Harteneck, Debra

ObjectiveThe relationship between inflammation, obesity, and adverse metabolic conditions is associated with adipose tissue macrophages (ATM). This study compared the measurements of human ATM using flow cytometry, immunohistochemistry (IHC), and real‐time polymerase chain reaction (RT‐PCR) of ATM markers.MethodsA new software program (AMCounter) was evaluated to help measure ATM using IHC, and this was compared to flow cytometry and RT‐PCR.ResultsIHC had good intraindividual reproducibility for total (CD68), proinflammatory (CD14), and anti‐inflammatory (CD206) ATM. The AMCounter improved interreader agreement and was more time efficient. Flow cytometry had acceptable intraindividual reproducibility for the percentage of CD68+ cells that were CD14+ or CD206+, but not for ATMs per gram of tissue. ATMs per gram of tissue was much greater using IHC than flow cytometry. The flow cytometry and IHC measures of ATM from the same biopsies were not correlated. There were statistically significant correlations between RT‐PCR CD68 and IHC CD68, CD14, and CD206 ATMs per 100 adipocytes. Also of interest were statistically significant correlations between RT‐PCR CD68 and IHC CD68, CD14, and adipose flow cytometry measures of CD68+, CD68+/CD14+, and CD68+/CD206+ ATMs per gram of tissue.ConclusionsThe AMCounter software helps provide reproducible and efficient measures of IHC ATMs. Flow cytometry, IHC, and RT‐PCR measures of adipose inflammation provide somewhat different information.

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.