2020A10 An infusion of 50 mL of 50% dextrose is given to a healthy 70kg adult.
Describe the possible metabolic pathways for the dextrose.

 

 

Utilisation:

Occurs if ↓insulin, ↑glucagon
Aerobic: -> 2 ATP (in all nucleated cells)

Anaerobic: -> 36 ATP (in all cells)

   Glycolysis

   Krebs cycle

->4 x NADH+

-> 2 x FADH2

->2 x GTP

-> 4 x CO2

 

   Oxidative phosphorylation

 

-> 1x ATP

-> 1 x H2O

Storage:

Occurs if ↑insulin, ↓glucagon

GLUT2: constitutive

GLUT4: inducible

Glycogenesis

Uptake into liver (GLUT2), skeletal muscle (GLUT4)

Dose is 25g. Limit is ~50g liver, 400g skeletal muscle

Can be later catabolised to yield glucose

 

De novo lipogenesis

Uptake into liver (GLUT2), adipose (GLUT4)

Conversion:

 

   Lactate (Cori cycle)

   Amino acids
   (glucose-alanine cycle)

   HMP shunt

For synthesis of nucleotides (ribose)

   Rapoport-Luebering shunt

Production of 2,3-DPG in RBCs

Pathology:

 

   Urination

Renal threshold ~10mM may be exceeded if large dose

Glycosuria continuous if taking SGLT2 inhibitor

   Glycosylation

Chronic hyperglycaemia -> damage to proteins -> microvascular complications (nephropathy, neuropathy)

 

 

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