Coordinated release of acylation stimulating protein (ASP) and triacylglycerol clearance by human adipose tissue in vivo in the postprandial period

Abstract

The objective of this study was to determine whether Acylation Stimulating Protein (ASP) is generated in vivo by human adipose tissue during the postprandial period. After a fat meal, samples from 12 subjects were obtained (up to 6 h) from an arterialized hand vein and an anterior abdominal wall vein that drains adipose tissue. Veno-arterial (V-A) gradients across the subcutaneous adipose tissue bed were calculated. The data demonstrate that ASP is produced in vivo (positive V-A gradient) with maximal production at 3-5 h postprandially. The plasma triacylglycerol (TAG) clearance was evidenced by a negative V-A gradient. It increased substantially after 3 h and remained prominant until the final time point. There was, therefore, a close temporal coordination between ASP generation and TAG clearance. In contrast, plasma insulin and non-esterified fatty acid (NEFA) had an early (1-2 h) postprandial change. Fatty acid incorporation into adipose tissue (FIAT) was calculated from V-A glycerol and non-esterified fatty acid (NEFA) differences postprandially. FIAT was negative during the first hour, implying net fat mobilization. FIAT then became increasingly positive, implying net fat deposition, and overall followed the same time course as ASP and TAG clearance. There was a direct positive correlation between total ASP production and total FIAT ( r ϭ 0.566, P Ͻ 0.05). These data demonstrate that ASP is generated in vivo by human adipocytes and that this process is accentuated postprandially, supporting the concept that ASP plays an important role in clearance of TAG from plasma and fatty acid storage in adipose tissue.

Increased postprandial fatty acid trapping in subcutaneous adipose tissue in obese women

“…The lean subjects demonstrated increased release of ASP after the initial postprandial period, just as has been observed previously (9). However, the variance was sufficiently large that, as opposed to our earlier study (9), there was no significant difference between ASP release in the first and second halves of the postprandial period. There was, however, no trend for the release of ASP to increase over time in the obese group, being already maximal at the onset.…”

“…Glycerol was measured in whole blood (16). Human ASP was assayed as previously described (9). The intra-assay variability was 4% whereas the interassay variability was 8%.…”

“…The intra-assay variability was 4% whereas the interassay variability was 8%. Fatty acid incorporation into adipose tissue (FIAT) was calculated as previously described (9).…”

“…Our initial study, which examined the in vivo release of ASP from normal human subcutaneous adipose tisssue, demonstrated that i ) ASP was released after an oral fat load, ii ) the release of ASP increased substantially in the second half of this period, and iii ) TG clearance and fatty acid uptake paralleled the changes in ASP release (9). Plasma insulin was also increased over this period and therefore both insulin and ASP could have contributed to the increase in fatty acid trapping by subcutaneous adipocytes that was evident in the postprandial period.…”

Hydrogenated fat consumption affects acylation-stimulating protein levels and cholesterol esterification rates in moderately hypercholesterolemic women

“…In this regard, in vivo (18,19) and in vitro (20) studies have shown that acylation-stimulating protein (ASP) is an important determinant of the rate of adipocyte TG uptake and redistribution. ASP action is achieved through an interaction with the cell membrane, which results in stimulation of the second messenger diacylglycerol.…”