Positive association between plasma homocysteine level and chronic kidney disease

Transcription

1 University of Wollongong Reserch Online Fculty of Socil Sciences - Ppers Fculty of Socil Sciences 2008 Positive ssocition between plsm homocysteine level nd chronic kidney disese Anoop Shnkr Ntionl University of Singpore Jie Wng University of Sydney Brin Chu University of Sydney Elen Rochtchin University of Sydney Victori Flood University of Wollongong, vflood@uow.edu.u See next pge for dditionl uthors Publiction Detils Shnkr, A., Wng, J. Jin., Chu, B., Rochtchin, E., Flood, V. & Mitchell, P. (2008). Positive ssocition between plsm homocysteine level nd chronic kidney disese. Kidney nd Blood Pressure Reserch, 31 (1), Reserch Online is the open ccess institutionl repository for the University of Wollongong. For further informtion contct the UOW Librry: reserch-pubs@uow.edu.u

2 Positive ssocition between plsm homocysteine level nd chronic kidney disese Abstrct BACKGROUND: Incresing experimentl evidence, including recently developed niml models, supports role for homocysteine in the development of chronic kidney disese (CKD). However, reltively few clinicl/ epidemiologicl studies hve exmined this hypothesis in humns. We exmined the reltionship between plsm homocysteine level nd CKD in popultion-bsed study of older Austrlins. METHODS: Community-bsed study ( ) mong 2,609 individuls (58.6% women), ged yers, free of clinicl crdiovsculr disese in the Blue Mountins region, west of Sydney, Austrli. The min outcome-ofinterest ws CKD (n = 461), defined s estimted glomerulr filtrtion rte of <60 ml>/min/1.73 m(2). RESULTS: Higher plsm homocysteine levels were positively ssocited with CKD, independent of smoking, body mss index, dibetes mellitus, hypertension, cholesterol levels, nd other confounders. The multivrible odds rtio (OR; 95% confidence intervls, CI) compring qurtile 4 of plsm homocysteine (>14 micromol/l) to qurtile 1 (< or =9 micromol/l) ws ( ),. This ssocition persisted in both men nd women seprtely. The results were lso consistent in subgroup nlyses by ctegories of dibetes mellitus nd hypertension. CONCLUSIONS: Higher plsm homocysteine levels re ssocited with CKD in community-bsed smple of older Austrlins. This ssocition ppered to be independent of dibetes mellitus nd hypertension. Keywords between, plsm, homocysteine, level, chronic, ssocition, positive, disese, kidney Disciplines Eduction Socil nd Behviorl Sciences Publiction Detils Shnkr, A., Wng, J. Jin., Chu, B., Rochtchin, E., Flood, V. & Mitchell, P. (2008). Positive ssocition between plsm homocysteine level nd chronic kidney disese. Kidney nd Blood Pressure Reserch, 31 (1), Authors Anoop Shnkr, Jie Wng, Brin Chu, Elen Rochtchin, Victori Flood, nd Pul Mitchell This journl rticle is vilble t Reserch Online:

3 Originl Pper Kidney Blood Press Res 2008;31:55 62 DOI: / Received: October 11, 2007 Accepted: December 6, 2007 Published online: Jnury 30, 2008 Positive Assocition between Plsm Homocysteine Level nd Chronic Kidney Disese Anoop Shnkr Jie Jin Wng b Brin Chu b Elen Rochtchin b Vicki Flood b, c Pul Mitchell b Division of Epidemiology, Deprtment of Community, Occuptionl, nd Fmily Medicine, Ntionl University of Singpore, Singpore; b Centre for Vision Reserch, Deprtment of Ophthlmology nd Westmed Millennium Institute, nd c Humn Nutrition Unit, Deprtments of Moleculr nd Microbil Biosciences nd School of Public Helth, University of Sydney, Sydney, N.S.W., Austrli Key Words Plsm homocysteine Chronic kidney disese Hypertension Blue Mountins Eye Study Abstrct Bckground: Incresing experimentl evidence, including recently developed niml models, supports role for homocysteine in the development of chronic kidney disese (CKD). However, reltively few clinicl/epidemiologicl studies hve exmined this hypothesis in humns. We exmined the reltionship between plsm homocysteine level nd CKD in popultion-bsed study of older Austrlins. Methods: Community-bsed study ( ) mong 2,609 individuls (58.6% women), ged yers, free of clinicl crdiovsculr disese in the Blue Mountins region, west of Sydney, Austrli. The min outcome-of-interest ws CKD (n = 461), defined s estimted glomerulr filtrtion rte of! 60 ml/min/1.73 m 2. Results: Higher plsm homocysteine levels were positively ssocited with CKD, independent of smoking, body mss index, dibetes mellitus, hypertension, cholesterol levels, nd other confounders. The multivrible odds rtio (OR; 95% confidence intervls, CI) compring qurtile 4 of plsm homocysteine ( 114 mol/l) to qurtile 1 ( ^ 9 mol/l) ws ( ), p-trend! This ssocition persisted in both men nd women seprtely. The results were lso consistent in subgroup nlyses by ctegories of dibetes mellitus nd hypertension. Conclusions: Higher plsm homocysteine levels re ssocited with CKD in community-bsed smple of older Austrlins. This ssocition ppered to be independent of dibetes mellitus nd hypertension. Introduction Copyright 2008 S. Krger AG, Bsel End-stge renl disese (ESRD) is n importnt public helth problem. There were estimted to be pproximtely 470,000 ptients with ESRD in the United Sttes in 2004 [1], nd bsed on erlier dt n estimted dditionl 8 million US dults hve chronic kidney disese (CKD), defined s glomerulr filtrtion rte (GFR) of! 60 ml/ min/1.73 m 2, who re t risk of progression to ESRD nd its ttendnt complictions [2, 3]. It is therefore importnt to identify fctors relted to CKD, kidney disese stge erlier in the continuum t which prevention/control of disese progression is more pplicble. Supported principlly by the Austrlin Ntionl Helth nd Medicl Reserch Council, Cnberr, Austrli (Project grnt ID nd ), nd in prt by the Kellogg s Foundtion, Austrli. Fx E-Mil krger@krger.ch S. Krger AG, Bsel /08/ $24.50/0 Accessible online t: Dr. Anoop Shnkr Deprtment of Community, Occuptionl, nd Fmily Medicine Ntionl University of Singpore Singpore (Singpore) Tel , Fx , E-Mil shnkr@nus.edu.sg

4 Homocysteine is sulfur-contining mino cid formed during the metbolism of the essentil mino cid methionine [4]. Previous epidemiologic studies hve reported n ssocition between plsm homocysteine levels nd therosclerotic vsculr disese [4 6], shown to be predictor of subsequent CKD [7]. Studies hve lso reported n ssocition between plsm homocysteine nd hypertension [8, 9], nother strong, independent predictor of CKD [10]. Homocysteine my directly cuse renl vsculr dmge through the production of rective oxygen species, effects on vsculr smooth muscle cells, endothelil injury, reduction in plsm nd tissue interstitium denosine levels, nd mesngil cell prolifertion nd poptosis [4, 11 16]. Experimentl niml models of homocysteine-induced glomerulr dmge hve lso been developed [14, 17]. However, few studies hve exmined the puttive ssocition between elevted plsm homocysteine nd CKD [18 20]. While one lrge study reported positive ssocition between homocysteine nd CKD in Jpnese popultion smple [18], two erlier studies did not find n independent ssocition [19, 20]. In prticulr, it is not cler if plsm homocysteine is relted to CKD independent of hypertension nd dibetes mellitus, two of its strong predictors. In this context, we exmined the ssocition between plsm homocysteine levels nd CKD in popultion-bsed smple of older Austrlin dults fter djusting for the mjor confounders nd strtifying by hypertension nd dibetes mellitus sttus. M e t h o d s The current report is bsed on the second Blue Mountins Eye Study (BMES II, ), popultion-bsed study of prticipnts ged 6 49 yers, living in two postcodes of the Blue Mountins region, west of Sydney, Austrli, which hs studied ge-relted eye diseses nd other helth outcomes in n older urbn Austrlin popultion. Detils of the study methods hve previously been described [21]. In brief, this cross-sectionl survey (BMES II, ) consisted of 3,509 prticipnts. It included 2,335 prticipnts (75.1% survivors from the bseline survey, BMES I, ) plus n dditionl 1,174 prticipnts (identified in repet door-to-door census, ) who hd become eligible by moving into the re or into the ge brcket of the originl survey. The Blue Mountins popultion is representtive of the Austrlin popultion. This study followed the recommendtions of the Declrtion of Helsinki, ws pproved by the Western Sydney Are Helth Service Humn Reserch Ethics Committee, nd written, informed consent ws obtined from ll prticipnts. The exmintion protocols involved mesurement of weight, height, systolic nd distolic blood pressures by trined interviewer, nd dministrtion of stndrdized questionnire collecting informtion regrding demogrphic chrcteristics, cigrette smoking, lcohol intke, physicl ctivity, nd pst medicl history. Fsting blood specimens were drwn from 2,961 prticipnts (84.4%), centrifuged onsite nd then couriered the sme dy to Westmed Hospitl, Sydney, Austrli, for hemtology nd clinicl biochemistry ssessment. Plsm totl homocysteine ws determined using the fluorescent polriztion immunossy method on n IMx Anlyzer. This system correltes well with HPLC nd gs chromtogrphy-mss spectrometry ssy methods [22]. Serum folte nd vitmin B 12 ssys were performed using the competitive-binding ssy method on Beckmn-Access nlyzer. White blood cell (WBC) count ws determined using Coulter counter method. Totl cholesterol, high-density lipoprotein cholesterol nd triglyceride were mesured on Reflotron reflectnce photometric nlyzer (Boehringer Mnnheim Dignostics [currently Roche Dignostics], Germny). Fsting plsm glucose ws mesured using the hexokinse method. Age ws defined s ge t the bseline exmintion; eduction ws ctegorized into beyond high school, high school, nd below high school, nd body mss index (BMI) ws clculted s weight (kg) divided by height squred (m 2 ). Dibetes sttus ws ctegorized using the Americn Dibetes Assocition criteri s follows: dibetes = dignosis by physicin nd use of dibetic medictions or fsting glucose levels t lest 7.0 mmol/l (126 mg/dl); fsting hyperglycemi = fsting glucose levels 6.1 mmol/l (110 mg/dl) or bove but less thn 7.0 mmol/l (126 mg/dl), nd normoglycemi = fsting glucose levels below 6.1 mmol/l (110mg/dl). Cigrette smoking ws ctegorized into current (current smoker or hd stopped smoking! 12 months before the study exmintion), former (positively nswered to hve you ever smoked regulrly before? nd hd stopped smoking t lest 12 months before the study exmintion), nd never smoker. Alcohol intke ws ctegorized s nondrinker,! once/week, 1 6 dys/week, 1 2 drinks/dy, 3 or more drinks/dy, nd don t know/missing. Physicl inctivity (yes, no) ws ctegorized s nswering negtively to hve you prticipted in ny recretionl exercise/wlk in the lst 2 weeks?. Detils of blood pressure mesurement nd prevlence of hypertension in this older Austrlin community hve been described previously [23]. Briefly, systolic nd distolic blood pressure ws recorded by trined observers from the right rm with mercury sphygmomnometer using cuff size pproprite for the prticipnt s rm circumference, fter they hd been comfortbly seted for t lest 10 min. Hypertension ws defined ccording to the Seventh Report of the Joint Ntionl Committee on Prevention, Detection, Evlution, nd Tretment of High Blood Pressure s systolic blood pressure of 140 mm Hg or higher, distolic blood pressure 90 mm Hg or higher, or combintion of selfreported hypertension dignosis nd use of ntihypertensive medictions [24]. Estimted GFR (egfr) ws the preferred mesure of kidney function in the current study. GFR ws indirectly estimted using the 4-vrible Modifiction of Diet in Renl Disese Study eqution [25]. The min outcome of interest ws CKD, defined s n egfr of! 60 ml/min/1.73 m 2, consistent with the Ntionl Kidney Foundtion Kidney Disese Outcomes Qulity Inititive 6 stge 2 chronic kidney disese [2]. To exmine the ssocition between plsm homocysteine nd hypertension nd CKD of the 2,961 individuls who prticipted in the survey nd hd plsm homocysteine mesured, the 56 Kidney Blood Press Res 2008;31:55 62 Shnkr /Wng /Chu /Rochtchin / Flood /Mitchell

5 Tble 1. Bseline chrcteristics of the cohort by qurtiles of plsm homocysteine Chrcteristics Qurtile of plsm homocysteine ( mol/l) p vlue qurtile 1 qurtile 2 qurtile 3 qurtile mol/l mol/l mol/l >14.9 mol/l Age, yers < Women, % < Smoking Current smoker, % Former smoker, % Alcohol use >3 drinks/dy, % Body mss index, kg/m Physiclly inctive, % < Dibetes mellitus, % Serum totl cholesterol, mmol/l Serum triglyceride, mmol/l Serum HDL cholesterol, mmol/l Men rteril pressure, mm Hg Hypertension, % < egfr, ml/min/1.73 m < Chronic kidney disese (%) < Women only Menopusl sttus, % Hormone replcement therpy,% < The dt presented re men 8 SD vlues or row percentges. The p vlues re bsed on nlysis of vrince or the 2 test, s pproprite. egfr = Estimted glomerulr filtrtion rte bsed on the Modifiction of Diet in Renl Diseses study eqution [25]. current study included 2,609 individuls free of clinicl crdiovsculr disese (1,080 men nd 1,529 women) fter excluding those with missing systolic or distolic blood pressure (n = 23), serum cretinine levels (n = 10), nd those with preexisting coronry hert disese (n = 223) or stroke (n = 96). S t t i s t i c l Me t h o d s Bseline plsm homocysteine ws ctegorized into qurtiles ( ^ 9.9, , , mol/l) for the min nlyses. Homocysteine ws lso nlyzed s continuous vrible (1 SD [4.6 mol/l] increse). We used 2 test nd nlysis of vrince to compre the reltionship of selected bseline chrcteristics by plsm homocysteine qurtiles. We were interested in two outcomes (1) hypertension nd (2) CKD. We used multivrible logistic regression models to determine the odds rtio (OR) nd 95% confidence intervl (CI) of hypertension (n = 1,986) nd CKD (n = 461), controlling for potentil confounders. We used 2 logistic regression models: n ge- (yers), sex-djusted model, nd multivrible-djusted model, dditionlly djusting for smoking (never, former, current), lcohol intke (nondrinker,!3 drinks/dy, 6 3 drinks/dy), BMI (kg/m 2 ), physiclly inctive (no, yes), dibetes mellitus (bsent, present), hypertension (bsent, present; djusted in models with CKD s the outcome), men rteril blood pressure (mm Hg; djusted in models with CKD s the outcome), serum totl cholesterol (mmol/l), HDL cholesterol (mmol/l), triglyceride (mmol/l); mong women we dditionlly djusted for menopusl sttus (bsent, present), nd ever use of hormone replcement therpy (no, yes). Logistic regression models with plsm homocysteine qurtiles s ordered ctegories scled to the medin for ech qurtile were used to ssess trends in OR. To exmine the consistency of the ssocition between homocysteine nd CKD, we performed nlyses within subgroups of mjor confounders, including gender (men, women), hypertension (bsent, present), nd dibetes mellitus (bsent, present). We formlly evluted effect modifiction by including cross-product interction terms in corresponding logistic regression models. We lso performed severl supplementry nlyses. First, we repeted the multivrible model dditionlly djusting for serum folte nd vitmin B 12 to exmine if the observed ssocition between plsm homocysteine nd CKD ws explined by these micronutrients. Second, to exmine if the observed ssocition between plsm homocysteine nd CKD ws explined by inflmmtion, we repeted the multivrible model dditionlly djusting for WBC count, nonspecific mrker of inflmmtion vilble in the current study. SAS version 9.2 ws used for ll nlyses. R e s u l t s Among the 2,609 dults ged 6 49 yers without clinicl crdiovsculr disese who were included in the current nlysis, 1,986 subjects hd hypertension nd 461 hd CKD. Tble 1 presents the chrcteristics of the study popultion by plsm homocysteine qurtiles. Subjects Homocysteine nd Kidney Disese Kidney Blood Press Res 2008;31:

6 Tble 2. Assocition between qurtiles of plsm homocysteine nd hypertension Plsm homocysteine qurtiles Number t risk Hypertension cses Age, sex OR (95% CI) Multivrible OR (95% CI) Whole cohort (n = 2,609) Qurtile 1 ( 9.9 mol/l) (referent) 1 (referent) Qurtile 2 ( mol/l) ( ) 1.26 ( ) Qurtile 3 ( mol/l) ( ) 1.30 ( ) Qurtile 4 (>14.9 mol/l) ( ) 1.41 ( ) p-trend One SD (4.6 mol/l) increse 2,609 1, ( ) 1.23 ( ) OR = Odds rtio; 95% CI = 95% confidence intervl. Estimted from logistic regression model djusted for ge (yers), sex, smoking (never, former, current), lcohol intke (nondrinker, <3 drinks/dy, 3 drinks/dy), body mss index (kg/ m 2 ), physiclly inctive (no, yes), dibetes mellitus (bsent, present), serum totl cholesterol (mmol/l), HDL cholesterol (mmol/l), triglyceride (mmol/l). Among women we dditionlly djusted for menopusl sttus (bsent, present), nd ever use of hormone replcement therpy (yes, no). Tble 3. Assocition between qurtiles of plsm homocysteine nd chronic kidney disese (CKD) Plsm homocysteine qurtiles Number t risk CKD cses Age, sex OR (95% CI) Multivrible OR (95% CI) Whole cohort (n = 2,609) Qurtile 1 ( 9.9 mol/l) (referent) 1 (referent) Qurtile 2 ( mol/l) ( ) 2.54 ( ) Qurtile 3 ( mol/l) ( ) 4.68 ( ) Qurtile 4 (>14.9 mol/l) ( ) ( ) < One SD (4.6 mol/l) increse 2, ( ) 2.12 ( ) OR = Odds rtio; 95% CI = 95% confidence intervl. Estimted from logistic regression model djusted for ge (yers), sex, smoking (never, former, current), lcohol intke (nondrinker, <3 drinks/dy, 3 drinks/dy), body mss index (kg/ m 2 ), physiclly inctive (no, yes), dibetes mellitus (bsent, present), hypertension (bsent, present), men rteril blood pressure (mm Hg), serum totl cholesterol (mmol/l), HDL cholesterol (mmol/l), triglyceride (mmol/l). Among women we dditionlly djusted for menopusl sttus (bsent, present), nd ever use of hormone replcement therpy (yes, no). with higher plsm homocysteine levels were more likely to be older, former smokers, physiclly inctive, dibetic, hypertensive, to hve consumed 1 3 drinks of lcohol/dy, higher BMI, higher serum totl cholesterol nd triglyceride levels, lower HDL cholesterol levels, nd higher men rteril pressure, nd were less likely to be women thn those with lower plsm homocysteine. The men egfr decresed nd the prevlence of CKD incresed with incresing plsm homocysteine qurtiles. In tble 2, incresing plsm homocysteine qurtiles were positively ssocited with hypertension in both the ge- nd sex-djusted nd multivrible-djusted models; models evluting trend in this ssocition were lso sttisticlly significnt. When plsm homocysteine ws nlyzed s continuous vrible (per SD increse) the positive ssocition with hypertension persisted. Also in relted subsidiry nlysis (dt not shown in tbles), we confirmed tht hypertension ws positively ssocited with CKD in the current study smple (multivrible OR 1.98, 95% CI ). Tble 3 presents the OR of CKD by incresing plsm homocysteine qurtiles. Incresing plsm homocysteine qurtiles were strongly positively ssocited with CKD. When plsm homocysteine ws nlyzed s con- 58 Kidney Blood Press Res 2008;31:55 62 Shnkr /Wng /Chu /Rochtchin / Flood /Mitchell

7 Tble 4. Assocition between qurtiles of plsm homocysteine nd chronic kidney disese (CKD) by gender Plsm homocysteine qurtiles Number t risk CKD cses Multivrible OR (95% CI) Men (n = 1,080) Qurtile 1 ( 9.9 mol/l) (referent) Qurtile 2 ( mol/l) ( ) Qurtile 3 ( mol/l) ( ) Qurtile 4 (>14.9 mol/l) ( ) Women (n = 1,529) Qurtile 1 ( 9.9 mol/l) (referent) Qurtile 2 ( mol/l) ( ) Qurtile 3 ( mol/l) ( ) Qurtile 4 (>14.9 mol/l) ( ) OR = Odds rtio; 95% CI = 95% confidence intervl. Estimted from logistic regression model djusted for ge (yers), sex, smoking (never, former, current), lcohol intke (nondrinker, <3 drinks/dy, 3 drinks/dy), body mss index (kg/m 2 ), physiclly inctive (no, yes), dibetes mellitus (bsent, present), hypertension (bsent, present), men rteril blood pressure (mm Hg), serum totl cholesterol (mmol/l), HDL cholesterol (mmol/l), triglyceride (mmol/l). Among women we dditionlly djusted for menopusl sttus (bsent, present), nd ever use of hormone replcement therpy (yes, no). tinuous vrible the positive ssocition with CKD persisted. Tble 4 shows cler positive ssocition between plsm homocysteine levels nd CKD in both men nd women. Similrly, consistent positive ssocition ws observed in subgroup nlyses fter strtifying by the presence of hypertension ( tble 5 ) or dibetes mellitus (tble 6 ). We lso performed severl supplementry nlyses. First, we repeted the min nlysis dditionlly djusting for serum folte nd vitmin B 12 in the multivrible model; the observed ssocition between plsm homocysteine qurtiles nd CKD remined lrgely unchnged. Compred to qurtile 1 of plsm homocysteine, the multivrible OR of CKD ws 2.87 (95% CI ) in qurtile 2; 5.62 ( ) in qurtile 3, nd ( ) in qurtile 4 (p-trend! ). Second, to exmine if the observed ssocition between plsm homocysteine nd CKD ws explined by inflmmtion, we repeted the multivrible model dditionlly djusting for WBC count; results remined similr here lso. Compred to qurtile 1 of plsm homocysteine, the multivrible OR of CKD ws 2.53 (95% CI ) in qurtile 2; 4.65 ( ) in qurtile 3, nd ( ) in qurtile 4 (p-trend! ). Discussion Higher plsm homocysteine levels were found to be positively ssocited with CKD in popultion-bsed smple of older Austrlins, free of clinicl crdiovsculr disese. This ssocition persisted fter djusting for ge, sex, BMI, smoking, lcohol intke, dibetes mellitus nd hypertension, nd ws consistently present in subgroup nlysis by gender nd importnt confounders. The OR for the likely presence of CKD incresed in dose-dependent mnner with incresing qurtiles of plsm homocysteine. Our results contribute to the literture by suggesting tht the puttive plsm homocysteine CKD ssocition ppers to be independent of both dibetes mellitus nd hypertension. Our finding of positive ssocition between higher plsm homocysteine levels nd CKD shows high internl vlidity s shown by the mgnitude of this ssocition, its independence from relted fctors such s smoking, lcohol intke, BMI, dibetes mellitus, hypertension, nd serum lipid levels, the presence of dose-response trend, nd the consistency of this ssocition in subgroup nlyses by gender, nd other importnt confounders. Also, severl lines of recent evidence suggest tht n ssocition between plsm homocysteine nd renl vsculr dmge nd subsequent CKD is plusible, including Homocysteine nd Kidney Disese Kidney Blood Press Res 2008;31:

8 Tble 5. Assocition between qurtiles of plsm homocysteine nd chronic kidney disese (CKD) by hypertension sttus Plsm homocysteine qurtiles Number t risk CKD cses Multivrible OR (95% CI) Normotensives (n = 623) Qurtile 1 ( 9.9 mol/l) (referent) Qurtile 2 ( mol/l) ( ) Qurtile 3 ( mol/l) ( ) Qurtile 4 (>14.9 mol/l) ( ) Hypertensives (n = 1,986) Qurtile 1 ( 9.9 mol/l) (referent) Qurtile 2 ( mol/l) ( ) Qurtile 3 ( mol/l) ( ) Qurtile 4 (>14.9 mol/l) ( ) OR = Odds rtio; 95% CI = 95% confidence intervl. Estimted from logistic regression model djusted for ge (yers), sex, smoking (never, former, current), lcohol intke (nondrinker, <3 drinks/dy, 3 drinks/dy), body mss index (kg/m 2 ), physiclly inctive (no, yes), dibetes mellitus (bsent, present), hypertension (bsent, present), men rteril blood pressure (mm Hg), serum totl cholesterol (mmol/l), HDL cholesterol (mmol/l), triglyceride (mmol/l). Among women we dditionlly djusted for menopusl sttus (bsent, present), nd ever use of hormone replcement therpy (yes, no). p-interction for the cross-product interction term between hypertension! homocysteine qurtiles = Tble 6. Assocition between qurtiles of plsm homocysteine nd chronic kidney disese (CKD) by dibetes sttus Plsm homocysteine qurtiles Number t risk CKD cses Multivrible OR (95% CI) Subjects without dibetes mellitus (n = 2,353) Qurtile 1 ( 9.9 mol/l) (referent) Qurtile 2 ( mol/l) ( ) Qurtile 3 ( mol/l) ( ) Qurtile 4 (>14.9 mol/l) ( ) Subjects with dibetes mellitus (n = 256) Qurtile 1 ( 9.9 mol/l) (referent) Qurtile 2 ( mol/l) ( ) Qurtile 3 ( mol/l) ( ) Qurtile 4 (>14.9 mol/l) ( ) OR = Odds rtio; 95% CI = 95% confidence intervl. Estimted from logistic regression model djusted for ge (yers), sex, smoking (never, former, current), lcohol intke (nondrinker, <3 drinks/dy, 3 drinks/dy), body mss index (kg/m 2 ), physiclly inctive (no, yes), dibetes mellitus (bsent, present), hypertension (bsent, present), men rteril blood pressure (mm Hg), serum totl cholesterol (mmol/l), HDL cholesterol (mmol/l), triglyceride (mmol/l). Among women we dditionlly djusted for menopusl sttus (bsent, present), nd ever use of hormone replcement therpy (yes, no). p-interction for the cross-product interction term between dibetes! homocysteine qurtiles = Kidney Blood Press Res 2008;31:55 62 Shnkr /Wng /Chu /Rochtchin / Flood /Mitchell

9 role of homocysteine in the production of rective oxygen species, effects on vsculr smooth muscle cells, endothelil injury, reduction in plsm nd tissue interstitium denosine levels, nd mesngil cell prolifertion nd poptosis [4, 11 16]. Furthermore, experimentl niml models of homocysteine-induced glomerulr dmge hve recently been developed [14, 17]. However, reltively few epidemiologicl studies to dte hve exmined the puttive ssocition between plsm homocysteine levels nd CKD [18 20], nd severl importnt questions regrding this ssocition need further clrifiction. First, while one lrge study reported positive ssocition between homocysteine nd CKD [18], two erlier studies did not confirm this ssocition mong those without dibetes [19, 20]. In the current study, the ssocition between plsm homocysteine nd CKD ws present both mong those with or without dibetes mellitus, suggesting n ssocition independent of dibetes. Second, hypertension is strong, independent predictor of CKD [10]. As plsm homocysteine is relted to hypertension in the current study ( tble 2 ) s well s in previous reports [8, 9], confounding by hypertension/high blood pressure needs to be considered in the observed ssocition with CKD. In the current study, the homocysteine CKD ssocition ppered to be independent of hypertension bsed on results in the strtified nlysis, nd ws present even fter djusting for men rteril pressure in the multivrible model. The min dvntges of our study include its lrge smple size, stble generl popultion smple bse, vilbility of rich covrite/confounder informtion, nd the use of stndrdized protocols for exposure nd outcome ssessment. The min study limittion is the cross-sectionl nture of the current study which precludes conclusions regrding the temporl nture of the ssocition between plsm homocysteine nd CKD. It is possible tht t lest prt of the observed ssocition is due to reverse cuslity, including plsm homocysteine elevtions secondry to reduced renl clernce, nd to disruptions in the norml extrrenl homocysteine metbolism involving unidentified uremic inhibitory substnces [26]. Also, blood pressure levels were bsed on single reding in the survey. This could hve resulted in slight misclssifiction of hypertension sttus (likely to be overestimtion). However, since we lso djusted for men rteril pressure in the multivrible models, the effect of hypertension sttus misclssifiction on the homocysteine CKD ssocition is likely to be miniml. In conclusion, higher plsm homocysteine levels were found to be positively ssocited with prevlent CKD in popultion-bsed smple of older Austrlins, free of clinicl crdiovsculr disese. This ssocition ppered to be independent of dibetes mellitus nd hypertension. Future prospective studies re needed to clrify the temporl sequence of this ssocition. As CKD is predictor of crdiovsculr disese nd mortlity [27], corollry observtion in light of our findings is tht t lest prt of the reported ssocition between plsm homocysteine nd crdiovsculr disese nd mortlity [4 6] my be medited by its effect on renl dysfunction. References 1 US Renl Dt System. USRDS 2006 Annul Dt Report: Atls of End-Stge Renl Disese in the United Sttes. Bethesd, Ntionl Institutes of Helth, Ntionl Institute of Dibetes nd Digestive nd Kidney Diseses, Ntionl Kidney Foundtion: K/DOQI clinicl prctice guidelines for chronic kidney disese: evlution, clssifiction, nd strtifiction. Am J Kidney Dis 2002; 39(suppl 1): S1 S Coresh J, Astor BC, Greene T, Eknoyn G, Levey AS: Prevlence of chronic kidney disese nd decresed kidney function in the dult US popultion: Third Ntionl Helth nd Nutrition Exmintion Survey. Am J Kidney Dis 2003; 41: Welch GN, Losclzo J: Homocysteine nd therothrombosis. N Engl J Med 1998; 338: Nygrd O, Nordrehug JE, Refsum H, Uelnd PM, Frstd M, Vollset SE: Plsm homocysteine levels nd mortlity in ptients with coronry rtery disese. N Engl J Med 1997; 337: Bots ML, Luner LJ, Lindemns J, Hoes AW, Hofmn A, Wittemn JC, Koudstl PJ, Grobbee DE: Homocysteine nd short-term risk of myocrdil infrction nd stroke in the elderly: the Rotterdm Study. Arch Intern Med 1999; 159: Elsyed EF, Tighiourt H, Griffith J, Kurth T, Levey AS, Slem D, Srnk MJ, Weiner DE: Crdiovsculr disese nd subsequent kidney disese. Arch Intern Med 2007; 167: Lim U, Cssno PA: Homocysteine nd blood pressure in the Third Ntionl Helth nd Nutrition Exmintion Survey, Am J Epidemiol 2002; 156: Bowmn TS, Gzino JM, Stmpfer MJ, Sesso HD: Homocysteine nd risk of developing hypertension in men. J Hum Hypertens 2006; 20: Hsu CY, McCulloch CE, Drbinin J, Go AS, Iribrren C: Elevted blood pressure nd risk of end-stge renl disese in subjects without bseline kidney disese. Arch Intern Med 2005; 165: Dimond JR: Anlogous pthobiologic mechnisms in glomerulosclerosis nd therosclerosis. Kidney Int Suppl 1991; 31:S29 S Kene WF, Ksiske BL, O Donnell MP: Lipids nd progressive glomerulosclerosis. A model nlogous to therosclerosis. Am J Nephrol 1988; 8: Remuzzi G, Bertni T: Pthophysiology of progressive nephropthies. N Engl J Med 1998; 339: Homocysteine nd Kidney Disese Kidney Blood Press Res 2008;31:

10 14 Chen YF, Li PL, Zou AP: Effect of hyperhomocysteinemi on plsm or tissue denosine levels nd renl function. Circultion 2002; 106: Ingrm AJ, Krepinsky JC, Jmes L, Austin RC, Tng D, Slptek AM, Thi K, Scholey JW: Activtion of mesngil cell MAPK in response to homocysteine. Kidney Int 2004; 66: Shstry S, Ingrm AJ, Scholey JW, Jmes LR: Homocysteine induces mesngil cell poptosis vi ctivtion of p38-mitogen-ctivted protein kinse. Kidney Int 2007; 71: Li N, Chen L, Muh RW, Li PL: Hyperhomocysteinemi ssocited with decresed renl trnssulfurtion ctivity in Dhl S rts. Hypertension 2006; 47: Ninomiy T, Kiyohr Y, Kubo M, Tnizki Y, Tnk K, Okubo K, Nkmur H, Ht J, Oishi Y, Kto I, Hirkt H, Iid M: Hyperhomocysteinemi nd the development of chronic kidney disese in generl popultion: the Hisym study. Am J Kidney Dis 2004; 44: Smuelsson O, Lee DM, Attmn PO, Knight- Gibson C, Mullen JK, Lrsson R, Mulec H, Weiss L, Alupovic P: The plsm levels of homocysteine re elevted in moderte renl insufficiency but do not predict the rte of progression. Nephron 1999; 82: Srnk MJ, Wng SR, Beck GJ, Kusek JW, Selhub J, Greene T, Levey AS: Homocysteine, cysteine, nd B vitmins s predictors of kidney disese progression. Am J Kidney Dis 2002; 40: Chi EM, Wng JJ, Rochtchin E, Smith W, Cumming RR, Mitchell P: Impct of bilterl visul impirment on helth-relted qulity of life: the Blue Mountins Eye Study. Invest Ophthlmol Vis Sci 2004; 45: Nexo E, Engbek F, Uelnd PM, Westby C, O Gormn P, Johnston C, Kse BF, Guttormsen AB, Alfheim I, McPrtlin J, Smith D, Moller J, Rsmussen K, Clrke R, Scott JM, Refsum H: Evlution of novel ssys in clinicl chemistry: quntifiction of plsm totl homocysteine. Clin Chem 2000; 46: Shnkr A, Wng JJ, Rochtchin E, Mitchell P: Positive ssocition between plsm fibrinogen level nd incident hypertension mong men: popultion-bsed cohort study. Hypertension 2006; 48: Chobnin AV, Bkris GL, Blck HR, Cushmn WC, Green LA, Izzo JL Jr, Jones DW, Mterson BJ, Opril S, Wright JT Jr, Roccell EJ, the Ntionl High Blood Pressure Eduction Progrm Coordinting Committee: Seventh Report of the Joint Ntionl Committee on Prevention, Detection, Evlution, nd Tretment of High Blood Pressure. Hypertension 2003; 42: Levey AS, Bosch JP, Lewis JB, Greene T, Rogers N, Roth D: A more ccurte method to estimte glomerulr filtrtion rte from serum cretinine: new prediction eqution. Modifiction of Diet in Renl Disese Study Group. Ann Intern Med 1999; 130: Friedmn AN, Bostom AG, Selhub J, Levey AS, Rosenberg IH: The kidney nd homocysteine metbolism. J Am Soc Nephrol 2001; 12: Vnholder R, Mssy Z, Argiles A, Spsovski G, Verbeke F, Lmeire N: Chronic kidney disese s cuse of crdiovsculr morbidity nd mortlity. Nephrol Dil Trnsplnt 2005; 20: Kidney Blood Press Res 2008;31:55 62 Shnkr /Wng /Chu /Rochtchin / Flood /Mitchell

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