Investigation of the relationship between β-hydroxybutyric acid and subfatin and some other adipokines in experimental pregnancy toxemia-induced New Zealand rabbi̇ts

Pregnancy toxemia is a significant metabolic disease affecting many animal species, leading to considerable economic losses due to its high morbidity and mortality rates. This study aims to investigate the potential of subfatin, a novel adipokine primarily expressed in adipose tissue, along with other adipokines such as adiponectin, leptin, adipsin, and apelin, as early diagnostic markers. These may serve as alternatives or supplements to β-hydroxybutyric acid (BHBA) measurements, which are commonly used in diagnosing pregnancy toxemia. The study sample consisted of 24 female and 3 male New Zealand rabbits aged 2.5 to 3 months. Following estrus synchronization with gonadotropin, pregnancy was confirmed by transabdominal ultrasonography on day 15 post-mating. Experimental and control groups were randomly assigned, each containing 12 animals. All animals were provided with water ad libitum throughout the study period. The control group received feed with a defined nutrient content ad libitum throughout the experiment, while the rabbits in the experimental group were fed only hay starting from the 20th day of pregnancy, creating a negative energy balance and thus inducing pregnancy toxemia. Blood samples were collected at four time points: before synchronization (SÖ), one day before mating (CÖ), on day 15 of gestation (G15), and daily from day 23 until parturition. Hematological and biochemical parameters, along with serum adipokine and immunoglobulin levels, were analyzed from these samples. Rabbits exhibiting severe pregnancy toxemia symptoms were treated with propylene glycol. Liver tissue was collected from aborted offspring despite treatment and from two randomly selected offspring per mother in the control group. Levels of subfatin, adiponectin, leptin, adipsin, apelin, and immunoglobulins were measured in liver tissue extracts using ELISA kits. In the statistical analyses of the study, it was determined that subfatin, adiponectin, apelin, and adipsin levels were significantly lower in the GTÖ and GT groups compared to the control group, whereas leptin levels did not differ. Regarding the correlation findings, a moderate and statistically significant positive relationship was found between adiponectin and subfatin, and between adiponectin and BHBA. Leptin levels showed a moderate positive correlation with adiponectin, apelin, glucose, and adipsin. In addition, a moderate positive correlation was identified between adiponectin and apelin, while a strong positive correlation was found between adiponectin and adipsin. Furthermore, a moderate positive correlation was observed between apelin and glucose. According to the ROC analysis results, subfatin demonstrated a moderate diagnostic performance (AUC=0.792), apelin (AUC=0.875) and adipsin (AUC=0.851) showed good diagnostic performance, and adiponectin exhibited a very good diagnostic performance (AUC=0.946) in the diagnosis of pregnancy toxemia. In conclusion, alterations in BHBA and adipokine levels—particularly subfatin—play a significant role as potential biomarkers for early diagnosis and risk assessment of pregnancy toxemia. Developing a risk classification system based on adipokine levels could represent a new step in preventive medicine.