Fasting-induced increases in aquaporin 7 and adipose triglyceride lipase mRNA expression in adipose tissue are attenuated by peroxisome proliferator-activated receptor alpha deficiency.
OBJECTIVE
To investigate the impact of peroxisome proliferator-activated receptor alpha 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.


METHODS
Studies using wild-type and peroxisome proliferator-activated receptor alpha 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 alpha 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 alpha 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 beta-adrenergic-stimulated net glycerol release was higher with isolated adipocytes from fasted peroxisome proliferator-activated receptor alpha null mice compared with those of fasted wild-type mice.


CONCLUSIONS
Peroxisome proliferator-activated receptor alpha 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 alpha null mice is not limiting for adipose triglyceride breakdown in vivo during fasting.
Walker
C G
CG
Centre for Diabetes and Metabolic Medicine, Institute of Cellular and Molecular Medicine, Queen Mary, University of London, London, UK.
Holness
M J
MJ
Gibbons
G F
GF
Sugden
M C
MC
D017667:Adipocytes / Q000502:physiology; D052436:Adipose Tissue, White / Q000166:cytology / Q000502:physiology*; D000818:Animals; D020346:Aquaporins / Q000235:genetics*; D001786:Blood Glucose; D002265:Carboxylic Ester Hydrolases / Q000235:genetics*; D048429:Cell Size; D015536:Down-Regulation / Q000502:physiology; D004435:Eating / Q000502:physiology; D005215:Fasting / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D007328:Insulin / Q000097:blood; D008049:Lipase; D008066:Lipolysis / Q000502:physiology; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008817:Mice, Mutant Strains; D047493:PPAR alpha / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D000217:Acyltransferases
D020346:Aquaporins; D001786:Blood Glucose; D002265:Carboxylic Ester Hydrolases; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D008049:Lipase; D047493:PPAR alpha; D012333:RNA, Messenger; C491927:Aqp7 protein, mouse; C494445:PNPLA2 protein, mouse; D000217:Acyltransferases