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Originally published In Press as doi:10.1194/jlr.M700519-JLR200 on January 5, 2008

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Journal of Lipid Research, Vol. 49, 870-879, April 2008
Copyright © 2008 by American Society for Biochemistry and Molecular Biology

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

Dalan R. Jensen1,*, Leslie A. Knaub*, John P. Konhilas§, Leslie A. Leinwand§, Paul S. MacLean*,{dagger} and Robert H. Eckel*

* Division of Endocrinology, Diabetes, and Metabolism, University of Colorado at Denver, Aurora, CO
{dagger} Center for Human Nutrition, University of Colorado at Denver, Aurora, CO
§ Department of Molecular, Cellular, and Developmental Biology, University of Colorado at Boulder, Boulder, CO

Published, JLR Papers in Press, January 5, 2008.

1 To whom correspondence should be addressed. e-mail: dalan.jensen{at}uchsc.edu

LPL is an enzyme involved in the breakdown and uptake of lipoprotein triglycerides. In the present study, we examined how the transgenic (Tg) overexpression of human LPL in mouse skeletal muscle affected tolerance to cold temperatures, cold-induced thermogenesis, and fuel utilization during this response. Tg mice and their nontransgenic controls were placed in an environmental chamber and housed in metabolic chambers that monitored oxygen consumption and carbon dioxide production with calorimetry. When exposed to 4°C, 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 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 muscles of Tg mice. These data suggest that Tg 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.

Supplementary key words metabolic rate • respiratory quotient • body temperature • fiber-typing • uncoupling proteins • activity • birds

Abbreviations: BAT, brown adipose tissue; MR, metabolic rate; NST, nonshivering thermogenesis; nTg, nontransgenic; PRCF, percent relative cumulative frequency; RQ, respiratory quotient; Tg, transgenic; UCP-1, uncoupling protein-1; WAT, white adipose tissue






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