Zugl.: Bonn, Univ., Diss., 2008

Tübingen, Univ., Diss., 2005.

Dresden, Techn. Univ., Diss., 2005.

Bonn, Universiẗat, Diss., 2008.

University, Diss., 2002--Köln.

Zugl.: Giessen, Univ., Diss., 2009

The occurrence of a functional intracellular renin-angiotensin system (RAS) has emerged as a new paradigm. Recently, we and others demonstrated intracellular synthesis of ANG II in cardiac myocytes and vascular smooth muscle cells that was dramatically stimulated in high glucose conditions. Cardiac fibroblasts significantly contribute to diabetes-induced diastolic dysfunction. The objective of the present study was to determine the existence of the intracellular RAS in cardiac fibroblasts and its role in extracellular matrix deposition. Neonatal rat ventricular fibroblasts were serum starved and exposed to isoproterenol or high glucose in the absence or presence of candesartan, which was used to prevent receptor-mediated uptake of ANG II. Under these conditions, an increase in ANG II levels in the cell lysate represented intracellular synthesis. Both isoproterenol and high glucose significantly increased intracellular ANG II levels. Confocal microscopy revealed perinuclear and nuclear distribution of intracellular ANG II. Consistent with intracellular synthesis, Western analysis showed increased intracellular levels of renin following stimulation with isoproterenol and high glucose. ANG II synthesis was catalyzed by renin and angiotensin-converting enzyme (ACE), but not chymase, as determined using specific inhibitors. High glucose resulted in increased transforming growth factor-β and collagen-1 synthesis by cardiac fibroblasts that was partially inhibited by candesartan but completely prevented by renin and ACE inhibitors. In conclusion, cardiac fibroblasts contain a functional intracellular RAS that participates in extracellular matrix formation in high glucose conditions, an observation that may be helpful in developing an appropriate therapeutic strategy in diabetic conditions.

No description available.

No description available.

Visceral adipose tissue (AT) mass increases risk for cardiovascular disease and diabetes. Glucocorticoids (GCs) cause preferential expansion of visceral compared to subcutaneous AT through poorly understood mechanisms. GCs are necessary for adipogenesis, the differentiation of adipose stem cells (ASCs) to mature adipocytes. However, this process may be impaired in visceral depots. Insufficient adipogenesis can lead to excessive hypertrophy of existing adipocytes. This hypertrophic expansion increases cell death and inflammation, driving AT dysfunction. To better understand the genes and pathways by which high GCs cause preferential expansion of visceral fat we performed transcriptomic profiling (microarray) on paired samples of visceral (Omental, Om) and abdominal subcutaneous (Abdsc) AT explants cultured with the GC receptor agonist, dexamethasone (Dex), for 7 days. Gene set enrichment analysis showed the transforming growth factor beta (TGFβ) signaling pathway, most notably the secreted anti-adipogenic factors, TGFβ and activin A, was highly enriched in Om and suppressed less by Dex. We hypothesized that Om AT and ASCs secrete factors that inhibit adipogenesis in an autocrine/paracrine manner. Conditioned media (CM) from Om tissue and ASCs suppressed differentiation by 70-80% compared to control; Dex attenuated this anti-adipogenic effect. Both TGFβ and activin A levels were 4-5 fold higher in CM from Om compared to Abdsc ASCs. Both factors signal via cell surface receptors that increase SMAD2 phosphorylation (P-SMAD2), basal levels of which were 3-4 fold higher in Om ASCs. Additionally, CM from Om ASCs increased P-SMAD2. siRNA mediated knockdown of activin A improved differentiation of Om ASCs, but did not reach levels observed in Abdsc. Blocking TGFβ and activin A signaling using SB431542 robustly increased adipogenesis of Om ASCs and prevented the anti-adipogenic effect of CM. GCs decreased production of TGFβ and activin A, but both remained higher in OmCM. Overnight Dex treatment decreased P-SMAD2 and increased the expression of the TGFβ co-receptor, TGFBR3, which decreases TGFβ signaling, in Abdsc ASCs. GCs failed to decrease P-SMAD2 and increased TGFBR3 in Om ASCs only at high concentrations. Taken together, these data implicate GC-TGFβ crosstalk as a determinant of depot differences in adipogenic capacity and hypertrophic vs. healthy hyperplastic expansion of AT. / 2019-11-01T00:00:00Z