Figure 3

TBI induces metabolic dysfunction that disappears between 2 and 4 weeks following TBI. TBI-treated flies = red; age-matched, uninjured control flies = dark grey. (A) TBI-treated flies die faster under starvation than age-matched, uninjured controls at 48 h (p < 0.0001) and 2 weeks (p < 0.01) post-TBI, but not at 4 weeks post-TBI, according to both Log-rank and Gehan-Breslow-Wilcoxon survival comparison tests. Representative survival curves shown (44–50 flies per condition); at least three independent replicates were performed yielding similar results. (B) Mass is unchanged following TBI, according to a two-way ANOVA, with Sidak’s multiple comparison correction (six replicates of 20 flies each per group). (C) TBI-treated flies display lower lipid stores (triacylglycerides, TAG) at 48 h (p < 0.001) and 2 weeks (p < 0.0001) post-TBI, but not at 4 weeks post-TBI, according to two-way ANOVA, with Sidak’s multiple comparison correction. Lipids were extracted from TBI-treated and age-matched control flies (six replicates of 20 flies each per group) and measured in triplicate with thin-layer chromatography (TLC) and amido black stain (representative images shown), normalized to mass of individual sample and a reference sample of pure coconut oil, which was included on all TLC plates as a standard. (D) TBI-treated flies at 2 weeks post-TBI do not display an increased rate of lipid utilization during starvation. TBI-treated flies display similar reductions in lipid amount after 18 h and 24 h of starvation, as their age-matched, uninjured control flies, according to two-way ANOVA, with Sidak’s multiple comparison correction (six replicates of 20 flies each per group). TBI leads to short-term mobilization of carbohydrates, but returns to normal levels by 2 weeks. (E) Glycogen and (F) Glucose levels are significantly decreased (p < 0.001 and < 0.05, respectively) in TBI-treated flies relative to controls at 48 h post-TBI, but not at 2 or 4 weeks post-TBI. (G) Trehalose levels are not significantly different at any timepoint post-TBI. Significance determined by two-way ANOVAs, with Sidak’s multiple comparison tests, for each carbohydrate.