of the subjects and all showed at least one abnormal value. In contrast, in university students with exercise habit, all showed normal results with cookie test. In addition, improved insulin sensitivity over non-exercise group was obverved. In summary, the cookie test provided more informations compared with OGTT using liquid glucose and with fewer side effects. Simultaneous evaluation of glucose intolerance, hyperinsulinemia, insulin resistance, and postprandial hyperlipidemia was also possible.     

Prenatal viral exposure followed by adult stress produces glucose intolerance in a mouse model

Aims/hypothesis It has been suggested that the uterine environment may influence metabolic disease occurring later in adult life, and that adult stress may promote disease outcome. Using a mouse model, we tested whether in utero exposure to Ljungan virus (LV) followed by adult exposure to stress produces diabetes. The influence of the timing of viral exposure over the course of pregnancy was also tested.Materials and methods Pregnant CD-1 mice were exposed i.p. to LV on pregnancy days 4, 8, 12 or 17. Adult male mice from these pregnancies were stressed by being kept in shared cages. Stress only, LV exposure in utero only, and no-stress/no virus exposure groups were also followed. Outcome variables included bodyweight, epididymal fat weight, baseline glucose, glucose tolerance tests (60 and 120 min) and serum insulin.Results We demonstrated that male mice developed a type 2-like diabetes, including obesity, as adults if infected during pregnancy with LV. Diabetes at the age of 11 weeks was more severe in mice whose mothers were infected earlier than in those whose mothers were infected later in pregnancy. Only animals infected in utero and kept under stress developed diabetes; infection or stress alone did not cause disease.Conclusions/interpretation This work demonstrates that a type 2 diabetes-like disease can be virus-induced in a mouse model. Early in utero viral insults can set the stage for disease occurring during adult life, but the final manifestation of diabetes is dependent on the combination of early viral exposure and stress in adult life.     

Wistar大鼠乳鼠与成年鼠心室肌细胞的分离与性质鉴定

目的 探索和优化稳定的适于电生理实验研究的乳鼠及成年大鼠心室肌细胞分离方法。方法 切碎乳鼠心室肌,胰蛋白酶消化,差速贴壁2 h纯化心室肌细胞,台盼蓝染色判定心肌细胞活力,体外培养48 h后分别行倒置显微镜观察细胞形态,免疫组化鉴定,微电极阵列记录细胞搏动频率和场电位。采用Langendorff灌流成年大鼠心脏,主动脉逆行插管,胶原酶域反复灌流消化约30 min,无钙台氏液冲洗心脏5 min,剪下心室肌组织,台氏液中室温下剪碎,吹打,孵育5 min后,用200目筛网过滤,将细胞悬液用逐步复钙法复钙后,室温静置1 h,用于膜片钳记录。结果 经4 -6次消化后,乳鼠心室组织消化完全,细胞存活率大于80%。倒置显微镜下观察,细胞呈梭形、多角形。 12 h有少部分细胞搏动,48 h细胞交织成网,搏动呈同步性,搏动频率30 - 80次/分。 琢鄄辅肌动蛋白（琢鄄actin）经免疫组化检测,纯度达96%。 Langendorff灌流酶解法可获得形态呈杆状、横纹清晰、膜周边光滑完整、立体感强的单个成年鼠心肌细胞,存活率85%,复钙后存活率50%,可用于膜片钳记录。结论 采用本方法可以获得高产量与高质量的用于电生理检测的心室肌细胞。     

Hypoxia causes glucose intolerance in humans

Hypoxic respiratory diseases are frequently accompanied by glucose intolerance. We examined whether hypoxia is a cause of glucose intolerance in healthy subjects. In a double-blind within-subject crossover design, hypoxic versus normoxic conditions were induced in 14 healthy men for 30 minutes by decreasing oxygen saturation to 75% (versus 96% in control subjects) under the conditions of a euglycemic clamp. The rate of dextrose infusion needed to maintain stable blood glucose levels was monitored. Neurohormonal stress response was evaluated by measuring catecholamine and cortisol concentrations as well as cardiovascular parameters, and symptoms of anxiety. To differentiate between the effects of stress hormonal response, and hypoxia itself, on glucose intolerance, we performed hypoglycemic clamps as a nonspecific control. We found a significant decrease in dextrose infusion rate over a period of 150 minutes after the start of hypoxia (p < 0.01). Hypoxia also increased plasma epinephrine concentration (p < 0.01), heart rate (p < 0.01), and symptoms of anxiety (p < 0.05), whereas the other parameters remained unaffected. Glucose intolerance was closely comparable between hypoxic and hypoglycemic conditions (p < 0.9) despite clear differences in stress hormonal responses. Hypoxia acutely causes glucose intolerance. One of the factors mediating this effect could be an elevated release of epinephrine.     

Peripheral and autonomic nerve function in glucose intolerance

In 19 middle aged subjects, glucose intolerant according to WHO criteria, obtained from a health survey, peripheral and autonomic nerve function were studied in comparison with 25 control subjects with normal glucose tolerance. Clinically detectable signs of peripheral nerve dysfunction were not more common in glucose intolerant subjects than in the control group. In measurements of sensory thresholds for vibration, nerve conduction velocities and autonomic nerve function, small differences, mainly non-significant, were found in favour of the controls. It is concluded that minor reduction of some peripheral nerve function may be associated with glucose intolerance, but it is not readily demonstrated. Clinically apparent polyneuropathy is not likely to develop.     

Blocking effect of naloxone, dihydroergotamine and adrenalectomy in lithium-induced hyperglycaemia and glucose intolerance in the rat

The direct effect of lithium administration on plasma glucose levels and glucose-induced insulin release, and the role of opioid and amine systems in these effects were examined in rats. Naloxone, an opiate antagonist, and dihydroergotamine, an alpha-adrenergic blocking agent, reversed the hyperglycaemia as well as the inhibition of glucose-stimulated insulin release induced by lithium. In adrenalectomized rats, administration of lithium induced hypoglycaemia and not hyperglycaemia as in the intact rats. The results suggest that the interaction of secreted endorphins with the sympathetic nervous system is the likely cause of the hyperglycaemia and the inhibition of the glucose-stimulated insulin release induced by lithium.     

Mechanisms of glucose intolerance in cystic fibrosis

Aims Although cystic fibrosis‐related diabetes (CFRD), a poor prognostic factor in cystic fibrosis (CF), is characterized by insulinopenia, the role of insulin resistance is unclear. Using a prospective study design, we measured insulin resistance, pancreatic β‐cell function and correlated glycaemic status with clinical parameters. Methods Oral glucose tolerance test was performed in 60 stable adult CF patients. Insulin sensitivity and β‐cell function were measured using the homeostatic model assessment (HOMA2), Stumvoll and oral glucose insulin sensitivity (OGIS) indices. Results Forty‐two (70%) had normal glucose tolerance (NGT), 10 (17%) impaired glucose tolerance (IGT) and eight (13%) CFRD. There was no difference in insulin sensitivity among the three groups (HOMA2: NGT 280, IGT 250, CFRD 339, P = 0.42; Stumvoll: NGT 0.128, IGT 0.126, CFRD 0.129, P = 0.76; and OGIS: NGT 515, IGT 472, CFRD 472, P = 0.12). Pancreatic β‐cell function (CFRD 50% vs. NGT 67%; P < 0.05) and first‐phase insulin secretion were reduced in CFRD (250 vs. NGT 509; P = 0.004). First‐phase insulin secretion was inversely correlated with 1‐h (r = ?0.74; P < 0.0001) and 2‐h glucose levels (r = ?0.34; P < 0.05). There was no difference in body mass index or poor lung function (forced expiratory volume in 1 s: CFRD 54% vs. NGT 65%; P = 0.43). However, there were more hospital admissions in the CFRD group (three vs. NGT one per patient per year; P < 0.05). Conclusions CFRD is characterized by qualitative and quantitative defects in insulin secretion, but not insulin resistance, and is associated with increased hospital admissions for pulmonary exacerbations.     

Birth weight is nongenetically associated with glucose intolerance in elderly twins, independent of adult obesity

OBJECTIVES: Using a unique twin approach, we examined the extent to which birth weight is determined by genetic and nongenetic factors and whether associations between birth weight and measures of glucose metabolism are of genetic or nongenetic origin. SETTING/SUBJECTS: An oral glucose tolerance test (OGTT) was performed in a population-based cohort of twins including 138 same-sex monozygotic (MZ) and 214 dizygotic (DZ) twin pairs aged 55-73 years whose birth weight was known. Heritability of birth weight was determined and regression analyses with intra-twin pair differences of birth weight and measures of glucose metabolism, with and without adjustment for adult obesity, were performed. RESULTS: The heritability of birth weight was estimated to be 38%. We demonstrated significant nongenetic associations between birth weight and measures of glucose homeostasis in MZ twins, with a reduction in fasting plasma glucose, 120 min post-OGTT plasma glucose, fasting plasma insulin and HOMA-IR index of 15.7%, 25.5%, 26.4% and 37.2%, respectively, for every 1 kg increase in birth weight. The nongenetic negative associations between birth weight and measures of glucose intolerance were independent of adult obesity, whereas the nongenetic association between birth weight and insulin resistance persisted, although not as strongly, after adjusting for current body size. CONCLUSIONS: We demonstrated a genetic component to birth weight in elderly twins. When adjusting for this influence, we found a nongenetic negative association between birth weight and glucose tolerance as well as insulin resistance that was partially independent of adult obesity. This implies that the foetal environment influences glucose homeostasis in elderly twins.