Transcriptome analysis reveals disruption of circadian rhythms in late gestation dairy cows may increase risk for fatty liver and reduced mammary remodeling

Abstract

Circadian disruption increased insulin resistance and decreased mammary development in late gestation, non-lactating (dry) cows. The objective was to measure the effect of circadian disruption on transcriptomes of the liver and mammary gland. At 35 d before expected calving (BEC) multiparous dry cows were assigned to either control (CON) or phase-shifted treatments (PS). CON was exposed to 16 h light and 8 h of dark. PS was exposed to 16 h light to 8 h dark, but phase of the light-dark cycle was shifted 6 h every 3 d. On d 21 BEC, liver and mammary were biopsied. RNA was isolated (n=6 CON, n=6 PS per tissue), libraries prepared and sequenced using paired end reads. Reads mapping to bovine genome averaged 27 M ± 2 M, and aligned to 14,222 protein coding genes in liver and 15,480 in mammary analysis. In the liver, 834 genes, and in the mammary gland, 862 genes were different (nominal P < 0.05) between PS and CON. In the liver, genes upregulated in PS functioned in cholesterol biosynthesis, endoplasmic reticulum stress, wound healing, and inflammation. Genes downregulated in liver function in cholesterol efflux. In the mammary gland, genes upregulated functioned in mRNA processing and transcription, downregulated genes encoded extracellular matrix proteins and proteases, cathepsins and lysosomal proteases, lipid transporters and regulated oxidative phosphorylation. Increased cholesterol synthesis and decreased efflux suggests circadian disruption potentially increases the risk of fatty liver in cows. Decreased remodeling and lipid transport in mammary may decrease milk production capacity during lactation.

Effect of circadian system disruption on the concentration and daily oscillations of cortisol, progesterone, melatonin, serotonin, growth hormone, and core body temperature in periparturient dairy cattle

“…In the second study, once per day sampling found no difference in MEL between treatments (data not shown). Evaluation of the effect of PS on mammary development in the second study showed PS treatment decreased mammary development and increased expression of genes in liver and muscle related to oxidative stress (Casey et al, 2021b;McCabe et al, 2021a). One potential explanation of different study findings is the negative effect that PS treatment had on mammary epithelial proliferation and cellular stress in the liver and muscle was potentially negated by the positive effects of greater MEL levels in the first study (Suarez-Trujillo et al, 2020).…”

Circadian disruption decreases gluconeogenic flux in late-gestation, nonlactating dairy cows

“…In a replicate study, cows experienced decreased insulin sensitivity as demonstrated by an intravenous glucose tolerance test, but did not develop hypoglycemia ( McCabe et al, 2021 ). Transcriptome analysis of liver tissue from the same animals found a potential for increased development of fatty liver ( Casey et al, 2021 ). These findings support a central role of circadian clocks in regulation of metabolism of ruminants, including factors that control glucose homeostasis.…”

“…The incision site was sutured closed using nonabsorbable #2 suture (Supramid). Cows were administered 10 mg/kg of ampicillin intravenously ( Casey et al, 2021 ) and were monitored once daily for 7 d wherein sutures were removed on d 7 after biopsy.…”

“…The RNA-sequencing analysis of liver tissue was previously described ( Casey et al, 2021 ) and performed by GENEWIZ LLC (South Plainfield, NJ) using 50 mg of tissue from control (n = 6) and PS (n = 6) cows. The RNeasy Plus Mini Kit (Qiagen) was used to isolate total RNA, and quality was accessed with the TapeStation System and RNA ScreenTape (Agilent) (RNA integrity number score was 7.5 ± 0.4).…”

“…Differential gene expression was generated using DESeq2. Differentially expressed genes were validated in Casey et al (2021) using real-time quantitative PCR. Data were deposited with Gene Expression Omnibus (GEO; accession number GSE168914).…”