Biochemistry and Nutrition (BAN 203) - Lecture 28

A condition where the body produces more ketone bodies than it can use, leading to an excess in both the blood (ketonemia) and urine (ketonuria).

A sweet, fruity smell on the breath, often a symptom of ketoacidosis, caused by the increased production of acetone.

The condition of having a low blood pH due to excess ketone bodies in the bloodstream.

The loss of water from the body due to excess glucose and ketone bodies being excreted in urine.

A state of extreme acidity in the blood caused by the accumulation of ketone bodies, often seen in uncontrolled type 1 diabetes.

Ketone bodies are a group of compounds produced by the liver during periods of prolonged fasting or starvation. They include acetoacetate, 3-hydroxybutyrate, and acetone. These compounds are used as an energy source for peripheral tissues when glucose is scarce, such as during fasting or diabetes.

Ketogenesis is the process of producing ketone bodies within the liver. It is activated when the liver is flooded with fatty acids, typically during fasting or prolonged starvation. The excess acetyl-CoA, produced by fatty acid breakdown, is channeled into ketone body synthesis.

Ketolysis is the process where peripheral tissues utilize ketone bodies as an energy source. This process occurs in extrahepatic tissues, such as the brain and muscles, but not in the liver itself. The breakdown of ketone bodies releases energy that can be used by the cells for various metabolic processes.

During prolonged periods of fasting, the liver produces ketone bodies because it is unable to utilize all the acetyl-CoA available from fatty acid breakdown. The liver is flooded with fatty acids released from adipose tissue, leading to an increase in acetyl-CoA, which is then channeled into ketone body synthesis. This process helps to spare glucose for use by vital tissues.

Ketone bodies are readily soluble in aqueous solutions, meaning they can be transported through the bloodstream without needing to be incorporated into lipoproteins or bound to albumin. This makes them convenient energy sources for peripheral tissues, especially during prolonged periods of fasting when glucose supplies are limited.

Diabetic patients often experience elevated ketone body levels (ketoacidosis) due to the inability of their cells to effectively use glucose for energy, leading to increased fat breakdown and ketone body production.

Individuals with disorders of fatty acid oxidation present with hypoketosis and hypoglycemia. These disorders impair the ability to break down fatty acids, leading to reduced levels of acetyl-CoA for ketone body production (hypoketosis). This also results in increased reliance on glucose for energy, causing low blood sugar (hypoglycemia).

Even the brain can utilize ketone bodies as a source of energy when blood levels rise sufficiently. This is particularly important during prolonged fasting, as ketone bodies can spare glucose for use by other vital tissues.