Uric acid secretion from adipose tissue and its increase in obesity

Hyperuricemia and acute gout after laparoscopic sleeve gastrectomy

The aim of this study was to evaluate the prevalence of hyperuricemia and acute gout after laparoscopic sleeve gastrectomy (LSG). Risk factors for developing gout were also examined. Eighty-five patients underwent LSG were enrolled in this prospective study. Serum uric acid levels, gout attacks and total water levels % derived by bioimpedance were examined pre-operatively and 1 month post-operatively. Hyperuricemia was identified in 30.6% pre-operatively and in 18.82% of patients post-operatively. From the patients' group with pre-operative hyperuricemia, 53.9% were normalized, 46.2% had increased uric acid post-operatively while gout was observed in 11.5%. From the patients group without pre-operative hyperuricemia, hyperuricemia and gout were observed in 6.8% and 5.1% post-operatively, respectively. The relative risk for developing hyperuricemia was 6.2 (95% confidence interval [CI] 2.2-17.8) and for developing gout was 2.3 (95% CI 2.2-17.8). Statistical significant differences for gout among the groups with and without gout were indicated concerning pre-operative use of medications (P < 0.001), age (P = 0.025), post-operative uric acid levels (P < 0.001) and post-operative total water levels % (P = 0.048). The prevalence of hyperuricemia was 18.8% and gout attack of 7.1% 1 month after LSG. From the cohort of patients with pre-operative hyperuricemia, a significant proportion normalized uric acid, while 11.5% developed gout. Patients without hyperuricemia pre-operatively developed hyperuricemia and gout in 6.8% and 5.1% post-operatively, respectively. The patients who had gout were younger and had 37% water levels post-operatively.

ASSOCIATION BETWEEN SERUM URIC ACID LEVEL AND BODY MASS INDEX IN SEX- AND AGE-SPECIFIC GROUPS IN SOUTHWESTERN CHINA

Objective: To investigate the sex- and age-specific association between serum uric acid level and body mass index (BMI). Methods: A total of 144,856 subjects aged 20 to 79 years were enrolled in this cross-sectional study. Serum uric acid level, renal function, hepatic function, and lipid profile were investigated. Results: The prevalence of hyperuricemia decreased with age in men but increased in women. In men, the correlation coefficient between the serum urate level and BMI declined steadily with age. Underweight was associated with a 53 to 68% and a 66% lower prevalence of hyperuricemia in men aged 20 to 69 years and in women aged 20 to 29 years, respectively. Overweight and obesity were correlated with a higher odds ratio (OR) (95% confidence interval [CI]) for hyperuricemia in both genders. In individuals with overweight or obesity, younger subjects had a higher OR (95% CI) for hyperuricemia than older subjects. Among subjects aged 20 to 59 years, as they gained weight, the OR (95% CI) for hyperuricemia increased faster in women than in men compared with their respective normal-weight controls. Conclusion: Underweight was associated with a lower prevalence of hyperuricemia in men aged ≤69 years. In individuals with overweight or obesity, younger subjects were more likely to develop hyperuricemia than older subjects. With active weight gain, the likelihood for developing hyperuricemia increased faster in women than in men compared with their respective normal-weight controls. Abbreviations: ALT = alanine aminotransferase; AST = aspartate aminotransferase; BMI = body mass index; CI = confidence interval; eGFR = estimated glomerular filtration rate; HDL-C = high-density-lipoprotein cholesterol; LDL-C = low-density-lipoprotein cholesterol; OR = odds ratio.

Anti-hyperuricemic effect of isorhamnetin in cultured hepatocytes and model mice: structure-activity relationships of methylquercetins as inhibitors of uric acid production

Hyperuricemia is an important risk factor for gout. Isorhamnetin (3'-O-methylquercetin) is an O-methylated flavonol, which occurs in onion, almond and sea buckthorn. It is also one of the metabolites of quercetin in mammals. In the present study, we investigated anti-hyperuricemic effect of isorhamnetin adopting both cultured hepatocytes and mice with hyperuricemia induced by purine bodies. In cultured hepatocytes, isorhamnetin as well as quercetin significantly and dose-dependently inhibited uric acid (UA) production. We also examined the inhibitory effects on UA production of other mono-methylquercetins, i.e., tamarixetin, 3-O-methylquercetin, azaleatin, and rhamnetin in addition to isorhamnetin for studying their structure-activity relationships. From the results obtained, hydroxyl groups at C-3, C-5, and especially C-7, but not C-3' and C-4' of quercetin are demonstrated to play a critical role in suppressing UA production in the AML12 hepatocytes. Oral administration of isorhamnetin significantly reduced plasma and hepatic UA levels in the hyperuricemic model mice. Isorhamnetin also decreased hepatic xanthine oxidase (XO) activity without changes in XO protein expression, indicating that anti-hyperuricemic effect of isorhamnetin could be, at least partly, attributable to suppression of UA production by directly inhibiting XO activity in the liver. These findings demonstrate that isorhamnetin has a potent anti-hyperuricemic effect and may be a potential candidate for prevention and remediation of hyperuricemia.

Obesity-Related Genetic Variants and Hyperuricemia Risk in Chinese Men

Objective: Obesity/metabolic syndrome and hyperuricemia are clinically associated; however, the association of obesity/metabolic syndrome-related genetic variants with hyperuricemia is not clear. Therefore, we assessed this association in Chinese men diagnosed with hyperuricemia in comparison to a non-hyperuricemia group. Methods: We genotyped 47 single nucleotide polymorphisms (SNPs) previously identified to be associated with obesity or metabolic syndrome in 474 adult males (aged ≥ 18 years) using multiplex polymerase chain reaction. Multivariate logistic regression was used to investigate the association between the genetic variations and hyperuricemia. Stratified analyses were applied to further assess the associations. Results: The obesity-related SNP in MSRA rs545854 significantly affected serum uric acid levels. In addition, the G-allele of rs545854 was positively associated with the risk of hyperuricemia [odds ratio (OR) = 2.80, 95% confidence interval (CI) = 1.19-6.64, P = 0.0188]. After adjusting the model for body mass index and central obesity, rs545854 was shown to be an independent factor increasing the risk of hyperuricemia (OR = 2.81, 95%CI = 1.18-6.70, P = 0.0196). Stratified analyses also showed a significant association between rs545854 and hyperuricemia among meat eaters (OR = 2.62, 95%CI = 1.09-6.26, P = 0.0308). Conclusion: The obesity-related SNP rs545854 was correlated with the serum uric acid level and risk of hyperuricemia in a male Chinese population. Therefore, men carrying this SNP could benefit from limiting their meat consumption to prevent hyperuricemia. These findings suggest an underlying genetic link between obesity and hyperuricemia worthy of further exploration.

Insulin Resistance Associated with Plasma Xanthine Oxidoreductase Activity Independent of Visceral Adiposity and Adiponectin Level: MedCity21 Health Examination Registry

BACKGROUND

Higher levels of uric acid production have been reported in individuals with visceral fat obesity, and obesity is known to enhance xanthine oxidoreductase (XOR) activity, although the precise mechanism remains unclear. We investigated the associations of visceral fat area (VFA), serum adiponectin level, and insulin resistance with plasma XOR activity using our novel highly sensitive assay based on [¹³C₂,¹⁵N₂] xanthine and liquid chromatography/triple quadrupole mass spectrometry.

METHODS

This cross-sectional study included 193 subjects (92 males and 101 females) registered in the MedCity21 health examination registry. Plasma XOR activity, serum adiponectin level, and VFA obtained by computed tomography were measured, and insulin resistance was determined based on the homeostasis model assessment (HOMA-IR) index.

RESULTS

The mean values for VFA, log HOMA-IR, and log plasma XOR activity were 76.8 ± 45.8 cm², 0.14 ± 0.30, and 1.50 ± 0.44 pmol/h/mL, respectively. Multiple regression analysis showed that HOMA-IR was significantly (p=0.020) associated with plasma XOR activity independent of other factors, including VFA and adiponectin level, as well as age, sex, alcohol drinking habit, smoking habit, alanine transaminase, HbA1c, and eGFR. The "sex∗HOMA - IR" interaction was not significant (p=0.020) associated with plasma XOR activity independent of other factors, including VFA and adiponectin level, as well as age, sex, alcohol drinking habit, smoking habit, alanine transaminase, HbA1c, and eGFR. The ".

CONCLUSIONS

Our results indicate that insulin resistance is associated with plasma XOR activity and that relationship is independent of visceral adiposity and adiponectin level, suggesting that the development of insulin resistance resulting from increased visceral adiposity and/or reduced serum adiponectin contributes to increased uric acid production by stimulating XOR activity.

Adipose oxidative stress and protein carbonylation

Increased oxidative stress and abundance of reactive oxygen species (ROS) are positively correlated with a variety of pathophysiologies, including cardiovascular disease, type 2 diabetes, Alzheimer's disease, and neuroinflammation. In adipose biology, diabetic obesity is correlated with increased ROS in an age- and depot-specific manner and is mechanistically linked to mitochondrial dysfunction, endoplasmic reticulum (ER) stress, potentiated lipolysis, and insulin resistance. The cellular quality control systems that homeostatically regulate oxidative stress in the lean state are down-regulated in obesity as a consequence of inflammatory cytokine pressure leading to the accumulation of oxidized biomolecules. New findings have linked protein, DNA, and lipid oxidation at the biochemical level, and the structures and potential functions of protein adducts such as carbonylation that accumulate in stressed cells have been characterized. The sum total of such regulation and biochemical changes results in alteration of cellular metabolism and function in the obese state relative to the lean state and underlies metabolic disease progression. In this review, we discuss the molecular mechanisms and events underlying these processes and their implications for human health and disease.

The brominated flame retardant BDE 47 upregulates purine metabolism and mitochondrial respiration to promote adipocyte differentiation

Adipocyte differentiation is closely associated with obesity and obesity-induced metabolic disorders. Epidemiological studies have demonstrated the association of obesity with environmental pollutants, such as polybrominated diphenyl ethers (PBDEs), common flame retardants in various consumer products. However, their obesogenic effects and mechanism are underexplored. We employed non-targeted metabolomics studies based on liquid chromatography-high resolution mass spectrometry to determine how 2,2',4,4'-tetra-brominated biphenyl ether (BDE 47), one of the main congeners of PBDEs detected in human tissue, promotes adipocyte differentiation of mouse preadipocyte 3 T3-L1 cells. The promoting effects of BDE 47 exposure (5 or 10 μM) on adipocyte differentiation were confirmed by enhancing lipid accumulation and expression levels of biomarkers of adipogenesis. For the first time, we demonstrated that BDE 47 upregulated purine metabolism and altered glutathione metabolism to promote oxidative stress and uric acid production in adipocytes. BDE 47 also elevated mitochondrial respiration and glycolysis in adipocytes to induce more ATP to combat oxidative stress. Antioxidant treatments, including the suppression of xanthine oxidase, inhibited the effects of BDE 47 on inducing oxidative stress and lipid accumulation. BDE 47 may be a potential environmental obesogen by providing a permissive oxidative environment to induce adipocyte differentiation.

Metabolic syndrome and cancer risk: The role of xanthine oxidoreductase

Obesity and related pathologies such as diabetes and metabolic syndrome are associated with chronic inflammation and cancer. The serum level of xanthine oxidoreductase (XOR) is correlated to obesity-associated metabolic disorders. XOR can play a role in the pathogenesis of both metabolic syndrome and cancer through the inflammatory response and the oxidative stress elicited by the products of its activity. The reactive oxygen and nitrogen species and the uric acid derived from XOR concur to the development of hypertension, dyslipidemia and insulin resistance and participate in both cell transformation and proliferation, as well as in the progression and metastasis process. Despite the availability of different drugs to inhibit in vivo XOR activity, the complexity of XOR inhibition effects should be carefully considered before clinical application, save in the case of symptomatic hyperuricemia.

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Metabolic syndrome (MS) increases the risk of cancer development.

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Xanthine oxidoreductase (XOR) plays a role in both MS and cancer.

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Uric acid, ROS and RNS produced by XOR cause inflammation and oxidative stress.

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Inflammation and oxidative stress contribute to the pathogenesis of MS and cancer.

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XOR activity can be pharmacologically controlled.

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.

Unexpected high plasma xanthine oxidoreductase activity in female subjects with low levels of uric acid

Hypouricemia is a high-risk factor of exercise-induced acute kidney injury (EIAKI) probably through a lack of an antioxidant effect of uric acid. Xanthine oxidoreductase (XOR) is an enzyme that catalyzes the formation of uric acid from hypoxanthine and xanthine, leading to an increase in superoxide and reactive oxygen species. Activation of XOR has been proposed to promote oxidative stress-related tissue injury. We measured plasma XOR activity by a sensitive and accurate assay using a combination of liquid chromatography and triple quadrupole mass spectrometry in subjects with relatively low levels of uric acid (≤4.0 mg/dL) who were recruited from 627 subjects (male/female: 292/335) in the Tanno-Sobetsu Study, a population-based cohort. The numbers of subjects with uric acid ≤4.0 mg/dL, ≤3.0 mg/dL and ≤2.0 mg/dL were 72 (11.5%, male/female: 5/67), 13 (2.1%, all females) and 2 (0.3%, both females), respectively. Plasma XOR activities in 5 male subjects were below the median value of the 292 male subjects. In 12 (17.9%) of the 67 female subjects with uric acid ≤4.0 mg/dL, plasma XOR activities were above the upper quartile value of the 335 female subjects. Eleven of the 12 female subjects with high plasma XOR activity and a low uric acid level had liver dysfunction and/or insulin resistance. In conclusion, unexpected high plasma XOR activities were found in some female subjects with relatively low levels of uric acid. Measurement of plasma XOR activity may help to identify hypouricemic patients with a high risk for EIAKI.

The impact of sarcopenic obesity on inflammation, lean body mass, and muscle strength in elderly women

Objective

The objective of this study was to apply the newly standardized definition for sarcopenia from the Foundation for the National Institutes of Health (FNIH) and the current definition for obesity to 1) determine the prevalence of sarcopenic obesity (SO) in obese elderly women; 2) compare the muscle strength, lean body mass, and markers of inflammation between obese elderly women with SO and nonsarcopenic obesity (NSO), and 3) elucidate the relationship between appendicular lean mass adjusted for body mass index (aLM/BMI) with muscle strength, lean body mass, and obesity indices.

Methods

A total of 64 elderly obese women (age: 68.35±6.04 years) underwent body composition analysis by dual-energy X-ray absorptiometry. Participants were classified into two groups according to the definition of SO and NSO. Blood samples were collected for total cholesterol, triglycerides, high-density lipoprotein, low-density lipoprotein, uric acid, urea, interleukin-6 (IL-6), glucose, and creatine kinase (CK) measurements.

Results

The SO group presented a significantly greater BMI, fat (%), glucose, a marginal trend toward significance for uric acid, and IL-6 compared to the NSO group. In addition, the SO group displayed lower values for muscle strength and lean body mass. From a correlation standpoint, a higher aLM/BMI was positively associated with lean body mass and muscle strength and negatively associated with a lower BMI and percentage body fat.

Conclusion

The definition criteria from FNIH and obesity permit the ability to illustrate the prevalence and identify SO in elderly women with low muscle mass, low muscle strength, and impaired markers of inflammation.

Uric Acid and Xanthine Levels in Pregnancy Complicated by Gestational Diabetes Mellitus-The Effect on Adverse Pregnancy Outcomes

Uric acid (UA) levels are associated with many diseases including those related to lifestyle. The aim of this study was to evaluate the influence of clinical and anthropometric parameters on UA and xanthine (X) levels during pregnancy and postpartum in women with physiological pregnancy and pregnancy complicated by gestational diabetes mellitus (GDM), and to evaluate their impact on adverse perinatal outcomes. A total of 143 participants were included. Analyte levels were determined by HPLC with ultraviolet detection (HPLC-UV). Several single-nucleotide polymorphisms (SNPs) in UA transporters were genotyped using commercial assays. UA levels were higher within GDM women with pre-gestational obesity, those in high-risk groups, and those who required insulin during pregnancy. X levels were higher in the GDM group during pregnancy and also postpartum. Positive correlations between UA and X levels with body mass index (BMI) and glycemia levels were found. Gestational age at delivery was negatively correlated with UA and X levels postpartum. Postpartum X levels were significantly higher in women who underwent caesarean sections. Our data support a possible link between increased UA levels and a high-risk GDM subtype. UA levels were higher among women whose glucose tolerance was severely disturbed. Mid-gestational UA and X levels were not linked to adverse perinatal outcomes.

Enhanced hepatic glycogen synthesis and suppressed adenosine deaminase activity by lithium attenuates hepatic triglyceride accumulation in nicotine-exposed rats

Reduced liver glycogen synthesis might signify increased glucose flux towards fat synthesis and triggers hepatic triglyceride accumulation and dysmetabolism. Adenosine deaminase (ADA) reduces adenosine content which increases glycogenolysis. In the present study, we evaluate the effect of modulating glycogen synthesis and ADA by lithium chloride (LiCl) on nicotine-induced dysmetabolism. Twenty four male Wistar rats (n = 6/group) were allotted into four groups namely; vehicle-treated (po), nicotine-treated (1.0 mg/kg; po), LiCl-treated (5.0 mg/kg; po) and nicotine + LiCl-treated groups. The treatments lasted for 8 weeks. Nicotine exposure resulted in reduced body weight gain, liver weight, visceral adiposity, glycogen content and synthase. Along with increased insulin resistance (IR), fasting plasma glucose, lactate, plasma and hepatic ADA, XO, UA, and triglyceride (TG), total cholesterol (TC), free fatty acid, lipid peroxidation and liver injury markers. However, plasma and hepatic glucose-6-phosphate dehydrogenase-dependent antioxidant defenses were not affected by nicotine exposure. Concurrent treatment with LiCl normalizes all alterations with exception of hepatic TC. This result shows that enhancement of hepatic glycogen synthesis and suppression of ADA/XO/uric acid pathway by lithium can salvage the liver from nicotine-induced TG accumulation.

Association between the prevalence of hyperuricemia and reproductive hormones in polycystic ovary syndrome

BACKGROUND

The prevalecne of hyperuricemia in polycystic ovary syndrome (PCOS) is still uncertain. We aimed to investigate the prevalence of hyperuricemia in PCOS and to determine the influence of reproductive hormones on uric acid concentration.

METHODS

This retrospective cross-sectional study was performed at a large reproductive medicine center. Between March 2007 and October 2016, a total of 1,183 women with PCOS and 10,772 women without PCOS were included. PCOS was diagnosed according to the Rotterdam criteria. Anthropometric parameters, blood pressure, uric acid, reproductive hormones, glucose and lipids were measured in all subjects.

RESULTS

The serum uric acid (SUA) level was higher in women with PCOS than in women without PCOS. The prevalence of hyperuricemia in women with PCOS (25.48%) was significantly higher than that in women without PCOS (8.74%). Analysis stratified for age and body mass index (BMI) showed that both the SUA level and the prevalence of hyperuricemia were higher in women with PCOS of different age and BMI groups than in women without PCOS. After adjusting for age, BMI and estimated glomerular filtration rate (eGFR), logistic regression analysis revealed that the luteinizing/follicle-stimulating hormone (LH/FSH) ratio (odds ratio (OR) = 1.20, 95% CI = 1.01-1.43) and testosterone level (OR = 1.56, 95% CI = 1.27-1.90) were positively associated with the prevalence of hyperuricemia in females with PCOS.

CONCLUSIONS

The serum uric acid (SUA) level and the prevalence of hyperuricemia markedly increased in women with PCOS. The testosterone level was positively associated with the SUA level and the prevalence of hyperuricemia in females with PCOS.

Two Glucose-Lowering Mechanisms of Canagliflozin Depending on Body Weight Changes in Drug-Naïve Subjects with Type 2 Diabetes

Objectives

The aim of this study was to investigate the relations between the changes in body weight and those of glycemic and non-glycemic parameters in drug-naïve subjects with type 2 diabetes mellitus (T2DM) treated with canagliflozin monotherapy.

Methods

Subjects received 50–100 mg/day canagliflozin monotherapy for 3 months (n = 36), and were then divided into two groups: (1) those who lost weight [changes in (Δ)BMI ≤ − 0.45, p < 0.00001: Group L(ost), n = 20); and (2) those who did not lose weight [ΔBMI > − 0.45, p = non-significant: Group N(eutral), n = 16]. At 3 months, the levels of glycemic and non-glycemic parameters were compared with those at baseline.

Results

Significant reductions of BMI levels (− 2.1%, p < 0.00001) were observed for the overall subjects. At baseline, fasting blood glucose (FBG) and HbA1c levels were significantly higher, and homeostasis model assessment-B (HOMA-B) levels were significantly lower in Group N versus Group L. Similar reductions of HbA1c (Group L: 9.54 ± 2.58% to 7.54 ± 1.27%, p < 0.05; Group N: 11.23 ± 2.27% to 9.19 ± 1.64%, p < 0.0002) and homeostasis model assessment-R (HOMA-R; Group L: − 32.3%, p < 0.005; Group N: − 36.5%, p < 0.02) levels were seen in these two groups. However, other parameters showed distinct regulatory patterns. (1) Group L: significant reductions in uric acid (UA) levels (− 6.9%, p < 0.02) were observed. Significant correlations between the changes in FBG and HOMA-R (R = 0.458, p < 0.05) were seen. (2) Group N: significant increases in HOMA-B (+ 69.4%, p < 0.007) and reductions in free fatty acid (FFA; − 25.8%, p < 0.02) levels were observed. Significant negative or positive correlations between the changes in (Δ)FBG and ΔHOMA-B (R = − 0.557, p < 0.03), and between ΔFBG and ΔHOMA-R (R = 0.458, p < 0.05) were seen.

Conclusions

These results indicate that (1) body weight changes with canagliflozin were not associated with its glycemic efficacy; and (2) distinct glucose-lowering pathways may exist with canagliflozin, reducing insulin resistance in those who lose weight and enhancing β-cell function, as well as reducing insulin resistance, possibly via the decreased FFA levels, in those who do not lose weight.

Serum Uric Acid Levels are Associated with Cardiometabolic Risk Factors in Healthy Young and Middle-Aged Adults

Background

Observational studies have highlighted an association between serum uric acid (SUA) levels and cardiovascular risk factors. Despite the growing body of evidences, several studies were conducted in older individuals or in carriers of diseases susceptible to affect SUA levels and cardiometabolic risk markers.

Objective

To evaluate the relationship of SUA with body adiposity, metabolic profile, oxidative stress, inflammatory biomarkers, blood pressure and endothelial function in healthy young and middle-aged adults.

Methods

149 Brazilian adults aged 20-55 years, both sexes, underwent evaluation of body adiposity, SUA, fasting glucose and insulin, lipid profile, malondialdehyde (MDA), high sensitivity C-reactive protein (hs-CRP), adiponectin, blood pressure and endothelial function. Endothelial function was assessed by the reactive hyperemia index (RHI) derived from peripheral arterial tonometry method. Participants were allocated in two groups according to SUA levels: control group (CG; n = 130; men ≤ 7 mg/dL, women ≤ 6 mg/dL) and hyperuricemia group (HG; n = 19; men > 7 mg/dL, women > 6 mg/dL). A P-value < 0.05 was considered statistically significant.

Results

After adjustment for confounders, participants in HG compared with those in CG displayed higher body mass index (BMI): 34.15(33.36-37.19) vs.31.80 (26.26-34.42) kg/m²,p = 0.008, higher MDA: 4.67(4.03-5.30) vs. 3.53(3.10-4.07) ng/mL, p < 0.0001 and lower RHI: 1.68 ± 0.30 vs. 2.05 ± 0.46, p = 0.03). In correlation analysis adjusted for confounders, SUA was positively associated (p < 0.05) with BMI, waist circumference, LDL-cholesterol, triglycerides and MDA, and negatively associated (p < 0.05) with HDL-cholesterol, adiponectin and RHI.

Conclusions

This study suggests that in healthy young and middle-aged adults higher SUA levels are associated with higher body adiposity, unfavorable lipid and inflammatory phenotype, higher oxidative stress and impaired endothelial function.

Serum uric acid potentially links metabolic health to measures of fuel use in lean and obese individuals

BACKGROUND AND AIMS

Uric acid (UA) is a byproduct of the high-energy purine metabolism and is conventionally regarded as a marker of cardio-metabolic impairment. Its potential relationship with energy homeostasis is unknown to date.

METHODS AND RESULTS

In a cross-sectional study on 121 otherwise healthy obese and 99 sex- and-age-matched lean subjects, UA levels were analyzed in relation to metabolic health, inflammatory markers, respiratory quotient (RQ) and resting energy expenditure (REE) as assessed by indirect calorimetry, fat mass (%FM) and fat-free mass (FFM) as determined by bioimpedance analysis. As expected, obese and lean subjects differed in BMI, glucolipid homeostasis, leptin and insulin levels, inflammatory markers, %FM and FFM (p < 0.001 for all). Likewise, UA levels (p < 0.001) and rates of hyperuricaemia (40.5% vs 3.0%, p < 0.0001) were also higher in obese than lean controls. Further, indirect calorimetry confirmed that obesity increased REE and decreased RQ significantly (p < 0.001). Beyond the expected metabolic correlates, in individual and merged groups UA levels were associated negatively with RQ and positively with REE (p < 0.0001 for both). In multivariable regression analysis, significant independent predictors of UA were BMI and sex. When BMI was replaced by measures of body composition, %FM and FFM emerged as significant predictors of serum UA (p < 0.0001).

CONCLUSIONS

A potential link relates serum UA to measures of resting energy expenditure and their determinants.

Dietary fish oil ameliorates adipose tissue dysfunction in insulin-resistant rats fed a sucrose-rich diet improving oxidative stress, peroxisome proliferator-activated receptor γ and uncoupling protein 2

This work aims to assess the possible beneficial effects of dietary fish oil (FO) on the pre-existing adipose tissue dysfunction through the improvement or reversion of the mechanisms underlying oxidative stress and pro-inflammatory cytokines in dyslipemic insulin-resistant rats. Wistar rats were fed a sucrose rich diet (SRD) for 6 months. After that half of the animals continued with the SRD until month 8 while in the other half corn oil was replaced by FO for 2 months (SRD + FO). A reference group consumed a control diet all the time. In an epididymal fat pad, we analyzed antioxidant and oxidant enzyme activities, ROS content, glutathione redox state, the protein level of peroxisome proliferator-activated receptor gamma (PPARγ) and the expression and protein levels of uncoupling protein 2 (UCP2) as well as oxidative stress biomarkers and TNF-α and IL-6 plasma levels. Besides these, insulin sensitivity and the composition of fatty acid phospholipids of adipose tissue were measured. Compared with the SRD the SRD + FO fed group showed a decrease of fat pad weight and the antioxidant and oxidant enzyme activities and ROS content returned to control values along with normal plasma TNF-α and IL-6 levels. FO normalized both the decrease of PPARγ protein and the increase of protein and expression of UCP2. Furthermore, FO increased the n-3/n-6 fatty acid ratio in the adipose tissue phospholipids and normalized dyslipidemia and insulin resistance. Finally, these findings reinforce the view that dietary FO may exert a beneficial effect in ameliorating the dyslipidemia and insulin resistance in this animal model.

Effects of Body Mass Index, Glycemic Control, and Hypoglycemic Drugs on Serum Uric Acid Levels in Type 2 Diabetic Patients

Background

Plasma uric acid has been shown to be associated with an increased risk of hypertension, cardiovascular disease, chronic kidney disease, insulin resistance, and metabolic syndrome. Conflicting data regarding plasma uric acid levels in type 2 diabetes mellitus and their role in the development and progression of diabetic complications have been observed by many studies. The present study aimed to evaluate plasma uric acid levels in type 2 diabetic patients and to determine the effects of hypoglycemic drugs and pharmacologic insulin on plasma uric acid concentration.

Subjects and methods

The study included 162 type 2 diabetic patients divided into three groups (insulin taking group (N=58), glibenclamide taking group (N=40), and metformin taking group (N=64), and 47 normal healthy controls. A questionnaire that included variables such as age, sex, duration of disease, and body mass index (BMI) were answered by all the participants. Blood samples were collected and estimated for serum uric acid (SUA), fasting blood sugar (FBS), and glycated hemoglobin (HbA1c) using standard methods and the data were statistically analyzed.

Results

Diabetic patients showed a significant increase in serum uric acid, fasting blood sugar, glycated hemoglobin, and body mass index when compared to control subjects. The serum uric acid levels of metformin and glibenclamide taking groups were significantly higher than the control group. The difference of serum uric concentration between the insulin taking group and both the control and metformin groups was statistically non-significant. On the other hand, obese diabetics showed a significantly higher serum uric acid than overweight and lean diabetics. Furthermore, serum uric acid had a significant strong positive correlation with body mass index.

Conclusion

Type 2 diabetes mellitus (T2DM) is associated with high serum uric acid levels. Hypoglycemic drugs and pharmacologic insulin do not have a large impact on SUA concentration, but obesity seems to be the primary determinant of SUA levels in T2DM patients. The condition of diabetes may have a direct effect on the oxidation of the purine nucleotides resulting in the increased uric acid (UA) levels. In addition, hyperinsulinemia could lead to hyperuricemia by increasing the rate of xanthine oxidase synthesis. There is a strong relationship between T2DM and obesity with high uric acid levels.

Tetragonia tetragonoides (Pall.) Kuntze (New Zealand Spinach) Prevents Obesity and Hyperuricemia in High-Fat Diet-Induced Obese Mice

Tetragonia tetragonoides (Pall.) Kuntze, called New Zealand spinach (NZS), is an edible plant used in salad in Western countries and has been used to treat gastrointestinal diseases in traditional medicine. We examined the anti-obesity and anti-hyperuricemic effects of NZS and the underlying mechanisms in high-fat diet (HFD)-induced obese mice. Mice were fed a normal-fat diet (NFD); high-fat diet (HFD); HFD with 75, 150, or 300 mg/kg NZS extract; or 245 mg/kg Garcinia cambogia (GC) extract. NZS decreased body weight gain, total white adipose tissue (WAT), liver weight, and size of adipocytes and improved hepatic and plasma lipid profiles. With NZS, the plasma levels of the leptin and uric acid were significantly decreased while the levels of the adiponectin were increased. Furthermore, NZS decreased the expression levels of adipogenesis-related genes and xanthine oxidoreductase (XOR), which is involved in uric acid production, while increasing that of proteins associated with fatty acid oxidation. UPLC analysis revealed that NZS contained 6-methoxykaempferol-3-O-β-d-glucosyl(1′′′→2′′)-β-d-glucopyranoside, 6-methoxykaempferol-3-O-β-d-glucosyl(1′′′→2′′)-β-d-glucopyranosyl-(6′′′′-caffeoyl)-7-O-β-d-glucopyranoside, and 6,4′-dimethoxykaempferol-3-O-β-d-glucosyl(1′′′→2′′)-β-d-glucopyranosyl-(6′′′′-caffeoyl)-7-O-β-d-glucopyranoside. These results suggest that NZS exerts anti-obesity, anti-hyperlipidemia, and anti-hyperuricemic effects in HFD-induced obese mice, which are partly explained by regulation of lipid-metabolism-related genes and proteins and decreased expression of XOR.

Activity of xanthine oxidase in plasma correlates with indices of insulin resistance and liver dysfunction in patients with type 2 diabetes mellitus and metabolic syndrome: A pilot exploratory study

Aims/Introduction

There is controversy as to whether hyperuricemia is an independent risk factor for cardiometabolic diseases. The serum level of uric acid is affected by a wide variety of factors involved in its production and excretion. In contrast, evidence has accumulated that locally‐ and systemically‐activated xanthine oxidase (XO), a rate‐limiting enzyme for production of uric acid, is linked to metabolic derangement in humans and rodents. We therefore explored the clinical implication of plasma XO activity in patients with type 2 diabetes mellitus and metabolic syndrome (MetS).

Materials and Methods

We enrolled 60 patients with type 2 diabetes mellitus and MetS. MetS was defined according to the 2005 International Diabetes Federation guidelines. Plasma XO activity was measured by highly‐sensitive fluorometric assay measuring the conversion of pterin to isoxanthopterin, and explored associations between the value of plasma XO activity and metabolic parameters.

Results

The value of plasma XO activity was correlated with indices of insulin resistance and the level of circulating liver transaminases. In contrast, the level of serum uric acid was not correlated with indices of insulin resistance. The value of plasma XO activity was not correlated with the serum uric acid level.

Conclusions

Plasma XO activity correlates with indices of insulin resistance and liver dysfunction in Japanese patients with type 2 diabetes mellitus and MetS. Through assessing the plasma XO activity, patients showing normal levels of serum uric acid with higher activity of XO can be screened, thereby possibly providing a clue to uncovering metabolic risks in type 2 diabetes mellitus and MetS patients.

Hypoxanthine Secretion from Human Adipose Tissue and its Increase in Hypoxia

OBJECTIVE

The production of uric acid in murine white adipose tissue (mWAT), and that such production was augmented in obese mice, was recently reported. However, little is known about the secretion of metabolites associated with purine catabolism in human WAT (hWAT). The present study analyzed this in hWAT.

METHODS

Freshly isolated hWAT and mWAT were cultured. The secretion of metabolites associated with purine catabolism was measured. Tissue distribution profiles of genes associated with purine metabolism and metabolite profiling of adipocytes in hypoxia were analyzed.

RESULTS

Secretion of hypoxanthine from hWAT was higher than those of xanthine and uric acid. On the other hand, secretion of uric acid was relatively higher than xanthine and hypoxanthine in mWAT. Xanthine oxidoreductase (XOR) mRNA expression levels in hWAT were markedly lower than that in the human liver. In murine tissues, XOR mRNA expression levels in mWAT were comparable with those in the liver. Cultured human adipocytes secreted hypoxanthine, and its secretion was increased under hypoxia. The metabolic analysis of human adipocytes showed that hypoxia increased metabolites associated with de novo biosynthesis of purine nucleotides.

CONCLUSIONS

The present study revealed that hypoxanthine was secreted from human adipose tissue, and the secretion might be increased in local hypoxia.

Plasma Xanthine Oxidoreductase Activity as a Novel Biomarker of Metabolic Disorders in a General Population

BACKGROUND

Xanthine oxidoreductase (XOR) is an enzyme that catalyzes the formation of uric acid from hypoxanthine and xanthine, leading to an increase in superoxide and reactive oxygen species. Activation of XOR promotes oxidative stress-related tissue injury. We investigated the associations between metabolic parameters and plasma XOR activity measured by a sensitive and accurate assay using a combination of liquid chromatography and triple quadrupole mass spectrometry to detect [13C2,15N2]-uric acid using [13C2,15N2]-xanthine as a substrate.

METHODS AND RESULTS

A total of 627 Japanese subjects (M/F, 292/335) from the Tanno-Sobetsu Study, a population-based cohort, were recruited. Plasma XOR activity was significantly higher in males than in females, and habitual smoking was associated with elevation of activity. Plasma XOR activity was positively correlated with body mass index (BMI; r=0.323, P<0.001), waist circumference, blood pressure, and levels of liver enzymes including alanine transaminase (r=0.694, P<0.001), uric acid (r=0.249, P<0.001), triglycerides (r=0.312, P<0.001), hemoglobin A1c, fasting glucose, insulin and HOMA-R (r=0.238, P<0.001) as a marker of insulin resistance and was negatively correlated with high-density lipoprotein cholesterol level. On stepwise and multivariate regression analyses, BMI, smoking and levels of alanine transaminase, uric acid, triglycerides and HOMA-R were independent predictors of plasma XOR activity after adjustment for age and gender.

CONCLUSIONS

Plasma XOR activity is a novel biomarker of metabolic disorders in a general population.

Increased plasma xanthine oxidoreductase activity deteriorates coronary artery spasm

Increased reactive oxygen species (ROS) contributes to the development of endothelial dysfunction, which is involved in coronary artery spasm (CAS). Xanthine oxidoreductase (XOR) plays a pivotal role in producing both uric acid and ROS. However, the association between plasma XOR activity and CAS has not been elucidated. The aim of this study was to investigate whether plasma XOR activity is associated with CAS. We measured XOR activity in 104 patients suspected for CAS, who presented without significant coronary artery stenosis and underwent intracoronary acetylcholine provocation tests. CAS was provoked in 44 patients and they had significantly higher XOR activity as compared with those without CAS. The patients were divided into three groups based on the XOR activity. The prevalence rate of CAS was increased with increasing XOR activity. A multivariate logistic regression analysis showed that the 3rd tertile group exhibited a higher incidence of CAS as compared with the 1st tertile group [odds ratio (OR) 6.9, P = 0.001) and the 2nd tertile group (OR 3.2, P = 0.033) after adjustment for conventional CAS risk factors, respectively. The C index was significantly improved by the addition of XOR activity to the baseline model based on CAS risk factors. Furthermore, the 3rd tertile group had the highest incidence of severe spasm defined as total obstruction, flow-limiting stenosis, diffuse spasm, multivessel spasm, and/or lethal arrhythmia. This is a first report to elucidate the association of plasma XOR activity with CAS. Increased plasma XOR activity is significantly associated with CAS.

Habitual exercise decreases plasma xanthine oxidoreductase activity in middle-aged and older women

The aim of present study was to investigate the association between plasma xanthine oxidoreductase activity, which has gained attention as a novel preventive target of cardiovascular disease, and various physiological parameters and was to determine the effects of habitual exercise on plasma xanthine oxidoreductase activity in middle-aged and older women. In the cross-sectional study, we investigated the association between plasma xanthine oxidoreductase activity and various physiological parameters in 94 middle-aged and older women. In the interventional study, subjects (n = 22) were divided into two groups: exercise (n = 12) or the control group (n = 10), whereby we examined the effect of 12-week aerobic exercise training on plasma xanthine oxidoreductase activity in middle-aged and older women. The cross-sectional study demonstrated that plasma xanthine oxidoreductase activity was significantly associated with various physiological parameters, including visceral fat and daily step counts. In the interventional study, the plasma xanthine oxidoreductase activity significantly decreased after the 12-week aerobic exercise training, its changes were inversely associated with the changes in daily step counts. Our results revealed that the plasma xanthine oxidoreductase activity was associated with visceral fat accumulation and lack of exercise, and it was decreased by the aerobic exercise training.

Multiplatform Metabolomics Investigation of Antiadipogenic Effects on 3T3-L1 Adipocytes by a Potent Diarylheptanoid

Obesity is fast becoming a serious health problem worldwide. Of the many possible antiobesity strategies, one interesting approach focuses on blocking adipocyte differentiation and lipid accumulation to counteract the rise in fat storage. However, there is currently no drug available for the treatment of obesity that works by inhibiting adipocyte differentiation. Here we use a broad-based metabolomics approach to interrogate and better understand metabolic changes that occur during adipocyte differentiation. In particular, we focus on changes induced by the antiadipogenic diarylheptanoid, which was isolated from a traditional Chinese medicine Dioscorea zingiberensis and identified as (3 R,5 R)-3,5-dihydroxy-1-(3,4-dihydroxyphenyl)-7-(4-hydroxyphenyl)-heptane (1). Targeted aqueous metabolic profiling indicated that a total of 14 metabolites involved in the TCA cycle, glycolysis, amino acid metabolism, and purine catabolism participate in regulating energy metabolism, lipogenesis, and lipolysis in adipocyte differentiation and can be modulated by diarylheptanoid 1. As indicated by lipidomics analysis, diarylheptanoid 1 restored the quantity and degree of unsaturation of long-chain free fatty acids and restored the levels of 171 lipids mainly from 10 lipid classes in adipocytes. In addition, carbohydrate metabolism in diarylheptanoid-1-treated adipocytes further demonstrated the delayed differentiation process by flux analysis. Our results provide valuable information for further understanding the metabolic adjustment in adipocytes subjected to diarylheptanoid 1 treatment. Moreover, this study offers new insight into developing antiadipogenic leading compounds based on metabolomics.

The role of xanthine oxidoreductase and uric acid in metabolic syndrome

Xanthine oxidoreductase (XOR) could contribute to the pathogenesis of metabolic syndrome through the oxidative stress and the inflammatory response induced by XOR-derived reactive oxygen species and uric acid. Hyperuricemia is strongly linked to hypertension, insulin resistance, obesity and hypertriglyceridemia. The serum level of XOR is correlated to triglyceride/high density lipoprotein cholesterol ratio, fasting glycemia, fasting insulinemia and insulin resistance index. Increased activity of endothelium-linked XOR may promote hypertension. In addition, XOR is implicated in pre-adipocyte differentiation and adipogenesis. XOR and uric acid play a role in cell transformation and proliferation as well as in the progression and metastatic process. Collected evidences confirm the contribution of XOR and uric acid in metabolic syndrome. However, in some circumstances XOR and uric acid may have anti-oxidant protective outcomes. The dual-face role of both XOR and uric acid explains the contradictory results obtained with XOR inhibitors and suggests caution in their therapeutic use.

Deoxyribonucleotide Triphosphate Metabolism in Cancer and Metabolic Disease

The maintenance of a healthy deoxyribonucleotide triphosphate (dNTP) pool is critical for the proper replication and repair of both nuclear and mitochondrial DNA. Temporal, spatial, and ratio imbalances of the four dNTPs have been shown to have a mutagenic and cytotoxic effect. It is, therefore, essential for cell homeostasis to maintain the balance between the processes of dNTP biosynthesis and degradation. Multiple oncogenic signaling pathways, such as c-Myc, p53, and mTORC1 feed into dNTP metabolism, and there is a clear role for dNTP imbalances in cancer initiation and progression. Additionally, multiple chemotherapeutics target these pathways to inhibit nucleotide synthesis. Less is understood about the role for dNTP levels in metabolic disorders and syndromes and whether alterations in dNTP levels change cancer incidence in these patients. For instance, while deficiencies in some metabolic pathways known to play a role in nucleotide synthesis are pro-tumorigenic (e.g., p53 mutations), others confer an advantage against the onset of cancer (G6PD). More recent evidence indicates that there are changes in nucleotide metabolism in diabetes, obesity, and insulin resistance; however, whether these changes play a mechanistic role is unclear. In this review, we will address the complex network of metabolic pathways, whereby cells can fuel dNTP biosynthesis and catabolism in cancer, and we will discuss the potential role for this pathway in metabolic disease.

Uric acid and blood pressure: exploring the role of uric acid production in The Maastricht Study

OBJECTIVE

Accumulation of reactive oxygen species by increased uric acid production has been suggested as a possible underlying mechanism for the association between uric acid and high blood pressure (BP). We, therefore, investigated the association between serum uric acid concentration and 24-h urinary uric acid excretion, as proxy for uric acid production, with ambulatory 24-h blood pressure and hypertension.

METHODS

Cross-sectional analyses were conducted among 2555 individuals [52% men, mean age 60.0 ± 8.2 years; 27% type 2 diabetes (by design)] from The Maastricht Study. Multivariable regression analyses were performed to investigate the association of serum uric acid and 24-h urinary uric acid excretion with 24-h pulse pressure, 24-h mean arterial pressure (MAP), and hypertension.

RESULTS

After adjustment for traditional hypertension risk factors, serum uric acid concentration (per SD of 81 μmol/l) was associated with higher 24-h MAP [β 0.63 mmHg; confidence interval (CI) 0.27-1.00] and positively associated with hypertension (odds ratio 1.43; CI 1.27-1.61). Urinary uric acid excretion (per SD of 140 mg/day/1.73 m) was associated with higher 24-h MAP (β 0.79 mmHg; CI 0.46-1.12) and with hypertension (odds ratio 1.13; CI 1.02-1.25). There was no significant association between serum and 24-h urinary uric acid excretion with 24-h pulse pressure. There was no interaction with sex or age for the aforementioned associations.

CONCLUSION

Higher serum and urinary uric acid concentrations were associated with higher 24-h MAP and hypertension. These results suggest that serum and 24-urinary uric acid concentrations, the latter as proxy for uric acid production are, independent of each other, associated with BP and hypertension.

Elevated serum uric acid predicts the development of moderate coronary artery calcification independent of conventional cardiovascular risk factors

BACKGROUND AND AIMS

Hyperuricemia was frequently noted in subjects with a high risk of cardiovascular disease (CVD). This study aimed to elucidate whether serum uric acid (SUA) is associated with development of moderate coronary artery calcification in generally healthy adults.

METHODS

A total of 9297 subjects underwent multidetector CT for the evaluation of CAC at least two times during their annual health examinations. Among them, 4461 participants without CVD history and who had no (scores 0) or minimal CAC (scores 1-10) in their first examination were enrolled. The association between SUA as a continuous and categorical variable and development of moderate coronary artery calcification (CAC score > 100) was assessed by Cox regression analysis. Receiver-operating characteristic (ROC) curves were constructed to investigate the diagnostic efficacy of SUA.

RESULTS

During a median follow-up of 4.1 years, 131 incident cases of moderate calcification developed. Baseline SUA concentration was significantly higher in subjects with progression to moderate coronary artery calcification (6.6 ± 1.3 vs. 5.8 ± 1.3 mg/dL, p < 0.001). SUA as a continuous variable (per 1 mg/dL) and divided into quartiles was positively associated with a higher risk of development of moderate calcification after adjustment for conventional CVD risk factors. The addition of SUA to the conventional CVD risk factors improved the predictive power for development of moderate coronary artery calcification.

CONCLUSIONS

SUA was an independent predictor for development of moderate coronary artery calcification in subjects with no or minimal calcification.

Hyperuricemia in Asian psoriatic arthritis patients

AIM

It is generally accepted that hyperuricemia is commonly associated with psoriatic arthritis (PsA). However, variations in ethnicity, diet and habitat may contribute to differences in prevalence and risk factors for hyperuricemia in PsA patients. Moreover, Asian specific data is deficient. The primary objective of the present study was to determine the prevalence of hyperuricemia among PsA patients. The secondary objective was to explore its associated risk factors.

METHODS

This was a multi-center, cross-sectional observational study of 160 PsA patients from local Rheumatology clinics. Serum uric acid (SUA) level and other clinical parameters were measured and hyperuricemia was defined as SUA level greater or equal to 360 umol/L in females and 420 umol/L in males.

RESULTS

Forty-nine of 160 patients (30.6%) had hyperuricemia, of which 32 were men, 17 were women. Among those with hyperuricemia, mean SUA level was 500.7 ± 95.9 umol/L and 427.8 ± 83.1 umol/L in males and females, respectively. Univariate analysis found: (i) overweight status; (ii) obesity; (iii) Psoriasis Area and Severity Index; (iv) body surface area; (v) severe skin involvement, as being potentially associated with hyperuricemia. Regression model identified overweight status increased the likelihood of hyperuricemia in PsA, with an odds ratio of 4.4 (95% CI: 2.0-9.5). Furthermore, there was moderately positive correlation (r = 0.37) between body mass index (BMI) and SUA level. No associations were found between arthritis conditions and duration, lipid profile, creatinine clearance; and hyperuricemia.

CONCLUSION

A significant proportion of PsA patients had asymptomatic hyperuricemia. It was closely related with BMI, which represented metabolic dysregulation; but not with severity of skin disease, joint involvement or renal function.

The link between insulin resistance parameters and serum uric acid is mediated by adiposity

BACKGROUND AND AIMS

Conflicting results suggest a link between serum uric acid (SUA), inflammation and glucose/insulin homeostasis; however, the role of adiposity in this relationship is not clear. Therefore, we evaluated the role of different adiposity factors, including central body mass index (BMI), peripheral waist circumference (WC), and visceral adiposity [visceral adipose tissue (apVAT)], on the association between SUA, inflammation and glucose/insulin homeostasis among US adults.

METHODS

Data were extracted from the 2005-2010 US National Health and Nutrition Examination Surveys. Overall, 16,502 participants were included in the analysis (mean age = 47.1 years, 48.2% men). Analysis of co-variance and "conceptus causal mediation" models were applied, while accounting for survey design.

RESULTS

Corrected models showed that subjects with higher SUA levels have a less favorable profile of inflammation and glucose/insulin homeostasis parameters (all p < 0.001). We found that all our potential mediators (BMI, WC and apVAT) had an impact (to various extents) on the link between variables, including serum C-reactive protein (CRP), apolipoprotein-B (apoB), insulin resistance markers, 2-h blood glucose (2hG) and triglyceride, and fasting blood glucose (FBG) (TyG) index (all p < .001), while none of the potential mediators (BMI, apVAT, WC) had an impact on the link between FBG and glycated hemoglobin with SUA (all p > 0.05). We have found that all of our mediators partially mediated the link between inflammation and glucose/insulin homeostasis parameters and SUA. Of note, apVAT fully mediated the association between SUA and 2hG.

CONCLUSIONS

By applying advanced statistical techniques, we shed light on the complex link of SUA with inflammation and glucose/insulin homeostasis and quantify the role of adiposity factors in that link.

Metabolomics Approach in the Study of the Well-Defined Polyherbal Preparation Zyflamend

Zyflamend is a highly controlled blend of 10 herbal extracts that synergistically impact multiple cell signaling pathways with anticancer and anti-inflammatory properties. More recently, its effects were shown to also modify cellular energetics, for example, activation of fatty acid oxidation and inhibition of lipogenesis. However, its general metabolic effects in vivo have yet to be explored. The objective of this study was to characterize the tissue specific metabolomes in response to supplementation of Zyflamend in mice, with a comparison of equivalent metabolomics data generated in plasma from humans supplemented with Zyflamend. Because Zyflamend has been shown to activate AMPK, the "energy sensor" of the cell, in vitro, the effects of Zyflamend on adiposity were also tested in the murine model. C57BL/6 mice were fed diets that mimicked the macro- and micronutrient composition of the U.S. diet with and without Zyflamend supplementation at human equivalent doses. Untargeted metabolomics was performed in liver, skeletal muscle, adipose, and plasma from mice consuming Zyflamend and in plasma from humans supplemented with Zyflamend at an equivalent dose. Adiposity in mice was significantly reduced in the Zyflamend-treated animals (compared with controls) without affecting body weight or weight gain. Based on KEGG pathway enrichment, purine and pyrimidine metabolism (potential regulators of AMPK) were particularly responsive to Zyflamend across all tissues, but only in mice. Consistent with the metabolomics data, Zyflamend activated AMPK and inhibited acetyl CoA-carboxylase in adipose tissue, key regulators of lipogenesis. Zyflamend reduces adipose tissue in mice through a mechanism that likely involves the activation of AMPK.

Gender-related association between uric acid, homocysteine, γ-glutamyltransferase, inflammatory biomarkers and metabolic syndrome in subjects affected by obesity

AIM

Evaluation of gender-related differences in uric acid (UA), homocysteine and inflammatory biomarkers as metabolic syndrome (MetS) determinants.

PATIENTS & METHODS

Anthropometric and routine data were obtained from 825 obese subjects (591 F, mean age 54 ± 14 years).

RESULTS

Hyperuricemia was 24% in both genders. Waist circumference, creatinine, triglycerides, C-reactive protein and γ-glutamyltransferase were identified as UA-independent determinants in females and creatinine and insulin in males. Hyperuricemia increased MetS risk in both genders (2.8-fold and 1.5-fold in males and females).

CONCLUSION

UA and γ-glutamyltransferase positively relate to MetS in both genders, although inflammatory abnormalities are closer related to UA and MetS in females. These differences in gender physiology may account for epidemiologic gender disparities and help to develop gender-targeted clinical strategies.

Serum uric acid levels are associated with homeostasis model assessment in obese nondiabetic patients: HOMA and uric acid

BACKGROUND

Hyperuricemia leads to insulin resistance, whereas insulin resistance decreases renal excretion of uric acid. The aim of this study was to evaluate whether there is a correlation between serum uric acid levels with homeostatic model assessment (HOMA) 1 in nondiabetic patients.

METHODS

We evaluated 88 nondiabetic patients, in whom uric acid levels were measured, in all of them HOMA of β-cell function (HOMA 1B) and HOMA of insulin resistance (HOMA 1IR) scores were performed. Uric acid and the HOMA 1 values were correlated using the Pearson coefficient.

RESULTS

We did not find any correlation between uric acid levels with both HOMA 1B (r = 0.102, p = 0.343), nor with HOMA 1IR (r = 0.158, p = 0.117). When patients were analyzed by sex, we found a significant correlation with HOMA 1IR (0.278, p = 0.01), but not with HOMA 1B (0.138, p = 0.257) in women. We found a correlation with HOMA 1B in men (r = 0.37, p = 0.044), but not with HOMA 1IR: 0.203, p = 0.283. The analysis performed based on body mass index did not show correlation in the patients with normal weight, (HOMA 1B r = 0.08, p = 0.5, HOMA 1IR = 0.034, p = 0.793), nor in the patients who were overweight (HOMA 1B: r = 0.05, p = 0.76, HOMA 1IR r = 0.145, p = 0.43). However, a significant correlation between uricemia with both HOMA 1B (0.559, p < 0.001), and HOMA 1IR (0.326, p < 0.05), was observed in obese patients.

CONCLUSION

Our results suggest that serum uric acid levels seem to be associated with insulin resistance in women, and in obese patients, but not in nonobese men. Uric acid also modifies β-cell function in men and in obese patients.

Metabolomic Profiling of Long-Term Weight Change: Role of Oxidative Stress and Urate Levels in Weight Gain

OBJECTIVE

To investigate the association between long-term weight change and blood metabolites.

METHODS

Change in BMI over 8.6 ± 3.79 years was assessed in 3,176 females from the TwinsUK cohort (age range: 18.3-79.6, baseline BMI: 25.11 ± 4.35) measured for 280 metabolites at follow-up. Statistically significant metabolites (adjusting for covariates) were included in a multivariable least absolute shrinkage and selection operator (LASSO) model. Findings were replicated in the Cooperative Health Research in the Region of Augsburg (KORA) study (n = 1,760; age range: 25-70, baseline BMI: 27.72 ± 4.53). The study examined whether the metabolites identified could prospectively predict weight change in KORA and in the Prostate, Lung, Colorectal, and Ovarian Cancer (PLCO) study (n = 471; age range: 55-74, baseline BMI: 27.24 ± 5.37).

RESULTS

Thirty metabolites were significantly associated with change in BMI per year in TwinsUK using Bonferroni correction. Four were independently associated with weight change in the multivariable LASSO model and replicated in KORA: namely, urate (meta-analysis β [95% CI] = 0.05 [0.040 to 0.063]; P = 1.37 × 10^-19 ), gamma-glutamyl valine (β [95% CI] = 0.06 [0.046 to 0.070]; P = 1.23 × 10^-20 ), butyrylcarnitine (β [95% CI] = 0.04 [0.028 to 0.051]; P = 6.72 × 10^-12 ), and 3-phenylpropionate (β [95% CI] = -0.03 [-0.041 to -0.019]; P = 9.8 × 10^-8 ), all involved in oxidative stress. Higher levels of urate at baseline were associated with weight gain in KORA and PLCO.

CONCLUSIONS

Metabolites linked to higher oxidative stress are associated with increased long-term weight gain.

Visceral adiposity index is strongly associated with hyperuricemia independently of metabolic health and obesity phenotypes

Visceral adiposity index (VAI) is a novel sex-specific index for visceral adipose function; however the association between VAI and hyperuricemia in China is unknown. We aimed to investigate this association, also whether it was independent of metabolic health and obesity phenotypes. 7632 adult subjects from the China Health and Nutrition Survey 2009 were retained. Subjects were categorized into four obesity phenotypes based on a cross-classification of BMI and metabolic health status by two representative criteria. VAI was the best predictors for hyperuricemia irrespective of obesity phenotypes, with area under curve (AUC) ranging 0.665–0.719. The odd ratio (OR) for hyperuricemia in the highest quartile of the VAI were 6.93 (95% CI 5.79–8.29) after adjusting for age and gender. Following further adjustments for metabolic obesity phenotypes and lifestyle confounders, the ORs were 4.88 (3.92–6.09) and 5.65 (4.68–6.82) according to these two criteria, respectively. A similar significant pattern was still found even after adjustment for blood pressure and other cardiovascular risks. Within each metabolic obesity phenotype, the significant association between VAI and hyperuricemia was consistently evident. In conclusion, the association of the VAI with hyperuricemia was significant, especially this association was independent of metabolic health and obesity phenotypes in the Chinese population.

Visceral fat mass: is it the link between uric acid and diabetes risk?

BACKGROUND

Uric acid (UA) has been suggested as a novel risk factor for diabetes. However, its definite role in this prevalent disease is still the subject of much discussion because it is always accompanied with other major risk factors such as obesity and high visceral adiposity. In order to clarify the role of UA in diabetes, this study aimed to investigate the associations between plasma UA and fasting plasma glucose, HbA1c, lipid profile and inflammatory markers after accounting for the contribution of other diabetes risk factors such as BMI and VAT fat mass.

METHODS

In the present cross-sectional study, 100 non-diabetic middle-aged males (n = 48) and females (n = 52) were recruited. Central fat distribution measures including android to gynoid fat ratio, VAT and subcutaneous adipose tissue (SAT) fat mass were determined using dual-energy X-ray absorptiometry (DXA). Biochemical analysis was done using methods well established for clinical and research laboratories. Multiple linear regression analysis was performed to analyse the association between plasma UA and the biochemical and central fat distribution measures.

RESULTS

UA was positivly associated with body mass index (BMI) (r (98) = 0.42, P ≤ 0.001), android to gynoid fat ratio (r (98) = 0.62, P ≤ 0.001) and VAT fat mass (r (96) = 0.55, P ≤ 0.001). UA was also positively associated with plasma glucose (r (98) = 0.33, P ≤ 0.001), hemoglobin A1c (r (93) = 0.25, P = 0.014), plasma triglyceride (r _s (95) = 0.40, P ≤ 0.001), HDL cholesterol (r (98) = - 0.61, P ≤ 0.001) and CRP (r _s (98) = 0.23, P = 0.026). However, these associations were no longer significant after accounting for BMI or/and VAT fat mass. No significant association was observed between UA and SAT fat mass (r (97) = 0.02, P ≥ 0.05), Total cholesterol (r (98) = 0.03, P ≥ 0.05), LDL cholesterol (r (98) = 0.13, P ≥ 0.05), TNF-α (r (97) = 0.12, P ≥ 0.05) and IL-6 (r (96) = -0.02, P ≥ 0.05).

CONCLUSION

Results from this study suggest, for the first time, that the association between plasma UA and glucose in a non-diabetic population is not direct but rather dependent on VAT fat mass.

Association between serum uric acid and metabolic syndrome components in prepubertal obese children (Tanner Stage I) from Nuevo León, Mexico - a preliminary study

BACKGROUND

Metabolic syndrome (MetS) is a major risk factor for cardiovascular disease and diabetes. Previous studies in obese children demonstrating a positive association between serum uric acid (sUA) and components of MetS are confounded by lack of uniformity in age and pubertal status of children. Therefore, we have examined the role of sUA in MetS and its components in pre-pubertal children (Tanner Stage I, age ≤ 9 years).

METHODS

Pre-pubertal obese children (32 boys, 27 girls, age 6-9 years) were recruited from Nuevo Leon, Mexico. For comparison, an equal number of children with normal body mass index (BMI) in the same age range (22 Boys, 39 girls, age 6-9 years) were also recruited from the same community. Presence of MetS and its components was defined according to the criteria of International Diabetes Federation. Fasting blood was analyzed for lipids, glucose, insulin, and uric acid.

RESULTS

Among the obese children, sUA was positively associated with insulin resistance and hypertriglyceridemia and negatively associated with high density lipoprotein-cholesterol (HDLc). Subjects were three times more likely to have a MetS diagnosis per one unit (md/dL) difference in sUA. Of the 59 obese pre-pubertal children, 20 were classified as having MetS defined by the presence of abdominal obesity and two or more of other components described under methods. Of these, 57.1% (20/61) had sUA between 5.1 and 7.1 mg/dl.

CONCLUSIONS

The findings of this study clearly indicate a positive relationship between uric acid and MetS and its components in pre-pubertal obese children with Tanner stage I and ≤9 years of age.

Associations of Body Mass Index With Laboratory and Biomarkers in Patients With Acute Heart Failure

BACKGROUND

Plasma concentrations of natriuretic peptides decline with obesity in patients with heart failure. Whether this is true for other biomarkers is unknown. We investigated a wide range of biomarker profiles in acute heart failure across the body mass index (BMI) spectrum.

METHODS AND RESULTS

A total of 48 biomarkers, assessing multiple pathophysiological pathways, were measured in 2033 patients included in PROTECT (Placebo-Controlled Randomized Study of the Selective A1 Adenosine Receptor Antagonist Rolofylline for Patients Hospitalized With Acute Decompensated Heart Failure and Volume Overload to Assess Treatment Effect on Congestion and Renal Function), a trial comparing the effects of rolofylline to placebo in patients with acute heart failure. Patients were classified into 4 groups according to BMI (<25, 25-30, 30-35, and >35 kg/m²). Of 2003 patients with known weight and height, mean age was 70±12 years and 67% were men. Patients with a higher BMI (>35 kg/m²) had higher blood pressures, were younger, and were more often women. Median levels of brain natriuretic peptide were 550 pg/mL in patients with a BMI <25 kg/m² and 319 pg/mL in patients with a BMI >35 kg/m² (P<0.001). Multivariable regression revealed that brain natriuretic peptide (β=-0.250; P<0.001) and receptor for advanced glycation endproducts (β=-0.095; P<0.007) were inversely correlated to BMI, whereas higher levels of uric acid (β=0.164; P<0.001), proadrenomedullin (β=0.171; P<0.001), creatinine (β=0.118; P=0.003), sodium (β=0.101; P=0.006), and bicarbonate (β=0.094; P=0.009) were associated with higher BMI. No significant interaction was seen between these 7 biomarkers and BMI on 180-day mortality.

CONCLUSIONS

The plasma concentrations of several biomarkers are either positively or negatively influenced by BMI. These findings suggest that these markers should be interpreted with caution in patients with obesity. Although concentrations differ, their prognostic value for mortality up to 180 days did not differ.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00354458.

Xanthine oxidoreductase activity is correlated with insulin resistance and subclinical inflammation in young humans

BACKGROUND AND AIMS

The enzyme xanthine oxidoreductase (XOR) catalyzes the formation of uric acid (UA) from hypoxanthine and xanthine, which in turn are products of purine metabolism starting from ribose-5-phosphate. Besides the synthesis of UA, basic research has suggested that XOR is involved in the regulation of reactive oxygen species, adipogenesis, and peroxisome proliferator-activated receptor-γ (PPAR-γ). XOR activity has shown to be much lower in humans than in rodents, which makes its accurate measurement difficult. Recently, a novel human plasma XOR activity assay has been established using a combination of liquid chromatography (LC) and triple quadrupole mass spectrometry (TQMS) to detect [¹³C₂,¹⁵N₂]UA using [¹³C₂,¹⁵N₂]xanthine as a substrate. Using this novel assay, we for the first time determine plasma XOR activity in humans, and evaluate its association with insulin resistance, high-sensitivity C-reactive protein (hsCRP) levels, and other parameters.

METHODS

Of the 29 volunteers who wished to participate in the study, 3 were excluded; of the remaining, 11 were female and 15 were male with a mean age of 25.9±3.3years. Blood samples were collected under fasting conditions in the early morning to measure XOR activity and other parameters.

RESULTS

The natural logarithmic value of XOR activity (ln-XOR) in plasma was 3.4±0.8pmol/h/mL. Ln-XOR had a positive correlation with UA and body mass index (BMI) and a negative correlation with quantitative insulin sensitivity check index (QUICKI) and adiponectin. In addition, ln-XOR had a positive correlation with hsCRP levels, which serves as a marker of chronic inflammation.

CONCLUSIONS

The present study has shown that XOR activity is correlated with serum UA levels in humans. Furthermore, even in young subjects, XOR activity is correlated with insulin resistance, BMI, and subclinical inflammation. Thus, XOR activity may be potentially involved in adiposity and subclinical inflammation in humans.