Ucp3 expression during weight gain and loss, cold exposure, and fasting in the collared lemming.
OBJECTIVE
To determine the gene sequence and tissue distribution of uncoupling protein 3 (Ucp3) in the collared lemming, we quantified mRNA expression of Ucp3 under known states of altered energy expenditure (photoperiod-induced weight gain and loss, cold exposure, and fasting) and measured mitochondrial oxygen consumption to assess possible functional changes in energy expenditure.


METHODS
The Ucp3 gene sequence information was obtained using the reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends methods. Northern blots were used to determine mRNA expression levels. Respirometry was used to measure oxygen consumption rates in isolated mitochondria.


RESULTS
The lemming Ucp3 gene has a 97% sequence similarity with other published Ucp3 sequences at the amino acid level. Ucp3 mRNA is expressed in muscle, heart, and brown adipose tissue of collared lemmings. Long-photoperiod lemmings have a higher expression of Ucp3 mRNA than short-photoperiod lemmings (p < 0.001) in both muscle and brown adipose tissue. Transferring lemmings from long to short photoperiods (inducing weight gain) significantly decreased Ucp3 mRNA expression (p < 0.01), whereas transferring lemmings from short to long photoperiods (inducing weight loss) significantly increased Ucp3 expression (p < 0.001). Muscle Ucp3 mRNA expression was significantly decreased by 10 days of mild (10 degrees C) cold exposure (p < 0.001). Muscle Ucp3 mRNA expression was significantly increased by fasting (p < 0.01) and was correlated to plasma free fatty acid levels (r = 0.7). Photoperiod transfer did not alter mitochondrial coupling.


CONCLUSIONS
These data suggest that UCP3 may not be involved in energy expenditure in the collared lemming.
Blaylock
Matthew L
ML
Webb Building 419, 1530 Third Avenue South, Birmingham, AL 35294-3360, USA.
Wang
Ruixue
R
Shan
Dan
D
Nagy
Tim R
TR
D000595:Amino Acid Sequence; D000818:Animals; D003411:Arvicolinae; D001483:Base Sequence; D001835:Body Weight / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D003080:Cold Temperature; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004734:Energy Metabolism / Q000235:genetics / Q000502:physiology*; D005215:Fasting / Q000502:physiology; D005784:Gene Amplification; D005786:Gene Expression Regulation; D007473:Ion Channels; D008297:Male; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D010101:Oxygen Consumption; D017440:Photoperiod; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D000071247:Uncoupling Protein 3; D015430:Weight Gain / Q000502:physiology; D015431:Weight Loss / Q000502:physiology
D002352:Carrier Proteins; D018076:DNA, Complementary; D007473:Ion Channels; D024101:Mitochondrial Proteins; D000071247:Uncoupling Protein 3