Early life exposure to green space and insulin resistance: An assessment from infancy to early adolescence

BACKGROUND

Recent studies suggest that greater exposure to natural vegetation, or "green space" is associated with lower diabetes risk, possibly through increasing physical activity. However, there is limited research on green space and insulin resistance in youth. We hypothesized greater green space at early-life sensitive time periods would be associated with lower insulin resistance in youth.

METHODS

We used data from Project Viva (N = 460), a pre-birth cohort study that recruited pregnant women in eastern Massachusetts, 1999-2002, and followed offspring into adolescence. We defined residential green space exposure at infancy (median age - 1.1 years), early childhood (3.2 years), mid-childhood (7.7 years), and early adolescence (12.8 years), using 30 m resolution Landsat satellite imagery to estimate the Normalized Difference Vegetation Index [NDVI]. Our main outcome was early adolescence estimated insulin resistance (HOMA-IR). We used multiple imputation to account for missing data and multiple linear regression models adjusted for age, sex, race/ethnicity, parental education, household income, and neighborhood median household income.

RESULTS

The highest green space tertile had the highest percentage of white participants (85%), college-educated mothers (87%) and fathers (85%), and households with income higher than US$70,000 (86%). Unadjusted models showed that participants living in the highest green space tertile at infancy had a 0.15 unit lower HOMA-IR (95% CI: -0.23, -0.06) in early adolescence, than those living in the lowest tertile. However, in adjusted models, we did not observe evidence of associations between green space from infancy to early adolescence and HOMA-IR in early adolescence, although some point estimates were in the hypothesized direction. For example, participants in the highest green space tertile in infancy had 0.03 units lower HOMA-IR (95%CI: -0.14, 0.08) than those living in the lowest tertile.

CONCLUSIONS

Exposure to green space at early life sensitive time periods was not associated with HOMA-IR in youth. Early-life longitudinal studies across diverse populations are needed to confirm or refute our results.

Comparison of a Mediterranean to a low-fat diet intervention in adults with type 1 diabetes and metabolic syndrome: A 6-month randomized trial

BACKGROUND AND AIMS

The metabolic syndrome (MS) is an emerging complication in patients with type 1 diabetes (T1D), with no preventive or therapeutic treatment reported yet. We wanted to compare the impact of two 6-month nutritional interventions, based on a Mediterranean (MED) or a low-fat diet, on waist circumference, anthropometric and metabolic outcomes in patients with both T1D and the MS.

METHODS AND RESULTS

Participants were randomized into 2 intervention groups: 1) MED-diet or 2) low-fat diet. The 6-month study included 9 teaching sessions with a registered dietitian. Anthropometric (primary outcome: waist circumference), metabolic and nutritional assessments were performed at inclusion, 3 and 6-month. We used mixed effects models to assess the effects of both interventions. 28 participants were included (50.9 ± 10.3 years old) with a mean BMI of 30.7 ± 3.3 kg/m² and a waist circumference of 105.5 ± 8.9 cm at inclusion. A trend towards a greater reduction of dietary fat intakes in the low-fat diet group was observed (P-interaction = 0.09). Waist circumference was reduced at 6-month in both groups (-3.5 cm low-fat; -1.5 cm MED-diet) with no significant difference between groups (P-interaction = 0.43). Body mass index also significantly decreased in both groups (-0.7 kg/m² low-fat; -1.1 kg/m² MED-diet; P-interaction = 0.56). No significant differences between groups were observed for other metabolic parameters.

CONCLUSIONS

This study suggests that a 6-month non-restrictive dietary intervention in patients with T1D and MS could contribute to weight management, without significant differences between interventions for anthropometric and metabolic parameters. Further studies should investigate the long-term benefits of these diets.

CLINICAL TRIAL REGISTRY

NCT02821585 (https://clinicaltrials.gov/).

Predictors of cardiovascular risk among patients with type 1 diabetes: A critical analysis of the metabolic syndrome and its components

Patients with type 1 diabetes (T1D) are at increased risk for cardiovascular diseases. The metabolic syndrome (MetS), a complex disorder defined by a cluster of interconnected factors including abdominal obesity, hypertension, dyslipidaemia and insulin resistance, has been proposed to identify patients with T1D at high cardiovascular risk. The MetS has been identified in 8-45% of patients with T1D, depending on the definition and cohort studied. However, clinicians and researchers face several issues with the criteria for MetS in patients with T1D, therefore questioning its value in routine care. For example, three criteria can lead to overestimation of MetS prevalence; the impaired fasting glucose criterion is irrelevant as it is automatically fulfilled; and the widespread use of antihypertensive and lipid-lowering medications for cardiac and renal preventative purposes can contribute to overestimations of the prevalence of raised blood pressure and elevated triglycerides. In cross-sectional studies, the MetS has been associated mostly with an increased risk of microvascular complications whereas, in prospective cohorts, the predictive value of MetS for micro- and macrovascular outcomes has been inconsistent. While identifying diabetes patients at increased risk for cardiovascular complications and early mortality is crucial from a prevention standpoint, for patients with T1D, the current definition of MetS may not be the most suitable tool. The aims of the present report are to review the applicability and limitations of the MetS in patients with T1D, and to discuss alternative avenues to identify high-risk patients.

The IVAIRE project--a randomized controlled study of the impact of ventilation on indoor air quality and the respiratory symptoms of asthmatic children in single family homes

A randomized controlled trial was carried out to measure the impact of an intervention on ventilation, indoor air contaminants, and asthma symptoms of children. Eighty-three asthmatic children living in low-ventilated homes were followed over 2 years. Several environmental parameters were measured during the summer, fall, and winter. The children were randomized after Year 1 (43 Intervention; 40 Control). The intervention included the installation of either a Heat Recovery Ventilator (HRV) or Energy Recovery Ventilator (ERV). During the fall and winter seasons, there was a significant increase in the mean ventilation rate in the homes of the intervention group. A statistically significant reduction in mean formaldehyde, airborne mold spores, toluene, styrene, limonene, and α-pinene concentrations was observed in the intervention group. There was no significant group difference in change in the number of days with symptoms per 14 days. However, there was a significant decrease in the proportion of children who experienced any wheezing (≥1 episode) and those with ≥4 episodes in the 12-month period in the intervention group. This study indicates that improved ventilation reduces air contaminants and may prevent wheezing. Due to lack of power, a bigger study is needed.

PRACTICAL IMPLICATIONS

Positive findings from this study include the fact that, upon recruitment, most of the single family homes with asthmatic children were already equipped with a mechanical ventilation system and had relatively good indoor air quality. However, the 8-h indoor guideline for formaldehyde (50 μg/m3) was frequently exceeded and the ventilation rates were low in most of the homes, even those with a ventilation system. Both ERVs and HRVs were equally effective at increasing air exchange rates above 0.30 ACH and at preventing formaldehyde concentrations from exceeding the 50 μg/m3 guideline during the fall and winter seasons. Furthermore, the ERVs were effective at preventing excessively low relative humidities in the homes. Based on observed difference of risk, intervention to increase ventilation in five sample homes and children would prevent 1 home to exceed the indoor air long-term formaldehyde guideline and prevent 1 asthmatic child experiencing at least one episode of wheezing over a year.

Efficacy of dual-hormone artificial pancreas to alleviate the carbohydrate-counting burden of type 1 diabetes: A randomized crossover trial

AIM

Carbohydrate-counting is a complex task for many patients with type 1 diabetes. This study examined whether an artificial pancreas, delivering insulin and glucagon based on glucose sensor readings, could alleviate the burden of carbohydrate-counting without degrading glucose control.

METHODS

Twelve adults were recruited into a randomized, three-way, crossover trial (ClinicalTrials.gov identifier No. NCT01930097). Participants were admitted on three occasions from 7AM to 9PM and consumed a low-carbohydrate breakfast (women: 30g; men: 50g), a medium-carbohydrate dinner (women: 50g; men: 70g) and a high-carbohydrate lunch (women: 90g; men: 120g). At each visit, glucose levels were randomly regulated by: (1) conventional pump therapy; (2) an artificial pancreas (AP) accompanied by prandial boluses, matching the meal's carbohydrate content based on insulin-to-carbohydrate ratios (AP with carbohydrate-counting); or (3) an AP accompanied by prandial boluses based on qualitative categorization (regular or large) of meal size (AP without carbohydrate-counting).

RESULTS

The AP without carbohydrate-counting achieved similar incremental AUC values compared with carbohydrate-counting after the low- (P=0.54) and medium- (P=0.38) carbohydrate meals, but yielded higher post-meal excursions after the high-carbohydrate meal (P=0.004). The AP with and without carbohydrate-counting yielded similar mean glucose levels (8.2±2.1mmol/L vs. 8.4±1.7mmol/L; P=0.52), and both strategies resulted in lower mean glucose compared with conventional pump therapy (9.6±2.0mmol/L; P=0.02 and P=0.03, respectively).

CONCLUSION

The AP with qualitative categorization of meal size could alleviate the burden of carbohydrate-counting without compromising glucose control, although more categories of meal sizes are probably needed to effectively control higher-carbohydrate meals.

In adult patients with type 1 diabetes healthy lifestyle associates with a better cardiometabolic profile

BACKGROUND/AIMS

Little is known about lifestyle habits of adults with type 1 diabetes (T1D) and their association with cardiometabolic risk (CMR) factors. The aims of the present study were to determine the prevalence of adults with T1D who adopted a healthy lifestyle and to explore the association between a healthy lifestyle and the cardiometabolic profile.

METHODS AND RESULTS

This is a cross-sectional analysis of 115 adults with T1D. Participants wore a motion sensor and completed a 3-day food record. The following CMR factors were assessed: body mass index, waist circumference, body composition (iDXA), glycated hemoglobin, lipids and blood pressure. Insulin resistance was estimated (estimated glucose disposal rate). Participants were classified according to the number of healthy lifestyle habits adopted (ranging from 0 to 3): regular physical activity (physical activity level ≥1.7), good diet quality (Canadian Healthy Eating Index score >80) and none-smoking status. The proportion of participants who adopted 3, 2, 1 or 0 lifestyle habits were 11%, 30%, 37%, and 23%, respectively. As the number of healthy lifestyle habits adopted increased, participants had significantly lower body mass index, waist circumference, body fat, total cholesterol, non-HDL-cholesterol, triglycerides and systolic blood pressure (p < 0.05). In addition, a trend for lower estimated insulin resistance was observed (p = 0.06). For each increase of one healthy lifestyle habit, body mass index decreased by 1.9 kg/m(2), waist circumference by 4.0 cm for men and 4.8 cm for women and trunk fat by 3.6% for men and 4.1% for women.

CONCLUSIONS

These results suggest the importance of a healthy lifestyle among adults with T1D in order to control CMR factors.