Dietary vitamin D ameliorates hepatic oxidative stress and inflammatory effects of diethylnitrosamine in rats

The generation of reactive oxygen species (ROS) plays an essential role in the pathogenesis of several diseases. Its implication in inflammation has suggested a possible link between oxidative stress and activation/release of cytokines in precancerous states. Recent observational studies have suggested an association between inflammation and vitamin D deficiency; hence, suggesting that vitamin D could play a role in the pathogenesis of diseases. This study examined the antioxidant and anti-inflammatory potentials of vitamin D in diethylnitrosamine (DEN)-induced oxidative stress and inflammation in rats. Rats were divided into four experimental groups. While groups one and two were administered twice weekly with 30 mg/kg body weight DEN for six weeks, groups three and four were given normal saline. Groups one and three were fed with vitamin D deficient diet, while groups two and four were fed vitamin D diet during the experiment. After that, biomarkers of oxidative stress status were assayed spectrophotometrically. The concentration of inflammatory cytokines was determined using enzyme-linked immunosorbent assay (ELISA). DEN-induced vitamin D deficient diet group had increased antioxidant enzymes' activities. Also, there were elevated concentrations of thiobarbituric acid reactive substances (TBARS) and inflammatory cytokines in the same group. Vitamin D diet, however, reduced oxidative stress effects through the reduction in the activities of TBARS and caused a significant (p < 0.05) increase in nitric oxide concentration. Vitamin D diet significantly (p < 0.05) reduced the level of interleukin 1β and TNF-α produced in the deficiency state. These findings show that vitamin D may play an essential role in the regulation of hepatic oxidative stress and inflammatory responses.

Stimulation of Diethylnitrosamine Metabolism Reduces Its General Toxic and Hepatocarcinogenic Effects

The general toxic and hepatocarcinogenic effects of diethylnitrosamine after stimulation of its metabolism with 1,4-bis[2-(3,5-dichloropyridyloxy)]-benzene (TCPOBOP) were studied. The hydroxylating activity of liver microsomes of C57Bl/6Mv mice towards p-nitrophenol increased more than 4-fold 3 days after injection of TCPOBOP. Injection of diethylnitrosamine 3 days after TCPOBOP caused a lesser body weight loss and decrease of food consumption in C57Bl/6Mv mice than in response to diethylnitrosamine without preinduction. Injection of diethylnitrosamine to suckling ICR mice after TCPOBOP induction of cytochrome P450 2e1 activity led to development of 2-fold lesser number of tumors and pretumorous nodes in the liver in comparison with animals injected with diethylnitrosamine without induction. These data indicated that metabolism stimulation reduced the general toxic and hepatocarcinogenic effects of diethylnitrosamine.