Prevention of fructose-induced hypertension by dietary vitamins

Association between serum aldehyde concentrations and metabolic syndrome in adults

The relationship between aldehyde exposure and metabolic syndrome is unclear; hence, we aimed to investigate the association between serum aldehyde concentrations and metabolic syndrome. We analyzed the data of 1471 participants from the National Health and Nutrition Examination Survey enrolled from 2013 to 2014. The association of serum aldehyde concentrations with metabolic syndrome was assessed via generalized linear models as well as restricted cubic splines, and endpoint events were further analyzed. After adjusting for covariates, both moderate (odds ratio [OR] = 2.73, 95% confidence interval [CI]: 1.34-5.56) and high (OR = 2.08, 95% CI: 1.06-4.07) concentrations of isovaleraldehyde were associated with the risk of metabolic syndrome. Interestingly, although a moderate concentration of valeraldehyde was associated with the risk of metabolic syndrome (OR = 1.08, 95% CI: 0.70-1.65), a high concentration was not (OR = 0.55, 95% CI: 0.17-1.79). Restricted cubic splines revealed a non-linear association between valeraldehyde and metabolic syndrome, and threshold effect analysis revealed that the inflection point for valeraldehyde concentration was 0.7 ng/mL. The results of the subgroup analysis revealed differences in the relationship of aldehyde exposure with components of metabolic syndrome. High isovaleraldehyde concentrations may increase the risk of metabolic syndrome, and valeraldehyde demonstrated a J-shaped relationship with the risk of metabolic syndrome.

Dietary Supplementation with D-Ribose-L-Cysteine Prevents Hepatic Stress and Pro-Inflammatory Responses in Male Wistar Rats Fed a High-Fructose High-Fat Diet

Diets rich in fats and fructose are associated with the pathogenesis of oxidative stress-induced non-alcoholic fatty liver disease. Therefore, we investigated the effect of D-ribose-L-cysteine (DRLC) in high-fructose high-fat (HFHF) diet-fed rats. Twenty rats (n = 5), divided into four groups, were simultaneously exposed to HFHF and/or DRLC (250 mg/kg) orally during the 8 weeks of the study. Results showed that HFHF precipitated pro-inflammation and selective disruption of the oxidative stress markers. There were significant decreases in the level of antioxidants such as superoxide dismutase (SOD), glutathione peroxidase (GPX), total antioxidant capacity (TAC), hepatic SOD and GPX. Significant increases in serum levels of uric acid (UA), tumour necrosis factor-alpha (TNF-α), C-reactive protein (CRP) and hepatic Xanthine oxidase (XO) were observed in the HFHF compared to the control. In the HFHF + DRLC group, oxidative stress was mitigated due to differences in serum levels of SOD, GPX, TAC, TNF-α, liver SOD, and XO relative to control. The administration of DRLC alone caused significant reductions in malondialdehyde, UA and CRP and a significant increase in SOD compared to the control. DRLC prevents hepatic and systemic oxidative stress and pro-inflammatory events in HFHF diet-fed rats.

D-ribose-L-cysteine prevents oxidative stress and cardiometabolic syndrome in high fructose high fat diet fed rats

Cardiometabolic syndrome has been linked with dietary modification. Therefore, we investigated the effects of D-ribose-L-cysteine (DRLC) in rats fed with high fructose high fat (HFHF) diet. Twenty rats (n = 5), divided into 4 groups were concurrently exposed to HFHF and/or DRLC (250 mg/kg, p.o) during the 8 weeks study. The result showed that compared to control group, HFHF group had significant impairment in lipid and glucose homeostasis, increased cardiac xanthine oxidase, systolic blood pressure, heart rate, %body weight change and fluid intake. Also, there were significant reductions in HDL-C, cardiac (GPX, NO&GGT), feed intake and relative heart weight in the latter, relative to the former. However, there were no significant differences in most of the observed physical and biochemical changes in HFHF + DRLC group compared to control. DRLC alone did not disrupt the level of biomarkers. Conclusively, DRLC prevented the manifestation of oxidative stress and cardiometabolic syndrome in HFHF-diet fed rats.

Treatment with isolated gold nanoparticles reverses brain damage caused by obesity

In this study, we performed two experiments. In the first experiment, the objective was to link gold nanoparticles (GNPs) with sodium diclofenac and/or soy lecithin and to determine their concentration in tissues and their toxicity using hepatic and renal analyzes in mice to evaluate their safety as therapeutic agents in the subsequent treatment of obesity. In the second experiment, we evaluated the effect of GNPs on inflammatory and biochemical parameters in obese mice. In the first experiment, we synthesized and characterized 18 nm GNPs that were administered intraperitoneally in isolation or in association with sodium diclofenac and/or soy lecithin in mice once daily for 1 or 14 days. Twenty-four hours after the single or final administration, the animals were euthanized, following which the tissues were removed for evaluating the concentration of GNPs, and serum samples were collected for hepatic and renal analysis. Hepatic damage was evaluated based on the levels of alanine aminotransferase (ALT), whereas renal damage was evaluated based on creatinine levels. A higher concentration of GNPs was detected in the tissues upon administration for 14 days, and there were no signs of hepatic or renal damage. In the second experiment, the mice were used as animal models of obesity and were fed a high-fat diet (obese group) and control diet (control group). After eight weeks of high-fat diet administration, the mice were treated with saline or with GNPs (average size of 18 nm) at a concentration of 70 mg/L (70 mg/kg) once a day, for 14 days, for 10 weeks. Body weight and food intake were measured frequently. After the experiment ended, the animals were euthanized, serum samples were collected for glucose and lipid profile analysis, the mesenteric fat content was weighed, and the brains were removed for inflammatory and biochemical analysis. In obese mice, although GNP administration did not reduce body and mesenteric fat weight, it reduced food intake. The glucose levels were reversed upon administration of GNPs, whereas the lipid profile was not altered in any of the groups. GNPs exerted a beneficial effect on inflammation and oxidative stress parameters, without reverting mitochondrial dysfunction. Our results indicate that the intraperitoneal administration of GNPs for 14 days results in a significant GNP concentration in adipose tissues, which could be an interesting finding for the treatment of inflammation associated with obesity. Based on the efficacy of GNPs in reducing dietary intake, inflammation, and oxidative stress, they can be considered potential alternative agents for the treatment of obesity.

Gender-specific association between carbohydrate consumption and blood pressure in Chinese adults

Background

The association between dietary carbohydrate consumption and blood pressure (BP) is controversial. The present study aimed to evaluate the possible gender-specific association of carbohydrate across the whole BP distribution.

Method

Cross-sectional survey including 2241 rural adults was conducted in northwestern China in 2010. BP was measured by trained medical personnel. Dietary information was collected by semiquantitative Food-Frequency Questionnaire. Multivariate quantile regression model was used to estimate the association between total carbohydrates consumption and systolic BP (SBP) and diastolic BP (DBP) at different quantiles. Gender-specific β coefficient and its 95% CI was calculated.

Results

The average carbohydrate intake was 267.4 (SD 112.0) g/day in males and 204.9 (SD 90.7) g/day in females, with only 10.6% of males and 6.5% females consumed at least 65% of total energy from carbohydrates. And more than 80% carbohydrates were derived from refined grains. In females, increased total carbohydrates intake was associated with adverse SBP and DBP. An additional 50 g carbohydrates per day was positively associated with SBP at low and high quantiles (10th-20th and 60th-80th) and with DBP almost across whole distribution (30th-90th), after adjusting for age, fortune index, family history of hypertension, body mass index, physical activity level, alcohol intake and smoke, energy, two nutrient principal components, protein and sodium intake. Both relatively low and high carbohydrate intake were associated with increased SBP, with minimum level observed at 130-150 g carbohydrate intake per day from restricted cubic splines. However, no significant associations were observed in males.

Conclusions

Higher total carbohydrates consumption might have an adverse impact on both SBP and DBP in Chinese females but not males. Additionally, the positive association varies across distribution of BP quantiles. Further research is warranted to validate these findings and clarify the causality.

Western Diet-Induced Metabolic Alterations Affect Circulating Markers of Liver Function before the Development of Steatosis

Since nutrition might have a significant impact on liver function, we analyzed the early effect of Western-type diet on hepatic tissue and lipid and drug metabolism in Wistar–Kyoto rats (n = 8); eight rats fed with a standard diet were used as controls. Histological analysis of liver tissue was performed, and plasma biochemical parameters were measured. Plasma concentration of six bile acids was determined by ultra-liquid chromatography-tandem mass spectrometry UHPLC-MS/MS. Hepatic gene expressions of enzymes involved in drug and lipid metabolism were assessed by means of real-time reverse transcription (qRT)-PCR. Liver of rats fed with a Western diet did not show macroscopic histological alterations, but number and diameter of lipid droplets increased, as well as DGAT1, GPAT4, SCD, FASN and SREBP2 expression. Furthermore, Western diet-fed animals showed an increase in the activation of hepatic stellate cells and macrophage number in liver tissue, as well as a significant increase in AST and bilirubin levels (p < 0.01), and in the LDL:HDL cholesterol ratio (p < 0.001). Plasma chenodeoxycholic acid concentration increased significantly, whereas cholic acid decreased (p < 0.05), and cytochrome P450 genes were generally downregulated. Significant changes in hepatic lipid and drug metabolism are early induced by the Western diet, prior to steatosis development. Such changes are associated with a peculiar alteration in circulating bile acids, which could represent an early marker of non-alcoholic fatty liver disease (NAFLD) development.

Beneficial Effect of Jojoba Seed Extracts on Hyperglycemia-Induced Oxidative Stress in RINm5f Beta Cells

Hyperglycemia occurs during diabetes and insulin resistance. It causes oxidative stress by increasing reactive oxygen species (ROS) levels, leading to cellular damage. Polyphenols play a central role in defense against oxidative stress. In our study, we investigated the antioxidant properties of simmondsin, a pure molecule present in jojoba seeds, and of the aqueous extract of jojoba seeds on fructose-induced oxidative stress in RINm5f beta cells. The exposure of RINm5f beta cells to fructose triggered the loss of cell viability (-48%, p < 0.001) and disruption of insulin secretion (p < 0.001) associated with of reactive oxygen species (ROS) production and a modulation of pro-oxidant and antioxidant signaling pathway. Cell pre-treatments with extracts considerably increased cell viability (+86% p < 0.001) for simmondsin and +74% (p < 0.001) for aqueous extract and insulin secretion. The extracts also markedly decreased ROS (-69% (p < 0.001) for simmondsin and -59% (p < 0.001) for aqueous extract) and caspase-3 activation and improved antioxidant defense, inhibiting p22phox and increasing nuclear factor (erythroid-derived 2)-like 2 (Nrf2) levels (+70%, p < 0.001) for aqueous extract. Simmondsin had no impact on Nrf2 levels. The richness and diversity of molecules present in jojoba seed extract makes jojoba a powerful agent to prevent the destruction of RINm5f beta cells induced by hyperglycemia.

A Mouse Model of Diet-Induced Obesity Resembling Most Features of Human Metabolic Syndrome

Increased chicken-derived fat and fructose consumption in the human diet is paralleled by an increasing prevalence of obesity and metabolic syndrome (MS). Herein, we aimed at developing and characterizing a mouse model of diet-induced obesity (DIO) resembling most of the key features of the human MS. To accomplish this, we fed male C57BL/6J mice for 4, 8, 12, and 16 weeks with either a low-fat diet (LFD) or a high-chicken-fat diet (HFD) and tap water with or without 10% fructose (F). This experimental design resulted in the following four experimental groups: LFD, LFD + F, HFD, and HFD + F. Over the feeding period, and on a weekly basis, the HFD + F group had more caloric intake and gained more weight than the other experimental groups. Compared to the other groups, and at the end of the feeding period, the HFD + F group had a higher adipogenic index, total cholesterol, low-density lipoprotein cholesterol, fasting basal glycemia, insulin resistance, hypertension, and atherogenic index and showed steatohepatitis and systemic oxidative stress/inflammation. A mouse model of DIO that will allow us to study the effect of MS in different organs and systems has been developed and characterized.

High-fructose and high-fat diet-induced disorders in rats: impact on diabetes risk, hepatic and vascular complications

BACKGROUND

As a result of the increased consumption of sugar-rich and fatty-products, and the increase in preference for such products, metabolic disorders are becoming more common at a younger age. Fructose is particularly used in prepared foods and carbonated beverages. We investigated the impact of regular consumption of fructose, in combination or not with fatty food, on the onset of metabolic syndrome and type 2 diabetes (T2D). We evaluated the metabolic, oxidative, and functional effects on the liver and blood vessels, both related to diabetes complications.

METHODS

High-fat diet (HFD), high-fructose beverages (HF) or both (HFHF) were compared to rats fed with normal diet (ND) for 8 months to induce T2D and its metabolic, oxidative, and functional complications. Metabolic control was determined by measuring body weight, fasting blood glucose, C-peptide, HOMA2-IR, leptin, and cholesterol; oxidative parameters were studied by lipid peroxidation and total antioxidant capacity in plasma and the use of ROS labelling on tissue. Histological analysis was performed on the liver and endothelial function was performed in main mesenteric artery using organ-baths.

RESULTS

After 2 months, HFHF and HFD increased body weight, leptin, HOMA2-IR associated to steatosis, oxidative stress in plasma and tissues, whereas HF had only a transient increase of leptin and c-peptide. Only HFHF induced fasting hyperglycaemia after 6 months and persistent hyperinsulinaemia and fasting hyperglycaemia with complicated steatosis (inflammation and fibrosis) after 8 months. HFHF and HFD induced endothelial dysfunction at 8 months of diet.

CONCLUSIONS

Six months, high fat and high carbohydrate induced T2D with widespread tissues effects. We demonstrated the role of oxidative stress in pathogenesis as well as in complications (hepatic and vascular), reinforcing interest in the use of antioxidants in the prevention and treatment of metabolic diseases, including T2D.

Antihypertensive and neuroprotective actions of pyridoxine and its derivatives

Vitamin B6 plays a crucial role in the nervous system as the amino acid decarboxylases involved in the synthesis of all putative neurotransmitters requires the coenzyme pyridoxal phosphate. Vitamin B6 in its various forms has antioxidant properties. Pyridoxal phosphate has a role in regulating cellular calcium transport through both the voltage-mediated and ATP-mediated purinergic mechanisms of cellular calcium influx and, hence, has a role in the control of hypertension. Pharmacological doses of vitamin B6 appear to decrease the high blood pressure associated with both genetic and nongenetic models of hypertension. Vitamin B6 has a crucial role in the normal function of the central and peripheral nervous systems. It also protects against ischemia and glutamate-induced neurotoxicity.

Protective effect of sitagliptin and rosuvastatin combination on vascular endothelial dysfunction in type-2 diabetes

The present investigation aimed to evaluate the protective effects of sitagliptin, glimepiride, rosuvastatin and their combinations on oxidative stress and endothelial dysfunction in the aortic tissues in fructose-fed type-2 diabetic rats. Sitagliptin (20 mg/kg, p.o.), glimepiride (2 mg/kg, p.o.), rosuvastatin (5 mg/kg, p.o.) and their combinations were administered for 6 w after induction of diabetes by fructose (66%, w/v solution, p.o. for 8 w) in wistar rats. The effects were examined on body weight, serum glucose, triglyceride, cholesterol, blood pressure, heart rate, nitric oxide and antioxidant defensive enzymes. After completion of treatment schedule, the blood pressure was determined by invasive method and vascular reactivity was tested with adrenaline, noradrenaline and phenylephrine. Endothelial dysfunction was determined by acetylcholine and sodium nitroprusside-induced vasorelaxation studies on isolated rat aortas. Long term treatments significantly decreased body weight gain, serum glucose, triglyceride and cholesterol levels; normalize the heart rate, and blood pressure in fructose fed rats. The treatments significantly improved vascular reactivity to catecholamines with reduction in elevated blood pressure in type-2 diabetic rats. The significant improvement in the relaxant response to acetylcholine and sodium nitroprusside was obtained on isolated aortas. All the treatments were effective in restoring defensive antioxidant enzymes. Sitagliptin and rosuvastatin were able to reverse endothelial dysfunction in type-2 diabetes, but better ameliorating potential was found when used in combination.

Animal models of insulin resistance and heart failure

The incidence of heart failure (HF) and diabetes mellitus is rapidly increasing and is associated with poor prognosis. In spite of the advances in therapy, HF remains a major health problem with high morbidity and mortality. When HF and diabetes coexist, clinical outcomes are significantly worse. The relationship between these two conditions has been studied in various experimental models. However, the mechanisms for this interrelationship are complex, incompletely understood, and have become a matter of considerable clinical and research interest. There are only few animal models that manifest both HF and diabetes. However, the translation of results from these models to human disease is limited, and new models are needed to expand our current understanding of this clinical interaction. In this review, we discuss mechanisms of insulin signaling and insulin resistance, the clinical association between insulin resistance and HF, and its proposed pathophysiologic mechanisms. Finally, we discuss available animal models of insulin resistance and HF and propose requirements for future new models.

Associations between dietary patterns and hypertension among Korean adults: the Korean National Health and Nutrition Examination Survey (2008-2010)

The objective of this study is to identify the dietary patterns associated with the risk of hypertensions among Korean adults using data from the Korean National Health and Nutrition Examination Survey (KNHANES, 2008-2010). This study analyzes data from 11,883 subjects who participated in the health and nutrition survey, aging from 20 to 64 years. We performed factor analysis based on the weekly mean intake frequencies of 36 food groups to identify major dietary patterns. We identified three major dietary patterns in both sexes, namely "traditional", "western" and "dairy and carbohydrate" patterns. Participants in the highest quartile of western pattern scores had significantly higher blood pressure, serum total cholesterol, and triglyceride levels than those in the lowest quartile. Although not statistically significant, a trend (P for trend = 0.0732) toward a positive association between the western dietary pattern and hypertension risk was observed after adjustments for age, sex, education, income, body mass index (BMI), smoking, physical activity, and energy intake. The dairy and carbohydrate pattern was inversely related with BMI and blood pressures and positively associated with serum high-density lipoprotein (HDL)-cholesterol. After adjusting the age, sex, education, income, BMI, smoking, physical activity and energy intake, the dairy and carbohydrate pattern showed inverse associations with hypertension prevalence (OR = 0.64, 95% CI = 0.55-0.75; P for trend < 0.0001). Intakes of fiber, sodium, and antioxidant vitamins were significantly higher in the top quartile for the traditional pattern than in the lowest quartile for the traditional pattern (P for trend < 0.0001). Intakes of fiber (P for trend < 0.0001), calcium (P for trend < 0.0001), retinol (P for trend = 0.0164), vitamin B₁ (P for trend = 0.001), vitamin B₂ (P for trend < 0.0001), niacin (P for trend = 0.0025), and vitamin C (P for trend < 0.0001) were significantly increased across quartiles for the dairy and carbohydrate pattern whereas sodium (P for trend < 0.0001) intake was decreased for this pattern. In conclusion, the dairy and carbohydrate pattern may be associated with a reduced risk of hypertension whereas the western pattern may be associated with an increased risk of hypertension among Korean adults.

Beneficial effect of genistein on lowering blood pressure and kidney toxicity in fructose-fed hypertensive rats

The study evaluates the effects of genistein on blood pressure (BP) and ultrastructural changes in kidney of fructose-fed hypertensive rats. Male Wistar rats were fed a diet containing 60 % starch or 60 % fructose as the source of carbohydrate. After 15 d, rats in each dietary group were divided into two groups and were treated with either genistein (1 mg/kg per d) in dimethylsulfoxide (DMSO) or 30 % DMSO alone. BP, pressor mechanisms, protein kinase C-βII (PKC-βII) expression, endothelial NO synthase (eNOS) expression and renal ultrastructural changes were evaluated after 60 d. Fructose-fed rats displayed significant elevation in BP and heart rate. Significant increase in plasma angiotensin-converting enzyme (ACE) activity, alterations in renal lipid profile, nitrite and kallikrein activity, enhanced expression of membrane-associated PKC-βII and decreased expression of eNOS were observed in them. Histology and electron microscopic studies showed structural changes in the kidney. Genistein administration lowered BP, restored ACE, PKC-βII and eNOS expression and preserved renal ultrastructural integrity. These findings demonstrate that genistein has effects on eNOS activity in renal cells, leading to eNOS activation and NO synthesis. These effects could have been mediated by activation of PKC-βII. The observed benefits of genistein make it a promising candidate for therapy of diabetic kidney disease.

Role of methylglyoxal in essential hypertension

Altered glucose metabolism due to insulin resistance is a common feature of essential hypertension in humans and in animal models. Elevated endogenous aldehydes in genetic (spontaneously hypertensive rats) and acquired (fructose-induced hypertensive rats) models of essential hypertension may be due to increased production of the reactive aldehyde methylglyoxal, resulting from altered glucose metabolism. Excess methylglyoxal binds sulfhydryl groups of membrane proteins, altering calcium channels and increasing cytosolic free Ca(2+) and blood pressure. It has been demonstrated that methylglyoxal, when given in drinking water to Wistar-Kyoto rats, leads to an increase in kidney aldehyde conjugates, cytosolic free Ca(2+) concentration, decreased serum nitric oxide, renal vascular hyperplasia and hypertension. N-acetylcysteine (NAC) in the diet of these animals prevented hypertension and associated biochemical and morphological changes. NAC normalizes blood pressure by directly binding to excess methylglyoxal, thus normalizing Ca(2+) channels, cytosolic Ca(2+) and nitric oxide. NAC also leads to increased levels of tissue glutathione, a storage form of cysteine. Glutathione acts as a cofactor in the enzymatic catabolism of methylglyoxal. Cysteine and other antioxidants, such as vitamins B(6), C and E, and lipoic acid, prevented hypertension and associated biochemical and morphological changes in both genetic and acquired rat models of hypertension. The antihypertensive effect of dietary antioxidants may be due to an increase in tissue cysteine and glutathione, which improves glucose metabolism and decreases tissue methylglyoxal. A diet rich in these antioxidants may be effective in preventing and controlling hypertension in humans.

The effects of phentolamine on fructose-fed rats

Metabolic syndrome (MS) is a combination of medical disorders that increase the risk of developing cardiovascular disease and diabetes. MS is associated with obesity, increased blood pressure, hyperlipidemia, and hyperglycemia. This study was designed to investigate the pharmacological profile of phentolamine, a nonselective α adrenergic receptor antagonist, in the prevention of increased blood pressure in fructose-fed rats. Phentolamine prevented the fructose-induced increase in systolic blood pressure without affecting insulin sensitivity and major metabolic parameters. The levels of plasma noradrenaline and angiotensin II, 2 proposed contributors to the development of fructose-induced elevated blood pressure, were examined. Neither noradrenaline nor angiotensin II levels were affected by phentolamine treatment. Since overproduction of nitric oxide has been shown to lead to an elevation in peroxynitrite, the role of oxidative stress, a proposed mechanism of fructose-induced elevated blood pressure and insulin resistance, was examined by measuring plasma levels of total nitrate/nitrite. Plasma nitrate/nitrite was significantly elevated in all fructose-fed animals, regardless of treatment with phentolamine. Another proposed contributor toward fructose-induced MS is an elevation in uric acid levels. In this experiment, plasma levels of uric acid were found to be increased by dietary fructose and were unaffected by phentolamine treatment.

A Regenerative Antioxidant Protocol of Vitamin E and α-Lipoic Acid Ameliorates Cardiovascular and Metabolic Changes in Fructose-Fed Rats

Type 2 diabetes is a major cause of cardiovascular disease. We have determined whether the metabolic and cardiovascular changes induced by a diet high in fructose in young adult male Wistar rats could be prevented or reversed by chronic intervention with natural antioxidants. We administered a regenerative antioxidant protocol using two natural compounds: α-lipoic acid together with vitamin E (α-tocopherol alone or a tocotrienol-rich fraction), given as either a prevention or reversal protocol in the food. These rats developed glucose intolerance, hypertension, and increased collagen deposition in the heart together with an increased ventricular stiffness. Treatment with a fixed combination of vitamin E (either α-tocopherol or tocotrienol-rich fraction, 0.84 g/kg food) and α-lipoic acid (1.6 g/kg food) normalized glucose tolerance, blood pressure, cardiac collagen deposition, and ventricular stiffness in both prevention and reversal protocols in these fructose-fed rats. These results suggest that adequate antioxidant therapy can both prevent and reverse the metabolic and cardiovascular damage in type 2 diabetes.

Kinin B1 receptor enhances the oxidative stress in a rat model of insulin resistance: outcome in hypertension, allodynia and metabolic complications

Background

Kinin B₁ receptor (B₁R) is induced by the oxidative stress in models of diabetes mellitus. This study aims at determining whether B₁R activation could perpetuate the oxidative stress which leads to diabetic complications.

Methods and Findings

Young Sprague-Dawley rats were fed with 10% D-Glucose or tap water (controls) for 8–12 weeks. A selective B₁R antagonist (SSR240612) was administered acutely (3–30 mg/kg) or daily for a period of 7 days (10 mg/kg) and the impact was measured on systolic blood pressure, allodynia, protein and/or mRNA B₁R expression, aortic superoxide anion (O₂^•−) production and expression of superoxide dismutase (MnSOD) and catalase. SSR240612 reduced dose-dependently (3–30 mg/kg) high blood pressure in 12-week glucose-fed rats, but had no effect in controls. Eight-week glucose-fed rats exhibited insulin resistance (HOMA index), hypertension, tactile and cold allodynia and significant increases of plasma levels of glucose and insulin. This was associated with higher aortic levels of O₂^•−, NADPH oxidase activity, MnSOD and catalase expression. All these abnormalities including B₁R overexpression (spinal cord, aorta, liver and gastrocnemius muscle) were normalized by the prolonged treatment with SSR240612. The production of O₂^•− in the aorta of glucose-fed rats was also measured in the presence and absence of inhibitors (10–100 µM) of NADPH oxidase (apocynin), xanthine oxidase (allopurinol) or nitric oxide synthase (L-NAME) with and without Sar[D-Phe⁸]des-Arg⁹-BK (20 µM; B₁R agonist). Data show that the greater aortic O₂^•− production induced by the B₁R agonist was blocked only by apocynin.

Conclusions

Activation of kinin B₁R increased O₂^•− through the activation of NADPH oxidase in the vasculature. Prolonged blockade of B₁R restored cardiovascular, sensory and metabolic abnormalities by reducing oxidative stress and B₁R gene expression in this model.

Renoprotective and blood pressure-lowering effect of dietary soy protein via protein kinase C beta II inhibition in a rat model of metabolic syndrome

We studied whether substitution of soy protein for casein can improve insulin sensitivity, lower blood pressure (BP), and inhibit protein kinase C betaII (PKCbetaII) activation in kidney in an acquired model of metabolic syndrome. Adult male rats were fed 4 different diets: (i) starch (60%) and casein (20%) (CCD), (ii) fructose (60%) and casein (20%) (FCD), (iii) fructose (60%) and soy protein (20%) (FSD), and (iv) starch (60%) and soy protein (20%) (CSD). Renal function parameters, BP, pressor mechanisms, PKCbetaII expression, oxidative stress, and renal histology were evaluated after 60 days. FCD rats displayed insulin resistance and significant changes in body weight, kidney weight, urine volume, plasma and urine electrolytes accompanied by significant changes in renal function parameters compared with CCD rats. Elevated BP, plasma angiotensin-converting enzyme (ACE) activity, renal oxidative stress, and reduced nitrite (NO) and kallikrein activity were observed. Western blot analysis revealed enhanced renal expression of membrane-associated PKCbetaII in the FCD group. Histology showed fatty infiltration and thickening of glomeruli while urinary protein profile revealed a 5-fold increase in albumin. Substitution of soy protein for casein improved insulin sensitivity, lowered BP and PKCbetaII activation and restored renal function. Antioxidant action, inhibitory effect on ACE and PKCbetaII activation, and increased availability of kinins and NO could be contributing mechanisms for the benefits of dietary soy protein.

Metabolic effects of fructose and the worldwide increase in obesity

While virtually absent in our diet a few hundred years ago, fructose has now become a major constituent of our modern diet. Our main sources of fructose are sucrose from beet or cane, high fructose corn syrup, fruits, and honey. Fructose has the same chemical formula as glucose (C(6)H(12)O(6)), but its metabolism differs markedly from that of glucose due to its almost complete hepatic extraction and rapid hepatic conversion into glucose, glycogen, lactate, and fat. Fructose was initially thought to be advisable for patients with diabetes due to its low glycemic index. However, chronically high consumption of fructose in rodents leads to hepatic and extrahepatic insulin resistance, obesity, type 2 diabetes mellitus, and high blood pressure. The evidence is less compelling in humans, but high fructose intake has indeed been shown to cause dyslipidemia and to impair hepatic insulin sensitivity. Hepatic de novo lipogenesis and lipotoxicity, oxidative stress, and hyperuricemia have all been proposed as mechanisms responsible for these adverse metabolic effects of fructose. Although there is compelling evidence that very high fructose intake can have deleterious metabolic effects in humans as in rodents, the role of fructose in the development of the current epidemic of metabolic disorders remains controversial. Epidemiological studies show growing evidence that consumption of sweetened beverages (containing either sucrose or a mixture of glucose and fructose) is associated with a high energy intake, increased body weight, and the occurrence of metabolic and cardiovascular disorders. There is, however, no unequivocal evidence that fructose intake at moderate doses is directly related with adverse metabolic effects. There has also been much concern that consumption of free fructose, as provided in high fructose corn syrup, may cause more adverse effects than consumption of fructose consumed with sucrose. There is, however, no direct evidence for more serious metabolic consequences of high fructose corn syrup versus sucrose consumption.

Sugary drinks in the pathogenesis of obesity and cardiovascular diseases

Soft drink overconsumption is now considered to be a major public health concern with implications for cardiovascular diseases. This follows a number of studies performed in animals suggesting that chronic consumption of refined sugars can contribute to metabolic and cardiovascular dysregulation. In particular, the monosaccharide fructose has been attracting increasing attention as the more harmful sugar component in terms of weight gain and metabolic disturbances. High-fructose corn syrup is gradually replacing sucrose as the main sweetener in soft drinks and has been blamed as a potential contributor to the current high prevalence of obesity. There is also considerable evidence that fructose, rather than glucose, is the more damaging sugar component in terms of cardiovascular risk. This review focuses on the potential role of sugar drinks, particularly the fructose component, in the pathogenesis of obesity and cardiovascular diseases.

The fructose-fed rat: a review on the mechanisms of fructose-induced insulin resistance and hypertension

The metabolic syndrome is an important public health concern that predisposes individuals to the development of cardiovascular disease and/or Type 2 diabetes. The fructose-fed rat is an animal model of acquired systolic hypertension that displays numerous features of the metabolic syndrome. This animal model is used to study the relationship between insulin resistance/compensatory hyperinsulinemia and the development of hypertension. Several mechanisms have been proposed to mediate the link between insulin resistance and hypertension. In this review, we have addressed the role of sympathetic nervous system overactivation, increased production of vasoconstrictors, such as endothelin-1 and angiotensin II, and prostanoids in the development of hypertension in fructose-fed rats. The roles of nitric oxide, impaired endothelium-dependent relaxation and sex hormones in the pathogenesis of the fructose-fed induced hypertensive rats have also been highlighted. More recently, increased formation of reactive oxygen species and elevated levels of uric acid have been reported to contribute to fructose-induced hypertension.

Adenylate kinase and AMP signaling networks: metabolic monitoring, signal communication and body energy sensing

Adenylate kinase and downstream AMP signaling is an integrated metabolic monitoring system which reads the cellular energy state in order to tune and report signals to metabolic sensors. A network of adenylate kinase isoforms (AK1-AK7) are distributed throughout intracellular compartments, interstitial space and body fluids to regulate energetic and metabolic signaling circuits, securing efficient cell energy economy, signal communication and stress response. The dynamics of adenylate kinase-catalyzed phosphotransfer regulates multiple intracellular and extracellular energy-dependent and nucleotide signaling processes, including excitation-contraction coupling, hormone secretion, cell and ciliary motility, nuclear transport, energetics of cell cycle, DNA synthesis and repair, and developmental programming. Metabolomic analyses indicate that cellular, interstitial and blood AMP levels are potential metabolic signals associated with vital functions including body energy sensing, sleep, hibernation and food intake. Either low or excess AMP signaling has been linked to human disease such as diabetes, obesity and hypertrophic cardiomyopathy. Recent studies indicate that derangements in adenylate kinase-mediated energetic signaling due to mutations in AK1, AK2 or AK7 isoforms are associated with hemolytic anemia, reticular dysgenesis and ciliary dyskinesia. Moreover, hormonal, food and antidiabetic drug actions are frequently coupled to alterations of cellular AMP levels and associated signaling. Thus, by monitoring energy state and generating and distributing AMP metabolic signals adenylate kinase represents a unique hub within the cellular homeostatic network.

Dietary starch intake of individuals and their blood pressure: the International Study of Macronutrients and Micronutrients and Blood Pressure

OBJECTIVE

Data from the Multiple Risk Factor Intervention Trial show an independent direct association between starch intake and blood pressure in American men at higher risk of coronary heart disease. Cross-sectional data from the International Study of Macronutrients and Micronutrients and Blood Pressure (INTERMAP) were used to assess relations of dietary starch intake to blood pressure in men and women from four countries.

METHODS

Data include 83 nutrients from four multipass 24-h dietary recalls and two timed 24-h urine collections; eight blood pressure readings; and questionnaire data, for 4680 participants aged 40-59 years from 17 population samples in Japan, People's Republic of China, United Kingdom, and United States of America.

RESULTS

In multiple linear regression analyses--adjusted for urinary sodium, urinary potassium, consumption of alcohol, cholesterol, saturated fatty acids, polyunsaturated fatty acids, calcium, and other variables--starch intake higher by two standard deviations (14.1% kJ) was associated with systolic/diastolic blood pressure differences of -1.0/-0.9 mmHg (P = 0.09, P < 0.05). Results were similar with additional control for fiber, magnesium, or phosphorus; reduced to -0.5/-0.7 mmHg (P = 0.47, P = 0.13) with separate adjustment for vegetable protein. Findings were similar for men analyzed separately, for American men, and for American men at higher coronary heart disease risk.

CONCLUSION

Our findings indicate that--if any--relations of starch intake to blood pressure are modestly inverse. Current dietary guidelines for hypertension prevention and control remain relevant.

Fructose, but not dextrose, accelerates the progression of chronic kidney disease

The metabolic syndrome has recently been recognized as a risk factor for kidney disease, but the mechanisms mediating this risk remain unclear. High fructose consumption by animals produces a model of the metabolic syndrome with hypertension, hyperlipidemia, and insulin resistance. The present study was conducted to test the hypothesis that consumption of a high-fructose diet could accelerate the progression of chronic kidney disease. Three groups of 14 male Sprague-Dawley rats were pair fed a specialized diet containing 60% fructose (FRU) or 60% dextrose (DEX) or standard rat chow (CON). After the animals were fed their assigned diet for 6 wk, five-sixths nephrectomy was performed, and the assigned diet was continued for 11 wk. Proteinuria was significantly increased and creatinine clearance was decreased in the FRU group compared with the CON and DEX groups, and blood urea nitrogen was higher in the FRU group than in the CON and DEX groups. Kidneys from the FRU group were markedly larger than kidneys from the CON and DEX groups. Glomerular sclerosis, tubular atrophy, tubular dilatation, and cellular infiltration appeared markedly worse in kidneys from the FRU group than in kidneys from the DEX and CON groups. Monocyte chemoattractant protein-1 (MCP-1) was measured in renal tissue homogenate and found to be increased in the FRU group. In vitro studies were conducted to determine the mechanism for increased renal MCP-1, and fructose stimulation of proximal tubular cells resulted in production of MCP-1. In conclusion, consumption of a high-fructose diet greatly accelerates progression of chronic kidney disease in the rat remnant kidney model.

Crocetin attenuates palmitate-induced insulin insensitivity and disordered tumor necrosis factor-alpha and adiponectin expression in rat adipocytes

BACKGROUND AND PURPOSE

A number of studies have implicated adipocyte-derived factors in the development of insulin resistance. Intracellular redox status has been reported to play a significant role in the modulation of insulin action. This study was designed to investigate the potential of crocetin, a potent antioxidant, to protect adipocytes against the induction of insulin insensitivity and disordered expression of tumor necrosis factor (TNF)-alpha and adiponectin in vitro.

EXPERIMENTAL APPROACH

We used palmitate to induce insulin resistance in freshly isolated rat adipocytes, and observed the effect of crocetin, N-acetylcysteine, diphenyleneiodonium, rotenone and oxypurinol. Insulin sensitivity was measured using 2-deoxy-D-[1-(3)H]-glucose uptake assay. Levels of glucose transporter 4, TNF-alpha and adiponectin were evaluated by immunoblot analysis, and levels of mRNA for TNF-alpha and adiponectin by reverse transcription-polymerase chain reaction analysis. Intracellular production of reactive oxygen species (ROS) was determined spectrofluorometrically using 2',7'-dichlorofluorescin diacetate.

KEY RESULTS

Palmitate induced a 45% decrease in insulin-stimulated glucose uptake in adipocytes. The mRNA and protein expression of TNF-alpha were enhanced by 64% and 59% respectively whereas the mRNA and protein expression of adiponectin were reduced by 43% and 36% respectively by palmitate treatment. These changes were accompanied by a 54% increase in intracellular ROS levels. Crocetin, N-acetylcysteine and diphenyleneiodonium were found to attenuate these abnormalities.

CONCLUSIONS AND IMPLICATIONS

Crocetin blocked the impaired insulin-stimulated glucose uptake and disordered TNF-alpha and adiponectin expression induced by palmitate in rat adipocytes. Inactivation of NADPH oxidase may account for these observations.

Effect of dietary chromium on resistance artery function and nitric oxide signaling in the sucrose-fed spontaneously hypertensive rat

BACKGROUND

Consumption of high-glycemic index foods contributes to the development of hypertension in some patients. Likewise, in spontaneously hypertensive rats (SHR), high sucrose promotes a secondary rise in systolic blood pressure (SBP). Chromium (III) (Cr(3+)) prevents sucrose-induced hypertension, but leaves the basal hypertension that characterizes SHR intact.

METHODS

Since hypertension entails increased peripheral resistance, we compared effects of Cr(3+) on resistance arteries from SHR fed low-glycemic (starch) versus high-glycemic (sucrose) index diets. Subgroups of SHR also received Cr(3+). Structure, stiffness, and vasodilation of mesenteric resistance arteries were studied using pressurized myography.

RESULTS

Sucrose increased SBP in SHR and, exclusively in sucrose-fed SHR, Cr(3+) reduced SBP and augmented acetylcholine or nitroprusside-dependent vasodilation. Neither sucrose nor Cr(3+) affected artery structure or stiffness. Since Cr(3+) enhanced vasodilation, we assessed endothelial NO synthase (eNOS), guanylate cyclase, cGMP-dependent protein kinase (PKG-1alpha and 1beta), and PKG activity by immunoblotting. Sucrose reduced eNOS, PKG-1beta, and PKG activity. Cr(3+) prevented the effects of sucrose on NO signaling.

CONCLUSION

In hypertension exacerbated by high-glycemic index diet, Cr(3+) reduces SBP. The BP-lowering effect of Cr(3+), selectively on sucrose-induced but not basal hypertension in SHR, involves at least in part, improving vasodilatory function vis-à-vis restoration of NO signaling in resistance arteries.

Beneficial impact of crocetin, a carotenoid from saffron, on insulin sensitivity in fructose-fed rats

Crocetin, a unique carotenoid with potent antioxidative and anti-inflammatory activities, is a major ingredient of saffron which is used as an important spice and food colorant in various parts of the world. In the present study, the effect of crocetin on insulin resistance and its related abnormalities induced by high-fructose diet were investigated in male Wistar rats. Compared to the control rats fed on normal laboratory diet, fructose-fed rats developed a series of pathological changes including insulin resistance, hyperinsulinemia, dyslipidemia and hypertension. Although having no evident effect on the body weight, fructose feeding caused a marked increase in the weight of epididymal white adipose tissue. Furthermore, a significant reduction in the expression of both protein and mRNA of adiponectin (an insulin-sensitizing adipocytokine) was observed, whereas those of tumor necrosis factor (TNF)-alpha and leptin were enhanced in epididymal white adipose tissue in fructose-fed rats. These disorders were effectively normalized in crocetin-treated rats. Crocetin was also demonstrated here to alleviate free fatty acid (FFA)-induced insulin insensitivity and dysregulated mRNA expression of adiponectin, TNF-alpha and leptin in primary cultured rat adipocytes. These findings suggest the possibility of crocetin treatment as a preventive strategy of insulin resistance and related diseases. The favorable impact on adiponectin, TNF-alpha and leptin expression in white adipose tissue may be involved in the improvement of insulin sensitivity observed in crocetin-treated rats.

Fructose-mediated stress signaling in the liver: implications for hepatic insulin resistance

Organisms reprogram metabolic pathways to adapt to changes in nutrient availability. This requires that nutrient-based stimuli are sensed, signals are transmitted, and highly specific responses are engaged. We propose that in the liver, the mitogen-activated protein kinase, c-jun N-terminal kinase (JNK), links excessive nutrient metabolism with impaired insulin regulation of glucose production. The liver, by virtue of its anatomic position and selective regulatory features, buffers and is highly responsive to changes in nutrient delivery. In particular, sugars such as sucrose and fructose uniquely regulate and are selectively metabolized by the liver. We propose that when hepatic fructose uptake exceeds requirements for glycogen and energy (hepatic sugar excess), the JNK-signaling pathway is engaged as part of the adaptive response.

Low ethanol intake prevents salt-induced hypertension in WKY rats

Low alcohol intake in humans lowers the risk of coronary heart disease and may lower blood pressure. In hypertension, insulin resistance with altered glucose metabolism leads to increased formation of aldehydes. We have shown that chronic low alcohol intake decreased systolic blood pressure (SBP) and tissue aldehyde conjugates in spontaneously hypertensive rats and demonstrated a strong link between elevated tissue aldehyde conjugates and hypertension in salt-induced hypertensive Wistar-Kyoto (WKY) rats. This study investigated the antihypertensive effect of chronic low alcohol consumption in high salt-treated WKY rats and its effect on tissue aldehyde conjugates, platelet cytosolic free calcium ([Ca2+]i, and renal vascular changes. Animals, aged 7 weeks, were divided into three groups of six animals each. The control group was given normal salt diet (0.7% NaCl) and regular drinking water; the high salt group was given a high salt diet (8% NaCl) and regular drinking water; the high salt + ethanol group was given a high salt diet and 0.25% ethanol in drinking water. After 10 weeks, SBP, platelet [Ca2+]i, and tissue aldehyde conjugates were significantly higher in rats in the high salt group as compared with controls. Animals on high salt diets also showed smooth muscle cell hyperplasia in the small arteries and arterioles of the kidney. Ethanol supplementation prevented the increase in SBP and platelet [Ca2+]i and aldehyde conjugates in liver and aorta. Kidney aldehyde conjugates and renal vascular changes were attenuated. These results suggest that chronic low ethanol intake prevents salt-induced hypertension and attenuates renal vascular changes in WKY rats by preventing an increase in tissue aldehyde conjugates and cytosolic [Ca2+]i.

Modelos experimentais de resistência à insulina e obesidade: lições aprendidas

Para melhor compreender o papel de cada um dos elementos envolvidos na fisiopatologia da obesidade e da resistência à insulina, pesquisadores utilizam-se de modelos experimentais, que podem determinar de maneira controlada o papel de cada um dos componentes da resistência à insulina e obesidade e, desta maneira, fornecer subsídios para a melhor compreensão da fisiopatolologia e tratamento da resistência à insulina e obesidade. A obesidade e a resistência à insulina experimentais podem ser verificadas quando ocorre diminuição da resposta à leptina, seja por menor produção ou alteração no seu receptor, modificações no receptor de insulina, por deleção do receptor ou alteração da transdução dos seu sinal, exacerbação do efeito de peptídeos orexígenos e/ou menor ação de peptídeos anorexígenos no hipotálamo, ou ainda secundária à hipertensão arterial, como nos ratos espontaneamente hipertensos. O excesso de glicocorticóides, a adição de uma dieta rica em frutose, ou ainda uma dieta hipercalórica, além da lesão hipotalâmica induzida pela administração neonatal de monoglutamato de sódio, são exemplos de obesidade e resistência à insulina induzidos.

Aldehyde sources, metabolism, molecular toxicity mechanisms, and possible effects on human health

Aldehydes are organic compounds that are widespread in nature. They can be formed endogenously by lipid peroxidation (LPO), carbohydrate or metabolism ascorbate autoxidation, amine oxidases, cytochrome P-450s, or myeloperoxidase-catalyzed metabolic activation. This review compares the reactivity of many aldehydes towards biomolecules particularly macromolecules. Furthermore, it includes not only aldehydes of environmental or occupational concerns but also dietary aldehydes and aldehydes formed endogenously by intermediary metabolism. Drugs that are aldehydes or form reactive aldehyde metabolites that cause side-effect toxicity are also included. The effects of these aldehydes on biological function, their contribution to human diseases, and the role of nucleic acid and protein carbonylation/oxidation in mutagenicity and cytotoxicity mechanisms, respectively, as well as carbonyl signal transduction and gene expression, are reviewed. Aldehyde metabolic activation and detoxication by metabolizing enzymes are also reviewed, as well as the toxicological and anticancer therapeutic effects of metabolizing enzyme inhibitors. The human health risks from clinical and animal research studies are reviewed, including aldehydes as haptens in allergenic hypersensitivity diseases, respiratory allergies, and idiosyncratic drug toxicity; the potential carcinogenic risks of the carbonyl body burden; and the toxic effects of aldehydes in liver disease, embryo toxicity/teratogenicity, diabetes/hypertension, sclerosing peritonitis, cerebral ischemia/neurodegenerative diseases, and other aging-associated diseases.

Hepatic adaptations to sucrose and fructose

The liver is an important site of postprandial glucose disposal, accounting for the removal of up to 30% of an oral glucose load. The liver is also centrally involved in dietary lipid and amino acid uptake, and the presence of either or both of these nutrients can influence hepatic glucose uptake. The composition of ingested carbohydrate also influences hepatic glucose metabolism. For example, fructose can increase hepatic glucose uptake. In addition, fructose extraction by the liver is exceedingly high, approaching 50% to 70% of fructose delivery. The selective hepatic metabolism of fructose, and the ability of fructose to increase hepatic glucose uptake can, under appropriate conditions (eg, diets enriched in sucrose or fructose, high fructose concentrations), provoke major adaptations in hepatic metabolism. Potential adaptations that can arise in response to these conditions and putative mechanisms driving these adaptations are the subject of this review.

Adsorption of Bile Acid by Chitosan-Orotic Acid Salt and Its Application as an Oral Preparation

The orotic acid (OT) salt of chitosan (CS), CS-OT, and that of a CS derivative, CP, were prepared, and the adsorption of primary or secondary bile acid was investigated. Calcium-induced alginate gel beads (Alg-Ca) containing CS-OT were also prepared and autoclaved, and the possibility of these beads to act as a vehicle for oral administration to prevent hyperlipidemia was investigated. When taurocholate (TCA) and glycocholate (GCA) were present together in the medium, CS-OT adsorbed identical amounts of both bile acids. This trend was seen in all CPs, although the capacity to adsorb bile acid was affected by the number and/or structure of the amino groups in the CP. On the other hand, taurodeoxycholate, a secondary bile acid was preferentially adsorbed over TCA and GCA. Alg-Ca containing CS-OT took up bile acids in a similar manner as CS-OT irrespective of the water content of the gel matrix. As all elements can be taken as a food, Alg-Ca containing CS-OT could serve as a useful dietary agent for the prevention of hyperlipidemia, which is a lifestyle-related disease.