Stimulatory effects of (-)-epicatechin and its enantiomer (+)-epicatechin on mouse frontal cortex neurogenesis markers and short-term memory: proof of concept

Consumption of (-)-epicatechin (Epi), a cacao flavanol improves cognition. The aim was to compare the effects of (-)-Epi or its stereoisomer (+)-Epi on mouse frontal cortex-dependent short-term working memory and modulators of neurogenesis. Three-month-old male mice (n = 7 per group) were provided by gavage either water (vehicle; Veh), (-)-Epi, at 1 mg kg-1 or (+)-Epi at 0.1 mg per kg of body weight for 15 days. After treatment, spontaneous alternation was evaluated by Y-maze. Brain frontal cortex was isolated for nitrate/nitrite measurements, Western blotting for nerve growth factor (NGF), microtubule associated protein 2 (MAP2), endothelial and neuronal nitric oxide synthase (eNOS and nNOS) and immunohistochemistry for neuronal specific protein (NeuN), doublecortin (DCX), capillary (CD31) and neurofilaments (NF200). Results demonstrate the stimulatory capacity of (-)-Epi and (+)-Epi on markers of neuronal proliferation as per increases in immunoreactive cells for NeuN (74 and 120% respectively), DCX (70 and 124%) as well as in NGF (34.4, 63.6%) and MAP2 (41.8, 63.8%). Capillary density yielded significant increases with (-)-Epi (∼80%) vs. (+)-Epi (∼160%). CD31 protein levels increased with (-)-Epi (∼70%) and (+)-Epi (∼140%). Effects correlated with nitrate/nitrite stimulation by (-)-Epi and (+)-Epi (110.2, 246.5%) and enhanced eNOS phosphorylation (Ser1177) with (-)-Epi and (+)-Epi (21.4, 41.2%) while nNOS phosphorylation only increased with (+)-Epi (18%). Neurofilament staining was increased in (-)-Epi by 135.6 and 84% with (+)-Epi. NF200 increased with (-)-Epi (116%) vs. (+)-Epi (84.5%). Frontal cortex-dependent short-term spatial working improved with (-)-Epi and (+)-Epi (15, 13%). In conclusion, results suggest that both enantiomers, but more effectively (+)-Epi, upregulate neurogenesis markers likely through stimulation of capillary formation and NO triggering, improvements in memory.

Neurological Restorative Effects of (-)-Epicatechin in a Model of Gulf War Illness

Gulf War Illness (GWI) afflicts US military personnel who served in the Persian Gulf War. Suspect causal agents include exposure to pyridostigmine (PB), permethrin (PM) and N,N-diethyl-m-toluamide (DEET). Prominent symptoms include cognitive deficits, such as memory impairment. In aging animal models, we have documented the beneficial effect of the flavanol (-)-epicatechin (Epi) on hippocampus structure and related function. Using a rat model of GWI, we examined the effects of Epi on hippocampus inflammation, oxidative stress, mitochondrial dysfunction, cell death/survival pathways, and memory endpoints. Male Wistar rats underwent 3 weeks of exposure to either vehicles or DEET, PM, PB, and stress. Subgroups of GWI rats were then allocated to receive orally 15 days of either water (vehicle) or 1 mg/kg/day of Epi treatment. Object recognition tasks were performed to assess memory. Hippocampus samples were analyzed. Epi treatment yields significant improvements in short- and long-term memory versus GWI rats. Hippocampus oxidative stress and pro-inflammatory cytokine levels showed significant increases with GWI that were largely normalized with Epi becoming comparable to controls. Significant increases in markers of hippocampus neuroinflammation and cell death were noted with GWI and were also largely reduced with Epi. Neuronal survival signaling pathways were adversely impacted by GWI and were partially or fully restored by Epi. Markers of mitochondrial function were adversely impacted by GWI and were fully restored by Epi. In conclusion, in an animal model of GWI, Epi beneficially impacts recognized markers of hippocampus neuroinflammation, oxidative stress, cell survival, neurotoxicity and mitochondrial function leading to improved memory.