Peroxisomal gene and protein expression increase in response to a high-lipid challenge in human skeletal muscle

Fig. 1.. Intramyocellular lipid is significantly correlated with peroxisomal biogenesis factor 19 (PEX19) protein in human skeletal muscle. TAG assay, BODIPY staining, and western blot were performed to quantify the neutral lipid and PEX19 content respectively in human skeletal muscle tissue extracts in the pre-high fat meal and post-7d diet protocol conditions. Results are shown as a scatter plot of paired variables and regression analysis (A) Serum TG and PEX19 (n = 21) (B) IMTG and PEX19 (n = 21), (C) lipid droplets and PEX19 (n = 18), (D) western blots for PEX19 protein and α-tubulin (loading control); data are mean ± SEM expressed as arbitrary units, (E) BODIPY: high lipid and low lipid droplets.

Fig. 2.. Mitochondrial-peroxisomal fatty acid oxidation is significantly correlated with intramyocellular lipid content in human skeletal muscle. Correlation between palmitate complete oxidation as 14CO2 and lipid droplet (fluorescent intensity) (N = 12; r = 0.70; P = 0.01) (B) palmitate (C16:0) oxidation with etomoxir and lipid droplet (N = 12; r = 0.65; P = 0.02), (C) correlation scatter plot between intramyofiber lipid droplets by BODIPY assessment and complete lignocerate (C24:0) oxidation (N = 12; r = 0.63; P = 0.02).

Fig. 3.. Peroxisomal mRNA is up-regulated in response to a high fat meal in human skeletal muscle in both lean and obese subjects. mRNA expression levels (A) PMP70, (B) PEX19, (C) PEX11A and (D) PEX5 were significantly up-regulated 4-h post - high fat meal. mRNA expression levels were quantified using RT-PCR. Data (mean ± SEM) were normalized to 18S and then compared to the lean subjects. *P ≤ 0.05 vs. pre-HFM. ** P < 0.05 between lean and obese. HFM: high fat meal (n = 4/group).

Fig. 4.. PMP70 mRNA is up-regulated after 7 days high fat diet in human skeletal muscle from obese subjects. mRNA levels for (A) PMP70, (B) PEX19, (C) PEX11A and (D) PEX5 by RT-PCR. *P ≤ 0.05 vs. pre-HFD. ** P < 0.05 between lean and obese. HFM: high fat meal. HFD: high fat diet. Data (mean ± SEM) were normalized to 18S and then compared to the lean subjects (n = 4/group).

Fig. 5.. Peroxisomal mRNA and protein responses to a high fatty acid treatment in human primary myotubes. Quantification of (A) PMP70, (B) CrOT, (C) PGC-1α, and (D) ERRα gene expression by RT-PCR after 12 h high fat incubation on day 5 of differentiation in human primary myotubes (n = 4/group). All data were normalized to 18S. (E) PMP70 protein content in human primary myotubes derived from lean vs. obese subjects after high fatty acid treatment for 48 h (n = 6/group). PMP70: peroxisomal membrane protein; CrOT: carnitine octanoyl transferase; ERRα: (estrogen related receptor α). Data are presented as mean ± SEM normalized to lean controls. *P ≪ 0.05 vs. control.