IV Fluids — Hypertonic Glucose

Immediate

50mls of 50% Glucose = bolus of 25g Glucose

• Hyperglycaemia – normal blood glucose is 4-7 when fasted, <11.1 when not fasted
• Glycosuria – resorption capacity of the renal PCT is exceeded when serum glucose >10-12mmol/l
  • resorption of glucose is via co-transport with Na⁺

Insulin

• Secreted from
  • Pancreatic beta cells in islets of Langerhans

• Mechanism of secretion
  • Glucose moves into beta cells via GLUT-2 transporters
  • Glucose –-(glucokinase)–>   Glucose-6-phosphate   –-(glycolysis)–>   ATP
  • ATP inhibits ATP sensitive  K⁺ channels
  • Cell depolarises → calcium influx
  • Calcium stimulates exocytosis of insulin-containing vesicles

• Response
  • Insulin release
    • Inhibits gluconeogenesis
    • Promotes muscular, adipose and peripheral cell glucose uptake
      • GLUT-4 transporter
    • Promotes hepatic glycogenesis
      • Glucose trapping
        • Hexokinase phosphorylates glucose (glucose-6-phosphate)
        • Negatively charged G6P cannot cross membrane, so is trapped in hepatocyte
      • Stimulates glycogen synthase
    • Inhibits glycogenolyis
      • Inhibits liver phosphorylase
    • Promotes FFA synthesis, fat deposition
    • Inhibits lipolysis
    • Promotes protein anabolism, inhibits catabolism in muscle
• Fate of glucose
  • Glycolysis -> pyruvate
  • Pyruvate and CoA -> acetyl CoA -> enters citrate cycle
  • FADH and NADH from citrate cycle -> electron transport chain
  • Yield from 1 glucose is around 38 ATP

• Pattern
  • Biphasic release
    •  Phase 1: Dumping of preformed insulin
    • Phase 2: Drop-off in insulin secretion, then rise up towards a higher peak when new insulin is made

Mooney 2016

Answer by Mooney