Abomasal infusion of arginine stimulates SCD and C/EBPß gene expression, and decreases CPT1ß gene expression in bovine adipose tissue independent of conjugated linoleic acid.

Based on previous research with bovine peadipocytes, we hypothesized that infusion of arginine into the abomasum of Angus steers stimulates stearoyl-CoA desaturase (SCD) gene expression in bovine subcutaneous (s.c.) adipose tissue, and that this would be attenuated by conjugated linoleic acid (CLA). Growing Angus steers were infused abomasally with L-arginine 50 g/day; n = 13; provided as L-arginine HCl) or L-alanine (isonitrogenous control, 100 g/day; n = 11) for 14 days. For the subsequent 14 days, half of the steers in each amino acid group were infused with CLA (100 g/day). Body weight gain and average daily gain were unaffected (P > 0.15) by infusion of arginine or CLA into the abomasum. The plasma concentrations of cis-9, trans-11 and trans-10, cis-12 CLA were increased CLA infusion (P = 0.001) and infusion of arginine increased plasma arginine (P = 0.01). Compared with day 0, fatty acid synthase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase enzyme activities in s.c. adipose tissue increased by day 14 in steers infused with either alanine or arginine (all P < 0.01). NADP-MDH activity was higher (P = 0.01) in steers infused with arginine than in steers infused with arginine plus CLA by day 28, but lipid synthesis in vitro from glucose and acetate was unaffected by infusion of either arginine or CLA (P > 0.40). By day 28, C/EBPß and SCD gene expression was higher, and CPT1ß gene expression was lower, in s.c. adipose tissue of steers infused with arginine than in steers infused with alanine (±CLA) (P = 0.05). CLA decreased adipose tissue oleic acid (18:1n-9) in alanine- or arginine-infused steers (P = 0.05), although CLA had no effect on SCD gene expression. The data indicate that supplemental arginine promotes adipogenic gene expression and may promote lipid accumulation in bovine adipose tissue. L-Arginine may beneficially improve beef quality for human consumption.

Immunogenic inhibition of prominent ruminal bacteria as a means to reduce lipolysis and biohydrogenation activity in vitro.

Lipolysis and biohydrogenation in ruminal animals promote the accumulation of saturated fatty acids in their meat and milk. Antibodies were generated against key ruminal lipase contributors Anaerovibrio lipolyticus, Butyrivibrio fibrisolvens, Propionibacterium avidum and acnes. An anti-Pseudomonas lipase antibody was generated to determine if an antibody against a purified protein would be more effective. Each bacterium was cultured and assayed without or with increasing levels of each antibody. Butyrivibrio fibrisolvens H17C also participates in biohydrogenation and therefore the antibody was tested to determine if it could effectively reduce biohydrogenation. Butyrivibrio fibrisolvens was assayed without and with the anti-B. fibrisolvens antibody and linoleic or α-linolenic acid. All antibodies were effective at reducing lipolysis with the anti-Pseudomonas lipase averaging a 78% reduction. The anti-B. fibrisolvens showed a tendency for a reduction (P=0.0713) in biohydrogenation products of α-linolenic acid. Results demonstrate that lipolysis and biohydrogenation can be immunologically inhibited in vitro.