Glucose-responsive artificial promoter-mediated insulin gene transfer improves glucose control in diabetic mice

AIM:To investigate the effect of insulin gene therapy using a glucose-responsive synthetic promoter in type 2 diabetic obese mice.METHODS:We employed a recently developed novel insulin gene therapy strategy using a synthetic promoter that regulates insulin gene expression in the liver in response to blood glucose level changes.We intravenously administered a recombinant adenovirus expressing furin-cleavable rat insulin under the control of the synthetic promoter(rAd-SP-rINSfur) into diabetic Lepr db/db mice.A recombinant adenovirus expressing β-galactosidase under the cytomegalovirus promoter was used as a control(rAd-CMV-βgal).Blood glucose levels and body weights were monitored for 50 d.Glucose and insulin tolerance tests were performed.Immunohistochemical staining was performed to investigate islet morphology and insulin content.RESULTS:Administration of rAd-SP-rINSfur lowered blood glucose levels and normoglycemia was maintained for 50 d,whereas the rAd-CMV-βgal control virus-injected mice remained hyperglycemic.Glucose tolerance tests showed that rAd-SP-rINSfur-treated mice cleared exogenous glucose from the blood more efficiently than control virus-injected mice at 4 wk [area under the curve(AUC):21 508.80 ± 2248.18 vs 62 640.00 ± 5014.28,P < 0.01] and at 6 wk(AUC:29 956.60 ± 1757.33 vs 60 016.60 ± 3794.47,P < 0.01).In addition,insulin sensitivity was also significantly improved in mice treated with rAd-SP-rINSfur compared with rAd-CMV-βgal-treated mice(AUC:9150.17 ± 1007.78 vs 11 994.20 ± 474.40,P < 0.05).The islets from rAd-SP-rINSfur-injected mice appeared to be smaller and to contain a higher concentration of insulin than those from rAd-CMV-βgal-injected mice.CONCLUSION:Based on these results,we suggest that insulin gene therapy might be one therapeutic option for remission of type 2 diabetes.

Glucose-responsive,antioxidative HA-PBA-FA/EN106 hydrogel enhanced diabetic wound healing through modulation of FEM1b-FNIP1 axis and promoting angiogenesis

The diabetic wounds remain to be unsettled clinically,with chronic wounds characterized by drug-resistant bacterial infections,compromised angiogenesis and oxidative damage to the microenvironment.To ameliorate oxidative stress and applying antioxidant treatment in the wound site,we explore the function of folliculininteracting protein 1(FNIP1),a mitochondrial gatekeeper protein works to alter mitochondrial morphology,reduce oxidative phosphorylation and protect cells from unwarranted ROS accumulation.And our in vitro experiments showed the effects of FNIP1 in ameliorating oxidative stress and rescued impaired angiogenesis of HUVECs in high glucose environment.To realize the drug delivery and local regulation of FNIP1 in diabetic wound sites,a novel designed glucose-responsive HA-PBA-FA/EN106 hydrogel is introduced for improving diabetic wound healing.Due to the dynamic phenylboronate ester structure with a phenylboronic acid group between hyaluronic acid(HA)and phenylboronic acid(PBA),the hydrogel is able to realize a glucose-responsive release of drugs.Fulvic acid(FA)is added in the hydrogel,which not only severs as crosslinking agent but also provides antibacterial and anti-inflammatory abilities.Moreover,the release of FEM1b-FNIP1 axis inhibitor EN106 ameliorated oxidative stress and stimulated angiogenesis through FEM1b-FNIP1 axis regulation.These in vivo and in vitro results demonstrated that accelerated diabetic wounds repair with the use of the HA-PBA-FA/EN106 hydrogel,which may provide a promising strategy for chronic diabetic wound repair.

11B 3Q MAS NMR Study on Glucose-Responsive Micelles Self-assembled from PEG-b-P(AA-co-AAPBA)

Phenylboronic acid (PBA) based glucose-responsive materials have attracted great interests in recent years for developing insulin delivery systems.It is desired to obtain PBA based materials that can response to glucose under physiological pH and understand the mechanism.By using 11B triple-quantum magic-angle spinning nuclear magnetic resonance (11B 3Q MAS NMR) measurements,the glucose-responsive mechanism of micelles self-assembled from poly(ethylene glycol)-b-ploy(acrylic acid-co-acrylamidophenylboronic acid) PEG-b-P(AA-co-AAPBA) is deeply investigated.Different configurations of phenylboronic acid during various steps of glucose-responsive behaviors are clearly analyzed in the 11B 3Q MAS NMR spectra and coordination between carboxyl and PBA is confirmed.By increasing the AA units in PEG-b-P(AA-co-AAPBA),the carboxyl can coordinate with PBA moieties and cause the glucose-responsiveness of micelles even in the weak acid environment.

Glucose-responsive oral insulin delivery for postprandial glycemic regulation

Controlling postprandial glucose levels for diabetic patients is critical to achieve the tight glycemic control that decreases the risk for developing long-term micro- and macrovascular complications.Herein,we report a glucose-responsive oral insulin delivery system based on Fc receptor (FcRn)-targeted liposomes with glucose-sensitive hyaluronic acid (HA) shell for postprandial glycemic regulation.After oral administration,the HA shell can quickly detach in the presence of increasing intestinal glucose concentration due to the competitive binding of glucose with the phenylboronic acid groups conjugated with HA.The exposed Fc groups on the surface of liposomes then facilitate enhanced intestinal absorption in an FcRn-mediated transport pathway.In vivo studies on chemically-induced type 1 diabetic mice show this oral glucose-responsive delivery approach can effectively reduce postprandial blood glucose excursions.This work is the first demonstration of an oral insulin delivery system directly triggered by increasing postprandial glucose concentrations in the intestine to provide an on-demand insulin release with ease of administration.

Injectable dual glucose-responsive hydrogel-micelle composite for mimicking physiological basal and prandial insulin delivery

For type 1 and advanced type 2 diabetic patients, insulin replacement therapy with simulating on-demand prandial and basal insulin secretion is the best option for optimal glycemic control. However, there is no insulin delivery system yet could mimic both controlled basal insulin release and rapid prandial insulin release in response to real-time blood glucose changes. Here we reported an artificial insulin delivery system, mimicking physiological basal and prandial insulin secretion, to achieve real-time glycemic control and reduce risk of hypoglycemia. A phenylboronic acid(PBA)/galactosyl-based glucose-responsive insulin delivery system was prepared with insulin-loaded micelles embedded in hydrogel matrix. At the hyperglycemic state, both the hydrogel and micelles could swell and achieve rapid glucose-responsive release of insulin, mimicking prandial insulin secretion.When the glucose level returned to the normal state, only the micelles partially responded to glucose and still released insulin gradually. The hydrogel with increased crosslinking density could slow down the diffusion speed of insulin inside, resulting in controlled release of insulin and simulating physiological basal insulin secretion. This hydrogel-micelle composite insulin delivery system could quickly reduce the blood glucose level in a mouse model of type 1 diabetes, and maintain normal blood glucose level without hypoglycemia for about 24 h. This kind of glucose-responsive hydrogel-micelle composite may be a promising candidate for delivery of insulin in the treatment of diabetes.

Polymer-grafted hollow mesoporous silica nanoparticles integrated with microneedle patches for glucose-responsive drug delivery

A glucose-mediated drug delivery system would be highly satisfactory fordiabetes diagnosis since it can intelligently release drug based on blood glucose levels.Herein,a glucose-responsive drug delivery system by integrating glucose-responsivepoly(3-acrylamidophenylboronic acid)(PAPBA)functionalized hollow mesoporous silicananoparticles(HMSNs)with transcutaneous microneedles(MNs)has been designed.Thegrafted PAPBA serves as gatekeeper to prevent drug release from HMSNs atnormoglycemic levels.In contrast,faster drug release is detected at a typicalhyperglycemic level,which is due to the change of hydrophilicity of PAPBA at highglucose concentration.After transdermal administration to diabetic rats,an effectivehypoglycemic effect is achieved compared with that of subcutaneous injection.Theseobservations indicate that the designed glucose-responsive drug delivery system has apotential application in diabetes treatment.

Glucose-responsive erythrocyte-bound nanoparticles for continuously modulated insulin release

Glucose-responsive closed-loop insulin delivery systems represent a promising treatment strategy for diabetes,but current systems generally cannot achieve long-term effects.In this study,we designed an erythrocyte-biomimetic glucose-responsive system(EGRS)by coupling glucose-responsive nanoparticles(GRNs)to red blood cells;these nanoparticles exhibited the dual functions of glucose-responsiveness and persistent presence in circulation.GRNs are generated by encapsulating with insulin through ion crosslinking,followed by coloading with glucose oxidase(GOx)and catalase(CAT),a process that endows the nanoparticles with glucose-responsiveness.Simultaneously,the GRNs are coupled with red blood cells to camouflage them from the immune system,therefore,these erythrocyte-coupled GRNs can circulate in the blood for a long time.Under conditions of hyperglycemia,GOx acts on blood glucose to produce gluconic acid,which causes the rupture of GRNs and efficient release of insulin.Conversely,insulin is only released at the basic rate during hypoglycemia.Thus,EGRS can efficiently and continuously respond to hyperglycemia to maintain blood glucose levels within the normal range.

Microneedle-array patch with pH-sensitive formulation for glucoseresponsive insulin delivery

Glucose-responsive insulin delivery systems show great promise to improve therapeutic outcomes and quality of life for people with diabetes.Herein,a new microneedle-array patch containing pH-sensitive insulin-loaded nanoparticles(NPs)(SNP(I))together with glucose oxidase(GOx)-and catalase(CAT)-loaded pH-insensitive NPs(iSNP(G+C))is constructed for transcutaneous glucose-responsive insulin delivery.SNP(I)are prepared via double emulsion from a pH-sensitive amphiphilic block copolymer,and undergo rapid dissociation to promote insulin release at a mild acidic environment induced by GOx in iSNP(G+C)under hyperglycemic conditions.CAT in iSNP(G+C)can further consume excess H_(2)O_(2) generated during GOx oxidation,and thus reduce the risk of inflammation toward the normal skin.The in vivo study on type 1 diabetic mice demonstrates that the platform can effectively regulate blood glucose levels within normal ranges for a prolonged period.