Florian Eichler, MD - US grants

[unreadable] DESCRIPTION (provided by applicant): The proposed interdisciplinary study allows the candidate to further develop his knowledge of MR physics and expertise in imaging studies of adrenomyeloneuropathy (AMN), a form of adrenoleukodystrophy (ALD), while providing rigorous exposure to the clinical and biological side of this research. The goal is to increase the candidate's expertise in multiple areas necessary to his proposed research project and future career development. These areas include genetics of peroxisomal disorders, lipid metabolism, and spatial aspects of nuclear magnetic resonance spectroscopy. The proposal builds nicely on the candidate's prior experience with Dr. Moser at Johns Hopkins and extends his studies to the animal model. The candidate is in a world-renown environment for both MR imaging and neuroscience. This Award will provide the guidance and tools necessary for him to become a successful, independent researcher. The 5 year research training program consists of 1) coursework and mentoring relationships on the science of high-field magnetic resonance that the candidate is currently lacking, 2) a 2 year rigorous training in animal imaging, and 3) collaborative translational studies with experts in the field of lipid metabolism and peroxisomal disorders. The research portion of this application will allow him to examine the histopathological and biochemical correlate of advanced MR techniques in the mouse model of ALD. This has never been done before and likely to reveal insight into the fundamental dynamics of demyelination. Further, the proposal encompasses application of novel therapeutics to normalize lipid metabolism and stabilize myelin membrane integrity. Hypotheses include: 1) in the animal model of ALD, measures of diffusion tensor imaging can assess the density of white matter tracts in the mouse and measures of single voxel proton MR spectroscopy reflect changes in lipid composition of the brain, and 2) in ALD patients, metabolic changes seen on proton MR spectroscopic imaging herald lesion development on conventional MRI. Our results will yield a noninvasive means of gauging the effects of experimental and therapeutic manipulations of lipid chemistry upon specific neuroanatomic structures. Ultimately, insights gained in these studies of ALD/AMN may prove beneficial to other neurodegenerative diseases, such as amyotrophic lateral sclerosis or Parkinson's and Alzheimer's diseases. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): The proposed interdisciplinary study addresses the debilitating disorder of hereditary sensory and autonomic neuropathy type 1 (HSAN1) and is based on the insight that mutant serine palmitoyltransferase (SPT) activity leads to production of two potentially neurotoxic sphingolipids. We were the first to identify the accumulation of these two atypical desoxysphingoid bases (DSB) in both mutant HSAN1 transgenic mice and HSAN1 patients. The studies bring together expertise in biochemistry (Uniformed Services University, USUHS) and neuroscience and neurogenetics (Massachusetts General Hospital). The project will (1) investigate mutant SPT isozymes in yeast and mammalian cells, (2) perform neurotoxicity studies of the atypical sphingolipids in mice, and (3) assess amino acid supplementation in mutant HSAN1 transgenic mice. The central premise underlying these investigations is that amino acid substrate selectivity alters desoxysphingoid bases and disease severity in HSAN1. Closely related is the premise that one can use behavioral testing and neuropathological examinations to assess the biochemical impact upon the clinicopathological phenotype. We will begin by expressing mutant SPT heterotrimers containing the known HSAN1 mutations in yeast and in mammalian cells (Aim 1). The Km and Vmax of each mutant enzyme for serine, alanine and glycine will be determined using these labeled amino acids. These experiments will allow us to determine whether the mutations differ in their abilities to condense the alternative substrates (alanine and glycine) and inform our studies in rodents. Neurotoxicity studies (Aim 2) will determine the role of DSB in peripheral neurodegeneration of HSAN1 in vivo. Lastly dietary supplementation of serine versus alanine and glycine in mutant HSAN1 transgenic mice will allow us to test behavior and neuropathology in vivo (Aim 3) and prepare for clinical studies in humans. These ex vivo and in vivo studies will give us insight about the synthesis, degradation and neurotoxicity of DSB in HSAN1. The experiments will not only elucidate a new and fundamental insight into neurometabolism but also lead to a potential new treatment for a neurogenetic disorder.

DESCRIPTION (provided by applicant): The study objective is to evaluate the efficacy of L-serine in subjects with hereditary sensory neuropathy type 1 (HSAN1). Hereditary sensory and autonomic neuropathy type I (HSAN1) is a progressive and debilitating illness for which currently no treatment exists. Two novel deoxysphingoid bases (DSB) were recently identified that accumulate in plasma of HSAN1 patients and mutant transgenic HSAN1 mice. The disease is caused by missense mutations in the SPTLC1 gene encoding a subunit of the enzyme serine palmitoyltransferase (SPT). In normal circumstances the SPT enzyme catalyzes the reaction of palmitoyl-CoA with serine to form sphinganine. The two newly identified DSB, deoxysphinganine and deoxymethylsphinganine, arise from condensation of palmitoyl-CoA with alanine and glycine respectively, suggesting that HSAN1 mutations alter amino acid selectivity of SPT. In support of this hypothesis it is shown that levels of DSB in humans and mice can be lowered by supplementation with the enzyme's normal substrate, serine. In this randomized, double-blind, placebo-controlled study, 20 research participants with HSAN1 will be enrolled with 10 subjects assigned to L-serine (400mg/kg/d) and 10 assigned to placebo who are each treated for 24 months. The progression of HSAN1 will be measured by the change in an established clinical rating scale and measures of intraepidermal nerve fiber density (IENFD) on skin biopsy. The percentage of failures [clinical decline of > 1 point on Charcot Marie Tooth Neurological Score (CMTNS) or > 30% decrease in IENFD] will be assessed at 6 month intervals. If patients in the placebo arm fail, they will be switched to L-serine. There will be an interim analysis at 12 and 18 months to assess for efficacy and futility, and accordingly the study will be stopped or continued.

DESCRIPTION (provided by applicant): The study objective is to determine whether 400 mg/kg/day oral L-serine is sufficiently safe and tolerable and possesses an adequately verified neuroprotective mechanism to justify further investigation in a future phase III trial in hereditar sensory and autonomic neuropathy type 1 (HSAN1). Hereditary sensory and autonomic neuropathy type I (HSAN1) is a progressive and debilitating illness for which currently no treatment exists. We recently identified two novel deoxysphingolipids (dSL) that accumulate in plasma of HSAN1 patients and mutant transgenic HSAN1 mice. The disease is caused by missense mutations in the SPTLC1 gene encoding a subunit of the enzyme serine palmitoyltransferase (SPT). In normal circumstances the SPT enzyme catalyzes the reaction of palmitoyl-CoA with serine to form sphinganine. The two newly identified dSL, deoxysphinganine and deoxymethylsphinganine, arise from condensation of palmitoyl-CoA with alanine and glycine respectively, suggesting that HSAN1 mutations alter amino acid selectivity of SPT. In support of this hypothesis we have shown that levels of dSL in humans and mice can be lowered by supplementation with the enzyme's normal substrate, serine. In this randomized, double-blind, placebo-controlled study we will enroll 20 research participants with HSAN1 with 10 subjects assigned to L-serine (400mg/kg/d) and 10 assigned to placebo who are each treated for 1 year, followed by cross-over to L-serine by all participants for one additional year. Pharmacokinetic studies will occur at the start of the first and second year allowing us to complete two PK series, with placebo at baseline providing information on diurnal patterns of dSL levels and an active arm at 1 year providing information on PK of L-serine on top of a stable background. Further, we will determine the impact of long-term reduction of dSL levels relative to neuropathy measures. We will study an existing neurological rating scale of sensory neuropathy, neurophysiological measures and intraepidermal nerve fiber density and assess their variability and sensitivity to L-serine intervention. Importantly it will let us decide on th best outcome measure for future Phase III trials.