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Basics of Fat Loss | Simple Science that You can Use – Thomas DeLauer


Hormone sensitive lipase is a complex chemically structured enzyme that acts as a catalyst for the hydrolysis of fat in your body

The levels of hormone-sensitive lipase (HSL) in your body are inversely proportional to the serum levels of insulin – what this means is that as the levels of HSL decrease, the insulin levels in your blood increase

Simply put, it’s what burns your fat deposits

The only site for regulation of fatty acid oxidation is at the level of hormone-sensitive lipase in adipose tissue (more later)

Under fasting conditions, with minimal insulin in the blood, glucagon promotes formation of the phosphorylated, active form of hormone-sensitive lipase

When epinephrine is present, it further shifts the equilibrium to active hormone-sensitive lipase, increasing the hydrolysis of triglycerides to produce free fatty acids (FFA) and glycerol

The glycerol is carried to the liver, where it enters gluconeogenesis, while the FFA are carried on serum albumin to the tissues where they are catabolized for energy

The liver uses some of the energy from fat mobilization to support gluconeogenesis

Adipose Triglyceride Lipase

Hormone-sensitive lipase (HSL) was the first lipase known to hydrolyze triacylglycerols in rat adipose tissue (1988) until the identification of adipose triglyceride lipase (ATGL) in 2004

While HSL could catalyze the hydrolysis of triacylglycerides and diacylglycerides as well as various cholesterol ester species, ATGL showed high substrate specificity for triacylglycerides

To date, three major lipases have been identified: Adipose triglyceride lipase (ATGL) performs the first step of TG hydrolysis, generating diglycerides (DGs) and FAs

Hormone-sensitive lipase (HSL) performs the second step and hydrolyzes DGs, generating monoglycerides (MGs) and FAs

In contrast to ATGL, HSL exhibits a broader substrate specificity, also hydrolyzing TGs, cholesteryl esters, MGs, and retinyl esters in addition to DGs

Monoglyceride lipase (MGL) is selective for MGs and generates glycerol and the third FA – thus, lipolysis constitutes a coordinated three-step process catalyzed by three different enzymes, which degrade TG into glycerol and FAs


Hormone-sensitive lipase (HSL) is presumed to be essential for lipolysis, which is defined as the mobilization of free fatty acids from adipocytes

Lipolysis is under the control of various hormones and cytokines in adipocytes – Lipolytic hormones such as catecholamines and ACTH stimulate cAMP-dependent protein kinase (PKA), which in turn phosphorylates hormone-sensitive lipase (HSL) and perilipin in adipocytes


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