Aspartate Aminotransferase (AST)

Overview

Aspartate aminotransferase (AST), also known as aspartate transaminase, is an enzyme found in various tissues throughout the body, including the liver, heart, skeletal muscle, kidneys, brain, and red blood cells^[1]. It plays a crucial role in amino acid metabolism by facilitating the transfer of amino groups between aspartate and glutamate^[1]. AST levels are commonly measured to assess liver health and detect tissue damage in other organs. Elevated AST levels can indicate conditions such as liver disease, myocardial infarction, or muscle damage^[2].

Scientific Background

AST catalyzes the reversible reaction between aspartate and α-ketoglutarate to form oxaloacetate and glutamate, relying on pyridoxal phosphate (PLP) as a cofactor^[1]. This enzyme is essential for both amino acid degradation and biosynthesis. In the liver, AST is involved in the citric acid cycle and urea production pathways^[1]. AST is structurally similar across different species, consisting of two identical subunits with a molecular weight of approximately 45 kD^[1]. Its activity is often compared with alanine transaminase (ALT) to determine the source of tissue damage, as ALT is more liver-specific^[3].

Measurement and Testing

AST levels are typically measured through a blood test, often as part of a liver panel or comprehensive metabolic panel^[5]. The test is used to detect liver damage, monitor liver disease treatment, and assess the effects of medications on the liver^[4]. Factors affecting AST results include recent muscle injury, alcohol consumption, and certain medications^[2]. Testing is recommended when symptoms of liver disease are present or when monitoring the efficacy of treatments^[4].

Reference Ranges

Standard reference ranges for AST vary slightly by laboratory but generally fall between 8-40 IU/L for males and 6-34 IU/L for females^[1]. These ranges can vary based on age, sex, and the specific laboratory conducting the test^[1]. Interpreting AST levels requires considering these demographic factors and comparing them with ALT levels to assess liver health^[3].

High Values

Elevated AST levels can result from liver damage (e.g., hepatitis), heart conditions (e.g., myocardial infarction), muscle injuries, or other organ damage^[2]. High AST levels are associated with increased risk of liver disease, cardiovascular events, and muscle disorders^[3]. Symptoms may include jaundice, fatigue, and abdominal pain in cases of liver damage^[4].

Low Values

Low AST levels are generally not considered clinically significant unless they are part of a broader pattern of abnormal liver enzyme levels^[3]. However, certain conditions like vitamin B6 deficiency can affect AST activity, as AST relies on pyridoxal phosphate as a cofactor^[1]. Low levels might not directly correlate with specific health risks but could indicate underlying metabolic issues^[1].

Improving Biomarker Levels

Improving AST levels involves addressing the underlying cause of elevation, such as treating liver disease or avoiding alcohol consumption^[3]. Lifestyle modifications include maintaining a healthy diet, exercising regularly, and managing stress^[4]. Vitamin B6 supplements may be beneficial if deficiency is suspected, but this should be done under medical supervision^[1].

Importance of Tracking

Monitoring AST levels is crucial for diagnosing and managing liver diseases, as well as assessing damage to other organs^[5]. Regular tracking helps healthcare providers make informed decisions about treatment efficacy and potential risks associated with elevated levels^[4]. It is essential for early detection and intervention in conditions like liver disease or myocardial infarction^[2].

Disclaimer

The information provided in this document is for educational purposes only and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.