Regulation of metabolism by neuronal mTORC1
Knockdown of mammalian target of rapamycin complex 1 (mTORC1) by 35% or 60% during adulthood does not impact longevity or body size. (a) Gene diagrams depicting the inducible Cre recombinase and recombination of the Raptor allele after Cre recombinase expression. (b) Tissue expression of Cre recombinase as measured by β-galactosidase (β-gal) activity in the β-gal reporter strain. (c) Cre expression in brain regions measured as β-gal activity. (d) Cre expression in whole brain lysates measured as β-gal activity during development. (e) Raptor mRNA expression levels of in the brain of neuronal mTORC1 animals. (f) mTORC1 formation levels as determined by immunoprecipitation of mTOR and immunoblotting for Raptor and mTOR.(g) Representative images and (h) quantification of mTORC1 signaling, measured as phosphorylated rpS6 by immunofluorescence in hippocampal tissue sections. mTORC1 signaling levels as determined by (i) phosphorylated rpS6 and (j) phosphorylated 4EBP in cortical lysates. (k) Cross-sectional body weight of adult male neuronal mTORC1 mice. (m) Lifespan of adult neuronal mTORC1 mice. Data are mean ± SEM. *p<0.05, ***p<0.001.
Adult neuronal mTORC1 regulates metabolism. (a) Glucose tolerance test (GTT). (b) Insulin tolerance test (ITT). (c) Body mass composition shown as percentage fat mass. (d) Oxygen consumption, (e) carbon dioxide production, (f) respiratory quotient, and (g) blood glucose and (h) blood lactate levels before and after running on a treadmill until exhaustion. (i) Distance traveled before exhaustion was reached. (j) Relative mRNA expression of mitochondrial genes in muscle tissue. (k) Relative phosphorylation levels of glycogen synthase (GS) measured by Western immunoblot. (l) Pyruvate tolerance test (PTT). (m) Area under the curve data from the PTT. (n) Relative mRNA expression of gluconeogenesis genes in the liver. Data are means ± SEM. n=4-15 per group. *p<0.05, different from control. **p<0.01, different from control.
Changes in organismal metabolism by neuronal mTORC1 knockdown are only partially driven by mTORC1 signaling from hypothalamus. (a) mRNA expression of gluconeogenesis genes in AML12 cells cultured with control or 35 KD mouse serum. (b) Glycogen content in C2C12 cells cultured with control or 35 KD mouse serum. Ratio of phosphorylated to total (c) glycogen synthase kinase 3β (pGSK3β) and (d) glycogen synthase (GS) in C2C12 cells cultured with control or 35 KD mouse serum. (e) Glycogen content in C2C12 cells cultured with control or 35 KD mouse serum or a mixture of both serums. (f) Glycogen content in C2C12 cells cultured with 35 KD filtered serum with whole control serum or filtered control serum with whole 35 KD mouse serum. (g) PTT in animals hypothalamic-specific mTORC1 KD animals and controls. (h) Area under the curve data from the PTT in animals hypothalamic-specific mTORC1 KD animals and controls. Data are means ± SEM. n=7-10 per group.