metabolism and insulin Flashcards
insulin resistance: define insulin resistance and explain the relation to diabetes, dyslipidaemia, hypertension and ischaemic heart disease, and explain the consequences on metabolism
define insulin resistance
where insulin is produced but target cells are not sensitive to it, resulting in elevated levels of blood glucose
insulin action in insulin resistance: effect on glucose
decrease hepatic glucose output (HGO), increase glucose muscle uptake
insulin action in insulin resistance: effect on protein
decrease proteolysis (breakdown of proteins into amino acids; oxidised for energy source in gluconeogenesis)
insulin action in insulin resistance: effect on lipid
decrease lipolysis (breakdown of lipids into glycerol and fatty acids using lipoprotein lipase)
why does lipolysis decrease when insulin acts in insulin resistance
after meal, lipids should be stored in adipocytes but can only enter as glycerol; once entered, stored as triglyceride by reaction of glycerol-3-P (from glucose) and non-esterified fatty acids (from triglycerides)
insulin action in insulin resistance: effect on ketone bodies
decrease ketogenesis (production of ketone bodies by the breakdown of fatty acids and ketogenic amino acids)
how is hepatic glucose output (HGO) increased
absence of insulin increases glycogenolysis and gluconeogenesis (triglycerides and glucogenic amino acids converted to glucose)
what part of triglycerides can the liver use in gluconeogenesis
glycerol, not non-esterified fatty acids
where does insulin resistance reside
liver, muscle and adipose tissue
what does insulin resistance effect
intermediary metabolism, glucose and fatty acids
with insulin resistance, what is there sufficient insulin to suppress
enough insulin to suppress lipolysis, ketogenesis and proteolysis, so break down of fat or protein doesn’t occur, so no weight loss
how are adipocytes in central circulation different to those in the limbs
central circulation anatomical sites have possibility of changing metabolism
how is insulin resistance and waist:hip circumference associated with ischaemic heart disease
if insulin resistant, gluconoegensis increases including breakdown of triglycerides in adipose tissue to glycerol and free fatty acids; increased production of free fatty acids is associated with the expansion of adipose mass, and due to atherosclerosis, ischaemic heart disease can be predicted by waist:hip circumference; obesity also increases amount of central adipocytes and are more likely to be insulin resistant as not enough insulin in circulation compared to mass; greater insulin production so greater mitogenic pathway stimulus
insulin resistance contributors to ischameic heart disease
dyslipidaemia and hypertension
how can an individual be insulin resistant with ischaemic heart disease, dyslipidaemia and hypertension without having type II diabetes mellitus
high insulin (hyperinsulinaemia) causes glucose to be normal but overstimulates mitogenic pathway so major growth and proliferation (high lipoproteins but low HDL, smooth muscle hypertrophy, ovarian function, clotting, energy expenditure)
