A number of proteins mutated in genetic lipodystrophies are involved in the control of triglyceride synthesis towards the lipid droplet (1-acylglycerol-3-phosphate-O-acyltransferase 2), or its functions (seipin, cell death-inducing DFF45-like effector C, perilipin, caveolin-1, cavin-1).
We conducted an open-label prospective study of patients with acquired forms of lipodystrophy and inherited forms of lipodystrophy secondary to mutations in the AGPAT2, SEIPIN (also known as BSCL2), LMNA and PPARgamma (also known as PPARG) genes.
Genetic forms are uncommon: recessive generalized congenital lipodystrophies result in most cases from mutations in the genes encoding seipin or the 1-acyl-glycerol-3-phosphate-acyltransferase 2(AGPAT2).
To gain insight into how altered AGPAT2 activity causes lipodystrophy, we examined the effect of knockdown of AGPAT2 expression in preadipocytes on TAG synthesis and storage, and on adipocyte differentiation.
The loss of body fat in inherited lipodystrophies can be caused by defects in the development and/or differentiation of adipose tissue as a consequence of mutations in a number of genes, including PPARG (encoding a nuclear hormone receptor), AGPAT2 (encoding an enzyme involved in the biosynthesis of triglyceride and phospholipids), AKT2 (encoding a protein involved in insulin signal transduction), and BSCL2 (encoding seipin, whose role in the adipocyte biology remains unclear).
Defects in several genes, such as those encoding an enzyme (AGPAT2), a nuclear receptor (PPARgamma), a nuclear lamina protein (LMNA) and its processing endoprotease (ZMPSTE24), a kinase (AKT2), and a protein of unknown function (BSCL2), have been found in patients with genetic lipodystrophies.
Congenital generalized lipodystrophy or Berardinelli-Seip syndrome, autosomal recessive, is characterized by a complete early lipoatrophy and severe insulin resistance and results, in most cases, from mutations either in the seipin gene of unknown function or AGPAT2 encoding an enzyme involved in triacylglycerol synthesis.
Phenotypic heterogeneity in body fat distribution in patients with congenital generalized lipodystrophy caused by mutations in the AGPAT2 or seipin genes.
In this study, we have performed mutation screening in AGPAT2 and the related AGPAT1 in patients with BSCL or other forms of lipodystrophy who have no detectable mutation in the seipin gene.
AGPAT2 is a key enzyme involved in triglyceride and phospholipid biosynthesis and, thus, the discovery of AGPAT2 mutations has heightened interest in the biochemical pathways of triglyceride synthesis and their implications in human physiology and in the pathophysiology of obesity, lipodystrophies and other adipose tissue disorders.
BSCL2 appears to be a more severe disorder than BSCL1 with a higher incidence of premature death and a lower prevalence of partial and/or delayed onset of lipodystrophy.