Sustained Elevation of Circulating Growth and Differentiation Factor ...

Bloch et al2 days for those who developed muscle wasting (p = 0.62,Mann-Whitney U test). Length of stay in hospital was alsosimilar in the two groups (median 8 for nonwasting and 9 forwasting patients, p = 0.44, Mann-Whitney U test). One patientdied at 21 days postoperatively in the wasting group; no patientsdied in the nonwasting group.Change in US RF csaThe mean change in US RF csafrom baseline over the weekfor the wasting group (n = 23) was a loss of 24.6% ± 13.7%(Fig. 1). The mean change in the nonwasting group (n = 19)was not significant (1.3% ± 5.9%).MyostatinBaseline plasma myostatin did not differ significantly betweenthe groups (p = 0.1). Unexpectedly, plasma myostatin concentrationfell significantly in both groups following surgery.In both groups, plasma myostatin concentration returned tobaseline at day 7 (Fig. 2).Growth and Differentiation Factor-15Baseline plasma GDF-15 also did not differ significantly betweenthe groups (p = 0.52). In contrast to myostatin, GDF-15 levels increased dramatically after surgery (p < 0.001 forboth groups). In the nonwasting patients, the increase inGDF-15 returned to baseline by day 7 (p > 0.05); however, inthe wasting group, the level remained significantly elevated(p < 0.01; Fig. 3). The ratio of the geometric mean of GDF-15 for nonwasting subjects to wasting subjects was 1.17 (0.97,1.41), suggesting that the geometric mean for the nonwastingsubjects was on average higher than that for the wastingsubjects over the week after cardiac surgery although the ratiofailed to achieve statistical significance of p = 0.10. This togethersuggests a higher relative exposure to circulating GDF-15Figure 3. Plasma growth and differentiation factor-15 (GDF-15) concentration(pg/mL) in nonwasting (n = 19) and wasting patients (thosewith > 9.24% muscle loss: n = 23) preoperatively (PO), on day 1 (D1),day 2 (D2), and day 7 (D7). Data presented as box and Whisker plotswith median, interquartile ranges, and 5–95% percentiles. *p < 0.05;**p < 0.01; ***p < 0.001; ns = not significant; repeated-measures Friedman’swith Dunn’s correction for comparison with preoperative baseline.in the wasting patients in comparison those in whom musclewasting did not develop.Insulin-Like Growth Factor-1Baseline plasma IGF-1 did not differ significantly betweenthe groups (p = 0.22). The pattern of change in IGF-1 levelsafter surgery was the same in both groups, the IGF-1 plasmaconcentration fell significantly at days 1 and 2 after surgery inboth groups (p < 0.001 for both). In the nonwasting group, theIGF-1 concentration returned to baseline by day 7 (p > 0.05).However, in wasting patients, it remained significantly reducedat day 7 (p < 0.01, Fig. 4).Figure 2. Plasma myostatin concentration (ng/mL) in nonwasting (n =19) and wasting patients (those with > 9.24% muscle loss: n = 23) preoperatively(PO), on day 1 (D1), day 2 (D2), and day 7 (D7). Data presentedas box and Whisker plots with median, interquartile ranges, and 5–95%percentiles. *p < 0.05; **p < 0.01; ***p < 0.001; ns = not significant;repeated-measures Freidman’s test with Dunn’s correction for comparisonwith preoperative baseline.Figure 4. Plasma insulin-like growth factor-1 (IGF-1) concentration(ng/mL) in nonwasting (n = 19) and wasting patients (those with> 9.24% muscle loss: n = 23) preoperatively (PO), on day 1 (D1),day 2 (D2), and day 7 (D7). Data presented as box and Whisker plotswith median, interquartile ranges, and 5–95% percentiles. *p < 0.05;**p < 0.01; ***p < 0.001; ns = not significant; repeated-measures Freidman’stest with Dunn’s correction for comparison with preoperativebaseline.986 www.ccmjournal.org April 2013 • Volume 41 • Number 4