Dietary phosphate restriction decreases stem cell proliferation and subsequent growth potential in neonatal pigs

Association Between Serum Calcium and Phosphorus Levels and Insulin-Like Growth Factor-1 in Chinese Children and Adolescents with Short Stature

Objective

The aim of this study was to investigate the effect of serum calcium and phosphorus levels on the insulin-like growth factor 1 (IGF-1) in Chinese children and adolescents with short stature.

Methods

In this cross-sectional analysis, the clinical data of 747 children with height below –2 SD who were evaluated at the Department of Endocrinology, Affiliated Hospital of Jining Medical University from March 1, 2013, to February 28, 2019, were selected. Anthropometric and biochemical indicators were measured. The relationship between the serum calcium and phosphorus levels and IGF-1 was analysed.

Results

The univariate analysis results showed that serum calcium or phosphorus was significantly associated with IGF-1 SDS. In addition, after adjusting for possible confounding factors, a linear relationship between serum calcium and IGF-1 SDS and a non-linear relationship between serum phosphorus and IGF-1 SDS were observed by smooth curve fitting. The results of the fully adjusted linear regression showed that serum calcium was positively associated with IGF-1 SDS (β 1.07, 95% CI 0.21, 1.92; p = 0.015). In the multivariate piecewise linear regression, when the serum phosphorus level was greater than 1.26 mmol/L, the IGF-1 SDS increased with the increase in serum phosphorus (β 1.92, 95% CI 1.36, 2.48; p < 0.001). However, we did not observe a significant relationship when the serum phosphorus level was less than 1.26 mmol/L (p = 0.223).

Conclusion

This study demonstrated that in Chinese children and adolescents with short stature, circulating calcium and phosphorus concentrations may be associated with the regulation of IGF-1 levels, and this relationship merits further investigation.

Satellite cells and their regulation in livestock

Satellite cells are the myogenic stem and progenitor population found in skeletal muscle. These cells typically reside in a quiescent state until called upon to support repair, regeneration, or muscle growth. The activities of satellite cells are orchestrated by systemic hormones, autocrine and paracrine growth factors, and the composition of the basal lamina of the muscle fiber. Several key intracellular signaling events are initiated in response to changes in the local environment causing exit from quiescence, proliferation, and differentiation. Signals emanating from Notch, wingless-type mouse mammary tumor virus integration site family members, and transforming growth factor-β proteins mediate the reversible exit from growth 0 phase while those initiated by members of the fibroblast growth factor and insulin-like growth factor families direct proliferation and differentiation. Many of these pathways impinge upon the myogenic regulatory factors (MRF), myogenic factor 5, myogenic differentiation factor D, myogenin and MRF4, and the lineage determinate, Paired box 7, to alter transcription and subsequent satellite cell decisions. In the recent past, insight into mouse transgenic models has led to a firm understanding of regulatory events that control satellite cell metabolism and myogenesis. Many of these niche-regulated functions offer subtle differences from their counterparts in livestock pointing to the existence of species-specific controls. The purpose of this review is to examine the mechanisms that mediate large animal satellite cell activity and their relationship to those present in rodents.

Dietary Calcium and Phosphorus Amounts Affect Development and Tissue-Specific Stem Cell Characteristics in Neonatal Pigs

BACKGROUND

Dietary calcium and phosphorus are required for bone and muscle development. Deficiencies of these macrominerals reduce bone mineral and muscle accretion potentially via alterations of mesenchymal stem cell (MSC) and satellite cell (SC) activities.

OBJECTIVES

With increasing interest in the role of early-life events on lifetime health outcomes, we aimed to elucidate the impact of dietary calcium and phosphorus, from deficiency through excess, on MSC and SC characteristics during neonatal development.

METHODS

Neonatal pigs [30 females, 1-d-old, 1.46 ± 0.04 kg body weight (BW)] were fed milk replacers for 16 d that were isonitrogenous and isocaloric with a consistent ratio of calcium to phosphorus, but either 25% deficient (calcium: 0.78%; phosphorus: 0.60%; CaPD), adequate (calcium: 1.08%; phosphorus: 0.84%; CaPA), or 25% in excess (calcium: 1.38%; phosphorus: 1.08%; CaPE) of calcium and phosphorus requirements based on sow-milk composition and extrapolation from NRC requirements for older pigs. BW and feed intake were recorded daily. Blood was collected for serum phosphorus, parathyroid hormone (PTH), and fibroblast growth factor 23 (FGF23) determination. Humeri were collected for MSC isolation and radii/ulnae bone were collected for analysis. Longissimus dorsi muscle was collected for SC isolation and analysis.

RESULTS

There was 4.6% increase in bone ash percentage in CaPE- versus CaPD-fed pigs (P < 0.05). In vivo proliferation indicated a 41.3% increase in MSCs in CaPA compared with CaPD and a 19% increase in SCs in CaPA compared with both CaPE and CaPD. MSCs from CaPD had 2- to 5-fold greater expression of peroxisome proliferator-activated receptor γ (PPARγ), fatty acid-binding protein 4 (FABP4), and lipoprotein lipase (LPL) but lower osteocalcin (BGLAP) and fibronectin (FN1) expression than CaPA (P < 0.05). SCs from CaPD-fed pigs had 19% lower in vivo proliferation than in CaPA-fed pigs.

CONCLUSIONS

These findings demonstrated that feeding a diet marginally deficient in calcium and phosphorus to neonatal pigs had a great impact on bone development, MSC, and SC characteristics. These dietary deficiencies may program future bone health and muscle development by altering MSC and SC activities.

Effects of trypsinization and of a combined trypsin, collagenase, and DNase digestion on liberation and in vitro function of satellite cells isolated from juvenile porcine muscles

Muscle stem cells, termed satellite cells (SC), and SC-derived myogenic progenitor cells (MPC) are involved in postnatal muscle growth, regeneration, and muscle adaptability. They can be released from their natural environment by mechanical disruption and tissue digestion. The literature contains several isolation protocols for porcine SC/MPC including various digestion procedures, but comparative studies are missing. In this report, classic trypsinization and a more complex trypsin, collagenase, and DNase (TCD) digestion were performed with skeletal muscle tissue from 4- to 5-d-old piglets. The two digestion procedures were compared regarding cell yield, viability, myogenic purity, and in vitro cell function. The TCD digestion tended to result in higher cell yields than digestion with solely trypsin (statistical trend p = 0.096), whereas cell size and viability did not differ. Isolated myogenic cells from both digestion procedures showed comparable proliferation rates, expressed the myogenic marker Desmin, and initiated myogenic differentiation in vitro at similar levels. Thus, TCD digestion tended to liberate slightly more cells without changes in the tested in vitro properties of the isolated cells. Both procedures are adequate for the isolation of SC/MPC from juvenile porcine muscles but the developmental state of the animal should always be considered.

Lowered dietary phosphorus affects intestinal and renal gene expression to maintain mineral homeostasis with immunomodulatory implications in weaned piglets

BACKGROUND

In monogastric animals, phosphorus (P) homeostasis is maintained by regulating intestinal absorption, bone mobilization, and renal excretion. Since P is a non-renewable resource, a shortage is imminent due to widespread over-usage in the farming and animal husbandry industries. As a consequence, P efficiency should be improved in pig production. We sought to characterize the transcriptional response in re-/absorbing and excreting tissues in pigs to diets varying in calcium: phosphorus ratios. Weaned piglets were assigned to one of three groups fed diets varying in digestible P content for a period of five weeks. Gene expression profiles were analyzed in jejunum, colon, and kidney.

RESULTS

Transcriptome analysis revealed that reduced dietary P intake affects gene expression in jejunum and kidney, but not in colon. The regulation of mineral homeostasis was reflected via altered mRNA abundances of CYP24A1, CYP27A1, TRPM6, SPP1, and VDR in jejunum and kidney. Moreover, lowered abundances of transcripts associated with the classical complement system pathway were observed in the jejunum. In kidney, shifted transcripts were involved in phospholipase C, calcium signaling, and NFAT signaling, which may have immunomodulatory implications.

CONCLUSIONS

Our results revealed local transcriptional consequences of variable P intake in intestinal and renal tissues. The adaptive responses are the result of organismal efforts to maintain systemic mineral homeostasis while modulating immune features at local tissue sites. Therefore, the deviation from the currently recommended dietary P supply must be carefully considered, as the endogenous mechanisms that respond to low P diets may impact important adaptive immune responses.

Molecular and functional heterogeneity of early postnatal porcine satellite cell populations is associated with bioenergetic profile

During postnatal development, hyperplastic and hypertrophic processes of skeletal muscle growth depend on the activation, proliferation, differentiation, and fusion of satellite cells (SC). Therefore, molecular and functional SC heterogeneity is an important component of muscle plasticity and will greatly affect long-term growth performance and muscle health. However, its regulation by cell intrinsic and extrinsic factors is far from clear. In particular, there is only minor information on the early postnatal period which is critical for muscle maturation and the establishment of adult SC pools. Here, we separated two SC subpopulations (P40/50, P50/70) from muscle of 4-day-old piglets. Our results characterize P40/50 as homogeneous population of committed (high expression of Myf5), fast-proliferating muscle progenitors. P50/70 constituted a slow-proliferating phenotype and contains high numbers of differentiated SC progeny. During culture, P50/70 is transformed to a population with lower differentiation potential that contains 40% Pax7-positive cells. A reversible state of low mitochondrial activity that results from active down-regulation of ATP-synthase is associated with the transition of some of the P50/70 cells to this more primitive fate typical for a reserve cell population. We assume that P40/50 and P50/70 subpopulations contribute unequally in the processes of myofiber growth and maintenance of the SC pool.

The Developmental Origins of Osteoporosis

Osteoporosis is one of the most prevalent skeletal disorders and has enormous public health consequences due to the morbidity and mortality of the resulting fractures. This article discusses the developmental origins of osteoporosis and outlines some of the modifiable and non-modifiable risk factors in both intrauterine and postnatal life that contribute to the later onset of osteoporosis. Evidence for the effects of birth size and early growth in both preterm and term born infants are discussed and the role of epigenetics within the programming hypothesis is highlighted. This review provides compelling evidence for the developmental origins of osteoporosis and highlights the importance of osteoporosis prevention at all stages of the life course.

Dietary calcium deficiency and excess both impact bone development and mesenchymal stem cell lineage priming in neonatal piglets

BACKGROUND

Optimizing calcium nutrition to maximize bone accretion during growth to prevent fragility fractures later in life has spurred greater interest in calcium nutrition in neonates.

OBJECTIVE

The aim of this study was to determine the effect of dietary calcium, from deficiency through excess, on bone growth, and the in vivo and in vitro behavior of mesenchymal stem cells (MSCs) in neonatal pigs.

METHODS

Twenty-four male and female piglets (24 ± 6 h old) were fed either a calcium-deficient [Ca-D; 0.6% Ca on a dry matter (DM) basis], a calcium-adequate diet (Ca-A; 0.9% Ca on a DM basis), or a calcium-excessive diet (Ca-E; 1.3% Ca on a DM basis) for 14 d to assess the impact of dietary calcium on calcium homeostasis and on the behavior of MSCs.

RESULTS

Growth rate was not affected by the Ca-E diet, although bone ash content was 16% higher (P < 0.05) and urinary calcium excretion was 5-fold higher, when normalized to creatinine, compared with the Ca-A group at trial completion. Serum parathyroid hormone (PTH) concentrations were elevated (P < 0.05) in Ca-D piglets in comparison with other groups at both 7 and 14 d. In vivo proliferation of MSCs was 30% higher (P < 0.05) in Ca-E piglets than the other groups. MSCs from both Ca-D- and Ca-E-fed piglets had greater adipogenic potential based on increased gene expression (P < 0.05) of peroxisome proliferator-activated receptor γ (Pparg) and adipocyte fatty acid-binding protein (Ap2) than MSCs from Ca-A piglets. Interestingly, only MSCs from Ca-E-fed piglets had greater (P < 0.05) gene expression of lipoprotein lipase (Lpl) during adipocytic differentiation than those from Ca-A piglets. To assess alterations in lineage allocation and priming, the most and least osteogenic (O+ and O-, respectively) and adipogenic (A+ and A-, respectively) colonies from each MSC isolation were selected on the basis of functional staining. The O+ colonies from Ca-D piglets expressed lower (P < 0.05) levels of osteocalcin (OC) mRNA than did those from other groups, whereas the O- colonies from Ca-E piglets expressed higher (P < 0.05) levels of mRNA of Pparg, Ap2, and Lpl than did those from other groups.

CONCLUSIONS

Neonatal calcium deficiency appears to reduce the osteogenic priming of MSCs while enlarging a subpopulation of potentially adipogenic cells, and excess dietary calcium appears to allow greater multipotency of MSCs. These programming alterations of MSCs could have long-term consequences for bone health.

The suckling piglet as an agrimedical model for the study of pediatric nutrition and metabolism

The neonatal pig ranks among the most prominent research models for the study of pediatric nutrition and metabolism. Its precocial development at birth affords ready adaptation to artificial rearing systems, and research using this model spans a wide array of nutrients. Sophisticated in vitro and in vivo methodologies supporting both invasive, reduction-science research as well as whole-animal preclinical investigations have been developed. Potential applications may dually benefit both agricultural and medical sciences (e.g., "agrimedical research"). The broad scope of this review is to outline the fundamental elements of the piglet model and to highlight key aspects of relevance to various macronutrients, including lipids, carbohydrates, proteins/amino acids, and calcium/phosphorus. The review examines similarities between piglets and infants and also piglet idiosyncrasies, concluding that, overall, the piglet represents an adaptable and robust model for pediatric nutrition and metabolism research.

A simplified but robust method for the isolation of avian and mammalian muscle satellite cells

Background

Current methods of isolation of muscle satellite cells from different animal species are highly variable making inter-species comparisons problematic. This variation mainly stems from the use of different proteolytic enzymes to release the satellite cells from the muscle tissue (sometimes a single enzyme is used but often a combination of enzymes is preferred) and the different extracellular matrix proteins used to coat culture ware. In addition, isolation of satellite cells is frequently laborious and sometimes may require pre-plating of the cell preparation on uncoated flasks or Percoll centrifugation to remove contaminating fibroblasts. The methodology employed to isolate and culture satellite cells in vitro can critically determine the fusion of myoblasts into multi-nucleated myotubes. These terminally differentiated myotubes resemble mature myofibres in the muscle tissue in vivo, therefore optimal fusion is a keystone of in vitro muscle culture. Hence, a simple method of muscle satellite cell isolation and culture of different vertebrate species that can result in a high fusion rate is highly desirable.

Results

We demonstrate here a relatively simple and rapid method of isolating highly enriched muscle satellite cells from different avian and mammalian species. In brief, muscle tissue was mechanically dissociated, digested with a single enzyme (pronase), triturated with a 10-ml pipette, filtered and directly plated onto collagen coated flasks. Following this method and after optimization of the cell culture conditions, excellent fusion rates were achieved in the duck, chicken, horse and cow (with more than 50% cell fusion), and to a lesser extent pig, pointing to pronase as a highly suitable enzyme to release satellite cells from muscle tissue.

Conclusions

Our simplified method presents a quick and simple alternative to isolating highly enriched muscle satellite cell cultures which can subsequently rapidly differentiate into well developed primary myotubes. The use of the same isolation protocol allows better inter-species comparisons of muscle satellite cells. Of all the farm animal species investigated, harvested chicken muscle cells showed the highest percentage of muscle satellite cells, and equine muscle cells presented the highest fusion index, an impressive ≈ 77%. Porcine cells displayed the lowest amount of satellite cells but still achieved a modest fusion rate of ≈ 41%.

Neonatal phosphate nutrition alters in vivo and in vitro satellite cell activity in pigs

Satellite cell activity is necessary for postnatal skeletal muscle growth. Severe phosphate (PO₄) deficiency can alter satellite cell activity, however the role of neonatal PO₄ nutrition on satellite cell biology remains obscure. Twenty-one piglets (1 day of age, 1.8 ± 0.2 kg BW) were pair-fed liquid diets that were either PO₄ adequate (0.9% total P), supra-adequate (1.2% total P) in PO₄ requirement or deficient (0.7% total P) in PO₄ content for 12 days. Body weight was recorded daily and blood samples collected every 6 days. At day 12, pigs were orally dosed with BrdU and 12 h later, satellite cells were isolated. Satellite cells were also cultured in vitro for 7 days to determine if PO₄ nutrition alters their ability to proceed through their myogenic lineage. Dietary PO₄ deficiency resulted in reduced (P < 0.05) sera PO₄ and parathyroid hormone (PTH) concentrations, while supra-adequate dietary PO₄ improved (P < 0.05) feed conversion efficiency as compared to the PO₄ adequate group. In vivo satellite cell proliferation was reduced (P < 0.05) among the PO₄ deficient pigs, and these cells had altered in vitro expression of markers of myogenic progression. Further work to better understand early nutritional programming of satellite cells and the potential benefits of emphasizing early PO₄ nutrition for future lean growth potential is warranted.

Nutrigenomics and Cancer Prevention

Mounting evidence continues to point to dietary habits as a modifier of cancer risk and tumor behavior; although it is clear that considerable variability occurs across studies. While genetic public health messages can be developed, the use of mean values may result in underexposure to some essential and nonessential food components, yet precipitate overexposure to nutrients. Undeniably, inconsistencies in the literature may reflect variation in timing of exposures to specific dietary constituents, interactions with the food matrix, processing technologies, or the genomic variation among individuals, which can influence absorption, metabolism, and/or the molecular target. Inter-individual variability in genetics, epigenetics, transcriptomics, proteomics, metabolomics, or microbiomics can influence the magnitude and direction of response to bioactive food components, as briefly reviewed in this article. Unquestionably, understanding nutrigenomics holds promise to reveal those who will benefit most from dietary interventions plus identify any who might be placed at risk due to overexposures.

Dietary calcium restriction affects mesenchymal stem cell activity and bone development in neonatal pigs

The effects of dietary calcium (Ca) deficiency on skeletal integrity are well characterized in growing and mature mammals; however, less is known about Ca nutrition during the neonatal period. In this study, we examined the effects of neonatal Ca nutrition on bone integrity, endocrine hormones, and mesenchymal stem cell (MSC) activity. Neonatal pigs (24 ± 6 h of age) received either a Ca-adequate (1.2 g/100 g) or an ~40% Ca-deficient diet for 18 d. Ca deficiency reduced (P < 0.05) bone flexural strength and bone mineral density without major differences in plasma indicators of Ca status. There were no meaningful differences in plasma Ca, phosphate (PO(4)), parathyroid hormone, or 1,25-dihydroxycholecalciferol due to Ca nutrition throughout the study. Calcium deficiency also reduced (P < 0.05) the in vivo proliferation of MSC by ~50%. In vitro studies utilizing homologous sera demonstrated that MSC activity was affected (P < 0.05) by both the Ca status of the pig and the sera as well as by their interaction. The results indicate that neonatal Ca nutrition is crucial for bone integrity and suggest that early-life Ca restriction may have long-term effects on bone integrity via programming of MSC.