To investigate whether increasing tricarboxylic acid (TCA) cycle activity and ketogenic capacity would augment fatty acid (FA) oxidation induced by the peroxisome proliferator-activated receptor-alpha (PPARα) agonist clofibrate, suckling newborn piglets (n = 54) were assigned to 8 groups following a 2 ( ± clofibrate) × 4 (glycerol succinate [SUC], triglycerides of 2-methylpentanoic acid [T2M], valeric acid [TC5] and hexanoic acid [TC6]) factorial design. Each group was fed an isocaloric milk formula containing either 0% or 0.35% clofibrate (wt/wt, dry matter basis) with 5% SUC, T2M, TC5 or TC6 for 5 d. Another 6 pigs served as newborn controls. Fatty acid oxidation was examined in fresh homogenates of liver collected on d 6 using [1-¹⁴C] palmitic acid (1 mM) as a substrate (0.265 μCi/μmol). Measurements were performed in the absence or presence of L-carnitine (1 mM) or inhibitors of 3-hydroxy-3-methylglutaryl-CoA synthase (L659699, 1.6 μM) or acetoacetate-CoA deacylase (iodoacetamide, 50 μM). Without clofibrate stimulation, ¹⁴C accumulation in CO₂ was higher from piglets fed diets containing T2M and TC5 than SUC, but similar to those fed TC6. Under clofibrate stimulation, accumulation also was higher in homogenates from piglets fed TC5 than all other dietary treatments. Interactions between clofibrate and carnitine or the inhibitors were observed (P = 0.0004) for acid soluble products (ASP). In vitro addition of carnitine increased ¹⁴C-ASP (P < 0.0001) above all other treatments, regardless of clofibrate treatment. The percentage of ¹⁴C in CO₂ was higher (P = 0.0023) in TC5 than in the control group. From these results we suggest that dietary supplementation of anaplerotic and ketogenic FA could impact FA oxidation and modify the metabolism of acetyl-CoA (product of β-oxidation) via alteration of TCA cycle activity, but the modification has no significant impact on the hepatic FA oxidative capacity induced by PPARα. In addition, the availability of carnitine is a critical element to maintain FA oxidation during the neonatal period.

To investigate the role of peroxisome proliferator-activated receptor alpha (PPARα) in carnitine status and intestinal fatty acid oxidation in neonates, a total of 72 suckled newborn piglets were assigned into 8 dietary treatments following a 2 (±0.35% clofibrate) × 4 (diets with: succinate+glycerol (Succ), tri-valerate (TC5), tri-hexanoate (TC6), or tri-2-methylpentanoate (TMPA)) factorial design. All pigs received experimental milk diets with isocaloric energy for 5 days. Carnitine statuses were evaluated, and fatty acid oxidation was measured in vitro using [1-¹⁴C]-palmitic acid (1 mM) as a substrate in absence or presence of L659699 (1.6 µM), iodoacetamide (50 µM), and carnitine (1 mM). Clofibrate increased concentrations of free (41%) and/or acyl-carnitine (44% and 15%) in liver and plasma but had no effects in the intestine. The effects on carnitine status were associated with the expression of genes involved in carnitine biosynthesis, absorption, and transportation. TC5 and TMPA stimulated the increased fatty acid oxidation rate induced by clofibrate, while TC6 had no effect on the increased fatty acid oxidation induced by clofibrate (p > 0.05). These results suggest that dietary clofibrate improved carnitine status and increased fatty acid oxidation. Propionyl-CoA, generated from TC5 and TMPA, could stimulate the increased fatty acid oxidation rate induced by clofibrate as anaplerotic carbon sources.

Maintaining an active fatty acid metabolism is important for renal growth, development, and health. We evaluated the effects of anaplerotic and ketogenic energy sources on fatty acid oxidation during stimulation with clofibrate, a pharmacologic peroxisome proliferator-activated receptor α (PPARα) agonist. Suckling newborn pigs (n = 72) were assigned into 8 dietary treatments following a 2 × 4 factorial design: ± clofibrate (0.35%) and diets containing 5% of either (1) glycerol-succinate (GlySuc), (2) tri-valerate (TriC5), (3) tri-hexanoate (TriC6), or (4) tri-2-methylpentanoate (Tri2MPA). Pigs were housed individually and fed the iso-caloric milk replacer diets for 5 d. Renal fatty acid oxidation was measured in vitro in fresh tissue homogenates using [1-¹⁴C]-labeled palmitic acid. The oxidation was 30% greater in pig received clofibrate and 25% greater (p < 0.05) in pigs fed the TriC6 diet compared to those fed diets with GlySuc, TriC5, and Tri2MPA. Addition of carnitine also stimulated the oxidation by twofold (p < 0.05). The effects of TriC6 and carnitine on palmitic acid oxidation were not altered by clofibrate stimulation. However, renal fatty acid composition was altered by clofibrate and Tri2MPA. In conclusion, modification of anaplerosis or ketogenesis via dietary substrates had no influence on in vitro renal palmitic acid oxidation induced by PPARα activation.

Milk carnitine content decreases quickly with lactation days and is accompanied by PPARα downregulation. This study aimed to investigate the effects of the maternal supplementation of the PPARα agonist, clofibrate, on milk carnitine content and carnitine status in neonates during lactation. Pregnant sows (n = 27) were fed diets containing either 0, 0.25, or 0.5% clofibrate from d107 gestation to d7 of lactation. Carnitines were determined in milk on d1, 3, 5, 7, 10, 14, and 19 post farrowing and in the plasma, intestine, and liver of piglets on d1, 7, 14, and 19. Milk carnitine decreased quadratically with lactation days (p < 0.0001). Hepatic and intestinal carnitines increased with postnatal age (p < 0.05). Correlations between levels were detected between milk and plasma (R² = 0.5, p < 0.0001) and milk and intestine (R² = 0.23; p < 0.05). Clofibrate increased BBH expression (p < 0.05) and tended to increase OCTN2 expression (p = 0.055) in intestine and TMLH in liver (p = 0.059). Hepatic ALD and TMLH increased (p < 0.0005) with postnatal age. However, gene modification had no effect on plasma and mucosa carnitine concentrations. We conclude that changes in carnitines within plasma and mucosa are mostly driven by milk carnitines during postnatal development.

To accelerate maturation of intestinal function and promote growth and development, the effect of maternal clofibrate on intestinal fatty acid metabolism was investigated in postnatal piglets. 27 pregnant sows were fed either 0, 0.25, or 0.5% clofibrate during late gestation and early lactation. [1-14C]-Oleic acid metabolism was measured in vitro in intestinal mucosa of piglets with/without L-carnitine and/or malonate. Clofibrate increased oleic acid metabolism on d1, and the increase was higher from 0.5 than 0.25% of maternal clofibrate (p < 0.005). Flux to CO2 increased with age while flux to acid soluble products (ASP) remained constant after d1. Flux to esterified products (ESP) increased on d7, but the increase was dampened by clofibrate (p < 0.0001). Carnitine increased flux to CO2 and malonate decreased it (p < 0.0001), but neither affected ASP or ESP. Intestinal NEFA and TG levels decreased linearly, and CPT activity increased quadratically with age. Clofibrate increased ACOX abundance but decreased the ratio of CPT1A and CPT1B on d1. Postnatal age increased FABP2 but decreased PPARα and RXRα. In conclusion, maternal supplementation of clofibrate promotes intestinal energy generation from fat oxidation in postnatal piglets, but the promotion is influenced by age, in which ACOX, FABP2 and CPT1 might play modulatory roles.

To accelerate maturation of intestinal function and promote growth and development, the effect of maternal clofibrate on intestinal fatty acid (FA) metabolism was investigated in suckling piglets. Twenty-seven pregnant sows were fed either 0, 0.25, or 0.5% clofibrate, a peroxisome proliferator-activated receptor α (PPARα) agonist, during late gestation and early lactation. [1-¹⁴C]-Oleic acid metabolism was measured in vitro in intestinal mucosa of piglets with/without L-carnitine and/or malonate. Clofibrate increased oleic acid metabolism on d1, and the increase was higher from 0.5% than 0.25% of maternal clofibrate (p < 0.005). Flux to CO₂ increased with age, while flux to acid-soluble products (ASP) remained constant after d1. Flux to esterified products (ESP) increased on d7, but the increase was dampened by clofibrate (p < 0.0001). Carnitine increased flux to CO_2, and malonate decreased it (p < 0.0001), but neither affected ASP or ESP. Intestinal non-esterified FA and triglyceride levels decreased linearly, and carnitine palmitoyl-transferase (CPT) activity increased quadratically with age. Clofibrate increased acyl-CoA oxidase (ACOX) abundance but decreased the ratio of CPT1A and CPT1B on d1. Postnatal age increased FA binding protein 2 (FABP2) but decreased PPARα. In conclusion, maternal supplementation of clofibrate promotes intestinal energy generation from fat oxidation in postnatal piglets, but the stimulation is influenced by age, in which ACOX, FABP2, and CPT1 might play modulatory roles.