SGLT2 inhibition with empagliflozin improves coronary microvascular function and cardiac contractility in prediabetic ob/ob-/- mice.

BACKGROUND: Sodium-glucose cotransporter 2 inhibitors (SGLT2i) is the first class of anti-diabetes treatment that reduces mortality and risk for hospitalization due to heart failure. In clinical studies it has been shown that SGLT2i's promote a general shift to fasting state metabolism characterized by reduced body weight and blood glucose, increase in glucagon/insulin ratio and modest increase in blood ketone levels. Therefore, we investigated the connection between metabolic changes and cardiovascular function in the ob/ob-/- mice; a rodent model of early diabetes with specific focus on coronary microvascular function. Due to leptin deficiency these mice develop metabolic syndrome/diabetes and hepatic steatosis. They also develop cardiac contractile and microvascular dysfunction and are thus a promising model for translational studies of cardiometabolic diseases. We investigated whether this mouse model responded in a human-like manner to empagliflozin treatment in terms of metabolic parameters and tested the hypothesis that it could exert direct effects on coronary microvascular function and contractile performance. METHODS: Lean, ob/ob-/- untreated and ob/ob-/- treated with SGLT2i were followed for 10 weeks. Coronary flow velocity reserve (CFVR) and fractional area change (FAC) were monitored with non-invasive Doppler ultrasound imaging. Food intake, urinary glucose excursion and glucose control via HbA1c measurements were followed throughout the study. Liver steatosis was assessed by histology and metabolic parameters determined at the end of the study. RESULTS: Sodium-glucose cotransporter 2 inhibitors treatment of ob/ob-/- animals resulted in a switch to a more catabolic state as observed in clinical studies: blood cholesterol and HbA1c were decreased whereas glucagon/insulin ratio and ketone levels were increased. SGLT2i treatment reduced liver triglyceride, steatosis and alanine aminotransferase, an indicator for liver dysfunction. L-Arginine/ADMA ratio, a marker for endothelial function was increased. SGLT2i treatment improved both cardiac contractile function and coronary microvascular function as indicated by improvement of FAC and CFVR, respectively. CONCLUSIONS: Sodium-glucose cotransporter 2 inhibitors treatment of ob/ob-/- mice mimics major clinical findings regarding metabolism and cardiovascular improvements and is thus a useful translational model. We demonstrate that SGLT2 inhibition improves coronary microvascular function and contractile performance, two measures with strong predictive values in humans for CV outcome, alongside with the known metabolic changes in a preclinical model for prediabetes and heart failure.

l-α-Lysophosphatidylinositol (LPI) aggravates myocardial ischemia/reperfusion injury via a GPR55/ROCK-dependent pathway.

The phospholipid l-α-lysophosphatidylinositol (LPI), an endogenous ligand for GPR55, is elevated in patients with acute coronary syndrome, and a GPR55 antagonist cannabidiol (CBD) reduces experimental ischemia/reperfusion (I/R) injury. While LPI activates multiple signaling pathways, little is known about which ones are important in cardiomyocytes. In this study we explored whether activation of the Rho kinase/ROCK/p38 MAPK pathway is responsible for LPI-induced extension of I/R injury. Using a high-throughput screening method (dynamic mass redistribution; DMR), mouse- and human-induced pluripotent stem cell (iPSC) cardiomyocytes exposed to LPI were shown to exhibit a rapid, sustained, and concentration-dependent (1 nmol L-1-30 µmol L-1) cellular response. Y-27632 (ROCK inhibitor; 10 & 50 µmol L-1) and CBD (1 µmol L-1) both abolished the DMR response to LPI (10 µmol L-1). In murine iPSC cardiomyocytes, LPI-induced ROCK and p38 MAPK phosphorylation, both of which were prevented by Y-27632 and CBD, but did not induce JNK activation or cleavage of caspase-3. In hearts isolated from wild type (WT) mice subjected to 30 minutes global I/R, LPI (10 µmol L-1) administered via the coronary circulation increased infarct size when applied prior to ischemia onset, but not when given at the time of reperfusion. The exacerbation of tissue injury by LPI was not seen in hearts from GPR55-/- mice or in the presence of Y-27632, confirming that injury is mediated via the GPR55/ROCK/p38 MAPK pathway. These findings suggest that raised levels of LPI in the vicinity of a developing infarct may worsen the outcome of AMI.

The APOE∗3-Leiden Heterozygous Glucokinase Knockout Mouse as Novel Translational Disease Model for Type 2 Diabetes, Dyslipidemia, and Diabetic Atherosclerosis.

BACKGROUND: There is a lack of predictive preclinical animal models combining atherosclerosis and type 2 diabetes. APOE∗3-Leiden (E3L) mice are a well-established model for diet-induced hyperlipidemia and atherosclerosis, and glucokinase+/- (GK+/-) mice are a translatable disease model for glucose control in type 2 diabetes. The respective mice respond similarly to lipid-lowering and antidiabetic drugs as humans. The objective of this study was to evaluate/characterize the APOE∗3-Leiden.glucokinase+/- (E3L.GK+/-) mouse as a novel disease model to study the metabolic syndrome and diabetic complications. METHODS: Female E3L.GK+/-, E3L, and GK+/- mice were fed fat- and cholesterol-containing diets for 37 weeks, and plasma parameters were measured throughout. Development of diabetic macro- and microvascular complications was evaluated. RESULTS: Cholesterol and triglyceride levels were significantly elevated in E3L and E3L.GK+/- mice compared to GK+/- mice, whereas fasting glucose was significantly increased in E3L.GK+/- and GK+/- mice compared to E3L. Atherosclerotic lesion size was increased 2.2-fold in E3L.GK+/- mice as compared to E3L (p = 0.037), which was predicted by glucose exposure (R 2 = 0.636, p = 0.001). E3L and E3L.GK+/- mice developed NASH with severe inflammation and fibrosis which, however, was not altered by introduction of the defective GK phenotype, whereas mild kidney pathology with tubular vacuolization was present in all three phenotypes. CONCLUSIONS: We conclude that the E3L.GK+/- mouse is a promising novel diet-inducible disease model for investigation of the etiology and evaluation of drug treatment on diabetic atherosclerosis.

Role of secretory phospholipases in atherogenesis.

Elevated circulating levels of secretory phospholipase A(2) (sPLA(2)) are associated with atherosclerotic cardiovascular disease. sPLA(2) can contribute to atherogenesis by hydrolyzing phospholipids of circulating lipoproteins and lipoproteins entrapped in the arterial wall and/or in cells that reside in the intima and that participate in the inflammatory response to lipoprotein deposition. This article reviews differences and similarities between sPLA(2)-IIA, sPLA(2)-V, and sPLA(2)-X, all of which are members of this family of enzymes with reported potential proatherogenic features. Published data suggest that each of the enzymes has a distinct profile characterized by differences in tissue expression and localization, capacity to act on phospholipids of cell membranes and lipoproteins, and their interaction with arterial proteoglycans. In addition, the article discusses results from the authors' laboratory showing that diet-induced or gene-induced hyperlipidemia in mice enhances the expression of sPLA(2)-V in different tissues, but not sPLA(2)-IIA. Such differences indicate that these enzymes may have different roles in atherosclerotic cardiovascular disease through their distinct profiles.

In vivo inhibition of nuclear factor of activated T-cells leads to atherosclerotic plaque regression in IGF-II/LDLR-/-ApoB100/100 mice.

AIMS: Despite vast clinical experience linking diabetes and atherosclerosis, the molecular mechanisms leading to accelerated vascular damage are still unclear. Here, we investigated the effects of nuclear factor of activated T-cells inhibition on plaque burden in a novel mouse model of type 2 diabetes that better replicates human disease. METHODS & RESULTS: IGF-II/LDLR-/-ApoB100/100 mice were generated by crossbreeding low-density lipoprotein receptor-deficient mice that synthesize only apolipoprotein B100 (LDLR-/-ApoB100/100) with transgenic mice overexpressing insulin-like growth factor-II in pancreatic ß cells. Mice have mild hyperglycaemia and hyperinsulinaemia and develop complex atherosclerotic lesions. In vivo treatment with the nuclear factor of activated T-cells blocker A-285222 for 4 weeks reduced atherosclerotic plaque area and degree of stenosis in the brachiocephalic artery of IGF-II/LDLR-/-ApoB100/100 mice, as assessed non-invasively using ultrasound biomicroscopy prior and after treatment, and histologically after termination. Treatment had no impact on plaque composition (i.e. muscle, collagen, macrophages). The reduced plaque area could not be explained by effects of A-285222 on plasma glucose, insulin or lipids. Inhibition of nuclear factor of activated T-cells was associated with increased expression of atheroprotective NOX4 and of the anti-oxidant enzyme catalase in aortic vascular smooth muscle cells. CONCLUSION: Targeting the nuclear factor of activated T-cells signalling pathway may be an attractive approach for the treatment of diabetic macrovascular complications.

Hyperglycemia does not affect tissue repair responses in shear stress-induced atherosclerotic plaques in ApoE-/- mice.

The mechanisms responsible for macrovascular complications in diabetes remain to be fully understood. Recent studies have identified impaired vascular repair as a possible cause of plaque vulnerability in diabetes. This notion is supported by observations of a reduced content of fibrous proteins and smooth muscle cell mitogens in carotid endarterectomy from diabetic patients along with findings of decreased circulating levels of endothelial progenitor cells. In the present study we used a diabetic mouse model to characterize how hyperglycemia affects arterial repair responses. We induced atherosclerotic plaque formation in ApoE-deficient (ApoE-/-) and heterozygous glucokinase knockout ApoE-deficient mice (ApoE-/- GK+/-) mice with a shear stress-modifying cast. There were no differences in cholesterol or triglyceride levels between the ApoE-/- and ApoE-/- GK+/- mice. Hyperglycemia did not affect the size of the formed atherosclerotic plaques, and no effects were seen on activation of cell proliferation, smooth muscle cell content or on the expression and localization of collagen, elastin and several other extracellular matrix proteins. The present study demonstrates that hyperglycemia per se has no significant effects on tissue repair processes in injured mouse carotid arteries, suggesting that other mechanisms are involved in diabetic plaque vulnerability.

Inhibition of sodium/hydrogen exchanger 3 in the gastrointestinal tract by tenapanor reduces paracellular phosphate permeability.

Hyperphosphatemia is common in patients with chronic kidney disease and is increasingly associated with poor clinical outcomes. Current management of hyperphosphatemia with dietary restriction and oral phosphate binders often proves inadequate. Tenapanor, a minimally absorbed, small-molecule inhibitor of the sodium/hydrogen exchanger isoform 3 (NHE3), acts locally in the gastrointestinal tract to inhibit sodium absorption. Because tenapanor also reduces intestinal phosphate absorption, it may have potential as a therapy for hyperphosphatemia. We investigated the mechanism by which tenapanor reduces gastrointestinal phosphate uptake, using in vivo studies in rodents and translational experiments on human small intestinal stem cell-derived enteroid monolayers to model ion transport physiology. We found that tenapanor produces its effect by modulating tight junctions, which increases transepithelial electrical resistance (TEER) and reduces permeability to phosphate, reducing paracellular phosphate absorption. NHE3-deficient monolayers mimicked the phosphate phenotype of tenapanor treatment, and tenapanor did not affect TEER or phosphate flux in the absence of NHE3. Tenapanor also prevents active transcellular phosphate absorption compensation by decreasing the expression of NaPi2b, the major active intestinal phosphate transporter. In healthy human volunteers, tenapanor (15 mg, given twice daily for 4 days) increased stool phosphorus and decreased urinary phosphorus excretion. We determined that tenapanor reduces intestinal phosphate absorption predominantly through reduction of passive paracellular phosphate flux, an effect mediated exclusively via on-target NHE3 inhibition.

Distinctiveness of secretory phospholipase A2 group IIA and V suggesting unique roles in atherosclerosis.

Clinical observations strongly support an association of circulating levels of secretory phospholipases A(2) (sPLA(2)) in atherosclerotic cardiovascular disease (ACVD). Two modes of action can provide causal support for these statistical correlations. One is the action of the enzymes on circulating lipoproteins and the other is direct action on the lipoproteins once in the arterial extracellular intima. In this review we discuss results suggesting a distinct profile of characteristics related to localization, action on plasma lipoproteins and interaction with arterial proteoglycans for sPLA(2)-IIA and sPLA(2)-V. The differences observed indicate that these enzymes may contribute to atherosclerosis through dissimilar pathways. Furthermore, we comment on recent animal studies from our laboratory indicating that the expression of type V enzyme is up-regulated by genetically and nutritionally-induced dyslipidemias but not the group type IIA enzyme, which is well known to be up-regulated by acute inflammation. The results suggest that if similar up-regulation occurs in humans in response to hyperlipidemia, it may create a distinctive link between the group V enzyme and the disease.

Secretory phospholipase A2 group V: lesion distribution, activation by arterial proteoglycans, and induction in aorta by a Western diet.

OBJECTIVE: To study the distribution of group V secretory phospholipase A2 (sPLA2) in human and mouse lesions and compare its expression by human vascular cells, its activity toward lipoproteins, and the interaction with arterial proteoglycans (proteoglycans) with those of sPLA2-IIA. In addition, we also investigated the effect of a Western diet and lipopolysaccharide challenge on the aortic expression of these enzymes in mouse models. METHODS AND RESULTS: Immunohistochemistry showed sPLA2-V in human and mouse lesions to be associated with smooth muscle cells and also surrounding foam cells in lipid core areas. mRNA of the enzyme was expressed in human lesions and human vascular cells, supporting the immunohistochemistry data. sPLA2-V but not sPLA2-IIA was active on lipoproteins in human serum. The association with proteoglycans enhanced 2- to 3-fold sPLA2-V activity toward low-density lipoproteins but not that of the group IIA enzyme. Experiments in mouse models showed that treatment with a Western diet induced expression of sPLA2-V but not that of sPLA2-IIA in aorta. On the other hand, lipopolysaccharide-induced acute inflammation augmented the expression of sPLA2-IIA but not that of sPLA2-V. CONCLUSIONS: These results indicate that these phospholipases could have different roles in atherosclerosis.

Radial artery intima-media thickness regresses after secondary prevention interventions in patients' post-acute coronary syndrome and is associated with cardiac and kidney biomarkers.

BACKGROUND: Radial artery intima-media thickness (rIMT) measured by ultra-high-resolution ultrasound is associated with increased cardiovascular risk and predicts outcomes. We performed non-invasive high-resolution ultrasound of the radial artery to investigate vascular changes in subjects presenting with acute coronary syndrome (ACS) and who had undergone percutaneous coronary intervention (PCI). PURPOSE: In the present work, we aimed to follow rIMT change over time post-acute coronary syndrome as a tool to monitor potential response to intensified medical therapy. METHODS: We examined 256 subjects who underwent PCI due to ACS and healthy controls (n= 39) and we measured a number of biomarkers, which are known to be associated with cardiovascular disease. Images of radial artery were acquired bilaterally in the longitudinal view using a 50 MHz transducer (Vevo 2100 VisualSonics, Inc, Toronto, Ontario, Canada). Carotid IMT (cIMT) and rIMT were measured at <1 month after index PCI followed by a repeated measurement of rIMT at 4 months from the ACS in a sub-set (n=117). RESULTS: rIMT measured within 1 month post ACS was significantly higher than rIMT after 4 months from ACS, (p < 0.0001), mean ± SD (rIMT right 0.35 ± 0.08; rIMT left 0.37 ± 0.08) vs. (rIMT right 0.29 ± 0.08; rIMT left 0.31 ± 0.09) respectively. There was no statistically significant change in cIMT. In healthy controls there were no changes in rIMT or cIMT overtime. High levels of CX3CL1 and myeloperoxidase measured within one month post ACS are associated with increase of rIMT, r=0.38 (p< 0.0001) and r=0.41 (p< 0.0001) respectively. CONCLUSIONS: rIMT seem to decrease systemically after ACS and is accompanied with corresponding biomarker change. The cause and clinical implications of the observed decrement in rIMT after ACS need further studies.

The effects of dual PPARα/γ agonism compared with ACE inhibition in the BTBRob/ob mouse model of diabetes and diabetic nephropathy.

The leptin-deficient BTBRob/ob mouse develops progressive albuminuria and morphological lesions similar to human diabetic nephropathy (DN), although whether glomerular hyperfiltration, a recognized feature of early DN that may contribute to renal injury, also occurs in this model is not known. Leptin replacement has been shown to reverse the signs of renal injury in this model, but in contrast, the expected renoprotection by angiotensin-converting enzyme (ACE) inhibition in BTBRob/ob mice seems to be limited. Therefore, to investigate the potential renal benefits of improved metabolic control in this model, we studied the effect of treatment with the dual peroxisome proliferator-activated receptor (PPAR) α/γ agonist AZD6610 and compared it with the ACE inhibitor enalapril. AZD6610 lowered plasma glucose and triglyceride concentrations and increased liver size, but had no significant effect in reducing albuminuria, whereas enalapril did have an effect. Nephrin and WT1 mRNA expression decreased in the kidneys of BTBRob/ob mice, consistent with podocyte injury and loss, but was unaffected by either drug treatment: at the protein level, both nephrin and WT1-positive cells per glomerulus were decreased. Mesangial matrix expansion was reduced in AZD6610-treated mice. GFR, measured by creatinine clearance, was increased in BTBRob/ob mice, but unaffected by either treatment. Unexpectedly, enalapril-treated mice showed intrarenal arteriolar vascular remodeling with concentric thickening of vessel walls. In summary, we found that the BTBRob/ob mouse model shows some similarities to the early changes seen in human DN, but that ACE inhibition or PPARα/γ agonism afforded limited or no kidney protection.

Chronic stress induces rapid occlusion of angioplasty-injured rat carotid artery by activating neuropeptide Y and its Y1 receptors.

OBJECTIVE: We reported previously that neuropeptide Y (NPY) induces an atherosclerotic-like lesion that is significantly reduced by NPY-Y1 and NPY-Y5 receptor (R) inhibitors. Because antagonists also inhibit neointima induced by angioplasty alone, we now test whether stress-induced endogenous NPY release mimic these changes. METHODS AND RESULTS: Rats were nonstressed or stressed (4 degrees C water; 2 hours per day for 14 days) starting immediately before and continuing after carotid artery angioplasty. Stress acutely and chronically increased blood pressure and doubled plasma NPY levels. After 14 days, angioplasty-induced neointima was markedly greater in stressed (than nonstressed) rats, in which most of the vessels became occluded with an atherosclerotic-like lesion containing macrophages, lipids, thrombus, and microvessels that was similar but more inflammatory than the injury in the NPY-treated vessels. Fourteen days after angioplasty combined with stress or NPY, Y1R and Y5R (mRNA and protein) became upregulated in areas of neointima, microvessels, and macrophages in injured carotid arteries. Stress- and NPY-induced changes were completely prevented by a selective Y1R antagonist (0.02 micromol/kg per minute for 14 days), whereas neointima induced by angioplasty alone was reduced by 60%. CONCLUSIONS: Because of sympathetic NPY release, stress may be a less-than-appreciated risk factor for restenosis/atherosclerosis, and Y1R antagonists a potential therapy for these conditions.

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.

Hyperglycemia Induced by Glucokinase Deficiency Accelerates Atherosclerosis Development and Impairs Lesion Regression in Combined Heterozygous Glucokinase and the Apolipoprotein E-Knockout Mice.

Aim. Models combining diabetes and atherosclerosis are important in evaluating the cardiovascular (CV) effects and safety of antidiabetes drugs in the development of treatments targeting CV complications. Our aim was to evaluate if crossing the heterozygous glucokinase knockout mouse (GK+/-) and hyperlipidemic mouse deficient in apolipoprotein E (ApoE-/-) will generate a disease model exhibiting a diabetic and macrovascular phenotype. Methods. The effects of defective glucokinase on the glucose metabolism and on the progression and regression of atherosclerosis on high-fat diets were studied in both genders of GK+/-ApoE-/- and ApoE-/- mice. Coronary vascular function of the female GK+/-ApoE-/- and ApoE-/- mice was also investigated. Results. GK+/-ApoE-/- mice show a stable hyperglycemia which was increased on Western diet. In oral glucose tolerance test, GK+/-ApoE-/- mice showed significant glucose intolerance and impaired glucose-stimulated insulin secretion. Plasma lipids were comparable with ApoE-/- mice; nevertheless the GK+/-ApoE-/- mice showed slightly increased atherosclerosis development. Conclusions. The GK+/-ApoE-/- mice showed a stable and reproducible hyperglycemia, accelerated atherosclerotic lesion progression, and no lesion regression after lipid lowering. This novel model provides a promising tool for drug discovery, enabling the evaluation of compound effects against both diabetic and cardiovascular endpoints simultaneously in one animal model.

Confocal scanning laser microscopy measurements of atherosclerotic lesions in mice aorta. A fast evaluation method for volume determinations.

Atherosclerotic lesion size in mice is routinely evaluated by morphometrical measurements on serial sections in order to obtain volume measurements. The technique of confocal scanning laser microscopy (CSLM) makes it possible to optically scan and thereby evaluate a tissue sample. We here describe a method for measuring lesion volume in ApoE/LDLr deficient mice at 20 and 30 weeks of age using the non-destructive procedure of CSLM. Whole mount preparations of opened aorta with the lumen side facing the cover slip were analysed under 10x magnification in a CSLM (Leica). The autofluorescence of the elastic fibres of the lamina interna as opposed to the non-fluorescing lesion was used to define the bottom and top of the lesion during scanning. Ten to forty images were collected 2.4 microm apart, depending on the size of the lesion, and the stack of images was then analysed using Imaris (Bitplane). After the CSLM evaluation, the aortas were de-mounted, embedded in paraffin, sectioned, stained in hematoxylin and eosin and the volume re-evaluated with conventional morphometry. Statistical evaluation showed that the results obtained with CSLM and the results of morphometry were positively correlated. Area measurements of the plaques using en face preparations of aorta showed that the plaque area was generally larger at the left side and a significant increase of plaque area along the length of the thoracic aorta. Our results showed that atherosclerotic lesions in mice can be quantitatively evaluated by CSLM.

Hypoxia increases LDL oxidation and expression of 15-lipoxygenase-2 in human macrophages.

OBJECTIVE: Macrophage-mediated oxidation of low-density lipoprotein (LDL) by enzymes, such as the lipoxygenases, is considered of major importance for the formation of oxidized LDL during atherogenesis. Macrophages have been identified in hypoxic areas in atherosclerotic plaques. METHODS AND RESULTS: To investigate the role of hypoxia in macrophage-mediated LDL oxidation, we incubated human monocyte-derived macrophages with LDL under normoxic (21% O2) or hypoxic (0% O2) conditions. The results showed that hypoxic macrophages oxidized LDL to a significantly higher extent than normoxic cells. Interestingly, the mRNA and protein expression of 15-lipoxygenase-2 (15-LOX-2) as well as the activity of this enzyme are elevated in macrophages incubated at hypoxia. Both the unspliced 15-LOX-2 and the spliced variant 15-LOX-2sv-a are found in macrophages. In addition, 15-LOX-2 was identified in carotid plaques in some macrophage-rich areas but was only expressed at low levels in nondiseased arteries. CONCLUSIONS: In summary, these observations show for the first time that 15-LOX-2 is expressed in hypoxic macrophages and in atherosclerotic plaques and suggest that 15-LOX-2 may be one of the factors involved in macrophage-mediated LDL oxidation at hypoxia.

Impaired Coronary and Renal Vascular Function in Spontaneously Type 2 Diabetic Leptin-Deficient Mice.

BACKGROUND: Type 2 diabetes is associated with macro- and microvascular complications in man. Microvascular dysfunction affects both cardiac and renal function and is now recognized as a main driver of cardiovascular mortality and morbidity. However, progression of microvascular dysfunction in experimental models is often obscured by macrovascular pathology and consequently demanding to study. The obese type 2 diabetic leptin-deficient (ob/ob) mouse lacks macrovascular complications, i.e. occlusive atherosclerotic disease, and may therefore be a potential model for microvascular dysfunction. The present study aimed to test the hypothesis that these mice with an insulin resistant phenotype might display microvascular dysfunction in both coronary and renal vascular beds. METHODS AND RESULTS: In this study we used non-invasive Doppler ultrasound imaging to characterize microvascular dysfunction during the progression of diabetes in ob/ob mice. Impaired coronary flow velocity reserve was observed in the ob/ob mice at 16 and 21 weeks of age compared to lean controls. In addition, renal resistivity index as well as pulsatility index was higher in the ob/ob mice at 21 weeks compared to lean controls. Moreover, plasma L-arginine was lower in ob/ob mice, while asymmetric dimethylarginine was unaltered. Furthermore, a decrease in renal vascular density was observed in the ob/ob mice. CONCLUSION: In parallel to previously described metabolic disturbances, the leptin-deficient ob/ob mice also display cardiac and renal microvascular dysfunction. This model may therefore be suitable for translational, mechanistic and interventional studies to improve the understanding of microvascular complications in type 2 diabetes.

Animal models of diabetic macrovascular complications: key players in the development of new therapeutic approaches.

Diabetes mellitus is a lifelong, incapacitating metabolic disease associated with chronic macrovascular complications (coronary heart disease, stroke, and peripheral vascular disease) and microvascular disorders leading to damage of the kidneys (nephropathy) and eyes (retinopathy). Based on the current trends, the rising prevalence of diabetes worldwide will lead to increased cardiovascular morbidity and mortality. Therefore, novel means to prevent and treat these complications are needed. Under the auspices of the IMI (Innovative Medicines Initiative), the SUMMIT (SUrrogate markers for Micro- and Macrovascular hard end points for Innovative diabetes Tools) consortium is working on the development of novel animal models that better replicate vascular complications of diabetes and on the characterization of the available models. In the past years, with the high level of genomic information available and more advanced molecular tools, a very large number of models has been created. Selecting the right model for a specific study is not a trivial task and will have an impact on the study results and their interpretation. This review gathers information on the available experimental animal models of diabetic macrovascular complications and evaluates their pros and cons for research purposes as well as for drug development.

Distribution of neuropeptide Y Y1 and Y2 receptors in the postmortem human heart.

In the present study, we present for the first time the presence and distribution of neuropeptide Y (NPY) receptors Y1 and Y2 in the human postmortem heart using specific antibodies raised against extracellular parts of the receptors. A more intensive staining against the Y2 than against the Y1 receptors was detected on both atrial and ventricular cardiomyocytes. Immunoreactivity against both receptors was identified on both conducting fibers and cardiac nerves. More vessels stained positively for the Y2 than for the Y1 receptor, but the Y1 receptors were more abundant in subendocardial than subepicardial vessels of the left ventricular wall.

The establishment of a network of European human research tissue banks.

This is a report of a workshop held on the establishment of human research tissue banking which was held in Levi, Finland 21-24 March 2002. There were 21 participants from 7 European countries. This meeting was attended by representatives from academia, research tissue banks and from the Biotech and Pharmaceutical Industries. The principal aim of the workshop was to find a way to progress the recommendations from ECVAM workshop 44 (ATLA 29, 125-134, 2001) and ECVAM workshop 32 (ATLA 26, 763-777, 1998). The workshop represented the first unofficial meeting of the European Network of Research Tissue Banks (ENRTB) steering group. It is expected that in the period preceding the next workshop the ENRTB steering group will co-ordinate the ethical, legislative and organisational aspects of research tissue banking. Key issues dealt with by the Levi workshop included the practical aspects of sharing expertise and experiences across the different European members. Such collaboration between research tissue banks and end users of such material seeks to ultimately enable shared access to human tissue for medical and pharmaco-toxicological research while maintaining strict adherence to differences in legal and ethical aspects related to the use of human tissue in individual countries.