Lead and Health: A Never-Ending Story Epidemiology Seminar Series November 15, 2012 Sung Kyun Park, Sc.D. Department of Epidemiology University of Michigan School of Public Health Email: sungkyun@umich.edu 1 Public Health: A Big Doctor? 소의 (小醫, small doctor), 중의 (中醫, medium doctor), 대의 (大醫, big doctor): A small doctor cures a disease, a medium doctor cures a human, and a big doctor cures a society (country) 小醫治病, 中醫治人, 大醫治國 Dongui Bogam (동의보감, 東醫寶鑑) Lead: Where is it? 3 http://blogs.webmd.com/healthy-children/uploaded_images/amjph00238-0084-712905.gif http://blogs.webmd.com/healthy-children/uploaded_images/amjph00238-0084-712901.gif http://blogs.webmd.com/healthy-children/uploaded_images/recall_train-771999.jpg http://blogs.webmd.com/healthy-children/uploaded_images/recall_train-771995.jpg Children's lead poisoning drops but exposure remains most common among poor http://upload.wikimedia.org/wikipedia/commons/thumb/9/92/Calcite-Galena-elm56c.jpg/170px-Calcite-Galena-elm56c.jpg http://upload.wikimedia.org/wikipedia/commons/thumb/8/8a/Lead_glazed_ceramic_cup_Tang_China_8th_century.jpg/220px-Lead_glazed_ceramic_cup_Tang_China_8th_century.jpg http://lead-alloy.com/yahoo_site_admin/assets/images/7images_pipes1.7131807_std.jpg http://www.earthyreport.com/site/wp-content/uploads/2011/10/leaded.gif 0.2 – 0.8 0.9 – 1.3 1.4 – 1.8 1.9 – 2.8 > 2.8 90th: 3.7 µg/dL 95th: 4.8 99th: 9.0 EHP 2012;120:1544-1550 P for trend < 0.001 Similar trends were found between blood lead and hypertension (blood pressure), renal disease, cognitive declines, etc. Lead standard: 10 µg/dL for children and pregnant women Questions Does the toxic effect of lead on chronic diseases begin at 3 µg/dL or even lower levels? or Does blood lead levels found in adults today (especially old persons) reflect past, cumulative lifetime exposure? Blood lead levels fig3 NHANES-III 2.76 g/dL NHANES 99-02 1.64 g/dL 6 Blood lead levels fig3 NHANES-III 2.76 g/dL NHANES 99-02 1.64 g/dL 7 Three compartment model of Pb metabolism (Rabinowitz et al. 1976) Diet & Air 3 BONE ~20-50* yrs 1 BLOOD 36 ± 5 days 2 SOFT TISSUE ~40 days URINE BILE, HAIR, SWEAT, NAILS 90-95% of body lead burden resides in bone in adults *from Wilker et al. JOEM 2011 Lead in blood vs. bone 9 CONCEPT EHP figure-1 Hu et al., EHP 1998 How can we measure bone lead levels?: K X-ray Fluorescence (KXRF) KXRF room in SPH-1 G832 (Picture courtesy of K Bakulski, Ph.D.) Slide31 Non-invasive Safe (radiation dose in microsieverts) Convenient (30 minutes/measure) Population data on bone lead: the Normative Aging Study Hu et al. Am J Epidem, 1996 07_MensChorus A Boston-based longitudinal study of aging begun in 1962: normal men, 95% white, 18-80yo, all social classes Mean age of 67 yrs at the time of bone lead test http://3.bp.blogspot.com/_F2xmLAzQ8Ho/Sowqm6t9zWI/AAAAAAAAEcE/Kpfc35t4Yoc/s200/va_seal.jpg Bone Lead and Health Effects Associated with High blood pressure (hypertension) Pulse pressure and ischemic heart disease EKG abnormalities (e.g., QT intervals) Total and CVD Mortality Renal function (serum creatinine) Cognitive declines Mental health Age-related cataract Age-related hearing loss Plasma homocysteine (ms in prep by Kelly Bakulski) Type-2 diabetes (ms in prep by Siying Huang) Traditional Epidemiology Exposure Disease Molecular Epidemiology Exposure Internal Dose Biologically Effective Dose Early Biologic Effect Altered Structure/ Function Clinical Disease Prognostic Significance Markers of Susceptibility . . . . . Markers of Exposure . . . . . . Markers of Disease Schulte and Perera, 1993 Gene-Environment Interaction Why gene-environment interaction? Disease are multifactorial Elucidate of biological mechanisms Identify susceptible populations Genes in the iron pathway and lead Why iron? Iron metabolism and HFE Iron homeostasis HFE (hemochromatosis): iron overload C282Y (cysteine  tyrosine at 282) H63D (histidine  aspartate at 63) Molecular mechanism 17 Tf Fe Fe TfR TfR HFE 2 Wild-type HFE Tf Fe Fe 2 C282Y homozygous HFE HFE TfR TfR Tf Fe Fe 18 (EHP 2007;115:1210-1215) Adjust for age, education, smoking, alcohol, first language, computer experience, diabetes P for interaction=0.03 Adjust for age, education, smoking, alcohol consumption, daily intakes of calcium, sodium, and potassium, calorie, physical activity, diabetes, family history of HTN, HDL, total cholesterol, waist circumference (EHP 2010;118:1261-6) 19 Pathway Analysis Why Pathway analysis? GWAS or SNP-based candidate gene approach: needle in a haystack The testing unit: an SNP If multiple SNPs in a pathway contribute to disease susceptibility, but individually each SNP has a relatively small effect, the single-SNP association could be too weak to be detected Pathway analysis combines association evidence from multiple genetic variants and thus potentially has a better chance of identifying the association of interest The testing unit: a gene (multiple SNPs) or a pathway (multiple genes) Haplotype analysis for TFR2 Nutrition-Environment Interaction Why nutrition-environment interaction? Elucidation of biological mechanisms Exposure already happened. What can we do? An economical intervention tool Homocysteine and B vitamins Homocysteine: an intermediate product of the one carbon metabolism B vitamins: cofactors that contribute to Hcy synthesis, CH3 transfer 25 Intakes Folate Low cardiovascular risk: low inflammation, less atherosclerosis ins5 Lead exposure and Plasma total Hcy Bakulski et al., (ms in preparation) 27 Analyses stratified by diet Mixed Effects Model, Random: intercept and slope Log(Hcy) = β0 + β1(blood Pb) + β2(time) + β3(baseline age) + β4(baseline age * time) + βxCov + ε stratifiedflipboth copy.tiff stratifiedfliplowonly copy.tiff Folate Folate B12 B12 B6 B6 Slide Courtesy of kelly bakulski, ph.d. Bakulski et al., (ms in preparation) Does exposure during adulthood matter? Wu et al., J Neurosci 2008 23-yr old monkeys EHP 2012;120:445-450 Differences in BP b/w women and men across young and middle age may stem from increased likelihood of prenatal lead exposure? Life-long exposure to lead and health science?_ob=MiamiCaptionURL&_method=retrieve&_udi=B6WXH-4PF6B3N-2&_image=B6WXH-4PF6B3N-2-B&_ba=&_user=99318&_rdoc=1&_fmt=full&_orig=search&_cdi=7159&view=c&_isHiQual=Y&_acct=C000007678&_version=1&_urlVersion=0&_userid=99318&md5=7a454c3abec06c7689e5398bb579b9fd White et al, Toxicol Appl Pharm 2007 Neonatal+Adult exposure +Healthy lifestyle Summary Health effects of lead are not over not a past problem but an ongoing problem There are more susceptible populations to lead exposure The findings from nutrition-lead and stress-lead interactions suggest that healthy lifestyle is important to reduce potential adverse health effects of lead Developmental period as a window of susceptibility to lead Thank you for your attention!!! Questions? Summary Health effects of lead are not over not a past problem but an ongoing problem There are more susceptible populations to lead exposure The findings from nutrition-lead and stress-lead interactions suggest that healthy lifestyle is important to reduce potential adverse health effects of lead Developmental period as a window of susceptibility to lead Life-long exposure to lead and health science?_ob=MiamiCaptionURL&_method=retrieve&_udi=B6WXH-4PF6B3N-2&_image=B6WXH-4PF6B3N-2-B&_ba=&_user=99318&_rdoc=1&_fmt=full&_orig=search&_cdi=7159&view=c&_isHiQual=Y&_acct=C000007678&_version=1&_urlVersion=0&_userid=99318&md5=7a454c3abec06c7689e5398bb579b9fd White et al, Toxicol Appl Pharm 2007 Neonatal+Adult exposure +Healthy lifestyle EHP 2012;120:445-450 Differences in BP b/w women and men across young and middle age may stem from increased likelihood of prenatal lead exposure? Does exposure during adulthood matter? Wu et al., J Neurosci 2008 23-yr old monkeys Analyses stratified by diet Mixed Effects Model, Random: intercept and slope Log(Hcy) = β0 + β1(blood Pb) + β2(time) + β3(baseline age) + β4(baseline age * time) + βxCov + ε stratifiedflipboth copy.tiff stratifiedfliplowonly copy.tiff Folate Folate B12 B12 B6 B6 Slide Courtesy of kelly bakulski, ph.d. Bakulski et al., (ms in preparation) Lead exposure and Plasma total Hcy Bakulski et al., (ms in preparation) 27 Low cardiovascular risk: low inflammation, less atherosclerosis ins5 Homocysteine and B vitamins Homocysteine: an intermediate product of the one carbon metabolism B vitamins: cofactors that contribute to Hcy synthesis, CH3 transfer 25 Intakes Folate Why nutrition-environment interaction? Elucidation of biological mechanisms Exposure already happened. What can we do? An economical intervention tool Nutrition-Environment Interaction Haplotype analysis for TFR2 Pathway Analysis Why Pathway analysis? GWAS or SNP-based candidate gene approach: needle in a haystack The testing unit: an SNP If multiple SNPs in a pathway contribute to disease susceptibility, but individually each SNP has a relatively small effect, the single-SNP association could be too weak to be detected Pathway analysis combines association evidence from multiple genetic variants and thus potentially has a better chance of identifying the association of interest The testing unit: a gene (multiple SNPs) or a pathway (multiple genes) Adjust for age, education, smoking, alcohol consumption, daily intakes of calcium, sodium, and potassium, calorie, physical activity, diabetes, family history of HTN, HDL, total cholesterol, waist circumference (EHP 2010;118:1261-6) 19 18 (EHP 2007;115:1210-1215) Adjust for age, education, smoking, alcohol, first language, computer experience, diabetes P for interaction=0.03 Iron metabolism and HFE Iron homeostasis HFE (hemochromatosis): iron overload C282Y (cysteine  tyrosine at 282) H63D (histidine  aspartate at 63) Molecular mechanism 17 Tf Fe Fe TfR TfR HFE 2 Wild-type HFE Tf Fe Fe 2 C282Y homozygous HFE HFE TfR TfR Tf Fe Fe Genes in the iron pathway and lead Why iron? Why gene-environment interaction? Disease are multifactorial Elucidate of biological mechanisms Identify susceptible populations Gene-Environment Interaction Traditional Epidemiology Exposure Disease Molecular Epidemiology Exposure Internal Dose Biologically Effective Dose Early Biologic Effect Altered Structure/ Function Clinical Disease Prognostic Significance Markers of Susceptibility . . . . . Markers of Exposure . . . . . . Markers of Disease Schulte and Perera, 1993 Bone Lead and Health Effects Associated with High blood pressure (hypertension) Pulse pressure and ischemic heart disease EKG abnormalities (e.g., QT intervals) Total and CVD Mortality Renal function (serum creatinine) Cognitive declines Mental health Age-related cataract Age-related hearing loss Plasma homocysteine (ms in prep by Kelly Bakulski) Type-2 diabetes (ms in prep by Siying Huang) Population data on bone lead: the Normative Aging Study Hu et al. Am J Epidem, 1996 07_MensChorus A Boston-based longitudinal study of aging begun in 1962: normal men, 95% white, 18-80yo, all social classes Mean age of 67 yrs at the time of bone lead test http://3.bp.blogspot.com/_F2xmLAzQ8Ho/Sowqm6t9zWI/AAAAAAAAEcE/Kpfc35t4Yoc/s200/va_seal.jpg How can we measure bone lead levels?: K X-ray Fluorescence (KXRF) KXRF room in SPH-1 G832 (Picture courtesy of K Bakulski, Ph.D.) Slide31 Non-invasive Safe (radiation dose in microsieverts) Convenient (30 minutes/measure) Lead in blood vs. bone 9 CONCEPT EHP figure-1 Hu et al., EHP 1998 Three compartment model of Pb metabolism (Rabinowitz et al. 1976) Diet & Air 3 BONE ~20-50* yrs 1 BLOOD 36 ± 5 days 2 SOFT TISSUE ~40 days URINE BILE, HAIR, SWEAT, NAILS 90-95% of body lead burden resides in bone in adults *from Wilker et al. JOEM 2011 Blood lead levels fig3 NHANES-III 2.76 g/dL NHANES 99-02 1.64 g/dL 7 Blood lead levels fig3 NHANES-III 2.76 g/dL NHANES 99-02 1.64 g/dL 6 Blood lead levels fig3 NHANES-III 2.76 g/dL NHANES 99-02 1.64 g/dL 7 Three compartment model of Pb metabolism (Rabinowitz et al. 1976) Diet & Air 3 BONE ~20-50* yrs 1 BLOOD 36 ± 5 days 2 SOFT TISSUE ~40 days URINE BILE, HAIR, SWEAT, NAILS 90-95% of body lead burden resides in bone in adults *from Wilker et al. JOEM 2011 Lead in blood vs. bone 9 CONCEPT EHP figure-1 Hu et al., EHP 1998 How can we measure bone lead levels?: K X-ray Fluorescence (KXRF) KXRF room in SPH-1 G832 (Picture courtesy of K Bakulski, Ph.D.) Slide31 Non-invasive Safe (radiation dose in microsieverts) Convenient (30 minutes/measure) Population data on bone lead: the Normative Aging Study Hu et al. Am J Epidem, 1996 07_MensChorus A Boston-based longitudinal study of aging begun in 1962: normal men, 95% white, 18-80yo, all social classes Mean age of 67 yrs at the time of bone lead test http://3.bp.blogspot.com/_F2xmLAzQ8Ho/Sowqm6t9zWI/AAAAAAAAEcE/Kpfc35t4Yoc/s200/va_seal.jpg Bone Lead and Health Effects Associated with High blood pressure (hypertension) Pulse pressure and ischemic heart disease EKG abnormalities (e.g., QT intervals) Total and CVD Mortality Renal function (serum creatinine) Cognitive declines Mental health Age-related cataract Age-related hearing loss Plasma homocysteine (ms in prep by Kelly Bakulski) Type-2 diabetes (ms in prep by Siying Huang) Traditional Epidemiology Exposure Disease Molecular Epidemiology Exposure Internal Dose Biologically Effective Dose Early Biologic Effect Altered Structure/ Function Clinical Disease Prognostic Significance Markers of Susceptibility . . . . . Markers of Exposure . . . . . . Markers of Disease Schulte and Perera, 1993 Gene-Environment Interaction Why gene-environment interaction? Disease are multifactorial Elucidate of biological mechanisms Identify susceptible populations Genes in the iron pathway and lead Why iron? Iron metabolism and HFE Iron homeostasis HFE (hemochromatosis): iron overload C282Y (cysteine  tyrosine at 282) H63D (histidine  aspartate at 63) Molecular mechanism 17 Tf Fe Fe TfR TfR HFE 2 Wild-type HFE Tf Fe Fe 2 C282Y homozygous HFE HFE TfR TfR Tf Fe Fe 18 (EHP 2007;115:1210-1215) Adjust for age, education, smoking, alcohol, first language, computer experience, diabetes P for interaction=0.03 Adjust for age, education, smoking, alcohol consumption, daily intakes of calcium, sodium, and potassium, calorie, physical activity, diabetes, family history of HTN, HDL, total cholesterol, waist circumference (EHP 2010;118:1261-6) 19 Pathway Analysis Why Pathway analysis? GWAS or SNP-based candidate gene approach: needle in a haystack The testing unit: an SNP If multiple SNPs in a pathway contribute to disease susceptibility, but individually each SNP has a relatively small effect, the single-SNP association could be too weak to be detected Pathway analysis combines association evidence from multiple genetic variants and thus potentially has a better chance of identifying the association of interest The testing unit: a gene (multiple SNPs) or a pathway (multiple genes) Haplotype analysis for TFR2 Nutrition-Environment Interaction Why nutrition-environment interaction? Elucidation of biological mechanisms Exposure already happened. What can we do? An economical intervention tool Homocysteine and B vitamins Homocysteine: an intermediate product of the one carbon metabolism B vitamins: cofactors that contribute to Hcy synthesis, CH3 transfer 25 Intakes Folate Low cardiovascular risk: low inflammation, less atherosclerosis ins5 Lead exposure and Plasma total Hcy Bakulski et al., (ms in preparation) 27 Analyses stratified by diet Mixed Effects Model, Random: intercept and slope Log(Hcy) = β0 + β1(blood Pb) + β2(time) + β3(baseline age) + β4(baseline age * time) + βxCov + ε stratifiedflipboth copy.tiff stratifiedfliplowonly copy.tiff Folate Folate B12 B12 B6 B6 Slide Courtesy of kelly bakulski, ph.d. Bakulski et al., (ms in preparation) Does exposure during adulthood matter? Wu et al., J Neurosci 2008 23-yr old monkeys EHP 2012;120:445-450 Differences in BP b/w women and men across young and middle age may stem from increased likelihood of prenatal lead exposure? Life-long exposure to lead and health science?_ob=MiamiCaptionURL&_method=retrieve&_udi=B6WXH-4PF6B3N-2&_image=B6WXH-4PF6B3N-2-B&_ba=&_user=99318&_rdoc=1&_fmt=full&_orig=search&_cdi=7159&view=c&_isHiQual=Y&_acct=C000007678&_version=1&_urlVersion=0&_userid=99318&md5=7a454c3abec06c7689e5398bb579b9fd White et al, Toxicol Appl Pharm 2007 Neonatal+Adult exposure +Healthy lifestyle Summary Health effects of lead are not over not a past problem but an ongoing problem There are more susceptible populations to lead exposure The findings from nutrition-lead and stress-lead interactions suggest that healthy lifestyle is important to reduce potential adverse health effects of lead Developmental period as a window of susceptibility to lead Thank you for your attention!!! Questions? Calcium, iron and BLLs Calcium supplementation during pregnancy on maternal BLLs: a RCT Ettinger et al., EHP 2009 Iron fortification in Children, India Zimmermann et al., Pediatrics 2006 Does stress enhance the lead toxicity? Peters et al., EHP 2007