Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is the buildup of extra fat in liver cells greater than 5% of liver weight. Non-alcoholic fatty liver disease is one of the most common and complex disorders in hepatology. It leads to a decrease in the quality of life and mortality in the working-age population. Hepatology is a branch of medicine concerned with the study, diagnosis, and management of diseases that affect the liver.

NAFLD includes two pathological conditions with different prognoses.

• Steatosis is an excessive fat accumulation in liver cells (benign condition). Steatosis can be the initial stage with the subsequent development of non-alcoholic steatohepatitis. However, the disease does not develop into a different form in most patients.
• Non-alcoholic steatohepatitis (NASH) is characterized by fat accumulation and inflammatory response in the liver, fibrosis, and subsequent cirrhosis. Steatohepatitis is a clinically progressive form of NAFLD and can lead to cardiovascular disease, cirrhosis, or liver cancer.

Facts about NAFLD

• The prevalence of NAFLD is highest in the age group of 40 to 60 years.
• NAFLD is more common in women (53–85%).
• Fatty hepatosis affects 10% to 25% of the general population.
• 75% - 90% of patients with steatosis suffer from obesity and diabetes.
• Approximately 6 million people in the United States have NAFLD.
• 600,000 of them have NASH-related cirrhosis.
• Overweight and obesity are influenced by cultural and geographic differences.

Why Liver Health is so Important?

The liver is an unpaired vital organ and the largest gland (an organ that produces specific chemicals) in the human body. It is located in the right upper area of the abdomen, under the diaphragm. The cells that make up the liver are called hepatocytes. The hepatic lobule is the structural and functional unit of the liver. It has the shape of a prism and consists of liver cells (hepatocytes), vessels and ducts.

The Main Functions of The Liver

• Protein metabolism. More than half of the proteins (the main building material of the body) are formed in the liver. Albumin, the major protein, is also secreted by the liver. It is necessary to control blood clotting (it helps the blood to make clots that stop bleeding).
• Lipid metabolism. The liver is responsible for producing cholesterol (a structural fat-like element of cells) and bile acids (help the body break down fats). Fat accumulation is also one of the functions of the liver. It maintains a balance between fat and carbohydrate metabolism. The liver converts carbohydrates into fats in case of excess sugar (the main source of energy).
• Carbohydrate metabolism. The liver converts glucose into glycogen for storage. When the body's blood sugar (glucose) decreases, glycogen is converted back into glucose to provide immediate energy.
• Pigment metabolism (pigment is a substance that gives color to tissue and skin). When erythrocytes (red blood cells) and hemoglobin (an iron-containing protein that transports oxygen) are destroyed, free bilirubin (bile pigment) is released into the bloodstream. Free (unconjugated) bilirubin is toxic to the body. It turns into non-toxic direct (conjugated) bilirubin in the liver. Then part of direct bilirubin is excreted from the body, and the rest goes back to the bloodstream.
• Vitamin metabolism. The liver is involved in producing vitamins and the absorption of fat-soluble vitamins (A, D, E, K). Excesses of these vitamins are stored in the liver or excreted from the body. In case of vitamin deficiency, the body uses the liver reserves.
• Barrier function. The goal is to neutralize, detoxify substances, both those produced internally and those coming from the environment. 
• Digestive function. The liver cells constantly produce bile. Bile is drained into the gallbladder and stored until needed. During the meal, it enters the intestinal lumen, thus helping with the digestion process.
• Enzymatic function. All biochemical reactions are accelerated by special substances – enzymes, which are found in the liver. And when the body urgently needs any substances (for example, glucose), liver enzymes speed up their production process.
• Immune function. The liver is involved in the development of immune cells (the immune system is the body's biological defense system), as well as many allergic reactions.
• Excretory function. The liver removes metabolic waste products together with bile, which then enters the intestine and leaves the body. 

Stages of NAFLD

• Stage I — minimal fat accumulation. The liver cells start to build up fat, but this process does not damage the organ so far.
• Stage II — moderate fat accumulation. Irreversible processes in cells lead to their destruction and death. The contents enter the intercellular space. This stage is also characterized by the formation of cysts (abnormal cell growth).
• Stage III — severe fat accumulation. Precirrhotic condition (cirrhosis is an irreversible chronic process, where healthy tissue is progressively replaced by scar tissue). 

According to the degree, liver cell involvement can be

• Focal — the accumulation of a small amount of fat in various liver parts with an asymptomatic course.
• Multifocal — the accumulation of numerous fatty droplets in various parts of the liver with symptoms.
• Zonal — fat deposition in different parts of the hepatic lobules (structural and functional liver units).
• Diffuse — liver involvement, which implies fat accumulation over the entire hepatic lobule with the onset of symptoms.

Etiology (the determination of a cause of disease) defines 2 types of steatosis

• Primary — congenital metabolic disorder.
• Secondary — a metabolic disorder that occurs due to concomitant diseases, unhealthy diet, and lifestyle. 

Risk Factors for NAFLD