2. Lipogenesis and Lipolysis

Tissues depending on fatty acids for energy:

A. Location

1. Lipolysis: Breakdown of Triglycerides into glycerol and fatty acids



2. Lipogenesis: Glucose conversion to Fatty Acids (REMEMBER, THE OPPOSITE DOES NOT HAPPEN)




B. Hormonal and dietary factors

Reactions: Glucose to acetyl Coa to FA (see figure)

**In ruminants, acetate, not glucose, in starting material for lipogenesis**

Acetyl Coa goes either to TCA cycle or to FA synthesis, depending on the metabolic status of the animal

Hormonal control:

1. Insulin:


2. Glucagon:


3. Thyroid hormone:


4. Glucocorticoids


5. Epinephrine


Dietary Control

1. High fat diet


2. High CHO diet



3. High protein diet


C. Ketone bodies formation

1. When lipolysis of body fats becomes excessive, ketone bodies will be formed:




2. Synthesized in the liver through excess Acetyl Coa "spilling" into the TCA cycle. An "overflow"

pathway exists where ketone bodies are formed.

3. Utilized by:

Brain (upon adaptation to starvation)
Kidney cortex
Skeletal muscles


"Ketosis" occurs when the rate of formation of the ketone bodies by the liver exceeds the

capacity of the peripheral tissues to use them up.

1. Diabetes mellitus:



2. Fasting or low carbohydrate intake:


3. Lactation: Potential problem in the dairy cow- What about the lactating sow or mare?

Dairy Cow:



Lactating sow:



Lactating mare:


4. Pregnancy toxemia in sheep


5. Severe exercise in the post absorptive state


D. Brown Adipose Tissue

1. Function: Non-shivering thermogenesis





2. Characteristics





3. Hormonal control: Activated by Norepinephrine