Peroxisome proliferator-activated receptor γ (PPARγ) is the target for thiazolidinones (TZDs), drugs that improve insulin sensitivity and fatty liver in humans and rodent models, related to a reduction in hepatic de novo lipogenesis (DNL). The systemic effects of TZDs are in contrast to reports suggesting hepatocyte-specific activation of PPARγ promotes DNL, triacylglycerol (TAG) uptake and fatty acid (FA) esterification. Since these hepatocyte-specific effects of PPARγ could counterbalance the positive therapeutic actions of systemic delivery of TZDs, the current study used a mouse model of adult-onset, liver (hepatocyte)-specific PPARγ knockdown (aLivPPARγkd). This model has advantages over existing congenital knockout models, by avoiding compensatory changes related to embryonic knockdown, thus better modeling the impact of altering PPARγ on adult physiology, where metabolic diseases most frequently develop. The impact of aLivPPARγkd on hepatic gene expression and endpoints in lipid metabolism was examined after 1 or 18wks (Chow-fed) or after 14wks of low- or high-fat [HF] diet. aLivPPARγkd reduced hepatic TAG content but did not impact endpoints in DNL or TAG uptake. However, aLivPPARγkd reduced the expression of the FA translocase (Cd36), in 18wk-Chow and HF-fed mice, associated with increased NEFA after HF-feeding. Also, aLivPPARγkd dramatically reduced Mogat1 expression, that was reflected by an increase in hepatic monoacylglycerol (MAG) levels, indicative of reduced MOGAT activity. These results, coupled with previous reports, suggest that Cd36-mediated FA uptake and MAG pathway-mediated FA esterification are major targets of hepatocyte PPARγ, where loss of this control explains in part the protection against steatosis observed after aLivPPARγkd.

Contract Research Organizations (CROs) conducting toxicology studies on behalf of biopharmaceutical sponsors and others routinely provide supportive care for animals to minimize pain and distress on studies. A large number of guidance documents govern the care of experimental animals, however there is currently no uniform approach on the communication between sponsor and their CRO partners in providing a standard definition of and strategies for administering supportive care in toxicity studies. This survey was conducted by the CRO Outreach Working Group (WG), a part of the 3Rs Translational and Predictive Sciences (TPS) Leadership Group of the International Consortium for Innovation and Quality in Pharmaceutical Development (IQ Consortium), to better understand the provision of supportive care on nonclinical studies. The survey aimed to define supportive care strategies, identify alternatives to supportive care, and understand regulatory feedback and implications about supportive care decisions. The survey was distributed to members of the 3Rs Leadership Group of the IQ Consortium and several CRO partners, representing 35 organizations as potential respondents. The results of the survey from 13 respondents provided positive feedback that helped in highlighting the existing best practices for supportive care. Areas of enhancements identified included greater consistency in the inclusion of sponsor veterinarians on project teams for externalized studies, the timing of initiation of supportive care, and increased sharing of regulatory outcomes. Suggested best practices include creating a plan of action for veterinary care prior to study start, and enhancing information sharing regarding expected toxicities from previous study findings. Improved communication regarding supportive care will pave the way for enhanced 3Rs initiatives, refining the existing animal care paradigm and helping to ensure the most ethical toxicology study designs.