Lipid digestion and metabolism: health topic on nutrition

Welcome again to my cool medical articles. Today, you will see lot of information about health especially about lipids.
Do not worry it will be short medical article but full of latest health and fitness news.
First part of my cool medical article will talk about lipid digestion and to make it easy as I can, I will talk about enzymes that digest lipids as follows:
  • 1.     Lingual lipase: this enzyme is excreted in mouth by von Ebner’s glands. It digests short and intermediate fatty acids and has a lesser effect on long chains. It continues digestion of lipids in stomach but to lesser extent as fats coalesce in stomach.
  • 2.     Gastric lipase: secreted by serous secreting glands and acts like lingual lipase on short and intermediate chains. It is inactivated by alkalinity of small intestine.
  • 3.     Pancreatic lipase: (the most potent enzyme) it can hydrolyze all types of fatty acids (short, intermediate and long chains fatty acids). It works very well in alkaline medium provided by bicarbonate.
  • 4.     Phospholipase: this enzyme specially digests phospholipids. It is part of pancreatic juice and secreted in inactive form then activated by trypsin in small intestine.
  • 5.     Cholesterol esterase: It is part of pancreatic juice too. It is secreted in active form and acts on all types of lipids from cholesterol to monoacylglysrol.

Added to above enzymes, Bile salts are very important to emulsify lipids to make it easy to digest by above enzymes. We should know any deficiency in bile salts or above enzymes mean unpleasant health events.
carnitine shuttle
In the second part of my amazing health article, I will go after absorption to answer health question you are asking now, how do we metabolize lipids?!
Lipids enter our mitochondria after acetylation by acyl-CoA synthase. This process is known as carnitine shuttle (shown in fig.1).

After entering mitochondria β-oxidation takes place (shown in fig.2 and fig.3). β-oxidation takes steps to produce acyl-CoA and new fatty acid which is shortened by two carbons.
Β-oxidation steps are:
beta oxidation
  • 1.     Activation by adding acyl-CoA
  • 2.     Oxidation (dehydrogenation) by acyl-CoA dehydrogenase.
  • 3.     Hydration by enoyl CoA hydratase
  • 4.     Oxidation (dehydrogenation) by 3-hydroxyacyl-CoA dehydrogenase
  • 5.     Thiolase

The new fatty acid enters this cycle again and again till all fatty acids are turned into acyl-CoA.

beta oxidation cycle

Acyl-CoA then enters citric acid cycle to produce energy(fig.4).
citric acid cycle

Last thing in this short medical article if you want to eat healthy fats just go to this medical article.
Waiting your comments and any health topics you want to read.
See you soon in my next article, good bye J

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