Prebiotic Inulin Supplementation and Peripheral Insulin Sensitivity in adults at Elevated Risk for Type 2 Diabetes: A Pilot Randomized Controlled Trial

Prediabetes affects 84.1 million adults, and many will progress to type 2 diabetes (T2D). The objective of this proof-of-concept trial was to determine the efficacy of inulin supplementation to improve glucose metabolism and reduce T2D risk. Adults (n = 24; BMI: 31.3 +/- 2.9 kg/m(2); age: 54.4 +/- 8.3 years) at risk for T2D were enrolled in this controlled feeding trial and consumed either inulin (10 g/day) or placebo (maltodextrin, 10 g/day) for six weeks. Assessments included peripheral insulin sensitivity, fasting glucose, and insulin, HOMA-IR, in vivo skeletal muscle substrate preference, Bifidobacteria copy number, intestinal permeability, and endotoxin concentrations. Participant retention was 92%. There were no baseline group differences except for fasting insulin (p = 0.003). The magnitude of reduction in fasting insulin concentrations with inulin (p = 0.003, inulin = Delta-2.9, placebo = Delta 2.3) was attenuated after adjustment for baseline concentrations (p = 0.04). After adjusting for baseline values, reduction in HOMA-IR with inulin (inulin = Delta-0.40, placebo=Delta 0.27; p = 0.004) remained significant. Bifidobacteria 16s increased (p = 0.04; inulin = Delta 3.1e(9), placebo = Delta-8.9e(8)) with inulin supplementation. Despite increases in gut Bifidobacteria, inulin supplementation did not improve peripheral insulin sensitivity. These findings question the need for larger investigations of inulin and insulin sensitivity in this population.

Automated summary

This proof-of-concept trial aimed to assess the efficacy of inulin supplementation in improving glucose metabolism and reducing the risk of T2D. The trial found that inulin supplementation led to a decrease in fasting insulin and HOMA-IR levels, as well as an increase in Bifidobacteria in the gut. However, despite the increase in gut bacteria, inulin supplementation did not improve peripheral insulin sensitivity, questioning the necessity for larger investigations in this population.