Arteriovenous blood metabolomics: An efficient method to determine the key metabolic pathway for milk synthesis in the intra-mammary gland

Cerebral venous biomarkers and veno-arterial gradients: untapped resources in Alzheimer's disease

Blood based biomarkers (BBB) derived from forearm veins for estimating brain changes is becoming ubiquitous in Alzheimer's Disease (AD) research and could soon become standard in routine clinical diagnosis. However, there are many peripheral sources of contamination through which concentrations of these metabolites can be raised or lowered after leaving the brain and entering the central venous pool. This raises the issue of potential false conclusions that could lead to erroneous diagnosis or research findings. We propose the use of simultaneous sampling of internal jugular venous and arterial blood to calculate veno-arterial gradient, which can reveal either a surplus or a deficit of metabolites exiting the brain. Methods for sampling internal jugular venous and arterial blood are described along with examples of the use of the veno-arterial gradient in non-AD brain research. Such methods in turn could help better establish the accuracy of forearm venous biomarkers.

Heat stress affects dairy cow health status through blood oxygen availability

BACKGROUND

Rises in global warming and extreme weather occurrence make the risk of heat stress (HS) induced by high ambient temperatures more likely in high-yielding dairy cows, resulting in low milk quality and yield. In animals, oxygen is involved in many physiological and metabolic processes, but the effects of HS on oxygen metabolism remain unclear. Thus, the current study aimed to investigate how oxygen metabolism plays a role in health status of dairy cows by measuring the milk yield, milk composition, and blood biochemical variables of cows under different levels of HS: none (No-HS), mild (Mild-HS), and moderate HS (Mod-HS).

RESULTS

The HS significantly increased rectal temperature (Ptreat < 0.01) and respiration rate (Ptreat < 0.01). Under Mod-HS, greater Na+ (P < 0.05) and lower total CO2, and pH (P < 0.05) were observed relative to those under No-HS and Mild-HS. Oxygen concentrations in both coccygeal artery and mammary vein (Ptreat < 0.01) were lower under Mod-HS than under No-HS. Coccygeal vein concentrations of heat shock protein 90 (HSP90) (P < 0.05) increased during Mod-HS compared with those in cows under No-HS. Malondialdehyde increased during Mod-HS, and glutathione peroxidase (P < 0.01) increased during Mild-HS. Coccygeal vein concentrations of vascular endothelial growth factor (P < 0.01), heme oxygenase-1 (P < 0.01), and hypoxia-inducible factor 1α (P < 0.01) were greater in cows under Mod-HS than those under No-HS. Red blood cell count (P < 0.01) and hemoglobin concentration (P < 0.01) were lower in the coccygeal vein of dairy cows under Mild- and Mod-HS than those of cows under No-HS.

CONCLUSIONS

Exposure to HS negatively impacts the health status and lactation performance of dairy cows by limiting oxygen metabolism and transportation. However, the specific mechanism by which HS affects mammary function in cows remains unclear and requires further exploration.

Comparative Genomic Analysis of the Thiolase Family and Functional Characterization of the Acetyl-Coenzyme A Acyltransferase-1 Gene for Milk Biosynthesis and Production of Buffalo and Cattle

Cattle and buffalo served as the first and second largest dairy animals, respectively, providing 96% milk products worldwide. Understanding the mechanisms underlying milk synthesis is critical to develop the technique to improve milk production. Thiolases, also known as acetyl-coenzyme A acetyltransferases (ACAT), are an enzyme family that plays vital roles in lipid metabolism, including ACAT1, ACAT2, ACAA1, ACAA2, and HADHB. Our present study showed that these five members were orthologous in six livestock species including buffalo and cattle. Transcriptomic data analyses derived from different lactations stages showed that ACAA1 displayed different expression patterns between buffalo and cattle. Immunohistochemistry staining revealed that ACAA1 were dominantly located in the mammary epithelial cells of these two dairy animals. Knockdown of ACAA1 inhibited mammary epithelial cell proliferation and triglyceride and β-casein secretion by regulating related gene expressions in cattle and buffalo. In contrast, ACAA1 overexpression promoted cell proliferation and triglyceride secretion. Finally, three novel SNPs (g.-681A>T, g.-23117C>T, and g.-24348G>T) were detected and showed significant association with milk production traits of Mediterranean buffaloes. In addition, g.-681A>T mutation located in the promoter region changed transcriptional activity significantly. Our findings suggested that ACAA1 play a key role in regulating buffalo and cattle milk synthesis and provided basic information to further understand the dairy animal lactation physiology.

Metagenomic and Metabolomic Insights Into the Mechanism Underlying the Disparity in Milk Yield of Holstein Cows

This study was conducted to investigate the metabolic mechanism underlying the disparity in the milk yield of Holstein cows. Eighteen lactating Holstein cows in their second parity and 56 (±14.81 SD) days in milking (DIM) were selected from 94 cows. Based on the milk yield of the cows, they were divided into two groups of nine cows each, the high milk yield group (HP) (44.57 ± 2.11 kg/day) and the low milk yield group (LP) (26.71 ± 0.70 kg/day). The experimental cows were fed the same diet and kept under the same management system for more than 60 days. Rumen metagenomics revealed that two Archaea genera, one Bacteria genus, eight Eukaryota genera, and two Virus genera differ between the HP and LP groups. The analysis of metabolites in the rumen fluid, milk, and serum showed that several metabolites differed between the HP and LP groups. Correlation analysis between the predominant microbiota and milk yield-associated metabolites (MP-metabolites) revealed that four Bacteria and two Eukaryota genera have a positive relationship with MP-metabolites. Pathway enrichment analysis of the differential metabolites revealed that five pathways were enriched in all the samples (two pathways in the milk, two pathways in the serum, and one pathway in the rumen fluid). Further investigation revealed that the low milk yield observed in the LP group might be due to an upregulation in dopamine levels in the rumen fluid and milk, which could inhibit the release of prolactin or suppress the action of oxytocin in the udder resulting in reduced milk yield. On the other hand, the high milk yield in the HP group is attributed to an upregulation in citrulline, and N-acetylornithine, which could be used as substrates for energy metabolism in the citric acid cycle and ultimately gluconeogenesis.

Multi-omics reveals functional genomic and metabolic mechanisms of milk production and quality in dairy cows

MOTIVATION

Enhancing the utilization of human-inedible crop by-products by ruminants to produce high-quality milk for human consumption is an emerging global task. We performed a multi-omics-based study to decipher the regulatory biological processes of milk production when cows fed low-quality crop by-products with the aim to improve their utilization.

RESULTS

Seven types of different high-throughput omics data were generated across three central organs [rumen, liver and mammary gland (MG)] and biofluids (rumen fluid and blood) that involved in milk production. The integrated multi-omics analysis including metabolomics, metagenomics and transcriptomics showed altered microbiome at compositional and functional levels, microbial metabolites in the rumen, down-regulated genes and associated functions in liver and MG. These changes simultaneously contributed to down-regulated three key metabolic nodes (propionate, glucose and amino acid) across these organs and biofluids that led to lowered milk yield and quality when cows consumed corn stover (CS). Hippuric acid was identified as a biomarker that led to low milk production in CS-fed cows, suggesting a future evaluation parameter related to the metabolic mechanism of low-quality forage utilization. This study unveils the milk production-related biological mechanism across different biofluids and tissues under a low-quality forage diet, which provides a novel understanding and potential improvement strategies for future crop by-products utilization and sustainable ruminant production.

AVAILABILITY AND IMPLEMENTATION

The raw files of metagenomics, metabolomics, and transcriptomics data can be accessed at NCBI SRA (No. SRR5028206), EMBI-EBI (No. MTBLS411), and GEO (NO. GSE78524) databases respectively.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Assessing metabolic properties of dairy cows fed low quality straws by integrative arterial and venous metabolomics

OBJECTIVE

This study was conducted to reveal potential metabolic differences of dairy cows fed corn stover (CS) and rice straw (RS) instead of alfalfa hay (AH) as main forage source.

METHODS

Thirty multiparous mid-late lactation Holstein dairy cows were selected and randomly assigned to three diets, AH, CS, or RS (n = 10). After 13 weeks of the feeding trial, coccygeal arterial and superficial epigastric venous plasma samples were collected before morning feeding for gas chromatography time-of-flight/mass spectrometry analyses.

RESULTS

In the artery, 8 and 13 metabolites were detected as differential metabolites between AH and CS, and between AH and RS, respectively. The relative abundance of phenylpropanoate (log2fold change [FC]) = 1.30, 1.09), panthenol (log2FC = 2.36, 2.20), threitol (log2FC = 1.00, 1.07), and 3,7,12-trihydroxycoprostane (log2FC = 0.79, 0.78) were greater in both CS and RS than in AH, and tyrosine (log2FC = -0.32), phenylalanine (log2FC = -0.30), and pyruvic acid (log2FC = -0.30) were lower in RS than in AH. In the vein, 1 and 7 metabolites were detected as differential metabolites between AH and CS, and between AH and RS, respectively. By comparing AH and RS, we found that metabolic pathways of phenylalanine, tyrosine, and tryptophan biosynthesis and phenylalanine metabolism were enriched by integrative artery and vein analysis. Furthermore, AH and RS, arterial phenylpropanoate and 4-hydroxyproline were positively, and phenylalanine was negatively correlated with milk urea nitrogen. Finally, in AH and CS, arterial panthenol was negatively correlated with feed efficiency.

CONCLUSION

Arterial metabolic profiles changed more than those in the veins from animals on three forage diets, differing in amino acids. We found that phenylalanine, tyrosine, and tryptophan biosynthesis and phenylalanine metabolism were restricted when cows were fed low-quality cereal straw diets.

Profiling solute-carrier transporters in key metabolic tissues during the postpartum evolution of mammary epithelial cells from nonsecretory to secretory

Modifications in the abundance of solute-carrier (SLC) transcripts in tandem with adjustments in genes-associated with energy homeostasis during the postpartum transition of the mammary epithelial cells (MEC) from nonsecretory to secretory is pivotal for supporting milk synthesis. The goal of this study was to identify differentially expressed SLC genes across key metabolic tissues between late pregnancy and onset of lactation. Total RNA was isolated from the mammary, liver, and adipose tissues collected from rat dams on day 20 of pregnancy (P20) and day 1 of lactation (L1) and gene expression was measured with Rat 230 2.0 Affymetrix GeneChips. LIMMA was utilized to identify the differential gene expression patterns between P20 and L1 tissues. Transcripts engaged in conveying anions, cations, carboxylates, sugars, amino acids, metals, nucleosides, vitamins, and fatty acids were significantly increased (P < 0.05) in MEC during the P20 to L1 shift. Downregulated (P < 0.05) genes in the mammary during the physiological transition included GLUT8 and SLC45a3. In the liver, SLC genes encoding for anion, carbonyl, and nucleotide sugar transporters were upregulated (P < 0.05) at L1. while genes facilitating transportation of anions and hexose were increased (P < 0.05), from P20 to L1 in the adipose tissue. GLUT1 and GLUT4 in the liver, along with GLUT4 and SGLT2 in the adipose tissue, were repressed (P < 0.05) at L1. Our results illustrate that MEC exhibit dynamic molecular plasticity during the nonsecretory to secretory transition and increase biosynthetic capacity through a coordinated tissue specific SLC transcriptome modification to facilitate substrate transfer.

Arterio-venous metabolomics exploration reveals major changes across liver and intestine in the obese Yucatan minipig

Blood circulation mainly aims at distributing the nutrients required for tissue metabolism and collecting safely the by-products of all tissues to be further metabolized or eliminated. The simultaneous study of arterial (A) and venous (V) specific metabolites therefore has appeared to be a more relevant approach to understand and study the metabolism of a given organ. We propose to implement this approach by applying a metabolomics (NMR) strategy on paired AV blood across the intestine and liver on high fat/high sugar (HFHS)-fed minipigs. Our objective was to unravel kinetically and sequentially the metabolic adaptations to early obesity/insulin resistance onset specifically on these two tissues. After two months of HFHS feeding our study of AV ratios of the metabolome highlighted three major features. First, the hepatic metabolism switched from carbohydrate to lipid utilization. Second, the energy demand of the intestine increased, resulting in an enhanced uptake of glutamine, glutamate, and the recruitment of novel energy substrates (choline and creatine). Third, the uptake of methionine and threonine was considered to be driven by an increased intestine turnover to cope with the new high-density diet. Finally, the unique combination of experimental data and modelling predictions suggested that HFHS feeding was associated with changes in tryptophan metabolism and fatty acid β-oxidation, which may play an important role in lipid hepatic accumulation and insulin sensitivity.