Evaluation of xanthosine treatment on gene expression of mammary glands in early lactating goats

Goat mammary gland metabolism: An integrated Omics analysis to unravel seasonal weight loss tolerance

Seasonal weight loss (SWL), is a major limitation to animal production. In the Canary Islands, there are two dairy goat breeds with different levels of tolerance to SWL: Majorera (tolerant) and Palmera (susceptible). Our team has studied the response of these breeds to SWL using different Omics tools. The objective of this study was to integrate such results in a data driven approach and using dedicated tools, namely the DIABLO method. The outputs of our analysis mainly separate unrestricted from restricted goats. Metabolites behave as "hub" molecules, grouping interactions with several genes and proteins. Unrestricted goats upregulated protein synthesis, along with arginine catabolism and adipogenesis pathways, which are related with higher anabolic rates and a larger proportion of secretory tissue, in agreement with their higher milk production. Contrarily, restricted goats seemingly increased the synthesis of acetyl-CoA through serine and acetate conversion into pyruvate. This may have occurred to increase fatty acid synthesis and/or to use them as an energy source in detriment to glucose, which was more available in the diet of unrestricted goats. Lastly, restricted Palmera upregulated the expression of PEBP4 and GPD1 genes compared to all other groups, which might support their use as putative biomarkers for SWL susceptibility. SIGNIFICANCE: Seasonal weight loss (SWL) is a major issue influencing animal production in the tropics and Mediterranean. By studying its impact on the mammary gland of tolerant and susceptible dairy goat breeds, using Omics, we aim at surveying the tissue for possible biomarkers that reflect these traits. In this study, data integration of three Omics (transcriptomics, proteomics and metabolomics) was performed using bioinformatic tools, to relate putative biomarkers and evaluate all three levels of information; in a novel approach. This information can enhance selection programs, lowering the impact of SWL on food production systems.

Xanthosine, a purine glycoside mediates hepatic glucose homeostasis through inhibition of gluconeogenesis and activation of glycogenesis via regulating the AMPK/ FoxO1/AKT/GSK3β signaling cascade

Type 2 Diabetes Mellitus (T2DM) is characterized by hepatic insulin resistance, which results in increased glucose production and reduced glycogen storage in the liver. There is no previous study in the literature that has explored the role of Xanthosine in hepatic insulin resistance. Moreover, mechanistic explanation for the beneficial effects of Xanthosine in lowering glucose production in diabetes is yet to be determined. This study for the first time investigated the beneficial effects of Tribulus terrestris (TT) and its active constituent, Xanthosine on gluconeogenesis and glycogenesis in Free Fatty Acid (FFA)-induced CC1 hepatocytes and streptozotocin (STZ)-induced Wistar rats. Xanthosine enhanced glucose uptake and decreased glucose production through phosphorylation of AMP-activated protein kinase (AMPK) and forkhead box transcription factor O1 (FoxO1), and downregulation of two rate limiting enzymes of gluconeogenesis, phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) expression in FFA-induced CC1 cells. Xanthosine also prevented FFA-induced decreases in the phosphorylation of AKT/Protein kinase B, glycogen synthase kinase-3β (GSK3β), and increased glycogen synthase (GS) phosphorylation to increase the glycogen content in the hepatocytes. Moreover, in STZ-induced diabetic rats, oral administration of TT n-butanol fraction (TTBF) enriched with compound Xanthosine (10, 50 & 100 mg/kg body weight) improved insulin sensitivity, reduced fasting blood glucose levels, improved glucose homeostasis by reducing gluconeogenesis via AMPK/FoxO1-mediated PEPCK and G6Pase down-regulation and increasing glycogenesis via AKT/GSK3β-mediated GS activation. Overall, Xanthosine may be developed further for treating insulin resistance and hyperglycemia in T2DM.

Symposium review: Determinants of milk production: Understanding population dynamics in the bovine mammary epithelium

The mammary gland undergoes distinct periods of growth, development, and secretory activity. During bovine lactation, a gradual decrease in the number of mammary epithelial cells largely accounts for the decline in milk production with advancing lactation. The net decline in cell number (approx. 50%) is due to cell death but is simultaneously accompanied by cell renewal. Although the rate of cell proliferation is slow, by the end of lactation most cells in the gland were formed after calving. Typically milking is terminated when cows are in the final 2 mo of pregnancy. This causes regenerative involution, wherein extensive cell replacement and mammary growth occurs. We hypothesized that replacement of senescent secretory cells and progenitor cells during the dry period increases milk yield in the next lactation. Analysis of global gene expression revealed networks and canonical pathways during regenerative involution that support cell turnover and mammary growth, and reflect oxidative stress, mitochondrial dysfunction, and endoplasmic reticulum (ER) stress. Immune responses consistent with influx of neutrophils, macrophages, and lymphocytes, and processes that support mammary differentiation and lactogenesis were also evident. Data also suggest that replication of stem and progenitor cells occurs during the dry period. Relying on long-term retention of bromodeoxyuridine-labeled DNA, we identified putative bovine mammary stem cells. These label-retaining epithelial cells (LREC) are in low abundance within mammary epithelium (<1%), predominantly estrogen receptor-negative, and localized in a basal or suprabasal layer of the epithelium. Analyses of gene expression in laser-microdissected LREC are consistent with the concept that LREC represent stem cells and progenitor cells, which differ in properties and location within the epithelial layer. We identified potential markers for these cells and have increased their number by infusing xanthosine through the teat canal of prepubertal heifers. Altering population dynamics of mammary stem and progenitor cells during the mammary cycle may be a means to increase efficiency of milk production.