FIGURE 9.

Starvation activates FoxO transcription factors and induces autophagy pathway gene expression in mouse hearts in vivo. To assess the effects of short term nutrient deficiency on induction of cardiomyocyte autophagy in vivo, adult FVBN mice (3 months) were fasted for 48 h. The phosphorylation status of FoxO transcription factors in heart cell extracts from fed and starved mice was examined by Western blot (A) and quantified by densitometric analysis in B. In fed mice, phosphorylated p-FoxO1 and p-FoxO3 are increased relative to starved mice, whereas the total FoxO1 and FoxO3 protein level was unchanged. In the starved mouse heart, p-FoxO1 and p-FoxO3 was reduced by 30% compared with the fed mouse heart. Decreased AKT phosphorylation and increased Sirt1 also were observed in starved mouse heart. The level of LC3II and the ratio of LC3II/LC3I from the starved mouse heart are both increased by 2.0-fold compared with the fed mouse heart, demonstrating that autophagy is induced in the starved mouse heart. Significance (*) was determined by Student's t test (p < 0.05; n = 3). C, expression of autophagy pathway genes in fed and starved mouse hearts was determined by quantitative real time RT-PCR. Significantly increased gene expression of LC3 (1.6-fold) and Gabrapl1 (2-fold) was observed in the starved mouse heart compared with the fed mouse heart. No significant change in Atg12 gene expression was observed between fed and starved mouse hearts. Significance (*) was determined by Student's t test (p < 0.05; n = 4).