Noninvasive Transcutaneous Auricular Vagal Nerve Stimulation Improves Gastric Slow Waves Impaired by Cold Stress in Healthy Subjects.

BACKGROUND/AIMS: Stress is known to inhibit gastric motility. The aim of this study was to investigate the effects and autonomic mechanisms of transcutaneous auricular vagal nerve stimulation (taVNS) on cold stress (CS)-induced impairment in gastric motility that are relevant to the brain-gut interactions in healthy volunteers. MATERIALS AND METHODS: Healthy volunteers (eight women; age 28.2 ± 1.8 years) were studied in four randomized sessions (control, CS, CS + taVNS, and CS + sham-electrical stimulation [sham-ES]). Each session was composed of 30 minutes in the fasting state and 30 minutes after a standard test meal. CS was induced during minutes 10 to 30 after the meal, whereas taVNS or sham-ES was performed during minutes 0 to 30 after the meal. The electrogastrogram and electrocardiogram were recorded for assessing gastric slow waves and autonomic functions, respectively. RESULTS: First, CS decreased the percentage of normal gastric slow waves (59.7% ± 9.8% vs 85.4% ± 4.5%, p < 0.001 vs control); this impairment was dramatically improved by taVNS (75.5% ± 6.3% vs 58.4% ± 12.5%, p < 0.001 vs sham-ES). Second, CS increased the symptom score (22.0 ± 12.1 vs 39.3 ± 11.5, p = 0.001 vs control); taVNS, but not sham-ES, reduced the symptom score (26.0 ± 12.2 vs 38.3 ± 21.6, p = 0.026 vs sham-ES). Third, CS decreased vagal activity assessed from the spectral analysis of heart rate variability (0.21 ± 0.10 vs 0.26 ± 0.11, p < 0.05 vs control) and increased the sympathovagal ratio (4.89 ± 1.94 vs 3.74 ± 1.32, p = 0.048 vs control); taVNS normalized CS-induced suppression in vagal activity (0.27 ± 0.13 vs 0.22 ± 0.10, p = 0.049 vs sham-ES; p > 0.05 vs control) and CS-induced increase in the sympathovagal ratio (3.28 ± 1.61 vs 4.28 ± 2.10, p = 0.042 vs sham-ES; p > 0.05 vs control). CONCLUSION: The noninvasive taVNS improves the CS-induced impairment in gastric pace-making activity, possibly by reversing the detrimental effect of CS on autonomic functions. taVNS may have a therapeutic potential for stress-induced gastric dysmotility.

Dual modulation of gut bacteria and fungi manifests the gut-based anti-hyperlipidemic effect of Coptidis Rhizoma.

Coptidis Rhizoma exhibits potent effects on ameliorating metabolic disease through modulation of gut bacteria. Gut fungi play a significant role on the homeostasis of the intestinal microecosystem and several types of metabolic disorders. Previous studies have mainly concentrated on the function of bacteria on the beneficial effects of Coptidis Rhizoma and its main component berberine, but whether gut fungi are linked to the improvement of glycolipid metabolism disorder of Coptidis Rhizoma is not clear. Here, the anti-hyperlipidemic effects of Coptidis Rhizoma was firstly confirmed in the high fat diet (HFD)-induced mice. The changes of gut fungi and bacteria of the mice treated with Coptidis Rhizoma and the interaction of intestinal fungi and bacteria were investigated. Coptidis Rhizoma significantly decreased serum lipids and inhibited the hepatic lipid accumulation in the HFD-fed mice. Mechanistically, Coptidis Rhizoma reduced the diversity of gut bacteria and fungi, meanwhile changed their composition. Fungus Aspergillus species (A. chevalieri, A. luteovirescens, A. oryzae, A. sp. F51) and Penicillium (P. expansum, P. janthinellum, P. sp. BAB-5649 and P. sp. GZU-BCECYN66-5) were decreased in Coptidis Rhizoma-treated group, while Tilletia bornmuelleri, Tilletia bromi were increased. Furthermore, there are complex association between intestinal fungi and bacteria. For example, fungus Aspergillus (Aspergillus chevalieri, Aspergillus luteovirescens, Aspergillus oryzae) was negative associated with bacterium Blautia coccoides, but positive associated with Lactobacillus (L. johnsonii, L. sparagasseri, L. taiwanensis, L. amylovorus). These results demonstrated that Coptidis Rhizoma might exhibit anti-hyperlipidemic effects through modulation of the intestinal bacteria and fungi composition, and regulation their interaction.