Serum mineral changes in alloxan diabetes before and after treatment with some hypoglycemic drugs

Zinc as a potential coadjuvant in therapy for type 2 diabetes

BACKGROUND

Type 2 diabetes is highly prevalent in populations having high rates of overweight and obesity. It is a chronic condition responsible for long-term severe dysfunction of several organs, including the kidneys, heart, blood vessels, and eyes. Although there are a number of pharmacologic products in the market to treat insulin resistance and impaired insulin secretion--the most prominent features of this disease--interventions directed at preserving the integrity and function of beta-cells in the long term are less available. The use of some nutrients with important cellular protective roles that may lead to a preservation of beta-cells has not been fully tested; among these, zinc may be an interesting candidate.

OBJECTIVE

To assess the potential of zinc supplementation as coadjuvant to diabetes therapy.

METHODS

This article reviews the available information on the use of zinc as part of diabetes therapy.

RESULTS

Cellular and animal models provide information on the insulin mimetic action of zinc, as well as its role as a regulator of oxidative stress, inflammation, apoptosis, and insulin secretion. Zinc supplementation studies in humans are limited, although some positive effects have been reported; mainly, a modest but significant reduction in fasting glucose and a trend to decreased glycated hemoglobin (HbA1c).

CONCLUSIONS

Zinc supplementation may have beneficial effects on glycemic control. Nevertheless, among the studies considered, the vast majority lasted for 6 months or less, suggesting the importance of conducting long-duration studies given the characteristics of type 2 diabetes as a chronic disease.

Zinc and diabetes--clinical links and molecular mechanisms

Zinc is an essential trace element crucial for the function of more than 300 enzymes and it is important for cellular processes like cell division and apoptosis. Hence, the concentration of zinc in the human body is tightly regulated and disturbances of zinc homeostasis have been associated with several diseases including diabetes mellitus, a disease characterized by high blood glucose concentrations as a consequence of decreased secretion or action of insulin. Zinc supplementation of animals and humans has been shown to ameliorate glycemic control in type 1 and 2 diabetes, the two major forms of diabetes mellitus, but the underlying molecular mechanisms have only slowly been elucidated. Zinc seems to exert insulin-like effects by supporting the signal transduction of insulin and by reducing the production of cytokines, which lead to beta-cell death during the inflammatory process in the pancreas in the course of the disease. Furthermore, zinc might play a role in the development of diabetes, since genetic polymorphisms in the gene of zinc transporter 8 and in metallothionein (MT)-encoding genes could be demonstrated to be associated with type 2 diabetes mellitus. The fact that antibodies against this zinc transporter have been detected in type 1 diabetic patients offers new diagnostic possibilities. This article reviews the influence of zinc on the diabetic state including the molecular mechanisms, the role of the zinc transporter 8 and MT for diabetes development and the resulting diagnostic and therapeutic options.

Serum enzyme changes due to trace amounts of some transition metal ions on the induction of experimental diabetes

The intravenous injection of zinc chloride immediately before and 15 minutes after alloxan or dithizone prevented the usual hyperglycaemia observed 24 hours after induction of diabetes. The intravenous injection of manganese chloride prevented any marked rise of blood glucose, while chromium and cobalt chlorides lowered the blood glucose level to a certain extent. In alloxan diabetic rats, serum GOT and GPT levels were significantly higher than normal. The serum GOT levels were higher in animals injected with chromium than cobalt, zinc and manganese; while serum GPT levels were higher in cobalt than in chromium, zinc and manganese. In dithizone diabetes, serum GOT and GPT were increased in animals injected with cobalt than chromium, zinc and manganese. Alloxan diabetic rats showed lower serum alkaline phosphatase levels and higher in animals injected with cobalt than chromium, zinc and manganese. For dithizone, there are statistically significant differences in all cases. In alloxan diabetes, coeruloplasmin was higher than normal, while intravenous injection of dithizone was without effect on serum coeruloplasmin.

Serum mineral changes due to exogenous ATP and certain trace elements in experimental diabetes

The intravenous injection of zinc or manganese chloride immediately before and 15 minutes after alloxan or dithizone prevented the usual hyperglycemia observed 24 hours after induction of diabetes. Injection of zinc chloride in alloxan diabetes led to normalization of sodium while zinc, copper, iron and magnesium remained high and calcium and potassium remained low as in alloxan. In case of dithizone diabetes, the administration of zinc salt led to an increase in serum zinc, magnesium and potassium and to a decrease in serum calcium while the sodium level returned to normal. Manganese plus alloxan led to a normalization of serum zinc, copper, potassium and sodium. In the case of dithizone plus manganese only magnesium was raised while the other elements were unchanged when compared to animals injected with dithizone only. Chromium and cobalt lowered the blood glucose to a certain extent however it did not affect most of the elements. The same changes occurred in all elements as with alloxan or dithizone alone. Pretreatment with ATP led to a normalization of serum zinc, copper, magnesium, sodium and potassium, while in case of iron it remained high and calcium remained low as that found in alloxan diabetic rats.

Serum enzyme changes in experimental diabetes before and after treatment with some hypoglycaemic drugs

In alloxan diabetes, serum GOT, GPT, and ceruloplasmin were significantly increased compared to normal rats, while the level of serum alkaline phosphatale was decreased. Treatment with insulin led to lowering of serum GOT, GPT, and ceruloplasmin while serum alkaline phosphatase remained low. Then lycanol or daonil were used for treatment, serum GOT, GPT, and ceruloplasmin were changes towards normalization, while ceruloplasmin returned to normal values. Serum-alkaline phosphatase increased after 7 and 14 days from treatment with oral hypolygylcaemic drugs. In dithizonized diabetic animals, the levels of serum GOT, GPT, and alkaline phosphatase were found to be higher than normal, while ceruloplasmin levels were unchanged. After treatment with insulin all serum enzyme activities were normalized.