This study tested the ability of a novel adipose tissue derived cytokine, C1q TNF Related Protein 3 (CTRP3), to prevent alcohol-induced hepatic lipid accumulation, or alcoholic fatty liver disease (ALD). Previous work has demonstrated that CTRP3 is effective at preventing high fat diet-induced fatty liver, however, the potential of CTRP3 to inhibit ALD has not been explored. To test the potential protective effects of CTRP3, transgenic mice overexpressing CTRP3 (Tg) or wildtype littermates (WT) were subjected to one of two different models of ALD. In the first model, known as the NIAAA model, mice were fed control or alcohol-containing liquid diets (5% v/v) for 10 days followed by a single gavage of ethanol (5 g/kg). In the second model, the chronic model, mice were fed control or alcohol-containing diets for 6 weeks with no gavage. This study found that CTRP3 reduced triglyceride accumulation in the chronic model of alcohol consumption by ~50%, whereas no reduction was observed in the NIAAA model. Further analysis of isolated primary hepatocytes from WT and Tg mice demonstrated that CTRP3 increased oxygen consumption in the presence of fatty acids, indicating that CTRP3 increases hepatic fatty acid utilization. In conclusion, this study indicates that CTRP3 attenuates hepatic triglyceride accumulation in response to long-term chronic but not short-term alcohol consumption.

Background: The typical western diet contains foods with modest amounts of lipid oxidation products. Previous work by us and others have demonstrated that mildly oxidized lipids promote a gain in fat mass while highly oxidized lipids decrease fat mass in rodents and triglyceride (TAG) accumulation in 3T3-L1 cells. Adipocyte differentiation is regulated by a key nuclear transcription factor known as PPARγ. Objective: To investigate if the alterations in triglyceride accumulation in 3T3-L1 cells pretreated with oxidized soy oil are due to 1) a change in PPARg DNA interactions 2) changes in the expression of SREBP-1c, PPARg, and/or its target genes. Main Methods: Confluent 3T3-L1 cells were pretreated for 24hours with 0.01% soy oil (SO) which was either unheated (unheated SO) or heated for 3, (3h-SO), 6 (6h-SO), or 9hours (9h-SO). The effect of 24hour soy oil exposure was assessed at several time points throughout the differentiation process. Alterations in PPARg DNA interaction was assessed using a PPARγ transcription factor assay kit while alterations in the expression of genes upstream and downstream of PPARγ was determined by RT-PCR. Primary and secondary products of oxidation within the SO were determined by spectrophotometry. Results: The 6hr-SO contained the greatest concentration of peroxides whereas both the 6hr-SO and 9hr-SO contained a significantly higher concentration of conjugated dienes and aldehydes.Nuclear extracts from 3T3-L1 cells pretreated with 6h-SO demonstrated the greatest reduction in PPARγ DNA binding. Compared to the unheated SO and mildly oxidized 3h-SO, cells treated with the 6h-SO had a significant reduction in SREBP-1c, PPARg, LPL, and GLUT4 expression occurring early in the differentiation process. Variations in the gene expression of 6hr-SO pretreated cells persisted within partially differentiated and mature adipocytes. Conclusions: Pre-treatment of preadipocytes with soy oil heated for ³ 6h greatly decreases the activity of PPARγ in the nucleus and adipogenic gene expression . These changes seen in early differentiation seem to correlate the best with the phenotype of reduced triglyceride accumulation seen in mature adipocytes.