Background: The limited bioavailability of free phytosterols restricts their clinical application in managing hypercholesterolemia. This study aimed to develop phytosterol nanoparticles (PNs) to enhance bioactivity and investigate their cholesterol-lowering efficacy and underlying mechanisms in vivo. Methods: Phytosterol nanoparticles (PNs) (93.35 nm) were engineered using soy protein isolate and administered orally at concentrations of 4.00–12.50 mg/mL to high-fat-diet-induced hypercholesterolemic mice (n = 60) over a 4-week period. Serum and hepatic lipid profiles, histopathology, gene/protein expression related to cholesterol metabolism, and fecal sterol content were evaluated. Results: PNs dose-dependently reduced serum total cholesterol (TC: 28.6–36.8%), triglycerides (TG: 22.4–30.1%), and LDL-C (31.2–39.5%), while increasing HDL-C by 18.7–23.4% compared to hyperlipidemic controls (p < 0.01). Hepatic TC and TG accumulation decreased by 34.2% and 41.7%, respectively, at the highest dose, with histopathology confirming attenuated fatty degeneration. Mechanistically, PNs simultaneously suppressed cholesterol synthesis through downregulating HMGCR (3.2-fold) and SREBP2 (2.8-fold), while enhancing cholesterol catabolism via CYP7A1 upregulation (2.1-fold) at protein level. Although less potent than simvastatin (p < 0.05), the nanoparticles exhibited unique dual-pathway modulation absent in conventional phytosterol formulations. Fecal analysis revealed dose-responsive cholesterol excretion (36.01 vs. 11.79 mg/g in controls), indicating enhanced enteric elimination. While slightly less potent than simvastatin (p < 0.05), PNs offered unique dual-pathway modulation absent in conventional phytosterol formulations. Conclusions: Nano-encapsulation significantly improves the bioavailability and hypocholesterolemic efficacy of phytosterols. PNs represent a promising nutraceutical strategy for cholesterol management by concurrently regulating cholesterol synthesis and catabolism, with potential application in both preventive and therapeutic contexts.

A total of 288 male Cobb broilers were randomly assigned to four dietary treatments: crumbled-pellet feed (CPF), hard-pellet feed (HPF), standard-nutrient soft-pellet feed (SPF), and low-nutrient SPF, each with eight replicates of nine birds. The 42-day trial was divided into stage 1 (days 1–21) and stage 2 (days 22–42). In stage 1, the broilers fed standard-nutrient SPF showed higher final body weight (FBW) and lower dry matter feed conversion ratio (DMFCR) than those fed CPF (p < 0.05), along with enhanced liver antioxidant capacity, reduced serum uric acid (UA) and creatinine (CREA), and improved intestinal morphology and disaccharidase activities compared with the CPF group. In stage 2, continued SPF feeding increased abdominal fat, serum total cholesterol (TC), and liver malondialdehyde (MDA) and reduced intestinal microbiota diversity (p < 0.05). In contrast, the broilers switched to HPF in stage 2 achieved growth performance comparable to that of the broilers fed SPF throughout both stages (TG3) but without health impairment. Low-nutrient SPF maintained growth despite reduced protein levels but increased dysbiosis risk. Under the conditions tested in this study, feeding standard-nutrient SPF in stage 1 followed by HPF in stage 2 appeared to be the most effective strategy among those tested, maximizing performance while preserving health. However, because the dietary formulations were intentionally adjusted to achieve the desired nutrient levels for each feed type, the observed effects reflect the combined influence of feed form and nutrient composition; further studies with iso-nutrient controls are needed to confirm the specific role of feed form.