Carbohydrates Flashcards
Metabolism of glucose molecule to pyruvate or lactate for production of energy
Glycolysis
Breakdown of glycogen to glucose for use as energy
Glycogenolysis
Formation of glucose-6-phosphate from noncarbohydrate sources
Gluconeogenesis
Conversion of glucose to glycogen for storage
Glycogenesis
Conversion of carbohydrates to fatty acids
Lipogenesis
Decomposition of fat
Lipolysis
serum or plasma should be refrigerated and separated from the cells within how many hours?
1 hour
separated unhemolyzed serum at roomm temperature is stable for? how about ref temperature
8 hrs; 48-72 hrs
Preferred additive for glucose measurement
sodium fluoride (gray top)
how many hours of fasting is required for FBS?
approximately 8 - 10 hr fast (not >16 hr)
What are the chemical methods for glucose measurement?
- Alkaline copper reduction
- Alkaline ferric reduction
What is the reaction in chemical methods for glucose measurement? what medium is it done?
redox reaction; alkaline medium
what are the methods under alkaline copper reduction?
- Folin-wu
- Nelson - Somogyi
- Campbell and King
- Benedicts
principle of Alkaline Copper reduction
reduction of cu3+ to cu2+ (deep-blue color) forming cuprous oxide (red)
What is the reagent and result in folin-wu method?
phosphomolybdic acid -> phophomolybdenum blue
What is the reagent and result in Nelson - Somogyi method?
arsenomolybdic acid -> arsenomolybdenum blue (BLUE OR BLUISH GREEN)
What is the reagent and result in campbell and king method?
neocuproin —> cuprous-neocuproine complex
(yellow-orange/yellow)
What is used in NS methos that enables measurement of true reducing substances only? It is used to remove saccharoids
Barium sulfate
This method is used for the detection of quantitation of reducing substances in body fluids like blood and urine
Benedict’s reagent
Stabilizing agent of benedict’s?
Citrate or Tartrate
it is also known as reverse colorimetric method
Alkaline Ferric reduction
color of ferrocyanide
colorless
methods under Alkaline Ferric reduction
- Johnson method
- Folin/ Prussian blue method
- Hagedorn-Jensen method
it is more specific that copper reduction
Alkaline Ferric reduction
at what nm is Johnson method
& Hagedorn-Jensen method measured?
420 nm
what are the two not reverse colorimetric in Alkaline Ferric reduction?
- Ferrocyanide + 2,4,6, tripyridyl-S-triazine
- Ferrocyanide + phosphomolybdic acid
What are the methods under condensation methods?
- with aromatic amines
- with phenols
what is the method used in condensation method with aromatic amines. it is also called the reference method
Ortho-toluidine method by Dubowski
Ortho-toluidine method is based on the ability of carbohydrates to form what?
Schiff bases with aromatic amines
what is the color of schiff base
green
O-Toluidine in a hot acidic
solution will yield a colored compound with an absorbance maximum at
630 nm
it is the most specific non-enzymatic method and it could be employed for CSF glucose level
Ortho-Toluidine
interfering substances in O-Toluidine
galactose, mannose and aldopentose
in condensation method with phenols, what is produced when glucose is mixed with acid?
water + hydroxymethylfurfural
what color will be produced if hydroxymethylfurfural is mixed with anthrone
green colored compound
what are the methods under the enzymatic method?
(a) Glucose Oxidase method
(b) Hexokinase method
(c) Glucose Dehydrogenase (GDH)
It is the most specific enzyme reacting with only b-d-glucose.
Glucose oxidase
it is suitable for measuring glucose in CSF but not directly in urine
Glucose oxidase
added to convert alpha to beta glucose
mutarotase
complete the reaction:
glucose + O2 + H2O — GOD —>
gluconic acid + H2O2
complete the reaction:
H2O2 + reduced chromogen — POD—>
oxidized chromogen + H2O
what is the relationship between h2o2 and glucose?
directly proportional
other name for trinder
Saifer Gernstenfield Method
Methods to quantify H2O2
- Gochman and Schmitz
- Trinder
3.Miskieweis
reaction in Gochman and Schmitz
3-methyl-2-benzathiazolinone hydrazone + N,Ndimethylaniline —> indamine dye (590-66- nm)
or
h202 + MBTH + DMA -> indamine dye (590-66- nm)
reaction in trinder
p-aminophenazone + phenol —-> purple product (quinoneimine)
or
h202 + PAP + PHBS -> Quinoneimine
reaction in miskieweis
2,2-azine-di(3-ethyl bezothiazoline-(6)-sulfonic acid —> colored chromogen
or
h202 + ABTS -> colored chromogen
what are the interferences under trinder?
- uric acid (false decrease in glu meas)
- ascorbic acid (oxidizing agent)
- bilirubin (if high, there’s color)
- tetracycline (inhibit peroxidase)
- hb & glutathione
measures the amount of oxygen consumed in the glucose oxidase method
POLAROGRAPHIC OXYGEN ELECTRODE
why is this two reactions included in polarographic oxygen electrode:
❖ H2O2 + ethanol —– catalase—— Acetaldehyde + H2O
❖ H2O2 + H+ + 2I- — molybdate —- I2 + 2H2O
To prevent the formation of oxygen from H2O2
it is sensitive because there are no interferences. it is applied directly to urine, serum, plasma, or csf
POLAROGRAPHIC OXYGEN ELECTRODE
what does POLAROGRAPHIC OXYGEN ELECTRODE use?
Clarke electrode
- more accurate, less interferences than glucose oxidase methods (REFERENCE method)
- HIGHLY SPECIFIC
- not affected by uric acid and ascorbic acid and anticoagulant
- can also be used for urine, CSF and serous fluid
- false decrease: hemolyzed sample and elevated bilirubin levels
Hexokinase method
− glucose + ATP —hexokinase —> glu-6-phosphate + ADP
− glu-6-phosphate + NADP —G-6-PD —> NADPH + H + 6-phosphogluconate (340 nm)
what method is this
keller method
- method in the test of metabolic alteration
- provides results that is is close
Glucose Dehydrogenase (GDH)
reaction in Glucose Dehydrogenase (GDH) method
Glucose + NAD —— GDH —– Gluconolactone + NADH + H+
what is the coenzyme 1 and 2 in GDH?
CoEI: NAD (Nicotinamide adenine dinucleotide)
CoEII: NADP (Nicotinamide adenine dinucleotide phosphate)
what does GDH utilize that is used for the determination of blood glucose in sample
automated kinetic assay
relationship of NADH and conc of glucose
proportional
principle of the device used in home monitoring of BGL
reflectance colorimetry or photometry
principle of the test strip in home monitoring of BGL
GOD
4 layers of the test strip in home monitoring of BGL
- Spreading
- Reagent
- Indicator
- Support
increased plasma glucose levels & caused by imbalance of hormones
HYPERGLYCEMIA
FBS of someone with hyperglycemia
> /= 126 mg/dL
what are the primary hyperglycemia?
T1 DM - insulin dependent - Juvenile
T2 DM - non-insulin dependent - adult onset
renal threshold for glucose
160-180 mg/dL
complication of hyperglycemia
- retinopathy
- neuropathy
- nephropathy
diagnosis test for hyperglycemia
- glucose tolerance test
- Postprandial glucose test
optimal test how body optimize glucose
- fbs
- Oral glucose tolerance tests
it is characterized by persistent hyperglycemia resulting from
defects in insulin secretion, insulin action, or both.
DIABETES MELLITUS
frequency of self-monitoring of bg in T1 dm patients
3-4x a day
frequency of self-monitoring of bg in T2 dm patients
unknown
type of DM due to autoimmune β-cell destruction, usually leading to absolute insulin deficiency
T1 DM - insulin dependent - Juvenile
type of DM due to a progressive loss of β-cell insulin secretion frequently on the background of insulin resistance
T2 DM - non-insulin dependent - adult onset
type of DM that is diagnosed in the 2nd or 3rd trimester of pregnancy
that was not clearly overt diabetes
Gestational diabetes mellitus
Gestational diabetes mellitus causes what?
fetal macrosomia
e.g. neonatal diabetes & maturity-onset diabetes of the young
[MODY]
monogenic diabetes syndromes
what are the autoantibodies present w/ TI DM
GAD - glutamic acid decarboxylase
ICA - islet cell antigen
IAA - insulin autoantibodies
what are the secondary hyperglycemia
- pancreatic disorder (pancreatitis)
- endocrine disorder (ACROMEGALY- adult: too much GH; PHEOCHTOMOCYTOMA - tumor on medulla of adrenal glands
- drugs (steroids)
- other diseases state (infection)
- misc. causes (pregnancy)
frequency of T1 DM
5-10%
frequency of T2 DM
90-95%
medication therapy for T1 DM
Insulin
medication therapy for T2 DM
Oral hypoglycemic agents
Oral hypoglycemic agents example
- metformin
- acarbose
- tolbutamide
risk factor for T2 DM
Genetic
Obesity (BMI)
Sedentary lifestyle
Race/ethnicity
risk factor for T1 DM
Genetic (HLA-DR/DQ on chr
6)
Autoimmune
Environmental
dose of 2-hour Postprandial Test
a gram / kg body wt.
normal result of 2-hour Postprandial Test
- peak value in 30 mins. (~150 mgs%);
- back to normal in 2 hrs
WHO standard glucose lead
75g
glucose lead for pregnant & suspected GDM
100g
glucose lead for children
1.75g glu/kg body wt. (max of 75g)
dose of 5-hour Postprandial Test
75 grams (WHO 1985)
normal result for 5-hour Postprandial Test
back to normal in 5 hours
5-hour PPT is only done when?
value of 2-hr PPT is >140 – 160 mgs%
- this test is used for GIT px
- Indications:
*Poor absorption of ingested CHO
*History of GIT surgery - fasting is required
INTRAVENOUS GLUCOSE TOLERANCE TEST (IVGTT)
dose for INTRAVENOUS GLUCOSE TOLERANCE TEST (IVGTT)
0.5g/kg (25 g/dL solution given intravenously)
dose for INSULIN TOLERANCE TEST
0.1 unit / kg
- it has sensitivity to insulin and has the ability to store glycogen
- has the ability to recover after induced hypoglycemia
- indirect test for the function of anterior PG & adrenal cortex
INSULIN TOLERANCE TEST
normal result for INSULIN TOLERANCE TEST
-In 30 mins, 50% decrease in FBS level;-
- Back to normal on 2nd hr
What clinical significance is this under?
❖ Delayed decrease in BGL
❖ DM, hyperadrenalism, Acromegaly
Insulin Resistance
- Stimulates pancreas to produce insulin
- Evaluates hypoglycemia caused by insulinoma
Orinase or Tolbutamide
normal result for TOLBUTAMIDE TOLERANCE TEST
- Normal: In 30 mins, 50% decrease in FBS level;
- back to normal on the 2nd hour
What clinical significance is this under?
- Normal fall of BGL but delay in regaining normal value
- Addison’s disease, hypofunction of anterior PG, hyperinsulinism, Von Gierke’s disease
Hypoglycemic Unresponsiveness
- Serves as an index of the quantity & availability of glycogen
- disease correlation: Von gierke’s disease; hepatocelullar damage (inability to store glycogen)
EPINEPHRINE TOLERANCE TEST
normal result for EPINEPHRINE TOLERANCE TEST
- Peak value after 30 mins.
- normal within 2 hours
- 35 – 45 mgs% increase in conc. between 45 – 60 mins.
Detects the presence of mucosal lactase
LACTOSE TOLERANCE TEST
Causes of Lactose Intolerance
- Deficiency of lactase
- Inhibition to lactase activity
- Body forgot milk LMAO
Defined as any degree of glucose intolerance that was first recognized during pregnancy, regardless of whether the condition may have predated the pregnancy or persisted after the pregnancy
GESTATIONAL DIABETES MELLITUS
GDM develop in how many percent of pregnancies and in what week of pregnancy do we screen it?
7%; 24-28 weeks of gestation
Diagnosis criteria of GDM in the one step strategy by the ADA
Fasting: >/=92 mg/dl (5.1 mmol/L)
1h: >/= 180 mg/dl (10 mmol/L)
2h: >/= 153 mg/dl (8.5 mmol/L)
Diagnosis criteria of GDM in the two step strategy by the NIH
Fasting: >/=95 mg/dl
1h: >/= 190 mg/dl
2h: >/= 165 mg/dl
3h: >/= 140 mg/dl
criteria used for two step strategy diagnosis of GDM
National Diabetes Data Group criteria
what do you perform in one step strategy diagnosis of GDM
75g OGTT
what do you perform in two step strategy diagnosis of GDM
50g GLT and 100g OGTT
when do you perform 100g OGTT in two step strategy diagnosis of GDM
50g GLT:
1h: >/= 130 mg/dl or 140 mg/dl
TRUE OR FALSE:
in the diagnosis of GDM in the two step strategy, it is positive if the px met at least three of the levels in the criteria
FALSE; TWO!!!!!!!!!!!!!
results from an imbalance between glucose utilization and production
HYPOGLYCEMIA
observable symptoms of hypoglycemia appear at about
50-55 mg/Dl
- hypoglycemia that is triggered by the ANS
- tremulousness, palpitations, anxiety
- diaphoresis, hunger, paresthesias
Neurogenic
state the whipple’s triad
- low bg concentration
- typical symptoms (3P’s)
- symptoms alleviated by glucose administration
diagnostic test for neurogenic hyperglycemia
5 hours GTT
- CNS hypoglycemia
- dizziness, tingling, difficulty concentrating, blurred vision
- confusion, behavioral changes, seizure, coma
Neuroglycopenic
the symptoms of this have been used to describe hypoglycemia since 1938.
whipple’s triad
TESTS FOR MONITORING DIABETIC PATIENTS
- Measure glycosylated hemoglobin (HbA1c)
- Microalbuminuria
- C peptide
- reflects pancreatic secretion of insulin
- reflects endogenous insulin production if patient is taking insulin
C peptide
what cleaves to give C peptide & insulin
proinsulin
- useful to assist in diagnosis at an early stage and before the development of proteinuria (>
0.5g/day) - earliest sign of diabetic renal nephropathy
dx: 2 out of 3 specimen collected within 6 month period are abnormal
Microalbuminuria
- test every 3-6 months
- provides an index of average BGL over the past 2-4 months
- non-enzymatic
- glucose molecules attach to hb molecules
Measure glycosylated hemoglobin (HbA1c)
other names of Measure glycosylated hemoglobin (HbA1c)
- fast hemoglobin
- glycated
- glycosylated
percentage of HbA; HbA2; and HbF in our body
HbA: 97%
HbA2: 2.5%
HbF: 0.5%
- major fraction and the most common HbA where glucose attach
- non-enzymatic condensation b/w glucose & the N-terminal of valine
HbA1c
- Cation-exchange resin or carboxymethyl cellulose resin
- HbA1 elutes from the 1st column
- False elevation: labile fractions, HbF
- Low values: Hb variants
ION-EXCHANGE CHROMATOGRAPHY
specimen for Measure glycosylated hemoglobin (HbA1c)
EDTA whole blood
interferences of Measure glycosylated hemoglobin
- carbamylated hb ( can occur w/ uremmia; hyperTG; hyperbilirubemia; use of salicilates
- disease state ongoing
- alcohol intake
- iron deficiency
- lead poisoning
- vit c & e (false decrease)
- Reference method
- Separate and quantify HbA1c as well as other hb types
HPLC (High-performance liquid chromatography)
Hb A1c — acid — 5-HMF
- specific for ketoamine-linked glucose
- unaffected by HbF, Hb variants, & labile intermediate
COLORIMETRY
- Antibodies against Hb A1c (sheep antiserum)
- partial cross reactivity with HbAia
RADIOIMMUNOASSAY (RIA)
- Citrate agar electrophoresis (pH 6.0-6.2)
- Good resolution of Hb A & HbA1
- no interference from Hb variants
- HbF migrates
ELECTROPHORESIS
- Scanned on high-resolution microdensitometer
- specific for Hb A1c and it is adequately resolved from HbA1a, A1b, S and F
ISOELECTRIC FOCUSING
- Use of affinity gel columns
- no interference from non-glycosylated Hb
- negligible interference from the labile intermediate
- minimal dependence on variation in ambient temp
AFFINITY CHROMATOGRAPHY
- widely used to assess short-term (3–6week) glycemic control because the average half-life of the proteins is 2–3 weeks.
- ADV:
*using serum samples and automated equipment, so are simple to perform and low in cost. *more reliable than other glycosylated protein assays - affected by the serum protein during illness
- Should not be performed if the serum albumin level is ≤3.0 mg/dL.
Fructosamine assays
Fructosamine assays interference
- High uric acid, triglyceride and bilirubin levels
- Presence of heparin or hemolysis
WHAT HORMONE?????!
- promotes cellular uptake of glucose
- increase glycogenesis, glycolysis, lipogenesis
- decrease glycogenolysis
- hypoglycemic agent
insulin
WHAT HORMONE?????!
- responsible for increasing blood sugar level
- increase glycogenolysis and gluconeogenesis
- synthesized by the a-cells
of islets of Langerhans in the pancreas and released
during stress and fasting states
glucagon
WHAT HORMONE?????!
- Increases plasma glucose by inhibiting insulin secretion
- increasing glycogenolysis
- promoting lipolysis
Epinephrine and Norepinephrine
WHAT HORMONE?????!
- inhibits secretion of insulin and glucagon; it also modulates them
- inhibits the release of growth hormone
somatostatin
WHAT HORMONE?????!
- stimulates gluconeogenesis
- decrease entry of glucose in cell
- stress hormone
Cortisol and corticosteroids
WHAT HORMONE?????!
- inhibits action of insulin
growth hormone
WHAT HORMONE?????!
- promotes glycogenolysis
- stimulate rate of gastric emptying & glucose absorption
thyroid hormone
other name for human placental lactogen
human chorionic somatomammotropin
hormone with anti-insulin activity
human placental lactogen
WHAT HORMONE?????!
- with anti-insulin activity and HYPERGLYCEMIC
- stimulates the adrenal cortex to release cortisol and increases plasma
glucose levels
- promoting gluconeogenesis
Adrenocorticotropic hormone (ACTH)
defect in von Gierke
disease
Glucose-6-
phosphatase
defect in Cori or Forbes’ disease
Glycogen
debranching
enzyme
defect in Anderson’s disease, amylopectinosis
Glycogen
branching
enzyme
defect in Hers disease
Glycogen
phosphorylase
defect in Fanconi-Bickel
syndrome
GLUT 2
defect in McArdle disease
Muscle
phosphorylase
defect in Tarui disease
Phosphofructokinase
defect in Pompe disease
Lysosomal acid alpha glucosidase
(GAA) (acid maltase)
