Neuroprotection of soyabean isoflavone co-administration with folic acid against beta-amyloid 1-40-induced neurotoxicity in rats

A Systematic Review of Dietary Supplements in Alzheimer's Disease

Alzheimer's is the most common neurodegenerative disease among the aging population, which has been a major global challenge. The pathogenesis of the disease is still undetermined but postulated to be involved in various mechanisms including oxidative stress, excitotoxicity, inflammation, cell death, genetic factors, protein accumulation, and degradation. There are few Food and Drug Administration (FDA)-approved drugs available for the treatment of Alzheimer's disease (AD) that have limited benefits along with associated adverse effects. A retrospective review of randomized double-blind controlled trials of various supplements used in AD patients was performed on a PubMed search from January 1983 to March 2022. We found 10 articles that have shown positive outcomes in various cognitive domains. We conclude that there should be a global standard to endorse the quality and safety of these supplements.

The Use of Bioactive Compounds in Hyperglycemia- and Amyloid Fibrils-Induced Toxicity in Type 2 Diabetes and Alzheimer’s Disease

It has become increasingly apparent that defective insulin signaling may increase the risk for developing Alzheimer’s disease (AD), influence neurodegeneration through promotion of amyloid formation or by increasing inflammatory responses to intraneuronal β-amyloid. Recent work has demonstrated that hyperglycemia is linked to cognitive decline, with elevated levels of glucose causing oxidative stress in vulnerable tissues such as the brain. The ability of β-amyloid peptide to form β-sheet-rich aggregates and induce apoptosis has made amyloid fibrils a leading target for the development of novel pharmacotherapies used in managing and treatment of neuropathological conditions such as AD-related cognitive decline. Additionally, deposits of β-sheets folded amylin, a glucose homeostasis regulator, are also present in diabetic patients. Thus, therapeutic compounds capable of reducing intracellular protein aggregation in models of neurodegenerative disorders may prove useful in ameliorating type 2 diabetes mellitus symptoms. Furthermore, both diabetes and neurodegenerative conditions, such as AD, are characterized by chronic inflammatory responses accompanied by the presence of dysregulated inflammatory biomarkers. This review presents current evidence describing the role of various small bioactive molecules known to ameliorate amyloidosis and subsequent effects in prevention and development of diabetes and AD. It also highlights the potential efficacy of peptide–drug conjugates capable of targeting intracellular targets.

Isoflavones derived from plant raw materials: bioavailability, anti-cancer, anti-aging potentials, and microbiome modulation

Isoflavones are secondary metabolites that represent the most abundant category of plant polyphenols. Dietary soy, kudzu, and red clover contain primarily genistein, daidzein, glycitein, puerarin, formononetin, and biochanin A. The structural similarity of these compounds to β-estradiol has demonstrated protection against age-related and hormone-dependent diseases in both genders. Demonstrative shreds of evidence confirmed the fundamental health benefits of the consumption of these isoflavones. These relevant activities are complex and largely driven by the source, active ingredients, dose, and administration period of the bioactive compounds. However, the preclinical and clinical studies of these compounds are greatly variable, controversial, and still with no consensus due to the non-standardized research protocols. In addition, absorption, distribution, metabolism, and excretion studies, and the safety profile of isoflavones have been far limited. This highlights a major gap in understanding the potentially critical role of these isoflavones as prospective replacement therapy. Our general review exclusively focuses attention on the crucial role of isoflavones derived from these plant materials and critically highlights their bioavailability, possible anticancer, antiaging potentials, and microbiome modulation. Despite their fundamental health benefits, plant isoflavones reveal prospective therapeutic effects that worth further standardized analysis.

The MTHFR C677T polymorphism influences the efficacy of folic acid supplementation on the nerve conduction studies in patients with diabetic polyneuropathy; A randomized, double blind, placebo-controlled study

Background:

Among patients with diabetic polyneuropathy, the status of folic acid, homocysteine, and nerve conduction studies (NCS) variations has been associated with methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms. The objective of the present study is to assess B9 vitamin supplementation associated with MTHRF C677T polymorphism can be effective on NCS variations in patients.

Materials and Methods:

This study is a randomized, double-blind, placebo-controlled study. Patients were randomly allocated to either intervention (1 mg of folic acid, n = 40) or placebo (n = 40) groups based on parallel group design. Blood samples were taken to determine the serum levels of folic acid and homocysteine. The NCS data were collected for the assessment of diabetic neuropathy. Genotyping was performed for C677T polymorphism of the MTHFR gene.

Results:

Four months after intervention, patients significantly observed change of serum folic acid and homocysteine levels based on C677T genotypes in the MTHFR gene. The amplitude of sensory peroneal nerve between intervention and placebo groups with CC genotype was significantly different (2.8 ± 1.6 vs. 1.9 ± 1.1). However, peak latency and amplitude of sensory sural nerve between CC (3.8 ± 1.8 vs. 4.0 ± 1.5 for peak latency and 3.5 ± 1.0 vs. 2.5 ± 1.0 for amplitude; and CT + TT genotypes (3.7 ± 1.7 vs. 3.9 ± 1.3 for peak latency and 3.2 ± 1.0 vs. 2.3 ± 1.1 for amplitude) were significant. Furthermore, significant difference for variables of motor tibial nerve and motor peroneal nerve amplitude was observed in different groups of MTHFR C677T genotypes (5.4 ± 2.9 vs. 4.6 ± 3.2 for onset-latency of tibial nerve between CC genotype; 4.8 ± 2.8 vs. 4.6 ± 3.2 for onset-latency of tibial nerve between CT + TT genotype; 0.6 ± 0.2 vs. 0.3 ± 0.1 for amplitude of tibial nerve between CC genotype; 0.5 ± 0.3 vs. 0.3 ± 0.2 for amplitude of tibial nerve between CT + TT genotype; 26.0 ± 13.3 vs. 23.2 ± 13.4 for velocity of tibial nerve between CC genotype; 26.0 ± 13.7 vs. 23.1 ± 9.6 for velocity of tibial nerve between CT + TT genotype; 1.6 ± 1.0 vs. 0.9 ± 0.7 for amplitude of peroneal nerve between CC genotype; 1.4 ± 0.7 vs. 0.9 ± 0.5 for amplitude of peroneal nerve between CT + TT genotype).

Conclusion:

The study determined that MTHFR C677T polymorphism effects the efficacy of folic acid supplementation on serum folic acid, homocysteine levels and some NCS parameters in diabetic polyneuropathy patients.

Effect of folic acid supplementation on nerve conduction velocity in diabetic polyneuropathy patients

OBJECTIVES

In diabetic polyneuropathy (DPN) patients, the effect of folic acid and homocysteine has been related to components of nerve conduction velocity (NCV). The objective of this study was to determine the effect of folic acid supplementation on NCV in DPN patients.

METHODS

Patients were randomized to receive either 1 mg of folic acid (n = 40) or placebo (n = 40) for 16 weeks. Blood samples were collected to assess serum folic acid and homocysteine concentrations, and NCV was performed for assessment of diabetic neuropathy.

RESULTS

At 16 weeks, in the supplemented group, serum levels of folic acid (p < 0.001) increased, homocysteine concentrations decreased (p < 0.001), with no change in serum vitamin B12 levels. There was a significant increase in sensory sural amplitude (p < 0.001), and components of motor nerves, including amplitude (p = 0.001) and velocity (p < 0.001), but decreased onset latency of peroneal (p = 0.019) and tibial (p = 0.011) motor nerves.

CONCLUSION

Our data suggest that supplementation with 1 mg of folic acid for 16 weeks may be useful for enhancing NCV in DPN patients.

Neuroprotective Effects of Soy Isoflavones on Scopolamine-Induced Amnesia in Mice

In the recent years, interest in soybean as a neuroprotective nutrient in the management of Alzheimer’s disease (AD) has increased and soy isoflavones (SI), as kinds of soybean phytochemicals, are thought to be biologically active components that confer this beneficial effect against neurodegenerative diseases. However, the neuroprotective effect of SI is not well understood. Therefore, the present study (30 days) was conducted to investigate the neuroprotective effects of soy isoflavones (SI) on scopolamine (SCOP)-induced memory impairments in Institute of Cancer Research (ICR) mice (aged 4 weeks) and to elucidate its underlying mechanisms of action. SI (40 mg/kg) administration improved the cognitive performance of SCOP-treated mice in an object location recognition task and the Morris water maze test. SI (40 mg/kg) administration significantly enhanced cholinergic system function and suppressed oxidative stress levels in the hippocampus of SCOP-treated mice. Furthermore, SI (40 mg/kg) treatment markedly upregulated the phosphorylation levels of extracellular signal-regulated kinase (ERK), cAMP response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) expression levels in the hippocampus. Taken together, these results demonstrated that soy isoflavones exerted a significant neuroprotective effect on cognitive dysfunctions induced by scopolamine, suggesting that soy isoflavones could be a good candidate for possible treatment of neurodegenerative diseases, such as Alzheimer’s disease (AD).

The toxic influence of dibromoacetic acid on the hippocampus and pre-frontal cortex of rat: involvement of neuroinflammation response and oxidative stress

Dibromoacetic acid (DBA) exsits in drinking water as a by-product of disinfection as a result of chlorination or ozonation processes. Hippocampus and pre-frontal cortex are the key structures in memory formation and weanling babies are more sensitive to environmental toxicant than adults, so this study was conducted to evaluate the potential neurotoxicity effects of DBA exposure when administered intragastrically for 4 weeks to weanling Sprague-Dawley rats, at concentration of 0, 20, 50, 125 mg/kg via the neurobehavioral and neurochemical effects. Results indicated that animals weight gain and food consumption were not significantly affected by DBA. However, morris water maze test showed varying degrees of changes between control and high-dose group. Additionally, the level of malondialdehyde (MDA) and generation of reactive oxygen species (ROS) in the hippocampus and pre-frontal cortex of rats increased significantly. The activities of total superoxide dismutase (SOD) and the glutathione (GSH) content in the hippocampus and pre-frontal cortex of rats decreased significantly after treatment with DBA. Treatment with DBA increased the protein and mRNA expression of Iba-1, NF-κB, TNF-α, IL-6, IL-1β and HO-1 in the hippocampus and pre-frontal cortex of rats. These data suggested that DBA had a toxic influence on the hippocampus and pre-frontal cortex of rats, and that the mechanism of toxicity might be associated with the neuroinflammation response and oxidative stress.

Protection against β-amyloid-induced neurotoxicity by naturally occurring Z-ligustilide through the concurrent regulation of p38 and PI3-K/Akt pathways

Alzheimer's disease (AD) is primarily characterized by the progressive loss of functional neurons in the brain. Therefore, compounds with neuroprotective property may have therapeutic value in treating AD. Z-ligustilide (Z-LIG) is an essential oil originally isolated from umbelliferous plants. In the current study, the neuroprotective effects and underlying mechanisms of Z-LIG against fibrillar aggregates of Aβ_25-35 and Aβ_1-42-induced neurotoxicity were investigated in both SH-SY5Y cells and differentiated PC12 cells. Z-LIG at 1-30 μM provided an effective neuroprotection, as evidenced by the increase in cell viability, as well as the decrease in LDH release and intracellular accumulation of reactive oxygen species. Additionally, Z-LIG markedly blocked Aβ fibrils-induced condensed nuclei and sub-G1 accumulation suggestive of apoptosis. Furthermore, Z-LIG substantially reversed the activation of phosphorylated p38 and the inhibition of phosphorylated Akt caused by Aβ_25-35. LY294002, the specific inhibitor of PI3-K, significantly abrogated the protein expression of up-regulated phosphorylated Akt offered by Z-LIG. Most importantly, siRNA-mediated knockdown of PI3-K and p38 significantly abolished the neuroprotective effects of Z-LIG. The results taken together indicate that Z-LIG protects against Aβ fibrils-induced neurotoxicity possibly through the inhibition of p38 and activation of PI3-K/Akt signaling pathways concurrently. Z-LIG might be a potential candidate for further preclinical study aimed at the prevention and treatment of AD.

Cognitive Effects of Soy Isoflavones in Patients with Alzheimer's Disease

BACKGROUND

In a previous trial, treatment with soy isoflavones was associated with improved nonverbal memory, construction abilities, verbal fluency, and speeded dexterity compared to treatment with placebo in cognitively healthy older adults.

OBJECTIVE

The current trial aimed to examine the potential cognitive benefits of soy isoflavones in patients with Alzheimer's disease.

METHODS

Sixty-five men and women over the age of 60 were treated with 100 mg/day soy isoflavones, or matching placebo capsules for six months. APOE genotype was determined for all participants. Cognitive outcomes and plasma isoflavone levels were measured at baseline, and at two additional time points: three and six months after baseline.

RESULTS

Of the sixty-five participants enrolled, thirty-four (52.3% ) were women, and 31 (47.7% ) were APOEɛ4 positive. Average age was 76.3 (SD = 7.2) years. Fifty-nine (90.8% ) subjects completed all study visits. Plasma isoflavone levels increased in subjects treated with soy isoflavones compared to baseline and to placebo, although intersubject variability in plasma levels was large. No significant differences in treatment effects for cognition emerged between treatment groups or genders. Exploratory analyses of associations between changes in cognition and plasma isoflavone levels revealed an association between equol levels, and speeded dexterity and verbal fluency.

CONCLUSIONS

Six months of 100 mg/day treatment with soy isoflavones did not benefit cognition in older men and women with Alzheimer's disease. However, our results suggest the need to examine the role of isoflavone metabolism, i.e., the ability to effectively metabolize soy isoflavones by converting daidzen to equol when attempting to fully clarify the cognitive effects of isoflavones.

The effect of soybean isoflavone on the dysregulation of NMDA receptor signaling pathway induced by β-amyloid peptides 1-42 in rats

Synaptic damage is the key factor of cognitive impairment. The purpose of this study was to understand the effect of soybean isoflavone (SIF) on synaptic damage induced by β-amyloid peptide 1-42 (Aβ1-42) in rats. Adult male Wistar rats were randomly divided into control, Aβ1-42, SIF, and SIF + Aβ1-42 (SIF pretreatment) groups according to body weight. SIF was treated orally by gavage in SIF and SIF + Aβ1-42 groups. After 14 days pretreatment with SIF or vehicle, Aβ1-42 was injected into the lateral cerebral ventricle of rats in Aβ1-42 and SIF + Aβ1-42 groups using miniosmotic pump. The level of Aβ1-42 and the expression of N-methyl-D-aspartic-acid receptor (NMDAR) were observed by immunohistochemistry. Reverse transcriptase polymerase chain reaction was used to detect the mRNA levels of NMDAR, calmodulin (CaM), calcium/CaM-dependent protein kinase II (CaMKII), cAMP-response element binding protein (CREB), and brain-derived neurotrophic factor (BDNF). The results showed that Aβ1-42 down-regulated mRNA and protein expression of the NR1 and NR2B subunits of NMDAR, SIF pretreatment could reverse these changes. The mRNA expression of CaM, CaMKII, CREB, and BDNF were down-regulated by Aβ1-42, but they were all regulated by SIF pretreatment. These results suggest that SIF pretreatment could antagonize the neuron damage in rats induced by Aβ1-42, and its mechanism might be associated with the NMDA receptor and CaM/CaMKII/CREB/BDNF signaling pathway, which are the synaptic plasticity-related molecules.

Genistein alleviates β-amyloid-induced inflammatory damage through regulating Toll-like receptor 4/nuclear factor κB

Genistein (GEN), a major soybean isoflavone (SIF), might possess neuroprotective properties through its anti-inflammatory activity. We hypothesized that GEN could prevent the inflammatory damage detected in C6 cells induced by β-amyloid peptides 25-35 (Aβ25-35). Accordingly, we evaluated the inflammatory damage induced by Aβ25-35 and the protective effect of GEN against Aβ25-35 in C6 cells. In our study, the C6 glial cells (rats glioma cell lines) were preincubated with or without GEN for 2 h following incubation with Aβ25-35 for another 24 h. Then, methylthiazolyl tetrazolium (MTT) assay was used to assess the cell viability. Immunofluorescence staining was used to identify the C6 cells. Inflammatory factors tumor necrosis factor (TNF)-α and interleukin (IL)-1β were analyzed by using enzyme-linked immunosorbent assay (ELISA). Western blot analysis and reverse transcription-polymerase chain reaction analysis were performed to assess the expression of Toll-like receptors 4 (TLR4), inhibitor of kappaB-alpha (IκB-α). The current results showed that GEN could alleviate Aβ25-35-induced cell apoptosis and prevent Aβ25-35-induced TNF-α and IL-1β release from C6 cells. In addition, GEN prevented Aβ25-35-induced upregulation of the gene and protein expression of TLR4, and GEN significantly upregulated the expression of IκB-α in C6 cells damaged by Aβ25-35. These results suggest that GEN can alleviate the inflammatory stress caused by Aβ25-35 treatment, which might be associated with the neuroprotective effect of GEN regulating the TLR4/NFκB signaling pathway.

An investigation into the ameliorating effect of black soybean extract on learning and memory impairment with assessment of neuroprotective effects

BACKGROUND

The physiological effects of the non-anthocyanin fraction (NAF) in a black soybean seed coat extract on Aβ-induced oxidative stress were investigated to confirm neuroprotection. In addition, we examined the preventive effect of NAF on cognitive defects induced by the intracerebroventricular (ICV) injection of Aβ.

METHODS

Levels of cellular oxidative stress were measured using 2',7'-dichlorofluorescein diacetate (DCF-DA). Neuronal cell viability was investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assay. To investigate in vivo anti-amnesic effects of NAF by using Y-maze and passive avoidance tests, the learning and memory impairment in mice was induced by Aβ. After in vivo assays, acetylcholinesterase (AChE) activity and level of malondialdehyde (MDA) in the mouse brain were determined to confirm the cognitive effect. Individual phenolics of NAF were qualitatively analyzed by using an ultra-performance liquid chromatography (UPLC) Accurate-Mass Quadrupole Time of-Flight (Q-TOF) UPLC/MS.

RESULTS

A NAF showed cell protective effects against oxidative stress-induced cytotoxicity. Intracellular ROS accumulated through Aβ1-40 treatment was significantly reduced in comparison to cells only treated with Aβ1-40. In MTT and LDH assay, the NAF also presented neuroprotective effects on Aβ1-40-treated cytotoxicity. Finally, the administration of this NAF in mice significantly reversed the Aβ1-40-induced cognitive defects in in vivo behavioral tests. After behavioral tests, the mice brains were collected in order to examine lipid peroxidation and AChE activity. AChE, preparation was inhibited by NAF in a dose-dependent manner. MDA generation in the brain homogenate of mice treated with the NAF was decreased. Q-TOF UPLC/MS analyses revealed three major phenolics from the non-anthocyanin fraction; epicatechin, procyanidin B1, and procyanidin B2.

CONCLUSIONS

The results suggest that the NAF in black soybean seed coat extracts may improve the cytotoxicity of Aβ in PC12 cells, possibly by reducing oxidative stress, and also have an anti-amnesic effect on the in vivo learning and memory deficits caused by Aβ. Q-TOF UPLC/MS analyses showed three major phenolics; (-)-epicatechin, procyanidin B1, and procyanidin B2. Above results suggest that (-)-epicatechins are the major components, and contributors to the anti-amnesic effect of the NAF from black soybean seed coat.

Genistein antagonizes inflammatory damage induced by β-amyloid peptide in microglia through TLR4 and NF-κB

OBJECTIVES

Microglia activation and neuroinflammation have been associated with the pathogenesis of neurodegenerative disorders such as Alzheimer's disease (AD). Toll-like receptor 4 (TLR4) and nuclear factor (NF)-κB-mediated signal pathways exert key modulating roles in the inflammatory processes. The aim of the present study was to investigate whether genistein (Gen) has a neuroprotective effect against inflammatory damage induced by β-amyloid peptide25-35 (Aβ25-35) through the TLR4 and NF-κB-mediated signal pathways.

METHODS

BV-2 microglia cells were preincubated with Gen for 2 h and then treated with 25 μM Aβ25-35 for another 24 h. The expression of inflammatory mediators, TLR4 and NF-κB and the activity of NF-κB were measured.

RESULTS

The results showed that Gen could attenuate the cytotoxicity and inflammatory damage induced by Aβ25-35. Gen also significantly reversed Aβ25-35-induced up-regulation of TLR4 and NF-κB expression and the DNA binding and transcriptional activities of NF-κB.

CONCLUSION

These results indicated that Gen could alleviate the inflammation caused by Aβ25-35 treatment, which might be associated with the regulation of the TLR4/NF-κB signal pathway.

Neuroprotective effects of folic acid on experimental diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is widely considered as a degenerative complication of diabetic patients. The clinical effectiveness of folic acid (FA) on DPN is uncertain. The objective of the present study was to determine the effect of FA in DPN using electromyography (EMG), histopathological examination, immunohistochemistry, inclined plane test, and malondialdehyde (MDA) levels as a marker for lipid peroxidation in experimental diabetic rats. A total of 21 Sprague Dawley rats were randomly divided into 3 groups: control group, diabetes group, and FA-treated group. In EMG, compound muscle action potential (CMAP) amplitude in the sciatic nerve was lower in the diabetes group compared with the control group. CMAP amplitude in the sciatic nerve was higher in the FA-treated group when compared with the diabetes group. Distal latency and CMAP duration in the sciatic nerve were lower in the FA-treated group when compared with the diabetes group. In histopathological examination of the sciatic nerve, peripheral fibrosis was present in the diabetic group; the fibrosis was lower in the FA-treated group. In comparison with the diabetes group, the expression of nerve growth factor (NGF) was higher in the FA-treated group. The scores for the inclined plane test were lower in the diabetes group and higher in the FA-treated group than the control group. The MDA levels were significantly lower in the FA-treated group when compared with the diabetes group.

The study suggests that FA can protect diabetic rats against DPN and that the underlying mechanism for this may be related to improvement of the expression of NGF and lower MDA levels.

Soybean isoflavone ameliorates β-amyloid 1-42-induced learning and memory deficit in rats by protecting synaptic structure and function

This research aims to investigate whether soybean isoflavone (SIF) could alleviate the learning and memory deficit induced by β-amyloid peptides 1-42 (Aβ 1-42) by protecting the synapses of rats. Adult male Wistar rats were randomly allocated to the following groups: (1) control group; (2) Aβ 1-42 group; (3) SIF group; (4) SIF + Aβ 1-42 group (SIF pretreatment group) according to body weight. The 80 mg/kg/day of SIF was administered orally by gavage to the rats in SIF and SIF+Aβ 1-42 groups. Aβ 1-42 was injected into the lateral cerebral ventricle of rats in Aβ 1-42 and SIF+Aβ 1-42 groups. The ability of learning and memory, ultramicrostructure of hippocampal synapses, and expression of synaptic related proteins were investigated. The Morris water maze results showed the escape latency and total distance were decreased in the rats of SIF pretreatment group compared to the rats in Aβ1-42 group. Furthermore, SIF pretreatment could alleviate the synaptic structural damage and antagonize the down-regulation expressions of below proteins induced by Aβ1-42: (1) mRNA and protein of the synaptophysin and postsynaptic density protein 95 (PSD-95); (2) protein of calmodulin (CaM), Ca(2+) /calmodulin-dependent protein kinase II (CaMK II), and cAMP response element binding protein (CREB); (3) phosphorylation levels of CaMK II and CREB (pCAMK II, pCREB). These results suggested that SIF pretreatment could ameliorate the impairment of learning and memory ability in rats induced by Aβ 1-42, and its mechanism might be associated with the protection of synaptic plasticity by improving the synaptic structure and regulating the synaptic related proteins.

The role of polyphenols in the modulation of sirtuins and other pathways involved in Alzheimer's disease

Alzheimer's disease (AD) is characterised by extracellular amyloid deposits, neurofibrillary tangles, synaptic loss, inflammation and extensive oxidative stress. Polyphenols, which include resveratrol, epigallocatechin gallate and curcumin, have gained considerable interest for their ability to reduce these hallmarks of disease and their potential to slow down cognitive decline. Although their antioxidant and free radical scavenging properties are well established, more recently polyphenols have been shown to produce other important effects including anti-amyloidogenic activity, cell signalling modulation, effects on telomere length and modulation of the sirtuin proteins. Brain accessible polyphenols with multiple effects on pathways involved in neurodegeneration and ageing may therefore prove efficacious in the treatment of age-related diseases such as AD, although the evidence for this so far is limited. This review aims to explore the known effects of polyphenols from various natural and synthetic sources on brain ageing and neurodegeneration, and to examine their multiple mechanisms of action, with an emphasis on the role that the sirtuin pathway may play and the implications this may have for the treatment of AD.

Soy isoflavone attenuates brain mitochondrial oxidative stress induced by β-amyloid peptides 1-42 injection in lateral cerebral ventricle

The aim of this study is to investigate whether soy isoflavone (SIF) reduces oxidative stress and improves the antioxidant ability in mitochondria of rat brain damaged by injection of beta-amyloid peptides 1-42 (Aβ1-42). Forty Wistar rats were randomly divided into control, Aβ1-42, SIF + Aβ1-42, and SIF groups according to body weight. The rats in the SIF + Aβ1-42 group and SIF group were intragastrically administered SIF suspension in 0.5% CMC-Na for 28 days, whereas the rats in control group and Aβ1-42 group were administered the same volume of 0.5% CMC-Na. On day 14, the rats in the Aβ1-42 group and SIF + Aβ1-42 group were injected with Aβ1-42 into the lateral cerebral ventricle with physiological saline. The rat brains were then sampled, and brain mitochondria were isolated. After this, the mitochondrial membrane potential (MMP) and mitochondrial redox state were measured. The contents of brain nuclear factor E2-related factor (Nrf2) and heme oxygenase-1 (HO-1) protein in brain tissue were quantitated by Western blot. The results showed that SIF maintained the MMP, elevated the reduced glutathione/oxidized glutathione (GSH/GSSG) ratio, and increased glutathione peroxidase (GPx) and manganese superoxide dismutase (MnSOD) protein expression in brain mitochondria. Additionally, SIF reversed the Aβ1-42-induced downregulation of the protein expression of Nrf2 and HO-1 in brain tissue. These results indicated that SIF could alleviate the oxidative damage and maintain the redox imbalance in brain mitochondria damaged by Aβ1-42. This might result from regulation of the Nrf2/HO-1 pathway.

Antagonizing effects of soybean isoflavones on β-amyloid peptide-induced oxidative damage in neuron mitochondria of rats

Soybean isoflavone (SIF) has been demonstrated to have neuroprotective effects induced by β-amyloid peptides (Aβ) through suppressing oxidative stress; however, the explicit mechanisms still remain uncovered. In the present study, 32 Wistar rats were randomly divided into four groups: an Aβ1-42-treated group, a SIF + Aβ1-42 group, a SIF-treated group and a control group. We measured the protein content of 8-hydroxydeoxyguanosine (8-OhdG) and mRNA expression of 8-oxoguanine DNA glycosylase (OGG1). The protein expression of OGG1, Bcl-xl, Bad, beta subunit of ATP synthase (ATPB) and pyruvate dehydrogenase (PDH) in brain was also measured. The results showed that the level of 8-OHdG in both SIF groups was significantly decreased compared to the Aβ1-42-treated group (p < 0.05), while the mRNA and protein expression of OGG1 in the SIF + Aβ1-42 groups were up-regulated compared with the Aβ1-42-treated groups (p < 0.05). The expression of Bcl-xl was up-regulated in the SIF-treated group compared with the Aβ1-42-treated groups (p < 0.05), while the expression of Bad was down-regulated in the two SIF-treated groups (p < 0.05). Aβ1-42 significantly down-regulated the expression of ATPase and PDH proteins compared with the control group (p < 0.05). SIF reversed the down-regulation effects on the mitochondrial energy metabolic enzymes induced by Aβ1-42 (p < 0.05) in the rats. These results suggest that SIF alleviate the oxidative stress in neurons and mitochondria of rat brains mediated by Aβ1-42, and these protective effects might be associated with the regulation of OGG1, Bad, Bcl-xl, ATPB and PDH.

Pattern recognition receptors involved in the inflammatory attenuating effects of soybean isoflavone in β-amyloid peptides 1-42 treated rats

Pattern recognition receptors (PRRs) play important roles in the inflammatory responses to Alzheimer's disease (AD). Our previous study indicated that soybean isoflavone (SIF) exhibited anti-inflammatory effect in rats treated by β-amyloid peptides1-42 (Aβ1-42). In present study, we further detected the effects of SIF against inflammation caused by Aβ1-42 treatment in rats. Serum inflammatory mediators and neurotrophic factors including transforming growth factor-β (TGF-β), inducible nitric oxide synthase (iNOS), brain-derived neurotrophic factor (BDNF) and S100β were detected by enzyme-like immunosorbent assay (ELISA). Reverse transcription-polymerase chain reaction (RT-PCR) and western blot methods were applied for detecting mRNA and protein expression of interleukin-1β (IL-1β), iNOS, tumor necrosis factor-α (TNF-α), TGF-β, BDNF, S100β, myeloid differentiation factor88 (Myd88), Toll-like receptor2 (TLR2), formyl peptide receptors (FPRs), inhibitor κB kinase (IKK) and inhibitor κB-α (IκB-α) in rat's brain tissue. Our results indicated that SIF could reduce the production of IL-1β, TNF-α and iNOS induced by Aβ1-42 in serum and brain of rats. SIF also significantly reversed Aβ1-42-induced up-regulation of TLR2, FPR, Myd88, IKK and decreased IκB-α mRNA and protein expressions in rats. These results suggested that TLR2 and FPR might involve in the inflammatory process induced by Aβ1-42 treatment, and SIF was an efficiency compound in reversing the inflammation caused by Aβ1-42 treatment.

Comparative study of quality characteristics of Korean soy sauce made with soybeans germinated under dark and light conditions

This study was conducted to evaluate the effects of germinating soybeans under dark and light conditions on the quality characteristics of Korean soy sauce made with germinated soybeans. The germination rate of soybeans germinated under dark conditions (GSD) was higher than that of soybeans germinated under light conditions (GSL), whereas the lengths of sprouts and relative weights of GSL did not differ from those of GSD. The L, a, b, and ΔT values of GSL were significantly lower than GSD. The color of GSD remained yellow, while GSL changed to a green color due to photosynthesis by chlorophyll. The total amino acid contents in soy sauce fermented with soybeans germinated under dark conditions (SSGD) and soy sauce fermented with soybeans germinated under light conditions (SSGL) were lower than in soy sauce fermented with non-germinated soybeans (SNGS). The levels of isoflavone content in SSGD and SSGL were significantly increased compared to the SNGS. In conclusion, the germination of soybeans under dark and light conditions is not only an increasing organoleptic preference, but also has implications for the health benefits of Korean soy sauce.

Soybean isoflavone alleviates β-amyloid 1-42 induced inflammatory response to improve learning and memory ability by down regulation of Toll-like receptor 4 expression and nuclear factor-κB activity in rats

β-amyloid 1-42 (Aβ1-42)-induced learning and memory impairment in rats is believed to be associated with inflammation. Cytokine production is a key pathologic event in the progression of inflammatory processes. In this rat study, soybean isoflavones (SIF) was used to investigate it's protective effects on inflammation caused by β-amyloid 1-42 (Aβ1-42), which is associated with learning and memory impairment in Alzheimer disease. We characterized the learning and memory ability. cytokine profiles of circulating interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) in the serum and the expression of Toll like receptor4 (TLR4) and nuclear factor-κB p65 (NF-κB p65) mRNA and protein in the brain tissue following intracerebroventricular administration of Aβ1-42 by miniosmotic pump for 14 days. The results showed that functional deficits of learning and memory in SIF treatment groups were significantly improved compared to the control group without SIF treatment in water maze test. The serum IL-1β and TNF-α level were significantly increased, and the expressions of TLR4 and NF-κB p65 mRNA and protein in the brain were up-regulated, indicating inflammation response was initiated following administration of Aβ1-42. After intragastric pre-treatment with SIF, inflammatory cytokines was significantly reduced and also SIF reversed the Aβ1-42 induced up-regulation of TLR4 and NF-κB p65 mRNA and protein expression in the brain and expression of NF-κB p65 in nuclei. These results suggested that SIF reduced the cytokine cascade and inflammatory response induced by Aβ1-42 which could result in the improvement of spatial learning and memory ability impairment in the rats.

Targeting NADPH oxidase and phospholipases A2 in Alzheimer's disease

Alzheimer's disease (AD) is marked by an increase in the production of extracellular beta amyloid plaques and intracellular neurofibrillary tangles associated with a decline in brain function. Increases in oxidative stress are regarded as an early sign of AD pathophysiology, although the source of reactive oxygen species (ROS) and the mechanism(s) whereby beta amyloid peptides (Abeta) impact oxidative stress have not been adequately investigated. Recent studies provide strong evidence for the involvement of NADPH oxidase and its downstream oxidative signaling pathways in the toxic effects elicited by Abeta. ROS produced by NADPH oxidase activate multiple signaling pathways leading to neuronal excitotoxicity and glial cell-mediated inflammation. This review describes recent studies demonstrating the neurotoxic effects of Abeta in conjunction with ROS produced by NADPH oxidase and the downstream pathways leading to activation of cytosolic phospholipase A(2) (PLA(2)) and secretory PLA(2). In addition, this review also describes recent studies using botanical antioxidants to protect against oxidative damage associated with AD. Investigating the metabolic and signaling pathways involving Abeta NADPH oxidase and PLA(2) can help understand the mechanisms underlying the neurodegenerative effects of oxidative stress in AD. This information should provide new therapeutic approaches for prevention of this debilitating disease.