Research progress of RP1L1 gene in disease.

Retinitis pigmentosa 1-like 1 (RP1L1) is a component of photoreceptor cilia. Pathogenic variants in RP1L1 cause photoreceptor diseases, suggesting that RP1L1 plays an important role in photoreceptor biology, although its exact function is unknown. To date, RP1L1 variants have been associated with occult macular dystrophy (cone degeneration) and retinitis pigmentosa (rod degeneration). Here, we summarize the reported RP1L1-associated photoreceptor pathogenic mutations. The association between RP1L1 and other diseases (mainly several tumors) is also summarized and RP1L1 is included in a wider range of diseases. Finally, it is necessary to further explore the influence mechanism of RP1L1 gene on the health of photoreceptors and how it participates in the occurrence and development of tumors.

Endothelial cell-specific mineralocorticoid receptor activation promotes diastolic dysfunction in diet-induced obese male mice.

Widespread consumption of diets high in fat and fructose (Western diet, WD) has led to increased prevalence of obesity and diastolic dysfunction (DD). DD is a prominent feature of heart failure with preserved ejection fraction (HFpEF). However, the underlying mechanisms of DD are poorly understood, and treatment options are still limited. We have previously shown that deletion of the cell-specific mineralocorticoid receptor in endothelial cells (ECMR) abrogates DD induced by WD feeding in female mice. However, the specific role of ECMR activation in the pathogenesis of DD in male mice has not been clarified. Therefore, we fed 4-wk-old ECMR knockout (ECMRKO) male mice and littermates (LM) with either a WD or chow diet (CD) for 16 wk. WD feeding resulted in DD characterized by increased left ventricle (LV) filling pressure (E/e') and diastolic stiffness [E/e'/LV inner diameter at end diastole (LVIDd)]. Compared with CD, WD in LM resulted in increased myocardial macrophage infiltration, oxidative stress, and increased myocardial phosphorylation of Akt, in concert with decreased phospholamban phosphorylation. WD also resulted in focal cardiomyocyte remodeling, characterized by areas of sarcomeric disorganization, loss of mitochondrial electron density, and mitochondrial fragmentation. Conversely, WD-induced DD and associated biochemical and structural abnormalities were prevented by ECMR deletion. In contrast with our previously reported observations in females, WD-fed male mice exhibited enhanced Akt signaling and a lower magnitude of cardiac injury. Collectively, our data support a critical role for ECMR in obesity-induced DD and suggest critical mechanistic differences in the genesis of DD between males and females.

Endothelial activation and dysfunction in metabolic syndrome, type 2 diabetes and coronavirus disease 2019.

The novel coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus-2 infection is a serious global concern. Increased morbidity and mortality is associated with older age, male gender, cardiovascular disease, diabetes, and smoking. As COVID-19 spreads from coastal borders, both state to state and country to country, our understanding of its pathophysiology has evolved. Age and type 2 diabetes mellitus (T2DM) play especially important roles in COVID-19 progression. T2DM is an age-related disease associated with metabolic syndrome, obesity, insulin resistance (hyperinsulinemia), hyperlipidemia, hypertension, hyperglycemia, and endothelial activation and dysfunction. This review evaluates the relationships and intersection between endothelial cell activation and dysfunction in T2DM and COVID-19. COVID-19 induces multiple injuries of the terminal bronchioles and alveolar blood-gas barrier and associated ultrastructural tissue remodeling. COVID-19 may unmask multiple vulnerabilities associated with T2DM including damage to the endothelial glycocalyx and multiple end-organ macro and microvascular diseases. Unmasking existing vulnerabilities in diabetic patients with COVID-19 is important. Globally, we must come together to better understand why T2DM is associated with increased COVID-19 morbidity and mortality.

The combination of a neprilysin inhibitor (sacubitril) and angiotensin-II receptor blocker (valsartan) attenuates glomerular and tubular injury in the Zucker Obese rat.

OBJECTIVE: Diabetic nephropathy (DN) is characterized by glomerular and tubulointerstitial injury, proteinuria and remodeling. Here we examined whether the combination of an inhibitor of neprilysin (sacubitril), a natriuretic peptide-degrading enzyme, and an angiotensin II type 1 receptor blocker (valsartan), suppresses renal injury in a pre-clinical model of early DN more effectively than valsartan monotherapy. METHODS: Sixty-four male Zucker Obese rats (ZO) at 16 weeks of age were distributed into 4 different groups: Group 1: saline control (ZOC); Group 2: sacubitril/valsartan (sac/val) (68 mg kg-1 day-1; ZOSV); and Group 3: valsartan (val) (31 mg kg-1 day-1; ZOV). Group 4 received hydralazine, an anti-hypertensive drug (30 mg kg-1 day-1, ZOH). Six Zucker Lean (ZL) rats received saline (Group 5) and served as lean controls (ZLC). Drugs were administered daily for 10 weeks by oral gavage. RESULTS: Mean arterial pressure (MAP) increased in ZOC (+ 28%), but not in ZOSV (- 4.2%), ZOV (- 3.9%) or ZOH (- 3.7%), during the 10 week-study period. ZOC were mildly hyperglycemic, hyperinsulinemic and hypercholesterolemic. ZOC exhibited proteinuria, hyperfiltration, elevated renal resistivity index (RRI), glomerular mesangial expansion and podocyte foot process flattening and effacement, reduced nephrin and podocin expression, tubulointerstitial and periarterial fibrosis, increased NOX2, NOX4 and AT1R expression, glomerular and tubular nitroso-oxidative stress, with associated increases in urinary markers of tubular injury. None of the drugs reduced fasting glucose or HbA1c. Hypercholesterolemia was reduced in ZOSV (- 43%) and ZOV (- 34%) (p < 0.05), but not in ZOH (- 13%) (ZOSV > ZOV > ZOH). Proteinuria was ameliorated in ZOSV (- 47%; p < 0.05) and ZOV (- 30%; p > 0.05), but was exacerbated in ZOH (+ 28%; p > 0.05) (ZOSV > ZOV > ZOH). Compared to ZOC, hyperfiltration was improved in ZOSV (p < 0.05 vs ZOC), but not in ZOV or ZOH. None of the drugs improved RRI. Mesangial expansion was reduced by all 3 treatments (ZOV > ZOSV > ZOH). Importantly, sac/val was more effective in improving podocyte and tubular mitochondrial ultrastructure than val or hydralazine (ZOSV > ZOV > ZOH) and this was associated with increases in nephrin and podocin gene expression in ZOSV (p < 0.05), but not ZOV or ZOH. Periarterial and tubulointerstitial fibrosis and nitroso-oxidative stress were reduced in all 3 treatment groups to a similar extent. Of the eight urinary proximal tubule cell injury markers examined, five were elevated in ZOC (p < 0.05). Clusterin and KIM-1 were reduced in ZOSV (p < 0.05), clusterin alone was reduced in ZOV and no markers were reduced in ZOH (ZOSV > ZOV > ZOH). CONCLUSIONS: Compared to val monotherapy, sac/val was more effective in reducing proteinuria, renal ultrastructure and tubular injury in a clinically relevant animal model of early DN. More importantly, these renoprotective effects were independent of improvements in blood pressure, glycemia and nitroso-oxidative stress. These novel findings warrant future clinical investigations designed to test whether sac/val may offer renoprotection in the setting of DN.

Glycemic control by the SGLT2 inhibitor empagliflozin decreases aortic stiffness, renal resistivity index and kidney injury.

BACKGROUND: Arterial stiffness is emerging as an independent risk factor for the development of chronic kidney disease. The sodium glucose co-transporter 2 (SGLT2) inhibitors, which lower serum glucose by inhibiting SGLT2-mediated glucose reabsorption in renal proximal tubules, have shown promise in reducing arterial stiffness and the risk of cardiovascular and kidney disease in individuals with type 2 diabetes mellitus. Since hyperglycemia contributes to arterial stiffness, we hypothesized that the SGLT2 inhibitor empagliflozin (EMPA) would improve endothelial function, reduce aortic stiffness, and attenuate kidney disease by lowering hyperglycemia in type 2 diabetic female mice (db/db). MATERIALS/METHODS: Ten-week-old female wild-type control (C57BLKS/J) and db/db (BKS.Cg-Dock7m+/+Leprdb/J) mice were divided into three groups: lean untreated controls (CkC, n = 17), untreated db/db (DbC, n = 19) and EMPA-treated db/db mice (DbE, n = 19). EMPA was mixed with normal mouse chow at a concentration to deliver 10 mg kg-1 day-1, and fed for 5 weeks, initiated at 11 weeks of age. RESULTS: Compared to CkC, DbC showed increased glucose levels, blood pressure, aortic and endothelial cell stiffness, and impaired endothelium-dependent vasorelaxation. Furthermore, DbC exhibited impaired activation of endothelial nitric oxide synthase, increased renal resistivity and pulsatility indexes, enhanced renal expression of advanced glycation end products, and periarterial and tubulointerstitial fibrosis. EMPA promoted glycosuria and blunted these vascular and renal impairments, without affecting increases in blood pressure. In addition, expression of "reversion inducing cysteine rich protein with Kazal motifs" (RECK), an anti-fibrotic mediator, was significantly suppressed in DbC kidneys and partially restored by EMPA. Confirming the in vivo data, EMPA reversed high glucose-induced RECK suppression in human proximal tubule cells. CONCLUSIONS: Empagliflozin ameliorates kidney injury in type 2 diabetic female mice by promoting glycosuria, and possibly by reducing systemic and renal artery stiffness, and reversing RECK suppression.

Dipeptidyl peptidase-4 (DPP-4) inhibition with linagliptin reduces western diet-induced myocardial TRAF3IP2 expression, inflammation and fibrosis in female mice.

BACKGROUND: Diastolic dysfunction (DD), a hallmark of obesity and primary defect in heart failure with preserved ejection fraction, is a predictor of future cardiovascular events. We previously reported that linagliptin, a dipeptidyl peptidase-4 inhibitor, improved DD in Zucker Obese rats, a genetic model of obesity and hypertension. Here we investigated the cardioprotective effects of linagliptin on development of DD in western diet (WD)-fed mice, a clinically relevant model of overnutrition and activation of the renin-angiotensin-aldosterone system. METHODS: Female C56Bl/6 J mice were fed an obesogenic WD high in fat and simple sugars, and supplemented or not with linagliptin for 16 weeks. RESULTS: WD induced oxidative stress, inflammation, upregulation of Angiotensin II type 1 receptor and mineralocorticoid receptor (MR) expression, interstitial fibrosis, ultrastructural abnormalities and DD. Linagliptin inhibited cardiac DPP-4 activity and prevented molecular impairments and associated functional and structural abnormalities. Further, WD upregulated the expression of TRAF3IP2, a cytoplasmic adapter molecule and a regulator of multiple inflammatory mediators. Linagliptin inhibited its expression, activation of its downstream signaling intermediates NF-κB, AP-1 and p38-MAPK, and induction of multiple inflammatory mediators and growth factors that are known to contribute to development and progression of hypertrophy, fibrosis and contractile dysfunction. Linagliptin also inhibited WD-induced collagens I and III expression. Supporting these in vivo observations, linagliptin inhibited aldosterone-mediated MR-dependent oxidative stress, upregulation of TRAF3IP2, proinflammatory cytokine, and growth factor expression, and collagen induction in cultured primary cardiac fibroblasts. More importantly, linagliptin inhibited aldosterone-induced fibroblast activation and migration. CONCLUSIONS: Together, these in vivo and in vitro results suggest that inhibition of DPP-4 activity by linagliptin reverses WD-induced DD, possibly by targeting TRAF3IP2 expression and its downstream inflammatory signaling.

Xanthine oxidase inhibition protects against Western diet-induced aortic stiffness and impaired vasorelaxation in female mice.

Consumption of a high-fat, high-fructose diet [Western diet (WD)] promotes vascular stiffness, a critical factor in the development of cardiovascular disease (CVD). Obese and diabetic women exhibit greater arterial stiffness than men, which contributes to the increased incidence of CVD in these women. Furthermore, high-fructose diets result in elevated plasma concentrations of uric acid via xanthine oxidase (XO) activation, and uric acid elevation is also associated with increased vascular stiffness. However, the mechanisms by which increased xanthine oxidase activity and uric acid contribute to vascular stiffness in obese females remain to be fully uncovered. Accordingly, we examined the impact of XO inhibition on endothelial function and vascular stiffness in female C57BL/6J mice fed a WD or regular chow for 16 wk. WD feeding resulted in increased arterial stiffness, measured by atomic force microscopy in aortic explants (16.19 ± 1.72 vs. 5.21 ± 0.54 kPa, P < 0.05), as well as abnormal aortic endothelium-dependent and -independent vasorelaxation. XO inhibition with allopurinol (widely utilized in the clinical setting) substantially improved vascular relaxation and attenuated stiffness (16.9 ± 0.50 vs. 3.44 ± 0.50 kPa, P < 0.05) while simultaneously lowering serum uric acid levels (0.55 ± 0.98 vs. 0.21 ± 0.04 mg/dL, P < 0.05). In addition, allopurinol improved WD-induced markers of fibrosis and oxidative stress in aortic tissue, as analyzed by immunohistochemistry and transmission electronic microscopy. Collectively, these results demonstrate that XO inhibition protects against WD-induced vascular oxidative stress, fibrosis, impaired vasorelaxation, and aortic stiffness in females. Furthermore, excessive oxidative stress resulting from XO activation appears to play a key role in mediating vascular dysfunction induced by chronic exposure to WD consumption in females.

Uric acid promotes left ventricular diastolic dysfunction in mice fed a Western diet.

The rising obesity rates parallel increased consumption of a Western diet, high in fat and fructose, which is associated with increased uric acid. Population-based data support that elevated serum uric acids are associated with left ventricular hypertrophy and diastolic dysfunction. However, the mechanism by which excess uric acid promotes these maladaptive cardiac effects has not been explored. In assessing the role of Western diet-induced increases in uric acid, we hypothesized that reductions in uric acid would prevent Western diet-induced development of cardiomyocyte hypertrophy, cardiac stiffness, and impaired diastolic relaxation by reducing growth and profibrotic signaling pathways. Four-weeks-old C57BL6/J male mice were fed excess fat (46%) and fructose (17.5%) with or without allopurinol (125 mg/L), a xanthine oxidase inhibitor, for 16 weeks. The Western diet-induced increases in serum uric acid along with increases in cardiac tissue xanthine oxidase activity temporally related to increases in body weight, fat mass, and insulin resistance without changes in blood pressure. The Western diet induced cardiomyocte hypertrophy, myocardial oxidative stress, interstitial fibrosis, and impaired diastolic relaxation. Further, the Western diet enhanced activation of the S6 kinase-1 growth pathway and the profibrotic transforming growth factor-ß1/Smad2/3 signaling pathway and macrophage proinflammatory polarization. All results improved with allopurinol treatment, which lowered cardiac xanthine oxidase as well as serum uric acid levels. These findings support the notion that increased production of uric acid with intake of a Western diet promotes cardiomyocyte hypertrophy, inflammation, and oxidative stress that lead to myocardial fibrosis and associated impaired diastolic relaxation.

Prevention of obesity-induced renal injury in male mice by DPP4 inhibition.

Therapies to prevent renal injury in obese hypertensive individuals are being actively sought due to the obesity epidemic arising from the Western diet (WD), which is high in fructose and fat. Recently, activation of the immune system and hyperuricemia, observed with high fructose intake, have been linked to the pathophysiology of hypertension and renal injury. Because dipeptidyl peptidase 4 (DPP4) is a driver of maladaptive T-cell/macrophage responses, renal-protective benefits of DPP4 inhibition in the WD-fed mice were examined. Mice fed a WD for 16 weeks were given the DPP4 inhibitor MK0626 in their diet beginning at 4 weeks of age. WD-fed mice were obese, hypertensive, and insulin-resistant and manifested proteinuria and increased plasma DPP4 activity and uric acid levels. WD-fed mice also had elevated kidney DPP4 activity and monocyte chemoattractant protein-1 and IL-12 levels and suppressed IL-10 levels in the kidney, suggesting macrophage-driven inflammation, glomerular and tubulointerstitial injury. WD-induced increases in DPP4 activation in the plasma and kidney and proteinuria in WD mice were abrogated by MK0626, although blood pressure and systemic insulin sensitivity were not improved. Contemporaneously, MK0626 reduced serum uric acid levels, renal oxidative stress, and IL-12 levels and increased IL-10 levels, suggesting that suppression of DPP4 activity leads to suppression of renal immune/inflammatory injury responses to a WD. Taken together, these results demonstrate that DPP4 inhibition prevents high-fructose/high-fat diet-induced glomerular and tubular injury independent of blood pressure/insulin sensitivity and offers a potentially novel therapy for diabetic and obesity-related kidney disease.

Pericytopathy: oxidative stress and impaired cellular longevity in the pancreas and skeletal muscle in metabolic syndrome and type 2 diabetes.

The pericyte's role has been extensively studied in retinal tissues of diabetic retinopathy; however, little is known regarding its role in such tissues as the pancreas and skeletal muscle. This supportive microvascular mural cell, plays an important and novel role in cellular and extracellular matrix remodeling in the pancreas and skeletal muscle of young rodent models representing the metabolic syndrome and type 2 diabetes mellitus (T2DM). Transmission electron microscopy can be used to evaluate these tissues from young rodent models of insulin resistance and T2DM, including the transgenic Ren2 rat, db/db obese insulin resistant - T2DM mouse, and human islet amyloid polypeptide (HIP) rat model of T2DM. With this method, the earliest pancreatic remodeling change was widening of the islet exocrine interface and pericyte hypercellularity, followed by pericyte differentiation into islet and pancreatic stellate cells with early fibrosis involving the islet exocrine interface and interlobular interstitium. In skeletal muscle there was a unique endothelial capillary connectivity via elongated longitudinal pericyte processes in addition to pericyte to pericyte and pericyte to myocyte cell-cell connections allowing for paracrine communication. Initial pericyte activation due to moderate oxidative stress signaling may be followed by hyperplasia, migration, and differentiation into adult mesenchymal cells. Continued robust oxidative stress may induce pericyte apoptosis and impaired cellular longevity. Circulating antipericyte autoantibodies have recently been characterized, and may provide a screening method to detect those patients who are developing pericyte loss and are at greater risk for the development of complications of T2DM due to pericytopathy and rarefaction. Once detected, these patients may be offered more aggressive treatment strategies such as early pharmacotherapy in addition to life style changes targeted to maintaining pericyte integrity. In conclusion, we have provided a review of current knowledge regarding the pericyte and novel ultrastructural findings regarding its role in metabolic syndrome and T2DM.

Nebivolol improves diastolic dysfunction and myocardial remodeling through reductions in oxidative stress in the Zucker obese rat.

Insulin resistance is associated with obesity and may be accompanied by left ventricular diastolic dysfunction and myocardial remodeling. Decreased insulin metabolic signaling and increased oxidative stress may promote these maladaptive changes. In this context, the beta-blocker nebivolol has been reported to improve insulin sensitivity, increase endothelial NO synthase activity, and reduce NADPH oxidase-induced superoxide generation. We hypothesized that nebivolol would attenuate diastolic dysfunction and myocardial remodeling by blunting myocardial oxidant stress and promoting insulin metabolic signaling in a rodent model of obesity, insulin resistance, and hypertension. Six-week-old male Zucker obese and age-matched Zucker lean rats were treated with nebivolol (10 mg x kg(-) x day(-1)) for 21 days, and myocardial function was assessed by cine MRI. Compared with untreated Zucker lean rats, untreated Zucker obese rats exhibited prolonged diastolic relaxation time (27.7+/-2.5 versus 40.9+/-2.0 ms; P<0.05) and reduced initial diastolic filling rate (6.2+/-0.5 versus 2.8+/-0.6 microL/ms; P<0.05) in conjunction with increased homeostatic model assessment of insulin resistance (7+/-2 versus 95+/-21; P<0.05), interstitial and pericapillary fibrosis, abnormal cardiomyocyte histoarchitecture, 3-nitrotyrosine, and NADPH oxidase-dependent superoxide. Nebivolol improved diastolic relaxation (32.8+/-0.7 ms; P<0.05 versus untreated Zucker obese), reduced fibrosis, and remodeling in Zucker obese rats, in concert with reductions in nitrotyrosine, NADPH oxidase-dependent superoxide, and improvements in the insulin metabolic signaling, endothelial NO synthase activation, and weight gain (381+/-7 versus 338+/-14 g; P<0.05). Results support the hypothesis that nebivolol reduces myocardial structural maladaptive changes and improves diastolic relaxation in concert with improvements in insulin sensitivity and endothelial NO synthase activation, concomitantly with reductions in oxidative stress.

Comparative effect of direct renin inhibition and AT1R blockade on glomerular filtration barrier injury in the transgenic Ren2 rat.

Renin-angiotensin system (RAS) activation contributes to kidney injury through oxidative stress. Renin is the rate-limiting step in angiotensin (ANG II) generation. Recent work suggests renin inhibition improves proteinuria comparable to ANG type 1 receptor (AT1R) blockade (ARB). Thereby, we investigated the relative impact of treatment with a renin inhibitor vs. an ARB on renal oxidative stress and associated glomerular structural and functional changes in the transgenic Ren2 rat, which manifests hypertension, albuminuria, and increased tissue RAS activity. Young Ren2 and age-matched Sprague-Dawley (SD) controls (age 6-9 wk) were treated with a renin inhibitor (aliskiren), an ARB (irbesartan), or vehicle for 21 days. Ren2 rats exhibited increases in systolic pressure (SBP), albuminuria, and renal 3-nitrotyrosine content as well as ultrastructural podocyte foot-process effacement and diminution of the podocyte-specific protein nephrin. Structural and functional alterations were accompanied by increased renal cortical ANG II, AT1R, as well as NADPH oxidase subunit (Nox2) expression compared with SD controls. Abnormalities were attenuated to a similar extent with both aliskiren and irbesartan treatment. Despite the fact the dose of irbesartan used caused a greater reduction in SBP than aliskerin treatment (P < 0.05), the effects on proteinuria, nephrin, and oxidative stress were similar between the two treatments. Our results highlight both the importance of pressor-related reductions on podocyte integrity and albuminuria as well as RAS-mediated oxidant stress largely comparable between ARB and renin inhibition treatment.

Direct renin inhibition improves systemic insulin resistance and skeletal muscle glucose transport in a transgenic rodent model of tissue renin overexpression.

Renin is the rate-limiting enzyme in renin-angiotensin system (RAS) activation. We sought to determine the impact of renin inhibition on whole-body insulin sensitivity and skeletal muscle RAS, oxidative stress, insulin signaling, and glucose transport in the transgenic TG(mRen2)27 rat (Ren2), which manifests increased tissue RAS activity, elevated serum aldosterone, hypertension, and insulin resistance. Young (aged 6-9 wk) Ren2 and age-matched Sprague Dawley control rats were treated with aliskiren [50 mg/kg . d, ip] or placebo for 21 d and administered an ip glucose tolerance test. Insulin metabolic signaling and 2-deoxyglucose uptake in soleus muscle were examined in relation to tissue renin-angiotensin-aldosterone system [angiotensin (Ang) II, mineralocorticoid receptor (MR), and Ang type I receptor (AT(1)R)] and measures of oxidative stress as well as structural changes evaluated by light and transmission electron microscopy. Ren2 rats demonstrated systemic insulin resistance with decreased skeletal muscle insulin metabolic signaling and glucose uptake. This was associated with increased Ang II, MR, AT(1)R, oxidative stress, and reduced tyrosine insulin receptor substrate-1 phosphorylation, protein kinase B/(Akt) phosphorylation and glucose transporter-4 immunostaining. The Ren2 also demonstrated perivascular fibrosis and mitochondrial remodeling. Renin inhibition improved systemic insulin sensitivity, insulin metabolic signaling, and glucose transport along with normalization of Ang II, AT(1)R, and MR levels, oxidative stress markers, fibrosis, and mitochondrial structural abnormalities. Our data suggest that renin inhibition improves systemic insulin sensitivity, skeletal muscle insulin metabolic signaling, and glucose transport in Ren2 rats. This is associated with reductions in skeletal muscle tissue Ang II, AT(1)R, and MR expression; oxidative stress; fibrosis; and mitochondrial abnormalities.

Cardioprotective role of sodium thiosulfate on chronic heart failure by modulating endogenous H2S generation.

BACKGROUND/AIMS: Sodium thiosulfate (STS) has been shown to be an antioxidant and calcium solubilizer, but the possible role of STS in dysfunctional ventricles remains unknown. Here, we assessed the effects of STS in the failing heart. METHODS: Heart failure was created by an arteriovenous fistula (AVF). Mice were divided into 4 groups: sham, AVF, sham + STS, and AVF + STS. STS (3 mg/ml) was supplemented with drinking water for 6 weeks in the appropriate surgery groups after surgery. RESULTS: M-mode echocardiograms showed ventricular contractile dysfunction with reduced aortic blood flow in AVF mice, whereas STS treatment prevented the decline in cardiac function. Ventricular collagen, MMP-2 and -9, and TIMP-1 were robustly increased with a decreasing trend in adenylate cyclase VI expression; however, STS supplementation reversed these effects in AVF mice. Among 2 enzymes that produce endogenous hydrogen sulfide (H(2)S), cystathionine-gamma-lyase (CSE) expression was attenuated in AVF mice with no changes in cystathionine-beta-synthase (CBS) expression. In addition, reduced production of H(2)S in AVF ventricular tissue was normalized with STS supplementation. Moreover, cardiac tissues were more responsive to H(2)S when AVF mice were supplemented with STS compared to AVF alone. CONCLUSIONS: These results suggested that STS modulated cardiac dysfunction and the extracellular matrix, in part, by increasing ventricular H(2)S generation.

Ultrastructure of islet microcirculation, pericytes and the islet exocrine interface in the HIP rat model of diabetes.

CONTEXT: The transgenic human islet amyloid polypeptide (HIP) rat model of type 2 diabetes mellitus (T2DM) parallels the functional and structural changes in human islets with T2DM. OBJECTIVE: The transmission electron microscope (TEM) was utilized to observe the ultrastructural changes in islet microcirculation. METHODS: Pancreatic tissue from male Sprague Dawley rats (2, 4, 8, 14 months) were used as controls (SDC) and compared to the 2-, 4-, 8- and 14-month-old HIP rat models. RESULTS: The 2-month-old HIP model demonstrated no islet or microcirculation remodeling changes when compared to the SDC models. The 4-month-old HIP model demonstrated significant pericapillary amyloid deposition and diminution of pericyte foot processes as compared to the SDC models. The 8-month-old model demonstrated extensive islet amyloid deposition associated with pericyte and beta-cell apoptosis when compared with SDC. The 14-month-old HIP model demonstrated a marked reduction of beta-cells and intra-islet capillaries with near complete replacement of islets by amyloidoses. Increased cellularity in the region of the islet exocrine interface was noted in the 4- to 14-month-old HIP models as compared to SDC. In contrast to intra-islet capillary rarefaction there was noticeable angiogenesis in the islet exocrine interface. Pericytes seemed to be closely associated with collagenosis, intra-islet adipogenesis and angiogenesis in the islet exocrine interface. CONCLUSION: The above novel findings regarding the microcirculation and pericytes could assist researchers and clinicians in a better morphological understanding of T2DM and lead to new strategies for prevention and treatment of T2DM.

Renin inhibition attenuates insulin resistance, oxidative stress, and pancreatic remodeling in the transgenic Ren2 rat.

Emerging evidence indicates that pancreatic tissue expresses all components of the renin-angiotensin system. However, the functional role is not well understood. This investigation examined renin inhibition on pancreas structure/function in the transgenic Ren2 rat harboring the mouse renin gene, a model of tissue renin overexpression. Renin is the rate-limiting step in the generation of angiotensin II (Ang II), which stimulates the generation of reactive oxygen species in a variety of tissues. Overexpression of renin in Ren2 rats results in hypertension, insulin resistance, and cardiovascular and renal damage. Young (6-7 wk old) insulin-resistant male Ren2 and age-matched insulin sensitive Sprague Dawley rats were treated with the renin inhibitor, aliskiren (50 mg/kg.d by ip injection), or placebo for 21 d. At 21 d, the Ren2 demonstrated insulin resistance with increased islet insulin, Ang II, and reduced total insulin receptor substrate (IRS)-1, IRS-2, and Akt immunostaining. There was increased islet nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and subunits (p47(phox) and Rac1) as well as increased nitrotyrosine immunostaining (each P < 0.05). These functional abnormalities were associated with a disordered islet architecture; increased islet-exocrine interface, pericapillary fibrosis, and structurally abnormal mitochondria and content in endocrine and exocrine pancreas. In vivo treatment with aliskiren normalized systemic insulin resistance and islet insulin, Ang II, NADPH oxidase activity/subunits, and nitrotyrosine and improved total IRS-1 and Akt phosphorylation (each P < 0.05) as well as islet/exocrine structural abnormalities. Collectively, these data suggest that pancreatic functional/structural changes are driven, in part, by tissue renin-angiotensin system-mediated increases in NADPH oxidase and reactive oxygen species generation, abnormalities attenuated with direct renin inhibition.

Low-dose spironolactone reduces reactive oxygen species generation and improves insulin-stimulated glucose transport in skeletal muscle in the TG(mRen2)27 rat.

Renin-angiotensin-aldosterone system (RAAS) activation mediates increases in reactive oxygen species (ROS) and impaired insulin signaling. The transgenic Ren2 rat manifests increased tissue renin-angiotensin system activity, elevated serum aldosterone, hypertension, and insulin resistance. To explore the role of aldosterone in the pathogenesis of insulin resistance, we investigated the impact of in vivo treatment with a mineralocorticoid receptor (MR) antagonist on insulin sensitivity in Ren2 and aged-matched Sprague-Dawley (SD) control rats. Both groups (age 6-8 wk) were implanted with subcutaneous time-release pellets containing spironolactone (0.24 mg/day) or placebo over 21 days. Systolic blood pressure (SBP) and intraperitoneal glucose tolerance test were determined. Soleus muscle insulin receptor substrate-1 (IRS-1), tyrosine phosphorylated IRS-1, protein kinase B (Akt) phosphorylation, GLUT4 levels, and insulin-stimulated 2-deoxyglucose uptake were evaluated in relation to NADPH subunit expression/oxidase activity and ROS production (chemiluminescence and 4-hydroxy-2-nonenal immunostaining). Along with increased soleus muscle NADPH oxidase activity and ROS, there was systemic insulin resistance and reduced muscle IRS-1 tyrosine phosphorylation, Akt phosphorylation/activation, and GLUT4 expression in the Ren2 group (each P < 0.05). Despite not decreasing blood pressure, low-dose spironolactone treatment improved soleus muscle insulin signaling parameters and systemic insulin sensitivity in concert with reductions in NADPH oxidase subunit expression/activity and ROS production (each P < 0.05). Our findings suggest that aldosterone contributes to insulin resistance in the transgenic Ren2, in part, by increasing NADPH oxidase activity in skeletal muscle tissue.

Oxidative stress contributes to pulmonary hypertension in the transgenic (mRen2)27 rat.

The transgenic (mRen2)27 (Ren2) rat overexpresses mouse renin in extrarenal tissues, causing increased local synthesis of ANG II, oxidative stress, and hypertension. However, little is known about the role of oxidative stress induced by the tissue renin-angiotensin system (RAS) as a contributing factor in pulmonary hypertension (PH). Using male Ren2 rats, we test the hypothesis that lung tissue RAS overexpression and resultant oxidative stress contribute to PH and pulmonary vascular remodeling. Mean arterial pressure (MAP), right ventricular systolic pressure (RVSP), and wall thickness of small pulmonary arteries (PA), as well as intrapulmonary NADPH oxidase activity and subunit protein expression and reactive oxygen species (ROS), were compared in age-matched Ren2 and Sprague-Dawley (SD) rats pretreated with the SOD/catalase mimetic tempol for 21 days. In placebo-treated Ren2 rats, MAP and RVSP, as well as intrapulmonary NADPH oxidase activity and subunits (Nox2, p22phox, and Rac-1) and ROS, were elevated compared with placebo-treated SD rats (P < 0.05). Tempol decreased RVSP (P < 0.05), but not MAP, in Ren2 rats. Tempol also reduced intrapulmonary NADPH oxidase activity, Nox2, p22phox, and Rac-1 protein expression, and ROS in Ren2 rats (P < 0.05). Compared with SD rats, the cross-sectional surface area of small PA was 38% greater (P < 0.001) and luminal surface area was 54% less (P < 0.001) in Ren2 rats. Wall surface area was reduced and luminal area was increased in tempol-treated SD and Ren2 rats compared with untreated controls (P < 0.05). Collectively, the results of this investigation support a seminal role for enhanced tissue RAS/oxidative stress as factors in development of PH and pulmonary vascular remodeling.

Calciphylaxis: calcific uremic arteriolopathy and the emerging role of sodium thiosulfate.

Calciphylaxis-calcific uremic arteriolopathy, is a serious disorder of arteriolar calcification of the arteriole media and is associated with endovascular fibrosis and thrombosis in subcutaneous adipose tissue. It frequently results in severe ischemia, intense pain, and tissue necrosis with nonhealing skin ulcerations. It usually occurs in chronic kidney disease and especially in patients requiring renal replacement therapy. It is associated with a very high mortality rate, and the number of reports and reviews seemed to have increased over the past 5 years. Advances in therapy and salvaging patients from this high mortality risk have recently been reported with the use of sodium thiosulfate. The new application for this old drug used to treat cyanide poisoning and recently preventing neurotoxic effects resulting in hearing loss in those patients with head and neck cancer receiving cisplatin and carboplatin therapy are discussed. Recently, multiple case reports have demonstrated that sodium thiosulfate therapy has resulted in rapid pain relief, healing of skin ulcerations, and prevention of high mortality risk. This emerging treatment and its success are relatively unknown to many physicians. The purpose of this report is to share with others the emerging role of sodium thiosulfate and its new application as a treatment option to be used in combination with other treatment modalities for calciphylaxis-calcific uremic arteriolopathy. Indeed, as with any new treatment this emerging therapy should be studied in greater detail, but this old drug seems to have a new life in the hands of treating physicians.