Insulin signalling

Question 1

what does insulin do as an adiposity signal?

Answer 1

decrease NPY/ AgPR, incraese POMC/CART

decrease food intake and body weight

insulin circulates at levels proportional to body weight

Question 2

describe the insulin receptor

Answer 2

there is an insulin receptor mediated transport system in the brain microvasculature that allows rapid access to the CNS

insulin receptors are expressed in the hypothalamus (mainly ARC)

Question 3

describe insulin regulation of ARC neurones

Answer 3

decreases NPY increases POMC

co expressed with leptin in ARC neurones

reduced NPY increases alpha MSH release in the hypothalamus and causes decreased food intake

MC3/4 oppose insulin/leptin

Question 4

what can AgRP neurones do?

Answer 4

regulate insulin suppression of HGP?

Question 5

describe HGP

Answer 5

mediated by ARC AgRP neurones and involves vagal afferents to the liver

insulin acts in ARC to help reduce HGP by inhibition of gluconeogenesis

insulin resistance diminishes ability of peripheral insulin to supress HGP

Question 6

what does insulin do in the hypothalamus?

Answer 6

modulates hypothalamic neuronal activity (diminished in obesity)

imporves insulin sensitivity

promotes lipogenesis and peripheral fat accumulation (WAT)

increases adaptive thermogenesis (BAT)

Question 7

describe ghrelin action

Answer 7

opposes insulin/leptin

rises before meals, falll after

decreases energy expenditure, increases body weight

decreased secretion in obese states (resistance occurs)

increases NPY/AgPR no effect on POMC

increases fat storage

LEAP2 opposes ghrelin

Question 8

insulin is….

Answer 8

anabolic and glucoregulatory

Question 9

how is reduced HGP mediated from the brain?

Answer 9

ARC AgRP neurons