Decrease in Insulin-Like Growth Factor-1 and Insulin-Like Growth Factor-1 Ratio in the First Week of Stroke Is Related to Positive Outcomes.

BACKGROUND: High insulin-like growth factor-1 (IGF-1), measured once during acute stroke, is associated with greater survival rates and lower stroke severity. However, information is lacking regarding how IGF-1 availability, determined by IGF-1's ratio to insulin-like growth factor binding protein-3 (IGFBP-3), relates to recovery and how the response of IGF-1 during the first week of stroke relates to outcomes. The purpose of this study was to determine the following: (1) the relationship between percent change in IGF-1 and IGF-1 ratio during the first week of stroke and stroke outcomes; and (2) the difference in percent change in IGF-1 and IGF-1 ratio in individuals being discharged home and individuals being discharged to inpatient facilities. METHODS: IGF-1 and IGFBP-3 were quantified from blood sampled twice (<72 hours of admission; 1 week post stroke) in 15 individuals with acute stroke. Length of stay, modified Rankin Scale at 1 month, and discharge destination were obtained from electronic medical records. RESULTS: Percent change in IGF-1 ratio was related to length of stay (r = .54; P = .04). Modified Rankin Scale (n = 10) was related to percent change in IGF-1 (r = .90; P < .001) and IGF-1 ratio (r = .75 P = .01). Individuals who went home (n = 7) had decreases in IGF-1 (-24 + 25%) and IGF-1 ratio (-36 + 50%), whereas individuals who went to inpatient facilities (n = 8) had increases in IGF-1 (37 + 46%) and IGF-1 ratio (30 + 40%). These differences were significant (IGF-1: P = .008; IGF-1 ratio: P = .01). CONCLUSION: Our findings suggest that a decrease in IGF-1 and IGF-1 ratio during the first week of stroke is associated with favorable outcomes: shorter length of stay, greater independence at 1 month on the modified Rankin Scale, and discharging home.

Estimated Prestroke Peak VO2 Is Related to Circulating IGF-1 Levels During Acute Stroke.

Background Insulin-like growth factor-1 (IGF-1) is neuroprotective after stroke and is regulated by insulin-like binding protein-3 (IGFBP-3). In healthy individuals, exercise and improved aerobic fitness (peak oxygen uptake; peak VO2) increases IGF-1 in circulation. Understanding the relationship between estimated prestroke aerobic fitness and IGF-1 and IGFBP-3 after stroke may provide insight into the benefits of exercise and aerobic fitness on stroke recovery. Objective The purpose of this study was to determine the relationship of IGF-1 and IGFBP-3 to estimated prestroke peak VO2 in individuals with acute stroke. We hypothesized that (1) estimated prestroke peak VO2 would be related to IGF-1 and IGFBP-3 and (2) individuals with higher than median IGF-1 levels will have higher estimated prestroke peak VO2 compared to those with lower than median levels. Methods Fifteen individuals with acute stroke had blood sampled within 72 hours of hospital admission. Prestroke peak VO2 was estimated using a nonexercise prediction equation. IGF-1 and IGFBP-3 levels were quantified using enzyme-linked immunoassay. Results Estimated prestroke peak VO2 was significantly related to circulating IGF-1 levels (r = .60; P = .02) but not IGFBP-3. Individuals with higher than median IGF-1 (117.9 ng/mL) had significantly better estimated aerobic fitness (32.4 ± 6.9 mL kg-1 min-1) than those with lower than median IGF-1 (20.7 ± 7.8 mL kg-1 min-1; P = .03). Conclusions Improving aerobic fitness prior to stroke may be beneficial by increasing baseline IGF-1 levels. These results set the groundwork for future clinical trials to determine whether high IGF-1 and aerobic fitness are beneficial to stroke recovery by providing neuroprotection and improving function.