diabetes physiology

Question 1

is glucagon and insulin an anabolic or catabolic hormone?

Answer 1

glucagon = catabolic = breakdown

insulin = anabolic = building

Question 2

glycogenolysis

Answer 2

liver breaks down glycogen into glucose

Question 3

gluconeogenesis

Answer 3

liver converts proteins + fats into glucose

Question 4

when is glucagon released? (in response to..)

Answer 4

low blood sugars

+ stress

Question 5

how does glucagon increase blood sugar levels

Answer 5

glycogenolysis (glycogen -> glucose)

gluconeogenesis (proteins + fats -> glucose)

Question 6

can ketones cross the blood brain barrier?

Answer 6

yes - brain cas use as fuel

water soluble fatty acids

Question 7

how can ketone levels be measured?

Answer 7

urine dipstick

blood via ketone meter

Question 8

where is insulin made?

Answer 8

rough endoplasmic reticulum of pancreatic beta cells

2 polypeptide chains linked by disulphide bonds

Question 9

insulin creation

Answer 9

initially large single chain = preproinsulin

preproinsulin -> proinsulin + single peptide -> C-peptide + insulin

(C peptide has no function)

Question 10

what do the 4 cell types of pancreatic islets secrete?

Answer 10

alpha = glucagon
beta(commonest) = insulin
delta = somastatin
PP-cell = pancreatic polypeptide

Question 11

how does glucose enter beta cells?

Answer 11

through GLUT2 (glucose transporter)

Question 12

How are thyroid hormones transported in the blood?

Answer 12

Thyroid hormones are lipophilic, and bind to thyroxine binding globulin (TBG) and thyroid binding pre-albumin (TBPA). A very small concentration of T3 and T4 travels freely in the bloodstream where it can interact with target cells.

Question 13

How is adrenal corticosteroid production regulated?

Answer 13

When low amounts of cortisol are detected, the hypothalamus releases corticotropin releasing hormone. This stimulated production of adrenocorticotropic hormone in the anterior pituitary, which acts upon the adrenal glands to raise cortisol. Increased cortisol has a negative feedback mechanism on both the hypothalamus and anterior pituitary, to stop levels rising too high.

Question 14

what is glucose phosphorylated by in pancreatic beta cells?

Answer 14

glucokinase

Question 15

what can be said about the amout of insulin released vs the amount of glucose than enters the pancreatic beta cell?

Answer 15

directly proportional

Question 16

activity of glucokinase in type 2 diabetes

Answer 16

maximmaly acitive at all times

Question 17

effect of chronic insulin secretion on mitochondria

Answer 17

mitochondrial exhaustion = reduced ATP production

Question 18

alpha cells reaction to low glucose

Answer 18

K-ATP channels open
voltage-gated sodium channels (NaV) contribute to APs
P/Q voltage gated calcium channels (CaV) enable Ca influx
glucagon exocytosis triggered

Question 19

alpha cells reaction to low glucose

Answer 19

K-ATP channels open
voltage-gated sodium channels (NaV) contribute to APs
P/Q voltage gated calcium channels (CaV) enable Ca influx
glucagon exocytosis triggered

Question 20

alpha cells reaction to high glucose

Answer 20

K-ATP channels closed - cell depolarised
presence of SGLT 2 glucose transporters contributes to non-voltage regulated sodium ion influx
NaV + CaV channels closed, glucagon not exocytosed

Question 21

relation between glucagon secretion and blood glucose

Answer 21

secretion of glucagon INVERSELY proportional to blood glucose

Question 22

mechanisms of insulin resistance (3)

Answer 22

1. impairment of insulin signalling - skeletal muscle insulin resistance
2. inflammation - adipose tissue insulin resitance (obesity induced inflammation)
3. pathway-selective hepatic insulin resistance

Question 23

gold standard measurement of insulin resistance?

Answer 23

hyperinsulinemic-euglycemic clamp

initial sample taken from artery then infuse insulin into vein + keep taking artery samples

Question 24

patient is given insulin infusion and potassium is lowered, by what mechanism is insulin causing this effect?

Answer 24

stimulation of the Na/K ATPase pump

Question 25

type 2 diabetic started on steroids, what monitoring is most important after starting?

Answer 25

four times daily capillary blood glucose

-> use of corticosteroids can worsen diabetic control due to their anti-insulin effects