Long-term caffeine consumption exacerbates renal failure in obese, diabetic, ZSF1 (fa-fa(cp)) rats

Association of unsweetened and sweetened tea consumption with the risk of new-onset chronic kidney disease: Findings from UK Biobank and Coronary Artery Risk Development in Young Adults (CARDIA) study

Background

The association between tea consumption and chronic kidney disease (CKD) remained inconsistent. We aimed to evaluate the association of tea consumption with new-onset CKD and examine the effects of common additives (milk and sweeteners) and genetic variations in caffeine metabolism on the association.

Methods

176 038 and 3104 participants free of CKD at baseline in the United Kingdom Biobank (UK Biobank) and Coronary Artery Risk Development in Young Adults (CARDIA) study were included, respectively. Dietary information was collected using 24-hour dietary recall questionnaires. The study outcome was new-onset CKD.

Results

In the UK Biobank, during a median follow-up of 12.13 years, 3535 (2.01%) participants developed CKD. Compared with tea non-consumers, the risk of new-onset CKD was significantly lower in unsweetened tea consumers (hazard ratio (HR) = 0.84, 95% confidence interval (CI) = 0.76-0.93), but not in sweetened tea consumers (HR = 0.96, 95% CI = 0.85-1.08), regardless of whether milk was added to tea. Accordingly, relative to tea non-consumers, the adjusted HRs (95% CIs) of new-onset CKD for participants who reported drinking unsweetened tea 1.5 or fewer, >1.5 to 2.5, >2.5 to 3.5, >3.5 to 4.5, and >4.5 drinks/d were HR = 0.86, 95% CI = 0.75-0.99; HR = 0.88, 95% CI = 0.78-1.00; HR = 0.83, 95% CI = 0.73-0.94; HR = 0.83, 95% CI = 0.72-0.95; and HR = 0.86, 95% CI = 0.75-0.99. Moreover, the association of unsweetened tea consumption with new-onset CKD was stronger among those with faster genetically predicted caffeine metabolism levels, although the interaction was insignificant (P-value interaction = 0.768). Consistently, in the CARDIA study, compared with tea non-consumers, a significantly lower risk of new-onset CKD was found in unsweetened tea consumers (HR = 0.80, 95% CI = 0.65-0.98) but not in sweetened tea consumers (HR = 0.97, 95% CI = 0.70-1.34).

Conclusions

Compared with tea non-consumers, consumption of unsweetened tea, but not sweetened tea, was significantly associated with a lower risk of new-onset CKD, regardless of whether milk was added.

Cardiorespiratory and Neuroprotective Effects of Caffeine in Neonate Animal Models

Caffeine is widely used to improve neonatal health in animals with low vitality. Due to its pharmacokinetics and pharmacodynamics, caffeine stimulates the cardiorespiratory system by antagonism of adenosine receptors and alteration in Ca+2 ion channel activity. Moreover, the availability of intracellular Ca+2 also has positive inotropic effects by increasing heart contractibility and by having a possible positive effect on neonate vitality. Nonetheless, since neonatal enzymatic and tissular systems are immature at birth, there is a controversy about whether caffeine is an effective therapy for newborns. This review aims to analyze the basic concepts of caffeine in neonatal animal models (rat and mouse pups, goat kids, lambs, and piglets), and it will discuss the neuroprotective effect and its physiological actions in reducing apnea in newborns.

Tea Consumption and New-Onset Acute Kidney Injury: The Effects of Milk or Sweeteners Addition and Caffeine/Coffee

Aims: To explore the relationship between tea consumption and the risk of incident acute kidney injury (AKI) and examine the effects of coffee consumption, genetic variation in caffeine metabolism, and the use of tea additives (milk and sweeteners) on this association. Methods: Using data from the UK Biobank, 498,621 participants who were free of AKI and had information on tea intake were included. Black tea is the main type consumed in this population. Dietary information was collected from standardized and validated Food-Frequency Questionnaire (FFQ). Outcome was incident AKI, determined via primary care data, hospital inpatient data, death register records, or self-reported data at follow-up visits. Results: After a median follow-up period of 12.0 years, 21,202 participants occurred AKI. Overall, there was a reversed J-shaped relation between tea consumption and incident AKI, with an inflection point at 3.5 cup/d (p for nonlinearity < 0.001). The relation was similar among participants with different genetically predicted caffeine metabolism (p-interaction = 0.684), while a more obvious positive association was found between heavy tea consumption and AKI when more coffee was consumed (p-interaction < 0.001). Meanwhile, there was a reversed J-shaped relationship for drinking tea with neither milk nor sweeteners, and a L-shaped association for drinking tea with milk (with or without sweeteners) with incident AKI. However, no significant association was found between drinking tea with sweeteners only and incident AKI. Conclusions: There was a reversed J-shaped relation between tea consumption and incident AKI, suggesting that light to moderate tea consumption, especially adding milk, can be part of a healthy diet.

Systematic review of the effect of caffeine therapy effect on cardiometabolic markers in rat models of the metabolic syndrome

This systematic review aimed to study caffeine's effect on the cardiometabolic markers of the metabolic syndrome and to evaluate caffeine's application as a potential therapeutic agent in rat models. The systematic review was structured and synthesized according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and the Population, Intervention, comparator, outcome (PICO) framework. A literature search was conducted in PubMed, Scopus, and ScienceDirect to identify studies that used caffeine as an intervention in the rat model of the metabolic syndrome or any of its components compared with no treatment or controls. Studies that did not mention the disease manifestations from the experimental model used, without rat subjects, and which induced renovascular hypertension were excluded. The risk of bias in the included studies was assessed using the Systematic Review Center for Laboratory Animal Experimentation risk-of-bias tool. The main outcomes assessed were caffeine's effect on obesity, dyslipidemia, hepatic steatosis, hepatic dysfunction, insulin resistance, and hypertension. Out of 228 studies retrieved from the search, 18 met our inclusion criteria and were included in the systematic review. Caffeine was found to favorably reduce obesity and insulin resistance in the rat model of the metabolic syndrome. The effects of caffeine on dyslipidemia, hepatic steatosis, hepatic dysfunction, and hypertension remain inconclusive. The main limitations of this study are the heterogeneity of the included studies in terms of the disease model used, experimental duration, methods to assess outcomes, including studies that were only published in English, measurement units used, and graphical data without and numerical mention in the results section. As a result, quantitative synthesis was unfeasible, and a qualitative descriptive synthesis was conducted; this might have led to the under characterization of caffeine's effect on metabolic syndrome and its potential as an adjuvant therapy in metabolic syndrome. Caffeine has favorable effects on the metabolic syndrome, chiefly reducing obesity and insulin resistance. Future research is encouraged to delve into caffeine's effect on dyslipidemia, hepatic steatosis, hepatic dysfunction, and hypertension, which is necessary if caffeine is to be used as a potential clinical adjuvant therapy to treat the metabolic syndrome.

CYP1A2 Genetic Variation, Coffee Intake, and Kidney Dysfunction

IMPORTANCE

Caffeine is detoxified by cytochrome P450 1A2 (CYP1A2), and genetic variation in CYP1A2 impacts the rate of caffeine clearance. Factors that may modify the association between coffee intake and kidney disease remain unclear.

OBJECTIVE

To assess whether CYP1A2 genotype modifies the association between coffee intake and kidney dysfunction.

DESIGN, SETTING, AND PARTICIPANTS

The Hypertension and Ambulatory Recording Venetia Study (HARVEST) was a prospective cohort study of individuals with stage 1 hypertension in Italy; HARVEST began on April 1, 1990, and follow-up is ongoing. The current study used data from April 1, 1990, to June 30, 2006, with follow-up of approximately 10 years. Blood pressure and biochemical data were collected monthly during the first 3 months, then every 6 months thereafter. Data were analyzed from January 2019 to March 2019. Participants were screened and recruited from general practice clinics. The present study included 1180 untreated participants aged 18 to 45 years with stage 1 hypertension; those with nephropathy, diabetes, urinary tract infection, and cardiovascular disease were excluded.

EXPOSURES

Coffee intake and CYP1A2 genotype rs762551 were exposures analyzed over a median follow-up of 7.5 (IQR, 3.1-10.9) years.

MAIN OUTCOMES AND MEASURES

Albuminuria (defined as an albumin level of ≥30 mg/24 h) and hyperfiltration (defined as an estimated glomerular filtration rate of ≥150 mL/min/1.73 m2) were the primary outcomes as indicators of kidney dysfunction.

RESULTS

Among 1180 participants, genotyping, lifestyle questionnaires, and urine analysis data were obtained from 604 individuals (438 [72.5%] male) with a mean (SD) age of 33.3 (8.5) years and a mean (SD) body mass index (calculated as weight in kilograms divided by height in meters squared) of 25.4 (3.4). A total of 158 participants (26.2%) consumed less than 1 cup of coffee per day, 379 (62.7%) consumed 1 to 3 cups per day, and 67 (11.1%) consumed more than 3 cups per day. Genotype frequencies for rs762551 (260 participants [43.1%] with genotype AA, 247 participants [40.8%] with genotype AC, and 97 participants [16.1%] with genotype CC) did not differ between coffee intake categories. The level of risk of developing albuminuria, hyperfiltration, and hypertension, assessed by Cox regression and survival analyses, was not associated with coffee intake in the entire group or among fast metabolizers. The risks of albuminuria (adjusted hazard ratio [aHR], 2.74; 95% CI, 1.63-4.62; P < .001), hyperfiltration (aHR, 2.11; 95% CI, 1.17-3.80; P = .01), and hypertension (aHR, 2.81; 95% CI, 1.51-5.23; P = .001) increased significantly among slow metabolizers who consumed more than 3 cups per day.

CONCLUSIONS AND RELEVANCE

In this study, the risks of albuminuria, hyperfiltration, and hypertension increased with heavy coffee intake only among those with the AC and CC genotypes of CYP1A2 at rs762551 associated with slow caffeine metabolism, suggesting that caffeine may play a role in the development of kidney disease in susceptible individuals.

Metabolic profiling identifies the significance of caffeine metabolism in CKD

Background: With the development of chronic kidney disease (CKD), there are various changes in metabolites. However, the effect of these metabolites on the etiology, progression and prognosis of CKD remains unclear. Objective: We aimed to identify significant metabolic pathways in CKD progression by screening metabolites through metabolic profiling, thus identifying potential targets for CKD treatment. Methods: Clinical data were collected from 145 CKD participants. GFR (mGFR) was measured by the iohexol method and participants were divided into four groups according to their mGFR. Untargeted metabolomics analysis was performed via UPLC-MS/MSUPLC-MSMS/MS assays. Metabolomic data were analyzed by MetaboAnalyst 5.0, one-way ANOVA, principal component analysis (PCA), and partial least squares discriminant analysis (PLS-DA) to identify differential metabolites for further analysis. The open database sources of MBRole2.0, including KEGG and HMDB, were used to identify significant metabolic pathways in CKD progression. Results: Four metabolic pathways were classified as important in CKD progression, among which the most significant was caffeine metabolism. A total of 12 differential metabolites were enriched in caffeine metabolism, four of which decreased with the deterioration of the CKD stage, and two of which increased with the deterioration of the CKD stage. Of the four decreased metabolites, the most important was caffeine. Conclusion: Caffeine metabolism appears to be the most important pathway in the progression of CKD as identified by metabolic profiling. Caffeine is the most important metabolite that decreases with the deterioration of the CKD stage.

Causal Association Between Tea Consumption and Kidney Function: A Mendelian Randomization Study

Background

Causal research concerning the consumption of tea and the risk of chronic kidney disease (CKD) is limited. This study identified the potential causal effects of tea intake on CKD, the estimated glomerular filtration rate (eGFR), and albuminuria.

Methods

Genome-wide association studies (GWASs) from UK Biobank were able to identify single-nucleotide polymorphisms (SNPs) associated with an extra cup of tea each day. The summary statistics for the kidney function from the CKDGen consortium include 11,765 participants (12,385 cases of CKD) and 54,116 participants for the urinary albumin-to-creatinine ratio who were mostly of European descent. A two-sample Mendelian randomization (MR) analysis was performed to test the relationship between the selected SNPs and the risk of CKD.

Results

A total of 2,672 SNPs associated with tea consumption (p < 5 × 10^-8) were found, 45 of which were independent and usable in CKDGen. Drinking more cups of tea per day indicates a protective effect for CKD G3-G5 [odds ratio (OR) = 0.803; p = 0.004] and increases eGFR (β = 0.019 log ml/min/1.73 m² per cup per day; p = 2.21 × 10^-5). Excluding two SNPs responsible for directional heterogeneity (Cochran Q p = 0.02), a high consumption of tea was also negatively correlated with a lower risk of albuminuria (OR = 0.758; p = 0.002).

Conclusion

From the perspective of genes, causal relationships exist between daily extra cup of tea and the reduced risk of CKD and albuminuria and increased eGFR.

Therapeutic potentials of agonist and antagonist of adenosine receptors in type 2 diabetes

Type 2 diabetes has been a global health challenge over the decades and is among the leading causes of death. Several treatment approaches have been developed, but more effective and new therapies are still needed. The role of adenosine in glucose and lipid homeostasis has offered a different therapeutic approach. Adenosine mediates its physiological role through the activation of adenosine receptors. These adenosine receptors have been implicated in glucose and lipid homeostasis. The ability of agonists and antagonists of adenosine receptors to activate or inhibit the adenosine signalling cascade and thereby affecting the balance of glucose and lipid homeostasis has challenged the studies of agonists and antagonists of adenosine receptors, both preclinical and clinical, as potential anti-diabetic drugs. This review provides a background on different anti-diabetic therapeutic approaches, outlining the role of adenosine receptors in glucose and lipid homeostasis, and mechanisms underlying the action of agonists/antagonists of adenosine receptors as a therapeutic potential towards type 2 diabetes.

Consumption of caffeinated beverages and kidney function decline in an elderly Mediterranean population with metabolic syndrome

It remains unclear whether caffeinated beverages could have deleterious renal effects in elderly population with underlying comorbid conditions. We investigated the associations between coffee, tea, or caffeine intake and 1-year changes in glomerular filtration rate (eGFR) in a large Spanish cohort of overweight/obese elderly with metabolic syndrome (MetS). This prospective analysis includes 5851 overweight/obese adults (55-75 years) with MetS from the PREDIMED-Plus study. We assessed coffee, tea, and caffeine consumption from a validated food-frequency questionnaire and creatinine-based eGFR using the Chronic Kidney Disease Epidemiology Collaboration equation. Multivariate-adjusted regression models were applied to test associations between baseline coffee, tea, or caffeine intake and 1-year eGFR changes. Caffeinated coffee (> 2 cups/day) and tea (at least 1 cup/day) drinkers had 0.88 and 0.93 mL/min/1.73 m² greater eGFR decrease respectively, compared to those with less than 1 cup/day of coffee consumption or non-tea drinkers. Furthermore, caffeinated coffee consumption of > 2 cups/day was associated with 1.19-fold increased risk of rapid eGFR decline > 3 mL/min/1.73 m² (95% CI 1.01-1.41). Similarly, individuals in the highest (median, 51.2 mg/day) tertile of caffeine intake had a 0.87 mL/min/1.73 m² greater eGFR decrease. Decaffeinated coffee was not associated with eGFR changes. In conclusion, higher consumption of caffeinated coffee, tea, and caffeine was associated with a greater 1-year eGFR decline in overweight/obese adults with MetS.

Tea consumption and serum uric acid levels among older adults in three large-scale population-based studies in China

Background and aims

The association between serum uric acid (SUA) and tea consumption has been studied in previous work, and there were arguments among various population group employed as well as different statistical approaches. The aim of this work is to investigate the tea effect on SUA levels among older adults by comparing three large-scale populations with both cross-sectional and longitudinal analyses.

Method

We examined the relationship between intake and SUA levels among older adults using linear regression. All the studies include the parameters SUA levels, tea intake, age, sex, education level, smoking status, alcohol drinking status, body mass index (BMI), and health history (diabetes, hypertension, and fasting plasma glucose). The cross-sectional analyses were conducted with 4579 older adults in the Weitang Geriatric Diseases Study (WGDS, ≥60 years), 2440 in the China Health and Nutrition Survey (CHNS, ≥60 years) and 1236 in the Chinese Longitudinal Healthy Longevity Survey (CLHLS, ≥62 years); and the longitudinal analyses were performed with 3870 (84.5%) in the WGDS and 420 (34.0%) in the CLHLS. Multivariable linear regression analyses were performed in both cross-sectional and longitudinal studies.

Results

Cross-sectional studies showed that tea consumers tended to have higher SUA levels than non-tea consumers in all the three datasets (P < 0.05). However, longitudinal associations of SUA levels with tea consumption had no statistical significance (P>0.05). The results of sex-stratified analyses were consistent with those of the whole datasets.

Conclusions

This work implied that any possible association between tea consumption and SUA levels could be very weak.

Could aspartame exacerbate caffeine effects on renal maturation in rat's offspring? A biochemical and histological study

BACKGROUND

Caffeine and aspartame (ASP) are mostly used as a diet regimen to reduce overweight. The risk increase if used during critical life periods that may affect the development of fetal organs.

OBJECTIVE

To evaluate the individual and combined effects of maternal exposure to caffeine and ASP during gestation and lactation on the kidneys' development of rats' offspring.

METHODS

Pregnant rats were divided randomly into four groups; Group I (control group). Group II (ASP group): ASP was given at a dose of 40 mg of /kg/day. Group III (Caffeine group): caffeine was given at a dose of 80 mg/kg/day. Group IV (ASP & caffeine group); where previous doses of ASP and caffeine were given at the same time. All the treatments were given by oral gavage from the first day of pregnancy until postnatal day 30. Kidneys of rats' offspring were dissected and tested for detection of oxidative stress markers and for histopathological & immunohistochemical examination.

RESULTS

This study showed a high significant increase in oxidative load (malondialdehyde) in renal tissues in group IV associated with decreased activities of total glutathione and antioxidant enzymes (superoxide dismutase and glutathione peroxidase). Histological and morphometric examination results showed delayed maturation of renal tissues in Group II and III, but more deleterious effects were observed in group IV with a lot of pathological changes in renal tissues.

CONCLUSION

The extensive use of caffeine and ASP should be controlled to avoid the risk of their toxicity.

A novel dual PPAR-γ agonist/sEH inhibitor treats diabetic complications in a rat model of type 2 diabetes

AIMS/HYPOTHESIS

The metabolic syndrome is a cluster of risk correlates that can progress to type 2 diabetes. The present study aims to evaluate a novel molecule with a dual action against the metabolic syndrome and type 2 diabetes.

METHODS

We developed and tested a novel dual modulator, RB394, which acts as a soluble epoxide hydrolase (sEH) inhibitor and a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist in rat models of the metabolic syndrome-the obese spontaneously hypertensive (SHROB) rat and the obese diabetic Zucker fatty/spontaneously hypertensive heart failure F1 hybrid (ZSF1) rat. In SHROB rats we studied the ability of RB394 to prevent metabolic syndrome phenotypes, while in ZSF1 obese diabetic rats we compared RB394 with the ACE inhibitor enalapril in the treatment of type 2 diabetes and associated comorbid conditions. RB394 (10 mg/kg daily) and enalapril (10 mg/kg daily) were administered orally for 8 weeks.

RESULTS

RB394 blunted the development of hypertension, insulin resistance, hyperlipidaemia and kidney injury in SHROB rats and reduced fasting blood glucose and HbA_1c, improved glucose tolerance, reduced blood pressure and improved lipid profiles in obese ZSF1 rats. A reduction in liver fibrosis and hepatosteatosis was evident in RB394-treated obese ZSF1 rats. Unlike RB394, enalapril did not demonstrate any positive effects in relation to diabetes, hyperlipidaemia or liver dysfunction in obese ZSF1 rats. RB394 ameliorated diabetic nephropathy by reducing renal interstitial fibrosis and renal tubular and glomerular injury in obese diabetic ZSF1 rats. Intriguingly, enalapril demonstrated a weaker action against diabetic nephropathy in obese ZSF1 rats.

CONCLUSIONS/INTERPRETATION

These findings demonstrate that a novel sHE inhibitor/PPAR-γ agonist molecule targets multiple risk factors of the metabolic syndrome and is a glucose-lowering agent with a strong ability to treat diabetic complications.

Review of animal studies on the cardiovascular effects of caffeine

To address the safety of caffeine levels in energy drinks, we previously conducted a detailed evaluation of epidemiology studies in humans consuming coffee/caffeine, in which we assessed multiple health effects (unpublished). To further evaluate the effects of caffeine on the cardiovascular system, we turned to animal studies, which often use pure caffeine (not coffee), frequently at higher doses than those typical of human exposure. We identified key scientific studies and reviews in which effects of coffee or caffeine were evaluated in animals by conducting a comprehensive PubMed literature search and analyzing the results. We found that the human equivalent dose (HED) for the no observed adverse effect level (NOAEL) for cardiovascular effects was 260 mg caffeine (2-3 cups of coffee) for a single dose of caffeine for a 70-kg adult, while the lowest observed adverse effect level (LOAEL) was 770 mg (7-8 cups of coffee) for a 70-kg adult. Overall, the doses associated with possible adverse cardiovascular effects were more than either the amount of caffeine consumed over a 24-hour period in two regular energy shots (400 mg/day) or the amount in two extra strength energy shots (460 mg/day).

Characterization of liver changes in ZSF1 rats, an animal model of metabolic syndrome

BACKGROUND

The non-alcoholic fatty liver disease is the hepatic counterpart of the metabolic syndrome. ZSF1 rats are a metabolic syndrome animal model in which liver changes have not been described yet.

AIM

The characterization of liver histological and innate immunity changes in ZSF1 rats.

METHODS

Five groups of rats were included (n = 7 each group): healthy Wistar-Kyoto control rats (Ctrl), hypertensive ZSF1 lean (Ln), ZSF1 obese rats with a normal diet (Ob), ZSF1 obese rates with a high-fat diet (Ob-HFD), and ZSF1 obese rats with low-intensity exercise training (Ob-Ex). The animals were sacrificed at 20 weeks of age, their livers were collected for: a) measurements of the area of steatosis, fibrosis and inflammation (histomorphological analysis); and b) innate immunity (toll-like receptor [TLR] 2, TLR4, peroxisome proliferator-activated receptor γ [PPARγ], toll interacting protein [TOLLIP]) and inflammatory marker (tumor necrosis factor-alpha [TNFα], interleukin 1 [IL-1]) expression analysis by real-time PCR.

RESULTS

Ob, Ob-HFD and Ob-Ex were significantly heavier than Ln and Ctrl animals. Ob, Ob-HFD and Ob-Ex animals had impaired glucose tolerance and insulin resistance. ZSF1 Ob, Ob-HFD and Ob-Ex presented a higher degree of steatosis (3,5x; p < 0.05) than Ctrl or ZSF1 Ln rats. Steatohepatitis and fibrosis were not observed in any of the groups. No differences in expression were observed between Ctrl, Ln and Ob animals (except for the significantly higher expression of TOLLIP observed in the Ob vs Ln comparison). Ob-HFD and Ob-Ex rats showed increased expression of PPARγ and TOLLIP as compared to other groups. However, both groups also showed increased expression of TLR2 and TLR4. Nevertheless, this did not translate into a differential expression of TNFα or IL-1 in any of the groups.

CONCLUSION

The ZSF1 model is associated with liver steatosis but not with steatohepatitis or a significantly increased expression of innate immunity or inflammation markers.

Perinatal exposure to energy drink induces oxidative damage in the liver, kidney and brain, and behavioral alterations in mice offspring

The worldwide consumption of energy drinks (EDs) has increased in recent years. EDs have several side effects and can be linked to liver injury, kidney damage and risk-seeking behavior. The impact of perinatal consumption of EDs on the newborns has not been previously investigated. In this study, we evaluated the effects of perinatal exposure to a caffeinated ED on the liver, kidney, brain, locomotor activity and anxiety in mice newborns. Pregnant mice received 2.5 or 5 ml ED by oral gavage from the first day of pregnancy until day 15 after birth. Perinatal exposure to the ED induced a significant increase in lipid peroxidation and declined antioxidant defenses in the liver, kidney, cerebrum, cerebellum and medulla oblongata of the newborns at days 21 and 35 after birth. ED induced several histological alterations, including vacuolations and lipid infiltration of hepatocytes, developing and degenerated glomeruli and dilated urinary spaces in the renal cortex, pyknosis and chromatolysis of the cerebral and medullary neurons, and degenerated and abnormal Purkinje cells in the cerebellum. In addition, ED increased the locomotion and induced anxiety-like behavior in mice newborns. In conclusion, perinatal exposure to EDs induces oxidative stress, tissue injury and behavioral alterations in the mice newborns. Therefore, the consumption of EDs during pregnancy and lactation has a negative impact on the newborns and should be treated as a significant health problem that warrants attention.

Collective and experimental research project for master's students on the pathophysiology of obesity

We describe here a collective and experimental research project-based learning (ERPBL) for master's students that can be used to illustrate some basic concepts on glucose/lipid homeostasis and renal function around a topical issue. The primary objective of this ERPBL was to strengthen students' knowledge and understanding of physiology and pathophysiology. The secondary objectives were to help students to develop technical/practical abilities and acquire transversal skills with real-world connections. Obesity is a worldwide public health problem that increases the risk for developing type 2 diabetes and nephropathies. To study the impact of western dietary habits, students evaluated the effects of a diet enriched with fat and cola [high-fat and cola diet (HFCD)] on metabolism and renal function in mice. Students mainly worked in tandem to prepare and perform experiments, but also collectively to compile, analyze, and discuss data. Students showed that HFCD-fed mice 1) developed obesity; 2) exhibited glucose homeostasis impairments associated to ectopic fat storage; and 3) displayed reduced glomerular filtration. The educational benefit of the program was estimated using three evaluation metrics: a conventional multicriteria assessment by teachers, a pre-/posttest, and a self-evaluation questionnaire. They showed that the current approach successfully strengthened scientific student knowledge and understanding of physiology/pathophysiology. In addition, it helped students develop new skills, such as technical and transversal skills. We concluded that this ERPBL dealing with the pathophysiology of obesity was strongly beneficial for master's students, thereby appearing as an efficient and performing educational tool.

Intermittent hypoxia alters dose dependent caffeine effects on renal prostanoids and receptors in neonatal rats

Caffeine, one of the most commonly prescribed drugs in preterm neonates, is given in standard or suprapharmacologic doses. Although known as a diuretic, its effects in the neonatal kidneys are not well studied. We tested the hypothesis that neonatal intermittent hypoxia (IH) and high caffeine doses (HCD) alter renal regulators of vasomotor tone and water balance. Newborn rats were randomized to room air, hyperoxia, or IH and treated with standard or high caffeine doses; or placebo saline. Renal prostanoids; histopathology; and cyclooxygenase (COX), prostanoid receptor, and aquaporin (AQP) immunoreactivity were determined. HCD in IH caused severe pathological changes in the glomeruli and proximal tubules, consistent with acute kidney injury. This was associated with reductions in anthropometric growth, PGI_2, and IP, DP, and AQP-4 immunoreactivity, well as a robust increase in COX-2, suggesting that the use of HCD should be avoided in preterm infants who experience frequent IH episodes.

High resolution molecular and histological analysis of renal disease progression in ZSF1 fa/faCP rats, a model of type 2 diabetic nephropathy

ZSF1 rats exhibit spontaneous nephropathy secondary to obesity, hypertension, and diabetes, and have gained interest as a model system with potentially high translational value to progressive human disease. To thoroughly characterize this model, and to better understand how closely it recapitulates human disease, we performed a high resolution longitudinal analysis of renal disease progression in ZSF1 rats spanning from early disease to end stage renal disease. Analyses included metabolic endpoints, renal histology and ultrastructure, evaluation of a urinary biomarker of fibrosis, and transcriptome analysis of glomerular-enriched tissue over the course of disease. Our findings support the translational value of the ZSF1 rat model, and are provided here to assist researchers in the determination of the model’s suitability for testing a particular mechanism of interest, the design of therapeutic intervention studies, and the identification of new targets and biomarkers for type 2 diabetic nephropathy.

Combined long-term caffeine intake and exercise inhibits the development of diabetic nephropathy in OLETF rats

This study was performed to examine the effects of long-term caffeine-intake, with and without exercise, on the progression of diabetic nephropathy (DN) in an obese diabetic rat model. Thirty-two male Otsuka Long-Evans Tokushima fatty (OLETF) rats were assigned to sedentary (OLETF-Sed), exercise (OLETF-Ex), caffeine-intake (OLETF-Caf), and combined (OLETF-Caf + Ex) groups. Caffeine-intake groups were fed rat chow containing caffeine (90.7 ± 4.7 mg/kg/day). The OLETF-Ex and OLETF-Caf + Ex groups were able to run voluntarily at any time using a rotatory wheel. Body weight (BW) and blood pressure (BP) were measured weekly from 24 to 29 wk of age. Pre- and posttreatment serum glucose, insulin, and creatinine concentrations were measured, and a 24 h urine sample was collected for measurement of creatinine clearance (Ccr) and albumin excretion (UE_Alb). After treatment, the kidneys were removed for morphological analysis. The OLETF-Caf and OLETF-Caf + Ex groups exhibited no BP increase during the study. Both the caffeine-intake groups exhibited a significant increase in urine volume (UV), electrolyte excretion, and Ccr, and decreased UE_Alb, following treatment. Furthermore, no structural damage was observed in the kidneys of rats from either caffeine-intake group, whereas the OLETF-Sed and OLETF-Ex groups exhibited DN progression. This study demonstrates that caffeine-intake alone and/or combined with exercise significantly decreases BW and improves glucose intolerance, without the progression of DN. Further research should be performed to examine whether the quantities of caffeine contained in a normal human daily intake also have a protective effect against kidney damage.NEW & NOTEWORTHY The present study showed that caffeine administration alone and/or combined with exercise results in an improvement of diabetic nephropathy (DN), including an increase in creatinine clearance and urinary Na excretion, a decrease in urinary protein excretion, and in renal morphological findings. To our knowledge, there are no other studies showing that caffeine administration inhibits DN progression.

The effect of coffee, tea, and caffeine consumption on serum uric acid and the risk of hyperuricemia in Korean Multi-Rural Communities Cohort

Caffeine, a commonly consumed food constituent, is known to exert beneficial physiological effects in humans. There is a lack of comprehensive population data for the effects of caffeine intake on urate metabolism. Therefore, the aim of this study was to determine whether coffee, tea, and caffeine intake influences serum uric acid and the risk of hyperuricemia in the Korean Multi-Rural Communities Cohort. We enrolled 9,400 participants in this study. An assessment of various dietary intake amounts of substances such as coffee and tea was performed using a food frequency questionnaire. The content of caffeine was calculated from coffee (74 mg/cup) and tea (15 mg/cup) intake information from the past year. Multivariate logistic regression models, multiple linear regression models, and analysis of covariance were applied to identify any association of dietary intake with serum uric acid levels or the risk of hyperuricemia. No trends for coffee, tea, or caffeine intake were found according to each quintile with serum uric acid in males, although there were weak, marginally significant trends between the content of coffee and caffeine intake and serum uric acid level in females (p = 0.07 for both). Tea intake in males and caffeine intake in females were significantly different between non-hyperuricemia and hyperuricemia (p = 0.04 and p = 0.04, respectively). In addition, a significant association of serum uric acid level with tea intake in males (β = 0.0006, p = 0.02) and with tea intake and caffeine intake in females (β = 0.0003, p = 0.04 and β = 0.0006, p = 0.02, respectively) was observed. There was no effect of coffee, tea, or caffeine intake on the risk of hyperuricemia in either males or females. This study suggests that caffeine consumption might have an effect on serum uric acid in females. However, coffee, tea, and caffeine intake amounts were not associated with the risk of hyperuricemia.

Cardiovascular effects of long-term caffeine administration in aged rats

AIM

To evaluate the possible beneficial effect of long-term caffeine administration on cardiovascular system in aged rats.

METHODS

This study was carried out on 20 senile male albino rats, aged 18-20 months. Rats were divided into caffeine-treated group, which received 25 mg/kg caffeine by gavage daily for 6 weeks, and control group. All rats were subjected to the following in vivo measurements: body weight, arterial blood pressure, heart rate and ECG recording. In vitro measurements included studying isolated hearts in a Langendorff apparatus for their intrinsic properties as well as plasma levels of lipids, malondialdehyde and nitrate.

RESULTS

Caffeine administration to aged rats significantly enhanced the baseline and maximum values achieved in response to isoproterenol infusion in isolated heart preparation for both maximum rate of tension development (dT/dt max) and time to peak tension (TPT). The responses of hearts isolated from caffeine group to the three doses of isoproterenol infusion also showed a significantly higher dT/dt max with shorter TPT and half relaxation time (1/2 RT) compared to controls. Plasma nitrate was significantly increased and ECG recording was nonsignificantly affected in caffeine group. The plasma levels of total cholesterol, LDL cholesterol as well as in vivo heart rate and systolic, diastolic and mean arterial blood pressures were all significantly increased associated with a significant decrease in HDL cholesterol in caffeine group.

CONCLUSION

Long-term caffeine administration in aged rats increased cardiac inotropy, lusitropy and preserved NO level, which points to a promising potential favorable effect on cardiac intrinsic properties.

Effects of tea consumption on renal function in a metropolitan Chinese population: the Guangzhou biobank cohort study

OBJECTIVE

Green tea consumption has been associated with many prophylactic health benefits. This study examined for the first time associations between tea consumption and renal function in a Chinese population.

DESIGN AND METHODS

Cross-sectional baseline data including demographics, and lifestyle and weekly consumption of green, black, and oolong tea were analyzed from 12,428 ambulatory subjects aged 50 to 85 years (67.3% female) that were randomly selected from the membership list of a community social and welfare association in Guangzhou, China.

INTERVENTION

Associations between tea consumption and renal function were assessed using regression analyses to adjust for potential confounding factors.

MAIN OUTCOME MEASURE

Renal function was assessed using the estimated glomerular filtration rate (eGFR) and in a subcohort of 1,910 participants using a spot urinary albumin-to-creatinine ratio.

RESULTS

Six thousand eight hundred and seventy-two participants drank at least 1 type of tea. Oolong tea consumption was negatively associated with eGFR (β-coefficient -0.019, P = .025), but in a gender-stratified analysis this was not the case. In men, black tea was positively associated with eGFR (β-coefficient 0.037, P = .013), but not in women (β-coefficient -0.002, P = .856). Otherwise, no statistically significant consistent associations between the measures of renal function and consumption of green tea, black tea, or oolong tea individually or total tea consumption were identified.

CONCLUSION

Overall there was no clear evidence to suggest any consistent association between renal function and tea consumption in this large population-based study of older Chinese individuals.

A population of selected renal cells augments renal function and extends survival in the ZSF1 model of progressive diabetic nephropathy

New treatment paradigms that slow or reverse progression of chronic kidney disease (CKD) are needed to relieve significant patient and healthcare burdens. We have shown that a population of selected renal cells (SRCs) stabilized disease progression in a mass reduction model of CKD. Here, we further define the cellular composition of SRCs and apply this novel therapeutic approach to the ZSF1 rat, a model of severe progressive nephropathy secondary to diabetes, obesity, dyslipidemia, and hypertension. Injection of syngeneic SRCs into the ZSF1 renal cortex elicited a regenerative response that significantly improved survival and stabilized disease progression to renal structure and function beyond 1 year posttreatment. Functional improvements included normalization of multiple nephron structures and functions including glomerular filtration, tubular protein handling, electrolyte balance, and the ability to concentrate urine. Improvements to blood pressure, including reduced levels of circulating renin, were also observed. These functional improvements following SRC treatment were accompanied by significant reductions in glomerular sclerosis, tubular degeneration, and interstitial inflammation and fibrosis. Collectively, these data support the utility of a novel renal cell-based approach for slowing renal disease progression associated with diabetic nephropathy in the setting of metabolic syndrome, one of the most common causes of end-stage renal disease.

Coffee extract attenuates changes in cardiovascular and hepatic structure and function without decreasing obesity in high-carbohydrate, high-fat diet-fed male rats

Coffee, a rich source of natural products, including caffeine, chlorogenic acid, and diterpenoid alcohols, has been part of the human diet since the 15th century. In this study, we characterized the effects of Colombian coffee extract (CE), which contains high concentrations of caffeine and diterpenoids, on a rat model of human metabolic syndrome. The 8-9 wk old male Wistar rats were divided into four groups. Two groups of rats were fed a corn starch-rich diet whereas the other two groups were given a high-carbohydrate, high-fat diet with 25% fructose in drinking water for 16 wk. One group fed each diet was supplemented with 5% aqueous CE for the final 8 wk of this protocol. The corn starch diet contained ~68% carbohydrates mainly as polysaccharides, whereas the high-carbohydrate, high-fat diet contained ~68% carbohydrates mainly as fructose and sucrose together with 24% fat, mainly as saturated and monounsaturated fat from beef tallow. The high-carbohydrate, high-fat diet-fed rats showed the symptoms of metabolic syndrome leading to cardiovascular remodeling and nonalcoholic fatty liver disease. CE supplementation attenuated impairment in glucose tolerance, hypertension, cardiovascular remodeling, and nonalcoholic fatty liver disease without changing abdominal obesity and dyslipidemia. This study suggests that CE can attenuate diet-induced changes in the structure and function of the heart and the liver without changing the abdominal fat deposition.

Diabetic nephropathy and long-term treatment effects of rosiglitazone and enalapril in obese ZSF1 rats

Diabetic nephropathy (DN) is a major cause of end-stage renal disease. Yet the pathogenic mechanisms underlying the development of DN are not fully defined, partially due to lack of suitable models that mimic the complex pathogenesis of renal disease in diabetic patients. In this study, we describe early and late renal manifestations of DN and renal responses to long-term treatments with rosiglitazone or high-dose enalapril in ZSF1 rats, a model of metabolic syndrome, diabetes, and chronic renal disease. At 8 weeks of age, obese ZSF1 rats developed metabolic syndrome and diabetes (hyperglycemia, glucosuria, hyperlipidemia, and hypertension) and early signs of renal disease (proteinuria, glomerular collagen IV deposition, tubulointerstitial inflammation, and renal hypertrophy). By 32 weeks of age, animals developed renal histopathology consistent with DN, including mesangial expansion, glomerulosclerosis, tubulointerstitial inflammation and fibrosis, tubular dilation and atrophy, and arteriolar thickening. Rosiglitazone markedly increased body weight but reduced food intake, improved glucose control, and attenuated hyperlipidemia and liver and kidney injury. In contrast, rosiglitazone markedly increased cardiac hypertrophy via a blood pressure-independent mechanism. High-dose enalapril did not improve glucose homeostasis, but normalized blood pressure, and nearly prevented diabetic renal injury. The ZSF1 model thus detects the clinical observations seen with rosiglitazone and enalapril in terms of primary and secondary endpoints of cardiac and renal effects. This and previous reports indicate that the obese ZSF1 rat meets currently accepted criteria for progressive experimental diabetic renal disease in rodents, suggesting that this may be the best available rat model for simulation of human DN.

Methylxanthines and the kidney

This chapter describes the effects of the natural methylxanthines caffeine and theophylline on kidney function. Theophylline in particular was used traditionally to increase urine out put until more potent diuretics became available in the middle of the last century. The mildly diuretic actions of both methylxanthines are mainly the result of inhibition of tubular fluid reabsorption along the renal proximal tubule. Based upon the use of specific adenosine receptor antagonists and the observation of a complete loss of diuresis in mice with targeted deletion of the A1AR gene, transport inhibition by methylxanthines is mediated mainly by antagonism of adenosine A1 receptors (A1AR) in the proximal tubule. Methylxanthines are weak renal vasodilators, and they act as competitive antagonists against adenosine-induced preglomerular vasoconstriction. Caffeine and theophylline stimulate the secretion of renin by inhibition of adenosine receptors and removal of the general inhibitory brake function of endogenous adenosine. Since enhanced intrarenal adenosine levels lead to reduced glomerular filtration rate in several pathological conditions theophylline has been tested for its therapeutic potential in the renal impairment following administration of nephrotoxic substances such as radiocontrast media, cisplatin, calcineurin inhibitors or following ischemia-reperfusion injury. In experimental animals functional improvements have been observed in all of these conditions, but available clinical data in humans are insufficient to affirm a definite therapeutic efficacy of methylxanthines in the prevention of nephrotoxic or postischemic renal injury.

Renal and metabolic effects of tempol in obese ZSF1 rats--distinct role for superoxide and hydrogen peroxide in diabetic renal injury

Oxidative stress, that is, overproduction of reactive oxygen species and reduced antioxidant system activity, is implicated in the pathogenesis of diabetic complications; and therefore, superoxide dismutase (SOD) mimetic tempol should be protective in diabetic kidney. However, the effects of tempol in metabolic syndrome-associated renal injury have not been thoroughly examined. In this study, we examined the effects of 9 weeks of treatment with tempol on metabolic status, renal oxidative stress, and kidney function and structure in obese, diabetic, hypertensive ZSF(1) rats and their nondiabetic, hypertensive, lean littermates. The obese rats had significantly reduced total SOD and catalase activity, increased peroxidase activity and lipid peroxidation, and higher level of protein oxidation in renal cortical tissue compared with their lean littermates. These changes were accompanied by renal injury (proteinuria; reduced excretory function; and markedly increased glomerular and interstitial inflammation, proliferation, and collagen IV synthesis). Tempol treatment slightly increased total SOD activity, significantly reduced lipid peroxidation and peroxidase activity, but had no effect on catalase and protein oxidation. Tempol had no effects on blood pressure, renal hemodynamics and excretory function, and proteinuria in obese rats, yet improved insulin sensitivity and reduced renal inflammatory, proliferative, and fibrotic changes. Because tempol possesses no catalase activity and, in diabetes, not only SOD but also catalase is inhibited, it is possible that the toxicity of hydrogen peroxide (H(2)O(2)) remains unaltered under tempol treatment. This study suggests that superoxide and H(2)O(2) may have distinct roles in the pathogenesis of diabetic renal injury, with superoxide mainly being involved in inflammatory, proliferative, and fibrotic changes, and H(2)O(2) in glomerular hemodynamics and proteinuria.

Early renal injury induced by caffeine consumption in obese, diabetic ZSF1 rats

Our previous studies indicate that prolonged caffeine consumption exacerbates renal failure in nephropathy associated with the metabolic syndrome. Reduced activity of the antioxidant defense system and beneficial effects of antioxidant therapy have been reported in diabetic rats and humans. The purpose of this study was to examine the early renal effects of caffeine consumption and the effects of concomitant antioxidant therapy in young obese, diabetic ZSF1 rats. Eleven-week-old male ZSF1 rats were randomized to drink tap water, caffeine (0.1%), tempol (1 mmol/L), or a solution containing caffeine and tempol for nine weeks. Caffeine significantly reduced body weight and glycosuria (weeks 2-9), improved glucose tolerance (week 9), had no effect on elevated plasma triglycerides, plasma cholesterol (week 9) and blood pressure (week 9), and significantly increased plasma cholesterol level (weeks 5 and 9). Yet, as early as after two weeks, caffeine greatly augmented proteinuria and increased renal vascular resistance (RVR) and heart rate (HR: week 9). Tempol had no effects on metabolic status and development of proteinuria, did not alter caffeine-induced metabolic changes and early proteinuria, and attenuated caffeine-induced increase in HR and RVR. Immunohistochemical analysis revealed significant glomerular and interstitial inflammation, proliferation, and fibrosis in control animals. Caffeine augmented the influx of glomerular and interstitial macrophages (ED1+ cells) influx, glomerular and tubular proliferative response, and glomerular collagen IV content. Tempol abolished the exacerbation of renal inflammation, proliferation, and fibrosis induced by caffeine. In conclusion, in nephropathy associated with the metabolic syndrome, caffeine--most likely through the interaction with adenosine receptors and interference with anti-inflammatory and/or glomerular hemodynamic effects of adenosine--augments proteinuria and stimulates some of the key proliferative mechanisms involved in glomerular remodeling and sclerosis. Tempol does not prevent early renal injury (i.e., proteinuria) induced by caffeine, yet abolishes late renal inflammatory, proliferative, and fibrotic change induced by chronic caffeine consumption in obese ZSF1 rats.

Dynamic blood pressure load and nephropathy in the ZSF1 (fa/facp) model of type 2 diabetes

Diabetes and increased blood pressure (BP) are believed to interact synergistically in the pathogenesis and progression of diabetic nephropathy. The present studies were performed to examine if there were differences in BP load and/or protective renal autoregulatory capacity between the obese diabetic Zucker fatty /spontaneously hypertensive heart failure F1 hybrid (ZSF1) ( fa/ facp) rats and their lean controls. By ∼26 wk of age, ZSF1 ( n = 13) but not their lean controls ( n = 16) had developed substantial proteinuria (180 ± 19 vs. 16 ± 1.4 mg/24 h) and glomerulosclerosis (19 ± 2.4 vs. 0.6 ± 0.2%; P < 0.001). However, average ambient systolic BP by radiotelemetry (12–26 wk of age) was modestly lower in ZSF1 than in lean controls (130 ± 1.4 vs. 137 ± 1.7 mmHg, P < 0.002), although the 24-h BP power spectra showed a mild increase at frequencies <0.1 Hz in the ZSF1. Autoregulatory capacity under anesthesia in response to step changes in perfusion pressure between 100 and 140 mmHg was similarly well preserved in both ZSF1 and lean controls at 16–18 wk of age [autoregulatory indexes (AI) <0.1]. Similarly, differences were not observed for dynamic autoregulation in conscious rats [transfer functions between BP (input) and renal blood flow (output) using chronic Transonic flow probes]. Collectively, these data indicate that the pathogenesis of nephropathy in the ZSF1 model of type 2 diabetic nephropathy is largely independent of differences in systemic BP and/or its potential renal transmission. However, these data do not exclude the possibility that the diabetic milieu may alter the glomerular capillaries in the ZSF1, such that there is an enhanced local susceptibility to injury with even normal glomerular pressures.

Caffeine and the Kidney: What Evidence Right Now?

Caffeine, or 1, 3, 7-trimethylxanthine, is one of the most frequently consumed active drugs worldwide. Its main mechanisms of action include inhibiting the phosphodiesteratic enzyme and adenosine receptors and activating the ryanodine receptors with several actions on all organs. What effect does caffeine have on the kidney? Is caffeine beneficial or dangerous? A review of the current literature reveals conflicting opinions regarding the prolithiasic effect of this substance, whereas its diuretic action is least disputed and more easily observed. Caffeine may have a toxic or preventive effect in some physiologic or pathologic conditions. Some of these incongruences may depend on several factors, such as dosage, prior chronic exposure, genetic-enzymatic axes, and concomitant drug consumption. While awaiting further insight from forthcoming studies on the issue, we may reach a preliminary conclusion that, as yet, there is no evidence contraindicating the consumption of the equivalent of 3 to 4 cups of coffee per day in healthy or nephropathic subjects. However, particular attention should be paid to the elderly, children, and patients on concomitant treatment with analgesics or diuretics, whereas in subjects with a family or clinical history of calcium lithiasis a moderate caffeine consumption should be associated with an adequate fluid intake. Further in-depth studies are required to investigate whether this beverage is beneficial to patients on hemodialysis.

2-Methoxyestradiol and 2-Ethoxyestradiol Retard the Progression of Renal Disease in Aged, Obese, Diabetic ZSF1 Rats

The metabolic syndrome is a main cause for cardiovascular disease and for the accelerating epidemic of chronic renal failure. Previous studies show that 2-hydroxyestradiol (2-HE), an estradiol metabolite with little estrogenic activity, decreases obesity and arterial blood pressure and attenuates the development of renal disease in young, obese, diabetic ZSF1 rats. In humans, however, diabetic renal disease is more frequent and severe in older patients. In vivo, 2-HE is readily converted to 2-methoxyestradiol (2-ME), an estradiol metabolite with no estrogenic activity. Accordingly, one purpose of this study was to determine whether 2-ME would provide benefit in aged rats with a very severe form of diabetic renal disease. Another objective was to determine whether synthetic analogs of estradiol metabolites might be beneficial in diabetic renal disease. To achieve these objectives we examined the effects of 2-ME and its analog 2-ethoxyestradiol (2-EE) in aged (35-week-old), obese ZSF1 rats. Animals were treated for 9 weeks with vehicle (PEG-400, 0.5 microL per hour), 2-ME or 2-EE (18 microg/kg per hour). Metabolic and renal function were measured at weeks 0, 3, 6, and 9, and renal hemodynamics and excretory function were assessed at week 9. Aged ZSF1 rats had elevated levels of glycosylated hemoglobin; increased renal cortical expression of proliferating cell nuclear antigen (PCNA), nuclear factor kappa B (NF-kappaB), and vascular endothelial growth factor (VEGF); glycosuria, hypertension; and proteinuria. 2-ME and 2-EE did not affect obesity or hypertension and had variable effects on glucose homeostasis, yet they attenuated proteinuria; increased renal blood flow and glomerular filtration; and reduced renal cortical expression of PCNA, NFkappaB, and VEGF. We conclude that 2ME and 2EE are strikingly renoprotective even in aged animals with severe diabetic renal disease. The present study warrants further investigation of 2-ME and analogs of estradiol metabolites for treatment of kidney disease associated with the metabolic syndrome.

An association between the methylenetetrahydrofolate reductase (MTHFR) C677T mutation and inflammation markers related to cardiovascular disease

BACKGROUND

Prospective studies have identified many markers of systemic inflammation that are powerful predictors of future cardiovascular events. The methylenetetrahydrofolate reductase (MTHFR) C677T genotype, a common polymorphism that induces hyperhomocysteinaemia, has been proposed as a genetic risk factor for cardiovascular disease. In this work, we evaluated the relationship between the levels of inflammation markers and MTHFR genotype among cardiovascular disease free subjects of the ATTICA study.

METHODS

During 2001-2002, we randomly enrolled for genetic evaluation 574 subjects from Attica region, Greece. In this work, we investigated demographic, lifestyle, clinical, biochemical and genetic information from 322 men (46+/-13 years) and 252 women (45+/-14 years). Among other characteristics, we measured various inflammatory markers levels in relation to C677T MTHFR genotype distribution.

RESULTS

The MTHFR genotypes distribution was: homozygous normal (CC) genotype, 41%; heterozygous (CT), 48%; and homozygous mutant (TT) genotype, 11%. C-reactive protein (CRA), fibrinogen, white blood cell (WBC) counts and amyloid-a levels were higher in TT compared to CC and CT genotypes (p<0.01), in both genders, even after controlling for various potential confounders.

CONCLUSION

The observed association between markers of systemic inflammation with MTHFR genotype may state a hypothesis for a common pathobiological mechanism between inflammation process and MTHFR, which is a key enzyme in homocysteine (Hcy) metabolism.

Simvastatin and l-Arginine Preserve Renal Function after Ischemia/Reperfusion Injury

BACKGROUND

HMG-CoA reductase inhibitors have been shown to have beneficial renal hemodynamic effects by increasing renal blood flow, independent of their lipid-lowering properties. Currently in organ transplantation, the calcineurin inhibitor cyclosporine A (CyA) is the immunosuppressant of choice. However, its use is limited by its nephrotoxic effects, namely its renal vasoconstrictor properties. The purpose of this study was to determine the effect of an HMG-CoA reductase inhibitor, simvastatin (Zocor), on renal function in rats and on urinary nitrite/nitrate production following ischemia/reperfusion injury (I/R) with concomitant cyclosporine treatment. In addition, L-NAME (N(G)-nitro-L-arginine methyl ester) and L-arginine were administered with CyA to the rats to test the hypothesis that simvastatin's beneficial effects were due to nitric oxide.

METHODS

Male Wistar rats (250 g) were anesthetized and the supra-aorta clamped for 40 minutes. The right kidney was removed. After recovery, the rats were divided into five groups: 1) controls, no ischemia, no treatment (CTRL, n = 8); 2) ischemia (ISCH) plus cyclosporine A only (CyA, 5 mg/kg/day i.p., n = 8); 3) ischemia plus CyA and simvastatin (SIM, 10 mg/kg/day, gavage, n = 8); 4) ischemia plus simvastatin plus L-NAME plus CyA (10 mg/kg/day, gavage, n = 8), and 5) ischemia plus simvastatin plus L-arginine (2% in drinking water, n = 7) plus CyA. Five to 7 days after I/R injury, the glomerular filtration rate (GFR) was determined using urinary iohexol clearance. Urinary nitrite/nitrate production was determined using nitrate reductase and the Greiss reaction. Data are expressed as mean +/- SEM, and intergroup comparisons were made using one-way analysis of variance.

RESULTS

The GFR values (mL/min) for all five groups are as follows: 1) CTRL = 1.25 +/- 0.10; 2) ISCH plus CyA only = 0.45 +/- 0.06 (P < 0.05 versus CTRL, ISCH only and simvastatin and cyclosporine and simvastatin plus L-arginine and cyclosporine); 3) CyA and SIM = 0.78 +/- 0.09, CyA and L-NAME = 0.62 +/- 0.12, and CyA and L-arginine and SIM = 1.57 +/- 0.12. Results in the control were significantly different from results in the ischemic only and the L-NAME groups (P < 0.05). The L-arginine plus cyclosporine and simvastatin group was significantly higher than the ischemic only group, ischemic plus simvastatin and cyclosporine and the L-NAME plus cyclosporine group (P < 0.05). No significant differences could be detected in the urinary nitric oxide concentrations.

CONCLUSIONS

: After I/R injury and cyclosporine treatment, simvastatin and L-arginine preserved renal function, compared with cyclosporine treatment alone, because simvastatin and L-arginine may not have a direct vasoconstrictor effect on the renal microcirculation. They may be suppressing endothelin or increasing other vasodilator mediators such as the vasodilator prostaglandins and/or nitric oxide.

Fructose feeding and intermittent hypoxia affect ventilatory responsiveness to hypoxia and hypercapnia in rats

We hypothesized that, in male rats, 10% fructose in drinking water would depress ventilatory responsiveness to acute hypoxia (10% O2 in N2) and hypercapnia (5% CO2 in O2) that would be depressed further by exposure to intermittent hypoxia. Minute ventilation (V̇e) in air and in response to acute hypoxia and hypercapnia was evaluated in 10 rats before fructose feeding (FF), during 6 wk of FF, and after FF was removed for 2 wk. During FF, five rats were exposed to intermittent air and five to intermittent hypoxia for 13 days. Six rats given tap water acted as control and were exposed to intermittent air and subsequently intermittent hypoxia. In FF rats, plasma insulin levels increased threefold in the rats exposed to intermittent hypoxia and during washout returned to levels observed in rats exposed to intermittent air. During FF, ventilatory responsiveness to acute hypoxia was depressed because of decreased tidal volume (Vt) responsiveness. During washout, V̇e decreased as a result of decreased Vt and frequency of breathing, and the ventilatory responsiveness to hypoxia in intermittent hypoxia rats did not recover. In all rats, the ventilatory responses to hypercapnia were decreased during FF and recovered after washout because of an increased Vt responsiveness. In the control group, hypoxic responsiveness was not depressed after intermittent hypoxia and was augmented after washout. Thus FF attenuated the ventilatory responsiveness of conscious rats to hypoxia and hypercapnia. Intermittent hypoxia interacted with FF to increase insulin levels and depress ventilatory responses to acute hypoxia that remained depressed during washout.

Effects of long-term captopril andl-arginine treatment on ventilation and blood pressure in obese male SHHF rats

We investigated the effects of captopril (Cap) and l-arginine (Arg) on hypertension and cardiopulmonary function. Our hypothesis was that Cap therapy or Arg will improve cardiopulmonary risk factors for hypertension and hypoventilation in the obese spontaneously hypertensive heart failure rat, which is characterized by hypertension, obesity, and disorders of lipid and carbohydrate metabolism. For the first study, one group of rats received Cap in drinking water, and a second group received deionized water (DI). For the second study, rats were further subdivided. Some Cap-treated rats continued on this treatment, and the other half were now given DI to determine whether there would be residual effects of Cap treatment. A subgroup of rats who had received DI was then given Arg, whereas the rest remained on DI. In the first study, Cap-treated rats exhibited decreases in systolic and diastolic blood pressures, frequency of breathing, and minute ventilation, but ventilatory control was maintained. In contrast, blood pressures and relative ventilation to metabolism were higher in the DI-treated group. Removal of Cap increased blood pressure and decreased tidal volume while these rats maintained frequency. Although Arg-treated rats did not exhibit a decrease of blood pressure, ventilation was maintained in this group by preserving tidal volume. Thus Cap and Arg affected ventilation through different mechanisms independent of blood pressure.

Management of Glomerular Proteinuria: A Commentary

ABSTRACT. It is widely accepted that proteinuria reduction is an appropriate therapeutic goal in chronic proteinuric kidney disease. Based on large randomized controlled clinical trials (RCT), ACE inhibitor (ACEI) and angiotensin receptor blocker (ARB) therapy have emerged as the most important antiproteinuric and renal protective interventions. However, there are numerous other interventions that have been shown to be antiproteinuric and, therefore, likely to be renoprotective. Unfortunately testing each of these antiproteinuric therapies in RCT is not feasible. The nephrologist has two choices: restrict antiproteinuric therapies to those shown to be effective in RCT or expand the use of antiproteinuric therapies to include those that, although unproven, are plausibly effective and prudent to use. The goal of this work is to provide the documentation needed for the nephrologist to choose between these strategies. This work describes 25 separate interventions that are either antiproteinuric or may block injurious mechanisms of proteinuria. Each intervention is assigned a level of recommendation (Level 1 is the highest; Level 3 is the lowest) according to the strength of the evidence supporting its antiproteinuric and renoprotective efficacy. Pathophysiologic mechanisms possibly involved are also discussed. The number of interventions at each level of recommendation are: Level 1, n = 7; Level 2, n = 9; Level 3, n = 9. Our experience indicates that we can achieve in most patients the majority of Level 1 and many of the Level 2 and 3 recommendations. We suggest that, until better information becomes available, a broad-based, multiple-risk factor intervention to reduce proteinuria can be justified in those with progressive nephropathies. This work is intended primarily for clinical nephrologists; therefore, each antiproteinuria intervention is described in practical detail.

Rapamycin preserves renal function compared with cyclosporine A after ischemia/reperfusion injury

OBJECTIVES

To determine the effect of cyclosporine and rapamycin administration on renal function after ischemia/reperfusion injury (I/R). Cyclosporine A has known nephrotoxic effects. Thus, cyclosporine therapy subsequent to I/R injury may further exacerbate graft dysfunction. Rapamycin is a newer agent that suppresses the immune system by a different mechanism.

METHODS

Male Wistar rats (250 g) were anesthetized, and the suprarenal aorta was clamped for 40 minutes. The right kidney was removed. After recovery, the rats were divided into four groups: group 1, controls, no ischemia and no treatment (n = 10); group 2, ischemia with no treatment (n = 8); group 3, ischemia plus rapamycin (0.17 mg/kg/day gavage, n = 8); and group 4, ischemia plus cyclosporine A (30 mg/kg/day intraperitoneally, n = 9). The glomerular filtration rate was measured 5 to 7 days after I/R injury using urinary iohexol clearance. Data are expressed as the mean +/- SEM, and intergroup comparisons were made using one-way analysis of variance.

RESULTS

The mean GFR value for the controls (no ischemia, no treatment) was 1.23 +/- 0.08 mL/min; for group 2 (ischemia, no treatment), it was 1.05 +/- 0.10 mL/min; for group 3 (ischemia plus rapamycin) 1.06 +/- 0.14 mL/min; and for group 4 (ischemia plus cyclosporine A) 0.44 +/- 0.06 mL/min (P <0.05 versus the other three groups). The mean arterial pressure was significantly lower in the ischemic rats treated with cyclosporine A (P <0.05 versus the other three groups).

CONCLUSIONS

After I/R injury, rapamycin may preserve renal function compared with cyclosporine treatment, because it does not have a direct vasoconstrictor effect on the renal microcirculation.

Simvastatin Attenuates Renal Ischemia/Reperfusion Injury in Rats Administered Cyclosporine A

BACKGROUND

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors increase renal blood flow independent of their lipid-lowering properties. In organ transplantation, the calcineurin inhibitor cyclosporine A (CyA) is the immunosuppressant of choice. However, its renal vasoconstrictor properties limit its use. This study aimed to determine the effect of an HMG-CoA reductase inhibitor, simvastatin (Zocor), on renal function in rats after ischemia/reperfusion injury (I/R) with concomitant CyA treatment.

METHODS

Male Wistar rats (250 g) were anesthetized and the suprarenal aorta clamped for 40 minutes. The right kidney was removed. After recovery, the rats were divided into 5 groups: (1) control rats, no ischemia, no treatment; (2) ischemia with no treatment; (3) ischemia plus CyA only; (4) ischemia plus CyA and low-dose simvastatin; and (5) ischemia plus CyA and high-dose simvastatin. Five to 7 days after I/R injury, glomerular filtration rate (GFR) was determined using urinary iohexol clearance.

RESULTS

The GFR values (mL/min) for all 5 groups were as follows: (1) 1.23 +/- 0.08; (2) 1.05 +/- 0.10; (3) 0.44 +/- 0.06 (P < 0.05 versus groups 1, 2, and 5; one-way analysis of variance); (4) 0.51 +/- 0.04 (P < 0.05 versus groups 1, 2, and 5; one-way analysis of variance); and (5) 0.85 +/- 0.11.

CONCLUSIONS

After I/R injury and cyclosporine treatment, simvastatin preserved renal function compared with cyclosporine treatment alone because it may not have a direct vasoconstrictor effect on the renal microcirculation. In fact, it may exhibit vasodilator properties on the renal microcirculation mediated by nitric oxide.