Improvement of cognitive function, glucose and lipid homeostasis and serum osteocalcin levels by liraglutide in diabetic rats

Transcranial Irradiation Mitigates Paradoxical Sleep Deprivation Effect in an Age-Dependent Manner: Role of BDNF and GLP-1

The growing prevalence of aged sleep-deprived nations is turning into a pandemic state. Acute sleep deprivation (SD) accompanies aging, changing the hippocampal cellular pattern, neurogenesis pathway expression, and aggravating cognitive deterioration. The present study investigated the ability of Near Infra Red (NIR) light laser to ameliorate cognitive impairment induced by SD in young and senile rats. Wistar rats ≤ 2 months (young) and ≥ 14 months (senile) were sleep-deprived for 72 h with or without transcranial administration of NIR laser of 830 nm. Our results showed that NIR photobiomodulation (PBM) attenuated cognitive deterioration made by SD in young, but not senile rats, while both sleep-deprived young and senile rats exhibited decreased anxiety (mania)-like behavior in response to PBM. NIR PBM had an inhibitory effect on AChE, enhanced the production of ACh, attenuated ROS, and regulated cell apoptosis factors such as Bax and Bcl-2. NIR increased mRNA expression of BDNF and GLP-1 in senile rats, thus facilitating neuronal survival and differentiation. The present findings also revealed that age exerts an additive factor to the cellular assaults produced by SD where hippocampal damages made in 2-month rats were less severe than those of the aged one. In conclusion, NIR PBM seems to promote cellular longevity of senile hippocampal cells by combating ROS, elevating neurotrophic factors, thus improving cognitive performance. The present findings provide NIR as a possible candidate for hippocampal neuronal insults accompanying aging and SD.

To investigate the association of serum osteocalcin with cognitive functional status in patients with type 2 diabetes: A systematic review with meta-analysis

BACKGROUND

To systematically evaluate the correlation between serum osteocalcin levels and cognitive function status in type 2 diabetes mellitus (T2D) patients.

METHODS

This review was conducted according to the PRISMA guidelines, and was developed and submitted to PROSPERO (CRD42022339295). We comprehensively searched PubMed, EMBASE, Web of Science, Scopus, ProQuest, and Chinese Databases (China National Knowledge Infrastructure, Wan Fang, Chinese Science and Technology Periodical Database, and China Biology Medicine) up to 1 June 2023. 3 investigators performed independent literature screening and data extraction of the included literature, and 2 investigators performed an independent quality assessment of case-control studies using the Newcastle-Ottawa-Scale tool. Data analysis was performed using Review Manager 5.4 software. For continuous various outcomes, mean difference (MD) or standardized MD with 95% confidence intervals (CIs) was applied for assessment by fixed-effect or random-effect model analysis. The heterogeneity test was performed by the Q statistic and quantified using I2, and publication bias was evaluated using a funnel plot.

RESULTS

9 studies with T2D were included (a total of 1310 subjects). Meta-analysis results indicated that cognitive function was more impaired in patients with lower serum osteocalcin levels [MD = 9.91, 95% CI (8.93, -10.89), I2 = 0%]. Serum osteocalcin levels were also significantly different between the 2 groups of T2D patients based on the degree of cognitive impairment [MD = -0.93, 95% CI (-1.09, -0.78), I2 = 41%]. It summarized the statistical correlation between serum osteocalcin and cognitive function scores in patients with T2D at r = 0.43 [summary Fisher's Z = 0.46, 95% CI (0.39, -0.50), I2 = 41%). After sensitivity analysis, the heterogeneity I2 decreased to 0%, indicating that the results of the meta-analysis are more reliable.

CONCLUSION SUBSECTIONS

Based on a meta-analysis of included studies, we concluded that there is a moderately strong positive correlation between serum osteocalcin levels and patients' cognitive function in T2D. An intervention to increase serum osteocalcin levels can contribute to delaying and improving cognitive decline in patients with T2D.

Ferulic acid alleviates high fat diet-induced cognitive impairment by inhibiting oxidative stress and apoptosis

Cognitive impairment has become a major public health problem. Growing evidence suggests that high-fat diet (HFD) can cause cognitive dysfunction and increase the risk of dementia. However, effective treatment for cognitive impairment is not available. Ferulic acid (FA) is a single phenolic compound with anti-inflammatory and antioxidant properties. Nevertheless, its role in regulating learning and memory in HFD-fed mice and the underlying mechanism remains unclear. In this study, we aimed to identify the neuroprotective mechanisms of FA in HFD induced cognitive impairment. We found that FA improved the survival rate of HT22 cells treated with palmitic acid (PA), inhibited cell apoptosis, and reduced oxidative stress via the IRS1/PI3K/AKT/GSK3β signaling pathway; Furthermore, FA treatment for 24 weeks improved the learning and memory of HFD-fed mice and decreased hyperlipidemia. Moreover, the expression of Nrf2 and Gpx4 proteins were decreased in HFD-fed mice. After FA treatment, the decline of these proteins was reversed. Our study showed that the neuroprotective effect of FA on cognitive impairment was related to the inhibition of oxidative stress and apoptosis and regulation of glucose and lipid metabolism. These findings suggested that FA can be developed as a potential agent for the treatment of HFD-induced cognitive impairment.

Effects of liraglutide on depressive behavior in a mouse depression model and cognition in the probe trial of Morris water maze test

BACKGROUND

We investigated the effects of liraglutide, a glucagon-like peptide-1 (GLP-1) agonist, on a depression-like phenotype in mice exposed to chronic unpredictable stress (CUS). Learning and memory were also assessed using the Morris water maze (MWM) test.

METHODS

Liraglutide (0.3 mg/kg/day for 21 days) was administered to mice with or without exposure to CUS. After 21 days of CUS, the forced swim test (FST) was performed to assess its antidepressant effect. To evaluate cognitive function, liraglutide was administered to mice under stress-free conditions for 21 days, and then the MWM test was performed on 6 consecutive days.

RESULTS

Chronic liraglutide treatment reduced FST immobility in mice with and without CUS. In the probe trial of the Morris water maze test, the search error rate was reduced and the time spent and path length in the target quadrant and the number of platform crossings were increased.

LIMITATION

Additional animal model experiments and molecular level studies are needed to support the results obtained in this study.

CONCLUSIONS

Liraglutide appears to exert antidepressant effects and could improve cognitive function. Based on these results, GLP-1 agonists could have potential as novel antidepressants.

Astaxanthin from Haematococcus pluvialis alleviates obesity by modulating lipid metabolism and gut microbiota in mice fed a high-fat diet

Obesity is a global chronic disease epidemic that is attributed to the abnormal accumulation of lipids in adipose tissue. Astaxanthin (AST) from Haematococcus pluvialis, a natural carotenoid, exhibits antioxidant, anti-lipogenic, anti-diabetic and other potent effects. Herein, we evaluated the effect of AST to illuminate its efficacy and mechanisms in high-fat diet-fed mice. AST supplementation not only significantly decreased body weight and lipid droplet accumulation in the liver but also modulated liver function and serum lipid levels. Lipidomic analysis revealed that 13 lipids might be potential biomarkers responsible for the effects of AST in lipid reduction, such as total free fatty acids (FFAs), triacylglycerols (TGs) and cholesterol esters (CEs). The gut microbiota sequencing results indicated that AST alleviated HFD-induced gut microbiota dysbiosis by optimizing the ratio of Firmicutes to Bacteroides and inhibiting the abundance of obesity-related pathogenic microbiota while promoting the abundance of probiotics related to glucose and lipid metabolism. In addition, qRT-PCR demonstrated that AST could regulate the gene expressions of the AMPK/SREBP1c pathway by downregulating lipogenesis correlated-genes and upregulating the lipid oxidant related-gene. The present study revealed the new function of AST in regulating lipid metabolism, which provided a theoretical basis for the development of high-quality AST functional food and the application of diet active substances in obesity, as demonstrated in mice.

Treating cognitive impairment in schizophrenia with GLP-1RAs: an overview of their therapeutic potential

INTRODUCTION

Schizophrenia is a neuropsychiatric disorder that affects approximately 1% of individuals worldwide. There are no available medications to treat cognitive impairment in this patient population currently. Preclinical evidence suggests that glucagon-like peptide-1 receptor agonists (GLP-1 RAs) improve cognitive function. There is a need to evaluate how GLP-1 RAs alter specific domains of cognition and whether they will be of therapeutic benefit in individuals with schizophrenia.

AREAS COVERED

This paper summarizes the effects of GLP-1 RAs on metabolic processes in the brain and how these mechanisms relate to improved cognitive function. We provide an overview of preclinical studies that demonstrate GLP-1 RAs improve cognition and comment on their potential therapeutic benefit in individuals with schizophrenia.

EXPERT OPINION

To understand the benefits of GLP-1 RAs in individuals with schizophrenia, further preclinical research with rodent models relevant to schizophrenia symptomology are needed. Moreover, preclinical studies must focus on using a wider range of behavioral assays to understand whether important aspects of cognition such as executive function, attention, and goal-directed behavior are improved using GLP-1 RAs. Further research into the specific mechanisms of how GLP-1 RAs affect cognitive function and their interactions with antipsychotic medication commonly prescribed is necessary.

Effects of Incretin-Related Diabetes Drugs on Bone Formation and Bone Resorption

Patients with type 2 diabetes have an increased risk of fracture compared to the general population. Glucose absorption is accelerated by incretin hormones, which induce insulin secretion from the pancreas. The level of the incretin hormone, glucagon-like peptide-1 (GLP-1), shows an immediate postprandial increase, and the circulating level of intact GLP-1 is reduced rapidly by dipeptidyl peptidase-4 (DPP-4)-mediated inactivation. Therefore, GLP-1 receptor agonists and DPP-4 inhibitors are effective in the treatment of type 2 diabetes. However, these incretin-related diabetic agents have been reported to affect bone metabolism, including bone formation and resorption. These agents enhance the expression of bone markers, and have been applied to improve bone quality and bone density. In addition, they have been reported to suppress chronic inflammation and reduce the levels of inflammatory cytokine expression. Previously, we reported that these incretin-related agents inhibited both the expression of inflammatory cytokines and inflammation-induced bone resorption. This review presents an overview of current knowledge regarding the effects of incretin-related diabetes drugs on osteoblast differentiation and bone formation as well as osteoclast differentiation and bone resorption. The mechanisms by which incretin-related diabetes drugs regulate bone formation and bone resorption are also discussed.