Splicing Cues of PKCdelta modulate adipogenesis and susceptibility to obesity

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 649-659-Basic Mechanisms of Obesity
Basic
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-656
Niketa A. Patel*1, Gay Carter2, Andre Apostolatos3, Rekha Patel3, Denise R. Cooper*4 and Michel M. Murr5
1James A. Haley Veteran's Hosp, Tampa, FL, 2J.A. Haley VA Hospital, Tampa, FL, 3University of South Florida, Tampa, FL, 4Univ of South Florida JA Haley, Tampa, FL, 5University of South Florida
Obesity continues to escalate as a significant public health problem and as the leading preventable cause of death. Genetic, environmental, behavioral, and socioeconomic factors cause excess weight gain and obesity. Dysregulated proliferation and differentiation of pre-adipocytes to mature adipocytes (dysregulated adipogenesis) within the fat tissues are central to obesity. Alternative splicing occurs in more than 85% of genes and is a powerful step in gene expression to diversify the genomic repertoire. Our data demonstrate that in lean adipocytes, expression of the signaling kinase protein kinase C delta (PKCδ) changes dramatically to its pro-survival variant PKCδVIII between days 2-4 when the cells terminally differentiate. Expression of PKCδVIII in obese preadipocytes is markedly increased. On day 0, lean pre-adipocytes (from the subcutaneous depot) which are serum-starved undergo increased apoptosis while the mature adipocytes (day 10) are more resistant to apoptosis upon serum-starvation. On day 0, lean preadipocytes expressed the apoptotic splice variants PKCδI, caspase 9a and lower levels of Bcl-xL. By day 4, cells started expressing the anti-apoptotic proteins Bcl2 and splice variants PKCδVIII, caspase 9b and Bcl-xL with a concurrent decrease in pro-apoptotic proteins. This represents a critical switch in adipocyte differentiation modulated by the splicing of apoptosis genes. Pre-adipocytes from the subcutaneous depot of obese patients are more resistant to apoptosis compared to lean on day 0 (AV and PI: lean 30.7%; obese 16.7%). Day 10 mature adipocytes demonstrate much lower susceptibility to serum deprived apoptosis (lean 18.7%; obese 10.4%). Obese preadipocytes expressed PKCδVIII, Bcl-xL, Bcl2 and caspase 9 on day 0 i.e. in the pre-adipocyte stage. We observed increased expression of PKCδVIII as determined by the PKCδ splice variant ratio observed on day 0.  Real-time qPCR analysis indicated that PKCδVIII expression was increased dramatically in obese samples along with a marked decrease in FOXO, SIRT1, adiponectin and PPARγ expression compared to lean samples. Over-expression of PKCδVIII had an inhibitory effect on adipogenesis as determined by expression of the adipogenesis marker genes PPARγ, SIRT1, FOXO1 and adiponectin by real time RT-PCR using SYBR. Further, overexpression of PKCδVIII increases Bcl2 and Bcl-xL expression on day 0. These results indicate developmentally regulated alternative splicing of PKCδVIII modulates adipogenesis.

Nothing to Disclose: NAP, GC, AA, RP, DRC, MMM

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: Supported by grant from VA Merit Review to N.A.P.