Phosphatidylserine

Phosphatidylserine (abbreviated Ptd-L-Ser or PS) is a phospholipid and is a component of the cell membrane. It plays a key role in cell cycle signaling, specifically in relation to apoptosis. It is a key pathway for viruses to enter cells via apoptotic mimicry.
Structure.
Phosphatidylserine is a phospholipid—more specifically a glycerophospholipid—which consists of two fatty acids attached in ester linkage to the first and second carbon of glycerol and serine attached through a phosphodiester linkage to the third carbon of the glycerol.
Phosphatidylserine sourced from plants differs in fatty acid composition from that sourced from animals.
Introduction.
Phosphatidylserine (PS) is the major acidic phospholipid class that accounts for 13–15 % of the phospholipids in the human cerebral cortex [1]. In the plasma membrane, PS is localized exclusively in the cytoplasmic leaflet where it forms part of protein docking sites necessary for the activation of several key signaling pathways. These include the Akt, protein kinase C (PKC) and Raf-1 signaling that is known to stimulate neuronal survival, neurite growth, and synaptogenesis [2–7]. Modulation of the PS level in the plasma membrane of neurons has a significant impact on these signaling processes.
Biosynthesis.
Phosphatidylserine is biosynthesized in bacteria by condensing the amino acid serine with CDP (cytidine diphosphate)-activated phosphatidic acid. In mammals, phosphatidylserine is produced by base-exchange reactions with phosphatidylcholine and phosphatidylethanolamine. Conversely, phosphatidylserine can also give rise to phosphatidylethanolamine and phosphatidylcholine, although in animals the pathway to generate phosphatidylcholine from phosphatidylserine only operates in the liver.
Dietary sources.
The average daily phosphatidylserine intake in a Western diet is estimated to be 130mg. Phosphatidylserine may be found in meat and fish. Only small amounts are found in dairy products and vegetables, with the exception of white beans and soy lecithin. Phosphatidylserine is found in soy lecithin at about 3% of total phospholipids.
Table 1. Phosphatidylserine content in different foods.
Supplementation.
Health claims.
A panel of the European Food Safety Authority concluded that a cause and effect relationship cannot be established between the consumption of phosphatidylserine and “memory and cognitive functioning in the elderly”, “mental health/cognitive function” and “stress reduction and enhanced memory function”. This conclusion follows because bovine brain cortex- and soy-based phosphatidylserine are different substances and might, therefore, have different biological activities. Therefore, the results of studies using phosphatidylserine from different sources cannot be generalized.
Cognition.
In May, 2003 the Food and Drug Administration gave "qualified health claim" status to phosphatidylserine thus allowing labels to state "consumption of phosphatidylserine may reduce the risk of dementia and cognitive dysfunction in the elderly" along with the disclaimer "very limited and preliminary scientific research suggests that phosphatidylserine may reduce the risk of cognitive dysfunction in the elderly." According to the FDA, there is a lack of scientific agreement amongst qualified experts that a relationship exists between phosphatidylserine and cognitive function.
More recent reviews have suggested that the relationship may be more robust, though the mechanism remains unclear. A 2020 meta-analysis of relevant clinical trials found that phosphatidylserine is likely effective for enhancing cognitive function in older people with mild cognitive impairment. Some studies have suggested that whether the phosphatidylserine is plant- or animal-derived may have significance, with the FDA's statement applying specifically to soy-derived products.
Safety.
Initially, phosphatidylserine supplements were derived from bovine cortex. However, due to the risk of potential transfer of infectious diseases such as bovine spongiform encephalopathy (or "mad cow disease"), soy-derived supplements became an alternative. A 2002 safety report determined supplementation in elder people at a dosage of 200mg three times daily to be safe. Concerns about the safety of soy products persist, and some manufacturers of phosphatidylserine use sunflower lecithin instead of soy lecithin as a source of raw material production.
References.
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