Fatness and Fitness With Cardiometabolic Risk Factors in Adolescents.

Context: The relative importance of fitness and fatness with cardiometabolic risk factors is uncertain during the crucial developmental stage of late adolescence. Objective: We aimed to compare the concurrent influences of cardiorespiratory fitness and fatness in relationship to cardiometabolic risk factors in adolescents from the Western Australian Pregnancy Cohort Study. Design, Setting, and Participants: Cross-sectional analysis was performed on 1128 participants with complete blood pressure (BP) data and 963 participants with complete blood biochemistry at 17 years of age. Fatness (waist circumference) and cardiorespiratory fitness (physical work capacity 170) were assessed as continuous measures to avoid the use of arbitrary cut points. Analyses used linear regression models adjusted for sex and potential lifestyle confounders. Main Outcome Measure: Cardiometabolic risk factors. Results: Fatness was positively associated with systolic BP (coefficient, 0.19; P < 0.001; ß coefficient, 0.20), triglycerides (log coefficient, 0.009; P < 0.001; ß coefficient, 0.24), low-density lipoprotein cholesterol (coefficient, 0.005; P = 0.007; ß coefficient, 0.10), and high-sensitivity C-reactive protein (log coefficient, 0.05; P < 0.001; ß coefficient, 0.35). There were no significant effects of fitness on any of these measures. A positive association between homeostasis model of assessment for insulin resistance and fatness (log coefficient, 0.02; P < 0.001; ß coefficient, 0.33) was attenuated by fitness (log coefficient, -0.0.18; P < 0.001; ß coefficient, -0.18). Fatness was inversely associated with high-density lipoprotein cholesterol (HDL-C) in both sexes (coefficient, -0.006; P < 0.001; ß coefficient, -0.23), whereas fitness was positively associated with HDL-C only in females (coefficient, 0.08; P = 0.03; ß coefficient, 0.15). Conclusions: The adverse effects of central adiposity seen across a broad range of cardiometabolic risk factors were only partially ameliorated by fitness in this adolescent population.

Correction: Dual Energy X-Ray Absorptiometry Compared with Anthropometry in Relation to Cardio-Metabolic Risk Factors in a Young Adult Population: Is the 'Gold Standard' Tarnished?

[This corrects the article DOI: 10.1371/journal.pone.0162164.].

Effects of muscle strength and endurance on blood pressure and related cardiometabolic risk factors from childhood to adolescence.

OBJECTIVE: This study aimed to examine the evolution of relationships between measures of muscle strength and endurance with individual cardiometabolic risk factors from childhood to late adolescence in a prospective population-based cohort. METHODS: Participants from the Western Australian Pregnancy Cohort (Raine) Study at ages 10, 14 and 17 were analysed, using longitudinal linear mixed model analyses. RESULTS: Handgrip strength after adjusting for the confounding effects of BMI was positively associated with SBP, but not DBP. The association between handgrip strength and SBP was stronger in men than women at all time points [coefficient (women): 0.18, P < 0.001; sex × handgrip strength coefficient: 0.09, P = 0.002]. The association was strongest at 10 years and significantly attenuated over time (year × handgrip coefficient from 10 to 14 years: -0.11, P = 0.003; year × handgrip coefficient from 10 to 17 years: -0.19, P ≤ 0.001). After the inclusion of BMI as a confounder, handgrip strength was significantly negatively associated with homeostatic model assessment of insulin resistance and high-sensitivity C-reactive protein over time in both sexes. Back muscle endurance was positively associated with SBP, but not DBP, after adjustment for the confounding effects of BMI (coefficient: 0.01, P = 0.002). There were small, albeit significant, inverse associations between back muscle endurance and log homeostatic model assessment of insulin resistance and log high-sensitivity C-reactive protein. CONCLUSION: The positive association between handgrip strength and back muscle endurance with SBP throughout childhood and adolescence contrasts with beneficial effects on other related traditional cardiometabolic risk factors. Mechanisms underlying these paradoxical effects on SBP warrant further investigation.

Dual Energy X-Ray Absorptiometry Compared with Anthropometry in Relation to Cardio-Metabolic Risk Factors in a Young Adult Population: Is the 'Gold Standard' Tarnished?

BACKGROUND AND AIMS: Assessment of adiposity using dual energy x-ray absorptiometry (DXA) has been considered more advantageous in comparison to anthropometry for predicting cardio-metabolic risk in the older population, by virtue of its ability to distinguish total and regional fat. Nonetheless, there is increasing uncertainty regarding the relative superiority of DXA and little comparative data exist in young adults. This study aimed to identify which measure of adiposity determined by either DXA or anthropometry is optimal within a range of cardio-metabolic risk factors in young adults. METHODS AND RESULTS: 1138 adults aged 20 years were assessed by DXA and standard anthropometry from the Western Australian Pregnancy Cohort (Raine) Study. Cross-sectional linear regression analyses were performed. Waist to height ratio was superior to any DXA measure with HDL-C. BMI was the superior model in relation to blood pressure than any DXA measure. Midriff fat mass (DXA) and waist circumference were comparable in relation to glucose. For all the other cardio-metabolic variables, anthropometric and DXA measures were comparable. DXA midriff fat mass compared with BMI or waist hip ratio was the superior measure for triglycerides, insulin and HOMA-IR. CONCLUSION: Although midriff fat mass (measured by DXA) was the superior measure with insulin sensitivity and triglycerides, the anthropometric measures were better or equal with various DXA measures for majority of the cardio-metabolic risk factors. Our findings suggest, clinical anthropometry is generally as useful as DXA in the evaluation of the individual cardio-metabolic risk factors in young adults.

Effect of maternal steroid on developing diaphragm integrity.

Antenatal steroids reduce the severity of initial respiratory distress of premature newborn babies but may have an adverse impact on other body organs. The study aimed to examine the effect of maternal steroids on postnatal respiratory muscle function during development and elucidate the mechanisms underlying the potential myopathy in newborn rats. Pregnant rats were treated with intramuscular injections of 0.5 mg/kg betamethasone 7 d and 3 d before birth. Newborn diaphragms were dissected for assessment of contractile function at 2 d, 7 d or 21 d postnatal age (PNA), compared with age-matched controls. The expression of myosin heavy chain (MHC) isoforms and atrophy-related genes and activity of intracellular molecular signalling were measured using quantitative PCR and/or Western blot. With advancing PNA, neonatal MHC gene expression decreased progressively while MHC IIb and IIx isoforms increased. Protein metabolic signalling showed high baseline activity at 2 d PNA, and significantly declined at 7 d and 21 d. Antenatal administration of betamethasone significantly decreased diaphragm force production, fatigue resistance, total fast fibre content and anabolic signalling activity (Akt and 4E-BP1) in 21 d diaphragm. These responses were not observed in 2 d or 7 d postnatal diaphragm. Results demonstrate that maternal betamethasone treatment causes postnatal diaphragmatic dysfunction at 21 d PNA, which is attributed to MHC II protein loss and impairment of the anabolic signalling pathway. Developmental modifications in MHC fibre composition and protein signalling account for the age-specific diaphragm dysfunction.