Alpha 1 MZ Liver
In this section we focus on the Alpha 1 MZ liver, which is the root cause of the clinical issues of Alpha 1 MZ individuals especially at a somewhat older age, when the liver has lost a significant portion of its capacity.
The liver produces a protein called Alpha 1 Antitrypsin based on your genotype. In case of an Alpha 1 MZ individual the "M" portion is correctly formed and is secreted in the blood stream, however the "Z" portion of the protein is not correctly formed, and is unable to leave the liver cell. (It is stuck..)
Because a part of the Alpha 1 Antitrypsin gets stuck, you have a shortage of Alpha 1 Antitrypsin in your body which may create a number of issues in your body. (Lung issues, Immunity issues, Connective tissue issues etc.)
However, the "Z" portion which gets stuck in your liver, also has an influence on the capacity of the liver to perform other important liver functions for your body, like e.g. the production of bile acid.
In case of an Alpha 1 MZ individual, about ~85% of the Z protein is retained within the liver cells together with ~6% of the "M" protein resulting in ~48% of usable "M" protein is secreted in your bloodstream..
From the 85% of the Z protein about 70% is degraded by the liver cell's intracellular quality control mechanisms and the remaining 15% accumulates in the liver cell as ordered polymers. These polymers are associated with liver diseases.
Liver structure
The liver is composed of smaller histological structures called lobules, which are roughly hexagonal in shape.
Each lobule is surrounded by branches of the hepatic artery (provide oxygen) and the portal vein (provide nutrients)
These vessels drain into capillary-like structures called sinusoids, which exchange materials directly with the hepatocytes. The sinusoids drain into a central vein, which feeds deoxygenated blood into the hepatic vein
Hepatocytes also produce bile, which is transported by vessels called canaliculi to bile ducts, which surround the lobule.
Under normal conditions, the AAT protein synthesis is mainly carried out by periportal hepatocytes that are considered the “professional” synthesizing protein cells. Under stimulation, midlobular and centrolobular hepatocytes, are progressively recruited according to lobular gradients and contribute to the increase of synthesis and secretion.
Pi MZ livers in normal condition show intermediate serum values as the M fraction is regularly exported, while 85% of the Z is retained. Under conditions of clinical stimulation such as inflammation or hormonal stimuli, the synthesis of both M and Z increases. The M fraction is regularly secreted, whilst the Z fraction is retained within the cell. The divergent destiny of the two fractions explains the paradoxical result that the more the serum increases the more hepatocytic storage is. In contrast, homozygous Pi ZZ individuals show low serum levels in both basal and stimulatory conditions. The term carrier is no longer applicable for the heterozygous condition as all Pi MZ individuals undergo storage and the storage predisposes to liver damage and a reduction of the liver capacity.
In Pi-MZ livers all hepatocytes from adjacent lobules are positively stained for AAT polyclonal AAT immunostaining. The intensity of the staining decreases from the Periportal zone, where the positivity involves the whole cytoplasm (type I positivity), to the Midlobular zone and the Pericentrum zones where crescent like and rectilinear double rows pictures are clearly seen.
In contrast, in Pi-ZZ patients, the positivity was mainly restricted to the periportal zone hepatocyte in the form of PAD positive globules filling up the entire cytoplasm (type I positivity), or unevenly distributed in the intralobular hepatocytes with type II positivity.
In Pi MZ patients it involved more hepatocytes and not only hepatocytes but also endothelial cells of portal vessels
Liver aging
The volume and blood flow of the liver gradually decrease with aging. According to studies, the liver volume decreases by 20–40% as one gets older. Persons aged 65 years or higher showed an approximately 35% decrease in the blood volume of the liver compared with those aged less than 40 years. Other studies observed a decrease also in the mass of the functional liver cells.
As a result of aging, hepatocyte polyploidy tends to occur more frequently over time, which is accompanied by a decreased number and dysfunction of mitochondria. Also, the area of smooth endoplasmic reticulum is reduced, causing decreased generation of smooth endoplasmic reticulum and reducing the synthesis of microsomal proteins in the liver.
Liver regeneration
Diploid and polyploid hepatocyte populations display very different turnover characteristics.
In a middle-aged individual, the annual cell division rate for diploid hepatocytes is approximately 71%, whereas it is only 10% among binucleated diploid and 1% among mononucleated tetraploid hepatocytes. This corresponds to average cell ages of 8-9 months for diploid hepatocytes, and 4.4 years for both binucleated diploid hepatocytes and mononucleated tetraploid hepatocytes. Given a total hepatocyte number of 2500 Billion in a human middle-aged liver, it is estimated that approximately 700 million hepatocytes are born every day.
An important statement in the context of Alpha 1 MZ and the corresponding liver damage & capacity loss especially during aging is:
“The beginning and development of liver diseases are governed by the intricate balance between liver damage and liver regeneration”
Fatty Liver
Within our Alpha1 MZ group, we see that many, if not all, MZs have fatty liver (~ 25% under healthy persons). Although our Western-style food is not helping here, there is also another important element, and this is the continuous Endoplasmic Reticulum stress in the MZ liver, which is affecting all lobule zones.
"There is a direct relationship between ER stress and fatty liver, as ER plays a crucial role in fatty acid synthesis and cholesterol metabolism. Hence, chronic ER stress may promote fatty liver disease."
You can find the related paper here.