If PQQ would offer these same sorts of benefits in human studies it would be a serious medical advance. Preliminary clinical studies are extremely encouraging and several larger clinical trials are currently either completed and waiting publication or are in process. In regards to improving cerebral function, while PQQ is somewhat effective on its own, when it is combined with another biological quinone (ubiquinone or coenzyme Q10) even better results may be noted. This synergistic effect was first seen in animal studies and further demonstrated in a human double-blind, placebo-controlled clinical trial conducted in Japan in 2007.
In this study of 71 middleaged and elderly people aged between 40 to 70, supplementation with 20 mg per day of PQQ resulted in improvements on tests of higher cognitive function compared to the placebo group, but in the group receiving 20 mg of PQQ along with 300 mg of CoQ10 the results were even more dramatic. PQQ and CoQ10 are both involved in mitochondrial energy production, so these results are not that surprising.
One question that many health care professionals may have regarding PQQ is what is an effective dosage? Specifically, if the nutritional requirement of PQQ is likely less than 500 mcg daily why is the recommended dosage 10 to 20 mg? In order to get a measured response in mitochondrial function in adult animals there is the need to feed higher amounts of PQQ much like why only 8 to 15 mg of vitamin C might protect against the overt signs of scurvy, the recommended dietary allowance currently stands at 75 to 90 milligram per day (for adults, excluding pregnant and lactating women) for optimal function, and even higher amounts are required for clinical applications. The current recommendation of 10 to 20 mg of PQQ daily is based upon the equivalent dose in animals has consistently improved various mitochondrial function. There are also some clinical and observational studies that justify the dosage, especially the 20 mg dosage for enhancing memory.
Rucker R., Chowanadisai W., Nakano M., “Potential physiological importance of pyrroloquinoline quinone,” Altern Med Rev, 2009 Sep; 14(3): 268-77.
Kumazawa T., Sato K., Seno H., et al., “Levels of pyrroloquinoline quinone in various foods,” Biochem J, 1995; 307: 331-333.
Paz M.A., Martin P., Fluckiger R., et al., “The catalysis of redox cycling by pyrroloquinoline quinone (PQQ), PQQ derivatives, and isomers and the specificity of inhibitors,” Anal Biochem, 1996; 238: 145-149.
Kasahara T., Kato T., “Nutritional biochemistry: a new redox-cofactor vitamin for mammals,” Nature, 2003; 422: 832.
Steinberg F., Stites T.E., Anderson P., et al., “Pyrroloquinoline quinone improves growth and reproductive performance in mice fed chemically defined diets,” Exp Biol Med (Maywood), 2003; 228: 160-166.
Chowanadisai W., Bauerly K.A., Tchaparian E., et al., “Pyrroloquinoline quinone stimulates mitochondrial biogenesis through cAMP response element-binding protein phosphorylation and increased PGC-1alpha expression,” Journal of Biological Chemistry, 2010; 285(1): 142-52.
Stites T., Storms D., Bauerly K., et al., “Pyrroloquinoline quinone modulates mitochondrial quantity and function in mice,“ J Nutr, 2006; 136: 390-396.
Chowanadisai W., Bauerly K., Tchaparian E., et al., “Pyrroloquinoline quinone (PQQ) stimulates mitochondrial biogenesis,” FASEB J, 2007; 21: 854.
Ohwada K., Takeda H., Yamazaki M., et al., “Pyrroloquinoline quinone (PQQ) prevents cognitive deficit caused by oxidative stress in rats,” J Clin Biochem Nutr, 2008; 42: 29-34.
Yamaguchi K., Sasano A., Urakami T., Tsuji T., Kondo K., “Stimulation of nerve growth factor production by pyrroloquinoline quinone and its derivatives in vitro and in vivo,” Biosci Biotechnol Biochem, 1993 Jul; 57(7): 1231-3.
Nunome K., Miyazaki S., Nakano M., Iguchi-Ariga S., Ariga H., “Pyrroloquinoline quinone prevents oxidative stress-induced neuronal death probably through changes in oxidative status of DJ-1,” Biol Pharm Bull, 2008 Jul; 31(7): 1321-6.
Zhang Y., Feustel P.J., Kimelberg H.K., “Neuroprotection by pyrroloquinoline quinone (PQQ) in reversible middle cerebral artery occlusion in the adult rat,” Brain Res, 2006; 1094: 200-206.
Hirakawa A., Shimizu K., Fukumitsu H., Furukawa S., “Pyrroloquinoline quinone attenuates iNOS gene expression in the injured spinal cord,” Biochem Biophys Res Commun, 2009; 378: 308-312.
Jensen F.E., Gardner G.J., Williams A.P., et al., “The putative essential nutrient pyrroloquinoline quinone is neuroprotective in a rodent model of hypoxic/ischemic brain injury,” Neuroscience, 1994; 62: 399-406.
Zhang P., Xu Y., Sun J., et al., “Protection of pyrroloquinoline quinone against methylmercury- induced neurotoxicity via reducing oxidative stress,” Free Radic Res, 2009; 43: 224-233.
Zhang Q., Shen M., Ding M., Shen D., Ding F., “The neuroprotective action of pyrroloquinoline quinone against glutamate-induced apoptosis in hippocampal neurons is mediated through the activation of PI3K/Akt pathway,” Toxicol Appl Pharmacol, 2011 Apr 1; 252(1): 62-72.
Kim J., Harada R., Kobayashi M., Kobayashi N., Sode K., “The inhibitory effect of pyrroloquinoline quinone on the amyloid formation and cytotoxicity of truncated alphasynuclein,” Mol Neurodegener, 2010 May 20; 5: 20.
Kim J., Kobayashi M., Fukuda M., et al., “Pyrroloquinoline quinone inhibits the fibrillation of amyloid proteins,” Prion, 2010 Jan; 4(1): 26-31.
Nakano M., Ubukata K., Yamamoto T., Yamaguchi H., “Effect of pyrroloquinoline quinone (PQQ) on mental status of middle-aged and elderly persons,” FOOD Style, 2009; 21: 13(7): 50-3.
http://pyrroloquinoline-quinone.com/pqq-info/ accessed 4/21/2011.