AIMTo investigate the enhancing effect on insulin absorption through GI tract in mice by using tomato lectin (TL) modified liposomes as the carrier.

METHODSTL-phosphatidylethanolamine (PE) conjugate (TL-PE) was synthesized by using carbodiimide cross-linking method, then the compound was incorporated into the conventional liposomes of insulin. The agglutination test was performed to examine TL biological activities after synthesis and incorporation. When TL modified liposomes were administrated orally to the normal mice or diabetic mice at insulin dose of 350 u x kg(-1), the hypoglycemic effect was determinated according to the blood glucose level.

RESULTSThe blood glucose levels of the normal mice were reduced by modified liposomes. The glucose levels were (85 +/- 5)% at 4 h, (54 +/- 11)% at 8 h, (57 +/- 6)% at 12 h postdose compared with the glucose levels prior to oral administration respectively. However, the conventional liposomes and saline have no hypoglycemic effect. The blood glucose levels of the diabetic mice were obviously reduced by TL modified liposomes, the glucose levels were (38 +/- 13)% at 4 h, (50 +/- 15)% at 8 h, (50 +/- 16)% at 12 h respectively.

CONCLUSIONTL modified liposomes promote the oral absorption of insulin due to the specific-site combination on GI cell membrane.