Tiger nut oil unsaponifiables ameliorate high-fat diet-induced metabolic dysfunction and cognitive impairment in mice

Tiger nut (Cyperus esculentus L.), a highly promising oil crop, produces oil rich in unsaturated fatty acids and contains various natural bioactive components. However, the role of these accompanying lipid constituents in the health effects of tiger nut oil has been insufficiently investigated. In this study, tiger nut oil unsaponifiables (TNU) were prepared via saponification followed by solvent extraction, and their chemical composition was identified by GC-MS. The effects of TNU on metabolic dysregulation and cognitive impairment were assessed in a high-fat diet (HFD)-induced obese mouse model. The refined tiger nut oil was found to contain 1.247 ± 0.021% unsaponifiable matter, with phytosterols, tocopherols, and squalene as the major constituents. TNU supplementation resulted in significant attenuation of HFD-induced weight gain and lipid accumulation, improvement in glucose homeostasis and insulin sensitivity, and reduction in hepatic lipid deposition and adipose tissue pathology. Moreover, the hepatic expression of lipogenic genes Srebp-1, Fas, and Acc was markedly downregulated by TNU. In parallel, TNU effectively rescued learning and memory deficits and spatial cognitive impairment in obese mice, suppressed aberrant microglial activation in the hippocampus, alleviated neuroinflammation, and upregulated the mRNA expression of the synaptic protein PSD-95 as well as the neurotrophic factors Bdnf, Ngf, and Ntf-3. In summary, TNU may ameliorate HFD-induced cognitive dysfunction by modulating disorders of glucose and lipid homeostasis and inhibiting the metabolic inflammation-neuroinflammation axis. This study contributes to a theoretical basis for the development of tiger nut oil as a functional dietary lipid resource.