+61 7 3365 3098; fax +61 7 3365 1766.Running title: Chronic complications in the STZ rat Key words: Diabetes, echocardiography, electrophysiology, neuropathic pain, cataracts, retinopathy Short abstract:The chronic complications of diabetes in humans include cardiomyopathy, neuropathic pain, cataract development and retinopathy. The rat is the most commonly used model of human disease. This study has determined whether chronic diabetes induced by streptozotocin in rats mimics the complications associated with human diabetes. 1 Abstract:Background: Diabetes in humans induces chronic complications such as cardiovascular

Spinal deformity in the form of kyphosis or kyphoscoliosis occurs in most patients with Duchenne muscular dystrophy (DMD), a fatal X-linked disorder caused by an absence of the subsarcolemmal protein dystrophin. Mdx mice, which also lack dystrophin, show thoracolumbar kyphosis that progresses with age. We hypothesize that paraspinal and respiratory muscle weakness and fibrosis are associated with the progression of spinal deformity in this mouse model, and similar to DMD patients there is evidence of altered thoracic conformation and area. We measured kyphosis in mdx and age-matched control mice by monthly radiographs and the application of a novel radiographic index, the kyphotic index, similar to that used in boys with DMD. Kyphotic index became significantly less in mdx at 9 mo of age (3.58 +/- 0.12 compared with 4.27 +/- 0.04 in the control strain; P < or = 0.01), indicating more severe kyphosis, and remained less from 10 to 17 mo of age. Thoracic area in 17-mo-old mdx was reduced by 14% compared with control mice (P < or = 0.05). Peak tetanic tension was significantly lower in mdx and fell 47% in old mdx latissimus dorsi muscles, 44% in intercostal strips, and 73% in diaphragm strips (P < or = 0.05). Fibrosis of these muscles and the longissimus dorsi, measured by hydroxyproline analysis and histological grading of picrosirius red-stained sections, was greater in mdx (P < 0.05). We conclude that kyphotic index is a useful measure in mdx and other kyphotic mouse strains, and assessment of paralumbar and accessory respiratory muscles enhance understanding of spinal deformity in muscular dystrophy.

Nitric oxide (NO) is essential for normal function of the cardiovascular system. This study has determined whether chronic administration of l-arginine, the biological precursor of NO, attenuates the development of structural and functional changes in hearts and blood vessels of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Uninephrectomized rats treated with DOCA (25 mg every 4th day sc) and 1% NaCl in the drinking water for 4 wk were treated with l-arginine (5% in food, 3.4 ± 0.3 g·kg body wt−1·day−1). Changes in cardiovascular structure and function were determined by echocardiography, microelectrode studies, histology, and studies in isolated hearts and thoracic aortic rings. DOCA-salt hypertensive rats developed hypertension, left ventricular hypertrophy with increased left ventricular wall thickness and decreased ventricular internal diameter, increased inflammatory cell infiltration, increased ventricular interstitial and perivascular collagen deposition, increased passive diastolic stiffness, prolonged action potential duration, increased oxidative stress, and inability to increase purine efflux in response to an increased workload. l-Arginine markedly attenuated or prevented these changes and also normalized the reduced efficacy of norepinephrine and acetylcholine in isolated thoracic aortic rings of DOCA-salt hypertensive rats. This study suggests that a functional NO deficit in blood vessels and heart due to decreased NO synthase activity or increased release of reactive oxygen species such as superoxide may be a key change initiating many aspects of the cardiovascular impairment observed in DOCA-salt hypertensive rats. These changes can be prevented or attenuated by administration of l-arginine.

Cyclooxygenase and lipoxygenase metabolism of arachidonic acid produces compounds important in cardiovascular control. Further, arachidonic acid can be metabolised by cytochrome p450 to produce epoxyeicosatrienoic acids (EETs). These derivatives are inactivated by soluble epoxide hydrolase (sEH). The potential role of these EETs in hypertension and cardiac remodelling has been determined using the selective sEH inhibitor, N-adamantyl-N'-dodecylurea (ADU), in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Experiments were performed on male Wistar rats following uninephrectomy alone (UNX rats) or uninephrectomy with administration of DOCA (25 mg every fourth day subcutaneously) and 1% NaCl in drinking water (DOCA-salt rats). ADU (10 mg/kg/d subcutaneously) was administered for 2 wk starting 2 wk after surgery. Cardiovascular structure and function were determined using organ wet weights, histological analysis of collagen and inflammation, isolated heart and thoracic aortic ring preparations, and electrophysiological measurements. DOCA-salt hypertensive rats developed hypertension, hypertrophy, perivascular and interstitial fibrosis, endothelial dysfunction, and prolongation of the cardiac action potential duration within 4 wk. Administration of ADU prevented the further increase in systolic blood pressure and left-ventricular wet weight and normalized endothelial function. ADU treatment did not change inflammatory cell infiltration, collagen deposition, or cardiac action potential duration. EETs may be involved in the development of hypertension and endothelial dysfunction in DOCA-salt rats, but not in excessive collagen deposition or electrophysiological abnormalities.

The phytoalexin resveratrol (3,4',5-trihydroxy-trans-stilbene) may attenuate cardiovascular disease in man. This study has determined whether treatment with resveratrol (1 mg/kg/day orally) prevented cardiac fibrosis and the decreased cardiovascular function in the DOCA-salt hypertensive rat as a model of human hypertension. Uninephrectomised rats (UNX) administered DOCA (25mg every 4th day sc) and 1% NaCl in drinking water for 28 days developed cardiac and vascular remodelling. In these DOCA-salt rats, resveratrol decreased inflammatory cell infiltration, decreased cardiac fibrosis (left ventricular interstitial and perivascular collagen content) and improved cardiac and vascular function. Resveratrol attenuated other features of cardiovascular remodelling such as increases in systolic blood pressure, left ventricular wet weight, left ventricular wall thickness, diastolic stiffness constant, as well as decreased cardiac contractility and prolonged action potential duration characteristic of DOCA-salt rats. In summary, resveratrol, at a nutritionally relevant dose, prevents or attenuates the adverse changes in the cardiovascular system. We propose that the anti-inflammatory and anti-fibrotic effects of resveratrol are responsible, at least in part, for its amelioration in cardiovascular remodelling in DOCA-salt rats. These actions of resveratrol could play an important role in the protective effects on the human cardiovascular system reported for this constituent of red wine.