Challenging the fructose hypothesis: new perspectives on fructose consumption and metabolism

High concentrations of fructose cause brain damage in mice

Excessive fructose consumption is associated with the incidence of obesity and systemic inflammation, resulting in increased oxidative damage and failure to the function of brain structures. Thus, we hypothesized that fructose consumption will significantly increase inflammation, oxidative damage, and mitochondrial dysfunction in the mouse brain and, consequently, memory damage. The effects of different fructose concentrations on inflammatory and biochemical parameters in the mouse brain were evaluated. Male Swiss mice were randomized into four groups: control, with exclusive water intake, 5%, 10%, and 20% fructose group. The 10% and 20% fructose groups showed an increase in epididymal fat, in addition to higher food consumption. Inflammatory markers were increased in epididymal fat and in some brain structures. In the evaluation of oxidative damage, it was possible to observe significant increases in the hypothalamus, prefrontal cortex, and hippocampus. In the epididymal fat and in the prefrontal cortex, there was a decrease in the activity of the mitochondrial respiratory chain complexes and an increase in the striatum. Furthermore, short memory was impaired in the 10% and 20% groups but not long memory. In conclusion, excess fructose consumption can cause fat accumulation, inflammation, oxidative damage, and mitochondrial dysfunction, which can damage brain structures and consequently memory.

Effects of Natural Alternative Sweeteners on Metabolic Diseases

The rising prevalence of obesity and diabetes is a significant health concern both in globally and is now regarded as a worldwide epidemic. Added sugars like sucrose and high-fructose corn syrup (HFCS) are a major concern due to their link with an increased incidence of diet-induced obesity and diabetes. The purpose of this review is to provide insight into the effects of natural sweeteners as alternatives to sucrose and HFCS, which are known to have negative impacts on metabolic diseases and to promote further research on sugar consumption with a focus on improving metabolic health. The collective evidences suggest that natural alternative sweeteners have positive impacts on various markers associated with obesity and diabetes, including body weight gain, hepatic fat accumulation, abnormal blood glucose or lipid homeostasis, and insulin resistance. Taken together, natural alternative sweeteners can be useful substitutes to decrease the risk of obesity and diabetes compared with sucrose and HFCS.

Longitudinal Associations of Dietary Sugars and Glycaemic Index with Indices of Glucose Metabolism and Body Fatness during 3-Year Weight Loss Maintenance: A PREVIEW Sub-Study

BACKGROUND

Dietary sugars are often linked to the development of overweight and type 2 diabetes (T2D) but inconsistencies remain.

OBJECTIVE

We investigated associations of added, free, and total sugars, and glycaemic index (GI) with indices of glucose metabolism (IGM) and indices of body fatness (IBF) during a 3-year weight loss maintenance intervention.

DESIGN

The PREVIEW (PREVention of diabetes through lifestyle Intervention and population studies in Europe and around the World) study was a randomised controlled trial designed to test the effects of four diet and physical activity interventions, after an 8-week weight-loss period, on the incidence of T2D. This secondary observational analysis included pooled data assessed at baseline (8), 26, 52, 104 and 156 weeks from 514 participants with overweight/obesity (age 25-70 year; BMI ≥ 25 kg⋅m^-2) and with/without prediabetes in centres that provided data on added sugars (Sydney and Helsinki) or free sugars (Nottingham). Linear mixed models with repeated measures were applied for IBF (total body fat, BMI, waist circumference) and for IGM (fasting insulin, HbA1c, fasting glucose, C-peptide). Model A was adjusted for age and intervention centre and Model B additionally adjusted for energy, protein, fibre, and saturated fat.

RESULTS

Total sugars were inversely associated with fasting insulin and C-peptide in all centres, and free sugars were inversely associated with fasting glucose and HbA1c (Model B: all p < 0.05). Positive associations were observed between GI and IGM (Model B: fasting insulin, HbA1c, and C-peptide: (all p < 0.01), but not for added sugars. Added sugar was positively associated with body fat percentage and BMI, and GI was associated with waist circumference (Model B: all p < 0.01), while free sugars showed no associations (Model B: p > 0.05).

CONCLUSIONS

Our findings suggest that added sugars and GI were independently associated with 3-y weight regain, but only GI was associated with 3-y changes in glucose metabolism in individuals at high risk of T2D.

Effects of early-life voluntary exercise and fructose on adult activity levels, body composition, aerobic capacity, and organ masses in mice bred for high voluntary wheel-running behavior

Fructose (C₆H₁₂O₆) is acutely obesogenic and is a risk factor for hypertension, cardiovascular disease, and nonalcoholic fatty liver disease. However, the possible long-lasting effects of early-life fructose consumption have not been studied. We tested for effects of early-life fructose and/or wheel access (voluntary exercise) in a line of selectively bred High Runner (HR) mice and a non-selected Control (C) line. Exposures began at weaning and continued for 3 weeks to sexual maturity, followed by a 23-week "washout" period (equivalent to ∼17 human years). Fructose increased total caloric intake, body mass, and body fat during juvenile exposure, but had no effect on juvenile wheel running and no important lasting effects on adult physical activity or body weight/composition. Interestingly, adult maximal aerobic capacity (VO₂max) was reduced in mice that had early-life fructose and wheel access. Consistent with previous studies, early-life exercise promoted adult wheel running. In a 3-way interaction, C mice that had early-life fructose and no wheel access gained body mass in response to 2 weeks of adult wheel access, while all other groups lost mass. Overall, we found some long-lasting positive effects of early-life exercise, but minimal effects of early-life fructose, regardless of the mouse line.

Nutritional Treatment of Hypertriglyceridemia in Childhood: From Healthy-Heart Counselling to Life-Saving Diet

Hypertriglyceridemia is a lipid disorder with a varying prevalence; it is very common if we consider triglyceride plasma values slightly above the threshold, whereas it is extremely rare if only severely elevated triglyceride levels are considered. In most cases, severe forms of hypertriglyceridemia are caused by genetic mutations in the genes that regulate triglyceride metabolism, thus leading to extreme triglyceride plasma values and acute pancreatitis risk. Secondary forms of hypertriglyceridemia are usually less severe and are mainly associated with weight excess, but they can also be linked to liver, kidney, endocrinologic, or autoimmune diseases or to some class of drugs. Nutritional intervention is the milestone treatment for patients with hypertriglyceridemia and it has to be modulated on the underlying cause and on triglyceride plasma levels. In pediatric patients, nutritional intervention must be tailored according to specific age-related energy, growth and neurodevelopment requests. Nutritional intervention is extremely strict in case of severe hypertriglyceridemia, whereas it is similar to good healthy nutritional habits counselling for mild forms, mainly related to wrong habits and lifestyles, and to secondary causes. The aim of this narrative review is to define different nutritional intervention for various forms of hypertriglyceridemia in children and adolescents.

Continuous glucose monitoring reveals similar glycemic variability in individuals with obesity despite increased HOMA-IR

Background/aims

Continuous glucose monitoring is a well-tolerated and versatile tool for management of diabetes and metabolic disease. While its use appears to be feasible to monitor glycemic profiles in diabetics, there is a paucity of data in individuals with obesity and normal glucose tolerance. The aim of this study is to investigate glucose fluctuations and insulin resistance patterns in normoglycemic participants with obesity vs. without obesity and contextualize these results against leading models for obesity.

Materials and methods

We designed a prospective, observational pilot study of two cohorts including 14 normoglycemic participants with obesity and 14 normoglycemic participants without obesity. Participants were monitored with continuous glucose monitoring (CGM) for five consecutive days. Insulin resistance levels were measured and glucometric data were extracted from CGM for all participants.

Results

Fasting serum insulin and homeostasis model assessment of insulin resistance (HOMA-IR) were significantly higher in the group with obesity (P < 0.05). While the group with obesity had a higher mean blood glucose (MBG), mean amplitude of glycemic excursions (MAGE), and continuous overall glycemic action-1 h (CONGA-1), these differences were not significant. On univariate linear regression, insulin resistance (HOMA-IR) was associated with body mass index (BMI), waist circumference (WC), cohort with obesity, cohort consuming a high glycemic diet, hemoglobin A1c (HbA1c), and fasting insulin levels. WC and fasting insulin levels remained predictors of HOMA-IR in our multivariable model.

Conclusion

While there is much excitement surrounding the use of commercial CGM products in obesity management, our results suggest that fasting insulin and HOMA-IR values may be more clinically useful than CGM data alone.

Physical activity enhances fecal lactobacilli in rats chronically drinking sweetened cola beverage

Overweight and obesity have been linked with increased intake of sugar-sweetened beverages. On the other hand, physical activity has been known to lead to weight loss. Therefore, we hypothesized that exercise might influence the Lactobacillus population in fecal microbiota as their changed abundance is often associated with shifts in the physical activity and diet. In our experiment, Wistar rats were allocated into groups with normal feed or added sugar-sweetened beverages with or without access to a running wheel. Interestingly, only a combination of physical activity and sweetened beverage intake was associated with a significant increase in fecal lactobacilli abundance, suggesting a connection between exercise and a rise in lactobacilli abundance. Moreover, physical activity has improved weight-related parameters and led to increased plasma and mRNA adiponectin levels. Ghrelin and leptin plasma levels were unaltered. Taken together, our results demonstrate that effect of physical activity on adiposity even during unhealthy feeding patterns is accompanied by increased lactobacilli abundance in the fecal microbiota population.

The Role of Fructose as a Cardiovascular Risk Factor: An Update

There is increasing presence of fructose in food and drinks, and some evidence suggests that its higher consumption increases cardiovascular risk, although the mechanisms still remain not fully elucidated. Cardiovascular diseases (CVD) are still responsible for one-third of deaths worldwide, and therefore, their prevention should be assessed and managed comprehensively and not by the evaluation of individual risk factor components. Lifestyle risk factors for CVD include low degree of physical activity, high body mass index, alcohol consumption, smoking, and nutritional factors. Indeed, nutritional risk factors for CVD include unhealthy dietary behaviors, such as high intake of refined foods, unhealthy fats, added sugars, and sodium and a low intake of fruits, vegetables, whole grains, fiber, fish, and nuts. Even though there is no definitive association between CVD incidence and high consumption of total sugar, such as sucrose and fructose, there is, however, evidence that total sugars, added sugars, and fructose are harmfully associated with CVD mortality. Since high fructose intake is associated with elevated plasma triglyceride levels, as well as insulin resistance, diabetes hyperuricemia, and non-alcoholic fatty liver disease, further longitudinal studies should be conducted to fully elucidate the potential association between certain sugars and CVD.

The Contribution of Dietary Fructose to Non-alcoholic Fatty Liver Disease

Fructose, especially industrial fructose (sucrose and high fructose corn syrup) is commonly used in all kinds of beverages and processed foods. Liver is the primary organ for fructose metabolism, recent studies suggest that excessive fructose intake is a driving force in non-alcoholic fatty liver disease (NAFLD). Dietary fructose metabolism begins at the intestine, along with its metabolites, may influence gut barrier and microbiota community, and contribute to increased nutrient absorption and lipogenic substrates overflow to the liver. Overwhelming fructose and the gut microbiota-derived fructose metabolites (e.g., acetate, butyric acid, butyrate and propionate) trigger the de novo lipogenesis in the liver, and result in lipid accumulation and hepatic steatosis. Fructose also reprograms the metabolic phenotype of liver cells (hepatocytes, macrophages, NK cells, etc.), and induces the occurrence of inflammation in the liver. Besides, there is endogenous fructose production that expands the fructose pool. Considering the close association of fructose metabolism and NAFLD, the drug development that focuses on blocking the absorption and metabolism of fructose might be promising strategies for NAFLD. Here we provide a systematic discussion of the underlying mechanisms of dietary fructose in contributing to the development and progression of NAFLD, and suggest the possible targets to prevent the pathogenetic process.

No Effect of Added Sugars in Soft Drink Compared With Sugars in Fruit on Cardiometabolic Risk Factors: Results From a 4-Week, Randomized Controlled Trial

High intakes of added sugar from soft drinks are associated with negative health outcomes such as the increased risk of gout and type 2 diabetes, weight gain and cardiovascular disease. Fruits are naturally high in sugars but their effect on cardiometabolic risk remains unknown. We examined the effect on cardiometabolic risk factors of consuming natural sugars from fruit or added sugars from sugar-sweetened soft drinks in overweight adults. Forty-eight healthy, overweight (BMI ≥ 28 kg/m²) men (n = 21) and women (n = 20) were randomized to either a fruit (n = 19) or sugar-sweetened soft drink (n = 22) intervention for 4 weeks. The fruit group received 6 items of fresh and dried fruit per day and the sugar-sweetened soft drink group received 955 ml of sugar-sweetened soft drink per day. The interventions were matched for both energy (fruit: 1,800 kJ/d; soft drink: 1,767 kJ/d) and fructose content (fruit: 51.8 g/d; soft drink: 51.7 g/d). The soft drink intervention provided 101 g total sugars, which was all added sugar and the fruit intervention provided 97 g total sugars, which were all natural sugars. Dietary intakes were otherwise ad libitum. Despite being asked to consume additional sugar (up to 1,800 additional kJ/d), there were no changes in weight, blood pressure or other cardiometabolic risk factors, except by uric acid, in any of the intervention groups. In conclusion, our findings do not provide any evidence that short-term regular intake of added sugars is linked to higher cardiometabolic risks, with exception of uric acid in overweight men. Public health interventions to prevent obesity and related diseases should focus on the quality of the whole diet rather than only focusing on reducing sugary drinks or sugar intakes.

Fructose Intake Impairs the Synergistic Vasomotor Manifestation of Nitric Oxide and Hydrogen Sulfide in Rat Aorta

In this study, we evaluated the effect of eight weeks of administration of 10% fructose solution to adult Wistar Kyoto (WKY) rats on systolic blood pressure (SBP), plasma and biometric parameters, vasoactive properties of the thoracic aorta (TA), NO synthase (NOS) activity, and the expression of enzymes producing NO and H2S. Eight weeks of fructose administration did not affect SBP, glycaemia, or the plasma levels of total cholesterol or low-density and high-density lipoprotein; however, it significantly increased the plasma levels of γ-glutamyl transferase and alanine transaminase. Chronic fructose intake deteriorated endothelium-dependent vasorelaxation (EDVR) and increased the sensitivity of adrenergic receptors to noradrenaline. Acute NOS inhibition evoked a reduction in EDVR that was similar between groups; however, it increased adrenergic contraction more in fructose-fed rats. CSE inhibition decreased EDVR in WKY but not in fructose-fed rats. The application of a H2S scavenger evoked a reduction in the EDVR in WKY rats and normalized the sensitivity of adrenergic receptors in rats treated with fructose. Fructose intake did not change NOS activity but reduced the expression of eNOS and CBS in the TA and CSE and CBS in the left ventricle. Based on our results, we could assume that the impaired vascular function induced by increased fructose intake was probably not directly associated with a decreased production of NO, but rather with impairment of the NO-H2S interaction and its manifestation in vasoactive responses.

Consumption of High-Fructose Corn Syrup Compared with Sucrose Promotes Adiposity and Increased Triglyceridemia but Comparable NAFLD Severity in Juvenile Iberian Pigs

BACKGROUND

Fructose consumption has been linked to nonalcoholic fatty liver disease (NAFLD) in children. However, the effect of high-fructose corn syrup (HFCS) compared with sucrose in pediatric NAFLD has not been investigated.

OBJECTIVES

We tested whether the isocaloric substitution of dietary sucrose by HFCS would increase the severity of NAFLD in juvenile pigs, and whether this effect would be associated with changes in gut histology, SCFA production, and microbial diversity.

METHODS

Iberian pigs, 53-d-old and pair-housed in pens balanced for weight and sex, were randomly assigned to receive a mash diet top-dressed with increasing amounts of sucrose (SUC; n = 3 pens; 281.6-486.8 g/kg diet) or HFCS (n = 4; 444.3-724.8 g/kg diet) during 16 wk. Diets exceeded the animal's energy requirements by providing sugars in excess, but met the requirements for all other nutrients. Animals were killed at 165 d of age after blood sampling, and liver, muscle, and gut were collected for histology, metabolome, and microbiome analyses. Data were analyzed by multivariate and univariate statistics.

RESULTS

Compared with SUC, HFCS increased subcutaneous fat, triacylglycerides in plasma, and butyrate in colon (P ≤ 0.05). In addition, HFCS decreased UMP and short-chain acyl carnitines in liver, and urea nitrogen and creatinine in serum (P ≤ 0.05). Microbiome analysis showed a 24.8% average dissimilarity between HFCS and SUC associated with changes in SCFA-producing bacteria. Body weight gain, intramuscular fat, histological and serum markers of liver injury, and circulating hormones, glucose, and proinflammatory cytokines did not differ between diets.

CONCLUSIONS

Fructose consumption derived from HFCS promoted butyrate synthesis, triglyceridemia, and subcutaneous lipid deposition in juvenile Iberian pigs, but did not increase serum and histological markers of NAFLD compared with a sucrose-enriched diet. Longer studies could be needed to observe differences in liver injury among sugar types.

Fructose and Non-Alcoholic Steatohepatitis

Background: The excessive consumption of free sugars is mainly responsible for the high prevalence of obesity and metabolic syndrome in industrialized countries. More and more studies indicate that fructose is involved in the pathophysiology and also in the degree of disease of non-alcoholic fatty liver disease (NAFLD). In epidemiologic studies, energy-adjusted higher fructose consumption correlates with NAFLD in overweight adults. In addition to glucose, fructose, as an equivalent component of conventional household sugar, appears to have negative metabolic effects in particular due to its exclusive hepatic metabolism. Liver-related mortality is strictly associated with the degree of fibrosis, whereas the most common cause of death in patients suffering from NAFLD and non-alcoholic steatohepatitis (NASH) are still cardiovascular diseases. In this review article, we have summarized the current state of knowledge regarding a relationship between fructose consumption, liver fibrosis and life expectancy in NASH. Method: Selective literature search in PubMed using the keywords 'non-alcoholic fatty liver', 'fructose', and 'fibrosis' was conducted. Results: The rate of overweight and obesity is significantly higher in both, adult and pediatric NASH patients. The consumption of free sugars is currently three times the maximum recommended amount of 10% of the energy intake. The current literature shows weight gain, negative effects on fat and carbohydrate metabolism and NASH with hypercaloric intake of fructose. Conclusions: Excessive fructose consumption is associated with negative health consequences. Whether this is due to an excess of energy or the particular metabolism of fructose remains open with the current study situation. The urgently needed reduction in sugar consumption could be achieved through a combination of binding nutritional policy measures including taxation of sugary soft drinks. Previous studies suggest that diet-related fructose intake exceeding the amount contained in vegetables and fruits lead to an increase of hepatic lipogenesis. Thus, further studies to clarify the protective contribution of low-fructose intake to positively influence NAFLD in industrial population are urgently required.

Fructose and high fructose corn syrup: are they a two-edged sword?

High-fructose syrups are used as sugar substitutes due to their physical and functional properties. High fructose corn syrup (HFCS) is used in bakery products, dairy products, breakfast cereals and beverages, but it has been reported that there might be a direct relationship between high fructose intake and adverse health effects such as obesity and the metabolic syndrome. Thus, fructose has recently received much attention, most of which was negative. Although studies have indicated that there might be a correlation between high fructose-rich diet and several adverse effects, however, the results of these studies cannot be certainly generalised to the effects of HFCS; because they have investigated pure fructose at very high concentrations in measurement of metabolic upsets. This review critically considered the advantages and possible disadvantages of HFCS application and consumption in food industry, as a current challenging issue between nutritionists and food technologists.

The Prospective Association of Dietary Sugar Intake in Adolescence With Risk Markers of Type 2 Diabetes in Young Adulthood

Purpose: To examine the prospective relevance of dietary sugar intake (based on dietary data as well as urinary excretion data) in adolescent years for insulin sensitivity and biomarkers of inflammation in young adulthood.

Methods: Overall 254 participants of the DONALD study who had at least two 3-day weighed dietary records for calculating intakes of fructose, glucose, sucrose, total, free, added sugars, total sugars from sugar-sweetened beverages (SSB), juice, and sweets/sugar or at least two complete 24 h urine samples (n = 221) for calculating sugar excretion (urinary fructose and urinary fructose + sucrose) in adolescence (females: 9–15 years, males: 10–16 years) and a fasting blood sample in adulthood (18–36 years), were included in multivariable linear regression analyses assessing their prospective associations with adult homeostasis model assessment insulin sensitivity (HOMA2-%S) and a pro-inflammatory score (based on CRP, IL-6, IL-18, leptin, chemerin, adiponectin).

Results: On the dietary intake level, no prospective associations were observed between adolescent fructose, sucrose, glucose, added, free, total sugar, or total sugar from SSB, juice or sweets/sugar intake and adult HOMA2-%S (p > 0.01). On the urinary level, however, higher excreted fructose levels were associated with improved adult HOMA2-%S (p = 0.008) among females only. No associations were observed between dietary or urinary sugars and the adult pro-inflammatory score (p > 0.01).

Conclusion: The present study did not provide support that dietary sugar consumed in adolescence is associated with adult insulin sensitivity. The one potential exception was the moderate dietary consumption of fructose, which showed a beneficial association with adult fasting insulin and insulin sensitivity.

Metabolic and Appetite Effects of Fructose and Glucose in Subjects with Type 1 Diabetes: A Randomized Crossover Clinical Trial

BACKGROUND

Fructose has been widely used for producing lower post-infusion glucose increase than other carbohydrates, but it seems that it promotes an increase in post-infusion triglycerides.

OBJECTIVE

The present study investigated the effects of fructose and glucose in metabolic variables and appetite sensations in patients with type 1 diabetes mellitus (T1DM).

METHODS

This is a single-blind, randomized, and crossover study (washout of 1-5 weeks), which evaluated 16 adult T1DM patients, accompanied at University Hospital. After eight hours of overnight fasting, there was an assessment of capillary blood glucose, anthropometric variables, appetite sensations, and laboratory tests (glycemia, lipemia, leptin and glucagon) were conducted. Subsequently, they received 200mL of solutions with water and 75g of crystal fructose or glucose. Appetite sensations and capillary blood glucose were evaluated in different post-infusion times. Blood was drawn after 180 minutes for the laboratory tests.

RESULTS

Blood glucose increased after the intake of both solutions, but glucose induced a higher elevation. None of them increased triglycerides or glucagon. Glucagon maintenance was similar among the solutions. Furthermore, both solutions reduced leptin and increased fullness, but only fructose increased the lack of interest in eating sweets.

CONCLUSION

Fructose induced a smaller increase in postprandial blood glucose than glucose, without changes in triglycerides and glucagon. In addition, leptin levels and appetite sensations were similar to glucose. Other studies are needed in order to confirm these findings, especially in the long term, so that their use becomes really reliable.

Knowledge attitudes and behaviors of adult individuals about high fructose corn syrup consumption; cross sectional survey study

OBJECTIVES

The purpose of this study is; to examine the knowledge and attitudes of individuals about ready-to food consumption and food products containing high fructose corn syrup (HFCS).

STUDY DESIGN

Research in the city center in the eastern Mediterranean region of Turkey was held with 18 individuals over the age of two shoppers at the supermarket.

METHODS

The study is a descriptive cross-sectional questionnaire-based study. The research was conducted between 15.09.2018 and 30.03.2019. Data were collected from 254 individuals using face-to-face interview technique. The questionnaire form consisted of questions created by the researcher to determine socio-demographic variables as well as information about ready-made food intake and foods containing high fructose corn syrup.

RESULTS

The suitability of the questionnaire for factor analysis was evaluated with the "Kaiser-Meyer-Olkin coefficient" and "Bartlett Sphericity Test". As a result of the exploratory factor analysis, the 21-item survey form explains 52% of the total variance. The questionnaire items consist of four factors. Cronbach's Alpha reliability of the questionnaire is 0.860 on the whole. In the sub-factors; The first factor was 0.859, the second factor was 0.764, the third factor was 0.652, and the fourth factor was 0.616. The findings obtained in the study were analyzed using the Independent Sample t Test, One Way Anova test, Mann Whitney U test and Tukey test. SPSS 21, USA was used to analyze the study. It was determined that the average age of the participants was 31.3 ± 11.7, the rate of paying attention to ingredients and nutritional values while purchasing ready-made foods was low, and 1/4 of them did not pay attention to high fructose corn syrup in their content. There was a significant correlation between the age and employment status of the participants and their knowledge and attitudes about the foods containing corn syrup (p < 0.05).

CONCLUSION

It was concluded that individuals should be educated about health risks while purchasing ready-made food products and should be more informed about foods containing HFCS. It is recommended that the questionnaire used in the study be tested in different sample groups in order to increase its validity and reliability evidence.

Fructose-Induced Intestinal Microbiota Shift Following Two Types of Short-Term High-Fructose Dietary Phases

High consumption of fructose and high-fructose corn syrup is related to the development of obesity-associated metabolic diseases, which have become the most relevant diet-induced diseases. However, the influences of a high-fructose diet on gut microbiota are still largely unknown. We therefore examined the effect of short-term high-fructose consumption on the human intestinal microbiota. Twelve healthy adult women were enrolled in a pilot intervention study. All study participants consecutively followed four different diets, first a low fructose diet (< 10 g/day fructose), then a fruit-rich diet (100 g/day fructose) followed by a low fructose diet (10 g/day fructose) and at last a high-fructose syrup (HFS) supplemented diet (100 g/day fructose). Fecal microbiota was analyzed by 16S rRNA sequencing. A high-fructose fruit diet significantly shifted the human gut microbiota by increasing the abundance of the phylum Firmicutes, in which beneficial butyrate producing bacteria such as Faecalibacterium, Anareostipes and Erysipelatoclostridium were elevated, and decreasing the abundance of the phylum Bacteroidetes including the genus Parabacteroides. An HFS diet induced substantial differences in microbiota composition compared to the fruit-rich diet leading to a lower Firmicutes and a higher Bacteroidetes abundance as well as reduced abundance of the genus Ruminococcus. Compared to a low-fructose diet we observed a decrease of Faecalibacterium and Erysipelatoclostridium after the HFS diet. Abundance of Bacteroidetes positively correlated with plasma cholesterol and LDL level, whereas abundance of Firmicutes was negatively correlated. Different formulations of high-fructose diets induce distinct alterations in gut microbiota composition. High-fructose intake by HFS causes a reduction of beneficial butyrate producing bacteria and a gut microbiota profile that may affect unfavorably host lipid metabolism whereas high consumption of fructose from fruit seems to modulate the composition of the gut microbiota in a beneficial way supporting digestive health and counteracting harmful effects of excessive fructose.

A Comprehensive Review on Source, Types, Effects, Nanotechnology, Detection, and Therapeutic Management of Reactive Carbonyl Species Associated with Various Chronic Diseases

Continuous oxidation of carbohydrates, lipids, and amino acids generate extremely reactive carbonyl species (RCS). Human body comprises some important RCS namely hexanal, acrolein, 4-hydroxy-2-nonenal, methylglyoxal, malondialdehyde, isolevuglandins, and 4-oxo-2- nonenal etc. These RCS damage important cellular components including proteins, nucleic acids, and lipids, which manifests cytotoxicity, mutagenicity, multitude of adducts and crosslinks that are connected to ageing and various chronic diseases like inflammatory disease, atherosclerosis, cerebral ischemia, diabetes, cancer, neurodegenerative diseases and cardiovascular disease. The constant prevalence of RCS in living cells suggests their importance in signal transduction and gene expression. Extensive knowledge of RCS properties, metabolism and relation with metabolic diseases would assist in development of effective approach to prevent numerous chronic diseases. Treatment approaches for RCS associated diseases involve endogenous RCS metabolizers, carbonyl metabolizing enzyme inducers, and RCS scavengers. Limited bioavailability and bio efficacy of RCS sequesters suggest importance of nanoparticles and nanocarriers. Identification of RCS and screening of compounds ability to sequester RCS employ several bioassays and analytical techniques. Present review describes in-depth study of RCS sources, types, properties, identification techniques, therapeutic approaches, nanocarriers, and their role in various diseases. This study will give an idea for therapeutic development to combat the RCS associated chronic diseases.

Molecular Study on the Potential Protective Effects of Bee Venom against Fructose-Induced Nonalcoholic Steatohepatitis in Rats

BACKGROUND

There is a causative relation between the increased hepatic steatohepatitis prevalence and sweeteners intake, fructose in particular. Despite an increasing understanding of the mechanisms of nonalcoholic steatohepatitis (NASH) pathogenesis, there are no drugs approved for it.

OBJECTIVES

Evaluate the effect of bee venom (BV) treatment on the fructose-induced NASH in rats and demonstrate its possible molecular mechanisms.

METHODS

NASH was induced in rats by 10% fructose in drinking water for 8 weeks. BV was administered (0.1 mg/kg, i.p.) 3 times per week during the last 2 weeks of the experiment. Sera were used for the determination of lipids, cholesterol, glucose, insulin, and liver enzymes. Hepatic gene expressions of farnesoid X receptor (FXR)α and the liver X receptor (LXR) were determined. Hepatic sterol regulatory element-binding protein (SREBP)1/2, oxidative stress, and inflammation parameters were measured. Liver parts were used for histopathological examination. Small intestine was removed for the determination of tight junction proteins.

RESULTS

Fructose caused overt histological damage in the liver, and this was associated with parallel changes in all parameters measured. BV effectively prevented these changes, presumably through amelioration of hepatic SREBP1/2, LXR, and FXRα expression as well as intestinal tight junction proteins.

CONCLUSION

These findings support the therapeutic usefulness of BV, a remedy with a favorable safety profile, in the prevention of fructose-induced NASH.

Fructose-mediated effects on gene expression and epigenetic mechanisms associated with NAFLD pathogenesis

Nonalcoholic fatty liver disease (NAFLD) is a chronic, frequently progressive condition that develops in response to excessive hepatocyte fat accumulation (i.e., steatosis) in the absence of significant alcohol consumption. Liver steatosis develops as a result of imbalanced lipid metabolism, driven largely by increased rates of de novo lipogenesis and hepatic fatty acid uptake and reduced fatty acid oxidation and/or disposal to the circulation. Fructose is a naturally occurring simple sugar, which is most commonly consumed in modern diets in the form of sucrose, a disaccharide comprised of one molecule of fructose covalently bonded with one molecule of glucose. A number of observational and experimental studies have demonstrated detrimental effects of dietary fructose consumption not only on diverse metabolic outcomes such as insulin resistance and obesity, but also on hepatic steatosis and NAFLD-related fibrosis. Despite the compelling evidence that excessive fructose consumption is associated with the presence of NAFLD and may even promote the development and progression of NAFLD to more clinically severe phenotypes, the molecular mechanisms by which fructose elicits effects on dysregulated liver metabolism remain unclear. Emerging data suggest that dietary fructose may directly alter the expression of genes involved in lipid metabolism, including those that increase hepatic fat accumulation or reduce hepatic fat removal. The aim of this review is to summarize the current research supporting a role for dietary fructose intake in the modulation of transcriptomic and epigenetic mechanisms underlying the pathogenesis of NAFLD.

Maternal high-fructose intake induces hypertension through activating histone codes on the (pro)renin receptor promoter

High-fructose intake induces hypertension via the renal expression of (pro)renin receptor (PRR) that stimulates the expression of sodium/hydrogen exchanger 3, Na/K/2Cl cotransporter 2, and genes of the intrarenal renin-angiotensin system. We hypothesize that maternal high-fructose intake induces hypertension in subsequent generation offspring through activating histone codes on the PRR promoter. Mice dams were offered 20% fructose solution during pregnancy and lactation, while the subsequent 1st to 4th generation offspring were raised without fructose. Blood pressure was measured via tail-cuff method. The mRNA and protein expression were determined using quantitative real-time polymerase chain reaction and western blotting, respectively. Histone modification was evaluated using a chromatin immunoprecipitation assay. Maternal high-fructose intake statistically significantly increased blood pressure in the 1st and 2nd generations of offspring compared to the control group. Expression levels of sodium transporters and PRR were increased in the kidneys of the 1st to 3rd generation offspring. Increased enrichment of active histone codes such as H3Ac and H3K4me2 but decreased enrichment of repressive histone codes such as H3K9me3 and H3K27me3 on the PRR promoter were observed in the 1st to 3rd not the 4th generation. Moreover, there was increased the mRNA expression for histone acetyltransferase and methyl transferases for H3K4 in the 1st and 2nd generation offspring compared to the control group. This study implicates that maternal high-fructose intake induces hypertension in multigenerational offspring through activating histone codes on the PRR promoter.

Metabolic effects of the dietary monosaccharides fructose, fructose-glucose, or glucose in mice fed a starch-containing moderate high-fat diet

Fructose consumption has been linked to obesity and increased hepatic de novo lipogenesis (DNL). Excessive caloric intake often confounds the results of fructose studies, and experimental diets are generally low-fat diets, not representative for westernized diets. Here, we compared the effects of dietary fructose with those of dietary glucose, in adult male and female mice on a starch-containing moderate high-fat (HF) diet. After 5 weeks fattening on a HF high-glucose (HF-G) diet, mice were stratified per sex and assigned to one of the three intervention diets for 6 weeks: HF high fructose (HF-F), HF with equimolar glucose and fructose (HF-GF), or HF-G. Bodyweight (BW) and food intake were measured weekly. Indirect calorimetry was performed on week 5; animals were sacrificed in food-deprived state on week 6. Data were analyzed within sex. BW gain was similar among animals on the HF-G, HF-GF, and HF-F diets. Cumulative food intake was slightly lower in HF-F animals (both sexes). However, energy expenditure was not affected, or were circulating insulin and glucose concentrations, and hepatic triglyceride levels at endpoint. Hepatic gene expression analysis showed only minor alterations in hexokinase and glycolysis-related expression in males, and no alterations in sugar transporters, or DNL-related enzymes. In females, no consistent alterations in hepatic or small intestine gene expression were seen. Concluding, partial or complete replacement of dietary glucose with fructose does not increase caloric intake, and does not affect BW, hepatic triglyceride levels, or insulin concentrations in male and female mice on a moderate high-fat diet.

IMPACT OF CURRENT DIET AT THE RISK OF NON-ALCOHOLIC FATTY LIVER DISEASE (NAFLD)

The nonalcoholic fatty liver disease (NAFLD) affects approximately 20%-30% of general population and is even more prevalent among obese individuals. The risk factors mainly associated with NAFLD are diseases related to the metabolic syndrome, genetics and environment. In this review, we provide a literature compilation evaluating the evidence behind dietary components, including calories intake, fat, protein, fibers and carbohydrate, especially fructose which could be a trigger to development and progression of the NAFLD. In fact, it has been demonstrated that diet is an important factor for the development of NAFLD and its association is complex and extends beyond total energy intake.

Intestinal Fructose and Glucose Metabolism in Health and Disease

The worldwide epidemics of obesity and diabetes have been linked to increased sugar consumption in humans. Here, we review fructose and glucose metabolism, as well as potential molecular mechanisms by which excessive sugar consumption is associated to metabolic diseases and insulin resistance in humans. To this end, we focus on understanding molecular and cellular mechanisms of fructose and glucose transport and sensing in the intestine, the intracellular signaling effects of dietary sugar metabolism, and its impact on glucose homeostasis in health and disease. Finally, the peripheral and central effects of dietary sugars on the gut-brain axis will be reviewed.

Repercussions of low fructose-drinking water in male rats

Fructose consumption has increased worldwide, and it has been associated with the development of metabolic diseases such as insulin resistance (IR) and steatosis. The aim was to evaluate if lower fructose concentrations may cause pancreatic structural abnormalities, leading to a glucose intolerance without steatosis in male rats. Young male rats orally received 7% fructose solution for 12 weeks. Body weight, food, water, and energy intake were measured. An oral glucose tolerance test (OGTT) was performed. After final experimental period, all rats were anaesthetized and killed. Blood samples were collected for biochemical analyses and organs (liver and pancreas) were processed for morphological analyses. Fructose consumption was not associated with lipid accumulation in liver. However, fructose administration was associated with an increased area under curve from OGTT and an increased percentage of insulin-positive cells, high beta cell mass and reduced pancreatic islet area. Fructose supplementation (7%) did not cause steatosis, but it led to abnormal morphology and function of pancreatic islet cells, contributing for glucose intolerance development. Our findings demonstrate that even low fructose concentrations may cause deleterious effects in animals.

Could the high consumption of high glycaemic index carbohydrates and sugars, associated with the nutritional transition to the Western type of diet, be the common cause of the obesity epidemic and the worldwide increasing incidences of Type 1 and Type 2 diabetes?

The globally increasing incidences of Type 1 diabetes (T1DM) and Type 2 diabetes (T2DM) can have a common background. If challenged by the contemporary high level of nutritional glucose stimulation, the β-cells in genetically predisposed individuals are at risk for damage which can lead to the diseases. The fat to carbohydrate dietary shift can also contribute to the associated obesity epidemic.

Food sources of fructose-containing sugars and glycaemic control: systematic review and meta-analysis of controlled intervention studies

OBJECTIVE

To assess the effect of different food sources of fructose-containing sugars on glycaemic control at different levels of energy control.

DESIGN

Systematic review and meta-analysis of controlled intervention studies.

DATA SOURCES

Medine, Embase, and the Cochrane Library up to 25 April 2018.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Controlled intervention studies of at least seven days' duration and assessing the effect of different food sources of fructose-containing sugars on glycaemic control in people with and without diabetes were included. Four study designs were prespecified on the basis of energy control: substitution studies (sugars in energy matched comparisons with other macronutrients), addition studies (excess energy from sugars added to diets), subtraction studies (energy from sugars subtracted from diets), and ad libitum studies (sugars freely replaced by other macronutrients without control for energy). Outcomes were glycated haemoglobin (HbA1c), fasting blood glucose, and fasting blood glucose insulin.

DATA EXTRACTION AND SYNTHESIS

Four independent reviewers extracted relevant data and assessed risk of bias. Data were pooled by random effects models and overall certainty of the evidence assessed by the GRADE approach (grading of recommendations assessment, development, and evaluation).

RESULTS

155 study comparisons (n=5086) were included. Total fructose-containing sugars had no harmful effect on any outcome in substitution or subtraction studies, with a decrease seen in HbA1c in substitution studies (mean difference -0.22% (95% confidence interval to -0.35% to -0.08%), -25.9 mmol/mol (-27.3 to -24.4)), but a harmful effect was seen on fasting insulin in addition studies (4.68 pmol/L (1.40 to 7.96)) and ad libitum studies (7.24 pmol/L (0.47 to 14.00)). There was interaction by food source, with specific food sources showing beneficial effects (fruit and fruit juice) or harmful effects (sweetened milk and mixed sources) in substitution studies and harmful effects (sugars-sweetened beverages and fruit juice) in addition studies on at least one outcome. Most of the evidence was low quality.

CONCLUSIONS

Energy control and food source appear to mediate the effect of fructose-containing sugars on glycaemic control. Although most food sources of these sugars (especially fruit) do not have a harmful effect in energy matched substitutions with other macronutrients, several food sources of fructose-containing sugars (especially sugars-sweetened beverages) adding excess energy to diets have harmful effects. However, certainty in these estimates is low, and more high quality randomised controlled trials are needed.

STUDY REGISTRATION

Clinicaltrials.gov (NCT02716870).

Consumption of Sugars, Sugary Foods, and Sugary Beverages in Relation to Adiposity-Related Cancer Risk in the Framingham Offspring Cohort (1991-2013)

Background: Higher sugar consumption may increase cancer risk by promoting insulin-glucose dysregulation, oxidative stress, hormonal imbalances, and excess adiposity. This prospective study investigates the association between dietary sugars (fructose and sucrose) and sugary foods and beverages in relation to combined and site-specific (breast, prostate, colorectal) adiposity-associated cancers.Methods: The analytic sample consisted of 3,184 adults, aged 26-84 years, from the Framingham Offspring cohort. Diet data were first collected between 1991 and 1995 using a food frequency questionnaire. Intakes of fructose, sucrose, sugary foods, and sugary beverages (fruit juice and sugar-sweetened beverages) were derived. Participants were followed up until 2013 to ascertain cancer incidence; 565 doctor-diagnosed adiposity-related cancers, including 124 breast, 157 prostate, and 68 colorectal cancers occurred. Multivariable-adjusted Cox proportional hazards models were used to evaluate associations. Tests for interaction with BMI and waist circumference were conducted.Results: No associations were observed between fructose, sucrose, sugary food consumption, and combined incidence of adiposity-related cancers or the examined site-specific cancers. While total consumption of sugary beverages was not associated with site-specific cancer risk, higher intakes of fruit juice were associated with 58% increased prostate cancer risk (HR: 1.58; 95% CI, 1.04-2.41) in multivariable-adjusted models. In exploratory stratified analyses, higher sugary beverage intakes increased overall adiposity-related cancer risk by 59% in participants with excessive central adiposity (HR: 1.59; 95% CI, 1.01-2.50; Ptrend = 0.057).Conclusions: In this cohort of American adults, higher sugary beverage consumption was associated with increased cancer risk among participants with central adiposity.Impact: These analyses suggest that avoiding sugary beverages represents a simple dietary modification that may be used as an effective cancer control strategy. Cancer Prev Res; 11(6); 347-58. ©2018 AACR.

Differential effects of high consumption of fructose or glucose on mesenteric arterial function in female rats

We have recently shown that type of supplemented simple sugar, not merely calorie intake, determines adverse effects on metabolism and aortic endothelial function in female rats. The aim of the current study was to investigate and compare the effects of high consumption of glucose or fructose on mesenteric arterial reactivity and systolic blood pressure (SBP). Sprague-Dawley female rats were supplemented with 20% w/v glucose or fructose in drinking water for 8 weeks. Here, we show that both sugars alter insulin signaling in mesenteric arteries (MA), assessed by a reduction in phosphorylated Akt, and increase in SBP. Furthermore, ingestion of glucose or fructose enhances inducible nitric oxide synthase (iNOS) expression and contractile responses to endothelin and phenylephrine in MA of rats. The endothelium-dependent vasodilation to acetylcholine and bradykinin as well as the relaxation responses to the nitric oxide donor sodium nitroprusside are impaired in MA of fructose- but not glucose-supplemented rats. In contrast, only glucose supplementation increases the expression of phosphorylated endothelial NOS (eNOS) in MA of rats. In conclusion, this study reveals that supplementation with fructose or glucose in liquid form enhances vasocontractile responses and increases iNOS expression in MA, effects which are accompanied by increased SBP in those groups. On the other hand, the preserved vasodilatory responses in MA from glucose-supplemented rats could be attributed to the enhanced level of phosphorylated eNOS expression in this group.

No Adverse Programming by Post-Weaning Dietary Fructose of Body Weight, Adiposity, Glucose Tolerance, or Metabolic Flexibility

SCOPE

Metabolic programming can occur not only in the perinatal period, but also post-weaning. This study aims to assess whether fructose, in comparison to glucose, in the post-weaning diet programs body weight, adiposity, glucose tolerance, metabolic flexibility, and health at adult age.

METHODS AND RESULTS

Three-week-old male and female C57BL6/JRccHsd mice are given an intervention diet with 32 energy percent (en%) glucose or fructose for only 3 weeks. Next, all animals are switched to the same 40 en% high fat diet for 9 weeks. Neither body weight nor adiposity differs significantly between the animals fed with glucose or fructose diets at any point during the study in both sexes. Glucose tolerance in adulthood is not affected by the post-weaning diet, nor are activity, energy expenditure, and metabolic flexibility, as measured by indirect calorimetry. At the end of the study, only in females fasting serum insulin levels and HOMA-IR index are lower in post-weaning fructose versus glucose diet (p = 0.02), without differences in pancreatic β-cell mass.

CONCLUSIONS

Our present findings indicate no adverse programming of body weight, adiposity, glucose tolerance, and metabolic flexibility by dietary (solid) fructose in comparison to glucose in the post-weaning diet in mice.

Sugars, exercise and health

BACKGROUND

There is a direct link between a variety of addictions and mood states to which exercise could be relieving. Sugar addiction has been recently counted as another binge/compulsive/addictive eating behavior, differently induced, leading to a high-significant health problem. Regularly exercising at moderate intensity has been shown to efficiently and positively impact upon physiological imbalances caused by several morbid conditions, including affective disorders. Even in a wider set of physchiatric diseases, physical exercise has been prescribed as a complementary therapeutic strategy.

METHOD

A comprehensive literature search was carried out in the Cochrane Library and MEDLINE databases (search terms: sugar addiction, food craving, exercise therapy, training, physical fitness, physical activity, rehabilitation and aerobic).

RESULTS

Seeking high-sugar diets, also in a reward- or craving-addiction fashion, can generate drastic metabolic derangements, often interpolated with affective disorders, for which exercise may represent a valuable, universal, non-pharmachological barrier.

LIMITATIONS

More research in humans is needed to confirm potential exercise-mechanisms that may break the bond between sugar over-consumption and affective disorders.

CONCLUSIONS

The purpose of this review is to address the importance of physical exercise in reversing the gloomy scenario of unhealthy diets and sedentary lifestyles in our modern society.

Fructose-induced inflammation and increased cortisol: A new mechanism for how sugar induces visceral adiposity

Traditionally, the leading hypothesis regarding the development of obesity involves caloric imbalance, whereby the amount of calories consumed exceeds the amount of calories burned which causes obesity. Another hypothesis for why we get fat has surfaced in the last decade which is the idea that the overconsumption of added sugars and refined carbohydrates induce insulin resistance and high insulin levels causing obesity. While insulin is a fat-storing hormone, this hypothesis does not explain visceral adiposity, or why certain people are found to have fat stored in and around their organs. We propose a new mechanism for body fattening, particular visceral adiposity. This hypothesis involves the overconsumption of fructose, which leads to inflammation in all cells that metabolize it rapidly. When fructose is metabolized in subcutaneous adipocytes, the subsequent inflammation leads to an increase in intracellular cortisol in order to help squelch the inflammation. Unfortunately, the increase in intracellular cortisol leads to an increased flux of fatty acids out of the subcutaneous adipocytes allowing more substrate for fat storage into visceral fat tissue. Moreover fructose-induced inflammation in the liver also leads to increased intracellular cortisol via an upregulation of 11-B hydroxysteroid dehydrogenase type 1 causing increased fat storage in the liver (i.e., fatty liver). In essence, the fructose-induced inflammatory cortisol response causes "thin on the outside, fat on the inside" (TOFI). Furthermore, fructose in the brain, either from fructose uptake via the blood brain barrier or endogenous formation from glucose via the polyol pathway stimulates an increased release of cortisol causing hepatic gluconeogenesis leading to overall insulin resistance and further body fattening. This review paper will discuss in detail the hypothesis that fructose-induced inflammation and cortisol activation causes visceral adiposity.

Transcriptomics, metabolomics and histology indicate that high-carbohydrate diet negatively affects the liver health of blunt snout bream (Megalobrama amblycephala)

Background

Global trend of the introduction of high levels of relatively cheap carbohydrates to reduce the amount of costly protein in the aquatic animal feed production has affected the aquaculture of an economically important cyprinid fish, blunt snout bream (Megalobrama amblycephala). This dietary shift has resulted in increased prevalence of metabolic disorders, often causing economic losses. High dietary intake of carbohydrates, associated with obesity, is one of the major causes of non-alcoholic fatty liver disease (NAFLD) in humans.

Results

We have conducted an eight-week feeding trial to better understand how a high-carbohydrate diet (HCBD) affects the liver health in this fish. Hepatosomatic index and lipid content were significantly (P < 0.05) higher in the HCBD group. Histology results also suggested pathological changes in the livers of HCBD group, with excessive lipid accumulation and indication of liver damage. Metabolomics and serum biochemistry analyses showed that a number of metabolites indicative of liver damage were increased in the HCBD group. This group also exhibited low levels of betaine, which is a metabolite crucial for maintaining the healthy liver functions. Transcriptomic and qPCR analyses indicated that HCBD had a strong impact on the expression of a large number of genes associated with the NAFLD and insulin signalling pathways, which may lead to the development of insulin resistance in hepatocytes, pathological liver changes, and eventually the NAFLD.

Conclusions

Transcriptomics, metabolomics and histology results all indicate early symptoms of liver damage. However whether these would actually lead to the development of NAFLD after a longer period of time, remains inconclusive. Additionally, a very high number of upregulated genes in the HCBD group associated with several neurodegenerative diseases is a strong indication of neurodegenerative changes caused by the high-carbohydrate diet in blunt snout bream. This suggests that fish might present a good model to study neurodegenerative changes associated with high-carbohydrate diet in humans.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4246-9) contains supplementary material, which is available to authorized users.

Divergent effects of glucose and fructose on hepatic lipogenesis and insulin signaling

Overconsumption of high-fat diet (HFD) and sugar-sweetened beverages are risk factors for developing obesity, insulin resistance, and fatty liver disease. Here we have dissected mechanisms underlying this association using mice fed either chow or HFD with or without fructose- or glucose-supplemented water. In chow-fed mice, there was no major physiological difference between fructose and glucose supplementation. On the other hand, mice on HFD supplemented with fructose developed more pronounced obesity, glucose intolerance, and hepatomegaly as compared to glucose-supplemented HFD mice, despite similar caloric intake. Fructose and glucose supplementation also had distinct effects on expression of the lipogenic transcription factors ChREBP and SREBP1c. While both sugars increased ChREBP-β, fructose supplementation uniquely increased SREBP1c and downstream fatty acid synthesis genes, resulting in reduced liver insulin signaling. In contrast, glucose enhanced total ChREBP expression and triglyceride synthesis but was associated with improved hepatic insulin signaling. Metabolomic and RNA sequence analysis confirmed dichotomous effects of fructose and glucose supplementation on liver metabolism in spite of inducing similar hepatic lipid accumulation. Ketohexokinase, the first enzyme of fructose metabolism, was increased in fructose-fed mice and in obese humans with steatohepatitis. Knockdown of ketohexokinase in liver improved hepatic steatosis and glucose tolerance in fructose-supplemented mice. Thus, fructose is a component of dietary sugar that is distinctively associated with poor metabolic outcomes, whereas increased glucose intake may be protective.

Influence of dietary macronutrients on liver fat accumulation and metabolism

The liver is a principal metabolic organ within the human body and has a major role in regulating carbohydrate, fat, and protein metabolism. With increasing rates of obesity, the prevalence of non-alcoholic fatty liver disease (NAFLD) is growing. It remains unclear why NAFLD, which is now defined as the hepatic manifestation of the metabolic syndrome, develops but lifestyle factors such as diet (ie, total calorie and specific nutrient intakes), appear to play a key role. Here we review the available observational and intervention studies that have investigated the influence of dietary macronutrients on liver fat content. Findings from observational studies are conflicting with some reporting that relative to healthy controls, patients with NAFLD consume diets higher in total fat/saturated fatty acids, whilst others find they consume diets higher in carbohydrates/sugars. From the limited number of intervention studies that have been undertaken, a consistent finding is a hypercaloric diet, regardless of whether the excess calories have been provided either as fat, sugar, or both, increases liver fat content. In contrast, a hypocaloric diet decreases liver fat content. Findings from both hyper- and hypo-caloric feeding studies provide some suggestion that macronutrient composition may also play a role in regulating liver fat content and this is supported by data from isocaloric feeding studies; fatty acid composition and/or carbohydrate content/type appear to influence whether there is accrual of liver fat or not. The mechanisms by which specific macronutrients, when consumed as part of an isocaloric diet, cause a change in liver fat remain to be fully elucidated.

Fructose: A Dietary Sugar in Crosstalk with Microbiota Contributing to the Development and Progression of Non-Alcoholic Liver Disease

Fructose is one of the key dietary catalysts in the development of non-alcoholic fatty liver disease (NAFLD). NAFLD comprises a complex disease spectrum, including steatosis (fatty liver), non-alcoholic steatohepatitis, hepatocyte injury, inflammation, and fibrosis. It is also the hepatic manifestation of the metabolic syndrome, which covers abdominal obesity, insulin resistance, dyslipidemia, glucose intolerance, or type 2 diabetes mellitus. Commensal bacteria modulate the host immune system, protect against exogenous pathogens, and are gatekeepers in intestinal barrier function and maturation. Dysbalanced intestinal microbiota composition influences a variety of NAFLD-associated clinical conditions. Conversely, nutritional supplementation with probiotics and preobiotics impacting composition of gut microbiota can improve the outcome of NAFLD. In crosstalk with the host immune system, the gut microbiota is able to modulate inflammation, insulin resistance, and intestinal permeability. Moreover, the composition of microbiota of an individual is a kind of fingerprint highly influenced by diet. In addition, not only the microbiota itself but also its metabolites influence the metabolism and host immune system. The gut microbiota can produce vitamins and a variety of nutrients including short-chain fatty acids. Holding a healthy balance of the microbiota is therefore highly important. In the present review, we discuss the impact of long-term intake of fructose on the composition of the intestinal microbiota and its biological consequences in regard to liver homeostasis and disease. In particular, we will refer about fructose-induced alterations of the tight junction proteins affecting the gut permeability, leading to the translocation of bacteria and bacterial endotoxins into the blood circulation.

Fructose-rich diet and insulin action in female rat heart: Estradiol friend or foe?

Increased intake of fructose in humans and laboratory animals is demonstrated to be a risk factor for development of metabolic disorders (insulin resistance, metabolic syndrome, type 2 diabetes) and cardiovascular diseases. On the other hand, estradiol is emphasized as a cardioprotective agent. The main goal of this review is to summarize recent findings on damaging cardiac effects of fructose-rich diet in females, mostly experimental animals, and to evaluate protective capacity of estradiol. Published results of our and other research groups indicate mostly detrimental effects of fructose-rich diet on cardiac insulin signaling molecules, glucose and fatty acid metabolism, nitric oxide production and ion transport, as well as renin-angiotensin system and inflammation. Some of these processes are involved in cardiac insulin signal transmission, others are regulated by insulin or have an influence on insulin action. Administration of estradiol to ovariectomized female rats, exposed to increased intake of fructose, was mostly beneficial to the heart, but sometimes it was ineffective or even detrimental, depending on the particular processes. We believe that these data, carefully translated to human population, could be useful for clinicians dealing with postmenopausal women susceptible to metabolic diseases and hormone replacement therapy.

What is the appropriate upper limit for added sugars consumption?

Dramatic increases in obesity and diabetes have occurred worldwide over the past 30 years. Some investigators have suggested that these increases may be due, in part, to increased added sugars consumption. Several scientific organizations, including the World Health Organization, the Scientific Advisory Council on Nutrition, the Dietary Guidelines Advisory Committee 2015, and the American Heart Association, have recommended significant restrictions on upper limits of sugars consumption. In this review, the scientific evidence related to sugars consumption and its putative link to various chronic conditions such as obesity, diabetes, heart disease, nonalcoholic fatty liver disease, and the metabolic syndrome is examined. While it appears prudent to avoid excessive calories from sugars, the scientific basis for restrictive guidelines is far from settled.

Added sugars and risk factors for obesity, diabetes and heart disease

The effects of added sugars on various chronic conditions are highly controversial. Some investigators have argued that added sugars increase the risk of obesity, diabetes and cardiovascular disease. However, few randomized controlled trials are available to support these assertions. The literature is further complicated by animal studies, as well as studies which compare pure fructose to pure glucose (neither of which is consumed to any appreciable degree in the human diet) and studies where large doses of added sugars beyond normal levels of human consumption have been administered. Various scientific and public health organizations have offered disparate recommendations for upper limits of added sugar. In this article, we will review recent randomized controlled trials and prospective cohort studies. We conclude that the normal added sugars in the human diet (for example, sucrose, high-fructose corn syrup and isoglucose) when consumed within the normal range of normal human consumption or substituted isoenergetically for other carbohydrates, do not appear to cause a unique risk of obesity, diabetes or cardiovascular disease.

High Dietary Fructose Intake on Cardiovascular Disease Related Parameters in Growing Rats

The objective of this study was to determine the effects of a high-fructose diet on cardiovascular disease (CVD)-related parameters in growing rats. Three-week-old female Sprague Dawley rats were randomly assigned to four experimental groups; a regular diet group (RD: fed regular diet based on AIN-93G, n = 8), a high-fructose diet group (30Frc: fed regular diet with 30% fructose, n = 8), a high-fat diet group (45Fat: fed regular diet with 45 kcal% fat, n = 8) or a high fructose with high-fat diet group (30Frc + 45Fat, fed diet 30% fructose with 45 kcal% fat, n = 8). After an eight-week treatment period, the body weight, total-fat weight, serum glucose, insulin, lipid profiles and pro-inflammatory cytokines, abdominal aortic wall thickness, and expressions of eNOS and ET-1 mRNA were analyzed. The result showed that total-fat weight was higher in the 30Frc, 45Fat, and 30Frc + 45Fat groups compared to the RD group (p < 0.05). Serum triglyceride (TG) levels were highest in the 30Frc group than the other groups (p < 0.05). The abdominal aorta of 30Frc, 45Fat, and 30Frc + 45Fat groups had higher wall thickness than the RD group (p < 0.05). Abdominal aortic eNOS mRNA level was decreased in 30Frc, 45Fat, and 30Frc + 45Fat groups compared to the RD group (p < 0.05), and also 45Fat and 30Frc + 45Fat groups had decreased mRNA expression of eNOS compared to the 30Frc group (p < 0.05). ET-1 mRNA level was higher in 30Frc, 45Fat, and 30Frc + 45Fat groups than the RD group (p < 0.05). Both high fructose consumption and high fat consumption in growing rats had similar negative effects on CVD-related parameters.

Relationship between Added Sugars Consumption and Chronic Disease Risk Factors: Current Understanding

Added sugars are a controversial and hotly debated topic. Consumption of added sugars has been implicated in increased risk of a variety of chronic diseases including obesity, cardiovascular disease, diabetes and non-alcoholic fatty liver disease (NAFLD) as well as cognitive decline and even some cancers. Support for these putative associations has been challenged, however, on a variety of fronts. The purpose of the current review is to summarize high impact evidence including systematic reviews, meta-analyses, and randomized controlled trials (RCTs), in an attempt to provide an overview of current evidence related to added sugars and health considerations. This paper is an extension of a symposium held at the Experimental Biology 2015 conference entitled “Sweeteners and Health: Current Understandings, Controversies, Recent Research Findings and Directions for Future Research”. We conclude based on high quality evidence from randomized controlled trials (RCT), systematic reviews and meta-analyses of cohort studies that singling out added sugars as unique culprits for metabolically based diseases such as obesity, diabetes and cardiovascular disease appears inconsistent with modern, high quality evidence and is very unlikely to yield health benefits. While it is prudent to consume added sugars in moderation, the reduction of these components of the diet without other reductions of caloric sources seems unlikely to achieve any meaningful benefit.

Controversies about sugars consumption: state of the science

INTRODUCTION

Few topics in nutrition generate more controversy and debate than the putative associations between added sugars and health. With this as background, a group of researchers in the area of sugars and health gathered at the European Nutrition Conference (FENS) in 2015 to discuss these controversies and provide evidence-based science. The purpose of the current article was to provide a brief summary of some of the highlights from each of the presenters and serve as an Introduction to the supplement which contains full articles based on their presentations.

Lower Doses of Fructose Extend Lifespan in Caenorhabditis elegans

Epidemiological studies indicate that the increased consumption of sugars including sucrose and fructose in beverages correlate with the prevalence of obesity, type-2 diabetes, insulin resistance, hyperinsulinemia, hypertriglyceridemia, and hypertension in humans. A few reports suggest that fructose extends lifespan in Saccharomyces cerevisiae. In Anopheles gambiae, fructose, glucose, or glucose plus fructose also extended lifespan. New results presented here suggest that fructose extends lifespan in Caenorhabditis elegans (C. elegans) wild type (N2). C. elegans were fed standard laboratory food source (E. coli OP50), maintained in liquid culture. Experimental groups received additional glucose (111 mM), fructose (55 mM, 111 mM, or 555 mM), sucrose (55 mM, 111 mM, or 555 mM), glucose (167 mM) plus fructose (167 mM) (G&F), or high fructose corn syrup (HFCS, 333 mM). In four replicate experiments, fructose dose-dependently increased mean lifespan at 55 mM or 111 m Min N2, but decreased lifespan at 555 mM (P < 0.001). Sucrose did not affect the lifespan. Glucose reduced lifespan (P < 0.001). Equal amount of G&F or HFCS reduced lifespan (P < 0.0001). Intestinal fat deposition (IFD) was increased at a higher dose of fructose (555 mM), glucose (111 mM), and sucrose (55 mM, 111 mM, and 555 mM). Here we report a biphasic effect of fructose increasing lifespan at lower doses and shortening lifespan at higher doses with an inverse effect on IFD. In view of reports that fructose increases lifespan in yeast, mosquitoes and now nematodes, while decreasing fat deposition (in nematodes) at lower concentrations, further research into the relationship of fructose to lifespan and fat accumulation in vertebrates and mammals is indicated.

Chemical constituents and health effects of sweet potato

Sweet potatoes are becoming a research focus in recent years due to their unique nutritional and functional properties. Bioactive carbohydrates, proteins, lipids, carotenoids, anthocyanins, conjugated phenolic acids, and minerals represent versatile nutrients in different parts (tubers, leaves, stems, and stalks) of sweet potato. The unique composition of sweet potato contributes to their various health benefits, such as antioxidative, hepatoprotective, antiinflammatory, antitumor, antidiabetic, antimicrobial, antiobesity, antiaging effects. Factors affecting the nutritional composition and bio-functions of sweet potato include the varieties, plant parts, extraction time and solvents, postharvest storage, and processing. The assays for bio-function evaluation also contribute to the variations among different studies. This review summarizes the current knowledge of the chemical composition of sweet potato, and their bio-functions studied in vitro and in vivo. Leaves, stems, and stalks of sweet potato remain much underutilized on commercial levels. Sweet potato can be further developed as a sustainable crop for diverse nutritionally enhanced and value-added food products to promote human health.