Neuronal damage and cognitive impairment associated with hypoglycemia: An integrated view

Neuronal glucose sensing mechanisms and circuits in the control of insulin and glucagon secretion

Glucose homeostasis is mainly under the control of the pancreatic islet hormones insulin and glucagon, which, respectively, stimulate glucose uptake and utilization by liver, fat, and muscle and glucose production by the liver. The balance between the secretions of these hormones is under the control of blood glucose concentrations. Indeed, pancreatic islet β-cells and α-cells can sense variations in glycemia and respond by an appropriate secretory response. However, the secretory activity of these cells is also under multiple additional metabolic, hormonal, and neuronal signals that combine to ensure the perfect control of glycemia over a lifetime. The central nervous system (CNS), which has an almost absolute requirement for glucose as a source of metabolic energy and thus a vital interest in ensuring that glycemic levels never fall below ∼5 mM, is equipped with populations of neurons responsive to changes in glucose concentrations. These neurons control pancreatic islet cell secretion activity in multiple ways: through both branches of the autonomic nervous system, through the hypothalamic-pituitary-adrenal axis, and by secreting vasopressin (AVP) in the blood at the level of the posterior pituitary. Here, we present the autonomic innervation of the pancreatic islets; the mechanisms of neuron activation by a rise or a fall in glucose concentration; how current viral tracing, chemogenetic, and optogenetic techniques allow integration of specific glucose sensing neurons in defined neuronal circuits that control endocrine pancreas function; and, finally, how genetic screens in mice can untangle the diversity of the hypothalamic mechanisms controlling the response to hypoglycemia.

Review of the lethal mechanism of insulin poisoning and the characteristic of forensic identification

Insulin, as the only hypoglycemic hormone in the body, plays a key role in blood sugar control. However, excessive insulin intake can lead to insulin poisoning and even death, which often occurs in clinical and forensic work. At present, some researches on insulin poisoning have been carried out at home and abroad, however, it seems that the mechanism and forensic characteristics of insulin poisoning are not clear and complete. Therefore, in this paper, we reviewed the potential mechanism of insulin poisoning, the methods of insulin detection and the forensic identification of poisoning cases, aiming at providing services for the forensic identification of insulin poisoning.

Effect of hypoglycemic events on cognitive function in individuals with type 2 diabetes mellitus: a dose-response meta-analysis

Background

Type 2 diabetes mellitus (T2DM) is widely acknowledged as a vital warning sign contributing to cognitive dysfunction. However, there is still a lack of consensus on whether hypoglycemic events resulting from poor glycemic control increase the risk of cognitive dysfunction in people with diabetes, and the potential dose-response correlation between hypoglycemic events and cognitive dysfunction remains unexplored. The primary objective of the current study was to assess the contribution of hypoglycemic events to cognitive dysfunction in T2DM patients and the dose-response correlation between the two.

Methods

A comprehensive search of nine major databases was executed from inception to May 2023. We screened all observational studies examining the connection between hypoglycemia and cognitive dysfunction. The DerSimonian-Laird method was used to compute the combined risk ratio (RR) and its 95% confidence interval (CI). Additionally, dose-response analysis was employed to investigate the correlation between the frequency of hypoglycemia and the likelihood of cognitive dysfunction.

Results

A total of 30 studies of different levels in 17 articles with 3,961,352 participants were included in this review. The pooled RR for the connection of hypoglycemia and the likelihood of cognitive dysfunction was 1.47 (95% CI: 1.35-1.60). Subgroup analyses showed that the pooled RR for the likelihood of cognitive dysfunction was 1.20 (95% CI: 1.11-1.31) for one episode of hypoglycemia, 1.41 (95% CI: 1.05-1.88) for two episodes of hypoglycemia, and 1.62 (95% CI: 1.20-2.91) for three or more episodes of hypoglycemia. Dose-response analysis showed a linear dose-response relationship between hypoglycemia and the likelihood of cognitive dysfunction (exp (b) = 1.178694, z = 7.12, p < 0.001).

Conclusion

Our investigations demonstrated a 47% heightened likelihood of cognitive dysfunction in individuals with hypoglycemia compared to those without. Furthermore, the likelihood of cognitive dysfunction climbed by 17.87% for every subsequent episode of hypoglycemia. Therefore, long-term monitoring of blood glucose, periodic screening of cognitive function, and moderate health education should be encouraged, which will be beneficial for people with diabetes to prevent hypoglycemic events and cognitive dysfunction.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, CRD42023432352.

SGLT2 inhibitors: a novel therapy for cognitive impairment via multifaceted effects on the nervous system

The rising prevalence of diabetes mellitus has casted a spotlight on one of its significant sequelae: cognitive impairment. Sodium-glucose cotransporter-2 (SGLT2) inhibitors, originally developed for diabetes management, are increasingly studied for their cognitive benefits. These benefits may include reduction of oxidative stress and neuroinflammation, decrease of amyloid burdens, enhancement of neuronal plasticity, and improved cerebral glucose utilization. The multifaceted effects and the relatively favorable side-effect profile of SGLT2 inhibitors render them a promising therapeutic candidate for cognitive disorders. Nonetheless, the application of SGLT2 inhibitors for cognitive impairment is not without its limitations, necessitating more comprehensive research to fully determine their therapeutic potential for cognitive treatment. In this review, we discuss the role of SGLT2 in neural function, elucidate the diabetes-cognition nexus, and synthesize current knowledge on the cognitive effects of SGLT2 inhibitors based on animal studies and clinical evidence. Research gaps are proposed to spur further investigation.

Effect of recurrent severe insulin-induced hypoglycemia on the cognitive function and brain oxidative status in the rats

BACKGROUND

Episodes of recurrent or severe hypoglycemia can occur in patients with diabetes mellitus, insulinoma, neonatal hypoglycemia, and medication errors. However, little is known about the short-term and long-term effects of repeated episodes of acute severe hypoglycemia on the brain, particularly in relation to hippocampal damage and cognitive dysfunction.

METHODS

Thirty-six wistar rats were randomly assigned to either the experimental or control group. The rats were exposed to severe hypoglycemia, and assessments were conducted to evaluate oxidative stress in brain tissue, cognitive function using the Morris water maze test, as well as histopathology and immunohistochemistry studies. The clinical and histopathological evaluations were conducted in the short-term and long-term.

RESULTS

The mortality rate attributed to hypoglycemia was 34%, occurring either during hypoglycemia or within 24 h after induction. Out of the 14 rats monitored for 7 to 90 days following severe/recurrent hypoglycemia, all exhibited clinical symptoms, which mostly resolved within three days after the last hypoglycemic episode, except for three rats. Despite the decrease in catalase activity in the brain, the total antioxidant capacity following severe insulin-induced hypoglycemia increased. The histopathology findings revealed that the severity of the hippocampal damage was higher compared to the brain cortex 90 days after hypoglycemia. Memory impairments with neuron loss particularly pronounced in the dentate gyrus region of the hippocampus were observed in the rats with severe hypoglycemia. Additionally, there was an increase in reactive astrocytes indicated by GFAP immunoreactivity in the brain cortex and hippocampus.

CONCLUSION

Recurrent episodes of severe hypoglycemia can lead to high mortality rates, memory impairments, and severe histopathological changes in the brain. While many histopathological and clinical changes improved after three months, it seems that the vulnerability of the hippocampus and the development of sustained changes in the hippocampus were greater and more severe compared to the brain cortex following severe and recurrent hypoglycemia. Furthermore, it does not appear that oxidative stress plays a central role in neuronal damage following severe insulin-induced hypoglycemia. Further research is necessary to assess the consequences of repeated hypoglycemic episodes on sustained damage across various brain regions.

Chemokine CX3CL1 (Fractalkine) Signaling and Diabetic Encephalopathy

Diabetes mellitus (DM) is the most common metabolic disease in humans, and its prevalence is increasing worldwide in parallel with the obesity pandemic. A lack of insulin or insulin resistance, and consequently hyperglycemia, leads to many systemic disorders, among which diabetic encephalopathy (DE) is a long-term complication of the central nervous system (CNS), characterized by cognitive impairment and motor dysfunctions. The role of oxidative stress and neuroinflammation in the pathomechanism of DE has been proven. Fractalkine (CX3CL1) has unique properties as an adhesion molecule and chemoattractant, and by acting on its only receptor, CX3CR1, it regulates the activity of microglia in physiological states and neuroinflammation. Depending on the clinical context, CX3CL1-CX3CR1 signaling may have neuroprotective effects by inhibiting the inflammatory process in microglia or, conversely, maintaining/intensifying inflammation and neurotoxicity. This review discusses the evidence supporting that the CX3CL1-CX3CR1 pair is neuroprotective and other evidence that it is neurotoxic. Therefore, interrupting the vicious cycle within neuron-microglia interactions by promoting neuroprotective effects or inhibiting the neurotoxic effects of the CX3CL1-CX3CR1 signaling axis may be a therapeutic goal in DE by limiting the inflammatory response. However, the optimal approach to prevent DE is simply tight glycemic control, because the elimination of dysglycemic states in the CNS abolishes the fundamental mechanisms that induce this vicious cycle.

Mitochondrial pyruvate transport regulates presynaptic metabolism and neurotransmission

Glucose has long been considered the primary fuel source for the brain. However, glucose levels fluctuate in the brain during sleep, intense circuit activity, or dietary restrictions, posing significant metabolic stress. Here, we demonstrate that the mammalian brain utilizes pyruvate as a fuel source, and pyruvate can support neuronal viability in the absence of glucose. Nerve terminals are sites of metabolic vulnerability within a neuron and we show that mitochondrial pyruvate uptake is a critical step in oxidative ATP production in hippocampal terminals. We find that the mitochondrial pyruvate carrier is post-translationally modified by lysine acetylation which in turn modulates mitochondrial pyruvate uptake. Importantly, our data reveal that the mitochondrial pyruvate carrier regulates distinct steps in synaptic transmission, namely, the spatiotemporal pattern of synaptic vesicle release and the efficiency of vesicle retrieval, functions that have profound implications for synaptic plasticity. In summary, we identify pyruvate as a potent neuronal fuel and mitochondrial pyruvate uptake as a critical node for the metabolic control of synaptic transmission in hippocampal terminals.

Unveiling peripheral neuropathy and cognitive dysfunction in diabetes: an observational and proof-of-concept study with video games and sensor-equipped insoles

Background

Proactive screening for cognitive dysfunction (CD) and peripheral neuropathy (PNP) in elderly patients with diabetes mellitus is essential for early intervention, yet clinical examination is time-consuming and prone to bias.

Objective

We aimed to investigate PNP and CD in a diabetes cohort and explore the possibility of identifying key features linked with the respective conditions by machine learning algorithms applied to data sets obtained in playful games controlled by sensor-equipped insoles.

Methods

In a cohort of patients diagnosed with diabetes (n=261) aged over 50 years PNP and CD were diagnosed based on complete physical examination (neuropathy symptom and disability scores, and Montreal Cognitive Assessment). In an observational and proof-of-concept study patients performed a 15 min lasting gaming session encompassing tutorials and four video games with 5,244 predefined features. The steering of video games was solely achieved by modulating plantar pressure values, which were measured by sensor-equipped insoles in real-time. Data sets were used to identify key features indicating game performance with correlation regarding CD and PNP findings. Thereby, machine learning models (e.g. gradient boosting and lasso and elastic-net regularized generalized linear models) were set up to distinguish patients in the different groups.

Results

PNP was diagnosed in 59% (n=153), CD in 34% (n=89) of participants, and 23% (n=61) suffered from both conditions. Multivariable regression analyses suggested that PNP was positively associated with CD in patients with diabetes (adjusted odds ratio = 1.95; 95% confidence interval: 1.03-3.76; P=0.04). Predictive game features were identified that significantly correlated with CD (n=59), PNP (n=40), or both (n=59). These features allowed to set up classification models that were enriched by individual risk profiles (i.e. gender, age, weight, BMI, diabetes type, and diabetes duration). The obtained models yielded good predictive performance with the area under the receiver-operating-characteristic curves reaching 0.95 for CD without PNP, 0.83 for PNP without CD, and 0.84 for CD and PNP combined.

Conclusions

The video game-based assessment was able to categorize patients with CD and/or PNP with high accuracy. Future studies with larger cohorts are needed to validate these results and potentially enhance the discriminative power of video games.

Ketogenic diet attenuates cognitive dysfunctions induced by hypoglycemia via inhibiting endoplasmic reticulum stress-dependent pathways

Hypoglycemia can potentially cause severe damage to the central nervous system. The ketogenic diet (KD), characterized by high-fat and extremely low-carbohydrate content, can modulate homeostasis and nutrient metabolism, thereby influencing body health. However, the effects and underlying mechanisms of KD on hypoglycemia-induced brain injury have not been thoroughly investigated. We aimed to explore the modulating effects of KD on cognitive functions and elucidate the underlying mechanisms. In this study, one-month-old mice were fed with KD for 2 weeks, and the changes in the gut microbiota were detected using the 16S rRNA gene amplicon sequencing method. The hypoglycemic model of mice was established using insulin, and the potential protective effect of KD on hypoglycemia-induced brain injury in mice was evaluated through immunofluorescence staining, western blotting, transmission electron microscopy, and Golgi staining. Our results showed that the intestinal flora of Dorea increased and Rikenella decreased in KD-fed mice. KD can not only alleviate anxiety-like behavior induced by hypoglycemia, but also increase the proportion of mushroom dendritic spines in the hippocampus by modulating changes in the gut microbiota. KD regulated synaptic plasticity by increasing the levels of SPN, PSD95, and SYP, which relieve cognitive impairment caused by hypoglycemia. Moreover, KD can promote the proliferation and survival of adult neural stem cells in the hippocampus, while reducing apoptosis by suppressing the activation of the IRE1-XBP1 and ATF6 endoplasmic reticulum stress pathways in mice with hypoglycemia. This study provides new evidence for demonstrating that KD may alleviate cognitive dysfunctions caused by hypoglycemia by modulating the gut microbiota.

Whisker-evoked neurovascular coupling is preserved during hypoglycemia in mouse cortical arterioles and capillaries

Hypoglycemia is a serious complication of insulin treatment of diabetes that can lead to coma and death. Neurovascular coupling, which mediates increased local blood flow in response to neuronal activity, increases glucose availability to active neurons. This mechanism could be essential for neuronal health during hypoglycemia, when total glucose supplies are low. Previous studies suggest, however, that neurovascular coupling (a transient blood flow increase in response to an increase in neuronal activity) may be reduced during hypoglycemia. Such a reduction in blood flow increase would exacerbate the effects of hypoglycemia, depriving active neurons of glucose. We have reexamined the effects of hypoglycemia on neurovascular coupling by simultaneously monitoring neuronal and vascular responses to whisker stimulation in the awake mouse somatosensory cortex. We find that neurovascular coupling at both penetrating arterioles and at 2nd order capillaries did not change significantly during insulin-induced hypoglycemia compared to euglycemia. In addition, we show that the basal diameter of both arterioles and capillaries increases during hypoglycemia (10.3 and 9.7% increases, respectively). Our results demonstrate that both neurovascular coupling and basal increases in vessel diameter are active mechanisms which help to maintain an adequate supply of glucose to the brain during hypoglycemia.

Blood biomarkers of neuronal injury in paediatric cerebral malaria and severe malarial anaemia

Persistent neurodisability is a known complication in paediatric survivors of cerebral malaria and severe malarial anaemia. Tau, ubiquitin C-terminal hydrolase-L1, neurofilament-light chain, and glial fibrillary acidic protein have proven utility as biomarkers that predict adverse neurologic outcomes in adult and paediatric disorders. In paediatric severe malaria, elevated tau is associated with mortality and neurocognitive complications. We aimed to investigate whether a multi-analyte panel including ubiquitin C-terminal hydrolase-L1, neurofilament-light chain, and glial fibrillary acidic protein can serve as biomarkers of brain injury associated with mortality and neurodisability in cerebral malaria and severe malarial anaemia. In a prospective cohort study of Ugandan children, 18 months to 12 years of age with cerebral malaria (n = 182), severe malarial anaemia (n = 158), and asymptomatic community children (n = 118), we measured admission blood levels of ubiquitin C-terminal hydrolase-L1, neurofilament-light chain, and glial fibrillary acidic protein. We investigated differences in biomarker levels, associations with mortality, blood-brain barrier integrity, neurodeficits and cognitive Z-scores in survivors up to 24-month follow-up. Admission ubiquitin C-terminal hydrolase-L1 levels were elevated >95th percentile of community children in 71 and 51%, and neurofilament-light chain levels were elevated >95th percentile of community children in 40 and 37% of children with cerebral malaria and severe malarial anaemia, respectively. Glial fibrillary acidic protein was not elevated in disease groups compared with controls. In cerebral malaria, elevated neurofilament-light chain was observed in 16 children who died in hospital compared with 166 survivors (P = 0.01); elevations in ubiquitin C-terminal hydrolase-L1 levels were associated with degree of blood-brain barrier disruption (P = 0.01); and the % predictive value for neurodeficits over follow-up (discharge, 6-, 12-, and 24 months) increased for ubiquitin C-terminal hydrolase-L1 (60, 67, 72, and 83), but not neurofilament-light chain (65, 68, 60, and 67). In cerebral malaria, elevated ubiquitin C-terminal hydrolase-L1 was associated with worse memory scores in children <5 years at malaria episode who crossed to over 5 years old during follow-up cognitive testing [β -1.13 (95% confidence interval -2.05, -0.21), P = 0.02], and elevated neurofilament-light chain was associated with worse attention in children ≥5 years at malaria episode and cognitive testing [β -1.08 (95% confidence interval -2.05, -1.05), P = 0.03]. In severe malarial anaemia, elevated ubiquitin C-terminal hydrolase-L1 was associated with worse attention in children <5 years at malaria episode and cognitive testing [β -0.42 (95% confidence interval -0.76, -0.07), P = 0.02]. Ubiquitin C-terminal hydrolase-L1 and neurofilament-light chain levels are elevated in paediatric cerebral malaria and severe malarial anaemia. In cerebral malaria, elevated neurofilament-light chain is associated with mortality whereas elevated ubiquitin C-terminal hydrolase-L1 is associated with blood-brain barrier dysfunction and neurodeficits over follow-up. In cerebral malaria, both markers are associated with worse cognition, while in severe malarial anaemia, only ubiquitin C-terminal hydrolase-L1 is associated with worse cognition.

Comparison on cognitive outcomes of antidiabetic agents for type 2 diabetes: A systematic review and network meta-analysis

We aimed to summarise current evidence on different antidiabetic drugs to delay cognitive impairment, including mild cognitive impairment, dementia, Alzheimer's disease (AD) and vascular dementia, among subjects with type 2 diabetes mellitus (T2DM). Medline, Cochrane and Embase databases were searched from inception to 31 July 2022. Two investigators independently reviewed and screened trials comparing antidiabetic drugs with no antidiabetic drugs, placebo, or other active antidiabetic drugs on cognitive outcomes in T2DM. Data were analysed using meta-analysis and network meta-analysis. Twenty-seven studies met the inclusion criteria, including 3 randomised controlled trials, 19 cohort studies and 5 case-control studies. Compared with non-user, SGLT-2i (OR 0.41 [95% CI 0.22-0.76]), GLP-1RA (OR 0.34 [95% CI 0.14-0.85]), thiazolidinedione (OR 0.60 [95% CI 0.51-0.69]), and DPP-4i (OR 0.78 [95% CI 0.61-0.99]) users had a decreased risk of dementia, whereas sulfonylurea (OR 1.43 [95% CI 1.11-1.82]) increased dementia risk. Network meta-analysis showed that SGLT-2i was most likely to rank best (SUCRA = 94.4%), GLP-1 RA second best (SUCRA = 92.7%), thiazolidinedione third best (SUCRA = 74.7%) and DPP-4i fourth best (SUCRA = 54.9%), while sulfonylurea second worst (SUCRA = 20.0%) for decreasing dementia outcomes, by synthesising evidence from direct and indirect comparisons of multiple intervention. Evidence suggests the effects of SGLT-2i ≈ GLP-1 RAs > thiazolidinedione > DPP-4i for delaying cognitive impairment, dementia and AD outcomes, whereas sulfonylurea was associated with the highest risk. These findings provide evidence for evaluating the optional treatment for clinical practice. PROSPERO REGISTRATION: Registration no. CRD42022347280.

Insulin enhances contextual fear memory independently of its effect in increasing plasma adrenaline

AIMS

Adrenaline enhances contextual fear memory consolidation possibly by activating liver β₂-adrenoceptors causing transient hyperglycaemia. Contrastingly, insulin-induced hypoglycaemia may culminate in blood adrenaline increment, hidering the separation of each hormone's action in contextual fear memory. Therefore, an Ad-deficient mouse model was used aiming to investigate if contextual fear memory consolidation following insulin administration requires or not subsequent increases in plasma adrenaline, which occurs in response to insulin-induced hypoglycemia.

MAIN METHODS

Fear conditioning was performed in wild-type (WT) and adrenaline-deficient (Pnmt-KO) male mice (129 × 1/SvJ) treated with insulin (2 U/kg, intraperitoneal (i.p.)) or vehicle (0.9 % NaCl (i.p.)). Blood glucose was quantified. Catecholamines were quantified using HPLC with electrochemical detection. Quantitative real-time polymerase chain reaction was used to assess mRNA expression of hippocampal Nr4a1, Nr4a2, Nr4a3, and Bdnf genes.

KEY FINDINGS

Insulin-treated WT mice showed increased freezing behaviour when compared to vehicle-treated WT mice. Also, plasma dopamine, noradrenaline, and adrenaline increased in this group. Insulin-treated Pnmt-KO animals showed increased freezing behaviour when compared with respective vehicle. However, no changes in plasma or tissue catecholamines were identified in insulin-treated Pnmt-KO mice when compared with respective vehicle. Furthermore, insulin-treated Pnmt-KO mice presented increased Bdnf mRNA expression when compared to vehicle-treated Pnmt-KO mice.

SIGNIFICANCE

Concluding, enhanced freezing behaviour after insulin treatment, even in adrenaline absence, may indicate a key role of insulin in contextual fear memory. Insulin may cause central molecular changes promoting contextual fear memory formation and/or retrieval. This work may indicate a further role of insulin in the process of contextual fear memory modulation.

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.

Mouse Models with SGLT2 Mutations: Toward Understanding the Role of SGLT2 beyond Glucose Reabsorption

The sodium–glucose cotransporter 2 (SGLT2) mainly carries out glucose reabsorption in the kidney. Familial renal glycosuria, which is a mutation of SGLT2, is known to excrete glucose in the urine, but blood glucose levels are almost normal. Therefore, SGLT2 inhibitors are attracting attention as a new therapeutic drug for diabetes, which is increasing worldwide. In fact, SGLT2 inhibitors not only suppress hyperglycemia but also reduce renal, heart, and cardiovascular diseases. However, whether long-term SGLT2 inhibition is completely harmless requires further investigation. In this context, mice with mutations in SGLT2 have been generated and detailed studies are being conducted, e.g., the SGLT2−/− mouse, Sweet Pee mouse, Jimbee mouse, and SAMP10-ΔSglt2 mouse. Biological changes associated with SGLT2 mutations have been reported in these model mice, suggesting that SGLT2 is not only responsible for sugar reabsorption but is also related to other functions, such as bone metabolism, longevity, and cognitive functions. In this review, we present the characteristics of these mutant mice. Moreover, because the relationship between diabetes and Alzheimer’s disease has been discussed, we examined the relationship between changes in glucose homeostasis and the amyloid precursor protein in SGLT2 mutant mice.

Association between severe hypoglycaemia and risk of dementia in patients with type 2 diabetes mellitus: A systematic review and meta-analysis

The aim of this systematic review was to analyse whether there is an association between severe hypoglycaemia and the incidence of dementia in patients with type 2 diabetes mellitus. We systematically searched the MEDLINE, Scopus, and Cochrane databases from their inception until September 2022 for observational studies on the association between hypoglycaemia and the risk of dementia. The DerSimonian and Laird method was used to compute a pooled estimate of the risk for such association. Risk ratio (RR) and its respective 95% confidence interval (95% CI). Two analyses were performed to estimate the risk of dementia: (i) any hypoglycaemia versus no hypoglycaemia and (ii) a dose-response analysis for one, two, or more than three hypoglycemic events versus no hypoglycaemia. PROSPERO registration number CRD42020219200. Seven studies were included. The pooled RR for the association of severe hypoglycaemia and risk of dementia was 1.47 (95% CI: 1.24-1.74). When the dose-response trend was analysed, the pooled RR for the risk of dementia was increased according to the hypoglycaemia events as follows: 1.29 (95% CI: 1.15-1.44) for one hypoglycemic event; 1.68 (95% CI: 1.38-2.04) for two hypoglycemic events; and 1.99 (95% CI: 1.48-2.68) for three or more hypoglycemic events. Our study demonstrates a 54% higher risk of dementia among people who suffer a hypoglycaemia event compared to nonhypoglycaemia. Considering our results and the prevalence of people suffering from diabetes mellitus, health education for both newly diagnosed and already diagnosed people could be a useful tool for glycaemic control, thus avoiding hypoglycaemic events.

SIRT3 alleviates mitochondrial dysfunction induced by recurrent low glucose and improves the supportive function of astrocytes to neurons

Hypoglycemia is an independent risk factor of cognitive impairment in patients with diabetes. Our previous study indicated that dysfunction of astrocytic mitochondria induced by recurrent low glucose (RLG) may account for hypoglycemia-associated neuronal injury and cognitive decline. Sirtuin 3 (SIRT3) is a key deacetylase for mitochondrial proteins and has recently been demonstrated to be an important regulator of mitochondrial function. However, whether mitochondrial dysfunction due to hypoglycemia is associated with astrocytic SIRT3 remains unclear, and few studies have focused on the impact of astrocytic SIRT3 on neuronal survival. In the present work, primary mouse cortical astrocytes cultured in normal glucose (5.5 mM) and high glucose (16.5 mM) were treated with five rounds of RLG (0.1 mM). The results showed that RLG suppressed SIRT3 expression in a glucose-dependent manner. High-glucose culture considerably increased the vulnerability of SIRT3 to RLG, leading to disrupted mitochondrial morphology in astrocytes. Overexpression of SIRT3 markedly improved astrocytic mitochondrial function and reduced RLG-induced oxidative stress. Moreover, SIRT3 suppressed a shift towards a neuroinflammatory A1-like reactive phenotype of astrocytes in response to RLG with reduced IL-1β, IL-6, and TNFα levels. Furthermore, it elevated brain-derived neurotrophic factor (BDNF) levels and promoted neurite growth by activating BDNF/TrkB signaling in the co-cultured neurons. The present study reveals the probable crosstalk between neurons and astrocytes after hypoglycemic exposure and provides a potential target in treating hypoglycemia-associated neuronal injury.

Targeting the liver in dementia and cognitive impairment: Dietary macronutrients and diabetic therapeutics

Many people living with dementia and cognitive impairment have dysfunctional mitochondrial and insulin-glucose metabolism resembling type 2 diabetes mellitus and old age. Evidence from human trials shows that nutritional interventions and anti-diabetic medicines that target nutrient-sensing pathways overcome these deficits in glucose and energy metabolism and can improve cognition and/or reduce symptoms of dementia. The liver is the main organ that mediates the systemic effects of diets and many diabetic medicines; therefore, it is an intermediate target for such dementia interventions. A challenge is the efficacy of these treatments in older age. Solutions include the targeted hepatic delivery of diabetic medicines using nanotechnologies and titration of macronutrients to optimize hepatic energy metabolism.

Intracellular energy controls dynamics of stress-induced ribonucleoprotein granules

Energy metabolism and membraneless organelles have been implicated in human diseases including neurodegeneration. How energy deficiency regulates ribonucleoprotein particles such as stress granules (SGs) is still unclear. Here we identified a unique type of granules induced by energy deficiency under physiological conditions and uncovered the mechanisms by which the dynamics of diverse stress-induced granules are regulated. Severe energy deficiency induced the rapid formation of energy deficiency-induced stress granules (eSGs) independently of eIF2α phosphorylation, whereas moderate energy deficiency delayed the clearance of conventional SGs. The formation of eSGs or the clearance of SGs was regulated by the mTOR-4EBP1-eIF4E pathway or eIF4A1, involving assembly of the eIF4F complex or RNA condensation, respectively. In neurons or brain organoids derived from patients carrying the C9orf72 repeat expansion associated with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), the eSG formation was enhanced, and the clearance of conventional SGs was impaired. These results reveal a critical role for intracellular energy in the regulation of diverse granules and suggest that disruptions in energy-controlled granule dynamics may contribute to the pathogenesis of relevant diseases.

Stress granules are associated with neurodegenerative diseases. Here, Wang et al. found intracellular energy deficiencies trigger a unique type of granules and disrupt granule disassembly through 4EBP1/eIF4A.

Description and Outcome of Severe Hypoglycemic Encephalopathy in the Intensive Care Unit

BACKGROUND

Disorders of consciousness due to severe hypoglycemia are rare but challenging to treat. The aim of this retrospective cohort study was to describe our multimodal neurological assessment of patients with hypoglycemic encephalopathy hospitalized in the intensive care unit and their neurological outcomes.

METHODS

Consecutive patients with disorders of consciousness related to hypoglycemia admitted for neuroprognostication from 2010 to 2020 were included. Multimodal neurological assessment included electroencephalography, somatosensory and cognitive event-related potentials, and morphological and quantitative magnetic resonance imaging (MRI) with quantification of fractional anisotropy. Neurological outcomes at 28 days, 3 months, 6 months, 1 year, and 2 years after hypoglycemia were retrieved.

RESULTS

Twenty patients were included. After 2 years, 75% of patients had died, 5% remained in a permanent vegetative state, 10% were in a minimally conscious state, and 10% were conscious but with severe disabilities (Glasgow Outcome Scale-Extended scores 3 and 4). All patients showed pathologic electroencephalography findings with heterogenous patterns. Morphological brain MRI revealed abnormalities in 95% of patients, with various localizations including cortical atrophy in 65% of patients. When performed, quantitative MRI showed decreased fractional anisotropy affecting widespread white matter tracts in all patients.

CONCLUSIONS

The overall prognosis of patients with severe hypoglycemic encephalopathy was poor, with only a small fraction of patients who slowly improved after intensive care unit discharge. Of note, patients who did not improve during the first 6 months did not recover consciousness. This study suggests that a multimodal approach capitalizing on advanced brain imaging and bedside electrophysiology techniques could improve diagnostic and prognostic performance in severe hypoglycemic encephalopathy.

Vitamin C deficiency induces hypoglycemia and cognitive disorder through S-nitrosylation-mediated activation of glycogen synthase kinase 3β

Vitamin C (VC, l-ascorbic acid) is an essential nutrient that plays a key role in metabolism and functions as a potent antioxidant in regulating the S-nitrosylation and denitrosylation of target proteins. The precise function of VC deprivation in glucose homeostasis is still unknown. In the absence of L-gulono-1,4-lactone oxidoreductase, an essential enzyme for the last step of VC synthesis, VC deprivation resulted in persistent hypoglycemia and subsequent impairment of cognitive functions in female but not male mouse pups. The cognitive disorders caused by VC deprivation were largely reversed when these female pups were given glucose. VC deprivation-induced S-nitrosylation of glycogen synthase kinase 3β (GSK3β) at Cys14, which activated GSK3β and inactivated glycogen synthase to decrease glycogen synthesis and storage under the feeding condition, while VC deprivation inactivated glycogen phosphorylase to decrease glycogenolysis under the fasting condition, ultimately leading to hypoglycemia and cognitive disorders. Treatment with Nω-Nitro-l-arginine methyl ester (l-NAME), a specific inhibitor of nitric oxide synthase, on the other hand, effectively prevented S-nitrosylation and activation of GSK3β in female pups in response to the VC deprivation and reversed hypoglycemia and cognitive disorders. Overall, this research identifies S-nitrosylation of GSK3β and subsequent GSK3β activation as a previously unknown mechanism controlling glucose homeostasis in female pups in response to VC deprivation, implying that VC supplementation in the prevention of hypoglycemia and cognitive disorders should be considered in the certain groups of people, particularly young females.

Corresponding risk factors between cognitive impairment and type 1 diabetes mellitus: a narrative review

Type 1 diabetes mellitus (T1DM) is a type of diabetes caused by the destruction of pancreatic β cells and the absolute lack of insulin secretion. T1DM usually starts in adolescence or develops directly as a severe disease state of ketoacidosis. T1DM and its complications make many people suffer and have psychological problems, which make us have to pay more attention to the prevention and early control of T1DM. Cognitive impairment (CI) is one of the major complications of T1DM. It can further develop into Alzheimer's disease, which can seriously affect the quality of life of the elderly. Furthermore, the relationship between T1DM and CI is unclear. Hence, we conducted a narrative review of the existing literature through a PubMed search. We summarized some risk factors that may be associated with the cognitive changes in T1DM patients, including onset age and duration, education and gender, glycemic states, microvascular complications, glycemic control, neuropsychology and emotion, intestinal flora, dyslipidemia, sleep quality. We aimed to provide some content related to CI in T1DM, and hoped that it could play a role in early prediction and treatment to reduce the prevalence.

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Corresponding risk factors between cognitive impairment and type 1 diabetes mellitus.

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Duration and age; Education and gender and Glycemic states.

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Diabetic ketoacidosis; Microvascular complications and Glycemic control–HbA1c.

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Neuropsychology and emotion; Intestinal flora; Dyslipidemia and Sleep Quality.

Astrocyte regulation of cerebral blood flow during hypoglycemia

Hypoglycemia triggers increases in cerebral blood flow (CBF), augmenting glucose supply to the brain. We have tested whether astrocytes, which can regulate vessel tone, contribute to this CBF increase. We hypothesized that hypoglycemia-induced adenosine signaling acts to increase astrocyte Ca2+ activity, which then causes the release of prostaglandins (PGs) and epoxyeicosatrienoic acids (EETs), leading to the dilation of brain arterioles and blood flow increases. We used an awake mouse model to investigate the effects of insulin-induced hypoglycemia on arterioles and astrocytes in the somatosensory cortex. During insulin-induced hypoglycemia, penetrating arterioles dilated and astrocyte Ca2+ signaling increased when blood glucose dropped below a threshold of ∼50 mg/dL. Application of the A2A adenosine receptor antagonist ZM-241385 eliminated hypoglycemia-evoked astrocyte Ca2+ increases and reduced arteriole dilations by 44% (p < 0.05). SC-560 and miconazole, which block the production of the astrocyte vasodilators PGs and EETs respectively, reduced arteriole dilations in response to hypoglycemia by 89% (p < 0.001) and 76% (p < 0.001). Hypoglycemia-induced arteriole dilations were decreased by 65% (p < 0.001) in IP3R2 knockout mice, which have reduced astrocyte Ca2+ signaling compared to wild-type. These results support the hypothesis that astrocytes contribute to hypoglycemia-induced increases in CBF by releasing vasodilators in a Ca2+-dependent manner.

Type 2 Diabetes Mellitus with Tight Glucose Control and Poor Pre-Injury Stair Climbing Capacity May Predict Postoperative Delirium: A Secondary Analysis

(1) Background: Previous evidence demonstrates that tight glycemic control and good physical function could reduce the risk of delirium. This study aimed to investigate whether the occurrence of postoperative delirium (POD) in older hip fracture surgery patients is associated with preoperative glycemic control factors or pre-injury physical performance. (2) Methods: Three-hundred and nine individuals aged over 65 years and scheduled for hip fracture surgery were included at a single center. Glycemic control factors and pre-injury physical performance were assessed preoperatively. The presence of delirium was assessed using the Confusion Assessment Method on postoperative hospitalization days. Univariate and multivariable logistic regression models and a risk prediction model of POD were established. (3) Results: Among the 309 patients, 52 (16.83%) experienced POD during the hospital stay. The numbers of pre-injury physical performance and type 2 diabetes mellitus (T2DM) patients were significantly different in the POD and non-POD groups. The multivariable model showed that development of delirium was significantly explained by preoperative fasting blood glucose (FBG) (OR 0.804, p = 0.004), stair climbing (OR 0.709, p = 0.003), T2DM (odds ratio (OR) 3.654, p = 0.001), and age-adjusted Charlson comorbidity index (ACCI) (OR 1.270, p = 0.038). The area under the receiver operating characteristic curve (AUROC) of the risk prediction model including those covariates was 0.770. (4) Conclusions: More older T2DM patients develop POD after hip fracture surgery than patients without T2DM. A simple assessment of preoperative FBG and pre-injury stair climbing capacity may identify those at high risk for the development of POD. Higher preoperative FBG and good pre-injury stair climbing capacity are protective factors for POD.

Intensive glycemic control and macrovascular, microvascular, hypoglycemia complications and mortality in older (age ≥60years) or frail adults with type 2 diabetes: a systematic review and meta-analysis from randomized controlled trial and observation studies

INTRODUCTION

Guidelines for type 2 diabetes (T2D) recommend individualized HbA1c targets to take into account patient age or frailty. We synthesized evidence from randomized controlled trials and observational studies for intensive glycemic control (HbA1c target ≤58 mmol/mol) versus standard care, in elderly (age ≥60 years) or frail adults with T2D.

METHODS

Searches were performed utilizing recognized terms for T2D, frailty, older age, and HbA1c control and outcomes of interest. Meta-analysis was performed where possible. Primary outcomes included all-cause mortality, severe hypoglycemia, and hospital admission rates. Vascular complications, cognitive decline, and falls/fractures were secondary outcomes.

RESULTS

7,528 studies were identified of which 15 different clinical studies were selected. No difference was noted in all-cause mortality with intensive control (pooled hazard ratio 0.96, 95% confidence interval 0.90-1.03), but risk of severe hypoglycemia increased (2.45, 2.22-2.72). Intensive control was associated reductions in microvascular (0.73, 0.68-0.79) and macrovascular complications (0.84, 0.79-0.89). Outcome data for risk of hospitalization, cognition, and falls/fractures were limited.

CONCLUSION

Intensive glycemic control was associated with reduced rates of complications but increased severe hypoglycemia. Significant heterogeneity exists and the impact of different drug regimens is unclear. Caution is needed when setting glycemic targets in elderly or frail individuals.

Severe Hypoglycemia Increases Dementia Risk and Related Mortality: A Nationwide, Population-based Cohort Study

CONTEXT

There are few studies focused on the relationship between hypoglycemia and new-onset dementia in patients with type 2 diabetes and no study regarding mortality of dementia after hypoglycemia.

OBJECTIVE

We investigated the effect of severe hypoglycemia on dementia subtypes and its relation to overall mortality in patients with type 2 diabetes.

METHODS

We evaluated incident dementia, including Alzheimer disease and vascular dementia, among health checkup participants aged 40 years or older in the National Health Insurance System in Korea from January 2009 to December 2015. Episodes of severe hypoglycemia were examined for 3 years before the date of the health checkup.

RESULTS

Among 2 032 689 participants (1 172 271 men, 860 418 women), 14 443 (0.7%) experienced severe hypoglycemia, during a mean follow-up period of 6.9 ± 1.7 years. Individuals in the severe hypoglycemia group were more likely to be diagnosed with dementia compared to individuals without severe hypoglycemia (23.3% vs 7.3%; P < .001) and the overall incidence of Alzheimer disease was higher than vascular dementia. Dementia risk rose with increasing number of severe hypoglycemic episodes (1 episode [hazard ratio (HR) = 1.54; 95% CI, 1.48-1.60], 2 or more episodes [HR = 1.80; 95% CI, 1.66-1.94]). Overall mortality was higher in participants with dementia, but without severe hypoglycemia (HR = 2.03; 95% CI, 1.96-2.10) and severe hypoglycemia, but without dementia (HR = 4.24; 95% CI, 4.29-4.40), and risk of death was highest in those with both severe hypoglycemia and dementia (HR = 5.08; 95% CI, 4.83-5.35).

CONCLUSION

Severe hypoglycemia is associated with dementia, especially Alzheimer disease and mortality; together, they have an additive effect on overall mortality.

Neurological Prognostication After Hypoglycemic Coma: Role of Clinical and EEG Findings

BACKGROUND

Hypoglycemic coma (HC) is an uncommon but severe clinical condition associated with poor neurological outcome. There is a dearth of robust neurological prognostic factors after HC. On the other hand, there is an increasing body of literature on reliable prognostic markers in the postanoxic coma, a similar-albeit not identical-situation. The objective of this study was thus to investigate the use and predictive value of these markers in HC.

METHODS

We conducted a retrospective, multicenter, cohort study within five centers of the Critical Care EEG Monitoring Research Consortium. We queried our electroencephalography (EEG) databases to identify all patients undergoing continuous EEG monitoring after admission to an intensive care unit with HC (defined as Glasgow Coma Scale < 8 on admission and a first blood glucose level < 50 mg/dL or not documented but in an obvious clinical context) between 01/01/2010 and 12/31/2020. We studied the association of findings at neurological examination (Glasgow Coma Scale motor subscale, pupillary light and corneal reflexes) and at continuous EEG monitoring(highly malignant patterns, reactivity, periodic discharges, seizures) with best neurological outcome within 3 months after hospital discharge, defined by the Cerebral Performance Category as favorable (1-3: recovery of consciousness) versus unfavorable (4-5: lack of recovery of consciousness).

RESULTS

We identified 60 patients (30 [50%] women; age 62 [51-72] years). Thirty-one and 29 patients had a favorable and unfavorable outcome, respectively. The presence of pupillary reflexes (24 [100%] vs. 17 [81%]; p value 0.04) and a motor subscore > 2 (22 [92%] vs. 12 [63%]; p value 0.03) at 48-72 h were associated with a favorable outcome. A highly malignant EEG pattern was observed in 7 of 29 (24%) patients with unfavorable outcome versus 0 of 31 (0%) with favorable outcome, whereas the presence of EEG reactivity was observed in 28 of 31 (90%) patients with favorable outcome versus 13 of 29 (45%) with unfavorable outcome (p < 0.001 for comparison of all background categories).

CONCLUSIONS

This preliminary study suggests that highly malignant EEG patterns might be reliable prognostic markers of unfavorable outcome after HC. Other EEG findings, including lack of EEG reactivity and seizures and clinical findings appear less accurate. These findings should be replicated in a larger multicenter prospective study.

Recurrent moderate hypoglycemia accelerates the progression of cognitive deficits through impairment of TRPC6/GLUT3 pathway in diabetic APP/PS1 mice

Currently, the most effective strategy for dealing with Alzheimer’s disease (AD) is delaying the onset of dementia. Severe hypoglycemia is strongly associated with dementia; however, the effects of recurrent moderate hypoglycemia (RH) on the progression of cognitive deficits in patients with diabetes with genetic susceptibility to AD remain unclear. Here, we report that insulin-controlled hyperglycemia slightly aggravated AD-type pathologies and cognitive impairment; however, RH significantly increased neuronal hyperactivity and accelerated the progression of cognitive deficits in streptozotocin-induced (STZ-induced) diabetic APP/PS1 mice. Glucose transporter 3–mediated (GLUT3-mediated) neuronal glucose uptake was not significantly altered under hyperglycemia but was markedly reduced by RH, which induced excessive mitochondrial fission in the hippocampus. Overexpression of GLUT3, specifically in the dentate gyrus (DG) area of the hippocampus, enhanced mitochondrial function and improved cognitive deficits. Activation of the transient receptor potential channel 6 (TRPC6) increased GLUT3-mediated glucose uptake in the brain and alleviated RH-induced cognitive deficits, and inactivation of the Ca²⁺/AMPK pathway was responsible for TRPC6-induced GLUT3 inhibition. Taken together, RH impairs brain GLUT3-mediated glucose uptake and further provokes neuronal mitochondrial dysfunction by inhibiting TRPC6 expression, which then accelerates progression of cognitive deficits in diabetic APP/PS1 mice. Avoiding RH is essential for glycemic control in patients with diabetes, and TRPC6/GLUT3 represents potent targets for delaying the onset of dementia in patients with diabetes.

Insulin-Induced Recurrent Hypoglycemia Up-Regulates Glucose Metabolism in the Brain Cortex of Chemically Induced Diabetic Rats

Diabetes is a chronic metabolic disease that seriously compromises human well-being. Various studies highlight the importance of maintaining a sufficient glucose supply to the brain and subsequently safeguarding cerebral glucose metabolism. The goal of the present work is to clarify and disclose the metabolic alterations induced by recurrent hypoglycemia in the context of long-term hyperglycemia to further comprehend the effects beyond brain harm. To this end, chemically induced diabetic rats underwent a protocol of repeatedly insulin-induced hypoglycemic episodes. The activity of key enzymes of glycolysis, the pentose phosphate pathway and the Krebs cycle was measured by spectrophotometry in extracts or isolated mitochondria from brain cortical tissue. Western blot analysis was used to determine the protein content of glucose and monocarboxylate transporters, players in the insulin signaling pathway and mitochondrial biogenesis and dynamics. We observed that recurrent hypoglycemia up-regulates the activity of mitochondrial hexokinase and Krebs cycle enzymes (namely, pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase and succinate dehydrogenase) and the protein levels of mitochondrial transcription factor A (TFAM). Both insults increased the nuclear factor erythroid 2–related factor 2 (NRF2) protein content and induced divergent effects in mitochondrial dynamics. Insulin-signaling downstream pathways were found to be down-regulated, and glycogen synthase kinase 3 beta (GSK3β) was found to be activated through both decreased phosphorylation at Ser9 and increased phosphorylation at Y216. Interestingly, no changes in the levels of cAMP response element-binding protein (CREB), which plays a key role in neuronal plasticity and memory, were caused by hypoglycemia and/or hyperglycemia. These findings provide experimental evidence that recurrent hypoglycemia, in the context of chronic hyperglycemia, has the capacity to evoke coordinated adaptive responses in the brain cortex that will ultimately contribute to sustaining brain cell health.

Cognitive Deficits in Type-1 Diabetes: Aspects of Glucose, Cerebrovascular and Amyloid Involvement

The evidence shows that individuals with type-1 diabetes mellitus (T1DM) are at greater risk of accelerated cognitive impairment and dementia. Although, to date the mechanisms are largely unknown. An emerging body of literature indicates that dysfunction of cerebral neurovascular network and plasma dyshomeostasis of soluble amyloid-β in association with impaired lipid metabolism are central to the onset and progression of cognitive deficits and dementia. However, the latter has not been extensively considered in T1DM. Therefore, in this review, we summarised the literature concerning altered lipid metabolism and cerebrovascular function in T1DM as an implication for potential pathways leading to cognitive decline and dementia.

A novel heterozygous mutation in the SLC5A2 gene causing severe glycosuria, mild failure to thrive, and subclinical hypoglycemia

Highlights A novel heterozygous mutation in the SLC5A2 gene in a 2-year-old girl with severe asymptomatic glycosuria, mild failure to thrive, and subclinical hypoglycemia: Continuous glucose monitoring identified 14% hypoglycemic excursions (< 70 mg/dl), reduced at 1% with 1 g/Kg uncooked cornstarch at bed-time milk and eliminated (0%) adjusting the dose at 1.5 g/Kg, as shown by Flash technology.

Defective involuntary attention to novelty in type 1 diabetes and impaired awareness of hypoglycaemia

AIM

To determine if there are differences in terms of neurophysiology and neurocognitive functioning in a group of type 1 diabetes (T1D) patients regarding hypoglycaemia awareness.

METHODS

27 patients with T1D were classified according to Clarke score as having impaired awareness of hypoglycaemia (IAH; n = 11) or normal awareness to hypoglycaemia (NAH; n = 16). We measured several clinical and sociodemographic variables and cognitive performance using neuropsychological tests. Electroencephalography was assessed during an auditory oddball task. We compared the groups in terms of clinical/sociodemographic variables as well as two event-related brain potentials (ERPs): The P3a which is associated with automatic orientation of attention to novelty, and the P3b which is associated with target detection and processing.

RESULTS

The IAH group performed significantly worse on the Trail Making Test part A (TMT-A) (p = 0.05). Compared to the NAH group, P3a and P3b amplitudes in the frontal-central sites were significantly lower in the IAH group (p < 0.05). The P3a was strongly associated with worse performance on the TMT-A in the IAH group (r = 0.540; p < 0.005) CONCLUSION: IAH is accompanied by decreased neurophysiological activity in ERPs associated with information processing and with the automatic orientation of attention to novelty and environmental changes. These findings suggest a possible framework to better understand the cognitive origin of IAH in this patient population.

Extreme Glycemic Fluctuations Debilitate NRG1, ErbB Receptors and Olig1 Function: Association with Regeneration, Cognition and Mood Alterations During Diabetes

Neuronal regeneration is crucial for maintaining intact neural interactions for perpetuation of cognitive and emotional functioning. The NRG1-ErbB receptor signaling is a key pathway for regeneration in adult brain and also associated with learning and mood stabilization by modulating synaptic transmission. Extreme glycemic stress is known to affect NRG1-ErbB-mediated regeneration in brain; yet, it remains unclear how the ErbB receptor subtypes are differentially affected due to such metabolic variations. Here, we assessed the alterations in NRG1, ErbB receptor subtypes to study the regenerative potential, both in rodents as well as in neuronal and glial cell models of hyperglycemia and hypoglycemic insults during hyperglycemia. The pro-oxidant and anti-oxidant status leading to degenerative changes in brain regions were determined. The spatial memory and anxiogenic behaviour of experimental rodents were tested using 'T' maze and Elevated Plus Maze. Our data revealed that the extreme glycemic discrepancies during diabetes and recurrent hypoglycemia lead to altered expression of NRG1, ErbB receptor subtypes, Syntaxin1 and Olig1 that shows association with impaired regeneration, synaptic dysfunction, demyelination, cognitive deficits and anxiety.

The Association Between Second-Line Oral Antihyperglycemic Medication on Types of Dementia in Type 2 Diabetes: A Nationwide Real-World Longitudinal Study

BACKGROUND

There are few reports that evaluated the association between various types of dementia and dual oral therapy with antihyperglycemic medication.

OBJECTIVE

The goal of this study was to investigate the association between treatment of dual antihyperglycemic medication and dementia subclass in type 2 diabetes mellitus using the Korean National Health Insurance System.

METHODS

This study included 701,193 individuals with diabetes prescribed dual oral therapy between 2009 and 2012 from the Korean National Health Insurance Service Database, which were tracked until 2017. All-cause, Alzheimer's (AD) and vascular dementia (VaD) were investigated by dual oral therapy. Adjustments were made for age, sex, income, diabetes duration, hypertension, dyslipidemia, smoking, drinking, exercise, body mass index, glucose level, and estimated glomerular filtration rate.

RESULTS

Dual therapy with metformin (Met) + dipeptidyl peptidase-4 inhibitor (DPP-4i), Met + thiazolidinedione (TZD), and sulfonylurea (SU) + thiazolidinediones (TZD) were significantly associated with all-cause dementia (HR = 0.904, 0.804, and 0.962, respectively) and VaD (HR = 0.865, 0.725, and 0.911, respectively), compared with Met + SU. Met + DPP-4i and Met + TZD were associated with significantly lower risk of AD (HR = 0.922 and 0.812), compared with Met + SU. Dual therapy with TZD was associated with a significantly lower risk of all-cause dementia, AD, and VaD than nonusers of TZD (HR = 0.918, 0.925 and 0.859, respectively).

CONCLUSION

Adding TZD or DPP-4i instead of SU as second-line anti-diabetic treatment may be considered for delaying or preventing dementia. Also, TZD users relative to TZD non-users on dual oral therapy were significantly associated with lower risk of various types of dementia.

Xanthohumol protect cognitive performance in diabetic model rats by inhibiting protein kinase B/nuclear factor kappa-B pathway

Xanthohumol (XN, 2', 4', 4-trihydroxy-6'-methoxy-3'-prenylchalcone), a polyphenol chalcone from hops (Humulus lupulus), has received increasing attention due to its multiple pharmacologic activities. As an active component in beers, its presence has been suggested to be linked to the epidemiologic observation of the beneficial effect of regular beer drinking. But regarding cardiovascular and immunologic effects of polyphenols and ethanol, benefits of beer drinking in patients with diabetes were still in doubt. Diabetes was induced in male Sprague-Dawley rats by administering a high-fat diet and an intraperitoneal 30 mg/kg streptozotocin injection. The animals were treated orally with saline or XN at 50 mg/kg/d for 4 weeks. At the end of the treatment, hippocampus from different groups were collected for biochemical examination. In this study, we found XN inhibit phosphorylation of protein kinase B and nuclear factor kappa-B which was overactivated in diabetic rats, followed by decreased blood glucose and increased body weight. Additionally, XN treatment significantly increased freezing time in a fear memory test. In further research, we found XN increased synaptic plasticity and dendritic spine density, while decreased reactive oxygen species in hippocampus slices from diabetic rats. All these results indicate that XN might be a promising drug to treat diabetic encephalopathy.

Recurrent non-severe hypoglycemia aggravates cognitive decline in diabetes and induces mitochondrial dysfunction in cultured astrocytes

The present study aimed to determine the relationship between astrocytes and recurrent non-severe hypoglycemia (RH)2 -associated cognitive decline in diabetes. RH induced cognitive impairment and neuronal cell death in the cerebral cortex of diabetic mice, accompanied by excessive activation of astrocytes. Levels of the neurotrophins BDNF and GDNF, together with BDNF and GDNF- related signaling, were downregulated by RH. In vitro, recurrent low glucose (RLG)3 impaired cell viability and induced apoptosis of high-glucose cultured astrocytes. Accumulating mitochondrial ROS and dysregulated mitochondrial functions, including abnormal morphology, decreased membrane potential, downregulated ATP levels, and disrupted bioenergetic status, were observed in these cells. SS-31 mediated protection of mitochondrial functions reversed RLG-induced cell viability defects and neurotrophin production. These findings demonstrate that RH induced astrocyte overactivation and mitochondrial dysfunction, leading to astrocyte-derived neurotrophin disturbance, which might contribute to diabetic cognitive decline. Targeting astrocyte mitochondria might represent a neuroprotective therapy for hypoglycemia-associated neurodegeneration in diabetes.

Insulin actions on hypothalamic glucose-sensing neurones

Subsequent to the discovery of insulin 100 years ago, great strides have been made in understanding its function, especially in the brain. It is now clear that insulin is a critical regulator of the neuronal circuitry controlling energy balance and glucose homeostasis. This review focuses on the effects of insulin and diabetes on the activity and glucose sensitivity of hypothalamic glucose-sensing neurones. We highlight the role of electrophysiological data in understanding how insulin regulates glucose-sensing neurones. A brief introduction describing the benefits and limitations of the major electrophysiological techniques used to investigate glucose-sensing neurones is provided. The mechanisms by which hypothalamic neurones sense glucose are discussed with an emphasis on those glucose-sensing neurones already shown to be modulated by insulin. Next, the literature pertaining to how insulin alters the activity and glucose sensitivity of these hypothalamic glucose-sensing neurones is described. In addition, the effects of impaired insulin signalling during diabetes and the ramifications of insulin-induced hypoglycaemia on hypothalamic glucose-sensing neurones are covered. To the extent that it is known, we present hypotheses concerning the mechanisms underlying the effects of these insulin-related pathologies. To conclude, electrophysiological data from the hippocampus are evaluated aiming to provide clues regarding how insulin might influence neuronal plasticity in glucose-sensing neurones. Although much has been accomplished subsequent to the discovery of insulin, the work described in our review suggests that the regulation of central glucose sensing by this hormone is both important and understudied.

Impaired attention in patients with adrenal insufficiency - Impact of unphysiological therapy

Patients with adrenal insufficiency (AI) are treated with glucocorticoid (GC) replacement therapy. Although current GC regimens aim to mimic the physiological circadian rhythm of cortisol secretion, temporary phases of hypo- and hypercortisolism are common undesired effects. Both conditions may lead to impairment in cognitive functioning. At present, little is known about cognitive functioning in patients with AI, especially regarding the effects of dosage and duration of glucocorticoid replacement therapy. There is also little data available comparing the effects of GC therapy on patients with primary (PAI) and secondary (SAI) forms of AI. In this study 40 adults with AI (21 PAI, 19 SAI) substituted with hydrocortisone (HC) and 20 matched healthy controls underwent 10 different neuropsychological tests evaluating memory, executive functioning, attention, psychomotricity and general intellectual ability. Furthermore demographic data, dosage of HC, duration of therapy and co-medication were evaluated. Patients were compared in groups with regard to diagnosis, dosage and duration of therapy. Patients showed worse performance than controls in attention, though patients with PAI and SAI seemed to be equally impaired. There were no limitations in intellectual abilities or memory function. High dosage of HC was found to impair attention, visual-motoric skills and executive functioning while the duration of therapy showed no significant impact on cognitive functions. In conclusion, our study showed that AI patients on HC replacement therapy reveal significant cognitive deficits concerning attention. There was no difference between patients with PAI and SAI. Furthermore, high dosage seems to have a negative impact especially on executive functioning.

Structural Gray and White Matter Differences in Patients With Type 1 Diabetes and Impaired Awareness of Hypoglycemia

CONTEXT

Type 1 diabetes (T1D) is associated with an increased risk of cognitive decline, where severe hypoglycemia (SH) and impaired awareness of hypoglycemia (IAH) may play a role. While there is evidence of a possible association between IAH and brain damage, the potential brain changes remain poorly characterized by magnetic resonance imaging (MRI).

OBJECTIVE

To investigate whether there are structural brain differences in a group of T1D patients with IAH compared with normal awareness of hypoglycemia (NAH).

DESIGN

General practice, population-based, cross-sectional study (July 2018 to July 2019).

SETTING

Endocrinology Department, Hospital Santa Creu i Sant Pau.

PARTICIPANTS

A total of 40 T1D patients (20 each with IAH and NAH) matched for age, sex, T1D duration, and education level.

MAIN OUTCOME MEASURES

Using different neuroimaging techniques, we compared whole-brain gray matter (GM) and white matter (WM) differences. We used voxel-based morphometry and cortical surface area analysis methods to assess GM differences, and fractional anisotropy (FA) to assess WM differences.

RESULTS

Compared with patients with T1D-NAH, patients with T1D-IAH had reduced GM volumes and cortical surface areas, especially in frontal and parietal regions (P < 0.05 corrected), and also showed reduced FA values in major WM tracts. The observed MRI differences correlated with both SH frequency and IAH severity.

CONCLUSIONS

MRI for patients with T1D show that IAH is associated with brain changes involving both GM and WM. Further research is needed to elucidate whether the observed differences are a consequence of increased SH episode frequency and increased IAH severity.

Low-glucose-sensitive TRPC6 dysfunction drives hypoglycemia-induced cognitive impairment in diabetes

Background

Recurrent moderate hypoglycemia (RH), a major adverse effect of hypoglycemic therapy in diabetic patients, is one of the main risk factors for cognitive impairment and dementia. Transient receptor potential canonical channel 6 (TRPC6) is a potential therapeutic target for Alzheimer's disease (AD) and its expression is highly regulated by glucose concentration.

Objective

To investigate whether RH regulates the expression of TRPC6 in brain and whether TRPC6 dysfunction can drive hypoglycemia‐associated cognitive impairment in diabetes, and reveal the underlying mechanism.

Methods

Histological staining, in vivo two‐photon Ca²⁺ imaging, and behavioral tests were used to measure neuronal death, brain network activity, and cognitive function in mice, respectively. High‐resolution respirometry and transmission electron microscope were used to assess mitochondrial structure and function. Intracellular calcium measurement and molecular biology techniques were conducted to uncover the underlying mechanism.

Results

Here, we report that the expression of TRPC6 in hippocampus was specifically repressed by RH in streptozocin‐induced type 1 diabetic mice, but not in nondiabetic mice. TRPC6 knockout directly leads to neuron loss, neuronal activity, and cognitive function impairment under diabetic condition, the degree of which is similar to that of RH. Activation of TRPC6 with hyperforin substantially improved RH‐induced cognitive impairment. Mechanistically, TRPC6 inhibited mitochondrial fission in the hippocampus of diabetic mice undergoing RH episodes by activating adenosine 5‘‐monophosphate‐activated protein kinase, and TRPC6‐mediated cytosolic calcium influx was required for this process. Clinically, dysfunction of TRPC6 was closely associated with cognitive impairment in type 2 diabetic patients with RH.

Conclusions

Our results indicate that TRPC6 is a critical sensitive cation channel to hypoglycemia and is a promising target to prevent RH‐induced cognitive impairment by properly orchestrating the mitochondrial dynamics in diabetic patients.

THE EFFECT OF AN 8-WEEK ANAEROBIC GYMNASTICS TRAINING ON BDNF, VEGF, AND SOME PHYSIOLOGICAL CHARACTERISTICS IN CHILDREN

The purpose of the present study was to observe changes in levels of brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), resting metabolic rate (RMR) and maximum oxygen consumption (VO2max) in the gymnast children after an anaerobic gymnastics training program. Thirty beginner gymnasts aged 8-12 years old were randomly assigned to control (n = 15) and experimental (n = 15) groups. The anaerobic gymnastics training was conducted for 8 weeks, 3 times per a week. Each session lasted 45 minutes: 10 min warm-up, 30 min core exercise, and 5 min cool down. The anthropometric and body composition of subjects were measured and growth factors were measured by using human  BDNF and VEGF PicoKine™ ELISA Kit and analysis was performed using sandwich enzyme-linked immunosorbent assay (Morland et al.) before and after the intervention, and VO2max, maximum heart rate and RMR were measured using a gas analyzer. At the baseline there were not any significant differences between both groups (p>0.05). But in the post-test, a significant difference was observed for BDNF(p=0.02) and VEGF(p=0.018) values between the two groups. Within-group there was a decrease in the value of the maximum heart rate indicator (P<0.05) and VO2max and BDNF increased significantly after an intervention (P<0.05). In conclusion, the results of the present study suggest that anaerobic gymnastic training increases the level of salivary BDNF and VEGF in children. These types of exercises may also improve cardiorespiratory fitness in children.

Effect of diet supplemented with P. ostreatus and L. subnudus on memory index and key enzymes linked with Alzheimer's disease in streptozotocin-induced diabetes rats

Mushrooms have been reported in folklore for the management of Alzheimer's disease (AD) and diabetes with limited scientific prove. This study aims to unravel the effect of diets supplemented with P. ostreatus and L. subnudus on diabetic encephalopathy (DE) in streptozotocin (STZ)-induced diabetic rats. The memory index, brain cholinesterase, arginase activity, and markers for oxidative stress were evaluated. STZ-induced diabetic rats exhibited memory deficits, elevated brain cholinesterase, arginase activity in comparison with nondiabetic rats. Also, markers for oxidative stress were altered in the brain of diabetic rat when compare with nondiabetic rats. Meanwhile, diabetic rats fed with supplemented-diets exhibited better memory index, reduced cholinesterase, arginase activity in comparison with untreated diabetic rats placed on a basal diet. Also, supplemented-diets restored altered markers of oxidative stress. Our findings indicated that P. ostreatus and L. subnudus-supplemented diets could prevent DE. Nevertheless, diets supplemented with L. subnudus had better nutraceutical potential than P. ostreatus. PRACTICAL APPLICATIONS: Diabetes mellitus is one of the most chronic diseases in the world. Also, it is a risk factor for several complications such as cognitive dysfunction, hypertension, and other health issues. Mushrooms are commonly consumed as food or as food supplements in many countries of the world and are a rich source of protein, chitin, and vitamins. Diet supplemented with P. ostreatus and L. subnudus were able to restore memory deficit in diabetic rats, proven to be a dietary intervention in the management of memory deficit linked with diabetes mellitus. Findings from this study show that consumption of P. ostreatus and L. subnudus as food or supplement could help in a diabetic state.

The Effects of Exercise Training on the Brain-Derived Neurotrophic Factor (BDNF) in the Patients with Type 2 Diabetes: A Systematic Review of the Randomized Controlled Trials

Purpose

Glucose dysregulation is one of the distinctive features of type 2 diabetes that is associated with an increased risk of cognitive impairment and dementia. The low concentrations of brain-derived neurotrophic factor (BDNF) are reported in people with insulin resistance, metabolic syndrome, and type 2 diabetes. BDNF can be increased by an adjustment in lifestyle including caloric restriction and exercise training. Studies have reported controversial findings about physical activity and its association with BDNF, but there is no comprehensive conclusions on this issue. The aim of this study was to systematically review the effects of exercise training on BDNF levels in patients with type 2 diabetes.

Methods

The electronic databases of Embase, Pedro, PubMed, Medline, Cochrane Library, as well as the Google Scholar search engine were used to obtain the related data about the role of exercise training on BDNF levels in patients with type 2 diabetes. The search period was set from inception to August 2019. Keywords of "exercise", "training", "physical activity", "brain-derived neurotrophic factor", "type 2 diabetes", and "randomized clinical trials", were used in persian and English. The PEDro scale was used to evaluate the quality of the included articles. Results. Finally, 11 articles (four human and seven animal articles) with medium to high quality were included in the study which 5 articles reported elevation (one human and four animal articles), 4 articles reported a reduction (one human and three animal articles), and 2 articles reported no changes (both of them in human articles) in BDNF level following the exercise training.

Conclusion

Decreased energy intake and increased energy expenditure through exercise training may modulate BDNF levels in patients with type 2 diabetes.

Nicotinamide mononucleotide administration after sever hypoglycemia improves neuronal survival and cognitive function in rats

Hypoglycemia-induced brain injury is a potential complication of insulin therapy in diabetic patients. Severe hypoglycemia triggers a cascade of events in vulnerable neurons that may lead to neuronal death and cognitive impairment even after glucose normalization. Oxidative stress and the activation of poly (ADP-ribose) polymerase-1 (PARP-1) are key events in this cascade. The production of reactive oxygen species (ROS) induces DNA damage and the consequent PARP-1 activation, which depletes NAD⁺ and ATP, resulting in brain injury. One of the key precursors of NAD⁺ is nicotinamide mononucleotide (NMN), which is converted to NAD⁺ and reduces production of ROS. Here we investigated whether NMN could reduce brain injury after severe hypoglycemia. We used a rat model of insulin-induced severe hypoglycemia and injected NMN (500 mmg/kg, i.p., one week) following 30 min of severe hypoglycemia, at the time of glucose administration. One week after severe hypoglycemia, hippocampal long-term potentiation (LTP), an electrophysiogic assay of synaptic plasticity, was examined and neuronal damage was assessed by Hematoxylin-Eosin staining. ROS accumulation, PARP-1 activation, NAD⁺ and ATP levels in hippocampus were also measured. Cognitive function was assessed using the Morris water maze 6 weeks after severe hypoglycemia. The addition of NMN reduced neuron death by 83 ± 3% (P < 0.05) after severe hypoglycemia. The hippocampal LTP was significantly reduced by severe hypoglycemia but showed recovery in the NMN addition group. NMN treatment also attenuated the severe hypoglycemia-induced spatial learning and memory impairment. Mechanically, we showed that NMN administration decreased ROS accumulation, suppressed PARP-1 activation, and restored levels of NAD⁺ and ATP in hippocampus. All these protective effects were reversed by 3-acetylpyridine (3-AP), which generates inactive NAD⁺. In summary, NMN administration following severe hypoglycemia could ameliorate neuronal damage and cognitive impairment caused by severe hypoglycemia. These results suggest that NMN may be a promising therapeutic drug to prevent hypoglycemia-induced brain injury.

Temporal analysis of histopathology and cytokine expression in the rat cerebral cortex after insulin-induced hypoglycemia

Hypoglycemic coma causes neuronal death in the cerebral neocortex; however, its unclear pathogenesis prevents the establishment of preventive measures. Inflammation plays a pivotal role in neuronal damage in the hypoglycemic state; however, the dynamics of glial cell activation or cytokine expression remain unknown. Here, we aimed to elucidate the spatiotemporal morphological changes of microglia and time-course cytokine expression profiles in the rat cerebral cortex after hypoglycemic coma. We performed histopathological and immunohistochemical (Iba1, neuronal nuclei, glial fibrillary acidic protein) analyses in the cingulate cortex and four areas of the neocortex: hindlimb area (HL), parietal cortex area 1 (Par1), parietal cortex area 2 (Par2), and perirhinal cortex (PRh). We measured tumor necrosis factor alpha (TNFα) and interleukin-6 messenger RNA (mRNA) expression by real-time reverse transcriptase-polymerase chain reaction. Necrotic neurons appeared in the neocortex as early as 3 h after hypoglycemic coma, while they were absent in the cingulate cortex. Neuronal nuclei-immunopositive neurons in the HL, Par2, and PRh were significantly less abundant than in the control at day 1. In Iba1 immunostaining, large rod-shaped cells were detected at 3-6 h after hypoglycemia, and commonly observed in the HL, Par2, and PRh. After 6 h, rod-shaped cells were rarely observed; instead, there was a prominent infiltration of hypertrophic and ameboid-shaped cells until day 7. The mRNA expression of TNFα was significantly higher than the control at 3-6 h after hypoglycemia in the neocortex, while it was significantly higher only at 3 h in the cingulate cortex. Our results indicate that early and transient appearance of rod-shaped microglia and persisting high TNFα expression levels characterize inflammatory responses to hypoglycemic neuronal damage in the cerebral neocortex, which might contribute to neuronal necrosis in response to transient hypoglycemic coma.

Hypoglycemia and Dementia Risk in Older Patients with Type 2 Diabetes Mellitus: A Propensity-Score Matched Analysis of a Population-Based Cohort Study

BACKGROUND

Type 2 diabetes mellitus (T2DM) is associated with an increased risk for dementia. The effects of hypoglycemia on dementia are controversial. Thus, we evaluated whether hypoglycemia increases the risk for dementia in senior patients with T2DM.

METHODS

We used the Korean National Health Insurance Service Senior cohort, which includes >10% of the entire senior population of South Korea. In total, 5,966 patients who had ever experienced at least one episode of hypoglycemia were matched with those who had not, using propensity score matching. The risk of dementia was assessed through a survival analysis of matched pairs.

RESULTS

Patients with underlying hypoglycemic events had an increased risk for all-cause dementia, Alzheimer's dementia (AD), and vascular dementia (VaD) compared with those who had not experienced a hypoglycemic event (hazard ratio [HR], 1.254; 95% confidence interval [CI], 1.166 to 1.349; P<0.001 for all-cause dementia; HR, 1.264; 95% CI, 1.162 to 1.375; P<0.001 for AD; HR, 1.286; 95% CI, 1.110 to 1.490; P<0.001 for VaD). According to number of hypoglycemic episodes, the HRs of dementia were 1.170, 1.201, and 1.358 in patients with one hypoglycemic episode, two or three episodes, and more than three episodes, respectively. In the subgroup analysis, hypoglycemia was associated with an increased risk for dementia in both sexes with or without T2DM microvascular or macrovascular complications.

CONCLUSION

Our findings suggest that patients with a history of hypoglycemia have a higher risk for dementia. This trend was similar for AD and VaD, the two most important subtypes of dementia.

Histopathological and immunohistochemical analysis of the cerebral white matter after transient hypoglycemia in rat

Patients with hypoglycemic coma show abnormal signals in the white matter on magnetic resonance imaging. However, the precise pathological changes in the white matter caused by hypoglycemic coma remain unclear in humans and experimental animals. This study aimed to reveal the distribution and time course of histopathological and immunohistochemical changes occurring in the white matter during the early stages of hypoglycemic coma in rats. Insulin-induced hypoglycemic coma of 15–30-min duration was induced in rats, followed by recovery using a glucose solution. Rat brains were collected after 6 and 24 hr and after 3, 5, 7, and 14 days. The brains were submitted for histological and immunohistochemical analysis for neurofilament 200 kDa (NF), myelin basic protein, olig-2, Iba-1, and glial fibrillary acidic protein (GFAP). Vacuolation was observed in the fiber bundles of the globus pallidus on days 1–14. Most of the vacuoles were located in GFAP-positive astrocytic processes or the extracellular space and appeared to be edematous. Additionally, myelin pallor and a decrease in NF-positive signals were observed on day 14. Microgliosis and astrogliosis were also detected. Observations similar to the globus pallidus, except for edema, were noted in the internal capsule. In the corpus callosum, a mild decrease in NF-positive signals, microgliosis, and astrogliosis were observed. These results suggest that after transient hypoglycemic coma, edema and/or degeneration occurred in the white matter, especially in the globus pallidus, internal capsule, and corpus callosum in the early stages.

Therapeutic strategies for ketosis induction and their potential efficacy for the treatment of acute brain injury and neurodegenerative diseases

The therapeutic use of ketone bodies (KB) against acute brain injury and neurodegenerative disorders has lately been suggested by many studies. Several mechanisms responsible for the protective action of KB have been described, including metabolic, anti-inflammatory and epigenetic. However, it is still not clear whether a specific mechanism of action can be associated with a particular neurological disorder. Different strategies to induce ketosis including the ketogenic diet (KD), caloric restriction (CR), intermittent fasting (IF), as well as the administration of medium chain triglycerides (MCTs), exogenous ketones or KB derivatives, have been used in animal models of brain injury and in humans. They have shown different degrees of success to prevent neuronal damage, motor alterations and cognitive decline. However, more investigation is needed in order to establish safe protocols for clinical application. Throughout the present review, we describe the different approaches that have been used to elevate blood KB and discuss their effectiveness considering their advantages and limitations, as tested in models of brain injury, neurodegeneration and clinical research. We also describe the mechanisms of action of KB in non-pathologic conditions and in association with their protective effect against neuronal damage in acute neurological disorders and neurodegenerative diseases.