Metabolomic markers mediate erythrocyte anisocytosis in older adults: Results from three independent aging cohorts

Longevity Humans Have Youthful Erythrocyte Function and Metabolic Signatures

Longevity individuals have lower susceptibility to chronic hypoxia, inflammation, oxidative stress, and aging-related diseases. It has long been speculated that "rejuvenation molecules" exist in their blood to promote extended lifespan. We unexpectedly discovered that longevity individuals exhibit erythrocyte oxygen release function similar to young individuals, whereas most elderly show reduced oxygen release capacity. Untargeted erythrocyte metabolomics profiling revealed that longevity individuals are characterized by youth-like metabolic reprogramming and these metabolites effectively differentiate the longevity from the elderly. Quantification analyses led us to identify multiple novel longevity-related metabolites within erythrocytes including adenosine, sphingosine-1-phosphate (S1P), and glutathione (GSH) related amino acids. Mechanistically, we revealed that increased bisphosphoglycerate mutase (BPGM) and reduced MFSD2B protein levels in the erythrocytes of longevity individuals collaboratively work together to induce elevation of intracellular S1P, promote the release of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from membrane to the cytosol, and thereby orchestrate glucose metabolic reprogramming toward Rapoport-Luebering Shunt to induce the 2,3-BPG production and trigger oxygen delivery. Furthermore, increased glutamine and glutamate transporter expression coupled with the enhanced intracellular metabolism underlie the elevated GSH production and the higher anti-oxidative stress capacity in the erythrocytes of longevity individuals. As such, longevity individuals displayed less systemic hypoxia-related metabolites and more antioxidative and anti-inflammatory metabolites in the plasma, thereby healthier clinical outcomes including lower inflammation parameters as well as better glucose-lipid metabolism, and liver and kidney function. Overall, we identified that youthful erythrocyte function and metabolism enable longevity individuals to better counteract peripheral tissue hypoxia, inflammation, and oxidative stress, thus maintaining healthspan.

Elevated mtDNA content in RBCs promotes oxidative stress may be responsible for faster senescence in men

BACKGROUND

Both we and others have found that RBC counts are significantly lower in older compared to younger. However, when gender is factored in, a significant age-related decrease of RBC counts is observed only in men but not in women.

METHODS

qPCR and confocal microscopy were used to detect the presence of mtDNA in RBCs. Flow cytometry and specific inhibitors were used to determine how RBCs uptake cf-mtDNA. The peripheral blood was collected from 202 young adults and 207 older adults and RBC and plasma were isolated. The levels of TLR9+RBCs and apoptotic RBCs after uptake of cf-mtDNA by RBCs were measured by flow cytometry. The kit detects changes in SOD and MDA levels after cf-mtDNA uptake by RBCs. Young RBCs (YR) and old RBCs (OR) from single individuals were separated by Percoll centrifugation.

RESULTS

We found a significant decrease in RBC counts and a significant increase in the RDW with aging only in men. We also found that significantly elevated mtDNA content in RBCs was observed only in men during aging and was not found in women. Further studies demonstrated that RBCs could take up cf-mtDNA via TLR9, and the uptake of mtDNA might lead to a decrease in the RBC number and an increase in RDW due to an increase of oxidative stress.

CONCLUSIONS

The RBC mtDNA content might be a potential marker of RBC aging and the elevated RBC mtDNA content might be the cause of faster senescence in males than females.

Plasma metabolomic markers underlying skeletal muscle mitochondrial function relationships with cognition and motor function

BACKGROUND

Lower skeletal muscle mitochondrial function is associated with future cognitive impairment and mobility decline, but the biological underpinnings for these associations are unclear. We examined metabolomic markers underlying skeletal muscle mitochondrial function, cognition and motor function.

METHODS

We analysed data from 560 participants from the Baltimore Longitudinal Study of Aging (mean age: 68.4 years, 56% women, 28% Black) who had data on skeletal muscle oxidative capacity (post-exercise recovery rate of phosphocreatine, kPCr) via 31P magnetic resonance spectroscopy and targeted plasma metabolomics using LASSO model. We then examined which kPCr-related markers were also associated with cognition and motor function in a larger sample (n = 918, mean age: 69.4, 55% women, 27% Black).

RESULTS

The LASSO model revealed 24 metabolites significantly predicting kPCr, with the top 5 being asymmetric dimethylarginine, lactic acid, lysophosphatidylcholine a C18:1, indoleacetic acid and triacylglyceride (17:1_34:3), also significant in multivariable linear regression. The kPCr metabolite score was associated with cognitive or motor function, with 2.5-minute usual gait speed showing the strongest association (r = 0.182). Five lipids (lysophosphatidylcholine a C18:1, phosphatidylcholine ae C42:3, cholesteryl ester 18:1, sphingomyelin C26:0, octadecenoic acid) and 2 amino acids (leucine, cystine) were associated with both cognitive and motor function measures.

CONCLUSION

Our findings add evidence to the hypothesis that mitochondrial function is implicated in the pathogenesis of cognitive and physical decline with aging and suggest that targeting specific metabolites may prevent cognitive and mobility decline through their effects on mitochondria. Future omics studies are warranted to confirm these findings and explore mechanisms underlying mitochondrial dysfunction in aging phenotypes.

Association between Red Blood Cell Distribution Width and Obstructive Sleep Apnea Syndrome: A Systematic Review and Meta-Analysis

Although polysomnography is the gold standard method to diagnose obstructive sleep apnea syndrome (OSAS), there is an ongoing quest for simpler and relatively inexpensive biomarkers of disease presence and severity. To address this issue, we conducted a systematic review of the potential diagnostic role of the red blood cell distribution width (RDW), a routine hematological parameter of red blood cell volume variability, in OSAS. A total of 1478 articles were initially identified in the databases PubMed, Web of Science, Scopus, Embase, and Google Scholar, from their inception to February 2023, and 20 were selected for final analysis. The RDW was significantly higher in OSAS than in non-OSAS subjects (SMD = 0.44, 95% CI 0.20 to 0.67, p < 0.001; low certainty of evidence). In univariate meta-regression, the mean oxygen saturation (SpO₂) was significantly associated with the effect size. No significant between-group differences were observed in subgroup analyses. Notably, in OSAS subjects, the RDW SMD progressively increased with disease severity. In conclusion, these results suggest that the RDW is a promising biomarker of OSAS (PROSPERO registration number: CRD42023398047).