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Department of Animal Sciences, Colorado State University, Fort Collins 80523
1 Correspondence:
phone: 970-491-6667; fax: 970-491-5326; E-mail:
khossner{at}agsci.colostate.edu.
The current study examined the acute effects of intravenous propionate infusion on plasma hormones and metabolites and the expression of adipose tissue lipogenic genes. Four yearling rams were assigned to one of two groups (saline or propionate infusion) in a crossover design. All sheep were cannulated in both jugular veins and infused with 1.2 M propionate at a rate of 64 µmol•min-1•kg BW-1 for 30 min. Blood samples were collected at -10, 0, 5, 10, 20, 30, 60, and 120 min after initiation of infusion. Subcutaneous adipose tissue biopsies were obtained from the tailhead at 0 and 2 h after propionate infusion and analyzed for gene expressions of lipoprotein lipase, acetyl CoA carboxylase, fatty acid synthase, peroxisome proliferator-activated receptor 
, leptin, and uncoupling protein-2 using a nonisotopic ribonuclease protection assay. The partial cDNA of the enoyl reductase region of ovine fatty acid synthase was cloned and sequenced from s.c. adipose tissue of sheep. The deduced amino acid sequence (210 amino acids) was 86% identical to human, 88% identical to rat, 88% identical to mouse, and 72% identical to chicken. Plasma glucose and insulin concentrations abruptly increased 5 min after beginning propionate infusion and further increased up until 30 min but were unaffected in saline-infused sheep (P < 0.05). Plasma concentration of NEFA decreased (P < 0.05) during propionate infusion, whereas IGF-I levels were unaltered. The amounts of lipoprotein lipase, acetyl CoA carboxylase, fatty acid synthase, peroxisome proliferator-activated receptor , and leptin mRNA increased (P < 0.05) in s.c. adipose tissue of propionate-infused sheep compared with those of saline-infused sheep. However, uncoupling protein-2 mRNA decreased (P < 0.05) in propionate-infused sheep. This study demonstrates that an acute nutrient challenge, in the form of i.v. propionate, can stimulate or inhibit the expression of various adipose tissue genes involved with lipogenesis and adipose tissue metabolism.
Key Words: Adipose Tissue • Complementary DNA • Fatty Acid Synthase • Lipogenesis • Propionate • Sheep
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