Glucose metabolic alterations in hippocampus of diabetes mellitus rats and the regulation of aerobic exercise

Function and therapeutic value of astrocytes in diabetic cognitive impairment

Diabetic cognitive impairment (DCI) is a complex complication of diabetes in the central nervous system, and its pathological mechanism is still being explored. Astrocytes are abundant glial cells in central nervous system that perform diverse functions in health and disease. Accumulating excellent research has identified astrocyte dysfunction in many neurodegenerative diseases (such as Alzheimer's disease, aging and Parkinson's disease), and summarized and discussed its pathological mechanisms and potential therapeutic value. However, the contribution of astrocytes to DCI has been largely overlooked. In this review, we first systematically summarized the effects and mechanisms of diabetes on brain astrocytes, and found that the diabetic environment (such as hyperglycemia, advanced glycation end products and cerebral insulin resistance) mediated brain reactive astrogliosis, which was specifically reflected in the changes of cell morphology and the remodeling of signature molecules. Secondly, we emphasized the contribution and potential targets of reactive astrogliosis to DCI, and found that reactive astrogliosis-induced increased blood-brain barrier permeability, glymphatic system dysfunction, neuroinflammation, abnormal cell communication and cholesterol metabolism dysregulation worsened cognitive function. In addition, we summarized effective strategies for treating DCI by targeting astrocytes. Finally, we discuss the application of new techniques in astrocytes, including single-cell transcriptome, in situ sequencing, and prospected new functions, new subsets and new targets of astrocytes in DCI.

Sex Modifies the Impact of Type 2 Diabetes Mellitus on the Murine Whole Brain Metabolome

Type 2 diabetes mellitus (T2DM) leads to the development of cardiovascular diseases, cognitive impairment, and dementia. There are sex differences in the presentation of T2DM and its associated complications. We sought to determine the impact of sex and T2DM on the brain metabolome to gain insights into the underlying mechanisms of T2DM-associated cognitive complications. Untargeted metabolomic analysis was performed, using liquid chromatography-mass spectrometry, on whole brain tissue from adult male and female db/db mice (a T2DM model) compared to wild-type (WT) C57Bl6/J mice. Regardless of sex, T2DM increased free fatty acids and decreased acylcarnitines in the brain. Sex impacted the number (103 versus 65 in males and females, respectively), and types of metabolites shifted by T2DM. Many choline-containing phospholipids were decreased by T2DM in males. Female-specific T2DM effects included changes in neuromodulatory metabolites (γ-aminobutyric acid, 2-linoleoyl glycerol, N-methylaspartic acid, and taurine). Further, there were more significantly different metabolites between sexes in the T2DM condition as compared to the WT controls (54 vs. 15 in T2DM and WT, respectively). T2DM alters the murine brain metabolome in both sex-independent and sex-dependent manners. This work extends our understanding of brain metabolic sex differences in T2DM, cognitive implications, and potential sex-specific metabolic therapeutic targets.

The effects of endurance exercise and metformin on memory impairment caused by diabetes

OBJECTIVES

Diabetes has a negative effect on learning and memory performance, and it is a risk factor for Alzheimer's disease and dementia development. The present study aims to investigate the effects of two kinds of endurance exercise including high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) as well as metformin on impaired memory and learning related to streptozotocin (STZ) induced diabetes in rats.

METHODS

Forty adult male rats (250 ± 20 g weight) were divided into five groups (n=8), including control, diabetic, as well as diabetic rats treated with metformin (300 mg/kg), and HIIT (20 m/min), and MICT (15 m/min) exercises. Diabetes was induced by STZ (60 mg/kg, i.p.). Serum glucose concentration and oxidative stress markers (SOD, CAT, thiol, and MDA) in the cortex and hippocampus were determined by colorimetric assay. Behavioral tests were performed with a passive avoidance test.

RESULTS

The diabetic groups treated with metformin and both HIIT, and MICT exercises improved the latency and the staying time in the darkroom and lightroom. The entrance frequency into the darkroom also was restored (p<0.01-p<0.001). In both HIIT and MICT exercises as well as metformin groups the oxidative stress induced by diabetes has been reversed and attenuation of the serum glucose level has been observed compared to non-treated diabetic ones (p<0.05-p<0.001).

CONCLUSIONS

The results of the present study revealed both HIIT and MICT exercises had protective effects against oxidative stress and behavioral impairments induced by diabetes and these effects were comparable to the effects of metformin.

"Adjust Zang and arouse spirit" electroacupuncture ameliorates cognitive impairment by reducing endoplasmic reticulum stress in db/db mice

Introduction

Diabetic cognitive impairment (DCI) is a chronic complication of the central nervous system (CNS) caused by diabetes that affects learning and memory capacities over time. Recently, acupuncture has been shown to improve cognitive impairment in streptozotocin-induced diabetic rats. However, the effects of electroacupuncture on DCI and its underlying mechanism have not yet been elucidated in detail.

Methods

In this study, we used db/db mice as DCI animal models which showed low cognitive, learning and memory functions. Electroacupuncture significantly ameliorated DCI, which is reflected by better spatial learning and memory function using behavioral tests. The db/db mice with cognitive impairment were randomly divided into a model group (Mod) and an electroacupuncture treatment group (Acup), while db/m mice were used as a normal control group (Con). First, the mice were subjected to behavioural tests using the Morris water maze (MWM), and body weight, blood glucose, insulin, triglycerides (TG) and total cholesterol (TC) were observed; HE, Nissl, and TUNEL staining were used to observe the morphological changes and neuronal apoptosis in the mice hippocampus; Finally, Western blot and rt-PCR were applied to detect the essential proteins and mRNA of ERS and insulin signalling pathway, as well as the expression levels of Tau and Aβ.

Results

Electroacupuncture significantly ameliorated DCI, which is reflected by better spatial learning and memory function using behavioral tests. Moreover, electroacupuncture attenuated diabetes-induced morphological structure change, neuronal apoptosis in the hippocampus of db/db mice. Our results revealed that electroacupuncture could regulate the expression levels of Tau and Aβ by improving hippocampal ERS levels in db/db mice, inhibiting JNK activation, attenuating IRS1 serine phosphorylation, and restoring normal transduction of the insulin signaling pathway.

Discussion

In summary, ERS and insulin signaling pathway paly causal roles in DCI development. Electroacupuncture can significantly alleviate the pathogenesis of DCI, improve mice's learning and memory ability, and improve cognitive dysfunction. This study adds to our understanding of the effect of acupuncture on DCI and opens the door to further research on DCI.

Hepatic Metabolic Profiling of Lifelong Exercise Training Rats

Regular physical exercise has been investigated as a primary preventive measure of several chronic diseases and premature death. Moreover, it has been shown to synchronize responses across multiple organs. In particular, hepatic tissue has proven to be a descriptive matrix to monitor the effect of physical activity. In this study, we performed an untargeted metabolomics-based analysis of hepatic tissue extracts from rats that have undergone either lifelong or chronic exercise training. For this purpose, 56 hepatic samples were collected and were analyzed by UHPLC-TOF-MS in negative ionization mode. This approach involved untargeted metabolite detection on hepatic tissue extracts accompanied by an in-house retention time/accurate mass library enabling confident metabolite identification. Unsupervised (PCA) and supervised (OPLS-DA) multivariate analysis showed significant metabolic perturbation on a panel of 28 metabolites, including amino acids, vitamins, nucleotides, and sugars. The training regime employed in this study resulted in a probable acceleration of the bioenergetic processes (glycolysis, glycogen metabolism), promoted catabolism of purines, and supplied biosynthetic precursors via the pentose phosphate pathway and pentose and glucuronate interconversions. Overall, the applied methodology was able to discriminate the different training schedules based on the rat liver metabolome.

Lactate Is Answerable for Brain Function and Treating Brain Diseases: Energy Substrates and Signal Molecule

Research to date has provided novel insights into lactate's positive role in multiple brain functions and several brain diseases. Although notable controversies and discrepancies remain, the neurobiological role and the metabolic mechanisms of brain lactate have now been described. A theoretical framework on the relevance between lactate and brain function and brain diseases is presented. This review begins with the source and route of lactate formation in the brain and food; goes on to uncover the regulatory effect of lactate on brain function; and progresses to gathering the application and concentration variation of lactate in several brain diseases (diabetic encephalopathy, Alzheimer's disease, stroke, traumatic brain injury, and epilepsy) treatment. Finally, the dual role of lactate in the brain is discussed. This review highlights the biological effect of lactate, especially L-lactate, in brain function and disease studies and amplifies our understanding of past research.

Exercise and Urtica dioica extract ameliorate hippocampal insulin signaling, oxidative stress, neuroinflammation, and cognitive function in STZ-induced diabetic rats

INTRODUCTION

Diabetes mellitus is related to cognitive impairments and molecular abnormalities of the hippocampus. A growing body of evidence suggests that Urtica dioica (Ud) and exercise training (ET) have potential therapeutic effects on diabetes and its related complications. Therefore, we hypothesized that the combined effect of exercise training (ET) and Ud might play an important role in insulin signaling pathway, oxidative stress, neuroinflammation, and cognitive impairment in diabetic rats.

METHODS

Forty animals were divided into five groups (N = 8): healthy-sedentary (H-sed), diabetes-sedentary (D-sed), diabetes-exercise training (D-ET), diabetes-Urtica dioica (D-Ud), diabetes-exercise training-Urtica dioica (D-ET-Ud). Streptozotocin (STZ) (Single dosage; 45 mg/kg, i.p.) was used to induce diabetes. Then, ET (moderate intensity/5day/week) and Ud extract (50 mg/kg, oral/daily) were administered for six weeks. We also investigated the effects of ET and Ud on cognitive performance (assessed through Morris Water Maze tests), antioxidant capacity, and lipid peroxidation markers in hippocampus. Furthermore, we measured levels of insulin sensitivity and signaling factors (insulin-Ins, insulin receptor-IR and insulin-like growth factor-1 receptor-IGF-1R), and neuroinflammatory markers (IL-1 β, TNF-α). This was followed by TUNEL assessment of the apoptosis rate in all regions of the hippocampus.

RESULTS

D-sed rats compared to H-sed animals showed significant impairments (P < 0.001) in hippocampal insulin sensitivity and signaling, oxidative stress, neuroinflammation, and apoptosis, which resulted in cognitive dysfunction. Ud extract and ET treatment effectively improved these impairments in D-ET (P < 0.001), D-Ud (P < 0.05), and D-ET-Ud (P < 0.001) groups compared to D-sed rats. Moreover, diabetes mediated hippocampal oxidative stress, neuroinflammation, insulin signaling deficits, apoptosis, and cognitive dysfunction was further reversed by chronic Ud+ET administration in D-ET-Ud rats (P < 0.001) compared to D-sed animals.

CONCLUSIONS

Ud extract and ET ameliorate cognitive dysfunction via improvement in hippocampal oxidative stress, neuroinflammation, insulin signaling pathway, and apoptosis in STZ-induced diabetic rats. The results of this study provide new experimental evidence for using Ud+ET in the treatment of hippocampal complications and cognitive dysfunction caused by diabetes.

The metabolic changes in the hippocampus of an atherosclerotic rat model and the regulation of aerobic training

Atherosclerosis has been associated with the progression of cognitive impairment and the effect of metabolic changes in the brain on cognitive function may be pronounced. The aim is to reveal the metabolic changes during atherosclerosis and clarify the possible role of exercise in regulating hippocampal metabolism. Hence, A rat model of atherosclerosis was established by high-fat diet feeding in combination with vitamin D3 intraperitoneal injection, then 4 weeks of aerobic exercise was conducted. Metabolomics based on GC-MS was applied to detect small molecules metabolites and western blot was used to detect the concentration of enzymes involved in metabolic changes in rat hippocampus. Compared to the control group, metabolites including xylulose 5-phosphate, threonine, succinate, and nonanoic acid were markedly elevated, whereas methyl arachidonic acid and methyl stearate decreased in the AS group, accompanied by a raised concentration of aldose reductase and glucose 6-phosphate dehydrogenase as well as a declined concentration of acetyl-CoA carboxylase and fatty acid synthase. After 4 weeks' aerobic exercise, the levels of succinic acid, branched chain amino acids, nonanoic acid, desmosterol, and aldose reductase decreased, whereas methyl arachidonic acid, methyl stearate, and glyceraldehyde-3-phosphate elevated in the hippocampus of the TAS group in comparison with the AS group. These results suggest that atherosclerosis could cause a severe metabolic disturbance, and aerobic exercise plays an important role in regulating atherosclerosis-induced disorder of glucose metabolism in the hippocampus.

Lowered levels of nicotinic acetylcholine receptors and elevated apoptosis in the hippocampus of brains from patients with type 2 diabetes mellitus and db/db mice

Cognitive impairment caused by diabetes has been gradually recognized. Generally, nicotinic acetylcholine receptors (nAChRs) play an important role in the pathogenesis in dementia disorders including Alzheimer's disease (AD). However, the expression of nAChRs in the brains of type 2 diabetes mellitus (T2DM) is unexplored. This study explored the alterations of nAChRs in the postmortem brains of patients with T2DM and brains of db/db mice. Morris water maze test was used to appraise the ability of spatial learning and memory; Western blotting and RT-qPCR were performed to determine the expressions of target protein and mRNA, respectively; TUNEL was used to detect the apoptosis of neurons. We found that the protein levels of nAChR α7 and α4 subunits were significantly decreased and the apoptosis rates in neurons elevated in the hippocampus of T2DM patients and db/db mice as comparison to controls. Furthermore, the db/db mice exhibited the impaired cognition, the elevated level of pro-apoptotic protein and the reduced level of anti-apoptotic and synaptic proteins. This study shows the lowered level of nAChR α7 and α4 subunits and the elevated apoptosis in the hippocampus of T2DM patients and db/db mice, which might help explain the impaired cognition in T2DM.

Urinary Metabolomics Study of the Intervention Effect of Hypoglycemic Decoction on Type 2 Diabetes Mellitus Rats Model

The hypoglycemic decoction (HD) is a traditional Chinese medicine (TCM) preparation for the treatment of diabetes mellitus (DM), with a remarkable therapeutic effect. However, its mechanism of action is still unclear at the metabolic level. In this study, the biochemical markers from type 2 DM (T2DM) rats, induced by a high-sugar and high-fat diet combined with streptozotocin (STZ), were detected. The metabolomics-based analysis using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) was conducted to evaluate urine samples from control, model, metformin, and HD groups. After oral administration of HD for 28 days, the general state, weight, fasting blood glucose (FBG), blood lipid level, oral glucose tolerance test (OGTT), fasting insulin (FINS), insulin sensitivity index (ISI), and homeostasis model assessment of insulin resistance (HOMA-IR) were significantly improved (P < 0.01). The western blotting showed that HD can enhance the protein expression of glucose transporter 4 (GLUT4) and adenosine monophosphate-activated protein kinase (AMPK). The metabolomics results revealed that after treatment with HD, the levels of L-carnitine, 1-methyladenosine, 1-methylhistamine, and 3-indoleacrylic acid were upregulated and the levels of riboflavin, phenylalanine, atrolactic acid, 2-oxoglutarate, citrate, isocitrate, cortisol, and glucose were downregulated. The main mechanism may be closely related to the regulation of the tricarboxylic acid (TCA) cycle, phenylalanine metabolism, glyoxylate metabolism, and dicarboxylate metabolism. Additionally, it was also found that HD can regulate the protein expression of GLUT4 and AMPK to interfere with TCA cycle and carbohydrate metabolism to treat T2DM.

Changes in whole metabolites after exenatide treatment in overweight/obese polycystic ovary syndrome patients

OBJECTIVE

Exenatide is a new agent for diabetes therapy, and its use in polycystic ovary syndrome (PCOS) has gradually increased; however, the clinical benefit and metabolic improvement need further evidence. This research aimed to study the changes in whole metabolites before and after exenatide treatment in overweight/obese PCOS patients to gain a better understanding of exenatide for the treatment of PCOS.

METHODS

Sixty-seven women, including 32 with PCOS and 35 age-matched controls, were recruited. The metabolite changes were detected with nontargeted gas chromatography-tandem mass spectrometry (NTGC-MS) before and after exenatide treatment, and changes in clinical biochemical characteristics were also observed.

RESULTS

A total of 62 metabolites were differentially expressed between the healthy and PCOS groups, and 31 differentially expressed metabolites were detected before and after exenatide treatment. Abnormal lipid metabolism and amino acid metabolism were the main metabolic disorders. Exenatide improved lipid and amino acid metabolism, especially amino acid metabolites. Three types of branched-chain amino acids (valine, leucine and isoleucine), two types of aromatic amino acids (phenylalanine and tyrosine) and lysine are important potential metabolites for the therapeutic efficacy of exenatide. Many abnormal metabolic disorders are related to insulin resistance, oxidative stress and even ovulatory dysfunction. Moreover, in this small sample clinical study, we also found that exenatide improved insulin sensitivity, reduced body weight and improved glycolipid metabolism in PCOS.

CONCLUSIONS

NTGC-MS-based metabolic pathway analysis revealed that exenatide has a beneficial effect on overweight/obese PCOS patients by regulating metabolic disorders, especially amino acid disorders.

Mechanisms of Aerobic Exercise Upregulating the Expression of Hippocampal Synaptic Plasticity-Associated Proteins in Diabetic Rats

We investigated the effects of aerobic exercise on the expression of hippocampal synaptic plasticity-associated proteins in rats with type 2 diabetes and their possible mechanisms. A type 2 diabetes rat model was established with 8 weeks of high-fat diet combined with a single intraperitoneal injection of streptozotocin (STZ). Then, a 4-week aerobic exercise intervention was conducted. Memory performance was measured with Y maze tests. The expression and activity of synaptic plasticity-associated proteins and of proteins involved in the PI3K/Akt/mTOR, AMPK/Sirt1, and NFκB/NLRP3/IL-1β signaling pathways were evaluated by western blot. Our results show that aerobic exercise promotes the expression of synaptic plasticity-associated proteins in the hippocampus of diabetic rats. Aerobic exercise also activates the PI3K/Akt/mTOR and AMPK/Sirt1 signaling pathways and inhibits the NFκB/NLRP3/IL-1β signaling pathway in the hippocampus of diabetic rats. Therefore, modulating the PI3K/Akt/mTOR, AMPK/Sirt1, and NFκB/NLRP3/IL-1β signaling pathways is probably the mechanism of aerobic exercise upregulating the expression of hippocampal synaptic plasticity-associated proteins in diabetic rats.