Paradoxes of nitric oxide in the diabetic kidney

Nonselective and A2a-Selective Inhibition of Adenosine Receptors Modulates Renal Perfusion and Excretion Depending on the Duration of Streptozotocin-Induced Diabetes in Rats

Long-lasting hyperglycaemia may alter the role of adenosine-dependent receptors (P1R) in the control of kidney function. We investigated how P1R activity affects renal circulation and excretion in diabetic (DM) and normoglycaemic (NG) rats; the receptors' interactions with bioavailable NO and H₂O₂ were also explored. The effects of adenosine deaminase (ADA, nonselective P1R inhibitor) and P1A2a-R-selective antagonist (CSC) were examined in anaesthetised rats, both after short-lasting (2-weeks, DM-14) and established (8-weeks, DM-60) streptozotocin-induced hyperglycaemia, and in normoglycaemic age-matched animals (NG-14, NG-60, respectively). The arterial blood pressure, perfusion of the whole kidney and its regions (cortex, outer-, and inner medulla), and renal excretion were determined, along with the in situ renal tissue NO and H₂O₂ signals (selective electrodes). The ADA treatment helped to assess the P1R-dependent difference in intrarenal baseline vascular tone (vasodilation in DM and vasoconstriction in NG rats), with the difference being more pronounced between DM-60 and NG-60 animals. The CSC treatment showed that in DM-60 rats, A2aR-dependent vasodilator tone was modified differently in individual kidney zones. Renal excretion studies after the ADA and CSC treatments showed that the balance of the opposing effects of A2aRs and other P1Rs on tubular transport, seen in the initial phase, was lost in established hyperglycaemia. Regardless of the duration of the diabetes, we observed a tonic effect of A2aR activity on NO bioavailability. Dissimilarly, the involvement of P1R in tissue production of H₂O₂, observed in normoglycaemia, decreased. Our functional study provides new information on the changing interaction of adenosine in the kidney, as well as its receptors and NO and H₂O₂, in the course of streptozotocin diabetes.

Role of Ang1-7 in renal haemodynamics and excretion in streptozotocin diabetic rats

The contribution of angiotensin (1-7) (Ang1-7) to control of extrarenal and renal function may be modified in diabetes. We investigated the effects of Ang1-7 supplementation on blood pressure, renal circulation and intrarenal reactivity (IVR) to vasoactive agents in normoglycaemic (NG) and streptozotocin diabetic rats (DM). In Sprague Dawley DM and NG rats, 3 weeks after streptozotocin (60 mg/kg i.p.) or solvent injection, Ang1-7 was administered (400 ng/min) over the next 2 weeks using subcutaneously implanted osmotic minipumps. For a period of 5 weeks, blood pressure (BP), 24 h water intake and diuresis were determined weekly. In anaesthetised rats, BP, renal total and cortical (CBF), outer (OMBF) and inner medullary (IMBF) perfusion and urine excretion were determined. To check IVR, a short-time infusion of acetylcholine or norepinephrine was randomly given to the renal artery. Unexpectedly, BP did not differ between NG and DM, and this was not modified by Ang-1-7 supplementation. Baseline IMBF was higher in NG vs. DM, and Ang1-7 treatment did not change it in NG but decreased it in DM. In the latter, Ang1-7 increased cortical IVR to vasoconstrictor and vasodilator stimuli. IMBF decrease after high acetylcholine dose seen in untreated NG was reverted to an increase in Ang1-7 treated rats. Irrespective of the glycaemia level, Ang1-7 did not modify BP. However, it impaired medullary circulation in DM, whereas in NG it rendered the medullary vasculature more sensitive to vasodilators. Possibly, the medullary hypoperfusion in DM was mediated by Ang1-7 activation of angiotensin AT-1 receptors which are upregulated by hyperglycaemia.

TRIM27 contributes to glomerular endothelial cell injury in lupus nephritis by mediating the FoxO1 signaling pathway

Tripartite motif-containing 27 (TRIM27) belongs to the triple motif (TRIM) protein family, which plays a role in a variety of biological activities. Our previous study showed that the TRIM27 protein was highly expressed in the glomerular endothelial cells of patients suffering from lupus nephritis (LN). However, whether TRIM27 is involved in the injury of glomerular endothelial cells in lupus nephritis remains to be clarified. Here, we detected the expression of the TRIM27 protein in glomerular endothelial cells in vivo and in vitro. In addition, the influence of TRIM27 knockdown on endothelial cell damage in MRL/lpr mice and cultured human renal glomerular endothelial cells (HRGECs) was explored. The results revealed that the expression of TRIM27 in endothelial cells was significantly enhanced in vivo and in vitro. Downregulating the expression of TRIM27 inhibited the breakdown of the glycocalyx and the injury of endothelial cells via the FoxO1 pathway. Moreover, HRGECs transfected with the WT-FoxO1 plasmid showed a reduction in impairment caused by LN plasma. Furthermore, suppression of the protein kinase B (Akt) pathway could attenuate damage by mediating the expression of TRIM27. Thus, the present study showed that TRIM27 participated in the injury of glomerular endothelial cells and served as a potential therapeutic target for the treatment of lupus nephritis.

Association of eNOS and MCP-1 Genetic Variants with Type 2 Diabetes and Diabetic Nephropathy Susceptibility: A Case-Control and Meta-Analysis Study

Type 2 diabetes (T2D) and its secondary complications result from the complex interplay of genetic and environmental factors. To understand the role of these factors on disease susceptibility, the present study was conducted to assess the association of eNOS and MCP-1 variants with T2D and diabetic nephropathy (DN) in two ethnically and geographically different cohorts from North India. A total of 1313 subjects from two cohorts were genotyped for eNOS (rs2070744, rs869109213 and rs1799983) and MCP-1 (rs1024611 and rs3917887) variants. Cohort-I (Punjab) comprised 461 T2D cases (204 T2D with DN and 257 T2D without DN) and 315 healthy controls. Cohort-II (Jammu and Kashmir) included 337 T2D (150 T2D with DN and 187 T2D without DN) and 200 controls. Allele, genotype and haplotype frequencies were compared among the studied participants, and phenotype-genotype interactions were determined. Meta-analysis was performed to investigate the association between the selected variants and disease susceptibility. All three eNOS variants were associated with 1.5-4.0-fold risk of DN in both cohorts. MCP-1 rs1024611 conferred twofold risk towards DN progression in cohort-II, while rs3917887 provided twofold risk for both T2D and DN in both cohorts. eNOS and MCP-1 haplotypes conferred risk for T2D and DN susceptibility. Phenotype-genotype interactions showed significant associations between the studied variants and anthropometric and biochemical parameters. In meta-analysis, all eNOS variants conferred risk towards DN progression, whereas no significant association was observed for MCP-1 rs1024611. We show evidences for an association of eNOS and MCP-1 variants with T2D and DN susceptibility.

Diabetic kidney disease in type 2 diabetes: a review of pathogenic mechanisms, patient-related factors and therapeutic options

The global prevalence of diabetic kidney disease is rapidly accelerating due to an increasing number of people living with type 2 diabetes. It has become a significant global problem, increasing human and financial pressures on already overburdened healthcare systems. Interest in diabetic kidney disease has increased over the last decade and progress has been made in determining the pathogenic mechanisms and patient-related factors involved in the development and pathogenesis of this disease. A greater understanding of these factors will catalyse the development of novel treatments and influence current practice. This review summarises the latest evidence for the factors involved in the development and progression of diabetic kidney disease, which will inform better management strategies targeting such factors to improve therapeutic outcomes in patients living with diabetes.

Synchronized research on endothelial dysfunction and microcirculation structure in dorsal skin of rats with type 2 diabetes mellitus

The aim of this study was to explore changes in the microvascular tone as measured by laser Doppler flowmetry (LDF) and the microcirculation structure of the dorsal skin of rats with type 2 diabetes mellitus. The diabetic rat model was induced by a diet of high-sugar and high-lipid fodder combined with the injection of streptozotocin into the abdominal cavity. Depending on the interval between the development of diabetes and the experiments, the diabetic rats were subdivided into three groups. The evaluation of microvascular tone was based on the amplitude responses of the LDF signal fluctuations in the appropriate frequency range in the dorsal skin of the rats during a thermal test (at 42 °C). The nitric oxide (NO) level in plasma was also used as a marker of endothelial dysfunction. Changes in the microcirculation structure in the diabetic rats were estimated by measuring the microvascular density in the choke vessels of the dorsal skin of the rats. The experimental results with respect to red blood cell (RBC)-related parameters showed decreased hematocrit and hemoglobin levels and increased standard deviation of the width of the RBC distribution in three diabetic rats. The increasing fluctuation amplitudes diminished in the endothelial frequency range in response to the thermal test and this was accompanied by abnormal NO levels in plasma of the diabetic groups as compared with healthy rats. A significant reduction in the microvascular density of the choke vessels of the dorsal skin was found only in the diabetic group at the most advanced stage of diabetes in this experiment. Thus, we suggest that endothelial dysfunction occurs in diabetic rats and changes in the microcirculation structure of the dorsal skin occur in a later stage of diabetes development. A. Photograph of measurement method by using a LDF probe and heating device in the dorsal skin of the rat. B. Dorsal skin LDF signals of a healthy rat during the thermal stimuli test. (a) Blood flow signal record for the test. Wavelet filtration of blood flow signal in (b) myogenic range, (c) neurogenic range, and (d) endothelial range.

Gasotransmitter synthesis and signalling in the renal glomerulus. Implications for glomerular diseases

Glomerular injury is a hallmark of kidney diseases such as diabetic nephropathy, IgA nephropathy or other forms of glomerulonephritis. Glomerular endothelial cells, mesangial cells, glomerular epithelial cells (podocytes) and, in an inflammatory context, infiltrating immune cells crosstalk to mediate signalling processes in the glomerulus. Under physiological conditions, mesangial cells act by the control of extracellular matrix production and degradation, by the synthesis of growth factors and by preserving a well-defined crosstalk with glomerular podocytes and endothelial cells to regulate glomerular structure and function. It is well known that mesangial cells are able to amplify an inflammatory process by the formation of cytokines, reactive oxygen species (ROS) and nitric oxide (NO). This exaggerated reaction may result in a vicious cycle with subsequent damage of neighboured podocytes and endothelial cells, loss of the filtration barrier and, finally destruction of the whole glomerulus. Unfortunately, all efforts to develop new therapies for the treatment of glomerular diseases by controlling unbridled ROS or NO production directly had so far no success. However, on-going research on ROS and NO defined these autacoids more as important signalling molecules than as endogenously produced cytotoxic compounds. New findings on signalling activities of ROS, NO but also hydrogen sulfide (H₂S) and carbon monoxide (CO) supported this paradigm shift. Because of their similar chemical properties and their similar signal transduction capacities, NO, H₂S and CO are meanwhile designated as the group of gasotransmitters. In this review, we describe the current knowledge of the signalling properties of gasotransmitters with a focus on glomerular cells and their role in glomerular diseases.

Interplay of the adenosine system and NO in control of renal haemodynamics and excretion: Comparison of normoglycaemic and streptozotocin diabetic rats

The adenosine (Ado) system may participate in regulation of kidney function in diabetes mellitus (DM), therefore we explored its role and interrelation with NO in the control of renal circulation and excretion in normoglycemic (NG) and streptozotocin-diabetic (DM) rats. Effects of theophylline (Theo), a non-selective Ado receptor antagonist, were examined in anaesthetized NG or in streptozotocin induced diabetic (DM) rats, untreated or after blockade of NO synthesis with l-NAME. We measured arterial blood pressure (MABP), whole kidney blood flow and renal regional flows: cortical and outer- and inner-medullary (IMBF), determined as laser-Doppler fluxes. Renal excretion of water, total solutes and sodium and in situ renal tissue NO signal (selective electrodes) were also determined. Theo experiments disclosed minor baseline vasoconstrictor and vasodilator tone in the kidney of NG and DM rats, respectively. NO blockade increased baseline MABP and decreased renal haemodynamics, similarly in NG and DM rats, indicating comparable vasodilator influence of NO in the two groups. Unexpectedly, in all rats with intact NO synthesis, Ado receptor blockade increased kidney tissue NO. In NO-deficient NG and DM rats, Ado receptor blockade induced comparable renal vasodilatation, suggesting similar vasoconstrictor influence of the Ado system. However, DM rats showed an unexplained association of decreased MABP and IMBF and increased NO signal. Higher baseline renal excretion in DM rats indicated inhibition of renal tubular reabsorption due to the prevalence of natriuretic A2 over antinatriuretic A1 receptors. In conclusion, the experiments provided new insights in functional interrelation of adenosine and NO in normoglycaemia and streptozotocin-diabetes.

Pyrrolidine dithiocarbamate reduces alloxan-induced kidney damage by decreasing nox4, inducible nitric oxide synthase, and metalloproteinase-2

We examined the effect of the NFκB inhibitor pyrrolidine-1-carbodithioic acid (PDTC) on inducible nitric oxide synthase (iNOS), matrix metalloproteinase-2 (MMP-2) activity, and oxidative and inflammatory kidney damage in alloxan-induced diabetes. Two weeks after diabetes induction (alloxan-130 mg/kg), control and diabetic rats received PDTC (100 mg/kg) or vehicle for 8 weeks. Body weight, glycemia, urea, and creatinine were measured. Kidney changes were measured in hematoxylin/eosin sections and ED1 by immunohistochemistry. Kidney thiobarbituric acid reactive substances (TBARS), superoxide anion (O2-), and nitrate/nitrite (NOx) levels, and catalase and superoxide dismutase (SOD) activities were analyzed. Also, kidney nox4 and iNOS expression, and NFkB nuclear translocation were measured by western blot, and MMP-2 by zymography. Glycemia and urea increased in alloxan rats, which were not modified by PDTC treatment. However, PDTC attenuated kidney structural alterations and macrophage infiltration in diabetic rats. While diabetes increased both TBARS and O₂^- levels, PDTC treatment reduced TBARS in diabetic and O₂^- in control kidneys. A decrease in NO_x levels was found in diabetic kidneys, which was prevented by PDTC. Diabetes reduced catalase activity, and PDTC increased catalase and SOD activities in both control and diabetic kidneys. PDTC treatment reduced MMP-2 activity and iNOS and p65 NFκB nuclear expression found increased in diabetic kidneys. Our results show that the NFκB inhibitor PDTC reduces renal damage through reduction of Nox4, iNOS, macrophages, and MMP-2 in the alloxan-induced diabetic model. These findings suggest that PDTC inhibits alloxan kidney damage via antioxidative and anti-inflammatory mechanisms.

Aspartic acid supplementation ameliorates symptoms of diabetic kidney disease in mice

Diabetic kidney disease (DKD) is among the most common and serious complications of both type 1 and type 2 diabetes. In this study, we used KK/Ta‐Ins2^Akita (KK‐Akita) mice as a model of DKD and KK/Ta (KK) mice as controls to identify novel factors related to the development/progression of DKD. Capillary electrophoresis coupled with mass spectrometry analysis revealed that circulating Asp (l‐aspartic acid) levels in diabetic KK‐Akita mice tend to be lower than those in control KK mice. Therefore, we evaluated the effect of Asp supplementation to prevent the progression of DKD in KK‐Akita mice. Mice were divided into three groups: (a) untreated KK mice (Control group), (b) untreated KK‐Akita mice (DKD group), and (c) treated (double‐volume Asp diet) KK‐Akita mice (Tx group). Kidney sections were stained with fluorescein isothiocyanate‐labeled lectins, wheat germ agglutinin (WGA), and anti‐endothelial nitric oxide synthase (eNOS) antibody for evaluation of endothelial surface layer (ESL) and NO synthesis. The mesangial area and glomerular size in the DKD group were significantly larger than those in the Control group; however, there was no significant difference in those between the DKD and Tx groups. Albuminuria, the ratio of foot process effacement, and thickness of glomerular basement membrane in the Tx group were significantly lower than those in the DKD group. Furthermore, the expression levels of glomerular WGA and microvascular eNOS in the Tx group improved significantly and approached the level in the Control group. In conclusion, the improvement of albuminuria in the Tx group may be caused by the reduction of oxidative stress in the kidneys, which may lead to the subsequent improvement of glomerular ESL.

Enhancing kidney DDAH-1 expression by adenovirus delivery reduces ADMA and ameliorates diabetic nephropathy

Endothelial dysfunction, characterized by reduced bioavailability of nitric oxide and increased oxidative stress, is a hallmark characteristic in diabetes and diabetic nephropathy (DN). High levels of asymmetric dimethylarginine (ADMA) are observed in several diseases including DN and are a strong prognostic marker for cardiovascular events in patients with diabetes and end-stage renal disease. ADMA, an endogenous endothelial nitric oxide synthase (NOS3) inhibitor, is selectively metabolized by dimethylarginine dimethylaminohydrolase (DDAH). Low DDAH levels have been associated with cardiac and renal dysfunction, but its effects on DN are unknown. We hypothesized that enhanced renal DDAH-1 expression would improve DN by reducing ADMA and restoring NOS3 levels. DBA/2J mice injected with multiple low doses of vehicle or streptozotocin were subsequently injected intrarenally with adenovirus expressing DDAH-1 (Ad-h-DDAH-1) or vector control [Ad-green fluorescent protein (GFP)], and mice were followed for 6 wk. Diabetes was associated with increased kidney ADMA and reduced kidney DDAH activity and DDAH-1 expression but had no effect on kidney DDAH-2 expression. Ad-GFP-treated diabetic mice showed significant increases in albuminuria, histological changes, glomerular macrophage recruitment, inflammatory cytokine and fibrotic markers, kidney ADMA levels, and urinary thiobarbituric acid reactive substances excretion as an indicator of oxidative stress, along with a significant reduction in kidney DDAH activity and kidney NOS3 mRNA compared with normal mice. In contrast, Ad-h-DDAH-1 treatment of diabetic mice reversed these effects. These data indicate, for the first time, that DDAH-1 mediates renal tissue protection in DN via the ADMA-NOS3-interaction. Enhanced renal DDAH-1 activity could be a novel therapeutic tool for treating patients with diabetes.

Piperazine ferulate ameliorates the development of diabetic nephropathy by regulating endothelial nitric oxide synthase

Diabetic nephropathy (DN) is among the most common complications of diabetes mellitus. The disorder is associated with a decrease in the activity of the nitric oxide synthase/nitric oxide system. Piperazine ferulate (PF) is widely used for the treatment of kidney disease in China. The aim of the present study was to examine the effects of PF on streptozotocin (STZ)‑induced DN and the underlying mechanism of this process. STZ‑induced diabetic mice were intragastrically administered PF (100, 200 and 400 mg/kg/body weight/day) for 12 weeks. At the end of the treatment period, the parameters of 24‑h albuminuria and blood urea nitrogen, creatinine and oxidative stress levels were measured. Hematoxylin and eosin staining, periodic acid‑Schiff staining and electron microscopy were used to evaluate the histopathological alterations. mRNA and protein expression of endothelial nitric oxide synthase (eNOS) were measured by quantitative polymerase chain reaction and western blotting, respectively. PF significantly decreased blood urea nitrogen and creatinine levels and 24‑h albuminuria, and it alleviated oxidative stress, improved glomerular basement membrane thickness and caused an upregulation in eNOS expression and activity levels in diabetic mice. In addition, high glucose decreased eNOS expression levels, whereas PF caused a reversal in the nitric oxide (NO) levels of glomerular endothelial cells. The present results suggested that PF exhibited renoprotective effects on DN. The mechanism of its action was associated with the regulation of eNOS expression and activity.

Cardioprotective effects of a ruthenium (II) Schiff base complex in diet-induced prediabetic rats

BACKGROUND

Prediabetes and the onset of cardiovascular diseases (CVD) are strongly related. Prolonged hyperglycemia has been identified as a major contributing factor in the pathogenesis of CVD and diabetic complications. The management of hyperglycemia and prediabetes-associated vascular complications rely on pharmacotherapy and lifestyle intervention strategies. However, patients still take the conventional drugs and neglect lifestyle intervention; therefore, newer alternative drugs are required. The synthesized ruthenium Schiff base complex has been shown to have elevated biological and antidiabetic activity. Thus, the research investigated the cardio-protective effects of ruthenium (II) Schiff base complex in diet-induced prediabetic (PD) rats.

MATERIALS AND METHODS

The rats were randomly allocated to respective groups and treated for 12 weeks. Ruthenium (15 mg/kg) was administered to PD rats once a day every third day. Blood pressure and plasma glucose were monitored throughout the study. Blood and heart tissue were collected for biochemical assays.

RESULTS

Ruthenium complex with dietary intervention lead to reduced mean arterial blood pressure which correlated with a restored heart to body weight ratio. Additionally, there was a significant decrease in tissue malondialdehyde and increased superoxide dismutase and glutathione peroxidase concentration in both the plasma and heart tissue. Furthermore, there was a decrease in plasma triglycerides, low-density lipoprotein with an increased high-density lipoprotein concentration in ruthenium-treated rats. This was further evidenced by reduced plasma tumor necrosis factor-α, IL-6, and cardiac C-reactive protein concentrations in ruthenium-treated rats.

CONCLUSION

Ruthenium coupled with dietary intervention decreased the risk of developing cardiac injury, thus preventing CVD in prediabetes. Therefore, this complex may be a beneficial therapeutic agent in the prevention of PD cardiovascular complications.

Endothelial cell-specific overexpression of endothelial nitric oxide synthase in Ins2Akita mice exacerbates diabetic nephropathy

Previous studies demonstrated that global deficiency of eNOS in diabetic mice exacerbated renal lesions and that overexpression of eNOS may protect against tissue injury. Our study revealed for the first time overexpression of eNOS leads to disease progression rather than protection. Transgenic mice selectively expressing eNOS in endothelial cells (eNOSTg) were cross bred with Ins2Akita type-1 (AK) diabetic mice to generate eNOS overexpressing eNOSTg/AK mice. Wild type, eNOSTg, AK and eNOSTg/AK mice were assessed for kidney function and blood glucose levels. Remarkably, overexpressing eNOSTg mice showed evidence of unpredicted glomerular injury with segmental mesangiolysis and occasional microaneurysms. Notably, in eNOSTg/AK mice overexpression of eNOS led to increased glomerular/endothelial injury that was associated with increased superoxide levels and renal dysfunction. Results indicate for the first time that overexpressing eNOS in endothelial cells cannot ameliorate diabetic lesions, but paradoxically leads to progression of nephropathy likely due to eNOS uncoupling and superoxide upsurge. This novel finding has a significant impact on current therapeutic strategies to improve endothelial function and prevent progression of diabetic renal disease. Further, the eNOSTg/AK model developed in this study has significant translational potentials for elucidating the underlying mechanism implicated in the deflected function of eNOS in diabetic nephropathy.

The effects of probiotic and selenium co-supplementation on mental health parameters and metabolic profiles in type 2 diabetic patients with coronary heart disease: A randomized, double-blind, placebo-controlled trial

BACKGROUND AND AIMS

The objective of this investigation was to assess the effects of probiotic and selenium co-supplementation on indicators of mental health and metabolic profiles in diabetic people with coronary heart disease (CHD).

METHODS

This randomized, double-blind, placebo-controlled trial was conducted among 54 diabetic people with CHD. Patients were randomly allocated into two groups to receive either 200 μg/day selenium plus 8 × 10⁹ CFU/day probiotic (n = 27) or placebo (n = 27) for 12 weeks.

RESULTS

Probiotic and selenium co-supplementation significantly decreased Beck Depression Inventory index (β -1.46; 95% CI, -2.61, -0.31; P = 0.01) and Beck Anxiety Inventory index (β -1.23; 95% CI, -2.33, -0.12; P = 0.02) compared with the placebo. Consuming probiotic plus selenium lowered fasting plasma glucose (β -10.80 mg/dL; 95% CI, -17.68, -3.92; P = 0.003), serum insulin levels (β -3.42 μIU/mL; 95% CI, -4.93, -1.90; P < 0.001), insulin resistance (β -0.96; 95% CI, -1.45, -0.47; P < 0.001), and enhanced insulin sensitivity (β 0.01; 95% CI, 0.007, 0.01; P < 0.001) compared with the placebo. Additionally, co-supplementation reduced triglycerides (β -34.45 mg/dL; 95% CI, -56.18, -12.72; P = 0.003), VLDL- (β -6.89 mg/dL; 95% CI, -11.23, -2.54; P = 0.003), total cholesterol (β -18.13 mg/dL; 95% CI, -23.42, -2.83; P = 0.02) and high sensitivity C-reactive protein (β -1043.28 ng/mL; 95% CI, -1929.67, -156.89; P = 0.02), and increased nitric oxide (β 7.86 μmol/L; 95% CI, 5.63, 10.09; P < 0.001), total antioxidant capacity (β 119.30 mmol/L; 95% CI, 63.04, 175.57; P < 0.001) and total glutathione (β 154.16 μmol/L; 95% CI, 82.57, 225.74; P < 0.001) compared with the placebo.

CONCLUSIONS

Probiotic and selenium co-supplementation to diabetic people with CHD improved indicators of mental health and metabolic profiles. Registered under Clinical Trials.gov Identifier no. http://www.irct.ir: IRCT20170513033941N28.

Effects of a Ruthenium Schiff Base Complex on Glucose Homeostasis in Diet-Induced Pre-Diabetic Rats

Pre-diabetes is a condition that precedes type 2 diabetes mellitus (T2DM) that is characterised by elevated glycated haemoglobin (HbA1c). The management of pre-diabetes includes the combination of dietary and pharmacological interventions to increase insulin sensitivity. However, poor patient compliance has been reported with regard to dietary interventions, therefore, new alternative drugs are required that can be effective even without the dietary intervention. In our laboratory, we have synthesised a novel ruthenium complex that has been shown to have elevated biological activity. This study investigated the effects of this complex in both the presence and absence of dietary intervention on glucose handling in a diet-induced pre-diabetes rat model. Pre-diabetic animals were randomly assigned to respective treatment groups. The ruthenium complex was administered to pre-diabetic rats once a day every third day for 12 weeks. The administration of the ruthenium complex resulted in reduced fasting blood glucose, food intake, and body weight gain which was associated with decreased plasma ghrelin, insulin, and HbA1c levels in both the presence and absence of dietary intervention. The administration of the ruthenium complex ameliorated glycaemic control and insulin sensitivity in pre-diabetic rats. The results of this study warrant further investigations as this compound could potentially be able to re-sensitize insulin resistant cells and reduce the incidence of T2DM.

The effects of vitamin D and probiotic co-supplementation on mental health parameters and metabolic status in type 2 diabetic patients with coronary heart disease: A randomized, double-blind, placebo-controlled trial

BACKGROUND

This study was carried out to evaluate the effects of vitamin D and probiotic co-supplementation on mental health parameters and metabolic status in diabetic people with coronary heart disease (CHD).

METHODS

This randomized, double-blind, placebo-controlled trial was carried out among 60 diabetic people with CHD, aged 45-85 years old. Subjects were randomly allocated into two groups to receive either 50,000 IU vitamin D every 2 weeks plus 8 × 10⁹ CFU/g probiotic of Lactocare Zisttakhmir Co (n = 30) or placebo (n = 30) for 12 weeks. Fasting blood samples were obtained at baseline and after the 12-week intervention to determine metabolic profiles.

RESULTS

After the 12-week intervention, compared with the placebo, vitamin D and probiotic co-supplementation resulted in significant improvements in beck depression inventory total score (-2.8 ± 3.8 vs. -0.9 ± 2.1, P = 0.01), beck anxiety inventory scores (-2.1 ± 2.3 vs. -0.8 ± 1.4, P = 0.009) and general health questionnaire scores (-3.9 ± 4.1 vs. -1.1 ± 3.4, P = 0.005). Compared with the placebo, vitamin D and probiotic co-supplementation resulted in significant reductions in serum insulin levels (-2.8 ± 3.8 vs. +0.2 ± 4.9 μIU/mL, P = 0.009), homeostasis model of assessment-estimated insulin resistance (-1.0 ± 1.6 vs. -0.1 ± 1.5, P = 0.02), and a significant increase in serum 25-OH-vitamin D (+11.8 ± 5.9 vs. +0.1 ± 1.4 ng/mL, P < 0.001), the quantitative insulin sensitivity check index (+0.03 ± 0.04 vs. -0.001 ± 0.01, P = 0.003) and serum HDL-cholesterol levels (+2.3 ± 3.5 vs. -0.5 ± 3.8 mg/dL, P = 0.004). In addition, changes in serum high sensitivity C-reactive protein (hs-CRP) (-950.0 ± 1811.2 vs. +260.5 ± 2298.2 ng/mL, P = 0.02), plasma nitric oxide (NO) (+1.7 ± 4.0 vs. -1.4 ± 6.7 μmol/L, P = 0.03) and plasma total antioxidant capacity (TAC) (+12.6 ± 41.6 vs. -116.9 ± 324.2 mmol/L, P = 0.03) in the supplemented group were significantly different from the changes in these indicators in the placebo group.

CONCLUSIONS

Overall, vitamin D and probiotic co-supplementation after 12 weeks among diabetic people with CHD had beneficial effects on mental health parameters, serum hs-CRP, plasma NO, TAC, glycemic control and HDL-cholesterol levels.

CLINICAL TRIAL REGISTRATION NUMBER

http://www.irct.ir: IRCT2017073033941N4.

Protective effect of C-peptide on experimentally induced diabetic nephropathy and the possible link between C-peptide and nitric oxide

Diabetic nephropathy one of the major microvascular diabetic complications. Besides hyperglycemia, other factors contribute to the development of diabetic complications as the proinsulin connecting peptide, C-peptide. We described the role of C-peptide replacement therapy on experimentally induced diabetic nephropathy, and its potential mechanisms of action by studying the role of nitric oxide (NO) as a mediator of C-peptide effects by in vivo modulating its production by NG-nitro-l-arginine methyl ester (L-NAME). Renal injury markers measured were serum urea, creatinine, tumor necrosis factor alpha, and angiotensin II, and malondialdehyde, total antioxidant, Bcl-2, and NO in renal tissue. In conclusion, diabetic induction resulted in islet degenerations and decreased insulin secretion with its metabolic consequences and subsequent renal complications. C-Peptide deficiencies in diabetes might have contributed to the metabolic and renal error, since C-peptide treatment to the diabetic rats completely corrected these errors. The beneficial effects of C-peptide are partially antagonized by L-NAME coadministration, indicating that NO partially mediates C-peptide effects.

The effects of synbiotic supplementation on hormonal status, biomarkers of inflammation and oxidative stress in subjects with polycystic ovary syndrome: a randomized, double-blind, placebo-controlled trial

BACKGROUND

To our knowledge, no reports are available indicating the effects of synbiotic supplementation on hormonal status, biomarkers of inflammation and oxidative stress in subjects with polycystic ovary syndrome (PCOS). This research was done to assess the effects of synbiotic supplementation on hormonal status, biomarkers of inflammation and oxidative stress in subjects with PCOS.

METHODS

This randomized double-blind, placebo-controlled trial was conducted on 60 subjects diagnosed with PCOS according to the Rotterdam criteria. Subjects were randomly assigned into two groups to take either synbiotic (n = 30) or placebo (n = 30) for 12 weeks. Endocrine, inflammation and oxidative stress biomarkers were quantified at baseline and after the 12-week intervention.

RESULTS

After the 12-week intervention, compared with the placebo, synbiotic supplementation significantly increased serum sex hormone-binding globulin (SHBG) (changes from baseline in synbiotic group: + 19.8 ± 47.3 vs. in placebo group: + 0.5 ± 5.4 nmol/L, p = 0.01), plasma nitric oxide (NO) (changes from baseline in synbiotic group: + 5.5 ± 4.8 vs. in placebo group: + 0.3 ± 9.1 μmol/L, p = 0.006), and decreased modified Ferriman Gallwey (mF-G) scores (changes from baseline in synbiotic group: - 1.3 ± 2.5 vs. in placebo group: - 0.1 ± 0.5, p = 0.01) and serum high-sensitivity C-reactive protein (hs-CRP) (changes from baseline in synbiotic group: - 950.0 ± 2246.6 vs. in placebo group: + 335.3 ± 2466.9 ng/mL, p = 0.02). We did not observe any significant effect of synbiotic supplementation on other hormonal status and biomarkers of oxidative stress.

CONCLUSIONS

Overall, synbiotic supplementation for 12 weeks in PCOS women had beneficial effects on SHBG, mFG scores, hs-CRP and NO levels, but did not affect other hormonal status and biomarkers of oxidative stress.

TRIAL REGISTRATION

This study was retrospectively registered in the Iranian website ( www.irct.ir ) for registration of clinical trials ( IRCT201509115623N53 ), on 2015-09-27.

The beneficial effects of probiotic administration on wound healing and metabolic status in patients with diabetic foot ulcer: A randomized, double-blind, placebo-controlled trial

BACKGROUND

This study was conducted to evaluate the effects of probiotic supplementation on wound healing and metabolic status in subjects with diabetic foot ulcer (DFU).

METHODS

This randomized, double-blind, placebo-controlled trial was conducted among 60 subjects (aged 40-85 years old) with grade 3 diabetic foot ulcer. Individuals were randomly divided into 2 groups (30 subjects each group) to receive either probiotic or placebo daily for 12 weeks.

RESULTS

After the 12-week intervention, compared with the placebo, probiotic supplementation led to significant reductions in ulcer length (-1.3 ± 0.9 vs. -0.8 ± 0.7 cm, P = .01), width (-1.1 ± 0.7 vs. -0.7 ± 0.7 cm, P = .02), and depth (-0.5 ± 0.3 vs. -0.3 ± 0.3 cm, P = .02). Furthermore, significant reductions in fasting plasma glucose (-29.6 ± 30.3 vs. -5.8 ± 39.8 mg/dL, P = .01), serum insulin concentrations (-4.3 ± 7.9 vs. +0.4 ± 8.5 μIU/mL, P = .03), and haemoglobin A1c (-0.6 ± 0.5 vs. -0.2 ± 0.4%, P = .003) and a significant rise in the quantitative insulin sensitivity check index (+0.01 ± 0.01 vs. -0.01 ± 0.02, P = .003) were seen following supplementation of probiotic compared with the placebo. Additionally, compared with the placebo, probiotic supplementation resulted in significant decreases in serum total cholesterol (-4.8 ± 16.1 vs. +7.0 ± 27.1 mg/dL, P = .04), high-sensitivity C-reactive protein (-9.0 ± 14.7 vs. -1.7 ± 8.6 mg/L, P = .02), plasma malondialdehyde (-0.8 ± 0.8 vs. -0.2 ± 0.8 μmol/L, P = .001), and significant increases in plasma nitric oxide (+6.2 ± 8.2 vs. +0.8 ± 8.0 μmol/L, P = .01) and total antioxidant capacity concentrations (+179.3 ± 97.2 vs. -85.1 ± 203.4 mmol/L, P < .001).

CONCLUSIONS

Overall, probiotic supplementation for 12 weeks among subjects with diabetic foot ulcer had beneficial effects on ulcer size, glycaemic control, total cholesterol, high-sensitivity C-reactive protein, plasma nitric oxide, total antioxidant capacity, and malondialdehyde levels.

Endothelial dysfunction in renal arcuate arteries of obese Zucker rats: The roles of nitric oxide, endothelium-derived hyperpolarizing factors, and calcium-activated K+ channels

The roles of nitric oxide (NO), endothelium-derived hyperpolarizing factors (EDHF), and calcium-activated K⁺ (K_Ca) channels in diabetes-associated endothelial dysfunction of small renal arteries are not clear. The present study investigated acetylcholine (ACh)-induced vasorelaxation of renal arcuate arteries from obese Zucker (OZ) rats at different diabetes durations, and the relative contribution of NO, EDHF, and K_Ca channels to the endothelial dysfunction. OZ rats of 7 weeks (prediabetic stage), 12 weeks (early diabetic stage), and 20 weeks (late diabetic stage), and time-matched lean control rats, were studied. Segments of arcuate arteries (130 to 180 μm) were isolated, cannulated and pressurized. Vascular endothelial functions were tested using ACh-induced vasodilation. Our experiments demonstrated: (1) ACh-elicited vasodilation was impaired in OZ rats of 20 weeks, but not in rats of 7 and 12 weeks; (2) inhibition of NO or EDHF (contributed by epoxyeicosatrienoic acids [EETs]) production significantly decreased ACh-induced vasodilation in both lean and OZ rats of 20 weeks. The reduction of ACh-induced vasodilation by inhibition of NO or EDHF formation was less in OZ rats, as compared to lean rats; and (3) inhibition of K_Ca channels markedly reduced ACh-induced vasodilation in lean control rats, but not in OZ rats of 20 weeks. Our observations indicated that endothelium-dependent vasodilation in renal arcuate arteries is impaired in diabetes mellitus; NO and EDHF, mainly EETs, dominate the ACh-induced vasodilation in renal arcuate arteries; the contribution of NO and EETs is impaired in diabetic rats; K_Ca channels are involved in ACh-induced vasodilation; and the activity of K_Ca channels is downregulated in diabetes mellitus.

Follow Up of Value of the Intrarenal Resistivity Indices and Different Renal Biomarkers for Early Identification of Diabetic Nephropathy in Type 1 Diabetic Patients

AIM

To evaluate intrarenal resistivity index (RI) and different biomarkers of diabetic nephropathy (DN) with clinical signs of DN and its progression over time as early detection of DN.

PATIENTS AND METHODS

This longitudinal study included 48 type 1 diabetic patients who were studied at baseline and after three years. A blood sample was taken for assessment of glycosylated haemoglobin (HbA1), lipid profile and a urine sample was taken for assessment of albumin/creatinine ratio, Neutrophil gelatinase-associated lipocalin (NGAL), liver-type fatty acid binding protein (L-FABP) and kidney injury molecule-1 (Kim-1) at baseline and after three years. Forty diabetic patients did renal Doppler at baseline & after three years.

RESULTS

HbA1, waist/hip ratio, albumin/creatinine ratio, lipid profile, NGAL, KIM-1, L-FABP and resistivity index (RI) were significantly increased in follow-up. Twenty patients (41.7%) showed progression to albuminuria. RI showed a significant increase in follow-up study. ROC curve showed that RI and NGAL had the highest sensitivity (100%), followed by L-FABP (90%) and lastly KIM-1 (63.6%) in the prediction of DN.

CONCLUSION

High RI, NGAL, KIM-1 & L-FABP can be considered as early markers of diabetic nephropathy in type 1 diabetics and are associated with its progression over time, independent of albuminuria.

Direct Observation of Enhanced Nitric Oxide in a Murine Model of Diabetic Nephropathy

Uncoupling of nitric oxide synthase (NOS) secondary to redox signaling is a central mechanism in endothelial and macrophage activation. To date studies on the production of nitric oxide (NO) during the development of diabetic complications show paradoxical results. We previously showed that recoupling eNOS by increasing the eNOS cofactor tetrahydrobiopterin (BH4) could restore endothelial function and prevent kidney injury in experimental kidney transplantation. Here, we employed a diabetic mouse model to investigate the effects of diabetes on renal tissue NO bioavailability. For this, we used in vivo NO trapping, followed by electron paramagnetic resonance spectroscopy. In addition, we investigated whether coupling of NOS by supplying the cofactor BH4 could restore glomerular endothelial barrier function. Our data show that overall NO availability at the tissue level is not reduced sixteen weeks after the induction of diabetes in apoE knockout mice, despite the presence of factors that cause endothelial dysfunction, and the presence of the endogenous NOS inhibitor ADMA. Targeting uncoupled NOS with the BH4 precursor sepiapterin further increases NO availability, but did not modify renal glomerular injury. Notably, glomerular heparanase activity as a driver for loss of glomerular barrier function was not reduced, pointing towards NOS-independent mechanisms. This was confirmed by unaltered increased glomerular presence of cathepsin L, the protease that activates heparanase.

VEGF and the diabetic kidney: More than too much of a good thing

Over a decade and a half has passed since the publication of early reports hinting at a pathogenetic role for vascular endothelial growth factor ("VEGF") in the development of diabetic kidney disease. In diabetic rats, renal mRNA levels of the VEGF-A isoform were upregulated and administration of a VEGF-A neutralizing antibody attenuated albuminuria: VEGF was "bad" in diabetic nephropathy. Since that time, our understanding of the complexity of the renal VEGF system has advanced. Unlike its experimental counterpart, human diabetic nephropathy is associated with diminished VEGF-A levels and experience in the oncological setting has taught us that VEGF blocking therapy can cause adverse renal effects in patients. Correspondingly, investigational studies in cultured cells and rodent models have demonstrated that the biological effects of the VEGF system are dependent not only on the amount of VEGF, but also the type of VEGF, its sites of action and the prevailing milieu. Here we reflect back on the discoveries that have been made since those initial reports that shone the spotlight on the importance of the VEGF system in the diabetic kidney and we consider that the role of VEGF in diabetic nephropathy extends well beyond being "too much of a good thing".

The Consumption of Synbiotic Bread Containing Lactobacillus sporogenes and Inulin Affects Nitric Oxide and Malondialdehyde in Patients with Type 2 Diabetes Mellitus: Randomized, Double-Blind, Placebo-Controlled Trial

OBJECTIVES

To our knowledge, no reports are available indicating the effects of synbiotic bread consumption on nitric oxide (NO), biomarkers of oxidative stress, and liver enzymes among patients with type 2 diabetes mellitus (T2DM). This study was performed to determine the effects of the daily consumption of synbiotic bread on NO, biomarkers of oxidative stress, and liver enzymes in patients with T2DM.

METHODS

This randomized, double-blind, placebo-controlled trial was performed among 81 patients with diabetes, aged 35-70 years old. After a 2-week run-in period, patients were randomly divided into 3 groups: group A (n = 27) received synbiotic bread containing viable and the heat-resistant probiotic Lactobacillus sporogenes (1 × 108 CFU) and 0.07 g inulin per 1 g, group B (n = 27) received probiotic bread containing Lactobacillus sporogenes (1 × 108 CFU), and group C (n = 27) received control bread for 8 weeks. Patients were asked to consume the synbiotic, probiotic, or control breads 3 times a day in 40 g packages for a total of 120 g/day. Fasting blood samples were taken at baseline and after an 8-week intervention for quantificationof related markers.

RESULTS

After 8 weeks, the consumption of synbiotic bread compared to the probiotic and control breads resulted in a significant rise in plasma NO (40.6 ± 34.4 vs 18.5 ± 36.2 and -0.8 ± 24.5 µmol/L, respectively, p < 0.001) and a significant reduction in malondialdehyde (MDA) levels (-0.7 ± 0.7 vs 0.6 ± 1.7 and 0.5 ± 1.5 µmol/L, respectively, p = 0.001). We did not find any significant effect of the synbiotic bread consumption on plasma total antioxidant capacity (TAC), plasma glutathione (GSH), catalase, serum liver enzymes, calcium, iron, magnesium levels, and blood pressure compared to the probiotic and control breads.

CONCLUSION

In conclusion, consumption of the synbiotic bread for 8 weeks among patients with T2DM had beneficial effects on plasma NO and MDA levels; however, it did not affect plasma TAC, GSH, catalase levels, serum liver enzymes, calcium, iron, magnesium levels, and blood pressure.

Antioxidant diet and sex interact to regulate NOS isoform expression and glomerular mesangium proliferation in Zucker diabetic rat kidney

Oxidative stress contributes substantially to the pathophysiology of diabetic nephropathy (DN). Consumption of an antioxidant-fortified (AO) diet from an early age prevents or delays later development of DN in the Zucker rat female with type 2 diabetes. We hypothesize this is due to effects on mesangial matrix and renal nitric oxide synthase (NOS) distribution and to sex-specific differences in NOS responses in the diabetic kidney. Total glomerular tuft area (GTA) and PAS-positive tuft area (PTA), endothelial (e), neuronal (n) and inducible (i) NOS were quantified in males and females on AO or regular (REG) diet at 6 and 20 weeks of age. eNOS was observed in glomeruli and tubules. nNOS predominantly localized to tubular epithelium in both cortex and medulla. iNOS was expressed in proximal and distal tubules and collecting ducts. Sex, diabetes duration and AO diet affected the distribution of the three isoforms. GTA and PTA increased with duration of hyperglycemia and showed a negative correlation with renal levels of all NOS isoforms. AO diet in both genders was associated with less PAS-positive staining and less mesangial expansion than the REG diet, an early increase in cortical iNOS in males, and sex-specific changes in cortical eNOS at 20 weeks. These effects of AO diet may contribute to sex-specific preservation of renal function in females.

Insulin resistance as a predictor of cardiovascular morbidity and end-stage renal disease

BACKGROUND

Cardiovascular disease (CVD) is the main risk factor of morbidity and mortality in chronic kidney disease (CKD) patients. Insulin resistance (IR) has been reported to be a strong risk factor for CVD. The purpose of this study was to examine the usefulness of IR as a predictor of cardiovascular morbidity and end-stage renal disease (ESRD).

METHODS

We followed during a period of 56months 119 type 2 diabetic CKD patients (stages 2 to 4) without history of CVD at the beginning of the study. Several laboratory parameters and left ventricular mass index (LVMI) were analyzed. The degree of IR was estimated by the Homeostasis Model Assessment (HOMA-IR). Cardiovascular morbidity was assessed according to the presence of cardiovascular hospital admission during the study period, defined by admissions caused by coronary heart disease, congestive heart failure, peripheral vascular disease and cerebrovascular disease. The population was divided in two groups: G-1 with cardiovascular admission (n=48) and G-2: without admission (n=71). The multiple logistic regression was used to assess predictors of cardiovascular morbidity and ESRD. The renal survival was evaluated by the Kaplan-Meier and long-rank test.

RESULTS

We found that G-1 patients showed significantly higher HOMA-IR (3.8 vs 0.77, p=0.0001) and that HOMA-IR upper tercile showed significantly higher age, eGFR, LVMI, phosphorus, iPTH and IL-6. In a multivariate logistic regression model HOMA-IR and IL-6 were independent risk factors of cardiovascular morbidity (OR=2.847 [95% CI 1.048-7.735, p=0.012] and OR=2.483 [95% CI 1.221-5.049, p=0.04], respectively). In a univariate logistic regression model patients in the upper tercile presented significantly more cardiovascular admissions that in the lower tercile. CKD progression to ESRD was observed in 24 patients and those in the upper HOMA-IR tercile showed a higher CKD progression to ESRD than the rest of study patients. A multivariate logistic regression model showed that HOMA-IR (OR=1.034, 95% CI (1.005-1.650) p=0.040) was an independent predictor of ESRD. Kaplan-Meier analysis showed a difference in renal survival in the HOMA-IR terciles (log rank=8.093; p=0.017).

CONCLUSION

In our study IR is an important risk factor for cardiovascular morbidity and ESRD in a diabetic CKD population.

Phosphodiesterase type 5 inhibitors and kidney disease

Chronic kidney disease (CKD) represents a worldwide health problem. Traditionally, the nephroprotective treatment for CKD aims to slow progression to end-stage renal disease and includes dietary protein restriction, correction of metabolic acidosis, and renin-angiotensin system blockers. However, current standard therapeutic options may not be enough for preventing CKD progression in a subset of patients making necessary to develop novel therapeutic options to further slow renal function loss. Phosphodiesterase type 5 (PDE5) inhibitors represent a class of drugs traditionally used to treat erectile dysfunction and pulmonary hypertension. However, recent evidence suggests that PDE5 inhibitors may have additional therapeutic effects, such as cardioprotection and cerebrovascular protection. In the current review, we summarize PDE5 inhibitors' utility in disease states and clinical conditions related to kidney disease such as systemic hypertension and acute and chronic kidney injury and discuss the mechanisms explaining possible kidney protective roles of PDE5 inhibitors. A recently completed phase 2 trials demonstrated that the long-acting PDE5 inhibitor PF-00489791 decreased albuminuria in patients with overt diabetic nephropathy when added on top of renin-angiotensin system blockade.

Differences Between Tg2576 and Wild Type Mice in the NMDA Receptor-Nitric Oxide Pathway After Prolonged Application of a Diet High in Advanced Glycation End Products

It has been suggested that advanced glycation end (AGE) products, via cognate receptor activation, are implicated in several diseases, including Alzheimer's disease. The NMDA receptor-nitric oxide pathway appears to be influenced by AGE products and involved in the pathogenesis of this type of dementia. In this study, C57BL/6J (WT) and transgenic (Tg2576) mice expressing human mutant amyloid precursor protein were kept on prolonged (8 months) diets containing regular or high amounts of AGE products. After the decapitation of 11-months old mice, brain tissue analyses were performed [expressions of the NR1, NR2A and NR2B subunits of NMDA receptors, activities of neuronal, endothelial and inducible nitric oxide synthase (nNOS, eNOS and iNOS)]. Moreover, levels of malondialdehyde and of human amyloid β 1-42 were estimated. We found increased activity of nNOS in WT mice maintained on a high compared to regular AGE diet; however, no similar differences were found in Tg2576 mice. In addition, we observed an increase in NR1 expression in Tg2576 compared to WT mice, both kept on a diet high in AGE products. Correlation analyses performed on mice kept on the regular AGE diet supported close links between particular subunits (NR2A-NR2B, in WT as well as in Tg2576 mice), between subunits and synthase (NR2A/NR2B-nNOS, only in WT mice) or between particular synthases (nNOS-iNOS, only in WT). Correlation analysis also revealed differences between WT mice kept on both diets (changed correlations between NR2A/NR2B-nNOS, between nNOS-eNOS and between eNOS-iNOS). Malondialdehyde levels were increased in both Tg2576 groups when compared to the corresponding WT mice, but no effects of the diets were observed. Analogously, no significant effects of diets were found in the levels of soluble or insoluble amyloid β 1-42 in Tg2576 mice. Our results demonstrate that prolonged ingestion of AGE products can influence the NMDA receptor-nitric oxide pathway in the brain and that only WT mice, not Tg2576 mice, are able to maintain homeostasis among subunits and synthases or among particular synthases. The prolonged application of AGE products enhanced differences between 11-months old Tg2576 and WT mice regarding this pathway. Observed differences in the pathway between WT mice kept on regular or high AGE diets suggest that the prolonged application of a diet low in AGE products could have beneficial effects in older or diabetic people and perhaps also in people with Alzheimer's disease.

Effects of beta-carotene fortified synbiotic food on metabolic control of patients with type 2 diabetes mellitus: A double-blind randomized cross-over controlled clinical trial

BACKGROUND & AIMS

The aim of the present study was to determine the beneficial effects of beta-carotene fortified synbiotic food intake on metabolic status in patients with type 2 diabetes mellitus (T2DM).

METHODS

This randomized double-blinded placebo-controlled crossover clinical trial was conducted among 51 patients with T2DM. Individuals were randomly assigned to take either a beta-carotene fortified synbiotic (n = 51) or control food (n = 51) for 6 weeks. The beta-carotene fortified synbiotic was containing Lactobacillus sporogenes (1 × 10(7) CFU), 0.1 g inulin and 0.05 g beta-carotene. Control food (the same substance without probiotic, inulin and beta-carotene) was packed in identical 9-g packages. Patients were requested to use the beta-carotene fortified synbiotic and control foods three times a day.

RESULTS

Beta-carotene fortified synbiotic food consumption resulted in a significant decrease in insulin (-1.00 ± 7.90 vs. +3.68 ± 6.91 μIU/mL, P = 0.002), HOMA-IR (-0.73 ± 3.96 vs. +1.82 ± vbnm4.09, P = 0.002), HOMA-B (-0.52 ± 19.75 vs. +8.71 ± 17.15, P = 0.01), triglycerides (-2.86 ± 49.53 vs. +20.14 ± 50.10 mg/dL, P = 0.02), VLDL-cholesterol levels (-0.57 ± 9.90 vs. +4.03 ± 10.02 mg/dL, P = 0.02) and total-/HDL-cholesterol ratio (-0.01 ± 1.08 vs. +0.64 ± 0.81, P = 0.001) compared to the control food. In addition, beta-carotene fortified synbiotic food consumption led to elevated plasma nitric oxide (NO) (+6.83 ± 16.14 vs. -3.76 ± 16.47 μmol/L, P = 0.001) and glutathione (GSH) (+36.58 ± 296.71 vs. -92.04 ± 243.05 μmol/L, P = 0.01).

CONCLUSIONS

Beta-carotene fortified synbiotic food intake in patients with T2DM for 6 weeks had favorable effects on insulin, HOMA-IR, HOMA-B, triglycerides, VLDL-cholesterol, total-/HDL-cholesterol ratio, NO and GSH levels.

Arginase inhibition: a new treatment for preventing progression of established diabetic nephropathy

Our previous publication showed that inhibition of arginase prevents the development of diabetic nephropathy (DN). However, identification of targets that retard the progression of established DN-which is more clinically relevant-is lacking. Therefore, we tested the hypothesis that arginase inhibition would prevent the progression of established DN. Effects of arginase inhibition were compared with treatment with the angiotensin-converting enzyme inhibitor captopril, a current standard of care in DN. Experiments were conducted in Ins2(Akita) mice treated with the arginase inhibitor S-(2-boronoethyl)-l-cysteine (BEC) or captopril starting at 6 wk of age for 12 wk (early treatment) or starting at 12 wk of age for 6 wk (late treatment). Early and late treatment with BEC resulted in protection from DN as indicated by reduced albuminuria, histological changes, kidney macrophage infiltration, urinary thiobarbituric acid-reactive substances, and restored nephrin expression, kidney nitrate/nitrite, kidney endothelial nitric oxide synthase phosphorylation, and renal medullary blood flow compared with vehicle-treated Ins2(Akita) mice at 18 wk of age. Interestingly, early treatment with captopril reduced albuminuria, histological changes, and kidney macrophage infiltration without affecting the other parameters, but late treatment with captopril was ineffective. These findings highlight the importance of arginase inhibition as a new potential therapeutic intervention in both early and late stages of diabetic renal injury.

Recent advances in renal hemodynamics: insights from bench experiments and computer simulations

It has been long known that the kidney plays an essential role in the control of body fluids and blood pressure and that impairment of renal function may lead to the development of diseases such as hypertension (Guyton AC, Coleman TG, Granger Annu Rev Physiol 34: 13-46, 1972). In this review, we highlight recent advances in our understanding of renal hemodynamics, obtained from experimental and theoretical studies. Some of these studies were published in response to a recent Call for Papers of this journal: Renal Hemodynamics: Integrating with the Nephron and Beyond.

Renal autoregulation in health and disease

Intrarenal autoregulatory mechanisms maintain renal blood flow (RBF) and glomerular filtration rate (GFR) independent of renal perfusion pressure (RPP) over a defined range (80-180 mmHg). Such autoregulation is mediated largely by the myogenic and the macula densa-tubuloglomerular feedback (MD-TGF) responses that regulate preglomerular vasomotor tone primarily of the afferent arteriole. Differences in response times allow separation of these mechanisms in the time and frequency domains. Mechanotransduction initiating the myogenic response requires a sensing mechanism activated by stretch of vascular smooth muscle cells (VSMCs) and coupled to intracellular signaling pathways eliciting plasma membrane depolarization and a rise in cytosolic free calcium concentration ([Ca(2+)]i). Proposed mechanosensors include epithelial sodium channels (ENaC), integrins, and/or transient receptor potential (TRP) channels. Increased [Ca(2+)]i occurs predominantly by Ca(2+) influx through L-type voltage-operated Ca(2+) channels (VOCC). Increased [Ca(2+)]i activates inositol trisphosphate receptors (IP3R) and ryanodine receptors (RyR) to mobilize Ca(2+) from sarcoplasmic reticular stores. Myogenic vasoconstriction is sustained by increased Ca(2+) sensitivity, mediated by protein kinase C and Rho/Rho-kinase that favors a positive balance between myosin light-chain kinase and phosphatase. Increased RPP activates MD-TGF by transducing a signal of epithelial MD salt reabsorption to adjust afferent arteriolar vasoconstriction. A combination of vascular and tubular mechanisms, novel to the kidney, provides for high autoregulatory efficiency that maintains RBF and GFR, stabilizes sodium excretion, and buffers transmission of RPP to sensitive glomerular capillaries, thereby protecting against hypertensive barotrauma. A unique aspect of the myogenic response in the renal vasculature is modulation of its strength and speed by the MD-TGF and by a connecting tubule glomerular feedback (CT-GF) mechanism. Reactive oxygen species and nitric oxide are modulators of myogenic and MD-TGF mechanisms. Attenuated renal autoregulation contributes to renal damage in many, but not all, models of renal, diabetic, and hypertensive diseases. This review provides a summary of our current knowledge regarding underlying mechanisms enabling renal autoregulation in health and disease and methods used for its study.

Renal endothelial dysfunction in diabetic nephropathy

Endothelial dysfunction has been posited to play an important role in the pathogenesis of diabetic nephropathy (DN). Due to the heterogeneity of endothelial cells (ECs), it is difficult to generalize about endothelial responses to diabetic stimuli. At present, there are limited techniques fordirectly measuring EC function in vivo, so diagnosis of endothelial disorders still largely depends on indirect assessment of mediators arising from EC injury. In the kidney microcirculation, both afferent and efferent arteries, arterioles and glomerular endothelial cells (GEnC) have all been implicated as targets of diabetic injury. Both hyperglycemia per se, as well as the metabolic consequences of glucose dysregulation, are thought to lead to endothelial cell dysfunction. In this regard, endothelial nitric oxide synthase (eNOS) plays a central role in EC dysfunction. Impaired eNOS activity can occur at numerous levels, including enzyme uncoupling, post-translational modifications, internalization and decreased expression. Reduced nitric oxide (NO) bioavailability exacerbates oxidative stress, further promoting endothelial dysfunction and injury. The injured ECs may then function as active signal transducers of metabolic, hemodynamic and inflammatory factors that modify the function and morphology of the vessel wall and interact with adjacent cells, which may activate a cascade of inflammatory and proliferative and profibrotic responses in progressive DN. Both pharmacological approaches and potential regenerative therapies hold promise for restoration of impaired endothelial cells in diabetic nephropathy.

Nitric oxide in the normal kidney and in patients with diabetic nephropathy

Nitric oxide (NO) is a gas with biological and regulatory properties, produced from arginine by the way of nitric oxide synthases (NOS), and with a very short half-life (few seconds). A "coupled" NOS activity leads to NO generation, whereas its uncoupling produces the reactive oxygen species peroxynitrite (ONOO(-)). Uncoupling is usually due to inflammation, oxidative stress, decreased cofactor availability, or excessive NO production. Competitive inhibitors of NO production are post-translationally methylated arginine residues in proteins, which are constantly released into the circulation. NO availability is altered in many clinical conditions associated with vascular dysfunction, such as diabetes mellitus. The kidney plays an important role in body NO homeostasis. This article provides an overview of current literature, on NO production/availability, with a focus on diabetic nephropathy. In diabetes, NO availability is usually decreased (with exception of the early, hyper filtration phase of nephropathy in Type 1 diabetes), and it could constitute a factor of the generalized vasculopathy present in diabetic nephropathy. NO generation in Type 2 diabetes with nephropathy is inversely associated with the dimethyl-arginine concentrations, which are therefore important modulators of NO synthesis independently from the classic stimulatory pathways (such as the insulin effect). A disturbed NO metabolism is present in diabetes associated with nephropathy. Although modulation of NO production is not yet a common therapeutical strategy, a number of yet experimental compounds need to be tested as potential interventions to treat the vascular dysfunction and nephropathy in diabetes, as well as in other diseased states. Finally, in diabetic nephropathy NO deficiency may be associated to that of hydrogen sulfide, another interesting gaseous mediator which is increasingly investigated.

Renal response to L-arginine in diabetic rats. A possible link between nitric oxide system and aquaporin-2

The aim of this study was to evaluate whether L-Arginine (L-Arg) supplementation modifies nitric oxide (NO) system and consequently aquaporin-2 (AQP2) expression in the renal outer medulla of streptozotocin-diabetic rats at an early time point after induction of diabetes. Male Wistar rats were divided in four groups: Control, Diabetic, Diabetic treated with L-Arginine and Control treated with L-Arginine. Nitric oxide synthase (NOS) activity was estimated by [¹⁴C] L-citrulline production in homogenates of the renal outer medulla and by NADPH-diaphorase staining in renal outer medullary tubules. Western blot was used to detect the expression of AQP2 and NOS types I and III; real time PCR was used to quantify AQP2 mRNA. The expression of both NOS isoforms, NOS I and NOS III, was decreased in the renal outer medulla of diabetic rats and L-Arg failed to prevent these decreases. However, L-Arg improved NO production, NADPH-diaphorase activity in collecting ducts and other tubular structures, and NOS activity in renal homogenates from diabetic rats. AQP2 protein and mRNA were decreased in the renal outer medulla of diabetic rats and L-Arg administration prevented these decreases. These results suggest that the decreased NOS activity in collecting ducts of the renal outer medulla may cause, at least in part, the decreased expression of AQP2 in this model of diabetes and constitute additional evidence supporting a role for NO in contributing to renal water reabsorption through the modulation of AQP2 expression in this pathological condition. However, we cannot discard that another pathway different from NOS also exists that links L-Arg to AQP2 expression.

Anaemia, a common but often unrecognized risk in diabetic patients: a review

Anaemia in patients with diabetes, both type 1 and type 2, is a frequent clinical finding. The mechanisms of anaemia are multifactorial and often not very well understood. Iatrogenic causes, including oral antidiabetic drugs, ACE inhibitors and ARBs, and renal insufficiency are the major causes of anaemia in patients with type 2 diabetes. In patients with type 1, the cause is often an associated autoimmune disease, and screening for autoimmune gastritis, pernicious anaemia, Hashimoto's thyroiditis, coeliac disease and Addison's disease is recommended. Other rare causes - including G6PD deficiency, microangiopathic haemolytic anaemia and thiamine-responsive megaloblastic anaemia - should be suspected in young patients or when the classical causes are excluded. Early detection and recognition of the cause(s) of anaemia in patients with diabetes could help to prevent other clinical manifestations as well as the complications of diabetes.

Homocysteine in renovascular complications: hydrogen sulfide is a modulator and plausible anaerobic ATP generator

Homocysteine (Hcy) is a non-protein amino acid derived from dietary methionine. High levels of Hcy, known as hyperhomocysteinemia (HHcy) is known to cause vascular complications. In the mammalian tissue, Hcy is metabolized by transsulfuration enzymes to produce hydrogen sulfide (H2S). H2S, a pungent smelling gas was previously known for its toxic effects in the central nervous system, recent studies however has revealed protective effects in a variety of diseases including hypertension, diabetes, inflammation, atherosclerosis, and renal disease progression and failure. Interestingly, under stress conditions including hypoxia, H2S can reduce metabolic demand and also act as a substrate for ATP production. This review highlights some of the recent advances in H2S research as a potential therapeutic agent targeting renovascular diseases associated with HHcy.

Diabetic nephropathy in a nonobese mouse model of type 2 diabetes mellitus

A large body of research has contributed to our understanding of the pathophysiology of diabetic nephropathy. Yet, many questions remain regarding the progression of a disease that accounts for nearly half the patients entering dialysis yearly. Several murine models of diabetic nephropathy secondary to Type 2 diabetes mellitus (T2DM) do exist, and some are more representative than others, but all have limitations. In this study, we aimed to identify a new mouse model of diabetic nephropathy secondary to T2DM in a previously described T2DM model, the MKR (MCK-KR-hIGF-IR) mouse. In this mouse model, T2DM develops as a result of functional inactivation of insulin-like growth factor-1 receptor (IGF-1R) in the skeletal muscle. These mice are lean, with marked insulin resistance, hyperinsulinemia, hyperglycemia, and dyslipidemia and thus are representative of nonobese human T2DM. We show that the MKR mice, when under stress (high-fat diet or unilateral nephrectomy), develop progressive diabetic nephropathy with marked albuminuria and meet the histopathological criteria as defined by the Animal Models of Diabetic Complications Consortium. Finally, these MKR mice are fertile and are on a common background strain, making it a novel model to study the progression of diabetic nephropathy.

Nitric oxide system and diabetic nephropathy

About 30% of patients with type 2 diabetes mellitus develop clinically overt nephropathy. Hyperglycemia is necessary, but not sufficient, to cause the renal damage that leads to kidney failure. Diabetic nephropathy (DN) is a multifactorial disorder that results from interaction between environmental and genetic factors. In the present article we will review the role of the nitric oxide synthase (NOS) in the pathogenesis of DN.Nitric oxide (NO) is a short-lived gaseous lipophilic molecule produced in almost all tissues, and it has three distinct genes that encode three NOS isoforms: neuronal (nNOS), inducible (iNOS) and endothelial (eNOS).The correct function of the endothelium depends on NO, participating in hemostasis control, vascular tone regulation, proliferation of vascular smooth muscle cells and blood pressure homeostasis, among other features. In the kidney, NO plays many different roles, including control of renal and glomerular hemodynamics. The net effect of NO in the kidney is to promote natriuresis and diuresis, along with renal adaptation to dietary salt intake.The eNOS gene has been considered a potential candidate gene for DN susceptibility. Three polymorphisms have been extensively researched: G894T missense mutation (rs1799983), a 27-bp repeat in intron 4, and the T786C single nucleotide polymorphism (SNP) in the promoter (rs2070744). However, the potential link between eNOS gene variants and the induction and progression of DN yielded contradictory results in the literature.In conclusion, NOS seems to be involve in the development and progression of DN. Despite the discrepant results of many studies, the eNOS gene is also a good candidate gene for DN.

l-Citrulline Protects from Kidney Damage in Type 1 Diabetic Mice

RATIONALE

Diabetic nephropathy (DN) is a major cause of end-stage renal disease, associated with endothelial dysfunction. Chronic supplementation of l-arginine (l-arg), the substrate for endothelial nitric oxide synthase (eNOS), failed to improve vascular function. l-Citrulline (l-cit) supplementation not only increases l-arg synthesis, but also inhibits cytosolic arginase I, a competitor of eNOS for the use of l-arg, in the vasculature.

AIMS

To investigate whether l-cit treatment reduces DN in streptozotocin (STZ)-induced type 1 diabetes (T1D) in mice and rats and to study its effects on arginase II (ArgII) function, the main renal isoform.

METHODS

STZ-C57BL6 mice received l-cit or vehicle supplemented in the drinking water. For comparative analysis, diabetic ArgII knock out mice and l-cit-treated STZ-rats were evaluated.

RESULTS

l-Citrulline exerted protective effects in kidneys of STZ-rats, and markedly reduced urinary albumin excretion, tubulo-interstitial fibrosis, and kidney hypertrophy, observed in untreated diabetic mice. Intriguingly, l-cit treatment was accompanied by a sustained elevation of tubular ArgII at 16 weeks and significantly enhanced plasma levels of the anti-inflammatory cytokine IL-10. Diabetic ArgII knock out mice showed greater blood urea nitrogen levels, hypertrophy, and dilated tubules than diabetic wild type (WT) mice. Despite a marked reduction in collagen deposition in ArgII knock out mice, their albuminuria was not significantly different from diabetic WT animals. l-Cit also restored nitric oxide/reactive oxygen species balance and barrier function in high glucose-treated monolayers of human glomerular endothelial cells. Moreover, l-cit also has the ability to establish an anti-inflammatory profile, characterized by increased IL-10 and reduced IL-1β and IL-12(p70) generation in the human proximal tubular cells.

CONCLUSION

l-Citrulline supplementation established an anti-inflammatory profile and significantly preserved the nephron function during T1D.

Pathophysiology of the diabetic kidney

Diabetes mellitus contributes greatly to morbidity, mortality, and overall health care costs. In major part, these outcomes derive from the high incidence of progressive kidney dysfunction in patients with diabetes making diabetic nephropathy a leading cause of end-stage renal disease. A better understanding of the molecular mechanism involved and of the early dysfunctions observed in the diabetic kidney may permit the development of new strategies to prevent diabetic nephropathy. Here we review the pathophysiological changes that occur in the kidney in response to hyperglycemia, including the cellular responses to high glucose and the responses in vascular, glomerular, podocyte, and tubular function. The molecular basis, characteristics, and consequences of the unique growth phenotypes observed in the diabetic kidney, including glomerular structures and tubular segments, are outlined. We delineate mechanisms of early diabetic glomerular hyperfiltration including primary vascular events as well as the primary role of tubular growth, hyperreabsorption, and tubuloglomerular communication as part of a "tubulocentric" concept of early diabetic kidney function. The latter also explains the "salt paradox" of the early diabetic kidney, that is, a unique and inverse relationship between glomerular filtration rate and dietary salt intake. The mechanisms and consequences of the intrarenal activation of the renin-angiotensin system and of diabetes-induced tubular glycogen accumulation are discussed. Moreover, we aim to link the changes that occur early in the diabetic kidney including the growth phenotype, oxidative stress, hypoxia, and formation of advanced glycation end products to mechanisms involved in progressive kidney disease.

Assessment of impaired vascular reactivity in a rat model of diabetic nephropathy: effect of nitric oxide synthesis inhibition on intrarenal diffusion and oxygenation measured by magnetic resonance imaging

Diabetes is associated with impaired vascular reactivity and the development of diabetic nephropathy. In a rat model of streptozotocin-induced diabetic nephropathy, the effects of systemic nitric oxide (NO) synthesis inhibition on intrarenal diffusion and oxygenation were determined by noninvasive magnetic resonance diffusion tensor imaging and blood O2 level-dependent (BOLD) imaging, respectively. Eight weeks after the induction of diabetes, 21 rats [ n = 7 rats each in the untreated control group, diabetes mellitus (DM) group, and DM with uninephrectomy (DM UNX) group] were examined by MRI. Diffusion tensor imaging and BOLD sequences were acquired before and after NO synthesis inhibition with N-nitro-l-arginine methyl ester (l-NAME). In the same rats, mean arterial pressure and vascular conductance were determined with and without the influence of l-NAME. In control animals, NO synthesis inhibition was associated with a significant increase of mean arterial pressure of 33.8 ± 4.3 mmHg ( P < 0.001) and a decrease of vascular conductance of −17.8 ± 2.0 μl·min−1·100 mmHg−1 ( P < 0.001). These changes were attenuated in both DM and DM UNX groups with no significant difference between before and after l-NAME measurements in DM UNX animals. Similarly, l-NAME challenge induced a significant reduction of renal transverse relaxation time (T2*) at MRI in control animals, indicating reduced renal oxygenation after l-NAME injection compared with baseline. DM UNX animals did not show a significant T2* reduction after NO synthesis inhibition in the renal cortex and attenuated T2* reduction in the outer medulla. MRI parameters of tissue diffusion were not affected by l-NAME in all groups. In conclusion, BOLD imaging proved valuable to noninvasively measure renal vascular reactivity upon NO synthesis inhibition in control animals and to detect impaired vascular reactivity in animals with diabetic nephropathy.

Role of the eNOS-NO system in regulating the antiproteinuric effects of VEGF receptor 2 inhibition in diabetes

Subtle perturbations in intraglomerular VEGF/VEGFR-2 signaling or in the influencing microenvironment can profoundly affect renal function, resulting in the apparently paradoxical observation that VEGF blockade attenuates proteinuria development in experimental diabetes despite exerting the opposite effect under other circumstances. In the present study, we sought to explore the role of eNOS-NO activity in regulating the differential response to VEGF blockade in the diabetic and nondiabetic settings. In a rodent model of accelerated renal injury, the transgenic (mRen-2)27 (Ren-2) rat, VEGFR-2 inhibition with the small molecule vandetanib resulted in an increase in urine protein excretion preceding a subsequent rise in systolic blood pressure. When compared to their normoglycaemic counterparts, diabetic Ren-2 rats exhibited an increase in the renal expression of eNOS and in urinary excretion of nitric oxide (NO) metabolites. In contrast to the heavy proteinuria observed with vandetanib in nondiabetic TGR(mRen-2)27 rats, VEGFR-2 inhibition reduced urine protein excretion in diabetic animals, despite a comparable magnitude of histological injury. However, proteinuria was markedly increased by concomitant treatment of diabetic Ren-2 rats with vandetanib and the nitric oxide synthase inhibitor L-NAME. These observations highlight the pivotal role that the eNOS-NO system plays in regulating the biologic response to VEGF within the glomerulus.