The Effects of Statin and Fibrate Drugs on Cholesterol Metabolism and Steroid Production in Two Fish Species

Abstract

Statins and fibrates are the most widely used pharmaceuticals in developed countries for the treatment of hyperlipidemia. They reach the aquatic environment mainly via wastewater treatment plants and have been detected at concentrations of ng to µg/L. They are “pseudopersistent” due to their continuous and increasing input into the aquatic environment. Cholesterol is essential to all animals, so inhibition of its synthesis by these drugs could have negative consequences in non-target species. Currently little is known regarding the possible effects of statins and fibrates on aquatic organisms. Thus, this thesis investigates the effects of atorvastatin (ATV; statin) and gemfibrozil (GEM; fibrate) on rainbow trout and zebrafish in vivo and in vitro. Intraperitoneal injection of ATV, GEM, or the combination of the two drugs (A+G) into rainbow trout resulted in a nearly 30% reduction of cellular cholesterol content. Additionally, gene expression related to lipid homeostasis (LDL-r, HMGCR-1, and SREBP-1) was elevated. Furthermore, plasma creatine kinase activity and skeletal muscle gene expression related to rhabdomyolysis (atrogin-1 and f-box 25) were elevated. Plasma cortisol concentration was reduced in injected trout, suggesting that either the reduction in cholesterol resulted in treated fish lacking a proper stress response or that the treated fish were simply not responsive to the stress protocol. Feeding zebrafish ATV, GEM, or A+G daily over a 30 day period resulted in nearly a 30% reduction of whole-body cholesterol content and a concomitant change in gene expression related to lipid homeostasis (SREBP-1, SREBP-2, HMGCR-1, PPARα, and PPARγ). Moreover, sex steroids (testosterone and estradiol) were also reduced. Finally, exposing rainbow trout hepatocytes to ATV at 4.5 or 45 µg/L for 3 or 6 h resulted in reduced 14C incorporation into cholesterol and cholesteryl ester. Elevated gene expression related to lipid homeostasis (HMGCR-1, SREBP-1, and PPARγ) also occurred. This thesis demonstrated that ATV and GEM affected fish cholesterol and steroid hormone contents, as well as molecular markers of rhabdomyolysis. Whether these changes impact fish fitness remains to be determined.