Prox1 heterozygous mice have a defective lymphatic vasculature and develop late-onset obesity. Chyle abnormally leaks from those vessels, accumulates in the surrounding tissues, and causes an increase in adipose tissue. We characterized the lymphatics of Prox1+/– mice to determine whether the extent of obesity correlated with the severity of lymphatic defects. The lymphatic vasculature in Prox1+/– mice exhibited reduced tracer clearance from the ear skin, dysfunctional perfusion of the lower legs, and reduced tracer uptake into the deep lymphatic collectors during mechanostimulation prior to the onset of obesity. Ear lymphatic vessels and leg collectors in Prox1+/– mice were disorganized and irregular, further confirming that defective lymphatic vessels are associated with obesity in Prox1+/– mice. We now provide conclusive in vivo evidence that demonstrates that leaky lymphatics mediate obesity in Prox1+/– mice, as restoration of lymphatic vasculature function was sufficient to rescue the obesity features in Prox1+/– mice. Finally, depth-lipomic profiling of lymph contents showed that free fatty acids induce adipogenesis in vitro.
Noelia Escobedo, Steven T. Proulx, Sinem Karaman, Miriam E. Dillard, Nicole Johnson, Michael Detmar, Guillermo Oliver
(A and B) Weight distribution in young (2–3 months of age) (A) and old (5–10 months of age) (B) WT and Prox1+/– mice. (C and D) Quantification of half-life of P20D800 dye in young (C) and old (D) WT and Prox1+/– mice. (E and F) Clearance rate (K rate) of P20D800 dye, as a measure of lymphatic ear clearance, in young (E) and old (F) WT and Prox1+/– mice. *P ≤ 0.05; ***P ≤ 0.0001, 2-tailed Student’s t test.