The relevance between abnormally elevated serum ceramide and cognitive impairment in Alzheimer's disease model mice and its mechanism.

RATIONALE: The plasma ceramide levels in Alzheimer's disease (AD) patients are found abnormally elevated, which is related to cognitive decline. OBJECTIVES: This research was aimed to investigate the mechanisms of aberrant elevated ceramides in the pathogenesis of AD. RESULTS: The ICR mice intracerebroventricularly injected with Aß1-42 and APP/PS1 transgenic mice were employed as AD mice. The cognitive deficiency, impaired episodic and spatial memory were observed without altered spontaneous ability. The serum levels of p-tau and ceramide were evidently elevated. The modified expressions and activities of glycogen synthase kinase-3ß (GSK-3ß) and protein phosphatase 2A (PP2A) influenced the serum content of p-tau. The levels of ceramide synthesis-related genes including sptlc1, sptlc2, cers2, and cers6 in the liver of AD mice were increased, while the ceramide degradation-related gene asah2 did not significantly change. The regulations of these genes were conducted by activated nuclear factor kappa-B (NF-κB) signaling. NF-κB, promoted by free fatty acid (FFA), also increased the hepatic concentrations of proinflammatory cytokines. The FFA amount was modulated by fatty acid synthesis-related genes acc1 and srebp-1c. Besides, the decreased levels of pre-proopiomelanocortin (pomc) mRNA and increased agouti-related protein (agrp) mRNA were found in the hypothalamus without significant alteration of melanocortin receptor 4 (MC4R) mRNA. The bioinformatic analyses proved the results using GEO datasets and AlzData. CONCLUSIONS: Ceramide was positively related to the increased p-tau and impaired cognitive function. The increased generation of ceramide and endoplasmic reticulum stress in the hypothalamus was positively related to fatty acid synthesis and NF-κB signaling via brain-liver axis.

Sodium butyrate ameliorates the cognitive impairment of Alzheimer's disease by regulating the metabolism of astrocytes.

RATIONALE: Energy metabolism disorder is a widespread feature that exists in the early clinical stages of Alzheimer's disease (AD). Astrocyte is the most numerous and the largest glial cell in the brain. By transporting energetic fuels such as lactate and ketones to neurons, astrocytes play a pivotal role in maintaining the cerebral energy homeostasis. Sodium butyrate (NaB), a type of short-chain fatty acid; its anti-inflammatory effect; and inhibition on histone deacetylases have been widely studied. METHODS: Spatial memory and cognitive ability of mice were assessed by using behavioral tests. Western blotting and ELISA kits were used to detect related protein levels and other biochemical markers, respectively. OBJECTIVES: To prove the therapeutic effect of NaB on AD cognitive impairment and provide possible research ideas for mechanism exploration. RESULTS: Administration of NaB could improve the cognitive impairments induced by Aß25-35 in mice. Furthermore, NaB could promote the differentiation of astrocytes towards A2-neuron-protective subtype, astroglial mitochondrial function, and lactate shuttle between astrocytes and neurons. CONCLUSION: These findings reveal the effect of sodium butyrate on astrocytes, which may improve the pathological status of AD and provide experimental basis for sodium butyrate treatment of AD.

GW9508 ameliorates cognitive impairment via the cAMP-CREB and JNK pathways in APPswe/PS1dE9 mouse model of Alzheimer's disease.

GPR40 was utilized as the drug target to the treatment of diabetes, but the function and mechanisms ameliorating the Alzheimer's disease (AD) remain unknown. In present study, the typical APP/PS1 mouse model was applied to explore the function and mechanism of GPR40 in AD. GPR40 agonist GW9508 and antagonist GW1100 were respectively given by i.c.v. injection to activate/inhibit the GPR40 in the brain of APP/PS1 mice which illustrated the function and mechanism of GPR40 in ameliorating AD symptoms. Morris water maze test, step-through test, Y-maze spontaneous alternation test, open field test and new object recognition test were used to test the cognitive function and memory ability of mice, while molecular biology experiments such as Western blot, immunofluorescence, JC-1 were used to detect the corresponding changes of signal pathways. The results revealed that treatment with GW9508 could significantly ameliorate cognitive deficits of APP/PS1 mice, upregulate the expression levels of cAMP, p-CREB and neurotrophic factors in vivo, while GW9508 also ameliorate Aß1-42-induced neuron damage and downregulate the expression levels of pathological protein such as p-JNK, JNK and apoptosis-related proteins such as IL-6, IL-1ß, TNF-α and caspase-3 in vitro. Meanwhile, high-content screening also showed that GW9508 promoted the cellular differentiation of SH-SY5Y cells, while GW1100 reversed the effects of GW9508. These results suggested that GPR40 was an underlying therapeutic target for the treatment of AD and GPR40 agonist could be explored as the emerging AD therapeutic drug.