Weight Phenotype Diagnostic Test Method: Body Mass Index or Body Fat Percent for Gene Expression

Obesity continues increasing at epidemic levels worldwide, as does the number of genetic studies that focus on obesity. Body mass index (BMI) is often used to characterize weight phenotypes and obesity status due to its simplicity. Refined measurements of body composition may be needed to understand variations in gene expression. This study explores gene expression when individuals are characterized as overweight based on BMI versus body fat percent. Individuals were recruited to a natural history protocol at the National Institutes of Health. Twelve Caucasian participants with the highest and lowest BMI were included. Whole-body air displacement plethysmography was performed to calculate body fat percent, and BMI was calculated. Fasting whole blood was collected and RNA extracted. Quantitative real time PCR array was used to determine expression of 96 obesity related genes. The PCR array from participants with high BMI compared to low BMI showed dysregulation of four genes: peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A), pro-opiomelanocortin (POMC), growth hormone secretagogue receptor (GHSR), and leptin (LEP), whereas participants with high body fat compared to low body fat showed dysregulation of one gene: PPARGC1A. This research showed differential gene expression and clinical indices depending on method of weight classification.