A high-fat diet impairs neurogenesis: Involvement of lipid peroxidation and brain-derived neurotrophic factor

Reversal of high-fat diet-induced cognitive impairment and oxidative stress in the brain through Zingiber officinale supplementation

Obesity is a significant health concern that is correlated with various adverse health outcomes. Diet-induced obesity (DIO) is associated with impaired cognitive function. Pharmacological treatments for obesity are limited and may have serious adverse effects. Zingiber officinale (ZO) has anti-inflammatory and antioxidant effects, in addition to metabolic effects. This study aimed to assess the effects of Zingiber officinale supplementation on cognitive function, anxiety levels, neurotrophin levels, and the inflammatory and oxidative status in the cortex following DIO in mice. Two-month-old male Swiss mice were fed DIO or standard chow for 4 months and subsequently subdivided into the following groups (n = 10 mice/group): (i) control - vehicle (CNT + vehicle); (ii) CNT supplemented with ZO (CNT + ZO); (iii) obese mice (DIO + vehicle); and (iv) obese mice supplemented with ZO (DIO + ZO) (n = 10). Zingiber officinale extract (400 mg/kg/day) was administered for 35 days via oral gavage. The DIO + vehicle group exhibited impaired recognition memory. The CNT + ZO group presented a greater number of crossings in the open field. No difference between the groups was observed in the plus maze test. DIO + vehicle increased the DCFH and carbonylation levels in the cortex. The DIO + vehicle group presented a reduction in catalase activity. The expression of inflammatory or neurotrophin markers in the cerebral cortex was not different. In conclusion, our findings indicate that supplementation with ZO reverses the cognitive impairment in DIO mice and enhances the antioxidant status of the cerebral cortex.

Aloe polysaccharides ameliorate obesity-associated cognitive dysfunction in high-fat diet-fed mice by targeting the gut microbiota and intestinal barrier integrity

Aloe polysaccharides (APs) display cognition-improving properties, but the underlying mechanisms remain unclear. Herein, AP supplementation for 24 weeks significantly improved cognitive behavioral disturbances caused by a high-fat diet. Moreover, APs notably reshaped the structure of the gut microbiota, which was manifested by increasing the relative abundance of Alloprevotella, Alistipes, Romboutsia, Turicibacter, Prevotellaceae_UCG-001, and Akkermansia while reducing the abundance of Parasutterella, Staphylococcus, Helicobacter, Enterococcus, and Erysipelatoclostridium. Notably, the gut barrier damage and LPS leakage caused by HF were recovered by APs. Additionally, with the improvement of intestinal barrier integrity, oxidative stress and inflammation in the brain and jejunum were significantly ameliorated. Furthermore, the expression of genes associated with cognitive impairment and the intestinal tract barrier was up-regulated (CREB, BDNF, TrkB, ZO-1 and occludin), while the expression of genes associated with inflammatory factors was down-regulated (IL-1β, IL-6, and TNF-α). Finally, we observed a significant correlation among cognition-related genes, gut microbiota, oxidative stress, and inflammation in the HF-AP group. Together, our findings suggest that altered gut microbiota composition and improved gut barrier integrity may be important targets for potentially improving high-fat diet-induced cognitive impairment.

Effect of high fat diet on maternal behavior, brain-derived neurotrophic factor and neural stem cell proliferation in mice expressing human placental lactogen during pregnancy

Maternal obesity is a serious health concern because it increases risks of neurological disorders, including anxiety and peripartum depression. In mice, a high fat diet (HFD) in pregnancy can negatively affect placental structure and function as well as maternal behavior reflected by impaired nest building and pup-retrieval. In humans, maternal obesity in pregnancy is associated with reduced placental lactogen (PL) gene expression, which has been linked to a higher risk of depression. PL acting predominantly through the prolactin receptor maintains energy homeostasis and is a marker of placenta villous trophoblast differentiation during pregnancy. Impaired neurogenesis and low serum levels of brain-derived neurotrophic factor (BDNF) have also been implicated in depression. Augmented neurogenesis in brain during pregnancy was reported in the subventricular zone (SVZ) of mice at gestation day 7 and linked to increased prolactin receptor signaling. Here, we used transgenic CD-1 mice that express human (h) PL during pregnancy to investigate whether the negative effects of diet on maternal behavior are mitigated in these (CD-1[hGH/PL]) mice. Specifically, we examined the effect of a HFD on nest building prepartum and pup retrieval postpartum, as well as on brain BDNF levels and neurogenesis. In contrast to wild-type CD-1[WT]mice, CD-1[hGH/PL] mice displayed significantly less anxiety-like behavior, and showed no impairment in prepartum nest building or postpartum pup-retrieval when fed a HFD. Furthermore, the HFD decreased prepartum and increased postpartum BDNF levels in CD-1[WT] but not CD-1[hGH/PL] mice. Finally, neurogenesis in the SVZ as well as phosphorylated mitogen-activated protein kinase, indicative of lactogenic signaling, appeared unaffected by pregnancy and diet at gestation day 7 in CD-1[hGH/PL] mice. These observations indicate that CD-1[hGH/PL] mice are resistant to the negative effects of HFD reported for CD-1[WT] mice, including effects on maternal behaviors and BDNF levels, and potentially, neurogenesis. This difference probably reflects a direct or indirect effect of the products of the hGH/PL transgene.

High-Caloric Diets in Adolescence Impair Specific GABAergic Subpopulations, Neurogenesis, and Alter Astrocyte Morphology

We compared the effects of two different high-caloric diets administered to 4-week-old rats for 12 weeks: a diet rich in sugar (30% sucrose) and a cafeteria diet rich in sugar and high-fat foods. We focused on the hippocampus, particularly on the gamma-aminobutyric acid (GABA)ergic system, including the Ca2+-binding proteins parvalbumin (PV), calretinin (CR), calbindin (CB), and the neuropeptides somatostatin (SST) and neuropeptide Y (NPY). We also analyzed the density of cholinergic varicosities, brain-derived neurotrophic factor (BDNF), reelin (RELN), and cyclin-dependent kinase-5 (CDK-5) mRNA levels, and glial fibrillary acidic protein (GFAP) expression. The cafeteria diet reduced PV-positive neurons in the granular layer, hilus, and CA1, as well as NPY-positive neurons in the hilus, without altering other GABAergic populations or overall GABA levels. The high-sugar diet induced a decrease in the number of PV-positive cells in CA3 and an increase in CB-positive cells in the hilus and CA1. No alterations were observed in the cholinergic varicosities. The cafeteria diet also reduced the relative mRNA expression of RELN without significant changes in BDNF and CDK5 levels. The cafeteria diet increased the number but reduced the length of the astrocyte processes. These data highlight the significance of determining the mechanisms mediating the observed effects of these diets and imply that the cognitive impairments previously found might be related to both the neuroinflammation process and the reduction in PV, NPY, and RELN expression in the hippocampal formation.

Associations between dietary habits and bipolar disorder: a diet-wide mendelian randomization study

Background

Diet/nutrition is critically important in the pathogenesis, progression, and treatment outcomes of various mental disorders. Current research predominantly focuses on the role of diet in the development and treatment of depression, with less attention given to the relationship between diet and Bipolar Disorder (BD).

Method

We employed Mendelian Randomization (MR) to investigate the relationship between 28 dietary habits and BD. An analysis was conducted using publicly available genome-wide association study data from the UK Biobank dataset. Various dietary habits were analyzed as exposures with BD as the outcome, mainly using the Inverse Variance Weighted (IVW) method.

Results

Intake of non-oily fish and sponge pudding both have a positive association with BD. Oily fish, dried fruit, apples, salt, and cooked vegetables intake also appeared potentially risky for BD, although the possibility of false positives cannot be ruled out. Sensitivity analysis further confirmed the robustness of these findings.

Conclusion

Our research provides evidence of a relationship between various dietary habits and BD. It underscores the need for careful dietary management and balance to reduce the risk of BD, suggesting caution with dietary preferences for fish and sponge pudding. Furthermore, more detailed studies are needed to further understand the potential impacts of high-sugar and high-protein diets on BD development.

Inactivation of a non-canonical gp130 signaling arm attenuates chronic systemic inflammation and multimorbidity induced by a high-fat diet

Interleukin-6 (IL-6) is a major pro-inflammatory cytokine for which the levels in plasma demonstrate a robust correlation with age and body mass index (BMI) as part of the senescence-associated secretory phenotype. IL-6 cytokines also play a crucial role in metabolic homeostasis and regenerative processes, primarily via the canonical STAT3 pathway. Thus, selective modulation of IL-6 signaling may offer a unique opportunity for therapeutic interventions. Recently, we discovered that a non-canonical signaling pathway downstream of tyrosine (Y) 814 within the intracellular domain of gp130, the IL-6 co-receptor, is responsible for the recruitment and activation of SRC family of kinases (SFK). Mice with constitutive genetic inactivation of gp130 Y814 (F814 mice) show accelerated resolution of inflammatory response and superior regenerative outcomes in skin wound healing and posttraumatic models of osteoarthritis. The current study was designed to explore if selective genetic or pharmacological inhibition of the non-canonical gp130-Y814/SFK signaling reduces systemic chronic inflammation and multimorbidity in a high-fat diet (HFD)-induced model of accelerated aging. F814 mice showed significantly reduced inflammatory response to HFD in adipose and liver tissue, with significantly reduced levels of systemic inflammation compared to wild type mice. F814 mice were also protected from HFD-induced bone loss and cartilage degeneration. Pharmacological inhibition of gp130-Y814/SFK in mice on HFD mirrored the effects observed in F814 mice on HFD; furthermore, this pharmacological treatment also demonstrated a marked increase in physical activity levels and protective effects against inflammation-associated suppression of neurogenesis in the brain tissue compared to the control group. These findings suggest that selective inhibition of SFK signaling downstream of gp130 receptor represents a promising strategy to alleviate systemic chronic inflammation. Increased degenerative changes and tissue senescence are inevitable in obese and aged organisms, but we demonstrated that the systemic response and inflammation-associated multi-morbidity can be therapeutically mitigated.

An acute bout of resistance exercise increases BDNF in hippocampus and restores the long-term memory of insulin-resistant rats

A sedentary lifestyle, inadequate diet, and obesity are substantial risk factors for Type 2 diabetes mellitus (T2DM) development. A major picture of T2DM is insulin resistance (IR), which causes many impairments in brain physiology, such as increased proinflammatory state and decreased brain-derived neurotrophic factor (BDNF) concentration, hence reducing cognitive function. Physical exercise is a non-pharmacological tool for managing T2DM/IR and its complications. Thus, this study investigated the effects of IR induction and the acute effects of resistance exercise (RE) on memory, neurotrophic, and inflammatory responses in the hippocampus and prefrontal cortex of insulin-resistant rats. IR was induced by a high-fat diet and fructose-rich beverage. Insulin-resistant rats performed acute resistance exercise (IR.RE; vertical ladder climb at 50-100% of the maximum load) or rest (IR.REST; 20 min). Cognitive parameters were assessed by novel object recognition (NOR) tasks, and biochemical analyses were performed to assess BDNF concentrations and inflammatory profile in the hippocampus and prefrontal cortex. Insulin-resistant rats had 20% worse long-term memory (LTM) (p < 0.01) and lower BDNF concentration in the hippocampus (-14.6%; p < 0.05) when compared to non-insulin-resistant rats (CON). An acute bout of RE restored LTM (-9.7% pre vs. post; p > 0.05) and increased BDNF concentration in the hippocampus (9.1%; p < 0.05) of insulin-resistant rats compared to REST. Thus, an acute bout of RE can attenuate the adverse effects of IR on memory and neurotrophic factors in rats, representing a therapeutic tool to alleviate the IR impact on the brain.

Impaired brain equanimity and neurogenesis in the diet-induced overweight mouse: a preventive role by syringic acid treatment

OBJECTIVES

In this study mice were fed a high-fat diet for 12 weeks to establish diet-induced obesity and syringic acid (SA) was assessed for anti-obese, neuroprotective, and neurogenesis.

METHOD

Animals were given HFD for 12 weeks to measure metabolic characteristics and then put through the Barns-maze and T-maze tests to measure memory. Additionally, the physiology of the blood-brain barrier, oxidative stress parameters, the expression of inflammatory genes, neurogenesis, and histopathology was evaluated in the brain.

RESULT

DIO raised body weight, BMI, and other metabolic parameters after 12 weeks of overfeeding. A reduced spontaneous alternation in behavior (working memory, reference memory, and total time to complete a task), decreased enzymatic and non-enzymatic antioxidants, oxidative biomarkers, increased neurogenesis, and impaired blood-brain barrier were all seen in DIO mice. SA (50 mg/kg) treatment of DIO mice (4 weeks after 8 weeks of HFD feeding) reduced diet-induced changes in lipid parameters associated with obesity, hepatological parameters, memory, blood-brain barrier, oxidative stress, neuroinflammation, and neurogenesis. SA also reduced the impact of malondialdehyde and enhanced the effects of antioxidants such as glutathione, superoxide dismutase (SOD), and total thiol (MDA). Syringic acid improved neurogenesis, cognition, and the blood-brain barrier while reducing neurodegeneration in the hippocampal area.

DISCUSSION

According to the results of the study, syringic acid therapy prevented neurodegeneration, oxidative stress, DIO, and memory loss. Syringic acid administration may be a useful treatment for obesity, memory loss, and neurogenesis, but more research and clinical testing is needed.

Role of ketogenic diet in neurodegenerative diseases focusing on Alzheimer diseases: The guardian angle

The ketogenic diet (KD) is a low-carbohydrate, adequate protein and high-fat diet. KD is primarily used to treat refractory epilepsy. KD was shown to be effective in treating different neurodegenerative diseases. Alzheimer disease (AD) is the first common neurodegenerative disease in the world characterized by memory and cognitive impairment. However, the underlying mechanism of KD in controlling of AD and other neurodegenerative diseases are not discussed widely. Therefore, this review aims to revise the fundamental mechanism of KD in different neurodegenerative diseases focusing on the AD. KD induces a fasting-like which modulates the central and peripheral metabolism by regulating mitochondrial dysfunction, oxidative stress, inflammation, gut-flora, and autophagy in different neurodegenerative diseases. Different studies highlighted that KD improves AD neuropathology by regulating synaptic neurotransmission and inhibiting of neuroinflammation and oxidative stress. In conclusion, KD improves cognitive function and attenuates the progression of AD neuropathology by reducing oxidative stress, mitochondrial dysfunction, and enhancing neuronal autophagy and brain BDNF.

Nutritional Support System (NSS) as a New Therapeutic Strategy for Cerebral Palsy

Cerebral palsy (CP) is part of a group of nonprogressive motor disorders. The disease affects movement and posture and constitutes the most frequent cause of motor disability in childhood. CP is characterized by spasticity, reflecting lesions in the pyramidal pathway. Treatment is currently focused on physical rehabilitation, and the annual progression of the disease is 2-3%. About 60% of these patients present severe degrees of malnutrition associated with dysphagia, gastrointestinal abnormalities, malabsorption, increased metabolism, and depression. These alterations promote sarcopenia functional dependence and affect the quality of life and delay the evolution of motor skills. Currently, there is evidence that the supplementation of several nutrients, dietary correction, and probiotics can improve neurological response by stimulating neuroplasticity, neuroregeneration, neurogenesis, and myelination. This therapeutic strategy could shorten the response period to treatment and increase both gross and fine motor skills. The interaction of nutrients and functional foods integrating a Nutritional Support System (NSS) has shown greater efficiency in neurological stimulation than when nutrients are supplied separately. The most studied elements in the neurological response are glutamine, arginine, zinc, selenium, cholecalciferol, nicotinic acid, thiamine, pyridoxine, folate, cobalamin, Spirulina, omega-3 fatty acids, ascorbic acid, glycine, tryptophan, and probiotics. The NSS represents a therapeutic alternative that will restore neurological function in patients with spasticity and pyramidal pathway lesions, both characteristics of patients with CP.

Early macrophage-mediated Bdnf expression in white adipose tissue during high-fat diet feeding

The expression of brain-derived neurotrophic factor (BDNF) is observed not only in the brain, but also in peripheral tissues including white adipose tissues (WATs). Here, we showed that the mRNA expression of Bdnf in inguinal WAT (iWAT) and epididymal WAT (eWAT) increased within 2 weeks of feeding mice with a high-fat diet (HFD). In mice on a 2-week HFD, the induction of Bdnf expression in WATs was significantly correlated with increases in body weight, suggesting that Bdnf expression may increase at an early stage of obesity. The mRNA expression of hypoxia-inducible factor 1α and platelet-derived growth factor, which are involved in neovascularization and the subsequent expansion of adipose tissues, increased in the iWAT of mice on the 2-week HFD. We also found that the expression of macrophage marker F4/80 in iWAT increased under the HFD. Interestingly, HFD-induced Bdnf expression in iWAT was not observed when macrophages were removed by the administration of clodronate liposomes. Accordingly, mice receiving clodronate liposomes also exhibited a significant reduction in the HFD-induced increase in body weight. In conclusion, increased body weight in HFD-induced obese model mice was accompanied by the induction of Bdnf expression in iWAT and was probably mediated by macrophages. Our findings imply a novel function for BDNF in iWAT at an early stage of obesity.

Fish oil supplementation counteracts the effect of high-fat and high-sucrose diets on the carbonylated proteome in the rat cerebral cortex

High daily intake of saturated fats and refined carbohydrates, which often leads to obesity and overweight, has been associated with cognitive impairment, premature brain aging and the aggravation of neurodegenerative diseases. Although the molecular pathology of obesity-related brain damage is not fully understood, the increased levels of oxidative stress induced by the diet seem to be definitively involved. Being protein carbonylation determinant for protein activity and function and a main consequence of oxidative stress, this study aims to investigate the effect of the long-term high-fat and sucrose diet intake on carbonylated proteome of the cerebral cortex of Sprague-Dawley rats. To achieve this goal, the study identified and quantified the carbonylated proteins and lipid peroxidation products in the cortex, and correlated them with biometrical, biochemical and other redox status parameters. Results demonstrated that the obesogenic diet selectively increased oxidative damage of specific proteins that participate in fundamental pathways for brain function, i.e. energy production, glucose metabolism and neurotransmission. This study also evaluated the antioxidant properties of fish oil to counteract diet-induced brain oxidative damage. Fish oil supplementation demonstrated a stronger capacity to modulate carbonylated proteome in the brain cortex. Data indicated that fish oils did not just decrease carbonylation of proteins affected by the obesogenic diet, but also decreased the oxidative damage of other proteins participating in the same metabolic functions, reinforcing the beneficial effect of the supplement on those pathways. The results could help contribute to the development of successful nutritional-based interventions to prevent cognitive decline and promote brain health.

The role of IGF-1 in exercise to improve obesity-related cognitive dysfunction

Obesity is an important factor that threatens human health. The occurrence of many chronic diseases is related to obesity, and cognitive function decline often occurs with the onset of obesity. With the further prevalence of obesity, it is bound to lead to a wider range of cognitive dysfunction (ORCD). Therefore, it is crucial to suppress ORCD through intervention. In this regard, exercise has been shown to be effective in preventing obesity and improving cognitive function as a non-drug treatment. There is sufficient evidence that exercise has a regulatory effect on a growth factor closely related to cognitive function-insulin-like growth factor 1 (IGF-1). IGF-1 may be an important mediator in improving ORCD through exercise. This article reviews the effects of obesity and IGF-1 on cognitive function and the regulation of exercise on IGF-1. It analyzes the mechanism by which exercise can improve ORCD by regulating IGF-1. Overall, this review provides evidence from relevant animal studies and human studies, showing that exercise plays a role in improving ORCD. It emphasizes the importance of IGF-1, which helps to understand the health effects of exercise and promotes research on the treatment of ORCD.

Neural stem cell self-renewal stimulation by store-operated calcium entries in adult mouse area postrema: influence of leptin

Neural stem cells (NSCs) persist in specific brain germinative niches and sustain neurogenesis throughout life in adult mammals. In addition to the two major stem cell niches in the subventricular zone and the hippocampal dentate gyrus, the area postrema located in the brainstem has been identified as a neurogenic zone as well. NSCs are regulated by signals from the microenvironment that adjust stem cell response to the needs of the organism. Evidence accumulated over the past decade indicates that Ca²⁺ channels play pivotal functions in NSC maintenance. In this study, we explored in area postrema NSCs the presence and roles of a subset of Ca²⁺ channels, the store-operated Ca²⁺ channels (SOCs) that have the capacity to transduce extracellular signals into Ca²⁺ signals. Our data show that NSCs derived from the area postrema express TRPC1 and Orai1, known to form SOCs, as well as their activator STIM1. Ca²⁺ imaging indicated that NSCs exhibit store-operated Ca²⁺ entries (SOCEs). Pharmacological blockade of SOCEs with SKF-96365, YM-58483 (also known as BTP2) or GSK-7975A resulted in decreased NSC proliferation and self-renewal, indicating a major role for SOCs in maintaining NSC activity within the area postrema. Furthermore, our results show that leptin, an adipose tissue-derived hormone whose ability to control energy homeostasis is dependent on the area postrema, decreased SOCEs and reduced self-renewal of NSCs in the area postrema. As aberrant SOC function has been linked to an increasing number of diseases, including brain disorders, our study opens new perspectives for NSCs in brain pathophysiology.

Associations of metabolic syndrome, its severity with cognitive impairment among hemodialysis patients

BACKGROUND

In the general population, metabolic syndrome (MetS) is associated with increased risk of cognitive impairment, including global and specific cognitive domains. These associations are not well studied in patients undergoing hemodialysis and were the focus of the current investigation.

METHODS

In this multicenter cross-sectional study, 5492 adult hemodialysis patients (3351 men; mean age: 54.4 ± 15.2 years) treated in twenty-two dialysis centers of Guizhou, China were included. The Mini-Mental State Examination (MMSE) was utilized to assess mild cognitive impairment (MCI). MetS was diagnosed with abdominal obesity, hypertension, hyperglycemia, and dyslipidemia. Multivariate logistic and linear regression models were used to examine the associations of MetS, its components, and metabolic scores with the risk of MCI. Restricted cubic spline analyses were performed to explore the dose-response associations.

RESULTS

Hemodialysis patients had a high prevalence of MetS (62.3%) and MCI (34.3%). MetS was positively associated with MCI risk with adjusted ORs of 1.22 [95% confidence interval (CI) 1.08-1.37, P = 0.001]. Compared to no MetS, adjusted ORs for MCI were 2.03 (95% CI 1.04-3.98) for 22.51 (95% CI 1.28-4.90) for 3, 2.35 (95% CI 1.20-4.62) for 4, and 2.94 (95% CI 1.48-5.84) for 5 components. Metabolic syndrome score, cardiometabolic index, and metabolic syndrome severity score were associated with increased risk of MCI. Further analysis showed that MetS was negatively associated with MMSE score, orientation, registration, recall and language (P < 0.05). Significant interaction effect of sex (P for interaction = 0.012) on the MetS-MCI was observed.

CONCLUSION

Metabolic syndrome was associated with MCI in hemodialysis patients in a positive dose-response effect.

Lipidomic analysis of brain and hippocampus from mice fed with high-fat diet and treated with fecal microbiota transplantation

BACKGROUND

Dietary fat intake affects brain composition and function. Different types of dietary fatty acids alter species and abundance of brain lipids in mice. The aim of this study is to explore whether the changes are effective through gut microbiota.

METHODS

In our study, 8-week-old male C57BL/6 mice were randomly divided into 7 groups and fed with high-fat diet (HFD) with different fatty acid compositions, control (CON) group, long-chain saturated fatty acid (LCSFA) group, medium-chain saturated fatty acid (MCSFA) group, n-3 polyunsaturated fatty acid (n-3 PUFA) group, n-6 polyunsaturated fatty acid (n-6 PUFA) group, monounsaturated fatty acid (MUFA) group and trans fatty acid (TFA) group. Then, the fecal microbiota transplant (FMT) was performed in other pseudo germ-free mice after antibiotic treatment. The experimental groups were orally perfused with gut microbiota that induced by HFD with different types of dietary fatty acids. The mice were fed with regular fodder before and after FMT. High-performance liquid chromatography-mass spectrometry (LC-MS) was used to analysis the composition of fatty acids in the brain of HFD-fed mice and hippocampus of mice treated with FMT which was collected from HFD-fed mice.

RESULTS

The content of acyl-carnitines (AcCa) increased and lysophosphatidylgylcerol (LPG) decreased in all kinds of HFD groups. phosphatidic acids (PA), phosphatidylethanolamine (PE) and sphingomyelin (SM) contents were significantly increased in the n-6 PUFA-fed HFD group. The HFD elevated the saturation of brain fatty acyl (FA). Lysophosphatidylcholine (LPC), lysodi-methylphosphatidylethanolamine (LdMePE), monolysocardiolipin (MLCL), dihexosylceramides (Hex2Cer), and wax ester (WE) significantly increased after LCSFA-fed FMT. MLCL reduced and cardiolipin (CL) raised significantly after n-3 PUFA-fed FMT.

CONCLUSIONS

The study revealed, HFD and FMT in mice had certain effects on the content and composition of fatty acids in the brain, especially on glycerol phospholipid (GP). The change of AcCa content in FA was a good indicator of dietary fatty acid intake. By altering the fecal microbiota, dietary fatty acids might affect brain lipids.

Long-Term Ingestion of Sicilian Black Bee Chestnut Honey and/or D-Limonene Counteracts Brain Damage Induced by High Fat-Diet in Obese Mice

Obesity is linked to neurodegeneration, which is mainly caused by inflammation and oxidative stress. We analyzed whether the long-term intake of honey and/or D-limonene, which are known for their antioxidant and anti-inflammatory actions, when ingested separately or in combination, can counteract the neurodegeneration occurring in high fat diet (HFD)-induced obesity. After 10 weeks of HFD, mice were divided into: HFD-, HFD + honey (HFD-H)-, HFD + D-limonene (HFD-L)-, HFD + honey + D-limonene (HFD-H + L)-fed groups, for another 10 weeks. Another group was fed a standard diet (STD). We analyzed the brain neurodegeneration, inflammation, oxidative stress, and gene expression of Alzheimer's disease (AD) markers. The HFD animals showed higher neuronal apoptosis, upregulation of pro-apoptotic genes Fas-L, Bim P27 and downregulation of anti-apoptotic factors BDNF and BCL2; increased gene expression of the pro-inflammatory IL-1β, IL-6 and TNF-α and elevated oxidative stress markers COX-2, iNOS, ROS and nitrite. The honey and D-limonene intake counteracted these alterations; however, they did so in a stronger manner when in combination. Genes involved in amyloid plaque processing (APP and TAU), synaptic function (Ache) and AD-related hyperphosphorylation were higher in HFD brains, and significantly downregulated in HFD-H, HFD-L and HFD-H + L. These results suggest that honey and limonene ingestion counteract obesity-related neurodegeneration and that joint consumption is more efficacious than a single administration.

Association of Dietary α-Carotene and β-Carotene Intake with Low Cognitive Performance in Older Adults: A Cross-Sectional Study from the National Health and Nutrition Examination Survey

This study aims to examine the relationships of dietary α-carotene and β-carotene intake with cognitive function. The data were selected from the National Health and Nutrition Examination Survey (NHANES) 2011-2014. A total of 2009 participants were included in this analysis. Dietary α-carotene and β-carotene intake were averaged by two 24-h dietary recalls. The Consortium to Establish a Registry for Alzheimer's Disease Word Learning subset (CERAD W-L), Animal Fluency Test (AFT), and Digit Symbol Substitution Test (DSST) were used to evaluate cognitive function. Logistic regression and restricted cubic spline models were applied to explore the associations of dietary α-carotene and β-carotene intake with cognitive performance. After adjusting for all confounding factors, compared with individuals in the lowest quartile of β-carotene dietary intake, those in the highest quartile had lower risks of both CERAD W-L decline [odds ratio (OR) = 0.63, 95% confidence interval (CI): 0.44-0.90] and AFT decline (OR = 0.66, 95% CI: 0.47-0.94). In addition, the third quartile of β-carotene dietary intake had a significantly decreased risk of lower DSST (OR = 0.67, 95% CI: 0.48-0.83). Compared with the lowest quartile of α-carotene intake, the OR of AFT decline in the highest intake quartile was 0.66 (95% CI: 0.46, 0.94). For males, both dietary α-carotene and β-carotene intake were associated with a decreased risk of AFT decline (OR = 0.42, 95% CI: 0.25-0.71; OR = 0.51, 95% CI: 0.30-0.85, respectively). For females, dietary α-carotene intake was associated with a decreased risk of CERAD W-L decline (OR = 0.55, 95% CI: 0.33-0.91) and dietary β-carotene intake was associated with decreased risks of both CERAD W-L and AFT decline (OR = 0.37, 95% CI: 0.21-0.64; OR = 0.58, 95% CI: 0.37-0.91, respectively). Our results suggested that higher dietary α-carotene and β-carotene intake had inverse effects on cognitive function decline among older adults.

Nutrition and adult neurogenesis in the hippocampus: Does what you eat help you remember?

Neurogenesis is a complex process by which neural progenitor cells (NPCs)/neural stem cells (NSCs) proliferate and differentiate into new neurons and other brain cells. In adulthood, the hippocampus is one of the areas with more neurogenesis activity, which is involved in the modulation of both emotional and cognitive hippocampal functions. This complex process is affected by many intrinsic and extrinsic factors, including nutrition. In this regard, preclinical studies performed in rats and mice demonstrate that high fats and/or sugars diets have a negative effect on adult hippocampal neurogenesis (AHN). In contrast, diets enriched with bioactive compounds, such as polyunsaturated fatty acids and polyphenols, as well as intermittent fasting or caloric restriction, can induce AHN. Interestingly, there is also growing evidence demonstrating that offspring AHN can be affected by maternal nutrition in the perinatal period. Therefore, nutritional interventions from early stages and throughout life are a promising perspective to alleviate neurodegenerative diseases by stimulating neurogenesis. The underlying mechanisms by which nutrients and dietary factors affect AHN are still being studied. Interestingly, recent evidence suggests that additional peripheral mediators may be involved. In this sense, the microbiota-gut-brain axis mediates bidirectional communication between the gut and the brain and could act as a link between nutritional factors and AHN. The aim of this mini-review is to summarize, the most recent findings related to the influence of nutrition and diet in the modulation of AHN. The importance of maternal nutrition in the AHN of the offspring and the role of the microbiota-gut-brain axis in the nutrition-neurogenesis relationship have also been included.

Malignant Brain Aging: The Formidable Link Between Dysregulated Signaling Through Mechanistic Target of Rapamycin Pathways and Alzheimer's Disease (Type 3 Diabetes)

Malignant brain aging corresponds to accelerated age-related declines in brain functions eventually derailing the self-sustaining forces that govern independent vitality. Malignant brain aging establishes the path toward dementing neurodegeneration, including Alzheimer's disease (AD). The full spectrum of AD includes progressive dysfunction of neurons, oligodendrocytes, astrocytes, microglia, and the microvascular systems, and is mechanistically driven by insulin and insulin-like growth factor (IGF) deficiencies and resistances with accompanying deficits in energy balance, increased cellular stress, inflammation, and impaired perfusion, mimicking the core features of diabetes mellitus. The underlying pathophysiological derangements result in mitochondrial dysfunction, abnormal protein aggregation, increased oxidative and endoplasmic reticulum stress, aberrant autophagy, and abnormal post-translational modification of proteins, all of which are signature features of both AD and dysregulated insulin/IGF-1-mechanistic target of rapamycin (mTOR) signaling. This article connects the dots from benign to malignant aging to neurodegeneration by reviewing the salient pathologies associated with initially adaptive and later dysfunctional mTOR signaling in the brain. Effective therapeutic and preventive measures must be two-pronged and designed to 1) address complex and shifting impairments in mTOR signaling through the re-purpose of effective anti-diabetes therapeutics that target the brain, and 2) minimize the impact of extrinsic mediators of benign to malignant aging transitions, e.g., inflammatory states, obesity, systemic insulin resistance diseases, and repeated bouts of general anesthesia, by minimizing exposures or implementing neuroprotective measures.

Metal Profiles in Autism Spectrum Disorders: A Crosstalk between Toxic and Essential Metals

Since hundreds of years ago, metals have been recognized as impacting our body's physiology. As a result, they have been studied as a potential cure for many ailments as well as a cause of acute or chronic poisoning. However, the link between aberrant metal levels and neuropsychiatric illnesses such as schizophrenia and neurodevelopmental disorders, such as autism spectrum disorders (ASDs), is a relatively new finding, despite some evident ASD-related consequences of shortage or excess of specific metals. In this review, we will summarize past and current results explaining the pathomechanisms of toxic metals at the cellular and molecular levels that are still not fully understood. While toxic metals may interfere with dozens of physiological processes concurrently, we will focus on ASD-relevant activity such as inflammation/immune activation, mitochondrial malfunction, increased oxidative stress, impairment of axonal myelination, and synapse formation and function. In particular, we will highlight the competition with essential metals that may explain why both the presence of certain toxic metals and the absence of certain essential metals have emerged as risk factors for ASD. Although often investigated separately, through the agonistic and antagonistic effects of metals, a common metal imbalance may result in relation to ASD.

Sexual dimorphism in spatial learning and brain metabolism after exposure to a western diet and early life stress in rats

Prolonged daily intake of Western-type diet rich in saturated fats and sugars, and exposure to early life stress have been independently linked to impaired neurodevelopment and behaviour in animal models. However, sex-specific effects of both environmental factors combined on spatial learning and memory, behavioural flexibility, and brain oxidative capacity have still not been addressed. The current study aimed to evaluate the impact of maternal and postnatal exposure to a high-fat and high-sugar diet (HFS), and exposure to early life stress by maternal separation in adult male and female Wistar rats. For this purpose, spatial learning and memory and behavioural flexibility were evaluated in the Morris water maze, and regional brain oxidative capacity and oxidative stress levels were measured in the hippocampus and medial prefrontal cortex. Spatial memory, regional brain oxidative metabolism, and levels of oxidative stress differed between females and males, suggesting sexual dimorphism in the effects of a HFS diet and early life stress. Males fed the HFS diet performed better than all other experimental groups independently of early life stress exposure. However, behavioural flexibility evaluated in the spatial reversal leaning task was impaired in males fed the HFS diet. In addition, exposure to maternal separation or the HFS diet increased the metabolic capacity of the prefrontal cortex and dorsal hippocampus in males and females. Levels of oxidative stress measured in the latter brain regions were also increased in groups fed the HFS diet, but maternal separation seemed to dampen regional brain oxidative stress levels. Therefore, these results suggest a compensatory effect resulting from the interaction between prolonged exposure to a HFS diet and early life stress.

Implication of saturated fats in the aetiology of childhood attention deficit/hyperactivity disorder - A narrative review

Attention Deficit/Hyperactivity Disorder (ADHD) is the most common mental health disorder in the paediatric population. ADHD is highly comorbid with obesity, and has also been associated with poor dietary patterns such as increased consumption of refined carbohydrates and saturated fats. Although ADHD in children was associated with high consumption of saturated fats, so far there has been no evidence-based attempt to integrate dietary strategies controlling for intake of saturated fats into the etiological framework of the disorder. Evidence from human studies and animal models has shown that diets high in saturated fats are detrimental for the development of dopaminergic neurocircuitries, synthesis of neurofactors (e.g. brain derived neurotrophic factor) and may promote brain inflammatory processes. Notably, animal models provide evidence that early life consumption of a high saturated fats diet may impair the development of central dopamine pathways. In the present paper, we review the impact of high saturated fats diets on neurobiological processes in human studies and animal models, and how these associations may be relevant to the neuropathophysiology of ADHD in children. The validation of this relationship and its underlying mechanisms through future investigative studies could have implications for the prevention or exacerbation of ADHD symptoms, improve the understanding of the pathogenesis of the disorder, and help design future dietary studies in patients with ADHD.

Melatonin treatment improves cognitive deficits by altering inflammatory and neurotrophic factors in the hippocampus of obese mice

Overweight and obesity are associated with an increased risk of developing dementia and cognitive deficits. Neuroinflammation is one of the most important mechanisms behind cognitive impairment in obese patients. In recent years, the neuroendocrine hormone melatonin has been suggested to have therapeutic effects for memory decline in several neuropsychiatric and neurological conditions. However, the effects of melatonin on cognitive function under obesity conditions still need to be clarified. The purpose of this study was to determine whether melatonin treatment can improve cognitive impairment in obese mice. To this end, male C57BL6 mice were treated with a high-fat diet (HFD) for 20 weeks to induce obesity. The animal received melatonin for 8 weeks. Cognitive functions were evaluated using the Y maze, object recognition test, and the Morris water maze. We measured inflammatory cytokines including tumor necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-17A, and brain-derived neurotrophic factor (BDNF) in the hippocampus of obese mice. Our results show that HFD-induced obesity significantly impaired working, spatial and recognition memory by increasing IFN-γ and IL-17A and decreasing BDNF levels in the hippocampus of mice. On the other hand, melatonin treatment effectively improved all cognitive impairments and reduced TNF-α, IFN-γ, and IL-17A and elevated BDNF levels in the hippocampus of obese mice. Taken together, this study suggests that melatonin treatment could have a beneficial role in the treatment of cognitive impairment in obesity.

Sexual dimorphism modulates metabolic and cognitive alterations under HFD nutrition and chronic stress exposure in mice. Correlation between spatial memory impairment and BDNF mRNA expression in hippocampus and spleen

AIMS

The accumulated evidence suggests that lifestyle - specifically dietary habits and stress exposure - plays a detrimental role in health. The purpose of the present study was to analyze the interplay of stress, diet, and sex in metabolic and cognitive alterations.

MAIN METHODS

For this purpose, one-month-old C57Bl/6J mice were fed with a standard diet or high-fat diet (HFD). After eight weeks, one subgroup of mice from each respective diet was exposed to 20 weeks of chronic mild stress (CMS), whilst the others were left undisturbed.

KEY FINDINGS

After 28 weeks of HFD feeding, mice from both sexes were overweight, with an increase in caloric intake and abdominal and subcutaneous fat pads. Stress exposure induced a decrease in body weight, related to a decrease in caloric efficiency in both males and females. Results indicate that males are more susceptible than the females in modulating metabolic and cognitive functions under HFD and CMS. Although both sexes demonstrated HFD-induced weight gain, fat accumulation, insulin resistance, high cholesterol, only males exposed to CMS but not females have (i) impaired glucose tolerance with higher glucose level; (ii) significant prolonged latency in Barnes test, suggesting cognitive impairment; (iii) increased IFN-gamma expression in hippocampus, suggesting greater neuroinflammatory response; (iv) poorer cognitive performance related to a decrease in hippocampal and spleen BDNF mRNA expression.

SIGNIFICANCE

The main finding in this study is the presence of a sexual dimorphism in modulating metabolic and cognitive functions under HFD and CMS, showing males are more susceptible than females. In addition, poorer cognitive performance was related to a decrease in hippocampal BDNF mRNA expression. Interestingly, these changes were observed in the spleen as well.

Walnut Prevents Cognitive Impairment by Regulating the Synaptic and Mitochondrial Dysfunction via JNK Signaling and Apoptosis Pathway in High-Fat Diet-Induced C57BL/6 Mice

This study was conducted to evaluate the protective effect of Juglans regia (walnut, Gimcheon 1ho cultivar, GC) on high-fat diet (HFD)-induced cognitive dysfunction in C57BL/6 mice. The main physiological compounds of GC were identified as pedunculagin/casuariin isomer, strictinin, tellimagrandin I, ellagic acid-O-pentoside, and ellagic acid were identified using UPLC Q-TOF/MS analysis. To evaluate the neuro-protective effect of GC, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), 2′,7′-dichlorodihydrofluorecein diacetate (DCF-DA) analysis were conducted in H₂O₂ and high glucose-induced neuronal PC12 cells and hippocampal HT22 cells. GC presented significant cell viability and inhibition of reactive oxygen species (ROS) production. GC ameliorated behavioral and memory dysfunction through Y-maze, passive avoidance, and Morris water maze tests. In addition, GC reduced white adipose tissue (WAT), liver fat mass, and serum dyslipidemia. To assess the inhibitory effect of antioxidant system deficit, lipid peroxidation, ferric reducing antioxidant power (FRAP), and advanced glycation end products (AGEs) were conducted. Administration of GC protected the antioxidant damage against HFD-induced diabetic oxidative stress. To estimate the ameliorating effect of GC, acetylcholine (ACh) level, acetylcholinesterase (AChE) activity, and expression of AChE and choline acetyltransferase (ChAT) were conducted, and the supplements of GC suppressed the cholinergic system impairment. Furthermore, GC restored mitochondrial dysfunction by regulating the mitochondrial ROS production and mitochondrial membrane potential (MMP) levels in cerebral tissues. Finally, GC ameliorated cerebral damage by synergically regulating the protein expression of the JNK signaling and apoptosis pathway. These findings suggest that GC could provide a potential functional food source to improve diabetic cognitive deficits and neuronal impairments.

Neurogenesis in aging and age-related neurodegenerative diseases

Adult neurogenesis, the process by which neurons are generated in certain areas of the adult brain, declines in an age-dependent manner and is one potential target for extending cognitive healthspan. Aging is a major risk factor for neurodegenerative diseases and, as lifespans are increasing, these health challenges are becoming more prevalent. An age-associated loss in neural stem cell number and/or activity could cause this decline in brain function, so interventions that reverse aging in stem cells might increase the human cognitive healthspan. In this review, we describe the involvement of adult neurogenesis in neurodegenerative diseases and address the molecular mechanistic aspects of neurogenesis that involve some of the key aggregation-prone proteins in the brain (i.e., tau, Aβ, α-synuclein, …). We summarize the research pertaining to interventions that increase neurogenesis and regulate known targets in aging research, such as mTOR and sirtuins. Lastly, we share our outlook on restoring the levels of neurogenesis to physiological levels in elderly individuals and those with neurodegeneration. We suggest that modulating neurogenesis represents a potential target for interventions that could help in the fight against neurodegeneration and cognitive decline.

Therapeutic application of GLP-1 and GIP receptor agonists in Parkinson's disease

INTRODUCTION

Diabetes is a risk factor for Parkinson's disease (PD) and shares similar dysregulated insulin pathways. Glucagon-like peptide-1 (GLP-1) analogs originally designed to treat diabetes have shown potent neuroprotective activity in preclinical studies of PD. They are neuroprotective by inhibiting inflammation, improving neuronal survival, maintenance of synapses, and dopaminergic transmission in the brain. Building on this, three clinical studies have reported impressive effects in patients with PD, testing exendin-4 (Exenatide, Bydureon) or liraglutide (Victoza, Saxenda). Glucose-dependent insulinotropic peptide (GIP) is another peptide hormone that has shown good effects in animal models of PD. Novel dual GLP-1/GIP agonists have been developed that can penetrate the blood-brain barrier (BBB) and show superior effects in animal models compared to GLP-1 drugs.

AREAS COVERED

The review summarizes preclinical and clinical studies testing GLP-1R agonists and dual GLP-1/GIPR agonists in PD and discusses possible mechanisms of action.

EXPERT OPINION

Current strategies to treat PD by lowering the levels of alpha-synuclein have not shown effects in clinical trials. It is time to move on from the 'misfolding protein' hypothesis. Growth factors such as GLP-1 that can cross the BBB have already shown impressive effects in patients and are the future of drug discovery in PD.

Maternal High-Energy Diet during Pregnancy and Lactation Impairs Neurogenesis and Alters the Behavior of Adult Offspring in a Phenotype-Dependent Manner

Obesity is one of the biggest and most costly health challenges the modern world encounters. Substantial evidence suggests that the risk of metabolic syndrome or obesity formation may be affected at a very early stage of development, in particular through fetal and/or neonatal overfeeding. Outcomes from epidemiological studies indicate that maternal nutrition during pregnancy and lactation has a profound impact on adult neurogenesis in the offspring. In the present study, an intergenerational dietary model employing overfeeding of experimental mice during prenatal and early postnatal development was applied to acquire mice with various body conditions. We investigated the impact of the maternal high-energy diet during pregnancy and lactation on adult neurogenesis in the olfactory neurogenic region involving the subventricular zone (SVZ) and the rostral migratory stream (RMS) and some behavioral tasks including memory, anxiety and nociception. Our findings show that a maternal high-energy diet administered during pregnancy and lactation modifies proliferation and differentiation, and induced degeneration of cells in the SVZ/RMS of offspring, but only in mice where extreme phenotype, such as significant overweight/adiposity or obesity is manifested. Thereafter, a maternal high-energy diet enhances anxiety-related behavior in offspring regardless of its body condition and impairs learning and memory in offspring with an extreme phenotype.

Early metabolic impairment as a contributor to neurodegenerative disease: Mechanisms and potential pharmacological intervention

The metabolic syndrome comprises a family of clinical and laboratory findings, including insulin resistance, hyperglycemia, hypertriglyceridemia, low high-density lipoprotein cholesterol levels, and hypertension, in addition to central obesity. The syndrome confers a high risk of cardiovascular mortality. Indeed, metabolic dysfunction has been shown to cause a direct insult to smooth muscle and endothelial components of the vasculature, which leads to vascular dysfunction and hyperreactivity. This, in turn, causes cerebral vasoconstriction and hypoperfusion, eventually contributing to cognitive deficits. Moreover, the metabolic syndrome disrupts key homeostatic processes in the brain, including apoptosis, autophagy, and neurogenesis. Impairment of such processes in the context of metabolic dysfunction has been implicated in the pathogenesis of neurodegenerative diseases, including Alzheimer, Parkinson, and Huntington diseases. The aim of this review is to elucidate the role that the metabolic syndrome plays in the pathogenesis of the latter disorders, with a focus on the role of perivascular adipose inflammation in the peripheral-to-central transduction of the inflammatory insult. This review delineates common signaling pathways that contribute to these pathologies. Moreover, the role of therapeutic agents aimed at treating the metabolic syndrome, as well as their risk factors that interfere with the aforementioned pathways, are discussed as potential interventions for neurodegenerative diseases.

Systems genetics in the rat HXB/BXH family identifies Tti2 as a pleiotropic quantitative trait gene for adult hippocampal neurogenesis and serum glucose

Neurogenesis in the adult hippocampus contributes to learning and memory in the healthy brain but is dysregulated in metabolic and neurodegenerative diseases. The molecular relationships between neural stem cell activity, adult neurogenesis, and global metabolism are largely unknown. Here we applied unbiased systems genetics methods to quantify genetic covariation among adult neurogenesis and metabolic phenotypes in peripheral tissues of a genetically diverse family of rat strains, derived from a cross between the spontaneously hypertensive (SHR/OlaIpcv) strain and Brown Norway (BN-Lx/Cub). The HXB/BXH family is a very well established model to dissect genetic variants that modulate metabolic and cardiovascular diseases and we have accumulated deep phenome and transcriptome data in a FAIR-compliant resource for systematic and integrative analyses. Here we measured rates of precursor cell proliferation, survival of new neurons, and gene expression in the hippocampus of the entire HXB/BXH family, including both parents. These data were combined with published metabolic phenotypes to detect a neurometabolic quantitative trait locus (QTL) for serum glucose and neuronal survival on Chromosome 16: 62.1-66.3 Mb. We subsequently fine-mapped the key phenotype to a locus that includes the Telo2-interacting protein 2 gene (Tti2)-a chaperone that modulates the activity and stability of PIKK kinases. To verify the hypothesis that differences in neurogenesis and glucose levels are caused by a polymorphism in Tti2, we generated a targeted frameshift mutation on the SHR/OlaIpcv background. Heterozygous SHR-Tti2+/- mutants had lower rates of hippocampal neurogenesis and hallmarks of dysglycemia compared to wild-type littermates. Our findings highlight Tti2 as a causal genetic link between glucose metabolism and structural brain plasticity. In humans, more than 800 genomic variants are linked to TTI2 expression, seven of which have associations to protein and blood stem cell factor concentrations, blood pressure and frontotemporal dementia.

Sex Differences in Metabolic and Behavioral Responses to Exercise but Not Exogenous Osteocalcin Treatment in Mice Fed a High Fat Diet

Background

Exercise helps improve glucose handling in diabetes and has been shown to improve mood and cognition in other conditions. Osteocalcin, a protein produced by bone osteoblasts, was reported to have endocrine actions to improve both metabolism and also improve age-related cognitive deficits in mice.

Methods

This study was designed to compare the effects of daily treadmill running exercise with injection of osteocalcin in high fat diet (HFD) induced diabetes in male and female C57BL/6J mice. Following established glucose intolerance and treatment for 8 weeks, mice were assessed for anxiety on an elevated plus maze, motivation by tail suspension test and cognition and memory in a puzzle box. Endogenous osteocalcin was measured by ELISA.

Results

Mice on HFD had high weight gain, glucose intolerance and increased white fat. Exercise increased circulating osteocalcin levels in female mice but decreased them in male mice. Exercise also decreased weight gain and improved glucose tolerance in female but not male mice; however, treatment with osteocalcin made no metabolic improvements in either males or females. HFD induced anxiety only in female mice and this was not improved by osteocalcin. Exercise induced anxiety only in male mice. HFD also increased depressive-like behavior in both sexes, and this was improved by either exercise or osteocalcin treatment. Cognitive deficits were seen in both male and female mice on HFD. Exercise improved cognitive performance in female but not male mice, while osteocalcin treatment improved cognitive performance in both sexes.

Conclusion

There were sex differences in the effects of exercise on endogenous osteocalcin regulation that correlated with improvements in cognitive but not metabolic outcomes. Exogenous osteocalcin did not improve metabolism but was effective in improving HFD-induced cognitive deficits. Sex is an important variable in hormonal and cognitive responses to exercise in diabetes.

Potential Roles of Glucagon-Like Peptide-1 and Its Analogues in Dementia Targeting Impaired Insulin Secretion and Neurodegeneration

Dementia is a chronic, irreversible condition marked by memory loss, cognitive decline, and mental instability. It is clinically related to various progressive neurological diseases, including Parkinson’s disease, Alzheimer’s disease, and Huntington’s. The primary cause of neurological disorders is insulin desensitization, demyelination, oxidative stress, and neuroinflammation accompanied by various aberrant proteins such as amyloid-β deposits, Lewy bodies accumulation, tau formation leading to neurofibrillary tangles. Impaired insulin signaling is directly associated with amyloid-β and α-synuclein deposition, as well as specific signaling cascades involved in neurodegenerative diseases. Insulin dysfunction may initiate various intracellular signaling cascades, including phosphoinositide 3-kinase (PI3K), c-Jun N-terminal kinases (JNK), and mitogen-activated protein kinase (MAPK). Neuronal death, inflammation, neuronal excitation, mitochondrial malfunction, and protein deposition are all influenced by insulin. Recent research has focused on GLP-1 receptor agonists as a potential therapeutic target. They increase glucose-dependent insulin secretion and are beneficial in neurodegenerative diseases by reducing oxidative stress and cytokine production. They reduce the deposition of abnormal proteins by crossing the blood-brain barrier. The purpose of this article is to discuss the role of insulin dysfunction in the pathogenesis of neurological diseases, specifically dementia. Additionally, we reviewed the therapeutic target (GLP-1) and its receptor activators as a possible treatment of dementia.

The possible protective role of N-acetyl cysteine on duodenal mucosa of high fat diet and orlistat treated adult male albino rats and the active role of tumor necrosis factor α (TNFα) and Interleukin 6 (IL6) (histological and biochemical study)

BACKGROUND

Obesity is a major universal health issue linked to a majority of illness.

AIM

To evaluate the histological and biochemical changes occurred in the duodenal mucosa of high fat diet HFD and orlistat fed rats and to assess the possible protective role of N-acetyl cysteine NAC supplementation.

MATERIAL AND METHOD

Sixty male albino rats weighing 180-200 g were classified randomly into control group I and three experimental groups (HFD group II, HFD + orlistat group III, and HFD + orlistat + NAC group IV). All experimental groups received HFD alone/and treatment for 6 weeks. Group III received orlistat (32 mg/kg/day) before meals and group IV received the same regimen as group III in addition to NAC (230 mg/kg/day) after meals. After completion of the experiment, duodenal sections were processed for histological examination, oxidative stress parameters, and semiqualitative real time PCR for proinflammatory mediators TNFα and IL6 evaluation. Also, plasma lipid parameters were assessed and morphometric duodenal results were analyzed statistically.

RESULTS

By histological examination of HFD and (HFD + orlistat) groups, we found severe to moderate duodenal structural disturbances, increased goblet cells, collagen fibers, and BAX and iNOS immunostaining. By Biochemical examination, both groups showed increased proinflammatory markers level (TNFα and IL6) with decreased all antioxidant parameters and increased MDA. Moreover, NAC treatment in group IV significantly reduced all structural changes, levels of proinflammatory mediators and increased all antioxidant parameter levels and decreased MDA.

CONCLUSION

All findings elucidated that NAC could be accounted to be a useful drug for protection of duodenal mucosa of HFD and orlistat treated animals.

Neurogenesis in the Maternal Rodent Brain: Impacts of Gestation-Related Hormonal Regulation, Stress, and Obesity

In order to maintain maternal behavior, it is important that the maternal rodent brain promotes neurogenesis. Maternal neurogenesis is altered by the dynamic shifts in reproductive hormone levels during pregnancy. Thus, lifestyle events such as gestational stress and obesity that can affect hormone production will affect neuroendocrine control of maternal neurogenesis. However, there is a lack of information about the regulation of maternal neurogenesis by placental hormones, which are key components of the reproductive hormonal profile during pregnancy. There is also little known about how maternal neurogenesis can be affected by health concerns such as gestational stress and obesity, and its relationship to peripartum mental health disorders. This review summarizes the changing levels of neurogenesis in mice and rats during gestation and postpartum as well as regulation of neurogenesis by pregnancy-related hormones. The influence of neurogenesis on maternal behavior is also discussed while bringing attention to the effect of health-related concerns during gestation, such as stress and obesity on neuroendocrine control of maternal neurogenesis. In doing so, this review identifies the gaps in the literature and specifically emphasizes the importance of further research on maternal brain physiology to address them.

Age-related immune alterations and cerebrovascular inflammation

Aging is associated with chronic systemic inflammation, which contributes to the development of many age-related diseases, including vascular disease. The world's population is aging, leading to an increasing prevalence of both stroke and vascular dementia. The inflammatory response to ischemic stroke is critical to both stroke pathophysiology and recovery. Age is a predictor of poor outcomes after stroke. The immune response to stroke is altered in aged individuals, which contributes to the disparate outcomes between young and aged patients. In this review, we describe the current knowledge of the effects of aging on the immune system and the cerebral vasculature and how these changes alter the immune response to stroke and vascular dementia in animal and human studies. Potential implications of these age-related immune alterations on chronic inflammation in vascular disease outcome are highlighted.

Lower synaptic density is associated with psychiatric and cognitive alterations in obesity

Obesity is a serious medical condition that often co-occurs with stress-related psychiatric disorders. It is recognized that the brain plays a key role in the (patho)physiology of obesity and that there is a bidirectional relationship between obesity and psychopathology, yet molecular mechanisms altered in obesity have not been fully elucidated. Thus, we investigated relationships between obesity and synaptic density in vivo using the radioligand [11C]UCB-J (which binds to synaptic glycoprotein SV2A) and positron emission tomography in individuals with obesity, and with or without stress-related psychiatric disorders. Regions of interest were the dorsolateral prefrontal cortex, orbitofrontal cortex, ventromedial, amygdala, hippocampus, and cerebellum. Forty individuals with a body mass index (BMI) ≥ 25 kg/m2 (overweight/obese), with (n = 28) or without (n = 12) psychiatric diagnosis, were compared to 30 age- and sex-matched normal weight individuals (BMI < 25), with (n = 14) or without (n = 16) psychiatric diagnosis. Overall, significantly lower synaptic density was observed in overweight/obese relative to normal weight participants (ηp2 = 0.193, F = 2.35, p = 0.042). Importantly, in participants with stress-related psychiatric diagnoses, we found BMI to be negatively correlated with synaptic density in all regions of interest (p ≤ 0.03), but no such relationship observed for mentally healthy controls (p ≥ 0.68). In the stress-related psychiatric groups, dorsolateral prefrontal cortex synaptic density was negatively associated with measures of worry (r = -0.46, p = 0.01), tension/anxiety (r = -0.38, p = 0.04), fatigue (r = -0.44, p = 0.02), and attentional difficulties (r = -0.44, p = 0.02). In summary, the findings of this novel in vivo experiment suggest compounding effects of obesity and stress-related psychopathology on the brain and the associated symptomatology that may impact functioning. This offers a novel biological mechanism for the relationship between overweight/obesity and stress-related psychiatric disorders that may guide future intervention development efforts.

Mini review: The relationship between energy status and adult hippocampal neurogenesis

The ability to generate new hippocampal neurons throughout adulthood and successfully integrate them into existing neural networks is critical to cognitive function, while disordered regulation of this process results in neurodegenerative or psychiatric disease. Consequently, identifying the molecular mechanisms promoting homeostatic hippocampal neurogenesis in adults is essential to understanding the etiologies of these disorders and developing therapeutic interventions. For example, recent evidence identifies a strong association between metabolic function and adult hippocampal neurogenesis. Hippocampal neural stem cell (NSC) fate dynamically fluctuates with changes in substrate availability and energy status (AMP/ATP and NAD⁺/NADH ratios). Furthermore, many metabolic hormones, such as insulin, insulin-like growth factors, and leptin exhibit dual functions also modulating hippocampal neurogenesis and neuron survivability. These diverse metabolic inputs to NSC's from various tissues seemingly suggest the existence of a system in which energy status can finely modulate hippocampal neurogenesis. Supporting this hypothesis, interventions promoting energy balance, such as caloric restriction, intermittent fasting, and exercise, have shown encouraging potential enhancing hippocampal neurogenesis and cognitive function. Overall, there is a clear relationship between whole body energy status, adult hippocampal neurogenesis, and neuron survival; however, the molecular mechanisms underlying this phenomenon are multifaceted. Thus, the aim of this review is to analyze the literature investigating energy status-mediated regulation of adult neurogenesis in the hippocampus, highlight the neurocircuitry and intracellular signaling involved, and propose impactful future directions in the field.

The Reactive Species Interactome in the Brain

Significance: Redox pioneer Helmut Sies attempted to explain reactive species' challenges faced by organelles, cells, tissues, and organs via three complementary definitions: (i) oxidative stress, that is, the disturbance in the prooxidant-antioxidant defense balance in favor of the prooxidants; (ii) oxidative eustress, the low physiological exposure to prooxidants; and (iii) oxidative distress, the supraphysiological exposure to prooxidants. Recent Advances: Identification, concentration, and interactions are the most important elements to improve our understanding of reactive species in physiology and pathology. In this context, the reactive species interactome (RSI) is a new multilevel redox regulatory system that identifies reactive species families, reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species, and it integrates their interactions with their downstream biological targets. Critical Issues: We propose a united view to fully combine reactive species identification, oxidative eustress and distress, and the RSI system. In this view, we also propose including the forgotten reactive carbonyl species, an increasingly rediscovered reactive species family related to the other reactive families, and key enzymes within the RSI. We focus on brain physiology and pathology to demonstrate why this united view should be considered. Future Directions: More studies are needed for an improved understanding of the contributions of reactive species through their identification, concentration, and interactions, including in the brain. Appreciating the RSI in its entirety should unveil new molecular players and mechanisms in physiology and pathology in the brain and elsewhere.

Hippocampal-specific insulin resistance elicits behavioral despair and hippocampal dendritic atrophy

Insulin resistance is a major contributor to the neuroplasticity deficits observed in patients with metabolic disorders. However, the relative contribution of peripheral versus central insulin resistance in the development of neuroplasticity deficits remains equivocal. To distinguish between peripheral and central insulin resistance, we developed a lentiviral vector containing an antisense sequence selective for the insulin receptor (LV-IRAS). We previously demonstrated that intra-hippocampal injection of this vector impairs synaptic transmission and hippocampal-dependent learning and memory in the absence of peripheral insulin resistance. In view of the increased risk for the development of neuropsychiatric disorders in patients with insulin resistance, the current study examined depressive and anxiety-like behaviors, as well as hippocampal structural plasticity in rats with hippocampal-specific insulin resistance. Following hippocampal administration of either the LV-control virus or the LV-IRAS, anhedonia was evaluated by the sucrose preference test, despair behavior was assessed in the forced swim test, and anxiety-like behaviors were determined in the elevated plus maze. Hippocampal neuron morphology was studied by Golgi-Cox staining. Rats with hippocampal insulin resistance exhibited anxiety-like behaviors and behavioral despair without differences in anhedonia, suggesting that some but not all components of depressive-like behaviors were affected. Morphologically, hippocampal-specific insulin resistance elicited atrophy of the basal dendrites of CA3 pyramidal neurons and dentate gyrus granule neurons, and also reduced the expression of immature dentate gyrus granule neurons. In conclusion, hippocampal-specific insulin resistance elicits structural deficits that are accompanied by behavioral despair and anxiety-like behaviors, identifying hippocampal insulin resistance as a key factor in depressive illness.

Muscle-generated BDNF (brain derived neurotrophic factor) maintains mitochondrial quality control in female mice

Mitochondrial remodeling is dysregulated in metabolic diseases but the underlying mechanism is not fully understood. We report here that BDNF (brain derived neurotrophic factor) provokes mitochondrial fission and clearance in skeletal muscle via the PRKAA/AMPK-PINK1-PRKN/Parkin and PRKAA-DNM1L/DRP1-MFF pathways. Depleting Bdnf expression in myotubes reduced fatty acid-induced mitofission and mitophagy, which was associated with mitochondrial elongation and impaired lipid handling. Muscle-specific bdnf knockout (MBKO) mice displayed defective mitofission and mitophagy, and accumulation of dysfunctional mitochondria in the muscle when they were fed with a high-fat diet (HFD). These animals also have exacerbated body weight gain, increased intramyocellular lipid deposition, reduced energy expenditure, poor metabolic flexibility, and more insulin resistance. In contrast, consuming a BDNF mimetic (7,8-dihydroxyflavone) increased mitochondrial content, and enhanced mitofission and mitophagy in the skeletal muscles. Hence, BDNF is an essential myokine to maintain mitochondrial quality and function, and its repression in obesity might contribute to impaired metabolism.Abbreviation: 7,8-DHF: 7,8-dihydroxyflavone; ACACA/ACC: acetyl Coenzyme A carboxylase alpha; ACAD: acyl-Coenzyme A dehydrogenase family; ACADVL: acyl-Coenzyme A dehydrogenase, very long chain; ACOT: acyl-CoA thioesterase; CAMKK2: calcium/calmodulin-dependent protein kinase kinase 2, beta; BDNF: brain derived neurotrophic factor; BNIP3: BCL2/adenovirus E1B interacting protein 3; BNIP3L/NIX: BCL2/adenovirus E1B interacting protein 3-like; CCL2/MCP-1: chemokine (C-C motif) ligand 2; CCL5: chemokine (C-C motif) ligand 5; CNS: central nervous system; CPT1B: carnitine palmitoyltransferase 1b, muscle; Cpt2: carnitine palmitoyltransferase 2; CREB: cAMP responsive element binding protein; DNM1L/DRP1: dynamin 1-like; E2: estrogen; EHHADH: enoyl-CoenzymeA hydratase/3-hydroxyacyl CoenzymeA dehydrogenase; ESR1/ER-alpha: estrogen receptor 1 (alpha); FA: fatty acid; FAO: fatty acid oxidation; FCCP: carbonyl cyanide-4-(trifluoromethoxy)phenylhydrazone; FFA: free fatty acids; FGF21: fibroblast growth factor 21; FUNDC1: FUN14 domain containing 1; HADHA: hydroxyacyl-CoA dehydrogenase trifunctional multienzyme complex subunit alpha; HFD: high-fat diet; iWAT: inguinal white adipose tissues; MAP1LC3A/LC3A: microtubule-associated protein 1 light chain 3 alpha; MBKO; muscle-specific bdnf knockout; IL6/IL-6: interleukin 6; MCEE: methylmalonyl CoA epimerase; MFF: mitochondrial fission factor; NTRK2/TRKB: neurotrophic tyrosine kinase, receptor, type 2; OPTN: optineurin; PA: palmitic acid; PARL: presenilin associated, rhomboid-like; PDH: pyruvate dehydrogenase; PINK1: PTEN induced putative kinase 1; PPARGC1A/PGC-1α: peroxisome proliferative activated receptor, gamma, coactivator 1 alpha; PRKAA/AMPK: protein kinase, AMP-activated, alpha 2 catalytic subunit; ROS: reactive oxygen species; TBK1: TANK-binding kinase 1; TG: triacylglycerides; TNF/TNFα: tumor necrosis factor; TOMM20: translocase of outer mitochondrial membrane 20; ULK1: unc-51 like kinase 1.

Orexin-A and endocannabinoids are involved in obesity-associated alteration of hippocampal neurogenesis, plasticity, and episodic memory in mice

The mammalian brain stores and distinguishes among episodic memories, i.e. memories formed during the personal experience, through a mechanism of pattern separation computed in the hippocampal dentate gyrus. Decision-making for food-related behaviors, such as the choice and intake of food, might be affected in obese subjects by alterations in the retrieval of episodic memories. Adult neurogenesis in the dentate gyrus regulates the pattern separation. Several molecular factors affect adult neurogenesis and exert a critical role in the development and plasticity of newborn neurons. Orexin-A/hypocretin-1 and downstream endocannabinoid 2-arachidonoylglycerol signaling are altered in obese mice. Here, we show that excessive orexin-A/2-arachidonoylglycerol/cannabinoid receptor type-1 signaling leads to the dysfunction of adult hippocampal neurogenesis and the subsequent inhibition of plasticity and impairment of pattern separation. By inhibiting orexin-A action at orexin-1 receptors we rescued both plasticity and pattern separation impairment in obese mice, thus providing a molecular and functional mechanism to explain alterations in episodic memory in obesity.

The authors show that adult hippocampal neurogenesis is altered in the dentate gyrus of obese mice with subsequent inhibition of long-term potentiation and impairment of pattern separation. Inhibition of orexin-A action at orexin-1 receptors rescued both impairments in obese mice.

Crème de la Créature: Dietary Influences on Behavior in Animal Models

In humans, alterations in cognitive, motivated, and affective behaviors have been described with consumption of processed diets high in refined sugars and saturated fats and with high body mass index, but the causes, mechanisms, and consequences of these changes remain poorly understood. Animal models have provided an opportunity to answer these questions and illuminate the ways in which diet composition, especially high-levels of added sugar and saturated fats, contribute to brain physiology, plasticity, and behavior. Here we review findings from invertebrate (flies) and vertebrate models (rodents, zebrafish) that implicate these diets with changes in multiple behaviors, including eating, learning and memory, and motivation, and discuss limitations, open questions, and future opportunities.

Effects of short-term exposure to genistein and overfeeding diet on the neural and retinal progenitor competence of adult zebrafish (Danio rerio)

Neurogenesis is a process that occurs throughout the life of a vertebrate. Among the different factors that may affect the natural occurrence of neurogenesis, obesity seems to decrease the proliferation capacity of progenitor neuronal cells. Conversely, the phytoestrogen genistein is known to attenuate some obesity effects beyond its neuroprotective action. Aiming to improve the understanding of how obesity and genistein trigger an impact on the neural and retinal progenitor competence of adult zebrafish, fish were exposed to genistein (GEN - 2 μg L^-1) alone or combined with two dietary groups (control and overfeed - OFD) for up to 9 weeks. Zebrafish were fed once per day with Artemia sp. in the control and GEN (2% of BW, control diet), and three times per day in the OFD and OFD + GEN groups (12% BW, overfeeding diet). To assess obesity induction, BMI, biometric parameters, and PPAR-γ protein were quantified. Afterwards, qRT-PCR and immunohistochemistry were performed to determine the cell proliferation and the presence of stem cells through PCNA and Sox-2. Our findings proved that overfeeding adult zebrafish increased the general growth and induced the development of fatty liver. However, for OFD + GEN, this effect was assuaged through the anti-adipogenic effect of GEN. This finding suggests that phytoestrogens could be beneficial to reduce the negative effects of obesity. Moreover, OF induced negative effects on retinal and brain homeostasis, decreasing the proliferation capacity of progenitor neuronal cells. With regard to retinal progenitor competence, genistein seems to mitigate the negative impacts of obesity, whereas the effects of obesity on the brain were exacerbated by this phytoestrogen which negatively influenced the homeostasis of zebrafish neural progenitor competence. This study highlighted the fact that the effects of phytoestrogens in adult neural progenitor competence are complex and could exhibit dissimilar effects depending on the tissue.

Blood-Brain Barrier Breakdown: An Emerging Biomarker of Cognitive Impairment in Normal Aging and Dementia

The blood–brain barrier (BBB) plays a vital role in maintaining the specialized microenvironment of the neural tissue. It separates the peripheral circulatory system from the brain parenchyma while facilitating communication. Alterations in the distinct physiological properties of the BBB lead to BBB breakdown associated with normal aging and various neurodegenerative diseases. In this review, we first briefly discuss the aging process, then review the phenotypes and mechanisms of BBB breakdown associated with normal aging that further cause neurodegeneration and cognitive impairments. We also summarize dementia such as Alzheimer's disease (AD) and vascular dementia (VaD) and subsequently discuss the phenotypes and mechanisms of BBB disruption in dementia correlated with cognition decline. Overlaps between AD and VaD are also discussed. Techniques that could identify biomarkers associated with BBB breakdown are briefly summarized. Finally, we concluded that BBB breakdown could be used as an emerging biomarker to assist to diagnose cognitive impairment associated with normal aging and dementia.

Perinatal exposure to high fat diet alters expression of MeCP2 in the hypothalamus

Obesity is a complex disease that is the result of a number of different factors including genetic, environmental, and endocrine abnormalities. Given that monogenic forms of obesity are rare, it is important to identify other mechanisms that contribute to its etiology. Methyl-Cp-G binding protein 2 (MeCP2) is a neuroepigenetic factor that binds to methylated regions of DNA to influence transcription. Past studies demonstrate that disruption in MeCP2 function produces obesity in mice. Using a diet-induced obesity mouse model, we show that perinatal exposure to high fat diet significantly decreases MeCP2 protein expression in the hypothalamus of female mice, effects not seen when high fat diet is given to mice during adulthood. Moreover, these effects are seen specifically in a subregion of the hypothalamus known as the arcuate nucleus with females having decreased MeCP2 expression in rostral areas and males having decreased MeCP2 expression in intermediate regions of the arcuate nucleus. Interestingly, mice gain more weight when exposed to high fat diet during adulthood relative to mice exposed to high fat diet perinatally, suggesting that perhaps high fat diet exposure during adulthood may be affecting mechanisms independent of MeCP2 function. Collectively, our data demonstrate that there are developmentally sensitive periods in which MeCP2 expression is influenced by high fat diet exposure and this occurs in a sexually dimorphic manner.

High fat diet and its effects on cognitive health: alterations of neuronal and vascular components of brain

It has been well recognized that intake of diets rich in saturated fats could result in development of metabolic disorders such as type 2 diabetes mellitus, obesity and cardiovascular diseases. Recent studies have suggested that intake of high fat diet (HFD) is also associated with cognitive dysfunction. Various preclinical studies have demonstrated the impact of short and long term HFD feeding on the biochemical and behavioural alterations. This review summarizes studies and the protocols used to assess the impacts of HFD feeding on cognitive performance in rodents. Further, it discuss the key mechanisms that are altered by HFD feeding, such as, insulin resistance, oxidative stress, neuro-inflammation, transcriptional dysregulation and loss of synaptic plasticity. Along with these, HFD feeding also alters the vascular components of brain such as loss of BBB integrity and reduced cerebral blood flow. It is highly possible that these factors are responsible for the development of cognitive deficits as a result of HFD feeding.

Tryptophan-metabolizing gut microbes regulate adult neurogenesis via the aryl hydrocarbon receptor

While modulatory effects of gut microbes on neurological phenotypes have been reported, the mechanisms remain largely unknown. Here, we demonstrate that indole, a tryptophan metabolite produced by tryptophanase-expressing gut microbes, elicits neurogenic effects in the adult mouse hippocampus. Neurogenesis is reduced in germ-free (GF) mice and in GF mice monocolonized with a single-gene tnaA knockout (KO) mutant Escherichia coli unable to produce indole. External administration of systemic indole increases adult neurogenesis in the dentate gyrus in these mouse models and in specific pathogen-free (SPF) control mice. Indole-treated mice display elevated synaptic markers postsynaptic density protein 95 and synaptophysin, suggesting synaptic maturation effects in vivo. By contrast, neurogenesis is not induced by indole in aryl hydrocarbon receptor KO (AhR-/-) mice or in ex vivo neurospheres derived from them. Neural progenitor cells exposed to indole exit the cell cycle, terminally differentiate, and mature into neurons that display longer and more branched neurites. These effects are not observed with kynurenine, another AhR ligand. The indole-AhR-mediated signaling pathway elevated the expression of β-catenin, Neurog2, and VEGF-α genes, thus identifying a molecular pathway connecting gut microbiota composition and their metabolic function to neurogenesis in the adult hippocampus. Our data have implications for the understanding of mechanisms of brain aging and for potential next-generation therapeutic opportunities.

Metformin restores hippocampal neurogenesis and learning and memory via regulating gut microbiota in the obese mouse model

Numerous studies have shown that over-nutritional obesity may lead to pre-diabetes, type 2 diabetes and cognitive decline. As the degree of metabolic disorders increases, the cognitive decline is getting worse. However, the cellular events that cause this cognitive dysfunction is yet to be clarified. We used a high-fat diet (HFD) consumption-induced obesity mouse model to test the effects of metformin on the hippocampal neurogenesis and learning and memory abilities of obese mice. 5-Bromo-2'-deoxyuridine (BrdU) labelling and retrovirus labeling were applied to detect hippocampal newborn neurons. Behavioral experiments were used to detect learning and memory abilities of mice. 16S rRNA gene sequencing was performed to detect the composition of gut microbiota. The positron emission tomography (PET) was conducted to detect the energy metabolism activity of different mouse brain regions. Our results reveal that metformin restores the impairment of neurogenesis in the dentate gyrus and finally prevents the cognitive decline of the obese mice. Moreover, the therapeutic effects of metformin are achieved by regulating the composition of gut microbiota of mice, which may inhibit microglia activation and neuroinflammation in the brain of obese mice. This study suggests that metformin may be taken as a promising candidate for the intervention of cognitive decline related to imbalance of gut microbiota caused by obesity.