The SGLT2 inhibitor Empagliflozin promotes post-stroke functional recovery in diabetic mice.

Type-2 diabetes (T2D) worsens stroke recovery, amplifying post-stroke disabilities. Currently, there are no therapies targeting this important clinical problem. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are potent anti-diabetic drugs that also efficiently reduce cardiovascular death and heart failure. In addition, SGLT2i facilitate several processes implicated in stroke recovery. However, the potential efficacy of SGLT2i to improve stroke recovery in T2D has not been investigated. Therefore, we determined whether a post-stroke intervention with the SGLT2i Empagliflozin could improve stroke recovery in T2D mice. T2D was induced in C57BL6J mice by 8 months of high-fat diet feeding. Hereafter, animals were subjected to transient middle cerebral artery occlusion and treated with vehicle or the SGLTi Empagliflozin (10 mg/kg/day) starting from 3 days after stroke. A similar study in non diabetic mice was also conducted. Stroke recovery was assessed using the forepaw grip strength test. To identify potential mechanisms involved in the Empagliflozin-mediated effects, several metabolic parameters were assessed. Additionally, neuronal survival, neuroinflammation, neurogenesis and cerebral vascularization were analyzed using immunohistochemistry/quantitative microscopy. Empagliflozin significantly improved stroke recovery in T2D but not in non-diabetic mice. Improvement of functional recovery was associated with lowered glycemia, increased serum levels of fibroblast growth factor-21 (FGF-21), and the normalization of T2D-induced aberration of parenchymal pericyte density. The global T2D-epidemic and the fact that T2D is a major risk factor for stroke are drastically increasing the number of people in need of efficacious therapies to improve stroke recovery. Our data provide a strong incentive for the potential use of SGLT2i for the treatment of post-stroke sequelae in T2D.

The Pre-Stroke Induction and Normalization of Insulin Resistance Respectively Worsens and Improves Functional Recovery.

Type 2 diabetes (T2D) impairs post-stroke recovery, and the underlying mechanisms are unknown. Insulin resistance (IR), a T2D hallmark that is also closely linked to aging, has been associated with impaired post-stroke recovery. However, whether IR worsens stroke recovery is unknown. We addressed this question in mouse models where early IR, with or without hyperglycemia, was induced by chronic high-fat diet feeding or sucrose supplementation in the drinking water, respectively. Furthermore, we used 10-month-old mice, spontaneously developing IR but not hyperglycemia, where IR was normalized pharmacologically pre-stroke with Rosiglitazone. Stroke was induced by transient middle cerebral artery occlusion and recovery was assessed by sensorimotor tests. Neuronal survival, neuroinflammation and the density of striatal cholinergic interneurons were also assessed by immunohistochemistry/quantitative microscopy. Pre-stroke induction and normalization of IR, respectively, worsened and improved post-stroke neurological recovery. Moreover, our data indicate a potential association of this impaired recovery with exacerbated neuroinflammation and a decreased density of striatal cholinergic interneurons. The global diabetes epidemic and population aging are dramatically increasing the percentage of people in need of post-stroke treatment/care. Our results suggest that future clinical studies should target pre-stroke IR to reduce stroke sequelae in both diabetics and elderly people with prediabetes.

A High-Fat Diet Increases Activation of the Glucagon-Like Peptide-1-Producing Neurons in the Nucleus Tractus Solitarii: an Effect that is Partially Reversed by Drugs Normalizing Glycemia.

Glucagon-like peptide-1 (GLP-1) is a peripheral incretin and centrally active peptide produced in the intestine and nucleus tractus solitarii (NTS), respectively. GLP-1 not only regulates metabolism but also improves cognition and is neuroprotective. While intestinal GLP-1-producing cells have been well characterized, less is known about GLP-1-producing neurons in NTS. We hypothesized that obesity-induced type 2 diabetes (T2D) impairs the function of NTS GLP-1-producing neurons and glycemia normalization counteracts this effect. We used immunohistochemistry/quantitative microscopy to investigate the number, potential atrophy, and activation (cFos-expression based) of NTS GLP-1-producing neurons, in non-diabetic versus obese/T2D mice (after 12 months of high-fat diet). NTS neuroinflammation was also assessed. The same parameters were quantified in obese/T2D mice treated from month 9 to 12 with two unrelated anti-hyperglycemic drugs: the dipeptidyl peptidase-4 inhibitor linagliptin and the sulfonylurea glimepiride. We show no effect of T2D on the number and volume but increased activation of NTS GLP-1-producing neurons. This effect was partially normalized by both anti-diabetic treatments, concurrent with decreased neuroinflammation. Increased activation of NTS GLP-1-producing neurons could represent an aberrant metabolic demand in T2D/obesity, attenuated by glycemia normalization. Whether this effect represents a pathophysiological process preceding GLP-1 signaling impairment in the CNS, remains to be investigated.

More than Addiction-The Nucleus Accumbens Contribution to Development of Mental Disorders and Neurodegenerative Diseases.

Stress and negative emotions evoked by social relationships and working conditions, frequently accompanied by the consumption of addictive substances, and metabolic and/or genetic predispositions, negatively affect brain function. One of the affected structures is nucleus accumbens (NAc). Although its function is commonly known to be associated with brain reward responses and addiction, a growing body of evidence also suggests its role in some mental disorders, such as depression and schizophrenia, as well as neurodegenerative diseases, such as Alzheimer's, Huntington's, and Parkinson's. This may result from disintegration of the extensive connections based on numerous neurotransmitter systems, as well as impairment of some neuroplasticity mechanisms in the NAc. The consequences of NAc lesions are both morphological and functional. They include changes in the NAc's volume, cell number, modifications of the neuronal dendritic tree and dendritic spines, and changes in the number of synapses. Alterations in the synaptic plasticity affect the efficiency of synaptic transmission. Modification of the number and structure of the receptors affects signaling pathways, the content of neuromodulators (e.g., BDNF) and transcription factors (e.g., pCREB, DeltaFosB, NFκB), and gene expression. Interestingly, changes in the NAc often have a different character and intensity compared to the changes observed in the other parts of the basal ganglia, in particular the dorsal striatum. In this review, we highlight the role of the NAc in various pathological processes in the context of its structural and functional damage, impaired connections with the other brain areas cooperating within functional systems, and progression of the pathological processes.

Diet-induced weight loss in obese/diabetic mice normalizes glucose metabolism and promotes functional recovery after stroke.

BACKGROUND: Post-stroke functional recovery is severely impaired by type 2 diabetes (T2D). This is an important clinical problem since T2D is one of the most common diseases. Because weight loss-based strategies have been shown to decrease stroke risk in people with T2D, we aimed to investigate whether diet-induced weight loss can also improve post-stroke functional recovery and identify some of the underlying mechanisms. METHODS: T2D/obesity was induced by 6 months of high-fat diet (HFD). Weight loss was achieved by a short- or long-term dietary change, replacing HFD with standard diet for 2 or 4 months, respectively. Stroke was induced by middle cerebral artery occlusion and post-stroke recovery was assessed by sensorimotor tests. Mechanisms involved in neurovascular damage in the post-stroke recovery phase, i.e. neuroinflammation, impaired angiogenesis and cellular atrophy of GABAergic parvalbumin (PV)+ interneurons were assessed by immunohistochemistry/quantitative microscopy. RESULTS: Both short- and long-term dietary change led to similar weight loss. However, only the latter enhanced functional recovery after stroke. This effect was associated with pre-stroke normalization of fasting glucose and insulin resistance, and with the reduction of T2D-induced cellular atrophy of PV+ interneurons. Moreover, stroke recovery was associated with decreased T2D-induced neuroinflammation and reduced astrocyte reactivity in the contralateral striatum. CONCLUSION: The global diabetes epidemic will dramatically increase the number of people in need of post-stroke treatment and care. Our results suggest that diet-induced weight loss leading to pre-stroke normalization of glucose metabolism has great potential to reduce the sequelae of stroke in the diabetic population.

Estimated glucose disposal rate and risk of stroke and mortality in type 2 diabetes: a nationwide cohort study.

BACKGROUND AND AIMS: Insulin resistance contributes to the development of type 2 diabetes (T2D) and is also a cardiovascular risk factor. The aim of this study was to investigate the potential association between insulin resistance measured by estimated glucose disposal rate (eGDR) and risk of stroke and mortality thereof in people with T2D. MATERIALS AND METHODS: Nationwide population based observational cohort study that included all T2D patients from the Swedish national diabetes registry between 2004 and 2016 with full data on eGDR and categorised as following: < 4, 4-6, 6-8, and ≥ 8 mg/kg/min. We calculated crude incidence rates and 95% confidence intervals (CIs) and used multiple Cox regression to estimate hazard ratios (HRs) to assess the association between the risk of stroke and death, according to the eGDR categories in which the lowest category < 4 (i.e., highest grade of insulin resistance), served as a reference. The relative importance attributed of each factor in the eGDR formula was measured by the R2 (± SE) values calculating the explainable log-likelihoods in the Cox regression. RESULTS: A total of 104 697 T2D individuals, 44.5% women, mean age of 63 years, were included. During a median follow up-time of 5.6 years, 4201 strokes occurred (4.0%). After multivariate adjustment the HRs (95% CI) for stroke in patients with eGDR categories between 4-6, 6-8 and > 8 were: 0.77 (0.69-0.87), 0.68 (0.58-0.80) and 0.60 (0.48-0.76), compared to the reference < 4. Corresponding numbers for the risk of death were: 0.82 (0.70-0.94), 0.75 (0.64-0.88) and 0.68 (0.53-0.89). The attributed relative risk R2 (± SE) for each variable in the eGDR formula and stroke was for: hypertension (0.045 ± 0.0024), HbA1c (0.013 ± 0.0014), and waist (0.006 ± 0.0009), respectively. CONCLUSION: A low eGDR (a measure of insulin resistance) is associated with an increased risk of stroke and death in individuals with T2D. The relative attributed risk was most important for hypertension.

The Stroke-Induced Increase of Somatostatin-Expressing Neurons is Inhibited by Diabetes: A Potential Mechanism at the Basis of Impaired Stroke Recovery.

Type 2 diabetes (T2D) hampers recovery after stroke, but the underling mechanisms are mostly unknown. In a recently published study (Pintana et al. in Clin Sci (Lond) 133(13):1367-1386, 2019), we showed that impaired recovery in T2D was associated with persistent atrophy of parvalbumin+ interneurons in the damaged striatum. In the current work, which is an extension of the abovementioned study, we investigated whether somatostatin (SOM)+ interneurons are also affected by T2D during the stroke recovery phase. C57Bl/6j mice were fed with high-fat diet or standard diet (SD) for 12 months and subjected to 30-min transient middle cerebral artery occlusion (tMCAO). SOM+ cell number/density in the striatum was assessed by immunohistochemistry 2 and 6 weeks after tMCAO in peri-infarct and infarct areas. This was possible by establishing a computer-based quantification method that compensates the post-stroke tissue deformation and the irregular cell distribution. SOM+ interneurons largely survived the stroke as seen at 2 weeks. Remarkably, 6 weeks after stroke, the number of SOM+ interneurons increased (vs. contralateral striatum) in SD-fed mice in both peri-infarct and infarct areas. However, this increase did not result from neurogenesis. T2D completely abolished this effect specifically in the in the infarct area. The results suggest that the up-regulation of SOM expression in the post-stroke phase could be related to neurological recovery and T2D could inhibit this process. We also present a new and precise method for cell counting in the stroke-damaged striatum that allows to reveal accurate, area-related effects of stroke on cell number.

Risk of first stroke in people with type 2 diabetes and its relation to glycaemic control: A nationwide observational study.

AIMS: To compare stroke incidence in people with type 2 diabetes (T2D) with that in a matched control group, and to investigate whether glucose exposure in people with T2D can predict a first-time stroke event and mortality. MATERIAL AND METHODS: In a nationwide observational cohort study, individuals with T2D were linked in the Swedish National Diabetes Register and matched with five individual population-based control subjects. We calculated crude incidence rates and 95% confidence intervals (CIs), and used Cox regression and multivariable hazard ratios (HRs), to estimate the risk of stroke and mortality in relation to glycated haemoglobin (HbA1c) levels. RESULTS: A total of 406 271 people with T2D (age 64.1 ± 12.4 years, 45.7% women) and 2086 440 control subjects (age 64.0 ± 12.4 years, 45.7% women) were included. During a median follow-up of 7.3 years, 26 380 people with T2D (6.5%) versus 92 375 control subjects (4.4%) were diagnosed with a stroke. The incidence rate was 10.12 events per 1000 person-years versus 7.26 events per 1000 person-years (HR 1.54, 95% CI 1.52-1.56). In the T2D group after multivariable adjustments, the HRs for stroke stratified by HbA1c level were: 54-64 mmol/mol: 1.27 (95% CI 1.22-1.32); 65-75 mmol/mol: 1.68 (95% CI 1.60-1.76); 76-86 mmol/mol: 1.89 (95% CI, 1.75-2.05); and > 87 mmol/mol: 2.14 (95% CI 1.90-2.42), respectively, compared with the reference category of HbA1c ≤53 mmol/mol. There was a stepwise increased risk of death after stroke, for every 10-mmol/mol categorical increment of HbA1c (HR 1.71; 95% CI 1.47-2.00) for the highest HbA1c category. CONCLUSIONS: An increased risk of stroke and death was associated with poor glycaemic control in people with T2D.

Leisure activity and social integration mitigate the risk of dementia related to cardiometabolic diseases: A population-based longitudinal study.

INTRODUCTION: The effect of comorbid cardiometabolic diseases (CMDs), including diabetes, heart diseases, and stroke, on dementia remains unclear. METHODS: A cohort of 2648 dementia-free adults aged ≥60 years was followed up for 12 years. An active lifestyle was defined in accordance with the engagement in leisure activities and/or a social network. Cox models were used in data analysis. RESULTS: The multiadjusted hazard ratio (HR, 95% confidence interval) of dementia was 1.41 (1.07-1.86) for one, 2.38 (1.58-3.59) for two, and 4.76 (2.04-11.13) for three CMDs. In joint exposure analysis, the HR of dementia was 3.36 (2.14-5.30) for participants with CMDs plus an inactive lifestyle and 1.32 (0.95-1.84) for those with CMDs plus an active lifestyle (reference: no CMDs plus active lifestyle). An active lifestyle delayed dementia onset by 3.50 years in people with CMDs. DISCUSSION: CMDs, especially when comorbid, are associated with increased dementia risk; however, leisure activities and social integration mitigate this risk.

GLP-1 secretion in acute ischemic stroke: association with functional outcome and comparison with healthy individuals.

BACKGROUND: Glucagon-like peptide-1 (GLP-1) treatment has been shown to reduce stroke incidence in diabetes and also to be neuroprotective in experimental stroke models. The prognostic value of endogenous levels of GLP-1 in the recovery phase after stroke remains to be elucidated. The aim of the study was to investigate the potential association between GLP-1 levels and functional outcome after stroke and to determine whether GLP-1 is altered in the acute phase of stroke compared to 3 months post stroke and to healthy controls. METHODS: Fasting GLP-1 was measured on hospital day 2-4 in patients without previously known diabetes (n = 59) that received recombinant tissue plasminogen activator (rtPA) for ischemic stroke. Fasting GLP-1 was measured again after 3 months and neurologic outcome was measured as modified Rankin Scale (mRS). mRS ≥ 2 was considered as unfavorable outcome. A control group of healthy individuals (n = 27) was recruited and their fasting GLP-1 was measured. RESULTS: Fasting GLP-1 was higher in the patients that suffered a stroke compared to healthy controls (25.1 vs. 18.0 pmol/L; p = 0.004). The GLP-1 levels did not change significantly at the 3-month follow up OGTT (25.8 vs. 25.6; p = 0.80). There was no significant association between GLP-1 levels and unfavorable mRS (OR 1.03, 95% CI 0.95-1.12, p = 0.50). CONCLUSIONS: Endogenous GLP-1 levels in patients that recently suffered an ischemic stroke are higher than in healthy controls and remained unchanged at the 3 months follow-up, possibly indicating an elevation of the levels of GLP-1 already pre-stroke. However, no association between endogenous GLP-1 and functional outcome of stroke 3 months post stroke was found.

Obesity-induced type 2 diabetes impairs neurological recovery after stroke in correlation with decreased neurogenesis and persistent atrophy of parvalbumin-positive interneurons.

Type 2 diabetes (T2D) hampers stroke recovery though largely undetermined mechanisms. Few preclinical studies have investigated the effect of genetic/toxin-induced diabetes on long-term stroke recovery. However, the effects of obesity-induced T2D are mostly unknown. We aimed to investigate whether obesity-induced T2D worsens long-term stroke recovery through the impairment of brain's self-repair mechanisms - stroke-induced neurogenesis and parvalbumin (PV)+ interneurons-mediated neuroplasticity. To mimic obesity-induced T2D in the middle-age, C57bl/6j mice were fed 12 months with high-fat diet (HFD) and subjected to transient middle cerebral artery occlusion (tMCAO). We evaluated neurological recovery by upper-limb grip strength at 1 and 6 weeks after tMCAO. Gray and white matter damage, stroke-induced neurogenesis, and survival and potential atrophy of PV-interneurons were quantitated by immunohistochemistry (IHC) at 2 and 6 weeks after tMCAO. Obesity/T2D impaired neurological function without exacerbating brain damage. Moreover, obesity/T2D diminished stroke-induced neural stem cell (NSC) proliferation and neuroblast formation in striatum and hippocampus at 2 weeks after tMCAO and abolished stroke-induced neurogenesis in hippocampus at 6 weeks. Finally, stroke resulted in the atrophy of surviving PV-interneurons 2 weeks after stroke in both non-diabetic and obese/T2D mice. However, after 6 weeks, this effect selectively persisted in obese/T2D mice. We show in a preclinical setting of clinical relevance that obesity/T2D impairs neurological functions in the stroke recovery phase in correlation with reduced neurogenesis and persistent atrophy of PV-interneurons, suggesting impaired neuroplasticity. These findings shed light on the mechanisms behind impaired stroke recovery in T2D and could facilitate the development of new stroke rehabilitative strategies for obese/T2D patients.

Prehospital exenatide in hyperglycemic stroke-A randomized trial.

OBJECTIVES: Hyperglycemia is a predictor for poor stroke outcome. Hyperglycemic stroke patients treated with thrombolysis have an increased risk of intracranial hemorrhage. Insulin is the gold standard for treating hyperglycemia but comes with a risk of hypoglycemia. Glucagon-like peptide-1 receptor agonists (GLP-1RA) are drugs used in type 2 diabetes that have a low risk of hypoglycemia and have been shown to exert neuroprotective effects. The primary objective was to determine whether prehospital administration of the GLP-1RA exenatide could lower plasma glucose in stroke patients. Secondary objective was to study tolerability and safety. MATERIALS & METHODS: Randomized controlled trial comparing exenatide administrated prehospitally with a control group receiving standard care for hyperglycemia. Patients with Face Arm Speech Test ≥1 and glucose ≥8 mmol/L were randomized. Glucose was monitored for 24 hours. All adverse events were recorded. RESULTS: Nineteen patients were randomized, eight received exenatide. An interim recruitment failure analysis with subsequent changes of the protocol was made. The study was stopped prematurely due to slow inclusion. No difference was observed in the main outcome of plasma glucose at 4 hours, control vs exenatide (mean, SD); 7.0 ± 1.9 vs 7.6 ± 1.6; P = .56). No major adverse events were reported. CONCLUSIONS: We found no evidence that prehospital exenatide had effect on hyperglycemia. However, it was given without adverse events in this study with limited sample size that was prematurely stopped due to slow inclusion.

The effect of DPP-4 inhibition to improve functional outcome after stroke is mediated by the SDF-1α/CXCR4 pathway.

BACKGROUND: Dipeptidyl peptidase-4 (DPP-4) inhibitors (gliptins) are approved drugs for the treatment of hyperglycemia in patients with type 2 diabetes. These effects are mainly mediated by inhibiting endogenous glucagon-like peptide-1 (GLP-1) cleavage. Interestingly, gliptins can also improve stroke outcome in rodents independently from GLP1. However, the underlying mechanisms are unknown. Stromal cell-derived factor-1α (SDF-1α) is a DPP-4 substrate and CXCR4 agonist promoting beneficial effects in injured brains. However, SDF-1α involvement in gliptin-mediated neuroprotection after ischemic injury is unproven. We aimed to determine whether the gliptin linagliptin improves stroke outcome via the SDF-1α/CXCR4 pathway, and identify additional effectors behind the efficacy. METHODS: Mice were subjected to stroke by transient middle cerebral artery occlusion (MCAO). linagliptin was administered for 3 days or 3 weeks from stroke onset. The CXCR4-antagonist AMD3100 was administered 1 day before MCAO until 3 days thereafter. Stroke outcome was assessed by measuring upper-limb function, infarct volume and neuronal survival. The plasma and brain levels of active GLP-1, GIP and SDF-1α were quantified by ELISA. To identify additional gliptin-mediated molecular effectors, brain samples were analyzed by mass spectrometry. RESULTS: Linagliptin specifically increased active SDF-1α but not glucose-dependent insulinotropic peptide (GIP) or GLP-1 brain levels. Blocking of SDF-1α/CXCR4 pathway abolished the positive effects of linagliptin on upper-limb function and histological outcome after stroke. Moreover, linagliptin treatment after stroke decreased the presence of peptides derived from neurogranin and from an isoform of the myelin basic protein. CONCLUSIONS: We showed that linagliptin improves functional stroke outcome in a SDF-1α/CXCR4-dependent manner. Considering that Calpain activity and intracellular Ca2+ regulate neurogranin and myelin basic protein detection, our data suggest a gliptin-mediated neuroprotective mechanism via the SDF-1α/CXCR4 pathway that could involve the regulation of Ca2+ homeostasis and the reduction of Calpain activity. These results provide new insights into restorative gliptin-mediated effects against stroke.

GLP-1R activation for the treatment of stroke: updating and future perspectives.

Stroke is the leading cause of adult disability in Westernized societies with increased incidence along ageing and it represents a major health and economical threat. Inactive lifestyle, smoking, hypertension, atherosclerosis, obesity and diabetes all dramatically increase the risk of stroke. While preventive strategies based on lifestyle changes and risk factor management can delay or decrease the likelihood of having a stroke, post stroke pharmacological strategies aimed at minimizing stroke-induced brain damage are highly needed. Unfortunately, several candidate drugs that have shown significant preclinical neuroprotective efficacy, have failed in clinical trials and no treatment for stroke based on neuroprotection is available today. Glucagon-like peptide 1 (GLP-1) is a peptide originating in the enteroendocrine L-cells of the intestine and secreted upon nutrient ingestion. The activation of the GLP-1R by GLP-1 enhances glucose-dependent insulin secretion, suppresses glucagon secretion and exerts multifarious extrapancreatic effects. Stable GLP-1 analogues and inhibitors of the proteolytic enzyme dipeptidyl peptidase 4 (DPP-4) (which counteract endogenous GLP-1 degradation) have been developed clinically for the treatment of type 2 diabetes. Besides their antidiabetic properties, experimental evidence has shown neurotrophic and neuroprotective effects of GLP-1R agonists and DPP-4 inhibitors in animal models of neurological disorders. Herein, we review recent experimental data on the neuroprotective effects mediated by GLP-1R activation in stroke. Due to the good safety profile of the drugs targeting the GLP-1R, we also discuss the high potential of GLP-1R stimulation in view of developing a safe clinical treatment against stroke based on neuroprotection in both diabetic and non-diabetic patients.

Nuclear magnetic resonance spectroscopy reveals biomarkers of stroke recovery in a mouse model of obesity-associated type 2 diabetes.

Obesity and type 2 diabetes (T2D) are known to exacerbate cerebral injury caused by stroke. Metabolomics can provide signatures of metabolic disease, and now we explored whether the analysis of plasma metabolites carries biomarkers of how obesity and T2D impact post-stroke recovery. Male mice were fed a high-fat diet (HFD) for 10 months leading to development of obesity with type 2 diabetes (T2D), or a standard diet (non-diabetic mice). Then, mice were subjected to either transient middle cerebral artery occlusion (tMCAO) or sham surgery and allowed to recover on standard diet for 2 months before serum samples were collected. Nuclear magnetic resonance (NMR) spectroscopy of serum samples was used to investigate metabolite signals and metabolic pathways that were associated with tMCAO recovery in either T2D or non-diabetic mice. Overall, after post-stroke recovery there were different serum metabolite profiles in T2D and non-diabetic mice. In non-diabetic mice, which show full neurological recovery after stroke, we observed a reduction of isovalerate, and an increase of kynurenate, uridine monophosphate, gluconate and N6-acetyllysine in tMCAO relative to sham mice. In contrast, in mice with T2D, which show impaired stroke recovery, there was a reduction of N,N-dimethylglycine, succinate and proline, and an increase of 2-oxocaproate in serum of tMCAO versus sham mice. Given the inability of T2D mice to recover from stroke, in contrast to non-diabetic mice, we propose that these specific metabolite changes following tMCAO might be used as biomarkers of neurophysiological recovery after stroke in T2D.

GalR3 activation promotes adult neural stem cell survival in response to a diabetic milieu.

Type 2 diabetes impairs adult neurogenesis which could play a role in the CNS complications of this serious disease. The goal of this study was to determine the potential role of galanin in protecting adult neural stem cells (NSCs) from glucolipotoxicity and to analyze whether apoptosis and the unfolded protein response were involved in the galanin-mediated effect. We also studied the regulation of galanin and its receptor subtypes under diabetes in NSCs in vitro and in the subventricular zone (SVZ) in vivo. The viability of mouse SVZ-derived NSCs and the involvement of apoptosis (Bcl-2, cleaved caspase-3) and unfolded protein response [C/EBP homologous protein (CHOP) Glucose-regulated protein 78/immunoglobulin heavy-chain binding protein (GRP78/BiP), spliced X-box binding protein 1 (XBP1), c-Jun N-terminal kinases (JNK) phosphorylation] were assessed in the presence of glucolipotoxic conditions after 24 h. The effect of diabetes on the regulation of galanin and its receptor subtypes was assessed on NSCs in vitro and in SVZ tissues isolated from normal and type 2 diabetes ob/ob mice. We show increased NSC viability following galanin receptor (GalR)3 activation. This protective effect correlated with decreased apoptosis and CHOP levels. We also report how galanin and its receptors are regulated by diabetes in vitro and in vivo. This study shows GalR3-mediated neuroprotection, supporting a potential future therapeutic development, based on GalR3 activation, for the treatment of brain disorders.

DPP-4 Inhibitor and Sulfonylurea Differentially Reverse Type 2 Diabetes-Induced Blood-Brain Barrier Leakage and Normalize Capillary Pericyte Coverage.

Microvascular pathology in the brain is one of the suggested mechanisms underlying the increased incidence and progression of neurodegenerative diseases in people with type 2 diabetes (T2D). Although accumulating data suggest a neuroprotective effect of antidiabetics, the underlying mechanisms are unclear. Here, we investigated whether two clinically used antidiabetics, the dipeptidyl peptidase-4 inhibitor linagliptin and the sulfonylurea glimepiride, which restore T2D-induced brain vascular pathology. Microvascular pathology was examined in the striatum of mice fed for 12 months with either normal chow diet or a high-fat diet (HFD) to induce T2D. A subgroup of HFD-fed mice was treated with either linagliptin or glimepiride for 3 months before sacrifice. We demonstrate that T2D caused leakage of the blood-brain barrier (BBB), induced angiogenesis, and reduced pericyte coverage of microvessels. However, linagliptin and glimepiride recovered the BBB integrity and restored the pericyte coverage differentially. Linagliptin normalized T2D-induced angiogenesis and restored pericyte coverage. In contrast, glimepiride enhanced T2D-induced angiogenesis and increased pericyte density, resulting in proper vascular coverage. Interestingly, glimepiride reduced microglial activation, increased microglial-vascular interaction, and increased collagen IV density. This study provides evidence that both DPP-4 inhibition and sulfonylurea reverse T2D-induced BBB leakage, which may contribute to antidiabetic neurorestorative effects.

GLP-1 secretion by microglial cells and decreased CNS expression in obesity.

BACKGROUND: Type 2 diabetes (T2D) is a strong risk factor for developing neurodegenerative pathologies. T2D patients have a deficiency in the intestinal incretin hormone GLP-1, which has been shown to exert neuroprotective and anti-inflammatory properties in the brain. METHODS: Here we investigate potential sources of GLP-1 in the CNS and the effect of diabetic conditions on the proglucagon mRNA expression in the CNS. The obese mouse model ob/ob, characterized by its high levels of free fatty acids, and the microglia cell line BV-2 were used as models. mRNA expression and protein secretion were analyzed by qPCR, immunofluorescence and ELISA. RESULTS: We show evidence for microglia as a central source of GLP-1 secretion. Furthermore, we observed that expression and secretion are stimulated by cAMP and dependent on microglial activation state. We also show that insulin-resistant conditions reduce the central mRNA expression of proglucagon. CONCLUSION: The findings that microglial mRNA expression of proglucagon and GLP-1 protein expression are affected by high levels of free fatty acids and that both mRNA expression levels of proglucagon and secretion levels of GLP-1 are affected by inflammatory stimuli could be of pathogenic importance for the premature neurodegeneration and cognitive decline commonly seen in T2D patients, and they may also be harnessed to advantage in therapeutic efforts to prevent or treat such disorders.