Exploring the Effects of Dietary Intake on Gut Microbiome Diversity and Composition of Older Adults with Type 1 Diabetes: A Pilot Study.

Background: Gut microbiome diversity and composition have been associated with type 1 diabetes (T1D) onset and progression. These features have not been explored among the growing number of older adults with T1D, including how they may differ by diet. Objectives: In the present observational study, we investigated differences in gut microbiome diversity and composition across quantiles of high and low macronutrient, fiber, and simple sugar intake. Methods: We collected observational data on routine diabetes management, diet, and other health indicators from older adults with T1D over 7-9 d, including 2 24-h dietary recall interviews, diabetes technology, and medical record data. Stool samples were collected for gut microbiome characterization using high-throughput sequencing of the 16S ribosomal RNA gene. Gut microbiome characteristics were assessed by Analysis of Compositions of Microbiomes with Bias Correction (ANCOM-BC2), Shannon index, and Bray-Curtis distances. Results: Among 17 older adults [mean (SD) age 73.5 (6.2) y; diabetes duration: 34.0 (16.0) y, and glycated hemoglobin: 7.0 (0.9) %], increased fat intake was associated with enriched genus Lactococcus, increased fiber intake was associated with enriched genus Hemophilus and unclassified Clostridium within family CAG:508, and increased fructose intake was associated with enrichment of unclassified genus SFMI01 within family Christensenellaceae. Greater carbohydrate intake was associated with depletion of the family Enterobacteriaceae. Microbial diversity differed significantly with greater fiber and fructose intake. Conclusions: We found statistically significant evidence suggesting that the gut microbiome of older adults with T1D may be modulated by macronutrient, fiber, and fructose intake. Similar trends between fiber intake differences and significantly different microbial community structure have been found in younger populations. Together with the literature, our other findings suggest that macronutrient, fiber, and fructose intakes may impact the gut microbiome differently in older adults with T1D.