Nutrients, Vol. 18, Pages 851: Green Tea Catechin Plus Inulin Improves Insulin Resistance Without Reducing Visceral Fat and Shows Exploratory Gut Microbiota Signals in Adults with Visceral Obesity: A Double-Blind Randomized Controlled Trial
Nutrients doi: 10.3390/nu18050851
Authors:
Chikara Iino
Keita Mikami
Keisuke Furusawa
Satoshi Sato
Kenta Yoshida
Tohru Yamaguchi
Hiroto Bushita
Keita Kinoshita
Yuji Matsui
Seiya Imoto
Takuro Iwane
Yoshinori Tamada
Koichi Murashita
Shigeyuki Nakaji
Tatsuya Mikami
Hirotake Sakuraba
Background: Green tea catechins and inulin may improve metabolic health and modulate the gut microbiota; however, double-blind trials evaluating visceral fat, insulin resistance, and microbiota concurrently are limited. Methods: We conducted a double-blind, parallel-group, randomized, placebo-controlled trial in Japanese adults aged 20–75 years with visceral fat area (VFA) ≥ 80 cm2 and BMI ≥ 23 kg/m2 (trial registration: Japan Registry of Clinical Trials (jRCT), jRCTs021230004 (registered 16 May 2023)). Participants were randomized to a catechin + inulin beverage (catechins 400 mg/day; inulin 2.3 g/day) or placebo for 12 weeks. The primary outcome was the change in VFA (bioelectrical impedance). Secondary outcomes included HOMA-IR, metabolic markers, liver fat assessed by the controlled attenuation parameter (CAP), and genus-level gut microbiota. Results: Ninety-six participants were randomized (catechin + inulin, n = 49; placebo, n = 47); 47 and 44, respectively, were included in the full analysis set for the primary outcome. The 12-week change in VFA did not differ between groups (mean change: +0.91 vs. +4.61 cm2; p = 0.243). HOMA-IR decreased in the catechin + inulin group and increased in the placebo group, yielding a significant between-group difference (mean change: −0.32 vs. +0.18; p = 0.020). No other secondary outcomes showed significant between-group differences. In exploratory microbiota analyses, no genus remained significant after false discovery rate correction; however, Coprococcus and Bifidobacterium showed nominal between-group differences (unadjusted p < 0.05). Changes in Coprococcus were inversely correlated with changes in HOMA-IR (r = −0.28; p = 0.010). Conclusions: Catechin plus inulin for 12 weeks did not reduce visceral fat but was associated with improved insulin resistance. Exploratory analyses suggest a potential association between increased Coprococcus and improved HOMA-IR, warranting further investigation.
Background: Green tea catechins and inulin may improve metabolic health and modulate the gut microbiota; however, double-blind trials evaluating visceral fat, insulin resistance, and microbiota concurrently are limited. Methods: We conducted a double-blind, parallel-group, randomized, placebo-controlled trial in Japanese adults aged 20–75 years with visceral fat area (VFA) ≥ 80 cm2 and BMI ≥ 23 kg/m2 (trial registration: Japan Registry of Clinical Trials (jRCT), jRCTs021230004 (registered 16 May 2023)). Participants were randomized to a catechin + inulin beverage (catechins 400 mg/day; inulin 2.3 g/day) or placebo for 12 weeks. The primary outcome was the change in VFA (bioelectrical impedance). Secondary outcomes included HOMA-IR, metabolic markers, liver fat assessed by the controlled attenuation parameter (CAP), and genus-level gut microbiota. Results: Ninety-six participants were randomized (catechin + inulin, n = 49; placebo, n = 47); 47 and 44, respectively, were included in the full analysis set for the primary outcome. The 12-week change in VFA did not differ between groups (mean change: +0.91 vs. +4.61 cm2; p = 0.243). HOMA-IR decreased in the catechin + inulin group and increased in the placebo group, yielding a significant between-group difference (mean change: −0.32 vs. +0.18; p = 0.020). No other secondary outcomes showed significant between-group differences. In exploratory microbiota analyses, no genus remained significant after false discovery rate correction; however, Coprococcus and Bifidobacterium showed nominal between-group differences (unadjusted p < 0.05). Changes in Coprococcus were inversely correlated with changes in HOMA-IR (r = −0.28; p = 0.010). Conclusions: Catechin plus inulin for 12 weeks did not reduce visceral fat but was associated with improved insulin resistance. Exploratory analyses suggest a potential association between increased Coprococcus and improved HOMA-IR, warranting further investigation. Read More