Insulin resistance in the horse: a review

Abstract

Insulin resistance (IR) is a state in which the tissues show a reduced sensitivity to insulin despite its normal or even increased concentration in blood. IR causes inability of peripheral tissues to respond to the hormone and to increase the glucose uptake from blood nor to raise the metabolism rate. The tissues resistance to insulin may refer to the prereceptor malfunctions, which reduce the concentration of insulin or decrease the number of insulin receptors; however, in most cases changes in signal transduction after insulin binding to the receptor are observed. The development of IR is determined by a number of genetic and environmental factors. One of the most relevant causes is obesity, which develops into a growing problem among the horse population all over the world. The accumulation of lipids in the tissues (lipotoxicity) and a mild inflammation caused by the release of proinflammatory adipokines and cytokines from the fat tissue are a common denominator that links obesity with IR. Both IR and obesity seem to cause metabolism malfunctions in horses and are the key components of equine metabolic syndrome; moreover, both may be the reason for endocrinological laminitis. The methods of prevention and treatment of IR include feeding the animals with low glycemic index food and increasing physical activity as well as pharmacological treatment, where levothyroxine sodium and metformin are of the highest importance. ARTICLE HISTORY

Inhibition of the Low Molecular Weight Protein Tyrosine Phosphatase (LMPTP) as a Potential Therapeutic Strategy for Hepatic Progenitor Cells Lipotoxicity—Short Communication

“…In human, excessive accumulation of toxic triglyceride in the liver cells contributes to the development of non-alcoholic fatty liver disease (NAFLD) [3]. IR occurs primarily in insulin-sensitive tissues, like liver, adipose tissue, and muscle, and may be caused by several mechanisms, e.g., endoplasmic reticulum (ER) stress, impaired mitochondrial dynamics, and autophagy [4,5,6,7].…”

Follicular metabolic alterations are associated with obesity in mares and can be mitigated by dietary supplementation

“…Starch-rich diets adversely affect oocyte quality in cows 79 , 80 and may negatively affect fertility of women 81 . Nevertheless, grain additives are commonly included in the modern equine diet and predispose to obesity and metabolic diseases 82 . We are also unable to differentiate between individual and synergistic effects of the OBD dietary supplementation components.…”

Trodusquemine (MSI-1436) Restores Metabolic Flexibility and Mitochondrial Dynamics in Insulin-Resistant Equine Hepatic Progenitor Cells (HPCs)

“…Recent evidence indicates that excessive consumption of high-carbohydrate (NSC) forage promotes hepatic de novo lipogenesis and leads to lipotoxicity. Dysregulation of glucose metabolism can also contribute to the development of insulin resistance, which is significant factor in the pathogenesis of equine metabolic syndrome (EMS) [14][15][16][17][18]. The binding of insulin to the insulin receptor (INSR), a tyrosine kinase receptor, initiates a series of phosphorylation events that activate intracellular signaling pathways responsible for transporting glucose into the liver through the GLUT2 transporter [19,20].…”

“…Furthermore, insulin resistance (IR) commonly occurs in insulin-sensitive tissues such as the liver, adipose tissue, and muscle due to various mechanisms, including endoplasmic reticulum (ER) stress, impaired mitochondrial dynamics, and autophagy dysfunction [15,16,18]. Consequently, the cell has developed various quality control processes to counteract the accumulation of mitochondrial damage [30].…”