Dementia and diabetes mellitus: association with apolipoprotein e4 polymorphism from a hospital in southern India

Diabetes mellitus and risk of incident dementia in APOE ɛ4 carriers: an updated meta-analysis

BACKGROUND AND AIM

Diabetes raises the risk of dementia, mortality, and cognitive decline in the elderly, potentially because of hereditary variables such as APOE. In this study, we aim to evaluate Diabetes mellitus and the risk of incident dementia in APOE ɛ4 carriers.

METHOD

We thoroughly searched PubMed (Medline), Scopus, and Google Scholar databases for related articles up to September 2023. The titles, abstracts, and full texts of articles were reviewed; data were extracted and analyzed.

RESULT

This meta-analysis included nine cohorts and seven cross-sectional articles with a total of 42,390 population. The study found that APOE ɛ4 carriers with type 2 diabetes (T2D) had a 48% higher risk of developing dementia compared to non-diabetic carriers (Hazard Ratio;1.48, 95%CI1.36-1.60). The frequency of dementia was 3 in 10 people (frequency: 0.3; 95%CI (0.15-0.48). No significant heterogeneity was observed. Egger's test, which we performed, revealed no indication of publication bias among the included articles (p = 0.2).

CONCLUSION

Overall, diabetes increases the risk of dementia, but further large-scale studies are still required to support the results of current research.

The Prevalence of Comorbidities and Associated Factors among Patients with Dementia in the Indian Setting: Meta-analysis of Observational Studies

BACKGROUND

Patients with dementia usually have multiple comorbidities. The presence of comorbidities may exacerbate the progression of dementia and decreases the patient's ability to participate in health maintenance activities. However, there is hardly any meta-analysis estimating the magnitude of comorbidities among patients with dementia in the Indian context.

METHODS

We searched PubMed, Scopus, and Google Scholar, and relevant studies conducted in India were included. The risk of bias was assessed and a random-effects meta-analysis model was used in which I2 statistics were calculated to measure heterogeneity among studies.

RESULTS

Fourteen studies were included in the meta-analysis based on the inclusion and exclusion criteria. Altogether, we found the coexistence of comorbid conditions such as hypertension (51.10%), diabetes (27.58%), stroke (15.99%), and factors like tobacco use (26.81 %) and alcohol use (9.19%) among patients with dementia in this setting. The level of heterogeneity was high due to differences in the methodologies in the included studies.

CONCLUSIONS

Our study found hypertension as the most common comorbid condition among patients with dementia in India. The observed lacuna of methodological limitations in the studies included in the current meta-analysis provides the urgent need for good quality research to successfully meet the challenges ahead while devising appropriate strategies to treat the comorbidities among patients with dementia.

APOE4 allele in north Indian elderly patients with dementia or late onset depression-a multiple-disease case control study

The objective of the study was to analyze the frequency of APOE4 allele in elderly patients with Alzheimer's or vascular dementia or depression; compare these to age/sex matched controls; compare the results with established literature and highlight new findings. A single center, multiple disease, case-control study was performed with three case groups- probable AD patients (n=36), vascular dementia patients (n=29) and depression patients (n=20) and with a control group (n=32). APOE genotyping was performed in whole blood samples collected from patients and controls by restriction isotyping using the enzymes AflIII and HaeII. There was significant difference in frequency distribution of E4 allele between the AD (12/72; 16.7%) and control groups (3/64; 4.7%) (P=0.03). However, no significant difference was found in any of the other comparisons. The current study demonstrates absence of a significant association between APOE4 positivity and presence of late-onset depression in the north Indian elderly and reinforces the higher APOE4 prevalence in LOAD patients but not in VD patients. It is the first study of its kind from the northern part of India involving multiple disease groups and lays the framework for larger cohort studies.

Fibroblast growth factor 21 ameliorates neurodegeneration in rat and cellular models of Alzheimer's disease

Our understanding of the mechanisms underlying process in Alzheimer's disease (AD) is far from completion and new therapeutic targets are urgently needed. Recently, the link between dementia and diabetes mellitus (DM) prompted us to search for new therapeutic strategies from glucose metabolism regulators for neurodegeneration. Previous studies have indicated that fibroblast growth factor 21 (FGF21), an attractive and potential therapeutic treatment for DM, may exert diverse effects in the central nervous system. However, the specific biological function and mechanisms of FGF21 on AD is still largely unknown. We report here a study in vivo and in vitro of the neuroprotective effects of FGF21 on cell apoptosis, tau hyperphosphorylation and oxidative stress induced by amyloid β-peptide 25–35. In the present study, the results also further provided evidence for molecular mechanisms by which FGF21 exerted its beneficial effects in neuron and suggested that the regulation of protein phosphatase 2A / mitogen-activated protein kinases / hypoxia-inducible factor-1α pathway may play a key role in mediating the neuroprotective effects of FGF21 against AD-like pathologies.

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In vivo and in vitro evidence for Aβ -induced neurodegeneration ameliorated by FGF21.

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FGF21 alleviated tau and oxidative stress pathologies in AD rat and cellular models.

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PP2A / MAPKs / HIF-1α pathway was involved in the neuroprotective effect of FGF21.

Reduced telomere length in subjects with dementia and diabetes mellitus type 2 is independent of apolipoprotein E4 genotype

Apolipoprotein E4 gene is associated with increased risk of dementia with comorbid diabetes mellitus. Both dementia and diabetes mellitus type 2 are independently associated with telomere shortening. We assessed relative telomere length and apolipoprotein E genotype in subjects with dementia (n=70) and cognitively normal control groups (n=55) with and without comorbid diabetes mellitus type 2. Relative telomere length was highest in the control group (Q2=0.91) followed by dementia (Q2=0.48) and dementia with comorbid diabetes mellitus type 2 (Q2=0.39). Apolipoprotein E4 allele frequency was highest in dementia with comorbid diabetes mellitus type 2 (0.26). Apolipoprotein E4 allele was not significantly associated with telomere attrition in both dementia and cognitively normal group irrespective of comorbid diabetes mellitus type 2 (P>0.05). The findings suggest that relative telomere length is unrelated to apolipoprotein E4 genotype in dementia and cognitive normal subjects with or without comorbid diabetes mellitus type 2.

Apolipoprotein E-low density lipoprotein receptor interaction affects spatial memory retention and brain ApoE levels in an isoform-dependent manner

Human apolipoprotein E (apoE) exists in three isoforms: apoE2, apoE3 and apoE4. APOE ε4 is a major genetic risk factor for cardiovascular disease (CVD) and Alzheimer's disease (AD). ApoE mediates cholesterol metabolism by binding various receptors. The low-density lipoprotein receptor (LDLR) has a high affinity for apoE, and is the only member of its receptor family to demonstrate an apoE isoform specific binding affinity (E4>E3>>E2). Evidence suggests that a functional interaction between apoE and LDLR influences the risk of CVD and AD. We hypothesize that the differential cognitive effects of the apoE isoforms are a direct result of their varying interactions with LDLR. To test this hypothesis, we have employed transgenic mice that express human apoE2, apoE3, or apoE4, and either human LDLR (hLDLR) or no LDLR (LDLR(-/-)). Our results show that plasma and brain apoE levels, cortical cholesterol, and spatial memory are all regulated by isoform-dependent interactions between apoE and LDLR. Conversely, both anxiety-like behavior and cued associative memory are strongly influenced by APOE genotype, but these processes appear to occur via an LDLR-independent mechanism. Both the lack of LDLR and the interaction between E4 and the LDLR were associated with significant impairments in the retention of long term spatial memory. Finally, levels of hippocampal apoE correlate with long term spatial memory retention in mice with human LDLR. In summary, we demonstrate that the apoE-LDLR interaction affects regional brain apoE levels, brain cholesterol, and cognitive function in an apoE isoform-dependent manner.