There has been much concern regarding the role of dietary fructose in the development of metabolic diseases. This concern arises from the continuous increase in fructose (and total added caloric sweeteners consumption) in recent decades, and from the increased use of high-fructose corn syrup (HFCS) as a sweetener. A large body of evidence shows that a high-fructose diet leads to the development of obesity, diabetes, and dyslipidemia in rodents. In humans, fructose has long been known to increase plasma triglyceride concentrations. In addition, when ingested in large amounts as part of a hypercaloric diet, it can cause hepatic insulin resistance, increased total and visceral fat mass, and accumulation of ectopic fat in the liver and skeletal muscle. These early effects may be instrumental in causing, in the long run, the development of the metabolic syndrome. There is however only limited evidence that fructose per se, when consumed in moderate amounts, has deleterious effects. Several effects of a high-fructose diet in humans can be observed with high-fat or high-glucose diets as well, suggesting that an excess caloric intake may be the main factor involved in the development of the metabolic syndrome. The major source of fructose in our diet is with sweetened beverages (and with other products in which caloric sweeteners have been added). The progressive replacement of sucrose by HFCS is however unlikely to be directly involved in the epidemy of metabolic disease, because HFCS appears to have basically the same metabolic effects as sucrose. Consumption of sweetened beverages is however clearly associated with excess calorie intake, and an increased risk of diabetes and cardiovascular diseases through an increase in body weight. This has led to the recommendation to limit the daily intake of sugar calories.Pure, white, and deadly: the dark side of sugar was suspected many years ago, when an association between sugar consumption and coronary heart diseases was recognized and emphasized by John Yudkin [1]. Sugar, a natural sweetener obtained from either sugar cane or beets, is a disaccharide composed of one glucose molecule linked through an α1-4 glycoside bond to a fructose molecule. Fructose, besides contributing to half the total content of sugar, can also be found as a hexose in fruits and honey. More recently, sweeteners started to be produced from corn through starch isolation and hydrolysis to glucose, followed by enzymatic isomerization of part of the glucose into fructose [2,3]. The resulting mixture, known as high-fructose corn syrup (HFCS), has several industrial advantages over sugar, the most important being its low price, and has progressively replaced sugar consumption in North America over the past 30 years.Fructose metabolism has been reviewed extensively elsewhere [4][5][6] and will be only briefly outlined here. In the gut, fructose is transported by specific transporters, GLUT5 [7,8]. In some subjects, fructose absorption is quantitatively limited, and some malabsorption occurs when lar...

A 7-d high-fructose diet increased ectopic lipid deposition in liver and muscle and fasting VLDL-triacylglycerols and decreased hepatic insulin sensitivity. Fructose-induced alterations in VLDL-triacylglycerols appeared to be of greater magnitude in the OffT2D group, which suggests that these individuals may be more prone to developing dyslipidemia when challenged by high fructose intakes. This trial was registered at clinicaltrials.gov as NCT00523562.

Background Classic galactosemia is a rare inborn error of carbohydrate metabolism, caused by a severe deficiency of the enzyme galactose-1-phosphate uridylyltransferase (GALT). A galactose-restricted diet has proven to be very effective to treat the neonatal life-threatening manifestations and has been the cornerstone of treatment for this severe disease. However, burdensome complications occur despite a lifelong diet. For rare diseases, a patient disease specific registry is fundamental to monitor the lifespan pathology and to evaluate the safety and efficacy of potential therapies. In 2014, the international Galactosemias Network (GalNet) developed a web-based patient registry for this disease, the GalNet Registry. The aim was to delineate the natural history of classic galactosemia based on a large dataset of patients. Methods Observational data derived from 15 countries and 32 centers including 509 patients were acquired between December 2014 and July 2018. Results Most affected patients experienced neonatal manifestations (79.8%) and despite following a diet developed brain impairments (85.0%), primary ovarian insufficiency (79.7%) and a diminished bone mineral density (26.5%). Newborn screening, age at onset of dietary treatment, strictness of the galactose-restricted diet, p.Gln188Arg mutation and GALT enzyme activity influenced the clinical picture. Detection by newborn screening and commencement of diet in the first week of life were associated with a more favorable outcome. A homozygous p.Gln188Arg mutation, GALT enzyme activity of ≤ 1% and strict galactose restriction were associated with a less favorable outcome. Conclusion This study describes the natural history of classic galactosemia based on the hitherto largest data set. Electronic supplementary material The online version of this article (10.1186/s13023-019-1047-z) contains supplementary material, which is available to authorized users.

OBJECTIVE -To compare the metabolic effects of fructose in healthy male and female subjects.RESEARCH DESIGN AND METHODS -Fasting metabolic profile and hepatic insulin sensitivity were assessed by means of a hyperglycemic clamp in 16 healthy young male and female subjects after a 6-day fructose overfeeding.RESULTS -Fructose overfeeding increased fasting triglyceride concentrations by 71 vs. 16% in male vs. female subjects, respectively (P Ͻ 0.05). Endogenous glucose production was increased by 12%, alanine aminotransferase concentration was increased by 38%, and fasting insulin concentrations were increased by 14% after fructose overfeeding in male subjects (all P Ͻ 0.05) but were not significantly altered in female subjects. Fasting plasma free fatty acids and lipid oxidation were inhibited by fructose in male but not in female subjects.CONCLUSIONS -Short-term fructose overfeeding produces hypertriglyceridemia and hepatic insulin resistance in men, but these effects are markedly blunted in healthy young women. Diabetes Care 31:1254-1256, 2008H igh fructose intake has been associated with adverse metabolic effects (1). Few studies have addressed whether the metabolic effects of fructose are sex dependent, however. In rats, several reports show that fructose has more pronounced adverse metabolic effects in males than in females (2,3); similarly, in humans, only men showed fructoseinduced hypertriglyceridemia (4,5). The aim of this study was to further assess whether the effects of short-term fructose overfeeding on fasting lipid metabolism and insulin sensitivity differ between men and women.RESEARCH DESIGN AND METHODS -Healthy, nonsmoking, Caucasian male (n ϭ 8, mean Ϯ SD age 22.5 Ϯ 0.93 years, BMI 22.5 Ϯ 1.4, and percent fat mass 14.2 Ϯ 3.1%) and female (n ϭ 8, age 22.9 Ϯ 0.62 years, BMI 21.0 Ϯ 1.4, and percent fat mass 24.6 Ϯ 2.5%) volunteers took part in the study. All subjects were in good health, and none were taking medications (except oral contraception for women).Each subject was studied on two occasions. On one occasion (control test), they were placed on a balanced, isoenergetic diet (100% energy requirements: 15% proteins, 35% lipids, 40% starch, and 10% mono-and disaccharides) for 6 days. On the other occasion, they were placed on the same isoenergetic diet supplemented with 3.5 g fructose ⅐ kg fat-free mass Ϫ1 ⅐ day Ϫ1 for 6 days (130% energy requirements: 11% proteins, 26% lipids, 30% starch, 8% glucose and disaccharides, and 25% fructose). The two dietary conditions were applied in a randomized order with a 4-week washout period. On the seventh day, subjects underwent a metabolic assessment including basal hormone and substrate concentrations, fasting endogenous glucose, and glucose metabolism during a two-step hyperglycemic clamp (6). Women who were not on oral contraceptive (n ϭ 2) were studied during the first 10 days of their menstrual cycle. Statistical analysisData are expressed as means Ϯ SEM. Comparisons between control diet and fructose supplementation were performed using the paired Wilco...

Aim To explore the clinical presentation, course, treatment and impact of early treatment in patients with remethylation disorders from the European Network and Registry for Homocystinurias and Methylation Defects (E‐HOD) international web‐based registry. Results This review comprises 238 patients (cobalamin C defect n = 161; methylenetetrahydrofolate reductase deficiency n = 50; cobalamin G defect n = 11; cobalamin E defect n = 10; cobalamin D defect n = 5; and cobalamin J defect n = 1) from 47 centres for whom the E‐HOD registry includes, as a minimum, data on medical history and enrolment visit. The duration of observation was 127 patient years. In 181 clinically diagnosed patients, the median age at presentation was 30 days (range 1 day to 42 years) and the median age at diagnosis was 3.7 months (range 3 days to 56 years). Seventy‐five percent of pre‐clinically diagnosed patients with cobalamin C disease became symptomatic within the first 15 days of life. Total homocysteine (tHcy), amino acids and urinary methylmalonic acid (MMA) were the most frequently assessed disease markers; confirmatory diagnostics were mainly molecular genetic studies. Remethylation disorders are multisystem diseases dominated by neurological and eye disease and failure to thrive. In this cohort, mortality, thromboembolic, psychiatric and renal disease were rarer than reported elsewhere. Early treatment correlates with lower overall morbidity but is less effective in preventing eye disease and cognitive impairment. The wide variation in treatment hampers the evaluation of particular therapeutic modalities. Conclusion Treatment improves the clinical course of remethylation disorders and reduces morbidity, especially if started early, but neurocognitive and eye symptoms are less responsive. Current treatment is highly variable. This study has the inevitable limitations of a retrospective, registry‐based design.

The increase in VLDL TAG concentration after ingestion of a high-fructose diet is more pronounced in men than in pre-menopausal women. We hypothesised that this may be due to a lower fructose-induced stimulation of de novo lipogenesis (DNL) in pre-menopausal women. To evaluate this hypothesis, nine healthy male and nine healthy female subjects were studied after ingestion of oral loads of fructose enriched with 13 C 6 fructose. Incorporation of 13 C into breath CO 2 , plasma glucose and plasma VLDL palmitate was monitored to evaluate total fructose oxidation, gluconeogenesis and hepatic DNL, respectively. Substrate oxidation was assessed by indirect calorimetry. After 13 C fructose ingestion, 44·0 (SD 3·2) % of labelled carbons were recovered in plasma glucose in males v. 41·9 (SD 2·3) % in females (NS), and 42·9 (SD 3·7) % of labelled carbons were recovered in breath CO 2 in males v. 43·0 (SD 4·5) % in females (NS), indicating similar gluconeogenesis from fructose and total fructose oxidation in males and females. The area under the curve for 13 C VLDL palmitate tracer-to-tracee ratio was four times lower in females (P,0·05), indicating a lower DNL. Furthermore, lipid oxidation was significantly suppressed in males (by 16·4 (SD 5·2), P, 0·05), but it was not suppressed in females (2 1·3 (SD 4·7) %). These results support the hypothesis that females may be protected against fructose-induced hypertriglyceridaemia because of a lower stimulation of DNL and a lower suppression of lipid oxidation. De novo lipogenesis: VLDL TAG: Endogenous glucose productionThe metabolic effects of a high-fructose diet have been widely studied in both animals and human subjects (1) . High-fructose diet is associated with the development of at least two features of the metabolic syndrome, i.e. insulin resistance and increased plasma VLDL TAG. The latter may in turn be associated with an increased production of small, dense LDL particle with high atherogenic potential (2,3) . It has been reported by several authors that a high-fructose diet increases plasma TAG less and does not reduce insulin sensitivity in both pre-menopausal women and female rodents compared with males (4 -11) . This may be due to a sex-specific difference in either fructose metabolism or adaptations to chronic fructose overfeeding. To our knowledge, whether the metabolism of an acute fructose load differs in females and males has not been specifically assessed. Fructose disposal relies mainly on the stimulation of carbohydrate oxidation (fructose oxidation in splanchnic organs and indirect oxidation of glucose and lactate synthesised from the fructose), gluconeogenesis, hepatic glycogen storage and hepatic de novo lipogenesis (DNL). The latter, although a quantitatively minor pathway for fructose disposal, may be closely linked to hepatic VLDL TAG production and synthesis of intra-hepatic lipids. Therefore, we hypothesised that fructose-induced stimulation of DNL may be blunted in pre-menopausal women.To evaluate this hypothesis, we compared the metabolic fate of i...

Treatment improves the clinical course of remethylation disorders and reduces morbidity, especially if started early, but neurocognitive and eye symptoms are less responsive. Current treatment is highly variable. This study has the inevitable limitations of a retrospective, registry-based design.

Fructose is one of the main sweetening agents in the human diet and its ingestion is increasing globally. Dietary sugar has particular effects on those whose capacity to metabolize fructose is limited. If intolerance to carbohydrates is a frequent finding in children, inborn errors of carbohydrate metabolism are rare conditions. Three inborn errors are known in the pathway of fructose metabolism; (1) essential or benign fructosuria due to fructokinase deficiency; (2) hereditary fructose intolerance; and (3) fructose-1,6-bisphosphatase deficiency. In this review the focus is set on the description of the clinical symptoms and biochemical anomalies in the three inborn errors of metabolism. The potential toxic effects of fructose in healthy humans also are discussed. Studies conducted in patients with inborn errors of fructose metabolism helped to understand fructose metabolism and its potential toxicity in healthy human. Influence of fructose on the glycolytic pathway and on purine catabolism is the cause of hypoglycemia, lactic acidosis and hyperuricemia. The discovery that fructose-mediated generation of uric acid may have a causal role in diabetes and obesity provided new understandings into pathogenesis for these frequent diseases.