Dysregulation of gene expression within the peroxisome proliferator activated receptor pathway in morbidly obese patients.
BACKGROUND
The causes of obesity are multifactorial but may include dysregulation of a family of related genes, such as the peroxisome proliferator activated receptor gamma (PPARgamma). When activated, the PPARgamma pathway promotes lipid metabolism. This study used microarray technology to evaluate differential gene expression profiles in obese patients undergoing bariatric surgery.


METHODS
The study enrolled six morbidly obese patients with a body mass index (BMI) exceeding 35 and four nonobese individuals. Blood samples were stabilized in PaxGene tubes (PreAnalytiX), and total RNA was extracted. Next, 100 ng of total RNA was amplified and labeled using the Ovation RNA Amplification System V2 with the Ovation whole-blood reagent (NuGen) before it was hybridized to an Affymetrix (Santa Clara, CA) focus array containing more than 8,500 verified genes. The data were analyzed using an analysis of variance (ANOVA) (p < 0.05) in the GeneSpring program, and potential pathways were identified with the Ingenuity program. Real-time quantitative reverse transcriptase-polymerase chain reaction was used to validate the array data.


RESULTS
A total of 97 upregulated genes and 125 downregulated genes were identified. More than a 1.5-fold change was identified between the morbidly obese patients and the control subjects for a cluster of dysregulated genes involving pathways regulating cell metabolism and lipid formation. Specifically, the PPARgamma pathway showed a plethora of dysregulated genes including tumor necrosis factor-alpha (TNFalpha). In morbidly obese patients, TNFalpha expression was increased (upregulated) 1.6-fold. These findings were confirmed using quantitative polymerase chain reaction with a 2.8-fold change.


CONCLUSIONS
Microarrays are a powerful tool for identifying biomarkers indicating morbid obesity by analyzing differential gene expression profiles. This study confirms the association of PPARgamma with morbid obesity. Also, these findings in blood support previous work documented in tissue (omentum, liver, and stomach). Based on these findings in blood, the authors plan to explore postoperative changes in gene expression by analyzing blood samples after bariatric surgery. Ultimately, these findings may promote the development of therapeutic agents targeted to specific dysfunctional genes.
Department of Surgery, George Washington University Medical Center, Washington, DC, USA.
A Katharine
AK
Hindle
Jadd
J
Koury
Tim
T
McCaffrey
Sidney W
SW
Fu
Fred
F
Brody
D000328:Adult; D000368:Aged; D015992:Body Mass Index; D005786:Gene Expression Regulation; D020022:Genetic Predisposition to Disease; D006801:Humans; D008875:Middle Aged; D009767:Obesity, Morbid / Q000097:blood / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D047495:PPAR gamma / Q000097:blood / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011379:Prognosis; D012313:RNA / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics*; D055815:Young Adult
D047495:PPAR gamma; D012313:RNA