[Show abstract][Hide abstract] ABSTRACT: Dysregulation of signaling pathways in adipose tissue leading to insulin resistance can contribute to the development of obesity-related metabolic disorders. Alström Syndrome, a recessive ciliopathy, caused by mutations in ALMS1, is characterized by progressive metabolic alterations such as childhood obesity, hyperinsulinemia, and type 2 diabetes. Here we investigated the role of Alms1 disruption in AT expansion and insulin responsiveness in a murine model for Alström Syndrome. A gene trap insertion in Alms1 on the insulin sensitive C57BL6/Ei genetic background leads to early hyperinsulinemia and a progressive increase in body weight. At 6 weeks of age, before the onset of the metabolic disease, the mutant mice had enlarged fat depots with hypertrophic adipocytes, but without signs of inflammation. Expression of lipogenic enzymes was increased. Pre-adipocytes isolated from mutant animals demonstrated normal adipogenic differentiation but gave rise to mature adipocytes with reduced insulin-stimulated glucose uptake. Assessment of whole body glucose homeostasis revealed glucose intolerance. Insulin stimulation resulted in proper AKT phosphorylation in adipose tissue. However, the total amount of glucose transporter 4 (SLC4A2) and its translocation to the plasma membrane were reduced in mutant adipose depots compared to wildtype littermates. Alterations in insulin stimulated trafficking of glucose transporter 4 are an early sign of metabolic dysfunction in Alström mutant mice, providing a possible explanation for the reduced glucose uptake and the compensatory hyperinsulinemia. The metabolic signaling deficits either reside downstream or are independent of AKT activation and suggest a role for ALMS1 in GLUT4 trafficking. Alström mutant mice represent an interesting model for the development of metabolic disease in which adipose tissue with a reduced glucose uptake can expand by de novo lipogenesis to an obese state.
PLoS ONE 01/2014; 9(10):e109540. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Alström syndrome (ALMS) is a rare autosomal recessive monogenic disease associated with obesity, hyperinsulinemia, and alterations of glucose metabolism that often lead to the development of type 2 diabetes at a young age.
To study the relationship between weight and metabolism in a group of ALMS patients and matched controls.
Fifteen ALMS patients (eight males, seven females; aged 3-51) were compared in a cross-sectional study with an age- and weight-matched control population. Anthropometric parameters, fat mass, glucose and insulin secretion in basal and dynamic oral glucose tolerance test (OGTT) conditions were measured. Furthermore, anthropometric and body composition data were obtained from an international group of 27 ALMS patients (13 males, 14 females, age range: 4-29 yr).
In ALMS we observed an inverse correlation between age and standard deviation scores for height, weight, and body mass index. The OGTT glycemic curves of ALMS subjects were similar to those of age-matched controls, whereas insulin response was clearly greater. In ALMS individuals the insulin response showed a reduction with age. We documented pathologic values of the derived indices homeostasis model assessment of insulin resistance (HOMA-IR), insulin sensitivity index, HOMA%β-cell and insulinogenic index in ALMS, but unlike the insulin-resistance indices, the β-cell function indices showed a significant reduction with age.
In ALMS the progression from the early onset obesity toward the impaired fasting glucose or impaired glucose tolerance and overt diabetes is mostly because of a progressive failure of β-cell insulin secretion without any further worsening of insulin resistance with age, even in the presence of weight reduction.
[Show abstract][Hide abstract] ABSTRACT: Alström Syndrome (ALMS) is a rare genetic disorder (483 living cases), characterized by many clinical manifestations, including blindness, obesity, type 2 diabetes and cardiomyopathy. ALMS is caused by mutations in the ALMS1 gene, encoding for a large protein with implicated roles in ciliary function, cellular quiescence and intracellular transport. Patients with ALMS have extensive fibrosis in nearly all tissues resulting in a progressive organ failure which is often the ultimate cause of death. To focus on the role of ALMS1 mutations in the generation and maintenance of this pathological fibrosis, we performed gene expression analysis, ultrastructural characterization and functional assays in 4 dermal fibroblast cultures from ALMS patients. Using a genome-wide gene expression analysis we found alterations in genes belonging to specific categories (cell cycle, extracellular matrix (ECM) and fibrosis, cellular architecture/motility and apoptosis). ALMS fibroblasts display cytoskeleton abnormalities and migration impairment, up-regulate the expression and production of collagens and despite the increase in the cell cycle length are more resistant to apoptosis. Therefore ALMS1-deficient fibroblasts showed a constitutively activated myofibroblast phenotype even if they do not derive from a fibrotic lesion. Our results support a genetic basis for the fibrosis observed in ALMS and show that both an excessive ECM production and a failure to eliminate myofibroblasts are key mechanisms. Furthermore, our findings suggest new roles for ALMS1 in both intra- and extra-cellular events which are essential not only for the normal cellular function but also for cell-cell and ECM-cell interactions.
PLoS ONE 01/2011; 6(4):e19081. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Alström syndrome (ALMS) is an autosomal recessive genetic disease with characteristic phenotypical features including multi-organ fibrosis, insulin resistance, obesity and type 2 diabetes. ALMS1, a ubiquitously expressed gene mutated in ALMS patients, gives rise to a protein of unknown function localized to basal bodies of ciliated cells and centrosomes. Together with Bardet-Biedl syndrome, ALMS is a member of genetic ciliopathies, but the link between cilia/centrosome deficits and metabolic abnormalities remains to be determined. In this study for the first time we quantified Alms1 expression in a cellular model of adipogenesis during the differentiation of 3T3-L1 cells. An early decrease in Alms1 mRNA was observed during preadipocyte to adipocyte conversion. However, acute treatment of preadipocytes with the adipogenic factors did not result in significant change of Alms1 expression. In addition, to study the possible relationship between Alms1 and the degree of fat cell insulin sensitivity, as assessed with an insulin-dependent 2-[1-3H]-deoxyglucose uptake assay, we induced either a reduction or an increase in 3T3-L1 adipocytes insulin sensitivity by a chronic treatment with insulin or rosiglitazone respectively. In all these conditions Alms1 expression remained unchanged. In conclusion, our results show that Alms1 is expressed at higher level in preadipocytes suggesting a role of the gene in the early phase of adipogenesis. Moreover, changes in fat cell insulin sensitivity do not imply any effect on Alms1 expression.
International Journal of Molecular Medicine 07/2008; 21(6):731-6. · 1.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To elucidate the pathogenesis of HAART-associated lipodystrophy, by investigating the effects of antiretroviral drugs on adipocyte differentiation and gene expression profile.
Analysis of gene expression profile by DNA microarrays and quantitative RT-PCR of 3T3-L1 preadipocytes treated with the nucleoside reverse transcriptase inhibitors (NRTI) lamivudine, zidovudine, stavudine, and zalcitabine, and with the protease inhibitors (PI) indinavir, saquinavir, and lopinavir during maturation into adipocytes.
Under standard adipogenic differentiation protocols, PI significantly inhibited adipocyte differentiation, as demonstrated by cell viability assay and Oil Red O staining and quantification, whereas NRTI had mild effects on adipogenesis. Gene expression profile analysis showed that treatment with NRTI modulated the expression of transcription factors, such as Aebp1, Pou5f1 and Phf6, which could play a key role in the determination of the adipocyte phenotype. PI also modulated gene expression toward inhibition of adipocyte differentiation, with up-regulation of the Wnt signaling gene Wnt10a and down-regulation of the expression of genes encoding master adipogenic transcription factors (e.g., C/EBPalpha and PPARgamma), oestrogen receptor beta, and adipocyte-specific markers (e.g., Adiponectin, Leptin, Mrap, Cd36, S100A8).
This study identifies new genes modulated by PI and NRTI in differentiating adipocytes. Abnormal expression of these genes, which include master adipogenic transcription factors and genes involved in lipid metabolism and cell cycle control, could contribute to the understanding of the pathogenesis of HAART-associated lipodystrophy.
AIDS 09/2006; 20(13):1691-705. · 6.41 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this work we realized a molecular and functional characterization of P2 receptors in several adipose tissue depots (subcuteneous, visceral, preadipocytes/stromal vascular fraction and adipocytes by RT-PCR, qPCR, sequencing, fluorescent dye Ca2+ sensitive, and immunoenzymatic assay. We evaluated also a gene expression in dermal fibroblasts from Alstrom patients using DNA microarray analysis. We found a modulation of genes coding proteins cell cycle related, extracellular matrix, cellular movement and insulin pathway.