TAG storage

Question 1

TAG storage

Answer 1

• TAG transported from liver to adipose tissue via VLDL
• Adipocytes produce LPL which hydrolyses TAG molecules in VLDL & chylomicron particles.
• LPL exported from adipocytes and form GAG complexes with Heparan sulfate
• Intracell acyl-CoA formed by means of cytosolic thiokinase activity -> diverted into TAG synthesis by means of Kennedy pathway.

Question 2

Fat mobilization in adipose tissue

Answer 2

• Glycerol cannot be utilised by adipocyte as it lacks Glycerol Kinase
• Insulin inactivates HSL
• Epinepherine stimulates HSL
• Glucagon has very littl effect on HSL
• During excercise:
  
  • Epinepherine activates HSL & periplipin, whereas insulin is anti-lipolytic
  • Epinepherine over-rides the effect of insulin in order to fight or flight

Question 3

Adipocytes secrete these adipokines

Answer 3

• Resistin: dampen myocyte, hepatocyte & adipocyte respones to insulin (also true of TNF-alpha)
• Adiponectin: sensitizes receptor-cells to insulin, involved in regulation of metabolic processes i.e. glucose & fatty acid oxidation particularly in the liver & muscle
• Leptin: appetite suppressant

Question 4

AMP-Dependent Protein Kinase (AMPK)

Answer 4

• AMPK enhances catabolic rxn (FA oxidation) and inhibits anabolic rxn (glycogen synthesis).
• Leptin enhances AMPK activity.
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Question 5

Congenital Generalised Lipodystrophy (CGL)

Answer 5

• AGPAT2 deficiency
• Acylglycerol 3-P Acyltransferse: converts Lysophosphatidic acid -> Phosphatidic acid
• AGPAT2 is principal isoform in adipose tissue
• Rare Autosomal disorder
• Lack of body fat
• Muscular appearance
• TAG & PL synthesis is compromised