title: PPARγ Regulates Mouse Meibocyte Differentiation and Lipid Synthesis.
abstract: Previous reports suggest that age-related meibomian gland atrophy is associated with decreased expression of the lipid-sensitive nuclear receptor, PPARγ. The purpose of this study was to identify the role of PPARγ in modulating meibocyte lipid synthesis.
  
  
  
  Cytoplasmic and nuclear fractions from meibomian glands of young (2M) and old (2Y) C57Bl6 mice were probed using antibodies specific for PPARγ. Mouse meibocytes were cultured, immortalized using a SV40 lentiviral vector, and evaluated for lipid synthesis using LipidTox staining and CARS/Raman microspectroscopy. Lipid synthesizing clones were tested for effects of PPARγ agonist, rosiglitazone, on lipid synthesis and PPARγ localization, post-translational modification and induction of PPARγ response genes.
  
  
  
  The cytoplasmic fraction in young mice contained both 50 and 72 kDa PPARγ bands that were absent or reduced by 75% in older mice, respectively. Cultured meibocytes produced neutral lipid containing equal amounts of wax and cholesterol esters, similar to mouse meibum. Addition of rosiglitazone (10-50 μM) significantly increased lipid production (P<.05) in meibocytes, associated with SUMO1 sumoylation and cytoplasmic accumulation of the 72 kDa PPARγ. Rosiglitazone also increased the localization of PPARγ to the cytoplasm and up-regulated of PPARγ, ADP and ADFP mRNA.
  
  
  
  This study confirms the loss of cytoplasmic/vesicular PPARγ localization in older, atrophic mouse meibomian glands. Furthermore, PPARγ stimulates lipid synthesis in mouse meibocytes, associated with PPARγ sumoylation and translocation to the cytoplasm. Taken together these data suggest that lipid synthesis in older mice is down regulated by a PPARγ mediated pathway.
authors.affiliation: Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA. Electronic address: jjester@uci.edu.
authors.forename: James V
authors.initials: JV
authors.lastname: Jester
authors.affiliation: Department of Chemistry and Beckman Laser Institute, University of California, Irvine, Irvine, CA.
authors.forename: Eric
authors.initials: E
authors.lastname: Potma
authors.affiliation: Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA.
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Brown
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation / Q000502:physiology*; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000502:physiology; D007004:Hypoglycemic Agents / Q000494:pharmacology; D008055:Lipids / Q000096:biosynthesis*; D008297:Male; D008537:Meibomian Glands / Q000166:cytology* / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D047495:PPAR gamma / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D000077154:Rosiglitazone; D045162:Thiazolidinediones / Q000494:pharmacology
chemical_list: D007004:Hypoglycemic Agents; D008055:Lipids; D047495:PPAR gamma; D045162:Thiazolidinediones; D000077154:Rosiglitazone
keywords: PPARγ; eyelid; lipid; meibocytes; meibomian gland; tear film