High-protein diet accelerates diabetes and kidney disease in the BTBRob/ob mouse.

There is a need for improved animal models that better translate to human kidney disease to predict outcome of pharmacological effects in the patient. The diabetic BTBRob/ob mouse model mimics key features of early diabetic nephropathy in humans, but with chronic injury limited to glomeruli. To explore if we could induce an accelerated and more advanced disease phenotype that closer translates to human disease, we challenged BTBRob/ob mice with a high-protein diet (HPD; 30%) and followed the progression of metabolic and renal changes up to 20 wk of age. Animals on the HPD showed enhanced metabolic derangements, evidenced by further increased levels of glucose, HbA1C, cholesterol, and alanine aminotransferase. The urinary albumin-to-creatinine ratio was markedly increased with a 53-fold change compared with lean controls, whereas BTBRob/ob mice on the standard diet only presented an 8-fold change. HPD resulted in more advanced mesangial expansion already at 14 wk of age compared with BTBRob/ob mice on the standard diet and also aggravated glomerular pathology as well as interstitial fibrosis. Gene expression analysis revealed that HPD triggered expression of markers of fibrosis and inflammation in the kidney and increased oxidative stress markers in urine. This study showed that HPD significantly aggravated renal injury in BTBRob/ob mice by further advancing albuminuria, glomerular, and tubulointerstitial pathology by 20 wk of age. This mouse model offers closer translation to humans and enables exploration of new end points for pharmacological efficacy studies that also holds promise to shorten study length.

Cardiac-Specific Overexpression of Oxytocin Receptor Leads to Cardiomyopathy in Mice.

BACKGROUND: Oxytocin (Oxt) and its receptor (Oxtr) gene system has been implicated in cardiomyogenesis and cardioprotection; however, effects of chronic activation of Oxtr are not known. We generated and investigated transgenic (TG) mice that overexpress Oxtr specifically in the heart. METHODS AND RESULTS: Cardiac-specific overexpression of Oxtr was obtained by having the α-major histocompatibility complex promoter drive the mouse Oxtr gene (α-Mhc-Oxtr). Left ventricular (LV) function and remodeling were assessed by magnetic resonance imaging and echocardiography. In α-Mhc-Oxtr TG mice, LV ejection fraction was severely compromised at 14 weeks of age compared with wild-type (WT) littermates (25 ± 6% vs 63 ± 3%; P < .001). LV end-diastolic volume was larger in the TG mice (103 ± 6 µL vs 67 ± 5 µL; P < .001). α-Mhc-Oxtr TG animals displayed cardiac fibrosis, atrial thrombus, and increased expression of pro-fibrogenic genes. Mortality of α-Mhc-Oxtr TG animals was 45% compared with 0% (P < .0001) of WT littermates by 20 weeks of age. Most cardiomyocytes of α-Mhc-Oxtr TG animals but not WT littermates (68.0 ± 12.1% vs 5.6 ± 2.4%; P = .008) were positive in staining for nuclear factor of activated T cells (NFAT). To study if thrombin inhibitor prevents thrombus formation, a cohort of 7-week-old α-Mhc-Oxtr TG mice were treated for 12 weeks with AZD0837, a potent thrombin inhibitor. Treatment with AZD0837 reduced thrombus formation (P < .05) and tended to attenuate fibrosis and increase survival. CONCLUSIONS: Cardiac-specific overexpression of Oxtr had negative consequences on LV function and survival in mice. The present findings necessitate further studies to investigate potential adverse effects of chronic Oxt administration. We provide a possible mechanism of Oxtr overexpression leading to heart failure by nuclear factor of activated T cell signaling. The recapitulation of human heart failure and the beneficial effects of the antithrombin inhibitor render the α-Mhc-Oxtr TG mice a promising tool in drug discovery for heart failure.

Dextran sulphate sodium induces acute colitis and alters hepatic function in hamsters.

Dextran sulphate sodium (DSS)-induced colitis in rodents is an experimental model for human inflammatory bowel disease (IBD). The aim of this study was to characterize the effect of DSS in hamster colon and liver. DSS (2-5%) was administrated in the drinking water for 4-6 days. Clinical symptoms were recorded daily, inflammatory and fatty acid-related metabolic markers were assessed in plasma, colon and liver. Six days of 3 or 5% DSS induced a severe wasting disease, whereas 2.5% DSS induced a colonic inflammation without severe systemic adverse effects. The systemic inflammatory response was characterized by an inverse production of albumin and the acute phase protein haptoglobin. The colonic inflammatory response was confined to the proximal colon, manifested by a high macroscopic inflammatory score, increased colon weight and expression of IL-1beta, IL-6 and iNOS, infiltration of inflammatory cells and epithelial disruption. In contrast, only a low/mild inflammatory response was observed in the distal colon of DSS-exposed hamsters. Significant hepatic-related metabolic alterations were also observed, with elevation of plasma triglycerides and increased liver expression of lipoprotein lipase and reduced expression of acyl-CoA oxidase and cytochrome P450A. Although liver weight was significantly reduced, no histopathological signs of inflammation or tissue damage were observed. In summary, hamsters exposed to 2.5% DSS for 6 days develop acute colitis resembling murine DSS-induced colitis. In addition, DSS-exposed hamster showed alterations in hepatic fatty acids metabolism resembling human IBD, suggesting that the model can potentially be used for target discovery and validation of hepatic-related metabolic alterations.

Role of ADAMTS-1 in atherosclerosis: remodeling of carotid artery, immunohistochemistry, and proteolysis of versican.

OBJECTIVE: We investigated the potential role of ADAMTS-1 (a disintegrin and metalloprotease with thrombospondin motif type I) in atherogenesis. METHODS AND RESULTS: ADAMTS-1 is expressed at the highest levels in the aorta when compared with other human tissues examined. Immunolocalization studies in human aorta and coronary artery indicate that ADAMTS-1 expression is mainly seen at low levels in the medial layer, but upregulated in the intima when plaque is present. We found that ADAMTS-1 mRNA levels are significantly higher in proliferating/migrating cultured primary aortic vascular smooth muscle cells (VSMCs) compared with resting/confluent cells. Using the mouse carotid artery flow cessation model, we show that there are differences in vessel remodeling in ADAMTS-1 transgenic/apoE-deficient mice compared with apoE deficiency alone, particularly a significant increase in intimal hyperplasia. We show that ADAMTS-1 can cleave the large versican containing proteoglycan population purified from cultured human aortic VSMCs. Finally, using versican peptide substrates, we show data suggesting that ADAMTS-1 cleaves versican at multiple sites. CONCLUSIONS: We hypothesize that ADAMTS-1 may promote atherogenesis by cleaving extracellular matrix proteins such as versican and promoting VSMC migration.