Mitochondrial DNA pathogenic mutations in multiple symmetric lipomatosis

Identification and characterization of a new pathologic mutation in a large Leber hereditary optic neuropathy pedigree

BACKGROUND

Most patients suffering from Leber hereditary optic neuropathy carry one of the three classic pathologic mutations, but not all individuals with these genetic alterations develop the disease. There are different risk factors that modify the penetrance of these mutations. The remaining patients carry one of a set of very rare genetic variants and, it appears that, some of the risk factors that modify the penetrance of the classical pathologic mutations may also affect the phenotype of these other rare mutations.

RESULTS

We describe a large family including 95 maternally related individuals, showing 30 patients with Leber hereditary optic neuropathy. The mutation responsible for the phenotype is a novel transition, m.3734A > G, in the mitochondrial gene encoding the ND1 subunit of respiratory complex I. Molecular-genetic, biochemical and cellular studies corroborate the pathogenicity of this genetic change.

CONCLUSIONS

With the study of this family, we confirm that, also for this very rare mutation, sex and age are important factors modifying penetrance. Moreover, this pedigree offers an excellent opportunity to search for other genetic or environmental factors that additionally contribute to modify penetrance.

Multiple Symmetric Lipomatosis: Lipectomy for Madelung Collar

Multiple symmetric lipomatosis (MSL) is a rare disease associated with metabolic disorders and alcoholism. In this report, we describe the clinical outcome and surgical protocol for eight men with Madelung collar who underwent treatment in a craniofacial and plastic surgery facility in Hanoi, Vietnam, between May 2018 and December 2020. We discuss the patients' clinical symptoms, subclinical signs, epidemiology, magnetic resonance imaging, computerized tomography, surgical protocol, complications, and postoperative indicators that we collected and evaluated. Each patient underwent surgery in two stages (i.e., in supine and prone positions). We injected a tumescent solution 10 min before the incision. Two surgeons performed each operation simultaneously. After surgery, we followed the patients for 6-27 months. All of the patients had a history of long-time alcohol abuse and had associated comorbidities that included liver disease, blood disorders, restricted neck movement, and orthopnea. We did not have to open the trachea or transfuse blood during any of the surgical procedures. Postoperatively, all patients were satisfied with their functional results and aesthetic appearance. One patient experienced a recurrence of his MSL. We believe our surgical protocol provides optimal results for patients with MSL and Madelung collar.

Multiple symmetric and multiple familial lipomatosis

Lipomas are the most common soft tissue tumors and are malignant in only 1% of cases. Lipomatosis is defined as the presence of multiple benign lipomas on the body, without lipoatrophy. Their impact on quality of life is significant. Different entities have been described such as symmetrical multiple lipomatosis (MSL), also called Madelung's disease and familial multiple lipomatosis (FML). MSL occurs preferentially in men (but also women) who are alcohol abuser. There are different subtypes of the disease, the most classic of which affects the upper body and the nuchal region with a buffalo hump appearance. A metabolic component with obesity is frequent. In contrast to Dercum's disease, there is no pain. SAOS, complications of the metabolic syndrome and of alcohol abuse including cancers, may be associated and should be screened. FML has been little described in the literature since Brodie's first report in 1846. FML occurs preferentially in the third decade but equally in women and men. Its autosomal dominant component is classically accepted with variable penetrance within the same family. Association with naevi, angiomas, polyneuropathies and with gastrointestinal comorbidities has been reported. Interestingly, and in contrast with most lipodystrophy disorders, the patients show an insulin sensitivity profile. A better understanding of the underlying pathophysiological mechanisms would open up avenues on therapeutic research, since treatments are only symptomatic to date.

Human Adipose-Derived Stem Cells in Madelung's Disease: Morphological and Functional Characterization

Madelung Disease (MD) is a syndrome characterized by the accumulation of aberrant symmetric adipose tissue deposits. The etiology of this disease is yet to be elucidated, even though the presence of comorbidities, either genetic or environmental, has been reported. For this reason, establishing an in vitro model for MD is considered crucial to get insights into its physiopathology. We previously established a protocol for isolation and culture of stem cells from diseased tissues. Therefore, we isolated human adipose-derived stem cells (ASC) from MD patients and compared these cells with those isolated from healthy subjects in terms of surface phenotype, growth kinetic, adipogenic differentiation potential, and molecular alterations. Moreover, we evaluated the ability of the MD-ASC secretome to affect healthy ASC. The results reported a difference in the growth kinetic and surface markers of MD-ASC compared to healthy ASC but not in adipogenic differentiation. The most commonly described mitochondrial mutations were not observed. Still, MD-ASC secretome was able to shift the healthy ASC phenotype to an MD phenotype. This work provides evidence of the possibility of exploiting a patient-based in vitro model for better understanding MD pathophysiology, possibly favoring the development of novel target therapies.

White Adipose Tissue Expansion in Multiple Symmetric Lipomatosis Is Associated with Upregulation of CK2, AKT and ERK1/2

Multiple symmetric lipomatosis (MSL) is a rare disorder characterized by overgrowing lipomatous tissue (LT) in the subcutaneous adipose tissue (SAT). What LT is and how it expands are not completely understood; previous data suggested that it could derive from brown AT precursors. In six MSL type I patients, we compared LT morphology by histological and immunohistochemistry (IHC) analysis, gene expression, by qPCR, kinase activity, by Western Blot and in vitro assay to paired-control SAT using AT from patients with pheochromocytoma as a human browning reference. In the stromal vascular fraction (SVF), we quantified adipose stem cells (ASCs) by flow cytometry, the proliferation rate, white and beige adipogenic potential and clonogenicity and adipogenicity by a limiting dilution assay. LT displayed white AT morphology and expression pattern and did not show increased levels of the brown-specific marker UCP1. In LT, we evidenced AKT, CK2 and ERK1/2 hyperactivation. LT-SVF contained increased ASCs, proliferated faster, sprouted clones and differentiated into adipocytes better than the control, displaying enhanced white adipogenic potential but not increased browning compared to SAT. In conclusion, LT is a white AT depot expanding by hyperplasia through increased stemness and enhanced white adipogenesis upregulating AKT, CK2 and ERK1/2, which could represent new targets to counteract MSL.

Cbl Proto-Oncogene B (CBLB) c.197A>T Mutation Induces Mild Metabolic Dysfunction in Partial Type I Multiple Symmetric Lipomatosis (MSL)

BACKGROUND

Multiple symmetric lipomatosis (MSL) is a rare disease showing chronic progression of multiple, symmetrical, and non-encapsulated subcutaneous lipoma. The cause of the disease remains unknown.

PATIENTS AND METHODS

This study reported and summarized 13 sporadic cases of Type I MSL patients in terms of histopathology and cellular and molecular biology and assessed the CBLB c.197A>T mutation in the IRS1-PI3K-Akt pathway.

RESULTS

The clinical data showed that these 13 Type I patients were all male with a mean age of 57.0 ± 6.6 years old and consumed alcohol heavily. The laboratory tests revealed that most of the patients had hyperuricemia, diabetes, hyperinsulinemia, or insulin resistance; however, their blood lipid levels were close to a normal range. The imaging data exhibited lipomas that only occurred subcutaneously but not viscerally, ie, Types Ia (15.4%), Ib (30.8%), and Ic (53.8%). The molecular analyses of adipocytes of isoprenaline stimulated human adipose tissue-derived mesenchymal stromal cells (hADSCs) isolated from the adipose tissue lipoma-like masses (ATLLM) demonstrated that these adipocytes did not express UCP-1. The Cbl proto-oncogene B (CBLB), an E3 ubiquitin-protein ligase, was associated with insulin resistance and obesity and was mutated (ie, CBLB c.197A>T) in four MSL patients after the whole genome and Sanger sequencing of the blood samples. Furthermore, the CBLB c.197A>T mutation induced hADSC resistance to insulin by inactivation of the IRS-1-PI3K-AKT pathway.

CONCLUSION

This study analyzed clinical, histopathological, and cellular and molecular biological characterizations of 13 Type I MSL patients and identified the CBLB c.197A>T heterozygous mutation that could be responsible for MSL metabolic dysfunction or even MSL development.