Effect of Medium Chain Triglycerides on TCA and Ketogenic Capacity of Proximal Intestinal Fatty Acid Oxidation in Clofibrate Feed Newborn Pigs

Abstract

Newborn pigs are much less efficient at utilizing milk fat as an energy source, than weaned pigs, due to a limited capacity of fatty acid oxidation. We have previously shown that clofibrate, a PPARα agonist, increases fatty acid oxidation levels in newborn pigs by increasing production of key metabolic enzymes. We hypothesize that feeding anaplerotic carbon sources or ketogenic fatty acids in conjunction with clofibrate will improve energy utilization in young pigs by increasing capacities of the TCA cycle or ketogenic activity. To test our hypothesis, suckling newborn pigs (N=48) from 6 litters, which received colostrum for 24 hours, from the North Carolina State University Swine Unit were randomly divided into a 2 (control vs clofibrate) × 4 (glycerol‐succinate, valerate, hexonoate, 2‐methylpentanoate) factorial design. All piglets were fed a standard milk replacer three times a day based on body weight (1.31±.2kg). All supplements, glycerol‐succinate (GS), triglycerides of valeric acid (triC5), hexanoic acid (triC6) or tri‐2‐methylpentanoate (2‐MPA), were fed at ~5% (w/w as fed to maintain an isocaloric diet). For the clofibrate treatment groups, clofibrate was included (.35%) only in the morning feedings. Milk was withheld on the sixth day when the mucosa was collected from the proximal small intestine. The mucosa (28.43±6.12 mg/mL protein) was homogenized and added to flasks that contained a buffer without (control) or with carnitine (1mM), L659699 (1.6 μM), or iodoacetamide (50 μM) and labeled [1–14C] palmitic acid (1mM) as the substrate. L659599 is an inhibitor of both mitochondria and cytosolic hydroxymethylglutaryl‐CoA synthase and iodoacetamide is an inhibitor of acetoacetate synthesis. After 30 mins, the reactions were terminated and 14C accumulation in CO2 and acid soluble products (ASP) was measured to determine fatty acid oxidation rates. The oxidation of palmitic acid (14C accumulations in CO2 +ASP; μmol/h.mg protein) was higher (P < 0.0001) in the pigs that received triC5 (1.54) and triC6 (1.51) than those that received GS (1.27) or 2‐MPA (1.47). No differences were detected between pigs receiving triC5 and triC6 or between GS and 2‐MPA. Clofibrate had no effects on the palmitic acid oxidation from pigs fed GS or triC6, but the 14C accumulation in CO2 and ASP was increased by 40% and 26% in pigs receiving triC5 and 2‐MPA (P <0.0003), respectively. Addition of carnitine with or without clofibrate increased palmitic acid oxidation by 44% as compared with the control (P < 0.0001), while oxidation was reduced by 9% by L659699 (P < 0.004). Oxidation rates in incubations with iodoacetamide were higher than with L659699 (P < 0.03), but were not different from controls (P =0.92). The results indicate that fatty acid oxidation in the mucosa of the proximal small intestine of newborn pigs could be increased by enhancing ketogenic activity and TCA cycle capacity, thus demonstrating that dietary supplementation of ketogenic fatty acid and anaplerotic carbon would be favorable to improve milk fat utilization in pigs during the postnatal period.Support or Funding InformationSupported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2015‐67015‐23245.