Influence of sex, strain, and species on trace metal status of insulin-deficient diabetic rodents

Streptozotocin (STZ)-Induced Diabetes Affects Tissue Trace Element Content in Rats in a Dose-Dependent Manner

The objective of the present study was investigation of tissue trace element distribution in a streptozotocin model of DM1 in rats. DM1 was modeled in 2-month-old male Wistar rats (n = 30) using intraperitoneal injection of 45 mg/kg b.w. (STZ1) and 55 mg/kg b.w. streptozotocin (STZ2), whereas control animals were injected with physiological saline. The rats were subjected to oral glucose tolerance test (OGTT) and HbA1c level assessment at day 14. At day 30, blood serum, liver, kidney, and heart samples were collected for tissue trace element assessment using inductively coupled plasma mass spectrometry (ICP-MS). STZ-treated rats were characterized by lack of significant weight gain and elevated HbA1c and blood glucose levels. ICP-MS analysis demonstrated a dose-dependent accumulation of Cu, Mn, Mo, and Se levels in the liver. Correspondingly, the dose-dependent increase in renal Cu, Mn, V, and Zn levels was significant, whereas the observed trend for kidney V and Mo accumulation was nearly significant. The patterns of trace element content in the myocardium of STZ-exposed rats were quite different from those observed for liver and kidney. Only cardiac Zn content was characterized by a significant decrease. Serum Co, Cr, Cu, Se, V, and Mo levels were characterized by a significant decrease in response to STZ-induced diabetes. Generally, the obtained data demonstrate that diabetes is associated with altered copper, manganese, molybdenum, chromium, and vanadium handling. In turn, only altered Zn status may provide a link to diabetic cardiotoxicity. However, the particular mechanisms of both impaired metal handling in STZ diabetes and their potential anti-diabetic activity require further investigation.

Tissue antioxidant status in streptozotocin-induced diabetes in rats. Effects of dietary manganese deficiency

Interactions between manganese (Mn) deficiency and streptozotocin (STZ)-diabetes with respect to tissue antioxidant status were investigated in male, Sprague-Dawley rats. All rats were fed either a Mn-deficient (1 ppm) or a Mn-sufficient (45 ppm) diet for 8 wk. Diabetes was then induced by tail-vein injection of STZ (60 mg/kg body weight), after which the rats were kept for an additional 4 or 8 wk. The control groups comprised rats not injected with STZ and fed either Mn-deficient or Mn-sufficient diets for a total of 12 wk. The Mn-deficient diet decreased the activities of manganese superoxide dismutase (MnSOD) in kidney and heart, and of copper-zinc superoxide dismutase (CuZnSOD) in kidney, in the non-diabetic animals. In the diabetic rats, the Mn-deficient diet induced more pronounced decreases in activities of these same enzymes, and also increased liver MnSOD activity. Plasma and hepatic vitamin E levels increased progressively with the duration of diabetes, independent of dietary Mn intake. Lipid peroxidation, as measured by H2O2-induced production of thiobarbituric acid reactive substances in erythrocytes, also increased, concomitant with decreased liver and kidney glutathione (GSH) levels. These findings demonstrate for the first time and interactive effective between Mn deficiency and STZ-diabetes, resulting in amplification of tissue antioxidant changes seen with either Mn deficiency or STZ-diabetes alone. This effect of Mn deprivation in experimental diabetes suggests a physiological role for Mn as an antioxidant nutrient.

Strain differences in kidney copper concentrations of male rats

The copper concentrations of the kidneys of male rats of six inbred (BN, F344, LEW, SHR, WAG/Cpb, and WAG/Rij) and one random-bred Wistar strain were determined.In inbred rats the mean concentration varied between strains and ranged from 7.10 μg/g for F 344 to 23.48 μg/g for WAG/Cpb. The calculated coefficient of genetic determination (g(2)) was 0.88. A remarkable discrepancy was found between the two WAG inbred strains; the WAG/Cpb had a 2.5 times higher kidney Cu concentration than the WAG/Rij.Kidney Cu concentrations of random-bred rats varied considerably; the coefficient of variation of the means was 28 and 34% in two samples taken with a 1-yr interval, respectively, indicating inhomogeneity within the population.The results indicate that the individual differences in kidney Cu concentration have a genetic basis.