Metabolism of ketone bodies

DR.J.SIVAKUMARASSISTANT PROFESSOR

Carbohydrates are essential for the metabolism of fat.

The acetyl CoA formed from fatty acids can enter and get oxidized in TCA cycle only when carbohydrates are available.

During starvation and diabetes mellitus, acetyl CoA takes the alternate route of formation of ketone bodies.

INTRODUCTION

primary ketone body-Acetoacetate Secondary ketone bodies-beta-hydroxy

butyrate and acetone Site-liver ,mitochondria

Ketone bodies

Ketogenesis

The ketone bodies are formed in the liver; but they are utilized by extra hepatic tissues.

The heart muscle and renal cortex prefer the ketone bodies to glucose as fuel.

Tissues like skeletal muscle and brain can also utilize the ketone bodies as alternate sources of energy, if glucose is not available.

Ketolysis

Organs which can use ketonebodies-placenta, Intestinal mucosal cells, brain and adipocytes.

Almost all tissues and cell types can use ketone bodies as fuel, with the exception of liver and RBC.

Contd..

KETOSIS

Utilization of ketone bodies

when the rate of synthesis exceeds the ability of extrahepatic tissues to utilize them, there will be accumulation of ketone bodies in blood.

This leads to ketonemia, excretion in urine (ketonuria) and smell of acetone in breath.

All these three together constitute the condition known as ketosis.

Contd..

Two important hormones-INSULIN and GLUCAGON.

Regulated at three levels

KETOGENESIS

Regulation

Diabetes mellitus Starvation The brain derives 75% of energy from

ketone bodies under conditions of fasting. Hyperemesis (vomiting) in early pregnancy

may also lead to starvation-like condition and may lead to ketosis.

CAUSES

METABOLIC ACIDOSIS KUSSMAUL’s respiration Smell of acetone OSMOTIC diuresis Dehydration Coma

Clinical features

ROTHERA’S test Serum elecrolytes ACID_BASE parameters GLUCOSE urea

Diagnosis of ketosis

Saturate 5 mL of urine with solid ammonium sulfate.

Add a few drops of freshly prepared sodium nitroprusside followed by 2 mL of liquor ammonia along the sides of the test tube.

Development of a purple ring indicates the presence of ketone bodies in urine

ROTHERA’S test

ROTHERA’s TEST

The most important cause is type 2 DM. intercurrent illness Metabolic acidosis Kussmaul respiration Osmotic diuresis

Diabetic Keto-Acidosis

Blood glucose levels Urinalysis ABG Urea and creatinine CXR

Investigations

The American Diabetes Association categorizes DKA in adults into one of three stages of severity:

Mild: blood pH mildly decreased to between 7.25 and 7.30 (normal 7.35–7.45); serum bicarbonate decreased to 15–18 mmol/l (normal above 20); the person is alert

Moderate: pH 7.00–7.25, bicarbonate 10–15, mild drowsiness may be present

Severe: pH below 7.00, bicarbonate below 10, stupor or coma may occur

CRITERIA

Fluid replacement Insulin Potassium Bicarbonate

management

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