Influence of spontaneous diabetes on tissue status of zinc, copper, and manganese in the BB Wistar rat

The concentrations of zinc, copper, and manganese in liver, kidney, duodenum, pancreas, testes, bone, and serum from control and untreated, spontaneously diabetic BB Wistar rats were compared. Chronic insulin deficiency resulted in significant alterations in the concentrations of one or more of these essential micronutrients in several tissues. The amounts of zinc and copper bound to metallothionein in the liver and kidney of untreated spontaneously diabetic rats were also markedly increased. The tissue trace metal status in diabetic rats was altered similarly in both male and female rats. Daily injections of insulin blocked many of the changes in the tissue concentrations of the metals. The effects of spontaneous diabetes on tissue trace metal status are quite similar to those reported for chemically induced diabetes. Thus, these results demonstrate that chronic endocrine imbalance is responsible for a series of tissue specific changes in the transport and metabolism of zinc, copper, and manganese.     

Elevated hypothalamic norepinephrine content in mice with the hereditary obese-hyperglycemic syndrome.

There is evidence that hypothalamic norepinephrine (NE) plays a role in the control of appetite in the rat. Using specific and sensitive radioenzymatic assays, we determined if there was a difference in the tissue (hypothalamus, cerebral cortex and kidney) concentration of NE or of dopamine (DA) in mice with the hereditary obese-hyperglycemic syndrome (ob/ob) and their normal weight littermates, both when they were in the rapid growth phase (2--3 months of age) and when they were mature (6--7 months of age). The concentration of NE was similar in the cerebral cortex of obese and normal mice and in the kidneys of obese and normal mice. The concentration of DA was similar in the hypothalamus of obese and normal mice. The concentration of DA was similar in the hypothalamus of obese and normal mice and in the cerebral cortex of obese and normal mice. These observations support the concept that alterations in hypothalamic NE may play a role in the obesity of ob/ob mice.     

Somatomedin-C in the kidney of streptozotocin diabetic rats

To evaluate the possible role of somatomedin-C, insulin-like growth factor I, in renal hypertrophy in early diabetes, kidney tissue SmC concentrations were measured in streptozotocin-induced (80 mg/kg ip) diabetic rats. Body weight, liver weight, plasma SmC concentration, and SmC concentration in the liver of diabetic rats were significantly lower than those of controls. Seven days after induction of diabetes, the kidney weight (898 +/- 95 mg) in diabetic rats was significantly greater than that in controls (755 +/- 69 mg), while SmC concentration in the kidney of diabetic rats (1.7 +/- 0.3 U/g kidney) was significantly lower than that of control rats (5.4 +/- 0.6 U/g kidney). These results suggest that renal SmC may not have an important role in renal hypertrophy in early stages of diabetes and that renal production of SmC may be impaired by insulin deficiency in rats.     

Streptozotocin-induced diabetes produces alterations in adenylate cyclase in rat cerebrum, cerebral microvessels and retina

Eight weeks following streptozotocin-induced diabetes mellitus in rats, the sensitivity of adenylate cyclase to dopamine (DA) and norepinephrine (NE) was reduced in homogenates of retina. Furthermore, the activation of adenylate cyclase in cerebral microvessels (capillaries) by NE, 5'-guanylyl imidodiphosphate (alone or with NE) and forskolin was reduced in diabetic rats versus appropriate controls. In diabetic rats enzyme sensitivity to only NE was attenuated in homogenates of cerebral cortex and cortical piaarachnoid. No differences between controls and diabetics were noted with respect to guanylate cyclase or cyclic AMP phosphodiesterases. The damage observed in retina and microvessels may play an important pathogenic role in diabetes-induced blindness and stroke.     

Insulin prevention of impaired renal calcium transport in alloxan-diabetic rats

The uptake of calcium-45 was measured in slices of kidney cortex from rats with alloxan-diabetes of increasing durations. Slices from untreated diabetic rats had significantly lower slice-to-medium ratios for calcium than did slices from control rats, reflecting decreased uptake of calcium by cortical slices from diabetic rats. Institution of daily insulin therapy immediately upon confirmation of diabetes prevented this depression of calcium uptake, even though the insulin therapy was insufficient to control blood glucose levels. After four weeks of untreated alloxan-diabetes, insulin therapy did not return calcium uptake by kidney cortex slices to control levels.     

Guanylate cyclase activity in rat liver and other tissues with starvation and streptozotocin-induced diabetes mellitus.

Guanylate cyclase activities in supernatant and particulate fractions of homogenates from various rat tissues were examined in fed and fasted normal animals and in those with diabetes mellitus induced with streptozotocin. With fasting guanylate cyclase activity in supernatant fractions increased in liver and epididymal fat, decreased in kidney and lung, and was unchanged in cerebral cortex and skeletal muscle. Lung particulate activity also decreased with fasting while particulate activities in other tissues were unchanged. In diabetic animals soluble but not particulate activity was less in several tissues and the effect of fasting on soluble liver guanylate cyclase was absent. The effect of fasting on soluble liver guanylate cyclase reversed with refeeding animals and was associated with a decrease in the apparent K_m for GTP as well as an increase in V. An inhibitory material was found in livers from fed but not fasted animals. The inhibitory material had properties of a nucleotide and inhibited guanylate cyclase in a competitive manner. Thus, soluble and particulate guanylate cyclase activities can be influenced independently of one another in the same and different tissues with fasting, refeeding, and diabetes mellitus. Some of these effects may be attributable to altered levels of small heat-stable inhibitory materials such as nucleotides.     

Serum, liver, and kidney proteomic analysis for the alloxan-induced type I diabetic mice after insulin gene transfer of naked plasmid through electroporation

Gene therapy has been reported to be effective in treating diabetes mellitus (DM), while little has been found out about the functional protein changes since. The liver and kidney play important roles in glucose absorption, metabolism, and excretion. Changes in the two organs may reflect pathologic alterations during DM, while the serum has a direct connection with most organs and pathological changes. We used alloxan to induce diabetic mice, electrotranferred the insulin gene into their sural muscles, and discovered that their blood glucose decreased to normal level. Consequently, proteomic approaches were applied to evaluate protein changes in the liver, kidney, and serum of normal, diabetic, and gene transferred mice. Forty-three proteins were found either up-regulated or down-reglulated in the liver, kidney, and serum of the alloxan-induced type I diabetic mice. Only five proteins in the liver, five proteins in the kidney, and seven proteins in the serum of diabetic mice were found to be back-regulated to normal levels after gene transfer. These back-regulated proteins are involved in lipid and glucose metabolism, associated with phosphorylation, signal transduction, oxidation, and immune inflammation. Our findings might promote a better understanding for the mechanism of DM, and provide novel targets for estimating the effects of gene therapy.     

Effect of short- and long-term diabetes on carnitine and myo-inositol in rats.

1. The effect of short- (2 wk) and long-term (20 wk) streptozotocin diabetes was studied on urine, blood, liver, heart, brain, skeletal muscle, pancreas and kidney concentrations of acid-soluble carnitine and free myo-inositol. 2. Short-term diabetic rats excreted significantly higher concentrations of carnitine as well as myoinositol than normal rats. Blood carnitine and myo-inositol were not different between normal and diabetic rats. Diabetes caused a decrease in liver, brain and pancreatic carnitine, but not in heart, skeletal muscle and kidney. Myo-inositol concentration was decreased in liver, heart and kidney but not in brain, pancreas and skeletal muscle. 3. Long-term diabetic rats had higher urinary excretions of both carnitine and myo-inositol. Blood carnitine did not change; however, myo-inositol was higher in diabetic than in normal rats. Diabetes caused a significant increase in liver and a decrease in heart, brain, skeletal muscle and pancreatic content of carnitine; no difference in kidney carnitine was noted. Myo-inositol content was elevated only in liver of diabetic rats. 4. We suggest that carnitine and myo-inositol concentrations are influenced both by short- and long-term diabetes through changes in tissue metabolism.     

Insulin resistance and the metabolism of branched-chain amino acids in humans

Peripheral resistance to insulin action is the major mechanism causing the metabolic syndrome and eventually type 2 diabetes mellitus. The metabolic derangement associated with insulin resistance is extensive and not restricted to carbohydrates. The branched-chain amino acids (BCAAs) are particularly responsive to the inhibitory insulin action on amino acid release by skeletal muscle and their metabolism is profoundly altered in conditions featuring insulin resistance, insulin deficiency, or both. Obesity, the metabolic syndrome and diabetes mellitus display a gradual increase in the plasma concentration of BCAAs, from the obesity-related low-grade insulin-resistant state to the severe deficiency of insulin action in diabetes ketoacidosis. Obesity-associated hyperinsulinemia succeeds in maintaining near-normal or slightly elevated plasma concentration of BCAAs, despite the insulin-resistant state. The low circulating levels of insulin and/or the deeper insulin resistance occurring in diabetes mellitus are associated with more marked elevation in the plasma concentration of BCAAs. In diabetes ketoacidosis, the increase in plasma BCAAs is striking, returning to normal when adequate metabolic control is achieved. The metabolism of BCAAs is also disturbed in other situations typically featuring insulin resistance, including kidney and liver dysfunction. However, notwithstanding the insulin-resistant state, the plasma level of BCAAs in these conditions is lower than in healthy subjects, suggesting that these organs are involved in maintaining BCAAs blood concentration. The pathogenesis of the decreased BCAAs plasma level in kidney and liver dysfunction is unclear, but a decreased afflux of these amino acids into the blood stream has been observed.     

Effect of diabetes on natriuresis in the presence of ouabain and ethacrynic acid in perfused rat kidney

1. The effect of diabetes on renal sodium retention was investigated. 2. The technique involved retrograde perfusion from the renal veins via the kidneys, and then through the renal arteries and dorsal aorta. 3. Sodium retention by diabetic rat kidney was 58% lower than that in the normal rats. 4. Ouabain (15 mM) in perfusate increased sodium retention by 30% in normal rat kidney as compared to a 54% increase in diabetic rat kidney. 5. Ethacrynic acid (1 mM) in perfusate resulted in a 42% reduction in sodium retention in the normal rat kidney as compared to a 43% decrease in the diabetic rat kidney. 6. Control of hyperglycemia in diabetic rats with insulin therapy resulted in sodium retention that is not significantly different from that of normal rats. 7. The results suggest that diabetes has no effect on the peritubular ouabain-sensitive Na--K-ATPase pump, or the luminal ethacrynic acid-sensitive Na-K counter transport pump. Furthermore, the data suggest a reversible effect of diabetes on sodium retention during insulin therapy.     

Streptozotocin-induced diabetes increases γ-glutamyltranspeptidase activity but not expression in rat liver

Earlier work describing increased biliary excretion of the acetaminophen-cysteine conjugate advanced the hypothesis that streptozotocin-induceddiabetes increases <γ > -glutamyltranspeptidase (GGT) expression in Sprague–Dawley rats. To test this hypothesis, rats were divided into control, diabetic, and insulin-treated diabetic groups. Diabetes was induced by intravenous injection of 45 mg streptozotocin/kg body weight and was effectively controlled by insulin treatment in the appropriate group. Densitometric quantification demonstrated that hepatic GGT activity in diabetic rats was significantly increased when compared to normal and insulin-treated diabetic controls. Histochemical staining of liver was greater in female than in male rats, and staining increased in female rat liver as the duration of diabetes lengthened from 30 to 90 days. GGT activity was increased by diabetes in liver canalicular-enriched and basolateral-enriched membrane preparations, and it was unchanged in renal brush border-enriched membranes. Total mRNA isolated from diabetic and insulin-treated diabetic rat livers did not conclusively demonstrate an elevation of GGT mRNA relative to normal. Western blot analysis showed no differences in the amount of GGT in diabetic versus normal rat livers. These data indicate that streptozotocin-induced diabetes does not alter the expression of, but does increase the activity of, GGT in liver. © 1998 John Wiley & Sons, Inc. J Biochem Toxicol 12: 219–225, 1998     

Antioxidative enzymes in the liver and kidney of alloxan induced diabetic rats and their implications in cadmium toxicity

The influence of insulin-dependent diabetes mellitus on the oxidative stress caused by cadmium in the liver and kidney of laboratory rats has been studied. The results suggest that cadmium and alloxan diabetes independently promote lipid peroxidation in both liver and kidney. However, lipid peroxidation diminished in the diabetic rats fed cadmium. Administration of cadmium to normal and diabetic rats depleted glutathione in liver only. No significant change was observed in the activity of glutathione peroxidase in kidney, whereas administration of cadmium to diabetic rats stimulated catalase activity when compared to cadmium-fed rats. The actual mechanism of these effects still remains to be confirmed, but an antagonistic relationship between cytotoxic mechanisms of diabetes mellitus and cadmium is speculated upon. The insulin-dependent activity of a unique form of cytochrome 450j may be involved.     

不同性别大鼠在2型糖尿病造模过程中的稳定性

目的研究不同性别大鼠在2型糖尿病造模过程中的成功率及模型的稳定性。方法高糖高脂饮食联合腹腔注射小剂量链脲佐菌素诱导建立雄、雌性大鼠2型糖尿病模型。成模后所有大鼠每周固定时间测血糖和体重。观察24周后,心脏穿刺取血,测定空腹血糖（FPG）、血清胰岛素（FINS）、HbA1c、甘油三脂（TG）、胆固醇（TC）、高密度脂蛋白-胆固醇（HDL-C）、低密度脂蛋白-胆固醇（LDL-C）。结果单纯高糖高脂饮食喂养,雄、雌性大鼠血糖与正常组无显著差异;STZ注射后,雄性大鼠血糖升高并逐渐平稳,而雌性需两次STZ注射,模型才比较稳定。实验结束时,雄、雌性糖尿病大鼠FPG、FINS、HOMA-IR以及TG、TC、LDL-C均显著升高,说明模型存在胰岛素抵抗和脂代谢紊乱。结论高糖高脂饲料加一次性小剂量链脲佐菌素腹腔注射,可成功建立雄性大鼠2型糖尿病模型,而同等剂量,雌性模型需两次STZ。雄、雌性糖尿病大鼠模型具有高血糖、脂质代谢紊乱和胰岛素抵抗特点。造模成功率及稳定性与性别有关,雄性大鼠较雌性大鼠成模率高,稳定性好,且耗时更短。     

Changes in liver gangliosides in streptozotocin-induced diabetic rats

Diabetes mellitus is associated with various structural and functional liver abnormalities that affect the glycogen and lipid metabolisms. The effects of streptozotocin-induced diabetes and of insulin supplementation to Sprague-Dawley diabetic rats on ganglioside patterns in liver were determined. Diabetic livers showed a tendency to hepatomegaly 3 weeks after STZ-induction of diabetes. The concentration of total gangliosides in diabetic and non-diabetic livers was similar, but the concentration of total gangliosides in the liver of insulin-stabilized rats was slightly increased. Bidimensional TLC chromatographic analysis of gangliosides isolated from normal diabetic and insulin-stabilized diabetic livers showed quantitative and qualitative changes. In comparison with normal controls, the densitometric analyses of diabetic liver ganglioside patterns had increased amounts of GM3, GM1, GD1b, and GT1b gangliosides, while GM2 could not be detected. The hepatic ganglioside pattern of insulin-stabilized diabetic rats was partially restored, resembling the profile of normal rats. The activity of GalNAcT, GalT-2 and SialT-4 transferases was measured in liver microsomal fractions of the different groups of animals. Diabetic rats showed an increased activity of GalNAcT and a decrease in the activity of GalT-2 and SialT-4 compared with the controls. The enzymatic activities found in insulin-treated rats showed a tendency to return to the values observed in normal control animals. The results evidenced that streptozotocin-induced diabetes affects the liver ganglioside pattern and the ganglioside synthesis enzyme activity. The alterations found in ganglioside metabolism could represent one of the earliest changes associated with the diabetic pathology.     

Beta-endorphin concentrations in the hypothalamus, pituitary and plasma of streptozotocin-diabetic rats with and without insulin substitution therapy

The concentrations of beta-endorphin like immunoreactivity (beta-END) in the hypothalamus, pituitary and plasma were studied in rats of either sex, one month after induction of diabetes by single iv injection of streptozotocin. As controls, both normal and undernourished rats, weight-matched with diabetic rats, were used. Diabetic male and female rats had a marked depletion of beta-END stores in the hypothalamus and neurointermediate lobe (NIL) but not in the anterior pituitary. Depletion of beta-END was reversed to normal by insulin replacement therapy. Severe undernourishment was not as effective as diabetes to reduce beta-END stores in the hypothalamus and NIL. A significant reduction of beta-END was observed only in the NIL of undernourished female rats. Plasma beta-END and beta-lipotropin (beta-LPH) concentrations were not significantly altered in diabetic rats. These results indicate that the lack of insulin may affect beta-END synthesis in the hypothalamus and NIL.     

Effects of alpha-lipoic acid on biomarkers of oxidative stress in streptozotocin-induced diabetic rats

Increased oxidative stress and impaired antioxidant defense mechanisms are important factors in the pathogenesis and progression of diabetes mellitus and other oxidant-related diseases. This study was designed to determine whether alpha-lipoic acid, which has been shown to have substantial antioxidant properties, when administered (10 mg/kg ip) once daily for 14 days to normal and diabetic female Sprague-Dawley rats would prevent diabetes-induced changes in biomarkers of oxidative stress in liver, kidney and heart. Serum glucose concentrations, aspartate aminotransferase activity, and glycated hemoglobin levels, which were increased in diabetes, were not significantly altered by alpha-lipoic acid treatment. Normal rats treated with a high dose of alpha-lipoic acid (50 mg/kg) survived but diabetic rats on similar treatment died during the course of the experiment. The activity of glutathione peroxidase was increased in livers of normal rats treated with alpha-lipoic acid, but decreased in diabetic rats after alpha-lipoic acid treatment. Hepatic catalase activity was decreased in both normal and diabetic rats after alpha-lipoic acid treatment. Concentrations of reduced glutathione and glutathione disulfide in liver were increased after alpha-lipoic acid treatment of normal rats, but were not altered in diabetics. In kidney, glutathione peroxidase activity was elevated in diabetic rats, and in both normal and diabetic animals after alpha-lipoic acid treatment. Superoxide dismutase activity in heart was decreased in diabetic rats but normalized after treatment with alpha-lipoic acid; other cardiac enzyme activities were not influenced by either diabetes or antioxidant treatment. These results suggest that after 14 days of treatment with an appropriate pharmacological dose, alpha-lipoic acid may reduce oxidative stress in STZ-induced diabetic rats, perhaps by modulating the thiol status of the cells.     

Anti-diabetic activities of Acanthopanax senticosus polysaccharide (ASP) in combination with metformin

Combination therapy had become very popular currently for the diabetes mellitus and its complications, because of long term unreasonable drug use and adverse reaction to human body. In this study, a polysaccharide (ASP) from the roots of Acanthopanax senticosus was evaluated as an adjuvant with metformin for antidiabetic therapy in alloxan-induced diabetic rats. The result identified ASP plus metformin had a more beneficial promotion for relieving the symptoms of diabetes and reversing liver and kidney damage to normal level than only metfomin administration to diabetic rats. The blood glucose, blood lipid (TC and TG), thiobarbituric acid reactive substances (TBARS), AST, ALT, ALP, total bilirubin, creatinine and urea levels in diabetic rats were decreased by combination of ASP and metformin. Furthermore, the body weight, liver glycogen formation, antioxidant substance (GSH) and antioxidant enzyme (SOD and GPX) levels increased evidently in diabetic mice treated with both ASP and metformin. In particular, sometimes ASP plus metformin could significantly reverse the pathophysiologic parameters of diabetic rats to normal level than only metformin administration. Therefore ASP could be developed to a new adjuvant combined with metformin for diabetes mellitus therapy in the future.     

Cyotomedical therapy for insulinopenic diabetes using microencapsulated pancreatic beta cell lines

Current therapy for type 1 diabetes mellitus involves a daily regimen of multiple subcutaneous or intramuscular injections of recombinant human insulin. To achieve long-term insulin delivery in vivo, we investigated the applicability of cytomedical therapy using beta TC6 cells or MIN6 cells, both of which are murine pancreatic beta cell lines that secrete insulin in a subphysiologically or physiologically regulated manner, respectively. We examined this therapy in the insulinopenic diabetic mice intraperitoneally injected with beta TC6 cells or MIN6 cells microencapsulated within alginate-poly(L)lysine-alginate membranes (APA-beta TC6 cells or APA-MIN6 cells). The diabetic mice treated with APA-beta TC6 cells fell into hypoglycemia, whereas those injected with APA-MIN6 cells maintained normal blood glucose concentrations for over 2 months without developing hypoglycemia. In addition, we also conducted an oral glucose tolerance test using these mice. The blood glucose concentrations of normal and of diabetic mice injected with APA-MIN6 cells similarly changed over time, although the blood insulin concentration increased later in the injected diabetic mice than in the former. These results suggest that cytomedicine utilizing microencapsulated pancreatic beta cell lines with a physiological glucose sensor may be a beneficial and safe therapy with which to treat diabetes mellitus.     

Succinic acid monoethyl ester, a novel insulinotropic agent: Effect on lipid composition and lipid peroxidation in streptozotocin–nicotin-amide induced type 2 diabetic rats

Succinic acid monoethyl ester (EMS) is recently proposed as an insulinotropic agent for the treatment of non-insulin dependent diabetes mellitus. Oxidative stress has been suggested to be a contributory factor in the development and complications of diabetes. In the present study the effect of EMS and Metformin on plasma glucose, insulin, serum and tissue lipid profile, lipoproteins and lipid peroxidation in streptozotocin–nicotinamide induced type 2 diabetic model was investigated. The carboxylic nutrient EMS was administered intraperitonially (8 μmol/g body weight) to streptozotocin diabetic rats for 30 days. The levels of thiobarbituric acid reactive substances (TBARS) and hydroperoxides in liver and kidney and serum and tissue lipids [cholesterol, triglycerides, phospholipids and free fatty acids] and very low density lipoprotein-cholesterol (VLDL-C) and low density lipoprotein-cholesterol (LDL-C), were significantly increased in diabetic rats, whereas the levels of high-density lipoprotein-cholesterol (HDL-C) and antiatherogenic index (AAI) (ratio of HDL to total cholesterol) were significantly decreased. The effect of EMS was compared with metformin, a reference drug. Treatment with EMS and metformin resulted in a significant reduction of plasma glucose with increase plasma insulin in diabetic rats. EMS also resulted in a significant decrease in serum and tissue lipids and lipid peroxidation products. These biochemical observations were supplemented by histopathological examination of liver and kidney section. Our results suggest the possible antihyperlipidemic and antiperoxidative effect of EMS apart from its antidiabetic effect.     

Enhanced growth hormone responses to growth hormone releasing hormone in male type I diabetic patients.

In a previous paper we have demonstrated that growth hormone (GH) responses to growth hormone releasing hormone (GHRH) are higher in premenopausal normal women than in age matched healthy men. As in type I diabetes mellitus various disturbances of GH secretion have been reported, the aim of our study was to assess the effect of sex on basal and GHRH stimulated GH secretion in type I diabetes mellitus. In 21 female and 23 male type I diabetic patients and 28 female and 30 male control subjects GH levels were measured before and after stimulation with GHRH (1 microgram/kg body weight i.v.) by radioimmunoassay. GH responses to GHRH were significantly higher in female than in male control subjects (p less than 0.02), whereas the GH levels following GHRH stimulation were similar in female and male type I diabetic patients. GH responses to GHRH were significantly higher in the male type I diabetic patients than in the male control subjects (p less than 0.001); in the female type I diabetic patients and the female control subjects, however, GH responses to GHRH were not statistically different. The absence of an effect of sex on GHRH stimulated GH responses in type I diabetes mellitus provides further evidence of an abnormal GH secretion in this disorder.