Plasma melatonin levels in patients with diabetic retinopathy secondary to type 2 diabetes

BACKGROUND Melatonin is reported to be related to diabetes mellitus(DM)risk;however,the effect of melatonin on diabetic retinopathy(DR)risk remains unclear.AIM The aim of this study was to determine the effect of melatonin on DR risk.METHODS A hospital-based case-control study was conducted from January 2020 to June 2020.DR was assessed using the Diabetic Retinopathy preferred practice pattern(PPP)-updated 2019 criteria.The participants were divided into the DM cases without DR(NDR)group,non-proliferative DR(NPDR)group and proliferative DR(PDR)group.Plasma melatonin concentration was detected with the enzymelinked immunosorbent assay kit.The relationship between plasma melatonin concentration and DR risk as well as severity was assessed.RESULTS It was found that plasma melatonin was 72.83±16.25,60.38±13.43,44.48±10.30 and 44.69±8.95 pg/mL in healthy controls,NDR group,NPDR and PDR group,respectively.In addition,it was found that plasma melatonin could be used as a potential diagnostic biomarker for DR(AUC=0.893,P<0.001).There was a significant positive relationship between total bilirubin and melatonin content(P<0.001)based on the correlation assay.Significant associations between total bilirubin and melatonin content were also detected in the NPDR(R2=0.360,P<0.001)and PDR(R2=0.183,P<0.001)groups.CONCLUSION The data obtained in this study demonstrated that plasma melatonin concentration was decreased in DR cases and could be used as a sensitive and specific marker for the diagnosis of DR.A significant positive relationship between total bilirubin and melatonin was detected.More related studies are required to understand the role of melatonin in DR.

Doxycycline and hydroxypropyl-b-cyclodextrin complex in poloxamer thermal sensitive hydrogel for ophthalmic delivery

The present study aimed to prepare a chemically and physically stable formulation of doxycycline(Doxy)in an in situ thermally sensitive hydrogel for ophthalmic delivery.An inclusion complex of Doxy and hydroxypropyl-b-cyclodextrin(HP-b-CD)was first developed to increase the stability of Doxy in aqueous solution.The physical characteristics(phase solubility profiles,thermal analysis,X-ray powder diffractograms and infrared spectra)of the Doxy-HP-b-CD inclusion complex indicated the formation of a stable 1:1 complex.Poloxamers P407(16–22%)and P188(0–5%)were mixed to obtain a hydrogel with an appropriate gelation temperature for opthalmic use.Formulation of the inclusion complex in the poloxamer hydrogel exhibited a suitable gelation temperature(33.3℃)after dilution with simulated tear fluid(Gel:STF=40:7,v/v).The release of Doxy from the poloxamer hydrogel followed a zero order equation suggesting it occurs through corrosion of the poloxamer hydrogel.Stability studies demonstrated that the inclusion of Doxy by HP-b-CD markedly improved its stability in aqueous solution both at 8 and 401C.This formulation of a doxycycline-HP-b-CD inclusion complex in an in situ thermally sensitive poloxamer hydrogel represents a potentially effective ophthalmic Doxy delivery system.