Interfacial Protein Fibril Polymorphisms Regulate In Vivo Adipose Expansion for Control of Obesity

Obesity is becoming a worldwide pandemic. Interfacial engineering of food lipid is expected to inhibit diet-induced obesity without damage to the eating enjoyment brought by high-fat diets. Unfortunately, this strategy has not been achieved yet. After screening different plant proteins, bromelain and papain were found to form wormlike and long-straight protein fibrils, respectively. The conversion of long-straight amyloid-like fibrils to wormlike fibrils was demonstrated in the fibrillation of bromelain. Using oil-in-water high internal phase emulsions (HIPEs) as a proof of concept, bromelain fibrils showed dramatically stronger interfacial stabilization capabilities than papain fibrils with high application potentials in the real-world formulation of high-fat food products such as mayonnaise. Compared with papain fibrils, oral administration of HIPEs stabilized by bromelain fibrils resulted in substantially higher fecal lipid contents and significantly decreased expression levels of the genes related to lipid absorption and transport in the intestine, including CD36, FATP-2, FATP-4, and APOA-4, without a difference in intervening gut microbiota. Consequently, dramatically less lipid absorption in the small intestine, markedly smaller chylomicron particles in the plasma, lower serum triglycerides, and controlled energy and lipid metabolism, as well as the inhibition of adipose expansion and overweight, were observed in the group with gavage of HIPEs stabilized by the bromelain fibrils rather than the papain fibrils. Furthermore, with the same calorie, substitution of all the fat in the standard high-fat feed of mice with the HIPEs emulsified by the bromelain fibrils showed a significantly stronger effect than the ones prepared by the papain fibrils on preventing high-fat-diet (HFD)-induced obesity including alleviation of adipose expansion and inflammation as well as fatty liver, also via inhibiting the absorption and transport of lipid in the intestine. The effect is ascribed to the suppressed lipolysis caused by a more compact and elastic interfacial layer formed by the wormlike fibrils than that of the long-straight fibrils, which are resistant to gastric environments and replacement by bile acids in digestion. Therefore, we provide an appealing and general strategy for controlling obesity by reducing the supply of free fatty acids (FAs) for absorption in the enteric lumen through protein fibril polymorphisms at the interface.