Background
The identification of factors related to obesity is very important for an early diagnosis of susceptibility to obesity and, accordingly, its prevention. The objective of the current study was to search for specific obesity-related factors in serum, as they can be measured non-invasively.
Material and Method
Male Sprague-Dawley rats were fed a high-fat (HF) diet for eight weeks to generate obesity-prone (OP) and obesity-resistant (OR) rats. After blood sampling, serum proteome analysis was conducted using two-dimensional gel electrophoresis (2-DE) combined with mass spectrometry (MS).
Results
Apolipoprotein A-I (apo A-I), beta-actin, and vitamin D-binding protein (DBP) prepeptide were up-regulated in both the OP and OR rats. Two down-regulated haptoglobulins were observed in the OP and OR rats. Alpha1-macroglobulin (alpha1-M) and an unknown protein product were decreased in the OP rats compared with the OR rats. Alpha1-M was nearly undetectable in the OP rats from the 2-DE map and was further confirmed to be down-regulated by ELISA.
Conclusions
The syntropic changes in the proteins apo A-I, beta-actin, DBP prepeptide, and haptoglobulin in the OP and OR rats might be a reflection of the HF diet. The unknown protein product should be isolated and identified. Alpha1-M is proved to be a potential serum factor related to obesity proneness and obesity resistance.

Keywords: alpha-Macroglobulins - metabolism, Proteome - metabolism, Obesity - metabolism, Dietary Fats - administration & dosage, serum, Body Composition