Aspartate Aminotransferase and Gamma Glutamyl Transferase Levels in Mares with Miscarriage and Healthy Pregnancies

Aspartate Aminotransferase and Gamma Glutamyl Transferase activities in mares

Abstract

Background: Hormonal and physiological changes during pregnancy period have significant effects on animals’ metabolisms. The purpose ofthe present study is to evaluate the variations of aspartate aminotransferase (AST) and gamma-glutamyl transferase (GGT) levels according to different gestation trimesters of the pregnant mares  to assess changes  of embryonic losses and abortions.

Materials, Methods & Results: Blood samples from 49 throughbred mares were analysed during this study. Age ratio of the mares is 5-18 years and their body condition score (BCS; score 1 to 9) varies between 5 and 6. Twentyeight mares had given birth to healthy foals at the end of a healthy gestation period (Group C), whereas 11 mares had embryonic losses (Group E) and 10 mares had late period abortions (Group A). Following the confirmation of pregnancy, one blood sample per gestation trimester were taken (14-16 days of pregnancy for 1^st trimester; 180 days for 2^nd trimester, 270 days for 3^rd trimester).  Early embryonic  losses (loss of a 16-25 days embryo) were observed in 6 of  11 mares in Group E and the  5 of 11 mares had late period embriyonic losses (loss of a 35-40 days embryo). In Group A, 6 mares had the abortion within 7^th month and the remaining 4 mares had the abortion within the 8^th month of pregnancy. Repeated Measures ANOVA, Kruskal-Wallis test and Mann-Whitney test were performed for statistical analysis, the mean AST level in Group C (n = 28) was higher during the 1^st trimester in comparison to 2 following trimesters (respectively: P = 0.011 ; P = 0.01). Besides, no statistical difference was observed between 2^nd and 3^rd  trimester regarding AST activation (P > 0.05). The mean GGT level in Group C was significantly decreased lower in the 3^rd  trimester compared to 1^st and 2^nd trimester (respectively: P = 0.007 ; P = 0.009). No statistical difference was observed between 2^nd and 3^rd  trimester regarding GGT activation (P > 0.05). Among all groups (C, E, A) no significant difference was observed on AST levels (P > 0.05), nonetheless GGT levels had a significant rise (P = 0.039) in Group A in comparison to the 1^st trimester levels of Group C. In Group A, there was a statistical decrease of AST during the 2^nd trimester in comparison to the 1^st trimester (P = 0.001), accompanied by a decrease of GGT activation during the 2^nd trimester compared to the 1^st trimester (P = 0.009).

Discussion: The aminotransferases are catalisors that play an important role on the metabolism of amino acids and carbonhydrates. Although serum AST levels were within the reference ranges during 3 trimesters in this study, serum AST levels were determined to be decreased in the 2^nd and 3^rd  trimesters in healthy pregnant mares compared to the 1^st trimester.  It is thought that these results can be obtained due to the increase in metabolic needs during pregnancy. In this study, serum GGT levels remained within physiological limits with a tendency to decrease as the pregnancy advances, in accordance with previous study results. Serum GGT levels that are used as an indicator to liver damage may vary during the pregnancy as a result of increased metabolic load. It is thought that the increase of serum GGT levels in Group A might be related to the fetal (chromosome-related) issues that may result to pregnancy losses. As a result, it is considered that serum AST and GGT levels in mares might be valuable parameters that predict embryonic loss or abortus cases.

Keywords: abortus, enzymes, serum levels, AST, GGT, embryonic loss, mares, pregnancy.