Chike F. Oguejiofor

Relationships between Circulating Urea Concentrations and Endometrial Function in Postpartum Dairy Cows

Simple Summary Dairy cows fed high levels of protein to increase milk yield tend to have reduced fertility but the reasons behind this are unclear. Differing dietary protein levels are reflected in altered urea concentrations in both blood and other tissues including the uterus. We showed that the circulating urea concentration was highly correlated to changed expression levels of many genes in the endometrium shortly after calving. These were predominantly associated with tissue repair, innate immunity and lipid metabolism. A subsequent study found no effect of altered urea concentration on endometrial gene expression in vitro implying that the dietary influence is indirect. Abstract Both high and low circulating urea concentrations, a product of protein metabolism, are associated with decreased fertility in dairy cows through poorly defined mechanisms. The rate of involution and the endometrial ability to mount an adequate innate immune response after calving are both critical for subsequent fertility. Study 1 used microarray analysis to identify genes whose endometrial expression 2 weeks postpartum correlated significantly with the mean plasma urea per cow, ranging from 3.2 to 6.6 mmol/L. The biological functions of 781 mapped genes were analysed using Ingenuity Pathway Analysis. These were predominantly associated with tissue turnover (e.g., BRINP1, FOXG1), immune function (e.g., IL17RB, CRISPLD2), inflammation (e.g., C3, SERPINF1, SERPINF2) and lipid metabolism (e.g., SCAP, ACBD5, SLC10A). Study 2 investigated the relationship between urea concentration and expression of 6 candidate genes (S100A8, HSP5A, IGF1R, IL17RB, BRINP1, CRISPLD2) in bovine endometrial cell culture. These were treated with 0, 2.5, 5.0 or 7.5 mmol/L urea, equivalent to low, medium and high circulating values with or without challenge by bacterial lipopolysaccharide (LPS). LPS increased S100A8 expression as expected but urea treatment had no effect on expression of any tested gene. Examination of the genes/pathways involved suggests that plasma urea levels may reflect variations in lipid metabolism. Our results suggest that it is the effects of lipid metabolism rather than the urea concentration which probably alter the rate of involution and innate immune response, in turn influencing subsequent fertility.

Increasing doses of diminazene aceturate: adverse reproductive effects in female Wistar rats.

Objective: To investigate the effects of comparatively high doses of diminazene aceturate on the reproductive performance of female rats in the early stage of pregnancy. Methods: After oestrus synchronisation and successful mating, 20 pregnant female rats were randomly divided into four groups (A-D). Group A rats served as the control and were given single intraperitoneal injection of 0.5 mL sterile water (vehicle only) while groups B, C and D rats were given single intraperitoneal doses of 7, 14 and 21 mg/kg body weight diminazene aceturate respectively, on day 7 of pregnancy. The gestation length, litter size and weight at birth, and areas of foetal resorption in the uterus were determined post partum. The post-implantation survival index (%) and the gestation index (group %) were also evaluated for rats in all the groups. Results: There was a graded increase in the number of observed resorbed foetuses as the dose of diminazene aceturate was increased, although only groups C (14 mg/kg) and D (21 mg/kg) revealed a significant decrease (P＜0.01, ANOVA) in the post implantation survival index of rat embryos. There was also a significant decrease P＜0.05) in the litter weights of rats in groups C and D. Conclusions: Although the pregnant rats showed no overt signs of systemic toxicity even at the highest dose of 21 mg/kg body weight diminazene aceturate in this study, it was concluded that the use of high doses of diminazene aceturate in an effort to combat resistant trypanosomes could have adverse reproductive effects on female animals in the early period of pregnancy.

Differential proteomic profiling of endometrium and plasma indicate the importance of hydrolysis in bovine endometritis

Endometritis is an important disease of dairy cows that leads to significant economic losses in the dairy cattle industry. To investigate the alteration of proteins associated with endometritis in the dairy cow, the isobaric tags for relative and absolute quantification (iTRAQ) technique was applied to quantitatively identify differentially expressed proteins (DEP) in the endometrium and peripheral plasma of Chinese Holstein cows with endometritis. Compared with the normal (control) group, 159 DEP in the endometrium and 137 DEP in the plasma were identified in cows with endometritis. Gene ontology analysis demonstrated that the predominant endometrial DEP were primarily involved in responses to stimulus and stress processes and mainly played a role in hydrolysis in the extracellular region. The predominant plasma DEP were mainly components of the cytosol and non-membrane-bound organelles, and they were involved in the response to stress and regulation of enzyme activity. Protein-protein interaction of tissue DEP revealed that some core seed proteins, such as RAC2, ITGB2, and CDH1 in the same network as CD14, MMP3, and MMP9, had important functions in the cross-talk of pathways related to extracellular proteolysis. In summary, significant enzymatic hydrolase activity in the extracellular region is proposed as a molecular mechanism by which altered proteins may promote inflammation and hence endometritis.