The Effect of OptiFibre Dietary Fiber on Carbohydrate Metabolism and Intestinal Microbiota Metabolism in Patients With Type 2 Diabetes Mellitus

This clinical trial investigates whether OptiFibre (partially hydrolyzed guar gum, PHGG) — a soluble dietary fiber supplement — can improve blood sugar control, lipid levels, and gut microbiota metabolite profiles in people living with type 2 diabetes. The gut microbiome is increasingly recognized as a key player in metabolic disease: certain gut bacteria ferment dietary fibers and produce short-chain fatty acids (SCFAs) like butyrate and propionate, which in turn influence insulin sensitivity and inflammation. By feeding the gut with a prebiotic fiber, the study aims to shift bacterial activity toward more beneficial metabolite production. Approximately 80 patients are enrolled, split evenly between an intervention group receiving OptiFibre and a control group whose data is drawn from archived patient records. Beyond glucose metabolism, the study also tracks waist circumference and body weight, recognizing that metabolic health in type 2 diabetes is multidimensional. The trial is registered through Pirogov Russian National Research Medical University and was completed as of May 2026. If positive, results would support dietary fiber supplementation as a low-risk, accessible adjunct strategy for managing type 2 diabetes through the gut-metabolism axis.

• Primary outcome data are not yet publicly reported; findings below reflect the study's pre-specified endpoints and design intentions (low confidence — abstract is pre-results/registration only).
• The trial is designed to detect changes in carbohydrate metabolism markers (e.g., fasting glucose, HbA1c) following OptiFibre PHGG supplementation in type 2 diabetes patients.
• Secondary endpoints include lipid profile changes, intestinal microbiota metabolite shifts (specifically short-chain fatty acids), and anthropometric outcomes (body weight and waist circumference).

This is a controlled observational/interventional hybrid study enrolling approximately 80 adults with confirmed type 2 diabetes mellitus at Pirogov Russian National Research Medical University. Participants are divided into two groups of 40: the main (study) group receives OptiFibre PHGG supplementation with prospective data collection, while the control group's data are gathered retrospectively from archived patient records. Key metabolic, lipid, and microbiota metabolite outcomes are assessed at baseline and follow-up. The retrospective control design and mixed methodology (part prospective, part archival) are notable structural features of this trial.

Because control-group data are collected retrospectively from archived records rather than through concurrent randomization, the study cannot fully control for confounding differences in diet, medications, or co-morbidities between groups, limiting causal inference. The relatively small sample size (40 per arm) may be underpowered to detect modest effect sizes in microbiota metabolite endpoints, which are inherently high-variance. The absence of published outcome data at the time of this synthesis means all findings-level statements carry low confidence and must be treated as anticipated rather than confirmed. A follow-on double-blind, placebo-controlled RCT with larger cohorts and standardized dietary background would be required to confirm any observed effects.

This trial extends [§25], which systematically reviewed gut microbiota-modulating interventions (including prebiotics and dietary fiber) in pediatric type 1 diabetes, by shifting the focus to type 2 diabetes in adults and providing prospective SCFA metabolite data — a mechanistic layer largely absent from the pediatric literature. It closely parallels [§103], a study examining psyllium fiber effects on gut microbiota fermentation in pediatric IBS, as both investigate how soluble dietary fibers reshape intestinal microbiota metabolite output, albeit in distinct disease contexts and age groups. The metabolomics-first framing of microbiota metabolite profiling also parallels [§86], which used deep metagenomic and metabolome signatures to characterize gut-metabolic interactions in post-stroke cognitive impairment — demonstrating that integrating microbiota and metabolite data in clinical cohorts is an emerging cross-disease methodology. More broadly, the study fits within the growing corpus represented by [§100], which frames microbiome interventions at the translational crossroads of ecology and causality, and aligns with [§101]'s emphasis on microbial metabolite-driven mechanisms (e.g., bile acid and SCFA axes) as actionable therapeutic targets in metabolic disease.

• Gut microbiota-modulating interventions in paediatric type 1 diabetes: a systematic review and meta-analysis
  Closest thematic comparator: a systematic review of prebiotic/fiber interventions on gut microbiota and carbohydrate metabolism in diabetes — different type (T1D vs T2D) and age group, but directly benchmarks the evidence base this trial seeks to extend.
• Psyllium in Pediatric IBS
  Both studies test soluble dietary fiber effects on intestinal microbiota metabolite fermentation; comparing fiber type (PHGG vs psyllium) and population (T2D adults vs pediatric IBS) helps isolate whether SCFA responses are fiber-specific or disease-context-specific.
• Integrated gut microbiota and metabolome signatures revealed by deep metagenomic sequencing in post-stroke cognitive impairment with type 2 diabetes
  Uses integrated metagenomics and metabolomics in a clinical disease cohort (post-stroke), providing a methodological blueprint for interpreting gut microbiota metabolite data that readers of this trial's eventual results can use for comparison.
• Effects of processed low-protein brown rice on patients with chronic kidney disease
  Examines a dietary intervention (low-protein processed rice) on metabolic and gut outcomes in a chronic disease population (CKD), offering a parallel design context for evaluating dietary fiber/food-based interventions on lab metabolic markers beyond diabetes.
• Letter to the Editor: Gut microbiota–bile acid crosstalk - Prevotellaceae NK3B31 and 7-ketolithocholic acid drive metabolic benefits of distal bowel resection with preservation of terminal ileum
  Highlights specific microbial metabolite pathways (bile acids, SCFAs) as mechanistic drivers of metabolic dysfunction — directly relevant to interpreting whether OptiFibre-induced microbiota shifts translate into meaningful metabolic signal in T2D.