What is the Difference Between Lipoprotein Lipase and Hormone Sensitive Lipase

The main difference between lipoprotein lipase and hormone sensitive lipase is that the lipoprotein lipase (LPL) is attached to the luminal surface of the endothelial cells in the capillaries of the adipose tissue whereas the hormone-sensitive lipase (HSL) occurs inside the adipocyte. 

Lipoprotein lipase and hormone-sensitive lipase are two types of lipases that mainly occur in the adipose tissue. They are water-soluble enzymes, which hydrolyze triglycerides. Furthermore, insulin activates lipoprotein lipase while insulin inhibits hormone-sensitive lipase. Moreover, the removal of the inhibitory effect of insulin activates hormone-sensitive lipase.

Key Areas Covered

1. What is Lipoprotein Lipase
     – Definition, Location, Role, Regulation
2. What is Hormone Sensitive Lipase
     – Definition, Location, Role, Regulation
3. What are the Similarities Between Lipoprotein Lipase and Hormone Sensitive Lipase
     – Outline of Common Features
4. What is the Difference Between Lipoprotein Lipase and Hormone Sensitive Lipase
     – Comparison of Key Differences

Key Terms

Adipocytes, Endothelial Cells, Hormone Sensitive Lipase (HSL), Insulin Effect, Lipoprotein Lipase (LPL)

What is Lipoprotein Lipase

Lipoprotein lipase (LPL) is a type of enzyme that belongs to the lipase family. It mainly occurs in the luminal surface of the endothelial cells of the adipose tissue. Generally, endothelial cells line the blood vessels or capillaries. Therefore, lipoprotein lipase occurs outside the adipocytes. This enzyme also occurs in the blood capillaries of the heart and muscles.

Figure 1: Lipoprotein Lipase Action

Furthermore, the main function of lipoprotein lipase is to hydrolyze extracellular triglycerides. Here, insulin activates the function of lipoprotein lipase in the adipose tissue. On the other hand, it inhibits the lipoprotein lipases in the heart and muscles. Glucagon and adrenaline are responsible for their activation. Therefore, after a meal, this enzyme becomes active and hydrolyzes the triglycerides in the bloodstream. Thus, a high-carbohydrate diet can is more likely to cause fat gain. Besides, during fasting, lipoprotein lipases in muscles and heart become active, allowing the use of the energy in triglycerides to their functioning.

What is Hormone Sensitive Lipase

Hormone-sensitive lipase (HSL) is another type of lipase especially found inside the adipocytes. In fact, there are two forms of the hormone-sensitive lipase; they are the short form and long form. Its short form occurs in the adipose tissue while the long form of the enzyme occurs in the steroidogenic tissues such as testis.

Figure 2: Hormone Sensitive Lipoprotein Action

Furthermore, the main function of the hormone-sensitive lipase is to metabolize the stored fat. That means; it hydrolyzes the triglycerides stored inside the adipocytes. Moreover, this enzyme can hydrolyze triacylglycerols, and thus, resulting in a fatty acid and a diglyceride. Also, it can hydrolyze diacylglycerols, and thus, resulting in a fatty acid and a monoglyceride. However, insulin inhibits the hormone-sensitive lipase. But, ACTH, and catecholamines like adrenaline and noradrenaline activate this enzyme. It is because the hormone-sensitive lipase metabolizes the energy stores. Moreover, the removal of the inhibitory effect of insulin also activates the enzyme.

Similarities Between Lipoprotein Lipase and Hormone Sensitive Lipase

• Lipoprotein lipase and hormone-sensitive lipase are two types of lipases found in adipose tissue.
• Both are water soluble.
• Also, they are responsible for the hydrolysis of triglycerides.
• Furthermore, both catalyze the rate-limiting steps for the turnover of triglycerides in the adipose tissue.
• Moreover, insulin is the hormone which regulates their activity.

Difference Between Lipoprotein Lipase and Hormone Sensitive Lipase

Definition

Lipoprotein lipase refers to the primary enzyme responsible for the hydrolysis of lipoprotein triglyceride into free fatty acids and monoglycerides while hormone-sensitive lipase refers to an intracellular neutral lipase that is capable of hydrolyzing triacylglycerols, diacylglycerols, monoacylglycerols, and cholesteryl esters, as well as other lipid and water-soluble substrates. Thus, this is the main difference between lipoprotein lipase and hormone sensitive lipase.

Occurrence

Lipoprotein lipase is attached to the luminal surface of the endothelial cells in the capillaries of the adipose tissue while the hormone-sensitive lipase occurs inside the adipocytes.

Hydrolysis

Another difference between lipoprotein lipase and hormone sensitive lipase is their role in hydrolysis. Lipoprotein lipase hydrolyzes the extracellular triglycerides in lipoproteins while hormone-sensitive lipase hydrolyzes various intracellular triglycerides inside the adipocyte.

Effect of Insulin

Moreover, insulin activates lipoprotein lipase while insulin inhibits hormone-sensitive lipase. Hence, this is another difference between lipoprotein lipase and hormone sensitive lipase.

Conclusion

Lipoprotein lipase is an enzyme responsible for the hydrolysis of triglycerides outside the adipocytes since it occurs in the luminal surface of the endothelial cells capillaries in the adipose tissue. On the other hand, hormone-sensitive lipase hydrolyzes triglycerides inside the adipocyte since it occurs inside the adipocyte. Also, insulin activates lipoprotein lipase while inhibiting hormone-sensitive lipase. Therefore, the main difference between lipoprotein lipase and hormone sensitive lipase is their location in the adipose tissue and the types of triglycerides they hydrolyze.

References:

1. Andrade Jr MC (2018) Lipoprotein Lipase: A General Review. Insights Enzyme Res Vol.2 No.1:13. doi:10.21767/2573-4466.100013
2. Kraemer, Fredric B, and Wen-Jun Shen. “Hormone-Sensitive Lipase Control of Intracellular Tri-(Di-)Acylglycerol and Cholesteryl Ester Hydrolysis.” Journal of LIPID RESEARCH, vol. 43, Oct. 2002, pp. 1585–1594., doi: 10.1194/jlr.R200009-JLR200.

Image Courtesy:

1. “Overview ANGPTL4” By Sander kersten – Own work (CC BY-SA 3.0) via Commons Wikimedia  
2. “ThermogeneseAdipozyten-en” By ThermogeneseAdipozyten.svg: chris 論derivative work: Burkhard (talk) – ThermogeneseAdipozyten.svg (Public Domain) via Commons Wikimedia