Leptin and its cardiovascular effects: Focus on angiogenesis

Leptin is an endocrine hormone synthesized by adipocytes. It plays a key role in the energy homeostasis in central and peripheral tissues and has additional roles are attributed to it, such as the regulation of reproduction, immune function, bone homeostasis, and angiogenesis. The plasma concentration of leptin significantly increases in obese individuals. In the present review, we give an introduction concerning leptin, its receptors, signaling pathways, and its effect on cardiovascular system, especially on angiogenesis.

Effect of blockade of neuropeptide Y receptor on aortic intima-media thickness and adipose tissue characteristics in normal and obese mice

OBJECTIVES

Atherosclerosis is an important risk factor for coronary heart disease. Neuropeptide Y (NPY) and its receptors, located in peripheral tissue such as white adipose tissue, have been linked to obesity and fat storage. The role of NPY in atherosclerosis has not yet been fully studied, so this study was conducted to further investigate the effect of BIIE 0246, an NPY receptor antagonist, on aortic intima-media thickness and size and number of adipocyte cells in normal and obese mice.

MATERIALS AND METHODS

Tests were performed on 24 male C57BL/6 mice. The animals were divided into four groups as follows: control (normal), obese (high-fat diet), normal+NPY receptor antagonist (1 μM, 100 µl/Kg BIIE0246 intraperitoneally) and obese+NPY receptor antagonist (n=6 each). After 14 days, the animals were sacrificed and epididymal adipose tissue and thoracic aorta were removed. Evaluations were made for adipocyte cell number and size and for aortic intima-media thickness.

RESULTS

The group on a high-fat diet showed a significantly decreased number of adipocyte cells and increased cell size (P<0.05). BIIE0246 application changed the cell number of adipocyte in normal mice (P=0.05); however, it did not change adipocyte cell size and aortic intima-media thickness in obese and normal mice (P>0.05).

CONCLUSION

NPY receptor antagonist had no effect on adipocyte cell size and aortic intima-media thickness; however, it decreased cell number in the normal group indicating likely involvement in the progression of obesity.

Effect of Blocking of Neuropeptide Y Y2 Receptor on Tumor Angiogenesis and Progression in Normal and Diet-Induced Obese C57BL/6 Mice

BACKGROUND

Obesity is a risk factor for some types of cancers. Angiogenesis is a necessary step in the multistage progression of tumors such as melanoma. Previous studies reported that neuropeptide Y (NPY) regulates angiogenesis by activating the Y2 receptor on endothelial cells. The present study examined the effects of the NPY Y2 receptor antagonist on tumor weight, angiogenesis and serum levels of vascular endothelial growth factor (VEGF), VEGF receptor-1 (VEGF-R1), and nitric oxide (NO).

METHODS

Twenty four male C57BL/6 mice were divided into control and obese groups. The control group was fed a normal diet whereas the obese group was fed a high fat diet. After 16 weeks, 2×10(6) B16F10 melanoma cells were injected subcutaneously into all animals. Half of the control and the obese animals received 1 µM, 100 µL/kg NPY Y2 receptor antagonist (BIIE 0246) intraperitoneally. After two weeks, the animals were sacrificed, and angiogenic factors and tumor weights and angiogenesis were analyzed.

RESULTS

Tumor weight in the obese mice was higher than in the control (p<0.05). Treatment with BIIE 0246 reduced tumor weight in the obese animals (p<0.05), without effect on control group (p>0.05). Administration of an NPY Y2 receptor antagonist decreased tumor angiogenesis (evaluated as capillary density/mm2) and serum VEGF concentration in the obese group without altering serum VEGF-R1 and NO concentrations.

CONCLUSIONS

Blockade of the NPY Y2 receptor suppressed tumor growth in obese mice by affecting tumor angiogenesis. Thus, it seems that NPY and its Y2 receptor antagonist might be new targets in melanoma tumor therapy.

Effect of aminoguanidine on cardiovascular responses and survival time during blood loss: A study in normotensive and deoxycorticosterone acetate-salt hypertensive rats

Introduction:

Hemorrhagic shock causes more circulatory disturbances and mortality in hypertensive than normotensive subjects. In the late phase of hemorrhagic shock, nitric oxide (NO) overproduction leads to vascular decompensation. In this study, we evaluated the effect of inducible NO synthase (iNOS) inhibitor, aminoguanidine (AG), on hemodynamic parameters and serum nitrite concentration in decompensated hemorrhagic shock model in normotensive and hypertensive male rats.

Materials and Methods:

Twenty-four male rats were divided into hypertensive and normotensive groups (n = 12 each). Hypertension was induced by subcutaneous injection of deoxycorticoesterone acetate (DOCA), 30 mg/kg in uninephrectomized rats. Decompensated hemorrhagic shock was induced by withdrawing blood until the mean arterial pressure (MAP) reached 40 mmHg. After 120 min, each group was assigned to aminguanidine (100 mg/kg) and control group. Hemodynamic parameters were monitored for next 60 min. Blood samples were taken before and after shock period and 60 min after treatment. Survival rate was monitored for 72 h.

Results:

Infusion of AG in normotensive animals caused a transient increase in MAP and increase of heart rate, whereas it did not affect those parameters in hypertensive animals. Hemorrhagic shock caused a significant rise in serum nitrite concentration in normotensive and hypertensive rats and infusion of AG did not significantly change it in both groups. No significant differences observed in survival rate between AG-treated and not treated groups.

Conclusion:

It seems that inhibition of iNOS with AG does not have beneficial effects on hemodynamatic parameters and survival rate during decompensated hemorrhagic shock in normotensive and hypertensive animals.

Alterations of plasma nitric oxide, vascular endothelial growth factor, and soluble form of its receptor (sFlt-1) after resistance exercise: An experimental study

BACKGROUND

This study was aimed to investigate the alterations of some plasma angiogenic factors after resistance exercise in male rats.

MATERIALS AND METHODS

TWENTY MALE RATS WERE DIVIDED INTO TWO GROUPS: Sedentary and trained (n = 10 each). The animals in the trained group undertook one training session per day, 3 days/week. After 4 weeks; plasma nitric oxide (NO), vascular endothelial growth factor (VEGF), and soluble form of VEGF receptor-1 (sFlt-1) concentrations were measured.

RESULTS

Plasma NO concentration was not different between groups (P > 0.05). Plasma VEGF concentration was also not different between sedentary and trained groups (142.73 ± 3.74 and 144.5 ± 5.1 pg/mL, respectively; P > 0.05). Resistance training did not significantly change plasma sFlt-1 concentration (P > 0.05). VEGF/sFlt-1 ratio did not alter after exercise.

CONCLUSION

Resistance training does not alter plasma angiogenic factors (NO, VEGF, and sFlt-1), at least in normal rats. More studies are needed to show the effect of resistance training on angiogenesis process.

Changes of serum angiogenic biomarkers and their correlations with serum leptin concentration

AIM

Obesity is considered as a major health problem. Angiogenic vessels by providing oxygen, nutrients and growth factors trigger growth and survival signals in adipocytes. We aimed to investigate the effect of high-fat diet (HFD) on serum angiogenic biomarkers including vascular endothelial growth factor (VEGF), soluble VEGF receptor 1 (sVEGFR1), nitric oxide (NO) concentrations and their correlations with serum leptin level in obese and control groups.

METHODS

Twenty male C57BL/6 mice were randomly assigned into the control and obese groups. Obese group received HFD for 15 weeks. At the end of experiment, blood samples were collected for blood glucose, serum insulin, VEGF, sVEGFR1, NO and leptin level measurements and correlation between serum angiogenic factors and leptin levels were analyzed.

RESULTS

HFD induced higher serum NO and leptin levels compared to the control group, while, it did not affect serum VEGF and sVEGFR1 concentrations. There was a strong positive correlation between serum leptin and NO levels (r=0.78), however, a weak correlation was found between serum leptin and VEGF and VEGFR-1 concentrations.

CONCLUSION

It seems that the angiogenic activities in obese mice are through the mechanisms that were not regulated by VEGF or VEGF receptors rather; other factors such as leptin and NO are involved (Tab. 1, Fig. 4, Ref. 32).

Moderate replacement of carbohydrates by dietary fats affects features of metabolic syndrome: a randomized crossover clinical trial

OBJECTIVE

Earlier studies on the management of metabolic syndrome (MetS) have mostly focused on very low carbohydrate diets, whereas long-term adherence to such diets is difficult for apparently healthy people. The aim of this study was to examine the effects of moderate replacement of carbohydrates by dietary fats on insulin resistance and features of MetS among women.

METHODS

This randomized crossover clinical trial was performed with 30 overweight or obese (body mass index [BMI] > 25 kg/m(2)) women with MetS. After a 2-wk run-in period, participants were randomly assigned to consume either a calorie-restricted high-carbohydrate (HC) diet (60%-65% of energy from carbohydrates and 20%-25% from fats) or a calorie-restricted moderately restricted carbohydrate (MRC) diet (43%-47% of total calories as carbohydrate and 36%-40% as dietary fats) for 6 wk. Protein contents of both diets were 15% to 17% of total energy. A 2-wk washout period was applied following which participants were crossed over to the alternate treatment arm for an additional 6 wk. Anthropometric, blood pressure, and biochemical measurements were performed before and after each phase of intervention.

RESULTS

Mean age and BMI of study participants was 42.4 y and 33 kg/m(2), respectively. A trend toward greater reduction in waist (-3.9 versus -2.6 cm; P = 0.07) and hip circumferences (-2.7 versus -1.5 cm; P = 0.07) as well as serum triglyceride (TG) levels (-31.3 versus 0.13 mg/dL; P = 0.07) was observed after consumption of an MRC diet compared with an HC diet. The TG to high-density lipoprotein cholesterol (HDL-C) ratio had a tendency to improve with the MRC diet rather than the HC diet (-0.9 versus -0.1; P = 0.06). Consumption of the MRC diet resulted in a greater reduction of systolic blood pressure (-8.93 versus -2.97 mm Hg; P = 0.06) and diastolic blood pressure (-12.7 versus -1.77 mm Hg; P = 0.001) compared with the HC diet. The prevalence of MetS was significantly decreased following the consumption of the MRC diet (P = 0.03). The two diets were not significantly different in terms of their effect on fasting plasma glucose, serum HDL-C, low-density lipoprotein cholesterol, and total cholesterol, insulin levels, and Homeostasis Model Assessment-Insulin Resistance.

CONCLUSION

Moderate replacement of carbohydrates by dietary fats was not associated with statistically different changes in fasting plasma glucose, insulin, or atherogenic dyslipidemia among individuals with the metabolic syndrome; however, it resulted in decreased diastolic blood pressure and lower prevalence of the metabolic syndrome.

Limbs' postischemic revascularization is not improved by losartan treatment in diabetic rats

OBJECTIVE

Most physiological actions of angiotensin II (Ang II) on cardiovascular system are mediated by angiotensin type 1 receptor (AT1R). Since peripheral artery disease is one of the most important complications of diabetes, in this study, we aimed to investigate the effect of losartan, an AT1R blocker, on skeletal muscle angiogenesis in diabetic hind limb ischemic rats.

METHODS

Twenty four male Wistar rats were randomly divided into four groups as follow: diabetic sham; diabetic sham + losartan (15 mg/kg/day); diabetic hindlimb ischemia; diabetic hindlimb ischemia + losartan. For induction of diabetes, streptozotocin was injected (55 mg/kg; i.p.). The animals were sacrificed after 21 days and the serum concentrations of vascular endothelial growth factor (VEGF), soluble VEGF receptor-1 (sFlt-1), nitric oxide (NO), capillary density, and capillary to fiber (cap⁄fib) ratio in ischemic legs were evaluated.

RESULTS

The serum NO concentrations were significantly decreased, sFlt-1 concentrations increased, and VEGF concentrations did not significantly change after experiment in diabetic sham and diabetic hind limb ischemic rats. Administration of losartan did not induce significant changes in serum NO, sFlt-1, and VEGF concentrations (p>0.05). Capillary density and cap⁄fib ratio in ischemic leg of diabetic rats were not affected by losartan treatment (p>0.05).

CONCLUSION

AT1R blocker, losartan, was not able to restore neovascularization in the ischemic leg of diabetic animals. Therefore, based on the present data, the losartan cannot be considered for treatment or prevention of peripheral artery disease in diabetic subjects.

Effect of DAPT, a gamma secretase inhibitor, on tumor angiogenesis in control mice

BACKGROUND

Notch signaling is a key factor for angiogenesis in physiological and pathological condition and γ-secretase is the regulator of Notch signaling. The main goal of this study was to assess the effect of (N-[N-(3,5-Diflurophenaacetyl-L-alanyl)]-S-phenylglycine t-Butyl Ester) DAPT, a γ-secretase inhibitor, on serum angiogenic biomarkers, and tumor angiogenesis in control mice.

MATERIALS AND METHODS

Tumor was induced by inoculation of colon adenocarcinoma cells (CT26) in 12 male Balb/C mice. When tumors size is reached to a 350 ± 50 mm(3), the animals were randomly divided into two groups: control and DAPT (n = 6/group). DAPT was injected subcutaneously 10 mg/kg/day. After 14 days, blood samples were taken and the tumors were harvested for immunohistochemical staining.

RESULTS

Administration of DAPT significantly increased serum nitric oxide concentration and reduced vascular endothelial growth factor receptors-1 (VEGFR1) concentration without changes on serum VEGF concentration. DAPT reduced tumor vascular density in control mice (280.6 ± 81 vs. 386 ± 59.9 CD31 positive cells/mm(2)), although, it was not statistically significant.

CONCLUSION

It seems that γ-secretase inhibitors can be considered for treatment of disorders with abnormal angiogenesis such as tumor angiogenesis.

Ghrelin does not modulate angiogenesis in matrigel plug in normal and diet-induced obese mice

BACKGROUND

The reciprocal interaction between adipocytes and angiogenesis is considered as an essential component in the development and expansion of adipose tissue. The aim of this study was to evaluate the effect of ghrelin on angiogenic response using in vivo angiogenesis assay of matrigel plug and its correlation with serum leptin levels in normal and diet-induced obese mice.

MATERIALS AND METHODS

This experimental study has been done on 24 male C57BL/6 mice which were randomly divided into four groups: Normal diet (ND) or control, ND + ghrelin, high-fat-diet (HFD) or obese and HFD + ghrelin (n = 6/group). Obese and control groups received HFD or standard diet for 14 weeks. Then, growth factor reduced matrigel plug (500 μl) containing bFGF (basic fibroblast growth factor; 100 ng) with or without ghrelin (100 μg/kg) was injected subcutaneously in the mid-ventral abdominal region of each mice. After 10 days, blood samples were taken and matrigel plugs were removed under anesthesia and angiogenic response was assessed by immunohisochemical staining.

RESULTS

HFD significantly increased angiogenesis in matrigel plug as expressed as the number of CD31-positive cells than standard diet (43 ± 5 vs. 13 ± 2.5 CD31(+) cells/field). Ghrelin did not alter angiogenesis in matrigel plug in both obese and control groups. There was a strong positive correlation between the number of CD31-positive cells and serum leptin concentration (r = 0.91).

CONCLUSION

Leptin as an angiogenic factor has a positive correlation with angiogenesis in matrigel plug model of angiogenesis and ghrelin could not alter angiogenesis.

Comparative effects of carbohydrate versus fat restriction on serum levels of adipocytokines, markers of inflammation, and endothelial function among women with the metabolic syndrome: a randomized cross-over clinical trial

BACKGROUND AND AIMS

Despite the efficacy of low-carbohydrate diets in the management of metabolic syndrome (MetS), it remains unknown if these favorable effects are mediated through changes in inflammation and endothelial dysfunction. We aimed to assess the effects of moderate substitution of dietary fats for carbohydrates on serum levels of adipocytokines, inflammatory indices, and biomarkers of endothelial function among women with the MetS.

METHODS

In a randomized cross-over clinical trial, 30 overweight or obese (BMI >25) women with the MetS were randomly allocated to follow either a high-carbohydrate (HC) (60-65% carbohydrates, 20-25% fats) diet or a moderately restricted carbohydrate (MRC) (43-47% carbohydrate, 36-40% fats) diet, each for 6 weeks. After a 2-week washout period, individuals were switched to the alternate diet for an additional 6 weeks. In a fasted state, markers of inflammation [high-sensitivity C-reactive protein (hs-CRP), high-sensitivity interleukin-6 (hs-IL-6), high-sensitivity tumor necrosis factor-α (hs-TNF-α), and serum amyloid A (SAA)], endothelial function [E-selectin, serum intercellular adhesion molecule 1 (sICAM-1), and serum vascular cell adhesion molecule 1 (sVCAM-1)], and adipocytokines (leptin and adiponectin) were measured in both study arms at baseline and after 6 weeks.

RESULTS

Consumption of an HC diet was associated with increased levels of SAA (3.27 ± 1.22 μg/ml) and decreased levels of adiponectin (-1.68 ± 2.30 ng/ml), while consumption of an MRC diet did not result in such unfavorable effects. Serum concentrations of leptin were reduced by the HC diet (p = 0.02), while they were not affected by the MRC diet. Changes in serum leptin levels were not significant between the two diets (p = 0.09). Serum concentrations of hs-CRP, hs-TNF-α, and IL-6 were not influenced by either diet. No significant differences between the two diets were found in terms of their effect on sICAM-1 and sVCAM-1 concentrations. Adherence to both diets resulted in a 9 ng/ml decrease in serum E-selectin levels (p < 0.05 for both).

CONCLUSIONS

Partial replacement of dietary carbohydrates by unsaturated fats prevents the increased levels of markers of systemic inflammation among women with the MetS.

Ghrelin Does not Alter Aortic Intima-Media Thickness and Adipose Tissue Characteristics in Control and Obese Mice

OBJECTIVE(S)

Atherosclerosis is a chronic immune-inflammatory disease that generally leads to ischemic heart disease. Ghrelin has several modulatory effects on cardiovascular system. In this study, we investigated the effect of ghrelin on aortic intima-media thickness, size and the number of adipocyte cells in obese and control mice.

MATERIALS AND METHODS

This study was conducted on 24 male C57BL/6 mice. The animals were divided into four groups: control, obese (received high fat diet), control+ghrelin (injected with 100 µg/Kg subcutaneously, bid) and obese+ghrelin (n=6 each). After 10 days, animals were sacrificed and epididymal adipose tissue and thoracic aortae were removed. Adipocyte cell number, size and aortic intima-media thickness were evaluated.

RESULTS

Ghrelin did not change adipocyte cell number and size and aortic intima-media thickness in obese and control mice. In this study, high fat diet significantly decreased the number of adipocyte cells while increased their size (P<0.05). Ghrelin administration had no significant effect on adipocyte cell number and size in obese and control groups (P >0.05). In addition, it could not alter aortic intima-media thickness in both groups.

CONCLUSION

Although ghrelin has several cardiovascular effects, it seems that it could not alter the size and number of adipocyte cells and aortic intima-media thickness in diet-induced obese mice.

The relationship between inflammatory markers, angiogenesis, and obesity

Obesity is recognized as a chronic low grade and systemic inflammatory disease. Angiogenesis is critical for adipose tissue expansion. Several evidences have demonstrated that angiogenesis sustains inflammation by preparing oxygen and nutrients for inflammatory cells and inflammation in turn can cause insulin resistance, type 2 diabetes, and cardiovascular disease. The understanding of mechanisms of obesity especially main roles of inflammation and angiogenesis in fat mass expansion can lead to therapeutic approaches in growing field of obesity and its related disorders. In this review, we studied the relationship between obesity, angiogenesis, and inflammation.

Effect of resistance training on plasma nitric oxide and asymmetric dimethylarginine concentrations in type I diabetic rats

BACKGROUND

Asymmetric dimethylarginine (ADMA) has a predominant role in progression of some cardiovascular diseases, including diabetes. It interferes with L-arginine in production of nitric oxide (NO) by inhibition of NO synthase. The purpose of this study was to evaluate the effect of resistance training on plasma NO and ADMA concentrations in type 1 diabetic male rats.

METHODS

Thirty-six male wistar rats were randomly divided into four groups: (1) control; (2) diabetic; (3) diabetic trained, and (4) control trained (n = 9 each). In the trained groups, the animals undertook one training session per day, 3 days/week, for 4 weeks. At the end of experiment, blood samples were taken and the concentrations of plasma glucose, insulin, lipid profile, NO and ADMA concentrations were determined.

RESULTS

plasma ADMA concentration showed a significant increase in diabetic rats compare to control group (0.73 ± 0.07 vs. 0.62 ± 0.04 μmol/l; P < 0.05). The plasma ADMA level in the trained diabetic and control were lower than the sedentary groups, although it was not statistically significant. Plasma NO concentration in diabetic group was lower than control (P < 0.05). Resistance training significantly increased plasma NO concentration in diabetic animals (P < 0.05).

CONCLUSION

Elevated ADMA level in diabetic animals can normalize during resistance exercise. Reduced ADMA level and increased NO level following resistance training might improve cardiovascular risk in diabetic subjects.

Comparing the long-term retention of a physiology course for medical students with the traditional and problem-based learning

The rapid improvements in medical sciences and the ever-increasing related data, however, require novel methods of instruction. One such method, which has been given less than due attention in Iran, is problem-based learning (PBL). In this study, we aimed to evaluate the impact of study skills and the PBL methods on short and long-term retention of information provided for medical students in the course of respiratory physiology and compare it with traditional learning method. In this study, 39 medical students from Medical School of Kerman University of Medical Sciences, Kerman, Iran (2006-2010) were enrolled in the study and allocated randomly in three equal groups (13 in each group). All groups underwent a pre-test to be assessed for their basic information regarding respiratory physiology. Two groups were instructed using the traditional method, and one group used PBL. Among the two groups of the traditional method, one was instructed about study skills and the other was not. Once the PBL group took the study skill workshop, they were aided by tutors for their education. In the final term test, those students who had learned study skills and were instructed with the traditional method scored higher compared to other groups (p < 0.05). However, in the 1 year (p < 0.05) and 4 year (p < 0.01) interval examinations, the PBL group achieved significantly higher scores. Despite the fact that PBL had no positive effect on the final term exam of our students, it yielded a more profound and retained understanding of the subject course. Moreover, considering the positive effect of study skills on long-term student scores, we recommend students to receive instructions regarding the appropriate study skills when initiated into universities.

The effect of L-arginine and L-NAME on myocardial capillary density in normal rats

Background:

This study evaluated the effect of L-arginine (Nitric Oxide (NO) precursor) and L-NG-Nitroarginine Methyl Ester (L-NAME) (NO synthase inhibitor) on myocardial capillary density in normal rats.

Materials and Methods:

Eighteen male rats were divided into three groups: Group 1: Received L-NAME (10 mg/kg/day; ip), Group 2: Received L-arginine (50 mg/kg/day; ip), and Group 3 (control) received normal saline. After 3 weeks, blood samples were taken and myocardial capillary density was evaluated using immunohistochemistry method.

Results:

Serum NO concentration in control group was 6.45 ± 0.44 μmol/lit. Treatment of animals with L-arginine increased serum NO concentration (7.90 ± 0.75 vs. 6.45 ± 0.44 μmol/lit, respectively) and L-NAME decreased (4.86 ± 0.40 vs. 6.45 ± 0.44 μmol/lit, respectively) compare to control group. L-arginine significantly increased serum vascular endothelial growth factor (VEGF) concentration (353.01 ± 7.03 vs. 100.5 ± 6.61 pg/ml; P < 0.05), however, did not change myocardial capillary density.

Conclusion:

Although L-arginine alters some serum angiogenic factors, either L-arginine or L-NAME could not improve myocardial capillary density in normal rats.

Myocardial capillary density in normal and diabetic male rats: Effect of bezafibrate

Cardiovascular disease is the common cause of mortality in diabetic subjects. Recently, it is indicated that peroxisome proliferator-activated receptors (PPARs) agonists have beneficial effect on cardiovascular system especially on angiogenesis. PPARs have three isotypes: PPARα, PPARβ/δ and PPARγ. In this study, we evaluated the effect of bezafibrate as pan PPAR agonist on myocardial capillary density in type I diabetic rats. Eighteen male wistar rats were randomly divided into three groups (n=6 each): control, diabetic and diabetic+bezafibrate (400 mg/kg/day) by gavage every day. Diabetes was induced by a single dose of streptozotocin (55 mg/kg), intraperitoneally. After 21 days, capillary density in the myocardial tissue was evaluated by immunohistochemical staining and reported as capillaries per mm(2). Blood samples were taken before and after the experiment. Diabetes was associated by lower serum nitric oxide (NO) concentration and reduced myocardial capillary density compared to control group (121.71 ± 13.32 vs. 158.78 ± 11.08 /mm(2); P<0.05). Administration of bezafibrate significantly increased serum NO level and improved angiogenesis in myocardial tissue of diabetic animals (170.24 ± 15.76 vs.121.71 ± 13.32 /mm(2); P<0.05). There was a positive correlation between serum NO concentration and myocardial capillary density (r=0.90). Activation of all isotypes of PPAR by bezafibrate improves heart capillary density in diabetic animals and it seems that it can be considered for treatment or prevention of coronary heart disease in diabetic subjects.

Imbalance of angiogenesis in diabetic complications: the mechanisms

Type 2 diabetes mellitus is a complex disease and a chronic health-care problem. Nowadays, because of alteration of lifestyle such as lack of exercise, intake of high fat diet subsequently obesity and aging population, the prevalence of diabetes mellitus is increasing quickly in around the world. The international diabetes federation estimated in 2008, that 246 million adults in worldwide suffered from diabetes mellitus and the prevalence of disease is expected to reach to 380 million by 2025. Although, mainly in management of diabetes focused on hyperglycemia, however, it is documented that abnormalities of angiogenesis may contribute in the pathogenesis of diabetes complications. Angiogenesis is the generation of new blood vessels from pre-existing ones. Normal angiogenesis depends on the intricate balance between angiogenic factors (such as VEGF, FGF₂, TGF-β, angiopoietins) and angiostatic factors (angiostatin, endostatin, thrombospondins). Vascular abnormalities in different tissues including retina and kidney can play a role in pathogenesis of micro-vascular complications of diabetes; also vascular impairment contributes in macrovascular complications e.g., diabetic neuropathy and impaired formation of coronary collaterals. Therefore, identifying of different mechanisms of the diabetic complications can give us an opportunity to prevent and/or treat the following complications and improves quality of life for patients and society. In this review, we studied the mechanisms of angiogenesis in micro-vascular and macro-vascular complications of diabetes mellitus.

Effect of experimentally induced metabolic acidosis on aortic endothelial permeability and serum nitric oxide concentration in normal and high-cholesterol fed rabbits

INTRODUCTION

Metabolic acidosis is present in end stage renal disease. There is a link between enhanced endothelial permeability and accelerated atherosclerosis. In this study, we investigated the effect of experimentally induced metabolic acidosis on aortic endothelial permeability and serum nitric oxide (NO) concentration in normal and high-cholesterol fed rabbits.

MATERIAL AND METHODS

Twenty-four male rabbits were divided into four groups: normal, hypercholesterolemic, acidemic, and hypercholesterolemic plus acidemic. Acidosis and hypercholesterolemia were induced by drinking water containing ammonium chloride (NH(4)Cl), and cholesterol-rich animal chow (1%), respectively. After 6 weeks, blood samples were taken and endothelial permeability was measured using the Evans blue dye injection method.

RESULTS

Hypercholesterolemic animals had higher aortic endothelial permeability compared with normal groups (16.18 ±0.91 µg EB/g tissue vs. 12.89 ±0.66 µg EB/g tissue, p < 0.05). Acidosis significantly increased endothelial permeability in the normal group (17.10 ±0.56 µg/g tissue vs. 12.89 ± 0.66 µg/g tissue; p < 0.05) but did not further increase endothelial permeability in hypercholesterolemic animals (16.18 ±0.91 µg EB/g tissue vs. 17.29 ±0.46 µg EB/g tissue; p > 0.05). Serum total cholesterol, low density lipoprotein (LDL) and NO concentrations in hypercholesterolemic animals were significantly higher than the normal group and acidosis could not change them either in the normal or in the high-cholesterol diet group.

CONCLUSIONS

Alterations of serum lipids and NO are not the main mechanism for accelerated atherosclerosis during metabolic acidosis. Acidosis increases aortic endothelial permeability at least in a normal diet which may be a possible mechanism for progression of atherosclerosis processes in end-stage renal disease.

Protective effects of subchronic caffeine administration on cisplatin induced urogenital toxicity in male mice

In Cisplatin treated group, the degeneration intensity of the kidneys the diameter of seminiferous tubules as well as the apoptotic index in testes and kidney were increased. In Caffeine+Cisplatin treated groups, the total body weight, the weight of testes and kidneys and also the histopathological data did not show significant differences. The motility of sperm in cisplatin group reduced but in Caffeine+Cisplatin groups this parameter was increased. These data suggest that caffeine recovers toxicity induced by cisplatin in both kidneys and testes of mice.