Protective effects of banana pectin against aluminum-induced cognitive impairment and aluminum accumulation in mice

Potential therapeutic natural compounds for the treatment of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a complicated neurodegenerative disease with cognitive impairment occurring in the older people, in which extracellular accumulation of β-amyloid and intracellular aggregation of hyperphosphorylated tau are regarded as the prevailing theories. However, the exact AD mechanism has not been determined. Moreover, there is no effective treatment available in phase III trials to eradicate AD, which is imperative to explore novel treatments.

PURPOSE

A number of up-to-date pre-clinical studies on cognitive impairment is beneficial to clarify the pathology of AD. This review recapitulates several advances in AD pathobiology and discusses the neuroprotective effects of natural compounds, such as phenolic compounds, natural polysaccharides and oligosaccharides, peptide, and lipids, underscoring the therapeutic potential for AD.

METHODS

Electronic databases involving PubMed, Web of Science, and Google Scholar were searched up to October 2023. Articles were conducted using the keywords like Alzheimer's disease, pathogenic mechanisms, natural compounds, and neuroprotection.

RESULT

This review summarized several AD pathologies and the neuroprotective effects of natural compounds such as natural polysaccharides and oligosaccharides, peptide, and lipids.

CONCLUSION

We have discussed the pathogenic mechanisms of AD and the effect natural products on neurodegenerative diseases particularly in treating AD. Specifically, we investigated the molecular pathways and links between natural compounds and Alzheimer's disease such as through NF-κB, Nrf2, and mTOR pathway. Further investigation is necessary in exploring the bioactivity and effectiveness of natural compounds in clinical trials, which may provide a promising treatment for AD patients.

Structural characterization of pectic polysaccharides from Amaranth caudatus leaves and the promotion effect on hippocampal glucagon-like peptide-1 level

In this study, decolorized pectic polysaccharides (D-ACLP) with molecular weight (Mw) distribution of 3483- 2,023,656 Da were prepared from Amaranth caudatus leaves. Purified polysaccharides (P-ACLP) with the Mw of 152,955 Da were further isolated from D-ACLP through gel filtration. The structure of P-ACLP was analyzed by 1D and 2D NMR spectra. P-ACLP were identified as rhamnogalacturonan-I (RG-I) containing dimeric arabinose side chains. The main chain of P-ACLP was composed of →4)-α-GalpA-(1→, →2)-β-Rhap-(1→, →3)-β-Galp-(1 → and →6)-β-Galp-(1→. There was a branched chain of α-Araf-(1 → 2)-α-Araf-(1 → connected to the O-6 position of →3)-β-Galp-(1→. The GalpA residues were partially methyl esterified at O-6 and acetylated at O-3. The 28-day consecutive gavage of D-ALCP (400 mg/kg) significantly elevated the hippocampal glucagon-like peptide-1 (GLP-1) levels in rats. The concentrations of butyric acid and total short chain fatty acids in the cecum contents also increased significantly. Moreover, D-ACLP could significantly increase the gut microbiota diversity and dramatically up-regulated the abundance of Actinobacteriota (phylum) and unclassified Oscillospiraceae (genus) in intestinal bacteria. Taking together, D-ACLP might promote the hippocampal GLP-1 level through the beneficial regulation of butyric acid-producing bacteria in gut microbiota. This study contributed to making full use of Amaranth caudatus leaves for cognitive dysfunction intervention in food industry.

Expression of DnMTs and MBDs in AlCl3-Induced Neurotoxicity Mouse Model

Alteration in DNA methylation after aluminum exposure has been shown to contribute in pathogenesis of Alzheimer's disease (AD). This study is aimed to determine the effect of Al exposure (42 and 60 days) on learning and memory and the expression of proteins involved in DNA methylation (MBD1, MBD2, MBD3, MeCP2 (methyl CpG binding protein 2), DnMT1 and DnMT3a). Male BALB/c mice were treated with AlCl₃ for either 42 days or 60 days. After treatment completion, learning and memory were compared to the control group using novel object recognition test, elevated plus maze test, open field test, and Morris water maze test. The treated animals and their respective controls were sacrificed after cognitive testing and samples from their whole cortex and hippocampus were harvested for gene expression analysis. Mice treated with AlCl₃ showed significant cognitive deficit with impaired short-term memory, elevated anxiety, and deterioration in spatial and reference memory. The AlCl₃ treatment showed significant reduction in the expression of MBDs in the whole cortex at 60 days of treatment as compared to control. AlCl₃-treated animals showed decreased expression of MBDs and DnMT3a in the hippocampus for longer treated animals but strikingly, MBD2 showed significantly increased expression in AlCl₃-treated animals at 60 days p ≤ 0.001. In conclusion, this study showed that AlCl₃-treated animals showed significant memory and cognitive deficits and it is associated with significant changes in the expression of proteins involved in DNA methylation mechanism. Moreover, different Al exposure duration had slightly different effects.

Metal/metalloid levels in hair of Shenzhen residents and the associated influencing factors

129 Shenzhen residents' hair samples were collected and the metal/metalloid concentrations of Hg, As, Pb, Cd, Cr, Cu, Mn, Zn, Fe and Ni were detected. Meanwhile, the relationships between metal/metalloid contents in human hair and gender, age, seafood diet habit, smoking habit, as well as the housing type (dwelling environment) were analyzed. Results showed that the average content of Hg, As, Pb, Cd, Cr, Cu, Mn, Zn, Fe and Ni in human hair of Shenzhen residents was 0.76 ± 0.96, 0.10 ± 0.04, 5.25 ± 4.88, 0.25 ± 0.33, 0.60 ± 0.31, 13.84 ± 3.67, 2.82 ± 2.01, 196.90 ± 145.01, 12.20 ± 5.10 and 0.34 ± 0.32 μg/g, respectively. Compared with other regions at home and abroad, most metal/metalloids in Shenzhen residents were at a moderate level, and the highly toxic elements (i.e. Pb, Cd, As and Hg) didn't exceed the upper limit of normal values in China. Statistical analysis showed that the young male people contained significantly higher (p < 0.05) level of Pb (in age group of 20-30 years old) and Fe (in age group of 20-40 years old) in hair than the female people. Smokers had significantly (p < 0.05) higher level of Cd (0.35 μg/g) but lower level of Zn (101.24 µg/g) than non-smokers (Cd: 0.17 μg/g; Zn: 252.63 µg/g). Hg and Pb contents in hair of Shenzhen people were positively related with the frequencies of seafood consumption and the age, respectively. Moreover, residents lived in private buildings (well decorated house) accumulated significantly higher (p < 0.05) levels of Pb, Cr, Fe and Ni as compared with those lived in public rental house and village house (no decoration or simple decoration), suggesting that decoration material was also an important way for human exposure to heavy metals.

Opinion on the re-evaluation of pectin (E 440i) and amidated pectin (E 440ii) as food additives in foods for infants below 16 weeks of age and follow-up of their re-evaluation as food additives for uses in foods for all population groups

Pectin (E 440i) and amidated pectin (E 440ii) were re-evaluated in 2017 by the former EFSA Panel on Food Additives and Nutrient sources added to Food (ANS). As a follow-up to this assessment, the Panel on Food Additives and Flavourings (FAF) was requested to assess the safety of pectins (E 440i,ii) for their uses as food additives in food for infants below 16 weeks of age. In addition, the FAF Panel was requested to address the issues already identified during the re-evaluation of the same food additive. The process involved the publication of a call for data to allow the interested business operators to provide the requested information to complete the risk assessment. Based on the information submitted in response to the call for data, the FAF Panel considered it feasible to amend the current specifications, in particular for the toxic elements arsenic, lead, cadmium, mercury and for sulfur dioxide and to introduce new specifications for aluminium and microbiological criteria. Studies on neonatal piglets, clinical studies and post-marketing data were made available during the call for data. Due to the low internal validity of the clinical studies, the Panel concluded that a reference point could not be derived from them, but the results of the adequate piglet study could serve to derive a reference point. When calculating the margin of safety for pectins exposure, this was below 1 for some scenarios. At the maximum permitted levels (MPLs), an internal methanol dose would be produced that could lead to adverse health effects in infants below 16 weeks of age. The FAF Panel recommended a reduction of the MPL of pectin (E 440i) and amidated pectin (E 440ii) in food categories 13.1.5.1 and 13.1.5.2, in order to reduce the exposure to both the additives themselves and to methanol.