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Fatty Liver

Causes

Although NASH has become more common, its underlying cause is still not clear. It most often occurs in persons who are middle-aged and overweight or obese. Many patients with NASH have elevated blood lipids, such as cholesterol and triglycerides, and many have diabetes or pre-diabetes, but not every obese person or every patient with diabetes has NASH. Furthermore, some patients with NASH are not obese, do not have diabetes, and have normal blood cholesterol and lipids. NASH can occur without any apparent risk factor and can even occur in children. Thus, NASH is not simply obesity that affects the liver.

While the underlying reason for the liver injury that causes NASH is not known, several factors are possible candidates:

• insulin resistance
• release of toxic inflammatory proteins by fat cells (cytokines)
• oxidative stress (deterioration of cells) inside liver cells

Treatment

Currently, no specific therapies for NASH exist. The most important recommendations given to persons with this disease are to:

• reduce their weight (if obese or overweight)
• follow a balanced and healthy diet
• increase physical activity
• avoid alcohol
• avoid unnecessary medications

These are standard recommendations, but they can make a difference. They are also helpful for other conditions, such as heart disease, diabetes, and high cholesterol.

A major attempt should be made to lower body weight into the healthy range. Weight loss can improve liver tests in patients with NASH and may reverse the disease to some extent. Research at present is focusing on how much weight loss improves the liver in patients with NASH and whether this improvement lasts over a period of time.

People with NASH often have other medical conditions, such as diabetes, high blood pressure, or elevated cholesterol. These conditions should be treated with medication and adequately controlled; having NASH or elevated liver enzymes should not lead people to avoid treating these other conditions.

Experimental approaches under evaluation in patients with NASH include antioxidants, such as vitamin E, selenium, and betaine. These medications act by reducing the oxidative stress that appears to increase inside the liver in patients with NASH. Whether these substances actually help treat the disease is not known, but the results of clinical trials should become available in the next few years.

Another experimental approach to treating NASH is the use of newer antidiabetic medications—even in persons without diabetes. Most patients with NASH have insulin resistance, meaning that the insulin normally present in the bloodstream is less effective for them in controlling blood glucose and fatty acids in the blood than it is for people who do not have NASH. The newer antidiabetic medications make the body more sensitive to insulin and may help reduce liver injury in patients with NASH. Studies of these medications—including metformin and pioglitazone—are being sponsored by the National Institutes of Health and should answer the question of whether these medications are beneficial in NASH.