Purpose: To investigate resistance to diet-induced obesity (DIO) and monosodium glutamate (MSG)-induced obesity as well as the underlying mechanisms.
Methods: Newborn mice were used to construct DIO and MSG-induced obesity models. Obesity indices, such as body weight, body length, Lee index, body temperature, food intake, fat weight, and leptin level, were examined. Mice that did not exhibit obesity were defined as the obesity-resistant group. The morphological changes of white adipose tissue were observed by hematoxylin and eosin staining, and expression levels of PR domain containing 16 (Prdm16) and uncoupling protein-1 (Ucp-1) in white adipose tissue were measured by Western blot.
Results: Obesity-resistant mice fed a high-fat diet showed resistance beginning at week 5 along with lower weights and lengths than those in the obesity group from weeks 5 to 12. MSG-induced obesity-resistant mice showed features consistent with resistance to obesity from week 1 along with higher body lengths relative to the obesity group; however, the weight difference was not significant until week 10, when body weights decreased significantly in obesity-resistant mice. The Lee index was lower in obesity-resistant mice than in the obesity group and the normal group, further suggesting obesity resistance. Additionally, obesity-resistant mice showed higher levels of leptin, whereas obese mice induced by a high-fat diet showed leptin resistance. Furthermore, Prdm16 and Ucp-1 levels were both downregulated in the obesity group and upregulated in obesity-resistant mice, showing that white fat browning was highest in obesity-resistant mice.
Conclusion: The phenotypes of mice with DIO and MSG-induced obesity differed. Obesity resistance might be related to Prdm16 and Ucp-1-mediated white adipocyte browning.
Keywords: obesity resistance, brown adipose tissue, Ucp-1, adipocyte browning