lectures - endocrine control of glucose homeostasis

what is the main fuel for cellular function

glucose

what is glucose homeostasis

balance between input and and utilization of glucose

what is the main location for making glucose through body sources

liver via glycogen degrad and gluconeo

what are the key targets for glucose regulating hormones

adipose tissue

skeletal muscle

liver

GLUT 1/3 are gound mainly in

brain and RBCs as they always need to have glucose supply

what does insulin do

↑ glucose oxidation

↑ glycogen synth - liver/muscle

↑ fat synth - adipose/liver

↑ protein synth - muscle, little in liver

↓ glycogen breakdown - liver/muscle

↓ glucose in blood

what does glucagon do

↑ glycogen breakdown

↑ gluconeo

↑ ketogenesis

↑ glucose in blood

in fed state what predominates

insulin

in fasted state what predominates

glucagon

insulin comes from what

pancreas

what is a general way to describe how insulin works on target organs

works like a key to unlock glucose channels

insulin acts on adipose and skeletal muscles to do what

↑ glucose uptake

how does insulin affect GLUT 4

triggers inert GLUT 4 transporters in mem allowing for glucose to enter

does GLUT 4 a major transporter in liver

no

insulin stimulated GLUT 4 trafficking occurs via

PI3K-AKT pathway

what is the major GLUT transporter in liver

GLUT 2

insulin acts of liver hepatocytes to activate

GLUT 2 and in turn hexokinase mediated conversion of glucose to G6P to keep intracellular glucose low

glucagon receptor signaling occurs via

cAMP-PKA pathway

Gs GPCR

what is the basal level ration of insulin:glucagon

more insulin in blood than glucagon

what hormones influence circulating glucose levels via primary mechs

GH, T3, GCs

what are primary mechs

hormones directly acting on tissues

describe GH in terms of affecting glucose levels

source - ant pit

targets - liver, muscle, adipose

function - ↑ gluconeo, ↓ glucose uptake

blood glucose - ↑

describe T3 in terms of affecting glucose levels

source - thyroid gland

targets - liver, muscle, adipose

function - ↑ gluconeo + glycogeno, ↑ glucose uptake

blood glucose - ↑

describe GCs in terms of affecting glucose levels

source - adrenal cortex

targets - liver, muscle, adipose

function - ↑ gluconeo, ↓ glucose uptake

blood glucose - ↑

what hormones influence circulating glucose levels via secondary mechs

GLP-1, estrogen, progesterone

what are secondary mechs

not acting directly on tissues, will involve release of another hormone to act on tissues

describe GLP-1 in terms of affecting glucose levels

source - intestinal L cells

targets - pancreas

function - ↑ insulin secretion ↓ glucagon secretion

blood glucose - ↓

describe estrogen in terms of affecting glucose levels

source - repro and metabolic tissues

targets - liver, muscle, adipose

function - ↑ insulin sensitivity

blood glucose - ↓

describe progesterone in terms of affecting glucose levels

source - repro and metabolic tissues

targets - liver, muscle, adipose

function - ↓ insulin sensitivity

blood glucose - ↑

what does progesterone do to mothers in terms of insulin

↓ insulin sensitivity in mother

why are there so many insulin receptor types

to make sure that insulin can still be effective if one receptor type fails

how does insulin regulate blood glucose levels

by inducing glucose uptake and metabolism in metabolic organs