Effects of brown algae (Sargassum thunbergii and Sargassum fusiforme) on the progression of some characteristics of alzheimer’s disease and microglial dysfunction in D-galactose-induced aging rat

The aim of this study was to investigate the protective effects of brown algae, namely Sargassum thunbergii (ST) and Sargassum fusiforme (SF), on memory and cognitive impairment, development of Alzheimer’s disease (AD), oxidative stress, and microglial activation in D-galactose (D-gal)-induced aging rats. Adult male Sprague Dawley rats were administered D-gal (150 mg/kg, i.p.) and a daily dose of hot water extract of ST (150 and 300 mg/kg) or SF (300 mg/kg) or phosphatidylserine [(PS) 30 mg/kg, positive control] for 13 weeks. ST, SF, and PS exhibited improved memory and cognition impairment in both radial arm maze and novel object recognition tests. Administration of ST, SF, and PS attenuated amyloid beta (Aβ) levels by decreasing Aβ production and increasing Aβ clearance-related proteins in the brains of D-gal-induced aging rats. However, only the ST group showed reduced expression of hyper-phosphorylated tau proteins in the brain by suppressing glycogen synthase kinase 3 beta (GSK3β) activities. Moreover, ST, SF, and PS also decreased acetylcholinesterase activity, oxidative stress, microglia activation, and inflammation, and increased the microglial M2 phenotype in the rat brain compared to D-gal-treated control rats. These results indicate that ST and SF could be potential candidates to ameliorate the risk of AD.