Fasting-induced increases in aquaporin 7 and adipose triglyceride lipase mRNA expression in adipose tissue are attenuated by peroxisome proliferator-activated receptor α deficiency

• Published in: International Journal of Obesity 2007-07, Vol.31 (7), p.1165-1171
• Main Authors: Walker, C G, Holness, M J, Gibbons, G F, Sugden, M C
• Format: Article
• Language: English
• Subjects: Adipocytes - physiology; Adipose Tissue, White - cytology; Adipose Tissue, White - physiology; Animals; Aquaporins; Aquaporins - genetics; Blood Glucose; Carboxylic Ester Hydrolases - genetics; Care and treatment; Cell Size; Cellular signal transduction; Down-Regulation - physiology; Eating - physiology; Epidemiology; Fasting - physiology; Fatty Acids, Nonesterified - blood; Health Promotion and Disease Prevention; Insulin - blood; Internal Medicine; Lipase; Lipolysis - physiology; Male; Medicine; Medicine & Public Health; Metabolic Diseases; Mice; Mice, Inbred Strains; Mice, Mutant Strains; original-article; Peroxisomal disorders; Physiological aspects; PPAR alpha - genetics; Public Health; Risk factors; RNA, Messenger - metabolism
• ISSN: 0307-0565; 1476-5497
• DOI: 10.1038/sj.ijo.0803555

Objective: To investigate the impact of peroxisome proliferator-activated receptor α deficiency on gene expression of adipose triglyceride lipase and the glycerol transporter aquaglyceroporin 7 in white adipose tissue in the fed and fasted states in relation to glycerol release by isolated adipocytes. Measurements: Studies using wild-type and peroxisome proliferator-activated receptor α null mice. Hormone and metabolite concentrations, real-time polymerase chain reaction (PCR), basal and stimulated adipocyte lipolysis, estimated by glycerol release. Results: Peroxisome proliferator-activated receptor α deficiency blocked the increase in aquaglyceroporin 7 transcript level and attenuated the increase in adipose triglyceride lipase transcript level in white adipose tissue elicited by fasting. Fasting glycerol levels were lower in peroxisome proliferator-activated receptor α null than wild-type mice, despite increased mobilization of adipocyte fat reserves in vivo as indicated by reduced adipose tissue masses (three distinct depots) and a significantly lower epididymal adipocyte diameter. Basal net glycerol release was unchanged but β -adrenergic-stimulated net glycerol release was higher with isolated adipocytes from fasted peroxisome proliferator-activated receptor α null mice compared with those of fasted wild-type mice. Conclusion: Peroxisome proliferator-activated receptor α deficiency prevents effects of fasting to increase adipocyte aquaglyceroporin 7 gene expression, and influences the regulation of inter-tissue glycerol flux after fasting via lowered adipocyte aquaglyceroporin 7 expression. Lowered gene expression of adipose triglyceride lipase and aquaglyceroporin 7 in peroxisome proliferator-activated receptor α null mice is not limiting for adipose triglyceride breakdown in vivo during fasting.