Sperm metabolism in pigs: a role for peroxisome proliferator-activated receptor gamma (PPARγ)

Peroxisome proliferator-activated receptor gamma (PPAR gamma) is a nuclear hormone receptor expressed predominantly in adipose tissue, also implicated in energy homeostasis. In this study, we used western blotting and immunofluorescence techniques to demonstrate for the first time that pig spermatozoa express PPAR gamma. To investigate the functional role of PPAR. in pig sperm, we evaluated its action on different events that characterize the biology of sperm cells, i.e. motility, capacitation, viability and acrosome reaction, using the PPAR gamma-agonist 15-deoxy-12,14-prostaglandin J2 (PGJ2). In responses to PGJ2 treatment, motility, cholesterol efflux and tyrosine phosphorylation were increased, which broadens the role of PPAR gamma from that previously described in the literature, as it also acts to improve sperm functionality. To further our understanding of the significance of PPA gamma in pig sperm, we focused its effects on lipid and glucose metabolism. Evaluation of triglyceride content and lipase, acyl-CoA dehydrogenase and G6PDH activities suggests that PPAR gamma induces energy expenditure in pig spermatozoa. These data represent a meaningful advance in the field of sperm energy metabolism. Taken together, our results demonstrate for the first time that PPAR gamma is expressed by pig sperm, thus improving its functionalities in terms of motility, capacitation, acrosome reaction, survival and metabolism.