![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
Departments of Clinical Nutrition, and Food and Nutrition, College of Health Sciences, Rush University Medical Center, Chicago, IL and * Department of Mathematics, San Francisco State University, San Francisco, CA
2To whom correspondence should be addressed. E-mail: vijay_ganji{at}rush.edu.
 |
ABSTRACT |
|---|
 TOP ABSTRACT SUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
6.8, 10.5, and 8.8% higher in boys than in girls in non-Hispanic White (NHW), non-Hispanic Black (NHB), and Mexican American/Hispanic (MA/H) children, respectively. Sex- and age-adjusted plasma tHcy concentrations (geometric means ± SE) were 5.04 ± 0.05, 5.01 ± 0.06, and 4.99 ± 0.06 µmol/L in the NHW, NHB, and MA/H groups, respectively. Race-ethnicity was not related to plasma tHcy in age-adjusted analysis for boys (P < 0.77) and girls (P < 0.26), and in sex- and age-adjusted analysis (P < 0.38) for all children. The plasma tHcy concentrations begin to rise between ages 8 and 11 y, and the age-related increase is greater in boys than in girls.
KEY WORDS: • children • homocysteine • National Health and Nutrition Examination Survey • United States
Elevated circulating total homocysteine (tHcy)3 is directly associated with increased risk for vascular diseases (1), pregnancy complications, and neural tube defects (NTD) (2). Homocysteine is either remethylated to methionine or transulfurated to cysteine. Methylene tetrahydrofolate reductase, a riboflavin-dependent enzyme, catalyzes 5,10-methylene tetrahydrofolate to 5-methyl tetrahydrofolate, which is required for remethylation of homocysteine to methionine by methionine synthase, a cobalamin-dependent enzyme (3). Transulfuration of homocysteine to cysteine is catalyzed by pyridoxal phosphate (vitamin B-6 coenzyme)–dependent enzymes such as cystathionine ß-synthase and 
-cystathionase (4). Genetic abnormalities in enzymes involved in homocysteine metabolism (5) and deficiency of folate, riboflavin, vitamin B-6, and cobalamin (6–8) lead to elevated tHcy concentrations in blood.
In children, increased circulating tHcy concentration is directly related to increased blood pressure and weight (9) and appears to predict parental risk of cardiovascular disease (10). Although there is an indication that treating high tHcy with homocysteine-lowering agents prevents premature vascular disease (11), whether elevated tHcy in the circulation is the cause of vascular diseases is not well understood.
Folic acid fortification has markedly improved the folate status of the U.S. population and has significantly reduced circulating tHcy concentrations in U.S. adults (12,13). Current reference values for tHcy concentrations for U.S. children and adolescents are based on data collected during the pre-folic acid fortification period (14). Reference data for tHcy concentrations based on a representative U.S. sample in the post-folic acid fortification scenario are lacking. Therefore, the objectives of this study were to report the plasma tHcy concentration distributions by sex, age, and race-ethnicity and to investigate the association between plasma tHcy and sex, age, and race-ethnicity utilizing the data from nationally representative sample surveys, 1999–2002, conducted after folic acid fortification.
|
SUBJECTS AND METHODS |
|---|
|
TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
The National Center for Health Statistics of the CDC conducts National Health and Nutrition Examination Surveys (NHANESs) on civilian, noninstitutionalized persons in the United States. These surveys are based on a complex, stratified, multistage probability sample survey design. The data used in this study were derived from data files released for public use (15,16). NHANES 1999–2000 and NHANES 2001–2002 were conducted as continuous annual surveys rather than periodic surveys. For this study, we concatenated the data from NHANES 1999–2000 and NHANES 2001–2002 into one analytic database, NHANES 1999–2002.
NHANES 1999–2002 study protocols were approved by the internal review committee of the CDC. Demographic, socioeconomic, dietary, and health-related data were collected in the participants’ homes as part of the household interview. All persons interviewed in the household were asked to complete the health examination component in a Mobile Examination Center (MEC). NHANES 1999–2000 was conducted between March 1999 and December 2000 among 9965 individuals (all were home interviewed; 9282 were examined in an MEC); NHANES 2001–2002 was conducted between January 2001 and December 2002 among 11,039 individuals (all were home interviewed; 10,477 were examined in an MEC). A detailed description of the survey methodology was given elsewhere (17). In the analysis, we included individuals 
18 y of age (n = 10,150). Children and adolescents with missing values for the plasma tHcy concentrations were excluded (n = 3532). Persons with race-ethnicities other than non-Hispanic White (NHW), non-Hispanic Black (NHB), and Mexican American/Hispanic (MA/H) were also excluded due to small sample size (n = 157). Thus, the final sample consisted of 6461 children and adolescents (3264 boys and 3197 girls).
Measurements.
Blood was collected by venipuncture at an MEC according to standard protocols. Subjects fasted for varying lengths of time. Blood was collected into tubes containing EDTA and immediately centrifuged (2900 x g for 10 min at 4–8°C) to yield plasma. Plasma tHcy was measured at the CDC laboratories using the fluorescence polarization immunoassay (Abbott Laboratories). Race-ethnicity information was based on self-reported data. Detailed methodology of blood collection and laboratory procedures was described elsewhere (18).
Statistical analysis.
SUDAAN statistical software (SUDAAN for Windows, version 9.0, Research Triangle Institute) was used to account for the complex survey design and differential probabilities of selection, and to make adjustments for noncoverage and nonresponse bias. Also, SAS (SAS for Windows, version 9.1, SAS Institute) in conjunction with SUDAAN was used to manage and analyze the data files.
Because the distribution of plasma tHcy was asymmetric (skewed to the right), we calculated sex- and age-specific geometric mean plasma tHcy concentrations for NHW, NHB, and MA/H groups. The difference in plasma tHcy between boys and girls within race-ethnicity was determined by t test. The Bonferroni multiple comparison test was used to compare the plasma tHcy among race-ethnicities within gender after testing the hypothesis with t test.
Additionally, we plotted the geometric mean plasma tHcy concentrations vs. age by race-ethnicity using the Cubic Spline Smoothing procedure to determine the rate of increase of tHcy concentrations in children. Age-adjusted plasma tHcy for boys and girls, and sex- and age-adjusted plasma tHcy for all subjects were determined for NHW, NHB, and MA/H using analysis of covariance (ANCOVA). Due to the asymmetric nature of plasma tHcy, we used natural log tHcy concentrations in the ANCOVA. Differences between age-adjusted, and sex- and age-adjusted plasma tHcy between race-ethnicities were tested with Bonferroni adjustment after establishing the nonequality of the means with ANCOVA. Interaction of sex and age with plasma tHcy was also included. In all analyses, 
= 0.05 was considered significant. Data were presented as means ± SE.
|
RESULTS |
|---|
|
TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
15 y old) compared with older children (16–18 y old) (P < 0.05). Regardless of race-ethnicity or sex, the difference in plasma tHcy between the group < 4 y old and the 4- to 7-y-old group was smaller than the differences between other age groups studied (P < 0.05). The NHW, NHB, and MA/H groups did not differ within gender.
|
15 y old. Additionally, age-adjusted tHcy for boys (5.20, 5.25, and 5.19 µmol/L for the NHW, NHB, and MA/H groups, respectively) and girls (4.87, 4.75, and 4.77 µmol/L for the NHW, NHB, and MA/H groups, respectively), and sex- and age-adjusted tHcy for all children (4.15, 4.04, and 4.21 µmol/L for the NHW, NHW, and MA/H groups, respectively) did not differ between race-ethnicities.
|
|
|
DISCUSSION |
|---|
|
TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
1.0 µmol/L decrease in circulating tHcy in U.S. children. However, caution should be exercised in comparing the data between NHANES III and NHANES 1999–2002 due to differences in tHcy measurement (19).
In the post-folic acid fortification period, we observed that girls had 6.2, 9.0, and 6.4% lower geometric mean plasma tHcy than boys in the NHW, NHB, and MA/H groups, respectively. The sex difference in tHcy may be explained by increased synthesis of creatine [methionine 
S-adenosylmethionine (methyl donor to guanidoacetate) S-adenosylhomocysteine homocysteine] due to higher muscle mass in boys than in girls (20), and by the differences in sex-related hormones (21). Must et al. (14) reported significantly higher tHcy in boys than in girls for the NHB and MA/H groups but not for NHW children in the pre-folic acid fortification era. In contrast, in the Bogalusa Heart Study population (n = 1137), investigators (22) reported no significant sex difference in 5- to 17-y-old White or Black children. The inconsistency in sex-related difference in plasma tHcy of children might be related to differences in vitamin nutritional status between the study populations (23).
Age was a significant determinant of tHcy in both boys and girls. Regardless of sex, in all race-ethnicities, the difference in tHcy between children < 4 y old and those 4–7 y old was smaller than the difference between the 8–11, 12–15, and 16–18 y old children. Age-related difference between 4 and 7 y and the 8–11 y olds ranged from 6.5 to 11%, suggesting that tHcy concentrations increase between ages 8 and 11 y (Fig. 1). Consistent with our findings, Must et al. (14) reported the divergence of tHcy concentrations at about the age of 10 y. It appears that the age-related increase is greater in boys than in girls during adolescence. In boys, the increase in tHcy coincides with an increase in androgens (24), whereas in women, estrogen is inversely related to tHcy (25). Thus, the higher tHcy in the 8–11, 12–15, and 16–18 y old groups compared with younger children, and the accelerated increase of plasma tHcy in boys compared with girls might be related to sex hormones and increased muscle mass.
In this study, race-ethnicity was not associated with plasma tHcy in U.S. children. Inconsistent results were reported by investigators examining the association between tHcy and race-ethnicity in children (9,14,22). Sex divergence in plasma tHcy occurred much earlier in the NHB group (8–11 y) than in the NHW group (16–18 y). Our observation of lack of association between race-ethnicity and tHcy supports the results reported by some (22) and contradicts the results reported by others (9,14). In the Bogalusa Heart Study, Greenlund et al. (22) reported no difference in tHcy between White and Black children. On the other hand, in the Child and Adolescent Trial for Cardiovascular Health study, Black children had higher tHcy than White children (9). Utilizing nationally representative sample survey data from the pre-folic acid fortification era (NHANES III), Must et al. (14) reported race-ethnicity differences in girls but not in boys. In their study, MA/H girls had significantly lower tHcy than NHB girls, and the age-specific tHcy concentrations were the lowest in all age groups of MA/H girls. However, we found no such race-ethnicity difference in tHcy concentrations in the post-folic acid fortification period. Similar to our results, in the post-folic acid fortification era, no difference in plasma tHcy was observed in young women of different race-ethnicity (26).
In conclusion, in the post-folic acid fortification era, age and sex but not race-ethnicity were significantly associated with plasma tHcy concentrations in U.S. children and adolescents. Our data support the notion that circulating tHcy concentrations increase between ages 8 and 11 y, and the age-related increase is greater in boys than in girls during adolescence. Although folic acid fortification has resulted in a significant decrease in circulating tHcy concentrations (10,11), whether this reduction in children will reduce the risk for vascular diseases in adulthood remains to be determined.
|
FOOTNOTES |
|---|
3 Abbreviations used: ANCOVA, analysis of covariance; MA/H, Mexican American/Hispanic; MEC, Mobile Examination Clinic; NHANES, National Health and Nutrition Examination Survey; NHB, non-Hispanic Black; NHW, non-Hispanic White; NTD, neural tube defect; tHcy, total homocysteine.
Manuscript received 25 February 2005. Initial review completed 31 March 2005. Revision accepted 7 July 2005.
|
LITERATURE CITED |
|---|
|
TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
1. Nygard, O., Vollset, S. E. & Refsum, H. M. (1995) Total plasma homocysteine and cardiovascular risk profile. The Hordaland Homocysteine Study. J. Am. Med. Assoc. 274:1536-1543.
2. Monsen, A.L.B. & Ueland, P. M. (2003) Homocysteine and methylmalonic acid in diagnosis and risk assessment from infancy to adolescence. Am. J. Clin. Nutr. 78:7-21.
3. Gerhard, G. T., Malinow, M. R., DeLoughery, T. G., Evans, A. J., Sexton, G., Connor, S. L., Wander, R. C. & Connor, W. E. (1999) Higher total homocysteine concentrations and lower folate concentrations in premenopausal black women than in premenopausal white women. Am. J. Clin. Nutr. 70:252-260.
4. Schirch, L. (1982) Serine hydroxymethyltransferase. Adv. Enzymol. Relat. Areas Mol. Biol. 53:83-112.[Medline]
5. Jacques, P. F., Kalmbach, R., Bagley, P. J., Russo, G. T., Rogers, G., Wilson, P. W., Rosenberg, I. H. & Selhub, J. (2002) The relationship between riboflavin and plasma total homocysteine in the Framingham offspring cohort is influenced by folate status and the C677T transition in the methylenetetrahydrofolate reductase gene. J. Nutr. 132:283-288.
6. Selhub, J., Jacques, P. F., Wilson, P.W.F., Rush, D. & Rosenberg, I. H. (1993) Vitamin status and intake as primary determinants of homocysteinemia in an elderly population. J. Am. Med. Assoc. 270:2693-2698.[Abstract]
7. Selhub, J., Jacques, P. F., Rosenberg, I. H., Rogers, G., Bowman, B. A., Gunter, E. W., Wright, J. D. & Johnson, C. L. (1999) Serum total homocysteine concentrations in the third National Health and Nutrition Examination Survey (1988–1994): population reference ranges and contribution of vitamin status to high homocysteine concentrations. Ann. Intern. Med. 131:331-339.
8. Pancharuniti, N., Lewis, C. A., Sauberlich, H. E., Perkins, L. L., Go, R. C., Alvarez, J. O., Macaluso, M., Acton, R. T., Copeland, R. B. & Cousins, A. L. (1994) Plasma homocysteine, folate, and vitamin B-12 concentrations and risk for early-onset coronary artery disease. Am. J. Clin. Nutr. 59:940-948.
9. Osganian, S. K., Stampfer, M. J., Spiegelman, D., Rimm, E., Cutler, J. A., Feldamn, H. A., Montgomery, D. H., Webber, L. S., Lytle, L. A., Bausserman, L. & Nader, P. R. (1999) Distribution of and factors associated with serum homocysteine levels in children: Child and Adolescent Trial for Cardiovascular Health. J. Am. Med. Assoc. 281:1189-1196.
10. Tonstad, S., Refsum, H., Siverston, M., Christophersen, B., Ose, L. & Ueland, P. M. (1996) Relation of total homocysteine and lipid levels in children to premature cardiovascular death in male relatives. Pediatr. Res. 40:47-52.[Medline]
11. Yap, S., Boers, G. H., Wilcken, B., Wilcken, D. E. & Brenton, D. P. (2001) Vascular outcome in patients with homocystinuria due to cystathionine ß-synthase deficiency treated chronically: a multicenter observational study. Arterioscler. Thromb. Vasc. Biol. 21:2080-2085.
12. Ganji, V. & Kafai, M. R. (2005) Trends in serum folate, red blood cell folate and circulating total homocysteine concentrations in the US: data from nationally representative sample surveys from pre- and post-folate fortification periods, 1988–2002. FASEB J. 19:A1619 (abs.).
13. Jacques, P. F., Selhub, J., Bostom, A. G., Wilson, P.F.W. & Rosenberg, I. H. (1999) The effect of folic acid fortification on plasma folate and total homocysteine concentrations. N. Engl. J. Med. 340:1449-1454.
14. Must, A., Jacques, P. F., Rogers, G., Rosenberg, I. H. & Selhub, J. (2003) Serum total homocysteine concentrations in children and adolescents: results from the Third National Health and Nutrition Examination Survey (NHANES III). J. Nutr. 133:2643-2649.
15. U.S. Department of Health and Human Services. National Center for Health Statistics () Serum total homocysteine concentrations in children and adolescents: results from the Third National Health and Nutrition Examination Survey (NHANES III). National Health and Nutrition Examination Survey, 1999–2000. Public use data files Center for Disease Control and Prevention Home Page: http://www.cdc.gov/nchs/about/major/nhanes/NHANES99–00.htm. [Last accessed 07/20/2004].
16. U.S. Department of Health and Human Services. National Center for Health Statistics () Serum total homocysteine concentrations in children and adolescents: results from the Third National Health and Nutrition Examination Survey (NHANES III). National Health and Nutrition Examination Survey, 1999–2000. Public use data files Center for Disease Control and Prevention Home Page: http://www.cdc.gov/nchs/about/major/nhanes/NHANES01–02.htm. [Last accessed 07/20/2004].
17. U.S. Department of Health and Human Services. National Center for Health Statistics () Serum total homocysteine concentrations in children and adolescents: results from the Third National Health and Nutrition Examination Survey (NHANES III). National Health and Nutrition Examination Survey, 1999-Current. Survey operations manuals, brochures, consent documents, March 2001. Public use data files Center for Disease Control and Prevention Home Page: http://www.cdc.gov/nchs/about/major/nhanes/currentnhanes.htm#. [Last accessed 07/20/2004].
18. U.S. Department of Health and Human Services. National Center for Health Statistics () Serum total homocysteine concentrations in children and adolescents: results from the Third National Health and Nutrition Examination Survey (NHANES III). National Health and Nutrition Examination Survey, 2001–2002. Laboratory Procedures Manual Center for Disease Control and Prevention Home Page: http://www.cdc.gov/nchs/about/major/nhanes/nhanes01–02.htm. [Last accessed 07/20/2004].
19. Pfeiffer, C. M., Caudill, S. P., Gunter, E. W., Bowman, B. A., Jacques, P. F., Selhub, J., Johnson, C. L., Miller, D. T. & Sampson, E. J. (2000) Analysis of factors influencing the comparison of homocysteine values between the Third National Health and Nutrition Examination Survey (NHANES) and NHANES 1999+. J. Nutr. 130:2850-2854.
20. Brattstrom, L., Lindgren, A., Israelsson, B., Anderson, A. & Hultberg, B. (1994) Homocysteine and cysteine: determinants of plasma levels in middle-aged and elderly subjects. J. Intern. Med. 236:633-641.[Medline]
21. Zmuda, J. M., Bausserman, L. L., Maceroni, D. & Thompson, P. D. (1997) The effect of supraphysiologic doses of testosterone on fasting total homocysteine levels in normal men. Atherosclerosis 130:199-202.[Medline]
22. Greenlund, K. J., Srinivasn, S. R., Xu, J., Dalferes, E., Myers, L., Pickoff, A. & Berenson, G. S. (1999) Plasma homocysteine distribution and its association with parental history of coronary artery disease in Black and White children. Circulation 99:2144-2149.
23. Monsen, A.L.B. & Ueland, P. M. (2003) Homocysteine and methylmalonic acid in diagnosis and risk assessment from infancy to adolescence. Am. J. Clin. Nutr. 78:7-21.
24. Giltay, E. J. & Gooren, L. J. (2000) Effects of sex steroid deprivation/administration on hair growth and skin sebum production in transsexual males and females. J. Clin. Endocrionol. Metab. 85:2913-2921.
25. Wouters, M. G., Moorrees, M. T., van der Mooren, M. J., Bloom, H. J., Boers, G. H., Schellekens, L. A., Thomas, C. M. & Eskes, T. K. (1995) Plasma homocysteine and menopausal status. Eur. J. Clin. Investig. 25:801-805.[Medline]
26. Caudill, M. A., Le, T., Moonie, S. A., Esfahani, S. T. & Cogger, E. A. (2001) Folate status in women of childbearing age residing in Southern California after folic acid fortification. J. Am. Coll. Nutr. 20:129-134.
This article has been cited by other articles:
|
|
 |
|
  C. M. Pfeiffer, J. D. Osterloh, J. Kennedy-Stephenson, M. F. Picciano, E. A. Yetley, J. I. Rader, and C. L. Johnson Trends in Circulating Concentrations of Total Homocysteine among US Adolescents and Adults: Findings from the 1991-1994 and 1999-2004 National Health and Nutrition Examination Surveys Clin. Chem., May 1, 2008; 54(5): 801 - 813. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. W. Friesen, E. M. Novak, D. Hasman, and S. M. Innis Relationship of Dimethylglycine, Choline, and Betaine with Oxoproline in Plasma of Pregnant Women and Their Newborn Infants J. Nutr., December 1, 2007; 137(12): 2641 - 2646. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
