The most significant pressures the liver has to deal with come from man-made chemicals such as petrol, preservatives, pollutants, pesticides, cigarette smoke, recreational drugs and medication. Almost everything we eat, breathe in or put into our body has to be detoxified by the liver.
The liver has various ways of ways of dealing with toxins, such as breaking them down into safer substances, eliminating them through bile or repackaging them into a safer form. As a last resort the liver will even store toxins itself to protect the rest of the body.
The liver filters toxins through the sinusoid channels, which are lined with immune cells called Kupffer cells. These engulf the toxin, digest it and excrete it. This process is called phagocytosis.
As most chemicals are relatively new it will be thousands of years before our body properly adapts to them. If the liver cannot figure out what to do with them it simply stores them, often in fat tissue. This is process is potentially damaging to the fabric of the liver.
The liver regulates the balance of sex hormones, thyroid hormones, cortisone and other adrenal hormones. It transforms or removes excess hormones from the body. If the liver cannot do this properly there is the risk of emotional imbalances. The levels of white blood cells and antibodies may also decline, compromising immunity and making us more prone to infection.
These kinds of hormonal imbalance are fairly common in chronic liver disease.
a) Sexual desire and function
Sexual desire depends upon a delicate balance of hormones. If this balance is upset by the hepatitis C virus (HCV) infection then both men and women can suffer loss of libido. Men can develop increased oestrogen levels that may affect sexual function. Women may suffer erratic hormone levels that cause severe PMT-type symptoms.
The fatigue that viral infections can cause may also make some people too tired to be interested in sex which can also lead to frustration and darker moods.
The various pressures of modern life can lead to excessive production of the stress hormone adrenaline. The liver is responsible for balancing and getting rid of adrenaline. If it cannot keep up with the levels of stress hormones being produced, it is forced to store them, often for up to a year. The presence of this stored adrenaline in the liver may lead to emotional instability as well as impairing the immune system and affecting the body’s ability to fight the virus. This means learning to identify and manage stress effectively is vital. See page on stress.
Lymph is a colourless fluid that circulates around the body in a network of channels. These channels are punctuated with lymph nodes where immune cells neutralise bacteria and pathogens. This is called the lymphatic system, and it is a vital part of the body’s immune system.
Lymph also carries proteins, sodium, potassium and other minerals around the body.
About a third of the lymph that the body requires is produced in the liver. Lymph made in the liver drains into the abdomen and the lymph channels. Although the liver itself does not have lymph nodes, HCV can infect the lymphatic system causing swelling of the lymph nodes.
The liver acts as a storage site for some vitamins, minerals and glucose. These provide a vital source of energy for the body which the liver transforms into glycogen for more efficient storage (see ‘metabolism’ below). The liver stores vitamins and minerals for the times when they may be lacking in the diet. It can store enough vitamin A and vitamin B12 for four years and enough vitamin D for 4 months.
Vitamins are a group of organic compounds that act as catalysts in various chemical reactions. The vitamins trigger these reactions and speed them up. A compound becomes classified as a ‘vitamin’ when a deficiency of it causes disease. Contrary to popular belief vitamins do not directly provide energy.
As catalysts they are required for the release of energy from protein, fat and carbohydrates. They are essential for normal growth and development and particularly important for the healthy functioning of red blood cells, hormones, genetic materials and the nervous system.
The liver stores vitamin A, D, E, K and B12. The first four of these are all fat soluble. This means that the bile secreted during digestion is essential for absorbing them so that the body can use them. If bile production is compromised by liver damage the proper absorption of these vitamins may be affected.
When taking multivitamins it is important to make sure the recommended doses of fat soluble vitamins are not exceeded. If this occurs it might result in liver damage.
The liver also stores iron and copper. Copper is essential as a vital link in many of the body’s different chemical reactions and in the formation of proteins within the liver. It also plays a role in using up the body’s iron stores, whenever they are needed.
The liver and metabolism
The word metabolism comes from the Greek work ‘metabole’ which means ‘to change’. In relation to the liver it refers to the processing of food digested by the stomach and intestine for its many uses by the body.
We derive our energy and build our cells and tissues using the energy given off from the breakdown of three major classes of nutrients. These are carbohydrates (simple and complex sugar), lipids (various fats and oils) and proteins (large molecules found in plant and animal tissues made up of amino acids). This process is called metabolism. The liver plays an essential role in the breaking down of all of these types of nutrients and converting them into substances essential to the body.
Glucose or blood sugar is made when carbohydrates are broken down. It is an essential energy source for all cells. Although we often eat at irregular intervals the energy supplied to the body’s cells remains constant. The liver plays a crucial role in this process. If more glucose is absorbed than the body needs at that moment the excess is turned into a substance called glycogen. This is then taken up by the liver for easier storage.
When blood concentrations of glucose begin to drop and the body needs to generate more energy and heat, the liver converts the glycogen back into glucose. It is then released back into the blood for transport to all other tissues.
The liver’s glycogen stores are limited. But when the supply of glycogen begins to run out the liver cells begin to produce glucose out of amino acids and other carbohydrates.
If the synthesis and storage of glucose is reduced by liver damage the blood sugar levels may be affected. This can lead to insufficient amounts of energy reaching the muscles and the brain. This can then result in fatigue, a general sense of feeling unwell or slowed thinking and memory recall.
Fats or lipids are broken down in the liver for use as energy. They are then moved to fat tissue. More than 90% of body energy is stored here and is the main source of fuel storage for the body.
Fats are insoluble in blood and water and so the liver produces special, fat-carrying proteins called lipoproteins. These lipoproteins circulate in the blood carrying essential fatty acids between the liver and body tissues.
The liver stores very little fat for its own use. Chronic hepatitis C can lead to an accumulation of fatty deposits in the liver. This condition is called ‘steatosis.’ It is thought to be linked to increased fibrosis progression and advanced liver damage. It can also cause a decreased response to treatment for hepatitis C.
The lipoproteins also transport cholesterol. Although cholesterol has a certain ‘unhealthy’ reputation, it is still essential for the correct functioning of the body. It is used to make bile salts, to synthesize vitamin D, to make sex hormones, to make other hormones for the immune system and in dealing with stress. Cholesterol is also vital for the health of nerve cells and for the brain.
Cholesterol only becomes a problem when it builds up in the body in places it should not be. A healthy liver ensures that it is transported to tissues where it is needed and away from the tissues where it is not needed and may cause damage.
If the liver is not functioning properly or is over burdened by cholesterol, fatty deposits containing cholesterol build up in the lining of arteries. These deposits can cause an obstruction to the blood flow and can also lead to heart attacks. They can also lead to a build up of cholesterol in bile which can result in the formation of gallstones.
The liver is one of the most important organs for making proteins. It produces or transforms millions of protein molecules a day. Proteins are made from amino acids. Some of these amino acids are already in the body. Others, called the essential amino acids, can only be obtained from our diet.
Proteins have many vital functions. We use them for the growth and maintenance of body tissues such as muscles, the heart, kidneys and blood vessels walls. The liver makes hundreds of different proteins with different functions. Some transport vitamins and minerals around the body. Some act as catalysts to speed up metabolic reactions (these proteins are called enzymes). While others regulate the overall pattern of all the different activities within a cell.
Protein synthesis affected by HCV
Albuminis usually present in high quantities in the blood. It is used to bind hormones, certain chemicals and drugs. Albumin also regulates the exchange of water between blood and tissues. If the concentration of water in the body fluids is not the same as that of the cells, there is a risk that fluid will burst out of the cells. During our lives the liver constantly monitors the pressure level to ensure this is balanced. If the liver cannot synthesize enough albumin a build up of fluid in the tissues may occur. This is usually a symptom associated with decompensated cirrhosis where fluid may build up in the ankles, the feet or the legs (Oedema) or in the abdomen (Ascites).
The liver stores and releases it around the body as and when it is needed. On its own iron is toxic to the body’s cells so the body attaches it to a protein. In the liver iron is bound to the protein ferritin.
When liver disease is related to an increase in the amounts of ferritin in the liver it may cause damage to the tissues and organs. This is called haemochromatosis.
Iron is also essential for making haemoglobin. This helps to transport the oxygen in the bloodstream. If there is not enough iron to make haemoglobin this may lead to lethargy and anaemia.
Ammonia is a toxic substance derived from the metabolism of proteins. The liver converts ammonia to urea, which is water-soluble, non-toxic and excreted by the kidneys. Liver dysfunction in decompensated cirrhosis can lead to an inability to convert this ammonia, which then builds up in the blood.