自发2型糖尿病模型OLETF大鼠肾周脂肪组织水通道蛋白7的表达

目的:观察自发2型糖尿病动物模型OLETF(Otsuka Long-Evans Tokushima Fatty)大鼠不同糖尿病病程阶段肾周脂肪组织水通道蛋白7 mRNA和蛋白表达的变化,探讨其在肥胖和糖尿病发生中的作用.方法:以OLETF大鼠30只为实验组,同种系非糖尿病LETO(Long-Evans Tokushima Otsuka)大鼠18只为正常对照.8周(基线)时两组大鼠各处死6只.随后OLETF大鼠分为末治疗组(OLETF组)12只及盐酸二甲双胍治疗组(OLETF/M组)12只.观察各组大鼠8、18、28周时的体重、血清甘油三酯、胆固醇、丙三醇、葡萄糖耐量试验的血糖与胰岛素水平以及肾周脂肪组织水通道蛋白7(aquaporin7,AQP7)mRNA和AQP7蛋白含量的变化.用Real-time PCR测定AQP7mRNA水平,Western blotting测定AQP7蛋白含量.结果:(1)OLETF组18周均发展为糖尿病[60分钟血糖(25.67±6.78)mmol/L,120分钟血糖(16.19±2.98)mmoL/L].OLETF组大鼠随周龄增加,其体重、血糖、胰岛素、血清甘油三酯均明显增加.血清丙三醇水平先增高后下降,8、18和28周的水平分别为(52.61±11.80)、(156.03±39.56)和(130.84±25.46)μmol/L.(2)OLETF/M组18周时达糖尿病标准[60分钟血糖(18.64±6.67)mmol/L,120分钟血糖(14.13±5.21)mmoL/L],但血糖水平低于OLETF组;28周时血糖下降均恢复为糖耐量异常[60分钟血糖(11.72 ±3.06)mmol/L,120分钟血糖(12.42±2.30)mmol/L].OLETF/M组的甘油三酯、胆固醇和丙三醇浓度较OLETF组降低.OLETF/M组与OLEFT组比较具体值为:甘油三酯18周(0.88±0.14)vs.(1.09 ±0.44)mmol/L,28周(1.06±0.51)vs.(2.20±1.51)mmol/L;胆同醇18周(2.18±0.14)vs.(2.30±0.21)mmol/L,28周(1.90±0.19)vs.(2.36±0.35)mmol/L,P<0.05;丙三醇18周(77.28±9.06)vs.(156.03±39.56)μmol/L,P<0.05,28周(58.44±14.03)vs.(130.84±25.46)μmol/L,P<0.01.(3)增加肾周脂肪组织AQP7 mRNA及蛋白表达:随周龄及肥胖增加,18及28周OLETF组AQP7 mRNA表达较同组8周龄大鼠分别上调了67.5%和41.7%,AQP7蛋白表达较同组8周龄大鼠分别上调了21.9%和8.9%;18及28周OLETF/M组AQP7 mRNA表达较同组8周龄大鼠分别上调了25%及8.3%,AQP7蛋白表达较同组8周龄大鼠分别上调了14.6%及1.6%.OLETF及OLETF/M组均呈先增高而后下降的趋势,于18周时增高,28周下降,与血清丙三醇变化趋势一致.OLETF/M组AQP7 mRNA及蛋白表达水平低于同周龄OLETF组,但两组差异无统计学意义.OLETF/M组的体重、胰岛素与OLETF组差异无统计学意义.OLETF/M组AQP7 mRNA及蛋白表达水平低于同周龄OLETF组,但两组差异无统计学意义.结论:内脏脂肪AQP7参与了糖脂代谢,与2型糖尿病和肥胖发病相关.二甲双胍可改善OLETF大鼠的脂代谢和糖代谢紊乱,但对AQP7 mRNA及蛋白表达未见明显影响.     

Glucose transporter levels in a male spontaneous non-insulin-dependent diabetes mellitus rat of the Otsuka Long-Evans Tokushima Fatty strain

Otsuka Long-Evans Tokushima Fatty (OLETF) rats are a new strain of spontaneous non-insulin-dependent diabetes mellitus (NIDDM) models. To evaluate the role of glucose transporters (GLUT) in the development of diabetes in this model, we examined the action of insulin on the translocation of GLUT4 and GLUT1 in isolated adipocytes, and the GLUT4 protein levels in muscles. Long-Evans Tokushima Otsuka (LETO) rats were used as a control strain. In adipocytes, the GLUT4 protein levels in OLETF rats at 30 weeks of age (diabetic stage) were considerably lower than those in LETO rats at the same age. At a pre-diabetic stage (7 weeks), there were no significant differences in GLUT4 protein levels in adipocytes between LETO and OLETF rats. However, the degree of GLUT4 translocation in OLETF rats was lower than that in LETO rats at 7 weeks of age. There were no differences in GLUT1 levels in adipocytes between the two strains. In muscles, the decrease in GLUT4 protein was observed in OLETF rats at 30 weeks of age. Whether such a difference is under the influence of hyperglycemia was also examined using rats rendered diabetic by 70% pancreatectomy. OLETF rats aged 7 weeks were subjected to partial pancreatectomy (Px) and sham pancreatectomy (sham). At 4 weeks after surgery, GLUT4 protein levels in adipose tissues and skeletal muscles were determined. GLUT4 decrease was observed for both tissues of hyperglycemic Px rats compared with euglycemic sham. Moreover, we examined the direct effect of glucose on GLUT4 protein using primary cultured adipocytes of OLETF rats at 5 weeks of age. After 7-day culture with normal (5.6 mmol/l) or high (25 mmol/l) concentrations of glucose, the GLUT4 protein levels in adipocytes decreased at 25 mmol/l glucose compared with 5.6 mmol/l glucose. These findings suggest an early defect in the insulin resistance of OLETF rats probably reflects impaired GLUT4 translocation. The GLUT4 decrease, which occurs later in the process appears to be a consequence, rather than a cause of diabetes in OLETF rats.     

Attenuation of early hyperglycaemia induced by streptozocin in fasting rats

Early hyperglycaemia induced by streptozocin was studied in fasting rats. It was found that the early hyperglycaemia was attenuated, the hypoglycaemia was prolonged, and the initiation of the permanent hyperglycaemia was delayed. The early hyperglycaemia induced by streptozocin was further attenuated in carbon tetrachloride pretreated fasting rats. It was speculated that the appearance of the early hyperglycaemia was liver related.     

Increased intestinal absorption of cefixime by nifedipine in the rat intestinal perfusion model: evidence for a neural regulation

In healthy volunteers, the simultaneous administration of nifedipine and cefixime has been shown to increase the oral absorption of the antibiotic. To investigate the pharmacological basis of this interaction, we used an in situ intestinal perfusion technique in the rat. pH 5.5 yielded optimum cefixime absorption, which was greater in segments from the duodenojejunum than in those from the jejunoileum. Cefixime absorption was similar when perfused at 0.5 and 1.0 mg/ml, suggesting transport saturation at the lower concentration. Cefixime arterial and portal blood concentrations after an intestinal perfusion of 0.5 mg/ml cefixime were significantly increased by a previous 15-min intestinal perfusion of 0.05 mg/ml nifedipine. Nifedipine did not significantly alter intestinal blood flow. At the end of the cefixime perfusion, intestinal blood flow was higher in the nifedipine group than in the control group (0.44 +/- 0.12 vs. 0.26 +/- 0.09 ml.min-1.g of intestine wt-1, respectively), although the difference did not reach statistical significance. The absorption kinetics of salicylic acid, which is strictly absorbed by passive diffusion, were unaffected by nifedipine. After 15 and 50 min of recirculation, residual salicylate levels fell from 85.1 +/- 5.6% to 57.1 +/- 2.8% with nifedipine compared with 87.4 +/- 1.4% to 52.8 +/- 1.6% without nifedipine. Thus, the improvement in cefixime absorption by nifedipine was not secondary to increased local blood flows or to induced passive diffusion mechanisms. Nifedipine did not affect intestinal motility. The action of nifedipine appears to indirect, involving a neural regulation, because any increase in cefixime absorption was prevented by tetrodotoxin and hexamethonium administration.     

Enhancement of intestinal water absorption and sodium transport by glycerol in rats

Advances in screening technologies allowing the identification of growth factor receptors solely by virtue of DNA or protein sequence comparison call for novel methods to isolate corresponding ligand growth factors. The EPH-like receptor tyrosine kinase (RTK) HEK (human EPH-like kinase) was identified previously as a membrane antigen on the LK63 human pre-B-cell line and overexpression in leukemic specimens and cell lines suggested a role in oncogenesis. We developed a biosensor-based approach using the immobilized HEK receptor exodomain to detect and monitor purification of the HEK ligand. A protein purification protocol, which included HEK affinity chromatography, achieved a 1.8 X 10(6)-fold purification of an approximately 23-kDa protein from human placental conditioned medium. Analysis of specific sHEK (soluble extracellular domain of HEK) ligand interactions in the first and final purification steps suggested a ligand concentration of 40 pM in the source material and a Kd of 2-3 nM. Since the purified ligand was N-terminally blocked, we generated tryptic peptides and N-terminal amino acid sequence analysis of 7 tryptic fragments of the S-pyridylethylated protein unequivocally matched the sequence for AL-1, a recently reported ligand for the related EPH-like RTK REK7 (Winslow, J.W., Moran, P., Valverde, J., Shih, A., Yuan, J.Q., Wong, S.C., Tsai, S.P., Goddard, A., Henzel, W.J., Hefti, F., Beck, K.D., & Caras, I.W. (1995) Neuron 14, 973-981). Our findings demonstrate the application of biosensor technology in ligand purification and show that AL-1, as has been found for other ligands of the EPH-like RTK family, binds more than one receptor.     

Studies on the relative biopotencies and intestinal absorption of different apo-beta-carotenoids in rats and chickens

1. The biopotencies relative to beta-carotene of several apocarotenoids, such as 8'-, 10'- and 12'-apo-beta-carotenal and methyl 8'-apo-beta-carotenoate, were investigated in rats, on a molar basis, by both curative-growth assay and liver-storage tests. 2. In the curative-growth assays, on a molar basis the biopotencies of 8'-, 10'- and 12'-apo-beta-carotenal and methyl 8'-apo-beta-carotenoate were 72, 78, 72 and 53% respectively, whereas on a weight basis the corresponding values were 93, 111, 111 and 63%, with respect to beta-carotene taken as 100%. In terms of yield of vitamin A, these values were much lower in the liver-storage tests. 3. When 8'-apo-beta-carotenal was fed, the unchanged aldehyde together with small amounts of the corresponding alcohol and larger proportions of the acid rapidly appeared in the tissues of both rats and chickens. The 8'-apocarotenol, 8'-apocarotenoic acid and its methyl ester were absorbed unchanged. The free acid disappeared most rapidly from the tissues, but its methyl ester persisted in the tissues longest. 4. On the basis of these observations it is suggested that most of an apocarotenal is oxidized to the corresponding acid, which, in turn, is mostly degraded to retinoic acid, with small proportions of it being attacked by the dioxygenase system giving retinal.     

Localization of the septal rage syndrome in Long-Evans rats.

Used lesion methods to study the anatomical localization of the septal rage syndrome in 38 male hooded Long-Evans rats. Previous studies have attributed this syndrome to incidental damage of structures peripheral to the septal nuclei, to the stria terminalis, and to the central core of the septal structures. Lesions were systematically varied so as to destroy different parts of the septum. Analyses show that the dorsal nuclei and structures of the anterior septal area mediate mechanisms pertaining to septal rage. Lesions of the posterior septal area resulted in rage scores that were similar to those of control Ss. (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition of the intestinal absorption of iron by sodium alginate and guar gum in rats

Na-alginate as well as guar gum inhibit the absorption of a 59Fe-labelled iron dose (360 nmol) from tied-off jejunal segments of either normal or iron-deficient rats. In order to inhibit the absorption of the iron dose by half as compared with normal rats to which ionized iron was administered 1.2--8 mg of guar gum and 8-30 mg Na-alginate was necessary. In iron-deficient rats the highest dose dose of Na-alginate tested, 100 mg, inhibited the absorption of iron by about 20%; the highest dose of guar gum, 30 mg, inhibited the amount of iron absorbed by about 25%. An artificial diet containing 10% of either guar gum and Na-alginate fed for 3 days inhibited the absorption of iron in normal but not in iron-deficient rats. Also, in these experiments guar gum proved to be more effective than Na-alginate.     

The effect of the live weight of rats on the intestinal in vitro absorption of nickel using everted intestinal sacs

The influence of the live weight of the experimental animals on the Ni absorption was investigated in vitro with everted sacs from rats. Totally 75 male rats in the live weight range from 30 to 250 g were used. With increasing live weight the Ni uptake by the intestinal wall and the Ni transfer across the intestinal wall decreased significantly. Ni transfer was already significantly reduced by 45% when body weight increased from 30 to 60 g. For the animals with a live weight above 200 g Ni transfer reached only about 10% of the Ni transfer measured for the animals with 30 g live weight. The decline of the Ni uptake by the intestinal wall was only slightly in the live weight range from 30 to 150 g. Within the live weights higher than 190 g Ni uptake by the intestinal wall decreased significantly to about 25% compared to the animals with 30 g live weight.     

Inhibitory mechanisms of oleanolic acid 3-O-monodesmosides on glucose absorption in rats

We examined the action mechanism of oleanolic acid 3-O-monodesmoside, momordin Ic (1), and oleanolic acid 3-O-glucuronide (2) for the inhibitory effect on the increase in serum glucose levels in oral glucose-loaded rats. Although 1 and 2 dose-dependently inhibited the increase in serum glucose levels in oral glucose-loaded rats, these compounds showed no significant effects on serum glucose levels in normal rats, intraperitoneal glucose-loaded rats, and alloxane-induced diabetic mice. Furthermore, 1 and 2 were found to suppress gastric emptying in rats, and also to inhibit the glucose uptake in rat small intestine concentration dependently in vitro. These results indicate that 1 and 2 given orally have neither insulin-like activity nor insulin releasing-activity. 1 and 2 apparently inhibited glucose absorption by suppressing the transfer of glucose from the stomach to the small intestine and by inhibiting the glucose transport system at the small intestinal brush border.     

Spontaneous glucose intolerance in the progeny of low dose streptozotocin-induced diabetic mice

Multiple low doses of streptozotocin (LDS) induce low-incidence diabetes mellitus in Balb/cHan and high-incidence diabetes in CD-1 mice. We studied offspring of diabetic parents in both strains. Group 1 consisted of litters from control mice with no streptozotocin treatment. Group 2 litters had an LDS diabetic mother and a control father, group 3 litters had control mother with LDS diabetic father, and group 4 litters had both, LDS diabetic mother and father. Diabetes was induced by 5 x 40 mg streptozotocin per kg on five consecutive days. Progeny of diabetic mothers showed a state of reduced glucose tolerance associated with reduced glucose disappearance during intravenous glucose tolerance test and increased insulin secretion of isolated islets of Langerhans. These metabolic abnormalities predominated in the male litters of both strains of mice. Amniotic insulin was increased in diabetic mothers during pregnancy. No histologic abnormalities were observed in group 2 progeny. Pancreases in male offspring of LDS diabetic CD-1 fathers (group 3) were studied for insulitis. Insulitis was found in 40% of mice with normal glucose tolerance. A single subdiabetogenic dose of streptozotocin (40 mg/kg) induced insulitis in 90% of pancreases accompanied by reduced insulin release of isolated islets. By contrast, male Balb/cHan progeny of diabetic fathers failed to develop insulitis. In conclusion, we found (1) parental LDS diabetes was transmitted more often to male offspring, (2) maternal LDS diabetes was associated with hyperinsulin secretion and glucose intolerance in the offspring and (3) paternal LDS diabetes was accompanied by insulitis and insulin secretion deficiency in CD-1 progeny.     

Source and amount of carbohydrate affect postprandial glucose and insulin in normal subjects

To determine if source and amount of carbohydrate affected postprandial glucose and insulin responses, seven nondiabetic subjects consumed 0, 25, 50, 75 or 100 g carbohydrate (total carbohydrate minus total dietary fiber) portions of barley, spaghetti, bread or potato. By ANOVA, both source and amount of carbohydrate had significant effects on incremental response areas for capillary glucose (P = 0.001), plasma glucose (P = 0.01) and plasma insulin (P = 0.03), but there was no source x amount interaction. By regression analysis, source of carbohydrate explained a similar amount of the variability of glucose and insulin responses, 46-64%, as the amount of carbohydrate, 47-57%. Together, carbohydrate source and amount accounted for 85-94% of the variability of mean glucose and insulin responses. We conclude that, for individual foods with different glycemic indices, both source and amount of carbohydrate influence the postprandial glucose and insulin responses of nondiabetic subjects.     

MR images of the hepatocellular carcinoma in Long-Evans cinnamon (LEC) rats

Long-Evans Cinnamon (LEC) rats which have an abnormal copper accumulation in the liver develop hereditary hepatitis and subsequent hepatocellular carcinoma (HCC). We studied the correlation of MR images of the HCCs developed in LEC rats and histopathological features. The HCCs of LEC rats had high intensity on T 1-weighted images and iso-low intensity on T 2*-weighted images. Histopathological examination showed that the HCCs were highly differentiated. Copper concentration in the HCCs was lower than that in the surrounding non-cancerous liver tissues. From these results, we suggest that copper accumulation may not be responsible for the high intensity of HCCs on T 1-weighted images.     

Influence of obstructive jaundice on jejunal absorption of glucose, electrolytes, and vitamin A in rats

Jejunal absorption of glucose, electrolytes, and vitamin A was investigated in rats. A Tyrode solution containing glucose, sodium, and potassium in concentrations two and four times higher than usual was infused through the jejunal loops of jaundiced and control rats during 40 min. The glucose values in the influx and effluent were not different during the experiment time. However, the concentrations of sodium and potassium of the effluent decreased with concentrations twice normal. The osmotic pressure of the effluent was directly related to the electrolytic concentration. When the perfusate fluid was four times higher, the differences between sham and jaundiced groups remained unchanged. The osmotic pressure means of the jaundiced group decreased during the experimental time. The absorption of vitamin A increased during the 40-min experiment time in the control rats. On the other hand, vitamin A concentration in the perfused lumen of the jaundiced group did not change over the time. These data indicate that obstructive jaundice has little influence on glucose and electrolytes absorption, while vitamin A is impaired by this condition.     

Ultrasonographic manifestations of carotid atherosclerosis and glucose intolerance in elderly eastern Finnish men

OBJECTIVE: To study the association of ultrasonographic manifestations of common carotid atherosclerosis with glucose intolerance in survivors of the cohort of men born in 1900-1919 in eastern Finland. RESEARCH DESIGN AND METHODS: Carotid ultrasonography was carried out for 182 men in 1989. Glucose tolerance status classified based on an oral glucose tolerance test in 1984 and 1989 surveys was used in both prospective and cross-sectional analyses. RESULTS: Carotid atherosclerosis was common in men aged 70-89 years. There was no significant difference in the maximal carotid intimal-medial thickness between diabetic and nondiabetic men and over different age-groups; it was 1.28, 1.33, and 1.36 mm in subjects with diabetes, impaired glucose tolerance, and normal glucose tolerance, respectively (P = 0.69). No association between the presence of a nonmineralized or a mineralized atherosclerotic lesion with diabetes was found. Fasting plasma insulin did not relate to ultrasonographically detectable atherosclerotic lesions. CONCLUSIONS: Hyperglycemia and hyperinsulinemia may not be main contributors to atherosclerosis in elderly men, partly because smoking is less common and total and LDL cholesterol concentrations are lower in diabetic men than in men with normal glucose tolerance.     

Contribution of luminal concentration of nutrients and osmolality to postprandial intestinal hyperemia in dogs

Intestinal blood flow is increased during digestion. This study assesses if the concentration of nutrients and/or osmolality of chyme in the intestinal lumen are factors determining the hyperemia. Six digested food mixtures containing different concentrations of nutrients and/or having different osmolalities were placed into the jejunal lumen, and their effects on local venous outflow compared. The 100% (999 mOsm/kg), 33% (291 mOsm/kg), and 20% (183 mOsm/kg) food mixtures all increased flow, but the 10% food mixture (94 mOsm/kg) did not. The hyperemic effect of 33 and 20% food was similar, but 100% food produced a greater increase in flow than did 33 or 20% food. Luminal placement of a 30% solution of a nonabsorbable substance polyethylene glycol (1000 mOsm/kg) did not alter flow. Also, the vascular effects of 20 or 10% food mixtures were not altered when these mixtures were made isotonic by the addition of NaCl. These studies indicate that lumen osmolality, within a range of 180 to 1000 mOsm/kg, is not a significant factor contributing to the local hyperemia occurring when nutrients are in the gut lumen. However, the concentration of nutrients in the lumen is a factor determining the local hyperemia.     

Clearance of postprandial and lipolytically modified human HDL in rabbits and rats

Triglyceride (TG) enrichment of high density lipoproteins (HDL) in hypertriglyceridemic states renders the particles vulnerable to lipolysis, which reduces their size. In the present study we modified the size and composition of HDL in vivo in hypertriglyceridemic humans by administering a bolus of intravenous heparin, and tested the subsequent clearance of the isolated HDL particles in rabbits and rats. HDL was isolated by ultracentrifugation from 21 moderately hypertriglyceridemic humans, 5 h after ingestion of a high fat meal and then 15 min after an intravenous heparin bolus (60 U/kg). Postprandial large TG-rich preheparin HDL and small, TG-poor postheparin HDL were labeled with either 125I or 131I. The clearance of apoA-I associated with each HDL tracer was determined by injecting the tracers 1) simultaneously (n = 13) and 2) sequentially (n = 8) into male New Zealand White rabbits, an hepatic lipase-deficient animal, and 3) by injecting the tracers simultaneously into male Sprague-Dawley rats (n = 8), an animal that has hepatic lipase. Die-away curves of each radiolabeled tracer were analyzed using a two-pool model that assumes the existence of an intravascular pool in dynamic equilibrium with an extravascular pool. In the rabbit studies, the fractional catabolic rate (FCR) of small, postheparin TG-poor HDL was greater than the FCR of the larger TG-rich HDL (11% greater in the simultaneous study, P < 0.001, and 45% greater in the sequential study, P < 0.001). Opposite results were observed in rats as large TG-rich preheparin particles showed a greater FCR (1.8-fold) than smaller TG-poor postheparin HDL (P < 0.05). These data suggest that although size and composition of HDL can influence its catabolism, the effect is not always in the same direction and depends on other factors present in vivo.