Browsing by Subject "Nutrition Surveys"

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    A population model of folate-mediated one-carbon metabolism.
    (Nutrients, 2013-07-05) Duncan, Tanya M; Reed, Michael C; Nijhout, H Frederik
    BACKGROUND: Previous mathematical models for hepatic and tissue one-carbon metabolism have been combined and extended to include a blood plasma compartment. We use this model to study how the concentrations of metabolites that can be measured in the plasma are related to their respective intracellular concentrations. METHODS: The model consists of a set of ordinary differential equations, one for each metabolite in each compartment, and kinetic equations for metabolism and for transport between compartments. The model was validated by comparison to a variety of experimental data such as the methionine load test and variation in folate intake. We further extended this model by introducing random and systematic variation in enzyme activity. OUTCOMES AND CONCLUSIONS: A database of 10,000 virtual individuals was generated, each with a quantitatively different one-carbon metabolism. Our population has distributions of folate and homocysteine in the plasma and tissues that are similar to those found in the NHANES data. The model reproduces many other sets of clinical data. We show that tissue and plasma folate is highly correlated, but liver and plasma folate much less so. Oxidative stress increases the plasma S-adenosylmethionine/S-adenosylhomocysteine (SAM/SAH) ratio. We show that many relationships among variables are nonlinear and in many cases we provide explanations. Sampling of subpopulations produces dramatically different apparent associations among variables. The model can be used to simulate populations with polymorphisms in genes for folate metabolism and variations in dietary input.
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    Cardiometabolic Risk Factors among Severely Obese Children and Adolescents in the United States, 1999-2012.
    (Childhood obesity (Print), 2016-02) Li, Linlin; Pérez, Adriana; Wu, Li-Tzy; Ranjit, Nalini; Brown, Henry S; Kelder, Steven H

    Background

    Severely obese children and adolescents are at high risk of suffering obesity-related comorbidities. This article is to examine the dose-response relationship between weight status and cardiometabolic risk factors among US adolescents.

    Methods

    Youths aged 6-19 years participating in the National Health and Nutrition Examination Surveys (NHANES) 1999-2012 were included (N = 20,905). Severe obesity was defined as BMI ≥120% of 95th percentile of gender-specific BMI-for-age or BMI ≥35 kg/m(2). Obesity-related cardiometabolic risk factors included blood pressure (BP), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), total cholesterol (TC), triglycerides, and fasting glucose (FG). Weighted multiple logistic regression was used to assess whether severe obesity significantly changed the odds of having cardiometabolic risk factors.

    Results

    The prevalence of high BP, high TC, low HDL, high triglycerides, high LDL, and high FG among severely obese adolescents was 9.9%, 16.5%, 40.0%, 30.0%, 13.0%, and 26.8%, respectively. Severely obese adolescents had at least twice the odds compared to normal weight adolescents of presenting high BP (OR = 5.3, 95% CI: 3.8-7.3); high TC (OR = 2.3, 95% CI: 1.8-3.0); low HDL (OR = 7.3, 95% CI: 6.1-8.8); high triglycerides (OR = 4.5, 95% CI: 3.4-5.9); high LDL (OR = 2.3, 95% CI: 1.5-3.5); and high FG (OR = 2.7, 95% CI: 1.8-4.0). Significant differences were also found between severely obese status and moderately obese status in the odds of having high BP (OR = 1.8, 95% CI: 1.7-2.2) and low HDL (OR = 1.9, 95% CI: 1.6-2.3).

    Conclusion

    Adolescents classified as severe status exhibit higher odds of having cardiometabolic risk factors compared to those with normal weight and moderately obese weight status.