Sex and depot differences in ex vivo adipose tissue fatty acid storage and glycerol-3-phosphate acyltransferase activity.
Adipose tissue fatty acid storage varies according to sex, adipose tissue depot, and degree of fat gain. However, the mechanism(s) for these variations is not completely understood. We examined whether differences in adipose tissue glycerol-3-phosphate acyltransferase (GPAT) might play a role in these variations. We optimized an enzyme activity assay for total GPAT and GPAT1 activity in human adipose tissue and measured GPAT activity. Omental and subcutaneous adipose tissue was collected from obese and nonobese adults for measures of GPAT and GPAT1 activities, ex vivo palmitate storage, acyl-CoA synthetase (ACS) and diacylglycerol-acyltransferase (DGAT) activities, and CD36 protein. Total GPAT and GPAT1 activities decreased as a function of adipocyte size in both omental (r = -0.71, P = 0.003) and subcutaneous (r = -0.58, P = 0.04) fat. The relative contribution of GPAT1 to total GPAT activity increased as a function of adipocyte size, accounting for up to 60% of GPAT activity in those with the largest adipocytes. We found strong, positive correlations between ACS, GPAT, and DGAT activities for both sexes and depots (r values 0.58-0.91) and between these storage factors and palmitate storage rates into TAG (r values 0.55-0.90). We conclude that: 1) total GPAT activity decreases as a function of adipocyte size; 2) GPAT1 can account for over half of adipose GPAT activity in hypertrophic obesity; and 3) ACS, GPAT, and DGAT are coordinately regulated.
Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota;
Maria
M
Morgan-Bathke
Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota; Guang'anmen Hospital, Beijing, China.
Liang
L
Chen
Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota; Department for Internal Medicine, Triemli Hospital, Zürich, Switzerland;
Elisabeth
E
Oberschneider
Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota;
Debra
D
Harteneck
Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota; jensen@mayo.edu.
Michael D
MD
Jensen
D000273:Adipose Tissue / Q000378:metabolism*; D050154:Adiposity; D000328:Adult; D000368:Aged; D005227:Fatty Acids / Q000378:metabolism*; D005260:Female; D005992:Glycerol-3-Phosphate O-Acyltransferase / Q000378:metabolism*; D006801:Humans; D050356:Lipid Metabolism; D008297:Male; D008875:Middle Aged; D009852:Omentum / Q000378:metabolism; D019308:Palmitic Acid / Q000378:metabolism; D012737:Sex Factors; D050151:Subcutaneous Fat / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism
D005227:Fatty Acids; D014280:Triglycerides; D019308:Palmitic Acid; D005992:Glycerol-3-Phosphate O-Acyltransferase
fat distribution; glycerol-3-phosphate acyltransferase 1; omental fat; subcutaneous fat