The role of glucose on cognition, risk of dementia, and related biomarkers in individuals without type 2 diabetes mellitus or the metabolic syndrome: a systematic review of observational studies

Hepatopancreatic metabolic disorders and their implications in the development of Alzheimer's disease and vascular dementia

Dementia has been faced with significant public health challenges and economic burdens that urges the need to develop safe and effective interventions. In recent years, an increasing number of studies have focused on the relationship between dementia and liver and pancreatic metabolic disorders that result in diseases such as diabetes, obesity, hypertension and dyslipidemia. Previous reports have shown that there is a plausible correlation between pathologies caused by hepatopancreatic dysfunctions and dementia. Glucose, insulin and IGF-1 metabolized in the liver and pancreas probably have an important influence on the pathophysiology of the most common dementias: Alzheimer's and vascular dementia. This current review highlights recent studies aimed at identifying convergent mechanisms, such as insulin resistance and other diseases, linked to altered hepatic and pancreatic metabolism, which are capable of causing brain changes that ultimately lead to dementia.

Tirzepatide ameliorates spatial learning and memory impairment through modulation of aberrant insulin resistance and inflammation response in diabetic rats

Background: One of the typical symptoms of diabetes mellitus patients was memory impairment, which was followed by gradual cognitive deterioration and for which there is no efficient treatment. The anti-diabetic incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) were demonstrated to have highly neuroprotective benefits in animal models of AD. We wanted to find out how the GLP-1/GIP dual agonist tirzepatide affected diabetes's impairment of spatial learning memory. Methods: High fat diet and streptozotocin injection-induced diabetic rats were injected intraperitoneally with Tirzepatide (1.35 mg/kg) once a week. The protective effects were assessed using the Morris water maze test, immunofluorescence, and Western blot analysis. Golgi staining was adopted for quantified dendritic spines. Results: Tirzepatide significantly improved impaired glucose tolerance, fasting blood glucose level, and insulin level in diabetic rats. Then, tirzepatide dramatically alleviated spatial learning and memory impairment, inhibited Aβ accumulation, prevented structural damage, boosted the synthesis of synaptic proteins and increased dendritic spines formation in diabetic hippocampus. Furthermore, some aberrant changes in signal molecules concerning inflammation signaling pathways were normalized after tirzepatide treatment in diabetic rats. Finally, PI3K/Akt/GSK3β signaling pathway was restored by tirzepatide. Conclusion: Tirzepatide obviously exerts a protective effect against spatial learning and memory impairment, potentially through regulating abnormal insulin resistance and inflammatory responses.

Metabolic Syndrome: A Strange Companion of Atrial Fibrillation; A Blessing in Disguise from the Neuropsychiatric Point of View

Background: The concept of metabolic syndrome (MetSy) brings together components that individually represent a risk factor for cardiovascular diseases, which over time can prove to be more harmful if a combined effect of these is exhibited. Method: A single-centre retrospective study in an academic medical unit was conducted. We analysed the link between the MetSy and the occurrence of neuropsychic complications among atrial fibrillation (AF) patients. We sifted through the files of the patients admitted during 2015-2016 to the Municipal Emergency University Hospital Timisoara, Romania, with the diagnosis of AF. We divided these AF patients into two groups: the first group comprised patients with atrial fibrillation and MetSy (267 patients), while the second group comprised AF patients without MetSy (843 patients). We analysed the occurrence of neuropsychic changes (stroke, Parkinson's disease, dementia, cognitive impairment, and silent lacunar infarction) among the two groups. Results: Cognitive impairment (p-value = 0.0081) and dementia (p-value < 0.0001) were less frequent in patients with AF and MetSy than in those with AF without MetSy. Regarding the presence of stroke and Parkinson's disease (PD), we could not demonstrate the existence of any statistically significant difference between the two groups. Using logistic regression (enter test), we found that MetSy might have a protective effect (OR = 0.4040, 95% CI [0.2132; 0.7654], p-value = 0.0054) for the occurrence of dementia in those patients. Furthermore, obesity was the only factor with a possible protective effect from all the constituents of the MetSy when analysed together (with a significance level of p-value = 0.0004 for the logistic regression). The protective effect of MetSy against stroke occurrence was supplementarily proven by a longer period of survival without stroke from the AF diagnosis (3.521 years, p = 0.0304) compared to patients with AF without MetSy (3.286 years to first stroke occurrence). Conclusions: Metabolic syndrome might offer protection against the occurrence of dementia among patients with AF, but no effect was noted when compared with the presence of stroke. Further studies on larger cohorts can help us reach a conclusion regarding the positive effects of the metabolic syndrome.

Plasma glucose is not associated with performance on standard cognitive screening tests in a mixed memory clinic cohort-An observational cross-sectional study

BACKGROUND

It has been shown under experimental conditions that cognitive performance, especially working memory, is impaired in patients with type I and type II diabetes mellitus during hyperglycemic and hypoglycemic conditions, perhaps due to altered cerebral glucose metabolism. It is not known if patients with neurodegenerative diseases, who also exhibit pathological cerebral glucose metabolism, are affected in a similar manner by their plasma glucose levels.

OBJECTIVE

We aimed to test if performance on two cognitive screening tests was associated with plasma glucose levels in a memory clinic cohort.

METHODS

We included patients from the Copenhagen Memory Clinic Cohort with an available Mini Mental-State Examination (MMSE) test score and a plasma glucose measurement performed in conjunction with cognitive testing. We built linear regression models with MMSE and Addenbrooke's Cognitive Examination (ACE) test scores as the outcome and plasma glucose as the explaining variable and adjusted models for age, sex, and diabetes (plasma glucose measurement >11.1 mmol/L). We explored non-linear relationships by adding quadratic terms and by fitting a cubic spline regression model.

RESULTS

In total, 2714 patients had an available MMSE score and a plasma glucose measurement. MMSE and ACE total scores were not associated with plasma glucose in a linear or non-linear fashion when we adjusted for age, sex, and diabetes.

CONCLUSION

Plasma glucose levels, predominantly within normal ranges, were not associated with performance on routinely applied cognitive tests and do not need to be taken into consideration when interpreting test results from memory clinic patients.

Association Between Types of Family Support and Glycemic Control for Adults With Cognitive Impairment

Background

Family support is important in assisting with diabetes self-management for individuals with cognitive impairment, but what types of family support are most effective remain unknown.

Objectives

We aimed to examine the association between the types of family support in diabetes self-management with glycemic control in middle-aged and older adults with cognitive impairment.

Methods

A total of 267 individuals were included with diabetes and cognitive impairment (27-point Telephone Interview for Cognitive Status score <12), using the data of 2003 Health and Retirement Study (HRS) Diabetes Study and 2004 wave of the HRS.

Results

Most respondents were White (68.9%), followed by Black (25.8%). The mean age was 73.4±8.4 years. Adults with strong family support (as indicated by a "strongly agree" response) in testing sugar and in handling feelings about diabetes had significantly lower A1C compared with those with less family support (mean ± standard deviation: 7.08±1.39 vs. 7.51±1.42, P=.03; 6.79±0.87 vs. 7.57±1.53; P=.007 respectively).

Conclusions

Our findings indicate that family members of individuals with cognitive impairment provide critical support to patients with diabetes and cognitive impairment, and may need additional intervention to assist with diabetes self-management tasks that require unique knowledge and skills.

Linking Diabetes to Alzheimer's Disease: Potential Roles of Glucose Metabolism and Alpha-Glucosidase

Alzheimer's disease (AD) and type 2 diabetes mellitus (DM) are more prevalent with ageing and cause a substantial global socio-economic burden. The biology of these two conditions is well elaborated, but whether AD and type 2 DM arise from coincidental roots in ageing or are linked by pathophysiological mechanisms remains unclear. Research findings involving animal models have identified mechanisms shared by both AD and type 2 DM. Deposition of β-amyloid peptides and formation of intracellular neurofibrillary tangles are pathological hallmarks of AD. Type 2 DM, on the other hand, is a metabolic disorder characterised by hyperglycaemia and insulin resistance. Several studies show that improving type 2 DM can delay or prevent the development of AD, and hence, prevention and control of type 2 DM may reduce the risk of AD later in life. Alpha-glucosidase is an enzyme that is commonly associated with hyperglycaemia in type 2 DM. However, it is uncertain if this enzyme may play a role in the progression of AD. This review explores the experimental evidence that depicts the relationship between dysregulation of glucose metabolism and AD. We also delineate the links between alpha-glucosidase and AD and the potential role of alpha-glucosidase inhibitors in treating AD.

Association between Blood Glucose Control and Subjective Cognitive Decline in Korean Patients with Diabetes Aged over 50 Years

This study aimed to investigate the association between blood glucose control and subjective cognitive decline in adult patients with diabetes. Using the 2018 data from the community health survey, we included 18,789 patients with diabetes aged ≥50 years who had complete responses recorded. Blood glucose control was the independent variable, and subjective cognitive decline was the dependent variable. Multivariable logistic regression analysis was used to analyze the association between blood glucose control and subjective cognitive decline. Multivariable logistic regression analysis showed that blood glucose control was inversely associated with subjective cognitive decline in patients with diabetes. Patients with uncontrolled blood glucose levels had higher odds of subjective cognitive decline than those with controlled blood glucose levels (odds ratio = 1.22; 95% confidence interval: 1.10, 1.34). Our findings suggest that patients with diabetes may demonstrate subjective cognitive decline if their blood glucose levels are not well-controlled.

Metabolic risk factors of cognitive impairment in young women with major psychiatric disorder

BACKGROUND

Cognitive performance improves clinical outcomes of patients with major psychiatric disorder (MPD), but is impaired by hyperglycemia. Psychotropic agents often induce metabolism syndrome (MetS). The identification of modifiable metabolic risk factors of cognitive impairment may enable targeted improvements of patient care.

OBJECTIVE

To investigate the relationship between MetS and cognitive impairment in young women with MPD, and to explore risk factors.

METHODS

We retrospectively studied women of 18-34 years of age receiving psychotropic medications for first-onset schizophrenia (SCH), bipolar disorder (BP), or major depressive disorder (MDD). Data were obtained at four time points: presentation but before psychotropic medication; 4-8 and 8-12 weeks of psychotropic therapy; and enrollment. MATRICS Consensus Cognitive Battery, (MCCB)-based Global Deficit Scores were used to assess cognitive impairment. Multiple logistic analysis was used to calculate risk factors. Multivariate models were used to investigate factors associated with cognitive impairment.

RESULTS

We evaluated 2,864 participants. Cognitive impairment was observed in 61.94% of study participants, and was most prevalent among patients with BP (69.38%). HbA1c within the 8-12 week-treatment interval was the most significant risk factor and highest in BP. Factors in SCH included pre-treatment waist circumference and elevated triglycerides during the 8-12 weeks treatment interval. Cumulative dosages of antipsychotics, antidepressants, and valproate were associated with cognitive impairment in all MPD subgroups, although lithium demonstrated a protect effect (all P < 0.001).

CONCLUSIONS

Cognitive impairment was associated with elevated HbA1c and cumulative medication dosages. Pre-treatment waist circumference and triglyceride level at 8-12 weeks were risk factors in SCH. Monitoring these indices may inform treatment revisions to improve clinical outcomes.