Fructose-induced hypertension in rats is concentration- and duration-dependent

Acute Intake of Fructose Increases Arterial Pressure in Humans: A Meta-Analysis and Systematic Review

Hypertension is a major cardiac risk factor. Higher blood pressures are becoming more prevalent due to changing dietary habits. Here, we evaluated the impact on blood pressure in human subjects after acutely ingesting fructose using meta-analysis. A total of 89 studies were collected from four different electronic databases from 1 January 2008 to 1 August 2023. Of these studies, 10 were selected that fulfilled all the criteria for this meta-analysis. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), and blood glucose level were analyzed using the Cohen's d analysis or standardized mean difference at a confidence interval (CI) of 95%. The SBP, DBP, and MAP showed medium effect size; HR and glucose level displayed small effect size. The standardized mean difference of normal diet groups and fructose diet groups showed a significant increase in SBP (p = 0.04, REM = 2.30), and DBP (p = 0.03, REM = 1.48) with heterogeneity of 57% and 62%, respectively. Acute fructose ingestion contributes to an increase in arterial pressure in humans. The different parameters of arterial pressure in humans correlated with each other. These findings support further rigorous investigation, retrospective of necessity, into the effect of chronic dietary of fructose in humans in order to better understand the impact on long term arterial pressure.

Dysregulation of mitochondrial dynamics mediated aortic perivascular adipose tissue-associated vascular reactivity impairment under excessive fructose intake

Excessive fructose intake presents the major risk factor for metabolic cardiovascular disease. Perivascular adipose tissue (PVAT) is a metabolic tissue and possesses a paracrine function in regulating aortic reactivity. However, whether and how PVAT alters vascular function under fructose overconsumption remains largely unknown. In this study, male Sprague-Dawley rats (8 weeks old) were fed a 60% high fructose diet (HFD) for 12 weeks. Fasting blood sugar, insulin, and triglycerides were significantly increased by HFD intake. Plasma adiponectin was significantly enhanced in the HFD group. The expression of uncoupling protein 1 (UCP1) and mitochondrial mass were reduced in the aortic PVAT of the HFD group. Concurrently, the expression of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) and mitochondrial transcription factor A (TFAM) were suppressed. Furthermore, decreased fusion proteins (OPA1, MFN1, and MFN2) were accompanied by increased fission proteins (FIS1 and phospho-DRP1). Notably, the upregulated α-smooth muscle actin (α-SMA) and osteocalcin in the PVAT were concurrent with the impaired reactivity of aortic contraction and relaxation. Coenzyme Q10 (Q, 10 mg/100 mL, 4 weeks) effectively reversed the aforementioned events induced by HFD. Together, these results suggested that the dysregulation of mitochondrial dynamics mediated HFD-triggered PVAT whitening to impair aortic reactivity. Fortunately, coenzyme Q10 treatment reversed HFD-induced PVAT whitening and aortic reactivity.

Impact of Normal and Overweight Pregnancy in GLUT4 and Glucose-Dependent Vascular Contractility

INTRODUCTION

Obesity during pregnancy can contribute to hypertensive complications through changes in glucose utilization. We investigated the impact of vascular glucose uptake, GLUT4 density, and endothelium on agonist-induced vasoconstriction in the aortas of overweight pregnant rats.

METHODS

Isolated aortic rings with or without endothelium from pregnant or nonpregnant rats fed a standard (SD) or hypercaloric diet (HD) were contracted with phenylephrine or serotonin (10-9 to 10-4M) using standard (11 mm) or without (0 mm) glucose Krebs solution. GLUT4 density in the aortas was measured using the en face method.

RESULTS

Aortas from overweight pregnant animals (PHD) showed increased Phe-induced vasoconstriction (p < 0.05 vs. pregnant standard diet [PSD]), which was endothelium-independent. The contraction decreased significantly in the absence of glucose. In contrast, vessels from pregnant SD rats maintained their contraction in glucose-free Krebs solution. 5-HT increases PHD aortic contraction only in the absence of glucose. The fetal aortas from PHD mothers showed blunted vasoconstriction. Overweight significantly reduced GLUT4 expression in maternal and fetal aortas (p < 0.05 vs. PSD).

CONCLUSIONS

Aortic contractility is independent of glucose uptake during healthy pregnancy. In contrast, overweight pregnancy increases contractility. This increase depends directly on smooth muscle glucose uptake and inversely on GLUT-4 density. The increased contraction observed in the vasculature of overweight mothers was inverted in the fetal aortas.

The effect of evening primrose oil (Oenothera biennis) on the level of adiponectin and some biochemical parameters in rats with fructose induced metabolic syndrome

The effect of evening primrose oil on adiponectin level and some biochemical parameters in model of fructose-induced metabolic syndrome were investigated. The rats were divided into 4 groups: control, evening primrose oil, fructose, fructose + evening primrose oil. Body weight, daily feed and water consumptions and systolic blood pressures of animals were measured. At the end of trial, blood samples were taken, livers were excised and histopathological examination was performed. Glucose, uric acid, triglyceride, T.cholesterol, LDL, HDL, VLDL, ALT, AST, ALP, LDH, adiponectin, insulin, IL-6, TNF-α, TAC, and TOS levels were analysed. Some analysed parameters and systolic blood pressure of fructose + evening primrose oil group decreased significantly compared to fructose group and adiponectin, TAC, and HDL levels were significantly increased. As conclusion, evening primrose oil can be considered as antioxidant agent by reducing oxidative stress, increasing adiponectin levels and insulin sensitivity, anti-inflammatory properties, exhibiting anti-atherogenic effect by regulating dyslipidemia and systolic blood pressure.

Independent effects of sex and stress on fructose-induced salt-sensitive hypertension

Proximal tubule fructose metabolism is key to fructose-induced hypertension, but the roles of sex and stress are unclear. We hypothesized that females are resistant to the salt-sensitive hypertension caused by low amounts of dietary fructose compared to males and that the magnitude of the increase in blood pressure (BP) depends, in part, on amplification of the stress response of renal sympathetic nerves. We measured systolic BP (SBP) in rats fed high salt with either no sugar (HS), 20% glucose (GHS) or 20% fructose (FHS) in the drinking water for 7-8 days. FHS increased SBP in both males (Δ22 ± 9 mmHg; p < 0.046) and females (Δ16 ± 3 mmHg; p < 0.0007), while neither GHS nor HS alone induced changes in SBP in either sex. The FHS-induced increase in SBP as measured by telemetry in the absence of added stress (8 ± 2 mmHg) was significantly lower than that measured by plethysmography (24 ± 5 mmHg) (p < 0.014). However, when BP was measured by telemetry simulating the stress of plethysmography, the increase in SBP was significantly greater (15 ± 3 mmHg) than under low stress (8 ± 1 mmHg) (p < 0.014). Moderate-stress also increased telemetric diastolic (p < 0.006) and mean BP (p < 0.006) compared to low-stress in FHS-fed animals. Norepinephrine excretion was greater in FHS-fed rats than HS-fed animals (Male: 6.4 ± 1.7 vs.1.8 ± 0.4 nmole/kg/day; p < 0.02. Female 54 ± 18 vs. 1.2 ± 0.6; p < 0.02). We conclude that fructose-induced salt-sensitive hypertension is similar in males and females unlike other forms of hypertension, and the increase in blood pressure depends in part on an augmented response of the sympathetic nervous system to stress.

Indapamide Increases IRS1 Expression and Modifies Adiponectin/NLRP3/PPARγ Crosstalk in Type 2 Diabetic Rats

The current study aimed to evaluate the anti-diabetic effects of canagliflozin (CANA) and indapamide (INDA) and their impacts as adiponectin modulators in experimentally induced type 2 diabetes mellitus (T2DM). T2DM was associated with a significant rise in blood glucose level and HbA1C%, andreduced adiponectin and insulin secretions. Moreover, the malondialdehyde (MDA) contents in both the epididymal adipocytes and soleus muscle significantly escalated, while the total antioxidant capacity (TAC) and epididymal adipocyte Nrf2 expression significantly declined. Moreover, serum TNF-α, epididymal adipocyte’s NOD-like receptor protein 3, NLRP3, NF-κB and CD68 expressions markedly escalated, and serum IL-10 significantly declined. Furthermore, there was a significant escalation in PPARγ expression in epididymal adipocytes, with a significant reduction in soleus muscle’s expression of IRS1. CANA and INDA treatments markedly reduced blood glucose levels, increased adiponectin and insulin secretion, enhanced anti-oxidant defenses, and reduced oxidative burden, with marked anti-inflammatory impact. Interestingly, the impact of indapamide on DM indices and oxidative and inflammatory changes was comparable to that of canagliflozin. Nevertheless, indapamide had a superior effect compared to canagliflozin on HbA1c%, expression of IRS1 and reduction of NF-κB and CD68 expressions. INDA could be effective in regulating T2DM, with underlined anti-diabetic, antioxidant, and anti-inflammatory properties. INDA increased IRS1 expression and modified adiponectin/NLRP3/PPARγ crosstalk. The impacts of INDA are comparable to those of the standard anti-diabetic drug CANA.

Neural mechanisms underlying the role of fructose in overfeeding

Fructose consumption has been linked with metabolic syndrome and obesity. Fructose-based sweeteners like high fructose corn syrup taste sweeter, improve food palatability, and are increasingly prevalent in our diet. The increase in fructose consumption precedes the rise in obesity and is a contributing driver to the obesity epidemic worldwide. The role of dietary fructose in obesity can be multifactorial by promoting visceral adiposity, hypertension, and insulin resistance. Interestingly, one emergent finding from human and animal studies is that dietary fructose promotes overfeeding. As the brain is a critical regulator of food intake, we reviewed the evidence that fructose can act in the brain and elucidated the major brain systems underlying fructose-induced overfeeding. We found that fructose acts on multiple interdependent brain systems to increase orexigenic drive and the incentive salience of food while decreasing the latency between food bouts and reducing cognitive control to disinhibit feeding. We concluded that the collective actions of fructose may promote feeding behavior by producing a hunger-like state in the brain.

Cilnidipine loaded poly (ε-caprolactone) nanoparticles for enhanced oral delivery: optimization using DoE, physical characterization, pharmacokinetic, and pharmacodynamic evaluation

Cilnidipine (CND), an anti-hypertensive drug, possesses low oral bioavailability due to its poor aqueous solubility, low dissolution rate, and high gut wall metabolism. In the present study, an attempt has been made to prepare CND loaded polycaprolactone based nanoparticles (CND-PCL-NPs) by nanoprecipitation method applying the concepts of Design of Experiments. Critical factors affecting particle size and loading efficiency (LE%) were assessed by a hybrid design approach, comprising of Mini Run Resolution IV design followed by Box-Behnken design. Particle size, PDI, zeta potential and LE% of optimized formulations of CND-PCL-NPs were 220.3 ± 2.6 nm, 0.25 ± 0.1, -19.5 ± 0.9 mV, and 46.4 ± 1.8%, respectively. No significant changes were observed in the physical stability of nanoparticles when stored at 25 °C/60% RH over a period of 3 months. Oral pharmacokinetic studies revealed that Fabs of CND-PCL-NPs (0.55) were significantly higher than the CND suspension (0.26). Pharmacodynamic studies have revealed that the mean percent reduction in systolic blood pressure (% ΔSBP) was significantly higher in the case of CND-PCL-NPs (42%) as compared to CND suspension (24%). Optimized CND-PCL-NPs offer great potential in providing higher and sustained antihypertensive effect compared to conventional formulations of CND.

Co-Treatment with Cefotaxime and High-Fructose Diet Inducing Nonalcoholic Fatty Liver Disease and Gut Microbial Dysbiosis in Mice

High fructose diet causes metabolic syndrome and induces host gut microbial dysbiosis and related obesity and nonalcoholic fatty liver disease (NAFLD). Several antibiotic treatments could prevent fatty liver. However, there are studies that have demonstrated that a high-fructose diet could influence the gut microbial dysbiosis and induce fatty liver. The purpose of this study was performed to partially modify the gut bacterial composition with a single cefotaxime treatment, which might affect the fructose-induced NAFLD severity. The C57BL/6JNarl male mice were divided into four groups including vehicle/chow diet (VE-CD), vehicle/high-fructose diet (VE-FD), antibiotic (cefotaxime (CF))/CD, and CF/FD. The results showed that body weight gain, moderate hepatic steatosis severity, epididymal white adipose tissue hypertrophy, and insulin resistance occurrence with NAFLD-related symptoms were observed only in the CF-FD group. The raised protein expression of hepatic lipogenesis was observed in the CF-FD group, but lipolysis protein expression was no difference. The diversity and composition of microbiota were significantly reduced in the CF-FD group. The Erysipelatoclostridium, Enterobacteriaceae, Lachnospiraceae, and Escherichia Shigella were in increased abundance in the feces of CF-FD group compared with VE-FD group. The novel model reveals that particular antibiotics such as cefotaxime co-treatment with high-fructose diet may affect the gut microbiota accelerating the NAFLD and obesity.

Fructose and high fructose corn syrup: are they a two-edged sword?

High-fructose syrups are used as sugar substitutes due to their physical and functional properties. High fructose corn syrup (HFCS) is used in bakery products, dairy products, breakfast cereals and beverages, but it has been reported that there might be a direct relationship between high fructose intake and adverse health effects such as obesity and the metabolic syndrome. Thus, fructose has recently received much attention, most of which was negative. Although studies have indicated that there might be a correlation between high fructose-rich diet and several adverse effects, however, the results of these studies cannot be certainly generalised to the effects of HFCS; because they have investigated pure fructose at very high concentrations in measurement of metabolic upsets. This review critically considered the advantages and possible disadvantages of HFCS application and consumption in food industry, as a current challenging issue between nutritionists and food technologists.

Effects of TNF-α antagonist infliximab on fructose-induced metabolic syndrome in rats

Public health issues have been raised regarding fructose toxicity and its serious metabolic disorders. Deleterious effects of high fructose intake on insulin sensitivity, body weight, lipid homeostasis have been identified. The new millennium has witnessed the emergence of a modern epidemic, the metabolic syndrome (MS), in approximately 25% of the world's adult population. The current study aimed to investigate the effect of the TNF-α antagonist infliximab on fructose-induced MS in rats. Rats were administered fructose (10%) in drinking water for 12 weeks to induce the experimental MS model. infliximab (5 mg/kg) was injected once weekly intraperitoneally starting on the 13th week for 4 weeks. Increase in body weight, blood glucose level, serum triglycerides (TGs), adiponectin level and blood pressure were present in MS rats. They also prompted increases in serum of leptin, TNF-α, and malondialdehyde (MDA) levels. Treatment with infliximab did not affect body weight, hyperglycemia or hypertension, but decreased serum TGs and increased serum HDL-c levels. Infliximab also decreased adiponectin levels. Surprisingly, infliximab increased MDA above its value in the MS group. These results reflect the fact that infliximab affects the manifestations of MS in rats. Though infliximab reduced TGs, increased HDL-c levels, reversed adiponectin resistance occurred by fructose, the drug failed to combat MS-mediated hyperglycemia, hypertension, and elevated MDA above the insult.

Pharmacological screening of fenofibrate-loaded solid dispersion in fructose-induced diabetic rat

OBJECTIVES

Hyperlipidaemia is a common phenomenon in diabetes mellitus. Fenofibrate (FF) is a good candidate for the treatment of lipid abnormalities in patients with type 2 diabetes. But the bioavailability as well as therapeutic efficacy of this drug is limited to its dissolution behaviour. Here, the authors assess the therapeutic efficacy of a newly formulated solid dispersion of fenofibrate (SDF) having enhanced dissolution profiles in contrast to pure FF using fructose-induced diabetic rat model.

METHODS

Fructose-induced diabetic rat model was developed to assess the pharmacological efficacy of the formulated SDF, and the results were compared with the effects of conventional FF therapy.

KEY FINDINGS

The 14 days treatment showed better improvement in lipid-lowering potency of SDF than pure FF. SDF containing one-third dose of pure FF showed similar effect in terms of triglyceride, total cholesterol and low-density lipoprotein lowering efficacy, whereas increased high-density lipoprotein at same extent. The similar dose of SDF produced more prominent effect than FF. Histological studies also demonstrated the enhanced lipid clearance from liver by SDF than FF that was concordant with the biochemical results.

CONCLUSIONS

This newly formulated SDF would be a promising alternative for conventional fenofibrate in treating hyperlipidaemia.

Acute Exposure to Fructose Impairs Endothelium-Dependent Relaxation via Oxidative Stress in Isolated Rat Aortic Rings

INTRODUCTION

Although both glucose and fructose are hexoses, their catabolism is quite different: the catabolism of fructose is initiated by ketohexokinase and is not regulated by negative feedback, which results in oxidative stress.

OBJECTIVE

We hypothesized that fructose impairs endothelium-dependent relaxation via oxidative stress in rat aortic rings.

METHODS

Sprague-Dawley rats were offered 20% fructose solution or tap water for 2 weeks, after which vascular reactivity was measured in isolated aortic rings. In a separate experiment, vascular reactivity was measured after acute exposure to ∼10 mM fructose in isolated aortic rings from untreated rats.

RESULTS

Although high-fructose intake statistically significantly increased blood pressure and body weight, it did not affect contraction and relaxation in aortic rings. The substitution of fructose for glucose in Krebs solution inhibited vascular relaxation in aortic rings, which was abolished by pretreatment with antioxidants. Decreasing the glucose concentration in Krebs solution inhibited vascular relaxation, whereas decreasing the fructose concentration in Krebs solution improved vascular relaxation in the aortic rings. Pretreatment with antioxidants improved the vascular relaxation in Krebs solution with fructose substituted for glucose.

CONCLUSIONS

These results indicate that fructose impairs endothelium-dependent relaxation via oxidative stress in isolated rat aortic rings.

ADHD pathogenesis in the immune, endocrine and nervous systems of juvenile and maturating SHR and WKY rats

RATIONALE

Attention-deficit/hyperactivity disorder (ADHD) is one of the most common neurobehavioural disorders with morphological and functional brain abnormalities. However, there is a growing body of evidence that abnormalities in the immune and endocrine systems may also account for the ADHD pathogenesis.

OBJECTIVES

To test ADHD pathogenesis in neurological, immune and endocrine systems, this study examined the concentrations of cytokines, chemokines, oxidative stress markers, metabolic parameters, steroid hormones and steroidogenic enzymes in the serum and/or tissues of spontaneously hypertensive rats (SHRs, animal model of ADHD) and Wistar Kyoto rats (WKYs, control animals). Moreover, the volume of the medial prefrontal cortex (mPFC) as well as the density of dopamine 2 (D2) receptor-expressing cells and tyrosine hydroxylase (TH)-positive nerve fibres in it was also elucidated.

METHODS

Peripheral blood, spleen and adrenal gland samples, as well as brain sections collected on day 35 (juvenile) and day 70 (maturating) from SHRs and WKYs, were processed by ELISA and immunohistochemistry, respectively.

RESULTS

The results show significant increases of serum and/or tissue concentrations of cytokines, chemokines and oxidative stress markers in juvenile SHRs when compared to the age-matched WKYs. These increases were accompanied by a lowered volume of the mPFC and up-regulation of D2 in this brain region. In maturating SHRs, the levels of inflammatory and oxidative stress markers were normalised and accompanied by elevated contents of steroid hormones.

CONCLUSIONS

Significant elevations of serum and/or tissue contents of cytokines, chemokines and oxidative stress markers as well as volumetric and neurochemical alterations in the mPFC of juvenile SHRs may suggest the cooperation of neurological and immune systems in the ADHD pathogenesis. Elevated levels of steroid hormones in maturating SHRs may be a compensatory effect involved in reducing inflammation and ADHD symptoms.

The Good, the Bad, and the Ugly of Pregnancy Nutrients and Developmental Programming of Adult Disease

Maternal nutrition plays a decisive role in developmental programming of many non-communicable diseases (NCDs). A variety of nutritional insults during gestation can cause programming and contribute to the development of adult-onset diseases. Nutritional interventions during pregnancy may serve as reprogramming strategies to reverse programming processes and prevent NCDs. In this review, firstly we summarize epidemiological evidence for nutritional programming of human disease. It will also discuss evidence from animal models, for the common mechanisms underlying nutritional programming, and potential nutritional interventions used as reprogramming strategies.

Translational insights on developmental origins of metabolic syndrome: Focus on fructose consumption

Metabolic syndrome (MetS) is a highly prevalent complex trait despite recent advances in pathophysiology and pharmacological treatment. MetS can begin in early life by so-called the developmental origins of health and disease (DOHaD). The DOHaD concept offers a novel approach to prevent MetS through reprogramming. High fructose (HF) intake has been associated with increased risk of MetS. HF diet becomes one of the most commonly used animal model to induce MetS. This review discusses the maternal HF diet induced programming process and reprogramming strategy to prevent MetS of developmental origin, with an emphasis on: (1) an overview of metabolic effects of fructose consumption on MetS; (2) insight from maternal HF animal models on MetS-related phenotypes; (3) impact of HF consumption induces organ-specific transcriptome changes; and (4) application of reprogramming strategy to prevent maternal HF consumption-induced MetS. Research into the preventions and treatments of MetS that begin early in life will have a lifelong impact and profound savings in disease burden and financial costs.

Hypertension Associated with Fructose and High Salt: Renal and Sympathetic Mechanisms

Hypertension is a leading cause of cardiovascular and chronic renal disease. Despite multiple important strides that have been made in our understanding of the etiology of hypertension, the mechanisms remain complex due to multiple factors, including the environment, heredity and diet. This review focuses on dietary contributions, providing evidence for the involvement of elevated fructose and salt consumption that parallels the increased incidence of hypertension worldwide. High fructose loads potentiate salt reabsorption by the kidney, leading to elevation in blood pressure. Several transporters, such as NHE3 and PAT1 are modulated in this milieu and play a crucial role in salt-sensitivity. High fructose ingestion also modulates the renin-angiotensin-aldosterone system. Recent attention has been shifted towards the contribution of the sympathetic nervous system, as clinical trials demonstrated significant reductions in blood pressure following renal sympathetic nerve ablation. New preclinical data demonstrates the activation of the renal sympathetic nerves in fructose-induced salt-sensitive hypertension, and reductions of blood pressure after renal nerve ablation. This review further demonstrates the interplay between sodium handling by the kidney, the renin-angiotensin-aldosterone system, and activation of the renal sympathetic nerves as important mechanisms in fructose and salt-induced hypertension.

Comparison of the effects of sulforaphane and pioglitazone on insulin resistance and associated dyslipidemia, hepatosteatosis, and endothelial dysfunction in fructose-fed rats

The purpose of this work was to compare the influences of sulforaphane (SFN) to those of the standard insulin sensitizer pioglitazone (PIO) on high fructose diet (HFrD)-induced insulin resistance, dyslipidemia, hepatosteatosis, and vascular dysfunction in rats. Male Sprague Dawley rats (150-200 g) were fed on a standard diet (control) or a high fructose diet (HFrD, 60% w/w fructose) for 60 days. From day 16, two subgroups of HFrD-fed rats received either SFN (0.5 mg/kg/day, orally) or PIO (5 mg/kg/day, orally) along with HFrD until the end of the experiment. Fructose-fed rats showed significant decreases in food intake, body weight and feeding efficiency; effects that were not altered by either treatment. Data from insulin tolerance test (ITT), oral glucose tolerance test (OGTT), and HOMA-IR and HOMA-β indices demonstrated impaired insulin sensitivity and glucose utilization in HFrD-fed rats. SFN and PIO treatments significantly reduced OGTT_AUC (Glass's Delta values = 1.12 and 0.84, respectively), decreased ITT_AUC (Glass's Delta values = 1.05 and 0.71, respectively), significantly diminished HOMA-IR index (by 55.6% and 77.6%, respectively), and increased HOMA-β value (by 1.8 and 1.3 fold, respectively) compared to the HFrD rats. Moreover, SFN and PIO ameliorated hepatic oxidative stress and reduced serum levels of C-reactive protein and lactate dehydrogenase in HFrD-fed rats. Furthermore, SFN and PIO administrations improved insulin resistance-associated heaptosteatosis and enhanced vascular responsiveness to acetylcholine-induced relaxations. However, only SFN was able to enhance serum HDL-C levels in HFrD group. These finding suggests that SFN elicited insulin-sensitizing, hepatoprotective, and vasculoprotective effects in HFrD insulin-resistant rats that were comparable to those exerted by PIO.

The suppressive effect of the three-herb extract mixture on vascular and liver inflammation in atherogenic diet with high fructose-fed mice

CONTEXT

Cynanchum wilfordii (Maximowicz) Hemsley (Apocynaceae), Arctium lappa L. var. rubescens Frivald (Asteraceae) and Dioscorea opposite Thunb (Dioscoreaceae) root extracts have been widely used as an alternative for intervening obesity.

OBJECTIVES

The synergistic effect of three-herb mixture of C. wilfordii, A. lappa and D. opposita was determined on aortic and liver inflammatory responses.

MATERIALS AND METHODS

CWE, ALE and DOE were prepared from the root of C. wilfordii, A. lappa and D. opposite by 70% ethanol extraction, respectively. CADE was prepared using a powder mixture of 2 CWE:1 ALE:1 DOE. C57BL/6 mice were fed an atherogenic diet combined with 10% fructose (ATHFR) in the presence of 200 mg/kg/day CWE, ALE, DOE or CADE for 8 weeks (each group, n = 6). Biochemical profiles, protein expression of vascular cell adhesion molecule-1 (VCAM-1) on the aorta and liver were determined.

RESULTS

CADE could significantly suppress the protein expression of VCAM-1 in both the aorta and liver (80% reduction) compared to ATHFR-fed mice. Impairment of liver function was significantly ameliorated by CADE supplement, as determined by GOT (60% reduction) and GPT (51% reduction) levels.

CONCLUSIONS

CADE should be considered when developing medications to suppress the vascular and liver inflammatory responses for individuals who are either non-responsive or resistant to lipid-lowering drugs.

Chronic Consumption of Fructose Induces Behavioral Alterations by Increasing Orexin and Dopamine Levels in the Rat Brain

It has been widely described that chronic intake of fructose causes metabolic alterations which can be associated with brain function impairment. In this study, we evaluated the effects of fructose intake on the sleep–wake cycle, locomotion, and neurochemical parameters in Wistar rats. The experimental group was fed with 10% fructose in drinking water for five weeks. After treatment, metabolic indicators were quantified in blood. Electroencephalographic recordings were used to evaluate the sleep architecture and the spectral power of frequency bands. Likewise, the locomotor activity and the concentrations of orexin A and monoamines were estimated. Our results show that fructose diet significantly increased the blood levels of glucose, cholesterol, and triglycerides. Fructose modified the sleep–wake cycle of rats, increasing the waking duration and conversely decreasing the non-rapid eye movement sleep. Furthermore, these effects were accompanied by increases of the spectral power at different frequency bands. Chronic consumption of fructose caused a slight increase in the locomotor activity as well as an increase of orexin A and dopamine levels in the hypothalamus and brainstem. Specifically, immunoreactivity for orexin A was increased in the ventral tegmental area after the intake of fructose. Our study suggests that fructose induces metabolic changes and stimulates the activity of orexinergic and dopaminergic neurons, which may be responsible for alterations of the sleep–wake cycle.

Characteristics of WBN/Kob diabetic fatty rats supplemented with a fructose-rich diet as a metabolic syndrome model: response to a GLP-1 receptor agonist

The incidence of metabolic syndrome is rapidly increasing worldwide, and adequate animal models are crucial for studies on its pathogenesis and therapy. In the search of an adequate experimental model to simulate human metabolic syndrome, the present study was performed to examine the pharmacological response of WBN/Kob-Lepr^fa (WBKDF) rats supplemented with a fructose-rich diet (FRD) to liraglutide, a GLP-1 receptor agonist. Male WBKDF rats fed FRD at 7 weeks of age were divided into 3 groups, and administered liraglutide (75, 300 µg/kg subcutaneously) or saline (control group), once daily for 4 weeks. All rats in the control group became overweight, and developed hyperglycemia, hypertension and dyslipidemia as they aged. The rats given liraglutide exhibited a dose-dependent reduction in body weight, visceral fat content and food intake compared with control rats. In addition, liraglutide suppressed the development of hyperglycemia, hypertension and dyslipidemia. An intravenous glucose tolerance test revealed that liraglutide improved glucose tolerance, insulin secretion and insulin resistance. On histological examination, decreased hepatic fatty degeneration was observed in the liraglutide groups. The present study demonstrated that liraglutide protected against obesity, hyperglycemia, hypertension, dyslipidemia, and hepatic steatosis in WBKDF rats fed FRD, suggesting that WBKDF rats fed FRD may be a useful model to investigate the etiology of human metabolic syndrome.

Losartan prevents the imbalance between renal dopaminergic and renin angiotensin systems induced by fructose overload. l-Dopa/dopamine index as new potential biomarker of renal dysfunction

BACKGROUND

The renin angiotensin system (RAS) and the renal dopaminergic system (RDS) act as autocrine and paracrine systems to regulate renal sodium management and inflammation and their alterations have been associated to hypertension and renal damage. Nearly 30-50% of hypertensive patients have insulin resistance (IR), with a strong correlation between hyperinsulinemia and microalbuminuria.

OBJECTIVE

The aim of this study was to demonstrate the existence of an imbalance between RAS and RDS associated to IR, hypertension and kidney damage induced by fructose overload (FO), as well as to establish their prevention, by pharmacological inhibition of RAS with losartan.

MATERIALS/METHODS

Ninety-six male Sprague-Dawley rats were randomly divided into four groups and studied at 4, 8 and 12 weeks: control group (C4, C8 and C12; tap water to drink); fructose-overloaded group (F4, F8 and F12; 10% w/v fructose solution to drink); losartan-treated control (L) group (L4, L8 and L12; losartan 30 mg/kg/day, in drinking water); and fructose-overloaded plus losartan group (F + L4, F + L8 and F + L12, in fructose solution).

RESULTS

FO induced metabolic and hemodynamic alterations as well as an imbalance between RAS and RDS, characterized by increased renal angiotensin II levels and AT₁R overexpression, reduced urinary excretion of dopamine, increased excretion of l-dopa (increased l-dopa/dopamine index) and down-regulation of D₁R and tubular dopamine transporters OCT-2, OCT-N1 and total OCTNs. This imbalance was accompanied by an overexpression of renal tubular Na⁺, K⁺-ATPase, pro-inflammatory (NF-kB, TNF-α, IL-6) and pro-fibrotic (TGF-β1 and collagen) markers and by renal damage (microalbuminuria and reduced nephrin expression). Losartan prevented the metabolic and hemodynamic alterations induced by FO from week 4. Increased urinary l-dopa/dopamine index and decreased D₁R renal expression associated to FO were also prevented by losartan since week 4. The same pattern was observed for renal expression of OCTs/OCTNs, Na⁺, K⁺-ATPase, pro-inflammatory and pro-fibrotic markers from week 8. The appearance of microalbuminuria and reduced nephrin expression was prevented by losartan at week 12.

CONCLUSION

The results of this study provide new insight regarding the mechanisms by which a pro-hypertensive and pro-inflammatory system, such as RAS, downregulates another anti-hypertensive and anti-inflammatory system such as RDS. Additionally, we propose the use of l-dopa/dopamine index as a biochemical marker of renal dysfunction in conditions characterized by sodium retention, IR and/or hypertension, and as a predictor of response to treatment and follow-up of these processes.

The role of the baroreflex and parasympathetic nervous system in fructose-induced cardiac and metabolic alterations

It is well-established that baroreflex sensitivity is essential for blood pressure control, and also plays a key role in the modulation of disease-induced metabolic alterations. In order to investigate the role of the baroreflex in the cardiometabolic and inflammatory derangements promoted by fructose overload, Wistar rats underwent sinoaortic denervation (SAD) or sham surgery and were studied 90 days after receiving tap water (Den and Ctrl) or a 10% fructose solution (Fruc and Den-Fruc). All experimental groups showed marked and similar degree of baroreflex impairment compared to Ctrl. As expected, fructose overload effectively induced metabolic syndrome; however, when it was associated with SAD, several alterations were attenuated. While Fruc rats displayed increased sympathetic modulation and tone and reduced vagal modulation compared to Ctrl animals, Den-Fruc rats showed greater vagal tone and modulation when compared to the Fruc group. Moreover, the Den-Fruc group showed augmented expression of β1 adrenergic receptors and TNF/IL-10 ratio and reduction of β2 in the left ventricle. The increase in vagal function was correlated with improved insulin sensitivity (r² = 0.76), and decreased abdominal fat (r² = -0.78) and β2 receptors (r² = -0.85). Our results showed that: (1) chronic fructose overload induced severe baroreflex impairment, i.e. in a similar magnitude to that observed in SAD rats, which is accompanied by cardiometabolic dysfunctions; (2) the compensatory enhancement in parasympathetic function in SAD rats submitted to fructose intake may point out the possibility of use of approaches that improve vagal function as therapeutic target to attenuate fructose-induced cardiometabolic dysfunctions.

Alterations in fatty acid metabolism and sirtuin signaling characterize early type-2 diabetic hearts of fructose-fed rats

Despite the fact that skeletal muscle insulin resistance is the hallmark of type‐2 diabetes mellitus (T2DM), inflexibility in substrate energy metabolism has been observed in other tissues such as liver, adipose tissue, and heart. In the heart, structural and functional changes ultimately lead to diabetic cardiomyopathy. However, little is known about the early biochemical changes that cause cardiac metabolic dysregulation and dysfunction. We used a dietary model of fructose‐induced T2DM (10% fructose in drinking water for 6 weeks) to study cardiac fatty acid metabolism in early T2DM and related signaling events in order to better understand mechanisms of disease. In early type‐2 diabetic hearts, flux through the fatty acid oxidation pathway was increased as a result of increased cellular uptake (CD36), mitochondrial uptake (CPT1B), as well as increased β‐hydroxyacyl‐CoA dehydrogenase and medium‐chain acyl‐CoA dehydrogenase activities, despite reduced mitochondrial mass. Long‐chain acyl‐CoA dehydrogenase activity was slightly decreased, resulting in the accumulation of long‐chain acylcarnitine species. Cardiac function and overall mitochondrial respiration were unaffected. However, evidence of oxidative stress and subtle changes in cardiolipin content and composition were found in early type‐2 diabetic mitochondria. Finally, we observed decreased activity of SIRT1, a pivotal regulator of fatty acid metabolism, despite increased protein levels. This indicates that the heart is no longer capable of further increasing its capacity for fatty acid oxidation. Along with increased oxidative stress, this may represent one of the earliest signs of dysfunction that will ultimately lead to inflammation and remodeling in the diabetic heart.

Maternal Melatonin Therapy Attenuated Maternal High-Fructose Combined with Post-Weaning High-Salt Diets-Induced Hypertension in Adult Male Rat Offspring

Consumption of food high in fructose and salt is associated with the epidemic of hypertension. Hypertension can originate from early life. Melatonin, a pleiotropic hormone, regulates blood pressure. We examined whether maternal melatonin therapy can prevent maternal high-fructose combined with post-weaning high-salt diet-induced programmed hypertension in adult offspring. Pregnant Sprague-Dawley rats received either a normal diet (ND) or a 60% fructose diet (HF) during pregnancy and the lactation period. Male offspring were on either the ND or a high-salt diet (HS, 1% NaCl) from weaning to 12 weeks of age and were assigned to five groups (n = 8/group): ND/ND, HF/ND, ND/HS, HF/HS, and HF/HS+melatonin. Melatonin (0.01% in drinking water) was administered during pregnancy and lactation. We observed that maternal HF combined with post-weaning HS diets induced hypertension in male adult offspring, which was attenuated by maternal melatonin therapy. The beneficial effects of maternal melatonin therapy on HF/HS-induced hypertension related to regulating several nutrient-sensing signals, including Sirt1, Sirt4, Prkaa2, Prkab2, Pparg, and Ppargc1a. Additionally, melatonin increased protein levels of mammalian targets of rapamycin (mTOR), decreased plasma asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine levels, and increased the l-arginine-to-ADMA ratio. The reprogramming effects by which maternal melatonin therapy protects against hypertension of developmental origin awaits further elucidation.

Assessment of fructose overload in the metabolic profile and oxidative/nitrosative stress in the kidney of senescent female rats

The aging process is a complex phenomenon that leads the body to several changes, affecting its integrity and resulting in chronic pathologies, which compromises health and quality of life of elderly people. Animals supplemented with fructose have been used as an experimental model for induction of insulin resistance. The objective of this study was to evaluate the metabolic effects and the levels of oxidative/nitrosative stress in the kidney of senescent rats with a high fructose intake. The animals were allocated into 4 groups: young control (Y), aged control (A), young fructose (YF) and aged fructose (AF). Groups Y and A received water and groups YF and AF received fructose (100g/L) in the water, both ad libitum. After 12weeks of high fructose intake, the animals were sacrificed to collect their kidneys, blood and the thoracic aorta. The results are presented as mean±SE, analyzed by the One-Way ANOVA test with Newman-Keuls post-test; significant at p<0.05. The fructose overload caused metabolic dysfunctions and insulin resistance, confirming the efficacy of the chosen model. In this study, we observed a body weight gain in the studied groups (except in the elderly fructose group), and an increase in general caloric intake, diuresis and adipose tissue; insulin resistance, increased fasting glucose, triglycerides and cholesterol in the fructose groups. We also found a loss of renal function, increased oxidative/nitrosative stress and inflammation, and a reduction of antioxidants and a lower vasodepressor response in the studied groups, especially those who consumed fructose. In summary, our data showed that aging or high fructose intake contributed to the increase of oxidative/nitrosative stress in animals, demonstrating that at the dose and the period of fructose treatment utilized in this study, fructose was not able to aggravate several aspects which were already altered by aging. We believe that the high fructose intake simulates most of the effects of aging, and this understanding would be useful to prevent or minimize many of the alterations caused by this condition.

Development and in vitro/in vivo performance of self-nanoemulsifying drug delivery systems loaded with candesartan cilexetil

Candesartan cilexetil is widely used in the management of hypertension and heart failure. The drug delivery encounters obstacles of poor aqueous solubility, efflux by intestinal P-glycoprotein and vulnerability to enzymatic degradation in small intestine. Self-nanoemulsifying drug delivery systems (SNEDDS) loaded with candesartan cilexetil were successfully developed to overcome such obstacles. Preliminary screening was carried out to select proper surfactant, co-surfactant and oil combination for successful SNEDDS formulation. All screened excipients were reported for their P-glycoprotein and cytochrome P450 3A4 (CYP3A4) modulation activity. Ternary and pseudo ternary diagrams were constructed to optimize the system. Peppermint oil and clove oil showed a high emulsification ability. The nature of obtained dispersions was identified to be nanoemulsions. Twenty-four formulations were evaluated for stability, robustness to dilution and self-emulsification efficiency. All formulations showed a very short emulsification time of <2min. The emulsification efficiency was significantly superior at pH6.8, at which the largest self-emulsifying region was also observed. Eight formulations were selected for further characterization according to cloud point measurement; mean droplet size, poly dispersity index (PDI) and zeta potential determination in addition to in vitro drug release study. All selected formulations showed very high cloud points (70-90°C), ultrafine mean droplet size (12±1.4 to 24.5±2.13nm), very low PDI values (0.015-0.1305) and almost a complete drug release after 12h. Formulation F15 (Peppermint oil 55% w/w: Cremophor RH40 25% w/w: Labrasol 20% w/w) was selected for further characterization. Its droplet size showed robustness to different dilution folds with different media and its TEM photograph showed spherical particles without any apparent aggregation even after 24h. Formulation F15 successfully controlled the systolic blood pressure of hypertensive rats for 24h with the maximum effect was observed after 2h. These results indicate that, SNEDDS could be promising delivery systems with a rapid onset of action and prolonged therapeutic effect of candesartan cilexetil.

Review of a causal role of fructose-containing sugars in myocardial susceptibility to ischemia/reperfusion injury

In 2012, the World Health Organization Global Status Report on noncommunicable diseases showed that 7.4 million deaths were due to ischemic heart disease. Consequently, cardiovascular disease is a significant health burden, especially when partnered with comorbidities such as obesity, metabolic syndrome, and type 2 diabetes mellitus. Of note, these diseases can all be induced or exacerbated by diet. Carbohydrates, in particular, fructose and glucose, generally form the largest part of the human diet. Accumulating evidence from animal studies suggests that if large amounts of fructose are consumed either in isolation or in combination with glucose (fructose-containing sugars), myocardial susceptibility to ischemia/reperfusion (I/R) injury increases. However, the underlying mechanisms that predisposes the myocardium to I/R injury in the fructose model are not elucidated, and no single mechanistic pathway has been described. Based on all available data on this topic, this review describes previously investigated mechanisms and highlights 3 main mechanistic pathways whereby fructose has shown to increase myocardial susceptibility to I/R injury. These pathways include (1) increased reactive oxygen species, resulting in reduced nitric oxide synthase and coronary flow; (2) elevated plasma fatty acids and insulin, leading to increased cardiac triglyceride content and lipotoxicity; and (3) disrupted myocardial calcium handling/homeostasis. Moreover, we highlight various factors that should be taken into account when the fructose animal model is used, such as rat strain, treatment periods, and doses. We argue that failure to do so would result in erratic inferences drawn from the existing body of evidence on fructose animal models.

PARP inhibition ameliorates nephropathy in an animal model of type 2 diabetes: focus on oxidative stress, inflammation, and fibrosis

Poly(ADP-ribose) polymerase (PARP) enzyme contributes to nephropathy, a serious diabetic complication which may lead to end-stage renal disease. The study aims to investigate the effect of PARP over-activation on kidney functions in a type 2 diabetic rat model. The study also tests the therapeutic use of PARP inhibitors in diabetic nephropathy. Type 2 diabetes was induced in adult male rats by high-fructose/high-fat diet and low streptozotocin dose. Then, the PARP inhibitor 4-aminobenzamide (4-AB) was administered daily for 10 weeks. At the end, urine samples were collected to measure urine creatinine, albumin, and total proteins. PARP activity, superoxide dismutase (SOD) activity, and nitrite content were measured in kidney tissue homogenate. Glucose, fructosamine, insulin, and tumor necrosis factor-alpha (TNF-α) were measured in serum. Furthermore, histological studies, collagen deposition, and immunofluorescence of nuclear factor kappa B (NFκB) and transforming growth factor beta1 (TGF-β1) were carried out. PARP enzyme activity was significantly higher in the diabetic group and was significantly reduced by 4-AB administration. Diabetic animals had clear nephropathy indicated by proteinuria and increased albumin excretion rate (AER) which were significantly decreased by PARP inhibition. In addition, PARP inhibition increased creatinine clearance in diabetic animals and reduced renal TGF-β1 and glomerular fibrosis. Moreover, PARP inhibition alleviated the elevated serum TNF-α level, renal NFκB, nitrite, and the decrease in SOD activity in diabetic animals. However, PARP inhibition did not significantly affect neither hyperglycemia nor insulin sensitivity. PARP enzyme inhibition alleviates diabetic nephropathy through decreasing inflammation, oxidative stress, and renal fibrosis.

Effects of high fructose intake on the development of hypertension in the spontaneously hypertensive rats: the role of AT1R/gp91PHOX signaling in the rostral ventrolateral medulla

Both genetic and dietary factors determine the development of hypertension. Whether dietary factor impacts the development of hereditary hypertension is unknown. Here, we evaluated the effect of daily high-fructose diet (HFD) on the development of hypertension in adolescent spontaneously hypertensive rats (SHR). Six-week-old SHR were randomly divided into two groups to receive HFD or normal diet (ND) for 3 weeks. The temporal profile of systolic blood pressure, alongside the sympathetic vasomotor activity, in the SHR-HFD showed significantly greater increases at 9-12 weeks of age compared with the age-matched SHR-ND group. Immunofluorescence was used to identify the distribution of reactive oxygen species (ROS), oxidants and antioxidants in rostral ventrolateral medulla (RVLM) where sympathetic premotor neurons reside. In RVLM of SHR-HFD, the levels of ROS accumulation and lipid peroxidation were elevated. The changes in protein expression were measured by Western blot. NADPH oxidase subunit gp91^phox and angiotensin II type I receptor were up-regulated in RVLM neuron. On the other hand, the expression of extracellular superoxide dismutase was suppressed. Both molecular and hemodynamic changes in the SHR-HFD were rescued by oral pioglitazone treatment from weeks 7 to 9. Furthermore, central infusion with tempol, a ROS scavenger, effectively ameliorated ROS accumulation in RVLM and diminished the heightened pressor response and enhanced sympathetic activity in the SHR-HFD. Together, these results suggest that HFD intake at adolescent SHR may impact the development of hypertension via increasing oxidative stress in RVLM which could be effectively attenuated by pioglitazone treatment.

Increased diuresis, renal vascular reactivity, and blood pressure levels in young rats fed high sodium, moderately high fructose, or their association: a comparative evaluation

Excessive intakes of sodium or fructose have been described as risk factors for hypertension. We hypothesized that even a moderately high fructose diet (6% fructose), either alone or in combination with high sodium (4% NaCl), may impair diuresis and renal and systemic vascular reactivity, contributing to the onset of high blood pressure in rats. Male Wistar rats were fed chow containing 4% NaCl (HS), 6% fructose (MHF), or both 4% NaCl and 6% fructose (HSMHF) for 6 weeks and had their diuresis, plasma creatinine, vascular reactivity of perfused kidneys and systemic arterial pressure evaluated. We found no differences in augmented diuresis among animals given HS, MHF, or HSMHF diets. After 6 weeks both the HS and HSMHF groups had increased weight in their left kidneys, but only the HSMHF group showed augmented plasma creatinine. The effects of phenylephrine on renal vascular perfusion pressure were similarly enhanced in kidneys from the HS, MHF, and HSMHF groups, but not on the systemic arterial pressure. Although when evaluated in anesthetized rats, only the HSMHF group presented augmented blood pressure, evaluation in conscious animals revealed that both the MHF and HSMHF diets, but not the HS alone, were able to induce tachycardia and hypertension. In conclusion, a MHF diet containing 6% fructose was enough to render the renal vascular bed hyperreactive to phenylephrine and to induce both hypertension and tachycardia. The combination of 6% fructose with 4% NaCl led to plasma accumulation of creatinine and accelerated the development of tachycardia.

Aminoguanidine Prevents Fructose-Induced Arterial Stiffening in Wistar Rats: Aortic Impedance Analysis

Fructose has been reported as a potent agent in forming advanced glycation end products (AGEs) and, thus, may play a significant role in the pathogenesis of diabetic complications. Herein, we determined the effects of aminoguanidine (AG), an inhibitor of AGEs, on the mechanical properties of the arterial system in fructose-fed (FF) rats, using aortic impedance analysis. Rats at 2 months were given 10% fructose in drinking water for 2 weeks and compared with untreated age-matched controls. Meanwhile, FF rats were treated for 2 weeks with AG (daily peritoneal injections of 50 mg kg−1) and compared with the untreated FF group. Neither fructose nor AG affects body weight, blood glucose level, and basal heart rate. In comparison with controls, FF rats showed a decrease in cardiac output in the absence of any significant changes in mean aortic pressure, having increased total peripheral resistance (Rp), at 51.1 ± 2.9 versus 66.2 ± 1.9 mm Hg sec ml−1 (P < 0.05). Fructose also contributed to an increase in aortic characteristic impedance (Zc), from 1.528 ± 0.094 to 1.933 ± 0.084 mm Hg sec ml−1 (P < 0.05) and a decrease in wave transit time (τ), from 22.6 ± 0.6 to 19.2 ± 0.7 msec (P < 0.05). The elevated Zc and the reduced τ suggest that fructose may cause a detriment to the aortic distensibility in animals. After exposure to AG, FF rats exhibited a significant improvement in physical properties of the resistance vessels, as evidenced by the reduction of 21.3% in Rp. Meanwhile, AG retarded the fructose-induced decline in aortic distensibility, as reflected in the decrease of 16.0% in Zc (P < 0.05) and the increase of 18.1% in τ (P < 0.05). By contrast, AG exerted no effects on the mechanical properties of Windkessel vessels, as well as resistance vessels, in normal diet controls. We conclude that AG may prevent the fructose-derived changes in arterial stiffening, possibly through inhibition of the fructose-derived advanced glycation end product formation in Wistar rats.

Metabolic syndrome and the hepatorenal reflex

Insufficient hepatic O₂ in animal and human studies has been shown to elicit a hepatorenal reflex in response to increased hepatic adenosine, resulting in the stimulation of renal as well as muscle sympathetic nerve activity and activating the renin angiotensin system. Low hepatic ATP, hyperuricemia, and hepatic lipid accumulation reported in metabolic syndrome (MetS) patients may reflect insufficient hepatic O₂ delivery, potentially accounting for the sympathetic overdrive associated with MetS. This theoretical concept is supported by experimental results in animals fed a high fructose diet to induce MetS. Hepatic fructose metabolism rapidly consumes ATP resulting in increased adenosine production and hyperuricemia as well as elevated renin release and sympathetic activity. This review makes the case for the hepatorenal reflex causing sympathetic overdrive and metabolic syndrome in response to exaggerated splanchnic oxygen consumption from excessive eating. This is strongly reinforced by the fact that MetS is cured in a matter of days in a significant percentage of patients by diet, bariatric surgery, or endoluminal sleeve, all of which would decrease splanchnic oxygen demand by limiting nutrient contact with the mucosa and reducing the nutrient load due to loss of appetite or dietary restriction.

Feeling the pressure: (patho) physiological mechanisms of weight gain and weight loss in humans

Obesity is an ongoing global epidemic and has adverse consequences for cardiovascular health. Obesity is often associated with hypertension, which is, itself, a common condition and an important cause of morbidity and mortality worldwide. Although animal models of obesity have provided extensive data on the links between obesity and hypertension, a greater understanding of the pathways linking obesity and hypertension in humans is likely to assist translation of animal data, and may, itself, identify important treatment strategies. Ultimately, this could have a substantial impact on human health, both at an individual and population level. The current review will focus specifically on studies of experimental weight gain and weight loss in humans and the following key areas, which are strongly related to blood pressure: cardiovascular function, autonomic nervous system function, metabolic function and the impact of cardiorespiratory fitness.

Metabolic syndrome and the hepatorenal reflex

Insufficient hepatic O₂ in animal and human studies has been shown to elicit a hepatorenal reflex in response to increased hepatic adenosine, resulting in stimulation of renal as well as muscle sympathetic nerve activity and activating the renin angiotensin system. Low hepatic ATP, hyperuricemia, and hepatic lipid accumulation reported in metabolic syndrome (MetS) patients may reflect insufficient hepatic O₂ delivery, potentially accounting for the sympathetic overdrive associated with MetS. This theoretical concept is supported by experimental results in animals fed a high fructose diet to induce MetS. Hepatic fructose metabolism rapidly consumes ATP resulting in increased adenosine production and hyperuricemia as well as elevated renin release and sympathetic activity. This review makes the case for the hepatorenal reflex causing sympathetic overdrive and metabolic syndrome in response to exaggerated splanchnic oxygen consumption from excessive eating. This is strongly reinforced by the fact that MetS is cured in a matter of days in a significant percentage of patients by diet, bariatric surgery, or endoluminal sleeve, all of which would decrease splanchnic oxygen demand by limiting nutrient contact with the mucosa and reducing the nutrient load due to the loss of appetite or dietary restriction.

Cinnamaldehyde Attenuates Cataractogenesis via Restoration of Hypertension and Oxidative Stress in Fructose-Fed Hypertensive rats

OBJECTIVES

Several studies have revealed that systemic hypertension is strongly associated with cataractogenesis. However, the pathophysiology and treatment is often unclear. In this study, we evaluated the anti-cataractogenic effect of cinnamaldehyde (CA), a natural organic compound, in rats with fructose-induced hypertension.

METHODS

The rats were divided into six groups. For six weeks, the normal group received a suspension of 0.5% carboxy methyl cellulose (10 mL/kg/day, p.o.) while five other groups received a 10% (w/v) fructose solution in their drinking water to induce hypertension. By the end of the third week hypertension had been induced in all the animals receiving fructose. From the beginning of the fourth week to the end of the sixth week, one of those five groups (control) continued to receive only 10% (w/v) fructose solution, one group (standard) received ramipril (1 mg/kg/day, p.o.) plus 10% (w/v) fructose solution, and three groups (experimental) received CA at doses of 20, 30, and 40 mg/kg/day p.o., plus 10% (w/v) fructose solution. Blood pressure was measured weekly using a non-invasive blood pressure apparatus. After six weeks, the animals were sacrificed, and the anti-cataractogenic effects on the eye lenses were evaluated.

RESULTS

Administration of fructose elevated both the systolic and the diastolic blood pressures, which were significantly reduced by CA at all dose levels. In the control group, a significant increase in the malonaldehyde (MDA) level and decreases in the total protein, Ca(2+)adenosine triphosphate (ATP)ase activity, glutathione peroxidase, catalase, superoxide dismutase and glutathione levels, as compared to the normal group, were observed. Administration of CA at all doses significantly restored the enzymatic, non-enzymatic, antioxidants, total protein, and Ca(2+)ATPase levels, but decreased the MDA level, as compared to the control group.

CONCLUSION

The present study revealed that CA modulated the antioxidant parameters of the serum and lens homogenates in hypertension-induced cataractogenic animals.

Pressor recovery after acute stress is impaired in high fructose-fed Lean Zucker rats

Insulin resistance is a powerful predictor of cardiovascular disease; however, the mechanistic link remains unclear. This study aims to determine if early cardiovascular changes associated with short‐term fructose feeding in the absence of obesity manifest as abnormal blood pressure control. Metabolic dysfunction was induced in Lean Zucker rats by short‐term high‐fructose feeding. Rats were implanted with telemetry devices for the measurement of mean arterial blood pressure (MAP) and subjected to air jet stress at 5 and 8 weeks after feeding. Additional animals were catheterized under anesthesia for the determination of MAP and blood flow responses in the hind limb and mesenteric vascular beds to intravenous injection of isoproterenol (0.001–0.5 μm), a β‐adrenergic agonist. Metabolic dysfunction in high‐fructose rats was not accompanied by changes in 24‐h MAP. Yet, animals fed a high‐fructose diet for 8 weeks exhibited a marked impairment in blood pressure recovery after air‐jet stress. Dose‐dependent decreases in MAP and peripheral blood flow in response to isoproterenol treatment were significantly attenuated in high‐fructose rats. These data suggest that impaired blood pressure recovery to acute mental stress precedes the onset of hypertension in the early stages of insulin resistance. Further, blunted responses to isoproterenol implicate β₂‐adrenergic sensitivity as a possible mechanism responsible for altered blood pressure control after short‐term high‐fructose feeding.

Ferulic acid, a natural polyphenol, alleviates insulin resistance and hypertension in fructose fed rats: Effect on endothelial-dependent relaxation

Ferulic acid (FER) is a polyphenolic compound contained in various types of fruits. It has a substantial therapeutic effect inhibitory activity against aldose reductase (AR) inhibition. In this study, we examined the effect of FER on fructose-fed rats in comparison to a standard AR inhibitor, zopolrestat (ZOP). We determined the protective role of FER against metabolic syndrome by examining serum insulin/Glucose levels, triglycerides (TGs), cholesterol and advanced glycation end product (AGE) in rats supplied with 10% fructose drinking water. In addition, blood pressure, vascular reactivity of isolated thoracic aortas and acetylcholine-induced NO were all evaluated to estimate the cardiovascular complications of metabolic syndrome (MetS) associated with fructose feeding. Animals were randomly divided into four groups: control, (+10% fructose, Fru), zopolrestat-treated fructose fed (Fru-zop) and ferulic acid-treated fructose fed rats (Fru-Fer). After 12 weeks of FER treatment, we found significant reduction in both hyperinsulinemia and elevated diastolic blood pressure associated with fructose-fed to levels comparable to those achieved with ZOP. Both FER and ZOP significantly augmented the impaired relaxation associated with fructose-fed, whereas neither showed any significant effect on the developed vasoconstriction. Isolated aortas from fructose-fed rats incubated with either FER or ZOP, reinstated normal relaxation response to acetylcholine (ACh). Furthermore, isolated aortas showed attenuated nitric oxide (NO) production following the addition of (ACh), while both FER and ZOP restored normal induction of NO. Taken together, the current study shows that, FER alleviated insulin resistance and hypertension associated with metabolic syndrome compared to the standard AR inhibitor (ZOP). This potential protective effect is at least mediated by restoring endothelial relaxation.

Effect of Caffeic Acid Phenethyl Ester on Vascular Damage Caused by Consumption of High Fructose Corn Syrup in Rats

Fructose corn syrup is cheap sweetener and prolongs the shelf life of products, but fructose intake causes hyperinsulinemia, hypertriglyceridemia, and hypertension. All of them are referred to as metabolic syndrome and they are risk factors for cardiovascular diseases. Hence, the harmful effects of increased fructose intake on health and their prevention should take greater consideration. Caffeic Acid Phenethyl Ester (CAPE) has beneficial effects on metabolic syndrome and vascular function which is important in the prevention of cardiovascular disease. However, there are no known studies about the effect of CAPE on fructose-induced vascular dysfunction. In this study, we examined the effect of CAPE on vascular dysfunction due to high fructose corn syrup (HFCS). HFCS (6 weeks, 30% fed with drinking water) caused vascular dysfunction, but treatment with CAPE (50 micromol/kg i.p. for the last two weeks) effectively restored this problem. Additionally, hypertension in HFCS-fed rats was also decreased in CAPE supplemented rats. CAPE supplements lowered HFCS consumption-induced raise in blood glucose, homocysteine, and cholesterol levels. The aorta tissue endothelial nitric oxide synthase (eNOS) production was decreased in rats given HFCS and in contrast CAPE supplementation efficiently increased its production. The presented results showed that HFCS-induced cardiovascular abnormalities could be prevented by CAPE treatment.

High fructose consumption induces DNA methylation at PPARα and CPT1A promoter regions in the rat liver

DNA methylation status is affected by environmental factors, including nutrition. Fructose consumption is considered a risk factor for the conditions that make up metabolic syndrome such as dyslipidemia. However, the pathogenetic mechanism by which fructose consumption leads to metabolic syndrome is unclear. Based on observations that epigenetic modifications are closely related to induction of metabolic syndrome, we hypothesized that fructose-induced metabolic syndrome is caused by epigenetic alterations. Male SD rats were designated to receive water or 20% fructose solution for 14 weeks. mRNA levels for peroxisome proliferator-activated receptor alpha (PPARα) and carnitine palmitoyltransferase 1A (CPT1A) was analyzed using Real-time PCR. Restriction digestion and real-time PCR (qAMP) was used for the analysis of DNA methylation status. Hepatic lipid accumulation was also observed by fructose intake. Fructose feeding also significantly decreased mRNA levels for PPARα and CPT1A. qAMP analysis demonstrated the hypermethylation of promoter regions of PPARα and CTP1A genes. Fructose-mediated attenuated gene expression may be mediated by alterations of DNA methylation status, and pathogenesis of metabolic syndrome induced by fructose relates to DNA methylation status.

Direct renal effects of a fructose-enriched diet: interaction with high salt intake

Consumption of fructose has increased during the last 50 years. Excessive fructose consumption has a detrimental effect on mammalian health but the mechanisms remain unclear. In humans, a direct relationship exists between dietary intake of added sugars and increased risk for cardiovascular disease mortality (52). While the causes for this are unclear, we recently showed that fructose provided in the drinking water induces a salt-dependent increase in blood pressure in Sprague-Dawley rats in a matter of days (6). However, little is known about the effects of fructose in renal salt handling and whether combined intake of high fructose and salt can lead to salt-sensitive hypertension before the development of metabolic abnormalities. The long-term (more than 4 wk) adverse effects of fructose intake on renal function are not just due to fructose but are also secondary to alterations in metabolism which may have an impact on renal function. This minireview focuses on the acute effect of fructose intake and its effect on salt regulation, as they affect blood pressure.

Beneficial effects of melatonin on serum nitric oxide, homocysteine, and ADMA levels in fructose-fed rats

CONTEXT

Melatonin, a pineal hormone and a potent antioxidant, has important roles in metabolic regulation.

OBJECTIVE

This study investigated serum asymmetric dimethylarginine (ADMA), homocysteine (Hcy), nitric oxide (NO) levels, known to be reliable markers of cardiovascular diseases, and determined possible protective effects of melatonin in fructose-fed rats.

MATERIALS AND METHODS

Sprague-Dawley rats were divided into four groups: control, fructose, melatonin, and fructose plus melatonin. Metabolic syndrome was induced in rats by 20% (w/v) fructose solution in tap water, and melatonin was administered at the dose of 20 mg/kg bw per day by oral gavage. After 8 weeks, serum lipids, glucose, insulin, ADMA, Hcy, and NOx (the stable end products of NO) levels were quantified.

RESULTS

Fructose administration caused a statistically significant increase in systolic blood pressure (SBP), serum insulin, triglycerides, and very low-density lipoprotein (VLDL)-cholesterol levels compared with the control group and the metabolic syndrome model was successfully demonstrated. In comparison with the control group, fructose caused a significant increase in serum ADMA, Hcy, and NOx levels. Melatonin counteracted the changes in SBP, serum ADMA, and Hcy levels found in rats both alone and administered with fructose.

DISCUSSION AND CONCLUSION

These results show that high fructose consumption leads to elevated SBP, atherogenic lipid profile, increased serum ADMA, and Hcy levels and melatonin treatment has beneficial effects on these biochemical parameters in rats. Melatonin might be beneficial for the prevention and/or treatment of the cardiovascular complications of metabolic syndrome not only by reducing the well-known risk factors of the disease but also by diminishing blood ADMA and Hcy levels.

Allopurinol alleviates hypertension and proteinuria in high fructose, high salt and high fat induced model of metabolic syndrome

Metabolic syndrome (MetS) is a global epidemic associated with great socioeconomic and public health impact. Prevalence of the MetS has been consistently associated with cardiorenal mortality. The objective of this study was to investigate the effect of allopurinol treatment on various components of an established MetS in rats. In a first group, MetS was induced in male Wistar rats by the addition of 10% fructose to drinking water and placing the rats on high-fat and high-salt diet for 12 weeks (M). In the second group, MetS was induced for 12 weeks plus allopurinol administration (20 mg/kg/d) orally for 4 weeks starting at week 9 (MA). The third group was control (C) group that received a normal diet. The M group had higher blood pressure (BP) (85.5 ± 3.17 vs 66.1 ± 3.3 mm Hg) and proteinuria (1.8 ± 0.3 vs 0.59 ± 0.13 g/d) compared with the C group. Allopurinol reversed the BP and proteinuria in MA rats to the control level. Allopurinol administration suppressed the low-grade inflammation associated with MetS and reversed the increases in kidney transforming growth factor beta and urine 8-isoprostane acid observed in the MA group to control levels. In addition, allopurinol reduced angiotensin II and angiotensin receptor type 1 levels in the kidney of MA rats compared with the M group. The administration of allopurinol for short term in an established MetS model reduced features of the MetS especially hypertension and proteinuria. Addition of allopurinol to the therapy of MetS may provide superior means to alleviate hypertension and proteinuria associated with MetS.