Liver is an important organ performing major and essential functions necessary for the maintenance of life in a healthy state. Liver is estimated to be responsible for over 500 functions, usually in combination with other organs of the body. Detoxification of an organism and the synthesis of various essential components are among the major essential and life sustaining functions of the liver. In addition, the liver functions as an accessory digestive organ that produces bile, a juice that helps in the breakdown and digestion of fat.
Architecture wise, the liver is a reddish-brown, wedge shaped organ consisting of two lobes of unequal size and shape. Liver is also considered as the heaviest organ and largest gland in the human body. Liver is located in the right upper quadrant of the abdominal cavity, towards the right of the stomach and just above the gallbladder. The liver is connected to major blood vessels: the hepatic artery and the portal vein. The hepatic artery carries the oxygen-rich blood into the liver, whereas the portal vein carries the blood rich in digestive nutrients.
These blood vessels subdivide into smaller vessels/capillaries called liver sinusoids, which then lead to lobules. These lobules are the actual functional units of the liver and each lobule is made up of millions of hepatocytes, which are the basic metabolic machinery of the liver. Because of its strategic location in the body and its crosstalk with all the major organs of the body, the liver is prone to many diseases. Hepatitis is the most common condition where the liver gets inflamed and leads to functional impairments.
Currently, the absolute number of Chronic liver disease (CLD) cases is estimated to be about 1.5 billion across the globe. The most common causes of prevalent diseases are Non-alcoholic fatty liver disease (NAFLD: 59%), followed by Hepatitis B (HBV-29%), Hepatitis C (HCV-9%) and Alcoholic Liver Disease (ALD-2%). Other CLDs accounting for about 1% of cases include primary biliary cholangitis, primary sclerosing cholangitis, alpha-1-antitrypsin deficiency, Wilson’s disease, and autoimmune hepatitis.
Among various CLDs, Non-alcoholic fatty liver disease (NAFLD) is increasing at a rapid pace and showing a uniform trend across the globe with huge consequences on the health care system. NAFLD has a 25% estimated global prevalence and it is greater than 30% in the Middle East and South America, followed by Asia (27%), USA (23%) and Europe (24%). By definition, NAFLD represents a spectrum of conditions ranging from simple accumulation of fats in the liver (called as steatosis), inflammation of liver (called as Non-alcoholic-steatohepatitis or NASH), fibrosis, cirrhosis and end stage liver disease called as hepatocellular carcinoma or simply liver cancer in absence of significant alcohol consumption.
Diabetes patients are at high risk of developing NAFLD and NASH. The prevalence of NAFLD can be as high as 60% to 70% in patients with diabetes mellitus (DM). The Indian Subcontinent is currently undergoing rapid social and economic change with a trend towards urbanization and an urban-rural economic divide. Not surprisingly, in rural India, the region characterized by traditional diet and lifestyle, the prevalence of NAFLD is low (about 9%), whereas urban areas mimic the western prevalence, with varying rates between 16% to 32%. Further, a study from India showed that NAFLD accounts for about two third cases of all cryptogenic liver cirrhosis. Mathematical modelling studies using the current estimates of NAFLD and obesity forecast that the burden of NAFLD and NASH will increase over the next decade. These models estimate that the United States will have a 168% increase in cirrhosis and about 178% increase in NAFLD-related deaths.
Asian peninsula, especially China, will have the largest absolute number of deaths related to NAFLD. Industrialization, changing lifestyles and dietary habits over the last three decades has set the stage for obesity and the NAFLD epidemic in India. Currently, NASH-related cirrhosis, along with hepatocellular carcinoma is the leading cause of liver transplant in India. With an estimated 64 million in the United States, 52 million in Europe and 338 million in mainland China and about 25 % ( >120 million) of population in India, the sheer volume of patients distinguish NAFLD apart from other chronic liver diseases. Therefore, in this context major focus is to detect the NAFLD patients at highest risk of liver-related complications and understand the cellular and molecular basis of NAFLD pathogenesis.
Mechanistically, NAFLD pathogenesis is a multifaceted phenomenon as reviewed by us and others in different publications and understanding the mechanistic basis of NAFLD and NAFLD-related damage is beyond the scope of this public awareness article. However, easy access to calorie-dense food and sedentary lifestyle together with the modern epidemics of diabetes mellitus (DM) and Obesity have set stage for bigger epidemics of NAFLD and NASH and lead to the development of a substantial health problem in India and across the globe. Various studies are providing evidence that the Indian population is more prone to NAFLD as compared to other races due to higher occurrence of Insulin resistance and higher blood fat levels.
Further, Indian estimates in 2019 showed that 77 million people had diabetes, which is expected to rise to greater than 130 million by 2045. This sheer number may account for the majority of cases and can lead to multi-organ damage including NAFLD. In this connection, an education of healthy lifestyle to children and adolescents in schools, colleges and Universities, and public awareness programmes/articles related to this epidemic may be the need of the hour. Efforts are also needed to develop the strong perception and understanding of both physicians and the general public towards this silent pandemic.
(Arjamand Mushtaq is working as ICMR-Senior Research Fellow at Centre for Interdisciplinary Research and Innovations; University of Kashmir & Dr. Nissar Ul Ashraf is Assistant Professor, Department of Biochemistry, GDC, Sopore)
