Energy hormone response to fasting-induced dyslipidemia in obese and non-obese donkeys.

Metabolic and endocrine disorders, such as dyslipidemia, are common in donkeys. Negative energy balance due to fasting, stressful conditions, or disease is a major trigger for fat mobilization often leading to dyslipidemia. The hormonal response to fasting has not been well characterized in donkeys. Therefore, this work aimed to study variations in insulin, glucagon, leptin, total adiponectin, ghrelin, and insulin-like growth factor-1 concentrations, insulin-to-glucagon (IGR) and glucagon-to-insulin (GIR) molar ratios, and lipid and carbohydrate parameters during a 66 h fasting period in 8 adult donkeys, and to determine differences depending on body condition. Obese donkeys developed earlier lipid mobilization (increased plasma total triglyceride and total cholesterol concentrations) compared to non-obese donkeys. Plasma glucose and leptin concentrations decreased in obese animals. After 60 h fasting, obese donkeys showed a significant increase in glucagon and decrease in leptin. GIR significantly increased, while insulin and IGR decreased in both groups. These findings support faster lipid mobilization in response to negative energy status in obese donkeys during fasting, which could be linked to greater glucagonemia and could explain the predisposition of these animals to dyslipidemia.

Effect of intravenous glucose and combined glucose-insulin challenges on energy-regulating hormones concentrations in donkeys.

Metabolic disorders are highly prevalent in donkeys. Differences in energy regulatory hormones and glucose dynamic testing, including the intravenous glucose tolerance test (IVGTT) and combined glucose-insulin test (CGIT), have been documented between donkeys and horses. The aims of this study were to characterise the insulin:glucagon (IGR) and glucagon:insulin (GIR) molar ratios, at baseline and in response to the IVGTT and CGIT in healthy donkeys, and to determine their correlation with endocrine (leptin, ghrelin and adiponectin) and morphometric variables. Median values and interquartile ranges (IQRs) for IGR and GIR in 49 healthy adult donkeys were 1.5 (IQR, 1.0-1.8) and 0.7 (IQR 0.5-0.9), respectively. IVGTT and CGIT were each performed on eight donkeys, while dynamic testing was performed on six donkeys due to loss of two donkeys from the study. IVGTT induced an increase in IGR (and a decrease in GIR) from 15 to 180min after the onset of the test, but had no effect on leptin, adiponectin or ghrelin concentrations. CGIT resulted in a significant elevation in IGR (and a decrease in GIR) from 15 to 120min after the onset of the test. Plasma leptin concentrations increased significantly at 240min. No correlations were found between ratios, hormones and morphometric measurements. The findings support differences between donkeys and horses, which are likely to be related to proportionally higher glucagon compared to insulin concentrations in donkeys, and may be relevant to disorders related to energy dysregulation in donkeys, including metabolic syndrome and dyslipidaemias.