Hexose-6-phosphate dehydrogenase (H6PD) is the initial component of a pentose phosphate pathway inside the endoplasmic reticulum (ER) that generates NADPH for ER enzymes. In liver H6PD is required for the 11-oxoreductase activity of 11␤-hydroxysteroid dehydrogenase type 1, which converts inactive 11-oxo-glucocorticoids to their active 11-hydroxyl counterparts; consequently, H6PD null mice are relatively insensitive to glucocorticoids, exhibiting fasting hypoglycemia, increased insulin sensitivity despite elevated circulating levels of corticosterone, and increased basal and insulin-stimulated glucose uptake in muscles normally enriched in type II (fast) fibers, which have increased glycogen content. Here, we show that H6PD null mice develop a severe skeletal myopathy characterized by switching of type II to type I (slow) fibers. Running wheel activity and electrically stimulated force generation in isolated skeletal muscle are both markedly reduced. Affected muscles have normal sarcomeric structure at the electron microscopy level but contain large intrafibrillar membranous vacuoles and abnormal triads indicative of defects in structure and function of the sarcoplasmic reticulum (SR). SR proteins involved in calcium metabolism, including the sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA), calreticulin, and calsequestrin, show dysregulated expression. Microarray analysis and real-time PCR demonstrate overexpression of genes encoding proteins in the unfolded protein response pathway. We propose that the absence of H6PD induces a progressive myopathy by altering the SR redox state, thereby impairing protein folding and activating the unfolded protein response pathway. These studies thus define a novel metabolic pathway that links ER stress to skeletal muscle integrity and function. H6PD3 is a bifunctional enzyme that catalyzes the first two steps of the pentose phosphate pathway (1). It is distinct from its cytosolic homolog, glucose-6-phosphate dehydrogenase, in being localized exclusively to the lumen of the endoplasmic reticulum (ER). H6PD converts glucose 6-phosphate to 6-phosphogluconolactonate with the concomitant production of NADPH, thereby maintaining adequate levels of reductive cofactors in the oxidizing environment of the ER (2, 3).One critical role for H6PD is providing NADPH to 11␤-hydroxysteroid dehydrogenase type 1 (11␤-HSD1), a bi-directional enzyme highly expressed in liver and adipose tissue. 11␤-HSD1 catalyzes both dehydrogenation and oxo-reduction of glucocorticoids, but in vivo it acts predominantly as a NADPHdependent oxoreductase that converts hormonally inactive cortisone to active cortisol (in rodents, 11-dehydrocorticosterone to corticosterone) (4). To investigate the functional interactions of H6PD and 11␤-HSD1 in vivo, we produced mice with a targeted inactivation of H6PD and showed that 11␤-HSD1 predominantly acts as a dehydrogenase in these mice (6). The resulting cellular resistance to corticosterone leads to activation of the hypothalamic-pituitary-adrenal axis and elevat...

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STUDY QUESTIONHow does the efficacy and safety of a fixed-ratio combination of recombinant human FSH plus recombinant human LH (follitropin alfa plus lutropin alfa; r-hFSH/r-hLH) compare with that of r-hFSH monotherapy for controlled ovarian stimulation (COS) in patients with poor ovarian response (POR)?SUMMARY ANSWERThe primary and secondary efficacy endpoints were comparable between treatment groups and the safety profile of both treatment regimens was favourable.WHAT IS KNOWN ALREADYAlthough meta-analyses of clinical trials have suggested some beneficial effect on reproductive outcomes with r-hLH supplementation in patients with POR, the definitions of POR were heterogeneous and limit the comparability across studies.STUDY DESIGN, SIZE, DURATIONPhase III, single-blind, active-comparator, randomized, parallel-group clinical trial. Patients were followed for a single ART cycle. A total of 939 women were randomized (1:1) to receive either r-hFSH/r-hLH or r-hFSH. Randomization, stratified by study site and participant age, was conducted via an interactive voice response system.PARTICIPANTS/MATERIALS, SETTING, METHODSWomen classified as having POR, based on criteria incorporating the ESHRE Bologna criteria, were down-regulated with a long GnRH agonist protocol and following successful down-regulation were randomized (1:1) to COS with r-hFSH/r-hLH or r-hFSH alone. The primary efficacy endpoint was the number of oocytes retrieved following COS. Safety endpoints included the incidence of adverse events, including ovarian hyperstimulation syndrome (OHSS). Post hoc analyses investigated safety outcomes and correlations between live birth and baseline characteristics (age and number of oocytes retrieved in previous ART treatment cycles or serum anti-Müllerian hormone (AMH)). The significance of the treatment effect was tested by generalized linear models (Poisson regression for counts and logistic regression for binary endpoints) adjusting for age and country.MAIN RESULTS AND THE ROLE OF CHANCEOf 949 subjects achieving down-regulation, 939 were randomized to r-hFSH/r-hLH (n = 477) or r-hFSH (n = 462) and received treatment.Efficacy assessment: In the intention-to-treat (ITT) population, the mean (SD) number of oocytes retrieved (primary endpoint) was 3.3 (2.71) in the r-hFSH/r-hLH group compared with 3.6 (2.82) in the r-hFSH group (between-group difference not statistically significant). The observed difference between treatment groups (r-hFSH/r-hLH and r-hFSH, respectively) for efficacy outcomes decreased over the course of pregnancy (biochemical pregnancy rate: 17.3% versus 23.9%; clinical pregnancy rate: 14.1% versus 16.8%; ongoing pregnancy rate: 11.0% versus 12.4%; and live birth rate: 10.6% versus 11.7%). An interaction (identified post hoc) between baseline characteristics related to POR and treatment effect was noted for live birth, with r-hFSH/r-hLH associated with a higher live birth rate for patients with moderate or severe POR, whereas r-hFSH was associated with a higher live birth rate for those with...

BackgroundSapropterin dihydrochloride, a synthetic formulation of BH4, the cofactor for phenylalanine hydroxylase (PAH, EC 1.14.16.1), was initially approved in Europe only for patients ≥4 years with BH4-responsive phenylketonuria. The aim of the SPARK (Safety Paediatric efficAcy phaRmacokinetic with Kuvan®) trial was to assess the efficacy (improvement in daily phenylalanine tolerance, neuromotor development and growth parameters), safety and pharmacokinetics of sapropterin dihydrochloride in children <4 years.ResultsIn total, 109 male or female children <4 years with confirmed BH4-responsive phenylketonuria or mild hyperphenylalaninemia and good adherence to dietary treatment were screened. 56 patients were randomly assigned (1:1) to 10 mg/kg/day oral sapropterin plus a phenylalanine-restricted diet or to only a phenylalanine-restricted diet for 26 weeks (27 to the sapropterin and diet group and 29 to the diet-only group; intention-to-treat population). Of these, 52 patients with ≥1 pharmacokinetic sample were included in the pharmacokinetic analysis, and 54 patients were included in the safety analysis. At week 26 in the sapropterin plus diet group, mean phenylalanine tolerance was 30.5 (95% confidence interval 18.7–42.3) mg/kg/day higher than in the diet-only group (p < 0.001). The safety profile of sapropterin, measured monthly, was acceptable and consistent with that seen in studies of older children. Using non-linear mixed effect modelling, a one-compartment model with flip-flop pharmacokinetic behaviour, in which the effect of weight was substantial, best described the pharmacokinetic profile. Patients in both groups had normal neuromotor development and stable growth parameters.ConclusionsThe addition of sapropterin to a phenylalanine-restricted diet was well tolerated and led to a significant improvement in phenylalanine tolerance in children <4 years with BH4-responsive phenylketonuria or mild hyperphenylalaninemia. The pharmacokinetic model favours once per day dosing with adjustment for weight. Based on the SPARK trial results, sapropterin has received EU approval to treat patients <4 years with BH4-responsive phenylketonuria.Trial registrationClinicalTrials.gov, NCT01376908. Registered June 17, 2011.Electronic supplementary materialThe online version of this article (doi:10.1186/s13023-017-0600-x) contains supplementary material, which is available to authorized users.

Hexose-6-phosphate dehydrogenase (EC 1.1.1.47) catalyzes the conversion of glucose 6-phosphate to 6-phosphogluconolactone within the lumen of the endoplasmic reticulum, thereby generating reduced nicotinamide adenine dinucleotide phosphate. Reduced nicotinamide adenine dinucleotide phosphate is a necessary cofactor for the reductase activity of 11beta-hydroxysteroid dehydrogenase type 1 (EC 1.1.1.146), which converts hormonally inactive cortisone to active cortisol (in rodents, 11-dehydrocorticosterone to corticosterone). Mice with targeted inactivation of hexose-6-phosphate dehydrogenase lack 11beta-hydroxysteroid dehydrogenase type 1 reductase activity, whereas dehydrogenase activity (corticosterone to 11-dehydrocorticosterone) is increased. We now report that both glucose output and glucose use are abnormal in these mice. Mutant mice have fasting hypoglycemia. In mutant primary hepatocytes, glucose output does not increase normally in response to glucagon. Mutant animals have lower hepatic glycogen content when fed and cannot mobilize it normally when fasting. As assessed by RT-PCR, responses of hepatic enzymes to fasting are blunted; enzymes involved in gluconeogenesis (phosphoenolpyruvate carboxykinase, tyrosine aminotransferase) are not appropriately up-regulated, and expression of glucokinase, an enzyme required for glycolysis, is not suppressed. Corticosterone has attenuated effects on expression of these enzymes in cultured mutant primary hepatocytes. Mutant mice have increased sensitivity to insulin, as assessed by homeostatic model assessment values and by increased glucose uptake by the muscle. The hypothalamic-pituitary-adrenal axis is also abnormal. Circulating ACTH, deoxycorticosterone, and corticosterone levels are increased in mutant animals, suggesting decreased negative feedback on the hypothalamic-pituitary-adrenal axis. Comparison with other animal models of adrenal insufficiency suggests that many of the observed abnormalities can be explained by blunted intracellular corticosterone actions, despite elevated circulating levels of this hormone.