Plasma MCP-1 and changes on cognitive function in community-dwelling older adults

Background

Monocyte Chemoattractant Protein-1 (MCP-1), a glial-derived chemokine, mediates neuroinflammation and may regulate memory outcomes among older adults. We aimed to explore the associations of plasma MCP-1 levels (alone and in combination with β-amyloid deposition—Aβ_42/40) with overall and domain-specific cognitive evolution among older adults.

Methods

Secondary analyses including 1097 subjects (mean age = 75.3 years ± 4.4; 63.8% women) from the Multidomain Alzheimer Preventive Trial (MAPT). MCP-1 (higher is worse) and Aβ_42/40 (lower is worse) were measured in plasma collected at year 1. MCP-1 in continuous and as a dichotomy (values in the highest quartile (MCP-1⁺)) were used, as well as a dichotomy of Aβ_42/40. Outcomes were measured annually over 4 years and included the following: cognitive composite z-score (CCS), the Mini-Mental State Examination (MMSE), and Clinical Dementia Rating (CDR) sum of boxes (overall cognitive function); composite executive function z-score, composite attention z-score, Free and Cued Selective Reminding Test (FCSRT - memory).

Results

Plasma MCP-1 as a continuous variable was associated with the worsening of episodic memory over 4 years of follow-up, specifically in measures of free and cued delayed recall. MCP-1⁺ was associated with worse evolution in the CCS (4-year between-group difference: β = −0.14, 95%CI = −0.26, −0.02) and the CDR sum of boxes (2-year: β = 0.19, 95%CI = 0.06, 0.32). In domain-specific analyses, MCP-1⁺ was associated with declines in the FCSRT delayed recall sub-domains. In the presence of low Aβ_42/40, MCP-1⁺ was not associated with greater declines in cognitive functions. The interaction with continuous biomarker values Aβ_42/40× MCP-1 × time was significant in models with CDR sum of boxes and FCSRT DTR as dependent variables.

Conclusions

Baseline plasma MCP-1 levels were associated with longitudinal declines in overall cognitive and episodic memory performance in older adults over a 4-year follow-up. How plasma MCP-1 interacts with Aβ_42/40 to determine cognitive decline at different stages of cognitive decline/dementia should be clarified by further research. The MCP-1 association on cognitive decline was strongest in those with amyloid plaques, as measured by blood plasma Aβ_42/40.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-021-00940-2.

Biomarkers of mitochondrial dysfunction and inflammaging in older adults and blood pressure variability

Most physiopathological mechanisms underlying blood pressure variability (BPV) are implicated in aging. Vascular aging is associated with chronic low-grade inflammation occurring in late life, known as "inflammaging" and the hallmark "mitochondrial dysfunction" due to age-related stress. We aimed to determine whether plasma levels of the pleiotropic stress-related mitokine growth/differentiation factor 15 (GDF-15) and two inflammatory biomarkers, interleukin 6 (IL-6) and tumor necrosis factor receptor 1 (TNFR-1), are associated with visit-to-visit BPV in a population of community-dwelling older adults. The study population consisted of 1096 community-dwelling participants [median age 75 (72-78) years; 699 females, 63.7%] aged ≥ 70 years from the MAPT study. Plasma blood sample was collected 12 months after enrolment and BP was assessed up to seven times over a 4-year period. Systolic (SBPV) and diastolic BPV (DBPV) were determined through several indicators taking into account BP change over time, the order of measurements and formulas independent of mean BP levels. Higher values of GDF-15 were significantly associated with increased SBPV (all indicators) after adjustment for relevant covariates [adjusted 1-SD increase in GDF-15: β (SE) = 0.07 (0.04), p < 0.044, for coefficient of variation%]. GDF-15 levels were not associated with DBPV. No significant associations were found between IL-6 and BPV, whereas TNFR1 was only partially related to DBPV. Unlike inflammation biomarkers, higher GDF-15 levels were associated with greater SBPV. Our findings support the age-related process of mitochondrial dysfunction underlying BP instability, suggesting that BPV might be a potential marker of aging.

Emotions, Beliefs, and Revisions

Emotions imply a revision of our beliefs inasmuch as they are triggered by a discrepancy between our expectancies and new situations. I will study the converse relation: how emotions, particularly recurrent emotions that reappear in similar situations in the long term, are incentives to revise not only our beliefs but also the order of priorities between their related desires. Understanding how affects can revise both beliefs—under their committing aspect—and the order of desires, implies seeing the dynamics of affects as interacting with external dynamics and the order of priorities as a weak one (“pseudo-distance”; Schlechta, 2004). These philosophical considerations shed new light on the diversity of emotions, on their different temporalities, and on the paradox of emotional sharing.

Rational choice, neuroeconomy and mixed emotions

Experimental psychology has shown differences between predictions of theory of decision and human choices. Emotions like regret can partly explain these differences. Neuroimagery used in combination with behavioural economics (neuroeconomics) has been used in order to try to disentangle the different emotional and rational factors (regret, rejoicing, reward, costs, uncertainty, trade-off between positive and negative aspects of different options). Emotions then appear as much more complex and mixed affective states than usually assumed. Not only might we feel a positive affect in punishing unfair partners, but mixed emotions can, for example, combine transmutation of previous anxiety into relief and elation by comparison with another less exciting option (elating relief). At the level of complexity of these mixed emotions--which we formally represent by comparisons between 'unexpected utilities' and expected ones--the main biases that Kahnemann and Tversky have shown can be explained. In spite of the complexity of these mixed emotions, some of these hypotheses might be partially tested by brain imagery.