Figure 8.
Endothelial-specific activation of mTORC1 signaling recapitulates adipose tissue phenotype of Myct1ecKOmice. (A)Tsc1ecKO mouse model. See Materials and methods for details. (B) Endothelial Tsc1 ablation activates sustained mTORC1 signaling in vivo. En face staining of aorta for p-S6 (gray) and VE-cadherin (magenta). Scale bar, 50 μm. (C) Quantification of mTORC1 activation in the aortic endothelium of wild-type and Tsc1ecKO mice. The percentage of p-S6+ cells was quantified in n = 5 mice per genotype and conditions; 300–500 cells were analyzed per aorta; mean ± SD; Welch’s t test, P = 0.0121 (*). (D) Workflow of Tsc1ecKO mouse analysis. (E) Wild-type and Tsc1ecKO mice were analyzed before significant difference in body weight. Quantification of body weight at the start and end of experiment. n = 10–12 mice per genotype; mean ± SD; multiple unpaired t tests, P > 0.05 at start, P = 0.116 at end. (F) Quantification of fat pad weight to body weight ratio relative to wild-type mice. n = 9 mice per genotype; mean ± SD; multiple unpaired t tests, P = 0.001 (*) for interscapular WAT (IsWAT), P = 0.027 for interscapular BAT (IsBAT), P < 0.001 (*) for inguinal (Ing), P < 0.001 (*) for retroperitoneal (RP), P < 0.001 (*) for gonadal (Gon), and P < 0.001 (*) for mesenteric (Mes). (G)Tsc1 ablation reduces size of adipocytes. Retroperitoneal thick sections stained for Laminin α4 (gray) and Pecam1 (magenta). Scale bar, 50 μm. (H) Quantification of adipocyte size in wild-type and Tsc1ecKO fat. n = 5 mice per genotype; mean ± SD; unpaired t test, P = 0.0056 (*). (I) Schematic view of the role of endothelial MYCT1–IFITM2/3 complexes in WAT homeostasis. MYCT1 interacts with IFITM2/3, limiting their function and allowing nutrient transport for energy storage. In the absence of MYCT1, IFITM2/3 accumulate in early endosomes and trigger continuous endolysosomal cargo degradation and hyperactivation of mTORC1 signaling in ECs, restricting energy storage in WAT. Icons used in A, D, and I were created with BioRender.com and modified in Affinity. Refer to the image caption for details. Panel A shows a diagram of the T s c 1 e c K O mouse model. Panel B presents en-face staining of the aorta for p-S 6 and V E-cadherin, highlighting the activation of m T O R C 1 signaling in vivo. Panel C quantifies the percentage of p-S 6 positive cells in the aortic endothelium of wildtype and T s c 1 e c K O mice. Panel D outlines the workflow of the T s c 1 e c K O mouse analysis. Panel E compares the body weight of wildtype and T s c 1 e c K O mice at the start and end of the experiment. Panel F quantifies the fat pad weight to body weight ratio relative to wildtype mice across different fat depots. Panel G shows retroperitoneal thick sections stained for Laminin 4 and Pecam1, illustrating the reduced size of adipocytes in T s c 1 e c K O mice. Panel H quantifies the adipocyte size in wildtype and T s c 1 e c K O fat. Panel I provides a schematic view of the role of endothelial M Y C T 1-I F I T M 2 slash 3 complexes in white adipose tissue homeostasis.

Endothelial-specific activation of mTORC1 signaling recapitulates adipose tissue phenotype of Myct1 ecKO mice. (A) Tsc1 ecKO mouse model. See Materials and methods for details. (B) Endothelial Tsc1 ablation activates sustained mTORC1 signaling in vivo. En face staining of aorta for p-S6 (gray) and VE-cadherin (magenta). Scale bar, 50 μm. (C) Quantification of mTORC1 activation in the aortic endothelium of wild-type and Tsc1ecKO mice. The percentage of p-S6+ cells was quantified in n = 5 mice per genotype and conditions; 300–500 cells were analyzed per aorta; mean ± SD; Welch’s t test, P = 0.0121 (*). (D) Workflow of Tsc1ecKO mouse analysis. (E) Wild-type and Tsc1ecKO mice were analyzed before significant difference in body weight. Quantification of body weight at the start and end of experiment. n = 10–12 mice per genotype; mean ± SD; multiple unpaired t tests, P > 0.05 at start, P = 0.116 at end. (F) Quantification of fat pad weight to body weight ratio relative to wild-type mice. n = 9 mice per genotype; mean ± SD; multiple unpaired t tests, P = 0.001 (*) for interscapular WAT (IsWAT), P = 0.027 for interscapular BAT (IsBAT), P < 0.001 (*) for inguinal (Ing), P < 0.001 (*) for retroperitoneal (RP), P < 0.001 (*) for gonadal (Gon), and P < 0.001 (*) for mesenteric (Mes). (G)Tsc1 ablation reduces size of adipocytes. Retroperitoneal thick sections stained for Laminin α4 (gray) and Pecam1 (magenta). Scale bar, 50 μm. (H) Quantification of adipocyte size in wild-type and Tsc1ecKO fat. n = 5 mice per genotype; mean ± SD; unpaired t test, P = 0.0056 (*). (I) Schematic view of the role of endothelial MYCT1–IFITM2/3 complexes in WAT homeostasis. MYCT1 interacts with IFITM2/3, limiting their function and allowing nutrient transport for energy storage. In the absence of MYCT1, IFITM2/3 accumulate in early endosomes and trigger continuous endolysosomal cargo degradation and hyperactivation of mTORC1 signaling in ECs, restricting energy storage in WAT. Icons used in A, D, and I were created with BioRender.com and modified in Affinity.

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