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Probiotics and prebiotics have received attention in alleviating neurodegenerative diseases. Lactobacillus plantarum ( L. plantarum ) 69-2 was combined with galactooligosaccharides (GOS) and supplemented in a d-galactose (d-gal)-induced neurodegeneration and memory impairment mice model to explore its effects on the brain and the regulation of short-chain fatty acids. The results showed that the L. plantarum -GOS supplementation inhibited d-gal-induced oxidative stress and increased the brain's nuclear factor erythroid 2-related factor 2 (Nrf2) levels. Butyrate, a metabolite of the gut microbiota regulated by L. plantarum combined with GOS, inhibits p-JNK expression, downregulates pro-apoptotic proteins expression and the activation of inflammatory mediators, and upregulates synaptic protein expression. This might be a potential mechanism for L. plantarum 69-2 combined with GOS supplementation to alleviate d-gal-induced neurodegeneration and memory impairment. This study sheds new light on the development of aging-related neuroprotective dietary supplements based on the gut-brain axis.

This study investigated the effects of a physiologically active peptide derived from rice bran (KF-8) on oxidative stress in d-galactose (d-gal)-induced aging mice and the underlying molecular mechanisms. The aging model was developed by subcutaneously injecting Institute of Cancer Research mice with 250 mg/kg d-gal daily for 12 weeks and simultaneously treating them with 30 mg/kg KF-8. The relative expression levels of Nrf2 and NF-κB in the liver were determined by the western blot. The regulation of Nrf2 and NF-κBp65 by KF-8 was further validated in NIH/3T3 cells. Compared with the control mice, the aging mice had significantly decreased body weights as well as superoxide dismutase and GSH-Px levels ( p < 0.05); however, they had increased serum reactive oxygen species and malondialdehyde and 8-hydroxydeoxyguanosine levels accompanied by aortic and brain injuries. They also had elevated RAGE, TLR4, IκB, Bax, and caspase-8 expressions and NF-κB/p65 phosphorylation but reduced BcL-2 expression in the liver. Moreover, in vitro experiments demonstrated that the pretreatment of H 2 O 2 -treated NIH/3T3 cells with KF-8 significantly mitigated the NF-κB signaling and attenuated the Nrf2 nuclear transport (both p < 0.05). In conclusion, KF-8 treatment inhibited aging-induced oxidative stress-related organ injury in mice by attenuating NF-κB/p38 signaling and preserving Nrf2 activity.

Oxidative stress and neuroinflammation are considered as crucial culprits in Alzheimer's disease (AD). Torularhodin, a carotenoid pigment, possesses powerful antioxidant activity. This study aimed to elucidate the protective effects of torularhodin in the AD-like mouse model and investigated the underlying mechanisms. Behavioral and histopathological results suggested that torularhodin relieved cognitive impairments, attenuated Aβ accumulation, and inhibited glial overactivation in d-gal/AlCl 3 -induced ICR mice. Simultaneously, torularhodin also markedly increased antioxidant enzyme capacities, lowered the contents of RAGE, and reduced levels of inflammatory cytokines. Western blot results showed that torularhodin ameliorated neuronal oxidative damage via activation of Nrf2 translocation, upregulation of HO-1, and inactivation of NF-κB in vivo and in vitro. Thus, torularhodin effectively ameliorated cognitive impairment, oxidative stress, and neuroinflammation, possibly through the Nrf2/NF-κB signaling pathways, suggesting torularhodin might offer a promising prevention strategy for neurodegenerative diseases.

Maltol, a maillard reaction product from ginseng ( Panax ginseng C. A. Meyer), has been confirmed to inhibit oxidative stress in several animal models. Its beneficial effect on oxidative stress related brain aging is still unclear. In this study, the mouse model of d-galactose (d-Gal)-induced brain aging was employed to investigate the therapeutic effects and potential mechanisms of maltol. Maltol treatment significantly restored memory impairment in mice as determined by the Morris water maze tests. Long-term d-Gal treatment reduced expression of cholinergic regulators, i.e., the cholineacetyltransferase (ChAT) (0.456 ± 0.10 vs 0.211 ± 0.03 U/mg prot), the acetylcholinesterase (AChE) (36.4 ± 5.21 vs 66.5 ± 9.96 U/g). Maltol treatment prevented the reduction of ChAT and AChE in the hippocampus. Maltol decreased oxidative stress levels by reducing levels of reactive oxygen species (ROS) and malondialdehyde (MDA) production in the brain and by elevating antioxidative enzymes. Furthermore, maltol treatment minimized oxidative stress by increasing the phosphorylation levels of phosphatidylinositol-3-kinase (PI3K), protein kinase B (Akt), nuclear factor-erythroid 2-related factor 2 (Nrf2), and hemeoxygenase-1 (HO-1). The above results clearly indicate that supplementation of maltol diminishes d-Gal-induced behavioral dysfunction and neurological deficits via activation of the PI3K/Akt-mediated Nrf2/HO-1 signaling pathway in brain. Maltol might become a potential drug to slow the brain aging process and stimulate endogenous antioxidant defense capacity. This study provides the novel evidence that maltol may slow age-associated brain aging.

Torularhodin is a natural product extracted from Sporidiobolus pararoseus and has a similar chemical structure to β-carotene. The antioxidative effects of torularhodin were investigated using DPPH, ABTS, a cell oxidative damage model in vitro, and a d-galactose-induced liver-injured mouse model in vivo. Cell experiments demonstrated that torularhodin had a powerful effect on oxidative damage caused by H 2 O 2 to AML12 cells. Torularhodin significantly reduced inflammatory cytokines and increased the activity of antioxidant enzymes both in mouse serum and the liver. The inhibition of d-galactose-induced oxidative damage in the liver was correlated with the torularhodin-mediated effects on improving the activity of Nrf2/HO-1, reducing the expression of Bax and NF-κB p65 by western blot analysis. RT-PCR results demonstrated torularhodin upregulated the antioxidative mRNA expression of Nrf2, NQO1, and HO-1 in the liver. In summary, torularhodin significantly scavenged free radicals and prevented oxidative damage in vitro and reduced d-galactose-induced liver oxidation via promotion of the Nrf2/HO-1 pathways in vivo.

Brain aging is commonly associated with neurodegenerative disorders, but the ameliorative effect of krill oil and the underlying mechanism remain unclear. In this study, the components of krill oil were measured, and the antiaging effects of krill oil were investigated in mice with d-galactose (d-gal)-induced brain aging via proteomics and gut microbiota analysis. Krill oil treatment decreased the expression of truncated dopamine- and cAMP-regulated phosphoproteins and proteins involved in the calcium signaling pathway. In addition, the concentrations of dopamine were increased in the serum ( p < 0.05) and brain ( p > 0.05) due to the enhanced expressions of tyrosine-3-monooxygenase and aromatic l-amino acid decarboxylase. Moreover, krill oil alleviated gut microbiota dysbiosis, decreased the abundance of bacteria that consume the precursor tyrosine, and increased the abundance of Lactobacillus spp. and short-chain fatty acid producers. This study revealed the beneficial effect of krill oil against d-gal-induced brain aging and clarified the underlying mechanism through proteomics and gut microbiota analysis.

Lycium ruthenicum Murr. (LR) is a perennial shrub commonly used as a nutritional food and medicine. Herein, we identified 12 anthocyanins from LR, with petunidin derivatives constituting approximately 97% of the total anthocyanin content. Furthermore, the potential mechanism of anthocyanins exerting neuroprotective effects in d-galactose (d-gal)-treated rats was explored. Behavioral results showed that anthocyanins relieved d-gal-induced memory disorder. Additionally, anthocyanins reduced receptor for advanced glycation end products (RAGE) and suppressed oxidative stress caused by d-gal. Anthocyanins suppressed microgliosis and astrocytosis and reduced the overexpression of nuclear factor kappa B (NF-κB), interleukin-1-β (IL-1β), cyclooxygenase-2 (COX-2), and tumor necrosis factor-α (TNF-α). Moreover, anthocyanins lowered C-jun N-terminal kinase ( p-JNK), caspase-3 levels, and the B-cell lymphoma 2-associated X protein/B-cell lymphoma 2 (Bax/Bcl-2) ratio. Thus, anthocyanins from LR attenuated memory disfunction, neuroinflammation, and neurodegeneration caused by d-gal, possibly through the RAGE/NF-κB/JNK pathway, representing a promising, safe candidate for prevention and therapy of neurodegenerative diseases.

To discern whether tuna oil modulates the expression of brain proteins and the gut microbiota structure during aging induced by d-galactose, we generated an aging mouse model with d-galactose treatment, and the mice showed aging and memory deterioration symptoms according to physiological and biochemical indices. Treatment with different doses of tuna oil alleviated the symptoms; the high dose showed a better effect. Subsequently, brain proteomic analysis showed the differentially expressed proteins were involved in damaged synaptic system repairment and signal transduction system enhancement. In addition, tuna oil treatment restored the diversity of gut microbiota, 27 key operational taxonomic units, which were identified using a redundancy analysis and were significantly correlated with at least one physiological index and three proteins or genes. These findings suggest that the combination of proteomics and gut microbiota is an effective strategy to gain novel insights regarding the effect of tuna oil treatment on the microbiota-gut-brain axis.

The neuroprotective effects of s-allyl cysteine, s-ethyl cysteine, and s-propyl cysteine in D-galactose (DG)-treated mice were examined. DG treatment increased the formation of Aβ(1-40) and Aβ(1-42), enhanced mRNA expression of β-amyloid precursor protein (APP) and β-site APP cleavage enzyme 1 (BACE1), and reduced neprilysin expression in brain (P < 0.05); however, the intake of three test compounds significantly decreased the production of Aβ(1-40) and Aβ(1-42) and suppressed the expression of APP and BACE1 (P < 0.05). DG treatments declined brain protein kinase C (PKC) activity and mRNA expression (P < 0.05). Intake of test compounds significantly retained PKC activity, and the expression of PKC-α and PKC-γ (P < 0.05). DG treatments elevated brain activity and mRNA expression of aldose reductase (AR) and sorbitol dehydrogenase as well as increased brain levels of carboxymethyllysine (CML), pentosidine, sorbitol, and fructose (P < 0.05). Test compounds significantly lowered AR activity, AR expression, and CML and pentosidine levels (P < 0.05). DG treatments also significantly increased the formation of reactive oxygen species (ROS) and protein carbonyl and decreased the activity of glutathione peroxidase (GPX), superoxide dismutase (SOD), and catalase (P < 0.05); however, the intake of test compounds in DG-treated mice significantly decreased ROS and protein carbonyl levels and restored brain GPX, SOD, and catalase activities (P < 0.05). These findings support that these compounds via their anti-Aβ, antiglycative, and antioxidative effects were potent agents against the progression of neurodegenerative disorders such as Alzheimer's disease.