Fig. 4: During starvation, AMPK is required in cortex glia for ketone body production and export to sustain ketone body-dependent associative memory in neurons.
From: Glia fuel neurons with locally synthesized ketone bodies to sustain memory under starvation
a, Inhibition of AMPKα expression in adult cortex glia impaired K-AM (F2,25 = 8.05, P = 0.002), while ARM was normal in fed flies (F2,33 = 1.76, P = 0.189). b, BODIPY LD staining and quantification in starved and fed flies expressing or not an AMPKα RNAi in cortex glia. In fed flies, inhibition of AMPKα expression in adult cortex glia did not change the LD mean area (t10 = 1.308, P = 0.220), whereas an increase in LD mean area was observed in starved flies as compared to controls (t10 = 2.660, P = 0.0239). c, Starvation strongly increased Bmm and CPT1 mRNA levels (Bmm: t6 = 4.25, P = 0.0054; CPT1: t6 = 7.28, P = 0.0003). d, In starved flies expressing AMPK RNAi in glial cells, Bmm and CPT1 mRNA levels did not differ from those of fed flies (Bmm: t5 = 1.34, P = 0.238; CPT1: t5 = 0.76, P = 0.482), whereas in the genotypic control groups, starvation induced a significant increase in each gene’s mRNA level (Bmm: t5 = 6.54, P = 0.001; CPT1: t5 = 8.55, P = 0.0004). e, Application of 10 mM acetoacetate (red dashed line) resulted in a decreased Laconic ratio followed by a plateau in cortex glia of starved control flies, showing lactate efflux from cortex glia after acetoacetate bath application (mean trace ± s.e.m.). Quantification of the mean Laconic ratio at the plateau was performed during the last 100 s of recording (red line). Inhibition of AMPKα expression in adult cortex glia impaired this lactate efflux evoked by acetoacetate application (t14 = 3.393, P = 0.004). n represents a group of 40–50 flies analysed together in a behavioural assay (a), one BODIPY-stained brain (b), mRNA extracted from a group of 50 flies (c and d) or the response of a single recorded fly (e). Data are expressed as the mean ± s.e.m. with dots as individual values, and analysed by one-way ANOVA with post hoc testing by Newman–Keuls pairwise comparisons test (a) or by unpaired two-sided t-test (b–e). Asterisks refer to the least-significant P value of a post hoc comparison between the genotype of interest and the genotypic controls (a) or the P value of the unpaired t-test comparison (b–e). ***P < 0.001, **P < 0.01, *P < 0.05. Scale bar, 20 µm (b).
