RESUMEN
Phytosterol metabolism is unknown in the hypercholesterolemia of genetic origin. We investigated the metabolism of phytosterols in a cholesterol-free, phytosterol-containing standard diet in hypercholesterolemic mice knockouts for low density lipoprotein receptor (LDLR) and apolipoprotein E (apoE) mice compared to wild-type mice (controls). Phytosterols were measured in mice tissues by GCMS. ApoE-KO mice absorbed less phytosterols than LDLR-KO and the latter absorbed less phytosterols than control mice, because the intestinal campesterol content was low in both KO mice, and sitosterol was low in the intestine in apoE-KO mice as compared to LDLR-KO mice. Although the diet contained nine times more sitosterol than campesterol, the concentration of sitosterol was lower than that of campesterol in plasma in LDLR-KO, and in the liver in controls and in LDLR-KO, but only in apoE-KO. On the other hand, in the intestine sitosterol was higher than campesterol in controls, and in LDLR-KO but with a tendency only in apoE-KO. Because of the high dietary supply of sitosterol, sitosterol was better taken up by the intestine than campesterol, but the amount of sitosterol was lower than that of campesterol in the liver, while in the whole body the amounts of these phytosterols do not differ from each other. Therefore, via intestinal lymph less sitosterol than campesterol was transferred to the body. However, as compared to controls, in apoE-KO mice, but not in LDLR-KO mice, the increase in campesterol and sitosterol in plasma and in the whole body indicating that apoE-KO mice have a marked defect in the elimination of both phytosterols from the body.
Asunto(s)
Alimentación Animal , Colesterol/análogos & derivados , Hígado/metabolismo , Fitosteroles , Receptores de LDL/deficiencia , Sitoesteroles , Animales , Colesterol/farmacocinética , Colesterol/farmacología , Hígado/patología , Ratones , Ratones Noqueados para ApoE , Fitosteroles/farmacocinética , Fitosteroles/farmacología , Receptores de LDL/metabolismo , Sitoesteroles/farmacocinética , Sitoesteroles/farmacología , Especificidad de la EspecieRESUMEN
In this work, phytosterol-biotransforming strains were selected from Mycobacterium sp., using a high concentration of beta-sitosterol. The selection was made by culturing the strains in a medium enriched with 14 g beta-sitosterol/l as the unique source of carbon. During 2 months, the bacterial cultures were transferred successively. The extraction of the biotransformation products was made with methanol and ethyl acetate. The qualitative and quantitative analysis was made by means of thin-layer chromatography, gas-liquid chromatography (GLC) and GLC-mass spectrometry. Under these conditions, it was observed that after seven transfers, the strains MYcobacterium sp. MB-3683 and the Mycobacterium fortuitum B-11045 increased their biotransformation capacity from 20% to 64% and from 34% to 55%, respectively. The products in the highest proportion identified for each trial were androstenedione and androstadienedione. The results suggest that the high substrate concentration could be a selective mechanism to obtain strains more efficient in the biotransformation of beta-sitosterol into steroidal bases.