Abstract
BackgroundVery low-protein (VLP) diets negatively impact calcium (Ca) metabolism and absorption. The objective of this study was to investigate the effect of supplemental branched-chain amino acids (BCAA) and limiting amino acids (LAA) on Ca digestibility, absorption and reabsorption in pigs fed with VLP diets. Forty-eight piglets were assigned to six treatments: positive control (PC), negative control (NC), and NC containing LAA 25%, LAA 50%, LAA + BCAA 25% (LB25) and LAA + BCAA 50% (LB50) more than recommendations.ResultsRelative to PC or NC, LB25 and LB50 had higher digestibility of Ca and plasma Ca and phosphorus (P), but lower plasma vitamin D3. LB50 tended to increase vitamin D receptor transcript and protein in the gut, but decreased mRNA or protein abundance of parathyroid hormone 1 receptor (PTH1R), calbindin 1 (CALB1), cytochrome P450 family 27 subfamily B member 1 and occludin in small intestine. LB50 increased the transcript of cytochrome P450 family 24 subfamily A member 1 and PTH1R but decreased the transcript of transient receptor potential cation channel subfamily V member 5, CALB1 and solute carrier family 17 member 4 in kidney.ConclusionOverall, BCAA increased Ca digestibility through regulating the transcellular and paracellular Ca absorption in the gut and reabsorption in kidney during protein restriction.
Highlights
Very low-protein (VLP) diets negatively impact calcium (Ca) metabolism and absorption
We recently showed that the branched-chain amino acid (BCAA) metabolism is significantly affected in pigs fed with VLP diets [4]
While Apparent fecal digestibility (AFD) of P was ~ 9% and 14% lower in LAA + BCAA 25% (LB25) and LAA + BCAA 50% (LB50) than positive control (PC) during Nursery phase 2 (N2) (Fig. 1B), that was higher for these groups compared to the rest treatments during Nursery phase 3 (N3)
Summary
Very low-protein (VLP) diets negatively impact calcium (Ca) metabolism and absorption. The objective of this study was to investigate the effect of supplemental branched-chain amino acids (BCAA) and limiting amino acids (LAA) on Ca digestibility, absorption and reabsorption in pigs fed with VLP diets. The BCAA-induced growth in pigs fed with VLP diets has been linked with improved muscle protein synthesis, blood amino acids profile, gut microbiota composition and feed intake [7, 11, 13,14,15]. Given the fact that low protein intake impairs the bone health [19, 20], reduces bone mineral density and bone mineral content [21] and digestibility of Ca [22, 23] and evidence on possible involvement of BCAA on Ca balance and absorption [16,17,18, 24], it is unknown whether supplementing VLP diets with BCAA would influence the dynamics of Ca (re)absorption. There are no previous reports on the effect of diets over-supplemented with BCAA on Ca digestibility during protein restriction
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