Losartan and metabolite EXP3179 activate endothelial function without lowering blood pressure in AT2 receptor KO mice.

BACKGROUND: We have documented profound release of nitric oxide (NO) and endothelium-derived hyperpolarization factor (EDHF) by angiotensin II (ANGII) receptor 1 (AT1) blocker (ARB) losartan and its unique metabolite EXP3179, a pleiotropic effect that may help rationalize the protective properties of ARBs. Since blood pressure (BP) lowering by ARBs likely require an ANGII-dependent switch from AT1 to ANGII receptor 2 (AT2) signaling, a receptor known to stimulate endothelial NO release, we investigated the contribution of AT1 and AT2 to losartan and EXP3179's endothelial function-activating properties. EXPERIMENTAL APPROACH: Two AT1 ligands were used in an attempt to block the AT1-dependent endothelium-enhancing effects of EXP3179. AT2-null mice were used to evaluate the acute ex vivo and chronic in vivo effects of EXP3179 (20µM) and losartan (0.6 g/l), respectively, on endothelial function, BP and aortic stiffness. KEY RESULTS: Ex vivo blockade of AT1 receptors did not attenuate EXP3179's effects on NO and EDHF-dependent endothelial function activation. We observed significant reductions in PE-induced contractility with EXP3179 in both WT and AT2 knockout (KO) aortic rings. In vivo, a 1-month chronic treatment with losartan did not affect pulse wave velocity (PWV) but decreased PE-induced contraction by 74.9 % in WT (p < 0.0001) and 47.3 % in AT2 KO (p < 0.05). Presence of AT2 was critical to losartan's BP lowering activity. CONCLUSION: In contrast to BP lowering, the endothelial function-enhancing effects of losartan and EXP3179 are mostly independent of the classic ANGII/AT1/AT2 pathway, which sheds light on ARB pleiotropism.

Apelin prevents diabetes-induced poor collateral vessel formation and blood flow reperfusion in ischemic limb.

Introduction: Peripheral arterial disease (PAD) is a major risk factor for lower-extremity amputation in diabetic patients. Unfortunately, previous clinical studies investigating therapeutic angiogenesis using the vascular endothelial growth factor (VEGF) have shown disappointing results in diabetic patients, which evokes the necessity for novel therapeutic agents. The apelinergic system (APJ receptor/apelin) is highly upregulated under hypoxic condition and acts as an activator of angiogenesis. Apelin treatment improves revascularization in nondiabetic models of ischemia, however, its role on angiogenesis in diabetic conditions remains poorly investigated. This study explored the impact of Pyr-apelin-13 in endothelial cell function and diabetic mouse model of hindlimb ischemia. Methods: Nondiabetic and diabetic mice underwent femoral artery ligation to induce limb ischemia. Diabetic mice were implanted subcutaneously with osmotic pumps delivering Pyr-apelin-13 for 28 days. Blood flow reperfusion was measured for 4 weeks post-surgery and exercise willingness was assessed with voluntary wheels. In vitro, bovine aortic endothelial cells (BAECs) were exposed to normal (NG) or high glucose (HG) levels and hypoxia. Cell migration, proliferation and tube formation assays were performed following either VEGF or Pyr-apelin-13 stimulation. Results and Discussion: Following limb ischemia, blood flow reperfusion, functional recovery of the limb and vascular density were improved in diabetic mice receiving Pyr-apelin-13 compared to untreated diabetic mice. In cultured BAECs, exposure to HG concentrations and hypoxia reduced VEGF proangiogenic actions, whereas apelin proangiogenic effects remained unaltered. Pyr-apelin-13 induced its proangiogenic actions through Akt/AMPK/eNOS and RhoA/ROCK signaling pathways under both NG or HG concentrations and hypoxia exposure. Our results identified the apelinergic system as a potential therapeutic target for angiogenic therapy in diabetic patients with PAD.

Deletion of protein tyrosine phosphatase SHP-1 restores SUMOylation of podocin and reverses the progression of diabetic kidney disease.

Both clinical and experimental data suggest that podocyte injury is involved in the onset and progression of diabetic kidney disease (DKD). Although the mechanisms underlying the development of podocyte loss are not completely understood, critical structural proteins such as podocin play a major role in podocyte survival and function. We have reported that the protein tyrosine phosphatase SHP-1 expression increased in podocytes of diabetic mice and glomeruli of patients with diabetes. However, the in vivo contribution of SHP-1 in podocytes is unknown. Conditional podocyte-specific SHP-1-deficient mice (Podo-SHP-1-/-) were generated to evaluate the impact of SHP-1 deletion at four weeks of age (early) prior to the onset of diabetes and after 20 weeks (late) of diabetes (DM; Ins2+/C96Y) on kidney function (albuminuria and glomerular filtration rate) and kidney pathology. Ablation of the SHP-1 gene specifically in podocytes prevented and even reversed the elevated albumin/creatinine ratio, glomerular filtration rate progression, mesangial cell expansion, glomerular hypertrophy, glomerular basement membrane thickening and podocyte foot process effacement induced by diabetes. Moreover, podocyte-specific deletion of SHP-1 at an early and late stage prevented diabetes-induced expression of collagen IV, fibronectin, transforming growth factor-ß, transforming protein RhoA, and serine/threonine kinase ROCK1, whereas it restored nephrin, podocin and cation channel TRPC6 expression. Mass spectrometry analysis revealed that SHP-1 reduced SUMO2 post-translational modification of podocin while podocyte-specific deletion of SHP-1 preserved slit diaphragm protein complexes in the diabetic context. Thus, our data uncovered a new role of SHP-1 in the regulation of cytoskeleton dynamics and slit diaphragm protein expression/stability, and its inhibition preserved podocyte function preventing DKD progression.

Tungsten toxicity on kidney tubular epithelial cells induces renal inflammation and M1-macrophage polarization.

Tungsten is widely used in medical, industrial, and military applications. The environmental exposure to tungsten has increased over the past several years, and few studies have addressed its potential toxicity. In this study, we evaluated the effects of chronic oral tungsten exposure (100 ppm) on renal inflammation in male mice. We found that 30- or 90-day tungsten exposure led to the accumulation of LAMP1-positive lysosomes in renal tubular epithelial cells. In addition, the kidneys of mice exposed to tungsten showed interstitial infiltration of leukocytes, myeloid cells, and macrophages together with increased levels of proinflammatory cytokines and p50/p65-NFkB subunits. In proximal tubule epithelial cells (HK-2) in vitro, tungsten induced a similar inflammatory status characterized by increased mRNA levels of CSF1, IL34, CXCL2, and CXCL10 and NFkB activation. Moreover, tungsten exposure reduced HK-2 cell viability and enhanced reactive oxygen species generation. Conditioned media from HK-2 cells treated with tungsten induced an M1-proinflammatory polarization of RAW macrophages as evidenced by increased levels of iNOS and interleukin-6 and decreased levels of the M2-antiinflammatory marker CD206. These effects were not observed when RAW cells were exposed to conditioned media from HK-2 cells treated with tungsten and supplemented with the antioxidant N-acetylcysteine (NAC). Similarly, direct tungsten exposure induced M1-proinflammatory polarization of RAW cells that was prevented by NAC co-treatment. Altogether, our data suggest that prolonged tungsten exposure leads to oxidative injury in the kidney ultimately leading to chronic renal inflammation characterized by a proinflammatory status in kidney tubular epithelial cells and immune cell infiltration.

Enhanced SHP-1 Expression in Podocyturia Is Associated with Kidney Dysfunction in Patients with Diabetes.

Background: Diabetic kidney disease (DKD) remains the leading cause of end stage kidney disease worldwide. Despite significant advances in kidney care, there is a need to improve noninvasive techniques to predict the progression of kidney disease better for patients with diabetes. After injury, podocytes are shed in urine and may be used as a biologic tool. We previously reported that SHP-1 is upregulated in the kidney of diabetic mice, leading to podocyte dysfunction and loss. Our objective was to evaluate the expression levels of SHP-1 in urinary podocytes and kidney tissues of patients with diabetes. Methods: In this prospective study, patients with and without diabetes were recruited for the quantification of SHP-1 in kidney tissues, urinary podocytes, and peripheral blood monocytes. Immunochemistry and mass spectrometry techniques were applied for kidney tissues. Urinary podocytes were counted, and expression of SHP-1 and podocyte markers were measured by quantitative PCR. Results: A total of 66 participants (diabetic n=48, nondiabetic n=18) were included in the analyses. Diabetes was associated with increased SHP-1 expression in kidney tissues (P=0.03). Nephrin and podocin mRNA was not significantly increased in urinary podocytes from patients with diabetes compared with those without diabetes, whereas levels of SHP-1 mRNA expression significantly correlated with HbA1c and estimated glomerular filtration rate (eGFR). Additionally, follow-up (up to 2 years post recruitment) evaluation indicated that SHP-1 mRNA expression continued to increase with eGFR decline. Conclusions: Levels of SHP-1 in urinary podocytes may serve as an additional marker of glomerular disease progression in this population.

Reduction of DUSP4 contributes to podocytes oxidative stress, insulin resistance and diabetic nephropathy.

Podocytes are insulin-sensitive cells, and their loss is critical in diabetic nephropathy (DN) progression that could lead to end-stage kidney disease. We have previously shown that decreased DUSP4 expression caused elevated JNK phosphorylation in the diabetic kidney and worsened DN characteristics. Yet, the role of DUSP4 in diabetic podocyte insulin resistance and the progression of DN remains unclear. Here, we report that HG-exposed podocytes exhibited reduced DUSP4 expression, increased phosphorylation of JNK and serine 307 of IRS1 as well as Nox4 expression, while decreasing insulin signaling actions. DUSP4 overexpression, JNK and Nox1/4 inhibition prevented HG-induced serine 307 phosphorylation of IRS1 and restored insulin actions. Diabetic mice showed renal dysfunction and insulin resistance, characteristics that were exacerbated in diabetic DUSP4 deficient mice due to Nox1/4 upregulation. Thus, our results demonstrated that diabetes-induced reduction of DUSP4 leads to JNK activation and elevated Nox4 expression, which contributes to podocyte dysfunction, insulin resistance and progression of DN.

Transcriptomic modulation in response to high-intensity interval training in monocytes of older women with type 2 diabetes.

PURPOSE: Type 2 diabetes is associated with a higher risk of cardiovascular diseases, lowering the quality of life and increasing mortality rates of affected individuals. Circulating monocytes are tightly involved in the atherosclerosis process leading to cardiovascular diseases (CVD), and their inflammatory profile can be modified by exercise. The objective was to exploratory identify genes associated with CVD that could be regulated by high-intensity interval training (HIIT) in monocytes of type 2 diabetes patients. METHODS: Next-generation RNA sequencing (RNA-seq) analyses were conducted on isolated circulating monocytes (CD14+) of six women aged 60 and over with type 2 diabetes who completed a 12-week supervised HIIT intervention on a treadmill. RESULTS: Following the intervention, a reduction of resting diastolic blood pressure was observed. Concomitant with this result, 56 genes were found to be downregulated following HIIT intervention in isolated monocytes. A large proportion of the regulated genes was involved in cellular adhesion, migration and differentiation into an "atherosclerosis-specific" macrophage phenotype. CONCLUSION: The downregulation of transcripts in monocytes globally suggests a favorable cardiovascular effect of the HIIT in older women with type 2 diabetes. In the context of precision medicine and personalized exercise prescription, shedding light on the fundamental mechanisms underlying HIIT effects on the gene profile of immune cells is essential to develop efficient nonpharmacological strategies to prevent CVD in high-risk population.

Foraging costs drive within-colony spatial segregation in shearwaters from two contrasting environments in the North Atlantic Ocean.

Foraging spatial segregation is frequent in central-place foragers during the breeding season, but very few studies have investigated foraging spatial segregation between adjacent sub-colonies. Here, we assessed for within-colony differences in the at-sea distribution, habitat use, trophic ecology and chick growth data of two Calonectris colonies differing in size, and breeding in two different environments in the North Atlantic Ocean. For this, we GPS tracked 52 Cory's shearwaters (Calonectris borealis) breeding in 2 small sub-colonies at Berlenga Island (Portugal) and 59 Cape Verde shearwaters (Calonectris edwardsii) breeding in 2 sub-colonies differing greatly in size at Raso Islet (Cabo Verde), over 2 consecutive breeding seasons (2017-2018), during chick-rearing. Cory's shearwaters from the two sub-colonies at Berlenga Island broadly overlapped in repeatedly used foraging patches close to the colony. In contrast, the foraging distribution of Cape Verde shearwaters was partially segregated in the colony surroundings, but overlapped at distant foraging areas off the west coast of Africa. Despite spatial segregation close to the colony, Cape Verde shearwaters from both sub-colonies departed in similar directions, foraged in similar habitats and exhibited mostly short trips within the archipelago of Cabo Verde. These results, corroborated with similar trophic ecology and chick growth rates between sub-colonies, support the idea that foraging spatial segregation in the colony surroundings was not likely driven by interference competition or directional bias. We suggest that high-quality prey patches are able to shape travel costs and foraging distribution of central-place foragers from neighbouring sub-colonies.

Diabetes Impaired Ischemia-Induced PDGF (Platelet-Derived Growth Factor) Signaling Actions and Vessel Formation Through the Activation of Scr Homology 2-Containing Phosphatase-1.

Objective: Critical limb ischemia is a major complication of diabetes characterized by insufficient collateral vessel development and proper growth factor signaling unresponsiveness. Although mainly deactivated by hypoxia, phosphatases are important players in the deregulation of proangiogenetic pathways. Previously, SHP-1 (Scr homology 2-containing phosphatase-1) was found to be associated with the downregulation of growth factor actions in the diabetic muscle. Thus, we aimed to gain further understanding of the impact of SHP-1 on smooth muscle cell (SMC) function under hypoxic and diabetic conditions. Approach and Results: Despite being inactivated under hypoxic conditions, high glucose level exposure sustained SHP-1 phosphatase activity in SMC and increased its interaction with PDGFR (platelet-derived growth factor receptor)-ß, thus reducing PDGF proangiogenic actions. Overexpression of an inactive form of SHP-1 fully restored PDGF-induced proliferation, migration, and signaling pathways in SMC exposed to high glucose and hypoxia. Nondiabetic and diabetic mice with deletion of SHP-1 specifically in SMC were generated. Ligation of the femoral artery was performed, and blood flow was measured for 4 weeks. Blood flow reperfusion, vascular density and maturation, and limb survival were all improved while vascular apoptosis was attenuated in diabetic SMC-specific SHP-1 null mice as compared to diabetic mice. Conclusions: Diabetes and high glucose level exposure maintained SHP-1 activity preventing hypoxia-induced PDGF actions in SMC. Specific deletion of SHP-1 in SMC partially restored blood flow reperfusion in the diabetic ischemic limb. Therefore, local modulation of SHP-1 activity in SMC could represent a potential therapeutic avenue to improve the proangiogenic properties of SMC under ischemia and diabetes.

Year-round at-sea distribution and trophic resources partitioning between two sympatric Sulids in the tropical Atlantic.

In the oligotrophic tropical marine environment resources are usually more patchily distributed and less abundant to top predators. Thus, spatial and trophic competition can emerge, especially between related seabird species belonging to the same ecological guild. Here we studied the foraging ecology of two sympatric species-brown booby (BRBO) Sula leucogaster (breeding) and red-footed boobies (RFBO) Sula sula (non-breeding)-at Raso islet (Cabo Verde), across different seasons. Sexual segregation was only observed during Jun-Oct, when RFBO were present, with larger females BRBO remaining closer to the colonies, while males and RFBO travelled further and exploited different habitats. Overall, species appeared to prefer areas with specific oceanic features, particularly those related with oceanic currents and responsible for enhancing primary productivity in tropical oceanic areas (e.g. Sea Surface Height and Ocean Mixed Layer Thickness). Female BRBOs showed high foraging-site fidelity during the period of sympatry, while exploiting the same prey species as the other birds. However, during the months of co-existence (Jun.-Oct.), isotopic mixing models suggested that female BRBO would consume a higher proportion of epipelagic fish, whereas female RFBO would consume more squid compared to the other birds, possibly due to habitat-specific prey availability and breeding energy-constraints for BRBO. We conclude that divergent parental roles, environmental conditions, habitat preference and competition could be mechanisms simultaneously underlying sexual segregation for BRBO during a period of co-existence, while inter-specific foraging differences appear to be more affected by habitat preference and different breeding stages. These results support previous statements that BRBO can adapt their foraging ecology to different circumstances of environmental conditions and competition, and that marine physical features play an important role in foraging decisions of boobies.

Fish oil replacement prevents, while docosahexaenoic acid-derived protectin DX mitigates end-stage-renal-disease in atherosclerotic diabetic mice.

Diabetic nephropathy (DN) remains the major cause of end-stage renal disease (ESRD). We used high-fat/high-sucrose (HFHS)-fed LDLr-/- /ApoB100/100 mice with transgenic overexpression of IGFII in pancreatic ß-cells (LRKOB100/IGFII) as a model of ESRD to test whether dietary long chain omega-3 polyunsaturated fatty acids LCω3FA-rich fish oil (FO) could prevent ESRD development. We further evaluated the potential of docosahexaenoic acid (DHA)-derived pro-resolving lipid mediators, 17-hydroxy-DHA (17-HDHA) and Protectin DX (PDX), to reverse established ESRD damage. HFHS-fed vehicle-treated LRKOB100/IGFII mice developed severe kidney dysfunction leading to ESRD, as revealed by advanced glomerular fibrosis and mesangial expansion along with reduced percent survival. The kidney failure outcome was associated with cardiac dysfunction, revealed by reduced heart rate and prolonged diastolic and systolic time. Dietary FO prevented kidney damage, lean mass loss, cardiac dysfunction, and death. 17-HDHA reduced podocyte foot process effacement while PDX treatment alleviated kidney fibrosis and mesangial expansion as compared to vehicle treatment. Only PDX therapy was effective at preserving the heart function and survival rate. These results show that dietary LCω3FA intake can prevent ESRD and cardiac dysfunction in LRKOB100/IGFII diabetic mice. Our data further reveals that PDX can protect against renal failure and cardiac dysfunction, offering a potential new therapeutic strategy against ESRD.

Endothelial deletion of PKCδ prevents VEGF inhibition and restores blood flow reperfusion in diabetic ischemic limb.

AIMS: Peripheral artery disease is a complication of diabetes leading to critical hindlimb ischemia. Diabetes-induced inhibition of VEGF actions is associated with the activation of protein kinase Cδ (PKCδ). We aim to specifically investigate the role of PKCδ in endothelial cell (EC) function and VEGF signaling. METHODS: Nondiabetic and diabetic mice, with (ec-Prkcd-/-) or without (ec-Prkcdf/f) endothelial deletion of PKCδ, underwent femoral artery ligation. Blood flow reperfusion was assessed up to 4 weeks post-surgery. Capillary density, EC apoptosis and VEGF signaling were evaluated in the ischemic muscle. Src homology region 2 domain-containing phosphatase-1 (SHP-1) phosphatase activity was assessed in vitro using primary ECs. RESULTS: Ischemic muscle of diabetic ec-Prkcdf/f mice exhibited reduced blood flow reperfusion and capillary density while apoptosis increased as compared to nondiabetic ec-Prkcdf/f mice. In contrast, blood flow reperfusion and capillary density were significantly improved in diabetic ec-Prkcd-/- mice. VEGF signaling pathway was restored in diabetic ec-Prkcd-/- mice. The deletion of PKCδ in ECs prevented diabetes-induced VEGF unresponsiveness through a reduction of SHP-1 phosphatase activity. CONCLUSIONS: Our data provide new highlights in mechanisms by which PKCδ activation in EC contributed to poor collateral vessel formation, thus, offering novel therapeutic targets to improve angiogenesis in the diabetic limb.

Saturated fatty acids induce insulin resistance in podocytes through inhibition of IRS1 via activation of both IKKß and mTORC1.

Diabetic nephropathy (DN), a microvascular complication of diabetes, is the leading cause of end-stage renal disease worldwide. Multiple studies have shown that podocyte dysfunction is a central event in the progression of the disease. Beside chronic hyperglycemia, dyslipidemia can induce insulin resistance and dysfunction in podocytes. However, the exact mechanisms of free fatty acid (FFA)-induced podocyte insulin unresponsiveness are poorly understood. We used a type 2 diabetic mouse model (db/db) and mouse podocytes exposed to palmitic acid for 24 h followed by an insulin stimulation. Renal function and pathology were evaluated at 25 weeks of age to confirm the DN development. Our results demonstrate that saturated FFA activated the serine/threonine kinases IκB kinase (IKK)ß/IκBα and mTORC1/S6K1, but not protein kinase C and c-jun N-terminal kinase, in podocytes and glomeruli of db/db mice. Activation of both kinases promoted serine 307 phosphorylation of IRS1, a residue known to provoke IRS1 inhibition. Using IKK, mTORC1 and ceramide production inhibitors, we were able to blunt IRS1 serine 307 phosphorylation and restore insulin stimulation of Akt. In conclusion, our results indicate that FFA and diabetes contribute to insulin resistance through the activation of IKKß and S6K1 leading to podocyte dysfunction and DN.

Inter-annual changes in oceanic conditions drives spatial and trophic consistency of a tropical marine predator.

Pelagic seabirds exhibit plasticity in foraging characteristics in relation to oceanographic conditions. This should be particularly relevant in tropical marine environments where food resources are naturally more unpredictable. We studied how inter-annual variations (2013-2018) in tropical oceanographic conditions (driver of oceanic productivity) can influence the spatial and trophic ecology of Cape Verde shearwater (Calonectris edwardsii) during the breeding season. During years of poor oceanographic conditions around the colony, birds engaged in longer trips to West Africa, showed higher spatial and behavioural consistency, and presented a wider isotopic niche. Opposite patterns were generally found for years of good oceanographic conditions, when birds foraged more on their colony surroundings. New foraging areas off West Africa were highlighted as relevant, especially during years of poor environmental conditions. This study highlights the need for long-term studies to assess variation in foraging areas and foraging decisions by seabird populations.

Growth Factor Deregulation and Emerging Role of Phosphatases in Diabetic Peripheral Artery Disease.

Peripheral artery disease is caused by atherosclerosis of lower extremity arteries leading to the loss of blood perfusion and subsequent critical ischemia. The presence of diabetes mellitus is an important risk factor that greatly increases the incidence, the progression and the severity of the disease. In addition to accelerated disease progression, diabetic patients are also more susceptible to develop serious impairment of their walking abilities through an increased risk of lower limb amputation. Hyperglycemia is known to alter the physiological development of collateral arteries in response to ischemia. Deregulation in the production of several critical pro-angiogenic factors has been reported in diabetes along with vascular cell unresponsiveness in initiating angiogenic processes. Among the multiple molecular mechanisms involved in the angiogenic response, protein tyrosine phosphatases are potent regulators by dephosphorylating pro-angiogenic tyrosine kinase receptors. However, evidence has indicated that diabetes-induced deregulation of phosphatases contributes to the progression of several micro and macrovascular complications. This review provides an overview of growth factor alterations in the context of diabetes and peripheral artery disease, as well as a description of the role of phosphatases in the regulation of angiogenic pathways followed by an analysis of the effects of hyperglycemia on the modulation of protein tyrosine phosphatase expression and activity. Knowledge of the role of phosphatases in diabetic peripheral artery disease will help the development of future therapeutics to locally regulate phosphatases and improve angiogenesis.

Ablation of angiotensin type 2 receptor prevents endothelial nitric oxide synthase glutathionylation and nitration in ischaemic abductor muscle of diabetic mice.

Peripheral artery disease is a severe complication of diabetes. We have reported that the deletion of angiotensin type 2 receptor in diabetic mice promoted vascular angiogenesis in the ischaemic muscle 4 weeks following ischaemia. However, the angiotensin type 2 receptor deletion beneficial effects occurred 2 weeks post surgery suggesting that angiotensin type 2 receptor may regulate other pro-angiogenic signalling pathways during the early phases of ischaemia. Nondiabetic and diabetic angiotensin type 2 receptor-deficient mice (Agtr2-/Y) underwent femoral artery ligation after 2 months of diabetes. Blood perfusion was measured every week up to 2 weeks post surgery. Expression of vascular endothelial growth factor, vascular endothelial growth factor receptor and endothelial nitric oxide synthase expression and activity were evaluated. Blood flow reperfusion in the ischaemic muscle of diabetic Agtr2+/Y mice was recovered at 35% as compared to a 68% recovery in diabetic Agtr2-/Y mice. The expression of vascular endothelial growth factor and its receptors was diminished in diabetic Agtr2+/Y mice, an observation not seen in diabetic Agtr2-/Y mice. Interestingly, Agtr2-/Y mice were protected from diabetes-induced glutathionylation, nitration and decreased endothelial nitric oxide synthase expression, which correlated with reduced endothelial cell death and enhanced vascular density in diabetic ischaemic muscle. In conclusion, our results suggest that the deletion of angiotensin type 2 receptor promotes blood flow reperfusion in diabetes by favouring endothelial cell survival and function.

Calcifediol Decreases Interleukin-6 Secretion by Cultured Human Trophoblasts From GDM Pregnancies.

Gestational diabetes mellitus (GDM) is often characterized by low maternal calcifediol (25OHD) and high inflammation levels. This study aimed to determine whether placental protein expressions of CYP27B1, vitamin D receptor (VDR), and CYP24A1 are impaired in GDM and to investigate the effect of a 25OHD treatment on IL-6 secretion by GDM trophoblasts compared with normoglycemic (NG) trophoblasts. Placental tissue samples were harvested to determine protein expression of CYP27B1, VDR, and CYP24A1 by immunoblots. Isolated trophoblasts were stimulated with 25OHD concentrations (25 to 2000 nM) once a day for 3 days and IL-6 secretion was quantified (ELISA). We recruited 17 NG women, 19 women with GDM treated with diet and exercise alone (GDM-d) and 9 women with GDM who necessitated insulin therapy (GDM-i). Protein expressions of CYP27B1 and VDR were significantly higher in placental tissue from GDM-d women compared with NG women (both P = 0.02), whereas no differences were detected between GDM-i and NG placental tissues. In cultured trophoblasts (two groups; n = 5 NG and n = 5 GDM-d), exposure to increasing 25OHD concentrations significantly decreased IL-6 secretion in the GDM-d group only (P = 0.006). After treatment with 25OHD (2000 nM), IL-6 secretion was lower in the GDM-d group compared with the NG group (P = 0.03). Our results suggest an upregulation of the VDR-1,25(OH)2D complex bioavailability in GDM-d placentas, possibly reflecting a compensatory mechanism aiming to ensure that vitamin D can exert its genomic and nongenomic effects in the target cells of the placental-fetal unit. Our findings support an anti-inflammatory effect of vitamin D at the feto-maternal interface in GDM-d pregnancies.

Mice lacking angiotensin type 2 receptor exhibit a sex-specific attenuation of insulin sensitivity.

The renin-angiotensin system modulates insulin action. Pharmacological stimulation of angiotensin type 2 receptor (AT2R) was shown to have beneficial metabolic effects in various animal models of insulin resistance and type 2 diabetes and also to increase insulin sensitivity in wild type mice. In this study we further explored the role of the AT2R on insulin action and glucose homeostasis by investigating the glycemic profile and in vivo insulin signaling status in insulin-target tissues from both male and female AT2R knockout (KO) mice. When compared to the respective wild-type (WT) group, glycemia and insulinemia was unaltered in AT2RKO mice regardless of sex. However, female AT2RKO mice displayed decreased insulin sensitivity compared to their WT littermates. This was accompanied by a compensatory increase in adiponectinemia and with a specific attenuation of the activity of main insulin signaling components (insulin receptor, Akt and ERK1/2) in adipose tissue with no apparent alterations in insulin signaling in either liver or skeletal muscle. These parameters remained unaltered in male AT2RKO mice as compared to male WT mice. Present data show that the AT2R has a physiological role in the conservation of insulin action in female but not in male mice. Our results suggest a sexual dimorphism in the control of insulin action and glucose homeostasis by the AT2R and reinforce the notion that pharmacological modulation of the balance between the AT1R and AT2R receptor could be important for treatment of metabolic syndrome and type 2 diabetes.

Diabetes-Induced DUSP4 Reduction Promotes Podocyte Dysfunction and Progression of Diabetic Nephropathy.

Diabetic nephropathy (DN) remains the leading cause of end-stage renal disease. Hyperglycemia-induced podocyte dysfunction is a major contributor of renal function impairment in DN. Previous studies showed that activation of mitogen-activated protein kinase (MAPK) in diabetes promotes podocyte dysfunction and cell death. Dual specificity phosphatases (DUSPs) are a family of phosphatases mainly responsible for MAPK inhibition. In this study, we demonstrated that diabetes and high glucose exposure decreased DUSP4 expression in cultured podocytes and glomeruli. Diabetes-induced DUSP4 reduction enhanced p38 and c-Jun N-terminal kinase (JNK) activity and podocyte dysfunction. The overexpression of DUSP4 prevented the activation of p38, JNK, caspase 3/7 activity, and NADPH oxidase 4 expression induced by high glucose level exposure. Deletion of DUSP4 exacerbated albuminuria and increased mesangial expansion and glomerular fibrosis in diabetic mice. These morphological changes were associated with profound podocyte foot process effacement, cell death, and sustained p38 and JNK activation. Moreover, inhibition of protein kinase C-δ prevented DUSP4 expression decline and p38/JNK activation in the podocytes and renal cortex of diabetic mice. Analysis of DUSP4 expression in the renal cortex of patients with diabetes revealed that decreased DUSP4 mRNA expression correlated with reduced estimated glomerular filtration rate (<60 mL/min/1.73 m2). Thus, this study demonstrates that preserving DUSP4 expression could protect against podocyte dysfunction and preserve glomerular function in DN.