Regulation of gluconeogenesis in type 2 diabetes mellitus: An investigation of the role of corticosteroids?

PhDType 2 diabetes mellitus (T2DM) is a complex disease involving various physiological factors, hormones and metabolites. Over expression of key gluconeogenic enzymes, such as PEPCK, cause features of T2DM including obesity and insulin resistance. Previous studies showed intravenous administration of corticotropin releasing factor (CRF) and sauvagine in rats cause marked hyperglycaemia, which is adrenal dependent. The 11-β hydroxylase inhibitor metyrapone augmented this hyperglycaemia raising important questions about the role of known and unknown corticosteroids in hepatic carbohydrate metabolism. The goal of this project was to identify and characterise the gluconeogenic activity of adrenal corticosteroids secreted under basal and stimulated conditions. This was accomplished by establishing a rapid, sensitive and robust multi-well assay for measurement of PEPCK activity in the hepatocyte cell line H4-II-E-C3. A sensitive fluorescent method for assay of glucose production by these cells was also developed. Extracts of media samples from adrenal glands incubated with sauvagine and metyrapone significantly increased hepatocyte glucose production (HGP) despite low corticosterone concentrations. HPLC characterisation of these extracts revealed increases in 11-deoxycorticosterone (DOC) and other unidentified peaks. However, none of these individual fractions significantly affected HGP in culture. Commercially available corticosterone, which contains DOC as an impurity, had greater gluconeogenic effect compared to purified corticosterone alone. Based on these observations and discrepancies in the literature, the effect of DOC on hepatic carbohydrate metabolism was characterised. Surprisingly, DOC suppressed the activity of gluconeogenic enzyme PEPCK in fed rat hepatocytes and enhanced insulin 4 stimulated glycogen stores in cultured hepatocytes at higher glucose concentrations (25 mM) over a 24 hour period. In serum-starved, fasted hepatocytes these effects were not significant, suggesting the need for a detailed investigation of the signalling pathways and regulatory control of DOC on GK, GS, G6Pase and PEPCK

The differences between the branded and generic medicines using solid dosage forms: In-vitro dissolution testing

AbstractIntroductionDissolution is the amount of substance that goes into solution per unit time under standardised conditions of liquid/solid interface, solvent composition and temperature. Dissolution is one of the most important tools to predict the in-vivo bioavailability and in some cases to determine bioequivalence and assure interchangeability.AimTo compare the differences in dissolution behaviour of solid dosage forms between innovators (reference products) and their generic counterparts (tested products).MethodsFour replicates for each batch of 37 tested medicines was carried out using A PT-DT70 dissolution tester from Pharma Test. A total of 13 branded medicines and 24 generic counterparts were obtained locally and internationally to detect any differences in their dissolution behaviour. They were tested according to the British Pharmacopeia, European Pharmacopeia and the US Pharmacopeia with the rate of dissolution determined by ultra-violet Spectrophotometery.ResultsMost tested medicines complied with the pharmacopoeial specifications and achieved 85% dissolution in 60min. However, some generic medicines showed significant differences in dissolution rate at 60 and 120min. Many generic medicines showed a slower dissolution rate than their branded counterparts such as the generic forms of omeprazole 20mg. Some showed an incomplete dissolution such as the generic form of nifedipine 10mg. Other generics showed faster dissolution rate than their branded counterpart such as the generic forms of meloxicam 15mg. Moreover, some generics from different batches of the same manufacturer showed significant differences in their dissolution rate such as the generic forms of meloxicam 7.5mg. Nevertheless, some generic medicines violated the EMA and the FDA guidelines for industry when they failed to achieve 85% dissolution at 60min, such as the generic form of diclofenac sodium 50mg.ConclusionMost medicines in this study complied with the pharmacopeial limits. However, some generics dissolved differently than their branded counterparts. This can clearly question the interchangeability between the branded and its generic counterpart or even among generics

Elevated hepatic 11 beta-hydroxysteroid dehydrogenase type 1 induces insulin resistance in uremia

This work was partly funded by the Barts and the London National Institute of Health Research Cardiovascular Biomedical Research Unit. P.W.C. is the recipient of a European Foundation for the Study of Diabetes/Lilly research fellowship. S.P.W., B.R.W., and J.R.S. are recipients of aWellcome Trust Seeding Drug Discovery Award for development of UE2316 and acknowledge the support of the British Heart Foundation Centre of Research Excellence