Impact of endotoxin on UCP homolog mRNA abundance, thermoregulation, and mitochondrial proton leak kinetics.
Linking tissue uncoupling protein (UCP) homolog abundance with functional metabolic outcomes and with expression of putative genetic regulators promises to better clarify UCP homolog physiological function. A murine endotoxemia model characterized by marked alterations in thermoregulation was employed to examine the association between heat production, UCP homolog expression, and mitochondrial proton leak ("uncoupling"). After intraperitoneal lipopolysaccharide (LPS, approximately 6 mg/kg) injection, colonic temperature (T(c)) in adult female C57BL6/J mice dropped to a nadir of approximately 30 degrees C by 8 h, preceded by a four- to fivefold drop in liver UCP2 and UCP5/brain mitochondrial carrier protein 1 mRNA levels, with no change in their hindlimb skeletal muscle (SKM) expression. SKM UCP3 mRNA rose fivefold during development of hypothermia and was correlated with an LPS-induced increase in plasma free fatty acid concentration. UCP2 and UCP5 transcripts recovered about three- to sixfold in both tissues starting at 6-8 h, preceding a recovery of T(c) between 16 and 24 h. SKM UCP3 followed an opposite pattern. Such results are not consistent with an important influence of UCP3 in driving heat production but do not preclude a role for UCP2 or UCP5 in this process. The transcription coactivator PGC-1 displayed a transient LPS-evoked rise (threefold) or drop (two- to fivefold) in SKM and liver expression, respectively. No differences between control and LPS-treated mouse liver or SKM in vitro mitochondrial proton leak were evident at time points corresponding to large differences in UCP homolog expression.
Yu
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Department of Endocrinology, Genentech, Inc., South San Francisco, California 94080, USA.
Barger
J L
JL
Boyer
B B
BB
Brand
M D
MD
Pan
G
G
Adams
S H
SH
D000818:Animals; D001831:Body Temperature; D001833:Body Temperature Regulation / Q000187:drug effects; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D019446:Endotoxemia / Q000139:chemically induced / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D007473:Ion Channels; D008070:Lipopolysaccharides / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D026901:Membrane Transport Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism; D008931:Mitochondria, Muscle / Q000187:drug effects / Q000378:metabolism; D024101:Mitochondrial Proteins; D008933:Mitochondrial Swelling; D000071245:Mitochondrial Uncoupling Proteins; D018482:Muscle, Skeletal / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011522:Protons; D012333:RNA, Messenger / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3
D002352:Carrier Proteins; D005230:Fatty Acids, Nonesterified; D007473:Ion Channels; D008070:Lipopolysaccharides; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D000071245:Mitochondrial Uncoupling Proteins; D009419:Nerve Tissue Proteins; D011506:Proteins; D011522:Protons; D012333:RNA, Messenger; C492124:Slc25a14 protein, mouse; D014157:Transcription Factors; C000604390:Ucp2 protein, mouse; C000604393:Ucp3 protein, mouse; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3; C111264:peroxisome-proliferator-activated receptor-gamma coactivator-1