The caveolin-1 regulated protein follistatin protects against diabetic kidney disease.

Glomerular matrix protein accumulation, mediated largely by mesangial cells, is central to the pathogenesis of diabetic kidney disease. Our previous studies showed that the membrane microdomains caveolae and their marker protein caveolin-1 regulate matrix protein synthesis in mesangial cells in response to diabetogenic stimuli, and that caveolin-1 knockout mice are protected against diabetic kidney disease. In a screen to identify the molecular mechanism underlying this protection, we also established that secreted antifibrotic glycoprotein follistatin is significantly upregulated by caveolin-1 deletion. Follistatin potently neutralizes activins, members of the transforming growth factor-ß superfamily. A role for activins in diabetic kidney disease has not yet been established. Therefore, in vitro, we confirmed the regulation of follistatin by caveolin-1 in primary mesangial cells and showed that follistatin controls both basal and glucose-induced matrix production through activin inhibition. In vivo, we found activin A upregulation by immunohistochemistry in both mouse and human diabetic kidney disease. Importantly, administration of follistatin to type 1 diabetic Akita mice attenuated early diabetic kidney disease, characterized by albuminuria, hyperfiltration, basement membrane thickening, loss of endothelial glycocalyx and podocyte nephrin, and glomerular matrix accumulation. Thus, activin A is an important mediator of high glucose-induced profibrotic responses in mesangial cells, and follistatin may be a potential novel therapy for the prevention of diabetic kidney disease.

N-3 polyunsaturated fatty acid supplementation does not reduce vulnerability to atrial fibrillation in remodeling atria.

BACKGROUND: Prophylactic supplementation with omega-3 polyunsaturated fatty acids (PUFAs) reduce vulnerability to atrial fibrillation (AF). The effect of PUFAs given after cardiac injury has occurred is unknown. OBJECTIVE: To investigate using a model of pacing-induced cardiac injury, the time course of development of injury and whether it was altered by postinjury PUFAs. METHODS: Sixty-five dogs were randomized to undergo simultaneous atrial and ventricular pacing (SAVP, 220 beats/min) for 0, 2, 7, or 14 days. Twenty-two dogs received PUFAs (850 mg/d) either prophylactically or after some pacing had occurred (postinjury). Electrophysiologic and echocardiographic measurements were taken at baseline and sacrifice. Atrial tissue samples were collected at sacrifice for histologic and molecular analyses. RESULTS: With no PUFAs, the inducibility of AF increased with pacing duration (P < .001). Postinjury PUFAs (started after 7 days of pacing) did not reduce the inducibility of AF after 14 days of pacing (9.3% ± 8.8% no PUFAs vs 9.7% ± 9.9% postinjury PUFAs; P = .91). Atrial myocyte size and fibrosis increased with pacing duration (P < .05). Postinjury PUFAs did not significantly attenuate the cell size increase after 14 days of pacing (no PUFAs 38% ± 30% vs postinjury PUFAs 19% ± 28%; P = .11). Similarly, postinjury PUFAs did not attenuate the increase in fibrosis after 14 days of pacing (no PUFAs 66% ± 51% vs postinjury PUFAs 63% ± 76%; P = .90). CONCLUSION: PUFA supplementation begun after cardiac injury has already occurred does not reduce atrial structural remodeling or vulnerability to AF.