The Importance of Methionine Metabolism in Comprehensive Detoxification · The Importance of...
Transcript of The Importance of Methionine Metabolism in Comprehensive Detoxification · The Importance of...
The Importance of Methionine Metabolism in Comprehensive
Detoxification and Health
David Quig, PhD
Disclosure
David Quig is the Vice President, Scientific Support, for Doctor’s Data, Inc.
David Quig, PhD
Environmental Toxins
• Centers for Disease Control and Prevention (C.D.C)
“The epidemic of epidemics of CVD and immunological and neurological diseases is likely associated with environmental toxins [toxicants]”
ATSDR/CDC/USPHS monographs on specific toxic metals
David Quig, PhD
Multiple Assailants, Individual Victims
• Knowledge of adverse effects have been based primarily on independent studies of SINGLE toxicants. (NIEHS)
• Toxicants (metals, chemicals) can elicit independent, additive or synergistic toxic effects. (C.D.C.)
• Individuals vary considerably in their sensitivity to toxicants and, susceptibility to toxic effects varies with age, gender, pregnancy status, nutritional status, total toxic load and genetics. (C.D.C.)
Single Nucleotide Polymorphisms (SNPs)
ATSDR/CDC Lead update(2007) Am J Clin Nutr(2009)89:425-30 Med Clin N
Am(2005)89:721 Int J Res Pub Hlth(2011)8:629-47 Env Hlth Perspect(1995)103:1048
David Quig, PhD
Endogenous Detoxification
• Chemical entities (environmental toxicants and endogenously produced toxins, including gut derived)
• Reactive oxygen species (ROS)
• Methionine metabolism- methylation / transsulfuration
• Toxic elements (intertwined effects, direct and epigenetic)
David Quig, PhD
The GI Microbiome and Toxicology
• The C.D.C. acknowledges that toxicokinetic models need to be revised to include the influence of the GI microbiome “pool.”*
• Strong evidence that toxicant disruption of the GI microbiome crosses generations (e.g. “bad microbiome from grandma”)
• Microorganisms that normally live in the GI tract perform many useful functions (train immune system, neurotransmitter production)
• Promote the expression of hepatic CYPs (Phase I)
• Detoxification of arsenic, lead, mercury and chemical entities
• Convert a phytoestrogen precursor (hops) to an anti-inflammatory, cardioprotective compound
• The metabolic activity of the GI microbiome rivals that of the liver!
Env Hlth perspect(2011)119:A341-46 Env Hlth Perspect(2009)117:A199-205 *Personal communication: R.Dietert, PhD Toxicologist, Cornell University [4/5/14]
David Quig, PhD
Detoxification of Organic Compounds: Endo- and Xenobiotics
• PhaseI – oxidative activation
• Phase II – conjugation
• Phase III –unidirectional excretion
• Optimal detoxification requires coordinated regulation of expression of genes encoding for enzymes in all three phases
J Neurosci(2008)28:265-72 Drug Metab Dispos(2001)29:779-80
David Quig, PhD
Phase I: Oxidative Activation • Cytochrome P450 enzymes (CYPs) add reactive & polar
groups to lipophilic substrates → reactive electrophiles (oxidation, hydroxylation, or N-, O-, S-dealkylations)
• Prosthetic heme is absolutely essential for CYP activities.
• Heme biosynthesis (porphyrinogen pathway) requires Fe and Zn.
Affected by anemias, and inherited enzyme defects
Inhibited by Pb, Hg, As and chemical entities (specific urine porphyrin profiles)
Drug Metab Rev(2011)43:1-26 Cell(2005)122:505-15 J Biol Org Chem (1997)2:411-17
David Quig, PhD
Toxicants Inhibit Phase I Detoxification
Toxicology in Vitro (2007)21:408-16 Molec Carcinogenesis (2000)28:225-35 Toxicol Letters(2004)148:153-8 Interdisip Toxicol(2013)6:159-84
Eur J Pharmacol(2005)510:127-134
Cytochrome P450 isozymes (CYPs)
Xenobiotic
Activated Xenobiotic
Hg, Pb, Cd, As, Co, X Cr6, glyphosate, O-antigen (K. pneumoniae, P. aeruginosa)
David Quig, PhD
Phase II: Conjugation
• Conjugation of activated toxins to increase hydrophilicity (e.g. GSH, sulfation, acetylation or glucuronidation)
• Catalyzed by broad-specificity transferases (glutathione S-transferases,UDP-glucuronosyl-transferases)
• Cannot cross lipid membranes at a sufficient rate without specific ATP-dependent export transporters (Phase III)
Drug Metab Rev(2011)43:1-26 Biofactors(2003)17:103-14 BBA(1999)1461:377-94
David Quig, PhD
Phase II: Glutathione Conjugation
Activated Xenobiotic
GS-conjugates
GSH
Glutathione S-transferases
Comp Biochem Physiol Clin Toxicol Pharmacol(2008)148:117-21 Molec Carcinogen(2000)28:225-35 Food & Chem Toxicol (2004) 42: 1563-71
Pb, MeHg, Hg, Cd, As, Cr6, Co
X *
ROS
David Quig, PhD
Further Metabolism of GS-conjugates
GS-conjugates
Cys(e) S-conjugate
glutamate
glycine
GGT (inducible)
dipepdidase
Phase III
Biol Pharm Bull(2001)24:1324-28
Membrane bound
N-acetyltransferase
Mercapturic Acids Urine Bile
Intestine
*
Phase III
David Quig, PhD
Hepatic Detoxification Profile • D-glucaric acid- indicator of induction of CYP enzymes
• Mercapturic acids- end products of GSH/Cys(e) conjugation
• 48 yof, ill after starting work in brand new energy efficient office complex (VOC commonly about 10-X > outdoor air)
First AM urine collection
David Quig, PhD
Oxidative Stress and GSH Depletion
Ox-LDL (apoB), endothelial dysfunction and, oxidized lipids, proteins and DNA (8-OH-dG)
↓ Cellular GSH
Cd, As, Pb, Hg, / Fe, Cu, Co
ROS ~ 4 million
.OH/cell/day (1o mitochondria)
Hg2+
GSH
GSH
Am J Ind Med(2007)50:757-64 Alcohol Res Hlth(2003)27:277-84 Free Rad Biol Med(1995)18:321-36
David Quig, PhD
Quenching Reactive Oxygen Species (radical /non-radical)
• Superoxide Dismutases (Cu,Zn and Mn)
SOD + 2 O2. + 2 H+ → O2 + H2O2
• GSH peroxidases - (selenium)
2 H2O2 + 2 rGSH → GS-SG + 2 H2O
(Also lipid peroxides → alcohols)
• GSH reductase (inhibited by Pb, Hg, Cu, Cd)
GS-SG + NADPH → 2 GSH (Mg and up to 10% of total body glucose “disposal”) Curr Vascular Pharmacol(2010)8:259-75 Curr Pharm Des(2009)15:2988-3002
Biochim Biophys Acta(2009)1780:869-72 Arch Biochem Biophys(2009)485:56-62
David Quig, PhD
Hair Elements- 48 yof, vegetarian
Mg
Zn
Se
David Quig, PhD
Serum Elements
Mg
David Quig, PhD
Whole Blood Elements
Mg
Zn
Se
As
David Quig, PhD
Red Blood Cell Elements
Se
Mg
Zn
As
David Quig, PhD
Phase III: Pump it Out! Membrane-bound efflux pumps- ↓ local cellular
toxins (Phase II conjugates and their metabolites)
• ENERGY DEPENDENT
• MRPs- multidrug resistance-associated proteins Differential tissue distribution & substrate specificities
• OATPs- organic anion-transport proteins
Kidney proximal tubule membrane
Hepatocyte canalicular membrane → bile → SI
Pharmacogenomics(2008)9:105-27 Clin Exp Pham Physiol(2010)37:115-20 Biofactors(2003)17:103-14
David Quig, PhD
Inflammation Compromises Detoxification • Inflammation of the intestines or liver compromises
detoxification
• Intestinal inflammation down-regulates hepatic efflux pump activity- suppression of basolateral secretion of toxins inhibits Phase II → increases oxidative stress
• Determine the cause(s) of GI inflammation (CSAP)
• Ameliorate inflammation- Optimize beneficial flora (↑butyrate), Vitamin D (dampens pro-inflammatory cytokines), curcumin and, ↑sIgA (S. boulardii, Lactobacillus GG, Bifidobacterium lactis Bb-12 )
Toxicol Sci(2009)107:27-39 Am J Physiol(2007)292:G1114-22 JBC(2006)281:17883-89 Gut(2003)52:1788-95 Gastroenterol(2008)135:529-38 Immunity(2007)26:812-26
J Appl Microbiol(2000)89:404-14
David Quig, PhD
Essential Methionine (Met)
• “Most important” essential amino acid (opinion!)
• The start codon that initiates the synthesis every new molecule of DNA and RNA is the sequence for methionine.
Met is required to start the synthesis of every protein.
• Met is required for all methylation reactions and, all gene expression is influenced by methylation (gene expression turned on or off, even viral DNA)
David Quig, PhD
Methionine is the Precursor for Very Important Molecules
• S-adenosyl methionine (SAM)
• Conditionally Essential Amino acids
Cysteine
Taurine
• Glutathione
• Essential Sulfate
David Quig, PhD
Consequences of Aberrant Methionine Metabolism
• ↓ Methionine – from remethylation of homocysteine
• ↓ Methylation (SAM)- DNA/RNA, proteins, NTs, PLs
• ↓ Transsulfuration- ↓cysteine, taurine, sulfate and GSH
Potential clinical consequences:
Aberrant neurotransmitter metabolism, developmental delay, psychiatric affects, oxidative stress, ↓ DNA synthesis & repair, immune dysregulation, compromised detoxification, and ↑risk for CVD, cancer and, maybe ASD
Am J Clin Nutr(2007)86:1581-5 Am J Clin Nutr(2001)74:723-9
J AutismDev(2008)38:1966-75
David Quig, PhD
Aberrant Methylation- Increased Risk for:
Cardiovascular Disease (CVD) Certain Cancers (e.g. colorectal)
Immune Dysfunction Birth Defects
Recurrent Pregnancy Losses Central Nervous System Demyelinization
Neuropsychiatric Disease (schizophrenia, bipolar, depression, autism?)
Developmental Delays Poor Healing (injury, surgery)
David Quig, PhD
David Quig, PhD
High SAM “switch”
+
X
X
THF
5-CH3THF
MTHFR
SAH
Homocysteine
Cystathionine
Cysteine
Glutathione
Methionine
SAM
5,10-methyleneTHF
BHMT MTases
Cellular Methylation
DNA, RNA, protein, neurotransmitters,
phospholipids, creatine
Methylation ATP Mg
Betaine or TMG B-12, Zn
MS
Transmethylation “Methionine Cycle”
“Short route”
“Long route”
Folate
Zn, B-6
Transsulfuration
P-5-P, Zn, Heme
P-5-P
Mg, K
David Quig, PhD
5,10-methylene THF
MTHFR
MTR BHMT
MTRR
CBS
AHCY
X
DMG DNA, RNA, protein, neurotransmitters,
phospholipids, creatine
Pb, BPA
X Hg, Ox. stress
Mol Aspects Med(2009)30:43-59 Environ Hlth Persp (2009)117:1466-71
Insufficient Folate, B-12 (B vitamins), Betaine, Zn
David Quig, PhD
Formation of THE Methyl Donor-SAM
• Up to 50% of dietary methionine is catabolized to SAM
• Methionine adenosyltransferase (MAT) activity requires ATP and Mg
• MAT inactivated by:
CCl4 , septic shock, episodes of hypoxia
Oxidative stress- reversible by GSH (if sufficient)
Bacterial lipopolysacharides (LPS, e.g. O-antigen from gut)
Hepatitis B, HepC-induced cirrhosis, alcohol-induced liver disease
Methodrexate (several pharmaceuticals)
Adv Nutr(2011)2:421-27 FASEB J(2002)16:15-26 J Nutr(2002)182:28775-815
David Quig, PhD
Methionine Synthase (MS) Pathway
• Transmethylation of homocysteine → methionine
• Activity Requires: (Zn)
Active form of Folate
5,10 Methylene-THF 5-methyl-THF
B-12 (methylated by 5-methyl-THF)
• MS pathway is inhibited in neuroblastoma cells by: ethanol, Pb, Al, Hg2+ (and thimerosal)
MTHFR
Mol Aspects Med(2009)30:42-59 NeurTox(2008)29:190-201 Molec Psychiatry(2004)9:358-70
B-2
David Quig, PhD
Single Nucleotide Polymorphisms (SNPs) • Subtle DNA sequence variations (≥ 1% of population)
Abundant in the human genome
Frequent in the general population
• SNPs do not cause disease.
• Most are inconsequential but some are associated with metabolic abnormalities and, ↑or ↓ risk of disease.
• Toxicants can exacerbate the effects of SNPs (e.g. metals)
• Multiple SNPs in a single gene increase odds for abnormal phenotypic expression.
• SNPs in multiple genes may be necessary to affect systems/health outcomes (gene-gene interactions)
Nature Genetics(2011) DOI: 10. 1038/ng.862
David Quig, PhD
MTHFR
THF
MTR
MTRR
Homocysteine
Methionine
SAM
AHCY
SAH BHMT
CBS
Cystathionine
Cysteine
Sulfite SUOX
Sulfate
B12
Think about the Big Picture (e.g. gene-gene interactions)
Impaired methylation/detoxification, ↑ risk CVD/stroke and cancer
Cumulative effects w/ AHCY, MTR, MTRR & CBS
SAH
David Quig, PhD
Methylation Profile: Phenotypic Expression An integrated metabolic profile reflecting the influence of genetic and
epigenetic factors on methionine metabolism (S.Jill James, PhD)
World J Gastroenterol(2009)15:257-63 AJCN(2004)80:1611-7 Cancer Res(1983)43:3451-8
Low Methylation Index, limited detoxification
** SAH
> 4 2.8 SAM : SAH
David Quig, PhD
Plasma SAH and Risk for CVD?
• Great overlap for Hcys between CVD patients and controls
• 30 CVD patients and 29 age- and sex-matched controls
Plasma Patients Controls
Homocysteine (umol/L)
12.8 (4.9) 11 (3.2)
SAH (nmol/L)
40 (21) 27 (7)*
AJCN(2007)86:1581-5 AJCN(2001)74:723-9
Mean ± SD, *(p<0.05)
David Quig, PhD
SAH and CVD: Prospective Study • 1,003 coronary angiography patients, 27-87 yrs. (China)
• Baseline Hcy and SAH- hazards model to evaluate risk for CV events (fatal CVDs, nonfatal MI and stroke)… 3 year follow up
• 93 participants had events. Age-sex adjusted hazard ratio of CV events was 3.38 for each 1-SD increase in plasma SAH concentration (95% CI: 2.12, 5.39)
• Hazard ratios across quartiles was 1.0, 2.25, 2.72, and 3.4
• No significant effects of age, sex, or “other risk factors”
• Elevated levels of plasma SAH appear to be independently associated with increased risk of coronary events
Am J Clin Nutr(2013)98:1162-9
David Quig, PhD
Cardiovascular Risk Factors: Non-lipid
73 yof, metabolic syndrome, quadruple by-pass surgery
Low Moderate High
25
Methylation / Transsulfuration?
David Quig, PhD
Patient’s Methionine Metabolism
*
2.0 SAM : SAH
Very Low Methylation Index
*
23 Hcys
49 SAH
David Quig, PhD
Arsenic Detoxification Requires Methylation
• Endogenous detoxification of AsIn entails sequential reduction and oxidative methylation reactions
• As+3 MMAic+5 MMAous
+3 DMA+5-GSH
• Requires SAM and As methyl transferase activity
• Low methionine, folate and cysteine all impede arsenic detoxification
Exp Biol Med(2007)232:3-13 J Biol Chem(2002)277:10795-803 Toxicol Sci(2005)85:847-58 Toxicol Appl Parmacol(2005)19:1202-10
ATSDR Toxicological Profile for Arsenic (2000)
ox red ox
David Quig, PhD
As Detoxification: Folate Supplementation
• DBPC trial- 130 Bangladeshi adults with “marginal folate status”
• Treatment- Folate (400 ug/day) verses placebo (12 weeks)
Plasma- total As; 13.6 % lower, MMA; 20 % lower but, NO Change AsIn
Urine- 10 % ↑ DMA/gm creatinine after 1 week, but no difference between groups after 12 wks. (↑ creatinine)
• Folate-induced methylation of AsIn increased detoxification and decorporation of As despite no change in exposure.
Am J Clin Nutr(2007)86:1202-9
David Quig, PhD
MTHFR SNPs and As Detoxification
• 170 subjects from an As-exposed region in Argentina
• Subjects with MTHFR homozygous variants excreted significantly more AsIn and less DMA5+ (↓DMA/MMA- skin cancer, peripheral vascular disease)
• Bladder cancer- cases (n=410) vs. controls (n=410)
3.5-fold increased risk with MTHFR/C677T variants
6.6-fold increased risk for smokers with C677T variants
Similar results for MTHFR/A1298C plus MTR/A2756G variants
J Toxicol Environ Hlth(2007)2:159-70 J Environ Sci Hlth(2007)25:1-22
Carcinogenesis(2004)25:1639-47
David Quig, PhD
Arsenic in our Population
• U.S.- well water > 5ppb inversely correlated with IQ * (verses As < 5 ppb, n=272 children, grades 3-5)
• Chicken- As-laden antiparasitic in chicken feed → inorganic As
• Rice milk- 19 samples exceeded the U.S. drinking water standard for inorganic As (10 ppb, W.H.O. < 5 ppb)
• Rice /products- (cereals etc.) 3.5-6.7 ug/serving
Rice bran and its products contain 10-X more As than bulk grain (brown rice >> white, brown rice syrup)
Apple juice- 168 samples, ND-45ppb (FDA level of concern = 23)
*Environ Hlth(2014)13:23-33 Environ Hlth Perspect(2012)120:a269 J Environ Monit(2008)10:428-31 Environ Sci Technol(2008)42:7542-46
Environ Sci Technol(2008)421051-57 www.fda.gov/FoodSafety/FoodContaminantsAdulteration/Metals/Metals/ucm273328.
David Quig, PhD
Glutathione (GSH) γ-glutamylcysteinylglycine SH Intracellular Functions
Most abundant intracellular thiol (1-10 mM)
Modulates DNA synthesis & immune function
Regulates nitric oxide homeostasis
Antioxidant defense / Redox control
Facilitates cellular Mg and glucose uptake
Conjugation of metals and chemicals
Mol Aspects Med(2009)30:42-59 Amino Acids(2012) doi:10.1155/2012/736837
Hypertension(1999)34:1002-6
David Quig, PhD
Low GSH in Patients with:
• Toxic metals/chemicals
• Fe or Cu overload
• Cardiovascular Disease
• COPD/asthma/ARDS
• Diabetes/dysglycemia
• Hypertension
• Chronic stress
• Anxiety
• Aging
• Neurological diseases
• Viral hepatitis/Hep C
• Cirrhosis
• Autism
• Chronic fatigue
• HIV infection (RBC GSH)* ↓synthesis of GCL, GS and GSR
• Extreme exercise / ETF
J Neurol Sci(2008)[Epub] AJCN(2004)80:1611-17 Prostaglandins Leukot Fatty Acids(2002)67:341-5 J Lab Clin Med(1992)120310-17 Clin Chim Acta(2003)333:19-39
*Frontiers in Pharmacology (2014) In press
David Quig, PhD
Manipulation of the GSH synthetic capacity is an important target in the treatment of many of these disorders.
Excellent review: Luschack V. Amino Acids(2012) doi:10.1155/2012/736837
David Quig, PhD
GSH, Oxidative Stress and CVD
• Serum rGSH levels are inversely correlated with arterial intimal media thickness (humans)1.
• Oxidative stress → Ox-LDL→ unregulated Ox-LDL uptake by macrophages→ oxidative damage to macrophages 2
Macsox in turn can oxidize normal and small dense LDL • Apo-E null rats - Oral liposomal GSH decreased Ox-LDL
uptake, Macsox, Mac cholesteryl ester content, and aortic lesion area by 30% (vs. control liposomes)3
1Am Coll Cardiol(2006)47:1005-11 2 Athersclerosis(2002)161:307-16 3Atherosclerosis(2007)195 :e61-e68
David Quig, PhD
GSH Peroxidase and GSH are Associated with Circulating Lipoproteins
Atherosclerosis(2007)195:e61-e68 (Personal communication, Dr. T. Guilford) Free Rad Res(2000)S85-97 Circulation(2003)107:2775-79
GSH
GPxSe
LDL
GSH
GPxSe
HDL
~5-X > in LDL
Paraoxinase 1 Hydrolyzes organophosphates, anti-oxidant /cardioprotective
David Quig, PhD
8-OH-dG*
GSH Status and Oxidative Stress
1,000 - 2,000 µmoles/L RBC GSH
*(8-hydroxy-2’-deoxyguanosine)
* First AM urine collection
59 yom, heavy smoker- elevated BP, and blood levels of lead and cadmium
Oxidized LDL < 45 U/L
David Quig, PhD
Increasing GSH Levels Exogenously • NOT oral encapsulated GSH (intestinal breakdown and use)
• Oral liposomal GSH- ↑ RBC1, brain and heart GSH, ↑ Co excretion, anti-atherosclerotic effects (apoE-null mice)
↑plasma rGSH, cysteine, taurine and sulfate (n=13 ASD)
1,000-X more effective than N-AC (human macrophages)2
• Intravenous GSH- T1/2 = 14 ± 1min. (2 gms., 10 adults)
90 min. post- Plasma GSH;↑48-X, cysteine; ↑ 14-X
Urine GSH; ↑ 300-X, cysteine; ↑ 10-X
Eur J Pharm(1992)43:667-9 Athero(2007)195 :61-68 1Quig unpublished(2013) Med Sci Monit(2012)17:677-82 J Cardiovasc Pharmacol(2013)61:233-39 2J Interferon
Cytokine Res(2013)33:270-9 Eur J Invest(1991)21:103-10
David Quig, PhD
Liposomal Glutathione
Glutathione
© FT Guilford 2014
Maintained in reduced state
David Quig, PhD
Pilot Study- Liposomal GSH and RBC GSH
RBC GSH (umoles/L)*
Baseline 728, 739
2 weeks 925 (26%)
2 months 1,218 (66%)
4 months 1,680 (128%)
57 yof, 14 yrs. Lyme’s Disease, moderate Pb and Cd retention
1 tsp. each AM w/o food. Blood drawn 24 hrs. after last dose. *Reference range- 1,000 – 2,000 ug/L
Quig, unpublished observations (2013)
David Quig, PhD
Increasing GSH Biosynthesis
• Adequate dietary protein
cysteine (N-AC), methionine with co-factors, “medicinal” whey protein (undenatured), [glutamine and/or α-ketoglutarate]
• Antioxidants : EMT, C, α-lipoic acid, curcumin*
Regenerate (reduce GS-SG) and spare rGSH
• B vitamins: B-6, riboflavin, niacin (NADPH), Mg
AJCN(2009)89:425-30 AJCN(2004)80:1611-17 FEBS J(2011)278:3152-63 J Appl Physiol(1999)871:1381-5 J Inorg Biochem(2004)98:266
* Free Rad Biol Med(2008)44:907-17
David Quig, PhD
Upregulate the Rate Limiting Enzyme in GSH Biosynthesis
• γ-glutamylcysteine ligase (GCL)
• Curcumin and quercetin ↑GSH levels by stimulating the transcription and activity of GCL
• Onion extract and quercetin ↑ GSH levels and mRNA for a GCL subunit promoter
• Oleanolic acid increases/maintains hepatic GSH
• Induction of gene expression of GCL
J Neurochem(2009)108:1410-22 Free Rad Biol Med(2002)32:386-93
J Pharmacol Exp Therap(1993)266:1607-13
David Quig, PhD
Low Bioavailability of Curcumin
curcumin glucuronide
Systemic bioavailability- increased with piperine that inhibits intestinal glucuronidation
Mol Pharmaceutics(2007)4:807-18 Eur J Cancer(2005)41:1955-68
Curcumin “Phytosome”-phosphatidylcholine complex
David Quig, PhD
Mg, K γ-glutamylcysteine GSH
ATP, glycine ADP, Pi GSH
Synthase
ATP, glutamine
γ-glutamylcysteine ligase
ADP, Pi
Mg, K
Cysteine ↑ Transcription of GCL
Curcumin Quercitin
Oleanolic acid
X Hg2+
X
David Quig, PhD
Mg, K γ-glutamylcysteine GSH
ATP, glycine ADP, Pi GSH
Synthase
ATP, glutamine
γ-glutamylcysteine ligase (GCL) SNPs
ADP, Pi
Mg, K
Cysteine
David Quig, PhD
GSH Biosynthesis (GCL) • GCL deficiency is rare- markedly ↓ RBC GSH leading to
hemolytic anemia and impaired neurological function
• GCL has catalytic (GCLC) and modulatory (GCLM) subunits
• Four clinical missense variants in GCLC- ↓ levels of GSH (cumulative effects with GSTM1 and GSTT1 SNPs)
• Possible Health Implications- oxidative damage, impaired detoxification, neurological and immune dysfunction, altered synthesis of proteins and DNA
• Optimize the phenotype- Monitor GSH status and oxidative stress (e.g. 8-OHdG), minimize exposure to toxic chemicals and metals, consider exogenous GSH (liposomal, daily).
Biochem(2011)26:6508-17 Sci Tot Environ(2007)1-3:37-47 Blood(2000)95:2193-96
David Quig, PhD
Metallothioneins- Cytosolic “Toxin Traps”
• ~30% cysteine (-SH)
• Highest concentrations- liver, kidneys, intestines, lungs and testis
Ann Rev Biochem (1986)55:913-51
Cd
David Quig, PhD
Metallothioneins- ROS and Metal Binding
• Excellent free radical scavengers (>rGSH)*
• Safe donation/storage of essential Zn and Cu
• Sequester toxic elements (Hg, Ag, Cd, Pb, Pt) in the cytosol
• Binding affinities: Bi> Hg >Ag > Cu > Cd > Zn
See Aschner M J, Alzheimers Dis(2005)8:139-45 Mut Res(2003)533:211-26 *Toxicol Letters(2003)136:193-8
David Quig, PhD
Zinc and ROS Increase Metallothionein (MT) Gene Expression
• Displaced Zn binds to a nuclear metal transcription factor (MTF-1) that binds to the metal response element (MRE, promotor region)
• ROS bind to and activate the antioxidant response element (ARE, Nrf2-mediated)
• Both mechanisms result in increased MT synthesis
Genes Dev(2005)19:891-6 Biochem Pharmacol(2009)77:1273-82 Biochem Pharmacol(2000)59:95-104
David Quig, PhD
Common Plant Compounds Induce Hepatic MT Synthesis
• Oleanolic (OA) and ursolic acids- common triterpenoids that have antioxidant, hepatoprotective, anti-inflammatory and anti-tumor properties (initiation and promotion)
• Induction of hepatic MT (Nrf2-mediated)- imparts protection from oxidative stress, CCl4 , Cd, acetaminophen and bromobenzene
• OA has long been used in China to treat hepatitis
• Available, synthesized and water soluble derivatives are “in the works” (Rx)
J Ethno-Pharmacol(2005)100:92-4 PNAS(2005)102:4584-89 Biochem Pharmacol(2009)77:1273-82
David Quig, PhD
Support for GSH and MT
• Antioxidants- vitamin C (TID), mixed tocopherols, lipoic acid, curcumin, etc.
• B vitamins, Mg, Se • Inducers: curcumin, quercitin, oleanolic acid, zinc • Appropriate intake of high BV protein and energy • Methionine (w/ co-factors) or N-AC based on need Excess cysteine is cytotoxic and neurotoxic,
synergistic with glutamate (excitotoxic)*
Amino Acids(2009)37:55-63 *Brain Research(1995)705:65-70
David Quig, PhD
SUOX
CDO
Amino Acids(2009)37:55-63 NeuroToxicol(2008)29:190-201
Excess Cysteine GSH GCL
Taurine B-6
Cysteine sulfinate
Sulfite
B-6
Sulfate
SUOX
O2 Cysteine Dioxygenase
* X Mo
David Quig, PhD
Essential Ionic Sulfate (SO42-)
• 80-90% of sulfate is derived from cysteine
• Sulfite oxidase (SUOX)- Mo-dependent, eliminates sulfite and produces sulfate
• Sulfate is important for:
The synthesis of cellular structural components (mucins) (sulfated extracellular mucopolysaccharides)
Regulation/balance of hormones and neurotransmitters
Sulfonation- Phase II Detoxification of phenols, steroidal hormones, tyramine, xenobiotics, and some drugs (e.g. acetaminophen, prednisone)
J Nutr Environ Med(2003)13:215-29 Neuropsychopharm(2004)15:305-9
Food Cosmetics Toxicol(1981)19:221-32
David Quig, PhD
Possible Health Implications
• Low sulfate / sulfation may be associated with:
Altered mucosal barriers (gut, lungs); intestinal permeability, food sensitivities, IBS, asthma, impaired detoxification, chemical sensitivity, migraines, Rheumatoid arthritis, Parkinson’s / Alzheimer's, ASD, systemic autoimmune disease (lupus)
Env Hlth Perspect(2007)115(S-1):51-54 BBA(2007)1774:527-39 Neuropsychopharm(2004)15:305-9
David Quig, PhD
Catechol-O-Methyltransferase (COMT) • CNS- inactivates catecholamine neurotransmitters
• Liver- inactivate carcinogenic catechol estrodiol derivatives
• V158M variants are associated with lower enzyme activity, 3-4 times lower with the MM genotype (slower catabolism and clearance)
• Possible Health Implications (MM, higher executive function)
Altered T1/2 of neuro-pharmaceuticals (e.g. L-dopa), some asthma and anti-HTN meds , ↑ risk of breast, colorectal and endometrial /ovarian cancer (VM) and, effect on anxiety, poor attention and mood
• Optimize phenotype- adjust medication dosages, evaluate risks of hormone replacement therapy, minimize cancer risks (life style), avoid exposure to Hg
Kor Circ J(2013)43:581-91 Cancer Res(1998)58:2269-77 J Toxicol Env Hlth(2009)72:599-609 Hereditary Cancer Clin Prac(2006)4:94-102 Hum
Reprod(2003)18:262-Neuropsychopharmacol(2005)30:2092-2102
David Quig, PhD
A COMT Variant Affects Mood with Chronic Hg0 Exposure in Females
• Association of COMT/V158M (rs4680) with symptoms, mood and Hg exposure in183 male dentists and 213 female dental assistants (random urine Hg as index of chronic exposure)
• Standardized symptoms* and mood** tests
• Overall- No correlations between Hg exposure and symptoms or mood scores… (a single random urine Hg assessment)
• Only females with the COMT/158MM variant had significant issues:
Tension, depression, fatigue, confusion and, overall mood score
• Decreased inactivation of catechol estradiols and catecholamines
J Toxicol Env Hlth(2009)72:599-609 *Percept Motor Skills(2002)95:845-67 **Profile of Mood States, Educational and Industrial Testing Service; 1971
David Quig, PhD
Vitamin D Receptor (VDR)
• Nuclear receptor- 1,25-OH2D3 binding affects gene transcription of as much as 1/3 of the human genome
• VDR/Fok1 SNP- associated with functional but, significantly less efficient vitamin D receptors (+/+ < +/-)
• Possible Health Implications ↑brain lesions and Pb-induced HTN (occupational), dysglycemia / diabetes, aberrant plasma rennin activity / risk for HTN, ↑risks for breast, colorectal, skin and prostate cancers, non-Hodgkin’s lymphoma and, risk for Alzheimer’s and CVD
• Optimize phenotype- Monitor/optimize D3 and BMI, HbA1c, BP, life style check (cancer risk), inflammation (gut- phase III detoxification) and, bone loss…Pb
Gene(2004)338:143-56 J Aging Res(2011)2011:1-11 Ind J Hum Genet (2011)17:201- 6 Carcinogenesis(2009)30:1170-80
David Quig, PhD
Vitamin D: Epidemic of Deficiency • Calcium / bone metabolism (bone lead)
• Inflammation, CVD, insulin resistance, microbiome depletion, ↓ immune response
• Serum or blood spot- D2 , D3 and total 25-OH-D
J Environ Res Public Hlth(2009)6:2585-2607 Autoimmune Rev(2010)11:709-15 Immunol Lett(2010)134:7-16 J Nutr(2008)138:2337-41 Osteoporos(2013)24:1115-9
J Clin Endocrinol Metab(2012)97:1953-61
Suboptimal (20 to < 40 ng/ml)
25.4
David Quig, PhD
Take Home Messages
• Endogenous detoxification processes are inducible and highly energy dependent.
• Phases I-III need to be coordinately regulated. • Normal methionine metabolism (methylation,
transsulfuration) is essential for detoxification. • Some toxicants inhibit Phase I, methylation and
Phase II detoxification processes. • Toxic metals are pro-oxidative and deplete anti-
oxidative enzymes, GSH and cysteine.
David Quig, PhD
Take Home Messages
• Metals / chemicals compete for natural processes of detoxification & decorporation (e.g. glutathione).
• GSH and MT are pivotal in protection against toxic elements, chemicals and oxidative stress.
• GSH and MT and can be effectively up-regulated in a sustained manner only if appropriate support is provided.
• Efficient detoxification requires comprehensive support of endogenous detoxification processes