The liver serves many functions in the human body and is a central organ to crucial processes such as digestion, blood sugar control, production of blood clotting factors, fat and cholesterol transport and the removal of waste and especially toxic substances.
The liver is among others responsible for transforming and synthetizing sugars, lipids and proteins. It plays an important role in the production and degradation of intestinal and systemic hormones. It detoxifies endogenous toxics such as ammonia, and xenobiotics such as drugs and alcohol.
The liver synthetizes all major plasma proteins beside gamma globulins, such as for example including albumin and coagulation factors. It stores and release carbohydrates, and vitamins.
The liver is also producing and excreting bile, allowing the elimination of waste such as bilirubin, and providing bile salts essential to digestion. Bile plays a key role in cholesterol metabolism. The liver has been called the “antechamber of the heart” because it collects and processes all of the gastrointestinal blood through the portal vein and transforms deeply the composition before delivering the blood to the right side of the heart. So, failure of liver or any hindrance to its normal activities can cause many diseases in the body leading to death in the advanced forms of liver ailment if no organ replacement is available.
The ability of the liver to carry out these key processes is so essential that liver mass is maintained within a very narrow range in relation to the overall body mass. If there is loss or gain of liver mass, such as through liver injury or pregnancy, respectively, compensatory proliferation or apoptosis of cells allow restoration of original liver/body mass ratio once the stimulus is removed. Liver regeneration is a highly controlled process regulated by a complex network on highly redundant signals.
Several signaling pathways are known to stimulate regeneration in the liver including cytokines, growth factors, hormones, and nuclear receptors (4). The robust programmed proliferative response to loss of parenchymal function is widely known as “liver regeneration” a unique situation in our organism. Repopulation of the liver can be achieved via one or two mechanisms: (1) hepatocyte proliferation, or (2) migration and differentiation of liver derived stem/progenitor cells.
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2. Lazo M, Clark JM. The epidemiology of nonalcoholic fatty liver disease: a global perspective. Semin Liver Dis. 2008;28:339–350. [PubMed]
4. Michalopoulos, G. K. Principles of Liver Regeneration and Growth Homeostasis. Comprehensive Physiology 3, 485-513, doi:10.1002/cphy.c120014 (2013).