Inactivated AMPK-α2 promotes the progression of diabetic brain damage by Cdk5 phosphorylation at Thr485 site.

Changes in brain energy metabolism in diabetes mellitus, including increased insulin resistance and mitochondrial dysfunction, are critically involved in diabetes-related neurodegeneration, and associate with early cognitive impairment as well. The aim of this study is to detect the specific phosphorylated-Thr485- AMP-activated protein kinase (AMPK-α2), regulated by cyclin-dependent kinase 5 (Cdk5) paly the inhibitory functional role of AMPK-α2, Which is maybe the link to the accelerated diabetic brain damage progression. Here, we used GK rats, the type 2 diabetic animal model for in vivo studies and performed In vitro kinase assay, high glucose treatment, -phosphorylated mutation and protein expression in both HEK-293T and HT-22 cell lines. In vitro, the results show that murine wild-type AMPK-α2 was phosphorylated by Cdk5 at a (S/T)PX(K/H/R) phosphorylation consensus sequence, which was associated with decreased AMPK-α2 activity. Surprisingly, mutation of Thr485 to alanine in AMPK-α2 results in the abolished Cdk5 effects, demonstrating that Thr485-phosphorylation is critical to AMPK-α2 inhibition by Cdk5. In addition, these alterations in AMPK-α2-phosphorylation and -activity induced by Cdk5 is specific at Thr485. Furthermore, in GK rats, the increased phosphorylated- Thr 485 of AMPK-α2 results in the decreased AMPK-α2 activity, which is correlated with the apoptosis of neurons in hippocamps. After high glucose treatment, the decreased survival showed in AMPK-α2T485A HT-22 cells compared to AMPK-α2WT. The down-regulated of p-CREB, SNAP25, synaptophysin as well as synapsin-1were shown in both GK rats and HT-22 cell line. Meanwhile, pre-treated with either the specific Cdk5-inhibitor (roscovitine) or the antidiabetic AMPK-α2-inhibitor (metformin) could restore the alterations in neuronal protein expression. Our results suggest that Cdk5-mediated phosphorylated- Thr485 in AMPK-α2 may be involved in the pathogenesis of diabetic brain damage.

Correlation Between Diabetic Cognitive Impairment and Diabetic Retinopathy in Patients With T2DM by 1H-MRS.

Objective: To explore the correlation between diabetic cognitive impairment (DCI) and diabetic retinopathy (DR) through examining the cognitive function and the metabolism of the cerebrum in Type 2 diabetes mellitus (T2DM) by 1H-MRS. Methods: Fifty-three patients with T2DM were enrolled for this study. According to the fundus examination, the patients were divided into the DR group (n = 26) and the T2DM without DR group (T2DM group, n = 27). Thirty healthy adults were selected as a control group (HC group, n = 30). Cognitive function was measured by Montreal Cognitive Assessment (MoCA). The peak areas of N-acetylaspartate (NAA), Cho-line (Cho), Creatine (Cr), and Myo-inositol (mI) as well as their ratios were detected by proton magnetic resonance spectroscopy (1H-MRS). The difference analysis between the three groups was performed by one-way ANOVA. When p < 0.05, LSD-t was applied. A partial correlation analysis (with age as a covariate) was used to analyze the correlation between metabolites in the DR group and MoCA scores. Among all T2DM patients, Chi-square test age, gender, education level, BMI, SBP, DBP, FPG, HbA1c, TC, TG, HDL-C, LDL-C, DR, and DCI correlation were measured. Differences were statistically significant while P < 0.05. Results: 1. The scores of MoCA in the DR group or in the T2DM group were significantly less than those in the HC group (F = 3.54, P < 0.05), and the scores of MoCA in the DR group were significantly less than those in the other groups (F = 3.61, P < 0.05). 2. There were significant differences for NAA in the bilateral hippocampus in DR patients, T2DM patients, and healthy controls (P < 0.05). 3. The NAA/Cr was significantly positively correlated with the score of MoCA in DR patients' left hippocampus (r = 0.781, P < 0.01). 4. Chi-square analysis found that there was a correlation between DR and DCI (x 2 = 4.6, df = 1, p = 0.032, plt: 0.05). There was no correlation between other influencing factors and DCI (P > 0.05). Conclusion: DCI is closely correlated with the DR in patients with T2DM. Hippocampal brain metabolism may have some changes in two sides of NAA in patients with DR, 1H-MRS may provide effective imaging strategies and methods for the early diagnosis of brain damage and quantitative assessment cognitive function in T2DM.

Metabolic encephalopathy secondary to diabetic ketoacidosis: a case report.

INTRODUCTION: Metabolic encephalopathy is a rare but potentially devastating complication of diabetic ketoacidosis (DKA). This case highlights the dramatic cognitive decline of a young man due to metabolic encephalopathy complicating DKA. The aims of this case report are to highlight metabolic encephalopathy as a complication of DKA and to explore the current research in diabetic related brain injury. The importance of investigation and treatment of reversible causes of encephalopathy is also demonstrated. CASE PRESENTATION: A 35-year-old man with a background of type 1 diabetes mellitus (T1DM) and relapsing remitting multiple sclerosis (RRMS) presented to the emergency department (ED) in a confused and agitated state. Prior to admission he worked as a caretaker in a school, smoked ten cigarettes per day, took excess alcohol and smoked cannabis twice per week. Following initial investigations, he was found to be in DKA. Despite timely and appropriate management his neurological symptoms and behavioural disturbance persisted. Neuroimaging revealed temporal lobe abnormalities consistent with an encephalopathic process. The patient underwent extensive investigation looking for evidence of autoimmune, infective, metabolic, toxic and paraneoplastic encephalopathy, with no obvious cause demonstrated. Due to persistent radiological abnormalities a temporal lobe biopsy was performed which showed marked astrocytic gliosis without evidence of vasculitis, inflammation, infarction or neoplasia. A diagnosis of metabolic encephalopathy secondary to DKA was reached. The patient's cognitive function remained impaired up to 18 months post presentation and he ultimately required residential care. CONCLUSIONS: Metabolic encephalopathy has been associated with acute insults such as DKA, but importantly, the risk of cerebral injury is also related to chronic hyperglycaemia. Mechanisms of cerebral injury in diabetes mellitus continue to be investigated. DKA poses a serious and significant neurological risk to patients with diabetes mellitus. To our knowledge this is the second case report describing this acute complication.

Vernonia Amygdalina Del. stimulated glucose uptake in brain tissues enhances antioxidative activities; and modulates functional chemistry and dysregulated metabolic pathways.

Brain glucose uptake is usually reduced in type 2 diabetes owing to downregulation of brain glucose transporters. The ability of Vernonia amygdalina to stimulate glucose uptake as well as ameliorate glucose-induced oxidative stress and proinflammation were investigated in rat brain. Hot infusion of V. amygdalina leaves was incubated with rat brain tissues for 2 h in the presence of glucose. Another incubation with glucose only, served as negative control while metformin served as positive control. Incubation of brain tissues with V. amygdalina led to significant (p < 0.05) increase in glucose uptake, reduced glutathione, nitric oxide and non-thiol proteins levels, superoxide dismutase, catalase and ATPase activities, while concomitantly decrease in myeloperoxidase activity and malondialdehyde level compared to the negative control. Incubation with glucose only, led to the development of nitrate, amide II and amide I functional groups which were removed on incubation with the infusion. LC-MS analysis revealed depletion of oxidative stress-induced 2-keto-glutaramic acid and cysteinyl-tyrosine metabolites in brain tissues, with concomitant generation of S-formylglutathione and adenosine tetraphosphate by the infusion. Pathway analysis of the metabolites revealed an activation of pyruvate metabolism pathway in the negative control, with the infusion reducing the intensity fold. LC-MS analysis of the infusion revealed the presence of l-serine, l-cysteine, l-proline, nicotinic acid, cumidine, salicylic acid, isoquinoline, 3-methyl-, and γ-octalactone. Except for l-serine, l-cysteine and l-proline, the other compounds were predicted to be permeable across the blood brain barrier. These results indicate the brain glucose uptake stimulatory and neuroprotective effect of V. amygdalina.

The diabetic brain and cognition.

The prevalence of both Alzheimer's disease (AD) and vascular dementia (VaD) is increasing with the aging of the population. Studies from the last several years have shown that people with diabetes have an increased risk for dementia and cognitive impairment. Therefore, the authors of this consensus review tried to elaborate on the role of diabetes, especially diabetes type 2 (T2DM) in both AD and VaD. Based on the clinical and experimental work of scientists from 18 countries participating in the International Congress on Vascular Disorders and on literature search using PUBMED, it can be concluded that T2DM is a risk factor for both, AD and VaD, based on a pathology of glucose utilization. This pathology is the consequence of a disturbance of insulin-related mechanisms leading to brain insulin resistance. Although the underlying pathological mechanisms for AD and VaD are different in many aspects, the contribution of T2DM and insulin resistant brain state (IRBS) to cerebrovascular disturbances in both disorders cannot be neglected. Therefore, early diagnosis of metabolic parameters including those relevant for T2DM is required. Moreover, it is possible that therapeutic options utilized today for diabetes treatment may also have an effect on the risk for dementia. T2DM/IRBS contribute to pathological processes in AD and VaD.

Cerebral ischemic damage in diabetes: an inflammatory perspective.

Stroke is one of the leading causes of death worldwide. A strong inflammatory response characterized by activation and release of cytokines, chemokines, adhesion molecules, and proteolytic enzymes contributes to brain damage following stroke. Stroke outcomes are worse among diabetics, resulting in increased mortality and disabilities. Diabetes involves chronic inflammation manifested by reactive oxygen species generation, expression of proinflammatory cytokines, and activation/expression of other inflammatory mediators. It appears that increased proinflammatory processes due to diabetes are further accelerated after cerebral ischemia, leading to increased ischemic damage. Hypoglycemia is an intrinsic side effect owing to glucose-lowering therapy in diabetics, and is known to induce proinflammatory changes as well as exacerbate cerebral damage in experimental stroke. Here, we present a review of available literature on the contribution of neuroinflammation to increased cerebral ischemic damage in diabetics. We also describe the role of hypoglycemia in neuroinflammation and cerebral ischemic damage in diabetics. Understanding the role of neuroinflammatory mechanisms in worsening stroke outcome in diabetics may help limit ischemic brain injury and improve clinical outcomes.

Effects of metformin on inflammation and short-term memory in streptozotocin-induced diabetic mice.

The aim of the present study was to analyze the action of metformin on short-term memory, glial cell activation and neuroinflammation caused by experimental diabetic encephalopathy in C57BL/6 mice. Diabetes was induced by the intraperitoneal injection of a dose of 90mg/kg of streptozotocin on two successive days. Mice with blood glucose levels ≥200dl/ml were considered diabetic and were given metformin hydrochloride at doses of 100mg/kg and 200mg/kg (by gavage, twice daily) for 21 days. On the final day of treatment, the mice underwent a T-maze test. On the 22nd day of treatment all the animals were anesthetized and euthanized. Diabetic animals treated with metformin had a higher spatial memory score. The hippocampus of the diabetic animals presented reactive gliosis, neuronal loss, NF-kB signaling activation, and high levels of IL-1 and VEGF. In addition, the T-maze test scores of these animals were low. Treatment with metformin reduced the expression of GFAP, Iba-1 (astrocyte and microglial markers) and the inflammation markers (p-IKB, IL-1 and VEGF), while enhancing p-AMPK and eNOS levels and increasing neuronal survival (Fox-1 and NeuN). Treatment with metformin also improved the spatial memory scores of diabetic animals. In conclusion, the present study showed that metformin can significantly reduce neuroinflammation and can decrease the loss of neurons in the hippocampus of diabetic animals, which can subsequently promote improvements in spatial memory.

High glucose, glucose fluctuation and carbonyl stress enhance brain microvascular endothelial barrier dysfunction: Implications for diabetic cerebral microvasculature.

We previously demonstrated that in normal glucose (5mM), methylglyoxal (MG, a model of carbonyl stress) induced brain microvascular endothelial cell (IHEC) dysfunction that was associated with occludin glycation and prevented by N-acetylcysteine (NAC). Herein, we investigated the impact of high glucose and low GSH, conditions that mimicked the diabetic state, on MG-induced IHEC dysfunction. MG-induced loss of transendothelial electrical resistance (TEER) was potentiated in IHECs cultured for 7 or 12 days in 25 mM glucose (hyperglycemia); moreover, barrier function remained disrupted 6h after cell transfer to normal glucose media (acute glycemic fluctuation). Notably, basal occludin glycation was elevated under these glycemic states. TEER loss was exaggerated by inhibition of glutathione (GSH) synthesis and abrogated by NAC, which corresponded to GSH decreases and increases, respectively. Significantly, glyoxalase II activity was attenuated in hyperglycemic cells. Moreover, hyperglycemia and GSH inhibition increased MG accumulation, consistent with a compromised capacity for MG elimination. α-Oxoaldehydes (MG plus glyoxal) levels were elevated in streptozotocin-induced diabetic rat plasma. Immunohistochemistry revealed a prevalence of MG-positive, but fewer occludin-positive microvessels in the diabetic brain in vivo, and Western analysis confirmed an increase in MG-occludin adducts. These results provide the first evidence that hyperglycemia and acute glucose fluctuation promote MG-occludin formation and exacerbate brain microvascular endothelial dysfunction. Low occludin expression and high glycated-occludin contents in diabetic brain in vivo are factors that would contribute to the dysfunction of the cerebral microvasculature during diabetes.