Dietary Phytase and Lactic Acid-Treated Cereal Grains Differently Affected Calcium and Phosphorus Homeostasis from Intestinal Uptake to Systemic Metabolism in a Pig Model

Abstract

High intestinal availability of dietary phosphorus (P) may impair calcium (Ca) homeostasis and bone integrity. In the present study, we investigated the effect of phytase supplementation in comparison to the soaking of cereal grains in 2.5% lactic acid (LA) on intestinal Ca and P absorption; intestinal, renal, and bone gene expression regarding Ca and P homeostasis; bone parameters; and serum levels of regulatory hormones in growing pigs. Thirty-two pigs were randomly assigned to one of four diets in a 2 × 2 factorial design in four replicate batches for 19 days. The diets comprised either untreated or LA-treated wheat and maize without and with phytase supplementation (500 phytase units/kg). Although both treatments improved the P balance, phytase and LA-treated cereals differently modulated gene expression related to intestinal absorption, and renal and bone metabolism of Ca and P, thereby altering homeostatic regulatory mechanisms as indicated by serum Ca, P, vitamin D, and fibroblast growth factor 23 levels. Moreover, phytase increased the gene expression related to reabsorption of Ca in the kidney, whereas LA-treated cereals decreased the expression of genes for osteoclastogenesis in bones, indicating an unbalanced systemic availability of minerals. In conclusion, high intestinal availability of dietary P may impair Ca homeostasis and bone integrity.

Short-Chain Fatty Acids Modulate Permeability, Motility and Gene Expression in the Porcine Fetal Jejunum Ex Vivo

“…In total, 22 target genes in the jejunal tissue samples coding for SCFA-sensing receptors, transporters, transcription factors and cytokines were analyzed (Table S1). Previously published primers for amplification of the target and housekeeping genes were checked for accuracy [19][20][21], or the primer sets were newly designed. Both tasks were accomplished using PrimerBLAST (www.ncbi.nlm.nih.gov/tools/primer-blast/ (accessed on 4 May 2022)).…”

“…After an initial denaturation step at 95 • C for 2 min, 40 cycles of 95 • C for 30 s followed, as well as primer annealing and elongation at 60 • C for 60 s. Melting curve analysis was performed to verify the specificity of the PCR amplification. For the calculation of the relative gene expression, ACTB, GAPDH, and B2M were identified to be the most stably expressed HKGs after assessment with NormFinder and BestKeeper and were used as endogenous controls [19]. The relative gene expression was calculated using the 2 −∆∆Cq method, for which the geometric mean of the HKG was used for normalization of the Cq values to determine the ∆Cq values.…”

Evaluation of serum parameters to predict the dietary intake of calcium and available phosphorus in growing pigs

“…As potential candidates, fibroblast growth factor 23 (FGF23), with its primary function to decrease systemic P and VitD levels ( Erben, 2016 ), is used in the early detection of bone abnormalities in humans ( Rupp et al, 2019 ), whereby evidence in pigs is still scarce. We could previously show that FGF23 has a certain role in the Ca homeostasis, but we could not find a clear association with the P metabolism ( Vötterl et al, 2020 ). Further regulators for bone mineralization that are linked to the P homeostasis are alkaline phosphatase (ALP), which enhances the local P concentration, and OCN, which binds P in the bone ( Penido and Alon, 2012 ; van Riet et al, 2013 ).…”

“…This resulted in the trend for the improved G:F ratio, indicating increased digestibility and conversion of nutrients of phytase-supplemented diets. Phytase supplementation increases the intestinal aP availability and absorption ( Vötterl et al, 2020 ), which likely induced the higher serum P of pigs receiving the Phy diet until experimental day 23. Afterward, however, serum P was lower in pigs fed the Phy compared with the Con diet, suggesting a reduced intestinal absorption but increased renal excretion as regulatory response in these pigs.…”

“…An auto analyzer for clinical chemistry using enzymatic colorimetric assays (Cobas 6000/c501; Roche Diagnostics GmbH, Rotkirch, Canton of Zug, Switzerland) was used to determine serum content of P, Ca, ALP, cholesterol, nonesterified fatty acids (NEFA), triglycerides, and urea. The Ca:P ratio in serum was calculated to assess the systemic availability of Ca and P and their association with the regulatory hormones ( Veum, 2010 ; Gerlinger et al, 2020 ; Vötterl et al, 2020 ). A porcine-specific enzyme-linked immunosorbent assay (ELISA) was used to determine FGF23 (Porcine FGF23 ELISA kit, Wuhan Fine Biotech Co., Ltd., Wuhan, Hubei, China; coefficient of variation [CV] < 10%).…”