Adipophilin protein expression in muscle--a possible protective role against insulin resistance.
Adipophilin is a 50 kDa protein that belongs to the PAT family (perilipin, adipophilin, TIP47, S3-12 and OXPAT), which comprises proteins involved in the coating of lipid droplets. Little is known about the functional role of adipophilin in muscle. Using the C2C12 cell line as a model, we demonstrate that palmitic acid-treated cells highly express the adipophilin protein in a dose-dependent way. Next, we show that oleic acid is a more potent inducer of adipophilin protein levels than palmitic acid. Cells treated with oleic acid have a higher adipophilin protein expression and higher triglyceride levels but less impairment of insulin signaling than cells treated with palmitic acid. Additionally, we show that peroxisome proliferator-activated receptor (PPAR)alpha, PPARbeta/delta and PPARgamma agonists all increase the expression of the adipophilin protein in C2C12 cells. This effect was most pronounced for the PPARalpha agonist GW7647. Furthermore, the expression of adipophilin as a 37 kDa N-terminally truncated protein is higher in the gastrocnemius than in the quadriceps of C57BL/6J mice, especially after an 8-week high-fat diet. The expression of adipophilin was higher in the muscle of mice fed a 4-week high-fat diet based on olive oil or safflower oil than in mice fed a 4-week high-fat diet based on palm oil. After 2 weeks of intervention, plasma glucose, plasma insulin and the homeostasis model assessment of insulin resistance index were lower in mice fed a 4-week high-fat diet based on olive oil or safflower oil than in mice fed a 4-week high-fat diet based on palm oil. Taken together, the results obtained in the present study indicate that adipophilin protein expression in muscle is involved in maintaining insulin sensitivity.
de Wilde
Janneke
J
Nutrigenomics Consortium, Top Institute Food and Nutrition, Wageningen, The Netherlands. j.dewilde@hb.unimaas.nl
Smit
Egbert
E
Snepvangers
Frank J M
FJ
de Wit
Nicole W J
NW
Mohren
Ronny
R
Hulshof
Martijn F M
MF
Mariman
Edwin C M
EC
D000818:Animals; D002460:Cell Line; D004041:Dietary Fats / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D007333:Insulin Resistance / Q000502:physiology*; D008565:Membrane Proteins; D051379:Mice; D018482:Muscle, Skeletal / Q000378:metabolism; D019301:Oleic Acid / Q000494:pharmacology; D000069463:Olive Oil; D000073878:Palm Oil; D019308:Palmitic Acid / Q000494:pharmacology; D010455:Peptides / Q000235:genetics*; D000070780:Perilipin-2; D047492:Peroxisome Proliferator-Activated Receptors / Q000502:physiology; D010938:Plant Oils / Q000494:pharmacology; D020543:Proteome / Q000187:drug effects; D012450:Safflower Oil / Q000378:metabolism
D004041:Dietary Fats; D007328:Insulin; D008565:Membrane Proteins; D000069463:Olive Oil; D010455:Peptides; D000070780:Perilipin-2; D047492:Peroxisome Proliferator-Activated Receptors; D010938:Plant Oils; C000602983:Plin2 protein, mouse; D020543:Proteome; D019301:Oleic Acid; D019308:Palmitic Acid; D000073878:Palm Oil; D012450:Safflower Oil