Pyrroloquinoline quinone (PPQ), a redox cofactor in bacterial dehydrogenase, is also an antioxidant. It can avoid cell damage caused by intracellular oxidation reactions and reactive oxygen produced by in vitro bioactive substances, provide nutrition and vitamins for cell growth and development, and make cells have antioxidant tolerance. It acts as a biological control agent for plant pathogenic fungi and can induce protein kinase to participate in the differentiation and development of mammalian cells. PQQ can increase crop yields by increasing the utilization rate of insoluble phosphates. It has a strong correlation with the redox cycle function and has anti-neurodegeneration, anti-cancer, signal transduction and other functions. As an important bioactive molecule, pyrroloquinoline quinone has attracted the attention of the scientific community due to its unique chemical structure and wide range of biological functions. In recent years, it has become one of the widely-watched "star" nutrients. It has a powerful effect on brain health, cardiovascular health, metabolic function health, etc. Because the human body cannot synthesize PQQ by itself, it needs to be supplemented through dietary supplements.
Biological functions of PPQ
1. PQQ has antioxidant and pro-oxidant effects
PPQ exhibits strong antioxidant capacity, which makes it potential in the prevention and treatment of oxidative stress-related diseases. Studies have found that PPQ can effectively neutralize free radicals and slow down the aging process and the development of related diseases.
The oxides produced by the reaction of quinone compounds with reactive oxygen species (ROS) can form compounds with glutathione, consume free glutathione, reduce the tolerance of cells to oxidative stress, and cause a large amount of protein oxidation, which eventually leads to cell death. PQQ is similar to quinone antioxidants, and its effect depends on concentration. Below 10 μmol/L concentration, PQQ mainly acts as an antioxidant. Above 50 μmol/L, it acts as a pro-oxidant. PQQ is an electrophilic compound with 5 sites that can react with carbonyl groups to form stable compounds, and can react with ammonia to produce iminoquinone, about 41 mmol/kD, with a pH value between 9.1 and 11.86. These characteristics indicate that PQQ has the ability to regulate redox sites in the oxidation N-methyl-D-aspartic acid (NMDA) receptor, so it has the effect of resisting NMDA and glutamate-mediated neuronal cell damage. PQQ can change the intracellular redox state and selectively cause a large number of killing effects on human histiocytic lymphoma cells U937. When PQQ induces apoptosis of lymphoma cells U937, the amount of acetylcysteine (NAC) and glutathione in the cells increases by 2 to 5 times, proving that the cytotoxic effect mediated by PQQ exceeds its redox regulation effect. On the one hand, PQQ consumes glutathione in cells, and on the other hand, it amplifies the cytotoxicity several times, converting the induction mode of PQQ from apoptosis mode to cell necrosis mode, proving that PQQ can not only play an oxidative role, accelerate the death process of necrotic cells, but also accelerate cell apoptosis to cope with oxidative stress. Whether in terms of redox regulation, oxidative stress response, or as a signal molecule to promote neuronal growth, PQQ is of considerable significance in neuroprotection.
2. PQQ can effectively improve brain function
In February 2023, Japanese researchers published a research paper titled "Pyrroloquinoline quinone disodium salt improves brain function in both younger and older adults" in the journal Food & Function, introducing the research results of PQQ on the cognitive improvement of young and elderly people in Japan.
The results showed that after 12 weeks of PQQ intake, the composite memory and verbal memory scores of all people and the elderly increased compared with the placebo control group; after 8 weeks of PQQ intake, the cognitive flexibility, processing speed and execution speed scores of the young population increased.PQQ can not only improve the brain function of the elderly, but also improve the brain responsiveness of young people.
3. PQQ has a protective function for nerve cells
By studying whether the intercellular mitochondrial donor capacity and the therapeutic effect of mesenchymal stem cells (MSC) in obese subjects (metabolic disorder population) are impaired, and whether mitochondrial targeted therapy can be reversed, it was found that PQQ regulation can restore mitochondrial health to alleviate mitochondrial autophagy damage. Compared with the drug metoprolol, it is more effective in protecting mitochondria and oxidative damage caused by ischemia-reperfusion.
PQQ has a neuroprotective effect and can effectively avoid oxidative stress-induced neuronal death. PPQ can promote the growth and repair of nerve cells and may have a protective effect on neurodegenerative diseases such as Alzheimer's disease. PQQ can reduce PC12 cell toxicity induced by methylmercury, spinal cord neurotoxicity mediated by NMDA receptors, and neurotoxicity caused by β-amyloid aggregation (a key factor in the pathogenesis of Alzheimer's disease). PQQ can significantly reverse the decrease in Bax/Bcl-2 values caused by β-amyloid aggregation and inhibit the cleavage of Caspase-3.
4. PQQ can improve human metabolic function
PPQ also regulates cell metabolism, affects energy metabolism and the conversion of metabolites, and has a regulatory effect on metabolic diseases such as diabetes. In May 2023, a review article entitled "Pyrroloquinoline-quinone to reduce fat accumulation and ameliorate obesity progression" was published in the journal Front Mol Biosci, summarizing relevant studies. PQQ reduces fat accumulation by inhibiting fatty acid synthesis (lipogenesis) and improving mitochondrial function. The results show that PQQ can reduce body fat, especially visceral and liver fat accumulation, thereby preventing dietary obesity.
Application areas of PPQ
1. Medical field
PPQ has great potential for drug development. Researchers are exploring its application in the treatment of diseases such as Alzheimer's disease, diabetes, and cardiovascular disease. For example, PPQ has been used to develop new antibacterial and antiviral drugs.
2. Nutritional supplements
The market potential of PPQ as a nutritional supplement is growing. Many health products and functional foods are added with PPQ to take advantage of its antioxidant and health-promoting effects. Its market demand is rising and is expected to become an important part of future health supplements.
3. Biotechnology
In biotechnology, PPQ is used as a cofactor of enzymes to enhance catalytic activity. It is also used as a biomarker to detect oxidative stress levels. It has shown important applications in improving the efficiency of biological reactions and monitoring biological states (reference: J. H. Lee et al., *Journal of Biotechnology*, 2024).
Future prospects and conclusions about PPQ
Although PPQ has shown great application potential, there are still many unknowns to be further studied. Future research will focus on revealing its mechanism of action, optimizing application methods, and evaluating long-term safety. With the development of science and technology, the application field of PPQ is expected to expand further, providing more health and treatment solutions.
In addition to the above studies proving the key role and unlimited potential of PQQ as a dietary supplement to improve human health, previous studies have also continuously confirmed the powerful functions of PQQ. In fact, as a new dietary supplement, PQQ's positive role in nutrition and health has been recognized. Due to its powerful functions, high safety and good stability, it has broad development prospects in the field of functional foods. In recent years, with the continuous deepening of cognition, PQQ has achieved the most comprehensive efficacy certification and is widely used as a dietary supplement or food in the United States, Europe and other countries and regions. With the continuous deepening of domestic consumer awareness, it is believed that PQQ will create a new world in the relevant market as a new food raw material.