Full-Spectrum Antioxidant Therapy Minimizing the Contribution of Oxidative Stress to Disease and Aging Mark F. McCarty, NutriGuard Research, Inc., [email protected] 1 Section Headings Abstract 3 Introduction 5 Spirulina and Phycocyanobilin – Getting to the Heart of Oxidative Stress 6 A Central Role for NADPH Oxidase in Oxidative Stress and Pathology 7 Why is Bilirubin so Protective? 8 Spirulina Can Pinch-Hit for Bilirubin! 11 Mitochondria – Another Key Source of Oxidant Stress 16 Astaxanthin – A Champion Antioxidant for Mitochondria and Cellular Membranes 17 Coenzyme Q10 – Mitochondrial Antioxidant and Bioenergy Cofactor 21 Coping with Peroxynitrite 24 Dr. Oster and High-Dose Folate 25 Vindication! 27 The Tremendous Trio of Antioxidant Protection 31 Boosting Uric Acid with Inosine 32 Allopurinol versus Xanthine Oxidase 34 Antioxidant Enzyme Induction 35 Green Tea Catechins 37 Melatonin as an Antioxidant 39 N-Acetylcysteine Boosts Glutathione 40 The Vitamin/Mineral Antioxidants 42 Carotenoids Afford Protection from Light-Generated Oxidants 48 Polyphenols Confer Vascular Protection 50 2 Boosting Nitric Oxide as a Complement to Antioxidant Measures 53 AMPK Activators – Metformin and Berberine 54 Potassium – Antioxidant Electrolyte for Vascular Protection and Bone Health 55 Protective “Carninutrients” with Antioxidant Potential 57 Glycine – Anti-inflammatory and Antioxidant Amino Acid 60 Controlling Iron Stores 62 Caloric Restriction and Vegan Diets vs. Mitochondrial Oxidative Stress 65 Promoting Mitochondrial Biogenesis as an Antioxidant Strategy 66 Uncouplers as Mitochondrial Antioxidants 67 Risk Factor Control – Statins and Angiotensin Antagonists 67 Oxidative Stress and Longevity 68 Resources 69 Appendix – A Few More Protective Nutraceuticals 71 References 83 3 Abstract Oxidative stress clearly plays a mediating role in many pathologies and in some functional decrements of aging, but clinical evaluations of antioxidant supplementation have so far yielded rather lackluster results. However, there is reason to suspect that this reflects the limited antioxidant efficacy of the regimens evaluated, and that clinically important benefits may be achievable with a more rational and insightful choice of agents that exploits functional complementarities. This essay reviews the range of nutraceutical antioxidant options available, and proposes a comprehensive strategy incorporating the following elements: NADPH oxidase can be down-regulated with spirulina or phycocyanobilin-enriched spirulina extracts – an effect which mimics the physiological protection afforded by bilirubin. Astaxanthin, by preventing oxidant-mediated structural damage to the mitochondrial inner membrane, may limit the up- regulation of mitochondrial superoxide production seen in many pathologies. High-dose folic acid has potent antioxidant activity in tissues which concentrate folates, and may have particular merit for controlling the pathogenic impact of peroxynitrite-derived radicals. Inosine, by boosting levels of its metabolite uric acid, may limit the damage mediated by peroxynitrite in oxidant-driven CNS disorders (unlikely to respond to high-dose folate). Induction of many antioxidant enzymes and amplification of glutathione synthesis can be achieved with clinically effective phase 2 inducers such as lipoic acid and green tea catechins, and with nocturnal melatonin administration. Glutathione synthesis can be boosted further by optimizing the availability of its rate-limiting substrate with supplemental N-acetylcysteine or cystine. A comprehensive regimen encompassing most or all of these elements in clinically meaningful doses can be expected to have broad and potent clinical utility, and may be designated “Full- Spectrum Antioxidant Therapy”. Ancillary strategies with antioxidant potential are also discussed here, including coenzyme Q10, the retinal xanthophyll carotenoids, polyphenols, potassium-rich diets, “carninutrients” (carnitine, creatine, taurine), glycine, phlebotomy, calorie restriction, vegan diet, and measures which promote mitochondrial biogenesis. Certain drugs can also aid control of oxidative stress in certain circumstances – allopurinol via inhibition of the pro-oxidant enzyme xanthine oxidase, and statins and angiotensin II antagonists via down- regulation of NADPH oxidase activation. Complementing full-spectrum antioxidant therapy with measures which amplify production of nitric oxide in the moderate physiological range – e.g. aerobic exercise training, quercetin/epicatechin, citrulline, metformin or berberine, and dietary nitrate – may potentiate the favorable impact of antioxidants on vascular health and dementia prevention, while also promoting bone density. 4 Introduction It is widely acknowledged among medical researchers that excessive oxidative stress is a key mediator of a vast array of diseases, and is also a cause of many of the functional decrements that accompany aging. Yet controlled clinical trials of “antioxidant therapy” – usually involving just vitamin E, beta-carotene, or vitamin C – have so far yielded rather paltry, often disappointing results. This may reflect the fact that the antioxidants chosen for these studies have rather limited impact on intracellular oxidative stress and its metabolic consequences, at least in persons whose baseline nutrition is reasonably decent. However, recent biomedical discoveries may make it feasible to achieve truly effective control of oxidative stress, using nutrients, foods, and phytochemicals that are currently available. This essay sets forth a proposal for a Full-Spectrum Antioxidant Therapy, in which the remarkable antioxidant potential of spirulina and its key phytochemical phycocyanobilin is complemented by a number of other effective antioxidant measures. What is proposed here is not a fixed regimen, but rather a general concept that can be tailored to the needs of individual people. For logistical reasons of cost or convenience – and, in the case of inosine, safety – it may not be feasible for a given person to employ all of these agents. And an individual’s specific health needs should of course be taken into consideration in the choice of a supplementation regimen. Moreover, the term “Therapy” is used here loosely, inasmuch as this strategy may be appropriate for healthy people who wish to remain that way. Ideally, Full-Spectrum Antioxidant Therapy should incorporate these key features: - Partial suppression of NADPH oxidase activity by ingestion of spirulina or phycocyanobilin-enriched spirulina extracts; - Moderating mitochondrial oxidant generation while promoting optimal mitochondrial function with supplemental astaxanthin and, in some circumstances, supplemental coenzyme Q10. - Scavenging of peroxynitrite-derived radicals by supplementation with high-dose folate and, optionally, inosine or dietary nucleic acids; - Induction of antioxidant enzymes and promotion of glutathione synthesis with phase 2- inducing nutraceuticals – most notably alpha-lipoic acid and green tea catechins- nocturnal melatonin supplementation, and N-acetylcysteine; - Insuring adequate intakes of nutritionally essential antioxidants such as selenium, vitamin C and gamma-tocopherol with appropriate nutritional insurance supplementation. 5 Spirulina and Phycocyanobilin – Getting to the Heart of Oxidative Stress To understand why spirulina has such exciting potential for coping with disorders associated with oxidative stress, we must first examine the physiological antioxidant role of bilirubin. Bilirubin is derived in the body from the breakdown of heme, an organic molecule that contains complexed iron and enables hemoglobin to carry oxygen; heme is also a component of many other vital enzymes. When heme is present in excess, an enzyme known as heme oxygenase-1 (HO-1) cleaves it, generating three derivatives: a free iron atom, carbon monoxide, and biliverdin. An enzyme called biliverdin reductase, found in all mammalian cells, then rapidly converts biliverdin to bilirubin. The mention of carbon monoxide understandably may raise some anxiety; in excess, this compound is a poison that can asphyxiate people whose heaters malfunction. But in the low concentrations generated by normal metabolism, it has a benign regulatory impact in our cells, and in fact can mimic some of the protective effects of the signaling molecule nitric oxide – both it and nitric oxide regulate cell behavior by activating soluble guanylate cyclase, which catalyzes cyclic GMP production. But the most intriguing factor generated by HO-1 activity is bilirubin. Bilirubin is extremely insoluble; the liver conjugates it to glucuronic acid so that is becomes sufficiently soluble to excrete in the bile. When people with liver disorders develop jaundice, the yellowish pallor of their eyes and skin reflects the high circulating levels of conjugated bilirubin in the blood which the damaged liver has failed to excrete. But bilirubin is much more than just an excretory product; when generated within cells, it has a very potent antioxidant activity. Indeed, that’s why HO-1 is considered to be an important antioxidant enzyme. By definition, oxidative stress is characterized by an excess of unstable compounds known as free radicals, and other unstable molecules – such as peroxides – which they can give rise to, and wish in turn can generate the hydroxyl free radical. Free radicals are unstable because they contain unpaired electrons, and therefore are highly prone to grab another electron from another molecule, or to donate an electron to another molecule. (Chemical compounds are most stable when they contain paired electrons.) Most biological antioxidants act as scavengers – when they encounter a free radical, they readily donate an electron to the radical, generating a more stable compound. This of course converts the antioxidant into a free radical – but antioxidants are characterized by the fact that they are fairly stable in free radical form, and therefore won’t steal electrons from other stable molecules. Moreover, cells have mechanisms for converting physiologically essential antioxidants – such as vitamin C, vitamin E, and glutathione – back to their native forms after they have donated electrons to free radicals. So scavenging antioxidants have the potential to defuse dangerous free radicals, protecting cellular proteins, fats, and nucleic acids from structural damage. For many years, it was presumed that the potent antioxidant activity of the bilirubin generated within cells by HO-1 activity reflected its ability to scavenge free radicals. Bilirubin is indeed an efficient scavenger of a wide range of free radicals, and the radical scavenging activity of the 6 free bilirubin bound to albumin in the blood stream contributes importantly to the antioxidant activity of the blood. But the notion that the bilirubin within cells is acting primarily as a free radical scavenger has frankly never made sense. Here’s why: most cells contain relatively high (millimolar) concentrations of the effective radical scavengers vitamin C and glutathione. In contrast, the concentrations of bilirubin generated within cells by HO-1 activity are in the low nanomolar range1 – in other words, a concentration over ten thousand times lower than those of glutathione and vitamin C. The rate at which scavenging antioxidants can defuse free radicals is proportionate to the concentration of the antioxidant; since the inherent capacity of bilirubin to donate electrons is not vastly higher than that of vitamin C or glutathione, it is readily seen that the scavenging activity of intracellular bilirubin will be almost negligible compared with that provided by vitamin C and glutathione. So why does generation of bilirubin via HO-1 activity have such a physiologically important antioxidant impact? Recent research has provided a satisfying and exciting answer. The fundamental source of most other free radicals in biological systems is a “progenitor” free radical known as superoxide. Superoxide is merely molecular oxygen (O2) with a single electron added to it. The chief fates of superoxide are to be converted to hydrogen peroxide and molecular oxygen – a reaction catalyzed by the enzyme superoxide dismutase – or to react spontaneously with nitric oxide to generate the very dangerous and unstable compound peroxynitrite. The hydrogen peroxide generated from superoxide, when present in very low concentrations, has a benign signaling function within many cells, reversibly altering the structure of cellular proteins by interacting with free sulfhydryl groups. But in excess it can lead to cell death or dysfunction, either by overdriving certain pro-inflammatory or cytotoxic signaling pathways, or by reacting with free iron or copper atoms to produce the vicious oxidant hydroxyl radical. Peroxynitrite, and other radicals derived from it, can have a range of adverse effects that we will discuss later. By donating an electron to iron or copper ions, superoxide can help to drive the production of hydroxyl radicals (the so-called “Haber-Weiss reaction”). Various enzymes and enzyme complexes within cells can produce superoxide by adding a single electron to molecular oxygen. During normal healthy metabolism, mitochondria – often called the “power plants” of the cell, because they generate large amounts of the energy catalyst molecule ATP – steadily produce small amounts of superoxide which are readily disposed of by antioxidant enzyme activity. However, when mitochondria become structurally disrupted in certain ways, or when they are “burning” excessive amounts of fuel, they can produce superoxide at an accelerated rate, and this may give rise to damaging oxidative stress. A Central Role for NADPH Oxidase in Oxidative Stress and Pathology Another key source of superoxide – and the most prominent source in many disease states – is an enzyme complex known as NADPH oxidase. (This complex actually occurs in several distinct isoforms;2 it is not crucial to go into the details of this now.) Concentrations of NAPDH oxidase are especially high in white cells of the immune system that function as phagocytes, engulfing and killing bacteria and other microorganisms. When phagocytes ingest bacteria, 7 NADPH oxidase becomes activated, and the resulting production of oxidative stress within phagocytic vacuoles helps to kill the ingulfed bacteria. Indeed, people in whom the phagocytic form of NADPH oxidase is genetically absent are said to have chronic granulomatous disease, and suffer from recurrent infections owing to their impaired capacity to kill certain types of bacteria. However, forms of NAPDH oxidase are found in many other types of cells, including cells that don’t participate in immune defense. In these cells, moderate activation of NAPDH oxidase generates hydrogen peroxide, and thereby can act in various ways to modulate cellular behavior in a physiologically appropriate way. But ongoing medical research is demonstrating that, in a remarkably high proportion of health disorders, NADPH oxidase becomes overactivated in affected tissues, and the resulting oxidative stress either exacerbates or even mediates the disorder. Here is a partial list3 of the disorders in which overactivity of NADPH oxidase is now believed to play a key pathogenic role: Atherosclerosis / Hypertension / Cardiac Hypertrophy / Congestive Heart Failure / Aortic Aneurysms / Sleep Apnea / Tissue Damage stemming from Heart Attack or Stroke / Insulin Resistance Syndrome / Major Complications of Diabetes, including Kidney Failure, Blindness, and Heart Disease / Erectile Dysfunction / Cartilage Loss in Osteoarthritis and Rheumatoid Arthritis / Osteoporosis / Inflammatory Carcinogenesis / Alzheimer’s Disease / Parkinson’s Disease / Liver Cirrhosis associated with Hepatitis or Alcoholism / Sun-Induced Skin Damage and Sunburn / Pulmonary Fibrosis / Periodontal Disease / Pre-eclampsia / Asthma / Allergies / Septic Shock / Scleroderma / Glaucoma-induced Blindness / Sickle Cell Anemia This no doubt is only a partial list, because there are other common disorders, such as macular degeneration and cataracts, which clearly are linked to increased oxidative stress, but in which the source of this oxidative stress has not yet been clearly defined. As if this list weren’t impressive (or depressing) enough, there is also evidence that NAPDH oxidase is chronically activated in many human cancers, and the resulting oxidative stress, by boosting growth factor activities, makes the cancer more aggressive, growing quicker and spreading more rapidly.4 And the adverse effects of cigarette smoke on the vascular tissue, and on other tissues distant from the lungs, appear to be mediated largely by reactive compounds that trigger NADPH oxidase activation.5-8 Clearly, whereas a little bit of NADPH oxidase activity is physiologically appropriate, excessive activity is very bad news indeed! Why is Bilirubin so Protective? So what does any of this have to do with bilirubin? 8 Simply this: Medical researchers have recently established that the physiological antioxidant role of bilirubin within cells reflects its ability to act as a very potent inhibitor of NAPDH oxidase activity.9-11 (The isoform specificity of this effect requires further clarification.) This in turn provides a very satisfying explanation for the antioxidant role of HO-1. When cells are exposed to excess oxidative stress, this triggers increased production of HO-1. This increase in HO-1 activity accelerates the conversion of cellular heme to, among other things, bilirubin; the increase in bilirubin then acts to suppress NADPH oxidase activity which, in a high proportion of circumstances, is the key source of the cell’s excessive oxidative stress.12 Clearly, the induction of HO-1 represents a physiological feedback mechanism that helps keep oxidative stress in check. This perspective makes it clear why bilirubin is very different from scavenging antioxidants like vitamins C or E. Here’s an analogy that should make this concept easier to grasp: Visualize a sink, with the tap jammed open. Water is spilling out into the sink; the sink is now full, and water is spilling out onto the floor. Think of the water on the floor as excessive oxidative stress. Scavenging antioxidants function like mops. Some mops work on one part of the floor, others work on another. None of the mops, by itself, can clean the whole floor. What does bilirubin do? It turns off the tap! In other words, bilirubin goes right to the source of the oxidative stress, turning it off, and preventing all of the downstream consequences of excessive oxidative stress. This latter consideration is very important. Antioxidants such as vitamin C and vitamin E can indeed dispose of some free radicals, but they do little to prevent the generation of hydrogen peroxide from superoxide. An excess of hydrogen peroxide is a key mediator of cell dysfunction and death in many disorders – which likely explains why supplementation with vitamins C and E hasn’t been notably successful in many controlled clinical studies. Bilirubin functions at a fundamentally higher level. These considerations suggest an important question: do moderate increases in bilirubin availability influence disease risk in humans? Recent genetic and epidemiological research suggests that the answer is yes. Humans often inherit slightly different forms of genes; these genetic variations are known as polymorphisms, and a specific form of a polymorphic gene is known as an allele. The gene for HO-1 is polymorphic, and some alleles of this gene are considered “high expression”; in people who carry these alleles of HO-1, an oxidative stress induces a higher expression of HO-1 than in a person who carries a low expression allele. Perhaps not surprisingly, genetic studies are showing that people who carry one or two high-expression alleles of HO-1 are at lower risk for certain disorders: coronary artery disease, emphysema (in smokers), restenosis after angioplasty or coronary stenting, abdominal aortic aneurysms, lung cancer (in smokers), and oral cancer (in 9 betel nut chewers).3, 13 No doubt this is just the beginning of genetic research into the health impacts of HO-1 polymorphisms. Perhaps the most intriguing study in this regard was conducted by Japanese researchers, who noticed a remarkable phenomenon: when they segregated Japanese women by age, and looked at the extent to which these women carried the high expression alleles of HO-1, they found that the high expression alleles were much more common in elderly women than in younger women.14 Does this mean the that the Japanese people have undergone remarkably rapid evolution in the last few decades? Not likely! No, the likely explanation is that the Japanese women who carried the low expression alleles tended to die off before they could become elderly! In other words, efficient induction of HO-1 increases average longevity. In light of what we now know about bilirubin and NADPH oxidase, it seems likely that efficient bilirubin production is largely responsible for this phenomenon. Another polymorphic gene that influences bilirubin level codes for the enzyme UDP- glucuronosyltransferase 1A1 – more humanely abbreviated as UGT1A1. This is the liver enzyme that hooks bilirubin to a glucuronic acid so that bilirubin can be excreted through the bile ducts. A low expression allele of this gene is fairly common in humans, and people who inherit two copies of this low expression allele have a moderate impairment of their capacity to conjugate bilirubin; as a result, free bilirubin levels in their blood are 2-3-fold higher than in other people. People who for genetic reasons maintain relatively high serum bilirubin levels (about 20 µM) are said to have Gilbert syndrome (in honor of the French physician who first characterized it), and they typically carry two copies of the low-expression form of UGT1A1. Despite the fact that these people are said to have a “syndrome”, there so far are no known adverse health consequences associated with it. (It can however be inconvenient, as physicians sometimes subject patients with Gilbert syndrome to batteries of liver tests, suspecting that the elevation of bilirubin may reflect liver disease!) In fact, recent studies have shown that people with Gilbert syndrome are at decidedly lower risk for coronary heart disease and colorectal cancer.15 And a remarkable recent Japanese study concluded that, in long-term diabetics, the patients who also had Gilbert syndrome were only about a third as likely to experience major common complications such as kidney failure, blindness, and coronary disease.16 (It is no coincidence that the Japanese physician who organized this study, Dr. Toyoshi Inoguchi, has devoted much of his career to demonstrating the key role of overactive NADPH oxidase in the induction of diabetic complications.)17 Even in people who don’t have Gilbert syndrome, relatively elevated serum bilirubin levels have been correlated with decreased risk for a number of health disorders, including coronary heart disease, lung cancer, chronic obstructive respiratory disease, diabetic complications, and rheumatoid arthritis.18-23 And in striking concordance with the Japanese HO-1 study cited above, Dr. Laura Horsfall and colleagues found that serum bilirubin correlated inversely with risk for total mortality.20 10