Advertisement

Pyrroloquinoline Quinone Stimulates Mitochondrial Biogenesis through cAMP Response Element-binding Protein Phosphorylation and Increased PGC-1α Expression*

Open AccessPublished:October 27, 2009DOI:https://doi.org/10.1074/jbc.M109.030130
      Bioactive compounds reported to stimulate mitochondrial biogenesis are linked to many health benefits such increased longevity, improved energy utilization, and protection from reactive oxygen species. Previously studies have shown that mice and rats fed diets lacking in pyrroloquinoline quinone (PQQ) have reduced mitochondrial content. Therefore, we hypothesized that PQQ can induce mitochondrial biogenesis in mouse hepatocytes. Exposure of mouse Hepa1–6 cells to 10–30 μm PQQ for 24–48 h resulted in increased citrate synthase and cytochrome c oxidase activity, Mitotracker staining, mitochondrial DNA content, and cellular oxygen respiration. The induction of this process occurred through the activation of cAMP response element-binding protein (CREB) and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a pathway known to regulate mitochondrial biogenesis. PQQ exposure stimulated phosphorylation of CREB at serine 133, activated the promoter of PGC-1α, and increased PGC-1α mRNA and protein expression. PQQ did not stimulate mitochondrial biogenesis after small interfering RNA-mediated reduction in either PGC-1α or CREB expression. Consistent with activation of the PGC-1α pathway, PQQ increased nuclear respiratory factor activation (NRF-1 and NRF-2) and Tfam, TFB1M, and TFB2M mRNA expression. Moreover, PQQ protected cells from mitochondrial inhibition by rotenone, 3-nitropropionic acid, antimycin A, and sodium azide. The ability of PQQ to stimulate mitochondrial biogenesis accounts in part for action of this compound and suggests that PQQ may be beneficial in diseases associated with mitochondrial dysfunction.

      Introduction

      Bioactive compounds, such as pyrroloquinoline quinone (PQQ),
      The abbreviations used are: PQQ
      pyrroloquinoline quinone
      CREB
      cAMP response element (CRE)-binding protein
      PGC-1α
      peroxisome proliferator-activated receptor-γ coactivator-1α
      siRNA
      small interfering RNA
      ROS
      reactive oxygen species
      IPQ
      imidazopyrroloquinoline
      FCCP
      carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone
      PBS
      phosphate buffer saline
      HBSS
      Hanks' balanced salt solution
      DMEM
      Dulbecco's minimal essential medium
      NRF
      nuclear respiratory factor
      ANOVA
      analysis of variance
      MTT
      3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide.
      resveratrol, genistein, hydroxy-tyrosol, and quercetin have been reported to improve mitochondrial respiratory control or stimulate mitochondrial biogenesis (
      • Stites T.
      • Storms D.
      • Bauerly K.
      • Mah J.
      • Harris C.
      • Fascetti A.
      • Rogers Q.
      • Tchaparian E.
      • Satre M.
      • Rucker R.B.
      ,
      • Baur J.A.
      • Pearson K.J.
      • Price N.L.
      • Jamieson H.A.
      • Lerin C.
      • Kalra A.
      • Prabhu V.V.
      • Allard J.S.
      • Lopez-Lluch G.
      • Lewis K.
      • Pistell P.J.
      • Poosala S.
      • Becker K.G.
      • Boss O.
      • Gwinn D.
      • Wang M.
      • Ramaswamy S.
      • Fishbein K.W.
      • Spencer R.G.
      • Lakatta E.G.
      • Le Couteur D.
      • Shaw R.J.
      • Navas P.
      • Puigserver P.
      • Ingram D.K.
      • de Cabo R.
      • Sinclair D.A.
      ,
      • Rasbach K.A.
      • Schnellmann R.G.
      ,
      • Liu Z.
      • Sun L.
      • Zhu L.
      • Jia X.
      • Li X.
      • Jia H.
      • Wang Y.
      • Weber P.
      • Long J.
      • Liu J.
      ,
      • Davis J.M.
      • Murphy E.A.
      • Carmichael M.D.
      • Davis B.
      ), which is potentially important to a number of health-related issues ranging from increased longevity, improved energy utilization, and protection from reactive oxygen species (
      • Liu J.
      • Ames B.N.
      ,
      • Nisoli E.
      • Clementi E.
      • Carruba M.O.
      • Moncada S.
      ,
      • Carter C.S.
      • Hofer T.
      • Seo A.Y.
      • Leeuwenburgh C.
      ). Furthermore, mitochondrial DNA depletion and mutations are associated with cardiomyopathy, lactic acidosis, developmental delay, failure to thrive, and impaired neurological function (
      • Debray F.G.
      • Lambert M.
      • Mitchell G.A.
      ). The response to most biofactors is observed after pharmacological intervention or dietary supplementation, although often near-gram amounts per kg of diet, or millimolar quantities, are needed for such responses in vivo. PQQ stimulates mitochondriogenesis with the addition of only milligram quantities of PQQ per kg of diet, or micromolar concentrations, in vivo. For example, PQQ deprivation depresses mitochondrial function, which is reversed when as little as 200–300 μg of PQQ/kg of diet are added (
      • Stites T.
      • Storms D.
      • Bauerly K.
      • Mah J.
      • Harris C.
      • Fascetti A.
      • Rogers Q.
      • Tchaparian E.
      • Satre M.
      • Rucker R.B.
      ,
      • Bauerly K.A.
      • Storms D.H.
      • Harris C.B.
      • Hajizadeh S.
      • Sun M.Y.
      • Cheung C.P.
      • Satre M.A.
      • Fascetti A.J.
      • Tchaparian E.
      • Rucker R.B.
      ). PQQ also remains detectable in tissues when there is no or little dietary exposure (
      • Steinberg F.
      • Stites T.E.
      • Anderson P.
      • Storms D.
      • Chan I.
      • Eghbali S.
      • Rucker R.
      ), which has not been observed for other dietary polyphenolic compounds known to promote mitochondriogenesis.
      Recently, PQQ produced by rhizobacterium has been identified as an important plant growth factor (
      • Choi O.
      • Kim J.
      • Kim J.G.
      • Jeong Y.
      • Moon J.S.
      • Park C.S.
      • Hwang I.
      ) and is a possible source of PQQ in plant-derived food. In this regard, the ubiquitous presence of PQQ in a broad range of plants leads to a relatively constant exposure in animal diets. More importantly, levels of PQQ from dietary intake from plants are sufficient to maintain the concentration of PQQ typical of tissues (
      • Kumazawa T.
      • Sato K.
      • Seno H.
      • Ishii A.
      • Suzuki O.
      ). From a chemical perspective, assays that measure redox cycling indicate that PQQ is also 100–1000 times more efficient than other quinones and enediols, such as ascorbic acid (
      • Stites T.E.
      • Mitchell A.E.
      • Rucker R.B.
      ). PQQ can undergo thousands of reductive or oxidative cycles without degradation or polymerization (
      • Stites T.E.
      • Mitchell A.E.
      • Rucker R.B.
      ).
      Peroxisome proliferator-activated receptor-γ coactivator-1 α (PGC-1α) is a transcriptional coactivator that induces mitochondrial biogenesis by binding to nuclear respiratory factors and enhancing their activity (
      • Gleyzer N.
      • Vercauteren K.
      • Scarpulla R.C.
      ). Nuclear respiratory factors are transcription factors that bind to cis-acting response elements in the promoter regions of many genes that control mitochondrial gene transcription and mitochondrial DNA replication (
      • Gleyzer N.
      • Vercauteren K.
      • Scarpulla R.C.
      ). PGC-1α is also associated with a reduction in reactive oxygen species (ROS) (
      • St.-Pierre J.
      • Drori S.
      • Uldry M.
      • Silvaggi J.M.
      • Rhee J.
      • Jäger S.
      • Handschin C.
      • Zheng K.
      • Lin J.
      • Yang W.
      • Simon D.K.
      • Bachoo R.
      • Spiegelman B.M.
      ,
      • Borniquel S.
      • Valle I.
      • Cadenas S.
      • Lamas S.
      • Monsalve M.
      ) and protection against various mitochondrial toxins (
      • St.-Pierre J.
      • Drori S.
      • Uldry M.
      • Silvaggi J.M.
      • Rhee J.
      • Jäger S.
      • Handschin C.
      • Zheng K.
      • Lin J.
      • Yang W.
      • Simon D.K.
      • Bachoo R.
      • Spiegelman B.M.
      ). Moreover, the phosphorylation of CREB is known to be an important regulator of PGC-1α (
      • Handschin C.
      • Rhee J.
      • Lin J.
      • Tarr P.T.
      • Spiegelman B.M.
      ).
      The function of PQQ in mammalian physiology remains controversial. PQQ has been proposed as a vitamin (
      • Kasahara T.
      • Kato T.
      ), but it has not been demonstrated that PQQ serves as an enzyme cofactor in mammalian tissues (
      • Felton L.M.
      • Anthony C.
      ,
      • Rucker R.
      • Storms D.
      • Sheets A.
      • Tchaparian E.
      • Fascetti A.
      ). Upon appreciation that mitochondrial content can be influenced by PQQ nutritional status and that reported beneficial effects of PQQ may be directly related to mitochondrial function, we hypothesized that PQQ may induce mitochondrial biogenesis through a mitochondrial-related cell signaling mechanism. Given that many mitochondrial-related events are regulated by PGC-1α and nuclear respiratory factors (
      • Gleyzer N.
      • Vercauteren K.
      • Scarpulla R.C.
      ), we hypothesized that PQQ may interact with a PGC-1α-related pathway. We used the mouse Hepa1–6 hepatocyte cell line as a model to investigate these hypotheses. We also explored whether PQQ may protect against the toxic effects of mitochondrial electron transport chain inhibition.

      DISCUSSION

      Previous studies (
      • Stites T.
      • Storms D.
      • Bauerly K.
      • Mah J.
      • Harris C.
      • Fascetti A.
      • Rogers Q.
      • Tchaparian E.
      • Satre M.
      • Rucker R.B.
      ,
      • Bauerly K.A.
      • Storms D.H.
      • Harris C.B.
      • Hajizadeh S.
      • Sun M.Y.
      • Cheung C.P.
      • Satre M.A.
      • Fascetti A.J.
      • Tchaparian E.
      • Rucker R.B.
      ) have shown that mitochondrial biogenesis in vivo is responsive to dietary PQQ status, but no mechanisms have been established. We show that PQQ influences PGC-1α activity, which is a major mechanism for the regulation of mitochondrial biogenesis (
      • Gleyzer N.
      • Vercauteren K.
      • Scarpulla R.C.
      ). A part of the process involves CREB, which has been identified as an activator of PGC-1α transcription by binding to the PGC-1α promoter. The induction of PGC-1α by CREB activation is responsive to numerous physiological stimuli, such as catecholamines (
      • Cao W.
      • Daniel K.W.
      • Robidoux J.
      • Puigserver P.
      • Medvedev A.V.
      • Bai X.
      • Floering L.M.
      • Spiegelman B.M.
      • Collins S.
      ,
      • Yoon J.C.
      • Puigserver P.
      • Chen G.
      • Donovan J.
      • Wu Z.
      • Rhee J.
      • Adelmant G.
      • Stafford J.
      • Kahn C.R.
      • Granner D.K.
      • Newgard C.B.
      • Spiegelman B.M.
      ), glucagon (
      • Yoon J.C.
      • Puigserver P.
      • Chen G.
      • Donovan J.
      • Wu Z.
      • Rhee J.
      • Adelmant G.
      • Stafford J.
      • Kahn C.R.
      • Granner D.K.
      • Newgard C.B.
      • Spiegelman B.M.
      ), and exercise (
      • Handschin C.
      • Rhee J.
      • Lin J.
      • Tarr P.T.
      • Spiegelman B.M.
      ). The ability of PQQ to stimulate CREB phosphorylation and activation appears important. PQQ elicited a transient, stimulatory increase in CREB activity. Although the effect lasted less than 8 h, it is similar to the serum stimulation of CREB phosphorylation observed in fibroblasts, which occurs within 1 h of serum exposure and declines after 6 h (
      • Herzig R.P.
      • Scacco S.
      • Scarpulla R.C.
      ). This response is followed by increases in cytochrome c and cytochrome oxidase expression after 12 h (
      • Herzig R.P.
      • Scacco S.
      • Scarpulla R.C.
      ). The increase in mitochondrial biogenesis and PGC-1α expression was present after 24–48 h after the start of PQQ exposure, which suggests that the increase in PGC-1α activity lasts longer than the increase in CREB activity. One possibility is that the transitory stimulation of PGC-1α expression by CREB leads to a stable increase in PGC-1α activity through a positive autoregulatory feedback pathway. For example, a positive autoregulatory loop for PGC-1 expression for the determination of muscle fiber type from type II to type I involves the binding of MEF2 to the PGC-1α promoter, which is enhanced with MEF2 and PGC-1α coactivation (
      • Handschin C.
      • Rhee J.
      • Lin J.
      • Tarr P.T.
      • Spiegelman B.M.
      ). Another positive autoregulatory loop involves the binding of peroxisome proliferator-activated receptor -γ, a co-activation target of PGC-1α, to the distal region of the PGC-1α promoter (
      • Hondares E.
      • Mora O.
      • Yubero P.
      • Rodriguez de la Concepción M.
      • Iglesias R.
      • Giralt M.
      • Villarroya F.
      ). Thus, it is possible that the activation of PGC-1α by PQQ can induce further lasting increases in either PGC-1α activity or expression by influencing an autoregulatory feedback pathway. Reduction of CREB expression by siRNA-mediated knockdown resulted in a reduction in both CREB and PGC-1α expression. This observation is similar to the reduction in PGC-1α mRNA expression found in livers of mice infected with an adenoviral-based CREB inhibitor (
      • Herzig S.
      • Long F.
      • Jhala U.S.
      • Hedrick S.
      • Quinn R.
      • Bauer A.
      • Rudolph D.
      • Schutz G.
      • Yoon C.
      • Puigserver P.
      • Spiegelman B.
      • Montminy M.
      ). Although siRNA-mediated knockdown of either CREB or PGC-1α was sufficient to eliminate PQQ-mediated mitochondrial biogenesis and the reduction of CREB by siRNA reduced PGC-1α expression, it is also possible that part of the PQQ-induced mitochondrial biogenesis may be due to CREB activation without the role of PGC-1α. CREB has been reported to bind to the D-loop of mitochondria in rodent brain tissue and primary neurons (
      • Ryu H.
      • Lee J.
      • Impey S.
      • Ratan R.R.
      • Ferrante R.J.
      ,
      • Lee J.
      • Kim C.H.
      • Simon D.K.
      • Aminova L.R.
      • Andreyev A.Y.
      • Kushnareva Y.E.
      • Murphy A.N.
      • Lonze B.E.
      • Kim K.S.
      • Ginty D.D.
      • Ferrante R.J.
      • Ryu H.
      • Ratan R.R.
      ). Although functions of the activation remain unresolved, the downstream consequences are consistent with the PGC-1α pathway. For example, the functional increases in citrate synthase and cytochrome activity, Mitotracker staining, mitochondrial DNA content, and cellular oxygen consumption occurred with increases in NRF-1 and NRF-2 activation and Tfam, TFB1M, and TFB2M mRNA expression. Although other nuclear co-activators related to PGC-1α exist, such as PGC-1β and PGC-1-related co-activator, evidence showing that siRNA-mediated PGC-1α knockdown is sufficient to reduce induction of mitochondrial biogenesis by PQQ suggests that the other co-activators are not involved, although this possibility cannot be excluded. CREB has been shown to regulate PGC-1α, and data shown here suggest that PQQ acts through CREB to regulate PGC-1α, but regulation of the PGC-1β and PGC-1-related co-activator by CREB has not yet been demonstrated. Also, it is recognized that the PGC-1 family of co-activators likely act and respond to differing physiological stimuli and processes (
      • Lin J.
      • Handschin C.
      • Spiegelman B.M.
      ).
      The observed increase in cell viability after PQQ incubation and mitochondrial inhibition by rotenone is greater than the observed increase in mitochondrial function by PQQ supplementation compared with basal culturing conditions. For example, the increases in mitochondrial parameters after PQQ incubation (30 μm for 24 h) range from 14% for Mitotracker staining to 23% for cellular oxygen respiration. For comparison, the same concentration and duration of PQQ leads to a 39% increase in cell viability and 134% increase in cellular oxygen respiration after rotenone exposure. Adipocyte cell lines established from PGC-1α-deficient mice show modest reductions in mitochondrial genes without significant impairment of brown adipocyte differentiation (
      • Uldry M.
      • Yang W.
      • St-Pierre J.
      • Lin J.
      • Seale P.
      • Spiegelman B.M.
      ). Adenoviral mediated-expression of PGC-1α in vascular endothelial cells, resulting in a multiple-fold increase in PGC-1α protein expression, leads to a 50% increase in mitochondrial biogenesis (
      • Valle I.
      • Alvarez-Barrientos A.
      • Arza E.
      • Lamas S.
      • Monsalve M.
      ). Overexpression of PGC-1β in C2C12 muscle cells results in a higher respiration rate compared with overexpression of PGC-1α (
      • St.-Pierre J.
      • Lin J.
      • Krauss S.
      • Tarr P.T.
      • Yang R.
      • Newgard C.B.
      • Spiegelman B.M.
      ). These studies show that alterations in PGC-1α expression have comparatively modest changes in mitochondrial biogenesis and are consistent with our observations linking PQQ to PGC-1α activity. It is likely that the rather modest reductions in mitochondrial biogenesis may be due to compensation by PGC-1β. The greater ability of PQQ to maintain and protect mitochondrial function against mitochondrial inhibition compared with increased mitochondrial activity relative to basal conditions may be because of a number of reasons. One possibility is that the stimulation of the mitochondrial biogenesis pathway facilitates recovery of mitochondria from damage induced by mitochondrial inhibition. Overexpression of PGC-1α in primary renal cells after oxidant exposure accelerates recovery of mitochondrial function (
      • Rasbach K.A.
      • Schnellmann R.G.
      ). Another possibility is that PQQ protects against reactive oxygen species, which can also be related to PGC-1α activation and protection from the action of mitochondrial inhibitors and reactive oxygen species (
      • St.-Pierre J.
      • Drori S.
      • Uldry M.
      • Silvaggi J.M.
      • Rhee J.
      • Jäger S.
      • Handschin C.
      • Zheng K.
      • Lin J.
      • Yang W.
      • Simon D.K.
      • Bachoo R.
      • Spiegelman B.M.
      ,
      • Valle I.
      • Alvarez-Barrientos A.
      • Arza E.
      • Lamas S.
      • Monsalve M.
      ,
      • Liang H.
      • Bai Y.
      • Li Y.
      • Richardson A.
      • Ward W.F.
      ). PQQ has been shown to protect neuroblastoma cells from 6-hydroxydopamine toxicity (
      • Hara H.
      • Hiramatsu H.
      • Adachi T.
      ,
      • Nunome K.
      • Miyazaki S.
      • Nakano M.
      • Iguchi-Ariga S.
      • Ariga H.
      ), possibly by preserving DJ-1 activity by preventing the oxidation of cysteines important for DJ-1 function (
      • Nunome K.
      • Miyazaki S.
      • Nakano M.
      • Iguchi-Ariga S.
      • Ariga H.
      ). Consequently, it is likely that several mechanisms are responsible for the cytoprotective property of PQQ. Protection from respiratory inhibitors by PQQ occurred by exposing cells to PQQ before the addition of the toxins, and PQQ was removed from the media before the application of the respiratory inhibitors. Unlike when oxygen consumption is measured immediately after PQQ incubation, we did not observe an increase in oxygen consumption after PQQ-supplemented media was replaced with control media for 24 h when determining the effects of PQQ and rotenone on oxygen consumption. This observation suggests that stimulation of mitochondrial biogenesis by PQQ can be transient and reversible. PQQ reverses inhibition along many parts of the mitochondrial oxidation phosphorylation complex, and many mitochondrial disorders show decreased mitochondrial function and increased reactive oxygen species production (
      • Pitkanen S.
      • Robinson B.H.
      ,
      • Wong A.
      • Yang J.
      • Cavadini P.
      • Gellera C.
      • Lonnerdal B.
      • Taroni F.
      • Cortopassi G.
      ). Previously we showed that PQQ-deficient animals are sensitive to diphenylene iodonium, which is a Complex I inhibitor and antiglycemic agent (
      • Stites T.
      • Storms D.
      • Bauerly K.
      • Mah J.
      • Harris C.
      • Fascetti A.
      • Rogers Q.
      • Tchaparian E.
      • Satre M.
      • Rucker R.B.
      ). Complex I and III are known to generate superoxide in the mitochondria (
      • Kudin A.P.
      • Bimpong-Buta N.Y.
      • Vielhaber S.
      • Elger C.E.
      • Kunz W.S.
      ), and inhibition of Complex I, II, III, or IV of the mitochondrial respiratory chain results in an increase in mitochondrial reactive oxygen species and oxidative damage (
      • St.-Pierre J.
      • Drori S.
      • Uldry M.
      • Silvaggi J.M.
      • Rhee J.
      • Jäger S.
      • Handschin C.
      • Zheng K.
      • Lin J.
      • Yang W.
      • Simon D.K.
      • Bachoo R.
      • Spiegelman B.M.
      ,
      • Smith T.S.
      • Bennett Jr., J.P.
      ,
      • Chen Q.
      • Vazquez E.J.
      • Moghaddas S.
      • Hoppel C.L.
      • Lesnefsky E.J.
      ,
      • Schulz J.B.
      • Henshaw D.R.
      • MacGarvey U.
      • Beal M.F.
      ). An improvement in oxygen utilization and flux (
      • Murphy M.P.
      ) may explain how PQQ can prevent an increase in mitochondrial superoxide, which may be a mechanism by which PQQ can protect cells against respiratory inhibition.
      The induction of mitochondrial biogenesis by PQQ has a number of health implications. PGC-1α elevation, particularly in muscle and adipose tissue, may also be helpful in that PGC-1α expression is decreased in obesity (
      • Semple R.K.
      • Crowley V.C.
      • Sewter C.P.
      • Laudes M.
      • Christodoulides C.
      • Considine R.V.
      • Vidal-Puig A.
      • O'Rahilly S.
      ,
      • Crunkhorn S.
      • Dearie F.
      • Mantzoros C.
      • Gami H.
      • da Silva W.S.
      • Espinoza D.
      • Faucette R.
      • Barry K.
      • Bianco A.C.
      • Patti M.E.
      ). CREB null and PGC-1α null mice have hepatic steatosis and impaired gluconeogenesis and β-oxidation (
      • Herzig S.
      • Long F.
      • Jhala U.S.
      • Hedrick S.
      • Quinn R.
      • Bauer A.
      • Rudolph D.
      • Schutz G.
      • Yoon C.
      • Puigserver P.
      • Spiegelman B.
      • Montminy M.
      ,
      • Herzig S.
      • Hedrick S.
      • Morantte I.
      • Koo S.H.
      • Galimi F.
      • Montminy M.
      ,
      • Leone T.C.
      • Lehman J.J.
      • Finck B.N.
      • Schaeffer P.J.
      • Wende A.R.
      • Boudina S.
      • Courtois M.
      • Wozniak D.F.
      • Sambandam N.
      • Bernal-Mizrachi C.
      • Chen Z.
      • Holloszy J.O.
      • Medeiros D.M.
      • Schmidt R.E.
      • Saffitz J.E.
      • Abel E.D.
      • Semenkovich C.F.
      • Kelly D.P.
      ). PQQ-deficient mice have elevated serum triglycerides, which is reversed upon PQQ repletion (
      • Stites T.
      • Storms D.
      • Bauerly K.
      • Mah J.
      • Harris C.
      • Fascetti A.
      • Rogers Q.
      • Tchaparian E.
      • Satre M.
      • Rucker R.B.
      ). In addition, mice with deletion of all CREB isoforms have reduced commissural structure formation and impaired fetal T cell development (
      • Rudolph D.
      • Tafuri A.
      • Gass P.
      • Hämmerling G.J.
      • Arnold B.
      • Schütz G.
      ), and other mouse models of CREB-targeted deletion show impaired memory and neurodegeneration (
      • Bourtchuladze R.
      • Frenguelli B.
      • Blendy J.
      • Cioffi D.
      • Schutz G.
      • Silva A.J.
      ,
      • Mantamadiotis T.
      • Lemberger T.
      • Bleckmann S.C.
      • Kern H.
      • Kretz O.
      • Martin Villalba A.
      • Tronche F.
      • Kellendonk C.
      • Gau D.
      • Kapfhammer J.
      • Otto C.
      • Schmid W.
      • Schütz G.
      ). Likewise, dietary PQQ deprivation results in immune dysfunction (
      • Steinberg F.M.
      • Gershwin M.E.
      • Rucker R.B.
      ). PQQ is also neuroprotective when administered by intraperitoneal injection (
      • Jensen F.E.
      • Gardner G.J.
      • Williams A.P.
      • Gallop P.M.
      • Aizenman E.
      • Rosenberg P.A.
      ,
      • Zhang Y.
      • Feustel P.J.
      • Kimelberg H.K.
      ) or diet supplementation (
      • Ohwada K.
      • Takeda H.
      • Yamazaki M.
      • Isogai H.
      • Nakano M.
      • Shimomura M.
      • Fukui K.
      • Urano S.
      ).
      Although other phytochemicals are associated with the activation of cell signaling pathways important to mitochondrial function, PQQ has properties that set it apart from other compounds. As an example, resveratrol and genisten have been demonstrated to affect cell-signaling pathways, including those important for mitochondrial biogenesis. Resveratrol can induce deacetylation of PGC-1α (
      • Baur J.A.
      • Pearson K.J.
      • Price N.L.
      • Jamieson H.A.
      • Lerin C.
      • Kalra A.
      • Prabhu V.V.
      • Allard J.S.
      • Lopez-Lluch G.
      • Lewis K.
      • Pistell P.J.
      • Poosala S.
      • Becker K.G.
      • Boss O.
      • Gwinn D.
      • Wang M.
      • Ramaswamy S.
      • Fishbein K.W.
      • Spencer R.G.
      • Lakatta E.G.
      • Le Couteur D.
      • Shaw R.J.
      • Navas P.
      • Puigserver P.
      • Ingram D.K.
      • de Cabo R.
      • Sinclair D.A.
      ) and AMP-activated protein kinase activation (
      • Baur J.A.
      • Pearson K.J.
      • Price N.L.
      • Jamieson H.A.
      • Lerin C.
      • Kalra A.
      • Prabhu V.V.
      • Allard J.S.
      • Lopez-Lluch G.
      • Lewis K.
      • Pistell P.J.
      • Poosala S.
      • Becker K.G.
      • Boss O.
      • Gwinn D.
      • Wang M.
      • Ramaswamy S.
      • Fishbein K.W.
      • Spencer R.G.
      • Lakatta E.G.
      • Le Couteur D.
      • Shaw R.J.
      • Navas P.
      • Puigserver P.
      • Ingram D.K.
      • de Cabo R.
      • Sinclair D.A.
      ), which are potential mechanisms for PGC-1α activation. Both resveratrol and genistein are relatively insoluble in water, and increasing its water solubility does not increase resveratrol absorption (
      • Das S.
      • Lin H.S.
      • Ho P.C.
      • Ng K.Y.
      ), although genistein bioavailability can be increased by complexing genistein with cyclodextrins (
      • Stancanelli R.
      • Mazzaglia A.
      • Tommasini S.
      • Calabrò M.L.
      • Villari V.
      • Guardo M.
      • Ficarra P.
      • Ficarra R.
      ). In contrast, PQQ is relatively water-soluble (>1 g of PQQ/liter of water) and is easily absorbed at low dietary concentrations intakes (
      • Smidt C.R.
      • Unkefer C.J.
      • Houck D.R.
      • Rucker R.B.
      ). Although genistein can induce PGC-1α protein expression and mitochondrial biogenesis (
      • Rasbach K.A.
      • Schnellmann R.G.
      ), genistein may also have phytoestrogenic properties because of its ability to activate the estrogen receptor (
      • Martin P.M.
      • Horwitz K.B.
      • Ryan D.S.
      • McGuire W.L.
      ).
      The observed effects of PQQ are also observed at concentrations lower than those for resveratrol and genistein, particularly in vivo. In cell cultures in vitro, PQQ causes changes in mitochondriogenesis and function at concentrations similar to those reported recently for small molecule activators of SIRT1 (
      • Milne J.C.
      • Lambert P.D.
      • Schenk S.
      • Carney D.P.
      • Smith J.J.
      • Gagne D.J.
      • Jin L.
      • Boss O.
      • Perni R.B.
      • Vu C.B.
      • Bemis J.E.
      • Xie R.
      • Disch J.S.
      • Ng P.Y.
      • Nunes J.J.
      • Lynch A.V.
      • Yang H.
      • Galonek H.
      • Israelian K.
      • Choy W.
      • Iffland A.
      • Lavu S.
      • Medvedik O.
      • Sinclair D.A.
      • Olefsky J.M.
      • Jirousek M.R.
      • Elliott P.J.
      • Westphal C.H.
      ), which are being explored for their therapeutic potential (
      • Westphal C.H.
      • Dipp M.A.
      • Guarente L.
      ). These observations suggest that further study related to PQQ is warranted. One important note is that PQQ can increase PGC-1α mRNA transcription, which is different from the post-translation regulation of PGC-1α by resveratrol and raises the likelihood that a combination of various compounds, such as are often present in fruits and vegetables, can stimulate mitochondrial biogenesis through different modes of action. Because mitochondria function as the principal energy source of the cell, compromised function of this key organelle is linked to numerous diseases and metabolic disorders (
      • Debray F.G.
      • Lambert M.
      • Mitchell G.A.
      ,
      • Lin J.
      • Handschin C.
      • Spiegelman B.M.
      ). In this regard, PQQ would appear to have therapeutic potential similar to resveratrol, genistein, hydroxytyrosol, quercetin, or other compounds that can induce mitochondrial biogenesis.

      Acknowledgments

      We thank Dr. Fawaz Haj for suggestions and critical reading of the manuscript. We thank Dr. Bruce Spiegelman for the plasmids generously provided through the Addgene plasmid repository. We thank Carol Oxford of the University of California Davis Optical Biology Shared Resource facility for scientific expertise. The ABI 7900 real-time thermocycler was funded by National Institutes of Health Grant DK 35747 (to the University of California, Davis, Clinical Nutrition Research Unit).

      REFERENCES

        • Stites T.
        • Storms D.
        • Bauerly K.
        • Mah J.
        • Harris C.
        • Fascetti A.
        • Rogers Q.
        • Tchaparian E.
        • Satre M.
        • Rucker R.B.
        J. Nutr. 2006; 136: 390-396
        • Baur J.A.
        • Pearson K.J.
        • Price N.L.
        • Jamieson H.A.
        • Lerin C.
        • Kalra A.
        • Prabhu V.V.
        • Allard J.S.
        • Lopez-Lluch G.
        • Lewis K.
        • Pistell P.J.
        • Poosala S.
        • Becker K.G.
        • Boss O.
        • Gwinn D.
        • Wang M.
        • Ramaswamy S.
        • Fishbein K.W.
        • Spencer R.G.
        • Lakatta E.G.
        • Le Couteur D.
        • Shaw R.J.
        • Navas P.
        • Puigserver P.
        • Ingram D.K.
        • de Cabo R.
        • Sinclair D.A.
        Nature. 2006; 444: 337-342
        • Rasbach K.A.
        • Schnellmann R.G.
        J. Pharmacol. Exp. Ther. 2008; 325: 536-543
        • Liu Z.
        • Sun L.
        • Zhu L.
        • Jia X.
        • Li X.
        • Jia H.
        • Wang Y.
        • Weber P.
        • Long J.
        • Liu J.
        J. Neurochem. 2007; 103: 2690-2700
        • Davis J.M.
        • Murphy E.A.
        • Carmichael M.D.
        • Davis B.
        Am. J. Physiol. Regul. Integr. Comp. Physiol. 2009; 296: R1071-1077
        • Liu J.
        • Ames B.N.
        Nutr. Neurosci. 2005; 8: 67-89
        • Nisoli E.
        • Clementi E.
        • Carruba M.O.
        • Moncada S.
        Circ. Res. 2007; 100: 795-806
        • Carter C.S.
        • Hofer T.
        • Seo A.Y.
        • Leeuwenburgh C.
        Appl. Physiol. Nutr. Metab. 2007; 32: 954-966
        • Debray F.G.
        • Lambert M.
        • Mitchell G.A.
        Curr. Opin. Pediatr. 2008; 20: 471-482
        • Bauerly K.A.
        • Storms D.H.
        • Harris C.B.
        • Hajizadeh S.
        • Sun M.Y.
        • Cheung C.P.
        • Satre M.A.
        • Fascetti A.J.
        • Tchaparian E.
        • Rucker R.B.
        Biochim. Biophys. Acta. 2006; 1760: 1741-1748
        • Steinberg F.
        • Stites T.E.
        • Anderson P.
        • Storms D.
        • Chan I.
        • Eghbali S.
        • Rucker R.
        Exp. Biol. Med. 2003; 228: 160-166
        • Choi O.
        • Kim J.
        • Kim J.G.
        • Jeong Y.
        • Moon J.S.
        • Park C.S.
        • Hwang I.
        Plant Physiol. 2008; 146: 657-668
        • Kumazawa T.
        • Sato K.
        • Seno H.
        • Ishii A.
        • Suzuki O.
        Biochem. J. 1995; 307: 331-333
        • Stites T.E.
        • Mitchell A.E.
        • Rucker R.B.
        J. Nutr. 2000; 130: 719-727
        • Gleyzer N.
        • Vercauteren K.
        • Scarpulla R.C.
        Mol. Cell. Biol. 2005; 25: 1354-1366
        • St.-Pierre J.
        • Drori S.
        • Uldry M.
        • Silvaggi J.M.
        • Rhee J.
        • Jäger S.
        • Handschin C.
        • Zheng K.
        • Lin J.
        • Yang W.
        • Simon D.K.
        • Bachoo R.
        • Spiegelman B.M.
        Cell. 2006; 127: 397-408
        • Borniquel S.
        • Valle I.
        • Cadenas S.
        • Lamas S.
        • Monsalve M.
        FASEB J. 2006; 20: 1889-1891
        • Handschin C.
        • Rhee J.
        • Lin J.
        • Tarr P.T.
        • Spiegelman B.M.
        Proc. Natl. Acad. Sci. U.S.A. 2003; 100: 7111-7116
        • Kasahara T.
        • Kato T.
        Nature. 2003; 422: 832
        • Felton L.M.
        • Anthony C.
        Nature. 2005; 433: E10-E12
        • Rucker R.
        • Storms D.
        • Sheets A.
        • Tchaparian E.
        • Fascetti A.
        Nature. 2005; 433: E10-E12
        • Mitchell A.E.
        • Jones A.D.
        • Mercer R.S.
        • Rucker R.B.
        Anal. Biochem. 1999; 269: 317-325
        • Rantanen A.
        • Jansson M.
        • Oldfors A.
        • Larsson N.G.
        Mamm. Genome. 2001; 12: 787-792
        • Choi Y.S.
        • Lee H.K.
        • Pak Y.K.
        Biochim. Biophys. Acta. 2002; 1574: 200-204
        • Zhang P.
        • Liu C.
        • Zhang C.
        • Zhang Y.
        • Shen P.
        • Zhang J.
        • Zhang C.Y.
        FEBS Lett. 2005; 579: 1446-1452
        • Vankoningsloo S.
        • De Pauw A.
        • Houbion A.
        • Tejerina S.
        • Demazy C.
        • de Longueville F.
        • Bertholet V.
        • Renard P.
        • Remacle J.
        • Holvoet P.
        • Raes M.
        • Arnould T.
        J. Cell Sci. 2006; 119: 1266-1282
        • Scarpulla R.C.
        J. Cell. Biochem. 2006; 97: 673-683
        • Wu Z.
        • Puigserver P.
        • Andersson U.
        • Zhang C.
        • Adelmant G.
        • Mootha V.
        • Troy A.
        • Cinti S.
        • Lowell B.
        • Scarpulla R.C.
        • Spiegelman B.M.
        Cell. 1999; 98: 115-124
        • Johannessen M.
        • Delghandi M.P.
        • Moens U.
        Cell. Signal. 2004; 16: 1211-1227
        • Gallop P.M.
        • Paz M.A.
        • Flückiger R.
        • Kagan H.M.
        Trends Biochem. Sci. 1989; 14: 343-346
        • He K.
        • Nukada H.
        • Urakami T.
        • Murphy M.P.
        Biochem. Pharmacol. 2003; 65: 67-74
        • Aizenman E.
        • Hartnett K.A.
        • Zhong C.
        • Gallop P.M.
        • Rosenberg P.A.
        J. Neurosci. 1992; 12: 2362-2369
        • Weydt P.
        • Pineda V.V.
        • Torrence A.E.
        • Libby R.T.
        • Satterfield T.F.
        • Lazarowski E.R.
        • Gilbert M.L.
        • Morton G.J.
        • Bammler T.K.
        • Strand A.D.
        • Cui L.
        • Beyer R.P.
        • Easley C.N.
        • Smith A.C.
        • Krainc D.
        • Luquet S.
        • Sweet I.R.
        • Schwartz M.W.
        • La Spada A.R.
        Cell Metab. 2006; 4: 349-362
        • Cao W.
        • Daniel K.W.
        • Robidoux J.
        • Puigserver P.
        • Medvedev A.V.
        • Bai X.
        • Floering L.M.
        • Spiegelman B.M.
        • Collins S.
        Mol. Cell. Biol. 2004; 24: 3057-3067
        • Yoon J.C.
        • Puigserver P.
        • Chen G.
        • Donovan J.
        • Wu Z.
        • Rhee J.
        • Adelmant G.
        • Stafford J.
        • Kahn C.R.
        • Granner D.K.
        • Newgard C.B.
        • Spiegelman B.M.
        Nature. 2001; 413: 131-138
        • Herzig R.P.
        • Scacco S.
        • Scarpulla R.C.
        J. Biol. Chem. 2000; 275: 13134-13141
        • Hondares E.
        • Mora O.
        • Yubero P.
        • Rodriguez de la Concepción M.
        • Iglesias R.
        • Giralt M.
        • Villarroya F.
        Endocrinology. 2006; 147: 2829-2838
        • Herzig S.
        • Long F.
        • Jhala U.S.
        • Hedrick S.
        • Quinn R.
        • Bauer A.
        • Rudolph D.
        • Schutz G.
        • Yoon C.
        • Puigserver P.
        • Spiegelman B.
        • Montminy M.
        Nature. 2001; 413: 179-183
        • Ryu H.
        • Lee J.
        • Impey S.
        • Ratan R.R.
        • Ferrante R.J.
        Proc. Natl. Acad. Sci. U.S.A. 2005; 102: 13915-13920
        • Lee J.
        • Kim C.H.
        • Simon D.K.
        • Aminova L.R.
        • Andreyev A.Y.
        • Kushnareva Y.E.
        • Murphy A.N.
        • Lonze B.E.
        • Kim K.S.
        • Ginty D.D.
        • Ferrante R.J.
        • Ryu H.
        • Ratan R.R.
        J. Biol. Chem. 2005; 280: 40398-40401
        • Lin J.
        • Handschin C.
        • Spiegelman B.M.
        Cell Metab. 2005; 1: 361-370
        • Uldry M.
        • Yang W.
        • St-Pierre J.
        • Lin J.
        • Seale P.
        • Spiegelman B.M.
        Cell Metab. 2006; 3: 333-341
        • Valle I.
        • Alvarez-Barrientos A.
        • Arza E.
        • Lamas S.
        • Monsalve M.
        Cardiovasc. Res. 2005; 66: 562-573
        • St.-Pierre J.
        • Lin J.
        • Krauss S.
        • Tarr P.T.
        • Yang R.
        • Newgard C.B.
        • Spiegelman B.M.
        J. Biol. Chem. 2003; 278: 26597-26603
        • Rasbach K.A.
        • Schnellmann R.G.
        Biochem. Biophys. Res. Commun. 2007; 355: 734-739
        • Liang H.
        • Bai Y.
        • Li Y.
        • Richardson A.
        • Ward W.F.
        Ann. N.Y. Acad. Sci. 2007; 1100: 264-279
        • Hara H.
        • Hiramatsu H.
        • Adachi T.
        Neurochem. Res. 2007; 32: 489-495
        • Nunome K.
        • Miyazaki S.
        • Nakano M.
        • Iguchi-Ariga S.
        • Ariga H.
        Biol. Pharm. Bull. 2008; 31: 1321-1326
        • Pitkanen S.
        • Robinson B.H.
        J. Clin. Invest. 1996; 98: 345-351
        • Wong A.
        • Yang J.
        • Cavadini P.
        • Gellera C.
        • Lonnerdal B.
        • Taroni F.
        • Cortopassi G.
        Hum. Mol. Genet. 1999; 8: 425-430
        • Kudin A.P.
        • Bimpong-Buta N.Y.
        • Vielhaber S.
        • Elger C.E.
        • Kunz W.S.
        J. Biol. Chem. 2004; 279: 4127-4135
        • Smith T.S.
        • Bennett Jr., J.P.
        Brain Res. 1997; 765: 183-188
        • Chen Q.
        • Vazquez E.J.
        • Moghaddas S.
        • Hoppel C.L.
        • Lesnefsky E.J.
        J. Biol. Chem. 2003; 278: 36027-36031
        • Schulz J.B.
        • Henshaw D.R.
        • MacGarvey U.
        • Beal M.F.
        Neurochem. Int. 1996; 29: 167-171
        • Murphy M.P.
        Biochem. J. 2009; 417: 1-13
        • Semple R.K.
        • Crowley V.C.
        • Sewter C.P.
        • Laudes M.
        • Christodoulides C.
        • Considine R.V.
        • Vidal-Puig A.
        • O'Rahilly S.
        Int. J. Obes. Relat. Metab. Disord. 2004; 28: 176-179
        • Crunkhorn S.
        • Dearie F.
        • Mantzoros C.
        • Gami H.
        • da Silva W.S.
        • Espinoza D.
        • Faucette R.
        • Barry K.
        • Bianco A.C.
        • Patti M.E.
        J. Biol. Chem. 2007; 282: 15439-15450
        • Herzig S.
        • Hedrick S.
        • Morantte I.
        • Koo S.H.
        • Galimi F.
        • Montminy M.
        Nature. 2003; 426: 190-193
        • Leone T.C.
        • Lehman J.J.
        • Finck B.N.
        • Schaeffer P.J.
        • Wende A.R.
        • Boudina S.
        • Courtois M.
        • Wozniak D.F.
        • Sambandam N.
        • Bernal-Mizrachi C.
        • Chen Z.
        • Holloszy J.O.
        • Medeiros D.M.
        • Schmidt R.E.
        • Saffitz J.E.
        • Abel E.D.
        • Semenkovich C.F.
        • Kelly D.P.
        PLoS Biol. 2005; 3: e101
        • Rudolph D.
        • Tafuri A.
        • Gass P.
        • Hämmerling G.J.
        • Arnold B.
        • Schütz G.
        Proc. Natl. Acad. Sci. U.S.A. 1998; 95: 4481-4486
        • Bourtchuladze R.
        • Frenguelli B.
        • Blendy J.
        • Cioffi D.
        • Schutz G.
        • Silva A.J.
        Cell. 1994; 79: 59-68
        • Mantamadiotis T.
        • Lemberger T.
        • Bleckmann S.C.
        • Kern H.
        • Kretz O.
        • Martin Villalba A.
        • Tronche F.
        • Kellendonk C.
        • Gau D.
        • Kapfhammer J.
        • Otto C.
        • Schmid W.
        • Schütz G.
        Nat. Genet. 2002; 31: 47-54
        • Steinberg F.M.
        • Gershwin M.E.
        • Rucker R.B.
        J. Nutr. 1994; 124: 744-753
        • Jensen F.E.
        • Gardner G.J.
        • Williams A.P.
        • Gallop P.M.
        • Aizenman E.
        • Rosenberg P.A.
        Neuroscience. 1994; 62: 399-406
        • Zhang Y.
        • Feustel P.J.
        • Kimelberg H.K.
        Brain Res. 2006; 1094: 200-206
        • Ohwada K.
        • Takeda H.
        • Yamazaki M.
        • Isogai H.
        • Nakano M.
        • Shimomura M.
        • Fukui K.
        • Urano S.
        J. Clin. Biochem. Nutr. 2008; 42: 29-34
        • Das S.
        • Lin H.S.
        • Ho P.C.
        • Ng K.Y.
        Pharm. Res. 2008; 25: 2593-2600
        • Stancanelli R.
        • Mazzaglia A.
        • Tommasini S.
        • Calabrò M.L.
        • Villari V.
        • Guardo M.
        • Ficarra P.
        • Ficarra R.
        J. Pharm. Biomed. Anal. 2007; 44: 980-984
        • Smidt C.R.
        • Unkefer C.J.
        • Houck D.R.
        • Rucker R.B.
        Proc. Soc. Exp. Biol. Med. 1991; 197: 27-31
        • Martin P.M.
        • Horwitz K.B.
        • Ryan D.S.
        • McGuire W.L.
        Endocrinology. 1978; 103: 1860-1867
        • Milne J.C.
        • Lambert P.D.
        • Schenk S.
        • Carney D.P.
        • Smith J.J.
        • Gagne D.J.
        • Jin L.
        • Boss O.
        • Perni R.B.
        • Vu C.B.
        • Bemis J.E.
        • Xie R.
        • Disch J.S.
        • Ng P.Y.
        • Nunes J.J.
        • Lynch A.V.
        • Yang H.
        • Galonek H.
        • Israelian K.
        • Choy W.
        • Iffland A.
        • Lavu S.
        • Medvedik O.
        • Sinclair D.A.
        • Olefsky J.M.
        • Jirousek M.R.
        • Elliott P.J.
        • Westphal C.H.
        Nature. 2007; 450: 712-716
        • Westphal C.H.
        • Dipp M.A.
        • Guarente L.
        Trends Biochem. Sci. 2007; 32: 555-560