Serum proteomic analysis reveals the differential dose effects of crocodile oil from Crocodylus siamensis on energy metabolism in rats

Background: Dietary fat composition is a potential major factor affecting energy metabolism. Crocodile oil (CO) is rich in mono- and poly-unsaturated fatty acids exhibiting anti-inflammatory and healing properties. Aim: This study investigated different levels of CO consumption on alterations and expression of proteins involved in energy metabolism in rats. Methods: Twenty-one male Sprague-Dawley rats were divided into three groups and administered sterile water (N) or different doses of CO (1% or 3% [v/w] CO) orally once daily for 8 weeks. Body weight gain, food intake, energy intake, blood lipid profiles, and serum energy-related metabolites were determined. The serum proteome was analyzed using shotgun proteomics, and the functions of several candidate proteins were classified using PANTHER software. Results: There were no significant differences in body weight or energy intake were observed between groups. However, both CO-treated groups showed significantly decreased serum triglyceride (TG) levels (p<0.05). Moreover, post-treatment serum TG levels in the 1% CO group were significantly lower than pre-treatment compared with other groups. The serum oxaloacetate level was also significantly higher in both CO groups than in the N group. The proteomic analysis classified 4,525 serum proteins and revealed more unique proteins involved in cellular metabolic activity in both CO-treated groups than in the N group. Self-organizing tree algorithm clustering of 295 shared differentially expressed proteins in both CO-treatment groups showed that upregulated hyper-expressed protein clusters in both CO groups were associated with catalytic activity and molecular activity on the same levels. Conclusion: CO simultaneously enhances energy metabolism and improves lipid profiles.