Studying activity of peripheral blood monocytes and adiponectin receptors expression in association with plasma adiponectin in patients with Alzheimer’s disease

Collaborative Research Grants Program 2020-2022

In the past ten years considerable information has been accumulated on the importance of adiponectin activity (APN) in the pathogenesis of Alzheimer’s disease (AD). However, the published data are controversial, and the role of adiponectin in the etiology of AD is not fully understood. Therefore, more studies are needed to reveal an association between plasma adiponectin leveland AD. Further insights into the various mechanisms through which APN is involved in AD pathology may contribute to deeper understanding of AD pathogenesis and provide clues for development of novel biomarkers and treatment strategies. The overall goal of the proposed research is studying expression of adiponectin receptors AdipoR1 and AdipoR2 on the surface of peripheral blood monocytes, their M1/M2 polarization phenotypes, anti-inflammatory response and phagocytic activity in association with plasmaadiponectin levels in patients with Alzheimer’s disease (AD) in comparison with age- and sex- matched healthy individuals.Specific aims:1. Study of AdipoR1 and AdipoR2 expression levels on the surface of peripheral blood monocytes collected from the patients with AD and age- and sex- matched healthy individuals in association with plasma adiponectin levels.2. Study of the M1/M2 polarization phenotypes of blood monocytes collected from the patients with AD and age- and sex- matched healthy individuals in association with plasma adiponectin levels.3. Study of pro-inflammatory and anti-inflammatory cytokine release by activated blood monocytes collected from the patients with AD and age- and sex- matched healthy individuals in association with plasma adiponectin levels.4. Study the effects of adiponectin treatment on phagocytic activity of Аβ42 in peripheral blood monocytes collected from the patients with AD and age- and sex- matched healthy individuals. The long-range goal of the proposed research is to provide novel information on some mechanisms through which adiponectin and peripheral blood monocytes could be involved in AD. 

Alzheimer's disease is currently on the list of diseases for which there is no early diagnosis, no prophylactics, and cure. Currently, about 36 million people are diagnosed with AD worldwide. According to current forecasts, by 2050, this indicator can grow to 135.46 million people if effective methods of preventing and treating this disease are not found (http://www.alzheimers.net/resources/alzheimers-statistics. As the most significant increases in dementia occur in low and middle-income countries, our research will add knowledge in understanding dementia in developing multiethnic countries such as Kazakhstan. Studying the relationships between human blood biomarkers, microbiomes and AD in different ethnic populations will help evaluate biogeography and lifestyle's contribution to the increase in the prevalence of dementia. These studies will also be of great practical importance since they can serve as a basis for developing new diagnostic biomarkers and prophylactics strategies.

Ø     The role of adiponectin (ADIPOQ) in Alzheimer’s disease (AD) has been documented, however, demonstrating controversial results. In our study, we investigated blood serum ADIPOQ levels, methylation of the adiponectin gene promoter, and adiponectin receptors (AdipoR1 and AdipoR2) expression in blood samples isolated from AD patients (n=98) and healthy controls (n=150). We have found that serum adiponectin levels were 3-fold higher in the AD group compared to the controls. A significant difference in the proportion of methylation of the CpG sites at −74 nt of the ADIPOQ promoter was detected in AD cases, and the levels of adiponectin in blood serum were significantly higher in methylated samples in the AD group compared to controls. The amount of AdipoR1 was significantly higher among AD subjects, while the expression of AdipoR2 did not vary between AD patients and controls. We have also analyzed cytokines in the serum of AD patients and normal controls and found significant positive correlations between serum adiponectin level and the following cytokines/chemokines: GM-CSF, IL-2, IL-13, IL-12p70, IL-15, IL-3, and negative correlations with SCD40L, EGF, GRO, MCP-1, MDC, IL-5, FGF-2, TGF-α, IL1RA. These findings may contribute to a deeper understanding of the etiological factors leading to the development of dementia and may serve as a basis for the development of predictive biomarkers of AD.

Ø     We have isolated PBMC from peripheral blood of AD patients and age-matched controls and assessed the percentage of circulating monocyte subsets (classical, non-classical, and intermediate). For cytometric analysis, we used a combination of antibodies (CD14, CD16, CD86, CD163, HLA-DR) and ID7000 spectral cytometer (SONY Biological Inc., Germany) that allowed identification and subtraction of autofluorescence, or FACSAria SORP conventional flow cytometer (BD Biosciences, USA). The AD patients and control groups were also examined in relation to cognitive loss, represented by Folstein Mini-Mental State Examination (MMSE) score. The AD group presented with lower MMSE scores than the control group. We observed a significant accumulation of the non-classical monocytes in AD patients with lower MMSE scores. A greater proportion of intermediate and non-classical monocytes in AD patients with a severe cognitive impairment suggested a shift to a pro-inflammatory phenotype. The non-classical monocytes subset increment did not correlate with the presence of comorbidities in AD patients, such as hypertension and diabetes.  These data highlight the potential role of circulating pro-inflammatory monocyte subsets in AD cognitive impairment.

Ø     We have investigated the diversity and composition of gut microbiotas isolated from AD (Alzheimer's disease) patients (n=41) and healthy seniors (n=43) from Nur-Sultan city (Kazakhstan). Our results demonstrated significant differences in bacterial abundance at phylum, class, order, and genus levels in AD patients compared to healthy aged individuals. We have also found correlations between some bacteria taxa and adiponectin. In addition, we report the correlations found between disease severity and certain fecal bacteria. This is the first reported study demonstrating gut microbiota alterations in AD in the Central Asian region (data are published).