Effects of early administration of insulin-like growth factor-1 on cognitive function in septic encephalopathy

Figures & data

Figure 1 IGF-1 cannot improve the survival rate of septic rats.

Notes: No statistically significant difference was found between the antibiotic and antibiotic + IGF-1 groups, while survival was significantly reduced in the saline and IGF-1 groups compared with the antibiotic and antibiotic + IGF-1 groups.
Abbreviation: IGF-1, insulin-like growth factor-1.

Figure 2 IGF-1 can improve the memory in a new environment of septic rats.

Notes: Compared with training session in each group, the number of crossings and rearings in testing session is reduced in sham-operative, antibiotic + IGF-1, and IGF-1 groups (Student’s t-test, ^*P<0.01), while no differences are found in antibiotic group (Student’s t-test, P=0.08 in crossing, P=0.12 in rearing) or saline group (Student’s t-test, P=0.52 in crossing, P=0.14 in rearing).
Abbreviation: IGF-1, insulin-like growth factor-1.

Figure 3 IGF-1 can improve the spatial learning and memory of septic rats.

Notes: (A) Compared with the sham-operation group, escape latency was longer in the antibiotic and saline groups on the third and fourth days, while no significant differences were found among the four groups on the first two days (ANOVA, P>0.1). (B) The number of times the rats reached the target quadrant was lower in the antibiotic and saline groups compared with the sham-operation group (ANOVA and Bonferroni’s test, ^*P<0.05); no statistically significant differences were found between the antibiotic and saline groups (ANOVA and Bonferroni’s test, P=0.43) or among the sham-operation, antibiotic + IGF-1, and IGF-1 groups (Bonferroni’s test, P>0.1).
Abbreviation: IGF-1, insulin-like growth factor-1.

Figure 4 IGF-1 can relieve the impairment of noxious memory in septic rats.

Notes: Compared with the training session, latency in the testing session was longer in the sham-operation, antibiotic + IGF-1, and IGF-1 groups (Nemenyi test, #P<0.001); no differences were found in the antibiotic (Nemenyi test, P=0.34) and saline (Nemenyi test, P=0.24) groups. Compared with the antibiotic and saline groups, latency was prolonged in the sham-operation, antibiotic + IGF-1, and IGF-1 groups in the testing session (Kruskal–Walls H-test and Nemenyi test, ^*P<0.01), while no differences were found between the antibiotic and saline groups (Nemenyi test, P=0.24) or among the sham-operation, antibiotic + IGF-1, and IGF-1 groups (Nemenyi test, P>0.1).
Abbreviation: IGF-1, insulin-like growth factor-1.

Figure 5 IGF-1 could not improve the depressive-like symptoms which might be caused by SE.

Notes: Compared with the sham-operative group, immobility time was prolonged in the antibiotic, antibiotic + IGF-1, saline, and IGF-1 groups (^*P<0.01). No significant differences were found among the four groups administered CLP (P>0.1).
Abbreviations: CLP, cecal ligation and puncture; IG F-1, insulin-like growth factor-1; SE, septic encephalopathy.

Figure 6 IGF-1 cannot improve the memory of septic rats in a new environment when it is administrated at 12, 24, or 36 hours after CLP.

Notes: Compared with their own data in the training session, the number of crossings and rearings was decreased in the testing session in the 0-hour and 6-hour IGF-1 groups (Student’s t-test, ^*P<0.05), while no differences were found in the 12-hour (Student’s t-test, P=0.34 in crossings, P=0.49 in rearings), 24-hour (Student’s t-test, P=0.33 in crossings, P=0.34 in rearings), and 36-hour (Student’s t-test, P=0.25 in crossings, P=0.28 in rearings) IGF-1 groups.
Abbreviations: CLP, cecal ligation and puncture; IGF-1, insulin-like growth factor-1.

Figure 7 IGF-1 cannot improve the spatial learning and memory of septic rats when it is administrated at 12, 24, or 36 hours after CLP.

Notes: (A) Escape latency was shorter in the 0-hour and 6-hour groups compared with the other groups on the third and fourth days. No differences were found on the first 2 days among groups (ANOVA, P>0.1). (B) The number of times the rats reached the target quadrant in the 0-hour and 6-hour IGF-1 groups was higher than that of the 12-hour, 24-hour, and 36-hour IGF-1 groups (ANOVA and Bonferroni’s test, ^*P<0.01). No differences were found among the 12-hour, 24-hour, and 36-hour IGF-1 groups, or between the 0-hour and 6-hour IGF-1 groups (Bonferroni’s test, P>0.1).
Abbreviations: CLP, cecal ligation and puncture; IGF-1, insulin-like growth factor-1.

Figure 8 IGF-1 cannot improve the impairment of noxious memory of septic rats when it is administrated at 12, 24, or 36 hours after CLP.

Notes: Latency is longer in 0-hour and 6-hour groups (Kruskal–Walls H-test and Nemenyi test, ^*P<0.01), while no differences exist neither between 0-hour and 6-hour IGF-1 groups (Nemenyi test, P=0.087) nor among 12-hour, 24-hour, and 36-hour IGF-1 groups (Nemenyi test, P>0.05). Compared with training session, latency is longer in testing session in 0-hour and 6-hour IGF-1 groups (Nemenyi test, ^#P<0.001), while no differences are found in 12-hour (Nemenyi test, P=0.09), 24-hour (Nemenyi test, P=0.17), and 36-hour (Nemenyi test, P=0.25) IGF-1 groups.
Abbreviations: CLP, cecal ligation and puncture; IGF-1, insulin-like growth factor-1.

Figure 9 Inhibition of cell apoptosis in the hippocampus is associated with improvement of memory and learning during sepsis.

Notes: (A) Cells stained with fluorescein-dUTP were visualized under a fluorescence microscope (40×). The nucleus was stained by DAPI (blue). Compared with the sham-operation group (n=9), the rates of apoptotic cells were higher in the antibiotic (n=9) and antibiotic + IGF-1 (n=7) groups (Kruskal–Walls H-test and Nemenyi test, ^*P<0.001). Compared with the antibiotic + IGF-1 group, the antibiotic group showed a higher rate of apoptotic cells (Kruskal–Walls H-test and Nemenyi test, ^#P<0.001). (B) Nissl’s staining was visualized under an optical microscope (40×). Neurons with normal morphology were predominant in the sham-operation and antibiotic + IGF-1 groups (black arrow), while those with early or end-stage apoptotic morphology were common in the antibiotic group (red arrow). The rates of neuron apoptosis in the antibiotic and antibiotic + IGF-1 groups were higher than that of the sham-operation group (ANOVA and Bonferroni’s test, ^*P<0.001). Besides, the rate of neuron apoptosis in the antibiotic group was higher than that of the antibiotic + IGF-1 group (ANOVA and Bonferroni’s test, ^#P<0.001).
Abbreviation: IGF-1, insulin-like growth factor-1.

Figure 10 Cytochorme C and TNFR are activated at different time points and IGF-1 can inhibit their expression.

Notes: (A) Six hours after CLP, the expression of cytochrome C and caspase-9 is increased in antibiotic group (n=8) (ANOVA and Bonferroni’s test, ^*P<0.005), but no differences exist between the sham-operative group (n=10) and antibiotic + IGF-1 group (n=9) (Bonferroni’s test, P=0.26 in cytochrome C, P=0.29 in caspase-9). The expression of TNFR and caspase-8 has no differences among the three groups (ANOVA and Bonferroni’s test, P>0.5). (B) Twelve hours after CLP, the expression of TNFR and caspase-8 is increased in antibiotic group (n=7) (ANOVA and Bonferroni’s test, ^*P<0.01), but no differences are found between the sham-operative group (n=10) and antibiotic + IGF-1 group (n=9) (Bonferroni’s test, P=0.25 in TNFR, P=0.43 in caspase-8). The expression of cytochrome C and caspase-9 is increased in antibiotic group (ANOVA and Bonferroni’s test, ^*P<0.005), whereas no differences are observed between the sham-operative and antibiotic + IGF-1 groups (Bonferroni’s test, P=0.63 in cytochrome C, P=0.15 in caspase-9).
Abbreviations: Caspase, cysteinyl aspartate specific proteinase; CLP, cecal ligation and puncture; Cyt C, cytochrome C; IGF-1, Insulin-like growth factor-1; TNFR, tumor necrosis factor receptor.

Figure S1 Experimental procedures.

Notes: (A) Experimental procedure for the first part. IGF-1, ceftriaxone, and saline were given and different duration and behavior tests were conducted 10 days after CLP. (B) Experimental procedure for the second part. IGF-1 was given at 0, 6, 12, 24, or 36 hours after surgery in each group, respectively, and then supplied every 12 hours for 10 days. Ceftriaxone and saline were given the same way as that in the first part and then behavior tests were conducted 10 days after CLP. (C) Experimental procedure for the third part. IGF-1, ceftriaxone, and saline were given at different time points. Western blot, TUNEL staining, and Nissl’s staining were conducted at 6 and 12 hours after surgery.

Abbreviations: CLP, cecal ligation and puncture; IGF-1, insulin-like growth factor-1.