An experiment to determine the optimal protein requirement of grouper Epinephelus coioides juveniles was conducted in floating net cages (1.5 m × 1 m × 1.5 m). Six isoenergetic fishmeal–casein-based experimental diets containing 350–600 g kg⁻¹ crude protein (CP) were fed to triplicate groups of 20 fish (10.7 ± 0.2 g) for 56 days. Weight gain (WG) and specific growth rate (SGR) increased with increasing dietary protein level from 350 to 450 g kg⁻¹ and then plateaued above these levels. Feed intake (FI) showed no significant difference among fish fed more than 350 g kg⁻¹ CP. Lowest feed conversion ratio (FCR) was found for fish fed 500 g kg⁻¹ CP but this was not significantly different from that of fish fed the 450 and 600 g kg⁻¹ CP. Lowest protein efficiency ratio (PER) was found for fish fed 550 and 600 g kg⁻¹ CP. Fish fed the 600 g kg⁻¹ CP had the highest body protein and moisture contents but the lowest body lipid content. Body ash content was unaffected by protein level for fish fed >400 g kg⁻¹ CP. Dietary protein level had no significant effect on hepatosomatic index (HSI). Fish fed the 350 g kg⁻¹ CP had significantly lower condition factor (CF) and viscerosomatic index (VSI). Based on broken-line regression analysis of SGR the optimal dietary protein requirement for E. coioides juveniles was determined to be close to 480 g kg⁻¹.

Chondrocyte senescence and reduced lubrication play pivotal roles in the pathogenesis of age‐related osteoarthritis (OA). In the present study, highly lubricated and drug‐loaded hydrogel microspheres are designed and fabricated through the radical polymerization of sulfobetaine (SB)‐modified hyaluronic acid methacrylate using microfluidic technology. The copolymer contains a large number of SB and carboxyl groups that can provide a high degree of lubrication through hydration and form electrostatic loading interactions with metformin (Met@SBHA), producing a high drug load for anti‐chondrocyte senescence. Mechanical, tribological, and drug release analyses demonstrated enhanced lubricative properties and prolonged drug dissemination of the Met@SBHA microspheres. RNA sequencing (RNA‐seq) analysis, network pharmacology, and in vitro assays revealed the extraordinary capacity of Met@SBHA to combat chondrocyte senescence. Additionally, inducible nitric oxide synthase (iNOS) has been identified as a promising protein modulated by Met in senescent chondrocytes, thereby exerting a significant influence on the iNOS/ONOO‐/P53 pathway. Notably, the intra‐articular administration of Met@SBHA in aged mice ameliorated cartilage senescence and OA pathogenesis. Based on the findings of this study, Met@SBHA emerges as an innovative and promising strategy in tackling age‐related OA serving the dual function of enhancing joint lubrication and mitigating cartilage senescence.