👤 Sarah H Elsea

Smith Magenis Syndrome (SMS) is a rare genetic disorder caused by RAI1 haploinsufficiency. Obesity in people with SMS is believed partially due to dysfunction of the proximal melanocortin 4 receptor (MC4R) pathway. We therefore studied effects of treatment with the MC4R agonist setmelanotide on obesity and hunger, as well as metabolic, cardiac and safety, in individuals with SMS. People with SMS received once-daily setmelanotide injections, with the dose titrated bi-weekly to a maximum of 3 mg over ∼1 month; and a full-dose treatment duration of 3mo. The primary outcome was percent change in body weight. Secondary outcomes included hunger, waist circumference, body composition, and safety. 12 individuals, ages 11-39 y, enrolled and 10 completed the full-dose treatment phase. Mean percent change in body weight at end-treatment was - 0.28 % [(95 % CI, -2.1 % to 1.5 %; n = 12; P = 0.66]. Participants experienced a significant decrease in total cholesterol associated with a significant decrease in HDL-cholesterol and a trend for lower LDL-cholesterol. Self-reported hunger was reduced at end-treatment (p = 0.011). All participants reported adverse events (AEs), most commonly injection-site reactions and skin hyperpigmentation. No AEs led to withdrawal or death. In this trial, setmelanotide did not significantly reduce body weight in participants with SMS. Participants reported significant differences in hunger, but such self-reports are difficult to interpret without a placebo-treated group. The changes in lipid profiles require further investigation. Results of this study do not suggest that dysfunction of the proximal MC4R pathway is the main etiology for obesity in people with SMS. Show less

Urea cycle disorders (UCDs) are genetic conditions characterized by nitrogen accumulation in the form of ammonia and caused by defects in the enzymes required to convert ammonia to urea for excretion. UCDs include a spectrum of enzyme deficiencies, namely n-acetylglutamate synthase deficiency (NAGS), carbamoyl phosphate synthetase I deficiency (CPS1), ornithine transcarbamylase deficiency (OTC), argininosuccinate lyase deficiency (ASL), citrullinemia type I (ASS1), and argininemia (ARG). Currently, sodium phenylbutyrate and glycerol phenylbutyrate are primary medications used to treat patients with UCDs, and long-term monitoring of these compounds is critical for preventing drug toxic levels. Therefore, a fast and simple ultra-performance liquid chromatography (UPLC-MS/MS) method was developed and validated for quantification of phenylbutyrate (PB), phenylacetate (PA), and phenylacetylglutamine (PAG) in plasma and urine. The separation of all three analytes was achieved in 2min, and the limits of detection were <0.04μg/ml. Intra-precision and inter-precision were <8.5% and 4% at two quality control concentrations, respectively. Average recoveries for all compounds ranged from 100% to 106%. With the developed assay, a strong correlation between PA and the PA/PAG ratio and an inverse correlation between PA/PAG ratio and plasma glutamine were observed in 35 patients with confirmed UCDs. Moreover, all individuals with a ratio ≥0.6 had plasma glutamine levels<1000μmol/l. Our data suggest that a PA/PAG ratio in the range of 0.6-1.5 will result in a plasma glutamine level<1000μmol/l without reaching toxic levels of PA. Show less

Wolfram syndrome (WFS) is a progressive neurodegenerative disease characterized by diabetes insipidus, diabetes mellitus, optic atrophy, and deafness. WFS1 and WFS2 are caused by recessive mutations in the genes Wolfram Syndrome 1 (WFS1) and CDGSH iron sulfur domain 2 (CISD2), respectively. To explore the function of CISD2, we performed genetic studies in flies with altered expression of its Drosophila orthologue, cisd2. Surprisingly, flies with strong ubiquitous RNAi-mediated knockdown of cisd2 had no obvious signs of altered life span, stress resistance, locomotor behavior or several other phenotypes. We subsequently found in a targeted genetic screen, however, that altered function of cisd2 modified the effects of overexpressing the fly orthologues of two lysosomal storage disease genes, palmitoyl-protein thioesterase 1 (PPT1 in humans, Ppt1 in flies) and ceroid-lipofuscinosis, neuronal 3 (CLN3 in humans, cln3 in flies), on eye morphology in flies. We also found that cln3 modified the effects of overexpressing Ppt1 in the eye and that overexpression of cln3 interacted with a loss of function mutation in cisd2 to disrupt locomotor ability in flies. Follow-up multi-species bioinformatic analyses suggested that a gene network centered on CISD2, PPT1 and CLN3 might impact disease through altered carbohydrate metabolism, protein folding and endopeptidase activity. Human genetic studies indicated that copy number variants (duplications and deletions) including CLN3, and possibly another gene in the CISD2/PPT1/CLN3 network, are over-represented in individuals with developmental delay. Our studies indicate that cisd2, Ppt1 and cln3 function in concert in flies, suggesting that CISD2, PPT1 and CLN3 might also function coordinately in humans. Further, our studies raise the possibility that WFS2 and some lysosomal storage disorders might be influenced by common mechanisms and that the underlying genes might have previously unappreciated effects on developmental delay. Show less