Paul F. Jacques

Long-term morbidity and mortality of overweight adolescents : a follow-up of the Harvard growth study of 1922 to 1935

BACKGROUND Overweight in adults is associated with increased morbidity and mortality. In contrast, the long-term effect of overweight in adolescence on morbidity and mortality is not known. METHODS We studied the relation between overweight and morbidity and mortality in 508 lean or overweight adolescents 13 to 18 years old who participated in the Harvard Growth Study of 1922 to 1935. Overweight adolescents were defined as those with a body-mass index that on two occasions was greater than the 75th percentile in subjects of the same age and sex in a large national survey. Lean adolescents were defined as those with a body-mass index between the 25th and 50th percentiles. Subjects who were still alive were interviewed in 1988 to obtain information about their medical history, weight, functional capacity, and other risk factors. For those who had died, information on the cause of death was obtained from death certificates. RESULTS Overweight in adolescent subjects was associated with an increased risk of mortality from all causes and disease-specific mortality among men, but not among women. The relative risks among men were 1.8 (95 percent confidence interval, 1.2 to 2.7; P = 0.004) for mortality from all causes and 2.3 (95 percent confidence interval, 1.4 to 4.1; P = 0.002) for mortality from coronary heart disease. The risk of morbidity from coronary heart disease and atherosclerosis was increased among men and women who had been overweight in adolescence. The risk of colorectal cancer and gout was increased among men and the risk of arthritis was increased among women who had been overweight in adolescence. Overweight in adolescence was a more powerful predictor of these risks than overweight in adulthood. CONCLUSIONS Overweight in adolescence predicted a broad range of adverse health effects that were independent of adult weight after 55 years of follow-up.

Vitamin D Deficiency and Risk of Cardiovascular Disease

Background— Vitamin D receptors have a broad tissue distribution that includes vascular smooth muscle, endothelium, and cardiomyocytes. A growing body of evidence suggests that vitamin D deficiency may adversely affect the cardiovascular system, but data from longitudinal studies are lacking. Methods and Results— We studied 1739 Framingham Offspring Study participants (mean age 59 years; 55% women; all white) without prior cardiovascular disease. Vitamin D status was assessed by measuring 25-dihydroxyvitamin D (25-OH D) levels. Prespecified thresholds were used to characterize varying degrees of 25-OH D deficiency (<15 ng/mL, <10 ng/mL). Multivariable Cox regression models were adjusted for conventional risk factors. Overall, 28% of individuals had levels <15 ng/mL, and 9% had levels <10 ng/mL. During a mean follow-up of 5.4 years, 120 individuals developed a first cardiovascular event. Individuals with 25-OH D <15 ng/mL had a multivariable-adjusted hazard ratio of 1.62 (95% confidence interval 1.11 to 2.36, P=0.01) for incident cardiovascular events compared with those with 25-OH D ≥15 ng/mL. This effect was evident in participants with hypertension (hazard ratio 2.13, 95% confidence interval 1.30 to 3.48) but not in those without hypertension (hazard ratio 1.04, 95% confidence interval 0.55 to 1.96). There was a graded increase in cardiovascular risk across categories of 25-OH D, with multivariable-adjusted hazard ratios of 1.53 (95% confidence interval 1.00 to 2.36) for levels 10 to <15 ng/mL and 1.80 (95% confidence interval 1.05 to 3.08) for levels <10 ng/mL (P for linear trend=0.01). Further adjustment for C-reactive protein, physical activity, or vitamin use did not affect the findings. Conclusions— Vitamin D deficiency is associated with incident cardiovascular disease. Further clinical and experimental studies may be warranted to determine whether correction of vitamin D deficiency could contribute to the prevention of cardiovascular disease.

Metabolite profiles and the risk of developing diabetes

Emerging technologies allow the high-throughput profiling of metabolic status from a blood specimen (metabolomics). We investigated whether metabolite profiles could predict the development of diabetes. Among 2,422 normoglycemic individuals followed for 12 years, 201 developed diabetes. Amino acids, amines and other polar metabolites were profiled in baseline specimens by liquid chromatography–tandem mass spectrometry (LC-MS). Cases and controls were matched for age, body mass index and fasting glucose. Five branched-chain and aromatic amino acids had highly significant associations with future diabetes: isoleucine, leucine, valine, tyrosine and phenylalanine. A combination of three amino acids predicted future diabetes (with a more than fivefold higher risk for individuals in top quartile). The results were replicated in an independent, prospective cohort. These findings underscore the potential key role of amino acid metabolism early in the pathogenesis of diabetes and suggest that amino acid profiles could aid in diabetes risk assessment.

Relation Between Folate Status, a Common Mutation in Methylenetetrahydrofolate Reductase, and Plasma Homocysteine Concentrations

BACKGROUND Methylenetetrahydrofolate reductase (MTHFR) synthesizes 5-methyltetrahydrofolate, the major carbon donor in remethylation of homocysteine to methionine. A common MTHFR mutation, an alanine-to-valine substitution, renders the enzyme thermolabile and may cause elevated plasma levels of the amino acid homocysteine. METHODS AND RESULTS To assess the potential interaction between this mutation and vitamin coenzymes in homocysteine metabolism, we screened 365 individuals from the NHLBI Family Heart Study. Among individuals with lower plasma folate concentrations ( < 15.4 nmol/L), those with the homozygous mutant genotype had total fasting homocysteine levels that were 24% greater (P<.05) than individuals with the normal genotype. A difference between genotypes was not seen among individuals with folate levels > or = 15.4 nmol/L. CONCLUSIONS Individuals with thermolabile MTHFR may have a higher folate requirement for regulation of plasma homocysteine concentrations; folate supplementation may be necessary to prevent fasting hyperhomocysteinemia in such persons.

The Effect of Folic Acid Fortification on Plasma Folate and Total Homocysteine Concentrations

BACKGROUND In 1996, the Food and Drug Administration issued a regulation requiring all enriched grain products to be fortified with folic acid to reduce the risk of neural-tube defects in newborns. Fortification (140 microg per 100 g) began in 1996, and the process was essentially complete by mid-1997. METHODS To assess the effect of folic acid fortification on folate status, we measured plasma folate and total homocysteine concentrations (a sensitive marker of folate status) using blood samples from the fifth examination (January 1991 to December 1994) of the Framingham Offspring Study cohort for baseline values and the sixth examination (January 1995 to August 1998) for follow-up values. We divided the cohort into two groups on the basis of the date of their follow-up examination: the study group consisted of 350 subjects who were seen after fortification (September 1997 to March 1998), and the control group consisted of 756 subjects who were seen before fortification (January 1995 to September 1996). RESULTS Among the subjects in the study group who did not use vitamin supplements, the mean folate concentrations increased from 4.6 to 10.0 ng per milliliter (11 to 23 nmol per liter) (P<0.001) from the baseline visit to the follow-up visit, and the prevalence of low folate concentrations (<3 ng per milliliter [7 nmol per liter]) decreased from 22.0 to 1.7 percent (P< 0.001). The mean total homocysteine concentration decreased from 10.1 to 9.4 micromol per liter during this period (P<0.001), and the prevalence of high homocysteine concentrations (>13 micromol per liter) decreased from 18.7 to 9.8 percent (P<0.001). In the control group, there were no statistically significant changes in concentrations of folate or homocysteine. CONCLUSIONS The fortification of enriched grain products with folic acid was associated with a substantial improvement in folate status in a population of middle-aged and older adults.

A common mutation in the 5,10-methylenetetrahydrofolate reductase gene affects genomic DNA methylation through an interaction with folate status

DNA methylation, an essential epigenetic feature of DNA that modulates gene expression and genomic integrity, is catalyzed by methyltransferases that use the universal methyl donor S-adenosyl-l-methionine. Methylenetetrahydrofolate reductase (MTHFR) catalyzes the synthesis of 5-methyltetrahydrofolate (5-methylTHF), the methyl donor for synthesis of methionine from homocysteine and precursor of S-adenosyl-l-methionine. In the present study we sought to determine the effect of folate status on genomic DNA methylation with an emphasis on the interaction with the common C677T mutation in the MTHFR gene. A liquid chromatography/MS method for the analysis of nucleotide bases was used to assess genomic DNA methylation in peripheral blood mononuclear cell DNA from 105 subjects homozygous for this mutation (T/T) and 187 homozygous for the wild-type (C/C) MTHFR genotype. The results show that genomic DNA methylation directly correlates with folate status and inversely with plasma homocysteine (tHcy) levels (P < 0.01). T/T genotypes had a diminished level of DNA methylation compared with those with the C/C wild-type (32.23 vs.62.24 ng 5-methylcytosine/μg DNA, P < 0.0001). When analyzed according to folate status, however, only the T/T subjects with low levels of folate accounted for the diminished DNA methylation (P < 0.0001). Moreover, in T/T subjects DNA methylation status correlated with the methylated proportion of red blood cell folate and was inversely related to the formylated proportion of red blood cell folates (P < 0.03) that is known to be solely represented in those individuals. These results indicate that the MTHFR C677T polymorphism influences DNA methylation status through an interaction with folate status.

Common genetic determinants of vitamin D insufficiency: a genome-wide association study

BACKGROUND Vitamin D is crucial for maintenance of musculoskeletal health, and might also have a role in extraskeletal tissues. Determinants of circulating 25-hydroxyvitamin D concentrations include sun exposure and diet, but high heritability suggests that genetic factors could also play a part. We aimed to identify common genetic variants affecting vitamin D concentrations and risk of insufficiency. METHODS We undertook a genome-wide association study of 25-hydroxyvitamin D concentrations in 33 996 individuals of European descent from 15 cohorts. Five epidemiological cohorts were designated as discovery cohorts (n=16 125), five as in-silico replication cohorts (n=9367), and five as de-novo replication cohorts (n=8504). 25-hydroxyvitamin D concentrations were measured by radioimmunoassay, chemiluminescent assay, ELISA, or mass spectrometry. Vitamin D insufficiency was defined as concentrations lower than 75 nmol/L or 50 nmol/L. We combined results of genome-wide analyses across cohorts using Z-score-weighted meta-analysis. Genotype scores were constructed for confirmed variants. FINDINGS Variants at three loci reached genome-wide significance in discovery cohorts for association with 25-hydroxyvitamin D concentrations, and were confirmed in replication cohorts: 4p12 (overall p=1.9x10(-109) for rs2282679, in GC); 11q12 (p=2.1x10(-27) for rs12785878, near DHCR7); and 11p15 (p=3.3x10(-20) for rs10741657, near CYP2R1). Variants at an additional locus (20q13, CYP24A1) were genome-wide significant in the pooled sample (p=6.0x10(-10) for rs6013897). Participants with a genotype score (combining the three confirmed variants) in the highest quartile were at increased risk of having 25-hydroxyvitamin D concentrations lower than 75 nmol/L (OR 2.47, 95% CI 2.20-2.78, p=2.3x10(-48)) or lower than 50 nmol/L (1.92, 1.70-2.16, p=1.0x10(-26)) compared with those in the lowest quartile. INTERPRETATION Variants near genes involved in cholesterol synthesis, hydroxylation, and vitamin D transport affect vitamin D status. Genetic variation at these loci identifies individuals who have substantially raised risk of vitamin D insufficiency. FUNDING Full funding sources listed at end of paper (see Acknowledgments).

Soft Drink Consumption and Risk of Developing Cardiometabolic Risk Factors and the Metabolic Syndrome in Middle-Aged Adults in the Community

Background— Consumption of soft drinks has been linked to obesity in children and adolescents, but it is unclear whether it increases metabolic risk in middle-aged individuals. Methods and Results— We related the incidence of metabolic syndrome and its components to soft drink consumption in participants in the Framingham Heart Study (6039 person-observations, 3470 in women; mean age 52.9 years) who were free of baseline metabolic syndrome. Metabolic syndrome was defined as the presence of ≥3 of the following: waist circumference ≥35 inches (women) or ≥40 inches (men); fasting blood glucose ≥100 mg/dL; serum triglycerides ≥150 mg/dL; blood pressure ≥135/85 mm Hg; and high-density lipoprotein cholesterol <40 mg/dL (men) or <50 mg/dL (women). Multivariable models included adjustments for age, sex, physical activity, smoking, dietary intake of saturated fat, trans fat, fiber, magnesium, total calories, and glycemic index. Cross-sectionally, individuals consuming ≥1 soft drink per day had a higher prevalence of metabolic syndrome (odds ratio [OR], 1.48; 95% CI, 1.30 to 1.69) than those consuming <1 drink per day. On follow-up (mean of 4 years), new-onset metabolic syndrome developed in 765 (18.7%) of 4095 participants consuming <1 drink per day and in 474 (22.6%) of 2059 persons consuming ≥1 soft drink per day. Consumption of ≥1 soft drink per day was associated with increased odds of developing metabolic syndrome (OR, 1.44; 95% CI, 1.20 to 1.74), obesity (OR, 1.31; 95% CI, 1.02 to 1.68), increased waist circumference (OR, 1.30; 95% CI, 1.09 to 1.56), impaired fasting glucose (OR, 1.25; 95% CI, 1.05 to 1.48), higher blood pressure (OR, 1.18; 95% CI, 0.96 to 1.44), hypertriglyceridemia (OR, 1.25; 95% CI, 1.04 to 1.51), and low high-density lipoprotein cholesterol (OR, 1.32; 95% CI 1.06 to 1.64). Conclusions— In middle-aged adults, soft drink consumption is associated with a higher prevalence and incidence of multiple metabolic risk factors.

A Temporal Association between Folic Acid Fortification and an Increase in Colorectal Cancer Rates May Be Illuminating Important Biological Principles: A Hypothesis

Nationwide fortification of enriched uncooked cereal grains with folic acid began in the United States and Canada in 1996 and 1997, respectively, and became mandatory in 1998. The rationale was to reduce the number of births complicated by neural tube defects. Concurrently, the United States and Canada experienced abrupt reversals of the downward trend in colorectal cancer (CRC) incidence that the two countries had enjoyed in the preceding decade: absolute rates of CRC began to increase in 1996 (United States) and 1998 (Canada), peaked in 1998 (United States) and 2000 (Canada), and have continued to exceed the pre-1996/1997 trends by 4 to 6 additional cases per 100,000 individuals. In each country, the increase in CRC incidence from the prefortification trend falls significantly outside of the downward linear fit based on nonparametric 95% confidence intervals. The statistically significant increase in rates is also evident when the data for each country are analyzed separately for men and women. Changes in the rate of colorectal endoscopic procedures do not seem to account for this increase in CRC incidence. These observations alone do not prove causality but are consistent with the known effects of folate on existing neoplasms, as shown in both preclinical and clinical studies. We therefore hypothesize that the institution of folic acid fortification may have been wholly or partly responsible for the observed increase in CRC rates in the mid-1990s. Further work is needed to definitively establish the nature of this relationship. In the meantime, deliberations about the institution or enhancement of fortification programs should be undertaken with these considerations in mind. (Cancer Epidemiol Biomarkers Prev 2007;16(7):1325–9)

Nonfasting plasma total homocysteine levels and stroke incidence in elderly persons: the Framingham Study.

Meta-analyses (1, 2) strongly suggest that mildly to moderately elevated circulating levels of the sulfur amino acid homocysteine, either fasting or nonfasting, confer an independent risk for clinical arteriosclerotic outcomes, including stroke. However, just four reports (3-6) have provided somewhat limited, conflicting prospective data on the potential relation between total homocysteine levels and stroke incidence. Only one of these studies (3) used a population-based sample. Samples from two studies were limited to middle-aged men (4, 5): One consisted of U.S. physicians responding to a survey (4), and the other was derived from family practice registries in Great Britain (5). The fourth study (6) was a longitudinal investigation that primarily included women with systemic lupus erythematosus (mean age at baseline, 35 years). No prospective studies have specifically evaluated mild hyperhomocysteinemia as a potential risk factor for stroke in men and women 60 years of age or older, an age group that experiences the most pronounced morbidity and mortality from cerebrovascular disease (7). Accordingly, we examined the association between baseline nonfasting plasma total homocysteine levels and incident stroke in a well-characterized, population-based cohort of elderly women and men who at baseline had not had stroke. Methods The study sample consisted of the original Framingham Study cohort (8). Baseline examinations for the current analyses took place between May 1979 and May 1982, with follow-up occurring through May 1992. Of 2351 persons examined during the baseline period, 1947 had not previously had stroke and had specimens available for measurement of plasma total homocysteine levels. Additional baseline covariables assessed for the current analyses were age, sex, cigarette smoking, diabetes, history of atrial fibrillation, history of coronary heart disease, systolic blood pressure, and creatinine levels. Detailed operational definitions for all these covariables are provided elsewhere (8). Stroke outcome ascertainment and definition methods used in the Framingham Study, including subtype classification, have been described in detail previously (8, 9). Total homocysteine levels were determined by high-performance liquid chromatography with fluorescence detection (10). Nonfasting plasma aliquots were stored at 20 C from the baseline examination period until mid-1997. Data from long-term storage studies conducted at 20 C have confirmed both the biochemical stability and long-term within-person reproducibility of total homocysteine determinations (10). Creatinine levels were measured in nonfasting plasma by the Jaffe method, adapted for autoanalyzers. The skewed total homocysteine data were natural log-transformed, and differences in geometric mean total homocysteine levels according to sex, diabetes, history of atrial fibrillation or coronary heart disease, and smoking status were compared by using unpaired t-tests. The Spearman rho was used to assess unadjusted rank-order correlations between untransformed total homocysteine levels and age, creatinine level, and systolic blood pressure. Unadjusted and adjusted (for age, sex, history of atrial fibrillation or coronary heart disease, diabetes, smoking, systolic blood pressure, and creatinine level) relative risk estimates (hazards ratios with 95% CIs) for total stroke, nonhemorrhagic stroke, and atherothrombotic brain infarction were generated by proportional hazards modeling. Total homocysteine level (natural log-transformed or expressed in quartiles) was the independent variable. All statistical analyses were performed by using SAS software, version 6.12 (SAS Institute, Inc., Cary, North Carolina). Results The study sample (n=1947) consisted of 1158 women (59.5%) and 789 men (40.5%). Four hundred thirteen patients (21.2%) were cigarette smokers, 340 (17.5%) had a history of coronary heart disease, 182 (9.3%) were diabetic, and 81 (4.2%) had a history of atrial fibrillation. Arithmetic means (SD) for key continuous variables were as follows: age, 70 7 years (range, 59 to 91 years); systolic blood pressure, 141 21 mm Hg (range, 86 to 225 mm Hg); creatinine level, 97.2 26.5 mol/L (range, 35.3 to 442 mol/L); and total homocysteine level, 12.65 7.19 mol/L (range, 4.13 to 219.84 mol/L). Geometric mean total homocysteine levels were higher in men than in women (12.35 compared with 11.32 mol/L; P<0.001), in patients with a history of atrial fibrillation than in those without (13.17 compared with 11.66 mol/L; P=0.003), and in patients with a history of coronary heart disease than in those without (12.49 compared with 11.57 mol/L; P<0.001). However, these levels did not differ according to the presence or absence of diabetes (11.83 compared with 11.71 mol/L; P>0.2) or between current cigarette smokers and nonsmokers (11.67 compared with 11.74 mol/L; P>0.2). Weak but significant Spearman correlations were observed between total homocysteine levels and age (r=0.212; P<0.001), creatinine level (r=0.178; P<0.001), and systolic blood pressure (r=0.111; P<0.001). Quartiles of total homocysteine were as follows: quartile 1, 4.13 to 9.25 mol/L; quartile 2, 9.26 to 11.43 mol/L; quartile 3, 11.44 to 14.23 mol/L; quartile 4, 14.24 to 219.84 mol/L. During a median follow-up of 9.9 years, 165 incident total strokes occurred; 153 of these were incident nonhemorrhagic strokes, and 100 were incident atherothrombotic brain infarctions. Five hundred twenty-four persons were censored during follow-up because of death from causes other than stroke. Age, systolic blood pressure, current smoking, diabetes, and history of atrial fibrillation or coronary heart disease were independently predictive of total stroke occurrence (Table 1). Levels of total homocysteine (natural log) as a continuous variable (data not shown) and across quartiles (P<0.001 for linear trend) were associated with all stroke outcomes in unadjusted and multivariable-adjusted proportional hazards analyses (Tables 1 and 2). The interaction term between sex and total homocysteine level (quartile analyses) was nonsignificant (P=0.1); thus, the stroke incidence analyses were not stratified by sex. Further adjustment for creatinine level did not change the results of any of these analyses (data not shown). Table 1. Predictors of Incident Total Stroke in Elderly Women and Men in the Framingham Study Cohort Table 2. Relative Risk Estimates in Elderly Women and Men in the Framingham Study Cohort: Comparison of Each of the Upper Three Quartiles to the Lowest Quartile of Nonfasting Plasma Total Homocysteine Level Discussion Our findings are consistent with previously reported data, derived primarily from elderly female and male participants in the Framingham Study (9, 11), indicating that age, systolic blood pressure, diabetes, cigarette smoking, and history of atrial fibrillation or coronary heart disease were independently predictive of stroke incidence. We report population-based evidence that elevated nonfasting total homocysteine levels are also independently associated with stroke incidence among elderly women and men. Four earlier studies (3-6) have examined the relation between total homocysteine levels and stroke incidence. Alfthan and colleagues (3) did not find an association between total homocysteine levels and incident stroke among Finnish men and women 40 to 64 years of age (total events, 76). Similarly, Verhoef and coworkers (4) found only a weak, nonsignificant association between total homocysteine level and stroke incidence (total events, 109) in a cohort of male physicians whose mean age was 59.7 years (upper quintile compared with lower four quintiles: odds ratio, 1.2 [CI, 0.7 to 2.0]). In contrast, Perry and colleagues (5) reported a robust, independent association between total homocysteine levels (across quartiles) and incident stroke (total events, 107) among British men whose mean age was 54.0 years (quartile 3 compared with quartile 1: odds ratio, 3.3 [CI, 0.9 to 11.5]; quartile 4 compared with quartile 1: odds ratio, 7.4 [CI, 1.9 to 29.0]). More recently, elevated total homocysteine levels were independently linked to the development of stroke outcomes in a cohort of predominantly younger women (mean age, 34.9 years) with systemic lupus erythematosus (6). The two negative studies (3, 4) were characterized by modest stroke event rates and overall exposure to lower total homocysteine levels on the basis of sound nutritional (4) or, possibly, favorable genetic (3) influences. More widespread exposure to elevated total homocysteine levels, due perhaps to worse nutritional status, may have accounted for the strong association between total homocysteine level and incident stroke reported by Perry and colleagues (5). The positive relation between total homocysteine level and stroke occurrence described by Petri and associates in the Hopkins Lupus Cohort (6) was confined to patients with the highest total homocysteine levels (>14 mol/L). Our analyses, which revealed an independent association between total homocysteine level and incident stroke (total events, 165), were performed in an elderly sample characterized, as expected, by a relatively higher stroke event rate (7, 9, 11, 12). This higher rate occurred in conjunction with an increased prevalence of mild hyperhomocysteinemia (that is, in approximately 25% of patients with total homocysteine level>14 mol/L) at the baseline examination. Despite the lack of substantiation by either proven or biologically plausible mechanisms, it has nevertheless been proposed that hyperhomocysteinemia is an epiphenomenon of clinical or even subclinical arteriosclerosis (13, 14). This hypothesis appears untenable in view of the following published findings from both human and animal studies. First, despite the absence of any traditional arteriosclerotic risk factors, 50% of untreated children and young adults with homocystinuria due to cystathionine synthase deficiency ex