Objectively-measured sedentary time, habitual physical activity and bone strength in adults aged 62 years: the Newcastle Thousand Families Study.

BACKGROUND: The influence of sedentary time and habitual physical activity on the bone health of middle aged adults is not well known. METHODS: Bone mineral density (BMD) and hip bone geometry were evaluated in 214 men (n = 92) and women (n = 112) aged 62.1 ± 0.5 years from the Newcastle Thousand Families Study birth cohort. Accelerometry was used to measure physical activity (PA) and sedentary time over 4 days. Regression models were adjusted for clinical risk factor covariates. RESULTS: Men were more sedentary than women (P < 0.05), and sedentary time was negatively associated with spine BMD in men, with 84 minutes more sedentary time corresponding to 0.268 g.cm-2 lower BMD (ß = -0.268; P = 0.017). In men, light PA and steps/day were positively associated with bone geometry and BMD. Steps/day was positively associated with bone geometry and femur BMD in women, with a positive difference of 1415 steps/day corresponding to 0.232 g.cm-2 greater BMD (ß = 0.232, P = 0.015). CONCLUSIONS: Sedentary time was unfavourably associated with bone strength in men born in North East England at age 62 years. Higher volumes of light PA, and meeting the public health daily step recommendations (10 000 steps/day) was positively associated with bone health in both sexes.

Mothers' perceptions of child weight status and the subsequent weight gain of their children: a population-based longitudinal study.

BACKGROUND: There is a plethora of cross-sectional work on maternal perceptions of child weight status showing that mothers typically do not classify their overweight child as being overweight according to commonly used clinical criteria. Awareness of overweight in their child is regarded as an important prerequisite for mothers to initiate appropriate action. The gap in the literature is determining whether, if mothers do classify their overweight child's weight status correctly, this is associated with a positive outcome for the child's body mass index (BMI) at a later stage. OBJECTIVE: To explore longitudinal perceptions of child weight status from mothers of a contemporary population-based birth cohort (Gateshead Millennium Study) and relationships of these perceptions with future child weight gain. METHODS: Data collected in the same cohort at 7, 12 and 15 years of age: mothers' responses to two items concerning their child's body size; child's and mother's BMI; pubertal maturation; demographic information. RESULTS: Mothers' perceptions of whether their child was overweight did not change markedly over time. Child BMI was the only significant predictor of mothers' classification of overweight status, and it was only at the extreme end of the overweight range and in the obese range that mothers reliably described their child as overweight. Even when mothers did appropriately classify their child as overweight at an earlier stage, this was not related to relatively lower child BMI a few years later. CONCLUSIONS: Mothers tend to classify their child as overweight in only more extreme cases. It is an important finding that no beneficial impact was shown on later child BMI in overweight children whose mothers classified their child's weight status as overweight at an earlier stage.

Longitudinal study of the associations between change in sedentary behavior and change in adiposity during childhood and adolescence: Gateshead Millennium Study.

BACKGROUND: Sedentary time (ST) has been reported to have a range of negative health effects in adults, however, the evidence for such effects among children and adolescents is sparse. The primary aim of the study was to examine associations between changes in sedentary behavior (time and fragmentation) and changes in adiposity across childhood and adolescence. METHODS: Participants were recruited as part of the Gateshead Millennium Study. Measures were taken at age 7 (n=502), 9 (n=506), 12 (n=420) and 15 years (n=306). Participants wore an ActiGraph GT1M and accelerometer epochs were 'sedentary' when recorded counts were ⩽25 counts per 15 s. ST was calculated and fragmentation (SF) was assessed by calculating the number of sedentary bouts per sedentary hour. Associations of changes in ST and SF with changes in adiposity (body mass index (BMI), and fat mass index (FMI)) were examined using bivariate linear spline models. RESULTS: Increasing ST by 1% per year was associated with an increase in BMI of 0.08 kg m-2 per year (95% CI: 0.06-0.10; P<0.001) and FMI of 0.15 kg m-2 per year (0.11-0.19; P<0.001). Change in SF was associated with BMI and FMI (P<0.001). An increase of 1 bout per sedentary hour per year (that is, sedentary time becoming more fragmented) was associated with an increase in BMI of 0.07 kg m-2 per year (0.06-0.09; P<0.001) and an increase in FMI of 0.14 kg m-2 per year (0.10-0.18; P<0.001) over the 8 years period. However, an increase in SF between 9-12 years was associated with a 0.09 kg m-2 per year decrease in BMI (-0.18-0.00; P=0.046) and 0.11 kg m-2 per year decrease in FMI (-0.22-0.00; P=0.049). CONCLUSIONS: Increased ST and increased SF from 7-15 years were associated with increased adiposity. This is the first study to show age-specific associations between change in objectively measured sedentary behavior and adiposity after adjustment of moderate-to-vigorous-intensity physical activity in children and adolescents. The study suggests that, targeting sedentary behavior for obesity prevention may be most effective during periods in which we see large increases in ST.

Wheel running in female C57BL/6J mice: impact of oestrus and dietary fat and effects on sleep and body mass.

OBJECTIVE: To examine the impact of two diets differing in fat content and of wheel-running exercise on body mass. METHODS: A total of 32 female C57BL/6J mice were assigned to either a high-fat (HF, 41% of dietary energy as fat) or low-fat (LF, 11% of dietary energy as fat) diet (16 per diet, individually housed). Eight mice from each diet group were housed with running wheels. Non-running mice were housed in similar cages, without wheels. Total cage activity (including non-exercise physical activity +wheel running) and sleep time were also measured using an infra-red-sensing device. Oestrus stage of the wheel-running mice was assessed daily for 17 days. RESULTS: After 8 weeks, HF mice were significantly heavier than LF mice (P=0.004), but there was no detectable difference in body fat mass. Wheel-running mice tended to have a lower body mass than non-running controls (P=0.056). Voluntary cage activity was greater in LF control mice than HF control mice, and in wheel-running mice compared with non-wheel-running mice. HF control mice slept more than LF control mice. Stage of oestrus was significantly correlated with running distance, with mice running farthest in the immediate preoestrus phase and least immediately after oestrus. CONCLUSION: This study shows that HF diets in female C57BL/6J mice may increase sleep time similar to the effect of daytime sleepiness observed in obese humans.

Birth weight and adolescent blood pressure measured at age 12 years in the Gateshead Millennium Study.

Birth weight and early growth have been associated with later blood pressure. However, not all studies consistently find a significant reduction in blood pressure with an increase in birth weight. In addition, the relative importance of birth weight and of other lifestyle and environmental factors is often overlooked and the association is rarely studied in adolescents. We investigated early life predictors, including birth weight, of adolescent blood pressure in the Gateshead Millennium Study (GMS). The GMS is a cohort of 1029 individuals born in 1999-2000 in Gateshead in Northern England. Throughout infancy and early childhood, detailed information were collected, including birth weight and measures of height and weight. Assessments of 491 returning participants at age 12 years included measures of body mass and blood pressure. Linear regression and path analysis were used to determine predictors and their relative importance on blood pressure. Birth weight was not directly associated with blood pressure at the age of 12. However, after adjustment for contemporaneous body mass index (BMI), an inverse association of standardized birth weight on systolic blood pressure was significant. The relative importance of birth weight on later systolic blood pressure was smaller than other contemporaneous body measures (height and BMI). There was no independent association of birth weight on blood pressure seen in this adolescent population. Contemporaneous body measures have an important role to play. Lifestyle factors that influence body mass or size, such as diet and physical activity, where interventions are directed at early prevention of hypertension should be targeted.

Determinants of changes in sedentary time and breaks in sedentary time among 9 and 12 year old children.

The current study aimed to identify the determinants of objectively measured changes in sedentary time and sedentary fragmentation from age 9- to age 12 years. Data were collected as part of the Gateshead Millennium Birth Cohort study from September 2008 to August 2009 and from January 2012 to November 2012. Participants were 9.3 (± 0.4) years at baseline (n = 508) and 12.5 (± 0.3) years at follow-up (n = 427). Sedentary behaviour was measured using an ActiGraph GT1M accelerometer. Twenty potential determinants were measured, within a socio-ecological model, and tested for their association with changes in sedentary time and the extent to which sedentary behaviour is prolonged or interrupted (fragmentation index). Univariate and multivariate linear regression analyses were conducted. Measurements taken during winter and a greater decrease in moderate-to-vigorous intensity physical activity (MVPA) over time were associated with larger increases in sedentary time (seasonality ß: - 3.03; 95% CI: - 4.52, - 1.54; and change in MVPA ß: - 1.68; 95% CI: - 1.94, - 1.41). Attendance at sport clubs was associated with smaller increases in sedentary time (- 1.99; - 3.44, - 0.54). Girls showed larger decreases in fragmentation index (- 0.52; - 1.01, - 0.02). Interventions aimed at decreasing the decline in MVPA and increasing/maintaining sport club attendance may prevent the rise in sedentary time as children grow older. In addition, winter could be targeted to prevent an increase in sedentary time and reduction in sedentary fragmentation during this season.

Gamma-Aminobutyric acid (GABA) transport across human intestinal epithelial (Caco-2) cell monolayers.

1. Transintestinal absorption of gamma-aminobutyric acid (GABA) via a pH-dependent mechanism is demonstrated in the model human intestinal epithelial cell line Caco-2. 2. Experiments with BCECF [2',7',-bis(2-carboxyethyl)-5(6)- carboxyfluorescein]-loaded Caco-2 cells demonstrate that GABA transport across the apical membrane is coupled to proton flow into the cell. 3. Short-circuit current (ISC) measurements using Caco-2 cell monolayers under voltage-clamped conditions demonstrate that pH-dependent GABA transport is a rheogenic process even in the absence of extracellular Na+, consistent with H+/GABA symport. 4. A range of GABA analogues were tested for their abilities to: (a) inhibit pH-dependent [3H]GABA uptake across the apical membrane; (b) stimulate H+ flow across the apical surface of BCECF-loaded Caco-2 cell monolayers; (c) increase inward ISC across voltage-clamped Caco-2 cell monolayers. 5. Nipecotic acid, isonipecotic acid, D,L-beta-aminobutyric acid, and 3-amino-1-propanesulphonic acid each caused a marked acidification of intracellular pH and an increase in ISC when superfused at the apical surface of Caco-2 cell monolayers. In contrast L-alpha-amino-n-butyric acid failed to induce proton flow or ISC. The ability of these compounds to induce proton or current flow across the apical surface of this intestinal epithelium was closely related to the relative inhibitory effects on [3H]GABA uptake. 6. These observations demonstrate H+/GABA symport and suggest that this transport mechanism may be accessible as a route for oral absorption of therapeutically-useful GABA analogues.

Surveillance of physical activity in the UK is flawed: validation of the Health Survey for England Physical Activity Questionnaire.

OBJECTIVE: Public health surveillance of physical activity in children in the UK depends on a parent-reported physical activity questionnaire which has not been validated. We aimed to validate this questionnaire against measurement of physical activity using accelerometry in 6-7-year-old children. METHODS: In 130 children aged 6-7 years (64 boys, 66 girls) we estimated habitual moderate-vigorous intensity physical activity (MVPA) using the Health Survey for England parent-report questionnaire for physical activity. For the same time period and the same children, we measured MVPA objectively using 7-day accelerometry with the Actigraph accelerometer. RESULTS: The questionnaire over-estimated MVPA significantly (paired t test, p<0.01). Mean error (bias) when using the questionnaire was 122 min/day (95% CI 124 to 169). Mean time spent in MVPA was 146 min/day (95% CI 124 to 169) using the questionnaire and 24 min/day (95% CI 22 to 26) using the accelerometer. Rank order correlations between MVPA measured by accelerometer and estimated by the questionnaire were not statistically significant. CONCLUSIONS: Public health surveillance of physical activity should not rely on this questionnaire. Levels of habitual physical activity in children are likely to be substantially lower than those reported in UK health surveys.