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Red Raspberry and Fructo-Oligosaccharide Supplementation, Metabolic Biomarkers, and the Gut Microbiota in Adults with Prediabetes: A Randomized Crossover Clinical Trial.

  • 2022-06-01
  • The Journal of nutrition 152(6)
    • Xuhuiqun Zhang
    • Anqi Zhao
    • Amandeep K Sandhu
    • Indika Edirisinghe
    • Britt M Burton-Freeman

Study Design

Type
Randomized Controlled Trial (RCT)
Sample size
n = 26
Population
Adults with prediabetes and insulin resistance (n=26) and metabolically healthy reference group (n=10)
Methods
Randomized crossover trial with two 4-week supplementation periods, consuming either RRB (125 g fresh equivalents) daily or RRB + 8g FOS daily, separated by a 4-week washout
Duration
4-week supplementation periods
Funding
Unclear

Background

Evidence suggests that the gut microbiota and cardiometabolic status are associated, suggesting dietary interventions that alter the microbiota may affect metabolic health.

Objectives

We investigated whether supplementation with (poly)phenol-dense red raspberries (RRB), alone or with a fructo-oligosaccharide (FOS) prebiotic, would improve biomarkers of cardiometabolic risk in individuals with prediabetes (PreDM) and insulin resistance (IR) and whether the effects are related to modulation of the gut microbiota.

Methods

Adults with PreDM-IR (n = 26; mean ± SEM age, 35 ± 2 years; fasting glucose, 5.7 ± 0.1 mmol/L; HOMA-IR, 3.3 ± 0.3) or who were metabolically healthy (reference group; n = 10; age, 31 ± 3 years; fasting glucose, 5.1 ± 0.2 mmol/L; HOMA-IR, 1.1 ± 0.1) participated in a randomized crossover trial with two 4-week supplementation periods, in which they consumed either RRB (125 g fresh equivalents) daily or RRB + 8g FOS daily, separated by a 4-week washout. The primary outcome variable was the change in the gut microbiota composition, assessed by shotgun sequencing before (baseline) and at the end of each supplementation period. Secondary outcomes were changes in glucoregulation, lipid metabolism, anti-inflammatory status, and anthropometry. The trial is registered at ClinicalTrials.gov, NCT03049631.

Results

In PreDM-IR, RRB supplementation reduced hepatic-IR (-30.1% ± 14.6%; P = 0.04) and reduced plasma total and LDL cholesterol [-4.9% ± 1.8% (P = 0.04) and -7.2% ± 2.3% (P = 0.003), respectively] from baseline. Adding FOS (RRB + FOS) improved β-cell function [insulin secretion rate, +70.2% ± 32.8% (P = 0.02); Disposition Index, +94.4% ± 50.2% (P = 0.04)], but had no significant effect on plasma cholesterol compared to baseline. RRB increased Eubacterium eligens (2-fold) and decreased Ruminococcus gnavus (-60% ± 34%), whereas RRB + FOS increased Bifidobacterium spp. (4-fold) and decreased Blautia wexlerae (-23% ± 12%) from baseline (all P values ≤ 0.05). R. gnavus was positively correlated with hepatic-IR, and E. eligens and Bifidobacterium catenulatum were negatively correlated with cholesterol concentrations (P ≤ 0.05).

Conclusions

Increased Bifidobacterium spp., concurrently with reduced R. gnavus, was associated with metabolic improvements in adults with PreDM-IR, warranting further research on the mechanisms involved in (poly)phenol/FOS-microbial interactions with host metabolism.

Research Insights

  • Red Raspberry→Improved Insulin Secretion Rate

    Adding FOS (RRB + FOS) improved β-cell function [insulin secretion rate, +70.2% ± 32.8% (P = 0.02); Disposition Index, +94.4% ± 50.2% (P = 0.04)]

    Effect
    Beneficial
    Effect size
    Large
    Dose
    125 g fresh equivalents/day
  • Red Raspberry→Improved Insulin Sensitivity

    Adding FOS (RRB + FOS) improved β-cell function [insulin secretion rate, +70.2% ± 32.8% (P = 0.02); Disposition Index, +94.4% ± 50.2% (P = 0.04)]

    Effect
    Beneficial
    Effect size
    Large
    Dose
    125 g fresh equivalents/day
  • Red Raspberry→Reduced Hepatic Insulin Resistance

    RRB supplementation reduced hepatic-IR (-30.1% ± 14.6%; P = 0.04)

    Effect
    Beneficial
    Effect size
    Large
    Dose
    125 g fresh equivalents/day
  • Red Raspberry→Reduced LDL Cholesterol

    but had no significant effect on plasma cholesterol compared to baseline

    Effect
    Neutral
    Effect size
    Small
    Dose
    125 g fresh equivalents/day
  • Red Raspberry→Reduced Total Cholesterol

    but had no significant effect on plasma cholesterol compared to baseline

    Effect
    Neutral
    Effect size
    Small
    Dose
    125 g fresh equivalents/day
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