BACKGROUND: Obesity is a major health concern and increases risk of metabolic syndrome, type 2 diabetes, dyslipidemia, cardiovascular diseases and many cancers. Obesity occurs with decreased physical activity and increased caloric intake. Clinical management is still limited. Brown adipose tissue is a thermogenic organ which expresses uncoupling protein 1. When activated it increases energy expenditure by up to 20%. Recent evidence suggests that white adipose tissue can be ‘browned’ and have similar characteristics, called beige fat.
AIMS: This project tested a “beiging” agent capsaicin to determine whether it could brown human fat and improve metabolism.
METHODS: We used a “Humanised Mouse Model” where human fat is inserted intra-abdominally in immune suppressed mice (to avoid rejection). Mice were fed ad libitum normal or a high fat diet (45% calories from fat) ± 0.03% capsaicin. Metabolic studies were conducted before and after fat transplant and 12 weeks on diets. These studies included glucose and insulin tolerance tests and metabolic cages. mRNA and histology samples were taken.
RESULTS: Results show increases in energy expenditure (vCO2 and vO2) in mice fed capsaicin compared to their respective controls. High fat diet + capsaicin fed mice showed improvements in glucose tolerance and insulin sensitivity. The human fat showed up-regulation of uncoupling protein 1.
CONCULSONS: These results indicate beiging of human white fat is possible and has the potential to improve metabolism. A 20% increase in energy expenditure has the potential to cause clinically significant improvements in obesity. Further studies will examine combination therapies to optimise browning.