Localization of 1-deoxysphingolipids to mitochondria induces mitochondrial dysfunction.

1-Deoxysphingolipids (deoxySLs) are atypical sphingolipids that are elevated in the plasma of patients with type 2 diabetes and hereditary sensory and autonomic neuropathy type 1 (HSAN1). Clinically, diabetic neuropathy and HSAN1 are very similar, suggesting the involvement of deoxySLs in the pathology of both diseases. However, very little is known about the biology of these lipids and the underlying pathomechanism. We synthesized an alkyne analog of 1-deoxysphinganine (doxSA), the metabolic precursor of all deoxySLs, to trace the metabolism and localization of deoxySLs. Our results indicate that the metabolism of these lipids is restricted to only some lipid species and that they are not converted to canonical sphingolipids or fatty acids. Furthermore, exogenously added alkyne-doxSA [(2S,3R)-2-aminooctadec-17-yn-3-ol] localized to mitochondria, causing mitochondrial fragmentation and dysfunction. The induced mitochondrial toxicity was also shown for natural doxSA, but not for sphinganine, and was rescued by inhibition of ceramide synthase activity. Our findings therefore indicate that mitochondrial enrichment of an N-acylated doxSA metabolite may contribute to the neurotoxicity seen in diabetic neuropathy and HSAN1. Hence, we provide a potential explanation for the characteristic vulnerability of peripheral nerves to elevated levels of deoxySLs.

[Anesthetic Management with Propofol Alone in a Patient with Hereditary Sensory and Autonomic Neuropathy].

Hereditary sensory and autonomic neuropathy (HSAN) is a rare peripheral nerve disorder associated with sensory dysfunction (pain, touch, and pressure) and various degrees of autonomic dysfunction. We administered general anesthesia for a 54-year-old woman with HSAN type II undergoing amputation of the left hallux. She had reduced sensation for pain, pressure, and temperature since birth and frequently injured her hands and legs. Before the operation, she did not report pain in the hallux. Only propofol was given for anesthesia without use of analgesia. Intraoperatively, her vital signs were stable. To evaluate the sympathetic nervous response to surgical stimulation, we measured the plasma catecholamine levels before tracheal intubation and just before and during surgery. Plasma catecholamine levels were normal at all time points, indicating no sympathetic responses to surgical stimulation. This case suggests that anesthesia for HSAN II patients can be safely managed with propofol alone.

Fenofibrate lowers atypical sphingolipids in plasma of dyslipidemic patients: A novel approach for treating diabetic neuropathy?

BACKGROUND: The condensation of palmitoyl-CoA and L-Serine is the first step in the de novo formation of sphingolipids and catalyzed by the serine-palmitoyltransferase (SPT). Besides other acyl-CoAs the SPT can also metabolize L-alanine and glycine, which forms an atypical category of neurotoxic 1-deoxy-sphingolipids (1-deoxySL). Several mutations in SPT are associated with pathologically increased 1-deoxySL levels, which cause the inherited sensory neuropathy HSAN1. 1-DeoxySL levels are also elevated in individuals with the metabolic syndrome and diabetes mellitus type II and seem to be involved in the pathology of the diabetic neuropathy. OBJECTIVE: In previous studies, we observed a strong correlation between plasma 1-deoxySLs and triglycerides (TGs). We were therefore interested whether lowering plasma TG levels also affects plasma sphingolipid and in particular, 1-deoxySL levels. METHODS: Sixty-six patients with dyslipidemia were treated for 6 wk with the TG-lowering drug fenofibrate (160 mg/d) or extended-release niacin (0.5 g/d for 3 wk, then 1 g/d) with 4 wk of washout between treatments. The sphingoid base profile was analyzed by liquid chromatography-mass spectrometry (LC-MS) before and after each treatment block. RESULTS: Fenofibrate significantly lowered 1-deoxySLs and other atypical sphingoid bases (P < .001) but had no effect on the typical sphingolipids. In contrast, extended-release niacin had no effect on 1-deoxySL levels although both treatments lowered plasma TG levels. CONCLUSIONS: The lowering of plasma 1-deoxySL levels by fenofibrate in dyslipidemic patients might be a novel therapeutic approach in the prevention and treatment of diabetic neuropathy.

Norepinephrine deficiency with normal blood pressure control in congenital insensitivity to pain with anhidrosis.

OBJECTIVE: Congenital insensitivity to pain with anhidrosis (CIPA) is caused by mutations in the NKTR1 gene. This affects the development of nerve growth factor (NGF)-dependent neurons including sympathetic cholinergic neurons in the skin, causing anhidrosis. Cardiovascular and blood pressure regulation appears normal, but the integrity of sympathetic adrenergic neurons has not been tested. METHODS: We examined the effect of posture on blood pressure, heart rate, plasma concentration of catecholamines, vasopressin, endothelin, and renin activity in 14 patients with CIPA, 10 patients with chronically deficient sympathetic activity (pure autonomic failure), and 15 normal age-matched controls. RESULTS: In all 14 patients with CIPA, plasma norepinephrine levels were very low or undetectable and failed to increase when the patient was upright, yet upright blood pressure was well maintained. Plasma epinephrine levels were normal and increased when the patient was upright. Plasma renin activity also increased appropriately when the patient was upright and after furosemide-induced volume depletion. Nitric oxide-mediated endothelial function was intact. Patients with pure autonomic failure also had very low levels of plasma norepinephrine both supine and upright, but in contrast to patients with CIPA failed to maintain blood pressure upright. INTERPRETATION: The results indicate that postganglionic sympathetic neurons are severely depleted in CIPA, but chromaffin cells of the adrenal medulla are spared. This confirms the differential effect of NGF signaling for sympathetic neural and chromaffin cell development. The finding that patients with CIPA maintain blood pressure well on standing challenges current concepts of the role of norepinephrine in the regulation of arterial pressure.

Lowering plasma 1-deoxysphingolipids improves neuropathy in diabetic rats.

1-Deoxysphingolipids (1-deoxySLs) are atypical neurotoxic sphingolipids that are formed by the serine-palmitoyltransferase (SPT). Pathologically elevated 1-deoxySL concentrations cause hereditary sensory and autonomic neuropathy type 1 (HSAN1), an axonal neuropathy associated with several missense mutations in SPT. Oral L-serine supplementation suppressed the formation of 1-deoxySLs in patients with HSAN1 and preserved nerve function in an HSAN1 mouse model. Because 1-deoxySLs also are elevated in patients with type 2 diabetes mellitus, L-serine supplementation could also be a therapeutic option for diabetic neuropathy (DN). This was tested in diabetic STZ rats in a preventive and therapeutic treatment scheme. Diabetic rats showed significantly increased plasma 1-deoxySL concentrations, and L-serine supplementation lowered 1-deoxySL concentrations in both treatment schemes (P < 0.0001). L-serine had no significant effect on hyperglycemia, body weight, or food intake. Mechanical sensitivity was significantly improved in the preventive (P < 0.01) and therapeutic schemes (P < 0.001). Nerve conduction velocity (NCV) significantly improved in only the preventive group (P < 0.05). Overall NCV showed a highly significant (P = 5.2E-12) inverse correlation with plasma 1-deoxySL concentrations. In summary, our data support the hypothesis that 1-deoxySLs are involved in the pathology of DN and that an oral L-serine supplementation could be a novel therapeutic option for treating DN.

Hereditary sensory and autonomic neuropathy type 1 (HSANI) caused by a novel mutation in SPTLC2.

OBJECTIVE: To describe the clinical and neurophysiologic phenotype of a family with hereditary sensory and autonomic neuropathy type 1 (HSANI) due to a novel mutation in SPTLC2 and to characterize the biochemical properties of this mutation. METHODS: We screened 107 patients with HSAN who were negative for other genetic causes for mutations in SPTLC2. The biochemical properties of a new mutation were characterized in cell-free and cell-based activity assays. RESULTS: A novel mutation (A182P) was found in 2 subjects of a single family. The phenotype of the 2 subjects was an ulcero-mutilating sensory-predominant neuropathy as described previously for patients with HSANI, but with prominent motor involvement and earlier disease onset in the first decade of life. Affected patients had elevated levels of plasma 1-deoxysphingolipids (1-deoxySLs). Biochemically, the A182P mutation was associated with a reduced canonical activity but an increased alternative activity with alanine, which results in largely increased 1-deoxySL levels, supporting their pathogenicity. CONCLUSION: This study confirms that mutations in SPTLC2 are associated with increased deoxySL formation causing HSANI.

Characterization of two mutations in the SPTLC1 subunit of serine palmitoyltransferase associated with hereditary sensory and autonomic neuropathy type I.

Hereditary sensory and autonomic neuropathy type I (HSAN-I) is an axonal peripheral neuropathy leading to progressive distal sensory loss and severe ulcerations. Mutations in SPTLC1 and SPTLC2, encoding the two subunits of serine palmitoyltransferase (SPT), the enzyme catalyzing the first and rate-limiting step in the de novo synthesis of sphingolipids, have been reported to cause HSAN-I. Here, we demonstrate that the SPTLC1 mutations p.S331F and p.A352V result in a reduction of SPT activity in vitro and are associated with increased levels of the deoxysphingoid bases 1-deoxy-sphinganine and 1-deoxymethyl-sphinganine in patients' plasma samples. Stably expressing p.S331F-SPTLC1 HEK293T cell lines likewise show accumulation of deoxysphingoid bases, but this accumulation is not observed in HEK293T cells overexpressing p.A352V-SPTLC1. These results confirm that the increased formation of deoxysphingoid bases is a key feature for HSAN-I as it is associated with all pathogenic SPTLC1 and SPTLC2 mutations reported so far, but also warrant for caution in the interpretation of in vitro data.

Lymphocyte TRPV 1-4 gene expression and MIF blood levels in a young girl clinically diagnosed with HSAN IV.

OBJECTIVE: Patients with congenital insensitivity to pain are unable to sense pain and temperature. They undergo many injuries, inflammatory state, and infections. Various mutations in the neurotrophic tyrosine kinase receptor gene have been implicated in this disorder. We measured the leukocyte expression of transient receptor potential vanilloid (TRPV) 1-4 genes and the blood macrophage migration inhibitory factor (MIF) concentration in a young girl clinically diagnosed with congenital insensitivity to pain. The investigation may help to define the interplay between nerve growth factor and TRPV 1-4 channels and between these sensors and MIF in this disease, and in broader terms in nociception. METHODS: TRPV 1-4 gene expression (real-time polymerase chain reaction) and MIF concentration (enzyme-linked immunosorbent assay) were determined in the blood of the girl, her family, and control participants. Statistical analysis of gene expression was carried out between samples and controls with a mathematical model based on the correction for exact polymerase chain reaction efficiencies, and the mean crossing point deviation between samples and controls. RESULTS: The TRPV 1--4 gene expression rates did not significantly differ from the values found in the control group. TRPV1 was almost doubly upregulated. MIF levels were much higher than the reference value. DISCUSSION: The high increase in the MIF concentration (likely due to the chronic or recurrent inflammatory state) may have contributed to the normal expression of TRPV 1-4 and to the relative upregulation of TRPV1. The role of this cytokine on the expression of these genes deserves further investigation.

Decreased first phase insulin response in children with congenital insensitivity to pain with anhidrosis.

Nerve growth factor (NGF) and its receptor tyrosine kinase A (TrkA) participate in endocrine pancreas morphogenesis and insulin secretion in vitro. Mutations in the TrkA gene cause the syndrome of congenital insensitivity to pain with anhydrosis (CIPA). We hypothesized that CIPA may represent a natural model for impaired NGF effect on insulin secretion in humans. Glucose challenge tests were performed in seven children with CIPA. We calculated the first phase insulin response (FPIR), the second phase insulin response (SPIR) and glucose disposal rate. FPIR was impaired in four and borderline in two patients. SPIR and glucose disposal rate were within the normal range. Oral glucose tolerance test was normal in all patients. Low FPIR in. CIPA suggests for the first time that the NGF-TrkA pathway may play a role in insulin secretion in response to glucose challenge in humans. Additional studies on the clinical significance of NGF-TrkA effects on insulin secretion are required.

Activity of partially inhibited serine palmitoyltransferase is sufficient for normal sphingolipid metabolism and viability of HSN1 patient cells.

Hereditary sensory neuropathy type I (HSN1) is a common degenerative disorder of peripheral sensory neurons. HSN1 is caused by mutations in the gene, encoding the long chain base 1 of serine palmitoyltransferase (SPT) [Nat. Genet. 27 (2001) 309]. Here, we show a 44% reduction of SPT activity in transformed lymphocytes from HSN1 patients with mutation T399G in the SPTLC1 gene. However, the decrease in SPT activity had no effect on de novo sphingolipid biosynthesis, cellular sphingolipid content, cell proliferation and death (apoptosis and necrosis). The removal of extracellular sphingolipids did not affect viability of HSN1 cells. We also found no significant difference in whole blood counts, viability, and permeability to Triton X-100 of primary lymphocytes from HSN1 patients. These results suggest that, despite the inhibition of mutant allele, the activity of nonmutant allele of STP may be sufficient for adequate sphingolipid biosynthesis and cell viability. Therefore, the neurodegeneration in HSN1 is likely to be caused by subtler and rather long-term effect(s) of these mutations such as loss of a cell-type selective facet of sphingolipid metabolism and/or function, or perhaps accumulation of toxic species, including abnormal protein(s) as in other neurodegenerations.

Peripheral neuropathy in systemic lupus erythematosus.

The prevalence of clinically apparent peripheral neuropathy in systemic lupus erythematosus is reported to be between 2% to 18%. The purpose of this prospective case-control study was to determine the prevalence of peripheral neuropathy (PN) using electrodiagnostic criteria. Subgroup analysis was performed to determine whether PN correlated with disease activity, renal involvement, or serum immune markers. Fifty-four systemic lupus erythematosus patients and 30 controls were recruited in the study. The right median, ulnar, peroneal, tibial, and sural sensory and motor nerve conduction studies were obtained. PN in our study was defined as any abnormal values in motor and sensory distal latency, sensory action potential, motor action potential, or conduction velocity affecting 2 or more nerves. Of the 54 patients studied, PN was present in 15 patients (27.8%) of which 4 were symptomatic. There was a significant correlation between PN and anti-SM antibody, and there was a trend showing decreased motor and sensory action potential amplitudes in our systemic lupus erythematosus group compared to the controls. This observation was also seen in an active disease group when compared to those with inactive disease. The amplitude of the action potential was more often affected than the distal latency, and sensory nerves were more susceptible than motor nerves. The sural sensory action potential amplitude appears to be the most sensitive indicator of PN which may be used as an index to monitor disease activity.

Fasting plasma and CSF amino acid levels in amyotrophic lateral sclerosis: a subtype analysis.

Data from the literature about plasma and CSF amino acid (AA) levels in amyotrophic lateral sclerosis (ALS) remain controversial. To refine such analyses we used HPLC, and report a study of plasma and CSF AA concentrations in patients with ALS, the type of the disease (spinal and bulbar onset) being precisely determined. In ALS, there is a decrease in the plasma levels of the large neutral amino acids (LNAA) alanine, isoleucine, leucine, methionine and tyrosine which was particularly striking in the bulbar type (p < 0.05). Plasma glutamate levels do not differ between ALS and controls, but are significantly increased in ALS with spinal onset and decreased in the bulbar type (p < 0.05 vs controls, p < 0.001 bulbar vs spinal). In CSF, the analysis of the whole ALS group shows no difference from controls. However, there is an increase of CSF serine, glutamine and alanine in ALS with spinal onset (p < 0.05). Our results do not support an abnormal profile of excitatory AA concentrations in ALS. The heterogeneous changes we observed, mainly concerning LNAAs, may be explained by a blood-CSF barrier disturbance in the disease. As AA levels clearly differ between ALS types, with low concentrations in bulbar ALS, this dual profile probably explains some of the discrepancies between previous studies.

[Duffy blood groups and HLA antigens in hereditary motor-sensory neuropathy]. / Studie krevní skupiny Duffy a HLA antigenu u hereditární motoricko-senzorické neuropatie.

The Duffa system (Fya Fyb) and HLA antigens were examined in 86 subjects (39 affected, 47 healthy) in 17 families with HMSN type I, II and III. They recorded the incidence of autosomal dominant as well as recessive (possibly sporadic) forms. In the autosomal dominant form of HMSN type I a close relationship was detected between genes coding the investigated disease and blood cell signs Fya and Fyb. Recombination was found only in 9.1% of the cases. Investigation HLA antigens revealed marked reduction of the B27 antigen in the investigated patients. A striking sign in families with the autosomal dominant form of HMSN type I was an identical haplotype of the majority of parents.

Quantitative detection of a variant prealbumin associated with type 1 familial amyloidotic polyneuropathy (Japanese type) by high performance liquid chromatography.

A simple and quantitative method for detecting the variant prealbumin associated with familial amyloidotic polyneuropathy has been developed. This method is based on (1) a rapid and simple high performance liquid chromatographic method for the purification of prealbumin, using an immunoadsorbent-affinity column with bound monospecific prealbumin antibody, (2) the presence of an extra methionine in the variant prealbumin at position 30, detected by cyanogen bromide cleavage, and (3) sensitive and quantitative detection of cleaved peptides by reversed phase high performance liquid chromatography. This non-radioisotopic method gives quantitatively reliable results on serum samples as small as 0.5 ml. This method is not only useful for the detection of patients and carriers of familial amyloidotic polyneuropathy, but also for determination of the ratio of normal to variant prealbumin in the serum samples.

Diagnostic radioimmunoassay for familial amyloidotic polyneuropathy before clinical onset.

The purpose of this study is to develop an early diagnostic method for familial amyloidotic polyneuropathy (FAP) before clinical manifestations appear around the age of 30 yr. Amyloid fibrils isolated from type I FAP (FAP1) of Portuguese, Swedish, and Japanese origins consist of a variant transthyretin (TTR) that contains a methionine-for-valine substitution at position 30 or a mixture of normal TTR and this variant form. The variant TTR is present in the serum of FAP1 patients and can be measured by a radioimmunoassay (RIA) based on a nonapeptide (positions 22-30) derived from the variant TTR. Serum levels of the variant TTR in 45 Japanese FAP1 patients range from 4.71 to 17.61 mg/dl with a mean value of 9.18 mg/dl. The variant TTR is not present in the serum of 100 normal individuals, in four cases of primary and six cases of secondary amyloidosis, nor in 26 non-inheriting members of families with FAP1. The variant TTR level is measured in 24 children of 15 FAP1 patients as well. The variant TTR is already present in nine symptom-free children with the mean serum level of 11.90 mg/dl, but it is not present in 15 other children. FAP1 patients can be differentiated from non-FAP by this noninvasive diagnostic method even within families. The RIA can be applied worldwide to this intractable disorder for early diagnosis during childhood and for appropriate genetic counseling.

[Plasma, intraerythrocytic and spinal fluid amino acid levels in a case of ulcero-mutilating acropathy]. / Dosaggio degli aminoacidi plasmatici intraeritrocitari e liquorali in un caso di acropatia ulcero-mutilante.

In a patient affected by Thevenard's disease (degenerative disease of the spinal ganglia and posterior roots) we measured levels of intraerythrocytic, plasmatic and cerebrospinal fluid aminoacids. In the plasma we found an increased concentration of taurine and glycine, expression of hypercatabolism, which was confirmed by the presence of a decreased level of the free intraerythrocytic aminoacids. In the cerebrospinal fluid we found increased concentrations of methionine, valine and lysine which indicates the presence of an enzymatic inhibition that involves the systemic transport of aminoacids at the barrier level. The increased levels of glutamic acid and arginine suggests an alteration of the synthesis of alpha-guanino butyric acid. We have also found an increase in the levels of valine, methionine, glycine, tyrosine which suggests the presence of an enzymatic alteration in the collateral reactions that biochemically feed into the Krebs cycle. The authors therefore conclude that the basis of this disease may be found in a metabolic defect biochemical synthesis.