Elevated circulating CD16+ monocytes and TLR4+ monocytes in older adults with multiple cardiometabolic disease risk
Melissa M Markofski1, Michael G Flynn2
1Deparment of Health & Human Performance, University of Houston, 3875 Holman St., Houston, TX 77204, USA.
Insights
Healthy older adults with fewer cardio-metabolic risks show lower inflammation. This includes reduced inflammatory monocytes and C-reactive protein, alongside higher aerobic capacity, indicating better cardiovascular health.
Area of Science:
- Cardiovascular Science
- Immunology
- Gerontology
Background:
- Cardio-metabolic diseases pose significant health risks, particularly in aging populations.
- Monocyte phenotype is increasingly recognized as a potential biomarker for disease risk.
- Understanding inflammation markers in relation to cardio-metabolic risk factors is crucial for preventative health strategies.
Purpose of the Study:
- To investigate the association between circulating monocyte phenotypes and cardio-metabolic disease risk in healthy older adults.
- To compare inflammatory markers and aerobic capacity between low-risk and elevated-risk groups.
- To identify specific monocyte subsets and cell-surface marker expressions related to metabolic health.
Main Methods:
- Secondary analysis of data from healthy men and women aged 55-75 years.
- Participants categorized into low-risk (<3 risk factors) and elevated-risk (≥3 risk factors) groups.
- Assessment of body composition, aerobic capacity (V̇02max), C-reactive protein (CRP), monocyte phenotype (CD14+CD16- and CD14+CD16+), and Toll-like receptor 4 (TLR4) expression.
Main Results:
- The low-risk group exhibited significantly lower waist circumference, body fat weight, CRP levels, and a higher V̇02max compared to the elevated-risk group.
- Individuals with lower cardio-metabolic risk had a higher proportion of classical (CD14+CD16-) monocytes and a lower proportion of inflammatory (CD14+CD16+) monocytes.
- A lower percentage of classical monocytes expressing TLR4 was observed in the low-risk group.
Conclusions:
- Fewer cardio-metabolic risk factors in older adults are associated with reduced systemic inflammation, characterized by lower CRP and specific monocyte profiles.
- Higher aerobic capacity is linked to a healthier inflammatory profile in this age group.
- Circulating monocyte phenotype, particularly the balance of classical and inflammatory subsets and TLR4 expression, may serve as indicators of cardio-metabolic health in older adults.
Abstract:
We endeavored to examine relationships between circulating monocyte phenotype and cardio-metabolic disease risk, in healthy, older adults. We performed a secondary data analysis on men and women, 55-75 yr, who were assigned to groups based on cardio-metabolic risk factors other than age. Subject in the low risk group (n = 16, 12 females) had fewer than three risk factors. Subjects in the elevated risk group (n = 29, 19 females) had three or more risk factors. Along with baseline screening for fitness and body composition, resting blood samples were assessed for markers of inflammation including: monocyte phenotype (inflammatory monocytes), monocyte cell-surface TLR4 expression, and serum C-reactive protein. The low risk group had a smaller (19.3% difference; p < 0.0001) waist circumference and lower body fat weight (36.3%; p < 0.0001), but higher V̇02max (45.5%; p = 0.0019). There were no mean differences (p > 0.05) between the low and elevated risk groups for BMI, serum cholesterol, fasting glucose, or leg press 1RM. The low risk group had lower CRP (114.7%, p = 0.0002), higher CD14+CD16- (classical) monocytes (6.7%; p = 0.0231) and fewer CD14+CD16+ (inflammatory) monocytes (46.2%; p = 0.0243) than the elevated risk group. The low risk group also had a lower percentage of CD14+CD16- monocytes that were positive for TLR4 (14.0%; p = 0.0328). Older men and women with fewer cardio-metabolic risk factors had lower serum and cellular markers of inflammation and higher aerobic capacity.
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