Fracture liaison services in Ireland-how do we compare to international standards?

In this first na tional survey of public hospitals in The Republic of Ireland, we found fracture liaison services (FLS) to be heterogeneous, limited in many cases and poorly supported. A national strategy is urgently needed to support the implementation and operation of an FLS, and thus help reduce the burden of fragility fractures for patients and the healthcare system.

INTRODUCTION

Fragility/low-trauma fractures are a global concern, whose incidence is rising as the population ages. Many are preventable, and people with a prior fragility fracture are at particularly high risk of further fractures. This patient group is the target of the International Osteoporosis Foundation (IOF) Capture the Fracture campaign, advocating global adoption of fracture liaison services (FLS), with the aim of preventing secondary fragility fractures. We wished to determine the current availability and standards of an FLS in Ireland, ahead of the launch of a National FLS database.

METHODS

We devised a questionnaire encompassing the thirteen IOF standards for an FLS and asked all 16 public hospitals with an orthopaedic trauma unit in Ireland, to complete for the calendar year 2019 in patients aged ≥ 50 years.

RESULTS

All sites returned the questionnaire, i.e. 100% response rate. Nine hospitals stated that they have an FLS, additionally one non-trauma hospital running a FLS responded, and were included. These 10 FLS had identified and managed 3444 non-hip fractures in the year 2019. This figure represents 19% of the expected non-hip fragility fracture numbers occurring annually in Ireland. Implementation of the IOF standards was very variable. All sites reported being inadequately resourced to provide a high-quality service necessary to be effective.

CONCLUSION

The existence and functioning of FLS in Ireland are heterogeneous and suboptimal. A national policy to support the implementation of this programme in line with international standards of patient care is urgently needed.

Development of an improved analytical method for the determination of carcinogenic polycyclic aromatic hydrocarbons in transformer oil

Polynuclear aromatic hydrocarbons (PAHs) are natural constituents of transformer oils and are essential in prolonging transformer in-service lifetime. Issues concerning PAH carcinogenicity demand methods that provide qualitative and quantitative information on the PAH composition of new and in-service oils to allow informed operational decisions to be made. However, current analytical methods focus on PAH fingerprinting, as opposed to quantitative analysis and are also cumbersome, relying on the use of large (>100 ml) volumes of organic solvents, some of which are hazardous. This paper reports a method for the improved quantification of carcinogenic PAHs in transformer oils that is both simple and repeatable. The method uses commercially available solid-phase extraction columns and millilitre volumes of relatively non-hazardous solvents. Extraction efficiencies of > or =74% were obtained for the Environmental Protection Agency priority PAHs. The method has potential for automation and high-throughput analysis and thus is of interest to industries that use transformer oils.

Determinants of the substrate specificity of human cytochrome P-450 CYP2D6: design and construction of a mutant with testosterone hydroxylase activity

Cytochrome P-450 CYP2D6, human debrisoquine hydroxylase, metabolizes more than 30 prescribed drugs, the vast majority of which are small molecules containing a basic nitrogen atom. In contrast, the similar mouse protein Cyp2d-9 was first characterized as a testosterone 16alpha-hydroxylase. No common substrates have been reported for the two enzymes. Here we investigate the structural basis of this difference in substrate specificity. We have earlier used a combination of NMR data and homology modelling to generate a three-dimensional model of CYP2D6 [Modi, Paine, Sutcliffe, Lian, Primrose, Wolf, C.R. and Roberts (1996) Biochemistry 35, 4541-4550]. We have now generated a homology model of Cyp2d-9 and compared the two models to identify specific amino acid residues that we believe form the substrate-binding site in each protein and therefore influence catalytic selectivity. Although there are many similarities in active site structure, the most notable difference is a phenylalanine residue (Phe-483) in CYP2D6, which in the model is located such that the bulky phenyl ring is positioned across the channel mouth, thus limiting the size of substrate that can access the active site. In Cyp2d-9, the corresponding position is occupied by an isoleucine residue, which imposes fewer steric restraints on the size of substrate that can access the active site. To investigate whether the amino acid residue at this position does indeed influence the catalytic selectivity of these enzymes, site-directed mutagenesis was used to change Phe-483 in CYP2D6 to isoleucine and also to tryptophan. CYP2D6, Cyp2d-9 and both mutant CYP2D6 proteins were co-expressed with NADPH cytochrome P-450 reductase as a functional mono-oxygenase system in Escherichia coli and their relative catalytic activities towards bufuralol and testosterone were determined. All four proteins exhibited catalytic activity towards bufuralol but only Cyp2d-9 catalysed the formation of 16alpha-hydroxytesterone. Uniquely, the CYP2D6F483I mutant acquired the ability to metabolize testosterone to a novel product, which was identified by MS and proton NMR spectroscopy as 15alpha-hydroxytestosterone. NMR spin relaxation experiments were used to measure distances between the haem iron and protons of testosterone bound to the CYP2D6F483I mutant. These experiments demonstrate that very minor modifications to the active site structure of CYP2D6 can have a profound influence on the substrate specificity of the enzyme.