Cardiac findings in generalized lipodystrophy

Primary disease of adipose tissue: When to think about and how to evaluate it in clinical practice?

Primary diseases of adipose tissue are rare disorders resulting from impairments in the physiological functions of adipose tissue (lipid stockage and endocrine function). It mainly refers to lipodystrophy syndromes with subcutaneous adipose tissue atrophy and/or altered body distribution of adipose tissue leading to insulin resistance, diabetes, hepatic steatosis, dyslipidemia, cardiovascular complications and polycystic ovary syndrome in women. Those syndromes are congenital or acquired, and lipoatrophy is partial or generalized. The diagnosis of lipodystrophy syndromes is often unrecognized, delayed and/or inaccurate, while it is of major importance to adapt investigations to search for specific comorbidities, in particular cardiovascular involvement, and set up multidisciplinary care, and in some cases specific treatment. Physicians have to recognize the clinical and biological elements allowing to establish the diagnosis. Lipodystrophic syndromes should be considered, notably, in patients with diabetes at a young age, with a normal or low BMI, negative pancreatic autoantibodies, presenting clinical signs of lipodystrophy and insulin resistance (acanthosis nigricans, hyperandrogenism, hepatic steatosis, high insulin doses). The association of diabetes and a family history of severe and/or early cardiovascular disease (coronary atherosclerosis, cardiomyopathy with rhythm and/or conduction disorders) may reveal Dunnigan syndrome, the most frequent form of familial lipodystrophy, due to LMNA pathogenic variants. Clinical assessment is primarily done through clinical examination: acanthosis nigricans, abnormal adipose tissue distribution, lipoatrophy, muscular hypertrophy, acromegaloid or Cushingoid features, lipomas, highly visible subcutaneous veins, may be revealing signs. The amount of circulating adipokines may reflect of adipose dysfunction with low leptinemia and adiponectinemia. Other biological metabolic parameters (hypertriglyceridemia, hyperinsulinemia, increased glycemia and hepatic enzymes) may also represent markers of insulin resistance. Quantification of total body fat by impedancemetry or dual-photon X-ray absorptiometry (DEXA) reveals decreased total body mass, in correlation with adipose tissue atrophy; metabolic magnetic resonance imaging can also quantify intraperitoneal and abdominal fat and the degree of hepatic steatosis. Histological analysis of adipose tissue showing structural abnormalities should be reserved for clinical research. Acquired lipodystrophic syndromes most often lead to similar clinical phenotype as congenital syndromes with generalized or partial lipoatrophy. The most frequent causes are old anti-HIV therapy or glucocorticoid treatments. Family history, history of treatments and clinical examination, including a careful physical examination, are keys for diagnosis.

Role of Seipin in Human Diseases and Experimental Animal Models

Seipin, a protein encoded by the Berardinelli-Seip congenital lipodystrophy type 2 (BSCL2) gene, is famous for its key role in the biogenesis of lipid droplets and type 2 congenital generalised lipodystrophy (CGL2). BSCL2 gene mutations result in genetic diseases including CGL2, progressive encephalopathy with or without lipodystrophy (also called Celia’s encephalopathy), and BSCL2-associated motor neuron diseases. Abnormal expression of seipin has also been found in hepatic steatosis, neurodegenerative diseases, glioblastoma stroke, cardiac hypertrophy, and other diseases. In the current study, we comprehensively summarise phenotypes, underlying mechanisms, and treatment of human diseases caused by BSCL2 gene mutations, paralleled by animal studies including systemic or specific Bscl2 gene knockout, or Bscl2 gene overexpression. In various animal models representing diseases that are not related to Bscl2 mutations, differential expression patterns and functional roles of seipin are also described. Furthermore, we highlight the potential therapeutic approaches by targeting seipin or its upstream and downstream signalling pathways. Taken together, restoring adipose tissue function and targeting seipin-related pathways are effective strategies for CGL2 treatment. Meanwhile, seipin-related pathways are also considered to have potential therapeutic value in diseases that are not caused by BSCL2 gene mutations.

Adipose tissue distribution is associated with cardio-metabolic alterations in adult patients with juvenile-onset dermatomyositis

OBJECTIVES

Primary aims were to compare adipose tissue distribution in adult patients with juvenile-onset DM (JDM), with matched controls. Secondary aims were to explore how adipose tissue distribution is associated with cardio-metabolic status (cardiac dysfunction and metabolic syndrome) in patients.

METHODS

Thirty-nine JDM patients (all aged ≥18 y, mean age 31.7 y and 51% female) were examined mean 22.7 y (s.d. 8.9 y) after disease onset and compared with 39 age/sex-matched controls. In patients, disease activity and lipodystrophy were assessed by validated tools and use of prednisolone noted. In all participants, dual-energy X-ray absorptiometry (DXA) and echocardiography were used to measure visceral adipose tissue (VAT)(g) and cardiac function, respectively. Risk factors for metabolic syndrome were measured and associations with adipose tissue distribution explored. For primary and secondary aims, respectively, P-values ≤0.05 and ≤0.01 were considered significant.

RESULTS

Patients exhibited a 2.4-fold increase in VAT, and reduced HDL-cholesterol values compared with controls (P-values ≤ 0.05). Metabolic syndrome was found in 25.7% of the patients and none of the controls. Cardiac dysfunction (systolic and/or diastolic) was found in 23.7% of patients and 8.1% of controls (P = 0.07). In patients, VAT levels were correlated with age, disease duration and occurrence of metabolic syndrome and cardiac dysfunction. Occurrence of lipodystrophy (P = 0.02) and male sex (P = 0.04) tended to be independently associated with cardiac dysfunction.

CONCLUSION

Adults with JDM showed more central adiposity and cardio-metabolic alterations than controls. Further, VAT was found increased with disease duration, which was associated with development of cardio-metabolic syndrome.

BSCL2/Seipin deficiency in hearts causes cardiac energy deficit and dysfunction via inducing excessive lipid catabolism

BACKGROUND

Heart failure (HF) is one of the leading causes of death worldwide and is associated with cardiac metabolic perturbations. Human Type 2 Berardinelli-Seip Congenital Lipodystrophy (BSCL2) disease is caused by mutations in the BSCL2 gene. Global lipodystrophic Bscl2^-/- mice exhibit hypertrophic cardiomyopathy with reduced cardiac steatosis. Whether BSCL2 plays a direct role in regulating cardiac substrate metabolism and/or contractile function remains unknown.

METHODS

We generated mice with cardiomyocyte-specific deletion of Bscl2 (Bscl2^cKO ) and studied their cardiac substrate utilisation, bioenergetics, lipidomics and contractile function under baseline or after either a treatment regimen using fatty acid oxidation (FAO) inhibitor trimetazidine (TMZ) or a prevention regimen with high-fat diet (HFD) feeding. Mice with partial ATGL deletion and cardiac-specific deletion of Bscl2 were also generated followed by cardiac phenotyping.

RESULTS

Different from hypertrophic cardiomyopathy in Bscl2^-/- mice, mice with cardiac-specific deletion of Bscl2 developed systolic dysfunction with dilation. Myocardial BSCL2 deletion led to elevated ATGL expression and FAO along with reduced cardiac lipid contents. Cardiac dysfunction in Bscl2^cKO mice was independent of mitochondrial dysfunction and oxidative stress, but associated with decreased metabolic reserve and ATP levels. Importantly, cardiac dysfunction in Bscl2^cKO mice could be partially reversed by FAO inhibitor TMZ, or prevented by genetic abolishment of one ATGL allele or HFD feeding. Lipidomic analysis further identified markedly reduced glycerolipids, glycerophospholipids, NEFA and acylcarnitines in Bscl2^cKO hearts, which were partially normalised by TMZ or HFD.

CONCLUSIONS

We identified a new form of cardiac dysfunction with excessive lipid utilisation which ultimately causes cardiac substrate depletion and bioenergetics failure. Our findings also uncover a crucial role of BSCL2 in controlling cardiac lipid catabolism and contractile function and provide novel insights into metabolically treating energy-starved HF using FAO inhibitor or HFD.

Interconnection between Cardiac Cachexia and Heart Failure—Protective Role of Cardiac Obesity

Cachexia may be caused by congestive heart failure, and it is then called cardiac cachexia, which leads to increased morbidity and mortality. Cardiac cachexia also worsens skeletal muscle degradation. Cardiac cachexia is the loss of edema-free muscle mass with or without affecting fat tissue. It is mainly caused by a loss of balance between protein synthesis and degradation, or it may result from intestinal malabsorption. The loss of balance in protein synthesis and degradation may be the consequence of altered endocrine mediators such as insulin, insulin-like growth factor 1, leptin, ghrelin, melanocortin, growth hormone and neuropeptide Y. In contrast to many other health problems, fat accumulation in the heart is protective in this condition. Fat in the heart can be divided into epicardial, myocardial and cardiac steatosis. In this review, we describe and discuss these topics, pointing out the interconnection between heart failure and cardiac cachexia and the protective role of cardiac obesity. We also set the basis for possible screening methods that may allow for a timely diagnosis of cardiac cachexia, since there is still no cure for this condition. Several therapeutic procedures are discussed including exercise, nutritional proposals, myostatin antibodies, ghrelin, anabolic steroids, anti-inflammatory substances, beta-adrenergic agonists, medroxyprogesterone acetate, megestrol acetate, cannabinoids, statins, thalidomide, proteasome inhibitors and pentoxifylline. However, to this date, there is no cure for cachexia.

Leptin Attenuates Cardiac Hypertrophy in Patients With Generalized Lipodystrophy

CONTEXT

Lipodystrophy syndromes are rare disorders of deficient adipose tissue, low leptin, and severe metabolic disease, affecting all adipose depots (generalized lipodystrophy, GLD) or only some (partial lipodystrophy, PLD). Left ventricular (LV) hypertrophy is common (especially in GLD); mechanisms may include hyperglycemia, dyslipidemia, or hyperinsulinemia.

OBJECTIVE

Determine effects of recombinant leptin (metreleptin) on cardiac structure and function in lipodystrophy.

METHODS

Open-label treatment study of 38 subjects (18 GLD, 20 PLD) at the National Institutes of Health before and after 1 (N = 27), and 3 to 5 years (N = 23) of metreleptin. Outcomes were echocardiograms, blood pressure (BP), triglycerides, A1c, and homeostasis model assessment of insulin resistance.

RESULTS

In GLD, metreleptin lowered triglycerides (median [interquartile range] 740 [403-1239], 138 [88-196], 211 [136-558] mg/dL at baseline, 1 year, 3-5 years, P < .0001), A1c (9.5 ± 3.0, 6.5 ± 1.6, 6.5 ± 1.9%, P < .001), and HOMA-IR (34.1 [15.2-43.5], 8.7 [2.4-16.0], 8.9 [2.1-16.4], P < .001). Only HOMA-IR improved in PLD (P < .01). Systolic BP decreased in GLD but not PLD. Metreleptin improved cardiac parameters in patients with GLD, including reduced posterior wall thickness (9.8 ± 1.7, 9.1 ± 1.3, 8.3 ± 1.7 mm, P < .01), and LV mass (140.7 ± 45.9, 128.7 ± 37.9, 110.9 ± 29.1 g, P < .01), and increased septal e' velocity (8.6 ± 1.7, 10.0 ± 2.1, 10.7 ± 2.4 cm/s, P < .01). Changes remained significant after adjustment for BP. In GLD, multivariate models suggested that reduced posterior wall thickness and LV mass index correlated with reduced triglycerides and increased septal e' velocity correlated with reduced A1c. No changes in echocardiographic parameters were seen in PLD.

CONCLUSION

Metreleptin attenuated cardiac hypertrophy and improved septal e' velocity in GLD, which may be mediated by reduced lipotoxicity and glucose toxicity. The applicability of these findings to leptin-sufficient populations remains to be determined.

Right Heart Morphology and Its Association With Excessive and Deficient Cardiac Visceral Adipose Tissue

Visceral adipose tissue is an independent risk factor for the development of atherosclerotic coronary disease, arterial hypertension, diabetes and metabolic syndrome. Right heart morphology often involves the presence of adipose tissue, which can be quantified by non-invasive imaging methods. The last decade brought a wealth of new insights into the function and morphology of adipose tissue, with great emphasis on its role in the pathogenesis of heart disease. Cardiac adipose tissue is involved in thermogenesis, mechanical protection of the heart and energy storage. However, it can also be an endocrine organ that synthesises numerous pro-inflammatory and anti-inflammatory cytokines, the effect of which is accomplished by paracrine and vasocrine mechanisms. Visceral adipose tissue has several compartments that differ in their embryological origin and vascularisation. Deficiency of cardiac adipose tissue, often due to chronic pathological conditions such as oncological diseases or chronic infectious diseases, predicts increased mortality and morbidity. To date, knowledge about the influence of visceral adipose tissue on cardiac morphology is limited, especially the effect on the morphology of the right heart in a state of excess or deficient visceral adipose tissue.

Early Left Ventricular Systolic Dysfunction Detected by Two-Dimensional Speckle-Tracking Echocardiography in Young Patients with Congenital Generalized Lipodystrophy

PURPOSE

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder characterized by the absence of functional adipocytes resulting in ectopic lipid storage, metabolic disorders and early cardiovascular disease. Two-dimensional speckle-tracking (2D-STE) allows the detection of early abnormalities in myocardial function. We aimed to evaluate myocardial deformation in a large sample of CGL patients using 2D-STE.

PATIENTS AND METHODS

A cross-sectional study of 22 patients with CGL and 22 healthy subjects, matched for sex and age, was conducted from 2013 to 2018. All participants had undergone standard conventional echocardiography (ECHO) and 2D-STE. Determination of blood glucose, lipids, insulin, and leptin were performed in all CGL patients.

RESULTS

In the CGL group the mean age was 14.6±10.7 years where 68.2% (n=15) were younger than 18 years old. All the patients had hypoleptinemia, 95.4% (21/22) low HDL-c, 86.4% (19/22) hypertriglyceridemia, 68.2% (15/22) diabetes, 50% (11/22) hepatic steatosis, 41% (9/22) insulin resistance, 41% (9/22) hypercholesterolemia, and 18.2% (4/22) hypertension. ECHO showed that 36.6% (8/22) of CGL patients presented diastolic dysfunction, 31.8% (7/22) left ventricular hypertrophy (LVH), 27.3% (6/22) increased left atrial volume index (LAVI), and 18.2% (4/22) increased left ventricular systolic diameter (LVDS) but normal ejection fraction (EF), whether using 2D-STE, 68.2% (15/22) of CGL patients showed abnormal global longitudinal strain (GLS) (p<0.01), and in almost LV segments. Positive association between abnormal GLS and A1c (r=0.57, p=0.005), glucose (r=0.5, p=0.018) and basal insulin (r= 0.69, p= 0.024), and negative association with leptin (r = -0.51, p = 0.005) were found in these patients.

CONCLUSION

The 2D-STE revealed precocious left ventricular systolic dysfunction in a young CGL population with normal systolic function by ECHO. Early exposure to common metabolic abnormalities as insulin resistance, hyperglycemia, and hypoleptinemia must be involved in myocardial damage in these patients.

Targeting ATGL to rescue BSCL2 lipodystrophy and its associated cardiomyopathy

Mutations in BSCL2 gene underlie human type 2 Berardinelli-Seip Congenital Lipodystrophy (BSCL2) disease. Global Bscl2-/- mice recapitulate human BSCL2 lipodystrophy and develop insulin resistance and hypertrophic cardiomyopathy. The pathological mechanisms underlying the development of lipodystrophy and cardiomyopathy in BSCL2 are controversial. Here we report that Bscl2-/- mice develop cardiac hypertrophy due to increased basal IGF1 receptor (IGF1R)-mediated PI3K/AKT signaling. Bscl2-/- hearts exhibited increased adipose triglyceride lipase (ATGL) protein stability and expression causing drastic reduction of glycerolipids. Excessive fatty acid oxidation was overt in Bscl2-/- hearts, partially attributing to the hyperacetylation of cardiac mitochondrial proteins. Intriguingly, pharmacological inhibition or genetic inactivation of ATGL could rescue adipocyte differentiation and lipodystrophy in Bscl2-/- cells and mice. Restoring a small portion of fat mass by ATGL partial deletion in Bscl2-/- mice not only reversed the systemic insulin resistance, but also ameliorated cardiac protein hyperacetylation, normalized cardiac substrate metabolism and improved contractile function. Collectively, our study uncovers novel pathways underlying lipodystrophy-induced cardiac hypertrophy and metabolic remodeling and pinpoints ATGL as a downstream target of BSCL2 in regulating the development of lipodystrophy and its associated cardiomyopathy.

Diagnosis and treatment of lipodystrophy: a step-by-step approach

AIM

Lipodystrophy syndromes are rare heterogeneous disorders characterized by deficiency of adipose tissue, usually a decrease in leptin levels and, frequently, severe metabolic abnormalities including diabetes mellitus and dyslipidemia.

PURPOSE

To describe the clinical presentation of known types of lipodystrophy, and suggest specific steps to recognize, diagnose and treat lipodystrophy in the clinical setting.

METHODS

Based on literature and in our own experience, we propose a stepwise approach for diagnosis of the different subtypes of rare lipodystrophy syndromes, describing its more frequent co-morbidities and establishing the therapeutical approach.

RESULTS

Lipodystrophy is classified as genetic or acquired and by the distribution of fat loss, which can be generalized or partial. Genes associated with many congenital forms of lipodystrophy have been identified that may assist in diagnosis. Because of its rarity and heterogeneity, lipodystrophy may frequently be unrecognized or misdiagnosed, which is concerning because it is progressive and its complications are potentially life threatening. A basic diagnostic algorithm is proposed. Effective management of lipodystrophy includes lifestyle changes and aggressive, evidence-based treatment of comorbidities. Leptin replacement therapy (metreleptin) has been found to improve metabolic parameters in many patients with lipodystrophy. Metreleptin is approved in the United States as replacement therapy to treat the complications of leptin deficiency in patients with congenital or acquired generalized lipodystrophy and has been submitted for approval in Europe.

CONCLUSIONS

Here, we describe the clinical presentation of known types of lipodystrophy, present an algorithm for differential diagnosis of lipodystrophy, and suggest specific steps to recognize and diagnose lipodystrophy in the clinical setting.

Causes of death in patients with Berardinelli-Seip congenital generalized lipodystrophy

INTRODUCTION

Berardinelli-Seip Congenital Lipodystrophy (BSCL) is a rare autosomal recessive disease that affects the development of adipocytes and leads to an inability to store fat in adipocytes. This study aimed to evaluate the life expectancy and the causes of death of patients with BSCL.

METHOD

We analyzed death certificates, and medical records of BSCL patients who died between 1997 and 2017. If the death certificate was incomplete or unavailable, we reviewed the medical records, and if they were not available too, we collected information from the patient's relatives to understand how the death happened. We calculated the potential years of life lost as a result of premature death.

RESULTS

Twenty patients (12 female and 8 male) died between 1997 and 2017. The mean age at the time of death was 27.1±12.4 years (women 25.2±12.5 vs. men 29.9±12.6 years, p = 0.41). Life expectancy for the study population was 62.9±4.8 years. The potential number of years of life lost was 35.6±16.6 years. The causes of deaths were divided into three major groups: infections (7 patients, 35%), liver disease (7 patients, 35%), and other causes (acute pancreatitis, one patient; renal failure, three patients; sudden death/myocardial infarction, two patients). Three patients had pulmonary fibrosis.

CONCLUSION

BSCL led to premature death, cutting the patients' lifespan by 30 or more years. The majority of these young patients died of liver disease or infection. Other studies are needed to understand better the mechanisms that predispose to infections, as well as to assess whether new therapies can alter the natural history of this disease.

Cardiac Manifestations of Congenital Generalized Lipodystrophy

IN BRIEF Congenital lipodystrophy is a rare genetic disorder characterized by a near-complete absence of fat cells, hypoleptinemia leading to a voracious appetite, and marked insulin resistance. This article focuses on the known cardiovascular manifestations of patients with congenital lipodystrophy, including cardiomyopathy, cardiac arrhythmias, and accelerated atherosclerosis arising from a markedly deranged metabolic milieu. Future research that targets leptin deficiency (metreleptin) and apoC3 mRNA (antisense oligonucleotide) could open a window for potential pharmacological treatment of this challenging disorder.

Leptin in congenital and HIV-associated lipodystrophy

Leptin is a hormone secreted by adipocytes that regulates energy metabolism via peripheral action on glucose synthesis and utilization as well as through central regulation of food intake. Patients with decreased amounts of fat in their adipose tissue (lipoatrophy) will have low leptin levels, and hypoleptinemic states have been associated with a variety of metabolic dysfunctions. Pronounced complications of insulin resistance, dyslipidemia and fatty liver are observed in patients suffering from congenital or acquired generalized lipodystrophy while somewhat less pronounced abnormalities are associated with human immunodeficiency virus (HIV) and the use of highly active antiretroviral therapy, the so-called HIV-associated lipodystrophy. Previous uncontrolled open-label studies have demonstrated that physiological doses of leptin repletion have corrected many of the metabolic derangements observed in subjects with rare fat maldistribution syndromes such as generalized lipodystrophy. In the much more commonly encountered HIV-associated lipodystrophy, leptin replacement has been shown to decrease central fat mass and to improve insulin sensitivity, dyslipidemia, and glucose levels. The United States Food and Drug Administration has recently granted approval for recombinant leptin therapy for congenital and acquired generalized lipodystrophy, however large, well-designed, placebo-controlled studies are needed to assess long-term efficacy, safety and adverse effects of leptin replacement. In this review, we present the role of leptin in the metabolic complications of congenital and acquired lipodystrophy and discuss current and emerging clinical therapeutic uses of leptin in humans with lipodystrophy.

Berardinelli-Seip congenital lipodystrophy in two siblings

Berardinelli-Seip congenital lipodystrophy (BSCL) is a very rare autosomal recessive disorder characterized by various dermatological and systemic manifestations such as lipoatrophy, hypertriglyceridemia, hepatomegaly, acanthosis nigricans, and acromegaloid features. BSCL type 2 is more common and severe, with onset in the neonatal period or in early infancy. The locus for BSCL2 has been identified on chromosome 11q13. Early recognition and differentiation from other congenital generalized lipodystrophies help in the initiation of appropriate preventive and therapeutic measures such as lifestyle modification and pharmacotherapy that helps postpone the onset of metabolic syndrome. We report BSCL type 2 in two siblings with several cutaneous manifestations like acanthosis nigricans, hypertrichosis, prominent subcutaneous veins, and increased lanugo hair.

Early infantile cardiomyopathy and liver disease: a multisystemic disorder caused by congenital lipodystrophy

Congenital generalized lipodystrophy is a rare inherited multisystemic disorder associated with disturbances of adipocyte functions. We report a young boy presenting at age 1 month with liver disease and severe hypertrophic cardiomyopathy. Despite this multisystemic involvement and contrasting with a cachectic appearance, the anthropometric parameters showed marked overgrowth (+4 DS), leading to diagnosis of congenital lipodystrophy, which was confirmed by the presence of the new homozygous c.259C>T (p.Gln87*) mutation in the AGPAT2 gene. Early infantile cardiomyopathy should be considered as a specific endophenotype in Berardinelli-Seip Congenital Lipodystrophy syndrome.

Identification of a novel nonsense mutation and a missense substitution in the AGPAT2 gene causing congenital generalized lipodystrophy type 1

Congenital generalized lipodystrophy (CGL) is an autosomal recessive disease characterized by the generalized scant of adipose tissue. CGL type 1 is caused by mutations in gene encoding 1-acylglycerol-3-phosphate O-acyltransferase-2 (AGPAT2). A clinical and molecular genetic investigation was performed in affected and unaffected members of two families with CGL type 1. The AGPAT2 coding region was sequenced in index cases of the two families. The presence of the identified mutations in relevant parents was tested. We identified a novel nonsense mutation (c.685G>T, p.Glu229*) and a missense substitution (c.514G>A, p.Glu172Lys). The unaffected parents in both families were heterozygous carrier of the relevant mutation. The results expand genotype-phenotype spectrum in CGL1 and will have applications in prenatal and early diagnosis of the disease. This is the first report of Persian families identified with AGPAT2 mutations.

Seipin: from human disease to molecular mechanism

The most-severe form of congenital generalized lipodystrophy (CGL) is caused by mutations in BSCL2/seipin. Seipin is a homo-oligomeric integral membrane protein in the endoplasmic reticulum that concentrates at junctions with cytoplasmic lipid droplets (LDs). While null mutations in seipin are responsible for lipodystrophy, dominant mutations cause peripheral neuropathy and other nervous system pathologies. We first review the clinical aspects of CGL and the discovery of the responsible genetic loci. The structure of seipin, its normal isoforms, and mutations found in patients are then presented. While the function of seipin is not clear, seipin gene manipulation in yeast, flies, mice, and human cells has recently yielded a trove of information that suggests roles in lipid metabolism and LD assembly and maintenance. A model is presented that attempts to bridge these new data to understand the role of this fascinating protein.

Monogenic diabetes secondary to congenital lipodystrophy in a 14-year-old Yemeni girl

A 14-year-old female from Yemen presented with intense abdominal pain and headache. She was born at term to distant cousins, developmentally delayed and significantly dysmorphic. Four years ago, she was diagnosed with diabetes mellitus and undiagnosed hepatic, cardiac, genetic, neurologic, endocrine, musculoskeletal, and gastrointestinal disorders. No therapy was prescribed. Admission laboratory data showed blood glucose = 391 mg/dl, hemoglobin A1c= 12.2%, C-peptide = 3.5 ng/ml, insulin = 6.8 uIU/ml, triglyceride =385 mg/dl, and serum leptin <0.5 ng/ml, (1.1-27.5). Chromosome analysis (46, XX) was normal and serology for Glutamic acid Decarboxylase (GAD), hepatitis and HIV were negative. Clinical examination and laboratory data suggested congenital generalized lipodystrophy (CGL, type BSCL-2). This case illustrates that CGL should be in the differential diagnosis for non-obese patients with diabetes and insulin resistance.

Severe cardiac phenotype of Berardinelli-Seip congenital lipodystrophy in an infant with homozygous E189X BSCL2 mutation

Berardinelli-Seip congenital lipodystrophy (BSCL) is a rare autosomal recessive condition associating insulin resistance, absence of subcutaneous fat and muscular hypertrophy. Disease-causing mutations have been described in AGPAT2 and BSCL2 genes. Hypertrophic cardiomyopathy is a classical late (third decade) complication which has only been occasionally described in childhood. We report on a 4-month-old Chinese male infant who presented with a severe BSCL "cardiac" phenotype comprising heart failure, hypertension and hypertrophic cardiomyopathy.

Novel subtype of congenital generalized lipodystrophy associated with muscular weakness and cervical spine instability

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder characterized by extreme paucity of adipose tissue from birth, and early onset of metabolic complications related to insulin resistance. Mutations in three genes, 1-acylglycerol 3-phosphate-O-acyltransferase 2 (AGPAT2), Berardinelli Seip Congenital Lipodystrophy 2 (BSCL2), and Caveolin-1 (CAV1) are associated with the three subtypes of this disorder, CGL1, CGL2 and CGL3, respectively. We report two siblings of Hispanic origin who displayed characteristic features of CGL such as generalized loss of subcutaneous fat from birth, acanthosis nigricans, acromegaloid habitus, umbilical prominence, hepatosplenomegaly, hypoleptinemia, dyslipidemia, and insulin resistance. However, no disease causing variants were detected in the DNA sequence of AGPAT2, BSCL2 or CAV1 genes. Further, whole body magnetic resonance imaging (MRI) in the two siblings revealed marked loss of subcutaneous, intraabdominal and intrathoracic fat like in other patients with CGL, but preservation of bone marrow fat which is invariably lost in all patients with CGL1 and CGL2, but not in the patient reported with CGL3. They also had generalized muscle weakness during infancy and early childhood associated with a nearly fivefold increase in serum creatine kinase (CK) levels, but with normal muscle biopsy and electrophysiologic studies. Both patients were also found to have atlantoaxial dislocation requiring surgical intervention. Thus, this pedigree represents a novel subtype of CGL characterized by generalized loss of body fat but with preservation of bone marrow fat, congenital muscular weakness and cervical spine instability. The genetic basis of this novel subtype remains to be determined.

Você conhece esta síndrome?

A lipodistrofia generalizada congênita (síndrome de Berardinelli-Seip), doença autossômica recessiva, caracteriza-se por escassez do tecido subcutâneo. A falta de tecido adiposo propicia disfunção metabólica dos lípides e carboidratos, resistência periférica à insulina, hipertrigliceridemia e hipermetabolismo. Outros achados são acantose nigricante, acromegalia, hepatomegalia e alterações musculares, ósseas, cardiovasculares e neurológicas. Relata-se o caso de paciente com essa síndrome, cujo diagnóstico foi realizado em um serviço de dermatologia.

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.

Lipotoxic diseases

I review evidence that leptin is a liporegulatory hormone that controls lipid homeostasis in nonadipose tissues during periods of overnutrition. When adipocytes store excess calories as triacylglycerol (TG), leptin secretion rises so as to prevent accumulation of lipids in nonadipose tissues, which are not adapted for TG storage. Whenever leptin action is lacking, whether through leptin deficiency or leptin resistance, overnutrition causes disease of nonadipose tissues with generalized steatosis, lipotoxicity, and lipoapoptosis. Examples of such disorders of liporegulation include generalized lipodystrophies, mutations of leptin and leptin receptor genes, and diet-induced obesity. Lipotoxicity of pancreatic beta-cells, myocardium, and skeletal muscle leads, respectively, to type 2 diabetes, cardiomyopathy, and insulin resistance. In humans this constellation of abnormalities is referred to as the metabolic syndrome, a major health problem in the United States. When lipids overaccumulate in nonadipose tissues during overnutrition, fatty acids enter deleterious pathways such as ceramide production, which, through increased nitric oxide formation, causes apoptosis of lipid-laden cells, such as beta-cells and cardiomyocytes. Lipoapoptosis can be prevented by caloric restriction, by thiazolidinedione treatment, and by administration of nitric oxide blockers. There is now substantial evidence that complications of human obesity may reflect lipotoxicity similar to that described in rodents.

The molecular basis of genetic lipodystrophies

OBJECTIVES

Hyperinsulinemia is often associated with a cluster of metabolic abnormalities, which usually presents before the onset of frank diabetes. Lipodystrophy syndromes are frequently associated with hyperinsulinemia and may act as models for insulin resistance. Lipodystrophy is characterized in broad terms by loss of subcutaneous adipose tissue. Despite heterogeneous causes, which include both genetic and acquired forms, lipodystrophy syndromes have similar metabolic attributes, including insulin resistance, hyperlipidemia and diabetes.

RESULTS

Recently, the molecular basis of two genetic forms of lipodystrophy, namely Dunnigan-type familial partial lipodystrophy (FPLD; MIM 151660) and Berardinelli-Seip complete lipodystrophy (BSCL; MIM 269700) have been reported. There is evidence for genetic heterogeneity for both types of lipodystrophy. In addition, murine models of lipodystrophy have provided key insights into alterations of metabolic pathways in lipodystrophy.

CONCLUSIONS

Delineation of the human molecular genetic basis of two distinct forms of inherited lipodystrophy may have relevance for the common insulin resistance syndrome and for acquired lipodystrophy syndromes.

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.

Diseases of liporegulation: new perspective on obesity and related disorders

Obesity-related diseases now threaten to reach epidemic proportions in the United States. Here we review in a rodent model of genetic obesity, the fa/fa Zucker diabetic fatty (ZDF) rat, the mechanisms involved in the most common complications of diet-induced human obesity, i.e., noninsulin-dependent diabetes mellitus, and myocardial dysfunction. In ZDF rats, hyperphagia leads to hyperinsulinemia, which up-regulates transcription factors that stimulate lipogenesis. This causes ectopic deposition of triacylglycerol in nonadipocytes, providing fatty acid (FA) substrate for damaging pathways of nonoxidative metabolism, such as ceramide synthesis. In beta cells and myocardium, the resulting functional impairment and apoptosis cause diabetes and cardiomyopathy. Interventions that lower ectopic lipid accumulation or block nonoxidative metabolism of FA and ceramide formation completely prevent these complications. Given the evidence for a similar etiology for the complications of human obesity, it would be appropriate to develop strategies to avert the predicted epidemic of lipotoxic disorders.

Mouse models of lipodystrophy

Lipodystrophies are a group of heterogeneous diseases characterized by the loss of adipose tissue and by abnormalities of carbohydrate and lipid metabolism, including insulin resistance, diabetes, and hyperlipidemia. In this review, we describe several mouse models that recapitulate various aspects of the lipodystrophy syndrome, offering insights into the etiology of this condition and potential therapeutic approaches. Studies on these mice suggest that adipose is the primary tissue affected in lipodystrophy, and that secondary leptin deficiency may be responsible for the associated insulin resistance.

Lipodystrophies

The lipodystrophies are rare disorders characterized by selective but variable loss of adipose tissue. Metabolic complications, such as insulin resistance, diabetes mellitus, hypertriglyceridemia, and fatty liver, increase in severity with the extent of fat loss. The lipodystrophies can be classified into two major types: familial and acquired. The main subtypes of familial lipodystrophies are congenital generalized lipodystrophy, an autosomal recessive disorder characterized by near complete lack of metabolically active adipose tissue from birth, and familial partial lipodystrophy, Dunnigan type, an autosomal dominant disorder characterized by loss of subcutaneous fat from the extremities at puberty and excess fat accumulation in the face and neck. Recently, a gene for congenital generalized lipodystrophy was localized to chromosome 9q34, and a gene for familial partial lipodystrophy, Dunnigan type, to chromosome 1q21-22; the genes, however, remain to be identified. Patients with acquired generalized lipodystrophy have generalized loss of subcutaneous fat, but those with acquired partial lipodystrophy have fat loss limited to the face, trunk, and upper extremities. Both varieties occur approximately three times more often in women, begin during childhood, and have underlying autoimmunity. Patients infected with the human immunodeficiency virus (HIV) who are receiving therapy that includes HIV-1 protease inhibitors have been reported to develop a lipodystrophy characterized by loss of subcutaneous fat from the extremities and face but excess fat deposition in the neck and trunk. Localized lipodystrophies can be caused by drugs, pressure, panniculitis, or unknown mechanisms. Current management of patients includes cosmetic surgery, diet, and drug therapy for control of diabetes and dyslipidemia.