Low BDNF is associated with cognitive deficits in patients with type 2 diabetes

Association between the HHEX polymorphism and delayed memory in first-episode schizophrenic patients

The hematopoietically-expressed homeobox gene (HHEX) played a critical role in regulating the immune system that the abnormality of which was involved in the psychopathology and cognitive deficits of psychiatric disorders. The aim of this study was to investigate the effect of HHEX rs1111875 polymorphism on the susceptibility and cognitive deficits of first-episode schizophrenic patients (FSP). We assessed cognitive function in 239 first-episode patients meeting DSM-IV for schizophrenia, and 368 healthy controls using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). The HHEX rs1111875 polymorphism was genotyped. Our results showed that the allelic and genotypic frequencies of HHEX rs1111875 polymorphism didn't differ between FSP and healthy controls (both p > 0.05) after adjusting for sex and age. Cognitive test scores in FSP were significantly lower than those in healthy controls on all scales (all p < 0.001) except for the visuospatial/constructional score (p > 0.05) after adjusting for covariates. There was a significant genotype (p < 0.05) rather than genotype × diagnosis (p > 0.05) effect on the delayed memory score after adjusting for covariates. The HHEX rs1111875 polymorphism was significantly associated with the delayed memory score in FSP (p < 0.05), but not in healthy controls (p > 0.05) after adjusting for covariates. Our findings supported that the HHEX rs1111875 polymorphism did not contribute to the susceptibility to FSP. However, this polymorphism might influence the delayed memory in FSP. Moreover, FSP had poorer cognitive function than healthy controls except for the visuospatial/constructional domain.

Brain-derived neurotrophic factor (BDNF) and other neurotrophic factors in type 2 diabetes mellitus and their association with neuropathy

BACKGROUND

Diabetes mellitus (DM) is associated with increased risk of morbidity and premature mortality due to its various complications. In an Indian study, the prevalence of diabetic peripheral neuropathy (DPN) in type 2 diabetic subjects was shown to be 29.2%. There is increasing evidence that a deficiency of nerve growth factor (NGF) in diabetes, as well as the calcitonin gene-related peptide (CGRP), may also contribute to the development of DPN. The aim of the current study was to evaluate nerve growth factor levels with neuropathy in type 2 DM.

MATERIALS AND METHODS

Forty healthy controls and 40 patients with type 2 DM were recruited; they were asked to report to Dept. of Physiology for initial history taking, general examination and neuropathy examination. A total of 5 mL of blood was collected for neurotrophic factor estimation as well as glycemic profile estimation.

RESULTS

The brain-derived neurotrophic factor (BDNF) values were significantly lower in the DM group whereas the insulin levels were also quite high in DM. The hot thresholds for both the upper limb and lower limb were greater in the DM group suggesting the impending neuropathy. Similarly, the Michigan scores were also greater in the DM group. The neuropathy parameters especially the Michigan A and B and the hot thresholds were positively correlated with duration of DM and glucose profile.

CONCLUSION

The neurotrophic factors especially BDNF are drastically reduced in DM patients and are negatively associated with neuropathy, and hence, BDNF can be utilized as a therapeutic target to treat and prevent neuropathy.

Untargeted Metabolomic Profiling Reveals Differentially Expressed Serum Metabolites and Pathways in Type 2 Diabetes Patients with and without Cognitive Decline: A Cross-Sectional Study

Diabetes is recognized as a risk factor for cognitive decline, but the underlying mechanisms remain elusive. We aimed to identify the metabolic pathways altered in diabetes-associated cognitive decline (DACD) using untargeted metabolomics. We conducted liquid chromatography-mass spectrometry-based untargeted metabolomics to profile serum metabolite levels in 100 patients with type 2 diabetes (T2D) (54 without and 46 with DACD). Multivariate statistical tools were used to identify the differentially expressed metabolites (DEMs), and enrichment and pathways analyses were used to identify the signaling pathways associated with the DEMs. The receiver operating characteristic (ROC) analysis was employed to assess the diagnostic accuracy of a set of metabolites. We identified twenty DEMs, seven up- and thirteen downregulated in the DACD vs. DM group. Chemometric analysis revealed distinct clustering between the two groups. Metabolite set enrichment analysis found significant enrichment in various metabolite sets, including galactose metabolism, arginine and unsaturated fatty acid biosynthesis, citrate cycle, fructose and mannose, alanine, aspartate, and glutamate metabolism. Pathway analysis identified six significantly altered pathways, including arginine and unsaturated fatty acid biosynthesis, and the metabolism of the citrate cycle, alanine, aspartate, glutamate, a-linolenic acid, and glycerophospholipids. Classifier models with AUC-ROC > 90% were developed using individual metabolites or a combination of individual metabolites and metabolite ratios. Our study provides evidence of perturbations in multiple metabolic pathways in patients with DACD. The distinct DEMs identified in this study hold promise as diagnostic biomarkers for DACD patients.

Association Between Dipeptidyl Peptidase-4 Inhibitor Use and Cognitive Functions, Brain-Derived Neurotrophic Factor, and Pentraxin-3 Levels in Patients With Type 2 Diabetes

Background Diabetes mellitus is an important risk factor for dementia, Alzheimer's disease, and other neurodegenerative diseases. Recent findings have made the relationship between the inhibition of the dipeptidyl peptidase-4 (DPP-4) enzyme and cognitive functions an important research topic. Objective This study aimed to evaluate the association between DPP-4 inhibitor use and cognitive functions, serum brain-derived neurotrophic factor (BDNF), and pentraxin-3 (PTX-3) levels in patients with type 2 diabetes, compared with the patients who only use metformin treatment. Design, patients, and methods A total of 50 patients with type 2 diabetes (hemoglobin A1c levels at ≤%7.5) who were under treatment with metformin±DPP-4 inhibitor (n=25) or only metformin (n=25) were included in this cross-sectional study. Serum BDNF and PTX-3 levels were assessed using an enzyme-linked immunosorbent assay. A standardized mini-mental test (sMMSE) was used to evaluate cognitive functions. Results There were no significant differences in the characteristics of the study groups. The mean sMMSE score of the patients receiving DPP-4±metformin treatment was statistically higher when compared with patients receiving only metformin treatment (27.16±1.95 vs. 25.40±3.07; p=0.041). The BDNF levels of the patients receiving DPP-4±metformin treatment were considerably higher than the patients receiving only metformin treatment (394.51±205.66 ng/ml vs. 180.63±297.94 ng/ml; p=0.001). The difference in PTX-3 levels between study groups was not statistically significant (5.47±3.44 vs. 3.79±2.53; p=0.055). Conclusion When compared to metformin alone, the use of DPP-4 inhibitors in the treatment of patients with type 2 diabetes was associated with increased serum BDNF levels and improved cognitive functions.

Flavonols as a Potential Pharmacological Intervention for Alleviating Cognitive Decline in Diabetes: Evidence from Preclinical Studies

Diabetes mellitus is a complex metabolic disease associated with reduced synaptic plasticity, atrophy of the hippocampus, and cognitive decline. Cognitive impairment results from several pathological mechanisms, including increased levels of advanced glycation end products (AGEs) and their receptors, prolonged oxidative stress and impaired activity of endogenous mechanisms of antioxidant defense, neuroinflammation driven by the nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB), decreased expression of brain-derived neurotrophic factor (BDNF), and disturbance of signaling pathways involved in neuronal survival and cognitive functioning. There is increasing evidence that dietary interventions can reduce the risk of various diabetic complications. In this context, flavonols, a highly abundant class of flavonoids in the human diet, are appreciated as a potential pharmacological intervention against cognitive decline in diabetes. In preclinical studies, flavonols have shown neuroprotective, antioxidative, anti-inflammatory, and memory-enhancing properties based on their ability to regulate glucose levels, attenuate oxidative stress and inflammation, promote the expression of neurotrophic factors, and regulate signaling pathways. The present review gives an overview of the molecular mechanisms involved in diabetes-induced cognitive dysfunctions and the results of preclinical studies showing that flavonols have the ability to alleviate cognitive impairment. Although the results from animal studies are promising, clinical and epidemiological studies are still needed to advance our knowledge on the potential of flavonols to improve cognitive decline in diabetic patients.

Prediction of Adverse Events Risk in Patients with Comorbid Post- Traumatic Stress Disorder and Alcohol Use Disorder Using Electronic Medical Records by Deep Learning Models

Background

Prediction of high-risk events in mental disorder patients is crucial. In our previous study, we developed a deep learning model: DeepBiomarker by using electronic medical records (EMR) to predict suicide related event (SRE) risk in post-traumatic stress disorder (PTSD) patients.

Methods

We applied DeepBiomarker2 through data integration of multimodal information: lab test, medication, co-morbidities, and social determinants of health. We analyzed EMRs of 5,565 patients from University of Pittsburgh Medical Center with a diagnosis of PTSD and alcohol use disorder (AUD) on risk of developing an adverse event (opioid use disorder, SREs, depression and death).

Results

DeepBiomarker2 predicted whether a PTSD + AUD patient will have a diagnosis of any adverse events (SREs, opioid use disorder, depression, death) within 3 months with area under the receiver operator curve (AUROC) of 0.94. We found piroxicam, vilazodone, dronabinol, tenofovir, suvorexant, empagliflozin, famciclovir, veramyst, amantadine, sulfasalazine, and lamivudine to have potential to reduce risk.

Conclusions

DeepBiomarker2 can predict multiple adverse event risk with high accuracy and identify potential risk and beneficial factors. Our results offer suggestions for personalized interventions in a variety of clinical and diverse populations.

Physical activity in a swimming pool attenuates memory impairment by reducing glutamate and inflammatory cytokines and increasing BDNF in the brain of mice with type 2 diabetes

Type 2 diabetes is a risk factor for the development of cognitive impairment. Increasing evidence suggests that regular exercise is beneficial for the treatment of clinical symptoms in diabetic patients. The current study aimed to evaluate whether increasing physical activity through swimming training can reduce memory impairment in an animal model of type 2 diabetes. Diabetes and non-diabetes mice underwent swimming training for four weeks, and then working, spatial, and recognition memory were evaluated using three behavioral tests. Body weight, glucose, and insulin resistance were monitored. We also measured inflammatory cytokines (interleukin (IL)- 6, IL-1β, and tumor-necrosis-factor (TNF)-α), an anti-inflammatory cytokine (IL-10), and brain-derived-neurotrophic-factor (BDNF), and glutamate levels in the hippocampus or prefrontal cortex of mice. The findings showed that diabetes increased body weight, glucose, and insulin resistance, impaired working, spatial and recognition memory, increased levels of IL-6, IL-1β, TNF-α, and glutamate levels, and decreased BDNF in the hippocampus of diabetic mice. While higher physical activity was associated with reduced body weight, glucose, and insulin resistance, attenuated memory impairment, IL-6, IL-1β, TNF-α, and glutamate, and increased BDNF levels in the hippocampus and prefrontal cortex of diabetic mice. This study shows that swimming training can normalize body weight and glucose-insulin axis and reduce inflammation and glutamate in the hippocampus and enhance the neurotrophic system in both the hippocampus and prefrontal cortex of diabetic mice. This study also suggests that higher physical activity through swimming training can improve cognitive impairment in a mouse model of type 2 diabetes.

Effects of high-intensity interval training, moderate-intensity continuous training, and guideline-based physical activity on cardiovascular metabolic markers, cognitive and motor function in elderly sedentary patients with type 2 diabetes (HIIT-DM): a protocol for a randomized controlled trial

Background and objective

Sedentary behavior is of increasing concern in older patients with type 2 diabetes mellitus (T2DM) due to its potential adverse effects on cardiovascular health, cognitive function, and motor function. While regular exercise has been shown to improve the health of individuals with T2DM, the most effective exercise program for elderly sedentary patients with T2DM remains unclear. Therefore, the objective of this study was to assess the impact of high-intensity interval training (HIIT), moderate-intensity continuous training (MICT), and guideline-based physical activity programs on the cardiovascular health, cognitive function, and motor function of this specific population.

Methods

This study will be a randomized, assessor-blind, three-arm controlled trial. A total of 330 (1:1:1) elderly sedentary patients diagnosed with T2DM will be randomly assigned the HIIT group (10 × 1-min at 85-95% peak HR, intersperse with 1-min active recovery at 60-70% peak HR), MICT (35 min at 65-75% peak HR), and guideline-based group (guideline group) for 12 weeks training. Participants in the guideline group will receive 1-time advice and weekly remote supervision through smartphones. The primary outcomes will be the change in glycosylated hemoglobin (HbA1c) and brain-derived neurotrophic factor (BDNF) after 12-weeks. Secondary outcomes will includes physical activity levels, anthropometric parameters (weight, waist circumference, hip circumference, and body mass index), physical measurements (fat percentage, muscle percentage, and fitness rate), cardiorespiratory fitness indicators (blood pressure, heart rate, vital capacity, and maximum oxygen), biochemical markers (high-density lipoprotein, low-density lipoprotein, triglycerides, total cholesterol, and HbA1c), inflammation level (C-reactive protein), cognitive function (reaction time and dual-task gait test performance), and motor function (static balance, dynamic balance, single-task gait test performance, and grip strength) after 12 weeks.

Discussion

The objective of this study is to evaluate the effect of 12 weeks of HIIT, MICT, and a guideline-based physical activity program on elderly sedentary patients diagnosed with T2DM. Our hypothesis is that both HIIT and MICT will yield improvements in glucose control, cognitive function, cardiopulmonary function, metabolite levels, motor function, and physical fitness compared to the guideline group. Additionally, we anticipate that HIIT will lead to greater benefits in these areas. The findings from this study will provide valuable insights into the selection of appropriate exercise regimens for elderly sedentary individuals with T2DM.

Ethics and dissemination

This study has been approved by the Ethics Review Committee of the Reproductive Hospital Affiliated with China Medical University (approval number: 202203). Informed consent will be obtained from all participants or their guardians. Upon completion, the authors will submit their findings to a peer-reviewed journal or academic conference for publication.

Clinical trial registration

Chinese Clinical Trial Registry, identifier ChiCTR2200061573.

Exploring Rosiglitazone's Potential to Treat Alzheimer's Disease through the Modulation of Brain-Derived Neurotrophic Factor

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that debilitates over 55 million individuals worldwide. Currently, treatments manage and alleviate its symptoms; however, there is still a need to find a therapy that prevents or halts disease progression. Since AD has been labeled as "type 3 diabetes" due to its similarity in pathological hallmarks, molecular pathways, and comorbidity with type 2 diabetes mellitus (T2DM), there is growing interest in using anti-diabetic drugs for its treatment. Rosiglitazone (RSG) is a peroxisome proliferator-activated receptor-gamma agonist that reduces hyperglycemia and hyperinsulinemia and improves insulin signaling. In cellular and rodent models of T2DM-associated cognitive decline and AD, RSG has been reported to improve cognitive impairment and reverse AD-like pathology; however, results from human clinical trials remain consistently unsuccessful. RSG has also been reported to modulate the expression of brain-derived neurotrophic factor (BDNF), a protein that regulates neuroplasticity and energy homeostasis and is implicated in both AD and T2DM. The present review investigates RSG's limitations and potential therapeutic benefits in pre-clinical models of AD through its modulation of BDNF expression.

Polyphenols and Neurodegenerative Diseases: Potential Effects and Mechanisms of Neuroprotection

The increase in people's longevity has, consequently, led to more brain involvement and neurodegenerative diseases, which can become complicated and lead to chronic degenerative diseases, thereby presenting greater public health problems. Medicinal plants have been used since ancient times and contain high concentrations of molecules, including polyphenols. It has been proven that polyphenols, which are present in various natural sources can provide curative effects against various diseases and brain disorders through neuroprotective effects. These neuroprotective effects are mainly attributed to their ability to cross the blood-brain barrier, eliminate reactive oxygen species, and cause the chelation of metal ions. Polyphenols increase the concentration of neurotrophic factors and bind directly to the membrane receptors of these neurotrophic factors, to modulate and activate the signaling cascades that allow the plasticity, survival, proliferation, and growth of neuronal cells, thereby allowing for better learning, memory, and cognition. Moreover, polyphenols have no serious adverse side effects resulting from their consumption.

Annona muricate Extract Supplementation Contributes to Improve Aberrant Multi-Organ Energy Metabolism via Muscle-Brain Connectivity in Diabetic Mice

Type 2 diabetes mellitus (T2DM) is related with the incidence of sarcopenia and cognitive impairment that reduces quality of life in the elderly. Recent evidence has demonstrated that sarcopenia is associated with cognitive dysfunction, and muscle-derived endocrine factors might contribute to cognitive function by the skeletal muscle-brain endocrine loop. This study investigated the beneficial effects of Annona muricata (AM, graviola) on multi-organ energy metabolism with muscle-brain connectivity via brain function-related myokines in mice. Body composition, fasting blood glucose level, insulin, HbA1c%, histopathological changes, and the protein levels of insulin-signaling, energy metabolism, neuroprotection, inflammation, and protein-degradation pathways were measured. AM extract (AME) treatment selectively enhanced insulin signaling in the skeletal muscle and hippocampus of T2DM mice. Furthermore, AME treatment effectively increased muscle-derived fibroblast growth factor 21 (FGF21), cathepsin-B (CTSB), irisin, brain-derived neurotrophic factor (BDNF), and liver-derived FGF21 that contribute to whole-body energy homeostasis. In particular, AME increased the levels of circulating myokines (FGF21, BDNF, irisin, and CTSB), and these were accordance with the hippocampal neurotrophic factors (BDNF and CTSB) in T2DM mice. In conclusion, we suggest that AME would be a potential nutraceutical for improving the energy metabolism associated with muscle-brain connectivity via brain function-related myokines in T2DM.

Pharmacological and physiological roles of adipokines and myokines in metabolic-related dementia

Dementia is a detrimental neuropathologic condition with considerable physical, mental, social, and financial impact on patients and society. Patients with metabolic syndrome (MetS), a group of diseases that occur in tandem and increase the risk of neurologic diseases, have a higher risk of dementia. The ratio between muscle and adipose tissue is crucial in MetS, as these contain many hormones, including myokines and adipokines, which are involved in crosstalk and local paracrine/autocrine interactions. Evidence suggests that abnormal adipokine and myokine synthesis and release may be implicated in various MetS, such as atherosclerosis, diabetic mellitus (DM), and dyslipidemia, but their precise role is unclear. Here we review the literature on adipokine and myokine involvement in MetS-induced dementia via glucose and insulin homeostasis regulation, neuroinflammation, vascular dysfunction, emotional changes, and cognitive function.

Acute bouts of aerobic and resistance exercise similarly alter inhibitory control and response time while inversely modifying plasma BDNF concentrations in middle-aged and older adults with type 2 diabetes

Impairments in several domains of cognitive functions are observed in people with Type 2 Diabetes Mellitus (T2DM), often accompanied by low Brain-derived neurotrophic factor (BDNF) concentrations. Although aerobic and resistance exercise enhances cognitive functions and raises BDNF concentrations in several populations, it remained uncertain in T2DM subjects. This study compared the effects of a single bout of aerobic (AER, 40 min of treadmill walk at 90-95% of the maximum walk speed) or resistance (RES, 3 × 10 repetitions in eight exercises at 70% of 10-RM) exercise on specific cognitive domain performance and plasma BDNF concentrations of physically active T2DM subjects. Eleven T2DM subjects (9 women/2 men; 63 ± 7 years) performed two counterbalanced trials on non-consecutive days. Stroop Color and Word (SCW) task [assessing the attention (congruent condition) and inhibitory control (incongruent condition)], Visual response time (assessing the response time), and blood collection (for plasma BDNF concentrations) were performed pre and post-exercise sessions. With distinct magnitude, both AER and RES improved the incongruent-SCW (d = - 0.26 vs. - 0.43 in AER and RES, respectively; p < 0.05), RT_(best) (d = - 0.31 vs. - 0.52, p < 0.05), and RT_(1-5) (d = - 0.64 vs. - 0.21, p < 0.05). The congruent-SCW and RT_(6-10) were not statistically different. Plasma BDNF concentrations were elevated 11% in AER (d = 0.30) but decreased by 15% in RES (d = - 0.43). A single session of aerobic or resistance exercise similarly improved the inhibitory control and response time of physically active T2DM subjects. Nevertheless, aerobic and resistance exercise sessions induced an opposite clinical effect in plasma BDNF concentrations.

The role of the brain-derived neurotrophic factor (BDNF) in anorexia nervosa

The brain-derived neurotrophic factor (BDNF) is a growth factor belonging to the neurotrophin family which plays a pivotal role in the differentiation, survival, and plasticity of neurons in the central nervous system. Evidence suggests that BDNF is an important signal molecule in the regulation of energy balance and thus implicated in body weight control. The discovery of BDNF-expressing neurons in the paraventricular hypothalamus which is important in the regulation of energy intake, physical activity, and thermogenesis gives more evidence to the suggested participation of BDNF in eating behavior. Until now it remains questionable whether BDNF can be used as a reliable biomarker for eating disorders such as anorexia nervosa (AN) as available findings on BDNF levels in patients with AN are ambiguous. AN is an eating disorder characterized by a pathological low body weight in combination with a body image disturbance typically developing during adolescence. A severe drive for thinness leads to restrictive eating behavior often accompanied by physical hyperactivity. During therapeutic weight restoration an increase of BDNF expression levels seems desirable as it might improve neuronal plasticity and survival which is essential for learning processes and thereby essential for the success of the psychotherapeutic treatment of patients. On the contrary, the well-known anorexigenic effect of BDNF might favor relapse in patients as soon as the BDNF levels significantly increase during weight rehabilitation. The present review summarizes the association between BDNF and general eating behavior and especially focuses on the eating disorder AN. In this regard findings from preclinical AN studies (activity-based anorexia model) are outlined as well.

Brain-derived neurotrophic factor in diabetes mellitus: A systematic review and meta-analysis

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is a neurotrophic factor expressed in several tissues, including the brain, gut, and pancreas. Activation of the BDNF/TrkB/CREB reduces hepatic gluconeogenesis, induces hepatic insulin signal transduction, and protects against pancreatic beta-cell loss in diabetes mellitus (DM). Several studies have investigated the possible association between BDNF and DM and its complications, but the results have been conflicting.

AIM

In the present study, we aimed at systematically reviewing the literature on the serum and plasma levels of BDNF in DM and its subgroups such as T2DM, DM patients with depression, and patients with retinopathy.

METHODS

A comprehensive search was conducted in PubMed, Scopus, and Web of Science. We identified 28 eligible studies and calculated the standardized mean difference (SMD) of outcomes as an effect measure.

RESULTS

The meta-analysis included 2734 patients with DM and 6004 controls. Serum BDNF levels were significantly lower in patients with DM vs. controls (SMD = -1.00, P<0.001). Plasma BDNF levels were not different in patients with DM compared with controls. When conducting subgroup analysis, serum BDNF levels were lower among patients with T2DM (SMD = -1.26, P<0.001), DM and depression (SMD = -1.69, P<0.001), and patients with diabetic retinopathy (DR) vs. controls (SMD = -1.03, P = 0.01).

CONCLUSIONS

Serum BDNF levels were lower in patients with DM, T2DM, DM with depression, and DM and DR than the controls. Our findings are in line with the hypothesis that decreased BDNF levels might impair glucose metabolism and contribute to the pathogenesis of DM and its complications.

Cognition and BDNF levels in prediabetes and diabetes: A mediation analysis of a cross-sectional study

AIM

Clinical and epidemiological studies suggest links between dementias and Type 2 diabetes (T2DM). The underlying mechanisms of diabetes-related cognitive impairment are largely unknown. This study aims to investigate the role of BDNF in cognitive impairment in prediabetes and T2DM.

METHODS

The study included 68 patients with prediabetes (preDM), 96 patients with T2DM, and 65 healthy controls. The cognitive function of the patients was evaluated with the Montreal Cognitive Assessment (MoCA) test and serum BDNF levels were measured by Elisa. The MoCA scores and BDNF levels were compared between diabetes groups after adjusting for age, gender, and education using ANCOVA. The role of BDNF in the diabetes-related cognitive impairment was investigated through mediation analysis.

RESULTS

Patients with T2DM had significantly lower cognitive performance, particularly in memory. Diabetes was found to be a predictor of both cognitive impairment and BDNF levels. A significant increase in serum BDNF levels was observed in patients with T2DM. However, the mediator role of BDNF in the pathology of cognitive impairment in diabetes was not determined.

CONCLUSION

Cognitive impairment is prevalent in patients with T2DM and should be included in routine screening for complications. The results of the mediation analysis suggest that although BDNF is a biomarker affected by T2DM and cognition, it does not play a mediator role between cognitive impairment and diabetes.

Brain Derived Neurotrophic Factor Interacts with White Matter Hyperintensities to Influence Processing Speed and Hippocampal Volume in Older Adults

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is a neurotrophin that plays an important role in regulating synaptic activity and plasticity.

OBJECTIVE

Given that type-2 diabetes (T2DM) increases the risk of cognitive decline, and studies have suggested lower BDNF levels may be a risk factor of diabetic neurovascular complications, we sought to investigate total white matter hyperintensities (WMH) as a moderator of the effect of BDNF on hippocampal volume and cognition.

METHODS

Older adults without dementia from the Alzheimer's Disease Neuroimaging Initiative (N = 454 including 49 with T2DM and 405 without diabetes) underwent neuropsychological evaluation, magnetic resonance imaging to quantify hippocampal and WMH volumes, and blood draw to assess BDNF.

RESULTS

Adjusting for age, sex, and APOE ɛ4 carrier status, there was a significant interaction between total WMH and BDNF on bilateral hippocampal volume in the non-T2DM group (t = 2.63, p = 0.009). Examination of main effect models with a dichotomous high/low BNDF group revealed a significant main effect for low BDNF (t = -4.98, p < 0.001), such that as WMH increased, bilateral hippocampal volume decreased. There was also a significant interaction between total WMH and BDNF on processing speed in the non-T2DM group (t = 2.91, p = 0.004). There was a significant main effect for low BDNF (t = -3.55, p < 0.001) such that as WMH increased, processing speed decreased. The interactions were not significant in the T2DM group.

CONCLUSION

These results further elucidate the protective role that BDNF plays on cognition, as well as the cognitive effects of WMH.

Alterations of peripheral cytokines, BDNF, and surface-based morphometry indices in T2DM patients without cognitive impairment

Purpose

This study aimed to investigate potential biological mechanisms underlying cognitive function alterations in Type 2 diabetes mellitus (T2DM) patients by integrating cortical morphology with peripheral cytokine levels and brain-derived neurotrophic factor (BDNF) levels, and to offer potential insights for the early detection of T2DM-related cognitive impairment.

Methods

This study included 16 T2DM patients with a Montreal Cognitive Assessment (MoCA) score of at least 26 points, as well as 16 healthy controls with normal cognitive function. The participants also completed the digit span test and digit symbol substitution test. Participants' serum levels of Interleukin 4 (IL-4), IL-6, IL-10, tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), and BDNF were also examined. Each subject underwent a high-resolution 3T structural brain MRI scan. Based on the aparc. a2009s atlas, we calculated the cortical thickness, sulcus depth, gyrification index, and fractal dimension for each participant using surface-based morphometry (SBM). Correlation analysis between cognitive measures, serum levels of cytokines and BDNF, and SBM indices were further performed.

Results

The levels of IL-4 and BDNF showed significant group differences. In the T2DM group, the sulcus depth exhibited a significant decrease in the left transverse frontopolar gyri and sulci, as well as in the right pole-occipital; the fractal dimension showed a significant increase in the right posterior-dorsal part of the cingulate gyrus; and the gyrification index significantly increased in the left inferior part of the precentral sulcus and right triangular part of the inferior frontal gyrus. Correlation analysis revealed a significant positive correlation between IL-10 levels and the sulcus depth of left transverse frontopolar gyri and sulci; a significant positive correlation between the sulcus depth of the right pole-occipital and the digit span test-forward scores, and a significant negative correlation between the gyrification index of the left inferior part of the precentral sulcus and the digit span test-backward scores among T2DM participants.

Conclusion

T2DM patients without cognitive impairment displayed reductions in IL 4 and BDNF levels, as well as significant alterations in their SBM indices, indicating that prior to the emergence of cognitive impairment, the SBM indices, peripheral cytokines, and BDNF may have altered in T2DM patients. IL-10 may lessen inflammation-related brain edema and preserve sulcus depth in T2DM patients through its anti-inflammatory activity.

Type 2 Diabetes Mellitus and Alzheimer's Disease: Shared Molecular Mechanisms and Potential Common Therapeutic Targets

The global prevalence of diabetes mellitus and Alzheimer's disease is increasing alarmingly with the aging of the population. Numerous epidemiological data suggest that there is a strong association between type 2 diabetes and an increased risk of dementia. These diseases are both degenerative and progressive and share common risk factors. The amyloid cascade plays a key role in the pathophysiology of Alzheimer's disease. The accumulation of amyloid beta peptides gradually leads to the hyperphosphorylation of tau proteins, which then form neurofibrillary tangles, resulting in neurodegeneration and cerebral atrophy. In Alzheimer's disease, apart from these processes, the alteration of glucose metabolism and insulin signaling in the brain seems to induce early neuronal loss and the impairment of synaptic plasticity, years before the clinical manifestation of the disease. The large amount of evidence on the existence of insulin resistance in the brain during Alzheimer's disease has led to the description of this disease as "type 3 diabetes". Available animal models have been valuable in the understanding of the relationships between type 2 diabetes and Alzheimer's disease, but to date, the mechanistical links are poorly understood. In this non-exhaustive review, we describe the main molecular mechanisms that may link these two diseases, with an emphasis on impaired insulin and IGF-1 signaling. We also focus on GSK3β and DYRK1A, markers of Alzheimer's disease, which are also closely associated with pancreatic β-cell dysfunction and type 2 diabetes, and thus may represent common therapeutic targets for both diseases.

Exercise Training Enhances BDNF/TrkB Signaling Pathway and Inhibits Apoptosis in Diabetic Cerebral Cortex

This study aimed to clarify the therapeutic effects of exercise training on neural BDNF/TrkB signaling and apoptotic pathways in diabetic cerebral cortex. Thirty-six male C57BL/6JNarl mice were randomly divided into three groups: control (CON-G), diabetic group (DM-G, 100 mg/kg streptozotocin, i.p.), and diabetic with exercise training group (DMEX-G, Swim training for 30 min/day, 5 days/week). After 12 weeks, H&E staining, TUNEL staining, and Western blotting were performed to detect the morphological changes, neural apoptosis, and protein levels in the cerebral cortex. The Bcl2, BclxL, and pBad were significant decreased in DM-G compared with CON-G, whereas they (excluded the Ras and pRaf1) were increased in DMEX-G. In addition, interstitial space and TUNEL(+) apoptotic cells found increased in DM-G with increases in Fas/FasL-mediated (FasL, Fas, FADD, cleaved-caspase-8, and cleaved-caspase-3) and mitochondria-initiated (tBid, Bax/Bcl2, Bak/BclxL, Bad, Apaf1, cytochrome c, and cleaved-caspase-9) apoptotic pathways. However, diabetes-induced neural apoptosis was less in DMEX-G than DM-G with observed raises in the BDNF/TrkB signaling pathway as well as decreases in Fas/FasL-mediated and mitochondria-initiated pathways. In conclusion, exercise training provided neuroprotective effects via enhanced neural BDNF/TrkB signaling pathway and prevent Fas/FasL-mediated and mitochondria-initiated apoptotic pathways in diabetic cerebral cortex.

Tetramethylpyrazine Attenuates Cognitive Impairment Via Suppressing Oxidative Stress, Neuroinflammation, and Apoptosis in Type 2 Diabetic Rats

Cognitive dysfunction is an important complication observed in type 2 diabetes mellitus (T2DM) patients. Tetramethylpyrazine (TMP) is known to exhibit anti-diabetic and neuroprotective properties. Therefore, the present study aimed to investigate the possible therapeutic effects of TMP against type 2 diabetes-associated cognitive impairment in rats. High-fat diet (HFD) followed by a low dose of streptozotocin (35 mg/kg) was used to induce diabetes in Sprague-Dawley rats. TMP (20, 40, and 80 mg/kg) and Pioglitazone (10 mg/kg) were administered for 4 weeks. The Morris water maze (MWM) and novel objective recognition task (NOR) tests were used to assess memory function. Fasting blood glucose (FBG), lipid profile, HOMA-IR, glycosylated hemoglobin (HbA1c), and glucose tolerance were measured. Acetylcholinesterase (AChE) and choline acetytransferase (ChAT) activity, acetylcholine (ACh) levels, oxidative stress, apoptotic (Bcl-2, Bax, caspase-3), and inflammatory markers (TNF-α, IL-1β, and NF-kβ) were assessed. BDNF, p-AKT, and p-CREB levels were also measured. In the present work, we observed that treatment of diabetic rats with TMP alleviated learning and memory deficits, improved insulin sensitivity, and attenuated hyperglycemia and dyslipidemia. Furthermore, treatment with TMP increased BDNF, p-Akt, and p-CREB levels, normalized cholinergic dysfunction, and suppressed oxidative, inflammatory, and apoptotic markers in the hippocampus. Collectively, our results suggest that the TMP may be an effective neuroprotective agent in alleviating type 2 diabetes-associated cognitive deficits.

Short communication: Serum levels of brain-derived neurotrophic factor and association with pro-inflammatory cytokines in acute and recovered anorexia nervosa

Brain-derived neurotrophic factor (BDNF) is a neuroprotective molecule known to be involved in neuroplasticity, learning and memory. Additionally, it may mitigate the effects of inflammation on the brain. There is inconclusive evidence as to whether reductions in BDNF found in AN are related to features associated with the illness such as changes in inflammatory markers and comorbidities, and whether they persist after recovery. This cross-sectional study measured BDNF and 36 inflammatory markers in the serum of individuals recovered from AN (rec-AN; n = 24), with acute AN (n = 56), and healthy controls (n = 51). We (a) compared BDNF concentrations between AN, rec-AN and controls including four pre-determined covariates; (b) assessed the relationship between BDNF and body mass index, eating disorder (ED) psychopathology and depression; and (c) correlated BDNF with inflammatory markers, stratified by group. The AN group showed reductions in BDNF compared to controls and rec-AN. BDNF was negatively associated with depression and ED psychopathology in the whole sample, but not the AN sample. BDNF was positively correlated with three inflammatory markers in the control group (interleukin (IL)-8, Eotaxin-3, tumor necrosis factor (TNF)-α) and negatively correlated with one (IL-16). The only pro-inflammatory marker associated with BDNF in the AN group was TNF-α, and no pro-inflammatory markers were associated with BDNF in the rec-AN group. These results indicate that BDNF serum concentrations may be a state marker of AN. In people with acute AN, BDNF levels seem to be linked to TNF-α signalling. However, BDNF concentrations do not appear to reflect AN symptom severity.

Diagnostic, Prognostic, and Mechanistic Biomarkers of Diabetes Mellitus-Associated Cognitive Decline

Cognitive dysfunctions such as mild cognitive impairment (MCI), Alzheimer’s disease (AD), and other forms of dementia are recognized as common comorbidities of type 2 diabetes mellitus (T2DM). Currently, there are no disease-modifying therapies or definitive clinical diagnostic and prognostic tools for dementia, and the mechanisms underpinning the link between T2DM and cognitive dysfunction remain equivocal. Some of the suggested pathophysiological mechanisms underlying cognitive decline in diabetes patients include hyperglycemia, insulin resistance and altered insulin signaling, neuroinflammation, cerebral microvascular injury, and buildup of cerebral amyloid and tau proteins. Given the skyrocketing global rates of diabetes and neurodegenerative disorders, there is an urgent need to discover novel biomarkers relevant to the co-morbidity of both conditions to guide future diagnostic approaches. This review aims to provide a comprehensive background of the potential risk factors, the identified biomarkers of diabetes-related cognitive decrements, and the underlying processes of diabetes-associated cognitive dysfunction. Aging, poor glycemic control, hypoglycemia and hyperglycemic episodes, depression, and vascular complications are associated with increased risk of dementia. Conclusive research studies that have attempted to find specific biomarkers are limited. However, the most frequent considerations in such investigations are related to C reactive protein, tau protein, brain-derived neurotrophic factor, advanced glycation end products, glycosylated hemoglobin, and adipokines.

Regulation of inflammation by VEGF/BDNF signaling in mouse retinal Müller glial cells exposed to high glucose

The inflammatory changes seem to play an important role in the development of diabetic retinopathy (DR). Anti-VEGF therapy has been testified to inhibit inflammation in animal models of diabetes, but the detailed mechanisms during this process are not yet clear. Müller glial cells (MGCs) in the mammalian retina are deeply involved in DR, while the BDNF overexpression reduces inflammation in diabetic mice. In this research, we aimed to explore the relationship between VEGF and BDNF in mouse retinal MGCs during inflammation of diabetes. We examined the expression of glutamine-synthetase (GS), glial fibrillary acidic protein (GFAP), vascular-endothelial growth factor (VEGF), interleukin-1beta (IL-1β), and tumor necrosis factor-alpha (TNF-α) at different time points after mouse retinal MGCs exposed to high glucose (25 mM). We also explored changes in the expression of brain-derived neurotrophic factor (BDNF), nuclear factor kappa B (NF-κB), IL-1β, and TNF-α in MGCs after treatments with anti-VEGF, VEGF siRNA, BDNF siRNA, BDNF recombination protein, and NF-κB inhibitor. In mouse retinal MGCs exposed to high glucose, BDNF was increased after treatments with anti-VEGF or VEGF siRNA. BDNF was decreased in MGCs from VEGF overexpressed mice. Moreover, the expressions of NF-κB, IL-1β, and TNF-α changed with BDNF: NF-κB, IL-1β, and TNF-α were increased after treatments with BDNF siRNA; NF-κB, IL-1β, and TNF-α were decreased after treatments with BDNF recombination protein. VEGF may regulate cytokines (IL-1β and TNF-α) by BDNF/NF-κB signaling pathway. The regulation of the VEGF/BDNF/NF-κB signaling pathway may be a significant therapeutic strategy for DR.

Methylation Status of Exon IV of the Brain-Derived Neurotrophic Factor (BDNF)-Encoding Gene in Patients with Non-Diabetic Hyperglycaemia (NDH) before and after a Lifestyle Intervention

BDNF signalling in hypothalamic neuronal circuits is thought to regulate mammalian food intake. In light of this, we investigated how a lifestyle intervention influenced serum levels and DNA methylation of BDNF gene in fat tissue and buffy coat of NDH individuals. In total, 20 participants underwent anthropometric measurements/fasting blood tests and adipose tissue biopsy pre-/post-lifestyle (6 months) intervention. DNA was extracted from adipose tissue and buffy coat, bisulphite converted, and pyrosequencing was used to determine methylation levels in exon IV of the BDNF gene. RNA was extracted from buffy coat for gene expression analysis and serum BDNF levels were measured by ELISA. No differences were found in BDNF serum levels, but buffy coat mean BDNF gene methylation decreased post-intervention. There were correlations between BDNF serum levels and/or methylation and cardiometabolic markers. (i) Pre-intervention: for BDNF methylation, we found positive correlations between mean methylation in fat tissue and waist-hip ratio, and negative correlations between mean methylation in buffy coat and weight. (ii) Post-intervention: we found correlations between BDNF mean methylation in buffy coat and HbA1c, BDNF methylation in buffy coat and circulating IGFBP-2, and BDNF serum and insulin. Higher BDNF % methylation levels are known to reduce BNDF expression. The fall in buffy coat mean BDNF methylation plus the association between lower BDNF methylation (so potentially higher BDNF) and higher HbA1c and serum IGFBP-2 (as a marker of insulin sensitivity) and between lower serum BDNF and higher circulating insulin are evidence for the degree of BDNF gene methylation being implicated in insulinisation and glucose homeostasis, particularly after lifestyle change in NDH individuals.

Novel Targets and Interventions for Cognitive Complications of Diabetes

Diabetes and cognitive dysfunction, ranging from mild cognitive impairment to dementia, often coexist in individuals over 65 years of age. Vascular contributions to cognitive impairment/dementia (VCID) are the second leading cause of dementias under the umbrella of Alzheimer's disease and related dementias (ADRD). Over half of dementia patients have VCID either as a single pathology or a mixed dementia with AD. While the prevalence of type 2 diabetes in individuals with dementia can be as high as 39% and diabetes increases the risk of cerebrovascular disease and stroke, VCID remains to be one of the less understood and less studied complications of diabetes. We have identified cerebrovascular dysfunction and compromised endothelial integrity leading to decreased cerebral blood flow and iron deposition into the brain, respectively, as targets for intervention for the prevention of VCID in diabetes. This review will focus on targeted therapies that improve endothelial function or remove iron without systemic effects, such as agents delivered intranasally, that may result in actionable and disease-modifying novel treatments in the high-risk diabetic population.

Neuroprotective Effect of SGLT2 Inhibitors

Patients with diabetes are at higher risk of cardiovascular diseases and cognitive impairment. SGLT2 inhibitors (Empagliflozin, Canagliflozin, Dapagliflozin, Ertugliflozin, Sotagliflozin) are newer hypoglycemic agents with many pleiotropic effects. In this review, we discuss their neuroprotective potential. SGLT2 inhibitors (SGLT2i) are lipid-soluble and reach the brain/serum ratio from 0.3 to 0.5. SGLT receptors are present in the central nervous system (CNS). Flozins are not fully SGLT2-selective and have an affinity for the SGLT1 receptor, which is associated with protection against ischemia/reperfusion brain damage. SGLT2i show an anti-inflammatory and anti-atherosclerotic effect, including reduction of proinflammatory cytokines, M2 macrophage polarization, JAK2/STAT1 and NLRP3 inflammasome inhibition, as well as cIMT regression. They also mitigate oxidative stress. SGLT2i improve endothelial function, prevent remodeling and exert a protective effect on the neurovascular unit, blood-brain barrier, pericytes, astrocytes, microglia, and oligodendrocytes. Flozins are also able to inhibit AChE, which contributes to cognitive improvement. Empagliflozin significantly increases the level of cerebral BDNF, which modulates neurotransmission and ensures growth, survival, and plasticity of neurons. Moreover, they may be able to restore the circadian rhythm of mTOR activation, which is quite a novel finding in the field of research on metabolic diseases and cognitive impairment. SGLT2i have a great potential to protect against atherosclerosis and cognitive impairment in patients with type 2 diabetes mellitus.

FEASibility testing a randomized controlled trial of an exercise program to improve cognition for T2DM patients (the FEAST trial): A study protocol

While cognitive dysfunction is an important concern in persons with type 2 diabetes mellitus (T2DM), it has received little attention in the T2DM literature. Although it often remains unrecognized, cognitive dysfunction associated with T2DM can lead to severe consequences. Prior research studies have consistently shown that aerobic exercise enhances cognitive function among healthy subjects. However, very few studies have examined the effects of aerobic exercise on cognitive function in persons with T2DM. In addition, one important single-nucleotide polymorphism that influences cognition in humans is the brain-derived neurotrophic factor (BDNF) Val66Met variant. Despite strong evidence suggesting aerobic exercise has a beneficial effect on cognitive function, there is significant variability in individual response to exercise programs on cognitive outcomes among Val/Val versus Met carriers. However, the evidence on how the BDNF Val66Met variant influences cognitive outcomes following an aerobic exercise intervention among individuals with T2DM is currently lacking. Therefore, the purpose of this randomized controlled trial is to pilot-test a 3-month supervised exercise program to improve plasma BDNF levels and cognition, overall and according to genotypes of the BDNF Val66Met variant. A total of 81 patients with T2DM will be randomly assigned to either aerobic exercise group (n = 54) or attention control group (n = 27) for 3 months. Outcomes of interest include postintervention changes in plasma BDNF levels, fasting blood glucose, hemoglobin A1c, body mass index, executive function, memory, and processing speed. This study will provide further evidence on use of exercise as a non-pharmaceutical, low-cost intervention to improve cognition in this population.

The effect of Melissa officinalis L. extract on learning and memory: Involvement of hippocampal expression of nitric oxide synthase and brain-derived neurotrophic factor in diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetes is a systemic disease, which can cause synaptic defects in the hippocampus. Hippocampus plays a crucial role in learning and memory. Melissa officinalis L. has been used as for memory enhancement in Persian Medicine.

AIM OF THE STUDY

The aim of this study was to evaluate the impact of the hydroalcoholic extract of Melissa officinalis L. on learning and memory, considering its impact on nitric oxide synthase and brain-derived neurotrophic factor expression in the hippocampus of diabetic rats.

MATERIALS AND METHODS

Melissa officinalis L. extract was obtained by maceration method. To evaluate phenolic and flavonoid compounds of the extract, the samples were analyzed by HPLC. The animals were randomly divided into 6 groups: vehicle-treated control, Melissa officinalis-treated control (50 mg/kg), vehicle-treated diabetic, and M. officinalis-treated diabetic (25, 50, or 100 mg/kg). Diabetes was induced by streptozotocin And Melissa officinalis L. was administered for 2 weeks once diabetes was induced. Passive avoidance and Y-maze tasks were performed for learning and memory assessment. At the end of learning and memory tasks, rats were sacrificed and their hippocampus removed, lysed, and homogenized. The RNA contents were purified and then used as the template for cDNA synthesis. Real-time PCR was used to evaluate nitric oxide synthase and brain-derived neurotrophic factor genes expression.

RESULTS

Rutin was main flavonoid compound and rosmarinic acid was the main phenolic compound of the Melissa officinalis extract. Streptozotocin induced diabetes and impaired learning and memory in diabetic rats. Melissa officinalis treated-control group showed a higher alternation score in the Y-maze task and step-through latency in the passive avoidance task compared to the vehicle treated diabetic group. Melissa officinalis-treated rats showed a higher alternation score in the Y-maze task in all doses compared to the vehicle treated diabetic group (P < 0.05). In addition, in the passive avoidance task Melissa officinalis increased step-through latency (P < 0.05) but not initial latency, in all doses. Furthermore, in diabetic rats, the expression of brain-derived neurotrophic factor and nitric oxide synthase genes decreased. However, hippocampal brain-derived neurotrophic factor and nitric oxide synthase gene expression was increased in Melissa officinalis-treated rats compared to diabetic rats (P < 0.05).

CONCLUSIONS

Melissa officinalis improved learning and memory in diabetic rats, which may have occurred by increasing brain-derived neurotrophic factor and nitric oxide synthase gene expression.

A systematic review and meta-analysis of association between brain-derived neurotrophic factor and type 2 diabetes and glycemic profile

Several epidemiologic studies have evaluated the relation between serum/plasma brain-derived neurotrophic factor (BDNF) levels and glycemic parameters, but the findings were conflicting. We performed a systematic review and meta-analysis to compare circulating BDNF levels in individuals with type 2 diabetes (T2D) or other glycemic disorders with healthy controls and to evaluate correlation between BDNF concentrations with glycemic profile. A systematic search up to July 2020 was conducted in reliable electronic databases (MEDLINE (Pubmed), EMBASE, Scopus) and Google scholar. Sixteen observational studies compared serum/plasma BDNF levels in diabetic patients (or individuals with glycemic disorders) vs. healthy controls or reported correlations between serum BDNF levels and glycemic parameters in adults were included in the review. Overall weighted mean difference (WMD) of circulating BDNF levels in 1306 patients with T2D (or other glycemic disorders) was 1.12 ng/mL lower than 1250 healthy subjects (WMD: − 1.12; 95%CI − 1.37, − 0.88, I² = 98.7%, P < 0.001). Subgroup analysis revealed that both diabetic patients and subjects with other glycemic disorders had lower serum/plasma BDNF levels than healthy controls (WMD: − 1.74; 95%CI − 2.15, − 1.33 and WMD: − 0.49; 95%CI − 0.82, − 0.16, respectively). No significant correlation was found between BDNF levels and glycemic parameters [fasting blood glucose (FBG) (Fisher’s Z = 0.05; 95%CI − 0.21, 0.11; n = 1400), homeostatic model assessment for insulin resistance (HOMA-IR) (Fisher’s Z = 0.12; 95%CI − 0.20, 0.44; n = 732) and glycosylated hemoglobin (HbA1c) (Fisher’s Z = 0.04; 95%CI − 0.05, 0.12; n = 2222)]. We found that diabetic patients and subjects with glycemic disorders had lower circulating BDNF levels than healthy controls. However, there was no significant correlation between BDNF concentrations and glycemic parameters including FBG, HOMA-IR and HbA1c. Further prospective investigations are required to confirm these findings.

Whole body hypoxic preconditioning-mediated multiorgan protection in db/db mice via nitric oxide-BDNF-GSK-3β-Nrf2 signaling pathway

The beneficial effects of hypoxic preconditioning are abolished in the diabetes. The present study was designed to investigate the protective effects and mechanisms of repeated episodes of whole body hypoxic preconditioning (WBHP) in db/db mice. The protective effects of preconditioning were explored on diabetesinduced vascular dysfunction, cognitive impairment and ischemia-reperfusion (IR)-induced increase in myocardial injury. Sixteen-week old db/db (diabetic) and C57BL/6 (non-diabetic) mice were employed. There was a significant impairment in cognitive function (Morris Water Maze test), endothelial function (acetylcholineinduced relaxation in aortic rings) and a significant increase in IR-induced heart injury (Langendorff apparatus) in db/db mice. WBHP stimulus was given by exposing mice to four alternate cycles of low (8%) and normal air O₂ for 10 min each. A single episode of WBHP failed to produce protection; however, two and three episodes of WBHP significantly produced beneficial effects on the heart, brain and blood vessels. There was a significant increase in the levels of brain-derived neurotrophic factor (BDNF) and nitric oxide (NO) in response to 3 episodes of WBHP. Moreover, pretreatment with the BDNF receptor, TrkB antagonist (ANA-12) and NO synthase inhibitor (LNAME) attenuated the protective effects imparted by three episodes of WBHP. These pharmacological agents abolished WBHP-induced restoration of p-GSK-3β/GSK-3β ratio and Nrf2 levels in IR-subjected hearts. It is concluded that repeated episodes of WHBP attenuate cognitive impairment, vascular dysfunction and enhancement in IRinduced myocardial injury in diabetic mice be due to increase in NO and BDNF levels that may eventually activate GSK-3β and Nrf2 signaling pathway to confer protection.

The effects of wheat germ consumption on mental health and brain-derived neurotrophic factor in subjects with type 2 diabetes mellitus: a randomized, double-blind, placebo-controlled trial

Objectives: Herbals, as bioactive foods, have been one of the most popular alternatives and complementary treatments in preventing and controlling type 2 diabetes mellitus (T2DM). The aim of the present trial was to examine the effects of wheat germ consumption on mental health and brain-derived neurotrophic factor (BDNF) among patients with T2DM.Methods: Eighty participants with T2DM were randomly allocated to receive 20 g wheat germ (n = 40) or placebo (n = 40) in a randomized double-blind clinical trial for 12 weeks. Depression, anxiety, stress scale-21 (DASS-21) questionnaire was used to assess the mental health of study participants. Serum BDNF was assessed at the baseline and end of intervention. Anthropometric indices were measured at the baseline, 6 and 12 weeks during the intervention.Results: A total of 75 subjects completed the trial. Compared with the placebo, wheat germ consumption led to a significant reduction in depression (P = .03) and stress (P = .04) scores. Moreover, a significant increase in serum BDNF concentrations was observed in the wheat germ group (P = .004), while there was no significant difference between the groups. Wheat germ intake had no significant effects on anthropometric indices and anxiety scores between the groups.Conclusion: Our findings showed that wheat germ consumption for 12 weeks could significantly reduce the stress and depression scores but had no significant effects on anxiety scale and anthropometric outcomes in patients with T2DM.

Relationship of Established Cardiovascular Risk Factors and Peripheral Biomarkers on Cognitive Function in Adults at Risk of Cognitive Deterioration

BACKGROUND

There is a paucity of information on the role of microvascular and inflammatory biomarkers in cognitive dysfunction.

OBJECTIVE

This study sought to evaluate the relationships between established and a number of peripheral biomarkers on cognitive patterns in 108 older adults with memory complaints.

METHODS

Participants in the AIBL Active study aged 60 years and older with at least one vascular risk factor and memory complaints completed a neuropsychological test battery and provided cross-sectional health data. Linear regression models adjusted for covariates examined associations between cognitive performance and a panel of vascular risk factors (Framingham cardiovascular scores, hs-CRP, homocysteine, fasting glucose, LDL-cholesterol) and peripheral biomarkers (TNF-α, BDNF, VCAM-1, ICAM-1, PAI-1, CD40L).

RESULTS

Higher fasting glucose and homocysteine levels were independent factors associated with poorer performance in Trail Making Test (TMT) B (adjusted β= 0.40±0.10 and 0.43±0.09, respectively). Increasing homocysteine levels were weakly associated with poorer global cognition and delayed recall (adjusted β= 0.23±0.10 and -0.20±0.10 respectively). Increasing Framingham cardiovascular scores were related to poorer performance in TMT B (β  = 0.42±0.19). There was early evidence of associations between increasing plasma TNF-α and poorer TMT B (adjusted β  = 0.21±0.10) and between increasing BDNF and better global cognition (β= -0.20±0.09).

CONCLUSION

This study provides evidence to support the associations between vascular risk factors (Framingham scores, fasting glucose, and homocysteine) and poorer cognitive functions. Additionally, we measured several peripheral biomarkers to further investigate their associations with cognition. The relationship between TNF-α, BDNF, and cognitive performance in various domains may offer new insights into potential mechanisms in vascular cognitive impairment.

Maternal diabetes-induced alterations in the expression of brain-derived neurotrophic factor in the developing rat hippocampus

Maternal diabetes during pregnancy affects the development of hippocampus in the offspring. Brain-derived neurotrophic factor (BDNF) has received increasing attention for its role in regulating the survival and differentiation of neuronal cells in developing and adult brain. In the current study, we evaluated the effects of maternal diabetes and insulin treatment on expression and distribution pattern of BDNF in the hippocampus of neonatal rats at the first two postnatal weeks. We found no differences in hippocampal expression of BDNF between diabetics with normal control or insulin treated neonatal rats at postnatal day (P0) (P > 0.05 each). Nevertheless, there was a marked BDNF downregulation in both sides' hippocampi of male/female diabetic group in two-week-old offspring (P ≤ 0.05 each). Furthermore, the numerical density of BDNF⁺ cells was significantly reduced in the right/left dentate gyrus (DG) of male and female newborns born to diabetic animals at all studied postnatal days (P ≤ 0.05 each). In addition, a lower number of reactive cells have shown in the all hippocampal subareas in the diabetic pups at P14 (P ≤ 0.05 each). Our results have demonstrated that the insulin-treatment improves some of the negative impacts of diabetes on the expression of hippocampal BDNF in the newborns. We conclude that diabetes in pregnancy bilaterally disrupts the expression of BDNF in the hippocampus of the both male and female newborns at early postnatal days. In addition, good glycemic control by insulin in the most cases is sufficient to prevent the alterations in expression of BDNF protein in developing hippocampus.

Diabetes mellitus, cognitive deficits and serum BDNF levels in chronic patients with schizophrenia: A case-control study

The relationship between serum BDNF levels and cognitive dysfunction in schizophrenia (SCZ) patients comorbid with type 2 diabetes mellitus (T2DM) has not been reported. Hence, this study aimed to explore whether and how the changes of serum BDNF levels were correlated with cognitive impairment in SCZ patients comorbid with T2DM. We recruited 472 inpatients with chronic SCZ (54 T2DM and 418 non-T2DM), and 225 healthy controls. Serum BDNF levels and routine biochemical parameters were measured. Psychopathological symptoms were evaluated by the Positive and Negative Syndrome Scale (PANSS) and cognitive function was assessed by the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). SCZ patients with T2DM had significantly higher serum BDNF levels than SCZ patients without T2DM (F = 11.31, p = 0.001). SCZ patients with T2DM scored higher in delayed memory than SCZ patients without T2DM (77.17 ± 18.44 vs.66.24 ± 19.51, p = 0.000), and still showed significance after controlling for confounders. Further stepwise multiple regression analysis identified serum BDNF as an independent contributor to the RBANS attention of SCZ patients with T2DM (β = 0.30, t = 2.09, p = 0.042). The increase of BDNF levels and better cognitive performance, especially delayed memory, may be related to the pathophysiological process of T2DM in chronic SCZ patients.

Influence of BDNF Genetic Polymorphisms in the Pathophysiology of Aging-related Diseases

For the first time in history, most of the population has a life expectancy equal or greater than 60 years. By the year 2050, it is expected that the world population in that age range will reach 2000 million, an increase of 900 million with respect to 2015, which poses new challenges for health systems. In this way, it is relevant to analyze the most common diseases associated with the aging process, namely Alzheimer´s disease, Parkinson Disease and Type II Diabetes, some of which may have a common genetic component that can be detected before manifesting, in order to delay their progress. Genetic inheritance and epigenetics are factors that could be linked in the development of these pathologies. Some researchers indicate that the BDNF gene is a common factor of these diseases, and apparently some of its polymorphisms favor the progression of them. In this regard, alterations in the level of BDNF expression and secretion, due to polymorphisms, could be linked to the development and/or progression of neurodegenerative and metabolic disorders. In this review we will deepen on the different polymorphisms in the BDNF gene and their possible association with age-related pathologies, to open the possibilities of potential therapeutic targets.

Glucose disturbances, cognitive deficits and white matter abnormalities in first-episode drug-naive schizophrenia

Disturbance of glucose metabolism may be implicated in cognitive deficits of schizophrenia in its early phases. Many studies have reported the important role of widespread disruption of white matter (WM) connectivity in pathogenesis, cognitive deficit and psychopathology of schizophrenia. However, no study has investigated their inter-relationships in drug-naive first episode (DNFE) patients with schizophrenia. Glucose metabolism parameters including fasting glucose, insulin and homeostasis model of assessment-insulin resistance (HOMA-IR) index, cognitive performance on the MATRICS Consensus Cognitive Battery (MCCB) and the voxel-wised WM fractional anisotropy (FA) values were examined using DTI in 39 DNFE schizophrenia and 31 control subjects. The Positive and Negative Syndrome Scale was utilized for clinical symptoms. The patients showed significantly greater fasting plasma levels of glucose and insulin and HOMA-IR, and poorer cognitive scores, together with widespread reduced FA values in five brain areas, including left and right corpus callosum, superior longitudinal fasciculus, posterior thalamic radiation, and corona radiata (all p < 0.05). Association analysis showed that glucose level was positively associated with Digital Sequence Test and Continuous Performance Test, but negatively with FA values in posterior thalamic radiation and left corpus callosum in patients (all p < 0.05). Furthermore, multiple regression analysis revealed that the interactions of glucose × FA in left corpus callosum, longitudinal fasciculus and corona radiata were independent contributors to the Brief Visuospatial Memory Test (BVMT) of MCCB, while the interaction of glucose × FA in left corpus callosum, or in longitudinal fasciculus was associated with MCCB mazes and Trail Making A Test, respectively. Therefore, abnormal glucose metabolism, cognitive impairment and widespread disruption of WM structure occur in an early course of schizophrenia onset. An interaction between glucose metabolism abnormality and the WM dysconnectivity may lead to cognitive impairment.

Antidepressants Promote and Prevent Cancers

The review states that antidepressants (ADs) increase brain-derived neurotrophic factor (BDNF) transmission concomitantly in the brain and the blood: ADs increasing BDNF synthesis in specific areas of the central nervous system (CNS) could presumably affect megakaryocyte's production of platelets. ADs increase BDNF levels in the CNS and improve mood. In the blood, ADs increase BDNF release from platelets. The hypothesis presented here is that the release of BDNF from platelets contributes to the ADs effects on neurogenesis and on tumor growth in the cancer disease. Oncological studies indicate that chemicals ADs exert an aggravating effect on the cancer disease, possibly by promoting proplatelets formation and enhancing BDNF release from platelets in the tumor.

The importance of BDNF and RAGE in diabetes-induced dementia

Diabetes-induced dementia is an emerging neurodisorder all over the world. The prevalence rates of dementia and diabetes have been gradually increasing worldwide. Diabetes has been known to lead to oxidative stress, inflammation aggravation, and hyperglycemia conditions in the brain. Various diabetic implications cause the lower secretion of brain-derived neurotrophic factor (BDNF) and the increase of receptor for advanced glycation end products (RAGE), ultimately leading to both cerebrovascular dysfunction and cognitive decline. Here, we summarized the significant evidences highlighting the specific mechanisms between BDNF and RAGE and cerebrovascular dysfunction and memory function and how these relate to diabetes-induced dementia. Especially, we review that the association between BDFN and RAGE in neuroinflammation, the reduction of long-term potentiation, and the vascular implications in brain.

From the gut to the heart: L. plantarum and inulin administration as a novel approach to control cardiac apoptosis via 5-HT2B and TrkB receptors in diabetes

BACKGROUND & AIMS

Type 2 diabetes mellitus, as a metabolic disorder, can lead to diabetic cardiomyopathy, identified by cardiomyocyte apoptosis and myocardial fibrosis. Brain-derived neurotrophic factor (BDNF) and serotonin are two neurotransmitters that can control cardiomyocyte apoptosis and myocardial fibrosis through their cardiac receptors. In the present study, we investigated the impacts of L. plantarum and inulin supplementation on the inhibition of cardiac apoptosis and fibrosis by modulating intestinal, serum, and cardiac levels of serotonin and BDNF as well as their cardiac receptors.

METHODS

Diabetes was induced by a high-fat diet and streptozotocin in male Wistar rats. Rats were divided into six groups and were supplemented with L. plantarum, inulin or their combination for 8 weeks. Finally, the rats were killed and levels of intestinal, serum, and cardiac parameters were evaluated.

RESULTS

Concurrent administration of L. plantarum and inulin caused a significant rise in the expression of cardiac serotonin and BDNF receptors (P < 0.001) as well as a significant fall in cardiac interstitial and perivascular fibrosis (P < 0.001, both) and apoptosis (P = 0.01). Moreover, there was a strong correlation of cardiac 5-Hydroxytryptamine 2B (5-HT2B) and tropomyosin receptor kinase B (TrkB) receptors with interstitial/perivascular fibrosis and apoptosis (P < 0.001, both).

CONCLUSIONS/INTERPRETATION

Results revealed beneficial effects of L. plantarum, inulin or their combination on intestinal, serum, and cardiac serotonin and BDNF accompanied by higher expression of their cardiac receptors and lower levels of cardiac apoptotic and fibrotic markers. It seems that L. plantarum and inulin supplementation could be considered as a novel adjunct therapy to reduce cardiac complications of type 2 diabetes mellitus.

Serum brain-derived neurotrophic factor and neurocognitive function in children with type 1 diabetes

BACKGROUND/PURPOSE

This study aimed to clarify whether brain-derived neurotrophic factor (BDNF) is a biomarker for cognitive dysfunction in children with type 1 diabetes.

METHODS

We conducted a cross-sectional case-control study of children aged between 6 and 18 years with type 1 diabetes and healthy volunteers. Serum BDNF level was measured in all of the studied children, and they all underwent intelligence tests with the Wechsler Intelligence Scale for Children, Fourth Edition (WISC-IV). We further compared the cognitive function and BDNF levels in the diabetic children with positive glutamic acid decarboxylase 65 antibody (GAD65-Ab) and those with negative GAD65-Ab.

RESULTS

Forty-five children with type 1 diabetes (mean age 14.0 ± 2.6 years, 42% male) and 50 normal controls (mean age 13.2 ± 2.3 years, 54% male) were recruited. The serum BDNF level was significantly lower in the diabetes group than in the controls (15.92 ± 7.2 vs. 18.5 ± 5.1 ng/mL, respectively, t = -2.03, p = 0.045) and much lower in the subgroup with GAD65-Ab positive type 1 diabetes. The average Full-Scale IQ, verbal comprehension, perceptual reasoning and working memory scores in the diabetes group were significantly lower than in the controls (all p < 0.05). Among the children with type 1 diabetes, poor glycemic control was related to lower general cognitive abilities (r = -0.34, p < 0.02), lower verbal comprehension (r = -0.305, p < 0.05), and lower perceptual reasoning scores (r = -0.346, p = 0.02).

CONCLUSION

The children with type 1 diabetes had a lower serum BDNF level and poorer neurocognitive function than normal healthy children, especially those with GAD65-Ab positive diabetes. Poor glycemic control was correlated with worse cognitive performance.

Resveratrol Prevents Cognitive Impairment in Type 2 Diabetic Mice by Upregulating Nrf2 Expression and Transcriptional Level

PURPOSE

This study aimed to determine whether the natural antioxidant resveratrol (RSV) prevents type 2 diabetes mellitus (T2DM)-induced cognitive impairment and to explore whether redox-associated factor nuclear factor erythroid 2-related factor 2 (Nrf2) plays a critical role in the neuroprotective effect of RSV.

MATERIALS AND METHODS

We established a T2DM model with 8-week-old male ICR mice by administration of a high-fat diet for 2 months and low-dose streptozotocin for 3 days. Then, diabetic and age-matched control mice were treated with or without RSV for 4 months every other day and subjected to the Morris water maze test. After the mice were euthanized, whole brains were sectioned for Nissl staining and immunofluorescence labeling. Hippocampal sections were observed by transmission electron microscopy to evaluate the ultrastructure of synapses. Inflammatory factors, oxidative stress-related indexes, and Nrf2 and downstream target gene expression were analyzed in hippocampal tissues by quantitative real-time PCR, Western blotting, and associated quantitative kits.

RESULTS

In the Morris water maze test, compared to control mice, T2DM mice showed learning and memory impairments, but RSV treatment prevented the learning and memory decline in T2DM mice. Similarly, RSV prevented T2DM-induced hippocampal neuron destruction and synaptic ultrastructural damage. The expression levels of inflammatory factors and oxidative stress-related indicators were increased in the T2DM group compared with the control group but were decreased significantly by RSV treatment in the T2DM group. Additionally, the expression of Nrf2 and its downstream target genes was decreased in the T2DM group compared with the control group and was significantly increased by RSV treatment in the T2DM group.

CONCLUSION

RSV prevented T2DM-induced cognitive impairment through anti-inflammatory and antioxidant activities. This effect was accompanied by the upregulation of Nrf2 transcriptional activity and the increased expression of downstream antioxidant genes.

Imaging of brain glucose uptake by PET in obesity and cognitive dysfunction: life-course perspective

The prevalence of obesity has reached epidemic proportions and keeps growing. Obesity seems implicated in the pathogenesis of cognitive dysfunction, Alzheimer's disease and dementia, and vice versa. Growing scientific efforts are being devoted to the identification of central mechanisms underlying the frequent association between obesity and cognitive dysfunction. Glucose brain handling undergoes dynamic changes during the life-course, suggesting that its alterations might precede and contribute to degenerative changes or signaling abnormalities. Imaging of the glucose analog 18F-labeled fluorodeoxyglucose (18FDG) by positron emission tomography (PET) is the gold-standard for the assessment of cerebral glucose metabolism in vivo. This review summarizes the current literature addressing brain glucose uptake measured by PET imaging, and the effect of insulin on brain metabolism, trying to embrace a life-course vision in the identification of patterns that may explain (and contribute to) the frequent association between obesity and cognitive dysfunction. The current evidence supports that brain hypermetabolism and brain insulin resistance occur in selected high-risk conditions as a transient phenomenon, eventually evolving toward normal or low values during life or disease progression. Associative studies suggest that brain hypermetabolism predicts low BDNF levels, hepatic and whole body insulin resistance, food desire and an unfavorable balance between anticipated reward from food and cognitive inhibitory control. Emerging mechanistic links involve the microbiota and the metabolome, which correlate with brain metabolism and cognition, deserving attention as potential future prevention targets.

Anticholinergic/sedative drug burden predicts worse memory acquisition in older racially/ethnically diverse patients with type 2 diabetes mellitus

OBJECTIVE

Anticholinergic/sedative drug use, measured by the Drug Burden Index (DBI), is linked to cognitive impairment in older adults. Yet, studies on the DBI's association with neuropsychological functioning are lacking, especially in underserved groups at increased risk of cognitive impairment. We examined cross-sectional relationships between total DBI (DBI_T ) and an age-adjusted analogue (Adj DBI_T ) with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) in diverse adults with type 2 diabetes mellitus (T2DM). Based on results of a prior study, we anticipated higher DBIs would be associated with worse memory at older ages.

METHODS

One hundred five adults with T2DM (age = 57 ± 9 years, 65% female, 62% Black, 27% Hispanic/Latino, Hb_A1c = 7.8 ± 1.8) participated. Although memory outcomes were normally distributed, DBI_T values were positively skewed. Spearman correlations assessed their bivariate relationships with RBANS. Adjusting for comorbidities, polypharmacy, Hb_A1c , and education, we tested the moderating effect of age on DBI-RBANS associations at mean ±1 standard deviations of age.

RESULTS

One third of the participants endorsed current sedative/anticholinergic use. Mean DBI_T was 0.385, and mean Adj DBI_T was 0.393 (ranges = 0.00-4.22). Drug burden negatively correlated with RBANS Immediate Memory (DBI_T r_s = -0.237, P = .013; Adj DBI_T r_s = -0.239, P = .014) but no other indices. There was a significant DBI*Age interaction; the negative effect of drug burden on Immediate Memory was significant for ages greater than or equal to 55 years old.

CONCLUSIONS

Sedative/anticholinergic drug exposure was prevalent in these diverse T2DM patients. Adjusting for covariates, greater drug burden was associated with worse memory acquisition among older adults only. Prospective studies should examine these relationships over time and assess whether dementia biomarkers affect the interaction.

Cognitive Impairments in First-Episode Drug-Naïve Versus Medicated Depressive Patients: RBANS in a Chinese Population

Cognitive deficits are a core feature of major depressive disorder (MDD). However, there are no previous studies that directly compare cognitive performance between first-episode drug-naive depressive patients (FDDP) and medicated depressive patients (MDP). Therefore, the aim of this study was to investigate whether there were the differences in cognitive functions between FDDP and MDP. Sixty-two FDDP, 111 MDP and 90 healthy controls were enrolled in a Chinese population. Cognitive functions were assessed using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). There were the differences in the RBANS total score (F = 26.55, p < 0.001), subscales of immediate memory (F = 3.95, p = 0.02), language (F = 54.11, p < 0.001) and delayed memory (F = 11.19, p = 0.001) among the three groups after controlling for gender, education, smoking and body mass index (BMI). These differences in the RBANS total score, subscales of language and delayed memory passed the Bonferroni corrections (all, p < 0.05). Compared to healthy controls, FDDP and MDP had poorer cognitive performance including the RBANS total score, and subscales of language and delayed memory (all, p < 0.05) after controlling for the variables. FDDP experienced greater language deficits than MDP (p < 0.05) after controlling for the variables. Education was correlated with the language score in FDDP (r = 0.61, p < 0.001). Multivariate regression analysis indicated that education was an independent contributor to the language score in FDDP (ß = 3.11, t = 5.48, p < 0.001). Our findings indicated that FDDP had poorer language performance than MDP. Moreover, education could influence the language performance in FDDP.

Hypothesis and Theory: Circulating Alzheimer's-Related Biomarkers in Type 2 Diabetes. Insight From the Goto-Kakizaki Rat

Epidemiological data suggest an increased risk of developing Alzheimer's disease (AD) in individuals with type 2 diabetes (T2D). AD is anatomically associated with an early progressive accumulation of Aβ leading to a gradual Tau hyperphosphorylation, which constitute the main characteristics of damaged brain in AD. Apart from these processes, mounting evidence suggests that specific features of diabetes, namely impaired glucose metabolism and insulin signaling in the brain, play a key role in AD. Moreover, several studies report a potential role of Aβ and Tau in peripheral tissues such as pancreatic β cells. Thus, it appears that several biological pathways associated with diabetes overlap with AD. The link between peripheral insulin resistance and brain insulin resistance with concomitant cognitive impairment may also potentially be mediated by a liver/pancreatic/brain axis, through the excessive trafficking of neurotoxic molecules across the blood-brain barrier. Insulin resistance incites inflammation and pro-inflammatory cytokine activation modulates the homocysteine cycle in T2D patients. Elevated plasma homocysteine level is a risk factor for AD pathology and is also closely associated with metabolic syndrome. We previously demonstrated a strong association between homocysteine metabolism and insulin via cystathionine beta synthase (CBS) activity, the enzyme implicated in the first step of the trans-sulfuration pathway, in Goto-Kakizaki (GK) rats, a spontaneous model of T2D, with close similarities with human T2D. CBS activity is also correlated with DYRK1A, a serine/threonine kinase regulating brain-derived neurotrophic factor (BDNF) levels, and Tau phosphorylation, which are implicated in a wide range of disease such as T2D and AD. We hypothesized that DYRK1A, BDNF, and Tau, could be among molecular factors linking T2D to AD. In this focused review, we briefly examine the main mechanisms linking AD to T2D and provide the first evidence that certain circulating AD biomarkers are found in diabetic GK rats. We propose that the spontaneous model of T2D in GK rat could be a suitable model to investigate molecular mechanisms linking T2D to AD.

Influence of Tacrolimus on Depressive-Like Behavior in Diabetic Rats Through Brain-Derived Neurotrophic Factor Regulation in the Hippocampus

The neurotoxicity of immunosuppressive agents and diabetes mellitus are known risk factors of neurological complications in kidney transplant recipients. The aim of the present study was to investigate the influence of tacrolimus on brain-derived neurotrophic factor (BDNF), the critical protein for maintenance of neuronal functions, in the hippocampus in a diabetic condition. A diabetic rat model was established by a single streptozotocin injection (60 mg/kg). Control and diabetic rats then received daily tacrolimus (1.5 mg/kg per day) injections for 6 weeks. BDNF expression in the hippocampus was examined in the dentate gyrus (DG) and CA3 region using immunohistochemistry. There was a significant decrease of BDNF expression in the DG and CA3 region in tacrolimus-treated and diabetic rats compared with that of the control group injected with vehicle only. However, there was no difference in BDNF expression between the two experimental groups. Tacrolimus treatment in diabetic rats further decreased the BDNF expression level in the DG and CA3 region. Interestingly, mossy fiber sprouting, demonstrated by prominent punctate immunolabeling of BDNF with synaptoporin, was observed in the diabetic group treated with tacrolimus, which localized at the stratum oriens of the CA3 region. These data suggest that tacrolimus treatment or a diabetic condition decreases BDNF expression in the hippocampus, and that tacrolimus treatment in the diabetic condition further injures the CA3 region of the hippocampus. In addition to BDNF expression, decreased locomotor activity and evident depressive behavior were observed in tacrolimus-treated diabetic rats. Moreover, there were significant decreases of the mRNA levels of γ-aminobutyric acid and serotonin receptors in the diabetic hippocampus with tacrolimus treatment. This finding suggests that tacrolimus treatment may cause further psychiatric and neurological complications for patients with diabetes, and should thus be used with caution.

BDNF Alleviates Neuroinflammation in the Hippocampus of Type 1 Diabetic Mice via Blocking the Aberrant HMGB1/RAGE/NF-κB Pathway

Diabetes is a systemic disease that can cause brain damage such as synaptic impairments in the hippocampus, which is partly because of neuroinflammation induced by hyperglycemia. Brain-derived neurotrophic factor (BDNF) is essential in modulating neuroplasticity. Its role in anti-inflammation in diabetes is largely unknown. In the present study, we investigated the effects of BDNF overexpression on reducing neuroinflammation and the underlying mechanism in mice with type 1 diabetes induced by streptozotocin (STZ). Animals were stereotactically microinjected in the hippocampus with recombinant adeno-associated virus (AAV) expressing BDNF or EGFP. After virus infection, four groups of mice, the EGFP+STZ, BDNF+STZ, EGFP Control and BDNF Control groups, received STZ or vehicle treatment as indicated. Three weeks later brain tissues were collected. We found that BDNF overexpression in the hippocampus significantly rescued STZ-induced decreases in mRNA and protein expression of two synaptic plasticity markers, spinophilin and synaptophysin. More interestingly, BDNF inhibited hyperglycemia-induced microglial activation and reduced elevated levels of inflammatory factors (TNF-α, IL-6). BDNF blocked the increase in HMGB1 levels and specifically, in levels of one of the HMGB1 receptors, RAGE. Downstream of HMGB1/RAGE, the increase in the protein level of phosphorylated NF-κB was also reversed by BDNF in STZ-treated mice. These results show that BDNF overexpression reduces neuroinflammation in the hippocampus of type 1 diabetic mice and suggest that the HMGB1/RAGE/NF-κB signaling pathway may contribute to alleviation of neuroinflammation by BDNF in diabetic mice.

Crucial players in Alzheimer's disease and diabetes mellitus: Friends or foes?

Alzheimer's disease (AD) and diabetes mellitus, especially type 2 (T2DM), are very common and widespread diseases in contemporary societies, and their incidence is steadily on the increase. T2DM is a multiple metabolic disorder, with several mechanisms including hyperglycaemia, insulin resistance, insulin receptor and insulin growth factor disturbances, glucose toxicity, formation of advanced glycation end products (AGEs) and the activity of their receptors. AD is the most common form of dementia, characterized by the accumulation of extracellular beta amyloid peptide aggregates and intracellular hyper-phosphorylated tau proteins, which are thought to drive and/or accelerate inflammatory and oxidative stress processes leading to neurodegeneration. The aim of this paper is to provide a comprehensive review of the evidence linking T2DM to the onset and development of AD and highlight the unknown or poorly studied "nooks and crannies" of this interesting relationship, hence providing an opportunity to stimulate new ideas for the analysis of comorbidities between AD and DM. Despite, indication of possible biomarkers of early diagnosis of T2DM and AD, this review is also an attempt to answer the question as to whether the crucial factors in the development of both conditions support the link between DM and AD.