p38α blocks brown adipose tissue thermogenesis through p38δ inhibition
Fig 6
Activation of p38δ is responsible for BAT activation.
(A) Immunoblot analysis of BAT lysate from Fab-Cre and p38αFab-KO mice fed an HFD for 8 weeks. Left: 23 °C; right: comparison of 23 °C versus 30 °C. (B) qRT-PCR analysis of mRNA expression of p38β (Mapk11), p38γ (Mapk12), and p38δ (Mapk13) in BAT Fab-Cre and p38αFab-KO mice fed an HFD for 8 weeks. mRNA was normalised to level of Gapdh mRNA (mean ± SEM, Fab-Cre n = 15 mice; p38αFab-KO n = 9 mice) (C) Body weight in Fab-Cre and p38δFab-KO male (8–10-wk-old) mice fed an ND over 8 weeks (mean ± SEM; Fab-Cre n = 6 mice; p38δFab-KO n = 6 mice). (D) Body, fat, and lean mass in p38δFab-KO and Fab-Cre mice after 8 weeks of ND measured by NMR (mean ± SEM; Fab-Cre n = 6 mice; p38δFab-KO n = 5 mice). (E) Comparison of energy balance between ND-fed Fab-Cre and p38δFab-KO mice. ND-fed mice were examined in a metabolic cage over a 3-day period to measure FI and EE. FI (upper left panel; mean ± SEM; Fab-Cre n = 12 mice; p38δFab-KO n = 10 mice) and EE (upper right panel; mean ± SEM; Fab-Cre n = 6 mice; p38δFab-KO n = 6 mice) over 2 days were corrected by lean mass. EE expressed as ANCOVA analysis (lower left panel; mean ± SEM; Fab-Cre n = 9 mice; p38δFab-KO n = 12 mice) and hour by hour over a 48-hour period (lower right panel; mean ± SEM; Fab-Cre n = 12 mice; p38δFab-KO n = 12 mice) are also shown. (F) Body temperature of ND-fed Fab-Cre and p38δFab-KO mice (mean ± SEM; Fab-Cre n = 9 mice; p38δFab-KO n = 11 mice). Skin temperature surrounding interscapular BAT in ND-fed Fab-Cre and p38δFab-KO. Right panels show representative infrared thermal images (mean ± SEM; Fab-Cre n = 10 mice; p38δFab-KO n = 12 mice). (G) Adipocytes differentiated from interscapular BAT were stimulated with 100 nM T3 for 48 hours. Immunoprecipitation from cell lysates of p38δ were evaluated by immunoblot with antibodies against phospho-p38 and p38δ. Adipocytes differentiated from sWAT were stimulated with 1 μM NE for 1 hour, and p38 phosphorylation was analysed by immunoblot. (H) Control mice (C57BL/6) were exposed to cold (4 °C) for the indicated time, and phosphorylation of the different p38s in BAT was evaluated by immunoblot (n = 5 for each group; representative blot presented). (I) Body temperature of ND-fed Fab-Cre and p38δFab-KO mice exposed to cold (4 °C) for 1 hour (mean ± SEM; Fab-Cre n = 10 mice; p38δFab-KO n = 8 mice). Skin temperature surrounding interscapular BAT in ND-fed Fab-Cre and p38δFab-KO after 1 hour of cold exposure. Right panels show representative infrared thermal images (mean ± SEM; Fab-Cre n = 9 mice; p38δFab-KO n = 8 mice). *p < 0.05; **p < 0.01; ***p < 0.001 (t test). See also S1 Data. BAT, brown adipose tissue; Creb, cAMP response element-binding; EE, energy expenditure; FI, food intake; HFD, high-fat diet; IR temperature, infrared temperature; ND, normal-chow diet; NE, norepinephrine; NMR, nuclear magnetic resonance; qRT-PCR, quantitative real-time polymerase chain reaction; sWAT, subcutaneous fat.