Associations of Physical Activity Intensities with Markers of Insulin Sensitivity

Prospective External Validation of an Algorithm Predicting Hourly Basal Insulin Infusion Rates from Characteristics of Patients with Type 1 Diabetes Treated with Insulin Pumps

BACKGROUND

We previously published an algorithm predicting 24 h basal insulin infusion profiles in insulin pump-treated subjects with type 1 diabetes profiles from six subject characteristics. This algorithm was to be externally validated in an independent environment and patient population.

METHODS

Thirty-two patients with pump-treated type diabetes were switched to their individually algorithm-derived basal insulin infusion profile, and the appropriateness of fasting glycemic control was scrutinized by means of a supervised 24 h fast. Primary endpoint was appropriate fasting glycemic control according to pre-defined criteria in at least 80% of the cohort.

RESULTS

In 24 out of 32 patients switching to the algorithm-derived basal insulin infusion rate and undergoing a 24-h fasting period, appropriate glycemic control was achieved (=75%, lower than the pre-defined threshold of 80%), two patients discontinued the fast due to hyperglycemia, and six finished the fasting period, however, with inappropriate fasting glycemic control (entirely due to hyperglycemic episodes). There were no obvious differences in baseline characteristics between those with appropriate vs. inappropriate fasting glycemic control on the basal insulin infusion rate provided by the algorithm.

CONCLUSION

In conclusion, when testing fasting glycemic control with an algorithm-derived individual basal insulin infusion profile during a 24 h fasting period in a cohort unrelated in terms of the hospital environment and catchment area, the success rate was lower than a pre-defined threshold for concluding utility of this algorithm. Therefore, applying this algorithm in order to initiate or optimize basal insulin infusion profiles in type 1 diabetes cannot be generally recommended.

Associations Between Wearable-Specific Indicators of Physical Activity Behaviour and Insulin Sensitivity and Glycated Haemoglobin in the General Population: Results from the ORISCAV-LUX 2 Study

BACKGROUND

Parameters derived from an acceleration signal, such as the time accumulated in sedentary behaviour or moderate to vigorous physical activity (MVPA), may not be sufficient to describe physical activity (PA) which is a complex behaviour. Incorporating more advanced wearable-specific indicators of PA behaviour (WIPAB) may be useful when characterising PA profiles and investigating associations with health. We investigated the associations of novel objective measures of PA behaviour with glycated haemoglobin (HbA1c) and insulin sensitivity (Quicki index).

METHODS

This observational study included 1026 adults (55% women) aged 18-79y who were recruited from the general population in Luxembourg. Participants provided ≥ 4 valid days of triaxial accelerometry data which was used to derive WIPAB variables related to the activity intensity, accumulation pattern and the temporal correlation and regularity of the acceleration time series.

RESULTS

Adjusted general linear models showed that more time spent in MVPA and a higher average acceleration were both associated with a higher insulin sensitivity. More time accumulated in sedentary behaviour was associated with lower insulin sensitivity. With regard to WIPAB variables, parameters that were indicative of higher PA intensity, including a shallower intensity gradient and higher average accelerations registered during the most active 8 h and 15 min of the day, were associated with higher insulin sensitivity. Results for the power law exponent alpha, and the proportion of daily time accumulated in sedentary bouts > 60 min, indicated that activity which was characterised by long sedentary bouts was associated with lower insulin sensitivity. A greater proportion of time spent in MVPA bouts > 10 min was associated with higher insulin sensitivity. A higher scaling exponent alpha at small time scales (< 90 min), which shows greater correlation in the acceleration time series over short durations, was associated with higher insulin sensitivity. When measured over the entirety of the time series, metrics that reflected a more complex, irregular and unpredictable activity profile, such as the sample entropy, were associated with lower HbA1c levels and higher insulin sensitivity.

CONCLUSION

Our investigation of novel WIPAB variables shows that parameters related to activity intensity, accumulation pattern, temporal correlation and regularity are associated with insulin sensitivity in an adult general population.

Physical activity influences heart rate variability in young adults, regardless of dextrose ingestion

INTRODUCTION

Cardiac autonomic modulation can be altered by carbohydrate ingestion. On the other hand, some of the protective effects of physical activity may be due to its impact on the autonomic nervous system.

PURPOSE

This cross-sectional study was conducted to evaluate whether physical activity level influences heart rate variability (HRV) under fasting and mainly, after dextrose ingestion.

METHODS

Healthy adults aged 18-40 years ( n  = 92; 54.35 % women) were separated into nonactive ( n  = 47) and active groups ( n  = 45), based on the physical activity level determined by International Physical Activity Questionnaire (IPAQ) and then compared.

RESULTS

There were no significant differences ( P  > 0.05) for age, body mass, BMI, abdominal circumference, blood pressure, fasting glucose and blood glucose at 60 min after dextrose ingestion between groups. Body fat (%) was lower in the active group ( P  = 0.02). The time-domain indices (RMSSD, SDNN and pNN50) were higher in the physically active group compared to the nonactive group (main effect of group, P  < 0.01). The SDNN index was higher at 60 min after dextrose ingestion compared to fasting (main effect of time, P  ≤ 0.01). However, no HRV indices showed significantly interaction effect (group x time; P  > 0.05).

CONCLUSION

The magnitude of HRV responses to glucose was not influenced by physical activity status. Young adults who met at least the minimum physical activity recommendations showed a higher cardiac autonomic modulation, regardless of dextrose ingestion.

Physical behaviors and their association with type 2 diabetes mellitus risk markers in urban South African middle-aged adults: an isotemporal substitutionapproach

INTRODUCTION

To examine the associations between physical behaviors and type 2 diabetes mellitus (T2DM) risk markers in middle-aged South African men and women.

RESEARCH DESIGN AND METHODS

This cross-sectional study included middle-aged men (n=403; age: median (IQR), 53.0 (47.8-58.8) years) and women (n=324; 53.4 (49.1-58.1) years) from Soweto, South Africa. Total movement volume (average movement in milli-g) and time (minutes/day) spent in different physical behaviors, including awake sitting/lying, standing, light intensity physical activity (LPA) and moderate-to-vigorous intensity physical activity (MVPA), were determined by combining the signals from two triaxial accelerometers worn simultaneously on the hip and thigh. All participants completed an oral glucose tolerance test, from which indicators of diabetes risk were derived. Associations between physical behaviors and T2DM risk were adjusted for sociodemographic factors and body composition.

RESULTS

Total movement volume was inversely associated with measures of fasting and 2-hour glucose and directly associated with insulin sensitivity, basal insulin clearance, and beta-cell function, but these associations were not independent of fat mass, except for basal insulin clearance in women. In men, replacing 30 min of sitting/lying, standing or LPA with the same amount of MVPA time was associated with 1.2-1.4 mmol/L lower fasting glucose and 12.3-13.4 mgl2/mUmin higher insulin sensitivity. In women, substituting sitting/lying with the same amount of standing time or LPA was associated with 0.5-0.8 mmol/L lower fasting glucose. Substituting 30 min sitting/lying with the same amount of standing time was also associated with 3.2 mgl2/mUmin higher insulin sensitivity, and substituting 30 min of sitting/lying, standing or LPA with the same amount of MVPA time was associated with 0.25-0.29 ng/mIU higher basal insulin clearance in women.

CONCLUSION

MVPA is important in reducing T2DM risk in men and women, but LPA appears to be important in women only. Longitudinal and intervention studies warranted to provide more specific PA recommendations.

Physical Activity Intensity and Type 2 Diabetes: Isotemporal Substitution Models in the "Seguimiento Universidad de Navarra" (SUN) Cohort

Which intensity of physical activity (PA) is associated with type 2 diabetes (T2D) prevention remains unclear. Isotemporal substitution models assess the relationship of replacing the amount of time spent in one activity for another. We aimed to assess T2D incidence associated with light-to-moderate physical activity (LMPA) and vigorous physical activity (VPA) using isotemporal substitution models of one hour (1 h) sitting by 1 h of LMPA or VPA. Furthermore, we evaluated the effect on T2D of an isotemporal substitution of 1 h sitting by 1 h of slow (light physical activity) or brisk–very brisk walking (moderate physical activity). In total, 20,060 participants (both sexes) of the SUN cohort (Spain) initially free of T2D followed-up during a median of 12 years were included. Cox regression models were fitted to assess the association between the substitution of 1 h LMPA, VPA, slow and brisk–very brisk pace by 1 h sitting and T2D. The replacement of 1 h sitting time by 1 h of VPA was associated with an adjusted HR of 0.52 (95% CI: 0.34–0.80), not observed for the substitution by 1 h of LMPA (HR 0.93; 95% CI: 0.73–1.20). An apparent inverse association was observed for the replacement of 1 h sitting time by 1 h of brisk/very brisk walking (HR: 0.69; 95% CI: 0.46–1.04), not observed by 1 h of slow pace. From equal conditions of duration and frequency of PA, the higher the intensity of PA, the greater the T2D prevention.

Child physical activity as a modifier of the relationship between prenatal exposure to maternal overweight/obesity and neurocognitive outcomes in offspring

BACKGROUND/OBJECTIVES

With rising obesity rates among pregnant women, more children are exposed in utero to maternal obesity. In prior epidemiological studies, exposure to maternal obesity was associated with lower intelligence quotient (IQ) scores and worse cognitive abilities in offspring. Further studies have shown that offspring exposed to maternal obesity, exhibit differences in the white matter microstructure properties, fractional anisotropy (FA) and mean diffusivity (MD). In contrast, physical activity was shown to improve cognition and white matter microstructure during childhood. We examined if child physical activity levels modify the relationship between prenatal exposure to maternal obesity with IQ and white matter microstructure in offspring.

SUBJECTS/METHODS

One hundred children (59% girls) age 7-11 years underwent brain magnetic resonance imaging and IQ testing. Maternal pre-pregnancy BMI was abstracted from electronic medical records. White matter was assessed using diffusion tensor imaging with the measures, global FA, MD. The 3-day physical activity recall was used to measure moderate-to-vigorous physical activity and vigorous physical activity (VPA). Linear regression was used to test for interactions between prenatal exposure to maternal overweight/obesity and child PA levels on child IQ and global FA/MD.

RESULTS

The relationship between prenatal exposure to maternal overweight/obesity and child IQ and global FA varied by child VPA levels. Children exposed to mothers with overweight/obesity who engaged in more VPA had higher IQ scores and global FA compared to exposed children who engaged in less VPA. Associations were independent of child age, sex, BMI Z-score and socioeconomic status. Children born to normal-weight mothers did not differ in either IQ or global FA by time in VPA.

CONCLUSIONS

Our findings support findings in rodent models and suggest that VPA during childhood modifies the relationship between prenatal exposure to maternal obesity and child IQ and white matter microstructure.

Higher blood glucose impairs cardiac autonomic modulation in fasting and after carbohydrate overload in adults

This study aimed to assess whether the blood glucose levels influence cardiac autonomic modulation under fasting and after carbohydrate overload conditions. Participants (n = 108) were separated into lower blood glucose and higher blood glucose groups, based on the median (90.5 mg·dL^-1) of fasting glucose assessed. The SD2, SDNN, LF indices, and LF/HF increased, and HF decreased after dextrose overload compared with fasting (p < 0.05). Body mass (78.9 vs 69.7 kg), abdominal circumference (90.2 vs 82.2 cm), systolic (113 vs 108 mm Hg) and diastolic (72 vs 67 mm Hg) blood pressure were higher (p < 0.05) in the higher blood glucose group. Heart rate variability (HRV) indices (SD1: 21.0 vs 26.5; SD2: 76.8: vs 86.1; RMSSD: 28.7 vs 37.5; SDNN: 56.1 vs 62.5 ms; pNN50: 10.6 vs 18.9%, HF: 328.4 vs 506.0; LF: 982.8 vs 1259.0 ms²), and the area under the curve of these indices after dextrose overload were lower in the higher blood glucose group (p < 0.05). Additionally, glycemia after dextrose overload was correlated with HRV indices (ρ = -0.216 to -0.273, p < 0.05). Individuals with higher blood glucose, even in the normality range, showed impairment in the cardiac autonomic modulation both at fasting and after carbohydrate overload. Novelty: Higher fasting blood glucose impairs cardiac autonomic modulation. Carbohydrate overload impairs cardiac autonomic modulation.

Activity Intensity, Volume, and Norms: Utility and Interpretation of Accelerometer Metrics

PURPOSE

The physical activity profile can be described from accelerometer data using two population-independent metrics: average acceleration (ACC, volume) and intensity gradient (IG, intensity). This article aims 1) to demonstrate how these metrics can be used to investigate the relative contributions of volume and intensity of physical activity for a range of health markers across data sets and 2) to illustrate the future potential of the metrics for generation of age and sex-specific percentile norms.

METHODS

Secondary data analyses were conducted on five diverse data sets using wrist-worn accelerometers (ActiGraph/GENEActiv/Axivity): children (n = 145), adolescent girls (n = 1669), office workers (n = 114), premenopausal (n = 1218) and postmenopausal (n = 1316) women, and adults with type 2 diabetes (n = 475). Open-source software (GGIR) was used to generate ACC and IG. Health markers were (a) zBMI (children), (b) %fat (adolescent girls and adults), (c) bone health (pre- and postmenopausal women), and (d) physical function (adults with type 2 diabetes).

RESULTS

Multiple regression analyses showed that IG, but not ACC, was independently associated with zBMI/%fat in children and adolescents. In adults, associations were stronger and the effects of ACC and IG were additive. For bone health and physical function, interactions showed associations were strongest if IG was high, largely irrespective of ACC. Exemplar illustrative percentile "norms" showed the expected age-related decline in physical activity, with greater drops in IG across age than ACC.

CONCLUSION

The ACC and the IG accelerometer metrics facilitate the investigation of whether volume and intensity of physical activity have independent, additive, or interactive effects on health markers. In future studies, the adoption of data-driven metrics would facilitate the generation of age- and sex-specific norms that would be beneficial to researchers.

Physical activity and lipidomics in a population at high risk of type 2 diabetes mellitus

The aim was to investigate how measurements of the lipidome differ according to the level and intensity of physical activity in a population at high risk of type 2 diabetes (T2DM). A targeted metabolomics platform provided quantitative molecular data on lipid species. Linear regression examined the associations between plasma lipid concentrations, particle size and time spent in objectively measured physical activity intensity domains, in increments of 500 counts per minute (cpm) (up to >4500 cpm (~>5.6METs)). Results are presented as % difference in the concentration (lower/higher) or particle size (smaller/larger) per 10 min of activity within each intensity. Five hundred and nine participants were included. Time spent in the lowest physical activity intensity domain (<500 cpm) was unfavourably associated with VLDL (2%), HDL (-2%) and Apolipoprotein A-1 particle concentrations (-2%) and HDL diameter (-2%). Conversely, time spent in intensities ≥1000 cpm were favourably associated with HDL subclass concentrations; with stronger associations seen at moderate intensities (2000-3999 cpm (~4.5METs)). For Apolipoprotein-B concentration and VLDL particle concentration and size, a negative association was consistently observed at the highest physical activity intensity only. If these associations are causal, HDL subclasses appear sensitive to light-intensities whereas only the high category of physical activity intensity was consistently associated with VLDL subclasses.

Exercise training attenuates insulin resistance and improves β-cell function in patients with systemic autoimmune myopathies: a pilot study

INTRODUCTION/OBJECTIVES

To assess the effects of exercise training on insulin resistance and β-cell function in patients with systemic autoimmune myopathies (SAMs).

METHOD

This quasi-experimental, prospective study includes 9 patients with SAMs (six with dermatomyositis, two with antisynthetase syndrome, and one with polymyositis). Patients were submitted to a 12-week, twice a week, exercise training program comprising aerobic and resistance exercises. Baseline and after the intervention, we evaluated disease status, aerobic capacity, muscle strength, body composition, insulin resistance, and β-cell function parameters.

RESULTS

The patients have a mean age of 46.7 years and stable disease. No clinical or laboratory parameter impairment was observed after the intervention. Compared with baseline, aerobic capacity, muscle strength, and function increased after 12 weeks (P < 0.05), while no changes were observed for body composition. Data from the oral glucose tolerance test showed that exercise did not change glucose area under the curve (AUC), whereas insulin and C-peptide AUC decreased significantly (P < 0.05). Furthermore, Matsuda index and HOMA2 percentage (both surrogates of insulin resistance) also improved (P < 0.05).

CONCLUSION

Exercise training improved aerobic capacity, muscle strength, and muscle function in patients with SAMs. In addition, exercise training led to an attenuation of insulin resistance and improvements in β-cell function parameters. These data indicate that exercise training can mitigate metabolic impairments, attenuating the cardiovascular risk in SAMs.Key Points• Exercise training improved aerobic capacity, muscle strength, and function without disease impairment• Exercise training was capable of improve insulin resistance and β-cell function in patients with SAM• These results suggest that exercise can mitigate metabolic impairments in patients with SAM, attenuating the cardiovascular risk.

Expert's Choice: 2018's Most Exciting Research in the Field of Pediatric Exercise Science

This commentary highlights 23 noteworthy publications from 2018, selected by leading scientists in pediatric exercise science. These publications have been deemed as significant or exciting in the field as they (a) reveal a new mechanism, (b) highlight a new measurement tool, (c) discuss a new concept or interpretation/application of an existing concept, or (d) describe a new therapeutic approach or clinical tool in youth. In some cases, findings in adults are highlighted, as they may have important implications in youth. The selected publications span the field of pediatric exercise science, specifically focusing on: aerobic exercise and training; neuromuscular physiology, exercise, and training; endocrinology and exercise; resistance training; physical activity and bone strength; growth, maturation, and exercise; physical activity and cognition; childhood obesity, physical activity, and exercise; pulmonary physiology or diseases, exercise, and training; immunology and exercise; cardiovascular physiology and disease; and physical activity, inactivity, and health.

Reallocating sitting time to standing or stepping through isotemporal analysis: associations with markers of chronic low-grade inflammation

Although high levels of sitting time are adversely related to health, it is unclear whether moving from sitting to standing provides a sufficient stimulus to elicit benefits upon markers of chronic low-grade inflammation in a population at high risk of type 2 diabetes (T2DM). Three hundred and seventy two participants (age = 66.8 ± 7.5years; body mass index (BMI) = 31.7 ± 5.5kg/m²; Male = 61%) were included. Sitting, standing and stepping was determined using the activPAL3^TM device. Linear regression modelling employing an isotemporal substitution approach was used to quantify the association of theoretically substituting 60 minutes of sitting per day for standing or stepping on interleukin-6 (IL-6), C-reactive protein (CRP) and leptin. Reallocating 60 minutes of sitting time per day for standing was associated with a -4% (95% CI -7%, -1%) reduction in IL-6 (p = 0.048). Reallocating 60 minutes of sitting time for light stepping was also associated with lower IL-6 levels (-28% (-46%, -4%; p = 0.025)). Substituting sitting for moderate-to-vigorous (MVPA) stepping was associated with lower CRP (-41% (-75%, -8%; p = 0.032)), leptin (-24% (-34%, -12%; p ≤ 0.001)) and IL-6 (-16% (-28%, 10%; p = 0.036). Theoretically replacing 60 minutes of sitting per day with an equal amount of either standing or stepping yields beneficial associations upon markers of chronic-low grade inflammation.