Aims/hypothesis High plasma copeptin, a marker of vasopressin (VP) secretion, has been shown to be associated with the metabolic syndrome and development of type 2 diabetes in humans. The present study was designed to determine the long-term influence of plasma VP concentration in a rodent model prone to metabolic dysfunction. Methods Obese Zucker rats and their lean counterparts were submitted for 4 weeks to one of three protocols inducing different levels of VP. Circulating VP was either reduced by increasing the daily water intake (low-VP), or increased by a chronic i.p. infusion of VP (high-VP). The control rats had normal VP levels that depended on their own regulation of water intake and VP secretion.Results Compared with controls with normal VP, lean rats with high-VP had a higher fasting glycaemia after 4 weeks. In obese rats, high-VP promoted hyperinsulinaemia, glucose intolerance, assessed by glucose and insulin tolerance tests, and an impaired response to a pyruvate challenge. Conversely, treatment with a selective arginine vasopressin receptor 1A (V1aR) antagonist reduced glucose intolerance. Low-VP obese rats had unchanged glucose tolerance but exhibited a drastic decrease in liver steatosis compared with control obese rats, associated with low hepatic triacylglycerol and cholesterol content, and reduced expression of hepatic lipogenic genes. These effects were independent of changes in body adiposity, and plasma sodium and osmolality did not differ among groups.Electronic supplementary material The online version of this article

OBJECTIVEPlasma copeptin, a surrogate for vasopressin, was associated with albuminuria in population-based studies. These associations are consistent with the effect of vasopressin on albuminuria observed in humans and rodents. The objective of this study was to determine whether plasma copeptin is an independent marker of risk of renal events in people with type 2 diabetes and albuminuria.RESEARCH DESIGN AND METHODSWe studied 3,101 participants of the DIABHYCAR trial (6-year follow-up) with type 2 diabetes and albuminuria. A renal event was defined as doubling of serum creatinine or development of end-stage renal disease.RESULTSDuring follow-up, 86 renal events occurred in 76 subjects (2.45%). Incidences by tertiles of baseline plasma copeptin were 1.06% (T1), 1.45% (T2), and 4.84% (T3). They were 2.43% (T1), 5.11% (T2), and 11.81% (T3) for the subset of subjects with macroalbuminuria at baseline (n = 729). Hazard ratio for plasma copeptin tertiles as a risk for renal events was 4.79 (95% CI, 2.48–9.24; P < 0.0001; for T3 vs. T1). In a stepwise regression analysis, urinary albumin excretion and plasma copeptin remained positively associated and HDL cholesterol and estimated glomerular filtration rate were inversely associated with the incidence of renal events. These independent predictors explained ∼18% of the variance of the outcome. The yearly variations of estimated glomerular filtration rate by copeptin tertiles were −1.43 ± 0.51 (T1), −2.29 ± 0.49 (T2), and −3.52 ± 0.44 mL/min/1.73 m2 per year (T3) (P = 0.005) in subjects with macroalbuminuria.CONCLUSIONSPlasma copeptin may help to identify subjects with diabetic chronic kidney disease who are at high risk for renal function decline.

Recent epidemiological studies have revealed novel relationships between low water intake or high vasopressin (AVP) and the risk of hyperglycemia and diabetes. AVP V and V receptors (R) are expressed in the liver and pancreatic islets, respectively. The present study was designed to determine the impact of different levels of circulating AVP on glucose homeostasis in normal Sprague-Dawley rats, as well as the respective roles of VR and VR. We showed that acute injection of AVP induces a dose-dependent increase in glycemia. Pretreatment with a selective VR antagonist, but not a VR antagonist, dose-dependently prevented the rise in glycemia. VR antagonism did not modify the hyperinsulinemic response, resulting from AVP-induced hyperglycemia, but enhanced the fall in glucagonemia. Acute administration of selective VR or VR agonists confirmed the involvement of VR in the hyperglycemic effect of AVP. In chronic experiments, AVP levels were altered in both directions. Sustained AVP infusion through implantable minipumps induced a time-dependent increase in fasting glycemia, whereas lowering endogenous AVP by increasing water intake had no effect. After 4 wk of AVP infusion, the rise in glycemia amounted to 1.1 mmol/l ( < 0.01) without significant change in insulinemia. This effect was attenuated by cotreatment with a VR antagonist. Similar results were observed in lean Zucker rats. These findings demonstrate for the first time a causal link between chronic high AVP and hyperglycemia through VR activation and, thus, provide a pathophysiological explanation for the relationship observed in human cohorts between the AVP-hydration axis and the risk of diabetes.

Apelin is a bioactive peptide identified as the endogenous ligand of the human orphan G protein-coupled receptor APJ in 1998. The present data show that apelin modulates the activity of magnocellular and parvocellular oxytocin (OXY) neurons in the lactating rat. A combination of in situ hybridization and immunohistochemistry demonstrated the presence of apelin receptor mRNA in hypothalamic OXY neurons. Double immunofluorescence labeling then revealed the colocalization of apelin with OXY in about 20% of the hypothalamic OXY-positive neurons. Intracerebroventricular apelin administration inhibited the activity of magnocellular and parvocellular OXY neurons, as shown by measuring the c-fos expression in OXY neurons or by direct electrophysiological measurements of the electrical activity of these neurons. This effect was correlated with a decrease in the amount of milk ejected. Thus, apelin inhibits the activity of OXY neurons through a direct action on apelin receptors expressed by these neurons in an autocrine and paracrine manner. In conclusion, these findings highlight the inhibitory role of apelin as an autocrine/paracrine peptide acting on OXY neurons during breastfeeding.

Methods: Male obese diabetic db/db mice were treated for 12 weeks with a selective V2R antagonist (SR121463) and compared to non-treated db/db and non-diabetic db/m mice. All animals were previously uninephrectomized.Results: The V2R antagonist did not alter glycaemia or glycosuria in db/db mice. It induced a two-fold increase in urine output and a 52% decrease in urine osmolality compared to nontreated db/db mice. After four weeks of treatment urinary albumin to creatinine ratio was 50% lower in treated mice compared to non-treated mice, and remained significantly lower until end of experiment. Glomerular filtration rate increased significantly over time in non-treated db/db mice but remained stable in treated mice.Conclusions: This study shows that vasopressin contributes to albuminuria and glomerular hyperfiltration via V2R in a mouse model of type 2 diabetes. It documents causality behind the association of vasopressin with renal disease observed in diabetic patients.

Impaired skin wound healing is a major medical problem in diabetic subjects. Kinins exert a number of vascular and other actions limiting organ damage in ischaemia or diabetes, but their role in skin injury is unknown. We investigated, through pharmacological manipulation of bradykinin B1 and B2 receptors (B1R and B2R respectively), the role of kinins in wound healing in non-diabetic and diabetic mice. Using two mouse models of diabetes (streptozotocin-induced and db/db mice) and non-diabetic mice, we assessed the effect of kinin receptor activation or inhibition by subtype-selective pharmacological agonists (B1R and B2R) and antagonist (B2R) on healing of experimental skin wounds. We also studied effects of agonists and antagonist on keratinocytes and fibroblasts in vitro. Levels of Bdkrb1 (encoding B1R) and Bdkrb2 (encoding B2R) mRNAs increased 1-2-fold in healthy and wounded diabetic skin compared with in non-diabetic skin. Diabetes delayed wound healing. The B1R agonist had no effect on wound healing. In contrast, the B2R agonist impaired wound repair in both non-diabetic and diabetic mice, inducing skin disorganization and epidermis thickening. In vitro, B2R activation unbalanced fibroblast/keratinocyte proliferation and increased keratinocyte migration. These effects were abolished by co-administration of B2R antagonist. Interestingly, in the two mouse models of diabetes, the B2R antagonist administered alone normalized wound healing. This effect was associated with the induction of Ccl2 (encoding monocyte chemoattractant protein 1)/Tnf (encoding tumour necrosis factor α) mRNAs. Thus stimulation of kinin B2 receptor impairs skin wound healing in mice. B2R activation occurs in the diabetic skin and delays wound healing. B2R blockade improves skin wound healing in diabetic mice and is a potential therapeutic approach to diabetic ulcers.

Tissue kallikrein (TK) is synthesized in arteries and distal renal tubule, the main target of aldosterone. Urinary kallikrein excretion increases in hyperaldosteronism. We tested the hypothesis that TK is involved in the cardiovascular and renal effects of high aldosterone. Kallikrein-deficient mice (TK-/-), and wild-type (WT) littermates, studied on two different genetic backgrounds, were treated with aldosterone and high-NaCl diet for 1 month. Control mice received vehicle and standard NaCl diet. Treatment induced 5- to 7-fold increase in plasma aldosterone, suppressed renin secretion, and increased urinary TK activity. In 129SvJ-C57BL/6J mice, blood pressure monitored by radiotelemetry was not different between control TK-/- and WT mice. In TK-/- mice, aldosterone induced larger increases in blood pressure than in WT mice (+47 vs. +27 mm Hg; genotype-treatment interaction, P < 0.05). Night-day difference was also exacerbated in treated TK-/- mice (P < 0.01). Moderate cardiac septal hypertrophy was observed in hypertensive animals without major change in heart function. Aldosterone-salt increased kidney weight similarly in both genotypes but induced a 2-fold increase in renal mRNA abundance of epithelial sodium channel subunits only in TK-/- mice. The hypertensive effect of TK deficiency was also documented in treated C57BL/6J mice. In this strain, aldosterone-induced hypertension was only observed in TK-/- mice (+16 mm Hg, P < 0.01). These findings show that TK deficiency exacerbates aldosterone-salt-induced hypertension. This effect may be due at least in part to enhanced sodium reabsorption in the distal nephron aggravating sodium retention. The study suggests that kallikrein plays an antihypertensive role in hyperaldosteronism.

Activation of the kallikrein-kinin system enhances cardiac and renal tolerance to ischemia. Here we investigated the effects of selective agonists of kinin B1 or B2 receptor (R) in brain ischemiareperfusion in diabetic and non-diabetic mice. The role of endogenous kinins was assessed in tissue kallikrein deficient mice (TK −/− ). Mice underwent 60min-middle cerebral artery occlusion (MCAO), eight weeks after type 1-diabetes induction. Treatment with B1R-, B2R-agonist or saline was started at reperfusion. Neurological deficit (ND), infarct size (IS), brain water content (BWC) were measured at day 0, 1 and 2 after injury. MCAO induced exaggerated ND, mortality and IS in diabetic mice. B2R-agonist increased ND and mortality to 60% and 80% in non-diabetic and diabetic mice respectively, by mechanisms involving hemodynamic failure and renal insufficiency. TK −/− mice displayed reduced ND and IS compared to wild-type littermate, consistent with suppression of B2R activity. B1R mRNA level increased in ischemic brain but B1R-agonist had no effect on ND, mortality or IS in non-diabetic mice. In contrast, in diabetic mice, B1R-agonist tested at two doses significantly reduced ND by 42-52% and IS by 66-71%, without effect on BWC or renal function. This suggests potential therapeutic interest of B1R agonism for cerebral protection in diabetes. Acute brain ischemia secondary to cerebral artery occlusion is a major cause of mortality or permanent disability. Risk of ischemic stroke is increased in diabetic patients and prognosis is poorer 1, 2 . Cerebral artery occlusion causes acute (minutes to hours) and delayed (hours to days or weeks) injury cascades, both implicating multiple pathogenic factors like thrombosis, neuron stunning or necrosis, brain oedema and inflammation 3, 4 . The complexity of mechanisms involved in brain damage explains in part that there is still no clinically effective neuroprotective treatment besides revascularization. The kallikrein-kinin system (KKS) is implicated in physiological vasodilatation, exerts antithrombotic and profibrinolytic actions and reduces oxidative stress in different organs [5][6][7][8] . KKS protects against cardiac and renal damage in the setting of acute ischemia secondary to arterial occlusion. Inhibition of KKS aggravates cardiac and renal ischemic lesions while activation of kinin receptors enhances cardiac tolerance to ischemia and reperfusion [9][10][11][12] . Kinins are generated by proteolytic cleavage of protein precursors, kininogens, by tissue kallikrein (TK) and are mainly inactivated in the circulation by the angiotensin I-converting enzyme (ACE/kininase II) 5 . Kinins, activate two receptor subtypes: B1 (B1R) and B2 (B2R). All components of KKS have been identified in brain tissue from rodents and humans 3, 13-18 . B1R gene expression is low in the brain under normal condition, but it is upregulated by inflammation and ischemia 19,20 . By contrast, B2R is constitutively present in different brain structures and in cerebral arteries and microvessels 18,21 .Role o...