Effects of Diabetes Mellitus-Related Dysglycemia on the Functions of Blood-Brain Barrier and the Risk of Dementia

Sugar utilization by microglia in Alzheimer's disease

Diabetes is a major risk factor for Alzheimer's disease (AD), yet the effect of specific carbohydrate sources in the diet on AD pathology remains unclear. The primary neuroimmune cell, microglia, undergo a metabolic shift during neuroinflammation associated with AD pathology. We utilized existing gene expression data and identified changes in sugar transporters (increased Slc2a1 (glucose) and decreased Slc2a5 (fructose) expression). To examine gene expression with respect to primary sugar source, N9 cells, a mouse microglia cell line, were cultured in glucose or fructose supplemented media and stimulated with lipopolysaccharide (LPS). RNA-sequencing analyses indicated significant changes between control and sugar supplemented media and several differentially expressed genes between glucose and fructose media. Concurrently, 5XFAD mice received equicaloric diets with specific carbohydrate sources: dextrose or fructose. Regardless of diet, sex, or genotype, all mice developed high blood sugar levels; confocal microscopy analyses indicated similar amyloid plaque burden and microglial response relative to the control diet, but there was a change in the microglial response between dextrose and fructose fed mice. Overall, these data indicate microglia preferentially express sugar transporters and sugar source may influence microglial reactivity in response to plaque pathology.

Triglyceride-glucose index: a novel prognostic marker for sepsis-associated encephalopathy severity and outcomes

Background

Sepsis-associated encephalopathy (SAE) is a complex condition with variable outcomes. This study investigates the potential of the Triglyceride-glucose (TyG) index as a marker for disease severity and prognosis in SAE patients.

Methods

We conducted a retrospective cohort study using data from the Medical Information Mart for Intensive Care (MIMIC-IV) database. Patients with sepsis who were admitted to the intensive care unit (ICU) were categorized into two groups based on the occurrence of SAE. Key clinical outcomes were 90-day survival (primary outcome) and length of ICU and hospital stays, as well as the use of vasoactive medications (secondary outcomes). The TyG index was calculated, and its association with disease severity scores and patient outcomes was analyzed using statistical methods, including survival analysis, Cox regression, and correlation analyses.

Results

The study population's median age was 65.96 years, predominantly male (60.1%). Higher TyG index scores correlated with elevated clinical severity scores (APSIII, LODS, OASIS, SAPSII, and CCI) and increased ICU and hospital stay durations. TyG index categorization revealed significant differences in 90-day survival probabilities, with "high TyG" associated with a 25% increased mortality risk compared to "low TyG." Furthermore, TyG index showed a moderate positive correlation with ICU stay duration and use of norepinephrine and vasopressin, but not with dopamine and epinephrine use.

Conclusion

The TyG index is a significant independent predictor of disease severity and prognosis in SAE patients. High TyG levels correlate with worse clinical outcomes and increased mortality risk, suggesting its potential as a valuable tool in managing SAE.

The interaction between dysfunction of vasculature and tauopathy in Alzheimer's disease and related dementias

Tauopathy is one of the pathological features of Alzheimer's disease and related dementias (ADRD). At present, there have been many studies on the formation, deposition, and intercellular transmission of tau in neurons and immune cells. The vasculature is an important component of the central nervous system. This review discusses the interaction between vasculature and tau in detail from three aspects. (1) The vascular risk factors (VRFs) discussed in this review include diabetes mellitus (DM), abnormal blood pressure (BP), and hypercholesterolemia. (2) In ADRD pathology, the hyperphosphorylation and deposition of tau interact with disrupted vasculature, such as different cells (endothelial cells, smooth muscular cells, and pericytes), the blood-brain barrier (BBB), and the cerebral lymphatic system. (3) The functions of vasculature are regulated by various signaling transductions. Endothelial nitric oxide synthase/nitric oxide, calcium signaling, Rho/Rho-associated coiled-coil containing Kinase, and receptors for advanced glycation end products are discussed in this review. Our findings indicate that the prevention and treatment of vascular health may be a potential target for ADRD combination therapy. HIGHLIGHTS: Persistent VRFs increase early disruption of vascular mechanisms and are strongly associated with tau pathology in ADRD. Cell dysfunction in the vasculature causes BBB leakage and drainage incapacity of the cerebral lymphatic system, which interacts with tau pathology. Signaling molecules in the vasculature regulate vasodilation and contraction, angiogenesis, and CBF. Abnormal signaling transduction is related to tau hyperphosphorylation and deposition.

Diabetes Mellitus Impairs Blood-Brain Barrier Integrality and Microglial Reactivity

Diabetes mellitus (DM), a chronic metabolic disorder that adversely affects the blood-brain barrier (BBB) and microglial function in the central nervous system (CNS), contributing to neuronal damage and neurodegenerative diseases. However, the underlying molecular mechanisms linking diabetes to BBB dysfunction and microglial dysregulation remain poorly understood. Here, we assessed the impacts of diabetes on BBB and microglial reactivity and investigated its mechanisms. We found diabetes severely disrupted the BBB integrity and microglial response to vascular injury. We also revealed a potential relationship between BBB disruption and impaired microglial function, whereby increasing BBB permeability led to a downregulation of microglial P2RY12 expression, thereby impairing microglial protection against cerebrovascular injury. Understanding these mechanisms may contribute to the developing of therapeutic strategies for diabetes-related neurological complications.

Regulation of the blood-brain barrier function by peripheral cues in health and disease

The blood-brain barrier (BBB) is formed by microvascular endothelial cells which are ensembled with pericytes, astrocytes, microglia and neurons in the neurovascular unit (NVU) that is crucial for neuronal function. Given that the NVU and the BBB are highly dynamic and regulated structures, their integrity is continuously challenged by intrinsic and extrinsic factors. Herein, factors from peripheral organs such as gonadal and adrenal hormones may influence vascular function also in CNS endothelial cells in a sex- and age-dependent manner. The communication between the periphery and the CNS likely takes place in specific areas of the brain among which the circumventricular organs have a central position due to their neurosensory or neurosecretory function, owing to physiologically leaky blood vessels. In acute and chronic pathological conditions like liver, kidney, pulmonary disease, toxins and metabolites are generated that reach the brain via the circulation and may directly or indirectly affect BBB functionality via the activation of the immunes system. For example, chronic kidney disease (CKD) currently affects more than 840 million people worldwide and is likely to increase along with western world comorbidities of the cardio-vascular system in continuously ageing societies. Toxins leading to the uremic syndrome, may further lead to neurological complications such as cognitive impairment and uremic encephalopathy. Here we summarize the effects of hormones, toxins and inflammatory reactions on the brain vasculature, highlighting the urgent demand for mechanistically exploring the communication between the periphery and the CNS, focusing on the BBB as a last line of defense for brain protection.

The effects of aerobic exercise on cognitive function in middle-aged and older individuals with type 2 diabetes: A pilot randomized controlled trial

AIM

The purposes of this pilot randomized controlled trial were to establish feasibility of participant recruitment and engagement in the exercise intervention.

METHODS

A total of 50 participants with type 2 diabetes were recruited from the study and randomly assigned to an aerobic exercise group or an attention control group.

RESULTS

Our study demonstrated the feasibility of the exercise program, achieving a recruitment rate of 2.94 persons per month, a 76% retention rate, and an 80.56% attendance rate. The adherence rates were 79.54% and 76.48% for the aerobic exercise and attention control groups, respectively. However, we were not able to detect any statistically significant difference between the two groups.

CONCLUSIONS

This pilot study established the feasibility of recruiting and engaging middle-aged older adults with type 2 diabetes in aerobic exercise. Based on these findings, a large-scale study assessing the effects of aerobic exercise on cognitive function in this population is needed.

Cognitive Disorders in Type 1 Diabetes: Role of Brain Glucose Variation, Insulin Activity, and Glucocorticoid Exposure

BACKGROUND

The number of patients with type 2 diabetes (T2D) and type 1 diabetes (T1D) is on the rise, partly due to a global increase in new T1D cases among children. Beyond the well-documented microvascular and macrovascular complications, there is now substantial evidence indicating that diabetes also impacts the brain, leading to neuropsychological impairments. The risk of developing neuropsychiatric symptoms is notably higher in childhood due to the ongoing maturation of the brain, which makes it more susceptible to damage. Despite this awareness, the specific effects of diabetes on cognitive function remain poorly understood.

SUMMARY

This review synthesizes literature on the impact of diabetes on cognition and its relationship with brain structural changes. It presents data and hypotheses to explain how T1D contributes to cognitive dysfunction, with a particular focus on children and adolescents. The emphasis on the pediatric population is intentional, as young diabetic patients typically have fewer comorbidities, reducing confounding factors and simplifying the investigation of cognitive alterations.

KEY MESSAGE

We examine the roles of hypo- and hyperglycemia, as well as the emerging role of glucocorticoids in the development of neuropsychological disorders. When specific mechanisms related to T1D are available, they are highlighted; otherwise, data and hypotheses applicable to both T1D and T2D are discussed.

Phytochemical analysis, identification of bioactive compounds using GC-MS, in vitro and in silico hypoglycemic potential, in vitro antioxidant potential, and in silico ADME analysis of Chlorophytum comosum root and leaf

Chlorophytum comosum is a plant with medicinal potential traditionally used to treat different diseases. The present study aimed to determine the bioactive compounds, hypoglycemic and antioxidant potential of C. comosum root and leaf. The ethyl acetate extracts of C. comosum root and leaf were analyzed by GC-MS to determine the bioactive compounds. The hypoglycemic potential of the extracts was evaluated by α-amylase, α-glucosidase, glucose diffusion inhibitory assays, and glucose adsorption assay. The ethyl acetate extract of C. comosum root inhibited α-amylase, α-glucosidase, and glucose diffusion in a concentration-dependent manner with IC50 values of 205.39 ± 0.15, 179.34 ± 0.3 and 535.248 μg/mL, respectively, and the leaf extract inhibited α-amylase and α-glucosidase enzymes with IC50 values of 547.99 ± 0.09, and 198.18 ± 0.25 μg/mL respectively. C. comosum root and leaf extracts also improved glucose adsorption. Heptadecanoic acid and dodecanoic acid were identified as potential compounds with hypoglycemic properties through molecular docking. The extracts were also assessed for their antioxidant activity using DPPH, ABTS, and FRAP assays. C. comosum root and leaf extracts were also able to scavenge DPPH radicals with IC50 values of 108.37 ± 0.06 and 181.79 ± 0.09 µM and ABTS radicals with IC50 values of 126.24 ± 0.13 and 264.409 ± 0.08 µM, respectively. The root and leaf extracts also reduced the ferricyanide complex to ferrocyanide with higher reducing powers of 2.24 ± 0.02 and 1.65 ± 0.03, respectively. The results showed that the ethyl acetate extract of C. comosum root has significant antioxidant and hypoglycemic potential compared to the leaf extract. Thus, it can also be studied to isolate the potential compounds with antihyperglycemic activities.

Dynamic changes in key factors of the blood-brain barrier in early diabetic mice

Chronic hyperglycemia can result in damage to the hippocampus and dysfunction of the blood-brain barrier (BBB), potentially leading to neurological disorders. This study examined the histological structure of the hippocampus and the expression of critical genes associated with the BBB at 2 early stage time points in a streptozotocin-induced diabetes mellitus (DM) mouse model. Routine histology revealed vascular congestion and dilation of Virchow-Robin spaces in the hippocampal CA1 region of the DM group. Neuronal alterations included rounding and swelling and reduction in Nissl bodies and increased apoptosis. Compared to the control group, TJP1 mRNA expression in the DM group was significantly lower (P < .05 or P < .01), while mRNA levels of JAM3, TJP3, CLDN5, CLDN3, and OCLN initially increased and then decreased. At 7, 14, and 21 days, mRNA levels of the receptor for advanced glycation end products (AGER) were greater in the DM group than in the control group (P < .05 or P < .01). These findings indicate that early-stage diabetes may cause structural and functional impairments in hippocampal CA1 in mice. These abnormalities may parallel alterations in the expression of key BBB tight junction molecules and elevated AGER expression in early DM patients.

Diabetic neuropathy: A NRF2 disease?

The transcription factor nuclear factor erythroid 2-related factor 2 (NRF2) has multifarious action with its target genes having redox-regulating functions and being involved in inflammation control, proteostasis, autophagy, and metabolic pathways. Therefore, the genes controlled by NRF2 are involved in the pathogenesis of myriad diseases, such as cardiovascular diseases, metabolic syndrome, neurodegenerative diseases, autoimmune disorders, and cancer. Amidst this large array of diseases, diabetic neuropathy (DN) occurs in half of patients diagnosed with diabetes and appears as an injury inflicted upon peripheral and autonomic nervous systems. As a complex effector factor, NRF2 has entered the spotlight during the search of new biomarkers and/or new therapy targets in DN. Due to the growing attention for NRF2 as a modulating factor in several diseases, including DN, this paper aims to update the recently discovered regulatory pathways of NRF2 in oxidative stress, inflammation and immunity. It presents the animal models that further facilitated the human studies in regard to NRF2 modulation and the possibilities of using NRF2 as DN biomarker and/or as target therapy.

Should dietary restrictions be imposed on Alzheimer's Disease patients affected by type 2 diabetes?

INTRODUCTION

Antidiabetic drugs, reduction of carbohydrates intake, maintaining normal weight and physical activity are the cornerstone of diabetes 2 treatment.

METHODS

This opinion article is not intended to challenge hundreds of studies unequivocally demonstrating the benefits of a healthy lifestyle including appropriate diet in controlling the consequences of T2DM. The article questions whether the benefits of dietary restrictions for the management of T2D in older adults who are already demented, are worth the potential detrimental effects on quality of life for the patients and their caregivers, as well as the effects of dietary restrictions on frailty, sarcopenia.

DISCUSSION

However, the benefit of dietary restrictions including carbohydrates restrictions, might not manifest in elderly Alzheimer and vascular dementia patients with type 2 diabetes. On the contrary, such restrictions might hinder the patients' and caregiver's quality of life and encumber attempts to maintain normal weight in a population which tends to be underweight. Therefore, the benefit/risk ratio of dietary restriction should be weighed in this population on an individual basis.

Adapted diabetes complications severity index predicts dementia risk in ageing type 2 diabetes mellitus patients

This study investigated the link between the adapted diabetes complication severity index at the time of type 2 diabetes mellitus diagnosis and diabetes-induced dementia risk in elderly patients. Elderly type 2 diabetes mellitus patients (age ≥ 60) were matched using propensity score matching. Cox regression was used to determine dementia hazard ratios; Kaplan-Meier method to assess cumulative incidence. The cohort included 256 214 elderly type 2 diabetes mellitus patients. Adapted diabetes complication severity index ≥ 1 showed higher dementia risk (adjusted hazard ratio: 1.30; 95% confidence interval: 1.27-1.34), increasing by 1.17-fold per adapted diabetes complication severity index point. Dementia risk rose progressively across adapted diabetes complication severity index scores (P < 0.0001). Higher adapted diabetes complication severity index scores at the time of type 2 diabetes mellitus diagnosis elevated dementia risk in elderly patients. Adapted diabetes complication severity index ≥ 1 is linked to increased dementia risk. Adapted diabetes complication severity index evaluation at the time of type 2 diabetes mellitus diagnosis could predict risk, aiding early interventions. Effective diabetes management is crucial for reducing dementia risk in this population.

Anti-Inflammatory Action of Resveratrol in the Central Nervous System in Relation to Glucose Concentration-An In Vitro Study on a Blood-Brain Barrier Model

Unbalanced blood glucose levels may cause inflammation within the central nervous system (CNS). This effect can be reversed by the action of a natural neuroprotective compound, resveratrol (RSV). The study aimed to investigate the anti-inflammatory effect of RSV on astrocyte cytokine profiles within an in vitro model of the blood-brain barrier (BBB) under varying glucose concentrations (2.2, 5.0, and 25.0 mmol/L), corresponding to hypo-, normo-, and hyperglycemia. The model included co-cultures of astrocytes (brain compartment, BC) and endothelial cells (microvascular compartment, MC), separated by 0.4 µm wide pores. Subsequent exposure to 0.2 μM LPS in the brain compartment (BC) and 50 μM RSV in the microvascular compartment (MC) of each well was carried out. Cytokine levels (IL-1 α, IL-1 β, IL-2, IL-4, IL-6, IL-8) in the BC were assessed using a Multi-Analyte ELISArray Kit before and after the addition of LPS and RSV. Statistical analysis was performed to determine significance levels. The results demonstrated that RSV reduced the concentration of all studied cytokines in the BC, regardless of glucose levels, with the most substantial decrease observed under normoglycemic conditions. Additionally, the concentration of RSV in the BC was highest under normoglycemic conditions compared to hypo- and hyperglycemia. These findings confirm that administration of RSV in the MC exerts anti-inflammatory effects within the BC, particularly under normoglycemia-simulating conditions. Further in vivo studies, including animal and human research, are warranted to elucidate the bioavailability of RSV within the central nervous system (CNS).

Glucose Fluctuation Inhibits Nrf2 Signaling Pathway in Hippocampal Tissues and Exacerbates Cognitive Impairment in Streptozotocin-Induced Diabetic Rats

Background

This research investigated whether glucose fluctuation (GF) can exacerbate cognitive impairment in streptozotocin-induced diabetic rats and explored the related mechanism.

Methods

After 4 weeks of feeding with diets containing high fats plus sugar, the rat model of diabetes mellitus (DM) was established by intraperitoneal injection of streptozotocin (STZ). Then, GF was triggered by means of alternating satiety and starvation for 24 h. The weight, blood glucose level, and water intake of the rats were recorded. The Morris water maze (MWM) test was carried out to appraise the cognitive function at the end of week 12. Moreover, the morphological structure of hippocampal neurons was viewed through HE and Nissl staining, and transmission electron microscopy (TEM) was performed for ultrastructure observation. The protein expression levels of Nrf2, HO-1, NQO-1, Bax, Bcl-2, and Caspase-3 in the hippocampal tissues of rats were measured via Western blotting, and the mRNA expressions of Nrf2, HO-1, and NQO-1 were examined using qRT-PCR. Finally, Western blotting and immunohistochemistry were conducted to detect BDNF levels.

Results

It was manifested that GF not only aggravated the impairment of spatial memory in rats with STZ-induced type 2 DM but also stimulated the loss, shrinkage, and apoptosis of hippocampal neurons. Regarding the expressions in murine hippocampal tissues, GF depressed Nrf2, HO-1, NQO-1, Bcl-2, and BDNF but boosted Caspase-3 and Bax.

Conclusions

GF aggravates cognitive impairment by inhibiting the Nrf2 signaling pathway and inducing oxidative stress and apoptosis in the hippocampal tissues.

Imaging diabetic cardiomyopathy in a type 1 diabetic rat model using 18F-FEPPA PET

OBJECTIVE

Diabetic patients often experience chronic inflammation and fibrosis in their cardiac tissues, highlighting the pressing need for the development of sensitive diagnostic methods for longitudinal assessment of diabetic cardiomyopathy. This study aims to evaluate the significance of an inflammatory marker known as translocator protein (TSPO) in a positron emission tomography (PET) protocol for longitudinally monitoring cardiac dysfunction in a diabetic animal model. Additionally, we compared the commonly used radiotracer, 18F-fluoro-2-deoxy-d-glucose (18F-FDG).

METHODS

Fourteen 7-week-old female Sprague-Dawley rats were used in this study. Longitudinal PET experiments were conducted using 18F-N-2-(2-fluoroethoxy)benzyl)-N-(4-phenoxypyridin-3-yl)acetamide (18F-FEPPA) (n = 3), the TSPO radiotracer, and 18F-FDG (n = 3), both before and after the onset of diabetes. Histological and immunohistochemical staining assays were also conducted in both the control (n = 4) and diabetes (n = 4) groups.

RESULTS

Results indicated a significant increase in cardiac tissue uptake of 18F-FEPPA after the onset of diabetes (P < 0.05), aligning with elevated TSPO levels observed in diabetic animals according to histological data. Conversely, the uptake of 18F-FDG in cardiac tissue significantly decreased after the onset of diabetes (P < 0.05).

CONCLUSION

These findings suggest that 18F-FEPPA can function as a sensitive probe for detecting chronic inflammation and fibrosis in the cardiac tissues of diabetic animals.

The effect of estrogen therapy on cerebral metabolism in diabetic female rats

The impact of estrogen on brain function, especially in individuals with diabetes, remains uncertain. This study aims to compare cerebral glucose metabolism levels in intact rats, ovariectomized (OVX) rats, and 17β-estradiol (E2)-treated OVX diabetic female rats. Sixteen rats were administered a single intraperitoneal injection of 70 mg/kg streptozotocin (STZ) to induce diabetes (intact, n = 6; OVX, n = 6; OVX+E2-treated, n = 4). Additionally, 18 rats received an equivalent solvent dose via intraperitoneal injection (intact, n = 6; OVX, n = 6; OVX+E2-treated, n = 6). After 4 weeks of STZ or solvent administration, positron emission tomography scans with 18F-fluorodeoxyglucose (18F-FDG) injection were employed to assess cerebral glucose metabolism. The diabetic rats exhibited substantial reductions in 18F-FDG uptake across all brain regions (all P < 0.01), in contrast to the control rats. Moreover, intact and OVX + E2-treated diabetic female rats displayed more pronounced decreases in cerebral glucose metabolism in the amygdala and hippocampus compared to OVX diabetic female rats (P < 0.05). These findings suggest that diabetes creates an environment wherein estrogen exacerbates neuropathology and intensifies neuronal activity.