Obesity is characterized by an increase in adipose mass and is the leading risk factor for type 2 diabetes. Increasing adipose thermogenic capacity, by activation of brown or beige fat, could be a treatment for metabolic diseases. Nevertheless, many approaches fail in maintaining transformed adipose tissue in vivo, in part, due to the limited understanding of how environmental factors control cell fate and maintenance. We have shown that mice with a null mutation in the laminin α4 exhibit resistance to obesity, enhanced expression of thermogenic fat markers (UCP1) in subcutaneous white adipose tissue (sWAT), increased energy expenditure and enhanced insulin sensitivity. The knockout (KO) of Lama4 results in complex changes in overall ECM composition. We used liquid chromatography/tandem mass spectrometry (LC/MS) to evaluate ECM composition in sWAT from wild type (WT)and KO mice. In addition to the expected absence of Lama4, collagen 1A1 (Col1A1) and collagen 3A1 (Col3A1) were significantly lower in KO mice. Also, integrins α7 (ITα7) and β1 (ITβ1) were dramatically reduced. Immunohistochemical staining confirmed lower levels of Itα7 in KO compared to WT mice (P<0.0001). Knocking down Itα7 with siRNA promoted UCP1 expression (P=0.003) in vitro. In addition, culture of ADSC on Lama4, Col3A1 and Col1A1 coated surfaces had lower UCP1 expression (P<0.0001). Finally, mRNA levels of ITα7 and Lama4 decreased following 12 days of beige differentiation in human ADSC (P<0.0001). These results demonstrate that ECM can regulate adipocyte thermogenic capacity. Specifically, Lama4, Itα7, Col1A1 and Col3A1 are involved in the modulation of metabolic function in adipocytes. A better understanding of the mechanisms underlying these interactions allows for the potential to specifically manipulate these cells to improve systemic energy metabolism and glucose homeostasis.
M.A. Gonzalez Porras: None. K. Stojkova: None. M.K. Vaicik: None. A.A. Goddi: None. R.N. Cohen: None. E. Brey: None.