Oral administration of angiotensin-(1-7) ameliorates type 2 diabetes in rats.

UNLABELLED: Diabetes mellitus type 2 (DM2) is a disease with increasing importance in modern societies and insufficient treatment options. Pharmacological stimulation of insulin signaling, which is blunted in DM2, is a promising approach to treat this disease. It has been shown that activation of the angiotensin (Ang)-(1-7)/Mas axis of the renin-angiotensin system leads to an improved glucose uptake. In this study, we intended to evaluate, whether this effect could be exploited therapeutically. We first confirmed that Ang-(1-7) improves insulin signaling and glucose uptake in vitro in cultured cardiomyocytes. We then evaluated the therapeutic effect of a newly developed hydro-xypropyl-ß-cyclodextrin-based Ang-(1-7) nano-formulation in a novel transgenic rat model of inducible insulin resistance and DM2. The chronic administration of this compound prevented the marked elevation in blood glucose levels in these rats at a dose of 30 µg/kg, reversed the established hyperglycemic state at a dose of 100 µg/kg, and resulted in improved insulin sensitivity, reduced plasma insulin and decreased diabetic nephropathy. In conclusion, an oral Ang-(1-7) formulation reverses hyperglycemia and its consequences in an animal model of DM2 and represents a novel therapeutic option for the treatment of DM2 and other cardio-metabolic diseases. KEY MESSAGE: A novel rat model with inducible diabetes can be used to evaluate new therapies. Angiotensin-(1-7) is effective in an oral formulation packaged in cyclodextrine. Angiotensin-(1-7) is a promising antidiabetic drug.

Inducible transgenic rat model for diabetes mellitus based on shRNA-mediated gene knockdown.

The rat is an important animal model in biomedical research, but gene targeting technology is not established for this species. Therefore, we aimed to produce transgenic knockdown rats using shRNA technology and pronuclear microinjection. To this purpose, we employed a tetracycline-inducible shRNA expression system targeting the insulin receptor (IR). Doxycycline (DOX) treatment of the resulting transgenic rats led to a dose-dependent and reversible increase in blood glucose caused by ubiquitous inhibition of IR expression and signalling. We could neither detect an interferon response nor disturbances in microRNA processing after DOX treatment excluding toxic effects of shRNA expression. Low dose DOX treatment induced a chronic state of diabetes mellitus. In conclusion, we have developed a technology which allows the specific, inducible, and reversible suppression of any gene of interest in the rat. Our first transgenic rat line generated with this method represents an inducible model for diabetes mellitus.

Effect of tryptophan hydroxylase 1 deficiency on the development of hypoxia-induced pulmonary hypertension.

Tryptophan hydroxylase 1 catalyzes the rate-limiting step in the synthesis of serotonin in the periphery. Recently, it has been shown that expression of the tryptophan hydroxylase 1 gene is increased in lungs and pulmonary endothelial cells from patients with idiopathic pulmonary arterial hypertension. Here we investigated the effect of genetic deletion of tryptophan hydroxylase 1 on hypoxia-induced pulmonary arterial hypertension in mice by measuring pulmonary hemodynamics and pulmonary vascular remodeling before and after 2 weeks of hypoxia. In wild-type mice, hypoxia increased right ventricular pressure and pulmonary vascular remodeling. These effects of hypoxia were attenuated in the tryptophan hydroxylase 1-/-mice. Hypoxia increased right ventricular hypertrophy in both wild-type and tryptophan hydroxylase 1-/-mice suggesting that in vivo peripheral serotonin has a differential effect on the pulmonary vasculature and right ventricular hypertrophy. Contractile responses to serotonin were increased in pulmonary arteries from tryptophan hydroxylase 1-/-mice. Hypoxia increased serotonin-mediated contraction in vessels from the wild-type mice, but this was not further increased by hypoxia in the tryptophan hydroxylase 1-/-mice. In conclusion, these results indicate that tryptophan hydroxylase 1 and peripheral serotonin play an essential role in the development of hypoxia-induced elevations in pulmonary pressures and hypoxia-induced pulmonary vascular remodeling. In addition, the results suggest that, in mice, serotonin has differential effects on the pulmonary vasculature and right ventricular hypertrophy.