Protective effects of blueberry drink on cognitive impairment induced by chronic mild stress in adult rats

Addressing Mental Health in Rural Settings: A Narrative Review of Blueberry Supplementation as a Natural Intervention

Depression and anxiety are major public health issues; however, there is an unmet need for novel, effective, and accessible treatments, particularly in rural communities. Blueberries are an unexplored nutraceutical for these conditions due to their excellent nutritional profile, with particularly high levels of polyphenols and anthocyanins and benefits on mood, cognition, and health. Here, we present a narrative review of the literature concerning the etiology and treatments of major depressive disorder (MDD) and generalized anxiety disorder (GAD). In both animal and human studies, blueberry supplementation can ameliorate behavioral symptoms of both anxiety and depression. The mechanistic underpinnings of these behavioral improvements are not fully defined, but likely involve biochemical alterations in the gut-brain axis, including to inflammatory cytokines, reactive oxygen species, and growth factors. We also review the limitations of traditional therapies in rural settings. Finally, we assess the potential benefit of nutraceutical interventions, particularly blueberries, as novel therapeutics for these distinct, yet related mental health issues.

Gardenin A treatment attenuates inflammatory markers, synuclein pathology and deficits in tyrosine hydroxylase expression and improves cognitive and motor function in A53T-α-syn mice

Oxidative stress and neuroinflammation are widespread in the Parkinson's disease (PD) brain and contribute to the synaptic degradation and dopaminergic cell loss that result in cognitive impairment and motor dysfunction. The polymethoxyflavone Gardenin A (GA) has been shown to activate the NRF2-regulated antioxidant pathway and inhibit the NFkB-dependent pro-inflammatory pathway in a Drosophila model of PD. Here, we evaluate the effects of GA on A53T alpha-synuclein overexpressing (A53TSyn) mice. A53TSyn mice were treated orally for 4 weeks with 0, 25, or 100 mg/kg GA. In the fourth week, mice underwent behavioral testing and tissue was harvested for immunohistochemical analysis of tyrosine hydroxylase (TH) and phosphorylated alpha synuclein (pSyn) expression, and quantification of synaptic, antioxidant and inflammatory gene expression. Results were compared to vehicle-treated C57BL6J mice. Treatment with 100 mg/kg GA improved associative memory and decreased abnormalities in mobility and gait in A53TSyn mice. GA treatment also reduced pSyn levels in both the cortex and hippocampus and attenuated the reduction in TH expression in the striatum seen in A53Tsyn mice. Additionally, GA increased cortical expression of NRF2-regulated antioxidant genes and decreased expression of NFkB-dependent pro-inflammatory genes. GA was readily detectable in the brains of treated mice and modulated the lipid profile in the deep gray brain tissue of those animals. While the beneficial effects of GA on cognitive deficits, motor dysfunction and PD pathology are promising, future studies are needed to further fully elucidate the mechanism of action of GA, optimizing dosing and confirm these effects in other PD models.

Gardenin A improves cognitive and motor function in A53T-α-syn mice

Oxidative stress and neuroinflammation are widespread in the Parkinson's disease (PD) brain and contribute to the synaptic degradation and dopaminergic cell loss that result in cognitive impairment and motor dysfunction. The polymethoxyflavone Gardenin A (GA) has been shown to activate the NRF2-regulated antioxidant pathway and inhibit the NFkB-dependent pro-inflammatory pathway in a Drosophila model of PD. Here, we evaluate the effects of GA on A53T alpha-synuclein overexpressing (A53TSyn) mice. A53TSyn mice were treated orally for 4 weeks with 0, 25, or 100 mg/kg GA. In the fourth week, mice underwent behavioral testing and tissue was harvested for immunohistochemical analysis of tyrosine hydroxylase (TH) and phosphorylated alpha synuclein (pSyn) expression, and quantification of synaptic, antioxidant and inflammatory gene expression. Results were compared to vehicle-treated C57BL6 mice. Treatment with 100 mg/kg GA improved associative memory and decreased abnormalities in mobility and gait in A53TSyn mice. GA treatment also reduced cortical and hippocampal levels of pSyn and attenuated the reduction in TH expression in the striatum. Additionally, GA increased cortical expression of NRF2-regulated antioxidant genes and decreased expression of NFkB-dependent pro-inflammatory genes. GA was readily detectable in the brains of treated mice and modulated the lipid profile in the deep gray brain tissue of those animals. While the beneficial effects of GA on cognitive deficits, motor dysfunction and PD pathology are promising, future studies are needed to further fully elucidate the mechanism of action of GA, optimizing dosing and confirm these effects in other PD models.

Significance Statement

The polymethoxyflavone Gardenin A can improve cognitive and motor function and attenuate both increases in phosphorylated alpha synuclein and reductions in tyrosine hydroxylase expression in A53T alpha synuclein overexpressing mice. These effects may be related to activation of the NRF2-regulated antioxidant response and downregulation of NFkB-dependent inflammatory response by Gardenin A in treated animals. The study also showed excellent brain bioavailability of Gardenin A and modifications of the lipid profile, possibly through interactions between Gardenin A with the lipid bilayer, following oral administration. The study confirms neuroprotective activity of Gardenin A previously reported in toxin induced Drosophila model of Parkinson's disease.

Anxiety-like Behavior in Female Sprague Dawley Rats Associated with Cecal Clostridiales

The relationship between the microbiota profile and exposure to stress is not well understood. Therefore, we used a rat model of unpredictable chronic mild stress (UCMS) to investigate this relationship. Depressive-like behaviors were measured in Female Sprague Dawley rats using the sucrose preference test and the Porsolt swim test. Anxiety-like behaviors were measured with the light-dark box test. Fecal corticosterone, cecal microbiota (composition and organic acids), plasma gut permeability (lipopolysaccharide-binding protein, LBP) and plasma inflammation (12 cytokines) markers were measured. Atypical behaviors were observed in female rats following UCMS, but no depressive-like behaviors were observed. Circulating concentrations of cytokines granulocyte-macrophage colony-stimulating factor and cytokine-induced neutrophil chemoattractant 1 were higher in UCMS-exposed female rats; plasma LBP and cecal organic acid levels remained unchanged. Our results reflect a resilient and adaptive phenotype for female SD rats. The relative abundance of taxa from the Clostridiales order and Desulfovibrionaceae family did, however, correlate both positively and negatively with anxiety-like behaviors and plasma cytokine concentrations, regardless of UCMS exposure, supporting the brain-to-gut influence of mild anxiety with a microbiota profile that may involve inflammatory pathways.

The Role of the Gut Microbiota in Dietary Interventions for Depression and Anxiety

There is emerging evidence that an unhealthy dietary pattern may increase the risk of developing depression or anxiety, whereas a healthy dietary pattern may decrease it. This nascent research suggests that dietary interventions could help prevent, or be an alternative or adjunct therapy for, depression and anxiety. The relation, however, is complex, affected by many confounding variables, and is also likely to be bidirectional, with dietary choices being affected by stress and depression. This complexity is reflected in the data, with sometimes conflicting results among studies. As the research evolves, all characteristics of the relation need to be considered to ensure that we obtain a full understanding, which can potentially be translated into clinical practice. A parallel and fast-growing body of research shows that the gut microbiota is linked with the brain in a bidirectional relation, commonly termed the microbiome-gut-brain axis. Preclinical evidence suggests that this axis plays a key role in the regulation of brain function and behavior. In this review we discuss possible reasons for the conflicting results in diet-mood research, and present examples of areas of the diet-mood relation in which the gut microbiota is likely to be involved, potentially explaining some of the conflicting results from diet and depression studies. We argue that because diet is one of the most significant factors that affects human gut microbiota structure and function, nutritional intervention studies need to consider the gut microbiota as an essential piece of the puzzle.

The relationships between thyroid-stimulating hormone and/or dopamine levels in peripheral blood and IQ in children with different urinary iodine concentrations

Environmental iodine deficiency or excess can lead to inappropriate iodine nutrition in the population. Little research has been performed to determine whether changes in thyroid-stimulating hormone (TSH) and/or dopamine (DA) concentrations in peripheral blood are involved in intellectual impairment caused by inappropriate iodine nutrition. 498 children aged 7-12 from areas with different water iodine concentrations were included in the study. Children's intelligence and levels of urinary iodine and fluoride, TSH, free triiodothyronine (FT₃), free thyroxine (FT₄), and DA were evaluated. The relationship between TSH and/or DA levels and intelligence quotient (IQ) in all participants and in the population with different urinary iodine concentrations (UIC) was evaluated by multivariate regression analysis. The proportion of people with low average and lower intelligence in UIC ≥ 300 μg/L group was significantly higher than that in control group but only a positive correlation was found between DA and IQ in the population with UIC < 100 μg/L (bootstrapped estimation P = 0.032). TSH and/or DA in peripheral blood may be not involved in the progressive decline in intelligence caused by iodine excess but DA had positive correlation with intelligence in iodine deficiency group, and no relationship between TSH concentration and IQ was found in the general population or in different UIC groups.

Glutathionyl-S-chlorogenic acid is present in fruit of Vaccinium species, potato tubers and apple juice

A hydroxycinnamate-like component was identified in highbush blueberry (Vaccinium corymbosum) fruit, which had identical UV and mass spectrometric properties to an S-linked glutathionyl conjugate of chlorogenic acid synthesized using a peroxidase-catalyzed reaction. The conjugate was present in fruits from all highbush blueberry genotypes grown in one season, reaching 7-20% of the relative abundance of 5-caffeoylquininc acid. It was enriched, along with anthocyanins, by fractionation on solid phase cation-exchange units. Mining of pre-existing LC-MS data confirmed that this conjugate was ubiquitous in highbush blueberries, but also present in other Vaccinium species. Similar data mining identified this conjugate in potato tubers with enrichment in peel tissues. In addition, the conjugate was also present in commercial apple juice and was stable to pasteurization and storage. Although glutathionyl conjugates of hydroxycinnamic acids have been noted previously, this is the first report of glutathionyl conjugates of chlorogenic acids in commonly-eaten fruits and vegetables.

Ginsenoside Rg1 Decreases Oxidative Stress and Down-Regulates Akt/mTOR Signalling to Attenuate Cognitive Impairment in Mice and Senescence of Neural Stem Cells Induced by D-Galactose

Adult hippocampal neurogenesis plays a pivotal role in learning and memory. The suppression of hippocampal neurogenesis induced by an increase of oxidative stress is closely related to cognitive impairment. Neural stem cells which persist in the adult vertebrate brain keep up the production of neurons over the lifespan. The balance between pro-oxidants and anti-oxidants is important for function and surviving of neural stem cells. Ginsenoside Rg1 is one of the most active components of Panax ginseng, and many studies suggest that ginsenosides have antioxidant properties. This research explored the effects and underlying mechanisms of ginsenoside Rg1 on protecting neural stem cells (NSCs) from oxidative stress. The sub-acute ageing of C57BL/6 mice was induced by subcutaneous injection of D-gal (120 mg kg^-1 day^-1) for 42 day. On the 14th day of D-gal injection, the mice were treated with ginsenoside Rg1 (20 mg kg^-1 day^-1, intraperitoneally) or normal saline for 28 days. The study monitored the effects of Rg1 on proliferation, senescence-associated and oxidative stress biomarkers, and Akt/mTOR signalling pathway in NSCs. Compared with the D-gal group, Rg1 improved cognitive impairment induced by D-galactose in mice by attenuating senescence of neural stem cells. Rg1 also decreased the level of oxidative stress, with increased the activity of superoxide dismutase and glutathione peroxidase in vivo and in vitro. Rg1 furthermore reduced the phosphorylation levels of protein kinase B (Akt) and the mechanistic target of rapamycin (mTOR) and down-regulated the levels of downstream p53, p16, p21 and Rb in D-gal treated NSCs. The results suggested that the protective effect of ginsenoside Rg1 on attenuating cognitive impairment in mice and senescence of NSCs induced by D-gal might be related to the reduction of oxidative stress and the down-regulation of Akt/mTOR signaling pathway.