Potential Biochemical Mechanisms of Brain Injury in Diabetes Mellitus

Effect of glycemic control on cognitive function in patients with type 1 diabetes mellitus: a systematic review and meta-analysis

BACKGROUND

It is controversial whether the level of glycemic control in patients with type 1 diabetes mellitus (T1DM) correlates with reduced cognitive function. This study explored the influence of glycemic management quality on cognitive function in T1DM patients by examining the association between glycemic control level and impaired cognitive function.

METHODS

The electronic databases PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure, China Science and Technology Journal database, Wanfang database, and China Biology Medicine disc database were systematically searched to identify eligible studies published before January 2023. Search, selection, and data extraction were performed by two independent reviewers. RevMan 5.4 software was used for meta-analysis, and standardized mean difference (SMD) between groups was calculated.

RESULTS

Six studies involving 351 patients with T1DM were included in this study. Compared with T1DM subjects with good glycemic control, those with poor glycemic control performed worse in full-scale intellectual quotient (P = 0.01, SMD = -0.79, 95%CI = -1.42 to -0.17), but no significant differences were observed in verbal intellectual quotient (P = 0.08, SMD = -1.03, 95%CI = -2.20 to 0.13), memory (P = 0.05, SMD = -0.41, 95%CI = -0.82 to 0.00), and attention (P = 0.23, SMD = -0.26, 95%CI = -0.69 to 0.16).

CONCLUSIONS

T1DM patients with suboptimal glycemic control may have a worse cognitive function, mainly focusing on the full-scale intellectual quotient. The current study highlights the significance of maintaining satisfactory glycemic control in T1DM patients to improve their health status and quality of life. Standardized tests should be employed in clinical neuropsychological practice to provide early and complete cognitive assessment of individuals with poor glycemic control.

SYSTEMATIC REVIEW REGISTRATION

The study protocol has been registered in the PROSPERO database (CRD42023390456).

Increased Apoptosis in Subcortical Regions of The Visual Pathway in Offspring Born to Diabetic Rats

OBJECTIVE

Diabetes in pregnancy is a prevalent disease that can affect the central nervous system of the fetus by hyperglycemia. This study aimed to investigate the impact of maternal diabetes on neuronal apoptosis in the superior colliculus (SC) and the lateral geniculate nucleus (LGN) in male neonates born to diabetic mothers.

MATERIALS AND METHODS

In this experimental study, female adult rats were separated into three groups: control, diabetic (induced using an intraperitoneal injection of streptozotocin), and insulin-treated diabetic [diabetes controlled by subcutaneous neutral protamine hagedorn (NPH)-insulin injection]. Male neonates from each group were euthanized on 0, 7, and 14 postnatal days (P0, P7, and P14, respectively), and apoptotic cells were identified using TUNEL staining.

RESULTS

The numerical density per unit area (NA) of apoptotic cells was significantly higher in SC and the dorsal LGN (dLGN) in neonates born to the diabetic rats compared to the control group at P0, P7, and P14. However, insulin treatment normalized the number of apoptotic cells.

CONCLUSION

This study demonstrated that maternal diabetes increased apoptosis in dLGN and SC of male neonates at P0, P7, and P14.

Neuroprotective Effect of Ponicidin Alleviating the Diabetic Cognitive Impairment: Regulation of Gut Microbiota

Cognitive impairment is a major complication of diabetes mellitus, which is caused by constitutive hyperglycaemia. Ponicidin is a diterpenoid isolated from a Chinese traditional herb (Rabdosia rubescens) and demonstrates the various pharmacological effects. The goal of this study was to scrutinise the neuroprotective effect of ponicidin against diabetic nephropathy (DN) induced by streptozotocin (STZ). Intraperitoneal administration of STZ (55 mg/kg) was used for the induction of diabetes and rats were received oral administration of ponicidin (5, 10 and 15 mg/kg) until 28 days. The body weight, food intake, water intake and blood glucose level were assessed at regular time interval. Plasma insulin level, antioxidant, inflammatory cytokines, apoptosis marker and faecal gut microbiota compositions were estimated. DN-induced group rats revealed the augmented glucose level, water intake, food intake and reduced body weight. Ponicidin significantly (P < 0.001) repressed the glucose level and water food intake and improved the body weight and plasma insulin. Ponicidin significantly (P < 0.001) repressed the malonaldehyde (MDA) level and boosted the level of glutathione (GSH), glutathione reductase (GR) and superoxide dismutase (SOD) in the brain and serum level. Ponicidin significantly (P < 0.001) repressed the level of interleukin-1β (IL-1β), tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) and enhanced the level of interleukin-4 (IL-4), interleukin-10 (IL-10) in the brain and serum level. DN group rats exhibited the enhanced relative abundance of Firmicutes, along with enhancing the Firmicutes/Bacteroidetes ratio and repressing the Bacteroidetes relative abundance. Ponicidin effectually restored the relative abundance of Allobaculum, Lactobacillus and Ruminococcus genera. Our findings clearly demonstrated that ponicidin has a neuroprotective effect against diabetic cognitive impairment through modulating the gut microbiome.

Large vessel occlusion stroke outcomes in diabetic vs. non-diabetic patients with acute stress hyperglycemia

Objective

This study assesses whether stress-induced hyperglycemia is a predictor of poor outcome at 3 months for patients with acute ischemic stroke (AIS) treated by endovascular treatment (EVT) and impacted by their previous blood glucose status.

Methods

This retrospective study collected data from 576 patients with AIS due to large vessel occlusion (LVO) treated by EVT from March 2019 to June 2022. The sample was composed of 230 and 346 patients with and without diabetes mellitus (DM), respectively, based on their premorbid diabetic status. Prognosis was assessed with modified Rankin Scale (mRS) at 3-month after AIS. Poor prognosis was defined as mRS>2. Stress-induced hyperglycemia was assessed by fasting glucose-to-glycated hemoglobin ratio (GAR). Each group was stratified into four groups by quartiles of GAR (Q1-Q4). Binary logistic regression analysis was used to identify relationship between different GAR quartiles and clinical outcome after EVT.

Results

In DM group, a poor prognosis was seen in 122 (53%) patients and GAR level was 1.27 ± 0.44. These variables were higher than non-DM group and the differences were statistically significant (p < 0.05, respectively). Patients with severe stress-induced hyperglycemia demonstrated greater incidence of 3-month poor prognosis (DM: Q1, 39.7%; Q2, 45.6%; Q3, 58.6%; Q4, 68.4%; p = 0.009. Non-DM: Q1, 31%; Q2, 32.6%; Q3, 42.5%; Q4, 64%; p < 0.001). However, the highest quartile of GAR was independently associated with poor prognosis at 3 months (OR 3.39, 95% CI 1.66-6.96, p = 0.001), compared to the lowest quartile in non-DM patients after logistic regression. This association was not observed from DM patients.

Conclusion

The outcome of patients with acute LVO stroke treated with EVT appears to be influenced by premorbid diabetes status. However, the poor prognosis at 3-month in patients with DM is not independently correlated with stress-induced hyperglycemia. This could be due to the long-term damage of persistent hyperglycemia and diabetic patients' adaptive response to stress following acute ischemic damage to the brain.

Expression of GABAAα1, GABAB1, and mGluR2 receptors in the lateral geniculate body of male neonates born to diabetic rats

Objectives

Diabetes during gestation is one of the most common pregnancy complications and has adverse effects on offspring, including a negative impact on the offspring's central nervous system (CNS). Diabetes is a metabolic disease associated with visual impairment. Due to the importance of the lateral geniculate body (LGB) in the visual pathway, the present study examined the effect of maternal diabetes on the expression of gamma-aminobutyric acid (GABA_Aα1 and GABA_B1) and metabotropic Glutamate (mGlu2) receptors in the LGB of male neonates of diabetic rats.

Materials and Methods

Diabetes was induced in female adult rats by a single intraperitoneal dose of streptozotocin (STZ) 65 (mg/kg). In the Insulin-treated diabetic rats, diabetes was controlled by subcutaneous NPH-insulin injection daily. After mating and delivery, male offspring were killed by carbon dioxide gas inhalation at P0, P7, and P14 (postnatal days 0, 7, and 14). The expression of GABA_Aα1, GABA_B1, and mGluR2 in the LGB of male neonates was determined using the immunohistochemistry (IHC) method.

Results

The expression of GABA_Aα1 and GABA_B1 was significantly reduced, whereas the expression of mGluR2 was markedly increased in the diabetic group compared with the control and insulin-treated groups at P0, P7, and P14.

Conclusion

The results of the present study showed that induction of diabetes altered the expression of GABA_Aα1, GABA_B1, and mGluR2 in the LGB of male neonates born to diabetic rats at P0, P7, and P14. Moreover, insulin treatment could reverse these effects of diabetes.

Diabetes and associated cognitive disorders: Role of the Hypothalamic-Pituitary Adrenal axis

Both diabetes types, types 1 and 2, are associated with cognitive impairments. Each period of life is concerned, and this is an increasing public health problem. Animal models have been developed to investigate the biological actors involved in such impairments. Many levels of the brain function (structure, volume, neurogenesis, neurotransmission, behavior) are involved. In this review, we detailed the part potentially played by the Hypothalamic-Pituitary Adrenal axis in these dysfunctions. Notably, regulating glucocorticoid levels, their receptors and their bioavailability appear to be relevant for future research studies, and treatment development.

A Tale of Two Diseases: Exploring Mechanisms Linking Diabetes Mellitus with Alzheimer's Disease

Dementias, including the type associated with Alzheimer's disease (AD), are on the rise worldwide. Similarly, type 2 diabetes mellitus (T2DM) is one of the most prevalent chronic diseases globally. Although mechanisms and treatments are well-established for T2DM, there remains much to be discovered. Recent research efforts have further investigated factors involved in the etiology of AD. Previously perceived to be unrelated diseases, commonalities between T2DM and AD have more recently been observed. As a result, AD has been labeled as "type 3 diabetes". In this review, we detail the shared processes that contribute to these two diseases. Insulin resistance, the main component of the pathogenesis of T2DM, is also present in AD, causing impaired brain glucose metabolism, neurodegeneration, and cognitive impairment. Dysregulation of insulin receptors and components of the insulin signaling pathway, including protein kinase B, glycogen synthase kinase 3β, and mammalian target of rapamycin are reported in both diseases. T2DM and AD also show evidence of inflammation, oxidative stress, mitochondrial dysfunction, advanced glycation end products, and amyloid deposition. The impact that changes in neurovascular structure and genetics have on the development of these conditions is also being examined. With the discovery of factors contributing to AD, innovative treatment approaches are being explored. Investigators are evaluating the efficacy of various T2DM medications for possible use in AD, including but not limited to glucagon-like peptide-1 receptor agonists, and peroxisome proliferator-activated receptor-gamma agonists. Furthermore, there are 136 active trials involving 121 therapeutic agents targeting novel AD biomarkers. With these efforts, we are one step closer to alleviating the ravaging impact of AD on our communities.

The accentuation in post-traumatic stress disorder-like symptoms induced by diabetes in rats is not associated with a further increase in astrocyte activation in the hippocampus

Individuals with post-traumatic stress disorder (PTSD) show increased rates of several serious metabolic diseases. However, little is known about pre-existing metabolic diseases and the development of PTSD. Therefore, we aimed to evaluate the course of post-traumatic stress disorder (PTSD) development in rats with preexisting diabetes. In addition, we quantified glial fibrillary acidic protein (GFAP) in the hippocampus of the experimental animals. For this, we used male Wistar rats and divided them into two groups: saline and alloxan (150 mg/Kg, i.p.). The animals were weighed, and plasma glucose was measured after 48 h of diabetes induction by alloxan. The animals were either exposed to inescapable footshocks or not, followed by social isolation. After 14 days, the animals were re-exposed to the box, and the freezing time was evaluated for 10 min. Over the following days, the animals were tested on the open field, social interaction and forced swimming tests. In another group of animals, elevated plus maze and object recognition tests were performed. Our results demonstrated that animals with diabetes had more pronounced PTSD-like symptoms as a reduction in social interaction, an increase in immobility time in forced swimming, a reduction in permanence in the open arms of the elevated plus maze, and a deficit in the object recognition index more accentuated. However, this did not reflect astrocyte activation in the hippocampus. In conclusion, diabetes accentuates post-traumatic stress disorder-like symptoms but not astrocyte activation in the hippocampus.

ZiBuPiYin Recipe Prevented and Treated Cognitive Decline in ZDF Rats With Diabetes-Associated Cognitive Decline via Microbiota-Gut-Brain Axis Dialogue

Gut microbiota is becoming one of the key determinants in human health and disease. Shifts in gut microbiota composition affect cognitive function and provide new insights for the prevention and treatment of neurological diseases. Diabetes-associated cognitive decline (DACD) is one of the central nervous system complications of type 2 diabetes mellitus (T2DM). ZiBuPiYin recipe (ZBPYR), a traditional Chinese medicine (TCM) formula, has long been used for the treatment of T2DM and prevention of DACD. However, the contribution of ZBPYR treatment to the interaction between the gut microbiota and metabolism for preventing and treating DACD remains to be clarified. Here, we investigate whether the gut microbiota plays a key role in ZBPYR-mediated prevention of DACD and treatment of T2DM via incorporating microbiomics and metabolomics, and investigate the links between the microbiota-gut-brain axis interaction and the efficacy of ZBPYR in ZDF rats. In the current study, we found that ZBPYR treatment produced lasting changes in gut microbiota community and metabolites and remotely affected hippocampus metabolic changes, thereby improving memory deficits and reversing β-amyloid deposition and insulin resistance in the brain of ZDF rats from T2DM to DACD. This may be related to a series of metabolic changes affected by gut microbiota, including alanine, aspartic acid, and glutamic acid metabolism; branched-chain amino acid metabolism; short-chain fatty acid metabolism; and linoleic acid/unsaturated fatty acid metabolism. In summary, this study demonstrates that prevention and treatment of DACD by ZBPYR partly depends on the gut microbiota, and the regulatory effects of bacteria-derived metabolites and microbiota-gut-brain axis are important protective mechanisms of ZBPYR.

Serum oxidized low density lipoprotein serves as a mediator for the inverse relationship between serum d-ribose and cognitive performance in type 2 diabetic patients

Chronic hyperglycemia, proinflammatory state, and oxidative stress are implicated in the etiology of mild cognitive impairment (MCI) in type 2 diabetes mellitus (T2DM) patients. However, roles and mechanisms of the diabetes-related dys-regulation of serum d-ribose in the pathogenesis remain unclear. This study was to assess: 1) changes of serum d-ribose in T2DM patients with or without MCI compared with healthy controls; and 2) associations of serum d-ribose with key biomarkers of ribosylation [advanced glycation end products (AGEs) and receptor for advanced glycation end products (RAGE)], inflammation (IL-6 and NF-κB) and oxidative stress [oxidized low density lipoproteins (ox-LDL), advanced oxidation protein products (AOPP), total thiol, and non-protein thiol)]. A cross-sectional study was conducted with 1564 initial participants including 362 T2DM patients. Based on their fasting blood glucose concentrations and Montreal cognitive assessment (MoCA) scores, we selected 89 participants and divided them into three groups: 27 healthy controls, 26 T2DM patients with normal cognition, 36 T2DM patients with MCI. All participants were gone through standard anthropometric tests and biochemical examinations of serum clinical profiles and concentrations of d-ribose, AGE, RAGE, IL-6, NF-κB, ox-LDL, AOPP, total thiol, and non-protein thiol. Serum concentrations of d-ribose, ox-LDL, and AOPP were greater (P < 0.05) in the T2DM-MCI patients than that in the T2DM or controls. Serum d-ribose exhibited a positive correlation (P < 0.05) with serum AGEs, RAGE, ox-LDL, and fasting blood glucose, but a negative correlation (P < 0.05) with MoCA score. This negative relationship remained (P < 0.05) after adjusting various covariates, and was found to be mediated (P < 0.05) by serum ox-LDL. In conclusion, our results reveal serum ox-LDL as a potential mediator for the inverse relationship between the elevation of serum d-ribose concentration and the decline of cognitive performance in the T2DM-MCI patients.