Dietary 23-Hydroxy Ursolic Acid Protects Against Diet-Induced Weight Gain and Hyperglycemia by Protecting Monocytes and Macrophages Against Nutrient Stress-Triggered Reprogramming and Dysfunction and Preventing Adipose Tissue Inflammation

The aim of this study was to determine whether the atheroprotective phytochemical 23-hydroxy ursolic acid protects against diet-induced obesity and hyperglycemia by preventing nutrient stress-induced monocyte reprogramming. After a two week run-in period on a defined, phytochemical-free low-fat maintenance diet, 12-week old female C57BL/6J mice were either kept on the maintenance diet for additional 13 weeks or switched to either a high-calorie diet, a high-calorie diet supplemented with either 0.05% 23-hydroxy ursolic acid or a high-calorie diet supplemented with 0.2% 23-hydroxy ursolic acid. Dietary supplementation with 23-hydroxy ursolic acid reduced weight gain and adipose tissue mass, prevented hyperglycemia, hyperleptinemia and adipose tissue inflammation, and preserved glucose tolerance. 23-Hydroxy ursolic acid also preserved blood monocyte mitogen-activated protein kinase phosphatase-1 activity, a biomarker of monocyte health, and reduced macrophage content in the adipose tissue. Targeted gene profiling by qRT-PCR using custom-designed TaqMan® Array Cards revealed that dietary 23-hydroxy ursolic acid converts macrophages into a transcriptionally hyperactive phenotype with enhanced antioxidant defenses and anti-inflammatory potential. In conclusion, our findings show that dietary 23-hydroxy ursolic acid exerts both anti-obesogenic effects through multiple mechanisms. These include improving glucose tolerance, preventing hyperleptinemia, maintaining blood monocyte function, reducing recruitment of monocyte-derived macrophages into adipose tissues during nutrient stress, and converting these macrophages into an anti-inflammatory, potentially inflammation-resolving phenotype, all contributing to reduced adipose tissue inflammation. Our data suggest that 23-hydroxy ursolic acid may serve as an oral therapeutic and dietary supplement suited for patients at risk for obesity, impaired glucose tolerance and cardiovascular disease.

Keywords: 23-hydroxy ursolic acid; MKP-1; antioxidant; macrophages; monocytes; obesity.