Enhanced apoB48 metabolism in lipoprotein lipase X447 homozygotes

Rationale: Lipoprotein lipase (LPL) X447 homozygotes are characterized by enhanced conversion of TRL apoB100. Here, we set out to investigate whether this LPL variant is also associated with enhanced apoB48 clearance. Therefore, we evaluated apoB48 kinetics in X447 homozygotes in the fed state by infusion of isotope L-[1-(13) C]-valine and subsequent compartmental modeling. Methods and results: ApoB48 metabolism was assessed in five X447 homozygotes (X/X genotype) and five S447 homozygotes (S/S genotype). Subjects were continuously fed and received infusion of stable isotope L-[1-(13) C]-valine. Results were analyzed by SAAM It modeling. Fasting (2.4-fold, p = 0.02) as well as non-fasting (1.6-fold, p = 0.09) apoB48 concentration was increased in the X447 homozygotes compared to S447 homozygotes. In addition, the X447 homozygotes exhibited a 1.7-fold higher apoB48 poolsize (p=0.04). Interestingly, apoB48 fractional catabolic rate (FCR) was 1.9-fold higher (p = 0.007) and apoB48 synthesis was more than two-fold higher (p = 0.006) in the X447 homozygotes compared to S447 homozygotes. Conclusion: In the present study, we show that X447 homozygotes exhibit enhanced apoB48 clearance. Previously, these homozygotes were shown to present with enhanced apoB 100 TRL conversion. Combined, this LPLS447X gain of function variant affects apoB48 as well as apoB 100 TRL metabolism. (c) 2006 Elsevier Ireland Ltd. All rights reserved.