Betaine Affects Muscle Lipid Metabolism Via Regulating the Fatty Acid Intake and Oxidation in Finishing Pig

This experiment was conducted to investigate how betaine affect muscle lipid metabolism. A total of 120 crossbred gilts ( Landrace × Yorkshire × Duroc ) with an initial body weight of 70.07kg (SD 0.70 kg) were randomly allocated into 3 treatments. Pigs were fed a corn-soybean meal basal diet supplemented with betaine at 0, 1250 or 2500 mg/kg, respectively. The feeding experiment lasted 42 days after a 7- day adaptation period. At the end of the trial, eighteen pigs (six from each dietary treatment) were euthanized and individual blood samples were collected and samples of longissimus muscle between the 6th and 7th rib were obtained on the left side of the carcass. All data were analyzed using one-way ANOVA of SAS 9.1. The results showed that betaine significantly increased the concentration of free fatty acid (FFA) in muscle (P<0.05) and decreased serum FFA numerically (P>0.05). Furthermore, the levels of serum cholesterol and high-density lipoprotein cholesterol were decreased (P<0.05) while total cholesterol content was increased in muscle (P<0.05) with dietary betaine supplementation. Experiments about key factors involved in fatty acid transportation showed that the gene expression of lipoprotein lipase, fatty acid translocase/cluster of differentiation (FAT/CD36), fatty acid binding protein (FABP3) and fatty acid transport protein (FATP1) were significantly increased with betaine supplementation (P<0.05). Besides, the protein expressions of FATP1 and FABP3 were enhanced as well (P<0.05). As for the key factors involved in fatty acid oxidation, though the level of carnitine and malony-CoA in muscle were not affected, both gene expression and protein expression of carnitine palmitransferase-1(CPT1) were significantly increased with betaine supplementation (P<0.05). Additionally, the gene expression of AMPKα2 and PPARα as well as the protein expression of p-AMPK was increased (P<0.05). The results suggest that betaine supplementation could promote fatty acid uptake in the muscle and enhance fatty acid oxidation, leading to an increase of fatty acid in muscle.