Plasma NEFA storage in adipose tissue in the postprandial state: sex-related and regional differences

Abstract

Aims/hypothesis: We recently reported that a small fraction of circulating NEFA is stored through direct uptake in subcutaneous fat in postabsorptive humans in vivo and that this pathway may favour lower-body fat distribution in women. Here, we examined sex-related and regional differences in storage of plasma NEFA in subcutaneous adipose tissue during postprandial conditions.

Methods: At 1 h after lunch, men and women of normal weight received an intravenous bolus of approximately 1.66 MBq [1-(14)C]oleate followed by timed subcutaneous fat biopsies. The preceding breakfast was either a normal- or high-fat meal; the high-fat breakfast was used to create postprandial oleate concentrations in the postabsorptive range.

Results: Storage of the NEFA tracer in adipose tissue (dpm/g lipid) was greater in women; in both sexes abdominal fat stored tracer more avidly than femoral fat. A greater fraction of the administered tracer was stored in whole body subcutaneous fat of women than in that of men (27 +/- 3 vs 8 +/- 1%, respectively, p < 0.0001). No significant differences in tracer storage were observed between participants consuming the high- vs normal-fat breakfast.

Conclusions/interpretation: Postprandial NEFA storage in subcutaneous fat through direct uptake accounts for approximately 25% of NEFA disposal in women, but for <10% in men in a wide range of circulating NEFA concentrations. It is greater in the upper- than lower-body subcutaneous fat, favouring upper-body fat accumulation in both sexes.

Figure 1

Schematic of study protocol. Subcutaneous adipose tissue biopsies were performed in the abdominal and femoral regions.

Figure 2

Plasma oleate (left panel) and palmitate concentrations (right panel) before and after the intravenous [1-¹⁴C]oleate bolus at time zero. Note the different scales of the Y axes. A meal (lunch) was consumed at −45 to −15 min. Subcutaneous abdominal and femoral adipose tissue biopsies were collected at 45 min after the tracer bolus. Values for women are represented by triangles and for men are represented by circles. The data are depicted for those consuming the high fat breakfast using solid symbols and for those consuming the normal fat breakfast using open symbols. Values are means±SE. For statistical comparisons see Results.

Figure 3

Plasma insulin (left panel) and glucose concentrations (right panel) before and after the intravenous [1-¹⁴C]oleate bolus at time zero. A meal (lunch) was consumed at −45 to −15 min. Subcutaneous abdominal and femoral adipose tissue biopsies were collected at 45 min after the tracer bolus. Values for women are represented by triangles and for men are represented by circles. The data are depicted for those consuming the high fat breakfast using solid symbols and for those consuming the normal fat breakfast using open symbols. Values are means±SE. For statistical comparisons see Results.

Figure 4

Time course of non-chylomicron triacylglycerol-fatty acid (TGFA) specific activity (SA) (top left panel), non-chylomicron concentration (bottom left panel) and plasma oleate SA (top right panel) after the intravenous [1-¹⁴C]oleate bolus at time zero. A meal (lunch) was consumed at −45 to −15 min (not depicted in the Figure). Subcutaneous abdominal and femoral adipose tissue biopsies were collected at 45 min after the tracer bolus (indicated by the arrow). Values for women are represented by triangles and for men are represented by circles. The data are depicted for those consuming the high fat breakfast using solid symbols and for those consuming the normal fat breakfast using open symbols. Values are means±SE. For statistical comparisons see Results.