Multiple symmetric lipomatosis may be the consequence of defective noradrenergic modulation of proliferation and differentiation of brown fat cells.
Multiple symmetric lipomatosis (MSL) is an inherited disorder in which enlarging and unencapsulated lipomas symmetrically develop in the subcutaneous tissue of the neck, shoulders, mammary, and truncal regions. In some cases, it is associated with mitochondrial DNA abnormalities. The pathogenesis of MSL is completely unknown, although the fat deposits may be due to a neoplastic-like proliferation of functionally defective brown adipocytes. It has recently been demonstrated that the beta(3)-adrenergic receptor is the functionally relevant adrenergic receptor subtype in brown adipocytes and that its stimulation by noradrenaline (NA) modulates the expression of genes, such as uncoupling protein (UCP)-1 and inducible nitric oxide synthase (iNOS), involved in fat cell proliferation and differentiation. Furthermore, Trp64Arg mutation of the beta(3)-adrenoceptor has been implicated in lower NA activity in adipose tissues. The aim of this study was to investigate the molecular and functional characteristics of MSL adipocytes and to analyse the effects of nitric oxide (NO) on the proliferation/differentiation of MSL adipocytes in culture, and the relevance of putative noradrenergic deficit in the development of lipomas in MSL patients. Cultured MSL adipocytes were able to synthesize UCP-1 (the selective marker of brown adipocytes), but unlike that of normally functioning brown fat cells, the expression of the UCP-1 gene was not significantly induced by NA. NA is also defective in inducing iNOS gene expression, thus leading to reduced NO production and a consequent reduction in the anti-proliferative, adipogenic (mitochondrial biogenesis) effects of NA on MSL cells. Furthermore, the transcriptional peroxisome proliferator-activated receptor gamma co-activator-1 (PGC-1), which plays a key role in the sympathetic-stimulated mitochondrial biogenesis of brown adipocytes, is expressed but not induced by NA in MSL cells, as it is in brown adipocytes. The study did not find any association between beta(3)-adrenoceptor gene polymorphism and noradrenergic signalling defects in MSL subjects with or without mitochondrial DNA mutations.
Nisoli
Enzo
E
Center for Study and Research on Obesity, Department of Preclinical Sciences, LITA Vialba, L. Sacco Hospital, University of Milan, Via G. B. Grassi 74, Italy. enzo.nisoli@unimi.it
Regianini
Laura
L
Briscini
Luca
L
Bulbarelli
Alessandra
A
Busetto
Luca
L
Coin
Alessandra
A
Enzi
Giuliano
G
Carruba
Michele O
MO
D017667:Adipocytes / Q000187:drug effects / Q000473:pathology*; D002001:Adipose Tissue, Brown / Q000473:pathology*; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004272:DNA, Mitochondrial / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007473:Ion Channels; D008069:Lipomatosis, Multiple Symmetrical / Q000235:genetics / Q000473:pathology* / Q000503:physiopathology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D024101:Mitochondrial Proteins; D009569:Nitric Oxide / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D009638:Norepinephrine / Q000494:pharmacology / Q000502:physiology*; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors; D000071256:Uncoupling Protein 1
D002352:Carrier Proteins; D004272:DNA, Mitochondrial; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C000604371:UCP1 protein, human; C000604373:Ucp1 protein, rat; D000071256:Uncoupling Protein 1; C111264:peroxisome-proliferator-activated receptor-gamma coactivator-1; D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D009638:Norepinephrine