长期高脂饮食对C57BL/6小鼠骨骼肌基因表达谱的影响

目的 运用基因芯片技术研究长期高脂饮食对C57BL/6小鼠骨骼肌基因表达谱的影响,探究长期高脂饮食导致小鼠肥胖、胰岛素抵抗(IR)和2型糖尿病(T2DM)的分子机制.方法 20只雄性4周龄C57 BL/6小鼠随机分为正常饮食组和高脂饮食组,各10只,分别饲以基础和高脂饲料.16周后,称量各组小鼠体重;测定血糖、空腹血清胰岛素(FINs)、高密度脂蛋白(HDL)、甘油三酯(TG)、总胆固醇(TC)和游离脂肪酸(FFAs)水平;随后,每组随机选取4只小鼠处死,分离股四头肌,提取总RNA进行基因芯片分析.结果 高脂饮食组与正常饮食组相比,体重显著增加;FINs水平显著升高;HDL水平无显著性差异,而TC、TG和FFA水平均显著升高.采用基因芯片相关统计软件分析数据,结果发现正常饮食组与高脂饮食组相比,骨骼肌共出现590个差异表达基因.其中表达上调基因有321个,表达下调基因有269个.结论长期高脂饮食可以引起C57BL/6小鼠骨骼肌基因谱发生显著变化.     

Effects of fenofibrate on high-fat diet-induced body weight gain and adiposity in female C57BL/6J mice

Our previous study suggested that fenofibrate affects obesity and lipid metabolism in a sexually dimorphic manner in part through the differential activation of hepatic peroxisome proliferator-activated receptor alpha (PPARalpha) in male and female C57BL/6J mice. To determine whether fenofibrate reduces body weight gain and adiposity in female sham-operated (Sham) and ovariectomized (OVX) C57BL/6J mice, the effects of fenofibrate on not only body weight, white adipose tissue (WAT) mass, and food intake, but also the expression of both leptin and PPARalpha target genes were measured. Compared to their respective low-fat diet-fed controls, both Sham and OVX mice exhibited increases in body weight and WAT mass when fed a high-fat diet. Fenofibrate treatment decreased body weight gain and WAT mass in OVX, but not in Sham mice. Furthermore, fenofibrate increased the mRNA levels of PPARalpha target genes encoding peroxisomal enzymes involved in fatty acid beta-oxidation, and reduced apolipoprotein C-III (apo C-III) mRNA, all of which were expressed at higher levels in OVX compared to Sham mice. However, leptin mRNA levels were found to positively correlate with WAT mass, and food intake was not changed in either OVX or Sham mice following fenofibrate treatment. These results suggest that fenofibrate differentially regulates body weight and adiposity due in part to differences in PPARalpha activation, but not to differences in leptin production, between female OVX and Sham mice.     

Effects of feeding a diet containing Gymnema sylvestre extract: attenuating progression of obesity in C57BL/6J mice

Objective: To investigate the effect of Gymnema sylvestre extract(GS) on initial anti-obesity, liver injury, and glucose homeostasis induced by a high-fat diet(HFD). Methods: The dry powder of GS was extracted with methanol, and gymnemic acid was identified by high performance liquid chromatography as deacyl gymnemic acid. Male C57BL/6J mice that fed on either a normal diet, normal diet containing 1 g/kg GS(CON+GS) HFD, or HFD containing 1.0 g/kg GS(HFD+GS) for 4 weeks were used to test the initial anti-obesity effect of GS. Body weight gain and food intake, and serum levels about lipid and liver injury markers were measured. Histopathology of adipose tissue and liver stained with hematoxylin and eosin(HE) and oil-red O were analyzed. After 4 weeks of GS extract feeding, intraperitoneal glucose tolerance test(IPGTT) was performed. Results: The methanol extracts of GS exerted significant anti-obesity effects in HFD+GS group. They decreased body weight gain, a lower food and energy efficiency ratio, and showed lower serum levels of total cholesterol(TC), triglyceride(TG), low-density lipoprotein(LDL)-cholesterol, very-low density lipoprotein(VLDL)-cholesterol and leptin compared with the HFD group. The decreases of abdominal as well as epididymal fat weight and adipocyte hypertrophy, lipid droplets in liver, and serum levels of aspartate aminotransferase(AST) and alanine transaminase(ALT) were also observed. The CON+GS group showed an effect of glucose homeostasis compared to the CON group. Conclusions: This study shows that GS provide the possibility as a key role in an initial anti-obesity effects feeding with a HFD.     

Diabetes induces endothelial dysfunction but does not increase neointimal formation in high-fat diet fed C57BL/6J mice

Studies of diabetic vascular disease have traditionally used murine models of type 1 diabetes and genetic models of type 2 diabetes. Because the majority of patients with type 2 diabetes have diet induced obesity, we sought to study the effect of diabetes on arterial disease in a mouse model of diet induced obesity/diabetes. C57Bl/6 mice fed a high-fat diet for 9 weeks developed type 2 diabetes characterized by elevated body weight, hyperglycemia, and hyperinsulinemia. Arteries from diabetic mice exhibited a marked decrease in endothelium-dependent vasodilation, a modest decrease in endothelium independent vasodilation, and an increase in sensitivity to adrenergic vasoconstricting agents. Insulin stimulated protein kinase B (akt) and endothelial nitric oxide synthase (eNOS) phosphorylation were preserved in arteries from diabetic mice; however, eNOS protein dimers were markedly diminished. Arterial nitrotyrosine staining indicated that increased levels of peroxynitrite contributed to eNOS dimer disruption in the diabetic mice. The abnormal vasomotion was not an acute response to the high-fat diet, as short term high-fat diet feeding had no effect on endothelium dependent dilation. A trend toward smaller neointimal lesions was noted in high-fat diet fed mice after femoral artery wire denudation injury. In summary, disrupted eNOS dimer formation rather than impaired insulin mediated eNOS phosphorylation contributed to the endothelial dysfunction in diet induced obese/diabetic mice. The lack of an increase in neointimal formation indicates that additional diabetes associated parameters (such as hyperlipidemia and atherosclerotic vascular disease) may need to be present to increase neointimal formation in this model.     

Hybrid C57BL/6J x FVB/NJ mice drink more alcohol than do C57BL/6J mice

BACKGROUND: From several recent strain surveys (28 strains: Bachmanov et al., personal communication; 22 strains: Finn et al., unpublished), and from data in >100 other published studies of 24-hr two-bottle ethanol preference, it is known that male C57BL/6 (B6) mice self-administer about 10-14 g/kg/day and that female B6 mice self-administer about 12-18 g/kg/day. No strain has been found to consume more ethanol than B6. In one of our laboratories (Texas), we noted a markedly greater intake of ethanol in an F1 hybrid of B6 and FVB/NJ (FVB) mice. METHODS: To confirm and extend this finding, we repeated the study at another site (Portland) using concentrations up to 30% ethanol and also tested B6xFVB F1 mice in restricted access drinking procedures that produce high levels of alcohol intake. RESULTS: At both sites, we found that B6xFVB F1 mice self-administered high levels of ethanol during two-bottle preference tests (females averaging from 20 to 35 g/kg/day, males 7-25 g/kg/day, depending on concentration). F1 hybrids of both sexes drank significantly more 20% ethanol than both the B6 and FVB strains. Female F1 hybrids also drank more 30% ethanol. In the restricted access tests, ethanol consumption in the F1 hybrids was equivalent to that in B6 mice. CONCLUSIONS: These data show that this new genetic model has some significant advantages when compared to existing inbred strains, and could be used to explore the genetic basis of high ethanol drinking in mice.     

Quercetin transiently increases energy expenditure but persistently decreases circulating markers of inflammation in C57BL/6J mice fed a high-fat diet

Quercetin, a polyphenolic compound and a major bioflavonoid in the human diet, has anti-inflammatory properties and has been postulated to enhance energy expenditure (EE). We sought to determine whether quercetin alters body weight, body composition, EE, and circulating markers of inflammation. At 6 weeks (W) of age, 2 cohorts of C57BL/6J mice (N = 80) were placed on one of 2 diets for 3W or 8W: (1) high fat (HF) (45% kcal fat) or (2) high fat + quercetin (HF + Q) (45% kcal fat + 0.8% quercetin). Quercetin concentrations in the diet and plasma were evaluated using mass spectrometry. Body weight, composition (nuclear magnetic resonance), and food consumption were measured weekly. Energy expenditure was measured by indirect calorimetry at 3 and 8W, and inflammatory markers were measured in plasma obtained at 8W. The presence of quercetin in the HF diet did not alter food consumption over time in the HF + Q group and did not differ from the HF group at any time point. However, circulating plasma quercetin concentrations declined between 3 and 8W. At 3W, EE was higher during both day and night phases (P < .0001) in the HF + Q group compared with the HF group; but this difference was not detected at 8W and did not translate into significant differences between the HF + Q and HF groups with respect to body weight or body composition. During the night phase, concentrations of the inflammatory markers (interferon-γ, interleukin-1α, and interleukin-4) were significantly lower when compared with HF treatment group (P < .05). Dietary supplementation with quercetin produces transient (3W) increases in EE that are not detected after 8W on the diet. A corresponding decrease in circulating quercetin between 3 and 8W suggests that metabolic adaptation may have diminished the impact of quercetin's early effect on EE and diminished its overall effect on nutrient partitioning and adiposity. However, quercetin at the levels provided was effective in reducing circulating markers of inflammation observed in animals on an HF diet at 8W.     

AMPK基因在C57BL／6J小鼠糖脂代谢中的作用

目的研究腺苷酸活化蛋白激酶（AMPK）基因在C57BL／6J小鼠糖脂代谢中的作用。方法分别取5周龄AMPK基因敲除（AMPK-KO）小鼠和C57BL／6J对照小鼠各24只,分为正常饲料（ND）喂养和高脂高糖饲料（HFD）喂养两组。喂养12周,每两周测定小鼠禁食4h血糖（FBG）,实验结束前行口服糖耐量实验（OGTT）,解剖取样,检测血生化指标、脂酶活性及相关蛋白的表达。结果AMPK-KO小鼠血糖、TC、LDL-C、HbA1c、6-磷酸葡萄糖脱氢酶（G6PD）活性、糖原合成酶激酶（GSK）活性、肝脏PPAR7蛋白表达量明显高于对照小鼠（P〈0．05）;其胰岛素含量、肝糖原含量、肌糖原含量、肝脂酶（HL）活性、脂蛋白酯酶（LPL）活性、总脂酶活性、葡萄糖激酶（GK）活性、肝组织P-AMPK蛋白、葡萄糖转运蛋白4（GluT-4）蛋白的表达量低于对照组（P〈0．05）。结论AMPK基因通过调节C57BL／6J小鼠糖脂代谢,在T2DM的发病中起重要作用。     

A genetic and physiological study of impaired glucose homeostasis control in C57BL/6J mice

Aims/hypothesis C57BL/6J mice exhibit impaired glucose tolerance. The aims of this study were to map the genetic loci underlying this phenotype, to further characterise the physiological defects and to identify candidate genes.Methods Glucose tolerance was measured in an intraperitoneal glucose tolerance test and genetic determinants mapped in an F2 intercross. Insulin sensitivity was measured by injecting insulin and following glucose disposal from the plasma. To measure beta cell function, insulin secretion and electrophysiological studies were carried out on isolated islets. Candidate genes were investigated by sequencing and quantitative RNA analysis.Results C57BL/6J mice showed normal insulin sensitivity and impaired insulin secretion. In beta cells, glucose did not stimulate a rise in intracellular calcium and its ability to close K_ATP channels was impaired. We identified three genetic loci responsible for the impaired glucose tolerance. Nicotinamide nucleotide transhydrogenase (Nnt) lies within one locus and is a nuclear-encoded mitochondrial proton pump. Expression of Nnt is more than sevenfold and fivefold lower respectively in C57BL/6J liver and islets. There is a missense mutation in exon 1 and a multi-exon deletion in the C57BL/6J gene. Glucokinase lies within the Gluchos2 locus and shows reduced enzyme activity in liver.Conclusions/interpretation The C57BL/6J mouse strain exhibits plasma glucose intolerance reminiscent of human type 2 diabetes. Our data suggest a defect in beta cell glucose metabolism that results in reduced electrical activity and insulin secretion. We have identified three loci that are responsible for the inherited impaired plasma glucose tolerance and identified a novel candidate gene for contribution to glucose intolerance through reduced beta cell activity.Electronic Supplementary Material Supplementary material is available for this article at .     

Body temperature of C57BL/6J mice with age

On the basis of a study of rectal temperature in a group of 180, C57BL/6J male mice, ranging in age from 3 months to 30 months, the following conclusions were drawn: 1) The positive correlation between body weight and body temperature typical for rodents was found only for young adults of the C57BL/6J strain; 2) body temperature of male C57BL/6J did not appear to decline until about 23.5 months, after which there was a significant negative correlation (r = -0.53) between age and temperature.     

Schedule-induced ethanol self-administration in DBA/2J and C57BL/6J mice

BACKGROUND: The purpose of these experiments was to provide an initial investigation into ethanol self-administration elicited in the schedule-induced polydipsia (SIP) paradigm. METHODS: Mature male mice were food deprived to between 80 and 85% of their baseline weight and received 20 daily 1 hr SIP test sessions in which a food pellet (20 mg) was delivered on a fixed-time 60 sec schedule. In different groups, the acquisition of drinking 5% (v/v) ethanol solution (experiment 1) or water (experiment 2) was recorded along with other behaviors that occurred in the test chambers. RESULTS: Results indicated that C57BL/6J mice drank significantly more ethanol than DBA/2J mice and that C57 mice achieved blood alcohol concentrations as high as 300 mg/dl. Blood alcohol concentrations were consistently correlated with g/kg ethanol intake. The groups did not differ in consumption of water. SIP test sessions using higher concentrations of ethanol (10-20% v/v, experiment 1) or sucrose solutions (0.1-2% w/v, experiment 2) then were performed. Group differences in ethanol consumption were maintained at all ethanol concentrations. Although DBAs drank more of a low concentration of sucrose (0.1%), when expressed as g/kg, sucrose intake was equivalent in the two strains at all concentrations. Analysis of the time course of drinking clearly showed that this behavior was adjunctive in nature. CONCLUSION: These results demonstrate the effectiveness of this procedure in inducing ethanol self-administration and its utility for investigating the genetic bases of vulnerability toward excessive ethanol consumption.     

Differential mechanisms and development of leptin resistance in A/J versus C57BL/6J mice during diet-induced obesity

Changes in the biological efficacy of leptin were evaluated in obesity-resistant (A/J) and obesity-prone (C57BL/6J) mice at weaning and after consuming a high-fat (HF) diet for 4 and 8 wk. There was no evidence of leptin resistance in either strain at the start of the study, but after 4 and 8 wk on the HF diet, C57BL/6J mice became unresponsive to ip leptin. C57BL/6J mice responded to intracerebroventricular leptin at these time points but developed peripheral resistance to sympathetic stimulation of retroperitoneal white adipose tissue. In contrast, intracerebroventricular leptin was fully effective in A/J mice, reproducing the complete profile of responses observed in weanling mice. A/J mice were also partially responsive to ip leptin at both time points, increasing uncoupling protein 1 mRNA expression in brown adipose tissue and decreasing leptin mRNA in white adipose tissue. The findings indicate that retention of leptin responsiveness is an important component of the ability of A/J mice to mount a robust adaptive thermogenic response and resist diet-induced obesity.     

Effects of sphingolipid synthesis inhibition on cholesterol gallstone formation in C57BL/6J mice

Background: Sphingolipids play a very important role in cell membrane formation, signal transduction and plasma lipoprotein metabolism. The first rate‐limiting step in the sphingolipid biosynthetic pathway is catalyzed by serine palmitoyltransferase (SPT), and myriocin is a potent and specific inhibitor of SPT. We investigated the impact of SPT inhibition on cholesterol gallstone formation in C57BL/6J mice. Methods: Three groups of eight‐week‐old C57BL/6J mice were utilized. Each group consisted of 20 mice; group A, B, and C were fed normal chow, lithogenic diet with phosphate buffered saline, and lithogenic diet with myriocin (0.3 mg/kg), respectively, for 6 weeks. The ceramide levels in both serum and bile were assessed by high performance liquid chromatography analysis. Protein expression of ERK, JNK and p38 in the extracted gallbladder were determined by Western‐blot analysis. Results: Myriocin treatment caused a significant decrease in the rate of cholesterol gallstone formation. The lithogenic diet mice (group B) showed the highest ceramide activities in both the serum and bile among all the tested groups and there was significant suppression of the ceramide levels in both the serum and bile of the myriocin‐treated mice (group C, p < 0.05). Phosphorylation of p38 in the gallbladder was increased in the lithogenic‐diet mice and the expression of phosphorylated p38 was significantly suppressed in the myriocin treated mice. Conclusions: SPT inhibition by myriocin suppressed gallstone formation and the levels of ceramide in both the serum and bile. p38 in the cellular signaling pathways might be associated with cholesterol gallstone formation.     

Effects of topiramate on ethanol and saccharin consumption and preferences in C57BL/6J mice

BACKGROUND: Topiramate has recently been found to be more effective than placebo as an adjunct treatment for alcohol dependence, but it has not yet been investigated in animal models of ethanol consumption. The current experiment examined the effects of topiramate on ethanol drinking in mice using a continuous access, two-bottle choice procedure. METHOD: C57BL/6J male mice were offered a 10% v/v ethanol solution versus tap water over 4 consecutive days per week. Mice were assigned to topiramate (1-50 mg/kg) or saline groups and received injections before the beginning of the dark phase of the light cycle. Topiramate dose increased over 5 successive weeks (1, 5, 10, 25, and 50 mg/kg). Fluid intake was measured 2, 4, and 23 hr after injection. Body weight and food intake were measured at the time of injection. In a second phase, mice were offered saccharin solutions (0.2 and 2.5% w/v) versus tap water after topiramate (50 mg/kg) or saline injections. RESULTS: Results revealed that high topiramate doses (25 and 50 mg/kg) increased water intake and decreased ethanol preference. Compared with saline controls, topiramate produced dose-dependent, bidirectional effects on ethanol dose, with 25 mg/kg of topiramate increasing ethanol dose at 4 and 23 hr after injection but 50 mg/kg topiramate decreasing ethanol dose at 2 hr after injection. During saccharin exposure, topiramate decreased saccharin preference (for 2.5% w/v saccharin solution) and marginally increased water intake but did not directly alter intake of the saccharin solutions. Topiramate had no effects on body weight or daily food intakes. CONCLUSIONS: Topiramate reduced ethanol preference in C57BL/6J mice, but this effect was primarily attributable to elevated water intake. Topiramate also reduced saccharin preference, likely through marginally significant increases in water intake. Increases in water intake and bidirectional effects of topiramate on ethanol dose complicate conclusions with regard to the effects of topiramate on ethanol reward.