[Show abstract][Hide abstract] ABSTRACT: Beradinelli-Seip congenital generalized lipodystrophy is a rare autosomal recessive disorder characterized by near-complete absence of adipose tissue, Herculean appearance, insulin resistance, hypoleptinaemia and diabetes mellitus. The aim of this study was to investigate the in vitro effects of pioglitazone on the expression of genes involved in adipogenesis in fibroblasts from a patient with this condition due to a seipin mutation.
Primary cultures of fibroblasts from the skin of the patient were obtained. Fibroblasts were treated with classic adipose differentiation medium, with and without pioglitazone. Several adipogenes were evaluated by real-time reverse transcriptase-polymerase chain reaction and western blotting. Intracellular localization of prelamin A was studied by immunofluorescence microscopy.
The expression of the adipogenic genes PPARG, LPL, LEP and SLC2A4 was reduced in lipodystrophic fibroblasts, while treatment with pioglitazone increased the expression of these genes. Moreover, and unexpectedly, we found an accumulation of farnesylated prelamin A in lipodystrophic fibroblasts.
The process of adipocyte differentiation is compromised in patients with Beradinelli-Seip congenital lipodystrophy owing to diminished expression of the regulatory genes involved, which pioglitazone treatment partially rescues. Prelamin A accumulation establishes a link with other types of familial lipodystrophies, as familial partial lipodystrophy.
Full-text · Article · Oct 2010 · Diabetic Medicine
[Show abstract][Hide abstract] ABSTRACT: Type 2 familial partial lipodystrophy (FPLD2) is characterised by loss of fat in the limbs and buttocks and results from mutations in the LMNA gene.
To evaluate the role of several genes involved in adipogenesis in order to better understand the underlying mechanisms of regional loss of subcutaneous adipose tissue (scAT) in patients with FPLD2.
In total, 7 patients with FPLD2 and 10 healthy control participants were studied. A minimal model was used to calculate the insulin sensitivity (IS). scAT was obtained from abdomen and thigh by biopsy. Relative gene expression was quantified by real-time reverse transcription PCR in a thermal cycler. Prelamin A western blot analysis was carried out on scAT and prelamin A nuclear localisation was determined using immunofluorescence. Adipocyte nuclei were examined by electron microscopy.
Patients with FPLD2 were found to have significantly lower IS. The expression of LMNA was similar in both groups. The expression of PPARG2, RB1, CCND3 and LPL in thigh but not in abdomen scAT was significantly reduced (67%, 25%, 38% and 66% respectively) in patients with FPLD2. Significantly higher levels of prelamin A were found in peripheral scAT of patients with FPLD2. Defects in the peripheral heterochromatin and a nuclear fibrous dense lamina were present in the adipocytes of patients with FPLD2.
In FPLD2 participants, prelamin A accumulation in peripheral scAT is associated with a reduced expression of several genes involved in adipogenesis, which could perturb the balance between proliferation and differentiation in adipocytes, leading to less efficient tissue regeneration.
Full-text · Article · Oct 2008 · Journal of Medical Genetics
[Show abstract][Hide abstract] ABSTRACT: Lipodystrophies are a heterogeneous group of diseases characterized by abnormal fat distribution. Familial partial lipodystrophy 2 (FPLD2) is due to mutations in the LMNA gene. Previous studies have suggested that LMNA mutations 5' to the nuclear localization signal (NLS) are more likely to underlie laminopathies with cardiac or skeletal muscle involvement, while mutations 3' to the NLS are more likely to underlie lipodystrophy and progeroid syndromes.
To study the clinical and molecular features of a subject with FPLD.
We carried out mutational analysis of LMNA gene in a woman with FPLD phenotype and in her relatives. Insulin resistance was evaluated by minimal model. Body composition was evaluated by dual-energy X-ray absorptiometry (DEXA). Echocardiography was done in affected subjects. 3T3-L1 preadipocytes were transfected with wild-type or mutant prelamin A constructs. In transfected cells, lamin A was detected using a Cy3-conjugated monoclonal anti-FLAG antibody.
The patient showed atypical fat distribution, insulin resistance, severe aortic stenosis and hypertrophic cardiomyopathy. She has an affected 11-year-old son, not yet lipodystrophic but with an incipient aortic disease. LMNA sequencing showed that mother and son were both heterozygous for a novel c.1772G > T missense mutation in exon 11, which causes the substitution of the cysteine at residue 591 by a phenylalanine (C591F). In mouse preadipocytes transfected with the mutant human LMNA gene, the mutant lamin A isoform was mislocated in the nucleus.
This patient shows a novel clinical form of FPLD2, due to a mutation affecting lamin A only, with cardiac involvement.