title: Physiological mechanisms of action of incretin and insulin in regulating skeletal muscle metabolism.
abstract: Type II diabetes (T2D) is a progressive condition affecting approximately 350 million adults worldwide. Whilst skeletal muscle insulin resistance and beta-cell dysfunction are recognised causes of T2D, progressive loss of lean muscle mass (reducing surface area for glucose disposal area) in tandem with ageing-related adiposity (i.e. sarcopenic obesity) also plays an important role in driving hyperglycaemia progression. The anabolic effects of nutrition on the muscle are driven by the uptake of amino acids, into skeletal muscle protein, and insulin plays a crucial role in regulating this. Meanwhile glucagon-like peptide (GLP-1) and glucose- dependent insulinotropic peptide (GIP) are incretin hormones released from the gut into the bloodstream in response to macronutrients, and have an established role in enhancing insulin secretion. Intriguingly, endocrine functions of incretins were recently shown to extend beyond classical insulinotropic effects, with GLP-1/GIP receptors being found in extra-pancreatic cells i.e., skeletal muscle and peripheral (muscle) microvasculature. Since, incretins have been shown to modulate blood flow and muscle glucose uptake in an insulin-independent manner, incretins may play a role in regulating nutrient-mediated modulation of muscle metabolism and microvascular tone, independently of their insulinotropic effects. In this review we will discuss the role of skeletal muscle in glucose homeostasis, disturbances related to insulin resistance, regulation of skeletal muscle metabolism, muscle microvascular abnormalities and disturbances of protein (PRO) metabolism seen in old age and T2D. We will also discuss the emerging non-insulinotropic role of GLP-1 in modulating skeletal muscle metabolism and microvascular blood flow.
authors.forename: Haitham
authors.initials: H
authors.lastname: Abdulla
authors.forename: Bethan
authors.initials: B
authors.lastname: Phillips
authors.forename: Kenneth
authors.initials: K
authors.lastname: Smith
authors.forename: Daniel
authors.initials: D
authors.lastname: Wilkinson
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Atherton
authors.affiliation: Division of Medical Sciences & Graduate Entry Medicine, School of Medicine, University of Nottingham, Royal Derby Hospital, Uttoxeter Road, DE22 3DT, UK. Iskandar.idris@nottingham.ac.uk.
authors.forename: Iskandar
authors.initials: I
authors.lastname: Idris
mesh_terms: D001783:Blood Flow Velocity / Q000187:drug effects; D001786:Blood Glucose / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000378:metabolism* / Q000503:physiopathology; D005749:Gastric Inhibitory Polypeptide / Q000378:metabolism; D005934:Glucagon / Q000378:metabolism; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006706:Homeostasis; D006801:Humans; D006943:Hyperglycemia / Q000378:metabolism / Q000503:physiopathology*; D007004:Hypoglycemic Agents / Q000378:metabolism* / Q000627:therapeutic use; D054795:Incretins / Q000378:metabolism* / Q000627:therapeutic use; D007328:Insulin / Q000378:metabolism / Q000627:therapeutic use*; D007333:Insulin Resistance; D008833:Microcirculation / Q000187:drug effects; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology
chemical_list: D001786:Blood Glucose; D007004:Hypoglycemic Agents; D054795:Incretins; D007328:Insulin; D005749:Gastric Inhibitory Polypeptide; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D005947:Glucose