Carbs Flashcards
What’s the general description of carbs?
- C=O (carbonyl) and -OH (hydroxyl/alcohol) functional groups
Carb classification
- Size of base carbon chain
- C=O location
- Number of sugars
- Stereochemistry
Galactase converts galactose to ____
Glucose
Which sugar can be directly used for energy? What happens to the ones that can’t?
Glucose
Others such as fructose, galactose, and lactose get converted to glucose first
Name two main polysaccharides and their sources
- Starch: plant
- Glycogen: animal
Most common non-reducing substance
Sucrose (table sugar)
Which body system can’t store/concentrate carbs?
Nervous system
But glucose is its main source of energy so must maintain constant supply in tissues
Purpose of villi
Increase surface area, which increases absorbed energy from food
Types of glucose pathways and explanations
:)
Describe glucose storage
Glucose -> Liver -> glycogen -> fat
Describe insulin production pathway (fed state)
- preproinsulin -> proinsulin (A, B, and C peptides) -> insulin + C-peptide
- Anabolic process
- Promotes cellular uptake of glucose
In which conditions is insulin increased?
- Lipogenesis (fat creation)
- Protein synthesis
- Glycogenesis
In which conditions is insulin decreased?
- Lipolysis (breakdown of fat)
- Ketone formation
- Gluconeogenesis (new glucose made from aa)
- Glycogenolysis
Describe “fasting” state
- Glucagon released from pancreatic alpha cells during stress and fasting states
- Goal: increase glucose levels (hyperglycemic agent)
- Catabolic
- Liver: glycogen -> glucose -> blood
- Muscle: glycogen -> G6-P
Function/source of epinephrine in fight or flight?
- Secreted from adrenal medulla
- Similar to glucagon
- Increases plasma glucose by increasing glycogenolysis/lipolysis, and inhibiting insulin secretion
List disorders that involve hyperglycemia
- Diabetes mellitus
- Endocrine disorders (acromegaly, Cushing’s syndrome, thyrotoxicosis, pheochromocytoma)
- Drugs (anesthetics, steroids)
Acromegaly
Increased growth hormone
Cushing’s syndrome
Increased cortisol
Thyrotoxicosis
Increased T4
Pheochromocytoma
Increased epinephrine
List 3 symptoms of diabetes mellitus
- Polyuria (too much urine made)
- Polydipsia (too much thirst)
- Unexplained weight loss
Diagnostic criteria for diabetes mellitus
- HbA1C >= 6.5%
- Fasting plasma glucose >= 126 mg/dL
- 2hr plasma glucose >= 200 mg/dL
- Random plasma glucose >= 200 mg/dL
Describe Type 1a diabetes
- Beta cell destruction due to autoimmunity -> absolute insulin deficiency
- Patients must take insulin to survive
- Usually young, with acute onset (days-wks)
- Islet-cell Ab
Describe Type1b diabetes
Idiopathic
Describe Type 2 diabetes
- Insulin resistance in peripheral tissue + insulin secretory defect of beta cells
- Variable insulin levels
- Highly associated with family history, age > 40, obesity, lack of exercise
- Smoking, high blood pressure, overweight, high fat/cholesterol lvls
Describe “other types” of hyperglycemia
- Pancreatic, hormonal disease
- pancreatitis, cystic fibrosis
- acromegaly, Cushing’s syndrome
- Drug/chem toxicity
- Insulin receptor abnormalities
- No renal/retinal complications
Lab findings in hyperglycemia
- Decreased/absent insulin
- Increased glucose in plasma/urine (greater than 180 mg/dL)
- Increased urine-specific gravity
- Increased serum/urine osmolality
- Ketones in serum/urine (ketonemia/ketonuria)
- Decreased blood/urine pH (acidosis)
- Electrolyte imbalance
Normal fasting glucose mg/dL
70-99 mg/dL
Provisional diabetes diagnosis mg/dL
FPG (fasting plasma glucose) >= 126 mg/dL
Generally describe gestational diabetes mellitus
- Pregnancy
- Frequent but temporary glucose intolerance
- Greater risk of perinatal complications
- Human placental lactogen
Describe glucose screening results for diagnosis of gestational diabetes mellitus
- glucose > 140 mg/dL 1 hr after 50g glucose load screening
2-step approach: - FPG >= 95 mg/dL
- FPG >= 180 mg/dL 1hr
- FPG >= 155 mg/dL 2hrs
- FPG >= 140 mg/dL 3 hrs
Patient prep for glucose tolerance test (to diagnose gestational diabetes)
- Normal diet 3 days before test
- No food after regular evening meal on day before test
- Take fasting blood and urine specimen
- Drink 100 g glucose load within 5 min
- Allow water, but NO food, chewing gum, smoking, or exercise during test
- Specimens taken 1, 2, and 3 hrs after ingestion
Normal glucose tolerance after 2hrs
PG = plasma glucose
2 hr PG <= 140 mg/dL
Provisional diabetes diagnosis
2 hr PG >= 200 mg/dL
List disorders associated with hypoglycemia
- Insulin overdose
- Drugs (sulfonylureas, antihistamines)
- Long-term alcoholism
- Insulinoma (pancreatic tumor)
- Galactosemia (missing enzyme that breaks down galactose)
- Glycogen storage diseases
Level 1 hypoglycemia criteria + description
- Glucose < 70 mg/dL
- Treat with fast-acting carb and ???dose adjustment of glucose lowering therapy???
Level 2 clinically significant hypoglycemia criteria + description
- Glucose < 54 mg/dL
- Sufficiently low to indicate serious/clinical importance
Level 3 severe hypoglycemia criteria + description
- NO specific glucose threshold
- Associated with severe cognitive impairment requiring external assistance for recovery
Serum/plasma glucose collection/processing criteria
Spin within 2-4 hrs to remove serum/plasma otherwise cells will continue to use up glucose -> false decrease
Renal threshold in proximal convoluted tubule
- Reabsorbs ALL glucose if <180 mg/dL
- Glycosuria if blood glucose > 180 mg/dL
- Diabetic nephropathy blows out glomerulus
Describe whole blood specimen requirements for glucose measurment
- Used with home glucose monitoring units
- Cellular use of glucose gives 7% decrease/hr
- NaF preserves glucose 24 hr, RT but can’t use specimen for enzyme assays, esp. urease
- Lithium iodoacetate preserves glucose and does NOT interfere w urease
- Capillary blood = fasting venous level + 5 mg/dL
Describe plasma/serum specimen requirements for glucose measurement
RR = reportable range
- 10-15% higher level than whole blood glucose
- RR: 70-105 mg/dL
CSF specimen reference ranges for glucose measurement
- RR: 60-70% of plasma glucose
- CSF glucose = 40-70 mg/dL
Urine specimen reference ranges for glucose measurement
- RR: <30 mg/dL
- Random < 500 mg/day
List 3 methods of glucose measurement
- Glucose oxidase
- Hexokinase
- Clinitest (uses copper reduction)
T/F: Redox rxns are highly specific for glucose
False: Least specific for glucose
Why don’t we use glucose to monitor diabetes? What do we use instead
Because its levels change fast. Instead, use glycated hemoglobin (HbA1C)
Describe glycated hemoglobin
- Making it is an irreversible rx occuring throughout the 120-day RBC lifespan
- Reflects timed average [glucose] over previous 4-8 wks
- HbA1C = 80% of total glyco-Hgb
- Ref range = 3-6% total Hgb
Considerations when measuring HbA1C
- Abnormal Hgb can also be glycated
- Variability in levels of “labile fraction” aka intermediates
For every ____ decrease in HbA1C, risk of _____ complications is reduced by _____
- 1%
- Microvascular
- 35%
List manual methods for managing diabetes
- Ion-exchange chromatography (HbA1C fast fraction elutes first
- Affinity chromatography (HbA1C elutes last)
Roche diagnostics method for managing diabetes
- Doesn’t have same risk of interference with Hgb variants
- Automated
- Based on turbidimetric inhibition immunoassay (TINIA) for hemolyzed whole blood
Glycated serum protein “other testing”
- Albumin (fructosamine) colored product
- Turnover 2-3 wks
- Rapid method using tetrazolium dye reduction
Describe glycogen storage diseases
- Lack of enzymes in glycogen metabolism
- Increased tissue glycogen
- Results in severely limited lifespan
- von Gierke’s disease (liver cells lack glucose-6-phosphatase, which prevents blood glucose from increasing
Lactose intolerance
- Deficiency in intestinal mucosal lactase
- GTT done as baseline
- 2nd day, give lactose instead of glucose
- normal: GTT curve
- abnormal: flat curve + pain
Ketones
- Complication of uncontrolled diabetes
- Acid-base imbalance
- Can be life-threatening
- Acetone, acetoacetate, beta-hydroxybutryate -> can act drunk without actually being drunk
Ref range serum or plasma fasting glucose
70-99 mg/dL
Ref range HbA1C
4.0-5.6%
