Fig. 4
Upregulation of β-oxidation proteins by the HFD, despite accompanying loss of CPT1B with ageing. a Scatter plot of normalized levels of β-oxidation proteins detected in mouse quadriceps via targeted proteomics Each dot represents the mean value of a specific protein on the HFD (y-axis) vs the LFD (x-axis). Prior to plotting, the levels of each protein were normalized to the average value of the same protein in all animals. Proteins along the dashed line are not regulated by the diet (mean LFD = mean HFD), while proteins above or below the line are up- or downregulated, respectively, by the HFD. CPT1B, carnitine palmitoyltransferase 1B. b Relative CPT1B content in all groups. c Total CPT activity measured in mitochondrial samples and corrected for the enrichment of the preparation (CSmito/CShomog) as mentioned in Fig. 3D. d, e Quantification of very-long-chain acyl-CoA dehydrogenase (VLCAD) and medium-chain ketoacyl-CoA thiolase (MCKAT). f, g Schematic representation of the effects of age and diet on the TCA cycle and ETC, respectively. Each box represents a protein that has been measured by our method, and the specific isoforms or subunits that have been measured are annotated. Red arrows represent the effect of diet (HFD vs LFD) while the grey arrows indicate the age effect (old vs young) based on significant two-way ANOVA results. PDH, pyruvate dehydrogenase complex; CS, citrate synthase; ACO2, aconitase; IDH, isocitrate dehydrogenase; OGCD, α-ketoglutarate dehydrogenase complex; SCL, succinyl-CoA ligase; SDH, succinate dehydrogenase (complex II); FH, fumarate dehydrogenase; MDH2, malate dehydrogenase; ANT, adenine nucleotide translocator; MPC, mitochondrial phosphate carrier protein; UCP, uncoupling protein. Data are shown as mean ± SEM and were analysed using two-way ANOVA, and multiple comparisons were performed using Tukey’s correction. N = 6–10 per group; **p < 0.01 (HFD vs LFD), *p < 0.05 (HFD vs LFD), matched ages, and #p < 0.05 (old vs young), matched diets. Supporting data values can be found in Additional file 10 and proteomics dataset in Additional files 4 and 5