Sleep apnea, a phenomenon characterized by transient interruption of breathing, not only leads to tiredness, headaches, lack of concentration and irritability. One study shows that this phenomenon is also related to the development and progression of the fatty liver, a disease that can cause chronic liver damage and in some cases, cancer.
The research led by Marco Arrese, deputy director of the CARE Chile UC Center for Aging and Regeneration and Doctoral Student in Medical Sciences Alejandra Hernández has been developed through research in in vitro models and animals. Thus, it was observed that the presence of sleep apnea is an aggravating liver disease that can condition a progression to more advanced states of it.
“In our experiments, we have explored the effects of intermittent hypoxia, a basic pathophysiological phenomenon that occurs in patients with sleep apnea and those who, when they sleep, suffer from abrupt airway occlusion, which determines the stopping of breathing for short periods,” says the hepatologist.
“This marked, rapid and transient decrease in oxygen saturation affects many tissues and especially the liver. This is of particular relevance if the liver is fatty, because it can exacerbate inflammation in this organ and can promote the generation of liver fibrosis, mechanism that determines the progression of this disease,” he adds.
Silent disease
Fatty liver is a generally asymptomatic and silent pathology, associated with overweight and obesity, characterized by an abnormal accumulation of fat in this organ, which can develop to liver fibrosis, cirrhosis and sometimes carcinoma Hepatocellular.
According to CARE figures, the disease affects 30% of Chileans. This can be aggravated by patients who generally increase the risk of diabetes, cardiovascular abnormalities and more serious liver conditions. “In addition, it is estimated that Chileans have more genetic characteristics that predispose liver diseases in general, and fatty liver disease in particular,” arrese says.
For these reasons it is crucial for the specialist to understand the mechanisms related to the onset and increase of this disease, which should also be detected and controlled early. This, in order to reverse its harmful effects.
Experiments
To delve into this phenomenon, for more than two years the doctor and his CARE team studied human and mouse liver cells, mimicking hypoxia through the use of cobalt chloride. At the level of experimentation, this chemical allows to reproduce the same phenomenon that occurred during sleep apnea.
“We observed that hypoxia induces stress in the liver cell and generates the production of inflammatory signals in liver tissue. This, through processes of conversation between each other cells. This is also discussed in animals that we subject to intermittent hypoxia phenomena. In them, we have seen that the transient reduction of oxygen concentration in the environment, increases inflammation induced by the fatty liver and promotes the generation of liver fibrosis, causing the damage at the level of this organ to progress,” he says.
Alongside preclinical studies, which are expected to be published in an international journal soon, scientists began a second phase of research with patients with sleep apnea, a group they are recruiting at this time. The intention is to be able to work in partnership with the Center of Sleep Medicine of the Catholic University and thus carry out different metabolic and liver tests that allow to characterize this population and analyze in depth what they have explored in other models.
“We are very optimistic, as this work with patients would be the first study of the type in all of Latin America. We find it relevant to continue to make progress in this area, with the intention also that specialist doctors who detect sleep apnea can expand their medical checkup at the liver level,” says Arrese.
Fatty liver
Weighing more than 1500 grams, the liver is the second largest organ in the body after the skin: it measures 10 cm and has a volume similar to that of a football. Its functions are multiple encompassing processes of metabolism and debugging of compounds. However, when the percentage of fat cells in the liver exceeds 5%, the condition called steatosis or fatty liver appears, in which case the organ increases its size, changes that in turn can begin to damage the liver.
Dr. Arrese explains that after this phenomenon, the body develops an inflammatory defense mechanism, in which liver cells are damaged. Then, with the progression of the disease, the liver initiates a repair process in which a healing tissue called fibrosis appears, which contributes to the progressive deterioration of this organ.
“Fibrosis is classified into four stages: mild, moderate and severe, which can be stopped and even reversed. But if it expands to most of the liver, we reach stage 4, cirrhosis, which, in its most advanced phases, may not be reversible. This is where there is also a risk of cancer developing,” says the CARE researcher.
