Assessing the ability of dihydrosterculic acid to activate PPARα
Authors: Halls Leah S. , Paton Chad M. 
Published: May 2024

Peroxisome proliferator-activated receptor α (PPARα) is a ligand-activated transcription factor associated with the expression of specific target genes involved in fatty acid β-oxidation. Activation of PPARα could potentially be utilized to treat diseases associated with the accumulation of hepatic lipids such as non-alcoholic fatty liver disease (NAFLD), which currently impacts approximately 25% of the world’s population. At present, a class of synthetic ligands called fibrates can be prescribed to help manage NAFLD but are weak agonists for PPARα and therefore have limited effcacy. Consequently, alternative ligands for PPARα must be established and no natural endogenous ligands have been conclusively identified. This study expands on our previous work and aims to identify the direct effects of dihydrosterculic acid (DHSA), a cyclopropyl fatty acid found in cottonseed oil (CSO), on PPARα activity. To identify downstream effects of DHSA, male mice were placed on a CSO- (DHSA-containing) or isocaloric oil-enriched diet for 6 weeks and tissues were sent for genome-wide RNA sequencing analysis. CSO-fed mice demonstrated increased PPARα gene expression in the liver and concomitant decreased triglyceride in plasma (-75.1±11.5 milligrams/deciliter (mg/dL); p<0.01) and liver (-86.7±71.7 mg/gram (g) protein; p=0.1) and decreased free fatty acid in liver (-16.5±3.4 micromolar (μM)/g protein; p<0.01) relative to the oil-enriched control diet. Confirmational tissue analysis of liver samples show an increase in PPARα target gene expression in the DHSA containing groups compared to control diet groups, indicating that DHSA could potentially serve as an endogenous ligand for PPARα to increase its transcriptional activity to increase fat oxidation. To further test this hypothesis, female PPARα knockout mice were fed a DHSA containing diet or control diet for 4 weeks (n=8). Following the 4-week period, the chow-fed wild type females gained more weight (1.3±0.6 g; p<0.05) than the PPARα knockout mice. Otherwise, there were no significant differences in body weight or food intake between diets or genotypes. Additional in vitro studies show increased PPARα target gene expression following treatments with DHSA, specifically for CPT1a (2.7±0.2 fold increase; p<0.01), ACOX1 (1.3±0.1 fold increase; p<0.05), and ACADVL (1.6±0.1 fold increase, p<0.01), which encode key enzymes in lipid oxidation pathways. SCD1, the rate limiting enzyme in lipogenesis, was also downregulated (0.5±0.03 fold decrease, p<0.01) in response to a 24-hour treatment with DHSA indicating a reduction in endogenous lipogenesis. From these results, we believe that DHSA could function through a PPARα-dependent mechanism. Further analysis of the tissues collected from the PPARα knockout mouse model will aid in determining the mechanism of DHSA as well as identifying its potential for the treatment of excess lipid accumulation. This project is funded by Cotton Incorporated. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.