Table 1.
Principal component analysis of biological function factors represented by blood biomarkers
| Factor and Item Variable | Loading | |
|---|---|---|
| Muscle mass and function | ||
| ALM/Ht2 | 0.703 | |
| Knee strength | 0.894 | |
| Gait speed | 0.487 | |
| Immune cell and inflammation homeostasis | ||
| Soluble tumor necrosis factor receptor 2 | 0.873 | |
| Soluble tumor necrosis factor receptor 1 | 0.842 | |
| TNF‐α | 0.576 | |
| CRP | 0.574 | |
| Interleukin‐6 (IL‐6) | 0.510 | |
| Interferon‐gamma‐inducible protein 10 kDa (IP‐10) | 0.384 | |
| Soluble glycoprotein 130 (sgp130) | 0.330 | |
| Acute phase protein immune stress response‐I | ||
| B‐2‐microglobulin | 0.830 | |
| Ferritin | 0.808 | |
| Albumin | −0.481 | |
| Acute phase protein immune stress response‐II | ||
| Soluble glycoprotein 130 | 0.742 | |
| Haptoglobin | 0.645 | |
| Transferrin | −0.606 | |
| Acute phase protein immune stress response‐III | ||
| Transferrin | 0.688 | |
| Albumin | 0.560 | |
| D‐Dimer | −0.655 | |
| Acute phase cytokine immune stress response‐IV | ||
| Interleukin‐6 | 0.974 | |
| TNF‐α | 0.974 | |
| Acute phase response/iron metabolism | ||
| Transferrin | 0.736 | |
| Ferritin | −0.736 | |
| Cellular immune activation and anti‐oxidation | ||
| Oxidized glutathione | 0.846 | |
| Neopterin | 0.846 | |
| Oxidative stress (lipid peroxidation) | ||
| Reduced glutathione | 0.714 | |
| 4‐hydroxynonenal (4HNE) | −0.714 | |
| 4‐Carbon methylation | ||
| Homocysteine | −0.849 | |
| Folate | 0.613 | |
| B12 | 0.547 | |
| Insulin signaling and energy homeostasis | ||
| C‐peptide | 0.880 | |
| Insulin | 0.811 | |
| Leptin | 0.742 | |
| Anabolic sex steroid homeostasis | ||
| Free testosterone | 0.806 | |
| Leptin | −0.806 | |
| Energy homeostasis | ||
| Active ghrelin | 0.762 | |
| IGF‐1 | 0.762 | |
| HPA stress response | ||
| Cortisol | 0.873 | |
| Dehydroepiandrosterone sulfate | −0.873 | |
| Myocyte protein signaling | ||
| Irisin | 0.707 | |
| Myostatin | −0.707 | |
| Adipocyte protein signaling | ||
| Adiponectin | 0.873 | |
| Obestatin | 0.873 | |
| Oxygen transport and delivery | ||
| Hemoglobin | 0.915 | |
| Red blood cell count | 0.915 | |
| Glomerular function | ||
| eGFR (cystatin) | 0.806 | |
| eGFR (creatinine) | 0.806 | |
| Thyroid‐mediated catabolic homeostasis | ||
| Thyroid‐stimulating hormone | 0.719 | |
| Triiodothyronine | 0.719 | |
| Mineral metabolism and bone modeling | ||
| Osteopontin | 0.708 | |
| Parathyroid hormone | 0.708 | |
Loadings shown in the table are factor loadings/component coefficients in principal component analysis. The factor loadings are the correlation coefficients between the variables and factors/components. The factors were represented by variables with the corresponding highest loadings among all the 40 included variables in the analysis.