A study of congenital generalized lipodystrophy (CGL) caused by BSCL2 gene mutation

Congenital generalized lipodystrophy (CGL) is an extremely rare genetic disease mainly characterized by absence of whole-body adipose tissue and metabolic dysfunctions such as insulin resistance, diabetes mellitus, hypertriglyceridemia, hepatic steatosis, and acanthosis nigricans. In this study, we reported a novel case of a young woman patient with CGL. The patient came to the hospital for early-onset lipodystrophy and diabetes. She was 19-year-old with a height of 160 cm, a weight of 46 kg, BMI of 17.9 kg/m², and a serum leptin level of 0.14 μg/L. Genomic DNA was extracted from blood samples of the patient and her family members, including her mother, father and brother. Genetic analysis revealed compound heterozygous mutations of the BSCL2 gene (c.560A>G and c.565G>T) in the patient. Her father carried a heterozygous mutation (c.565G>T), and her mother carried a heterozygous mutation (c.560A>G) in the BSCL2 gene. The mutant p.Y187C plasmid was transfected into HEK293T cells. The protein expression of SEIPIN and its interaction with glycerol-3-phosphate acyltransferase (GPAT3) were observed to be reduced. In addition, based on primary cultured skin fibroblasts from the patient, SEIPIN protein was decreased, and lipid droplets were much smaller when fatty acid was stimulated compared with those observed from healthy subject controls. However, histone deacetylase inhibitors (HDACis) was found capable of rescuing SEIPIN protein in fibroblasts of the patient. In addition, we further summarized and discussed gene mutations of BSCL2 reported in the current literature. Collectively, these findings have expanded the clinical phenotype and pathogenic gene spectrum of CGL, which might help clinicians to achieve better management of lipodystrophy.

Definitive diagnosis of mandibular hypoplasia, deafness, progeroid features and lipodystrophy (MDPL) syndrome caused by a recurrent de novo mutation in the POLD1 gene

Segmental progeroid syndromes with lipodystrophy are extremely rare, heterogeneous, and complex multi-system disorders that are characterized by phenotypic features of premature aging affecting various tissues and organs. In this study, we present a "sporadic/isolated" Japanese woman who was ultimately diagnosed with mandibular hypoplasia, deafness, progeroid features, and progressive lipodystrophy (MDPL) syndrome (MIM #615381) using whole exome sequencing analysis. She had been suspected as having atypical Werner syndrome and/or progeroid syndrome based on observations spanning a 30-year period; however, repeated genetic testing by Sanger sequencing did not identify any causative mutation related to various subtypes of congenital partial lipodystrophy (CPLD) and/or mandibular dysplasia with lipodystrophy (MAD). Recently, MDPL syndrome has been described as a new entity showing progressive lipodystrophy. Furthermore, polymerase delta 1 (POLD1) gene mutations on chromosome 19 have been identified in patients with MDPL syndrome. To date, 21 cases with POLD1-related MDPL syndrome have been reported worldwide, albeit almost entirely of European origin. Here, we identified a de novo mutation in exon 15 (p.Ser605del) of the POLD1 gene in a Japanese case by whole exome sequencing. To the best of our knowledge, this is the first identified case of MDPL syndrome in Japan. Our results provide further evidence that mutations in POLD1 are responsible for MDPL syndrome and serve as a common genetic determinant across different ethnicities.

Human congenital perilipin deficiency and insulin resistance

Lipid droplets (LDs) can form in all eukaryotic cells, but white adipocytes are uniquely adapted to store energy as neutral lipid within a large unilocular LD. Non-esterified fatty acids can then be released from the LD store by lipases for use in oxidative tissues. Perilipin was the first mammalian LD protein to be identified in adipocytes where it plays a key role in co-ordinating access of lipases to the core triacylglycerol. We recently identified the first human loss-of-function mutations in PLIN1 in patients with a novel form of familial partial lipodystrophy, severe insulin resistance, diabetes, dyslipidaemia and fatty liver. Adipose tissue samples from affected patients revealed remarkably similar features to those previously observed in samples from obese insulin resistant patients, namely macrophage infiltration and fibrosis. Cellular mechanistic studies suggest that the mutations lead to increased basal lipolysis, which is likely to be a major factor in the subsequent inflammatory response. Perilipin is almost exclusively expressed in white adipocytes, so the serious metabolic sequelae observed in these patients suggest that primary defects in adipose tissue can lead to all the typical features seen in patients with the metabolic syndrome. They also suggest that lipolytic inhibitors may be therapeutically useful in these patients.

An autosomal recessive syndrome of joint contractures, muscular atrophy, microcytic anemia, and panniculitis-associated lipodystrophy

CONTEXT

Genetic lipodystrophies are rare disorders characterized by partial or complete loss of adipose tissue and predisposition to insulin resistance and its complications such as diabetes mellitus, hypertriglyceridemia, hepatic steatosis, acanthosis nigricans, and polycystic ovarian syndrome.

OBJECTIVE

The objective of the study was to report a novel autosomal recessive lipodystrophy syndrome.

RESULTS

We report the detailed phenotype of two males and one female patient, 26-34 yr old, belonging to two pedigrees with an autosomal recessive syndrome presenting with childhood-onset lipodystrophy, muscle atrophy, severe joint contractures, erythematous skin lesions, and microcytic anemia. Other variable clinical features include hypergammaglobulinemia, hepatosplenomegaly, generalized seizures, and basal ganglia calcification. None of the patients had diabetes mellitus or acanthosis nigricans. Two had mild hypertriglyceridemia and all had low levels of high-density lipoprotein cholesterol. Skin biopsy of an erythematous nodular skin lesion from one of the patients revealed evidence of panniculitis. The lipodystrophy initially affected the upper body but later became generalized involving abdomen and lower extremities as well.

CONCLUSIONS

We conclude that these patients represent a novel autoinflammatory syndrome resulting in joint contractures, muscle atrophy, microcytic anemia, and panniculitis-induced lipodystrophy. The molecular genetic basis of this disorder remains to be elucidated.

Les syndromes lipodystrophiques : des adipopathies congénitales ou acquises

Lipodystrophic syndromes regroup a heterogeneous group of genetic or acquired diseases. Lipodystrophy, an altered development and/or repartition of body fat, is associated with alterations of lipid and glucose metabolism with insulin resistance. Genetic forms, rare, can be generalized and recessive resulting from mutations in the seipin or AGPAT2 gene. Partial lipodystrophies are dominant and observed in patients mutated in the gene encoding PPAR-gamma or lamin A/C, a gene seen also mutated in patients with syndromes of premature aging. Acquired forms are common and regroup the highly prevalent Metabolic Syndrome, hypercorticism together with lipodystrophy related to antiretroviral treatment of HIV-infected patients.

Regional cerebral blood flow in a patient with Nasu-Hakola disease

We report a functional neuroimaging study of a 43-year-old woman with Nasu-Hakola disease (NHD). Regional cerebral blood flow (rCBF) images were measured with technetium-99m ethyl cysteinate dimer single photon emission computed tomography (SPECT). rCBF was decreased in the bilateral frontal lobes and thalamus. This finding was consistent with the known underlying neuropathology in patients with NHD. Brain SPECT is useful for demonstrating the pathophysiologic brain region in patients with NHD.

Longevity, lipotoxicity and leptin: the adipocyte defense against feasting and famine

In this review, we propose that actions of the lipid-lowering, apoptosis-inhibiting effects of certain "longevity genes" oppose the life-shortening consequences of lipotoxicity and lipoapoptosis. We note that lipotoxicity occurs whenever leptin action is deficient, or whenever satiety is overridden, as in forced or voluntary overfeeding ("supersizing"). The role of hyperleptinemia, we suggest, is to extend survival during famine by permitting the storage of surplus calories in adipocytes without concomitant injury to nonadipose tissues from ectopic lipid deposits. It achieves this lipid partitioning by (1) restraining the level of overnutrition so as not to exceed the available adipocyte storage space and (2) enhancing oxidation of any ectopic lipid overflow: The mechanisms of lipoapoptosis are discussed, and the possibility that metabolic syndrome is the human equivalent of rodent lipotoxicity is suggested.

Congenital generalized lipodystrophy: profile of the disease and gender differences in two siblings

Congenital generalized Lipodystrophy (BSCL) or Berardinelli-Seip syndrome (Mendelian inheritance in man, catalog no. 269700) is a rare autosomal recessive syndrome characterized by paucity of body fat since birth and insulin resistance. The pathophysiology of this condition is unclear, but defects in insulin function and impaired adipogenesis have been described as important factors in the etiology of the disease. Recently, two gene loci have been identified to harbor the mutations causing this disorder: BSCL1 mapped to human chromosome 9q34 (1, 2) and BSCL2 mapped to human chromosome 11q13 (1, 3). This report describes the natural history of the disease in two siblings (female and male) of Lebanese origin who have mutations in the BSCL2 locus (669delGTATC).

Proteinuric nephropathy in acquired and congenital generalized lipodystrophy: baseline characteristics and course during recombinant leptin therapy

Generalized lipodystrophy is characterized by adipose tissue absence, hypoleptinemia, hypertriglyceridemia, insulin resistance, diabetes, hepatomegaly, and nonalcoholic steatohepatitis. In the course of recruiting patients for treatment with recombinant leptin, we were struck by the frequency and severity of proteinuria. We evaluated 25 patients with generalized lipodystrophy. Eighteen were treated with recombinant leptin, and we have followed 15 on leptin for 4-36 months. We followed renal parameters at baseline and during follow-up visits. Renal biopsies were performed as clinically indicated. At baseline, 22 of 25 patients (88%) had elevated urine albumin excretion (>30 mg/24 h), 15 (60%) had macroalbuminuria (>300 mg/24 h), and five (20%) had nephrotic-range proteinuria (>3500 mg/24 h). Twenty-three (92%) had elevated creatinine clearance (>125 ml/min.1.73 m(2)). Eleven of 15 patients (73%) treated with recombinant leptin exhibited reduction in proteinuria, associated with reduction of hyperfiltration. Four patients who did not improve are discussed individually. Renal biopsy findings were remarkable for focal segmental glomerulosclerosis in four patients, membranoproliferative glomerulonephritis in two patients, and diabetic nephropathy in one patient. In conclusion, generalized lipodystrophy is associated with proteinuria and unique renal pathologies, including focal segmental glomerulosclerosis and membranoproliferative glomerulonephritis. The majority treated with recombinant leptin demonstrated reduction in proteinuria and hyperfiltration.

Mutations in Gng3lg and AGPAT2 in Berardinelli-Seip congenital lipodystrophy and Brunzell syndrome: phenotype variability suggests important modifier effects

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder caused by mutations in AGPAT2 and Gng3lg. We screened for mutations in AGPAT2 and Gng3lg in 26 families with CGL and one family with Brunzell syndrome. We found mutations in either AGPAT2 or Gng3lg in all but four probands, including three novel mutations in AGPAT2, A712T (Lys215X), IVS3-1G-->C, and C636A (Phe189X). In three siblings with Brunzell syndrome, we identified a splice site mutation (IVS4-2A-->G) in AGPAT2, showing that AGPAT2 mutations can also cause Brunzell syndrome. Eighteen CGL patients from 15 families from the same region of northeastern Brazil were homozygous for a frameshift mutation (669insA of AF05149) in Gng3lg. Despite having the same mutation, the subjects had widely divergent clinical manifestations. In our subjects, there did not appear to be any distinguishing clinical characteristics between CGL subjects with AGPAT2 or Gng3lg mutations with the exception of mental retardation in carriers of Gng3lg. In summary, mutations in AGPAT2 and Gng3lg are approximately equally represented in CGL; despite harboring the same Gng3lg mutation, subjects may have widely divergent clinical manifestations, suggesting modifying influences of other genes and/or environment; and Brunzell syndrome may be caused by a mutation in AGPAT2.

Gene and phenotype analysis of congenital generalized lipodystrophy in Japanese: a novel homozygous nonsense mutation in seipin gene

Congenital generalized lipodystrophy (CGL), Berardinelli-Seip syndrome, is a rare metabolic disorder characterized by a near total lack of adipose tissue from birth or early infancy. Recently, seipin, encoding a 398-amino acid protein of unknown function, and AGPAT2, encoding 1-acyl-sn-glycerol-3-phosphate acyltransferase 2, were identified as causative genes for CGL. Seipin mutations were found in patients from families originating from Europe and the Middle East. AGPAT2 mutations were found predominantly in African ancestry. However, no information is available on these genes in the pathogenesis of CGL in Asian ancestry. We examined the sequences of the entire coding region of seipin and AGPAT2 in four Japanese CGL patients from independent families. Their average body fat content was 4.7 +/- 0.5%, and the plasma leptin level was 1.15 +/- 0.14 ng/ml. We identified a novel nonsense mutation of seipin at codon 275 (R275X). Of four CGL patients, three were homozygous for R275X. No seipin mutation was found in any exon in one patient. We did not find any AGPAT2 mutations in our Japanese patients, suggesting that AGPAT2 is a minor causative gene, if any, for CGL in Japanese. This is the first report on gene and phenotype analysis of CGL in Japanese.

Genetic basis of congenital generalized lipodystrophy

Congenital generalized lipodystrophy (CGL) is an autosomal recessive disorder characterized by extreme lack of body fat and severe insulin resistance since birth. Recently, mutations have been reported in 1-acylglycerol-3-phosphate-O-acyltransferase 2 (AGPAT2) and Berardinelli-Seip congenital lipodystrophy 2 (BSCL2 or Seipin) genes in affected subjects from pedigrees linked to chromosomes 9q34 and 11q13, respectively. The AGPAT2 catalyses the acylation of the lysophosphatidic acid at the sn-2 position to form phosphatidic acid, a key intermediate in the biosynthesis of triacylglycerol and glycerophospholipids. High expression of AGPAT2 mRNA in adipose tissue compared to other isoforms suggests that the mutations might affect the adipose tissue the most. The function of BSCL2 remains unknown. Several CGL pedigrees reveal no mutation in either of the above genes and are not linked to these loci, suggesting additional genetic loci for CGL. Thus, several distinct mechanisms can lead to extreme lack of adipose tissue in humans and cause CGL.

Mutations in the seipin and AGPAT2 genes clustering in consanguineous families with Berardinelli-Seip congenital lipodystrophy from two separate geographical regions of Brazil

Berardinelli-Seip congenital lipodystrophy (BSCL) is characterized by a near total congenital absence of fat and predisposition to develop diabetes mellitus. In this study, we investigated the presence of mutations in the Seipin and 1-acylglycerol phosphate acyltransferase 2 (AGPAT2) genes in 32 affected subjects with BSCL from 17 consanguineous pedigrees living in two separate geographical regions, the northeastern and southeastern regions, of Brazil. All, except one, of the 22 BSCL subjects from 15 families living in the northeastern region were found to have a homozygous 669insA mutation in the Seipin gene. In contrast, all 10 BSCL subjects from two families living in the southeastern region were found to a have a homozygous 1036-bp deletion including exons 3 and 4 of AGPAT2. These results support genetic heterogeneity among BSCL patients in Brazil. Our finding of a single mutation in the Seipin and AGPAT2 genes in the pedigrees from the northeastern and southeastern regions, respectively, will be useful in genetic counseling of subjects from these large pedigrees from Brazil.

Phenotypic heterogeneity in body fat distribution in patients with congenital generalized lipodystrophy caused by mutations in the AGPAT2 or seipin genes

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive syndrome characterized by extreme paucity of adipose tissue since birth, acanthosis nigricans, severe insulin resistance, marked hypertriglyceridemia, and early-onset diabetes mellitus. Recently, we reported mutations in the 1-acylglycerol-3-phosphate O-acyltransferase 2 (AGPAT2) gene in CGL pedigrees linked to chromosome 9q34 (CGL1 subtype), and mutations in the Seipin gene were reported in pedigrees linked to chromosome 11q13 (CGL2 subtype). Whether the two subtypes have differences in body fat distribution has not been investigated. We, therefore, compared whole-body adipose tissue distribution by magnetic resonance imaging in 10 CGL patients, of whom seven (six females, one male) had CGL1 and three (two males, one female) had CGL2. Both subtypes had marked lack of metabolically active adipose tissue located at most sc, intermuscular, bone marrow, intraabdominal, and intrathoracic regions. Paucity of mechanical adipose tissue in the palms, soles, orbits, scalp, and periarticular regions was noted in CGL2, whereas it was well preserved in CGL1 patients. We conclude that CGL patients with Seipin mutations have a more severe lack of body fat, which affects both metabolically active and mechanical adipose tissue, compared with patients with mutations in the AGPAT2 gene.

Phenotypic and genetic heterogeneity in congenital generalized lipodystrophy

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder characterized by near complete absence of adipose tissue from birth. Recently, mutations in 1-acylglycerol-3-phosphate O-acyltransferase 2 (AGPAT2) and Berardinelli-Seip congenital lipodystrophy 2 (BSCL2) genes were reported in pedigrees linked to chromosomes 9q34 and 11q13, respectively. There are limited data regarding phenotypic differences between the various subtypes of CGL. Furthermore, whether there are additional loci for CGL remains unknown. Therefore, we genotyped 45 pedigrees with CGL for AGPAT2 and BSCL2 loci and compared the phenotypes in the various subtypes. Twenty-six pedigrees harbored mutations, including seven novel variants, in the AGPAT2 gene, and 11 pedigrees harbored mutations in the BSCL2 gene, including five novel variants. Eight pedigrees had no substantial alterations in either gene. Of these, three informative pedigrees showed no linkage to markers spanning the AGPAT2 and BSCL2 loci, and in six of the affected subjects, the transcripts of AGPAT2 and BSCL2 were normal. All subtypes of CGL showed high prevalence of diabetes, hypertriglyceridemia, and acanthosis nigricans. However, patients with BSCL2 mutations had lower serum leptin levels, an earlier onset of diabetes, and higher prevalence of mild mental retardation compared with other subtypes. We conclude that besides AGPAT2 and BSCL2, there may be additional loci for CGL. The genetic heterogeneity in CGL patients is accompanied by phenotypic heterogeneity.

Congenital generalized lipodystrophy, mental retardation, deafness, short stature, and slender bones: a newly recognized syndrome?

We present three patients with congenital generalized lipodystrophy, sensorineural deafness, low birth weight, short stature, delayed cognitive development, and progressive bone changes characterized by overtubulation and rarefaction of long bones with dense metaphyseal striations occurring in adolescence. Abnormalities of lipid and carbohydrate metabolism, hepatosplenomegaly, acanthosis nigricans, and hirsutism were not found. Comparison of the condition of these patients with known syndromic lipodystrophies suggests that they represent a previously unrecognized genetic disorder. The occurrence in sibs born to consanguineous parents and a third patient from the same tribal unit suggest autosomal recessive inheritance.

Localization, cDNA sequence and genomic organization of the rat seipin gene (Bscl2) and sequence analysis in inbred rat models of Type 2 diabetes mellitus

Mutations in the gene encoding seipin cause Berardinelli-Seip congenital lipodystrophy 2, with symptoms including near-absence of adipose tissue and altered glucose tolerance. Radiation hybrid analysis localized the seipin gene (Bscl2) in rat to a major quantitative trait locus in rat chromosome 1 linked to glucose intolerance in the Goto-Kakizaki (GK) rat model of Type 2 diabetes. We determined the genomic organization of Bscl2 and screened coding exons and flanking intron sequences for mutations in GK, Wistar and Brown Norway rats, as well as in the Otsuka Long-Evans Tokushima Fatty (OLETF) diabetic rat. Two silent single nucleotide polymorphisms that were identified also were found in non-diabetic rat strains. We conclude that mutations in the gene for seipin are unlikely to contribute to diabetes in GK and OLETF rats.

Genotype-phenotype relationships in Berardinelli-Seip congenital lipodystrophy

Generalised lipodystrophy of the Berardinelli-Seip type (BSCL) is a rare autosomal recessive human disorder with severe adverse metabolic consequences. A gene on chromosome 9 (BSCL1) has recently been identified, predominantly in African-American families. More recently, mutations in a previously undescribed gene of unknown function (BSCL2) on chromosome 11, termed seipin, have been found to be responsible for this disorder in a number of European and Middle Eastern families. We have studied the genotype/phenotype relationships in 70 affected subjects from 44 apparently unrelated pedigrees of diverse ethnic origin. In all subjects, hepatic dysfunction, hyperlipidaemia, diabetes mellitus, and hypertrophic cardiomyopathy were significant contributors to morbidity with no clear differences in their prevalence between subjects with BSCL1 or BSCL2 and those with evidence against cosegregation with either chromosome 9 or 11 (designated BSCLX). BSCL2 appears to be a more severe disorder than BSCL1 with a higher incidence of premature death and a lower prevalence of partial and/or delayed onset of lipodystrophy. Notably, subjects with BSCL2 had a significantly higher prevalence of intellectual impairment than those with BSCL1 or BSCLX (p<0.0001, OR 17.0, CI 3.6 to 79.0). The higher prevalence of intellectual impairment and the increased risk of premature death in BSCL2 compared to BSCL1 emphasise the importance of molecular diagnosis of this syndrome and have clear implications for genetic counselling.

Heterogeneity for congenital generalized lipodystrophy in seventeen patients from Oman

Seventeen children with congenital generalized lipodystrophy or Berardinelli-Seip Congenital Lipodystrophy (BSCL) from 12 consanguineous sibships were observed in Oman. All children had widespread absence of adipose tissue from infancy together with apparent muscle hypertrophy and hepatomegaly. They did not appear to represent a single homogenous entity, and it was possible to subclassify the cases into two distinct groups. In the first group of seven cases, the features were similar to other published cases with acanthosis nigricans, raised insulin levels, and insulin resistance. In this group, there was an association between the degree of acanthosis nigricans and the severity of the disorder. Molecular analysis of these cases showed homozygosity at the BSCL2 locus on chromosome 11q13 in four of the seven cases. In the second group of ten cases, there were striking abnormalities in both skeletal and nonskeletal muscle. Reduced exercise tolerance and percussion myoxedema were observed in skeletal muscle, while infantile hypertrophic pyloric stenosis, prominent veins (phlebomegaly), disturbance of cardiac rhythm, and cardiomyopathy were observed in nonskeletal muscle. There was evidence against homozygosity in some cases for the known loci for BSCL, and this group may represent a new clinical syndrome with lipodystrophy at a different genetic location.

Induction of adipocyte differentiation by a thiazolidinedione in cultured, subepidermal, fibroblast-like cells of an infant with congenital generalized lipodystrophy

Congenital generalized lipodystrophy (CGL) is characterized by the absence of adipose tissue from birth due to a hypothetical differentiation block. The genetic causes of CGL are still not completely understood. Subepidermal, fibroblast-like cells were prepared from the sc tissue of an infant with CGL. Preadipocytes from sc adipose tissue and foreskin fibroblasts from three healthy patients, respectively, were used as controls. Adipose differentiation was induced in cultured cells by exposure to 10 nM insulin, 200 pM T(3), 1 microM cortisol, and 2 microM rosiglitazone. Under these conditions 42% of the subepidermal, fibroblast-like CGL cells developed into mature adipocytes. Adipogenic differentiation was dependent on rosiglitazone. The differentiation rate was comparable in cultures of preadipocytes from control patients maintained under the same conditions (53%, 38%, and 20%). In contrast, foreskin fibroblasts did not differentiate into adipocytes. Morphological changes in CGL cells during differentiation were associated with the expression of fat cell-specific mRNAs (PPARgamma, leptin, and glut-4). In addition, these cells revealed characteristic features of mature adipocytes, such as lipogenesis or leptin secretion. Taken together, we show that adipocyte precursor cells were present in subepidermal tissue of a patient with CGL and were able to differentiate into adipocytes in the presence of a thiazolidinedione. These findings strongly support clinical trials with thiazolidinediones in patients with CGL.

AGPAT2 is mutated in congenital generalized lipodystrophy linked to chromosome 9q34

Congenital generalized lipodystrophy is an autosomal recessive disorder characterized by marked paucity of adipose tissue, extreme insulin resistance, hypertriglyceridemia, hepatic steatosis and early onset of diabetes. We report several different mutations of the gene (AGPAT2) encoding 1-acylglycerol-3-phosphate O-acyltransferase 2 in 20 affected individuals from 11 pedigrees of diverse ethnicities showing linkage to chromosome 9q34. The AGPAT2 enzyme catalyzes the acylation of lysophosphatidic acid to form phosphatidic acid, a key intermediate in the biosynthesis of triacylglycerol and glycerophospholipids. AGPAT2 mRNA is highly expressed in adipose tissue. We conclude that mutations in AGPAT2 may cause congenital generalized lipodystrophy by inhibiting triacylglycerol synthesis and storage in adipocytes.

Molecular analysis of Berardinelli-Seip congenital lipodystrophy in Oman: evidence for multiple loci

Congenital generalized lipodystrophy (CGL) is a rare disorder characterized by the absence of body fat and insulin resistance and accompanied by other features, including acanthosis nigricans, organomegaly, hyperandrogenism, and diabetes. We have examined case subjects from 11 families in Oman with CGL. All subjects were the progeny of consanguineous marriages; therefore, a homozygosity mapping strategy was used to investigate the reported loci, 11q13 and 9q34. Three subjects could be linked to 11q13, and mutations were found within the seipin gene. An additional eight subjects were linked to 9q34, but the locus was in a 9-cM interval with no known microsatellites, so further fine mapping was not possible. However, two sibships (four subjects) did not map to either locus, raising the possibility of more than two lipodystrophy loci within the Oman population.

Triglyceride-induced diabetes mellitus in congenital generalized lipodystrophy

High levels of triglycerides and free fatty acids have been implicated in the pathogenesis of type 2 diabetes mellitus (DM). Congenital generalized lipodystrophy (CGL) is an autosomal recessive syndrome characterized by intense whole body reduction of subcutaneous fat. Its clinical manifestations appear during the first years of life. However, DM is usually a late event. We report a patient with CGL, diagnosed at 4 months of age, who has severe hypertriglyceridemia (serum triglyceride 12.34 mmol/l and cholesterol 3.90 mmol/l), muscular hypertrophy, hepatomegaly and DM (fasting glycemia 25.9 mmol/l). Hepatic biopsy revealed steatosis and fibrosis. A modified normolipidic (composed of medium chain triglycerides) normocaloric normoproteic milky diet and insulin therapy were instituted. After 1 month treatment a reduction of serum glucose and triglyceride levels (4.13 mmol/I and 7.7 mmol/l, respectively) was noted, with later normalization, which led to the discontinuation of insulin therapy. The patient has been maintaining good control with diet alone, presenting normal serum lipid levels (triglycerides 1.07 mmol/l, total cholesterol 2.71 mmol/l) and the following glycemic profile at OGTT: 0' 4.4 mmol/l; 30' 7.0 mmol/l; 60' 3.8 mmol/l; 90' 5.3 mmol/l, and 120' 5.2 mmol/l. The disappearance of hepatic steatosis was evidenced by a biopsy obtained 1 year after the beginning of treatment. In conolusion, this report suggests that the DM occurring in CGL can be precipitated by high triglyceride levels.

Cardiomyopathy in congenital complete lipodystrophy

Molecular genetic studies have pointed to a relationship between congenital lipodystrophy syndromes and some cardiac disorders. For instance, mutations in LMNA cause either lipodystrophy or cardiomyopathy, indicating that different mutations in the same gene can produce these clinical syndromes. The present authors describe a 10-year-old female with Berardinelli-Seip congenital complete lipodystrophy (MIM 606158) caused by homozygosity for a frameshift mutation in BSCL2. In addition to the typical attributes of complete lipodystrophy, this subject had hypertrophic cardiomyopathy diagnosed in the first year of her life; its progress has been followed with non-invasive imaging. The mechanism underlying the hypertrophic cardiomyopathy in complete lipodystrophy is unclear. It may result from a direct effect of the mutant gene or it might be secondary to the effects of hyperinsulinemia on cardiac development. The variability of the associated cardiomyopathy in patients with complete generalized lipodystrophy may be caused by differential effects of mutations in the same gene or of mutations in different genes which underlie the lipodystrophy phenotype.

Leptin-replacement therapy for lipodystrophy

BACKGROUND

The adipocyte hormone leptin is important in regulating energy homeostasis. Since severe lipodystrophy is associated with leptin deficiency, insulin resistance, hypertriglyceridemia, and hepatic steatosis, we assessed whether leptin replacement would ameliorate this condition.

METHODS

Nine female patients (age range, 15 to 42 years; eight with diabetes mellitus) who had lipodystrophy and serum leptin levels of less than 4 ng per milliliter (0.32 nmol per milliliter) received recombinant methionyl human leptin (recombinant leptin). Recombinant leptin was administered subcutaneously twice a day for four months at escalating doses to achieve low, intermediate, and high physiologic replacement levels of leptin.

RESULTS

During treatment with recombinant leptin, the serum leptin level increased from a mean (+/- SE) of 1.3 +/- 0.3 ng per milliliter to 11.1 +/- 2.5 ng per milliliter (0.1 +/- 0.02 to 0.9 +/- 0.2 nmol per milliliter). The absolute decrease in the glycosylated hemoglobin value was 1.9 percent (95 percent confidence interval, 1.1 to 2.7 percent; P=0.001) in the eight patients with diabetes. Four months of therapy decreased average triglyceride levels by 60 percent (95 percent confidence interval, 43 to 77 percent; P<0.001) and liver volume by an average of 28 percent (95 percent confidence interval, 20 to 36 percent; P=0.002) in all nine patients and led to the discontinuation of or a large reduction in antidiabetes therapy. Self-reported daily caloric intake and the measured resting metabolic rate also decreased significantly with therapy. Overall, recombinant leptin therapy was well tolerated.

CONCLUSIONS

Leptin-replacement therapy improved glycemic control and decreased triglyceride levels in patients with lipodystrophy and leptin deficiency. Leptin deficiency contributes to the insulin resistance and other metabolic abnormalities associated with severe lipodystrophy.

Congenital generalized lipodystrophy in a 4-month-old infant

Congenital generalized lipodystrophy (CGL, Berardinelli-Seip syndrome) is a rare autosomal recessive disorder with a clinical presentation of paucity of adipose tissue, muscular hypertrophy, organomegaly, and insulin-resistant diabetes. A 4-month-old Taiwanese female infant had hepatosplenomegaly and low body weight gain despite a voracious appetite. Hypermetabolism, hyperhidrosis, loss of subcutaneous fat, muscular hypertrophy, acanthosis nigricans, hypertrichosis, and marked hypertriglyceridemia were also noted. Liver histology revealed fatty change and portal-to-portal bridging fibrosis. Clinical features, serum biochemistry, and liver histology were compatible with the diagnosis of CGL. She was given a special diet characterized by calorie restriction and partial substitution of long-chain triglycerides with medium-chain triglycerides. The serum triglyceride concentration subsequently decreased. This present case suggests that extensive fatty infiltration and subsequent cirrhosis of the liver may be the earliest complication of CGL.

Identification of the gene altered in Berardinelli-Seip congenital lipodystrophy on chromosome 11q13

Congenital generalized lipodystrophy, or Berardinelli-Seip syndrome (BSCL), is a rare autosomal recessive disease characterized by a near-absence of adipose tissue from birth or early infancy and severe insulin resistance. Other clinical and biological features include acanthosis nigricans, hyperandrogenism, muscular hypertrophy, hepatomegaly, altered glucose tolerance or diabetes mellitus, and hypertriglyceridemia. A locus (BSCL1) has been mapped to 9q34 with evidence of heterogeneity. Here, we report a genome screen of nine BSCL families from two geographical clusters (in Lebanon and Norway). We identified a new disease locus, designated BSCL2, within the 2.5-Mb interval flanked by markers D11S4076 and D11S480 on chromosome 11q13. Analysis of 20 additional families of various ethnic origins led to the identification of 11 families in which the disease cosegregates with the 11q13 locus; the remaining families provide confirmation of linkage to 9q34. Sequence analysis of genes located in the 11q13 interval disclosed mutations in a gene homologous to the murine guanine nucleotide-binding protein (G protein), gamma3-linked gene (Gng3lg) in all BSCL2-linked families. BSCL2 is most highly expressed in brain and testis and encodes a protein (which we have called seipin) of unknown function. Most of the variants are null mutations and probably result in a severe disruption of the protein. These findings are of general importance for understanding the molecular mechanisms underlying regulation of body fat distribution and insulin resistance.

Lipodystrophy

Congenital lipodystrophy is an uncommon autosomal recessive disorder that occurs mainly in females and is characterized by loss of subcutaneous fat, insulin-dependent diabetes mellitus, and masculinization due to defective metabolism of fat. Acquired lipodystrophy is now most commonly encountered in patients infected with HIV who take protease inhibitors. We present an illustrative case of lipodystrophy and review the presenting signs allowing for an accurate clinical diagnosis.

Leptin reverses insulin resistance and diabetes mellitus in mice with congenital lipodystrophy

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder characterized by a paucity of adipose (fat) tissue which is evident at birth and is accompanied by a severe resistance to insulin, leading to hyperinsulinaemia, hyperglycaemia and enlarged fatty liver. We have developed a mouse model that mimics these features of CGL: the syndrome occurs in transgenic mice expressing a truncated version of a nuclear protein known as nSREBP-1c (for sterol-regulatory-element-binding protein-1c) under the control of the adipose-specific aP2 enhancer. Adipose tissue from these mice was markedly deficient in messenger RNAs encoding several fat-specific proteins, including leptin, a fat-derived hormone that regulates food intake and energy metabolism. Here we show that insulin resistance in our lipodystrophic mice can be overcome by a continuous systemic infusion of low doses of recombinant leptin, an effect that is not mimicked by chronic food restriction. Our results support the idea that leptin modulates insulin sensitivity and glucose disposal independently of its effect on food intake, and that leptin deficiency accounts for the insulin resistance found in CGL.

A gene for congenital generalized lipodystrophy maps to human chromosome 9q34

Congenital generalized lipodystrophy (CGL, Berardinelli-Seip Syndrome, OMIM # 269700) is a rare autosomal recessive disorder characterized by near complete absence of adipose tissue from birth. Affected individuals have marked insulin resistance, hypertriglyceridemia and acanthosis nigricans, and develop diabetes mellitus during teenage years. The genetic defect for CGL is unknown. A semi-automated genome-wide scan with a set of highly polymorphic short tandem repeats (STR) was carried out in 17 well-characterized pedigrees and identified a locus for CGL to chromosome 9q34. The maximum two-point lod score obtained was 3.6 at D9S1818 (theta(max) = 0.05). There was evidence for genetic heterogeneity (alpha = 0.73) and 2 of the pedigrees were unlinked. Multipoint linkage analysis excluding the 2 unlinked families yielded a peak lod score of 5.4 between loci D9S1818 and D9S1826. The CGL1 critical region harbors a plausible candidate gene encoding the retinoid X receptor alpha (RXRA) that plays a central role in adipocyte differentiation. Identification of the CGL gene(s) will contribute to our understanding of the adipocyte differentiation and elucidation of the mechanisms of insulin resistance in disorders of adipose tissue.

Newborn radial nerve palsy: report of four cases and review of published reports

Four newborns presented with isolated radial nerve palsy during the first 2 days of life. In three, there was a history of failure of progression of labor, which may have resulted in prolonged radial nerve compression. Furthermore, three infants had fat necrosis of the upper arm above the elbow, suggestive of compression of the radial nerve in the region of the spiral groove. Significant recovery of function was evident within 1 month in all four infants. The authors review published reports about the rare condition of isolated radial nerve palsy in the newborn.

The IGF-I/IGFBP system in congenital partial lipodystrophy

BACKGROUND AND OBJECTIVES

Insulin and IGF-I interact at many levels. Little is known about the insulin-like growth factor-I/insulin-like growth factor binding proteins (IGF-I/IGFBP) system in congenital partial lipodystrophy, a syndrome characterized by insulin resistance, hyperinsulinaemia and absence of truncal and limb fat. Some cases have acromegaloid features with thick skin and large hands and feet in association with normal levels of circulating growth hormone.

METHODS

In four females known with congenital partial lipodystrophy, hyperinsulinaemia with acromegaloid features, the number and affinity of the IGF-I receptors on peripheral blood mononuclear cells (PBMCs), and the concentration of circulating insulin, total and free IGF-I, IGFBP-1 and IGFBP-3 levels were measured in the fasting and the fed state. Cultures of PBMCs of the patients with lipodystrophy were also used to study the effect of IGF-I stimulation on thymidine uptake in vitro.

MEASUREMENTS

In the subjects with lipodystrophy the affinity and the number of the IGF-I receptors on peripheral mononuclear cells (PBMCs) and erythrocytes did not differ significantly from controls in the fasting state. Insulin levels were significantly higher in subjects with lipodystrophy both in the fasting as well in the fed state. Total IGF-I, free IGF-I and IGFBP-3 levels did not differ but serum IGFBP-1 levels were lower in lipodystrophy subjects than in healthy controls. The free IGF-I/IGFBP-1 ratio was increased in lipodystrophy subjects both in the fasting and the fed states. The effects of IGF-I stimulation on thymidine uptake by PBMCs of lipodystrophy subjects in the absence of IGFBP-1 were not different from healthy controls cultures in vitro. When a combination of IGFBP-1 (in a concentration comparable to the fasting serum IGFBP-1 levels in lipodystrophy patients found in our study) and IGF-I was added to PBMC cultures from lipodystrophy patients no decrease in thymidine uptake by PBMCs was found.

CONCLUSIONS

In the four subjects with lipodystrophy hyperinsulinaemia, lowered free IGF-I and IGFBP-1 levels, but increased free IGF-I/IGBP-1 ratios were observed. Low IGFBP-1 concentrations in culture media did not reduce the stimulating IGF-I effect on thymidine uptake by PBMCs from lipodystrophy patients. Our data suggest that the observed increased IGF-I/IGFBP-1 ratio in lipodystrophy patients contributes to an unopposed biological effect of IGF-I on IGF-I receptors, thereby inducing the development of acromegaloid features, acanthosis nigricans and polycystic ovaries in some patients with congenital partial lipodystrophy.

Uncommon allele in apo AI-CIII-AIV gene cluster in a family with congenital generalized lipodystrophy

Congenital generalized lipodystrophy is a rare inherited disease. One of its features is a disturbance in lipid metabolism characterized by hypercholesterolemia and hypertriglyceridemia. A brother and a sister with congenital generalized lipodystrophy, an 8-year old male and a 12-year old female were studied. The mother and a 6-year old brother were healthy. The genetic analysis of Sstl RFLP of the apo AI-CIII-AIV gene cluster showed the presence of the rare Sstl allele (S2) in the patients but not in the healthy mother and brother. As this uncommon allele has been reported to be related to high plasma triglyceride levels, this association could be relevant in explaining in part the hypertriglyceridemia observed in these patients.

Congenital total lipodystrophy and peripheral pulmonary artery stenosis

Multiple peripheral pulmonary artery stenoses were detected in three patients with congenital generalised lipodystrophy. This association, which has not been described before, may be clinically important in patients with lipodystrophy who present with impaired exercise tolerance or heart murmurs.

Genetics of the Berardinelli-Seip syndrome (congenital generalized lipodystrophy) in Norway: epidemiology and gene mapping. Berardinelli-Seip Study Group

Five of the six families with the Berardinelli-Seip syndrome in Norway cluster in six adjacent rural municipalities of south-western Norway. The six patients from this area were born between 1951 and 1973, none between 1974 and 1995. The absence of new cases may be explained by a decrease in the intraregion marriage rate and inbreeding. Genealogical investigations show that the mutation must have occurred at least 400 years ago. The sixth family was clinically different and geographically sporadic from a Finnish-descent rural East Norwegian population. A genetic linkage study of all six families revealed fresh crossovers versus the disease allele in nine DNA marker systems and the absence of recombination in three (maximum lod score + 1.3). None of the last showed allelic association. These families are included in an international effort to map the CLBS locus. The patients have been included in the homozygosity testing of totally 28 patients in an international collaborative study. The three patients, assumed identical in descent from both parents, were jointly homozygous in none of the 250 dinucleotide markers tested. A heterochromatic 9qh + segregated from one parent in two families.

Studies of insulin resistance in congenital generalized lipodystrophy

Two well-characterized patients with congenital, generalized lipodystrophy have been studied by the euglycaemic hyperinsulinaemic clamp technique in combination with indirect calorimetry. Furthermore, glycogen synthase in muscle biopsies was studied in one patient with regard to enzyme activity, immunoreactive protein and mRNA levels. The patients had fasting hyperinsulinaemia, and the rate of total glucose disposal was severely impaired, primarily due to a decreased non-oxidative glucose metabolism. In the patient studied with muscle biopsy, the expected activation of glycogen synthase by insulin did not occur. In both patients there was severely increased hepatic glucose output in the basal state, suggesting a failure of insulin to suppress hepatic gluconeogenesis. During insulin infusion a substantially elevated rate of lipid oxidation remained in the patients, in contrast to the almost completely suppressed lipid oxidation in the controls. It is concluded that patients with congenital generalized lipodystrophy may present severe insulin resistance with regard to hepatic glucose production as well as muscle glycogen synthesis and lipid oxidation. The results suggest a postreceptor defect in the action of insulin in congenital generalized lipodystrophy. The further localization of such a defect is hampered by the still incomplete understanding of the pathways that link insulin-stimulated tyrosine phosphorylation to the ultimate action of insulin upon target cells.

Radiological features in generalized lipodystrophy

Seven patients with congenital generalized lipodystrophy and one patient with acquired generalized lipodystrophy have been followed up for 38 years. Various radiological techniques have been used, and the major findings are summarized. All patients had an advanced skeletal age. A sclerotic skeleton was a major feature in childhood in the congenital form, later turning into osteolytic lesions or more distinct sclerotic patches in adolescence or early adulthood. In the acquired form the skeleton was slightly osteoporotic without cystic changes. Ultrasonography and computerized tomography examinations revealed hepatosplenomegaly with fatty infiltration in both types. Lack of subcutaneous and intraabdominal fat was easily confirmed with computerized tomography. Five patients with the congenital for underwent pneumoencephalography, which revealed dilated brain ventricles and basal cisterns. Cardiomegaly and large kidneys were also a major feature.

Generalized lipodystrophy, congenital and acquired (lipoatrophy)

This review is based on longitudinal studies on our seven patients with congenital generalized lipodystrophy, our patient with acquired generalized lipodystrophy, and published papers on these subjects. An inability to store energy in adipose tissue is of pathogenetic importance. In congenital lipodystrophy, insulin resistance is present from birth, resulting in hyperinsulinaemia, dyslipidaemia. and insulin-resistant diabetes with an anabolic syndrome worsened by a voracious appetite. Clinically, we observed increased height velocity in pre-school age children, and organomegaly with hypertrophic cardiomyopathy, which seems to be lethal in early adulthood: three of our patients died at the ages of 24, 32 and 37 years. The oldest alive, 39 years, suffers from stenocardia. Regarding treatment, it is most important to reduce energy consumption. The congenital form is recessively inherited. The aetiology may be related to insulin receptor or postreceptor mechanisms. Acquired generalized lipodystrophy seems to be an autoimmune disorder with secondary destruction of the adipose organ: the anabolic syndrome with insulin-resistant diabetes is secondary. Our patient died when 24 years old from pneumonia.