Development of tools to facilitate the diagnosis of hereditary fructose intolerance.

Although hereditary fructose intolerance (HFI) is an inborn error of fructose metabolism that classically presents at infancy, the diagnosis is often missed or delayed. In this study, we aimed to develop tools to facilitate the diagnosis of HFI. The intake of fructose-containing food products, that is, fruit, fruit juice and sugar-sweetened beverages, was assessed by a 3-day food diary in adult HFI patients (n = 15) and age, sex, and BMI-matched controls (n = 15). Furthermore, glycosylation of transferrin was examined using high-resolution mass spectrometry and abnormally glycosylated transferrin was expressed as ratio of normal glycosylated transferrin. We found that the sensitivity and specificity of the 3-day food diary for the intake of at least one fructose-containing food product were both 100%. Both mono-glyco:diglyco transferrin and a-glyco+mono-glyco:di-glyco transferrin were greater in HFI patients and had a high-discriminatory power (area under the receiver operating characteristic curve: 0.97 and 0.94, respectively). In this well-characterized cohort of adult HFI patients, the 3-day food questionnaire and the glycosylation pattern of transferrin are valuable tools to facilitate the recognition and diagnosis of HFI in adult patients.

Pyridoxamine reduces methylglyoxal and markers of glycation and endothelial dysfunction, but does not improve insulin sensitivity or vascular function in abdominally obese individuals: A randomized double-blind placebo-controlled trial.

AIM: To investigate the effects of pyridoxamine (PM), a B6 vitamer and dicarbonyl scavenger, on glycation and a large panel of metabolic and vascular measurements in a randomized double-blind placebo-controlled trial in abdominally obese individuals. MATERIALS AND METHODS: Individuals (54% female; mean age 50 years; mean body mass index 32 kg/m2 ) were randomized to an 8-week intervention with either placebo (n = 36), 25 mg PM (n = 36) or 200 mg PM (n = 36). We assessed insulin sensitivity, ß-cell function, insulin-mediated microvascular recruitment, skin microvascular function, flow-mediated dilation, and plasma inflammation and endothelial function markers. PM metabolites, dicarbonyls and advanced glycation endproducts (AGEs) were measured using ultra-performance liquid chromatography tandem mass spectrometry. Treatment effects were evaluated by one-way ANCOVA. RESULTS: In the high PM dose group, we found a reduction of plasma methylglyoxal (MGO) and protein-bound Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1), as compared to placebo. We found a reduction of the endothelial dysfunction marker soluble vascular cell adhesion molecule-1 (sVCAM-1) in the low and high PM dose group and of soluble intercellular adhesion molecule-1 (sICAM-1) in the high PM dose, as compared to placebo. We found no treatment effects on insulin sensitivity, vascular function or other functional outcome measurements. CONCLUSIONS: This study shows that PM is metabolically active and reduces MGO, AGEs, sVCAM-1 and sICAM-1, but does not affect insulin sensitivity and vascular function in abdominally obese individuals. The reduction in adhesion markers is promising because these are important in the pathogenesis of endothelial damage and atherosclerosis.

Effects of fructose restriction on blood pressure: Secondary analysis of a double-blind randomized controlled trial.

BACKGROUND: Despite convincing animal data, there is an ongoing debate on whether and how fructose affects blood pressure in humans. The aim of this study was to investigate the effects of fructose restriction on blood pressure, and the role of endothelial function herein. METHODS: forty-four overweight individuals were asked to follow a fructose-restricted diet (<7.5 g/meal and <10 g/day) for 6 weeks. They were randomly assigned to double-blind supplementation with glucose (=intervention group) or fructose (=control group) powder three times daily. Office blood pressure was measured with an automated device, and endothelial function was assessed by reactive hyperemia peripheral arterial tonometry, skin laser doppler flowmetry, and serum sE-selectin. RESULTS: Thirty-seven participants completed the study. Systolic blood pressure decreased significantly in the intervention group (change from baseline: -3.3 mmHg; 95%CI:-8.8,- 0.3), but this change was not statistically different from the control group. In contrast, diastolic blood pressure decreased significantly in the intervention group in comparison to controls (difference: -4.0 mmHg; 95%CI:-9.5,-0.5). Furthermore, the change in fructose intake was associated with the change in diastolic blood pressure (beta: 0.085 mmHg; 95% CI: 0.032;0.138). The endothelial markers were not affected by the intervention. Finally, the effects of the intervention on diastolic blood pressure appeared to be higher in individuals consuming high amounts of salt at baseline (difference: -9.0 mmHg; 95%CI:-14.5,-2.5). CONCLUSIONS: Six-week fructose restriction per se results in a dose-dependent decrease in diastolic blood pressure. Further studies are warranted to elucidate the effects of fructose restriction on salt-sensitive hypertension in humans. TRIAL REGISTRATION: www. CLINICALTRIALS: gov; NCT03067428.

Intrahepatic lipid content is independently associated with soluble E-selectin levels: The Maastricht study.

BACKGROUND: Evidence is accumulating that liver sinusoidal endothelial cells are involved in the pathogenesis of non-alcoholic fatty liver disease. Previous studies have suggested that the endothelial biomarker soluble E-selectin (sE-selectin) is to an important extent liver-derived. AIMS: To study the relationship of intrahepatic lipid (IHL) content with sE-selectin at the population level. METHODS: This study was conducted in participants of The Maastricht Study (n = 1,634), a population-based cohort study enriched with patients with type 2 diabetes. We assessed the cross-sectional association between IHL content, quantified by MRI, and sE-selectin via multivariable regression with adjustment for age, sex, type 2 diabetes, educational level, BMI, Dutch Healthy Diet index, physical activity, and the Matsuda index. RESULTS: Standardized IHL content was associated with (log) sE-selectin (age-, sex- and type 2 diabetes-adjusted regression coefficient [B]: 0.048 [95%CI:0.038;0.058], p<0.001), even after full adjustment (B: 0.030 [0.019;0.042], p<0.001). Such an association was not observed for soluble vascular cell adhesion molecule 1 (sVCAM-1) levels. CONCLUSION: IHL content is an independent determinant of sE-selectin at the population level. These findings support further studies to unravel the involvement of liver sinusoidal endothelial cells in the different stages of non-alcoholic fatty liver disease and the specific role of E-selectin herein.

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

BACKGROUND: There is an ongoing debate on whether fructose plays a role in the development of nonalcoholic fatty liver disease. OBJECTIVES: The 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. METHODS: Between 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. RESULTS: Thirty-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. CONCLUSIONS: Six 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.

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

BACKGROUND: The 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). METHODS: Fructose 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. RESULTS: The 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). CONCLUSION: Fructose 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.

Kidney and vascular function in adult patients with hereditary fructose intolerance.

Objective: Previous studies have shown that patients with hereditary fructose intolerance (HFI) are characterized by a greater intrahepatic triglyceride content, despite a fructose-restricted diet. The present study aimed to examine the long-term consequences of HFI on other aldolase-B-expressing organs, i.e. the kidney and vascular endothelium. Methods: Fifteen adult HFI patients were compared to healthy control individuals matched for age, sex and body mass index. Aortic stiffness was assessed by carotid-femoral pulse wave velocity (cf-PWV) and endothelial function by peripheral arterial tonometry, skin laser doppler flowmetry and the endothelial function biomarkers soluble E-selectin [sE-selectin] and von Willebrand factor. Serum creatinine and cystatin C were measured to estimate the glomerular filtration rate (eGFR). Urinary glucose and amino acid excretion and the ratio of tubular maximum reabsorption of phosphate to GFR (TmP/GFR) were determined as measures of proximal tubular function. Results: Median systolic blood pressure was significantly higher in HFI patients (127 versus 122 mmHg, p = .045). Pulse pressure and cf-PWV did not differ between the groups (p = .37 and p = .49, respectively). Of all endothelial function markers, only sE-selectin was significantly higher in HFI patients (p = .004). eGFR was significantly higher in HFI patients than healthy controls (119 versus 104 ml/min/1.73m2, p = .001, respectively). All measurements of proximal tubular function did not differ significantly between the groups. Conclusions: Adult HFI patients treated with a fructose-restricted diet are characterized by a higher sE-selectin level and slightly higher systolic blood pressure, which in time could contribute to a greater cardiovascular risk. The exact cause and, hence, clinical consequences of the higher eGFR in HFI patients, deserves further study.

Incidence of type 2 diabetes in familial combined hyperlipidemia.

OBJECTIVE: Familial combined hyperlipidemia (FCHL) is common among survivors of a premature myocardial infarction. FCHL patients are characterized by visceral obesity, fatty liver, and insulin resistance. The aim of the present study was to determine the incidence and determinants of type 2 diabetes (T2D) in a longitudinal cohort of FCHL pedigrees. RESEARCH DESIGN AND METHODS: FCHL patients, their unaffected relatives and spouses included in our baseline cohort in 1998-2005 (n=596) were re-invited to determine the incidence of self-reported T2D (that was confirmed by medical records), used as the primary outcome measure. The Fatty Liver Index (FLI) and Homeostasis Model Assessment Insulin Resistance (HOMA2-IR) were used as markers of fatty liver and insulin resistance, respectively. A subset of the original cohort underwent ultrasound of the liver, and subcutaneous and visceral fat in 2002-2005 (n=275; 'ultrasound subcohort'). RESULTS: Follow-up data (median: 15 years) was acquired for 76%. The incidence rate of T2D was significantly higher in FCHL patients compared with spouses (19.2 per 1000 person-years vs 2.8 per 1000 person-years; HR : 6.3, 95% CI: 2.4 to 16.8), whereas no differences were observed between unaffected relatives and spouses (HR: 0.9, 95% CI: 0.3 to 2.6). Cox's proportional hazard regression analyses showed that baseline HOMA2-IR and FLI≥60, but not waist circumference, BMI, or the FCHL affected state, were independently associated with incident T2D. Similar results were obtained in the ultrasound subcohort (median follow-up: 11 years), in which baseline HOMA2-IR and fatty liver (assessed by ultrasound) were independently associated with incident T2D. CONCLUSION: This study further corroborates the suggestion that the liver plays a central role in the pathogenesis of cardiometabolic complications in FCHL. It supports periodical screening for T2D in this high-risk population.

The endothelial function biomarker soluble E-selectin is associated with nonalcoholic fatty liver disease.

BACKGROUND & AIMS: Plasma soluble E-selectin (sE-selectin) is a frequently used biomarker of systemic endothelial dysfunction. The present study explored the relationship between nonalcoholic fatty liver disease (NAFLD) and plasma sE-selectin levels. METHODS: Expression of E-selectin in liver, visceral adipose tissue (VAT) and muscle was studied in relation to plasma sE-selectin in severely obese individuals (n = 74). The course of hepatic E-selectin expression in relation to hepatic steatosis and inflammation was examined in C57BL/6J LDLR-/- mice on a Western-type diet. The relationship between biomarkers of NAFLD, that is, plasma aminotransferase (ALT) and NAFLD susceptibility genes (rs738409 [PNPLA3] and rs1260326 [GCKR]), and plasma sE-selectin was studied in the combined CODAM (n = 571) and Hoorn (n = 694) studies. RESULTS: E-selectin expression in liver, not VAT or muscle, was associated with plasma sE-selectin in severely obese individuals (ß = 0.26; 95% CI: 0.05-0.47). NAFLD severity was associated with hepatic E-selectin expression (P = .02) and plasma sE-selectin (P = .003). LDLR-/- mice on a Western-type diet displayed increased hepatic E-selectin expression that followed the same course as hepatic inflammation, but not steatosis. In the CODAM study, plasma ALT was associated with plasma sE-selectin, independent of potential confounders (ß = 0.25; 95% CI: 0.16-0.34). Both rs738409 and rs1260326 were associated with higher plasma sE-selectin in the combined CODAM and Hoorn studies (P = .01 and P = .004 respectively). CONCLUSIONS: NAFLD and related markers are associated with higher expression of hepatic E-selectin and higher levels of plasma sE-selectin. Further studies are required to investigate the role of E-selectin in the pathogenesis of NAFLD and the applicability of sE-selectin as a plasma biomarker of NAFLD/NASH.

Non-alcoholic fatty liver disease and cardiovascular disease: assessing the evidence for causality.

Non-alcoholic fatty liver disease (NAFLD) is highly prevalent among individuals with type 2 diabetes. Although epidemiological studies have shown that NAFLD is associated with cardiovascular disease (CVD), it remains unknown whether NAFLD is an active contributor or an innocent bystander. Plasma lipids, low-grade inflammation, impaired fibrinolysis and hepatokines are potential mediators of the relationship between NAFLD and CVD. The Mendelian randomisation approach can help to make causal inferences. Studies that used common variants in PNPLA3, TM6SF2 and GCKR as instruments to investigate the relationship between NAFLD and coronary artery disease (CAD) have reported contrasting results. Variants in PNPLA3 and TM6SF2 were found to protect against CAD, whereas variants in GCKR were positively associated with CAD. Since all three genes have been associated with non-alcoholic steatohepatitis, the second stage of NAFLD, the question of whether low-grade inflammation is an important mediator of the relationship between NAFLD and CAD arises. In contrast, the differential effects of these genes on plasma lipids (i.e. lipid-lowering for PNPLA3 and TM6SF2, and lipid-raising for GCKR) strongly suggest that plasma lipids account for their differential effects on CAD risk. This concept has recently been confirmed in an extended set of 12 NAFLD susceptibility genes. From these studies it appears that plasma lipids are an important mediator between NAFLD and CVD risk. These findings have important clinical implications, particularly for the design of anti-NAFLD drugs that also affect lipid metabolism.

Relationship Between Nonalcoholic Fatty Liver Disease Susceptibility Genes and Coronary Artery Disease.

Coronary artery disease (CAD) is the principal cause of death in patients with nonalcoholic fatty liver disease (NAFLD). The aim of the present study was to investigate whether NAFLD is causally involved in the pathogenesis of CAD. For this, previously reported NAFLD susceptibility genes were clustered and tested for an association with CAD in the Coronary Artery Disease Genome-Wide Replication and Meta-Analysis plus the Coronary Artery Disease Genetics (CARDIoGRAMplusC4D) Consortium data set. The role of plasma lipids as a potential mediator was explored by using data from the Global Lipids Genetics Consortium. Statistical analyses revealed that the combination of 12 NAFLD genes was not associated with CAD in 60,801 CAD cases and 123,504 controls (odds ratio [OR] per NAFLD risk allele, 1.0; 95% confidence interval [CI], 0.99-1.00). In a subsequent sensitivity analysis, a positive relationship was observed after exclusion of gene variants that are implicated in NAFLD through impaired very low-density lipoprotein secretion (i.e., microsomal triglyceride transfer protein [MTTP], patatin-like phospholipase domain containing 3 [PNPLA3], phosphatidylethanolamine N-methyltransferase [PEMT], and transmembrane 6 superfamily member 2 [TM6SF2]) (OR, 1.01; 95% CI, 1.00-1.02). Clustering of the excluded genes showed a significant negative relationship with CAD (OR, 0.97; 95% CI, 0.96-0.99). A substantial proportion of the observed heterogeneity between the individual NAFLD genes in relation to CAD could be explained by plasma lipids, as reflected by a strong relationship between plasma lipids and CAD risk conferred by the NAFLD susceptibility genes (r = 0.76; P = 0.004 for low-density lipoprotein cholesterol). Conclusion: NAFLD susceptibility genes do not cause CAD per se. The relationship between these genes and CAD appears to depend to a large extent on plasma lipids. These observations strongly suggest taking plasma lipids into account when designing a new drug to target NAFLD.

Patients With Aldolase B Deficiency Are Characterized by Increased Intrahepatic Triglyceride Content.

CONTEXT: There is an ongoing debate about whether and how fructose is involved in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). A recent experimental study showed an increased intrahepatic triglyceride (IHTG) content in mice deficient for aldolase B (aldo B-/-), the enzyme that converts fructose-1-phosphate to triose phosphates. OBJECTIVE: To translate these experimental findings to the human situation. DESIGN: Case-control study. SETTING: Outpatient clinic for inborn errors of metabolism. PATIENTS OR OTHER PARTICIPANTS: Patients with hereditary fructose intolerance, a rare inborn error of metabolism caused by a defect in aldolase B (n = 15), and healthy persons matched for age, sex, and body mass index (BMI) (n =15). MAIN OUTCOME MEASURE: IHTG content, assessed by proton magnetic resonance spectroscopy. RESULTS: IHTG content was higher in aldo B-/- patients than controls (2.5% vs 0.6%; P = 0.001) on a background of lean body mass (median BMI, 20.4 and 21.8 kg/m2, respectively). Glucose excursions during an oral glucose load were higher in aldo B-/- patients (P = 0.043). Hypoglycosylated transferrin, a surrogate marker for hepatic fructose-1-phosphate concentrations, was more abundant in aldo B-/- patients than in controls (P < 0.001). Finally, plasma ß-hydroxybutyrate, a biomarker of hepatic ß-oxidation, was lower in aldo B-/- patients than controls (P = 0.009). CONCLUSIONS: This study extends previous experimental findings by demonstrating that aldolase B deficiency also results in IHTG accumulation in humans. It suggests that the accumulation of fructose-1-phosphate and impairment of ß-oxidation are involved in the pathogenesis.

Association of common gene variants in glucokinase regulatory protein with cardiorenal disease: A systematic review and meta-analysis.

BACKGROUND: Small-molecules that disrupt the binding between glucokinase and glucokinase regulatory protein (GKRP) in the liver represent a potential new class of glucose-lowering drugs. It will, however, take years before their effects on clinically relevant cardiovascular endpoints are known. The purpose of this study was to estimate the effects of these drugs on cardiorenal outcomes by studying variants in the GKRP gene (GCKR) that mimic glucokinase-GKRP disruptors. METHODS: The MEDLINE and EMBASE databases were searched for studies reporting on the association between GCKR variants (rs1260326, rs780094, and rs780093) and coronary artery disease (CAD), estimated glomerular filtration rate (eGFR), and chronic kidney disease (CKD). RESULTS: In total 5 CAD studies (n = 274,625 individuals), 7 eGFR studies (n = 195,195 individuals), and 4 CKD studies (n = 31,642 cases and n = 408,432 controls) were included. Meta-analysis revealed a significant association between GCKR variants and CAD (OR:1.02 per risk allele, 95%CI:1.00-1.04, p = 0.01). Sensitivity analyses showed that replacement of one large, influential CAD study by two other, partly overlapping studies resulted in similar point estimates, albeit less precise (OR:1.02; 95%CI:0.98-1.06 and OR: 1.02; 95%CI: 0.99-1.04). GCKR was associated with an improved eGFR (+0.49 ml/min, 95%CI:0.10-0.89, p = 0.01) and a trend towards protection from CKD (OR:0.98, 95%CI:0.95-1.01, p = 0.13). CONCLUSION: This study suggests that increased glucokinase-GKRP disruption has beneficial effects on eGFR, but these may be offset by a disadvantageous effect on coronary artery disease risk. Further studies are warranted to elucidate the mechanistic link between hepatic glucose metabolism and eGFR.

A Common Gene Variant in Glucokinase Regulatory Protein Interacts With Glucose Metabolism on Diabetic Dyslipidemia: the Combined CODAM and Hoorn Studies.

OBJECTIVE: Small molecules that disrupt the binding between glucokinase and glucokinase regulatory protein (GKRP) are potential new glucose-lowering targets. They stimulate hepatic glucose disposal by increasing glucokinase activity in the liver. It can, however, be anticipated that increased hepatic glucokinase activity might be accompanied by the development of hypertriglyceridemia, particularly in type 2 diabetes. We examined whether the strength of association between rs1260326, a common, functional gene variant in GKRP, and plasma lipids is affected by glucose metabolism. RESEARCH DESIGN AND METHODS: rs1260326 was genotyped in subjects with normal glucose metabolism (n = 497), subjects with impaired glucose metabolism (n = 256), and patients with type 2 diabetes (n = 351) in the combined Hoorn and Cohort on Diabetes and Atherosclerosis Maastricht (CODAM) studies. RESULTS: The strength of association between the rs1260326 minor T allele and plasma triglycerides increased from normal glucose metabolism to impaired glucose metabolism to type 2 diabetes (P for interaction = 0.002). The inverse relation between rs1260326 and plasma HDL cholesterol was again most prominent in type 2 diabetes (P for interaction = 0.004). Similar trends were observed when the Hoorn and CODAM cohorts were analyzed separately. Comparable results were obtained when glucose metabolism strata were replaced by continuous indices of glucose metabolism, i.e., HbA1c and fasting plasma glucose. CONCLUSIONS: These findings illustrate that common gene variants, such as rs1260326, can have substantial effect sizes when they are studied in specific populations, such as type 2 diabetes. Moreover, our results shed light on potential side effects of small molecule disruptors of the GKRP-glucokinase complex, especially when glucose control is suboptimal.