Bethany Barone Gibbs

A randomized trial of exercise for blood pressure reduction in type 2 diabetes: Effect on flow-mediated dilation and circulating biomarkers of endothelial function

OBJECTIVE To investigate the effect of an exercise intervention on flow-mediated dilation (FMD) and circulating endothelial biomarkers in adults with type 2 diabetes (T2DM). METHODS Sedentary adults (n = 140), aged 40-65, with T2DM and untreated pre or Stage I hypertension or treated hypertension were randomized to a 6-month, supervised, exercise program (3× week) or a sedentary control. Assessments included BMI, body and visceral fat, blood pressure, lipids, HbA1c, insulin sensitivity (QUICKI), fitness, FMD, E-selectin, P-selectin, intracellular and vascular cellular adhesion molecules (ICAM, VCAM), and tissue plasminogen activator (tPA). Intervention effects were compared by t-tests. Pearsons correlations were calculated between changes in cardiovascular risk factors and endothelial outcomes. RESULTS Exercisers significantly improved BMI (-0.6 kg/m(2)), body fat % (-1.4%), HbA1c (-0.5%), and fitness (2.9 mL/kg min) vs. controls (p < 0.05). However, there were no differences between groups in changes in FMD, E-selectin, P-selectin, ICAM, VCAM, or tPA. Among exercisers, changes in cardiovascular risk factors correlated with several biomarkers. Decreased P-selectin correlated with decreased BMI (r = 0.29, p = 0.04) and increased HDL cholesterol (r = -0.36, p = 0.01). Decreased ICAM correlated with decreased triglycerides and HbA1c (r = 0.30, p = 0.04; r = 0.31, p = 0.03) and increased QUICKI (r = - 0.28, p = 0.05). Decreased tPA correlated with decreased total body and visceral fat (r = 0.28, p = 0.05; r = 0.38, p = 0.008) and increased QUICKI (r = -0.38, p = 0.007). CONCLUSIONS While exercise resulted in improved fitness, body composition, and glycemic control, there were no changes in FMD or circulating endothelial biomarkers. The associations of changes in cardiovascular risk factors and endothelial biomarkers suggest that improvement in risk factors could mediate the exercise-induced improvements in endothelial function seen in prior studies.

Effect of improved fitness beyond weight loss on cardiovascular risk factors in individuals with type 2 diabetes in the Look AHEAD study

Background Because lifestyle-induced improvements in cardiovascular risk factors vary substantially across individuals with type 2 diabetes, we investigated the extent to which increases in fitness explain cardiovascular risk factor improvements independent of weight loss in a lifestyle intervention. Methods We studied 1-year changes in Look AHEAD, a randomized trial comparing an intensive lifestyle intervention (ILI) to a diabetes support and education (DSE) control group in adults with type 2 diabetes. Assessments included weight, fitness, blood pressure (BP), glucose, HbA1c, and lipids. We evaluated the effects of changes in weight and fitness on changes in cardiovascular risk factors by study arm, using R2 from multiple linear regression. Results Analyses included participants with fitness data at baseline and 1-year (n = 4408; 41% male, 36% non-white; mean age 58.7 ± 6.8 years). Weight change alone improved R2 for explaining changes in risk factors up to 8.2% in ILI and 1.7% in DSE. Fitness change alone improved R2 up to 3.9% in ILI and 0.8% in DSE. After adjusting for weight change, fitness was independently associated (p < 0.05) with improvements in R2 for glucose (+0.7%), HbA1c (+1.1%), high-density lipoprotein (HDL) cholesterol (+0.4%), and triglycerides (+0.2%) in ILI and diastolic BP (+0.3%), glucose (+0.3%), HbA1c (+0.4%), and triglycerides (+0.1%) in DSE. Taken together, weight and fitness changes explained from 0.1–9.3% of the variability in cardiovascular risk factor changes. Conclusion Increased fitness explained statistically significant but small improvements in several cardiovascular risk factors beyond weight loss. Further research identifying other factors that explain cardiovascular risk factor change is needed.

Short- and Long-Term Eating Habit Modification Predicts Weight Change in Overweight, Postmenopausal Women: Results from the WOMAN Study

BACKGROUND Standard behavioral obesity treatment produces poor long-term results. Focusing on healthy eating behaviors rather than energy intake may be an alternative strategy. In addition, important behaviors might differ for short- vs long-term weight control. OBJECTIVE Our aim was to describe and compare associations between changes in eating behaviors and weight after 6 and 48 months. DESIGN We performed secondary analysis of data collected during a randomized weight-loss intervention trial with 48-month follow-up. PARTICIPANTS We studied 481 overweight and obese postmenopausal women enrolled in the Women on the Move through Activity and Nutrition (WOMAN) Study. MAIN OUTCOME MEASURES We measured changes in weight from baseline to 6 and 48 months. STATISTICAL ANALYSES PERFORMED Linear regression models were used to examine the associations between 6- and 48-month changes in eating habits assessed by the Conner Diet Habit Survey and changes in weight. Analyses were conducted in the combined study population and stratified by randomization group. RESULTS At 6 months in the combined population, weight loss was independently associated with decreased desserts (P<0.001), restaurant eating (P=0.042), sugar-sweetened beverages (P=0.009), and fried foods (P<0.001), and increased fish consumption (P=0.003). Results were similar in intervention participants; only reduced desserts and fried foods associated with weight loss in controls. At 48 months in the combined population, weight loss was again associated with decreased desserts (P=0.003) and sugar-sweetened beverages (P=0.011), but also decreased meats/cheeses (P=0.024) and increased fruits/vegetables (P<0.001). Decreased meats/cheeses predicted weight loss in intervention participants; desserts, sugar-sweetened beverages, and fruits/vegetables were independently associated in controls. CONCLUSIONS Changes in eating behaviors were associated with weight change, although important behaviors differed for short- and long-term weight change and by randomization group. Future studies should determine whether interventions targeting these behaviors could improve long-term obesity treatment outcomes.

Short-Term Weight Loss with Diet and Physical Activity in Young Adults: the IDEA Study

This study examined the effect of a behavioral weight loss intervention (BWLI) on young adults (age = 18‐35 years).

Cross-sectional and Longitudinal Associations Between Objectively Measured Sedentary Time and Metabolic Disease: The Coronary Artery Risk Development in Young Adults (CARDIA) Study

OBJECTIVE Prolonged sedentary time (ST) might be contributing to the diabetes epidemic, but most studies have been cross-sectional and few have objectively measured ST. The purpose of this study was to evaluate cross-sectional and 5-year longitudinal relationships between ST and metabolic parameters and outcomes. RESEARCH DESIGN AND METHODS This was an analysis of 2,027 Coronary Artery Risk Development in Young Adults (CARDIA) study participants (aged 38–50 years, 57% female, and mean BMI of 29.0 ± 7.0 kg/m2) with accelerometry data (≥4 days with ≥10 h/day) measured at the year 20 follow-up exam (2005–2006). Metabolic variables (fasting glucose, fasting insulin, 2-h postchallenge glucose, HOMA of insulin resistance [HOMA-IR], and HbA1c) and outcomes (impaired fasting glucose [IFG], impaired glucose tolerance [IGT], prediabetes by HbA1c, and diabetes) were assessed concurrently and 5 years later. RESULTS Average ST was 8.1 ± 1.7 h/day or 55 ± 10% of wear time. Each additional hour per day of ST was cross-sectionally associated with a 3% higher fasting insulin and HOMA-IR (both P < 0.01) but not 5-year changes in metabolic parameters. Having ≥10 h/day vs. <6 h/day of ST was associated with an odds ratio (OR) = 2.74 (95% CI 1.13, 6.62) for IGT and an OR = 3.80 (95% CI 1.39, 10.35) for diabetes. ST was not associated with prevalent IFG, prevalent prediabetes by HbA1c, or 5-year incidence of any metabolic outcomes (all P > 0.05). CONCLUSIONS ST was independently related to insulin, HOMA-IR, and prevalent diabetes and IGT but did not predict 5-year changes in metabolic parameters or incidence of metabolic outcomes. These results suggest that higher ST may not be a risk factor for future metabolic outcomes, but more research with repeated ST measurement and longer follow-up is needed.

Association of the degree of adiposity and duration of obesity with measures of cardiac structure and function: the CARDIA study.

Examine whether there are independent influences of a greater degree of adiposity and longer duration of obesity on cardiac structure and function.

Sedentary screen time and left ventricular structure and function: the CARDIA study.

INTRODUCTION Sedentary screen time (watching TV or using a computer) predicts cardiovascular outcomes independently from moderate and vigorous physical activity and could affect left ventricular structure and function through the adverse consequences of sedentary behavior. PURPOSE This study aimed to determine whether sedentary screen time is associated with measures of left ventricular structure and function. METHODS The Coronary Artery Risk Development in Young Adults Study measured screen time by questionnaire and left ventricular structure and function by echocardiography in 2854 black and white participants, age 43-55 yr, in 2010-2011. Generalized linear models evaluated cross-sectional trends for echocardiography measures across higher categories of screen time and adjusting for demographics, smoking, alcohol, and physical activity. Further models adjusted for potential intermediate factors (blood pressure, antihypertensive medication use, diabetes, and body mass index). RESULTS The relationship between screen time and left ventricular mass (LVM) differed in blacks versus whites. Among whites, higher screen time was associated with larger LVM (P < 0.001), after adjustment for height, demographics, and lifestyle variables. Associations between screen time and LVM persisted when adjusting for blood pressure, antihypertensive medication use, and diabetes (P = 0.008) but not with additional adjustment for body mass index (P = 0.503). Similar relationships were observed for screen time with LVM indexed to height, relative wall thickness, and mass-to-volume ratio. Screen time was not associated with left ventricular structure among blacks or left ventricular function in either race group. CONCLUSIONS Sedentary screen time is associated with greater LVM in white adults, and this relationship was largely explained by higher overall adiposity. The lack of association in blacks supports a potential qualitative difference in the cardiovascular consequences of sedentary screen-based behavior.

Energy expenditure of deskwork when sitting, standing or alternating positions

Background Recent guidelines recommend accruing 2-4h of standing or light activity during the working day. Use of sit-stand desks could achieve this goal, but whether standing can meaningfully increase energy expenditure (EE) is unclear. Aims To study EE, heart rate, feelings and productivity during deskwork while sitting, standing or alternating positions. Methods We measured EE by indirect calorimetry in working adults over three randomly ordered 60-min conditions while performing deskwork: continuous sitting (SIT), 30min of each standing and sitting (STAND-SIT) and continuous standing (STAND). We also assessed heart rate, productivity and self-reported energy, fatigue and pain. Linear mixed models compared minute-by-minute EE and heart rate across conditions. Non-parametric tests compared remaining outcomes across conditions. Results The study group comprised 18 working adults. Compared with SIT, STAND-SIT engendered an additional 5.5±12.4 kcal/h (7.8% increase) and STAND engendered an additional 8.2±15.9 kcal/h (11.5% increase) (both P < 0.001). Alternating positions to achieve the recommended 4h/day of standing could result in an additional 56.9 kcal/day for an 88.9kg man and 48.3 kcal/day for a 75.5kg woman. STAND-SIT and STAND also increased heart rate over SIT by 7.5±6.8 and 13.7±8.8 bpm, respectively (both P < 0.001). We observed no meaningful differences in feelings or productivity. Conclusions Desk-based workers could increase EE without added discomfort by using a sit-stand desk. These findings inform future research on sit-stand desks as a part of workplace interventions to increase EE and potentially improve health.

The association of arterial shear and flow-mediated dilation in diabetes.

While adjusting flow-mediated dilation (FMD), a measure of vascular function, for shear rate may be important when evaluating endothelial-dependent vasodilation, the relationship of FMD with shear rate in study populations with cardiovascular risk factors is unclear. We aimed to investigate the association of four measures of shear rate (peak shear rate (SRpeak) and shear rate area under the curve through 30 seconds (SRAUC 0–30), 60 seconds (SRAUC 0–60), and time to peak dilation (SRAUC 0–ttp)) with FMD in 50 study subjects with type 2 diabetes and mild hypertension undergoing baseline FMD testing for an exercise intervention trial. Associations among measures of shear rate and FMD were evaluated using Pearson’s correlations and R2. The four measures of shear rate were highly correlated within subjects, with Pearson’s correlations ranging from 0.783 (p < 0.001) to 0.972 (p < 0.001). FMD was associated with each measure of shear rate, having a correlation of 0.576 (p < 0.001) with SRAUC 0–30, 0.529 (p < 0.001) with SRAUC 0–60, and 0.512 (p < 0.001) with SRpeak. Nine of 50 subjects (18%) did not dilate following the shear stimulus. Among the 41 responders, FMD had a correlation of 0.517 (p < 0.001) with SRAUC 0–ttp and similar correlations to those found in the full sample for SRAUC 0–30, SRAUC 0–60, and SRpeak. In conclusion, shear rate appears to explain up to a third of between-person variability in FMD response and our results support the reporting of shear rate and FMD with and without adjustment for shear rate in similar clinical populations with CVD risk factors.

Reducing Sedentary Behavior Versus Increasing Moderate-to-Vigorous Intensity Physical Activity in Older Adults: A 12-Week Randomized, Clinical Trial.

Objective: To compare the effects of behavioral interventions targeting decreased sedentary behavior versus increased moderate-to-vigorous intensity physical activity (MVPA) in older adults. Method: Inactive older adults (N = 38, 68 ± 7 years old, 71% female) were randomized to 12-week interventions targeting decreased sedentary behavior (Sit Less) or increased MVPA (Get Active). The SenseWear armband was used to objectively assess activity in real time. Assessments included a blinded armband, the Community Health Activites Model Program for Senior (CHAMPS) questionnaire, 400-meter walk, and the Short Physical Performance Battery (SPPB). Results: Objectively measured MVPA increased in Get Active (75 ± 22 min/week, p < .001); self-reported MVPA increased in both groups (p < .05). Sedentary behavior did not change in either group (all p > .05). Only the Sit Less group improved the SPPB score (0.5 ± 0.3, p = .046). Discussion: Targeting reduced sedentary behavior had a greater effect on physical function among inactive but high functioning older adults over 12 weeks. Future studies of longer duration and combining increased MVPA with reduced sedentary behavior are needed.