Sodium transport through the cerebral sodium-glucose transporter exacerbates neuron damage during cerebral ischaemia

SGLT1 and SGLT2 inhibition, circulating metabolites, and cerebral small vessel disease: a mediation Mendelian Randomization study

BACKGROUND

Sodium-glucose cotransporter 2 (SGLT2) and SGLT1 inhibitors may have additional beneficial metabolic effects on circulating metabolites beyond glucose regulation, which could contribute to a reduction in the burden of cerebral small vessel disease (CSVD). Accordingly, we used Mendelian Randomization (MR) to examine the role of circulating metabolites in mediating SGLT2 and SGLT1 inhibition in CSVD.

METHODS

Genetic instruments for SGLT1/2 inhibition were identified as genetic variants, which were both associated with the expression of encoding genes of SGLT1/2 inhibitors and glycated hemoglobin A1c (HbA1c) level. A two-sample two-step MR was used to determine the causal effects of SGLT1/2 inhibition on CSVD manifestations and the mediating effects of 1400 circulating metabolites linking SGLT1/2 inhibition with CSVD manifestations.

RESULTS

A lower risk of deep cerebral microbleeds (CMBs) and small vessel stroke (SVS) was linked to genetically predicted SGLT2 inhibition. Better white matter structure integrity was also achieved, as evidenced by decreased mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD), as well as lower deep (DWMH) and periventrivular white matter hyperintensity (PWMH) volume. Inhibiting SGLT2 could also lessen the incidence of severe enlarged perivascular spaces (EPVS) located at white matter, basal ganglia (BG) and hippocampus (HIP). SGLT1 inhibition could preserve white matter integrity, shown as decreased MD of white matter and DWMH volume. The effect of SGLT2 inhibition on SVS and MD of white matter through the concentration of 4-acetamidobutanoate and the cholesterol to oleoyl-linoleoyl-glycerol (18:1 to 18:2) ratio, with a mediated proportion of 30.3% and 35.5% of the total effect, respectively.

CONCLUSIONS

SGLT2 and SGLT1 inhibition play protective roles in CSVD development. The SGLT2 inhibition could lower the risk of SVS and improve the integrity of white matter microstructure via modulating the level of 4-acetamidobutanoate and cholesterol metabolism. Further mechanistic and clinical studies research are needed to validate our findings.

Increased serum SGLT2 and its potential diagnostic and prognostic value in patients with acute ischemic stroke

BACKGROUND

Recently acquired data suggests that sodium-glucose cotransporter-2 (SGLT2) may be a therapeutic target for cerebral ischemia. The specific impact of SGLT2 in acute ischemic stroke (AIS) remains unknown. We aimed to explore the levels of SGLT2 in AIS patients and its association with functional prognosis.

METHODS

In this study, 132 AIS patients and 44 healthy controls were recruited prospectively to determine serum SGLT2 levels. Logistic regression analysis was employed to assess the association between serum SGLT2 level and stroke risk as well as 3-month outcome. Receiver operating characteristic (ROC) curves were utilized to evaluate predictive values for blood biomarkers.

RESULTS

Serum SGLT2 levels were significantly higher (P =.000) in AIS patients (47.1 (interquartile range [IQR]: 42.4-50.9) ng/mL) than healthy controls (35.7 (IQR: 28.6-39.5) ng/mL). The optimal SGLT2 cutoff point for diagnosing AIS was 39.55 ng/mL, with a sensitivity of 90.2 % and specificity of 77.3 %. Serum levels of SGLT2 were negatively correlated with the onset time of AIS (linear fit R2 = 0.056, P =.006), but were not associated with National Institutes of Health Stroke Scale (NIHSS) scores (r = 0.007, P >.05) and lesion volume (r = -0.151, P >.05). SGLT2 was not remarkably different between patients with unfavorable and favorable outcomes (46.7 (IQR: 41.9-49.6) ng/mL vs 47.6 (IQR: 42.5-51.9) ng/mL; P =.321).

CONCLUSIONS

The serum SGLT2 concentration may be a potential biomarker for the diagnosis of AIS. However, it does not exhibit any association with disease severity or functional prognosis.

Phlorizin, an Important Glucoside: Research Progress on Its Biological Activity and Mechanism

Phlorizin, as a flavonoid from a wide range of sources, is gradually becoming known for its biological activity. Phlorizin can exert antioxidant effects by regulating the IL-1β/IKB-α/NF-KB signaling pathway. At the same time, it exerts its antibacterial activity by reducing intracellular DNA agglutination, reducing intracellular protein and energy synthesis, and destroying intracellular metabolism. In addition, phlorizin also has various pharmacological effects such as antiviral, antidiabetic, antitumor, and hepatoprotective effects. Based on domestic and foreign research reports, this article reviews the plant sources, extraction, and biological activities of phlorizin, providing a reference for improving the clinical application of phlorizin.

The role of mitochondrial dynamics in cerebral ischemia-reperfusion injury

Stroke is one of the leading causes of death and long-term disability worldwide. More than 80 % of strokes are ischemic, caused by an occlusion of cerebral arteries. Without question, restoration of blood supply as soon as possible is the first therapeutic strategy. Nonetheless paradoxically, reperfusion can further aggravate the injury through a series of reactions known as cerebral ischemia-reperfusion injury (CIRI). Mitochondria play a vital role in promoting nerve survival and neurological function recovery and mitochondrial dysfunction is considered one of the characteristics of CIRI. Neurons often die due to oxidative stress and an imbalance in energy metabolism following CIRI, and there is a strong association with mitochondrial dysfunction. Altered mitochondrial dynamics is the first reaction of mitochondrial stress. Mitochondrial dynamics refers to the maintenance of the integrity, distribution, and size of mitochondria as well as their ability to resist external stimuli through a continuous cycle of mitochondrial fission and fusion. Therefore, improving mitochondrial dynamics is a vital means of treating CIRI. This review discusses the relationship between mitochondria and CIRI and emphasizes improving mitochondrial dynamics as a potential therapeutic approach to improve the prognosis of CIRI.

Sodium-glucose cotransporter 2 inhibitors and neurological disorders: a scoping review

Background

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are a group of antidiabetic medications with a favourable cardiovascular, renal and overall safety profile. Given the limited treatment options available for neurological disorders, it is important to determine whether the pleiotropic effects of SGLT2i can be utilised in their prevention and management.

Methods

All articles published before 20 March 2021 were systematically searched in MEDLINE, EMBASE, Scopus, Web of Science, APA PsycINFO and ClinicalTrials.gov. Overall, 1395 titles were screened, ultimately resulting in 160 articles being included in the qualitative analysis. Screening and data extraction were conducted by two independent authors and studies were excluded if they were not an original research study.

Findings

Of the 160 studies, 134 addressed stroke, 19 cognitive impairment, 4 epilepsy and 4 movement disorders, encompassing a range from systematic reviews and randomised controlled trials to bioinformatic and animal studies. Most animal studies demonstrated significant improvements in behavioural and neurological deficits, which were reflected in beneficial changes in neurovascular units, synaptogenesis, neurotransmitter levels and target receptors' docking energies. The evidence from the minority clinical literature was conflicting and many studies did not reach statistical significance.

Interpretation

SGLT2i may exert neurological benefits through three mechanisms: reduction in cardiovascular risk factors, augmentation of ketogenesis and anti-inflammatory pathways. Most clinical studies were observational, meaning that a causal relationship could not be established, while randomised controlled trials were heterogeneous and powered to detect cardiovascular or renal outcomes. We suggest that a longitudinal study should be conducted and specifically powered to detect neurological outcomes.

The Role of Combined SGLT1/SGLT2 Inhibition in Reducing the Incidence of Stroke and Myocardial Infarction in Patients with Type 2 Diabetes Mellitus

PURPOSE

In patients with type 2 diabetes mellitus (T2DM), both sodium-glucose cotransporter 2 inhibitors (SGLT2is) and glucagon-like peptide receptor agonists (GLP-1 RAs) have demonstrated significant improvements in cardiovascular and kidney outcomes independent of their glycemic benefits. This paper will briefly compare the effect of SGLT2is and GLP-1 RAs to that of the SGLT1/2 inhibitor sotagliflozin on the incidence of myocardial infarction (MI) and stroke in patients with T2DM and further postulate mechanisms to account for these findings.

METHODS AND RESULTS

Thus far, the results from SCORED and SOLOIST (trials studying the SGLT1/2 inhibitor sotagliflozin) suggest that an increase in SGLT1 inhibition when added to SGLT2 inhibition may contribute to reductions in MI and stroke in patients with T2DM. This benefit is beyond what SGLT2is alone can accomplish and at least similar to GLP-1 RAs but with the added benefit of a reduction in hospitalizations and urgent visits for HF. Larger and longer studies are required to confirm the effectiveness of SGLT1/SGLT2 inhibition in reducing MI and stroke in patients with T2DM and elucidate the mechanisms associated with this finding.

CONCLUSIONS

The role of SGLT1/2 inhibition as an addition to GLP-1 RAs in patients with and without T2DM at increased risk for MI and stroke requires further study. Regardless, the finding that a relative increase in SGLT1/2 inhibition reduces the risk of MI and stroke as well as hospitalizations and urgent visits for heart failure could improve quality of life and reduce the healthcare burden associated with T2DM.

Blood-Brain Barrier Damage in Ischemic Stroke and Its Regulation by Endothelial Mechanotransduction

Ischemic stroke, a major cause of mortality in the United States, often contributes to disruption of the blood-brain barrier (BBB). The BBB along with its supportive cells, collectively referred to as the “neurovascular unit,” is the brain’s multicellular microvasculature that bi-directionally regulates the transport of blood, ions, oxygen, and cells from the circulation into the brain. It is thus vital for the maintenance of central nervous system homeostasis. BBB disruption, which is associated with the altered expression of tight junction proteins and BBB transporters, is believed to exacerbate brain injury caused by ischemic stroke and limits the therapeutic potential of current clinical therapies, such as recombinant tissue plasminogen activator. Accumulating evidence suggests that endothelial mechanobiology, the conversion of mechanical forces into biochemical signals, helps regulate function of the peripheral vasculature and may similarly maintain BBB integrity. For example, the endothelial glycocalyx (GCX), a glycoprotein-proteoglycan layer extending into the lumen of bloods vessel, is abundantly expressed on endothelial cells of the BBB and has been shown to regulate BBB permeability. In this review, we will focus on our understanding of the mechanisms underlying BBB damage after ischemic stroke, highlighting current and potential future novel pharmacological strategies for BBB protection and recovery. Finally, we will address the current knowledge of endothelial mechanotransduction in BBB maintenance, specifically focusing on a potential role of the endothelial GCX.

Glucose transporters in brain in health and disease

Energy demand of neurons in brain that is covered by glucose supply from the blood is ensured by glucose transporters in capillaries and brain cells. In brain, the facilitative diffusion glucose transporters GLUT1-6 and GLUT8, and the Na⁺-d-glucose cotransporters SGLT1 are expressed. The glucose transporters mediate uptake of d-glucose across the blood-brain barrier and delivery of d-glucose to astrocytes and neurons. They are critically involved in regulatory adaptations to varying energy demands in response to differing neuronal activities and glucose supply. In this review, a comprehensive overview about verified and proposed roles of cerebral glucose transporters during health and diseases is presented. Our current knowledge is mainly based on experiments performed in rodents. First, the functional properties of human glucose transporters expressed in brain and their cerebral locations are described. Thereafter, proposed physiological functions of GLUT1, GLUT2, GLUT3, GLUT4, and SGLT1 for energy supply to neurons, glucose sensing, central regulation of glucohomeostasis, and feeding behavior are compiled, and their roles in learning and memory formation are discussed. In addition, diseases are described in which functional changes of cerebral glucose transporters are relevant. These are GLUT1 deficiency syndrome (GLUT1-SD), diabetes mellitus, Alzheimer’s disease (AD), stroke, and traumatic brain injury (TBI). GLUT1-SD is caused by defect mutations in GLUT1. Diabetes and AD are associated with changed expression of glucose transporters in brain, and transporter-related energy deficiency of neurons may contribute to pathogenesis of AD. Stroke and TBI are associated with changes of glucose transporter expression that influence clinical outcome.

Cerebrovascular Disease and Cognition in Chronic Kidney Disease Patients

Chronic kidney disease (CKD) affects both brain structure and function. Patients with CKD have a higher risk of both ischemic and hemorrhagic strokes. Age, prior disease history, hypertension, diabetes, atrial fibrillation, smoking, diet, obesity, and sedimentary lifestyle are most common risk factors. Renal-specific pathophysiologic derangements, such as oxidative stress, chronic inflammation, endothelial dysfunction, vascular calcification, anemia, gut dysbiosis, and uremic toxins are important mediators. Dialysis initiation constitutes the highest stroke risk period. CKD significantly worsens stroke outcomes. It is essential to understand the risks and benefits of established stroke therapeutics in patients with CKD, especially in those on dialysis. Subclinical cerebrovascular disease, such as of silent brain infarction, white matter lesions, cerebral microbleeds, and cerebral atrophy are more prevalent with declining renal function. This may lead to functional brain damage manifesting as cognitive impairment. Cognitive dysfunction has been linked to poor compliance with medications, and is associated with greater morbidity and mortality. Thus, understanding the interaction between renal impairment and brain is important in to minimize the risk of neurologic injury in patients with CKD. This article reviews the link between chronic kidney disease and brain abnormalities associated with CKD in detail.

Chronic kidney disease in the pathogenesis of acute ischemic stroke

Chronic kidney disease has a graded and independent inverse impact on cerebrovascular health. Both thrombotic and hemorrhagic complications are highly prevalent in chronic kidney disease patients. Growing evidence suggests that in chronic kidney disease patients, ischemic strokes are more common than hemorrhagic strokes. Chronic kidney disease is asymptomatic until an advanced stage, but mild to moderate chronic kidney disease incites various pathogenic mechanisms such as inflammation, oxidative stress, neurohormonal imbalance, formation of uremic toxins and vascular calcification which damage the endothelium and blood vessels. Cognitive dysfunction, dementia, transient infarcts, and white matter lesions are widespread in mild to moderate chronic kidney disease patients. Uremic toxins produced after chronic kidney disease can pass through the blood-brain barrier and mediate cognitive dysfunction and neurodegeneration. Furthermore, chronic kidney disease precipitates vascular risk factors that can lead to atherosclerosis, hypertension, atrial fibrillation, and diabetes. Chronic kidney disease also exacerbates stroke pathogenesis, worsens recovery outcomes, and limits the eligibility of stroke patients to receive available stroke therapeutics. This review highlights the mechanisms involved in the advancement of chronic kidney disease and its possible association with stroke.

Activation of c-Jun N-terminal kinase and p38 after cerebral ischemia upregulates cerebral sodium-glucose transporter type 1

Cerebral ischemic stress increases cerebral sodium-glucose transporter type 1 (SGLT-1). However, the mechanism by which cerebral ischemia leads to the up-regulation of SGLT-1 remains unclear. In peripheral tissue, the activation of mitogen-activated protein kinases (MAPKs) increases SGLT-1. MAPK pathways [c-Jun N-terminal kinase (JNK), p38 MAPK, and extracellular signal-regulated protein kinase (ERK)] are activated by cerebral ischemic stress. Therefore, we confirmed the involvement of MAPKs in the up-regulation of cerebral SGLT-1 after cerebral ischemia. Male ddY mice were subjected to middle cerebral artery occlusion (MCAO). Protein expression was assessed by western blotting. Mice received an intracerebroventricular (i.c.v.) injection of SP600125 (JNK inhibitor), SB203580 (p38 inhibitor), and PD98059 (MEK inhibitor) immediately after reperfusion. The infarction and behavioral abnormalities were assessed on days 1 and 3 after MCAO. The MAPK inhibitors suppressed the activation of JNK, p38, and ERK 3 h after MCAO. SP600125 and SB203580 administration ameliorated cerebral ischemic neuronal damage, whereas PD98059 administration exacerbated cerebral ischemic neuronal damage. SP600125 and SB203580 significantly suppressed the increase in SGLT-1 12 h after MCAO. PD98059 had no effect on SGLT-1 expression after MCAO. Our results indicate that the activation of JNK and p38 participate in the up-regulation of cerebral SGLT-1 after MCAO.

Sodium-glucose transporter as a novel therapeutic target in disease

Glucose is the primary energy fuel of life. A glucose transporter, the sodium-glucose transporter (SGLT), is receiving attention as a novel therapeutic target in disease. This review summarizes the physiological role of SGLT in cerebral ischemia, cancer, cardiac disease, and intestinal ischemia, which has encouraged analysis of SGLT function. In cerebral ischemia and cardiomyopathy, SGLT-1 is involved in worsening of the injury. In addition, SGLT-1 promotes the development of cancer. On the other hand, SGLT-1 has a protective effect against cardiac and intestinal ischemia. Interestingly, SGLT-1 expression levels are increased in some diseased tissue, such as in cerebral ischemia and cancer. This suggests that SGLT-1 may have an important role in many diseases. This review discusses the potential of SGLT as a target for novel therapeutic agents.

Blood-Brain Barrier Protection as a Therapeutic Strategy for Acute Ischemic Stroke

The blood-brain barrier (BBB) is a vital component of the neurovascular unit (NVU) containing tight junctional (TJ) proteins and different ion and nutrient transporters which maintain normal brain physiology. BBB disruption is a major pathological hallmark in the course of ischemic stroke which is regulated by the actions of different factors working at different stages of cerebral ischemia including matrix metalloproteinases (MMPs), inflammatory modulators, vesicular trafficking, oxidative pathways, and junctional-cytoskeletal interactions. These components interact further to disrupt maintenance of both the paracellular and transport barriers of the central nervous system (CNS) to worsen ischemic brain injury and the propensity for hemorrhagic transformation (HT) associated with injury and/or thrombolytic therapy with tissue-type plasminogen activator (tPA). We propose that these complex molecular pathways should be evaluated further so that they could be targeted alone or in combination to protect the BBB during cerebral ischemia. These types of novel interventions should be guided by advanced imaging techniques for better diagnosis of BBB damage which may exert significant therapeutic benefit including the extension of therapeutic window of tPA. This review will focus on the different stages and mechanisms of BBB damage in acute ischemic stroke and novel therapeutic strategies to target those pathways for better therapeutic outcome in stroke.