Fat oxidation decreases age, yet, no studies have previously investigated if aging affects the maximal fat oxidation rate (MFO) during exercise in men and women differently. We hypothesized that increased age would be associated with a decline in MFO and this would be more pronounced in women due to the menopause, compared to men. In this cross-sectional study design, 435 (247/188, male /female) subjects of varying ages performed a DXA-scan, a submaximal graded exercise test and a V̇O2max test, to measure MFO and cardiorespiratory fitness (CRF) by indirect calorimetry. Subjects were stratified into 12 groups according to sex (M/F), age (<45, 45-55 and >55 years), CRF (below average (BA) and above average (AA)). Women <45 years had a higher MFO relative to fat free mass (FFM) (mg/min/kg) compared to men, regardless of CRF. However, there were no differences in MFO (mg/min/kg FFM) between men and women, in the groups between 45-55 and >55 years. In summary, we found that women <45 years display a higher MFO (mg/min/kg FFM) compared to men and that this sexual divergence is abolished after the age of 45 years. Novelty: • Maximal fat oxidation rate is higher in young women compared to men • This sex related difference is attenuated after the age of 45 years • Cardiorespiratory fitness does not influence this sex related difference
Study question Do children conceived after assisted reproductive technologies (ART) with frozen or fresh embryo transfer have altered cardiovascular autonomic nervous function compared to naturally conceived children? Summary answer Cardiovascular autonomic nervous function was comparable in singletons conceived after ART with frozen or fresh embryo transfer, and naturally conceived children. What is known already Cardiovascular autonomic nervous function (CANF) exert important homeostatic mechanisms to prevent major arterial blood pressure fluctuations by adjusting heart rate, cardiac contractility, and peripheral vascular tone. CANF is impaired in children with obesity and diabetes mellitus, and conductance artery stiffness is documented to influence CANF. Previous studies have reported that children conceived after ART are at risk of increased carotid intima-media thickness; insulin resistance; arterial stiffness; and hypertension. This is the first study to investigate CANF in children conceived after ART. Study design, size, duration CANF was studied in 110 singletons aged 7-12 years conceived after frozen embryo transfer (FET, N = 35), fresh embryo transfer (fresh-ET, N = 39) or natural conception (NC, N = 36). Children were born between 2009 and 2013. This study was conducted between June 2019 and October 2021. Participants/materials, setting, methods Participants were identified through the Danish IVF and Medical Birth Registries. CANF was evaluated by heart rate (HR) changes (ratio to rest) during deep breathing; Valsalva; and active stand test with continuous non-invasive hemodynamic measurements. Anthropometric measures, fasting blood samples, and maternal questionnaires were collected. Neonatal and maternal pregnancy data were collected from the Medical Birth Registry. Children with a history of congenital heart disease or mothers with gestational diabetes or diabetes mellitus were excluded. Main results and the role of chance A total of 110 singletons with a median age of 9.0 years were included in this study. We found no significant associations between conception method and our measures of CANF. For FET, fresh-ET, and NC, respectively, the HR-ratio for deep breathing was 1.62 (0.2 SD), 1.62 (0.16) and 1.63 (0.17) (ANOVA-P = 0.97). For Valsalva, the HR-ratio was 1.97 (0.4), 1.88 (0.41) and 1.63 (0.17), respectively (ANOVA-P = 0.24). For the active stand test, the HR-ratio was 1.43 (0.17), 1.41 (0.2) and 1.43 (0.19), respectively (ANOVA-P = 0.91). Associations remained non-significant after adjustment for age, sex, body surface area, body mass index, and mean arterial pressure. In the multivariate analysis, several other factors were significantly associated with HR-ratio for deep breathing: age (β = -0.06, P = 0.03), body surface area (β = 0.79, P = 0.01), body mass index (β = -0.03, P = 0.04), and mean arterial pressure (β =-0.01, P = 0.03), but not with other measures of CANF. All data for CANF were within reference limits. Also, mothers in the ART groups were older at childbirth than NC group as expected. No significant differences were observed in clinical characteristics, including neonatal and other maternal data. Limitations, reasons for caution This study is limited by its observational design to draw any firm conclusion on causality. Also, it is a limitation that the pubertal status was not systematically assessed as pubertal hormones may play a role in CANF. Wider implications of the findings This study contributes to the current knowledge about cardiovascular health risks in ART children. Reassuringly, this study found that children conceived after ART (frozen or fresh-ET) did not exhibit impaired cardiovascular autonomic nervous function compared to naturally conceived children. Trial registration number NCT03719703
Background Cardiovascular autonomic nervous functions (CANF) exert important homeostatic mechanisms to prevent major arterial blood pressure fluctuations by adjusting heart rate (HR), cardiac contractility, and peripheral vascular tone. Children conceived by assisted reproductive technologies (ART) are at risk of increased carotid intima-media thickness, insulin resistance, arterial stiffness, and hypertension. CANF is impaired in children with obesity and diabetes mellitus, and conductance artery stiffness is documented to influence CANF. CANF may therefore be hypothetized to be impaired in children conceived by ART. Purpose This is the first study to investigate whether children conceived by ART have impaired CANF as compared to naturally conceived children. Method CANF was studied in 105 singletons aged 7–12 years conceived naturally (NC, N=33) or by ART (frozen embryo transfer (FET, N=34) and fresh embryo transfer (Fresh ET, N=38)). CANF was evaluated with continuous non-invasive hemodynamic measurements (Finapres®) by the HR and blood pressure changes seen relative to rest during active standing, deep breathing and Valsalva, respectively. Results The descriptive data showed no difference in CANF measurements between our study groups (Table 1). In the multivariate analysis, only the Valsalva HR-ratio to rest was significantly higher in children conceived by FET as compared to NC children after adjustments for age, sex, BMI and maternal age at delivery (Figure 1). For all meaures, the effect size (Hedges d) ranged from 0.02 to 0.48. Conclusion In this study only the Valsalva HR-response between FET and NC groups were statistically significant after adjustment for confounders, and in general effect sizes were small. Our study suggests that children conceived by ART do not have a significantly impaired cardiovascular autonomic nervous function as compared to naturally conceived children. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Novo Nordisk Foundation
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