Increasing Endoglin Deletion in Endothelial Cells Exacerbates the Severity of Brain Arteriovenous Malformation in Mouse.

Endoglin (ENG) mutation causes type 1 hereditary hemorrhagic telangiectasia (HHT1). HHT1 patients have arteriovenous malformations (AVMs) in multiple organs, including the brain. In mice, Eng deletion induced by R26RCreER or SM22αCre leads to AVM development in the brain and other organs. We hypothesized that an increase in Eng- negative ECs will enhance AVM severity. To increase EC Eng deletion, we used a codon-improved cre (icre), which is more potent in recombination of the floxed alleles than the wild-type (WT) cre. R26RCreER;Engf/f mice that have a Rosa promoter driving and tamoxifen (TM)-inducible WT cre expression globally, and PdgfbiCreER;Engf/f mice that have a Pdgfb promoter driving and TM-inducible icre expression in ECs were treated with three intra-peritoneal injections of TM (2.5 mg/25 g of body weight) to delete Eng globally or in the ECs. AAV-VEGF was stereotactically injected into the brain to induce brain focal angiogenesis and brain AVM. We found that icre caused more Eng deletion in the brain, indicated by a lower level of Eng proteins (p < 0.001) and fewer Eng-positive ECs (p = 0.01) than mice with WT cre. Mice with icre-mediated Eng deletion have more abnormal vessels (p = 0.02), CD68+ macrophages (p = 0.002), and hemorrhage (p = 0.04) and less vascular pericyte and smooth muscle coverage than mice with WT cre. In addition, arteriovenous shunts were detected in the intestines of icre mice, a phenotype that has not been detected in WT cre mice before. RNA-seq analysis showed that 8 out of the 10 top upregulated pathways identified by gene ontology (GO) analysis are related to inflammation. Therefore, the increase in Eng deletion in ECs exacerbates AVM severity, which is associated with enhanced inflammation. Strategies that can reduce Eng-negative ECs could be used to develop new therapies to reduce AVM severity for HHT1 patients

Potentiation of Acetylcholine-Induced Relaxation of Aorta in Male UC Davis Type 2 Diabetes Mellitus (UCD-T2DM) Rats: Sex-Specific Responses

Previous reports suggest that diabetes may differentially affect the vascular beds of females and males. The objectives of this study were to examine whether there were (1) sex differences in aortic function and (2) alterations in the relative contribution of endothelium-derived relaxing factors in modulating aortic reactivity in UC Davis Type 2 Diabetes Mellitus (UCD-T2DM) rats. Endothelium-dependent vasorelaxation (EDV) in response to acetylcholine (ACh) was measured in aortic rings before and after exposure to pharmacological inhibitors. Relaxation responses to sodium nitroprusside were assessed in endothelium-denuded rings. Moreover, contractile responses to phenylephrine (PE) were measured before and after incubation of aortic rings with a nitric oxide synthase (NOS) inhibitor in the presence of indomethacin. Metabolic parameters and expression of molecules associated with vascular and insulin signaling as well as reactive oxygen species generation were determined. Diabetes slightly but significantly impaired EDV in response to ACh in aortas from females but potentiated the relaxation response in males. The potentiation of EDV in diabetic male aortas was accompanied by a traces of nitric oxide (NO)- and prostanoid-independent relaxation and elevated aortic expression of small- and intermediate conductance Ca2+-activated K+ channels in this group. The smooth muscle sensitivity to NO was not altered, whereas the responsiveness to PE was significantly enhanced in aortas of diabetic groups in both sexes. Endothelium-derived NO during smooth muscle contraction, as assessed by the potentiation of the response to PE after NOS inhibition, was reduced in aortas of diabetic rats regardless of sex. Accordingly, decreases in pAkt and peNOS were observed in aortas from diabetic rats in both sexes compared with controls. Our data suggest that a decrease in insulin sensitivity via pAkt-peNOS-dependent signaling and an increase in oxidative stress may contribute to the elevated contractile responses observed in diabetic aortas in both sexes. This study demonstrates that aortic function in UCD-T2DM rats is altered in both sexes. Here, we provide the first evidence of sexual dimorphism in aortic relaxation in UCD-T2DM rats

Type of supplemented simple sugar, not merely calorie intake, determines adverse effects on metabolism and aortic function in female rats.

High consumption of simple sugars causes adverse cardiometabolic effects. We investigated the mechanisms underlying the metabolic and vascular effects of glucose or fructose intake and determined whether these effects are exclusively related to increased calorie consumption. Female Sprague-Dawley rats were supplemented with 20% wt/vol glucose or fructose for 2 mo, and plasma analytes and aortic response to vasodilator and vasoconstrictor agents were determined. Expression of molecules associated with lipid metabolism, insulin signaling, and vascular response were evaluated in hepatic and/or aortic tissues. Caloric intake was increased in both sugar-supplemented groups vs. control and in glucose- vs. fructose-supplemented rats. Hepatic lipogenesis was induced in both groups. Plasma triglycerides were increased only in the fructose group, together with decreased expression of carnitine palmitoyltransferase-1A and increased microsomal triglyceride transfer protein expression in the liver. Plasma adiponectin and peroxisome proliferator-activated receptor (PPAR)-α expression was increased only by glucose supplementation. Insulin signaling in liver and aorta was impaired in both sugar-supplemented groups, but the effect was more pronounced in the fructose group. Fructose supplementation attenuated aortic relaxation response to a nitric oxide (NO) donor, whereas glucose potentiated it. Phenylephrine-induced maximal contractions were reduced in the glucose group, which could be related to increased endothelial NO synthase (eNOS) phosphorylation and subsequent elevated basal NO in the glucose group. In conclusion, despite higher caloric intake in glucose-supplemented rats, fructose caused worse metabolic and vascular responses. This may be because of the elevated adiponectin level and the subsequent enhancement of PPARα and eNOS phosphorylation in glucose-supplemented rats

The Effects of Dietary Sugar Intake and Type 2 Diabetes on Mesenteric Arterial Function in Rats

This study was designed to investigate the effects of dietary intake of sugars as well as type 2 diabetes (T2D) on mesenteric arterial function in rats with respect to sex. To test the effects of simple sugars, Sprague-Dawley female rats were supplemented with 20% w/v glucose or fructose in drinking water for 8 weeks. To study the effects of T2D and sex, two diabetic rat models were used- Zucker Diabetic Fatty (ZDF) (an established monogenic model of T2D) and UC Davis Type 2 Diabetes Mellitus (UCD-T2DM, (a novel and validated polygenic model of T2D). The plasma analytes for metabolic parameters and mesenteric arterial responses to vasodilator and vasoconstrictor agents were determined. The expression of molecules associated with vascular response (eg. endothelial nitric oxide (NO) synthase (eNOS) and small conductance calcium-dependent potassium channels (SKCa)) were also evaluated in mesenteric arterial tissues. The main objectives of the study were whether 1) the mesenteric arterial function was impaired in sugar-supplemented and diabetic rats, 2) sex differences exist in the development of abnormal vascular responses, and 3) there were changes in the relative contributions of endothelium-derived relaxing factors (EDRFs) in modulating vascular reactivity of mesenteric arteries (MA). In the study of examining the effects of sugar supplementation, we demonstrated that only fructose intake causes hypertriglyceridemia and increases in body and liver weight in female rats. Our data also showed that the endothelium-dependent vasodilation (EDV) was impaired in MA of animals supplemented with fructose but not glucose. In the study of assessing the effect of diabetes, EDV was impaired in MA from both models of diabetes compared to controls, regardless of sex. In female ZDF, the relative importance of endothelium-derived hyperpolarizing factor (EDHF, a major EDRF) was reduced along with a decrease in SKca mRNA expression, while importance of NO as well as eNOS mRNA expressions were increased in MA of this experimental group. In MA of male ZDF, however, the role of NO was reduced. Furthermore, vascular smooth muscle sensitivity to NO was increased in ZDF rats, regardless of sex. In UCD-T2DM model, MA of female diabetic rats showed a greater impairment of EDV compared to that in pre-diabetic and male diabetic rats as well as a reduction in eNOS mRNA expression compared to their male counterparts. Diabetes also significantly increased sensitivity of MA to contractile agents in females compared to males and pre-diabetic females. Finally, the relative importance of EDHF to vascular regulation was lost in pre-diabetic and diabetic rats, regardless of sex. Accordingly, the mRNA expression of SKca was decreased in MA of both pre-diabetic and diabetic male and female rats. In conclusion, this study suggests that the type of sugar supplementation determines adverse metabolic and vascular changes in female rats. Furthermore, the 9 effects of type 2 diabetes on MA are sex- and rat model- specific. Finally, we showed a greater predisposition of MA to vascular injury in diabetic female UCD-T2DM rats

Risk factors for hemorrhage of brain arteriovenous malformation.

Patients with brain arteriovenous malformation (bAVM) are at risk of intracranial hemorrhage (ICH). Overall, bAVM accounts for 25% of hemorrhagic strokes in adults <50 years of age. The treatment of unruptured bAVMs has become controversial, because the natural history of these patients may be less morbid than invasive therapies. Available treatments include observation, surgical resection, endovascular embolization, stereotactic radiosurgery, or combination thereof. Knowing the risk factors for bAVM hemorrhage is crucial for selecting appropriate therapeutic strategies. In this review, we discussed several biological risk factors, which may contribute to bAVM hemorrhage

Sexual dimorphism in aortic endothelial function of Zucker diabetic fatty rats: Possible involvement of superoxide production

Little is known about the interaction between diabetes and sex in vasculature. This study was designed to investigate whether there were sex differences in rat aortic endothelium-dependent vasodilation (EDV) in Zucker diabetic fatty (ZDF) rats, and the potential role of superoxide. EDV to acetylcholine (ACh) was measured in aortic rings pre-contracted with phenylephrine before and after pretreatment with apocynin (100 ?M), a NADPH oxidase (Nox) inhibitor. In addition, the level of Nox (a potent source of superoxide) and PKC? mRNA expression were determined using real-time RT-PCR. ACh-induced relaxations were significantly greater in female lean rats compared with male lean rats. Accordingly, male lean rats had higher PKC?I expression level than female lean rats. Diabetes significantly impaired EDV in aortic rings from female ZDF rats, however, potentiated the relaxation in males. Pre-incubation of aortic rings with apocynin increased EDV only in diabetic female group, suggesting impairment of EDV in female ZDF aorta was partly due to an increase in the activity of superoxide. Accordingly, the levels of Nox1, Nox4, and PKC? mRNA expression were substantially enhanced in aorta of female ZDF rats compared to those in lean animals. These data suggest that an elevation of superoxide may partially contribute to the predisposition of the female aorta to injury in type 2 diabetes. Grant Funding Source: NIH/NIDCR

Sex-based alteration of relative importance of EDRFs in modulating vascular reactivity in Zucker diabetic fatty rats

Little is known about interaction of sex and diabetes in vasculature. Our study investigates the effects of type 2 diabetes on endothelium-dependent and -independent relaxations. Also, if there are sex-based changes in relative contributions of endothelium derived relaxing factors (EDRFs) in modulating vascular reactivity of mesenteric arteries (MA) from ZDF rats. Relaxation responses to acetylcholine (ACh) in MA pre-contracted with phenylephrine (PE) were obtained before and after pretreatment with indomethacin (cyclooxygenase inhibitor), L-NAME (nitric oxide synthase inhibitor) or barium chloride (Kir blocker) plus ouabain (Na+-K+-ATPase inhibitor). Vascular responses to sodium nitroprusside (SNP) were also measured in MA. ACh-induced relaxations were significantly impaired in MA of diabetic rats, regardless of sex. In diabetic females, the relative importance of endothelium derived hyperpolarizing factor (EDHF) in relaxation to ACh was reduced, while in diabetic males, role of nitric oxide (NO) was reduced. Interestingly, relaxation to SNP was enhanced in diabetic animals, irrespective of sex. In summary, the relative importance of NO and EDHF in regulating vascular tone of rat MA is altered in type 2 diabetes with respect to sex. Furthermore, increased smooth muscle sensitivity to NO may be an attempt to compensate for impaired endothelial function in both diabetic male and female rats. Grant Funding Source: Supported by NIDCR