Pancreas Flashcards

(60 cards)

1
Q

Pancreas

Islets of Langerhans cell types

A

All derived from pancreatic buds (embryologically)

  • Alpha cells
  • Beta cells
  • Delta cells
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2
Q

Pancreatic Alpha cells

Factoids

A
  • 20% of the islet cells
  • Secret glucagon
  • Located at the periphery
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3
Q

Pancreatic Beta cells

Factoids

A
  • Major cell type
  • Secret insulin (along with C peptide [long term marker])
  • Located in the center
  • Receive blood first
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4
Q

Pancreatic Delta cells

Factoids

A
  • 5% of islet cells
  • Secrete somatostatin
  • Interspersed throughout the pancreas
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5
Q

Insulin

Factoids

A
  • It is a peptide hormone
  • Works through tyrosine kinase
  • Anabolic
  • Released along with C peptide (its long term marker)
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6
Q

Insulin

Effects on Glucose metabolism

A
  • Increases glucose uptake by adipose tissue and skeletal muscles (GLUT-4)
  • Increases glucose uptake by liver (by stimulating glucokinase)
  • Decreases glucose breakdown
  • Increases glucose storage
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7
Q

Insulin

Effects on Protein metabolism

A
  • Increases amino acids uptake
  • Increases protein synthesis
  • Decreases protein degradation
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8
Q

Insulin

Effects on Fat metabolism

A
  • Decreases hormone sensitive lipase activity
  • Increases fatty acids uptake (by stimulating lipoprotein lipase)
  • Increases triglycerides synthesis
  • Increases acetyl CoA carboxylase enzyme activity
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9
Q

Insulin

Glucose storage mechanism

A

Through stimulating the following enzymes (by dephosphorylation):

  • Glucokinase
  • Glycogen synthase
  • PFK-1 (via PFK-2)
  • Pyruvate kinase
  • Acetyl CoA carboxylase
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10
Q

Glucagon

Glucose release mechanism

A

Through stimulating the following enzymes (by phosphorylation):

  • Glycogen phosphatase
  • Pyruvate carboxylase
  • PEPCK
  • Fructose 1,6-bisphosphatase
  • Glucose-6-phosphatase
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11
Q

Insulin

Secretion Stimuli

A
  • Glucose
  • Amino acids like arginine
  • Intestinal hormones:
  • GIP (gastric inhibitory peptide or glucose-dependent insulinotropic peptide)
  • GLP-1 (glucagon like peptide): Exenatide is its synthetic analog
  • Glucagon
  • Hyperkalemia
  • Dipeptidyl peptidase-IV (DPP-IV) [breaks down GLP-1] inhibitors like Sitagliptin
  • Drugs that block ATP-sensitive K+ channels like sulfonylureas
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12
Q

Insulin

Secretion Inhibitors

A
  • Somatostatin
  • Sympathetic innervation and norepinephrine (alpha-2 receptors)
  • Hypokalemia (like in hydrochlorothiazide)
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13
Q

Glucagon

Effects

A
  • Glycogenolysis
  • Gluconeogeneis
  • Increases urea production
  • Increases ketone bodies by inhibiting acetyl CoA carboxylase (though it is not the main regulator [insulin is])
  • Increases lipolysis by stimulating hormone sensitive lipase
  • Inotropic effect on the heart (cause it is working through Gs cAMP)
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14
Q

Insulin

Other Effects

A
  • Moves K+ into cells by stimulating Na+/K+ ATPase
  • Increases Na+ retention (kidneys)
  • Decreases glucagon release
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15
Q

Glucagon

Secretion Stimuli

A
  • Hypoglycemia

- Amino acids like arginine

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16
Q

Glucagon

Secretion Inhibitors

A
  • Hyperglycemia
  • Insulin
  • Somatostatin
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17
Q

Insulin

Synthesis

A
  • Preproinsulin synthesized in RER

- Then cleavage of presignal will produce proinsulin (insulin and C peptide) that is stored in secretory granules

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18
Q

Insulin

Secretion

A
  • Increased metabolism of glucose in Beta cells will increase ATP production
  • ATP will block the ATP sensitive K+ channels which results in generating an action potential (membrane depolarization)
  • This depolarization will cause Ca++ entry into the cells which in turn causes cleavage of proinsulin and exocytosis of insulin and C peptide equally
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19
Q

Insulin-dependent glucose transports

Names and Locations

A

GLUT-4: in adipose tissue and striated muscles (exercise also increases their expression)

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20
Q

Insulin-independent glucose transports

Names and Locations

A
  • GLUT-1: RBCs, brain, cornea and placenta (insulin does not cross the placenta)
  • GLUT-2 (bidirectional): beta islet cells, liver, kidneys, and small intestine
  • GLUT-3: brain and placenta
  • GLUT-5 (fructose): spermatocytes and GI tract
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21
Q

Glucose

Hormonal Control

A
  • When it is low, glucagon will raise it
  • When it is very low, epinephrine will release glucose from liver and GH will inhibit GLUT-4 mediated uptake of glucose by the adipose tissue and skeletal muscles
  • When it remains very low, cortisol will release glucose from liver and also makes amino acids from skeletal muscles available to the liver for gluconeogenesis
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22
Q

Diabetes Mellitus Type 1 vs. Type 2

Primary Cause, Insulin necessary for Rx, Age, Association with obesity

A
  • 1: autoimmune destruction of Beta cells (due to glutamic acid decarboxylase antibodies [type IV hypersensitivity]). 2: increase resistance to insulin (post-receptor alternation), progressive pancreatic beta-cells failure
  • 1: Always. 2: Sometimes
  • 1: < 30 years. 2: > 40 years
  • 1: No. 2: Yes
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23
Q

Diabetes Mellitus Type 1 vs. Type 2

Genetic predisposition, HLA system association, Glucose intolerance, Insulin sensitivity

A
  • 1: Relatively weak (50% concordance in identical twins), ploygenic. 2: Relatively strong (90% concordance in identical twins), ploygenic
  • 1: Yes (HLA-DR3 and -DR4). 2: No
  • 1: Severe. 2: Mild to moderate
  • 1: High. 2: Low
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24
Q

Diabetes Mellitus Type 1 vs. Type 2

Ketoacidosis, Beta-cell numbers, Serum insulin level, Classic symptoms [Presentation]

A
  • 1: Common. 2: Rare
  • 1: decreased (with islet lymphocytic infiltration [insulitis] and fibrosis). 2: variable (with islet amyloid polypeptide (IAPP) deposits)
  • 1: Low. 2: variable
  • 1: Common. 2: sometimes
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25
Insulin Deficiency | Metabolic Effects
- Decreased tissue glucose uptake, Increased glycogenolysis and gluconeogenesis ---> hyperglycemia (increased plasma osmolarity and thirst) and glycosuria (osmotic diuresis, loss of water, Na+ and K+, hypovolemia, circulation failure and decreased tissue perfusion, coma/death) - Increased proteolysis ---> decreased protein and weight loss ---> increased gluconeogenesis - Increased lipolysis ---> increased plasma free fatty acids ---> Increased ketogenesis, ketonemia and ketonuria (vomiting) ---> Anion gap metabolic acidosis (hyperventilation) Notes: * vomiting and hyperventilation both contribute to loss of water, Na+ and K+ * circulation failure and decreased tissue perfusion will lead to increase in serum lactate which will also contribute to the anion gap metabolic acidosis
26
Insulin Deficiency | Effects on Na+ and K+
- Na+: * Losing body stores because of polyuria * May see hypernatremia because of dehydration * May see hyponatremia because of water shift from hyperglycemia - K+: * Moves from intracellular to extracellular (decreased Na+/K+ ATPase activity) * May see initial hyperkalemia * Watch closely after insulin treatment
27
Hyperosmolar Hyperglycemia Non-ketotic syndrome (Hyperosmolar Coma) (Cause, Presentation)
- State of profound hyperglycemia induced dehydration and increased serum osmolarity. Classically seen in elderly type 2 diabetics with limited ability to drink (can also be seen in type 1) - Thirst, polyuria, lethargy, focal neurological deficits (e.g. seizures), that can progress to coma and death if left untreated
28
Hyperosmolar Hyperglycemia Non-ketotic syndrome (Hyperosmolar Coma) (Pathophysiology)
- Fluid shift from hyperglycemia - Polyuria ---> decreased extracellular volume ---> reflex activation of sympathetics ---> decreased renal flow and GFR ---> decreased glucose clearance. Combined with increase in counterregulatory hormones ---> increase in glucose - Loss of intracellular fluid from brain ---> possible coma
29
Hyperosmolar Hyperglycemia Non-ketotic syndrome (Hyperosmolar Coma) (Labs)
- Hyperglycemia (often > 600 mg/dL) - Increased serum osmolarity (> 320 mOsm/kg) - No acidosis (ketone production inhibited by the presence of insulin
30
Hyperosmolar Hyperglycemia Non-ketotic syndrome (Hyperosmolar Coma) (Treatment)
- Aggressive IV fluids - Electrolyte replacement - Insulin therapy - Treat the initiating event
31
``` Diabetic Ketoacidosis (Causes) ```
- Insulin non-compliance | - Increased insulin requirements from stress like infection
32
``` Diabetic Ketoacidosis (Pathophysiology) ```
- Excess fat breakdown and increased ketogenesis from increased free fatty acids (due to increased activity of acetyl CoA carboxylase and unopposed effects of glucagon) ----> ketone bodies (beta-hydroxybutyrate > acetoacetate) - Decreased blood pH and bicarbonates due to metabolic acidosis - The increased hydrogen ion secretion will diminish K+ secretion, but the higher than normal tubular flow will promote K+ secretion - Usually occurs in type 1, as endogenous insulin in type 2 usually prevents lipolysis
33
``` Diabetic Ketoacidosis (Presentation) ```
- Delirium/psychosis - Kussmaul respiration (rapid/deep breathing) - Abdominal pain/nausea/vomiting - Dehydration - Fruity breath odor (exhaled acetone)
34
``` Diabetic Ketoacidosis (Labs) ```
- Hyperglycemia - Increased H+ and decreased HCO3- (anion gap metabolic acidosis) - Increased blood ketone levels - Leukocytosis - Hyperkalemia and depleted intracellular K+ - Hyponatremia (for every 100 mg/dL increase in glucose there will be 1.6 meq decrease in Na+)
35
``` Diabetic Ketoacidosis (Complications) ```
- Life-threatening mucormycosis (usually caused by Rhizopus infection) - Cerebral edema - Cardiac arrhythmias - Heart failure
36
``` Diabetic Ketoacidosis (Treatment) ```
- IV fluids (about 2-3 liters) - IV insulin and K+ when K+ level reaches normal range (to replete intracellular stores) - Bicarbonate (if pH is < 7) - Glucose if necessary to prevent hypoglycemia - Treat the underlying cause: non-compliance with medications, infection, pregnancy, or any serious illness
37
Glucagonoma | Cause, Presentation
- Tumor of pancreatic alpha cells with overproduction of glucagon - Dermatitis (necrolytic migratory erythema), diabetes (hyperglycemia), DVT, declining weight and depression
38
Glucagonoma | Treatment
- Surgery | - Octreotide
39
Insulinoma | Cause, Presentation
- Tumor of pancreatic beta cells with overproduction of insulin - Hypoglycemia (lethargy, syncope, diplopia)
40
Insulinoma | Association, Diagnosis
- 10% associated with MEN 1 syndrome | - Dx: decreased blood glucose with increased insulin and C-peptide levels (vs. exogenous insulin use)
41
Insulinoma | Treatment
Surgical resection
42
Somatostatinoma | Cause, Presentation
- Tumor of pancreatic delta cells with overproduction of somatostatin that leads to decrease secretion of secretin, cholecystokinin, glucagon, insulin and gastrin - Diabetes/glucose intolerance, steatorrhea, and gallstones
43
Somatostatinoma | Treatment
- Surgical resection | - Octreotide
44
Diabetes Mellitus | Complications Pathophysiology
- Non-enzymatic glycation: * Small vessel disease (diffuse thickening of basement membrane): + Retinopathy (hemorrhage, exudates, microaneurysms, vessel proliferation) + Glaucoma + Neuropathy + Nephropathy (nodular glomerulosclerosis [Kimmelstiel-Wilson nodules] which lead to progressive proteinuria, arteriolosclerosis which lead to hypertension) ---> chronic renal failure * Large vessel atherosclerosis, CAD, peripheral vascular occlusive disease, gangrene ---> limb loss, cerebrovascular disease. MI most common cause of death - Osmotic damage (sorbitol accumulation in organs with aldose reductase and decreased or absent sorbitol dehydrogenase): * Neuropathy (motor, sensory [glove and stocking distribution], and autonomic degeneration) * Cataracts
45
Diabetes Mellitus | Complications
- Vascular: * Atherosclerosis, MI and CHF * Stroke (CVA) * Peripheral vascular disease (lower extremities loss of hair, claudication, non-healing ulcer, and gangrene) - Diabetic nephropathy (affects both afferent and efferent artrioles): * Diffuse glomerulosclerosis * Nodular glomerulosclerosis * Pyelonephritis * Necrotizing papillitis * Renal failure - Diabetic retinopathy: * Non-proliferative phase: microaneurysms, retinal hemorrhages, and exudates * Proliferative phase: neovascularization (via VEGF) * Fibrosis phase: vitreous humor fibrosis and retinal detachment * High rates of cataracts and glaucoma - Diabetic neuropathy: * Peripheral neuropathy (glove and stocking) * Autonomic neuropathy like gastroparesis, esophageal dysmotility, orthostatic hypotension, neurogenic bladder and sexual impotence
46
Diabetes Mellitus | Treatment Complications
- Dawn phenomenon: morning hyperglycemia due to the normal nocturnal release of counterregulatory hormones (e.g. glucagon, epinephrine, cortisol), which increase insulin resistance and blood glucose levels. Rx: Increase P.M. NPH insulin - Somogyi effect: rebound hyperglycemia that results from excess exogenous insulin, which causes hypoglycemia overnight and stimulates the release of counterregulatory hormones that in turn increase blood glucose levels. Rx: decrease P.M. NPH insulin
47
Diabetic cardiovascular complications | Management
- The goal Bp should be below 130/80 mmHg. ACEIs/ARBs are first line - Decrease the LDL to < 100 mg/dL and triglycerides to less than 150 mg/dL with statins - Low dose aspirin - Annual screening exams
48
Diabetic Nephropathy | Management
- Annual screening for microalbuminuria (30-300 mg per 24 hours) [dipstick for urine trace positive at 300 mg of protein per 24 hours] - When microalbuminuria is +ve start ACEIs or ARBs
49
Diabetic Gastroparesis | Treatment
Metoclopromide or erythromycin
50
Diabetic Retinopathy | Treatment
- Non-proliferative phase is treated with tight control of blood glucose - Proliferative phase is treated with laser photo-coagulation (which markedly retards the progression to blindness)
51
Diabetic Neuropathic pain | Treatment
- Pregabalin - Gabapentin - Tricyclic antidepressants
52
Diabetes Mellitus | Diagnosis
- 2 fasting (> 8 hours) blood glucose more than 125 mg/dL - Single random blood glucose above 200 mg/dL with symptoms - Post-prandial (2 hours after oral glucose tolerance test [75 g of glucose in water]) more than 200 mg/dL - HbA1C more than 6.5%
53
``` Diabetes Mellitus (Health Maintenance) ```
- Pneumococcal vaccine - Yearly eye exam to check for proliferative retinopathy - Statin medication if LDL is above 100 mg/dL - ACEIs or ARBs if blood pressure is greater than 130/80 mmHg - ACEIs or ARBs if urine tests +ve for microalbuminuria - Aspirin, used regularly in all diabetic patients above the age of 30 - Foot exam for neuropathy and ulcers
54
Diabetes Mellitus | Screening recommendations
- Patients with no risk factors: test HbA1C at age of 45; retest every 3 years if its < 5.7% and no other risk factors develop - Patients with impaired fasting glucose (>110 but less than 125 mg/dL) or impaired glucose tolerance: follow up with frequent retesting
55
Diabetes Mellitus | Treatment Goals
- Tight control of blood glucose in the range of 80-120 mg/dL - HbA1C is less than 8% in children and less than 7% in adults
56
Metabolic Syndrome | Factoids
- Also known as insulin resistance syndrome or syndrome X | - Associated with high risk of CAD and mortality from a cardiovascular event
57
Metabolic Syndrome | Diagnosis
3 out of 5: - Abdominal obesity (increased waist girth): > 40 inches in men and > 35 inches in women - Triglycerides > 150 mg/dL - HDL < 40 mg/dL in men and < 50 mg/dL in women - Bp more than 130/85 mmHg or a requirement for antihypertensive drugs - Fasting glucose > 100 mg/dL
58
Metabolic Syndrome | Treatment
- Intensive weight loss - Aggressive cholesterol management and Bp control - Metformin (has shown to slow onset of diabetes in high risk population)
59
Diabetes Mellitus | Lifestyle Modifications
- Diet: low-fat, moderate carbohydrates, low calorie personalized diet - Weight loss: 5-10% weight loss with a combination of diet and exercise - Exercise: moderate-intensity exercise for 30 minutes 5 days per week
60
Diabetes Mellitus | Treatment Algorithm
- Type 1 and gestational DM are treated with basal insulin (like Glargine) + mealtime insulin (rapid acting ones) - Type 2: do liver function tests first then: * If abnormal then give insulin * If normal then check renal function + if abnormal don't give metformin + If normal then give metformin