Abstract 13186: Lipoprotein-Associated Phospholipase A(2) is Expressed in Human Adipose Tissue and Correlates with HbA1C in Obese Subjects
Background: Elevated circulating lipoprotein-associated phospholipase A(2) (Lp-PLA2) is an independent risk factor for coronary artery disease (CAD), and Lp-PLA2 activity is elevated in plasma of type 2 diabetics. Few studies have considered the presence of Lp-PLA2 in non-vascular tissues despite its elevated presence in diabetics, and while it is known that Lp-PLA2 has multiple glycosylation sites the role of glycosylation in humans is unknown. The purpose of this study was to determine if LpPLA2 is expressed in adipose tissue. We hypothesized that Lp-PLA2 would be present in human adipose tissue and would be related to glucose homeostasis.
Methods: Visceral adipose tissue from 15 morbidly obese (mean BMI= 50 kg/m2, mean age= 45 yrs) and 13 lean (mean BMI =25 kg/m2, mean age= 44 yrs) subjects was collected during bariatric surgery or a comparable non-bariatric surgery, respectively. Lp-PLA2 protein in visceral adipose lysates was examined by western blotting. Hemoglobin A1C (HbA1C) was measured in available pre-surgical samples from the same cohort (lean= 8, obese= 11).
Results: HbA1C was significantly (p= 0.009) higher in obese subjects (6.409 ± 0.36) than lean (5.150 ± 0.10). In adipose lysates a 45 kD band representing unmodified Lp-PLA2, in addition to bands at approximately 56 kD were detected. Analyses were performed hypothesizing that the 56 kD band represents the glycosylated (GL) enzyme. When lean and obese data were combined, there was no correlation between the ratio of GL Lp-PLA2 to unmodified and HbA1C (r= 0.020, p= 0.934), but there was a correlation between the ratio of GL to unmodified Lp-PLA2 and age (r= 0.332, p =0.131). When data from obese subjects were analyzed separately from lean, the ratio of GL Lp-PLA2 to unmodified was correlated with HbA1C (r=0.360, p= 0.277) and age (r= 0.692, p= 0.006). Controlling for age did not change these correlations, but controlling for BMI strengthened the correlation with HbA1C (r= 0.504, p=0.138).
Conclusions: These results show for the first time that Lp-PLA2 is expressed in human visceral adipose tissue. Moreover, in morbidly obese subjects there is a relationship between modified Lp-PLA2 and HbA1C. The roles of different sources of Lp-PLA2, and the function of GL Lp-PLA2 in humans are yet to be determined.
- © 2011 by American Heart Association, Inc.