Engineered protease-stable SP2 and SP9 peptides attenuate MASLD via bile acid micelle disruption and PPAR activation

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a pervasive global health challenge, often progressing to more severe conditions like MASH and cirrhosis. Current pharmacological therapies are limited in efficacy, and natural bioactive compounds frequently suffer from poor druggability due to gastrointestinal (GI) instability. A critical gap exists for therapies that can effectively target the gut-liver axis and modulate hepatic lipid metabolism without significant systemic exposure, addressing both intestinal absorption and liver metabolic pathways.

Researchers engineered two protease-resistant peptide analogs, SP2 and SP9, derived from soystatin (SP), to overcome GI degradation. They evaluated the peptides' bile acid micellar-disruptive capacities in degradative GI environments. In MASLD animal models, the peptides' effects on serum and hepatic lipids, as well as hepatic steatosis, were assessed and compared to cholestyramine at equivalent doses. Pharmacokinetic analysis determined systemic exposure. Further mechanistic studies investigated the peptides' impact on PPAR signaling, fatty acid β-oxidation, bile acid pool, and gut microbiome. Finally, a Lactobacillus plantarum WCSF1 strain was engineered to continuously secrete SP2 and SP9-repeats in situ, and its efficacy in attenuating MASLD activity scores and improving lipid profiles was evaluated.

The engineered peptides, SP2 and SP9, maintained potent bile acid micellar-disruptive capacities even in the degradative GI environment. In MASLD models, these peptides significantly reduced serum and hepatic lipids, while also resolving hepatic steatosis. This effect was found to be superior to that of cholestyramine at the same dose and equivalent weight. Pharmacokinetic analysis confirmed that SP2 and SP9 exhibited gut-localized activity with negligible systemic exposure. Their mechanism involves a "dual-hit" lipid-lowering strategy: physically, they block intestinal cholesterol absorption by impairing micelle formation, similar to cholestyramine. Biologically, they reprogram hepatic lipid metabolism by activating the peroxisome proliferator-activated receptor (PPAR) signaling pathway and fatty acid β-oxidation, concurrently modulating the bile acid pool linked to an altered gut microbiome. The peptides also mitigated oxidative hepatocellular damage through the downregulation of oxidative phosphorylation. > Engineered Lactobacillus plantarum WCSF1 continuously secreting SP2 and SP9-repeats in situ significantly attenuated MASLD activity scores and improved lipid profiles in animal models.