Conducting an investigator-initiated randomized double-blinded intervention trial in acute decompensation of inborn errors of metabolism: Lessons from the N-Carbamylglutamate Consortium.

Organic acidemias and urea cycle disorders are ultra-rare inborn errors of metabolism characterized by episodic acute decompensation, often associated with hyperammonemia, resulting in brain edema and encephalopathy. Retrospective reports and translational studies suggest that N-carbamylglutamate (NCG) may be effective in reducing ammonia levels during acute decompensation in two organic acidemias, propionic and methylmalonic acidemia (PA and MMA), and in two urea cycle disorders, carbamylphosphate synthetase 1 and ornithine transcarbamylase deficiency (CPSD and OTCD). We established the 9-site N-carbamylglutamate Consortium (NCGC) in order to conduct two randomized double-blind, placebo-controlled trials of NCG in acute hyperammonemia of PA, MMA, CPSD and OTCD. Conducting clinical trials is challenging in any disease, but poses unique barriers and risks in the ultra-rare disorders. As the number of clinical trials in orphan diseases increases, evaluating the successes and opportunities for improvement in such trials is essential. We summarize herein the design, methods, experiences, challenges and lessons from the NCGC-conducted trials.

Plasma fatty acids in premature infants with hyperbilirubinemia: before-and-after nutrition support with fish oil emulsion.

Infants who are dependent on parenteral nutrition (PN) sometimes develop PN-associated cholestasis (PNAC). A compassionate use protocol, approved by the U.S. Food and Drug Administration and the institutional review board, guided enrollment of hospitalized infants with PNAC (<1 year of age, PN dependence for >3 weeks). Plasma concentrations of essential fatty acids were monitored before and after a soybean-based PN lipid, infused at 3 g/kg body weight/d, was replaced by an experimental fish oil-based intravenous fat emulsion (FO-IVFE) at 1.0 g/kg/d. All participants were born premature (n = 10; 20% male). At enrollment, infants were (mean ± SD) 86.5 ± 53.5 days of life and weighed 2.24 ± 0.87 kg; direct bilirubin was 5.5 ± 1.3 mg/dL. After treatment, blood concentrations significantly increased from baseline (P < .017) for circulating eicosapentaenoic acid (6.3 ± 3.0 to 147.8 ± 53.1 µg/mL), docosahexaenoic acid (20.7 ± 6.5 to 163.7 ± 43.4 µg/mL), pristanic acid (0.01 ± 0.01 to 0.17 ± 0.03 µg/mL), and phytanic acid (0.06 ± 0.03 to 0.64 ± 0.15 µg/mL). In contrast, total plasma ω-6 fatty acids (including linoleic acid) decreased (P < .017). The triene/tetraene ratio remained below the threshold value of 0.2 that defines ω-6 deficiency. No adverse effects were observed attributable to FO-IVFE. Discontinuation of FO-IVFE was typically due to infants (body weight 3.76 ± 1.68 kg) transitioning to enteral feeding rather than for resolution of hyperbilirubinemia (direct bilirubin 7.9 ± 4.8 mg/dL). These exploratory results suggest that FO-IVFE raises circulating ω-3 fatty acids in premature infants without development of ω-6 deficiency in the 8.3 ± 5.8-week time frame of this study.

Parenteral nutrition-associated conjugated hyperbilirubinemia in hospitalized infants.

Parenteral nutrition-associated conjugated hyperbilirubinemia (PNAC), commonly defined as direct bilirubin ≥2 mg/dL (34.2 µmol/L), is primarily a pediatric disease with premature infants being the most susceptible. Severe morbidity and increased mortality are associated with bilirubin >10 mg/dL (171.0 µmol/L). The lack of knowledge regarding the cause of PNAC has stymied development of prevention and treatment strategies. A systematic search of published reports was conducted to provide data on histopathology of PNAC and to review prospective, randomized, controlled trials in hospitalized infants. In experiments of young animals, parenteral nutrition (PN) with and without soy oil emulsion is directly linked to hyperbilirubinemia, and the effects are exaggerated by overfeeding. In infants, the most consistently reported risk factor for PNAC is the duration of PN. The only known effective modality is the transition to full enteral feeding and discontinuation of PN. Emerging clinical research is evaluating the role of lipid source (soy vs fish) and motility agents, such as erythromycin. Different trace element preparations are associated with varying severity of cholestasis, a finding that also deserves more study. This article reviews the prevalence, risk factors, clinical presentation, and treatment options for PNAC in neonatal intensive care units.

Increased poly(ADP-ribose) polymerase (PARP)-1 expression and activity are associated with inflammation but not goblet cell metaplasia in murine models of allergen-induced airway inflammation.

Inflammation plays a key role in lung injury and in the pathogenesis of asthma. Two murine models of allergic airway inflammation-sensitization and challenge to ovalbumin (OVA) and intratracheal exposure to interleukin-13 (IL13)-were used to evaluate the expression of poly(ADP-ribose) polymerase-1 (PARP-1) in allergic airway inflammation. Inflammation is prominent in OVA-induced allergic asthma, but this inflammation is greatly reduced by a PARP-1 inhibitor and almost eliminated when PARP-1 knockout mice are subjected to the OVA model. The present study temporally evaluated PARP-1 protein expression, localization, and activity, as well as inflammation and goblet cell metaplasia (GCM), in murine lungs following a single OVA challenge or IL13 exposure. Following OVA challenge PARP-1 protein expression and activity were greatly increased, being maximal at 3 to 5 days following OVA exposure and beginning to decrease by day 8. These changes correlated with the timing and degree of inflammation and GCM. In contrast, PARP-1 protein or activity did not change following single IL13 exposure, though GCM was manifested without inflammation. This study demonstrates that both PARP-1 protein and activity are increased by allergen-activated inflammatory mediators, excluding IL13, and that PARP-1 increase does not appear necessary for GCM, one of the characteristic markers of allergic airway inflammation in murine models.

Increased tumor growth in mice with diet-induced obesity: impact of ovarian hormones.

Obesity increases the risk of many cancers in both males and females. This study describes a link between obesity, obesity-associated metabolic alterations, and the risk of developing cancer in male and female mice. The goal of this study was to evaluate the relationship between gender and obesity and to determine the role of estrogen status in obese females and its effect on tumor growth. We examined the susceptibility of C57BL/6 mice to diet-induced obesity, insulin resistance/glucose intolerance, and tumors. Mice were injected sc with one of two tumorigenic cell lines, Lewis lung carcinoma, or mouse colon 38-adenocarcinoma. Results show that tumor growth rate was increased in obese mice vs. control mice irrespective of the tumor cell type. To investigate the effect of estrogen status on tumor development in obese females, we compared metabolic parameters and tumor growth in ovariectomized (ovx) and intact obese female mice. Obese ovx female mice developed insulin resistance and glucose intolerance similar to that observed in obese males. Our results demonstrate that body adiposity increased in ovx females irrespective of the diet administered and that tumor growth correlated positively with body adiposity. Overall, these data point to more rapid tumor growth in obese mice and suggest that endogenous sex steroids, together with diet, affect adiposity, insulin sensitivity, and tumor growth in female mice.

Metabolic effects of IGF-I deficiency: lessons from mouse models.

Insulin and insulin-like growth factors (IGFs) belong to the most biologically characterized family of peptides involved in metabolism, growth and development. The cellular responses to the IGFs are mediated primarily by the IGF-I receptor. The IGF-I receptor is a member of the family of tyrosine kinase growth factor receptors, and is highly homologous (70%) to the insulin receptor, especially in the tyrosine kinase domain (84%) ADDIN. Upon ligand binding to the extracellular region, the intrinsic tyrosine kinase domain of the receptor is activated. In the past it was believed that insulin activates primarily metabolic processes while IGFs promote cell growth and differentiation. However, in the last two decades many animal models of IGFI deficiency and excess revealed the importance of IGF-I in carbohydrate and lipid metabolism and now it is clear that these peptide hormones together with growth hormone (GH) work in a coordinate and interdependent manner. In the circulation, IGFs are bound in a binary complex with a family of high affinity IGF-binding proteins (IGFBPs) ADDIN. However, most of the circulating IGF-I associates with a high molecular weight complex approximately 150 KDa consisting of IGFBP-3 and the acid labile subunit (ALS) ADDIN. Once the ternary complex dissociates, the binary complexes of IGFBP-IGFs are removed from the circulation and by crossing the endothelium to reach the target tissues and to interact with cell surface receptors. In the present review we will summarize the role of GH and IGF in somatic growth and focus on the metabolic effects of IGF-I deficiency as assessed in various mouse models.

Insulin-like growth factor-I stimulates both cell growth and lipogenesis during differentiation of human mesenchymal stem cells into adipocytes.

Insulin is known to regulate adipocyte differentiation and lipid accumulation, but the specific mechanism by which precursor cells differentiate into adipocytes is not clearly understood. This study evaluated the role of the IGF-I receptor in the process of adipocyte differentiation in bone marrow-derived human mesenchymal stem cells (HMSCs). The results demonstrated that nanomolar concentrations of IGF-I adequately replaced micromolar concentrations of insulin in supporting differentiation and lipid accumulation in HMSCs. The addition of IGF-I specifically increased cell proliferation and lipid accumulation in HMSCs, but a mixture of differentiation factors including dexamethasone, indomethacin, and 3-isobutyl-1-methylxanthine did not. These effects were blocked by the alphaIR-3 antibody, which inhibits IGF-I receptor activity. We also describe the pattern of differentiation with regard to cell growth, lipid accumulation, and morphologic changes and define the changes in these parameters that are influenced by IGF-I. Finally, peroxisome proliferator activating receptor-gamma immunoreactivity was also increased in response to IGF-I, and this effect was blocked in cells treated with the alphaIR-3 antibody. Taken together, these findings suggest that IGF-I plays a critical role in adipocyte differentiation and lipid accumulation.

Ontogeny of poly(ADP-ribose) polymerase-1 in lung and developmental implications.

Poly(ADP-ribose) polymerase 1 (PARP-1) is the predominant NAD-dependent modifying enzyme in DNA repair, transcription, and apoptosis; its involvement in development has not been defined. Here, we report expression and cellular localization of PARP-1 in developing rat and human fetal lung, in vivo and in explant culture, and effects of inhibiting PARP-1 activity on lung surfactant protein (SP) expression. PARP-1 was expressed as 113-kD (p113) and 85-kD (p85) fragment in both rat and human lung. In rat lung, p113 content by Western was maximal at Embryonic Days 16-18, decreased sharply by Embryonic Day 20, and continued to decrease postnatally. p85 level was constant in the fetus and decreased postnatally. In human fetal lung, both PARP-1 mRNA expression and protein content changed little between 15 and 24 wk. Immunohistochemistry for PARP-1 in Embryonic Day 18 rat lung showed predominantly nuclear staining in most cells. In later gestation and postnatally, PARP-1 staining was primarily cytoplasmic and progressively restricted to a subset of cells, mainly bronchial epithelial and smooth muscle cells. Cell subfractionation showed that p113 localized to nucleus and p85 to cytoplasm. Inhibition of PARP-1 activity by 5-iodo-6-amino-1,2-benzopyrone in fetal rat lung explant culture did not affect SP-A and -B mRNA, but significantly increased SP-C mRNA. These findings indicate that in lung (i) PARP-1 is abundantly expressed during fetal development; (ii) p113 and p85 levels are differentially regulated; (iii) PARP-1 undergoes complex developmental changes in cellular and subcellular expression, including extensive cytoplasmic localization; and (iv) inhibition of PARP-1 activity differentially affects expression of SPs.

Maternally administered dexamethasone transiently increases apoptosis in lungs of fetal rats.

In late gestation, morphological maturation of fetal lung includes septal thinning of potential airspaces, a process accelerated by exogenous glucocorticoids. Apoptosis occurs in normal fetal lung. Glucocorticoids increase apoptosis in several tissues. The authors hypothesized that exogenous glucocorticoids would increase apoptosis in fetal lung, primarily in the interstitium. They administered dexamethasone (DEX), 1 mg/kg, or vehicle (Control) to pregnant rats at 19 days of gestation. Fetuses were delivered at 3, 7, 12, or 24 hours post injection. DEX decreased fetal body weight and lung weight, DNA, and protein 12 hours post injection. Using the terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) reaction to label apoptotic cells in lung, they calculated an apoptotic index (AI, apoptotic cells/1000 total cells) for each fetus. Average DEX AI (3.6+/-2.6, mean+/-SD) was greater than Control (1.7+/-0.5) (P<.02). All DEX AIs were greater than Control AIs at 3, 7, and 12 hours, but were similar to Controls at 24 hours post injection. Apoptotic cells appeared to be interstitial, based on colocalization with vimentin staining. Presence of apoptotic cells was confirmed by electron microscopy and detection of the nucleosomal ladder pattern on DNA electrophoresis. The authors conclude that maternal administration of dexamethasone increases apoptosis in fetal lung, primarily in the interstitium. They speculate that apoptosis may contribute to morphological fetal lung maturation induced by endogenous glucocorticoids.

Effects of oligohydramnios on lung growth and maturation in the fetal rat.

Oligohydramnios (OH) retards fetal lung growth by producing less lung distension than normal. To examine effects of decreased distension on fetal lung development, we produced OH in rats by puncture of uterus and fetal membranes at 16 days of gestation; fetuses were delivered at 21 or 22 days of gestation. Controls were position-matched littermates in the opposite uterine horn. OH lungs had lower weights and less DNA, protein, and water, but no differences in saturated phosphatidylcholine, surfactant proteins (SP)-A and -B, and mRNA for SP-A, -B, -C, and -D. To evaluate effects on epithelial differentiation, we used RTI(40) and RTII(70), proteins specific in lung to luminal surfaces of alveolar type I and II cells, respectively. At 22 days of gestation, OH lungs had less RTI(40) mRNA (P < 0.05) and protein (P < 0.001), but RTII(70) did not differ from controls. With OH, type I cells (in proportion to type II cells) covered less distal air space perimeter (P < 0.01). We conclude that OH, which retards lung growth, has little effect on surfactant and impedes formation of type I cells relative to type II cells.