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Cirrhosis is a chronic liver disease that can lead to muscle wasting or sarcopenia. This condition is characterized by a progressive and generalized loss of muscle mass, which has a detrimental impact on patient survival and quality of life. Muscle wasting is observed in approximately 40% of patients with cirrhosis, and its prevalence increases with disease severity. While the exact mechanisms behind sarcopenia are not fully understood, it is believed to be related to metabolic starvation, hormonal dysfunction, defective ureagenesis, and chronic inflammation. Nutritional interventions and exercise may help improve muscle wasting, but more research is needed to understand the effectiveness of these approaches in cirrhotic patients.
| Characteristics | Values |
|---|---|
| Definition | Muscle wasting is defined as the progressive and generalized loss of muscle mass |
| Prevalence | Muscle depletion is found in approximately 40% of patients with cirrhosis |
| Diagnosis | CT and MRI scans are the gold standards for research purposes; there is no widely accepted method to quantify muscle wasting |
| Risk Factors | Dietary restrictions, decreased taste sensation, decreased appetite, nausea, early satiety, intestinal bacterial overgrowth, malnutrition, hormonal dysfunction, defective ureagenesis, chronic inflammation, metabolic starvation disorder, anabolic resistance, hyperammonemia, endotoxemia, cytokines, altered circulating hormones |
| Complications | Sarcopenia, decreased survival, lower quality of life, increased risk of other complications, worse post-liver transplant outcomes, sepsis |
| Treatment | Nutritional supplementation alone is ineffective; high doses of leucine and branched-chain amino acids, ammonia-lowering measures, exercise |
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What You'll Learn
Cirrhosis is a metabolic starvation disorder
Sarcopenia is the major component of malnutrition, which occurs in the majority of patients with liver disease. It is associated with lower muscle contractile function and a decreased quality of life. Sarcopenia increases mortality, the risk of developing other complications of cirrhosis, and worsens post-liver transplant outcomes.
The mechanisms behind sarcopenia are not fully understood, but it is believed to be related to cirrhosis being a state of anabolic resistance. This means that standard replacement of nutrients is generally ineffective. Potential reasons for this include molecular and metabolic perturbations that result in lower protein synthesis and increased autophagic proteolysis. To overcome anabolic resistance, strategies that have been beneficial include shortening the postabsorptive or fasting state by avoiding fasting-induced proteolysis and lipolysis. This can be achieved through frequent feeding and late-evening snacks.
There are no effective therapies to prevent or reverse sarcopenia in liver disease. However, nutritional supplementation with high doses of leucine and potentially other branched-chain amino acids, as well as long-term ammonia-lowering measures, may be beneficial. Hyperammonemia, or elevated ammonia levels, is the best-studied mediator of the liver-muscle axis. Other causal factors include endotoxemia, cytokines, and altered circulating hormones.
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Cirrhosis is a state of anabolic resistance
Cirrhosis, or liver cirrhosis, is a chronic condition of the liver where normal functioning tissue, or parenchyma, is replaced with scar tissue (fibrosis) and regenerative nodules as a result of chronic liver disease. This condition affects the liver's ability to function properly, including its role in metabolism and blood flow. The disease typically develops slowly, and symptoms may take a long time to emerge. Early symptoms include tiredness, weakness, loss of appetite, weight loss, and nausea.
Muscle wasting, a progressive and generalized loss of muscle mass, is a common feature of cirrhosis, found in approximately 40% of patients. This muscle depletion is multifactorial and is associated with malnutrition, which is a common feature of cirrhosis. Malnutrition in cirrhotic patients can be caused by reduced nutrient intake due to dietary restrictions, decreased taste sensation, and decreased appetite. It can also be caused by reduced intestinal absorption due to drug-related diarrhea or intestinal bacterial overgrowth.
The loss of muscle mass in cirrhosis has detrimental effects on survival. Studies have shown that decreased muscle size is an independent predictor of mortality in cirrhosis. This loss of muscle mass is termed sarcopenia, which was coined in 1988 to describe the loss of skeletal muscle mass and function. Sarcopenia contributes to adverse outcomes, including increased mortality and decreased quality of life.
While the exact mechanisms are not fully understood, it is known that hyperammonemia, or increased ammonia levels in the skeletal muscle, plays a role in cirrhosis-related anabolic resistance. This leads to signaling perturbations, mitochondrial dysfunction, modifications of contractile proteins, and impaired ribosomal function, all of which contribute to impaired responses to anabolic stimuli.
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Nutritional interventions may improve muscle wasting
Malnutrition is a common feature of cirrhosis, and it is associated with muscle depletion. Muscle wasting can be assessed using computed tomography (CT) scans or magnetic resonance imaging (MRI). These techniques can accurately distinguish between fat and other soft tissues and provide quantitative measurements of skeletal muscle size. However, they are costly and expose patients to radiation, limiting their use in routine clinical practice.
To address sarcopenia, targeted interventions with sufficient macronutrient and micronutrient support, such as Vitamin D and balanced amino acid intake, are recommended. The European Association for the Study of the Liver (EASL) suggests a protein intake of 1.2–1.5 g/kg/day and an energy consumption of 30–35 kcal/kg/day. High-calorie and high-protein diets, combined with BCAA-enriched evening snacks, can help mitigate the muscle-wasting effects of fasting and maintain nitrogen balance.
Additionally, it is essential to manage underlying medical conditions, boost macronutrient intake, consider micronutrient intake, and treat other systems to maximize nutrition and improve muscle mass. Patients should undergo multidisciplinary team management, including their primary care provider, gastroenterologist/hepatologist, registered dietician, and certified exercise physiologist/physical therapist.
Furthermore, disease-specific interventions can be implemented. For example, treating inflammatory conditions causing cirrhosis, such as curing HCV and alcohol cessation through behavioural and pharmacotherapies, can improve overall health and nutrition. Addressing specific complications of cirrhosis, such as ascites and portal hypertension, may also positively impact nutrition and muscle wasting.
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Hyperammonemia is a pathogenic agent in muscle wasting
Cirrhosis is a chronic liver disease that affects approximately 40% of patients and is a risk factor for muscle wasting. Muscle wasting, defined as the progressive and generalized loss of muscle mass, has detrimental effects on survival rates. Malnutrition, which is common in cirrhosis, is significantly associated with muscle depletion, although the two are distinct.
The liver-muscle axis is significantly impacted by hyperammonemia, which is the best-studied mediator of this axis in the context of muscle wasting. Hyperammonemia causes increased ammonia uptake by the skeletal muscle, leading to elevated muscle ammonia concentrations. This imbalance in skeletal muscle protein metabolism results in impaired muscle protein synthesis and increased muscle autophagy, contributing to muscle loss in liver disease. Additionally, ammonia may activate p65-NF-kB, leading to increased expression of myostatin, which inhibits protein synthesis and activates proteolysis.
The treatment of hyperammonemia involves reducing ammonia production and increasing its removal. This is achieved by lowering protein intake while maintaining caloric intake, administering enteral lactulose, and, in cases of coma, monitoring intracranial pressure. Long-term ammonia-lowering strategies and myostatin-blocking agents are also recommended.
While exercise is known to increase muscle mass and improve contractility in healthy individuals, its impact on cirrhosis patients is not well understood. Research by Dr. Srinivasan Dasarathy and colleagues focuses on understanding the mechanistic basis of exercise responses in patients with chronic diseases, including cirrhosis.
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Muscle wasting is an independent predictor of mortality in cirrhosis
Cirrhosis is a state of anabolic resistance. It is a consequence of various causes, including obesity, non-alcoholic fatty liver disease, high alcohol consumption, hepatitis B or C infection, autoimmune diseases, cholestatic diseases, and iron or copper overload. The disease evolves from an asymptomatic phase (compensated cirrhosis) to a symptomatic phase (decompensated cirrhosis). Progressive portal hypertension, systemic inflammation, and liver failure drive disease outcomes. The management of liver cirrhosis is centred on the treatment of the causes and complications, and liver transplantation may be required in some cases.
Muscle wasting, defined as the progressive and generalized loss of muscle mass, is a common feature of chronic liver disease found in approximately 40% of patients with cirrhosis. Its prevalence increases with disease severity. Several mechanisms contribute to muscle wasting in liver cirrhosis, including reduced nutrient intake due to dietary restrictions, decreased taste sensation, and nausea. In addition, reduced intestinal absorption due to pancreatic insufficiency, drug-related diarrhea, or intestinal bacterial overgrowth can also lead to muscle wasting.
Cross-sectional analytic morphometry using computed tomography (CT) scan or magnetic resonance imaging (MRI) are considered the gold standards for assessing muscle size in cirrhosis for research purposes. These techniques can accurately distinguish between fat and other soft tissues and provide quantitative measurements of skeletal muscle size. However, they are not suitable for routine clinical practice due to their high cost and potential unavailability at some sites.
Several studies have found that muscle wasting is an independent predictor of mortality in patients with cirrhosis. The presence of sarcopenia, or low muscle mass, has been associated with increased risk of death in these patients. In a study of 112 patients with cirrhosis, 45 (40%) had sarcopenia, and the median survival time for sarcopenic individuals was significantly lower than for non-sarcopenic patients. Another study of 142 cirrhotic patients on the liver transplant waiting list found that sarcopenia was a predictive factor for overall waiting-list mortality.
The impact of nutritional interventions and exercise on muscle wasting and survival in cirrhosis is an area of ongoing research.
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Frequently asked questions
Cirrhosis is a chronic liver disease that is a risk factor for muscle wasting.
Muscle wasting, also known as sarcopenia, is the progressive and generalised loss of muscle mass.
The mechanisms behind sarcopenia are not fully understood, but it is believed that cirrhosis causes anabolic resistance, which leads to lower protein synthesis and increased autophagic proteolysis. Other factors include reduced nutrient intake due to dietary restrictions, hormonal dysfunction, and metabolic perturbations.
Muscle wasting has been found to have a detrimental impact on the survival of patients with cirrhosis, increasing mortality risk and decreasing quality of life. It also increases the risk of developing other complications and worsens post-liver transplant outcomes.
