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BLOOD GLUCOSE HOMEOSTASIS Dr. Vijay Marakala, MBBS, MD.
BIOCHEMISTRYIMS, MSU.
BLOOD GLUCOSE HOMEOSTASIS -OUTLINE
Normal plasma glucose
Factors maintaining
blood glucose
Post-prandial regulation
Regulation during fasting Clinical aspect
BLOOD GLUCOSE HOMEOSTASIS
• Blood glucose level is tightly controlled because the brain constantly needs glucose
• Severe hypoglycemia can cause coma and death • Chronic hyperglycemia results in
Glycation of proteins, Endothelial dysfunction Diabetes
NORMAL VALUES
FASTING BLOOD SUGAR[FBS] /FASTING PLASMA GLUCOSE [FPG]
70-110mg/dL 4-6.1mmol/L
BLOOD GLUCOSE
REGULATION OF BLOOD GLUCOSE
The plasma
glucose level
depends on the
balance between
glucose entering
and leaving the
extracellular fluid GLYCOGENESISGLYCOLYSIS
GLUCONEOGENESISGLYCOGENOLYSIS
LIPOGENESIS
DIET
Use Storage Conversion
Supply
70-110mg/dL 4-6.1mmol/L
FACTORS MAINTAINING BLOOD GLUCOSE
Factors which cause entry ofglucose into blood
• Absorption from intestines• Glycogenolysis• Gluconeogenesis• Hyperglycemic hormones
Factors leading to depletion of glucose in blood
• Utilization by tissues for energy
• Glycogen synthesis• Conversion of glucose into
fat • Hypoglycemic hormone
POST-PRANDIAL REGULATION
GLUCOSEABSORPTION
GLYCOGENESIS
LIPOGENESIS
UTILIZATION BY TISSUE FOR ENERGY GLYCOLYSISTCA CYCLEETC
REGULATION DURING FASTING
GLUCOSE
GLYCOGENOLYSISLIPOLYSIS
GLYCEROL, LACTATE, PYRUVATE, GLUCOGENIC AMINO ACIDS
GLUCONEOGENESIS
FFAALTERNATE
SOURCE OF ENERGY
HORMONAL REGULATION
HYPERGLYCEMIC HORMONES• Glucagon• Cortisol• Epinephrine• Growth hormone
HYPOGLYCEMIC HORMONES• Insulin
HORMONAL REGULATION
The pancreas detects the change in blood glucose concentration and releases the appropriate hormone
High blood glucose
Signal to release
Hypoglycemic hormone
insulin
Low blood glucose
Signal to
release
Hyperglycemic hormone glucagon
HYPERGLYCEMIC HORMONESGLUCAGON Promotes Glycogenolysis, gluconeogenesis
Depresses glycogen synthesis
EPINEPHRINE Promotes Glycogenolysis, gluconeogenesis
Favours uptake of amino acids
CORTISOL Increases gluconeogenesis
Releases amino acids from the muscle
GROWTH HORMONE
Decreases glycolysis
Mobilizes fatty acids from adipose tissue
HORMONAL REGULATION
HORMONAL REGULATION - INSULIN
INSULIN
GLYCOGENESISGLYCOLYSIS
GLUCONEOGENESIS
GLUCOSE UPTAKE IN MUSCLE AND ADIPOSE TISSUE
GLYCOGENOLYSIS LIPOLYSIS
LIPOGENESIS
+ + + +
- --
FED STATE
HORMONAL REGULATION - INSULIN Glucose is diffused into cells through
transporters such as GLUT4 GLUT4 is present in cytoplasmic
vesicles Insulin binding to its receptor causes
vesicles to diffuse into plasma membrane
Brain and liver have non-insulin dependent glucose transporter
FASTING STATE
HORMONAL REGULATION
INSULIN favours glycolysis by activating the key enzymes of glycolysis
GLUCAGON inhibits key enzymes of glycolysis
GlucokinasePhosphofructokinasePyruvate kinase
Insulin & glucagon has opposing action
RENAL REGULATION
Tubular maximum
Renal threshold Glycosuria
Glucosuria Occurs When the Renal Threshold for Glucose Is Exceeded
Glucosuria occurs when the venous blood glucose concentration exceeds 180mg/dL [9.5–10.0 mmol/L]
BLOOD GLUCOSE – CLINICAL ASPECT
Estimation Common terms
Value interpretaio
n
BLOOD GLUCOSE ESTIMATION • The blood is collected using an anticoagulant (potassium
oxalate) and an inhibitor of glycolysis (sodium fluoride).
• Fluoride inhibits the enzyme, enolase, and so glycolysis on the whole is inhibited
• The glucose oxidase (GOD) method is the one most widely used.
NORMAL VALUES- common terms• A FBS is taken after at least eight
hours of fastingFASTING PLASMA
GLUCOSE [FPG/FBS]
• Test done any time of day without regard to time since last meal.
RANDOM PLASMA GLUCOSE [RBS/RPG]
• The test done about 2 hr after a good meal
POST-PRANDIAL BLOOD GLUCOS
[PPBS]
NORMAL VALUES
FASTING FBS
• 70-110mg/dL• 4-6.1mmol/L
RANDOMRBS
• < 140 mg/dl• <7.8 mmol/l
POST-PRANDIALPPBS
• 140 mg/dL• 7.8 mmol/L
02/05/2023 24
After overnight fast
FPG and urine sample is collected
Give 75gm of anhydrous glucose in about 300ml of water
Blood & urine specimens are collected at after 2hours
Blood tests GLUCOSE TOLERANCE TEST
02/05/2023 25
The Diabetes Expert Committee criteria for evaluating the standard oral glucose tolerance test.
Normal Glucose Tolerance
Impaired Glucose Tolerance
Diabetes Mellitus
Fasting plasma glucose (mg/dL)
< 110<6.1mmol/L
110–125 ≥126 >7mmol/L
Two hours after glucose load (mg/dL)
< 140<7.8mmol/L
≥140–199 ≥200 >11.1mmol/L
Blood tests GLUCOSE TOLERANCE TEST
02/05/2023 26