Biallelic CAV1 null variants induce congenital generalized lipodystrophy with achalasia.

OBJECTIVE: CAV1 encodes caveolin-1, a major protein of plasma membrane microdomains called caveolae, involved in several signaling pathways. Caveolin-1 is also located at the adipocyte lipid droplet. Heterozygous pathogenic variants of CAV1 induce rare heterogeneous disorders including pulmonary arterial hypertension and neonatal progeroid syndrome. Only one patient was previously reported with a CAV1 homozygous pathogenic variant, associated with congenital generalized lipodystrophy (CGL3). We aimed to further delineate genetic transmission, clinical, metabolic, and cellular characteristics of CGL3. DESIGN/METHODS: In a large consanguineous kindred referred for CGL, we performed next-generation sequencing, as well as clinical, imagery, and metabolic investigations. We studied skin fibroblasts from the index case and the previously reported patient with CGL3. RESULTS: Four patients, aged 8 months to 18 years, carried a new homozygous p.(His79Glnfs*3) CAV1 variant. They all displayed generalized lipodystrophy since infancy, insulin resistance, low HDL-cholesterol, and/or high triglycerides, but no pulmonary hypertension. Two patients also presented at the age of 15 and 18 years with dysphagia due to achalasia, and one patient had retinitis pigmentosa. Heterozygous parents and relatives (n = 9) were asymptomatic, without any metabolic abnormality. Patients' fibroblasts showed a complete loss of caveolae and no protein expression of caveolin-1 and its caveolin-2 and cavin-1 partners. Patients' fibroblasts also displayed insulin resistance, increased oxidative stress, and premature senescence. CONCLUSIONS: The CAV1 null variant investigated herein leads to an autosomal recessive congenital lipodystrophy syndrome. Loss of caveolin-1 and/or caveolae induces specific manifestations including achalasia which requires specific management. Overlapping phenotypic traits between the different CAV1-related diseases require further studies.

Altered subcutaneous adipose tissue parameters after switching ART-controlled HIV+ patients to raltegravir/maraviroc.

OBJECTIVE: To evaluate the effect on anthropometric, metabolic and adipose tissue parameters of switching ART-controlled persons living with HIV (PLWH) from a protease inhibitor regimen to raltegravir/maraviroc. DESIGN: Sub-study of the ANRS157 ROCnRAL study with the investigation of subcutaneous abdominal adipose tissue (SCAT) biopsy at inclusion and study end. METHODS: We performed lipoaspiration of paired SCAT samples, histology on fresh/fixed samples and examined the transcriptomic profile analyzed using Illumina microarrays after RNA extraction. Statistical analyses used the Wilcoxon-paired test. RESULTS: The patients (n = 8) were mainly male (7/8), aged (mean ±â€Šstandard error of the mean) 54.9 ±â€Š1.2 years, BMI 26.1 ±â€Š1.2 kg/m2, CD4+ 699 ±â€Š56 cells/mm3, all viral load (VL) <50 copies/ml. After a follow-up of 6 ±â€Š0.5 months, all PLWH remained with VL <50 copies/ml. BMI, trunk and limb fat amounts were unchanged yet systemic insulin resistance increased. Adipose tissue histology was unchanged except for borderline increased adipocyte diameter (P = 0.1). Among the 16 094 RNA transcripts, 458 genes were up-regulated and 244 were down-regulated. Analyses of the Kyoto Encyclopedia of Genes and Genomes and Gene Ontology databases, evaluating modifications in the main functional pathways, revealed that genes related to immune recognition/function were less expressed as were genes encoding T-cell receptor and receptor signaling pathways. The gene expression profiles indicated decreased inflammation but genes involved in adipogenesis and insulin resistance were overexpressed. CONCLUSION: After 6 months of raltegravir/maraviroc, adipogenesis-related gene profile was enhanced in SCAT, in agreement with a tendency for increased adipocyte size. Enhanced SCAT insulin resistance-related profile was concordant with higher systemic insulin resistance. However, the immune activation/inflammation profile was globally lowered. We propose that raltegravir/maraviroc might favor SCAT gain but reduce inflammation/immune activation.

Molecular and Cellular Bases of Lipodystrophy Syndromes.

Lipodystrophy syndromes are rare diseases originating from a generalized or partial loss of adipose tissue. Adipose tissue dysfunction results from heterogeneous genetic or acquired causes, but leads to similar metabolic complications with insulin resistance, diabetes, hypertriglyceridemia, nonalcoholic fatty liver disease, dysfunctions of the gonadotropic axis and endocrine defects of adipose tissue with leptin and adiponectin deficiency. Diagnosis, based on clinical and metabolic investigations, and on genetic analyses, is of major importance to adapt medical care and genetic counseling. Molecular and cellular bases of these syndromes involve, among others, altered adipocyte differentiation, structure and/or regulation of the adipocyte lipid droplet, and/or premature cellular senescence. Lipodystrophy syndromes frequently present as systemic diseases with multi-tissue involvement. After an update on the main molecular bases and clinical forms of lipodystrophy, we will focus on topics that have recently emerged in the field. We will discuss the links between lipodystrophy and premature ageing and/or immuno-inflammatory aggressions of adipose tissue, as well as the relationships between lipomatosis and lipodystrophy. Finally, the indications of substitutive therapy with metreleptin, an analog of leptin, which is approved in Europe and USA, will be discussed.

LIPE-related lipodystrophic syndrome: clinical features and disease modeling using adipose stem cells.

OBJECTIVE: The term Multiple Symmetric Lipomatosis (MSL) describes a heterogeneous group of rare monogenic disorders and multifactorial conditions, characterized by upper-body adipose masses. Biallelic variants in LIPE encoding hormone-sensitive lipase (HSL), a key lipolytic enzyme, were implicated in three families worldwide. We aimed to further delineate LIPE-related clinical features and pathophysiological determinants. METHODS: A gene panel was used to identify pathogenic variants. The disease features were reviewed at the French lipodystrophy reference center. The immunohistological, ultrastructural, and protein expression characteristics of lipomatous tissue were determined in surgical samples from one patient. The functional impact of variants was investigated by developing a model of adipose stem cells (ASCs) isolated from lipomatous tissue. RESULTS: We identified new biallelic LIPE null variants in three unrelated patients referred for MSL and/or partial lipodystrophy. The hallmarks of the disease, appearing in adulthood, included lower-limb lipoatrophy, upper-body and abdominal pseudo-lipomatous masses, diabetes and/or insulin resistance, hypertriglyceridemia, liver steatosis, high blood pressure, and neuromuscular manifestations. Ophthalmological investigations revealed numerous auto-fluorescent drusen-like retinal deposits in all patients. Lipomatous tissue and patient ASCs showed loss of HSL and decreased expression of adipogenic and mature adipocyte markers. LIPE-mutated ASCs displayed impaired adipocyte differentiation, decreased insulin response, defective lipolysis, and mitochondrial dysfunction. CONSLUSIONS: Biallelic LIPE null variants result in a multisystemic disease requiring multidisciplinary care. Loss of HSL expression impairs adipocyte differentiation, consistent with the lipodystrophy/MSL phenotype and associated metabolic complications. Detailed ophthalmological examination could reveal retinal damage, further pointing to the nervous tissue as an important disease target.

MFN2-associated lipomatosis: Clinical spectrum and impact on adipose tissue.

BACKGROUND: Multiple symmetric lipomatosis (MSL) is characterized by upper-body lipomatous masses frequently associated with metabolic and neurological signs. MFN2 pathogenic variants were recently implicated in a very rare autosomal recessive form of MSL. MFN2 encodes mitofusin-2, a mitochondrial fusion protein previously involved in Charcot-Marie-Tooth neuropathy. OBJECTIVE: To investigate the clinical, metabolic, tissular, and molecular characteristics of MFN2-associated MSL. METHODS: We sequenced MFN2 in 66 patients referred for altered fat distribution with one or several lipomas or lipoma-like regions and performed clinical and metabolic investigations in patients with positive genetic testing. Lipomatous tissues were studied in 3 patients. RESULTS: Six patients from 5 families carried a homozygous p.Arg707Trp pathogenic variant, representing the largest reported series of MFN2-associated MSL. Patients presented both lipomatous masses and a lipodystrophic syndrome (lipoatrophy, low leptinemia and adiponectinemia, hypertriglyceridemia, insulin resistance and/or diabetes). Charcot-Marie-Tooth neuropathy was of highly variable clinical severity. Lipomatous tissue mainly contained hyperplastic unilocular adipocytes, with few multilocular cells. It displayed numerous mitochondrial alterations (increased number and size, structural defects). As compared to control subcutaneous fat, mRNA and protein expression of leptin and adiponectin was strikingly decreased, whereas the CITED1 and fibroblast growth factor 21 (FGF21) thermogenic markers were strongly overexpressed. Consistently, serum FGF21 was markedly increased, and 18F-FDG-PET-scan revealed increased fat metabolic activity. CONCLUSION: MFN2-related MSL is a novel mitochondrial lipodystrophic syndrome involving both lipomatous masses and lipoatrophy. Its complex neurological and metabolic phenotype justifies careful clinical evaluation and multidisciplinary care. Low leptinemia and adiponectinemia, high serum FGF21, and increased 18F-FDG body fat uptake may be disease markers.

Functional Human Beige Adipocytes From Induced Pluripotent Stem Cells.

Activation of thermogenic beige adipocytes has recently emerged as a promising therapeutic target in obesity and diabetes. Relevant human models for beige adipocyte differentiation are essential to implement such therapeutic strategies. We report a straightforward and efficient protocol to generate functional human beige adipocytes from human induced pluripotent stem cells (hiPSCs). Without overexpression of exogenous adipogenic genes, our method recapitulates an adipogenic developmental pathway through successive mesodermal and adipogenic progenitor stages. hiPSC-derived adipocytes are insulin sensitive and display beige-specific markers and functional properties, including upregulation of thermogenic genes, increased mitochondrial content, and increased oxygen consumption upon activation with cAMP analogs. Engraftment of hiPSC-derived adipocytes in mice produces well-organized and vascularized adipose tissue, capable of ß-adrenergic-responsive glucose uptake. Our model of human beige adipocyte development provides a new and scalable tool for disease modeling and therapeutic screening.

Improved adipose tissue function with initiation of protease inhibitor-only ART.

OBJECTIVES: Use of ART containing HIV PIs has previously been associated with toxicity in subcutaneous adipose tissue (SAT), potentially contributing to the development of lipodystrophy and insulin resistance. However, the effect of PIs on SAT function in ART-naive patients independent of other ART classes is unknown. This study aimed to elucidate the effect of initiating PI-only ART on SAT function in ART-naive subjects. METHODS: In the HIVNAT-019 study, 48 HIV-infected, ART-naive Thai adults commencing PI-only ART comprising lopinavir/ritonavir/saquinavir for 24 weeks underwent assessments of fasting metabolic parameters and body composition. In a molecular substudy, 20 subjects underwent SAT biopsies at weeks 0, 2 and 24 for transcriptional, protein, mitochondrial DNA (mtDNA) and histological analyses. ClinicalTrials.gov registration number: NCT00400738. RESULTS: Over 24 weeks, limb fat increased (+416.4 g, P = 0.023), coinciding with larger adipocytes as indicated by decreased adipocyte density in biopsies (-32.3 cells/mm2, P = 0.047) and increased mRNA expression of adipogenesis regulator PPARG at week 2 (+58.1%, P = 0.003). Increases in mtDNA over 24 weeks (+600 copies/cell, P = 0.041), decreased NRF1 mRNA expression at week 2 (-33.7%, P < 0.001) and increased COX2/COX4 protein ratio at week 24 (+288%, P = 0.038) indicated improved mitochondrial function. Despite decreased AKT2 mRNA at week 2 (-28.6%, P = 0.002) and increased PTPN1 mRNA at week 24 (+50.3%, P = 0.016) suggesting insulin resistance, clinical insulin sensitivity [by homeostasis model assessment (HOMA-IR)] was unchanged. CONCLUSIONS: Initiation of PI-only ART showed little evidence of SAT toxicity, the changes observed being consistent with a return to health rather than contributing to lipodystrophy.

[Clinical and molecular consequences of microsatellite instability in human cancers]. / Conséquences cliniques et moléculaires de l'instabilité des microsatellites dans les cancers humains.

During each cell division, DNA polymerase makes mistakes while copying DNA. These errors, more frequent at the level of repeated sequences called microsatellites are normally repaired by a system called MMR (mismatch repair). Tumors defective in their MMR system accumulate mutations (deletions and insertions of some nucleotides) at the level of microsatellites and are called MSI (microsatellite instability). Microsatellites are numerous and scattered throughout the genome, in coding and non-coding regions. The instability of non-coding microsatellites is not known to have a major role in the process of cell transformation, but is a good indicator of the MSI status. On the other hand, instability by deletion or insertion in a coding region leads to a frameshift within the gene containing the repeat. The consequence is, the more often, the inactivation of this gene that potentially plays a role in initiation and/or MSI tumor progression. The MSI phenotype was first described in about 15 % of colorectal cancers that maybe of sporadic or hereditary (Lynch syndrome, or HNPCC for hereditary non-polyposis colorectal cancer) origin. It is also associated with about 15 % of gastric and endometrial tumors, and to a lesser extent with other human tumors. Besides a fundamental interest because of its original transformation mechanism, the analysis of MSI tumors is also important for clinical reasons. It was indeed shown that MSI tumors were associated with a better prognosis than non-MSI (also called MSS for microsatellite stable) tumors, and responded differently to conventional chemotherapeutic drugs used for the management of colorectal cancers. All these points will be discussed in details in the present review.

Specific clinical and biological features characterize inflammatory bowel disease associated colorectal cancers showing microsatellite instability.

PURPOSE: Microsatellite instability (MSI) due to mismatch repair (MMR) deficiency has been reported to occur at variable frequencies in inflammatory bowel disease-associated intestinal neoplasias (IBD-Ns). We investigated a large series of IBD-N for associations between MSI and several biologic and clinical parameters related to tumors, patients, and their treatment. PATIENTS AND METHODS: A total of 277 IBD-Ns in 205 patients were screened for MSI. Biologic and clinical variables of patients with high levels of DNA microsatellite instability high (MSI-H) were collected and compared with those associated with 33 MSI-H non-IBD colorectal cancers (CRCs). RESULTS: A total of 27 IBD-Ns from 17 patients were found to be MSI-H. Compared with sporadic MSI-H CRCs, patients presented with a younger age at diagnosis, and there was no female predominance and no right-sided predominance. Unlike sporadic MSI-H CRCs, MSI-H IBD-Ns presented with heterogeneous mismatch repair defects involving MLH1, MSH2, MSH6, or PMS2, and a low frequency of MLH1 promoter methylation. They exhibited frequent BRAF mutations and frameshift mutations in genes containing coding repeat sequences. CONCLUSION: The mechanisms underlying MMR deficiency in MSI-H IBD-Ns are different from those in sporadic MSI-H tumors and seem to be more related to those observed in hereditary MSI-H tumors. However, BRAF mutations were observed in MSI-H IBD-Ns, similar to sporadic MSI-H tumors, but unlike hereditary MSI-H tumors. Finally, the mutational events in target genes for instability are the same in MSI-H IBD-N tumors as in non-IBD sporadic and hereditary colorectal MSI-H cancers, indicating a colon-related repertoire of target gene alterations.