Effects of Dietary Anaplerotic and Ketogenic Energy Sources on Renal Fatty Acid Oxidation Induced by Clofibrate in Suckling Neonatal Pigs

Abstract

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.

Keywords: PPARα activation; Renal fatty acid oxidation; anaplerotic and ketogenic energy.

Figure 1

The main effect of clofibrate on palmitic acid oxidation. Data (Lsmeans ± SEM) are ¹⁴C-accumulations in CO₂, acid soluble products (ASP) and CO₂ + ASP (n = 32). ^abc Treatments (newborn, clof− (no clofibrate supplementation) and clof+ (clofibrate supplementation)) for CO₂, ASP and CO₂ + ASP with different superscripts differ (p < 0.05).

Figure 2

The main effect of dietary treatments on [1-¹⁴C]-palmitic acid oxidation. GlySuc (diet supplement with glycerol and succinate), TriC5 (triglyceride of valerate), TriC6 (triglyceride of hexanoate), and Tri2MPA (triglyceride of 2MPA). Data (Lsmeans ± SEM) are ¹⁴C-accumulations in CO₂, acid soluble products (ASP) and CO₂ + ASP (n = 16). ^a,b Treatments for CO₂, ASP, and CO₂ + ASP with different superscripts differ (p < 0.05).

Figure 3

The main effect of carnitine and inhibitors of 3-hydroxy-3-methyl-glutaryl-CoA synthase (HMGCS) and acetoacetyl-CoA deacylase (AACD) on palmitic acid oxidation. Fresh kidney homogenates were incubated with palmitic acid only (control), and carnitine, iodoacetamide (Idoacet), or L659699. Data in A (Lsmeans ± SEM) are ¹⁴C-accumulations in CO₂, acid soluble products (ASP), and CO₂ + ASP (n = 16). Data in B (Lsmeans± SEM) are the percentage of the ¹⁴C-accumulations in CO₂, acid soluble products (ASP), and CO₂ + ASP (n = 16). ^a,b Treatments in (A) and (B) for CO₂, ASP, and CO₂ + ASP with different superscripts differ (p < 0.05).

Figure 4

The effect of clofibrate and dietary treatments on citrate synthase and propionyl-CoA carboxylase activity. Data (Lsmeans ± SEM) are specific activities (nmol/(h.mg of tissue protein)); n = 16). * indicates difference in (A) between pigs fed GlySuc with and without clofibrate (p < 0.004). ^a,b,c,d Treatments cross columns in (B) with different superscripts differ (p < 0.05). ^# indicate difference in (A,B) between newborn and 5 d-old pigs (p < 0.05).

Figure 5

The effect of dietary clofibrate fed to pigs for five days on acetyl-CoA carboxylase activity. Data (Lsmeans ± SE) are specific activities (nmol/(h.mg of tissue protein)). No significant difference was observed between pigs with and without clofibrate (p = 0.06). ^# The enzyme activity was on average 3.7-fold greater from 5 d-old pigs than newborn pigs (p < 0.04).