Metabolic activity is directed to maintaining fuel


Metabolic activity is directed to maintaining fuel supplies for catabolic pathways to
those tissues/organs with higher needs.

Metabolic environment in fasting state:

Decreased glucose

Decreased insulin

Decreased entry of glucose

And an increase in cortisol, epinephrine and
glucagon

Starvation for Several Days

In this clinical scenario, the individual has not had food for at least three days. The
metabolic environment is outlined below with the metabolic response. Study Figure 7.8
which illustrates the metabolic response and follow the summary comments.

Metabolic environment: decreased glucose; decreased insulin; decreased uptake of
glucose; and an increase in Cortisol, epinephrine, and glucagon
The metabolic strategy in the environment is:

Maintain blood glucose above hypoglycemia > 2.5 mmol/L in order
to supply brain and RBC

Minimize the breakdown of muscle

Increase dependency on FFA, ketones as energy source for liver, brain, muscle


The body is relying on stored triglycerides (in adipose tissue) to supply the nutrient
requirements for muscle, liver, brain and others.

The brain eventually will need to switch to using ketones as the chief nutrient when little
glucose is being generated by the liver via gluconeogenesis.

Fatty acids produced by adipose tissue are utilized by the liver to produce ketones and
muscles process fatty acids via fatty acid oxidation. After two weeks, fatty acids are the
preferred fuel for muscles. Glycerol is utilized by the liver to form ketones.

The acetyl-CoA will be in excess at some point due to production exceeding utilization.
This leads to high concentrations of ketones that affect acid-base balance.

Protein degradation in muscle rises rapidly in the first days of starvation but this slows
down after several weeks as the brain switches to ketone bodies for fuel.

After two weeks there is a decrease in hormones: glucagon, catecholamines, and growth
hormone
Injury: Metabolic Response to Stress
Injury from infection, surgery, trauma, or burns causes a HYPERMETABOLIC RESPONSE

Increase in energy expenditure

Increase in temperature

Increase in liver gluconeogenesis which leads to hyperglycemia

Increase in hepatic protein synthesis of acute phase proteins

Increase in cardiac muscle protein synthesis

Increased levels of glucagon, cortisol, catecholamines and insulin

Increased levels of cytokines (Interlukin I)


Injury results in protein catabolism and the amino acids are utilized in liver for the
gluconeogenesis pathway
Carbohydrate Disorders
We have studied:

the metabolic pathways that impact on carbohydrate metabolism

the intracellular and extracellular contributors (nutrients- polysaccharides, lipids,
proteins)

action of hormones (insulin, glucagon, epinephrine, cortisol, thyroid) that regulate the
flow of carbohydrates

organ/tissue systems and their role in carbohydrate metabolism

he body’s response to decreased nutrient supply and injury
