The effects of the DASH dietary pattern on clinical outcomes and quality of life in adults with uncontrolled asthma: Design and methods of the ALOHA Trial

BACKGROUND

Poor diet quality is an important risk factor for increased asthma prevalence and poor asthma control. To address the question of whether adults with asthma can benefit from following a healthy diet, this trial will test the efficacy and mechanisms of action of a behavioral intervention promoting the Dietary Approaches to Stop Hypertension (DASH) dietary pattern with sodium reduction among patients with uncontrolled asthma.

METHODS

In this 2-arm randomized clinical trial, 320 racially/ethnically and socioeconomically diverse adults with uncontrolled asthma on standard controller therapy will be randomized to either a control or an intervention group and assessed at baseline, 3, 6 and 12 months. Control and intervention participants will receive education on lung health, asthma, and other general health topics; additionally, the intervention group will receive DASH behavioral counseling over 12 months. The primary hypothesis is that the DASH behavioral intervention, compared with the education-only control, will lead to significantly more participants with minimum clinically important improvement (responders) in asthma-specific quality of life at 12 months. Secondary hypotheses will test the intervention effects on other asthma (e.g., asthma control, lung function) and non-asthma outcomes (e.g., quality of life). Additionally, therapeutic (e.g., short chain fatty acids, cytokines) and nutritional biomarkers (e.g., dietary inflammatory index, carotenoids) will be assessed to understand the mechanisms of the intervention effect.

CONCLUSION

This trial can substantially advance asthma care by providing rigorous evidence on the benefits of a behavioral dietary intervention and mechanistic insights into the role of diet quality in asthma.

CLINICALTRIALS

gov #: NCT05251402.

Response of pancreatic beta-cells to improved insulin sensitivity in women at high risk for type 2 diabetes

The purpose of this study was to examine the response of pancreatic beta-cells to changes in insulin sensitivity in women at high risk for type 2 diabetes. Oral glucose tolerance tests (OGTTs) and frequently sampled intravenous glucose tolerance tests (FSIGTs) were conducted on Latino women with impaired glucose tolerance and a history of gestational diabetes before and after 12 weeks of treatment with 400 mg/day troglitazone (n = 13) or placebo (n = 12). Insulin sensitivity was assessed by minimal model analysis, and beta-cell insulin release was assessed as acute insulin responses to glucose (AIRg) and tolbutamide (AIRt) during FSIGTs and as the 30-min incremental insulin response (30-min dINS) during OGTTs. Beta-cell compensation for insulin resistance was assessed as the product (disposition index) of minimal model insulin sensitivity and each of the 3 measures of beta-cell insulin release. In the placebo group, there was no significant change in insulin sensitivity or in any measure of insulin release, beta-cell compensation for insulin resistance, or glucose tolerance. Troglitazone treatment resulted in a significant increase in insulin sensitivity, as reported previously. In response, AIRg did not change significantly, so that the disposition index for AIRg increased significantly from baseline (P = 0.004) and compared with placebo (P = 0.02). AIRt (P = 0.001) and 30-min dINS (P = 0.02) fell with improved insulin sensitivity during troglitazone treatment, so that the disposition index for each of these measures of beta-cell function did not change significantly from baseline (P > 0.20) or compared with placebo (P > 0.3). Minimal model analysis revealed that 89% of the change from baseline in insulin sensitivity during troglitazone treatment was accounted for by lowered plasma insulin concentrations. Neither oral nor intravenous glucose tolerance changed significantly from baseline or compared with placebo during troglitazone treatment. The predominant response of beta-cells to improved insulin sensitivity in women at high risk for type 2 diabetes was a reduction in insulin release to maintain nearly constant glucose tolerance.

Effect of troglitazone on insulin sensitivity and pancreatic beta-cell function in women at high risk for NIDDM

We conducted a randomized placebo-controlled study to determine the effects of the thiazolidinedione compound troglitazone on whole-body insulin sensitivity (SI), pancreatic beta-cell function, and glucose tolerance in 42 Latino women with impaired glucose tolerance (IGT) and a history of gestational diabetes mellitus (GDM), characteristics that carry an 80% risk of developing NIDDM within 5 years. After baseline oral (OGTT) and intravenous (IVGTT) glucose tolerance testing, subjects were assigned to take placebo or 200 or 400 mg troglitazone daily for 12 weeks (14 subjects per treatment group). An OGTT and IVGTT were repeated during the 12th week of treatment. Five subjects failed to complete the trial for personal reasons, and medication compliance averaged 90% in the remaining subjects, none of whom experienced a serious adverse event. SI, calculated by minimal model analysis of IVGTT results, changed by only 4 +/- 14% during 12 weeks of placebo administration, but increased 40 +/- 22 and 88 +/- 22% above basal during treatment with 200 and 400 mg troglitazone, respectively (P = 0.01 among groups). Troglitazone administration was also associated with a dose-dependent reduction in the total insulin area during IVGTTs, which was highly significant (P < 0.001), and with a reduction during OGTTs, which approached statistical significance (P = 0.09). Glucose tolerance improved slightly in all groups, but the magnitude of change did not differ significantly among groups, whether it was assessed as the number of subjects who continued to manifest IGT at 12 weeks (P = 0.64 among groups), the change in total glucose area during OGTTs (P = 0.58), or the change in fractional glucose disappearance rates during IVGTTs (P = 0.28). Among the women who received troglitazone, the greatest improvement in SI occurred in the women who had the highest diastolic blood pressures and the best IVGTT insulin responses during baseline testing. Our findings indicate that troglitazone improved whole-body insulin sensitivity and lowered circulating insulin concentrations in women with prior GDM who are at very high risk for NIDDM. The lack of improvement in glucose tolerance despite improved insulin sensitivity may be a manifestation of the beta-cell defect that predisposes the women to NIDDM. The overall pattern of response to troglitazone in our high-risk patients indicates that the drug is an ideal agent with which to test whether the amelioration of insulin resistance can delay or prevent diabetes in women with limited beta-cell reserve.