In a lay man’s term, NASH is a type of liver disease in which inflammation and damage caused by a buildup of fat in the liver. The process is often very ‘silent’ and most of the victims are not aware of it. NASH doesn’t have many symptoms until its later stages when it leads to problems like cirrhosis and liver failure. Right now, the only way to treat NASH is through weight loss and maintaining a healthy weight and diet.
Simple steatosis is the infiltration of liver cells with fat, associated with the disturbance of the metabolism. Fatty liver may happen because of alcoholism, malnutrition, pregnancy, or drug therapy. The liver is the only organ in our body that is able to regenerate. With most organs, such as the heart, the damaged tissue is replaced with a scar, like on the skin. The liver, however, is able to replace damaged tissue with new cells. Fatty liver is generally benign and reversible.
As the name suggests nonalcoholic fatty liver disease has nothing to do with excessive alcohol intake. The evolution of simple steatosis to NASH is a complex process, caused by the interaction of several genetic and environmental factors. Insulin resistance together with pro-inflammatory mediators are believed to play a major role in the pathogenesis of NAFLD. There are different stages in the evolution of NAFLD. Stages 1 and 2 are reversible, but stages 3 and 4 are not, and that’s when it becomes dangerous as there is no treatment to date other than a liver transplant [2].
Figure: Transition from normal to liver carcinoma
Research suggests that certain health conditions make someone more likely to develop NAFLD or NASH.
Causes of NASH
- Obesity, especially with a large waist size
- High blood pressure
- High levels of triglycerides or abnormal levels of cholesterol in their blood
- Type 2 diabetes
- Metabolic syndrome
The growing global epidemic of obesity has led the World Health Organization (WHO) to estimate that, in 2016, more than 1.9 billion adults (39% of the adult population) were overweight, and 650 million (13% of the adult population) were considered obese. Of these, nonalcoholic fatty liver disease (NAFLD) is becoming one of the most important causes of liver disease throughout the world, with an estimated global prevalence rate of about 24%. In fact, the highest prevalence of NAFLD has been reported from South America and the Middle East, whereas the lowest prevalence has been reported from Africa [3].
NASH poses a diagnostic dilemma for the doctors, as it is often asymptomatic and even when symptoms do develop, they are frequently non-specific (malaise, fatigue and vague abdominal pain). Although mild to moderate elevation of the liver-specific enzymes AST and ALT can be seen in people with NASH, normal laboratory findings do not exclude the condition. To further complicate matters, the elevation of these markers does not correlate with the degree of inflammation or fibrosis [4]. Though liver biopsy/histopathology still remains the ‘gold standard’ for diagnosis of NASH. However, a specialized ultrasound machine ‘FibroScan’ now available can accurately measure fibrosis (thickening and scarring) and steatosis (fatty change) of the liver. FibroScan is helping the healthcare provider to know more about the liver disease in a fast and cost-effective way. More importantly, it is a non-invasive procedure.
Over consumptions of fructose, meat, saturated fat, and cholesterol coupled with lower consumption of fiber, fish and vitamins all lead to dyslipidemia and insulin resistance. Very few RCTs have looked at dietary interventions on liver injury in NASH but of the small ones that do exist they showed histological improvement with only minimal weight loss. Unfortunately, most large trials on dietary interventions are not applicable; patients often relapse once the intervention is over and physicians cannot sustain the major interventional requirements needed. Alongside this, while multiple therapies are being investigated, weight loss is the only treatment with sufficient evidence suggesting it is both beneficial and safe. New drugs have shown modest results in terms of reduction of hepatic steatosis, inflammation, and fibrosis. However, public health prevention strategies are the most important measure [4].
How to Prevent NASH
- Choose a healthy plant-based diet that’s rich in fruits, vegetables, whole grains, and healthy fats
- Maintain a healthy weight. If overweight or obese, reduce the number of calories you eat each day. Your Body Mass Index (BMI) should not cross 30
- Exercise most days of the week
- If you have diabetes, keep your blood sugar at your target level
- Limit alcohol, or do not drink
- Avoid fried and junk foods
Researchers from the University of Sydney, Australia determined that patients with a sedentary lifestyle who engage in routine physical activities lower their risk of NAFLD. The lower risk of problems associated with fatty liver was not contingent upon weight loss, but a direct result from the increased aerobic exercise. Daily brisk walking for 4-5 km per day can also play an important role to keep the liver in proper shape.
According to experts, NASH is very closely linked to the global epidemic of obesity and diabetes, and like other chronic hepatitis, it can potentially progress to cirrhosis and even cancer! It is vital that health education starts in school and continues into young adulthood. As this global problem can only be effectively tackled through proper knowledge dissemination.
References:
- Ramsey L. Millions of people are living with a ‘silent’ disease they’ve likely never heard of. Business Insider Jul 6, 2017. [https://tinyurl.com/v5luohm]
- NASH: A silent killer disease! Assessed from: https://tinyurl.com/rpb86kl
- Younossi Z M. The epidemiology of nonalcoholic steatohepatitis. CLD Clinical Liver Disease 2018; 11(4): 92-94
- NASH – The silent killer you’ve never heard of. Assessed from: https://tinyurl.com/tlnfw2s
Dr. Sanjoy Kumar Pal is a Professor of Biology in Skyline University Nigeria. He has a PhD. in Animal Genetics from Indian Veterinary Research Institute, India.
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