Plasma MT levels in diabetic and renal failure patients

Abstract

Metallothionein (MT) has various functions such as storage of essential metals, detoxification of heavy metals, and scavenging of free radicals. To investigate these functions of MT, various models of experimental animals, plants, and cultured cells are used. Recently, MT transgenic mice, MT-null and MT-overexpressed mice, are used, but the roles of MT are still unclear. Changes in MT levels in human have been studied in many countries with environmental pollution along with certain diseases and nutritional mineral deficiency. Since MT was discovered as a Cd binding protein, interactions between MT and Cd exposure have been studied. And it is confirmed that levels of urinary MT and β2-microglobulin increased with Cd exposure. Indeed, the level of urinary MT has been used as a clinical parameter of renal dysfunction induced by Cd. And it is known that Cd-MT induces a renal dysfunction, although intracellular MT acts to reduce the toxicity of heavy metals. Smoking is also reported to increase the renal Cd and MT levels. The changes in metabolism of Zn and Cu may have a marked effect in MT levels in liver, kidney, and pancreas. Marked differences in MT content in several organs and plasma have been reported in certain diseases such as primary biliary cirrhosis, Wilson diseases, and amyotrophic lateral sclerosis. An increase in MT has been shown in human fetal liver and various types of tumors of thyroid, testis, urinary bladder, salivary gland, breast, and colorectal [1]. However, it is still unclear whether the change in MT either in tissue or biological fluids are always related to change in mineral metabolism or due to certain changes in inflammation or cancers. There are only few reports on plasma levels of MT, because sensitive methods of MT measurement such as ELISA were not readily available in most laboratories. Recent reports suggest that MT may behave as an acute phase protein in certain diseases such as myocardial infarction [2]. Analysis of plasma and urinary MT levels will provide importantly on the role of MT in various pathological status and changes in mineral metabolism. In this report, the changes in plasma and urinary MT levels in diabetes and chronic renal failure (CRF) patients are discussed.