Urinary Fructose Research Articles

In house cost effective seminal and urinary fructose testing in andrology laboratories

In house cost effective seminal and urinary fructose testing in andrology laboratories

Sugars measured enzymatically in a fasting overnight urine sample are not sensitive biomarkers of dietary added sugar intake in postmenopausal women.

Restricting dietary sugar is a leading recommendation, but limited biomarkers assessing intake exist. Although 24-h urinary sucrose (U-Suc) and urinary fructose (U-Fruc) excretion has been used with mixed success, collection is burdensome. This study aimed to test the sensitivity of an enzymatic assay of U-Suc and U-Fruc to detect changing added sugar intake using low-burden overnight urine samples in 30 postmenopausal women. Women consumed usual dietary intake during day 1 and usual intake plus a sugar sweetened beverage during day 2. Weighed, photographed food records assessed intake. Enzymatic assay measured U-Suc and U-Fruc from fasting overnight samples; liquid chromatography mass spectrometry (LC-MS) validated U-Suc findings. Dietary added sugars increased significantly during day 2 (p < 0.001), but urinary sugars were not significantly increased. Enzymatic assay detected urinary sugars in 75% (U-Suc) and 35% (U-Fruc) of samples. Dietary sucrose was not associated with U-Suc, however dietary fructose was significantly associated with U-Fruc [β = 0.031; p < 0.05] among women with detectable urinary sugars. Participants with detectable U-Fruc consumed more energy from added sugars [12.6% kcal day 1; 21.5% kcal day 2] than participants with undetectable U-Fruc [9.3% kcal day 1; 17.4% kcal day 2], p < 0.05. Using LC-MS, U-Suc predicted sucrose and added sugar intake [β = 0.017, β = 0.013 respectively; both p < 0.05]. Urinary sugars measured enzymatically from overnight urine samples were not sensitive biomarkers of changing added sugar intake in postmenopausal women. However, urinary fructose measured by enzymatic assay or LC-MS may differentiate low versus high added sugar consumers.

Rationale, Design and Baseline Characteristics for the Strategies to Oppose SUGARS With Non-nutritive Sweeteners or Water (STOP Sugars NOW) Trial

ObjectivesHealth authorities recommend reducing added or free sugars to ≤5–10% energy. Much attention has focussed of the reduction of SSBs with the recommendation that SSBs be replaced with unsweetened healthy alternatives such as water but not non-nutritive sweetened beverages (NSBs). There are concerns that non-nutritive sweeteners do not have the intended benefits and may induce glucose intolerance through changes in the gut microbiome. Whether NSBs have benefits similar to water in their intended substitution for SSBs is unclear. MethodsTo address this question, we have undertaken the STOP Sugars NOW trial (NCT03543644), a pragmatic “head-to-head” crossover randomized controlled trial of the effect of NSBs (the intended substitution) versus water (the standard of care) as a replacement strategy for SSBs on glucose tolerance and gut microbiome diversity. We recruited overweight or obese participants with a high waist circumference who regularly consume ≥1 SSBs/day. Each participant underwent a ≥2-week run-in period followed by three 4- week treatment phases in random order (usual SSBs, equivalent NSBs, or water) with each phase separated by a ≥4-week washout. The two primary outcomes are change in glucose tolerance and gut microbiome beta- diversity. Adherence to the interventions will be assessed by objective biomarkers of added sugars (13C/12C isotopic ratio in serum fatty acids and urinary fructose and sucrose) and non-nutritive sweeteners (urinary sucralose and acesulfame-potassium). ResultsThe trial started on June 1st, 2018 with the first participant undergoing randomization on August 1st, 2019 and the last participant finishing on October 15th, 2020. We screened 1,086 individuals, out of which 80 were randomized. Baseline characteristics showed a mean age of 41.8 ± 13.0 y, BMI of 33.7 ± 6.8 kg/m2, waist circumference of 108.7 ± 13.5 cm, and mean SSBs intake of 2 SSBs/day. ConclusionsThe results of this trial will directly inform public health guidance on the use of NSBs in sugars reduction strategies. Funding SourcesCIHR.

Effects of fructose restriction on liver steatosis (FRUITLESS); a double-blind randomized controlled trial

ABSTRACTBackgroundThere is an ongoing debate on whether fructose plays a role in the development of nonalcoholic fatty liver disease.ObjectivesThe aim of this study was to investigate the effects of fructose restriction on intrahepatic lipid (IHL) content in a double-blind randomized controlled trial using an isocaloric comparator.MethodsBetween March 2017 and October 2019, 44 adult overweight individuals with a fatty liver index ≥ 60 consumed a 6-wk fructose-restricted diet (<7.5 g/meal and <10 g/d) and were randomly assigned to supplementation with sachets of glucose (= intervention group) or fructose (= control group) 3 times daily. Participants and assessors were blinded to the allocation. IHL content, assessed by proton magnetic resonance spectroscopy, was the primary outcome and glucose tolerance and serum lipids were the secondary outcomes. All measurements were conducted in Maastricht University Medical Center.ResultsThirty-seven participants completed the study protocol. After 6 wk of fructose restriction, dietary fructose intake and urinary fructose excretion were significantly lower in the intervention group (difference: −57.0 g/d; 95% CI: −77.9, −39.5 g/d; and −38.8 μmol/d; 95% CI: −91.2, −10.7 μmol/d, respectively). Although IHL content decreased in both the intervention and control groups (P < 0.001 and P = 0.003, respectively), the change in IHL content was more pronounced in the intervention group (difference: −0.7% point, 95% CI: −2.0, −0.03% point). The changes in glucose tolerance and serum lipids were not significantly different between groups.ConclusionsSix weeks of fructose restriction per se led to a small, but statistically significant, decrease in IHL content in comparison with an isocaloric control group.This trial was registered at clinicaltrials.gov as NCT03067428.

The Relationship between Daily Fructose Consumption and Oxidized Low-Density Lipoprotein and Low-Density Lipoprotein Particle Size in Children with Obesity.

PurposeObesity has become a very significant health problem in childhood. Fructose taken in an uncontrolled manner and consumed in excessive amounts is rapidly metabolized in the body and gets converted into fatty acids. This single center prospective case-control study aims to investigate the relationship between fructose consumption and obesity and the role of fructose consumption in development of atherosclerotic diseases.MethodsA total of 40 obese and 40 healthy children who were of similar ages (between 8 and 18 years) and sexes were included in the study. In the patient and control groups, the urine fructose levels, as well as the levels of oxidized low-density lipoprotein (LDL), small dense LDL, Apolipoprotein A and Apolipoprotein B values, which have been shown to play a role in development of atherosclerotic diseases, were measured.ResultsThe levels of oxidized LDL and small dense LDL and the ratio of Apolipoprotein A/Apolipoprotein B were found to be significantly higher in the patient group.ConclusionWe found that urinary fructose levels were higher in the obese children than the healthy children. Our results suggest that overconsumption of fructose in children triggers atherogenic diseases by increasing the levels of small dense LDL and oxidized LDL and the ratio of Apolipoprotein B/Apolipoprotein A.

Development and validation of a UPLC-MS/MS method to quantify fructose in serum and urine

BackgroundThe study of the involvement of fructose in the pathogenesis of cardiometabolic disease requires accurate and precise measurements of serum and urinary fructose. The aim of the present study was to develop and validate such a method by Ultra Performance Liquid Chromatography–tandem Mass Spectrometry (UPLC-MS/MS). MethodsFructose was quantified using hydrophilic interaction UPLC-MS/MS with a labelled internal standard. Serum fructose levels were determined in healthy individuals (n = 3) after a 15-gram oral fructose load. Twenty-four hours urinary fructose levels were determined in individuals consuming low (median: 1.4 g/day, interquartile range [IQR]: 0.9–2.0; n = 10), normal (31 g/day, 23–49; n = 15) and high (70 g/day, 55–84; n = 16) amounts of fructose. ResultsThe calibration curves showed perfect linearity in water, artificial, serum, and urine matrices (r2 > 0.99). Intra- and inter-day assay variation of serum and urinary fructose ranged from 0.3 to 5.1% with an accuracy of ~98%. Fasting serum fructose levels (5.7 ± 0.6 µmol/L) increased 60 min after a 15-gram oral fructose load (to 150.3 ± 41.7 µmol/L) and returned to normal after 180 min (8.4 ± 0.6 µmol/L). Twenty-four hours urinary fructose levels were significantly lower in low fructose consumers when compared to normal and high fructose consumers (median: 36.1 µmol/24 h, IQR: 26.4–64.2; 142.3 µmol/24 h, 98.8–203.0; and 238.9 µmol/24 h, 127.1–366.1; p = 0.004 and p < 0.001, respectively). ConclusionFructose concentrations can be measured accurately and precisely with this newly-developed UPLC-MS/MS method. Its robustness makes it suitable for assessing the value of fructose in clinical studies.

Sugar intake among German adolescents: trends from 1990 to 2016 based on biomarker excretion in 24-h urine samples.

Trend analyses based on dietary records suggest decreases in the intakes of total sugar (TS), added and free sugar since 2005 among children and adolescents in Germany. In terms of age trends, TS intake decreased with increasing age. However, self-reported sugar intake in epidemiological studies is criticised, as it may be prone to bias due to selective underreporting. Furthermore, adolescents are more susceptible to underreporting than children. We thus analysed time and age trends in urinary fructose excretion (FE), sucrose excretion (SE) and the sum of both (FE + SE) as biomarkers for sugar intake among 8·5-16·5-year-old adolescents. Urinary sugar excretion was measured by UPLC-MS/MS in 997 24-h urine samples collected from 239 boys and 253 girls participating in the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study cohort between 1990 and 2016. Time and age trends of log-transformed FE, SE and FE + SE were analysed using polynomial mixed-effects regression models. Between 1990 and 2016, FE as well as FE + SE decreased (linear time trend: P = 0·0272 and P < 0·0001, respectively). A minor increase in excretion during adolescence was confined to FE (linear age trend: P = 0·0017). The present 24-h excretion measurements support a previously reported dietary record-based decline in sugar intake since 2005. However, the previously seen dietary record-based decrease in TS from childhood to late adolescence was not confirmed by our biomarker analysis, suggesting a constant sugar intake for the period of adolescence.

Fructose reabsorption by rat proximal tubules: role of Na+-linked cotransporters and the effect of dietary fructose.

Fructose consumption has increased because of widespread use of high-fructose corn syrup by the food industry. Renal proximal tubules are thought to reabsorb fructose. However, fructose reabsorption (Jfructose) by proximal tubules has not yet been directly demonstrated, nor the effects of dietary fructose on Jfructose. This segment expresses Na+- and glucose-linked transporters (SGLTs) 1, 2, 4, and 5 and glucose transporters (GLUTs) 2 and 5. SGLT4 and -5 transport fructose, but SGLT1 and -2 do not. Knocking out SGLT5 increases urinary fructose excretion. We hypothesize that Jfructose in the S2 portion of the proximal tubule is mediated by luminal entry via SGLT4/5 and basolateral exit by GLUT2 and that it is enhanced by a fructose-enriched diet. We measured Jfructose by proximal straight tubules from rats consuming either tap water (Controls) or 20% fructose (FRU). Basal Jfructose in Controls was 14.1 ± 1.5 pmol·mm-1·min-1. SGLT inhibition with phlorizin reduced Jfructose to 4.9 ± 1.4 pmol·mm-1·min-1 ( P < 0.008), whereas removal of Na+ diminished Jfructose by 86 ± 5% ( P < 0.0001). A fructose-enriched diet increased Jfructose from 12.8 ± 2.5 to 19.3 ± 0.5 pmol·mm-1·min-1, a 51% increase ( P < 0.03). Using immunofluorescence, we detected luminal SGLT4 and SGLT5 and basolateral GLUT2; GLUT5 was undetectable. The expression of apical transporters SGLT4 and SGLT5 was higher in FRU than in Controls [137 ± 10% ( P < 0.01) and 38 ± 14% ( P < 0.04), respectively]. GLUT2 was also elevated by 88 ± 27% ( P < 0.02) in FRU. We conclude that Jfructose by proximal tubules occurs primarily via Na+-linked cotransport processes, and a fructose-enriched diet enhances reabsorption. Transport across luminal and basolateral membranes is likely mediated by SGLT4/5 and GLUT2, respectively.

Ketohexokinase knockout mice, a model for essential fructosuria, exhibit altered fructose metabolism and are protected from diet-induced metabolic defects.

Fructose consumption in humans and animals has been linked to enhanced de novo lipogenesis, dyslipidemia, and insulin resistance. Hereditary deficiency of ketohexokinase (KHK), the first enzymatic step in fructose metabolism, leads to essential fructosuria in humans, characterized by elevated levels of blood and urinary fructose following fructose ingestion but is otherwise clinically benign. To address whether KHK deficiency is associated with altered glucose and lipid metabolism, a Khk knockout (KO) mouse line was generated and characterized. NMR spectroscopic analysis of plasma following ingestion of [6-13C] fructose revealed striking differences in biomarkers of fructose metabolism. Significantly elevated urine and plasma 13C-fructose levels were observed in Khk KO vs. wild-type (WT) control mice, as was reduced conversion of 13C-fructose into plasma 13C-glucose and 13C-lactate. In addition, the observation of significant levels of fructose-6-phosphate in skeletal muscle tissue of Khk KO, but not WT, mice suggests a potential mechanism, whereby fructose is metabolized via muscle hexokinase in the absence of KHK. Khk KO mice on a standard chow diet displayed no metabolic abnormalities with respect to ambient glucose, glucose tolerance, body weight, food intake, and circulating trigylcerides, β-hydroxybutyrate, and lactate. When placed on a high-fat and high-fructose (HF/HFruc) diet, Khk KO mice had markedly reduced liver weight, triglyceride levels, and insulin levels. Together, these results suggest that Khk KO mice may serve as a good model for essential fructosuria in humans and that inhibition of KHK offers the potential to protect from diet-induced hepatic steatosis and insulin resistance.

Urinary sucrose and fructose to validate self-reported sugar intake in children and adolescents: results from the I.Family study.

Excessive consumption of free sugar increases the risk for non-communicable diseases where a proper assessment of this intake is necessary to correctly estimate its association with certain diseases. Urinary sugars have been suggested as objective biomarkers for total and free sugar intake in adults but less is known about this marker in children and adolescents. Therefore, the aim of this exploratory study is to evaluate the relative validity of self-reported intake using urinary sugars in children and adolescents. The study was conducted in a convenience subsample of 228 participants aged 5-18years of the I.Family study that investigates the determinants of food choices, lifestyle and health in European families. Total, free and intrinsic sugar intake (g/day) and sugar density (g/1000kcal) were assessed using 24-h dietary recalls (24HDRs). Urinary sucrose (USUC) and urinary fructose (UFRU) were measured in morning urine samples and corrected for creatinine excretion (USUC/Cr, UFRU/Cr). Correlation coefficients, the method of triads and linear regression models were used to investigate the relationship between intake of different types of sugar and urinary sugars. The correlation between usual sugar density calculated from multiple 24HDRs and the sum of USUC/Cr and UFRU/Cr (USUC/Cr + UFRU/Cr) was 0.38 (p < 0.001). The method of triads revealed validity coefficients for the 24HDR from 0.64 to 0.87. Linear regression models showed statistically significant positive associations between USUC/Cr + UFRU/Cr and the intake of total and free sugar. These findings support the relative validity of total and free sugar intake assessed by self-reported 24HDRs in children and adolescents.

A pilot study with early adolescents: dealing with diet, tobacco and air pollution using practical experiences and biological markers

BackgroundTobacco use and the Western diet are two of the most important and investigated topics in relation to adolescents’ health. In addition, air pollution is a crucial subject for future generations. School is a key social environment that should promote healthy behaviors in children and adolescents. In this field many different programs have been conducted, with mixed results and effectiveness. Research data suggest that comprehensive and multicomponent approaches may have a greater effect on tobacco use and diet, especially when integrated into a community-wide approach.MethodsThe present work describes a multi-area pilot study called “La Scuola della Salute” (the School of Health) with a focus on the methodological aspects of the intervention. In our study we assessed different web-based and practical experiences related to adolescents’ smoking and dietary behaviors and awareness of smoke-related air pollution. Furthermore, to make adolescents more conscious of smoking and dietary behaviors, we conducted experiential workshops that addressed smoking and environmental pollution, food education, and lifestyle. Teachers and school administrators were involved in the project.ResultsAt baseline we investigated dietary habits, tobacco use, and individual and social characteristics by means of lifestyle questionnaires. In addition, we collected anthropometric parameters and performance indicators such as exhaled carbon monoxide and urinary fructose to assess smoking and nutrition habits. At the end of the intervention lifestyle questionnaire and biological markers were collected again: knowledge about these topics was significantly improved, and the urinary fructose was able to estimate the levels of obesity in the classes.ConclusionsThe integrated approach, combined with the use of biological markers, could be an innovative approach to the promotion of healthy lifestyles among adolescents, but further research is needed.

A pilot study with early adolescents: dealing with diet, tobacco and air pollution using practical experiences and biological markers

Background: Tobacco use and the Western diet are two of the most important and investigated topics in relation to adolescents’ health. In addition, air pollution is a crucial subject for future generations. School is a key social environment that should promote healthy behaviors in children and adolescents. In this field many different programs have been conducted, with mixed results and effectiveness. Research data suggest that comprehensive and multicomponent approaches may have a greater effect on tobacco use and diet, especially when integrated into a community-wide approach. Methods: The present work describes a multi-area pilot study called “La Scuola della Salute” (the School of Health) with a focus on the methodological aspects of the intervention. In our study we assessed different web-based and practical experiences related to adolescents’ smoking and dietary behaviors and awareness of smoke-related air pollution. Furthermore, to make adolescents more conscious of smoking and dietary behaviors, we conducted experiential workshops that addressed smoking and environmental pollution, food education, and lifestyle. Teachers and school administrators were involved in the project. Results: At baseline we investigated dietary habits, tobacco use, and individual and social characteristics by means of lifestyle questionnaires. In addition, we collected anthropometric parameters and performance indicators such as exhaled carbon monoxide and urinary fructose to assess smoking and nutrition habits. At the end of the intervention lifestyle questionnaire and biological markers were collected again: knowledge about these topics was significantly improved, and the urinary fructose was able to estimate the levels of obesity in the classes. Conclusions: The integrated approach, combined with the use of biological markers, could be an innovative approach to the promotion of healthy lifestyles among adolescents, but further research is needed.

Protective role of fructokinase blockade in the pathogenesis of acute kidney injury in mice

Acute kidney injury is associated with high mortality, especially in intensive care unit patients. The polyol pathway is a metabolic route able to convert glucose into fructose. Here we show the detrimental role of endogenous fructose production by the polyol pathway and its metabolism through fructokinase in the pathogenesis of ischaemic acute kidney injury (iAKI). Consistent with elevated urinary fructose in AKI patients, mice undergoing iAKI show significant polyol pathway activation in the kidney cortex characterized by high levels of aldose reductase, sorbitol and endogenous fructose. Wild type but not fructokinase knockout animals demonstrate severe kidney injury associated with ATP depletion, elevated uric acid, oxidative stress and inflammation. Interestingly, both the renal injury and dysfunction in wild-type mice undergoing iAKI is significantly ameliorated when exposed to luteolin, a recently discovered fructokinase inhibitor. This study demonstrates a role for fructokinase and endogenous fructose as mediators of acute renal disease.

Lord Walton of Detchant

OBJECTIVE—To investigate fructose metabolic changes in patients with diabetes. RESEARCH DESIGN AND METHODS—Serum and urinary fructose concentrations were determined in healthy subjects (n = 23) and in nondiabetic (n =...

Hyponatremia with Persistent Elevated Urinary Fractional Uric Acid Excretion: Evidence for Proximal Tubular Injury?

Background/Aims: Hyponatremia associated with high urinary fractional excretion of uric acid which persists after serum sodium is corrected is the cardinal feature of salt losing nephropathy (SLN). We hypothesize that low grade proximal tubular injury is present in SLN because the proximal tubule is the main site of uric acid and sodium transport. Methods: Five subjects with SLN were compared to four subjects with recurrent hyponatremia and three healthy individuals. Urinary NGAL (neutrophil gelatinase associated lipocalin, a marker of tubular injury) and fasting urinary fructose levels (a marker of proximal tubular injury) were measured. Results: Subjects with SLN (n=5) showed elevated fractional uric acid excretion (22 ± 6 vs 4 ± 2 percent, p<0.0001), elevated urinary NGAL levels (62 ± 37 vs 9 ± 7 ng/mg creatinine, p=0.001) and fasting urinary fructose levels compared with the 7 controls (383 ± 465 vs 60 ± 34µmole/µg creatinine, p <0.001). A strong correlation between urinary NGAL levels and urinary fructose levels was observed (r =0.87, p‹0.001). Conclusion: High urinary fractional excretion of uric acid in SLN is associated with elevated NGAL and fasting urinary fructose levels suggesting that SLN may involve tubular injury.

Urinary sugars excretion as an estimate of sugars intakes is limited in its relationship to cardio‐metabolic risk factors

BackgroundConclusive evidence on the role of free sugars intakes in cardio‐metabolic disease development is confounded by bias in self‐reported measures of intake.ObjectiveTo examine associations between urinary sugars excretion as an objective biomarker for free sugars intakes and cardio‐metabolic risk factors.MethodsIn an 8‐wk intervention study, participants consumed different beverages (orange juice, sugar sweetened beverages, diet soft drink, or milk). For the analyses we used data of 41 participants. Linear regression was used to examine urinary sugars excretion against body mass index (BMI), waist circumference (WC), and biochemical indicators (CRP, total cholesterol, LDL, HDL, TAG, insulin, uric acid, AST, and ALT).ResultsUrinary fructose excretion was associated with total cholesterol (B=0.009; p=0.031). Change in urinary sucrose and fructose together was associated with waist circumference (B=0.014; p=0.033). When corrected for baseline measures and sex, the change in urinary sucrose and urinary fructose were not associated with BMI, blood pressure, or percentage body fat, nor was urinary sucrose excretion associated with any of the biochemical indicators. Changes in urinary sugars excretion and self reported values were not associated with treatment (p=0.964 and p=0.536 respectively).ConclusionThe results of this study show no convincing evidence for the change in sugars intakes and the association with cardio‐metabolic risk factors.

Association between fructose, uric acid and blood pressure

Sugars, and in particular fructose, consumption has been associated with increased systolic and diastolic blood pressure (BP), mediated by increased serum uric acid concentration, which interferes with the renin‐angiotensin mechanism and inhibits nitric oxide release from endothelial cells. Uric acid can also increase sodium sensitivity.Investigating associations between dietary sugars and health endpoints is difficult because of measurement error in self‐reported intake. Dietary biomarkers may help us elucidate true associations.We have assessed total sugars and total fructose intake (including fructose from sucrose) in a cross‐sectional analysis of 1366 participants (624 men, 742 women), 39 – 77 years of age, of the Norfolk cohort of the European Prospective Investigation into Cancer (EPIC) study using 7‐day diaries and sucrose and fructose measured in spot urines, as biomarkers of sugars intake. Other study measurements include serum uric acid and BP. Associations were investigated using linear regression analyses with log‐transformed variables, stratified by sex and adjusted for age and BMI. Urinary concentrations were adjusted by specific gravity.Total sugars consumption (mean ± SD) was 111.7 ± 40.3 g/d, of which 44.3 ± 17.9 g/d was total fructose. Serum uric acid was 344 ± 66 µM. Serum uric acid concentration was not associated with systolic BP in men and women. Intake of total sugars and total fructose assessed by 7‐d diary or biomarker was not significantly associated with serum uric acid or with BP.Our results do not support an association between fructose intake and increased BP. Adjusted (age, BMI) systolic BP mm Hg (mean, 95% CI) by quintile of total fructose intake in 624 men and 742 women of EPIC Norfolk. Intake was measured by biomarker (urinary fructose) and 7DD (adjusted for total energy intake). Men (n=624) Women (n=742) Intake Biomarker 7DD Biomarker 7DD Q1 137.4 (136.3; 138.6) 136.9 (135.9; 138.0) 132.2 (131.0; 133.5) 131.2 (129.9; 132.6) Q2 136.7 (135.6; 137.8) 137.1 (135.8; 138.3) 132.7 (131.4; 134.0) 131.8 (130.5; 133.1) Q3 136.9 (135.7; 138.0) 137.1 (135.9; 138.3) 132.5 (131.3; 133.8) 133.5 (132.2; 134.8) Q4 137.4 (136.2; 138.5) 136.8 (135.6; 138.1) 132.3 (131.0; 133.6) 132.2 (130.8; 133.5) Q5 137.0 (135.8; 138.2) 137.5 (131.7; 132.9) 131.8 (130.3; 133.2) 132.9 (131.7; 134.0)

Simultaneous analysis of urinary fructose and sucrose by isotope dilution tandem LCMS (959.14)

Objective: Sugar intake has increased vastly in the US diet during past decades and has been associated with obesity, metabolic syndrome, type 2 diabetes, cardiovascular disease, and cancer. Measuring sugar intake by FFQ is not reliable and urinary fructose and sucrose excretion as a biomarker is recommended but existing methods for their analysis are complex, expensive or unreliable (GCMS, enzymatic kits, doubly labeled water). A simple liquid chromatography mass spectrometry (LCMS) method was therefore established for urinary fructose and sucrose.Methods: This study evaluated many extraction, chemical derivatization and electrospray ionization (ESI) tandem MS variations in positive and negative mode using isotope dilution and reversed, normal or reversed reversed phase LC protocols.Results: While sucrose was measurable reliably by many LCMS protocols myriads of interferences with fructose measurements could be avoided by derivatization of fructose to its dansyl hydrazone or by selective application of organic solvents during urine extraction.Conclusions: A reliable, simple, fast and inexpensive isotope dilution tandem ESI LCMS assay for fructose and sucrose was established requiring 20 uL or less of urine.Grant Funding Source: This research was supported by National Cancer Institute grants P30 CA71789.

Comparison and validation of 2 analytical methods for measurement of urinary sucrose and fructose excretion

Urinary sugars excretion has been proposed as a potential biomarker for intake of sugars. In this study, we compared 2 analytical methods (gas chromatography [GC] and enzymatic reactions—UV absorption) for quantifying urinary fructose and sucrose using 24-hour urine samples from a randomized crossover controlled feeding study. All samples were successfully quantified by the GC method; however, 21% and 1.9% of samples were below the detection limit of the enzymatic method for sucrose and fructose, respectively. Although the correlation between the 2 methods was good for fructose (Pearson correlation, 0.71), the correlation was weak for sucrose (Pearson correlation, 0.27). We favor the GC method because of its better sensitivity, simplicity, and the ability to quantify fructose and sucrose directly in the same run. Of the 106 samples from 53 participants with complete urine collection after 2 study diets, 24-hour urinary fructose excretion was significantly associated with fructose intake. The sum of 24-hour urinary fructose and sucrose was significantly associated with total sugars consumption. However, variation in intakes of sugars explained only a modest amount of variation in urinary sugars excretion. In the unadjusted models, fructose intake explained 24.3% of urinary fructose excretion, and intake of total sugars explained 16.3% of the sum of urinary fructose and sucrose. The adjusted models explained 44.3% of urinary fructose excretion and 41.7% of the sum of urinary fructose and sucrose. Therefore, we caution using these biomarkers to predict sugars consumption before other factors that determine urinary sugars excretion are understood.

SGLT5 Reabsorbs Fructose in the Kidney but Its Deficiency Paradoxically Exacerbates Hepatic Steatosis Induced by Fructose

Although excessive fructose intake is epidemiologically linked with dyslipidemia, obesity, and diabetes, the mechanisms regulating plasma fructose are not well known. Cells transfected with sodium/glucose cotransporter 5 (SGLT5), which is expressed exclusively in the kidney, transport fructose in vitro; however, the physiological role of this transporter in fructose metabolism remains unclear. To determine whether SGLT5 functions as a fructose transporter in vivo, we established a line of mice lacking the gene encoding SGLT5. Sodium-dependent fructose uptake disappeared in renal brush border membrane vesicles from SGLT5-deficient mice, and the increased urinary fructose in SGLT5-deficient mice indicated that SGLT5 was the major fructose reabsorption transporter in the kidney. From this, we hypothesized that urinary fructose excretion induced by SGLT5 deficiency would ameliorate fructose-induced hepatic steatosis. To test this hypothesis we compared SGLT5-deficient mice with wild-type mice under conditions of long-term fructose consumption. Paradoxically, however, fructose-induced hepatic steatosis was exacerbated in the SGLT5-deficient mice, and the massive urinary fructose excretion was accompanied by reduced levels of plasma triglycerides and epididymal fat but fasting hyperinsulinemia compared with fructose-fed wild-type mice. There was no difference in food consumption, water intake, or plasma fructose between the two types of mice. No compensatory effect by other transporters reportedly involved in fructose uptake in the liver and kidney were indicated at the mRNA level. These surprising findings indicated a previously unrecognized link through SGLT5 between renal fructose reabsorption and hepatic lipid metabolism.