Impacts of fat mobilization on bovine endometrium function

• In cows with high milk production, negative relationships between negative energy balance (NEB), inducing non-esterified fatty acids (NEFAs) in the peripheral circulation, and reproductive performances are well documented. Three major NEFAs; oleic (OA), palmitic (PA) and stearic acids (SA) have adverse effects on reproductive cells. In this thesis, the effects of NEB on gene expression in specific endometrial cells were studied from an in vivo model. Full endometrial biopsies were collected from Swedish Red Breed cows with different NEB status at 80 days postpartum. The three types of endometrial cells (stroma; ST, glandular epithelium; GE, and luminal epithelium; LE) were isolated from a tissue sample by using laser microdissection. Cell type-specific gene expression was identified in those cell types by RNA sequencing. The effects of the severity of NEB on endometrial gene expression were identified and it was found that the response to NEB was specific in the different cell types. Changes in gene expression are more profound in ST in which genes encoding proteins involved in energy metabolism, cell structure and peri-implantation processes were affected. Over-expression of genes associated with inflammatory response was observed in GE, whereas under-expression of genes related to adaptive immunity was observed in LE. In an in vitro study, we investigated the effects of the three NEFAs on phenotypic and gene expression responses of bovine endometrial epithelial cells (bEECs) in culture. Cultured postprimary bEECs were exposed to different concentrations of OA, PA and SA or their mixture. Cell viability, proliferation, apoptosis, lipid accumulation, pro-inflammatory cytokines (IL-6 and IL-8) production were examined at 24 and 48 h. Elevated NEFA dosage decreased cell viability and proliferation, while apoptosis, lipid accumulation and cytokine production were increased. The negative effects of OA and PA were stronger than those induced by SA. Gene expression changes of bEECs induced by 300 µM of either OA or PA for 2 h were further determined by using RNA sequencing. Oleic acid induced stronger changes in gene expression than PA. The up-regulation of pathways related to energy metabolism, apoptosis and oxidative stress signaling were observed whereas significance was not reached following use of PA. In conclusion, these results indicate that metabolic stress can affect endometrial functions in various ways. The gene expression changes in vivo suggests that severe NEB have long term effects on endometrial cells and that the responses are specific to cell types. The results from in vitro studies clearly show that NEFAs, especially OA and PA, alters many functions of bEECs and are detrimental to the sub-population of epithelial cells. Taken together, the results document that metabolic imbalance during the post-partum period alters several functions in the endometrium in a specific way in the different cell types and strongly stimulate pro-inflammatory mechanisms especially in epithelial cells.

Ämnesord

LANTBRUKSVETENSKAPER  -- Veterinärmedicin -- Klinisk vetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Veterinary Science -- Clinical Science (hsv//eng)

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