Transcriptomic analysis of adipose, hepatic, and mammary gland tissues in lactating cows with elevated peripheral serotonin

Abstract

Lactation is a highly energy intensive state, particularly for dairy cattle, which have been genetically selected for copious milk secretion. Blood serotonin content is greatly increased during lactation, at least in part because of increased production by the lactating mammary glands. We hypothesized that increasing peripheral serotonin in lactating cows, by infusion of the serotonin precursor 5-hydroxytryptophan (5-HTP), would alter gene expression in metabolically active tissues to support energy partitioning towards lactation.To test this hypothesis, multiparous midlactation Holstein cows (n=8/treatment) were intravenously infused with 5-HTP (1mg/kg bodyweight) or saline over two 10-day treatment periods. Treatments were infused via jugular catheters for 1h/day starting at 0700, on days 1–3 and 8–10, with no infusions on days 4–7. On day 10, 6h after the last infusion, biopsies of subcutaneous white adipose (WAT), hepatic, and mammary tissues were performed. Total RNAs were extracted from these tissues, and followed by whole transcriptome sequencing. Adapter-trimmed sequences were mapped to the cattle reference genome (ARS-UCD 1.2) using STAR. Differential gene expression analysis was done using DEseq2. A combinatory cutoff of mean read count≥5, fold-change≥2, and p-value<0.01 was used to determine differentially expressed genes (DEG). Relative to saline-infused cows, 5-HTP cows had 152 genes downregulated and 38 upregulated in WAT, 117 genes downregulated and 141 upregulated in hepatic tissue, and 79 genes downregulated and 86 upregulated in mammary tissue.DEG from each tissue were then analyzed by QIAGEN Ingenuity Pathway Analysis (IPA) to identify enriched pathways and functions impacted by 5-HTP. In WAT, downregulated genes were enriched in triacylglycerol biosynthesis and upregulated genes were enriched in PPAR signaling, with upregulated gene enrichment in several apoptosis-related pathways as well. Decreased biological function categories in WAT included carbohydrate metabolism and lipid metabolism. In hepatic tissue, downregulated genes were enriched in superpathway of cholesterol biosynthesis while upregulated genes were enriched in cAMP-mediated signaling and citrulline biosynthesis. In mammary tissue, 5-HTP infusion exclusively upregulated genes involved in lipid metabolism, including functions in transport, export, flux and efflux of lipids and cholesterol. In conclusion, lactating cows with elevated peripheral serotonin developed a systemic response, altering the expression of genes in energy metabolic pathways, including reduced lipid synthesis and cell survival in WAT, reduced cholesterol synthesis in the liver, and increased lipid trafficking in the mammary tissue. Together, these changes may function to shift energy partitioning towards milk synthesis. This work was supported by USDA-NIFA Predoctoral Fellowship grant #2021-67034-35172 and research funding provided by Adisseo Bluestar Co. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.