Prevention of Severe Hypoglycemia-Induced Brain Damage and Cognitive Impairment With Verapamil

Perioperative Glycemic Management in Cardiac Surgery: A Narrative Review

Diabetes and hyperglycemic events in cardiac surgical patients are associated with postoperative morbidity and mortality. The causes of dysglycemia, the abnormal fluctuations in blood glucose concentrations, in the perioperative period include surgical stress, surgical techniques, medications administered perioperatively, and patient factors. Both hyperglycemia and hypoglycemia lead to poor outcomes after cardiac surgery. While trying to control blood glucose concentration tightly for better postoperative outcomes, hypoglycemia is the main adverse event. Currently, there is no definite consensus on the optimum perioperative blood glucose concentration to be maintained in cardiac surgical patients. This review provides an overview of perioperative glucose homeostasis, the pathophysiology of dysglycemia, factors that affect glycemic control in cardiac surgery, and current practices for glycemic control in cardiac surgery.

Perioperative glycemic management in adults presenting for elective cardiac and non-cardiac surgery

Perioperative dysglycemia is associated with adverse outcomes in both cardiac and non-cardiac surgical patients. Hyperglycemia in the perioperative period is associated with an increased risk of postoperative infections, length of stay, and mortality. Hypoglycemia can induce neuronal damage, leading to significant cognitive deficits, as well as death. This review endeavors to summarize existing literature on perioperative dysglycemia and provides updates on pharmacotherapy and management of perioperative hyperglycemia and hypoglycemia in surgical patients.

Mito-TEMPO, a Mitochondria-Targeted Antioxidant, Improves Cognitive Dysfunction due to Hypoglycemia: an Association with Reduced Pericyte Loss and Blood-Brain Barrier Leakage

Hypoglycemia is associated with cognitive dysfunction, but the exact mechanisms have not been elucidated. Our previous study found that severe hypoglycemia could lead to cognitive dysfunction in a type 1 diabetes (T1D) mouse model. Thus, the aim of this study was to further investigate whether the mechanism of severe hypoglycemia leading to cognitive dysfunction is related to oxidative stress-mediated pericyte loss and blood-brain barrier (BBB) leakage. A streptozotocin T1D model (150 mg/kg, one-time intraperitoneal injection), using male C57BL/6J mice, was used to induce hypoglycemia. Brain tissue was extracted to examine for neuronal damage, permeability of BBB was investigated through Evans blue staining and electron microscopy, reactive oxygen species and adenosine triphosphate in brain tissue were assayed, and the functional changes of pericytes were determined. Cognitive function was tested using Morris water maze. Also, an in vitro glucose deprivation model was constructed. The results showed that BBB leakage after hypoglycemia is associated with excessive activation of oxidative stress and mitochondrial dysfunction due to glucose deprivation/reperfusion. Interventions using the mitochondria-targeted antioxidant Mito-TEMPO in both in vivo and in vitro models reduced mitochondrial oxidative stress, decreased pericyte loss and apoptosis, and attenuated BBB leakage and neuronal damage, ultimately leading to improved cognitive function.

β-Hydroxybutyrate Alleviates Low Glucose-Induced Apoptosis via Modulation of ROS-Mediated p38 MAPK Signaling

Hypoglycemia has emerged as a prominent complication in anti-diabetic drug therapy or negative energy balance of animals, which causes brain damage, cognitive impairment, and even death. Brain injury induced by hypoglycemia is closely related to oxidative stress and the production of reactive oxygen species (ROS). The intracellular accumulation of ROS leads to neuronal damage, even death. Ketone body β-hydroxybutyrate (BHBA) not only serves as alternative energy source for glucose in extrahepatic tissues, but is also involved in cellular signaling transduction. Previous studies showed that BHBA reduces apoptosis by inhibiting the excessive production of ROS and activation of caspase-3. However, the effects of BHBA on apoptosis induced by glucose deprivation and its related molecular mechanisms have been seldom reported. In the present study, PC12 cells and primary cortical neurons were used to establish a low glucose injury model. The effects of BHBA on the survival and apoptosis in a glucose deficient condition and related molecular mechanisms were investigated by using flow cytometry, immunofluorescence, and western blotting. PC12 cells were incubated with 1 mM glucose for 24 h as a low glucose cell model, in which ROS accumulation and cell mortality were significantly increased. After 24 h and 48 h treatment with different concentrations of BHBA (0 mM, 0.05 mM, 0.5 mM, 1 mM, 2 mM), ROS production was significantly inhibited. Moreover, cell apoptosis rate was decreased and survival rate was significantly increased in 1 mM and 2 mM BHBA groups. In primary cortical neurons, at 24 h after treatment with 2 mM BHBA, the injured length and branch of neurites were significantly improved. Meanwhile, the intracellular ROS level, the proportion of c-Fos⁺ cells, apoptosis rate, and nuclear translocation of NF-κB protein after treatment with BHBA were significantly decreased when compared with that in low glucose cells. Importantly, the expression of p38, p-p38, NF-κB, and caspase-3 were significantly decreased, while the expression of p-ERK was significantly increased in both PC12 cells and primary cortical neurons. Our results demonstrate that BHBA decreased the accumulation of intracellular ROS, and further inhibited cell apoptosis by mediating the p38 MAPK signaling pathway and caspase-3 apoptosis cascade during glucose deprivation. In addition, BHBA inhibited apoptosis by activating ERK phosphorylation and alleviated the damage of low glucose to PC12 cells and primary cortical neurons. These results provide new insight into the anti-apoptotic effect of BHBA in a glucose deficient condition and the related signaling cascade.

Docosahexaenoic acid reduces hypoglycemia-induced neuronal necroptosis via the peroxisome proliferator-activated receptor γ/nuclear factor-κB pathway

DHA has been shown to be neuroprotective and important to neurogenesis, but its role in HG-induced brain injury and the underlying mechanisms remain unknown. To elucidate the therapeutic effect of DHA, we established a mouse model with insulin-induced hypoglycemic brain injury and an in vitro model of HT-22 cells using a sugar-free medium. DHA treatment significantly reduced neuronal death and improved HG-induced learning and memory deficits. Moreover, DHA inhibited neuronal necroptosis and decreased the concentrations of TNF-α, IL-1β and TNFR1. DHA also activated PPAR-γ and suppressed the NF-κB pathway in mouse brain tissues. In vitro, DHA treatment restored the viability and decreased necroptosis of HT-22 cells treated with glucose deprivation. However, the inhibition of PPAR-γ with T0070907 reversed neuroprotective and anti-necroptosis effects of DHA in HG-induced brain injury, which is associated with the activation of the downstream NF-κB pathway. We conclude that DHA displays a protective effect against HG-induced brain injury through the PPAR-γ/NF-κB pathway and represents a promising method to prevent HG-induced brain injury.

Severe Hypoglycemia Contributing to Cognitive Dysfunction in Diabetic Mice Is Associated With Pericyte and Blood-Brain Barrier Dysfunction

Background: Severe hypoglycemia can cause cognitive impairment in diabetic patients, but the underlying molecular mechanism remains unclear.

Objective: To assess the effect of severe hypoglycemia on cognitive function in diabetic mice to clarify the relationship between the mechanism and dysfunction of pericytes and the blood–brain barrier (BBB).

Method: We established type 1 diabetes mellitus in 80 male C57BL/6J mice by intraperitoneal injection of streptozotocin (150 mg/kg). Further intraperitoneal injection of short-acting insulin induced severe hypoglycemia. The mice were divided into normal, diabetes, and diabetic + severe hypoglycemia groups, and their blood glucose and general weight index were examined. Pericyte and BBB morphology and function were detected by histological and western blot analyses, BBB permeability was detected by Evans blue staining, and cognitive function was detected with the Morris water maze.

Results: Severe hypoglycemia aggravated the histological damage, BBB damage, brain edema, and pericyte loss in the diabetic mice. It also reduced the expression of the BBB tight junction proteins occludin and claudin-5, the expression of the pericyte-specific markers PDGFR-β (platelet-derived growth factor receptor-β) and α-SMA, and increased the expression of the inflammatory factor MMP9. At the same time, diabetic mice with severe hypoglycemia had significantly reduced cognitive function.

Conclusion: Severe hypoglycemia leads to cognitive dysfunction in diabetic mice, and its possible mechanism is related to pericyte dysfunction and BBB destruction.

Thioredoxin interacting protein regulates age-associated neuroinflammation

Immune system hypersensitivity is believed to contribute to mental frailty in the elderly. Solid evidence indicates NOD-like receptor pyrin domain containing-3 (NLRP3)-inflammasome activation intimately connects aging-associated chronic inflammation (inflammaging) to senile cognitive decline. Thioredoxin interacting protein (TXNIP), an inducible protein involved in oxidative stress, is essential for NLRP3 inflammasome activity. This study aims to find whether TXNIP/NLRP3 inflammasome pathway is involved in senile dementia. According to our studies on sex-matched mice, TXNIP was significantly upregulated in aged animals, paralleled by the NLRP3-inflammasome over-activity leading to enhanced caspase-1 cleavage and IL-1β maturation, in both sexes. This was closely associated with depletion of the anti-aging and cognition enhancing protein klotho, in aged males. Txnip knockout reversed age-related NLRP3-hyperactivity and enhanced thioredoxin (TRX) levels. Further, TXNIP inhibition along with verapamil replicated TXNIP/NLRP3-inflammasome downregulation in aged animals, with FOXO-1 and mTOR upregulation. These alterations concurred with substantial improvements in both cognitive and sensorimotor abilities. Together, these findings substantiate the pivotal role of TXNIP to drive inflammaging in parallel with klotho depletion and functional decline, and delineate thioredoxin system as a potential target to decelerate senile dementia.

Potential Biochemical Mechanisms of Brain Injury in Diabetes Mellitus

The goal of this review was to summarize current biochemical mechanisms of and risk factors for diabetic brain injury. We mainly summarized mechanisms published in the past three years and focused on diabetes induced cognitive impairment, diabetes-linked Alzheimer’s disease, and diabetic stroke. We think there is a need to conduct further studies with increased sample sizes and prolonged period of follow-ups to clarify the effect of DM on brain dysfunction. Additionally, we also think that enhancing experimental reproducibility using animal models in conjunction with application of advanced devices should be considered when new experiments are designed. It is expected that further investigation of the underlying mechanisms of diabetic cognitive impairment will provide novel insights into therapeutic approaches for ameliorating diabetes-associated injury in the brain.

TDZD-8 alleviates delayed neurological sequelae following acute carbon monoxide poisoning involving tau protein phosphorylation

Objective: Acute carbon monoxide （CO）poisoning can cause delayed neurological sequelae (DNS). Glycogen synthase kinase 3β (GSK-3β) /Tau protein pathway is reported to play a key role in neurological abnormalities. In the present study, we aimed to determine the role of GSK-3β/Tau in DNS following acute CO poisoning.Methods: 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8), a specific non-competitive inhibitor of GSK-3β, was used to inhibit GSK-3β. Twenty-four male Sprague-Dawley rats were randomly assigned to the three groups: Control group, CO group and CO-TDZD-8 group. Rats breathed 1000 ppm CO for 40 minutes and then 3000 ppm for up to 20 minutes until they lost consciousness. TDZD-8 (1 mg/kg) was administered intravenously three times after the end of CO exposure at 0, 24, 48 hours late. Learning and memory abilities were observed using the Morris Water Maze (MWM). Brain histological changes were evaluated by hematoxylin-eosin staining. Moreover, the expression levels of Tau and GSK-3β were detected after acute carbon monoxide poisoning.Results: TDZD-8 significantly attenuated the learning and memory dysfunction induced by acute CO poisoning, ameliorated the histology structure of damaged neural cells in cortex and hippocampus CA1 area. TDZD-8 clearly decreased p-Tau expression, reversed the reduction of p-GSK-3β induced by acute CO poisoning.Conclusions: The therapeutic effect of TDZD-8 in alleviating DNS caused by acute CO poisoning is related to the inactivation of Tau by intensifying the level of GSK-3β phosphorylation.

Increased calcium channel in the lamina propria of aging rat

The alterations of the extracellular matrix (ECM) in lamina propria of the vocal folds are important changes that are associated with decreased vibrations and increased stiffness in aging vocal fold. The aim of this study was to investigate the differences in gene expression of lamina propria using next generation sequencing (NGS) in young and aging rats and to identify genes that affect aging-related ECM changes for developing novel therapeutic target molecule. Among the 40 genes suggested in the NGS analysis, voltage-gated calcium channels (VGCC) subunit alpha1 S (CACNA1S), VGCC auxiliary subunit beta 1 (CACNB1), and VGCC auxiliary subunit gamma 1 (CACNG1) were increased in the lamina propria of the old rats compared to the young rats. The synthesis of collagen I and III in hVFFs decreased after si-CACNA1S and verapamil treatment. The expression and activity of matrix metalloproteinases (MMP)-1 and -8 were increased in hVFFs after the treatment of verapamil. However, there was no change in the expression of MMP-2 and -9. These results suggest that some calcium channels may be related with the alteration of aging-related ECM in vocal folds. Calcium channel has promising potential as a novel therapeutic target for the remodeling ECM of aging lamina propria.

The Correlation between Serum Uric Acid and Renal Function in Elderly Chinese Diabetes with Normoalbuminuria

OBJECTIVE

The elder diabetic patients increases rapidly in China and often accompany with hyperuricemia. Recently evidences show that renal function has been impaired in part of diabetic patients with normoalbuminuria. Therefore, we investigated the relationship between serum uric acid (SUA) and renal function in Chinese elder diabetes with normoalbuminuria.

METHODS

The physical examination data from 1052 cases of diabetic residents with normoalbuminuria aged 70 years and over in the Jiangchuan community of Minhang District, Shanghai, from October 2011 to September 2014 was analyzed retrospectively. Each received height, body weight, waist circumference (WC), waist-to-hip ratio (WHR), blood pressure (BP), and collected samples of fasting blood and morning urine to detect blood routine, blood glucose, glycosylated hemoglobin (HbA1c), blood lipids, serum creatinine, urinary albumin, urine creatinine, and urine PH value. Correlation between SUA and renal function, an index of which is estimated using estimated glomerular filtration rate (eGFR), was analyzed.

RESULTS

The prevalence of hyperuricemia was 21.10%. Levels of WC and triglyceride (TG) increased and the levels of HbA1c, high density lipoprotein-cholesterol (HDL-C), eGFR, and urine PH decreased while the levels of SUA increased. Moreover, negative correlation of eGFR with age, WC, leukocyte, and SUA (Pearson r=0.415) was observed via Pearson correlation analysis. It indicates the strong association between SUA and eGFR. Furthermore, eGFR independently associated with SUA, age, leukocyte, hemoglobin (Hb), and fasting blood glucose (FBG) was confirmed by multiple linear stepwise regression analysis.

CONCLUSION

SUA may play an important role in the decrease of eGFR in elderly Chinese diabetic patients with normoalbuminuria.