Biodegradable four-arm star-shaped poly(ethylene glycol)-block-poly(L-lactic acid) copolymer (sPEG-b-PLLA), four-arm star-shaped poly(L-lactic acid) (sPLLA), linearly poly(ethylene glycol)-block-poly(L-lactic acid) copolymer (PEG-b-PLLA) and linearly poly(L-lactic acid) (PLLA) were synthesized from L-lactice acid, pentaerythritol, poly(ethylene glycol) and star-shaped poly(ethylene glycol), using the method of melt polycondensation, and the products were characterized and confirmed by 1H NMR spectroscopy, FT-IR and GPC. Four types of ibuprofen loaded microspheres based on the above four types of polymers, i.e., IBU/PLLA, IBU/sPLLA, IBU/PEG-b-PLLA, and IBU/sPEG-b-PLLA microspheres were prepared using the method of solvent evaporation, and the optimized preparation technology was obtained via orthogonal experiments, and the drug-encapsulating properties and in vitro drug-releasing properties were studied. The results showed that compared with IBU/PLLA and IBU/PEG-b-PLLA microspheres, the drug encapsulate efficiency of IBU/sPLLA and IBU/sPEG-b-PLLA microspheres were higher and the in vitro drug releasing rate slowed down, which mainly due to the faster degradation of sPLLA and sPEG-b-PLLA for the star-shaped structure and the block copolymerization of sPEG. The drug releasing curves of these three types of microspheres could be fit by first-order equation, and the releasing mechanism was non-Fickian diffusing, i.e., the synergetic effect of polymer degradation and drug diffusion.

Aim To study the effects of HiHi and HiLo on the lipid metabolism in rats through blood lipids and fatty acid oxidation in gastrocnemius of rats. Methods Thirty male SD rats were selected by means of adaptive training, and then divided into 3 groups randomly: living low-training low group (LoLo), living high-training high group (HiHi), and living high-training low group (HiLo). The rats ran on a treadmill 60 min a day at the speed of 35 m/min under normoxic condition or 30 m/min under hypoxic condition (13.6% of ambient FIO_2), 6 days a week for 4 weeks. The samples from blood and gastrocnemius were removed 24 hours after the last training by the end of 4-week experiment. TC, TG, HDL and LDL were tested with a full-automatic biochemical analyzer. LPL, leptin and AD were measured using ELISA. Real-time quantitative PCR was adopted to test the expression of PPARa and CPT-1 mRNA in rats' gastrocnemius. Results Compared to the LoLo, TC and TG decreased significantly (P0.05) and LPL and AD increased significantly (P<0.01) in HiHi.' PPARa mRNA and CPT-1 mRNA expressions in gastrocnemius were significantly higher in HiHi(P<0.05) than in LoLo, and significant descent of HDL(P<0.05) and CPT-1 mRNA expression(P<0.01) revealed in HiLo, as compared to the LoLo. Compared to the HiLo, HDL(P<0.05), and LPL, AD and CPT-1 mRNA expression(P<0.01) enhanced in HiHi. Conclusion (l) HiHi was more superior in regulation of blood lipids than LoLo due to increasing of LPL, and could facilitate fatty acid oxidation because of enhancement of CPT-1 mRNA, AD and PPARa mRNA. (2) Comparing to the normoxic training, HiLo had no beneficial effect on the blood lipid metabolism and decreased the fatty acid oxidation in gastrocnemius.(3 )HiHi was more superior in the effeet of HDL thah HiLo due to increasing of LPL, and could facilitate fatty acid oxidation because of enhancement of AD and CPT-1 mRNA.