Kefir peptides exhibit antidepressant-like activity in mice through the BDNF/TrkB pathway

Depression is a prevalent, stress-related mental disorder that can lead to serious psychiatric diseases with morbidity and high mortality. Although some functional fermented dairy drinks have promising anxiolytic and antidepressant effects, the mechanism is still not clear. To determine the antidepressant-like effect and the potential molecule mechanism of kefir peptides (KP), various behavioral tests, including the elevated plus maze test, open field test, forced swimming test, and tail suspension test, were used. Administration of 150 mg/kg KP in mice reduced the duration of immobility in the forced swimming test and tail suspension test, elevated the time spent in the open arm and center zone in the elevated plus maze test, and increased the total distance traveled, average speed, and time spent in the center zone in the open field test compared with the mock group. These results indicated that KP dramatically ameliorated the depression-like behaviors. Kefir peptides were further isolated and identified using high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry, from which 3 peptides were identified and designated KFP-1, KFP-3, and KFP-5. Among these peptides, administration of KFP-3 (15 AA residues) remarkably decreased immobility time in the forced swimming test and increased mobility time in the tail suspension test. Therefore, KFP-3 may be the major active peptide with antidepressant activity in KP. Overexpression of brain-derived neurotrophic factor, phosphorylated tropomyosin receptor kinase B, and phosphorylated ERK1/2 protein levels could be detected in the hippocampus under KP administration. Therefore, we suggest that KP improves depressive-like behaviors by activating the brain-derived neurotrophic factor-phosphorylated tropomyosin receptor kinase B signaling pathway. Kefir peptides may serve as a new type of antidepressant dairy product and may provide potent antidepressant effects for clinical use.

Effect of Resveratrol on Reactive Oxygen Species-Induced Cognitive Impairment in Rats with Angiotensin II-Induced Early Alzheimer's Disease †

Recent studies have indicated that several anti-hypertensive drugs may delay the development and progression of Alzheimer’s disease (AD). However, the relationships among AD, hypertension, and oxidative stress remain to be elucidated. Here, we aimed to determine whether reactive oxygen species (ROS) reduction by resveratrol in the brain leads to cognitive impairment reduction in rats with angiotensin II (Ang-II)-induced early AD. Male Wistar Kyoto (WKY) rats with Ang-II-induced AD were treated with losartan or resveratrol for two weeks. Our results show decreased blood pressure, increased hippocampal brain-derived neurotrophic factor (BDNF) level, and decreased nucleus tractus solitarius (NTS) ROS production in the Ang-II groups with losartan (10 mg/kg), or resveratrol (10 mg/kg/day) treatment. Furthermore, losartan inhibition of hippocampal Tau^T231 phosphorylation activated Akt^S473 phosphorylation, and significantly abolished Ang-II-induced Aβ precursors, active caspase 3, and glycogen synthase kinase 3β (GSK-3β)^Y216 expressions. Consistently, resveratrol showed similar effects compared to losartan. Both losartan and resveratrol restored hippocampal-dependent contextual memory by NADPH oxidase 2 (NOX2) deletion and superoxide dismutase 2 (SOD2) elevation. Our results suggest that both losartan and resveratrol exert neuroprotective effects against memory impairment and hippocampal damage by oxidative stress reduction in early stage AD rat model. These novel findings indicate that resveratrol may represent a pharmacological option similar to losartan for patients with hypertension at risk of AD during old age.