Category Archives: PQQ

PQQ Stimulates Osteoblastic Bone Formation in Testosterone-Deficient Mice


Pyrroloquinoline quinone prevents testosterone deficiency-induced osteoporosis by stimulating osteoblastic bone formation and inhibiting osteoclastic bone resorption.

Accumulating evidences suggest that oxidative stress caused and deteriorated the aging related osteoporosis and pyrroloquinoline quinone (PQQ) is a powerful antioxidant. However, it is unclear whether PQQ can prevent testosterone deficiency-induced osteoporosis. In this study, the orchidectomized (ORX) mice were supplemented in diet with/without PQQ for 48 weeks, and compared with each other and with sham mice. Results showed that bone mineral density, trabecular bone volume, collagen deposition and osteoblast number were decreased significantly in ORX mice compared with shame mice, whereas PQQ supplementation largely prevented these alterations. In contrast, osteoclast surface and ratio of RANKL and OPG mRNA relative expression levels were increased significantly in ORX mice compared with shame mice, but were decreased significantly by PQQ supplementation. Furthermore, we found that CFU-f and ALP positive CFU-f forming efficiency and the proliferation of mesenchymal stem cells were reduced significantly in ORX mice compared with shame mice, but were increased significantly by PQQ supplementation. Reactive oxygen species (ROS) levels in thymus were increased, antioxidant enzymes SOD-1, SOD-2, Prdx I and Prdx IV protein expression levels in bony tissue were down-regulated, whereas the protein expression levels of DNA damage response related molecules including γ-H2AX, p53, Chk2 and NFκB-p65 in bony tissue were up-regulated significantly in ORX mice compared with shame mice, whereas PQQ supplementation largely rescued these alterations observed in ORX mice. Our results indicate that PQQ supplementation can prevent testosterone deficiency-induced osteoporosis by inhibiting oxidative stress and DNA damage, stimulating osteoblastic bone formation and inhibiting osteoclastic bone resorption.

Wu X, Li J, Zhang H, Wang H…
Am J Transl Res 2017
PMID: 28386349 | Free Full Text

PQQ Increases Osteoblasts in Bmi-1 Knockout Mice


Effect and mechanism of pyrroloquinoline quinone on anti-osteoporosis in Bmi-1 knockout mice-Anti-oxidant effect of pyrroloquinoline quinone.

Pyrroloquinoline quinone (PQQ), considered as an ROS scavenger,could protect mitochondrial activity from damage of oxidative stress. To determine the role of PQQ supplement in rescuing long bone osteoporosis in Bmi-1(-/-) mice. We fed Bmi-1 knockout mice a diet supplemented with PQQ (BKO+PQQ), BKO mice with normal diet (BKO) and wild type mice with normal diet (WT) as controls. We compared the differences of skeletal phenotype by means of imaging, histopathological and molecular biology methods in three groups of animals. Results showed that BKO+PQQ mice increased morphology of tibia, decreased X-ray transmittance, and increased bone density, thickness of cortical bone, width of growth plate and trabecular bone mass compared with BKO mice. Our study also investigated that, compared mice BKO, PCNA positive cells percentage of tibial growth plate areas significantly increased in BKO+PQQ mice, and TUNEL positive cells percentage was significantly decreased. To detect the effect of PQQ on osteoblast formation of tibiae. Our results showed, compared with BKO mice, osteogenic cell, osteoblast number areas, ALP, Col I and OCN positive areas significantly increased in tibia of BKO+PQQ mice. Further studies showed that supplemental PQQ played a role in anti-osteoporosis by up-regulating antioxidant capacity, inhibiting oxidative stress and reducing DNA damage, down-regulating CDKI proteins levels, and decreasing cell apoptosis. This study not only reveals the mechanism of PQQ supplementation in anti-osteoporosis, but also provides the experimental and theoretical basis for the clinical application of PQQ in osteoporosis.

Huang Y, Chen N, Miao D
Am J Transl Res 2017
PMID: 29118900 | Free Full Text

PQQ Inhibits Osteoclasts


Inhibition of receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation by pyrroloquinoline quinine (PQQ).

The effect of pyrroloquinoline quinine (PQQ) on receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation was examined using RAW 264.7 macrophage-like cells. RANKL led to the formation of osteoclasts identified as tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells in the culture of RAW 264.7 cells. However, PQQ inhibited the appearance of osteoclasts and prevented the decrease of F4/80 macrophage maturation marker on RANKL-stimulated cells, suggesting a preventive action of PQQ on RANKL-induced osteoclast differentiation. PQQ inhibited the activation of nuclear factor of activated T cells (NFATc1), a key transcription factor of osteoclastogenesis, in RANKL-stimulated cells. On the other hand, PQQ did not inhibit the signaling pathway from RANK/RANKL binding to NFATc1 activation, including NF-κB and mitogen-activated protein kinases (MAPKs). PQQ augmented the expression of type I interferon receptor (IFNAR) and enhanced the IFN-β-mediated janus kinase (JAK1) and signal transducer and activator of transcription (STAT1) expression. Moreover, PQQ reduced the expression level of c-Fos leading to the activation of NFATc1. Taken together, PQQ was suggested to prevent RANKL-induced osteoclast formation via the inactivation of NFATc1 by reduced c-Fos expression. The reduced c-Fos expression might be mediated by the enhanced IFN-β signaling due to augmented IFNAR expression.

Odkhuu E, Koide N, Haque A, Tsolmongyn B…
Immunol. Lett. Feb 2012
PMID: 22193059

Review: PQQ Involved with Nitric Oxide in Bones?


Is the antioxidant, anti-inflammatory putative new vitamin, PQQ, involved with nitric oxide in bone metabolism?

Our laboratory recently isolated free PQQ (2,7,9-tricarboxy-pyrroloquinoline quinone, methoxatin), a bacterial redox cofactor, from red cells, neutrophils, serum and milk and found free PQQ in CSF, synovial fluid and bile. The metabolism and functions of PQQ and ascorbate may be coupled. Physiologically, free PQQ catalyzes dioxygen-superoxide interconversion, and participates in both superoxide generation (respiratory burst) and scavenging (cell protection). Using a labeled aromatic o-diamine, superoxide formation by activated neutrophils was inhibited and the labeled phenazine adduct of PQQ could be isolated from the inhibited cells (Karnovsky et al., 1992). PQQ may convert xanthine oxidase to xanthine dehydrogenase (XD) and could be the physiological coenzyme of XD. PQQ plus copper, form a potent amine-oxidizing system. Shah et al., 1992 found that PQQ-Cu2+ catalyzes the oxidation of epsilon-amino groups in collagen and elastin. Rucker’s lab (Smidt et al., 1991) has found that PQQ may be a vitamin for mouse pups. Watanabe et al., 1988 and Nishigori et al., 1989, showed that injected PQQ protects animals against oxidative stress injury. PQQ’s in vivo antioxidant action, spares reduced glutathione. PQQ, as an actively transported organic anion, concentrates in cells. In other experiments (Aizenman et al., 1992), PQQ protected neurons against the neurotoxin action of the glutamate-receptor against NMDA. We shall consider possible roles for PQQ in the biosynthesis of nitric oxide (NO, endothelium-derived relaxing factor, EDRF) from L-arginine and in NO removal by superoxide. NO has now been linked to the inhibition of osteoclastic bone resorption.

Gallop PM, Paz MA, Flückiger R, Henson E
Connect. Tissue Res. 1993
PMID: 8403896