Fatty acids released into the bloodstream result from the difference between hydrolysis of triglycerides in adipocytes during lipolysis and reutilization of the FFAs by fat cells through a futile cycle, termed re-esterification. FFAs are esterified with glycerol 3-phosphate.

What is esterification of triglycerides?

The main reaction involved is the transesterification of triglycerides into esters. When an acid oil, such as spent or waste oil, is used, the amount of free fatty acids range from 3% to 40%, and another reaction takes place simultaneously with the transesterification, the direct esterification of the free fatty acid.

What is lipolysis stimulated by?

Lipolysis is triggered by the activation of adenyl cyclase, which converts adenosine triphosphate (ATP) into cyclic adenosine monophosphate (cAMP). Catecholamines, acting via beta-adrenergic receptors (βADRs), stimulate adenyl cyclase but this action is counteracted by activation of alpha-adrenergic receptor (αADR).