Increased thermoregulation in cold exposed transgenic mice overexpressing lipoprotein lipase in skeletal muscle: An avian phenotype?

Dalan R. Jensen, Leslie A. Knaub, John P. Konhilas, Leslie A. Leinwand, Paul S. MacLean, and Robert H. Eckel

Medicine/Endocrinology, University of Colorado Denver, Aurora, CO 80045

Corresponding Author: Dalan.Jensen{at}UCHSC.edu

Lipoprotein lipase (LPL) is an enzyme involved in the breakdown and uptake of lipoprotein triglycerides. In the present study, we examined how the transgenic overexpression of human LPL in mouse skeletal muscle affected tolerance to cold temperatures, cold-induced thermogenesis, and fuel utilization during this response. Transgenic mice (Tg) and their non-transgenic controls (nTg) were placed in an environmental chamber and housed in metabolic chambers that monitored oxygen consumption and carbon dioxide production with calorimetry. When exposed to 4C, an attenuation in the decline in body temperature in Tg mice was accompanied by an increased metabolic rate (15%, p<0.001) and a reduction in respiratory quotient (p<0.05). Activity levels, the expression of uncoupling proteins (UCPs) in brown fat and muscle, and lean mass failed to explain the enhanced cold tolerance and thermogenesis in Tg mice. The more oxidative Type IIa fibers were favored over the more glycolytic Type IIb fibers (p<0.001) in the gastrocnemius and quadriceps muscle of Tg mice. These data suggest that transgenic overexpression of LPL in skeletal muscle increases cold tolerance by enhancing the capacity for fat oxidation, producing an avian-like phenotype in which skeletal muscle contributes significantly to the thermogenic response to cold temperatures.

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