In recent years, Anhua dark Tea and its active components have been proven to be effective in improving hyperuricemia by inhibiting key enzymes involved in uric acid regulation in the body and modulating the expression of uric acid transport proteins. This article systematically discusses the uric acid lowering effect and mechanism of Anhua dark tea, aiming to provide a theoretical basis for scientifically regulating uric acid levels through tea consumption and to offer research ideas for the development of functional tea products that lower uric acid.
1. What is Hyperuricemia?
Hyperuricemia (HUA) is a condition where an excessive amount of uric acid is produced or too little is excreted by the kidneys, leading to a supersaturated state of urate in the extracellular fluid and causing elevated uric acid levels in the blood. It is closely related to cardiovascular diseases and organ damage. Hyperuricemia can be diagnosed when fasting serum uric acid levels are above 420 μmol/L on two separate occasions.
It is reported that there are approximately 177 million people with hyperuricemia in China, primarily affecting middle-aged and elderly men and postmenopausal women, with a trend toward younger individuals in recent years.
1.1 Hyperuricemia and Its Causes
Hyperuricemia can be classified into primary and secondary types. Primary hyperuricemia, also known as gout, refers to high uric acid levels caused by congenital purine metabolism disorders and impaired uric acid excretion, after excluding other diseases. Secondary hyperuricemia is due to reduced uric acid excretion caused by kidney disease or certain medications, increased uric acid production from bone marrow hyperplasia diseases and tumor chemotherapy.
1.2 Main Harms of Hyperuricemia
Epidemiological and clinical studies have found that hyperuricemia is closely related to a series of cardiovascular diseases such as coronary heart disease, Hypertension, heart failure, stroke, and atherosclerosis, and it can cause harm to organs and tissues such as the liver, kidneys, and joints in the human body.
2. The Uric Acid Lowering Effect and Mechanism of Anhua Dark Tea
2.1 The Uric Acid Lowering Effect of Anhua Dark Tea Anhua dark tea is a unique microbially fermented tea in China. During processing, microbial Fermentation produces active components in dark tea that differ from those in other tea categories. In vitro experiments have shown that Anhua dark teas like Fu brick tea, Tianjian tea, and Qianliang tea can reduce blood uric acid levels in mice with hyperuricemia induced by potassium oxonate.
The fungus Eurotium cristatum, commonly known as “Golden Flowers,” is the dominant strain during the fermentation process of Fu brick tea and plays a unique role in the uric acid lowering effect of Anhua dark tea. Studies have shown that Green Tea, Black Tea, and red brick tea fermented with Eurotium cristatum can reduce uric acid levels in mice with hyperuricemia induced by potassium oxonate, and the uric acid lowering effect is significantly enhanced after flowering. Theaflavins, thearubigins, and theabrownins formed by the oxidation and polymerization of polyphenols during the fermentation of Anhua dark tea have also been reported to have uric acid lowering effects.
2.2 The Uric Acid Lowering Mechanism of Anhua Dark Tea
Adenosine deaminase (ADA) and xanthine oxidase (XOD) are two key enzymes in purine metabolism that produce uric acid. ADA is a thiol enzyme that catalyzes the conversion of deoxyadenosine or adenosine to hypoxanthine, which is then converted to uric acid via XOD. XOD is the final key enzyme in uric acid metabolism, catalyzing the conversion of hypoxanthine to xanthine and then to uric acid. Water extracts of Anhua dark tea can inhibit the activity of ADA and XOD in the livers of mice, reducing the concentration of uric acid in mice with hyperuricemia. This suggests that Anhua dark tea can improve hyperuricemia by inhibiting the activity of enzymes related to uric acid generation, thus reducing the metabolic production of uric acid in the body. Multiple in vitro experiments have also proven that theaflavins, theabrownins, and green and black teas fermented with Eurotium cristatum can inhibit enzyme activity and thereby exhibit a uric acid lowering effect.
The main reason for the onset of gout is generally considered to be the intake of foods high in purines, but impaired renal excretion of uric acid is also one of the primary causes. Excessive production of uric acid in the body is not the main cause of gout; nearly 90% of uric acid is reabsorbed by the kidneys and then returned to the blood. Several transport proteins have been found to be involved in the renal reabsorption process of uric acid. Among them, urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) play a critical role, and their expression levels directly affect serum uric acid levels. Studies have shown that Anhua dark tea can significantly downregulate the mRNA and protein expression levels of uric acid reabsorption proteins URAT1 and GLUT9. Additionally, organic cation transporter 1 (OCT1), a member of the uric acid secretion protein family, is a transporter involved in the re-secretion process of uric acid and can promote the excretion of uric acid into urine. The expression level of OCT1 is directly related to kidney injury. After modeling, the mRNA and protein expression levels of OCT1 in mice were significantly downregulated, indicating a certain degree of kidney damage. Research has found that Anhua dark tea does not significantly affect the mRNA and protein expression levels of OCT1. This indicates that Anhua dark tea can promote uric acid excretion by inhibiting the reabsorption of uric acid in the kidneys.
3. Outlook
The uric acid lowering effect of Anhua dark tea and its functional components holds broad application and development prospects, but there are still many challenges:
1. The uric acid lowering effects of some specific functional components in Anhua dark tea are not yet clear.
2. Studies on the mechanisms of the uric acid lowering effect of Anhua dark tea are not comprehensive enough.
3. The pathways and targets of action of uric acid lowering active components in the body are unclear.
4. The mechanism of how uric acid lowering active components interact with uric acid in the intestine is unknown.
5. It is unclear whether gut microbiota affects uric acid metabolism.
In future research, focus should be placed on studying the uric acid lowering effects of various Anhua dark teas and specific functional components of Anhua dark tea. Furthermore, the effective components and mechanisms of the uric acid lowering effect of Anhua dark tea need to be further clarified.
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