Rifampicin-induced Hepatic Lipid Accumulation In Mice And Its Mechanisms

Objective Rifampicin is a well-known antitubercular agent. A link between rifampicin and nonalcoholic fatty liver disease(NAFLD) has been demonstrated in vivo and vitro studies, but the molecular mechanism of rifampicin-induced hepatic lipid accumulation has not been thoroughly understood. The present study aims to observe the time-course of rifampicin(RIF)-induced fatty liver disease in mice and to investigate the possible mechanisms in rifampicin-induced lipid accumulation.Methods Forty-two healthy male mice were randomly divided into seven groups( control, 8 h, 24 h, 3 d, 1 week, 2 weeks, 4 weeks), and mice were administered with RIF 200 mg/kg daily by gavage. All mice were sacrificed at 6 h after the last administration to collect serum and liver tissues. All their body weight and liver weight was measured for calculating liver to body weight ratio. The level of alanine aminotranferase(ALT) in serum was measured. Hepatic pathological changes were observed by HE staining. The levels of triglyceride(TG), cholesterol ester(TCH), very low density lipoprotein(VLDL), high-density lipoprotein(HDL) in serum were measured. Liver tissue was dissected for measuring TG. The lipid accumulation of liver was observed by oil red O staining. Real-time RT-PCR was used to detect the m RNA levels of enzymes and regulatory factors involved in fatty acid synthesis(Acc, Fas and Scd-1), enzymes and regulatory factors involved in fatty acids(Cd36, Fatp and L-fabp). We detected the expression levels of hepatic nuclear SREBP-1c, LXR-α, PXR and PPARγ.Results Compared with control group, liver weight and liver to body weight ratio began to rise gradually 24 h after RIF-treated mice, Compared with mice in control group, the serum levels of ALT slightly increased in 8 h, 24 h, 3 d, 1 week and 2 weeks groups, and significantly increased in 4 weeks group. HE staining showed 8 h and 24 h after RIF’s treatment, liver tissue did not see clear change. 3 d group was smaller vacuoles, part of the nucleus to one side, and starting from 1 week liver tissue that was dramatically increasing number of large circular cavity. The levels of TG, VLDL in the serum were moderately elevated in 8 h and 24 h group; the most obvious was elevated in 3 d group, and begin to decline from 1 week. Serum levels of TCH, HDL in RIF-treated groups were relatively lower than control group. The liver TG levels significantly increased from 8 h, and peaked in 1 week group, then presented downward trend in 2 weeks and 4 weeks group but higher than control group. The results of oil red O staining showed that 8 h and 24 h after RIF’s treatment, there was a small amount of lipid deposition in the liver, and large circular lipid drops in liver tissue dramatically increased after 3 d. m RNA levels of Fas, Acc and Scd-1, several key genes for fatty acid synthesis, were elevated in rifampicin-treated mice. In addition, the class B scavenger receptor CD36 was progressively up-regulated by rifampicin. Interestingly, hepatic SREBP-1c and LXR-α, two important transcription factors that regulate genes for hepatic fatty acid synthesis, were not activated by rifampicin. Instead, hepatic PXR was rapidly activated in rifampicin-treated mice. Hepatic PPARγ, a downstream target of PXR, was transcriptionally up-regulated.Conclusions All these results suggest that administration of rifampicin causes hepatic steatosis in mice and shows the obvious time-effect relationship. Rifampicin up-regulates key genes for hepatic fatty acid synthesis and elevates hepatic lipid syntheses independent of SREBP-1c and LXR-α activation. The increased hepatic lipid syntheses and uptake of fatty acids from circulation into liver jointly contribute to rifampicin-induced hepatic lipid accumulation. The increased uptake of fatty acids from circulation into liver might be partially attributed to rifampicin-induced up-regulation of PPARγ and its target genes.