Genetic Markers Are Associated with the Ruminal Microbiome and Metabolome in Grain and Sugar Challenged Dairy Heifers

Dairy heifers were subjected to a non-life-threatening challenge designed to induce ruminal acidosis by feeding grain and sugar. Large among animal variation in clinical signs of acidosis, rumen metabolite concentrations, and the rumen microbiome occurred. This exploratory study investigates sources of the variation by examining associations between the genome, metabolome, and microbiome, albeit with a limited population. The broader objective is to provide a rationale for a larger field study to identify markers for susceptibility to ruminal acidosis. Initially, heifers (n = 40) allocated to five feed additive groups were fed 20-days pre-challenge with a total mixed ration and additives. Fructose (0.1% of bodyweight/day) was added for the last 10 days pre-challenge. On day 21 heifers were challenged with 1.0% of bodyweight dry matter wheat + 0.2% of bodyweight fructose + additives. Rumen samples were collected via stomach tube weekly (day 0, 7, and 14) and at five times over 3.6 h after challenge and analyzed for pH and volatile fatty acid, ammonia, D-, and L-lactate concentrations. Relative abundance of bacteria and archaea were determined using Illumina MiSeq. Genotyping was undertaken using a 150K Illumina SNPchip. Genome-wide association was performed for metabolite and microbiome measures (n = 33). Few genome associations occurred with rumen pH, concentration of acetate, propionate, total volatile fatty acids, or ammonia, or the relative abundance of the Firmicutes, Bacteroidetes, and Spirochaetes phyla. Metabolites and microbial phyla that had markers associated and quantitative trait loci (QTL) were: acetate to propionate ratio (A:P), D-, L-, and total lactate, butyrate, acidosis eigenvalue, Actinobacteria, Chloroflexi, Euryarchaeota, Fibrobacteres, Planctomycetes, Proteobacteria, and Tenericutes. A putative genomic region overlapped for Actinobacteria, Euryarchaeota, and Fibrobacteres and covered the region that codes for matrix extracellular phosphoglycoprotein (MEPE). Other overlapping regions were: (1) Chloroflexi, Tenericutes, and A:P, (2) L- and total lactate and Actinobacteria, and (3) Actinobacteria, Euryarchaeota, Fibrobacteres, and A:P. Genome-wide associations with the metabolome and microbiome occurred despite the small population, suggesting that markers for ruminal acidosis susceptibility exist. The findings may explain some of the variation in metabolomic and microbial data and provide a rationale for a larger study with a population that has variation in acidosis.

Regulatory roles of miRNA-758 and matrix extracellular phosphoglycoprotein in cervical cancer

The present study aimed to examine the role and underlying mechanism of miRNA-758 (miR-758) expression in cancer tissues, blood and cervical exfoliated cells from patients with cervical cancer. A total of 49 patients with cervical cancer and 26 healthy people for cervical cancer screening were included in the present study. The patients with cervical cancer were treated with resection, and the tumor and adjacent tissues, blood and cervical exfoliated cells were collected. The expression levels of miR-758 and matrix extracellular phosphoglycoprotein (MEPE) mRNA in each sample were detected by reverse transcription-quantitative polymerase chain reaction. In addition, western blot analysis was used to detect the MEPE protein in tumor tissues, while ELISA was applied to detect the MEPE protein expression in the blood and cervical exfoliated cells. Compared with the normal control, MEPE mRNA expression was upregulated in cervical cancer tissues, blood and cervical exfoliated cells. At the protein level, MEPE was also upregulated significantly in patients with cervical cancer. miR-758 expression was decreased significantly in cervical cancer tissues, blood and cervical exfoliated cells (P<0.05), which was opposite to the trend observed for MEPE mRNA expression. Furthermore, MEPE expression was increased in the tumor tissue, blood and cervical exfoliated cells of cervical cancer patients, which was associated to the downregulated miR-758. Therefore, miR-758 may regulate the infiltration and invasion of cervical cancer by targeting MEPE.

ASARM peptides: PHEX-dependent and -independent regulation of serum phosphate

Increased acidic serine aspartate-rich MEPE-associated motif (ASARM) peptides cause mineralization defects in X-linked hypophosphatemic rickets mice (HYP) and "directly" inhibit renal phosphate uptake in vitro. However, ASARM peptides also bind to phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX) and are a physiological substrate for this bone-expressed, phosphate-regulating enzyme. We therefore tested the hypothesis that circulating ASARM peptides also "indirectly" contribute to a bone-renal PHEX-dependent hypophosphatemia in normal mice. Male mice (n = 5; 12 wk) were fed for 8 wk with a normal phosphorus and vitamin D(3) diet (1% P(i) diet) or a reduced phosphorus and vitamin D(3) diet (0.1% P(i) diet). For the final 4 wk, transplantation of mini-osmotic pumps supplied a continuous infusion of either ASARM peptide (5 mg·day(-1)·kg(-1)) or vehicle. HYP, autosomal recessive hypophosphatemic rickets (ARHR), and normal mice (no pumps or ASARM infusion; 0.4% P(i) diet) were used in a separate experiment designed to measure and compare circulating ASARM peptides in disease and health. ASARM treatment decreased serum phosphate concentration and renal phosphate cotransporter (NPT2A) mRNA with the 1% P(i) diet. This was accompanied by a twofold increase in serum ASARM and 1,25-dihydroxy vitamin D(3) [1,25 (OH)(2)D(3)] levels without changes in parathyroid hormone. For both diets, ASARM-treated mice showed significant increases in serum fibroblast growth factor 23 (FGF23; +50%) and reduced serum osteocalcin (-30%) and osteopontin (-25%). Circulating ASARM peptides showed a significant inverse correlation with serum P(i) and a significant positive correlation with fractional excretion of phosphate. We conclude that constitutive overexpression of ASARM peptides plays a "component" PHEX-independent part in the HYP and ARHR hypophosphatemia. In contrast, with wild-type mice, ASARM peptides likely play a bone PHEX-dependent role in renal phosphate regulation and FGF23 expression. They may also coordinate FGF23 expression by competitively modulating PHEX/DMP1 interactions and thus bone-renal mineral regulation.

MEPE's diverse effects on mineralization

Matrix extracellular phosphoglycoprotein (MEPE) is an inhibitor of mineralization in situ and in cell cultures where altered expression is associated with oncogenic osteomalacia and hypophosphatemic rickets. The purpose of this study was to determine whether the intact protein or the peptide(s) originating from this protein was responsible for the inhibition. The ability of the intact protein and the acidic, serine- and aspartate-rich MEPE-associated motif (ASARM) peptide to promote or inhibit de novo hydroxyapatite formation and growth of hydroxyapatite seed crystals, in both phosphorylated and dephosphorylated forms, was assessed at room temperature in a dynamic gel diffusion system at 3.5 and 5 days. The most effective nucleator concentration was also examined when associated with fibrillar type I collagen. The phosphorylated intact protein was an effective promoter of mineralization in the gelatin gel diffusion system, while the ASARM peptide was an effective inhibitor. When dephosphorylated both the intact protein and the ASARM peptide had no effect on mineralization. Associated with collagen fibrils, some of the effect of the intact protein was lost. This study demonstrates the importance of posttranslational modification for the site-specific activity of MEPE and its ASARM peptide.

FGF-23 in bone biology

Recent studies have demonstrated that levels of fibroblast growth factor 23 (FGF-23), a key regulator of phosphorus and vitamin D metabolism, rise dramatically as renal function declines and may play a key initiating role in disordered mineral and bone metabolism in patients with chronic kidney disease (CKD). The physiologic importance of FGF-23 in mineral metabolism was first identified in human genetic and acquired rachitic diseases and further characterized in animal models. FGF-23 and its regulators, including phosphate regulating endopeptidase homolog, dentin matrix 1 (DMP1), and matrix extracellular phosphoglycoprotein, are made primarily in bone, specifically in osteocytes. Dysregulation of these proteins results in osteomalacia, implicating the osteocyte in the regulation of skeletal mineralization. Studies in pediatric patients with CKD, the majority of whom have altered skeletal mineralization in early stages of CKD, have demonstrated that skeletal expression of both FGF-23 and its regulator, DMP1, are increased in early stages of CKD and that expression of these proteins is associated with alterations in skeletal mineralization. Thus, dysregulation of osteocytic proteins occur very early in the course of CKD and appear to be central to altered bone and mineral metabolism in this patient population.

Phosphatonins: new hormones that control phosphorus homeostasis

Phosphorus (Pi) plays an important role in nucleic acid synthesis, energy metabolism, bone mineralization and cell signaling, and is also present in sugars, phospholipids and phosphoproteins. Phosphate homeostasis is controlled by processes that regulate the intestinal absorption and renal excretion of Pi, and bone turnover. These processes are influenced by peptide and sterol hormones, such as parathyroid hormone and 1α,25-dihydroxyvitamin D (1α,25[OH]₂D₃). Recently, a new class of phosphate-regulating peptides has been discovered: phosphatonins. These factors, such as FGF-23, secreted frizzled-related protein-4, matrix extracellular phosphoglycoprotein and FGF-7, are circulating peptides with potent phosphaturic activity. These peptides inhibit Na/Pi transporters in renal epithelial cells and, therefore, increase renal Pi excretion. In addition, FGF-23 and secreted frizzled-related protein-4 inhibit 25-hydroxyvitamin D 1α-hydroxylase activity, reducing 1α,25(OH)2D3 synthesis and, thus, intestinal Pi absorption. Phosphatonins have been associated with hypophosphatemic diseases, such as tumor-induced osteomalacia, X-linked hypophosphatemic rickets, autosomal dominant hypophosphatemic rickets, autosomal recessive hypophosphatemic rickets and hyperphosphatemic disease (e.g., tumoral calcinosis). The aim of this article is to review the role of phosphatonins in Pi metabolism in normal and pathologic conditions and also to investigate the correlations among the various phosphatonins.