Poria and Diuretic Mechanism
Eshed Haklai
Poria cocos has long been used in Traditional Chinese Medicine as a regulator of body fluids and a diuretic. Modern research suggests that it influences signaling pathways within the kidney. Understanding the underlying biochemical mechanisms is important, because it transforms a traditional claim from a theoretical concept into a therapeutically relevant effect that can be explained at the molecular level:
Does the mushroom alter how much water the kidney retains or excretes?
Does it protect kidney cells from cell loss?
And does it reduce fibrosis, which disrupts water-electrolyte balance?
Poria cocos and the Kidneys
The diuretic effect of Poria cocos has been examined in several studies.
In one study conducted on rats, the animals were first given a sodium solution and then treated with ethanolic and aqueous extracts of Poria. The results showed that rats receiving the alcoholic extract had an increased urine volume and increased sodium excretion.
Another study examined Poria extracts prepared using different solvents and found that all extracts increased urine output, with what the researchers described as a “smart excretion” effect: sodium excretion increased, while potassium excretion did not. Extracts from Poria mycelium were also studied and were found to have diuretic effects and to support sodium excretion.
The excretion of fluids and sodium in urine is a key regulatory mechanism in the body, among other things for blood pressure control, and is therefore physiologically significant. These studies provide scientific support for a long-standing claim in Traditional Chinese Medicine that Poria cocos promotes urination. To better understand the mechanism behind this effect, it is important to become familiar with a group of proteins known as AQPs.
Poria and AQP2:
In kidney cells involved in water reabsorption, proteins called aquaporins (AQP) can be found. There are four main types of aquaporins, but the most central among them is AQP2. These proteins are located in the cell membrane and function as water channels, allowing rapid and selective water transport. AQP2 plays a key role in the process of water reabsorption in the kidney. Changes in the amount or cellular localization of AQP2 significantly affect how much water the kidney returns to the body, and therefore have direct implications for blood pressure regulation, blood volume, and the development of edema.
In a study on collecting duct cells (the kidney region responsible for the final regulation of urine concentration and a primary target for hormones involved in fluid balance), Poria extract was shown to reduce the upregulation of AQP2. In other words, it reduced water reabsorption, leading to increased urine excretion. The extract also protected the cells from cell death under conditions of high extracellular salt concentration. Additionally, Poria extract was found to inhibit the enzyme SGK-1. This enzyme increases AQP2 activity, and its inhibition may represent one of the mechanisms through which Poria exerts its diuretic effect.
An additional proposed mechanism: the AVP-V2R axis
Another mechanism was proposed in a study on mice with heart failure.
Arginine vasopressin (AVP) is a hormone secreted from the posterior pituitary gland when the body senses a reduction in blood volume or an increase in blood osmolality. After its release, AVP binds to the V2 receptor (V2R) on collecting duct cells in the kidney. This binding triggers a cascade of intracellular events that ultimately cause AQP2 to move to the cell membrane, forming water channels that reabsorb water back into the bloodstream. This process is known as the AVP-V2R axis and serves as a key water-retention mechanism in the kidney. When this axis is inhibited, a diuretic effect occurs.
In this study, Poria extract suppressed this axis: lower levels of vasopressin were found in the blood, reduced expression of the V2 receptor was observed in the kidney, and AQP2 expression was decreased.
Summary
It is fascinating to see how traditional knowledge is confirmed by modern science. This article presents Poria cocos, a mushroom that has been described in Traditional Chinese Medicine for centuries as draining dampness and promoting urination. In recent decades, scientific research has begun to elucidate the mechanisms underlying these effects.
The key protein influencing urine volume is a water channel located in the membrane of kidney cells, which allows rapid water reabsorption into the body. This protein is AQP2. When AQP2 is active, urine volume decreases and blood volume increases.
Various Poria extracts have been shown to inhibit AQP2 through two proposed mechanisms:
Inhibition of the intracellular regulatory enzyme SGK-1, leading to reduced AQP2 activity.
Suppression of the AVP–V2R hormonal axis, which originates in the pituitary gland and serves to maintain adequate blood volume.
Further reading about Poria cocos can be found here.