Congenital Generalized Lipodystrophy Type Research Articles

Characteristic findings of skeletal muscle MRI in caveolinopathies

Caveolinopathies, caused by CAV3 mutations, can include several phenotypes such as rippling muscle disease, limb-girdle muscular dystrophy type 1C, distal myopathy, familial hypertrophic cardiomyopathy, and idiopathic hyperCKemia. Here we present characteristic skeletal muscle imaging findings in four patients with genetically defined childhood-onset RMD caused by CAV3 mutations and in one patient with congenital generalized lipodystrophy type 4 with muscular dystrophy due to polymerase I and transcript release factor (PTRF) mutations, which may have caused secondary deficiency of caveolin-3. Muscle MRI revealed that the rectus femoris and semitendinosus muscles were most commonly affected in the rippling muscle disease patients. Peripheral changes in the rectus femoris were specific and observed even in one of the younger patients in this study. Furthermore, muscle involvement extended to the semitendinosus muscles, biceps femoris, and gracilis with disease progression or increase in its severity. Similar patterns of involvement were observed on reviewing skeletal muscle images of various previously reported phenotypes of caveolinopathy; interestingly, patients with secondary deficiency of caveolin due to PTRF mutations revealed the same pattern. Thus, primary caveolinopathies and secondary deficiency of caveolin demonstrated specific findings on skeletal muscle imaging, regardless of the broad phenotypic spectrum of these two conditions.

Early commitment of cardiovascular autonomic modulation in Brazilian patients with congenital generalized lipodystrophy

BackgroundMetabolic abnormalities in congenital generalized lipodystrophy (CGL) are associated with microvascular complications. However, the evaluation of different types of neuropathy in these patients, including the commitment of cardiovascular autonomic modulation, is scarce. The objective of the present study was to determine the prevalence of cardiovascular autonomic neuropathy (CAN) in patients with CGL compared with individuals with type 1 diabetes and healthy subjects.MethodsTen patients with CGL, 20 patients with type 1 diabetes and 20 healthy subjects were included in the study. Controls were paired 1:2 for age, gender, BMI and pubertal stage. Heart rate variability (HRV) was analyzed using cardiovascular autonomic reflex tests, including postural hypotension test, Valsalva (VAL), respiratory (E/I) and orthostatic (30/15) coefficients, and spectral analysis of the HRV, determining very low (VLF), low (LF) and high (HF) frequencies components. The diagnosis of CAN was defined as the presence of at least two altered tests.ResultsCAN was detected in 40% of the CGL patients, 5% in type 1 diabetes patients and was absent in healthy individuals (p < 0.05). We observed a significant reduction in the E/I, VLF, LF and HF in CGL cases vs. type 1 diabetes and healthy individuals and lower levels of 30/15 and VAL in CGL vs. healthy individuals. A significant positive correlation was observed between leptin and 30/15 coefficient (r = 0.396; p = 0.036) after adjusting for insulin resistance and triglycerides. Autonomic cardiovascular tests were associated with HbA1c, HOMA-IR, triglycerides and albumin/creatinine ratio in CGL cases.ConclusionsWe observed a high prevalence of CAN in young patients with CGL, suggesting that insulin resistance, hypertriglyceridemia and hypoleptinemia, may have been involved in early CAN development. Additional studies are needed to evaluate the role of leptinemia in the physiopathogenesis of the condition.

Clinical spectra of neuromuscular manifestations in patients with lipodystrophy: A multicenter study

Lipodystrophy is a heterogeneous group of disorders characterized by loss of adipose tissue. Here, we report on clinical spectra of neuromuscular manifestations of Turkish patients with lipodystrophy. Seventy-four patients with lipodystrophy and 20 healthy controls were included. Peripheral sensorimotor neuropathy was a common finding (67.4%) in lipodystrophic patients with diabetes. Neuropathic foot ulcers were observed in 4 patients. Drop foot developed in 1 patient with congenital generalized lipodystrophy type 1. Muscle symptoms and hypertrophy were consistent findings in congenital generalized lipodystrophy (21/21) and familial partial lipodystrophy (25/34); on the other hand, overt myopathy with elevated creatine kinase activity was a distinctive characteristic of congenital generalized lipodystrophy type 4. Muscle biopsies revealed myopathic changes at different levels. Accumulation of triglycerides was observed which contributes to insulin resistance. All patients with congenital generalized lipodystrophy suffered from tight Achilles tendons at various levels. Scoliosis was observed in congenital generalized lipodystrophy type 4 (2/2) and familial partial lipodystrophy type 2 (2/17). Atlantoaxial instability was unique to congenital generalized lipodystrophy type 4 (2/2). Bone cysts were detected in congenital generalized lipodystrophy type 1 (7/10) and congenital generalized lipodystrophy type 2 (2/8). Our study suggests that lipodystrophies are associated with a wide spectrum of neuromuscular abnormalities.

Clinical spectra of neuromuscular manifestations in patients with lipodystrophy: A multicenter study

Lipodystrophy is a heterogeneous group of disorders characterized by loss of adipose tissue. Here, we report on clinical spectra of neuromuscular manifestations of Turkish patients with lipodystrophy. Seventy-four patients with lipodystrophy and 20 healthy controls were included. Peripheral sensorimotor neuropathy was a common finding (67.4%) in lipodystrophic patients with diabetes. Neuropathic foot ulcers were observed in 4 patients. Drop foot developed in 1 patient with congenital generalized lipodystrophy type 1. Muscle symptoms and hypertrophy were consistent findings in congenital generalized lipodystrophy (21/21) and familial partial lipodystrophy (25/34); on the other hand, overt myopathy with elevated creatine kinase activity was a distinctive characteristic of congenital generalized lipodystrophy type 4. Muscle biopsies revealed myopathic changes at different levels. Accumulation of triglycerides was observed which contributes to insulin resistance. All patients with congenital generalized lipodystrophy suffered from tight Achilles tendons at various levels. Scoliosis was observed in congenital generalized lipodystrophy type 4 (2/2) and familial partial lipodystrophy type 2 (2/17). Atlantoaxial instability was unique to congenital generalized lipodystrophy type 4 (2/2). Bone cysts were detected in congenital generalized lipodystrophy type 1 (7/10) and congenital generalized lipodystrophy type 2 (2/8). Our study suggests that lipodystrophies are associated with a wide spectrum of neuromuscular abnormalities.

PTRF/Cavin-1 Deficiency Causes Cardiac Dysfunction Accompanied by Cardiomyocyte Hypertrophy and Cardiac Fibrosis

Mutations in the PTRF/Cavin-1 gene cause congenital generalized lipodystrophy type 4 (CGL4) associated with myopathy. Additionally, long-QT syndrome and fatal cardiac arrhythmia are observed in patients with CGL4 who have homozygous PTRF/Cavin-1 mutations. PTRF/Cavin-1 deficiency shows reductions of caveolae and caveolin-3 (Cav3) protein expression in skeletal muscle, and Cav3 deficiency in the heart causes cardiac hypertrophy with loss of caveolae. However, it remains unknown how loss of PTRF/Cavin-1 affects cardiac morphology and function. Here, we present a characterization of the hearts of PTRF/Cavin-1-null (PTRF−/−) mice. Electron microscopy revealed the reduction of caveolae in cardiomyocytes of PTRF−/− mice. PTRF−/− mice at 16 weeks of age developed a progressive cardiomyopathic phenotype with wall thickening of left ventricles and reduced fractional shortening evaluated by echocardiography. Electrocardiography revealed that PTRF−/− mice at 24 weeks of age had low voltages and wide QRS complexes in limb leads. Histological analysis showed cardiomyocyte hypertrophy accompanied by progressive interstitial/perivascular fibrosis. Hypertrophy-related fetal gene expression was also induced in PTRF−/− hearts. Western blotting analysis and quantitative RT-PCR revealed that Cav3 expression was suppressed in PTRF−/− hearts compared with that in wild-type (WT) ones. ERK1/2 was activated in PTRF−/− hearts compared with that in WT ones. These results suggest that loss of PTRF/Cavin-1 protein expression is sufficient to induce a molecular program leading to cardiomyocyte hypertrophy and cardiomyopathy, which is partly attributable to Cav3 reduction in the heart.

Progressive Myoclonus Epilepsy in Congenital Generalized Lipodystrophy type 2: Report of 3 cases and literature review

PurposeA small case series with a neurodegenerative disorder involving central nervous system and related to Seipin mutations was recently reported. Herein we describe clinical and EEG features of three patients presenting with Progressive Myoclonus Epilepsy (PME) and Congenital Generalized Lipodystrophy type 2 (CGL2) related to novel Seipin mutations. MethodsThe EEG-clinical picture was evaluated at epilepsy onset and in the follow-up period. The molecular analysis of BSCL2, Laforin and Malin genes was performed to patients and/or their parents by Denaturing High Performance Liquid Chromatography and automated nucleotide sequencing. Skin specimens collected from a patient were processed for histochemical and ultrastructural analysis. ResultsThe CGL2-PME syndrome co-segregated with two different BSCL2 genotypes: the homozygosity for c.782_783dupG involving exon 8 (two cases), or the compound heterozygosity for c.782_783dupG/c.828_829delAA (one case). Periodic-Acid Schiff positive osmiophilic material in the cytoplasm of fibrocytes and eccrine-gland cells were found in skin specimens. The lack of Lafora’s bodies in skin specimens and the molecular analysis excluding mutations in Laforin and Malin genes ruled out Lafora disease. ConclusionThe spectrum of CGL2 associated to BSCL2 gene mutations may include PMEs. Selected mutations in BSCL2 gene seem to be related to PMEs in patients with CGL2 phenotype.

Spectrum of clinical manifestations in two young Turkish patients with congenital generalized lipodystrophy type 4

Congenital generalized lipodystrophy type 4 is an extremely rare autosomal recessive disorder. We report our clinical experience on two unrelated Turkish patients with congenital generalized lipodystrophy type 4. A 13-year-old girl (patient-1) presented with generalized lipodystrophy and myopathy. Further tests revealed ventricular and supraventricular arrhythmias, gastrointestinal dysmotility, atlantoaxial instability, lumbosacral scoliosis, and metabolic abnormalities associated with insulin resistance. A 16-year-old girl (patient-2) with congenital generalized lipodystrophy type 4 was previously reported. Here, we report on her long term clinical follow-up. She received several course of anti-arrhythmic treatments for catecholaminergic polymorphic ventricular tachycardia and rapid atrial fibrillation. An implantable cardioverter defibrillator was also placed. A homozygous PTRF mutation, c.259C > T (p.Gln87*), was identified in patient-1. Congenital generalized lipodystrophy type 4 was caused by homozygous PTRF c.481-482insGTGA (p.Lys161Serfs*41) mutation in patient-2. Our data indicate that patients with congenital generalized lipodystrophy type 4 should be meticulously evaluated for cardiac, neuromuscular, gastrointestinal and skeletal diseases, as well as metabolic abnormalities associated with insulin resistance.

Metabolic complications in an animal model of congenital generalized lipodystrophy type 2

Metabolic complications in an animal model of congenital generalized lipodystrophy type 2

Region-specific variation in the properties of skeletal adipocytes reveals regulated and constitutive marrow adipose tissues.

Marrow adipose tissue (MAT) accumulates in diverse clinical conditions but remains poorly understood. Here we show region-specific variation in MAT adipocyte development, regulation, size, lipid composition, gene expression and genetic determinants. Early MAT formation in mice is conserved, whereas later development is strain dependent. Proximal, but not distal tibial, MAT is lost with 21-day cold exposure. Rat MAT adipocytes from distal sites have an increased proportion of monounsaturated fatty acids and expression of Scd1/Scd2, Cebpa and Cebpb. Humans also have increased distal marrow fat unsaturation. We define proximal ‘regulated’ MAT (rMAT) as single adipocytes interspersed with active haematopoiesis, whereas distal ‘constitutive’ MAT (cMAT) has low haematopoiesis, contains larger adipocytes, develops earlier and remains preserved upon systemic challenges. Loss of rMAT occurs in mice with congenital generalized lipodystrophy type 4, whereas both rMAT and cMAT are preserved in mice with congenital generalized lipodystrophy type 3. Consideration of these MAT subpopulations may be important for future studies linking MAT to bone biology, haematopoiesis and whole-body metabolism.

Congenital generalized lipodystrophy: identification of novel variants and expansion of clinical spectrum.

Congenital generalized lipodystrophy (CGL) is an autosomal recessive disorder with two major subtypes. Variants in AGPAT2 result in CGL type 1 with milder manifestations, whereas BSCL2 variants cause CGL type 2 with more severe features. Muscle hypertrophy caused by lack of adipose tissue is present early in life in CGL patients. Our aim was to investigate 10 CGL patients from 7 different countries and report genotype-phenotype relationships. Genetic analysis identified disease-causing variants in AGPAT2 (five patients) and in BSCL2 (five patients), including three novel variants; c.134C>A (p.Ser45*), c.216C>G (p.Tyr72*) in AGPAT2 and c.458C>A (p.Ser153*) in BSCL2. We also report possible novel clinical features such as anemia, breast enlargement, steatorrhea, intraventricular hemorrhage and nephrolithiasis in CGL patients. Generalized lipodystrophy and muscular hypertrophy were the only features in all of our patients. Hepatomegaly was the second common feature. Some manifestations were exclusively noticed in our CGL2 patients; hypertrichosis, high-pitched voice and umbilical hernia. Bone cysts and history of seizures were noticed only in CGL1 patients. The findings of this study expand our knowledge of genotype-phenotype correlations in CGL patients. These results have important clinical applications in diagnosis and management of the CGL patients as well as in genetic counseling in families at-risk.

Seipin knockout impairs proliferation and differentiation of adult stem/progenitor cells in hippocampal dentate gyrus via reduction of PPARγ

ABSTRACTThe seipin gene (BSCL2) was originally identified in humans as a loss-of-function gene associated with congenital generalized lipodystrophy type 2 (CGL2). Neuronal seipin-knockout (seipin-nKO) mice display a depression-like phenotype with a reduced level of hippocampal peroxisome proliferator-activated receptor gamma (PPARγ). The present study investigated the influence of seipin deficiency on adult neurogenesis in the hippocampal dentate gyrus (DG) and the underlying mechanisms of the effects. We show that the proliferative capability of stem cells in seipin-nKO mice was substantially reduced compared to in wild-type (WT) mice, and that this could be rescued by the PPARγ agonist rosiglitazone (rosi). In seipin-nKO mice, neuronal differentiation of progenitor cells was inhibited, with the enhancement of astrogliogenesis; both of these effects were recovered by rosi treatment during early stages of progenitor cell differentiation. In addition, rosi treatment could correct the decline in hippocampal ERK2 phosphorylation and cyclin A mRNA level in seipin-nKO mice. The MEK inhibitor U0126 abolished the rosi-rescued cell proliferation and cyclin A expression in seipin-nKO mice. In seipin-nKO mice, the hippocampal Wnt3 protein level was less than that in WT mice, and there was a reduction of neurogenin 1 (Neurog1) and neurogenic differentiation 1 (NeuroD1) mRNA, levels of which were corrected by rosi treatment. STAT3 phosphorylation (Tyr705) was enhanced in seipin-nKO mice, and was further elevated by rosi treatment. Finally, rosi treatment for 10 days could alleviate the depression-like phenotype in seipin-nKO mice, and this alleviation was blocked by the MEK inhibitor U0126. The results indicate that, by reducing PPARγ, seipin deficiency impairs proliferation and differentiation of neural stem and progenitor cells, respectively, in the adult DG, which might be responsible for the production of the depression-like phenotype in seipin-nKO mice.

Divergent Metabolic Phenotype between Two Sisters with Congenital Generalized Lipodystrophy Due to Double AGPAT2 Homozygous Mutations. A Clinical, Genetic and In Silico Study

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder characterized by extreme reduction of white adipose tissue (WAT) mass. CGL type 1 is the most frequent form and is caused by mutations in AGPAT2. Genetic and clinical studies were performed in two affected sisters of a Chilean family. These patients have notoriously dissimilar metabolic abnormalities that correlate with differential levels of circulating leptin and soluble leptin receptor fraction. Sequencing of AGPAT2 exons and exon-intron boundaries revealed two homozygous mutations in both sisters. Missense mutation c.299G>A changes a conserved serine in the acyltransferase NHX4D motif of AGPAT2 (p.Ser100Asn). Intronic c.493-1G>C mutation destroy a conserved splicing site that likely leads to exon 4 skipping and deletion of whole AGPAT2 substrate binding domain. In silico protein modeling provided insights of the mechanisms of lack of catalytic activity owing to both mutations.

Size control of lipid droplets in budding yeast requires a collaboration of Fld1 and Ldb16

The human congenital generalized lipodystrophy type 2 protein seipin (Fld1 in budding yeast) controls lipid droplet (LD) size through an unknown mechanism. Here, we report that deletion of yeast LDB16/YCL005W, similar to deletion of FLD1, causes supersized and small clustered LDs, altered phospholipid metabolism and impaired distribution of a subset of LD proteins. Ldb16 is a transmembrane protein in the endoplasmic reticulum (ER) that assembles together with Fld1 at ER-LD contact sites, a region that probably links neutral lipid synthesis with LD assembly. The formation of the Fld1-Ldb16 complex involves putative transmembrane segments of both proteins, thus, directly contributing to the maintenance of LD morphology. The stability of Ldb16 requires Fld1, as Ldb16 is subjected to ER-associated degradation (ERAD) in the absence of Fld1 but is stabilized when Fld1 is present. Strikingly, human seipin, but not yeast Fld1, complements the defects in LDs in ldb16Δ yeast, implying that seipin can substitute for the function of the Fld1-Ldb16 complex. We propose that human seipin might adopt the architecture of the yeast Fld1-Ldb16 complex in order to properly maintain the size of LDs.

Altered Lipid Metabolism in Residual White Adipose Tissues of Bscl2 Deficient Mice

Mutations in BSCL2 underlie human congenital generalized lipodystrophy type 2 disease. We previously reported that Bscl2 −/− mice develop lipodystrophy of white adipose tissue (WAT) due to unbridled lipolysis. The residual epididymal WAT (EWAT) displays a browning phenotype with much smaller lipid droplets (LD) and higher expression of brown adipose tissue marker proteins. Here we used targeted lipidomics and gene expression profiling to analyze lipid profiles as well as genes involved in lipid metabolism in WAT of wild-type and Bscl2−/− mice. Analysis of total saponified fatty acids revealed that the residual EWAT of Bscl2−/− mice contained a much higher proportion of oleic18:1n9 acid concomitant with a lower proportion of palmitic16:0 acid, as well as increased n3- polyunsaturated fatty acids (PUFA) remodeling. The acyl chains in major species of triacylglyceride (TG) and diacylglyceride (DG) in the residual EWAT of Bscl2−/− mice were also enriched with dietary fatty acids. These changes could be reflected by upregulation of several fatty acid elongases and desaturases. Meanwhile, Bscl2−/− adipocytes from EWAT had increased gene expression in lipid uptake and TG synthesis but not de novo lipogenesis. Both mitochondria and peroxisomal β-oxidation genes were also markedly increased in Bscl2−/− adipocytes, highlighting that these machineries were accelerated to shunt the lipolysis liberated fatty acids through uncoupling to dissipate energy. The residual subcutaneous white adipose tissue (ScWAT) was not browning but displays similar changes in lipid metabolism. Overall, our data emphasize that, other than being essential for adipocyte differentiation, Bscl2 is also important in fatty acid remodeling and energy homeostasis.

Bezafibrato em lactente portador de lipodistrofia generalizada congênita e hipertrigliceridemia grave

Congenital generalized lipodystrophy (CGL) with severe hypertriglyceridemia in a children less than 1 year of age is associated with worse metabolic risk. We used data from patient records, as well as extensive literature research to write the manuscript. We report the case of an infant with typical phenotype of CGL and hypertriglyceridemia of 1,360 mg/dL who was treated with bezafibrate at a dose of 30 to 60 mg/day from age 11 months to 5.5 years old, with a measurement of nadir of triglycerides of 55 mg/dL. Clinical evolution and clinical laboratory tests before and after bezafibrate were carried out over 5 years and 6 months. Phenotype was classified as CGL type 2. Despite the efficient control of hypertriglyceridemia and absence of development of diabetes mellitus, the use of bezafibrate did not prevent the onset of hepatic steatosis during evolution. Hypolipidemic therapy with bezafibrate proved effective in maintaining the levels of triglycerides, cholesterol and its fractions at normal levels, and its use was not correlated with severe side effects during the described period.

Novel PTRF mutation in a child with mild myopathy and very mild congenital lipodystrophy

BackgroundMutations in the PTRF gene, coding for cavin-1, cause congenital generalized lipodystrophy type 4 (CGL4) associated with myopathy. In CGL4, symptoms are variable comprising, in addition to myopathy, smooth and skeletal muscle hypertrophy, cardiac arrhythmias, and skeletal abnormalities. Secondary features are atlantoaxial instability, acanthosis nigricans, hepatomegaly, umbilical prominence and metabolic abnormalities related to insulin resistance, such as diabetes mellitus, hyperlipidemia and hepatic steatosis.Case presentationWe describe a 3 year-old child of Moroccan origin with mild muscle phenotype, mainly characterized by mounding, muscle pain, hyperCKemia and mild caveolin 3 reduction on muscle biopsy. No CAV3 gene mutation was detected; instead we found a novel mutation, a homozygous single base pair deletion, in the PTRF gene. Only after detection of this mutation a mild generalized loss of subcutaneous fat, at first underestimated, was noticed and the diagnosis of lipodystrophy inferred.ConclusionsThe PTRF gene should be investigated in patients with hyperCKemia, mild myopathy associated with spontaneous or percussion-induced muscle contractions like rippling or mounding, and no CAV3 mutation. The analysis should be performed even if cardiac or metabolic alterations are absent, particularly in young patients in whom lipodystrophy may be difficult to ascertain.

Seipin differentially regulates lipogenesis and adipogenesis through a conserved core sequence and an evolutionarily acquired C-terminus

Homozygous mutations in BSCL2 (Berardinelli-Seip congenital lipodystrophy)/seipin cause CGL2 (congenital generalized lipodystrophy type 2). Recent data suggest that seipin regulates LD (lipid droplet) dynamics and adipocyte differentiation, but whether these roles are mechanistically linked remains unclear. To understand how seipin regulates these processes, we investigated the evolutionary changes of seipin orthologues, and studied individual domains in regulating lipid accumulation in non-adipocytes and adipocytes. Mammalian seipins comprise at least two distinct functional domains, a conserved core sequence and an evolutionarily acquired C-terminus. Despite its requirement for adipocyte formation, seipin overexpression inhibited oleate-induced LD formation and accumulation in nonadipocytes, which was mediated by the core sequence. In contrast, seipin overexpression did not inhibit LD accumulation during adipocyte differentiation or the adipogenic process in 3T3-L1 cells. However, adipogenesis and LD accumulation were impaired in 3T3-L1 cells expressing a seipin mutant lacking the C-terminus. Furthermore, expression of the same mutant without the C-terminus failed to rescue the adipogenic defects in seipin-knockdown cells, demonstrating the importance of the C-terminus for seipin's function in adipocyte development. We propose that seipin is involved in lipid homoeostasis by restricting lipogenesis and LD accumulation in non-adipocytes, while promoting adipogenesis to accommodate excess energy storage.

Congenital generalized lipodystrophy type 4 with muscular dystrophy: Clinical and pathological manifestations in early childhood

A boy with congenital generalized lipodystrophy type 4 with muscular dystrophy presented in infancy with delay in motor milestones and a persistent elevation of CK. There was no associated mental retardation. He was followed up to 3 years and 11 months; he had a homozygous c.696_697insC mutation in polymerase I and transcript release factor (PTRF). He started to walk at 2 years and 6 months although he did not have mental retardation. Insulin resistance appeared at 3 years and 11 months of age. PTRF immunostaining positivity was absent in the muscle but caveolin-3 was preserved in the sarcolemma at 16 months of age. Secondary deficiency of caveolins may be closely associated with disease progression.

Seipin regulates excitatory synaptic transmission in cortical neurons

Heterozygosity for missense mutations in Seipin, namely N88S and S90L, leads to a broad spectrum of motor neuropathy, while a number of loss-of-function mutations in Seipin are associated with the Berardinelli-Seip congenital generalized lipodystrophy type 2 (CGL2, BSCL2), a condition that is characterized by severe lipoatrophy, insulin resistance, and intellectual impairment. The mechanisms by which Seipin mutations lead to motor neuropathy, lipodystrophy, and insulin resistance, and the role Seipin plays in central nervous system (CNS) remain unknown. The goal of this study is to understand the functions of Seipin in the CNS using a loss-of-function approach, i.e. by knockdown (KD) of Seipin gene expression. Excitatory post-synaptic currents (EPSCs) were impaired in Seipin-KD neurons, while the inhibitory post-synaptic currents (IPSCs) remained unaffected. Expression of a shRNA-resistant human Seipin rescued the impairment of EPSC produced by Seipin KD. Furthermore, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-induced whole-cell currents were significantly reduced in Seipin KD neurons, which could be rescued by expression of a shRNA-resistant human Seipin. Fluorescent imaging and biochemical studies revealed reduced level of surface AMPA receptors, while no obvious ultrastructural changes in the pre-synapse were found. These data suggest that Seipin regulates excitatory synaptic function through a post-synaptic mechanism.

G.P.47 Congenital generalized lipodystrophy type 4 with muscular dystrophy: Clinical manifestations in early childhood

Congenital generalized lipodystrophies are rare autosomal recessive disorders which are characterized by near total loss of subcutaneous adipose tissue since birth, insulin resistance, diabetes, hypertriglyceridemia and hepatic steatosis. Recently Hayashi et al. described congenital generalized lipodystrophy type 4 with muscular dystrophy caused by PTRF (polymerase I and transcript release factor) mutations. Since the disease is a rare disorder, when and how the disease characteristic symptoms appear remains unknown. We followed a Japanese boy from early infancy to 3years and 11months (3y 11m). He was noticed to have decreased subcutaneous fat tissue on his face at 7m. The lip dystrophy progressed to extremities and muscle appeared to be hypertrophic at 1y 4m, but developmental mile stones were delayed; he sat alone at 1y 4m and walked alone at 2y 6m. Muscle biopsy done at 1y 4m showed fiber necrosis and regeneration with fibrosis consistent with muscular dystrophy. Strikingly PTRF protein was absent with an immunohistochemical staining though caveolin-3 was positive. He had a homozygous mutation of c.696_697insC in PTRF gene. He had no insulin resistant diabetes but insulin resistant index was already elevated at 3y 11m though it was normal level at 2y 6m. Caveolin-1 deficient mice that demonstrate a loss of caveolae, have been reported to show insulin resistance due to decrease of insulin receptor. Because PTRF is an essential compartment for stabilization of caveolae, PTRF-deficient mice have been described to have no detectable caveolae and show decreased level of insulin receptor. Therefore patients with deficiency of PTRF are thought to have insulin resistance as same as those with caveoline-1-deficiency. Caveolin-3 expression in our patient was almost normal despite PTRF deficiency, but it is likely that caveolins decrease secondarily with disease progression, then the insulin resistance progresses.