The effect of zinc-methionine supplementation on antioxidant status and expression of interleukin-4 and interleukin-6 genes in female rats under heat stress

During heat stress, the animal body requires more antioxidant compounds and activity of antioxidant enzymes. Zinc plays a role in the structure and activity of antioxidant enzymes. One of the ways to supply the zinc requirement, is to use organic zinc supplements, which zinc combined with methionine, and have more intestinal absorption

This study was done to evaluate the effects of different doses of zinc-methionine supplementation on the blood antioxidant status and the expression of interleukin 4 and 6 genes in rats exposed to heat stress.

In a completely random design, 20 female rats were divided into four treatment groups with five replicates. Rats were kept at a temperature of 31±2 °C for 20 hours and at a temperature of 38±2 °C for 4 hours per day (to create heat stress). The rats in the control group were fed standard pellets without additives, and the three experimental groups were fed standard pellets plus 15, 30 and 45 mg zinc-methionine supplement per kilogram of dry matter for 30 days. At the end of the experiment, a blood sample was collected from the inferior vena cava. Total antioxidant capacity, malondialdehyde concentration, antioxidant enzymes, liver enzymes in the serum and the expression of interleukin-4 and interleukin-6 genes were measured.

Serum zinc concentration increased linearly with increasing zinc dose in the diet (P<0.05). The serum activity of two enzymes, alanine aminotransferase and aspartate aminotransferase decreased linearly with increasing zinc-methionine dose in the diet (P<0.01). The highest activity of glutathione reductase and glutathione peroxidase was observed in the group receiving 30 mg/kg, and the lowest activity of these enzymes was observed in the control group. In general, the relative expression of the interleukin-4 gene was increased, and the relative expression of the interleukin-6 gene was decreased (P<0.05). The highest expression of interleukin-4 gene belonged to the group receiving 30 mg, and the highest relative expression of interleukin-6 gene belonged to the control group and the group receiving 15 mg/kg.

The results of this study showed that the dose of up to 30 mg of zinc-methionine per kg of diet used in this study increases the activity of superoxide dismutase enzyme and glutathione peroxidase enzyme activity, decreases the activity of liver enzymes in the serum, increases the expression of the anti-inflammatory gene (Interleukin-4) and decreases the expression of inflammatory gene (Interleukin-6), which indicates the reduction of oxidative stress and the reduction of the effects of heat stress in the body of the rat.