Background and aims: The oral administration of insulin has so far been precluded by gastro-intestinal enzyme degradation and poor intestinal absorption. Preliminary evidence for peptide uptake by the gut has recently been obtained, by our research group, following the administration of nanostructured lipid-carrier suspensions loaded with glargine insulin in healthy animal models.
Methods and results: In this experimental study, glargine insulin-loaded nanostructured lipid carriers have been converted into solid oral dosage forms (tablets, capsules), that are more suitable for administration in humans and have prolonged shelf-life. The liquid and solid oral dosage forms were tested for glargine insulin uptake and glucose responsivity in healthy and streptozotocin-induced diabetic rats (6 animals in each group). A suitable composition gave redispersible solid oral dosage forms from glargine insulin-loaded carriers, using both spray-drying and freeze-drying. It was observed that the liquid and solid formulations had relevant hypoglycaemic effects in healthy rats, while only capsules were efficacious in diabetic rats; probably because of gut alterations in these animal models. Detected glargine insulinaemia was consistent with a glycaemic profile.
Conclusion: The formulations under study showed their potential as oral glucose-lowering agents, particularly when used as capsules. However, further study is needed to produce a useful orally-active insulin preparation.
Keywords: Insulin therapy; Nanostructured lipid carrier; Oral therapies.
Copyright © 2020 The Italian Diabetes Society, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved.