Anti-hyperuricemic and nephroprotective effects of whey protein hydrolysate in potassium oxonate induced hyperuricemic rats

BACKGROUND

Hyperuricemia (HUA) is a serious public health concern globally that needs to be solved. It is closely related to gout and other metabolic diseases. To develop a safe and effective dietary supplementation for alleviating HUA, we investigated the effects of whey protein hydrolysate (WPH) on HUA and associated renal dysfunction and explored their underlying mechanism.

RESULTS

Potassium oxonate was used to induce HUA in model rats, who were then administered WPH for 21 days. The results showed that WPH significantly inhibited xanthine oxidase and adenosine deaminase activity in serum and liver, decreased uric acid (UA), creatinine, and blood urea nitrogen levels in serum, and increased the UA excretion in urine. In addition, WPH downregulated the expression of urate transporter 1 and upregulated the expression of organic anion transporter 1, adenosine triphosphate binding cassette subfamily G member 2, organic cation/carnitine transporters 1 and 2, and organic cation transporter 1 in kidneys.

CONCLUSION

These findings demonstrated for the first time that WPH could alleviate HUA by inhibiting UA production and promoting UA excretion, and improve the renal dysfunction caused by HUA. Thus, WPH may be a potential functional ingredient for the prevention and treatment of HUA and associated renal dysfunction. © 2021 Society of Chemical Industry.

Dietary Interventions for Gout and Effect on Cardiovascular Risk Factors: A Systematic Review

Gout is one of the most prevalent inflammatory rheumatic disease. It is preceded by hyperuricemia and associated with an increased risk for cardiovascular disease, both related to unhealthy diets. The objective of this systematic review is to better define the most appropriate diet addressing both disease activity and traditional cardiovascular risk factors in hyperuricemic patients. We included clinical trials with patients diagnosed with hyperuricemia or gout, investigating the effect of dietary interventions on serum uric acid (SUA) levels, gout flares and—if available—cardiovascular risk factors. Eighteen articles were included, which were too heterogeneous to perform a meta-analysis. Overall, the risk of bias of the studies was moderate to high. We distinguished four groups of dietary interventions: Calorie restriction and fasting, purine-low diets, Mediterranean-style diets, and supplements. Overall, fasting resulted in an increase of SUA, whilst small (SUA change +0.3 to −2.9 mg/dL) but significant effects were found after low-calorie, purine-low, and Mediterranean-style diets. Studies investigating the effect on cardiovascular risk factors were limited and inconclusive. Since Mediterranean-style diets/DASH (Dietary Approach to Stop Hypertension) have shown to be effective for the reduction of cardiovascular risk factors in other at-risk populations, we recommend further investigation of such diets for the treatment of gout.

Dietary Antioxidant Supplements and Uric Acid in Chronic Kidney Disease: A Review

Increased serum levels of uric acid have been associated with the onset and development of chronic kidney disease (CKD), cardiovascular disease, and mortality, through several molecular pathogenetic mechanisms, such as inflammation and oxidative stress. Oxidative stress is present even in the early stages of CKD, progresses parallelly with the deterioration of kidney function, and is even more exacerbated in end-stage renal disease patients undergoing maintenance hemodialysis. Although acting in the plasma as an antioxidant, once uric acid enters the intracellular environment; it behaves as a powerful pro-oxidant. Exogenous intake of antioxidants has been repeatedly shown to prevent inflammation, atherosclerosis and oxidative stress in CKD patients. Moreover, certain antioxidants have been proposed to exert uric acid-lowering properties. This review aims to present the available data regarding the effects of antioxidant supplements on both oxidative stress and uric acid serum levels, in a population particularly susceptible to oxidative damage such as CKD patients.

Male asymptomatic hyperuricemia patients display a lower number of NKG2D+ NK cells before and after a low-purine diet

BACKGROUND

Aberrant activation of the immune system has been reported in asymptomatic hyperuricemia (HUA) patients. However, very few studies have elucidated the role of natural killer (NK) cells in this disease.

METHODS

In this study, we evaluated the relationship between NK cells and HUA in 16 control subjects and 20 patients, who were all on a low-purine diet. We analyzed the number of circulating NK cells, its subsets, interferon-γ, and CD107 NK cells, by flow cytometry, before and after 4 and 24 weeks of diet control. We also assessed the potential association of the NK cells with clinical measures.

RESULTS

The patients consistently had a lower number of NKG2D NK cells before and after low-purine diet, even the serum uric acid (SUA) levels <7 mg/dL after diet control. Moreover, a lower number of NK cells and a higher number of CD107a NK cells were observed on recruitment. Low-purine diet was benefit on the improvement of the SUA levels, body mass index (BMI), and the number and functions of NK cells. Furthermore, the number of CD3CD56 NK cells and NKG2D NK cells negatively correlated with the BMI before and after diet control.

CONCLUSION

The consistent lower number of NKG2D NK cells and correlated with BMI before and after low-purine diet may be involved in the occurrence and development of HUA.

Effect of Soy Sauce on Serum Uric Acid Levels in Hyperuricemic Rats and Identification of Flazin as a Potent Xanthine Oxidase Inhibitor

This is the first report on the ability of soy sauce to effectively reduce the serum uric acid levels and xanthine oxidase (XOD) activities of hyperuricemic rats. Soy sauce was partitioned sequentially into ethyl acetate and water fractions. The ethyl acetate fraction with strong XOD inhibition effect was purified further. On the basis of xanthine oxidase inhibitory (XOI) activity-guided purification, nine compounds including 3,4-dihydroxy ethyl cinnamate, diisobutyl terephthalate, harman, daidzein, flazin, catechol, thymine, genistein, and uracil were obtained. It was the first time that 3,4-dihydroxy ethyl cinnamate and diisobutyl terephthalate had been identified from soy sauce. Flazin with hydroxymethyl furan ketone group at C-1 and carboxyl at C-3 exhibited the strongest XOI activity (IC50 = 0.51 ± 0.05 mM). According to fluorescence quenching and molecular docking experiments, flazin could enter into the catalytic center of XOD to interact with Lys1045, Gln1194, and Arg912 mainly by hydrophobic forces and hydrogen bonds. Flazin, catechol, and genistein not only were potent XOD inhibitors but also held certain antioxidant activities. According to ADME (absorption, distribution, metabolism, and excretion) simulation in silico, flazin had good oral bioavailability in vivo.

Screening and characterization of purine nucleoside degrading lactic acid bacteria isolated from Chinese sauerkraut and evaluation of the serum uric acid lowering effect in hyperuricemic rats

Hyperuricemia is well known as the cause of gout. In recent years, it has also been recognized as a risk factor for arteriosclerosis, cerebrovascular and cardiovascular diseases, and nephropathy in diabetic patients. Foods high in purine compounds are more potent in exacerbating hyperuricemia. Therefore, the development of probiotics that efficiently degrade purine compounds is a promising potential therapy for the prevention of hyperuricemia. In this study, fifty-five lactic acid bacteria isolated from Chinese sauerkraut were evaluated for the ability to degrade inosine and guanosine, the two key intermediates in purine metabolism. After a preliminary screening based on HPLC, three candidate strains with the highest nucleoside degrading rates were selected for further characterization. The tested biological characteristics of candidate strains included acid tolerance, bile tolerance, anti-pathogenic bacteria activity, cell adhesion ability, resistance to antibiotics and the ability to produce hydrogen peroxide. Among the selected strains, DM9218 showed the best probiotic potential compared with other strains despite its poor bile resistance. Analysis of 16S rRNA sequences showed that DM9218 has the highest similarity (99%) to Lactobacillus plantarum WCFS1. The acclimated strain DM9218-A showed better resistance to 0.3% bile salt, and its survival in gastrointestinal tract of rats was proven by PCR-DGGE. Furthermore, the effects of DM9218-A in a hyperuricemia rat model were evaluated. The level of serum uric acid in hyperuricemic rat can be efficiently reduced by the intragastric administration of DM9218-A (P<0.05). The preventive treatment of DM9218-A caused a greater reduction in serum uric acid concentration in hyperuricemic rats than the later treatment (P<0.05). Our results suggest that DM9218-A may be a promising candidate as an adjunctive treatment in patients with hyperuricemia during the onset period of disease. DM9218-A also has potential as a probiotic in the prevention of hyperuricemia in the normal population.

[The principles of nutrition therapy of gout and hyperuricemia]

In 2012 the updated guidelines for the treatment of gout were published by the American College of Rheumatology (ACR), which underline the necessity of comprehensive treatment in this condition. According to the European League Against Rheumatism (EULAR), treatment of comorbidities, lifestyle modifications and proper diet may be of significant importance. In the primary care settings in Poland there is virtually no access to qualified dieticians. The nutritional counseling is sometimes implemented--usually to a very limited extent--by primary care physicians. It is believed that proper diet may improve the prognosis and quality of life in patients with gout. The aim of the work is to present the principles of nutrition therapy in gout and hyperuricemia, in the context of their pathogenesis. The key principles of nutrition therapy in the above mentioned conditions include a restriction of purine amount in the diet and reaching the proper body weight. Optimal hydration and alcohol elimination are also beneficial. Furthermore, some food ingredients can affect the plasma level of uric acid in the mechanisms irrelevant of their purine load.

Low protein diet inhibits uric acid synthesis and attenuates renal damage in streptozotocin-induced diabetic rats

AIM

Several studies indicated that hyperuricemia may link to the worsening of diabetic nephropathy (DN). Meanwhile, low protein diet (LPD) retards exacerbation of renal damage in chronic kidney disease. We then assessed whether LPD influences uric acid metabolism and benefits the progression of DN in streptozotocin- (STZ-) induced diabetic rats.

METHODS

STZ-induced and control rats were both fed with LPD (5%) and normal protein diet (18%), respectively, for 12 weeks. Vital signs, blood and urinary samples for UA metabolism were taken and analyzed every 3 weeks. Kidneys were removed at the end of the experiment.

RESULTS

Diabetic rats developed into constantly high levels of serum UA (SUA), creatinine (SCr) and 24 h amounts of urinary albumin excretion (UAE), creatinine (UCr), urea nitrogen (UUN), and uric acid (UUA). LPD significantly decreased SUA, UAE, and blood glucose, yet left SCr, UCr, and UUN unchanged. A stepwise regression showed that high UUA is an independent risk factor for DN. LPD remarkably ameliorated degrees of enlarged glomeruli, proliferated mesangial cells, and hyaline-degenerated tubular epithelial cells in diabetic rats. Expression of TNF-α in tubulointerstitium significantly decreased in LPD-fed diabetic rats.

CONCLUSION

LPD inhibits endogenous uric acid synthesis and might accordingly attenuate renal damage in STZ-induced diabetic rats.

The year in gout: 2011-2012

From an epidemiologic view, gout is an increasingly prevalent and increasingly pressing clinical problem. This fact, together with technical advances in biology, pharmacology, and imaging techniques, have led to a decade of increasingly rapid progress in our collective understanding of gout and hyperuricemia. Here we review some of the most important recent advances in gout over the past 12 to 18 months.

Dietary factors associated with hyperuricemia in adults

OBJECTIVES

Although diet has long been assumed to be associated with hyperuricemia, the association between diet and hyperuricemia remains to be verified.

METHODS

The Nutrition and Health Survey in Taiwan (NAHSIT) implemented between 1993 and 1996 was a nationwide survey using a stratified multistage sampling design. A food frequency questionnaire (FFQ), 24-hour diet recall, and blood samples were utilized. Hyperuricemia was defined as serum urate >7.7 mg/dL for men and >6.6 mg/dL for women.

RESULTS

In total, 2176 adults, 987 (45%) men and 1189 (55%) women, were recruited. Mean serum urate was 6.81 +/- 1.66 mg/dL (range, 2.5-16.8 mg/dL) and 5.47 +/- 1.55 mg/dL (range, 1.4-11.5 mg/dL) for men and women, respectively. Multiple logistic regression analysis indicated that beer consumption in both the FFQ and the 24-hour diet recall were significantly associated with hyperuricemia in men after adjusting for age, total caloric intake, body mass index, and geographic area. In FFQ, the adjusted odds ratio was 1.49 for men who imbibed 0.1 to 11.6 g ethanol (<1 standard drink) daily and 1.56 for men who imbibed > or =11.7 g ethanol (> or =1 standard drink) daily, when compared with that for men who did not drink beer (P = 0.035). In the 24-hour diet recall, the adjusted odds ratio for men who drank <5 cans of beer daily was 1.13, and for men who drank > or =5 cans daily was 1.28 when compared with that for men who did not drink beer (P = 0.003).

CONCLUSIONS

This cross-sectional survey demonstrated that beer intake is independently associated with increased risk of hyperuricemia in men. Restricted beer intake may help prevent hyperuricemia in the population. The finding of elevated mean serum urate levels over recent decades warrants further study.

Response to a urate-lowering diet according to polymorphisms in the apolipoprotein AI-CIII-AIV cluster

OBJECTIVE

The apolipoprotein AI-CIII-AIV cluster has been associated with the response to a urate-lowering diet, and polymorphisms in the apolipoprotein CIII gene have been associated with hyperuricemia and hypertriglyceridemia. We assessed the influence of polymorphisms in the apolipoprotein AI-CIII-AIV cluster on the response to a urate-lowering diet in patients with hyperuricemia.

METHODS

A urate-lowering diet was followed for 2 weeks by 64 men with hyperuricemia. Plasma concentrations of triglycerides, cholesterol, glucose, and uric acid, and the uric acid clearance and 24-hour uric acid urinary excretory fraction were measured before and after the diet. The data were analyzed in association with the polymorphisms of the apolipoprotein AI-CIII-AIV gene cluster.

RESULTS

After the urate-lowering diet, the plasma levels of triglycerides, cholesterol, glucose, and uric acid and 24-hour uric acid excretion all fell significantly. Paired sample ANOVA showed that the decrease was mainly due to the diet, except for the plasma triglycerides, which were influenced by allele X2 of the XmnI polymorphism of the apolipoprotein AI gene.

CONCLUSION

The response of the biological variables to a urate-lowering diet was mainly influenced by diet. Changes in triglycerides were also influenced by the apolipoprotein AI XmnI polymorphism (p = 0.04), suggesting a gene-diet interaction (p = 0.03).

[Diet therapy in combined disorders of purine and lipid metabolism in children]

Authors examined 539 schoolgirls in the age 7-16 years old. Dosorders of lipid metabolism occurred in 48.4% of cases; hyperuricemia more than 0.32 mmol/l--in 25% of cases; excessive body weight and obesity--in 15% of cases. So more than half of female population some metabolic disorders. High frequency of metabolic disorders prove the necessity of dietetic correction in dependence on type of prevailed metabolic changes. Diet counted all the amount of metabolic disorders must be most effective.