Neuroinflammation plays a significant role in the aging process and the pathophysiology of neurodegenerative diseases, such as Alzheimer’s disease. Accordingly, possible therapeutic strategies aimed at anti-inflammatory effects may be beneficial to brain health. Walnut kernels contain large quantities of unsaturated fatty acids, peptides, and phenolic compounds that have anti-inflammatory effects. The long-term intake of walnuts has been found to improve cognitive function and memory in rats and humans. However, the modulatory effect of walnuts on neuroinflammation has received much less attention. This review focuses on the potential influence and main regulating mechanisms of walnuts and their active ingredients on neuroinflammation, including the regulation of microglia activation induced by amyloid β or lipopolysaccharides, inhibition of peripheral inflammation mediated by macrophages, reduction in oxidative stress by decreasing free radical levels and boosting antioxidant defenses, and control of gut microbes to maintain homeostasis. However, the majority of evidence of the beneficial effects of walnuts or their components on neuroinflammation and neurodegeneration comes from experimental work, whereas evidence from clinical studies on the beneficial effects is scarcer and less conclusive. This review aims to provide new insights into the neuroinflammation-regulating mechanisms and natural active ingredients of walnuts and the development of walnut-based functional foods for the alleviation of neurodegenerative diseases.

Exploring approaches to regulate meristem is of special importance and broad interest. In this study, we found that the flavonoid scutellarin, which has a 6-hydroxyl and a 7-glucoside, increased root length through the transcription factor NUTCRACKER (NUC). This root lengthening disappeared in NUC-knockout and reappeared in NUC-rescue plants. Scutellarin induced NUC expression and promoted the division of cortex/endodermal initials. In contrast, naringenin, which has same chemical backbone but without 6-hydroxyl and with 7-hydroxyl group, showed the opposite or no effects. Our results demonstrate that scutellarin promotes root length through NUC-mediated regulatory pathways and reveal that flavonoids with and without the 6-hydroxyl and 7-glucoside have positive and negative effects on meristem size, respectively.