Regional variation in high-density lipoprotein binding to human adipocyte plasma membranes of massively obese subjects

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Abstract
Obesity is associated with significant changes in cholesterol and lipoprotein metabolism. High density lipoprotein (HDL) cholesterol is often reduced and adipose tissue cholesterol stores are increased in obese individuals. This prompted a study on the binding of HLD fractions (HDL2 and HDL3) to adipocyte plasma membranes obtained from massively obese subjects (BMI>37 kg m-2) undergoing gastroplasty. Regional variation in HDL binding to these adipocyte plasma membranes was demonstrated. Membranes derived from the abdominal subcutaneous depot exhibited similar binding affinity (Kd) but higher binding capacity (Bmax) for HDL2 and HDL3 than that from the omental depot. There was significant inter-individual variation in Bmax but the amount of HDL2 or HDL3 bound to the two depots of the same individual was positively correlated (HDL2, r=0.66, P<0.05; HDL3. r=0.88, P < 0.01). While HDL2 binding showed a higher affinity (lower Kd) than HDL3, a significant positive correlation existed between HDL2 and HDL3 binding to the same adipocyte membranes (r=0.89, P < 0.01). A significant inverse correlation (P < 0.05) was also observed between HDL2 and HDL3 binding to adipocyte membranes and plasma HDL-cholesterol concentration. These results suggest that adipose tissue is an important site of HDL metabolism and the subcutaneous fat depot may play a proportionally mroe significant role due to its higher HDL binding capacity. It is further suggested that increased HDL binding and metabolism by the expanded adipose tissue mass may contribute to reduced plasma HDL-cholesterol levels frequently associated with obesity.