The aim of the study was to evaluate gastric bypass, intestinal slow release, and bioavailability of L–Lysine encapsulated in solid lipid microcapsules (L–SLMs), compared to free L–Lysine, in swine. The pharmacokinetics profile of L–SLMs was characterized in vitro and validated in vivo. In vitro, the release of L–Lys from SLMs was evaluated incubating a 0.5 g sample at 40°C first in gastric phase (pepsin buffer, pH=1.5; 2h) and then in intestinal phase (pancreatin buffer; pH=7.5; 8h). L–Lys quantification was performed via Kjeldahl method. In vivo, 12 weaner piglets (BW=15 ± 2 kg) were fed corn meal and divided in 3 groups (n=4) receiving an oral dose of either saline solution (placebo), free L–Lys at 0.17 g/kg BW (control) or L–SLMs at 0.38 g/kg BW (treatment), which provided the same amount of L–Lys. Plasma samples were collected before oral admistration and hourly until 24h. L–Lys was quantified by LC–MS/MS. Data were analyzed using Two–Way ANOVA, with differences considered significant at P<0.05. In vitro, the gastroprotection of L–Lys from SLMs was 84% at 2h, while the intestinal release was 80% at 8h. In vivo, free L–Lys showed a plasma peak concentration of 1054.10 µM after 1h and completely disappeared after 8h. Conversely, L–SLMs displayed a plasma peak concentration of 1184 µM at 3–4h, and then the hematic L–Lys concentration gradually decreased to 0 until 24h. The bioavailability was higher for L–SLMs compared to free L–Lys (AUC=7902 µM×h and 3175 µM×h, respectively). Overall, the administration of L–Lys in SLMs has the potential to guarantee intestinal slow release and enhanced bioavailability of L–Lys compared to not protected L–Lys.
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