Sunday November 29, 2009
Double trouble
Diabetes and hyperlipidaemia are both risk factors for fatty liver.
HAVE you ever wondered if diabetes, hyperlipidaemia, and liver disease have anything in common? The answer is an emphatic yes.
Diabetes is a condition whereby the body does not produce or properly utilise insulin, resulting in high levels of sugar (glucose) in the blood (defined as fasting blood glucose ≥ 5.6 mmol/L). Insulin maintains blood sugar at normal levels and prevents blood glucose from becoming too elevated. The cells that insulin mainly targets include fat cells, muscle cells, and liver cells.
Fatty liver occurs when fats start to accumulate in liver cells or hepatocytes. Fatty liver, which is caused by factors apart from alcohol, is termed non-alcoholic fatty liver disease (NAFLD).
Basically, NAFLD can be divided into three stages, depending on the severity – simple fatty liver, non-alcoholic steatohepatitis (NASH), and cirrhosis.
As the condition becomes more severe, liver cells become inflamed and scarring of the liver is common. There is anecdotal evidence that supports the concept that insulin resistance is the process common to all stages of NAFLD.
Insulin resistance leads to changes in the metabolism of glucose, as well as fat. The result is elevated glucose levels and increased uptake of triglycerides into the liver cells. Diabetes and fatty liver
What is insulin resistance and how does it relate to NAFLD? Insulin resistance is a state whereby normal signaling pathways that convey biochemical messages between insulin and its target cells are disrupted. This results in insulin not exerting its normal or full effects. As a result, the body is resistant to the effects of insulin.
In insulin resistance, a defect to the insulin receptors (liver cells, fat cells, muscle cells) causes insulin to be less effective than normal. The pancreas must then produce more insulin in order to maintain normal blood glucose levels.
Initially in this process, the increased insulin levels are sufficient to maintain normal blood glucose. However, as the insulin resistance progresses, even very high levels of insulin become ineffective. This degree of insulin resistance leads to elevated blood sugars and type 2 diabetes mellitus.
Insulin resistance leads to changes in the processing (metabolism) of sugar and fats (lipids) in the liver. The result of these changes is an increased uptake of triglycerides into the liver cells. These triglycerides come from the diet as well as from abdominal fat and peripheral muscles. They are then stored in tiny sacs inside the liver cells, resulting in fatty liver.
NAFLD is the most common chronic liver disease seen in patients with type 2 diabetes mellitus. About 88%, or close to nine out of 10, diabetic adults have NAFLD.
The risk of death from liver disease is 2.5-fold higher among patients with type 2 diabetes mellitus compared to the general population.
Death from chronic liver disease is also the fourth most common cause of death among diabetics, accounting for approximately one in 20 deaths.
A study found that cirrhosis, a severe form of NAFLD characterised by irreversible scarring of the liver, developed in one out of every four diabetics with NAFLD.
Hyperlipidaemia and fatty liver
Many people are unaware that hyperlipidaemia is also associated with fatty liver. In fact, hyperlipidaemia increases the risk of an individual in developing the latter condition. Hyperlipidaemia simply implies that the amount of fats in the bloodstream is elevated, and these fats include both cholesterol and triglycerides.
At proper levels, fats perform important functions in the body. But when present in excess, they can cause health problems. Hyperlipidaemia is often known to cause hardening of blood vessels, which leads to conditions such as stroke and heart diseases.
A study conducted in Canada indicates that high levels of fats circulating in the blood are associated with fat accumulation in the liver and the degree of accumulation increases as more fats are present in blood.
It also shows that approximately one half of hyperlipidaemic patients will have evidence of fatty accumulation in the liver.
In over 55% of these patients, the degree of accumulation would be considered moderate or severe.
Those at risk
Fatty liver, if left untreated, can progress to cirrhosis, where irreversible scarring of the liver occurs. In a survey done in Malaysia on individuals aged 18 and above, it was found that the prevalence of individuals with high cholesterol levels is 20.7%. This means that more than three million individuals in our country have cholesterol levels in the high range. These people are at risk of developing NAFLD.
The risk factors and settings for NAFLD in Asian populations resemble that of their Western counterparts in aspects such as the age at which they present with the condition and the prevalence of diabetes. The increasing number of diabetic cases puts a very large population at risk of developing NAFLD.
It may be the right time for individuals with diabetes, hyperlipidaemia, or fatty liver to look beyond each of these conditions per se and understand that somehow or other, there is an association between them.
It is imperative for us to manage each condition appropriately before they become more severe and further complications arise.
References:
1. Adams, L.A. Endocrine Research. 2007.
2. Falck-Ytter Y, Thiruppathi S, Dasarathy S, Rogers N, McCollough AJ. Hepatology. 2006.
3. Fan, J. et al. Journal of Gastroenterology and Hepatology. 2007.
4. Michel Mendler. Fatty Liver: Nonalcoholic Fatty Liver Disease (NAFLD) and Nonalcoholic Steatohepatitis (NASH). Available at http://www.medicinenet.com/fatty _liver/page5.htm. Accessed June 2009.
5. Assy, N. et al. Digestive Diseases and Sciences. 2000.
6. Amarapurakar, D.N. et al. Journal of Gastroenterology and Hepatology. 2007.
7. Ministry of Health. Hypertension & Hypercholesterolemia. The Third National Health and Morbidity Survey 2006. Malaysia.
This article is courtesy of sanofi-aventis. The information provided is for educational purposes only and should not be considered as medical advice. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this column. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.
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