Insulin Resistance
Basic Information 
• Insulin is the primary hormone that controls energy metabolism.
• The pancreatic β cells secrete insulin in response to glucose and glucagon.
• Insulin secretion is also regulated by sympathetic and parasympathetic systems: epinephrine (stress) inhibits and acetylcholine (food intake) stimulates insulin secretion.
• Somatostatin inhibits insulin secretion.
• Insulin regulates three major fuels: carbohydrates, proteins, and fats.
• The liver, skeletal muscle, and adipose tissue are the major targets for insulin.
Liver: Insulin decreases glycogen, gluconeogenesis, and ketogenesis, and stimulates glycogen and fatty acid synthesis.
• Understanding insulin physiology is central to understanding the pathogenesis of equine pathological conditions such as hyperlipemia, pituitary pars intermedia dysfunction (Cushing’s disease), equine metabolic syndrome (EMS), and polysaccharide storage myopathy.
Definition
Insulin resistance (IR) is defined as a decreased response to endogenous or exogenous insulin
