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Title: UNCOUPLING PROTEIN EXPRESSION IN SKELETAL MUSCLE AND ADIPOSE TISSUE IN RESPONSE TO IN VIVO PORCINE SOMATOTROPIN TREATMENT

Author
item Ramsay, Timothy
item Mitchell, Alva
item Richards, Mark

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2006
Publication Date: 8/1/2008
Citation: Ramsay, T.G., Mitchell, A.D., Richards, M.P. 2008. Uncoupling protein expression in skeletal muscle and adipose tissue in response to in vivo porcine somatotropin treatment. Domestic Animal Endorcinology. 35(2): 130-141.

Interpretive Summary: The uncoupling proteins are thought to be involved in waste heat production, reducing the energy efficiency of growth in animals. Previous studies have detected their presence in swine and their regulation by the endocrine system. This study attempted to determine whether the uncoupling proteins 2 and 3 contribute to the increased heat production observed in somatropin treated swine. The data demonstrate that the uncoupling proteins are responsive to somatotropin treatment in finishing swine. Secondly, uncoupling protein response is highly tissue specific. Correlation analysis indicated a potential role for insulin like growth factor 1 in the regulation of the uncoupling proteins. These results suggest the possibility to manipulate the efficiency of growth in finishing animals by altering the expression of genes associated with heat production and metabolism at a time when changes in body composition can be critical for improving profitability.

Technical Abstract: The present study was performed to examine the response of uncoupling protein (UCP) 2 and UCP3 genes to porcine (p) ST stimuli in finishing pigs. Twelve crossbred barrows (Yorkshire x Landrace) were used in this study. Animals were individually fed a basal diet containing 18% CP, 1.2% lysine, and 3.5 Mcal of DE/kg ad libitum. At 90 kg, six pigs were treated with daily injections of recombinant pST (10 mg) in sterile bicarbonate buffer. The other six pigs were injected with sterile bicarbonate buffer (controls). With initiation of pST treatment, the amount of feed offered was 85% of calculated ad libitum intake, based upon BW and adjusted every 3 d. Diet restriction was performed to correct for the effects of the known inhibition in feed intake due to pST treatment in swine. Animals were maintained on treatment for 2 wk. A blood sample was obtained from each pig on d14 of treatment 6 h after pST injection. Tissue samples were collected on d15, frozen in liquid nitrogen and stored at -80ºC prior to analysis for mRNA abundance. Total RNA was amplified by reverse transcription - PCR with subsequent quantification of transcripts by capillary electrophoresis with laser-induced fluorescence detection. Samples included outer subcutaneous adipose tissue (OSQ), middle subcutaneous adipose tissue (MSQ), leaf fat, liver, longissimus (LM) and biceps femoris (BF). Treatment with pST increased serum triglycerides (p = 0.037) and non-esterified fatty acid (P = 0.002) concentrations relative to control pigs. Serum glucose concentration was unaffected by pST treatment in swine (p = 0.268). Serum IGF-I (P = 0.002), insulin (P = 0.004), thyroxine (P = 0.002) and triiodothyronine (P = 0.005) concentrations were elevated by pST treatment while serum cortisol concentration was unaffected (P = 0.699). UCP2 mRNA abundance was increased in liver (P = 0.001) and all three sites of adipose tissue deposition by pST treatment (P < 0.05). Administration of pST increased UCP3 mRNA abundance by 42% in LM (P = 0.003) relative to control animals. The present data suggest that pST or the metabolic adaptations to pST have a role in regulating UCP2 and UCP3 expression.