Effect of cobalt on the liver glycogen content in the streptozotocin-induced diabetic rats

Department of Environmental Life Science, Graduate School of Medical Science, Yamagata University, Yonezawa, Yamagata, 992-8510, Japan.
Molecular and Cellular Biochemistry (Impact Factor: 2.39). 10/2005; 277(1-2):127-30. DOI: 10.1007/s11010-005-5777-y
Source: PubMed


Cobalt decreases blood glucose in diabetic rats but the mechanisms involved are unclear. To determine the contribution of glycogen metabolism to glycemia-lowering effect, glycogen contents of liver and muscle in the streptozotocin-induced diabetic rats were determined. The liver glycogen was depleted in diabetic rats. But when cobalt was administered to the rats, the glycogen returned to the level of healthy rats, concomitantly with the decrease in blood glucose. The cobalt treatment had no effect on the muscle glycogen in the diabetic rats. The tissue-specific responses of glycogen metabolism suggest the involvement of suppressed glucagon signaling due to cobalt treatment.

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    • "After centrifugation, the supernatant was removed, and the pellet was re-suspended in deionized water, and homogenized again. Hepatic glycogen storage was determined according to the technique proposed by Nomura et al. (2005). "
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    ABSTRACT: The aim of this sstudy was to evaluate the liver glycogen storage in pregnant rats presenting neonatal streptozotocin-induced diabetes and to establish a relation with glycemia and insulin levels. Wistar rats were divided in to two groups: 1) Mild Diabetes (STZ) - received streptozotocin (glycemia from 120 to 300 mg/dL), 2) Control - received vehicle (glycemia below 120 mg/dL). At days 0, 7, 14 and 21 of the pregnancy, body weight and glycemia were evaluated. At day 21 of the pregnancy, the rats were anesthetized for blood and liver collection so as to determine insulin and liver glycogen, which showed no changes in the STZ group as compared to the controls. In the STZ group, maternal weight gain were lower as compared to those in the control group. Significantly increased glycemia was observed at days 0 and 14 of the pregnancy in the STZ group. Therefore, neonatally induced diabetes in the rats did not cause metabolic changes that impaired insulin and liver glycogen relation in these rats.
    Full-text · Article · Apr 2012 · Brazilian Archives of Biology and Technology
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    • "Some of these are increased GLUT-1-mediated glucose transport (Ybarra et al. 1997) and decreased hepatic gluconeogenesis (Saker et al. 1998). Cobalt has also been shown to normalize hepatic glycogen levels in STZ rats (Nomura et al. 2005) although its effects on glucagon are unclear. Furthermore, one of the mechanisms suggested to decrease hyperglycemia is to attenuate the oxidative insult induced by diabetes. "
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    ABSTRACT: Diabetes is a metabolic disorder characterized by elevated blood glucose levels. Although conventional treatments such as insulin and other drugs reduce blood glucose, there is still a therapeutic need for effective orally administered drugs. Trace elements like vanadium and tungstate have been successfully demonstrated to reduce blood glucose in experimental diabetes with minimal chronic complications. We investigated the anti-hyperglycemic effects of cobalt in streptozotocin-diabetic rats. Normal and diabetic rats were provided with drinking water containing 3.5 mM cobalt chloride for three weeks followed by 4 mM for four weeks. Body weights and fluid consumption were monitored on a daily basis, while food intake was recorded twice every week. Prior to termination, an oral glucose tolerance test was performed on the animals. Diabetic rats lost significant body weight (357 +/- 2 gm) compared to controls (482 +/- 3 gm). Body weight was further reduced by cobalt treatment (290 +/- 2 gm). Although it was difficult to establish a dosing regimen without weight loss, food and fluid consumption in cobalt-treated diabetic rats improved significantly compared to untreated diabetics. Plasma glucose levels were significantly reduced with reference to diabetic controls (29.3 +/- 0.9 mM) by the fourth week to a lower but still hyperglycemic level (13.6 +/- 3.4 mM). Cobalt-treated diabetic rats demonstrated an enhanced ability to clear a glucose load compared to untreated diabetics. Cobalt treatment neither affected the feeding and drinking patterns nor plasma glucose in normoglycemic animals although body weights decreased compared to untreated controls. We conclude that chronic cobalt treatment decreases plasma glucose levels in STZ-diabetic rats and improves tolerance to glucose.
    Full-text · Article · May 2007 · BioMetals
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    • "As the principal storage form of glucose in animal cells and the key determinant of the body's tendency to store or breakdown nutrients (Pencek et al. 2005), liver glycogen is converted through many steps to enter the TCA cycle to produce ATP, which was used by many cells to maintain homeostasis. Studies have shown a direct correlation between liver glycogen levels and exercise (Chen and Ianuzzo 1982; Nomura et al. 2005; Pencek et al. 2005). Depletion of muscle glycogen in prolonged heavy exercise led to inability to continue such exercise (Richter and Galbo 1986; Spriet and Peters 1998). "
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    ABSTRACT: The present study examined the effects of derivatives of galactosides and glucosides in a polysaccharide extract from Euphorbia kansui (Euphorbiaceae) on exercise-induced oxidative stress in mice. Exhaustive swimming exercise significantly increases the degree of lipid peroxidation in terms of malondialdehyde content and reduces the antioxidant activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx). Our findings revealed that chronic oral treatment with the extract elevates enzymatic activities of SOD and GPx accompanied by a corresponding decrease in malondialdehyde. The antioxidative activities of these compounds against exercise-induced oxidative stress are correlated with various activities such as reducing the production of superoxide and hydroxyl radicals, inhibiting lipid peroxidation, enhancing antioxidative defenses, and increasing the production of SOD and GPx activity and expression in different tissues. These compounds may be involved in glycogen metabolism to meet the requirement of working skeletal muscles and act as antioxidants by terminating the chain reaction of lipid peroxidation to maintain the morphological stability of mitochondria in spinal motor neurons. These observations suggest that E. kansui has antioxidative and antifatigue properties and can be given as prophylactic and (or) therapeutic supplements for increasing antioxidant enzyme activities and preventing lipid peroxidation during strenuous exercise.
    Preview · Article · Nov 2006 · Canadian Journal of Physiology and Pharmacology
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