The primary objective of the proposed studies is to elucidate the molecular basis of the lipodystrophy syndrome (LDS) in HIV+ patients treated with HIV protease inhibitors (PIs). LDS is characterized by lipoatrophy of subcutaneous adipose tissue with accompanying hypertrophy of visceral adipose tissue. Patients with LDS often show signs of insulin resistance and hypertriglyceridemia. Our central hypothesis is that the lipoatrophy is related to a selective atrophic effect of PIs on the subcutaneous adipocyte leading to a compensatory increase in visceral adiposity. The increased visceral adiposity promotes insulin resistance, increased flux of non-esterified fatty acid to the liver and increased very low density lipoprotein- triglyceride production and secretion. Our preliminary results using model preadipocyte cell lines (3T3-L1 and -F442A) demonstrate that several PIs inhibit preadipocyte differentiation and/or antagonize the adipocyte phenotype (promote loss of triglyceride, loss of adipocyte-specific protein expression and decreased viability perhaps via an apoptotic mechanism). Thus, PIs may promote subcutaneous lipoatrophy in patients with LDS by compromising adipocyte viability and/or preventing replacement of lost adipocytes by inhibiting adipogenesis. We hypothesize that PIs block adipogenesis by preventing expression of the adipogenic transcription factors CCAAT/enhancer-binding protein (C/EBP) alpha and peroxisome proliferator-activated receptor (PPAR) gamma as these are the earliest observable molecular markers to be repressed by PIs. Potential PI-dependent effects to be investigated and that may block expression of C/EBPalpha and/or PPARgamma include: 1) Inhibition of C/EBPbeta/delta-dependent transcriptional activation of C/EBPalpha and PPARgamma gene expression, 2) Failure to derepress C/EBP undifferentiated protein (CUP)/AP-2alpha- and Sp1-dependent repression of C/EBPalpha gene expression and 3) Failure to inactivate antiadipogenic Wnt signaling pathways. We hypothesize that subcutaneous adipocytes are more susceptible than visceral adipocytes to the antagonistic effects of PIs. Human primary adipocytes will be isolated from subcutaneous and visceral depots and examined for differential PI-induced effects. Potential PI- dependent mechanisms to be investigated include: 1) Activation of downstream signaling components in the TNFalpha signal transduction pathway and 2) Inhibition of GLUT4 glucose transporter function. An in vivo preadipocyte implantation technique in mice will be used to test proposed molecular mechanisms of PI action. The long term objective of the proposed research is to facilitate the design of anti-HIV therapeutics that lack lipoatrophic potential.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
1R01DK060787-01
Application #
6423684
Study Section
Metabolism Study Section (MET)
Program Officer
Haft, Carol R
Project Start
2002-02-01
Project End
2006-01-31
Budget Start
2002-02-01
Budget End
2003-01-31
Support Year
1
Fiscal Year
2002
Total Cost
$268,140
Indirect Cost
Name
Johns Hopkins University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
045911138
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Dowell, Paul; Lane, M Daniel (2005) C/EBPalpha reverses the anti-adipogenic effects of the HIV protease inhibitor nelfinavir. Biochem Biophys Res Commun 327:571-4
Zhang, Jiang-Wen; Tang, Qi-Qun; Vinson, Charles et al. (2004) Dominant-negative C/EBP disrupts mitotic clonal expansion and differentiation of 3T3-L1 preadipocytes. Proc Natl Acad Sci U S A 101:43-7