a. Lipoprotein Apo — C — II → is activator of Lipoprotein lipase
b. Insulin — acts on Insulin Receptor — that activate the Tyrosine Kinase activity of β-subunits. Probably in Insulin deficiency ‘Activity of Tyrosine kinase is decreased.
c. Starvation and Diabetes mellitus have almost same metabolic changes ie. due to Insulin deficiency and glucagon excess. Or ↑ratio of Glucagon/Insulin: -
This Leads to following changes in enzyme activity: -
a. Activity of Enzymes of Glycogenesis, glycolysis and pyruvate oxidation — are decreased
b. Eg. Glycogen synthase↓, glucokinase↓phosphofructokinase, ↓ pyruvate kinase .↓, pyruvate dehydrogenase↓
c. Activity of the Enzymes of Gluconeogenesis are Increased: eg. pyruvate carboxylase ↑phosphoenolpyruvatecarboxykinase↑, fructose 1,6-biphosphophatase ↑, Glucose-6- phosphatase ↑.
d. Activity of the Enzymes of Pentose phosphate — pathway and Lipogenesis are decreased:- eg G-6-P-dehydrogenase; 6-phosphogulconate de-Hase↓, Malic enzyme↓., ATP-citrate Lyase↓,acetyl Co A- carboxylase ↓ fatty acid synthase ↓
a. ↑ratio of Glucagon/Insulin ie in excess of glucagon and deficiency of Insulin as in starvation and DM →↑ed lipolysis due to ↑ed activity of— hormone sensitive Lipase and activation of carnitine-palmitoyl-transferase system of mitochondrial membrane →Leads to ↑edketogenesis.