Insulin and Diabetes Flashcards
Criteria for the Diagnosis of Diabetes
- A1C greater than or equal to 6.5%
- Fasting plasma glucose greater than or equal to 126 mg/dL
- 2-h plasma glucose greater than 200 mg/dL during an OGTT
- A random plasma glucose greater than 200 mg/dL
Glucose intolerance in type 1 diabetes characterized by
no functioning insulin-secreting pancreatic beta cells, dependency on exogenous insulin and a tendency towards ketoacidosis
Type 1 diabetes is thought to be caused by
antibodies that destroy pancreatic beta cells that may be triggered by viruses, chemicals etc. in genetically predisposed individuals
Role of glucagon
increased glucagon levels in the presence of increased blood glucose levels
Hyperlipidemia in diabetes
increased fatty acid mobilization from fat cells; increased fatty acid oxidation - ketoacidosis
What happens in hyperglucemia (due to lack of insulin)
- decreased glucose uptake in cells where glucose uptake is insulin-dependent
- decreased glycogen synthesis
- increased conversion of amino acids to glucose
Cardiovascular complications from diabetes
micro and macro angiopathies
Neuropathy complications from diabetes
increased blood glucose levels lead to increased utilization of the polyol pathway (Aldose Reductase); increased cytosolic water in neural cells
Nephropathy complications from diabetes
renal vascular changes and changes in the glomerular basement membrane
Ocular complications from diabetes
cataracts, retinal microaneurysms and hemorrhage
Increased susceptibility to what? with diabetes
increased susceptibility to infections
Conventional therapy goals of insulin therapy and monitoring
reduce acute symptoms - polyuria, dehydration and ketoacidosis
Intensive therapy goals of insulin therapy and monitoring
keep blood glucose levels below 150 mg/dL; prevent/delay onset of complications; increased risk of hypoglycemia
Oxidation products of glucose react irreversibly with proteins to form
Advanced glycation end-products (AGE)
Advanced glycation end-products (AGE) results in
loss of normal protein function; acceleration of aging process; theorized to account for many long-term complications of diabetes
AGE precursor, methylglyoxal, inhibits
vasorelaxation stimulated by acetylcholine/NO
Role of the alpha subunits in the insulin receptor
regulatory unit of the receptor; represses the catalytic activity of the beta subunit; repression is relieved by insulin binding
Role of the beta subunits in the insulin receptor
contain the tyrosine kinase catalytic domains (autophosphorylation)
Insulin effects on the liver
inhibits: glycogenolysis; ketogenesis; and gluconeogenesis
stimulates: glycogen synthesis and triglyceride synthesis
Insulin effects on the skeletal muscle
glucose transport; amino acid transport
Insulin effects of the adipose tissue
triglyceride storage and glucose transport
Glucose disposal in a fasting state
75% is non-insulin dependent (Liver, GI, brain)
25% is insulin-dependent (skeletal muscle)
Glucagon is secreted in a fasting state to prevent
hypoglycemia
Glucose disposal in a fed state
80-85% is insulin-dependent (skeletal muscle)
4-5% is insulin-dependent in adipose tissue
Glucagon secretion is inhibited
In a fed state, insulin inhibits the release of what?
inhibits release of FFA from adipose tissue
What does decreased serum FFA regulate?
enhances insulin action of skeletal muscle; reduces hepatic glucose production
GLUT1
constitutive; widely expressed
GLUT2
constitutive; beta-cells and liver
GLUT3
constitutive; neurons
GLUT4
insulin-induced; skeletal muscle and adipocytes
Pancreatic polypeptide hormones
glucagon; somatostatin; insulin; amylin
Actions of glucagon
Stimulates glycogen breakdown; increases blood glucose
Actions of somatostatin
general inhibitor of secretion
Actions of insulin
stimulates uptake and utilization of glucose
Actions of amylin
co-secreted with insulin; slows gastric emptying; decreases food intake; inhibits glucagon secretion
Where is insulin synthesized?
synthesized as a single peptide and deposited in secretory granules in the beta cells
What happens to insulin in the beta cell secretory granules?
insulin is cleaved to A and B chains, and C (connecting) peptide by proconvertases
Human insulin cDNA in plasmid expressed in E. coli
Humulin
Human insulin cDNA in plasmid expressed in transformed yeast
Novolin
Units/concentration of insulin
100 units/ml
28 units/mg insulin
Lispro
Humalog
Aspart
Novolog
Glulisine
Apidra
Glargine
Lantus
Detemir
Levemir
Degludec
Tresiba
Ultra rapid onset/very short action insulins
Lispro (Humalog); Aspart (Novolog); Glulisine (Apidra)
Rapid onset/short action insulin
Regular
Intermediate onset/action insulin
NPH
Slow onset/long action insulin
Glargine (Lantus); Detemir (Levemir); Degludec (Tresiba)
What happens when you delay the absorption of insulins
prolong the onset and duration
What happens when you increase the absorption of insulins
decrease time to onset and duration
Absorption and duration of action of NPH
slow absorption, long duration of action
What decreases the self-association of Lispro (Humalong)?
reversing positions of P28 and K29 on insulin B chain
Onset of Humalog (Lispro) compared to regular insulin
regular: 30-60 minutes
Lispro: 5-15 minutes
Difference between human insulin and Aspart (Novolog)
Proline 29 in B chain is switched to Aspartate
Onset of Aspart (Novolog)
rapid onset: 5-15 min, short duration
Difference between human insulin and Glulisine (Apidra)
Asn 3 and Lys 29 in B chain are switched to Lys and Glu
Difference between human insulin and Glargine (Lantus)
Asn 21 of alpha-chain is changed to Gly
2 Arg residues added to the end of the beta-chain
Difference between human insulin and Detemir (Levemir)
Thr 30 of beta-chain is deleted, and Lys 29 is myristylated
Binds serum albumin extensively
Difference between human insulin and Degludec (Tresiba)
Thr 30 of beta-chain is replaced by gamma-Glu/C16 fatty acid
Binds serum albumin extensively
Routes of administration for insulins
- subcutaneous - all preparations
- insulin infusion pump - rapidly acting
- IV - regular
- Inhalation - Afrezza
Afrezza (Regular Human Insulin) is contraindicated in which patients?
contraindicated in patients with asthma and COPD; may reduce lung function (decrease FEV)
Inhaled insulin
Afrezza
Types of patients using insulin
- Type 1 diabetics
- Patients with ketosis and hyperosmolar coma
- Some Type II diabetics
Mode of action of insulin in a diabetic patient
- decreased liver glucose output
- increase fat storage
- increase glucose uptake
Hypoglycemia treated with
glucose or glucagon
Adverse reactions to insulin
Lipodystrophy; lipoatrophy; insulin resistance
lipodystrophy
lump of fat at overused injection site
lipoatrophy
concavities in subcutaneous tissue
insulin resistance
immune response to insulin
Agents that increase blood glucose in diabetics
catecholamines; glucocorticoids; oral contraceptives; thyroid hormone; calcitonin; somatropin; isoniazid; phenothiazines; morphine
Agents that increase the risk of insulin hypoglycemia
ethanol; beta blockers; ACE inhibitors; fluoxetine; somatostatin; anabolic steroids; MAO inhibitors; exercise
Overview of treatment of type II diabetes
- Diet + exercise
- Diet + exercise + oral antidiabetic drugs/GLP-1 analogs
- Diet + exercise + insulin
Effects of sulfonylurea receptors
- binds to sulfonylurea receptors
- inactivates K+ channel
- decreased cell polarization
- activates voltage sensitive Ca2+ channels
- increase Ca2+ and activity of microfilaments
- increased exocytosis of insulin containing granules
1st generation sulfonylureas
- Tolbutamide
- Tolazamide
- Chlorpropamide
2nd generation sulfonylureas
- Glipizide
- Glyburide/Glibenclamide
- Glimepiride
Repaglinide
a non-sulfonylurea hypoglucemic agent
Sulfonylureas vs. “Glinides”
- mechanism of action is the same
- glinides have a quick onset and a short duration of action
- glinides are taken before each meal
Starlix (Nateglinide)
non-sulfonylurea Katp channel blocker
Starlix (Nateglinide) is synergistic with
metformin
Adverse effects of sulfonylureas
lasting and prolonged hypoglycemia (due to long half life); G.I. problems; weight gain and increased numbers of secondary failures
Lasting and prolonged hypoglycemia with sulfonylureas has been mistaken for what in the elderly?
has been misdiagnosed as stroke and has lead to permanent neurological damage and death with elderly patients
Drugs which may enhance the action of sulfonylureas and increase the risk of hypoglycemia
salicylates; phenylbutazone; sulfonamides; clofibrate
Drugs having their own hypoglycemic effects which may be additive to the sulfonylureas
alcohol (associated with severe sulfonylurea hypoglycemic reactions); and high dise salicylates
Drugs which cause hyperglycemia which in turn oppose the action of sulfonylureas and insulin therapy
oral contraceptives; epinephrine; thiazide diuretics; corticosteroids; thyroid
The incretin effect
oral glucose stimulates a larger insulin response than IV glucose in humans
Why does the incretin effect happen?
GLP-1 (from the L-cells in the intestine) potentiates excitation-secretion and excitation-transcription coupling in the beta-cell
The incretin effect is diminished in which patients
Type II diabetic patients
Benefits of GLP-1 analog treatment in type II diabetics
reduce hyperglycemia with low risk of hypoglycemia; weight loss; increase beta cell mass(?)
GLP-1 analogs
Exenatide; Victoza (Liraglutide); Tanzeum (Albiglutide); Dulaglutide (Trulicity)
Exenatide co-administered with
metformin, TzDs, or sulfonylureas
Adverse effects of Exenatide
nausea and vomiting; risk of pancreatitis
Victoza (Liraglutide) co-adminstered with
metformin, TzDs, and sulfonylureas
Adverse effects of Victoza (Liraglutide)
nausea and vomiting, pancreatitis, risk of thyroid tumors - monitor calcitonin levels
Adverse effects of Dulaglutide (Trulicity)
risk of thyroid C-cell tumors, contraindicated in patients with a family history of medullary thyroid cancer
Inhibitors of Dipeptidyl Peptidase 4 (DPP-4) - the enzyme that degrades GLP-1
Januvia (Sitagliptin); Onglyza (Saxagliptin); Tradjenta (Linagliptin); Nesina (Alogliptin)
Side effects of DPP IV inhibitors
nausea, vomiting, constipation, headache, severe skin reactions; reduced WBC counts (infections); potential increased risk of cancers
Symlin (Pramlintide) is what kind of analog
amylin analog
MOA of alpha-glucosidase inhibitors
decrease the absorption of carbohydrate from the intestine via inhibition of gut alpha-glucosidases on the brush border (sucrase, maltase, glucoamylase)
Strategy for inhibition of sodium glucose transporter 2 (SGLT2)
decrease the threshold for glucose excretion in urine; reduce blood glucose levels
SGLT2 inhibitors
Dapagliflozin; Empagliflozin; Canagliflozin
Adverse effects of Canagliflozin
increase risk of genital/UT infections; increased urine flow/volume depletion; increased risk of hypoglycemia with SU and insulin; contraindicated in patients with renal impairement
Do not use Dapagliflozin in patients with
bladder cancer
Causes of insulin resistance
- Polymorphisms in insulin signaling pathway proteins (rare)
- Obesity - especially accumulation of fat in the abdominal cavity
- inactivity
Role of fatty acids in obesity-induced insulin resistance
FFA levels are increased in obese people; acutely raising FFA levels causes insulin resistance; acute lowering of plasma FFA levels reduces chronic IR
Oral antidiabetic drugs - non-hypoglycemic agents
Metformin
Advantages of biguanides over sulfonylureas
rarely causes hypoglycemia; rarely causes weight gain
MOA of metformin
activator of AMP-activated kinase (AMPK); increase the efficiency of sensitivity to insulin in liver, fat and muscle cells
Metformin contraindications
contraindicated in those disorders which increase the tendency toward lactic acidosis
metformin effects on blood lipid profile
decreased serum triglycerides; decreased serum LDL
Thiazolidinediones
Rosiglitazone (Avandia); Pioglitazone (Actos)
MOA of Thiazolidinediones
decrease insulin resistance or improve target cell response to insulin (activators of PPARy)
Main target of Thiazolidinediones
adipocytes - enhances adipocyte differentiation; enhances FFA uptake into subQ fat; reduces serum FFA; shifts lipids into fat cells from non-fat cells
Why is thiazolidinedione prescribing restricted?
due to cardiovascular toxicities; both are contraindicated in CHF
Factors regulated by activation of PPARy
Resistin; Adiponectin; TNFalpha; Leptin; Angiotensinogen; Plasminogen Activator Inhibitor 1