Fructose-rich diet leads to reduced aerobic capacity and to liver injury in rats

Aspartate Aminotransferase/Alanine Aminotransferase Ratio: A Predictor of All-Cause Mortality Rate Among Japanese Community-Dwelling Individuals

Introduction An elevated ratio of aspartate aminotransferase (AST) to alanine aminotransferase (ALT) not only independently affects aging-related health but also plays a critical role in mortality. However, there is limited predictive data on all-cause mortality, particularly in the context of community-dwelling individuals in Japan. This study examined the association between the AST/ALT ratio and survival prognosis in a cohort study using two follow-up studies based on 19-year and 7-year intervals. Methods The study included 1,573 male (63 ± 14 years; range, 20-90 years) and 1,980 female participants (65 ± 12 years; range, 19-89 years). The participants were those involved in a Nomura cohort study conducted in 2002 (first cohort) and 2014 (second cohort) that continued to participate throughout the follow-up periods (follow-up rates were 90.3% and 97.4% for each cohort). A Cox proportional hazards model was adopted to calculate the multivariate-adjusted hazard ratios (HRs) of death from the baseline health check-up to the follow-up periods while controlling for potential confounding factors. Results The follow-up survey revealed that there were 473 male deaths (30.1% of total male participants) and 432 female deaths (21.8% of total female participants). The univariate Cox regression analysis showed that HRs for all-cause mortality were greater for participants in higher AST/ALT ratio quartiles (p < 0.001). The multivariate Cox regression analysis with adjusted variables showed a significant association between those in the fourth AST/ALT ratio quartile (HR: 1.83, 95% confidence interval, 1.46-2.29) and the risk of all-cause mortality. This association holds irrespective of gender, age, and elevated gamma-glutamyl transpeptidase, particularly in the case of participants with a body mass index < 25 kg/m2 without a history of cardiovascular disease or diabetes. Conclusions Our results reveal that an elevated AST/ALT ratio is an independent factor that can predict the risk of all-cause mortality among community-dwelling individuals.

Non-linear association between aspartate aminotransferase to alanine aminotransferase ratio and mortality in critically ill older patients: A retrospective cohort study

BACKGROUND

The aspartate aminotransferase to alanine aminotransferase (AST/ALT) ratio has been shown to be associated with poor clinical outcomes across various patient groups. However, little is unclear about the association between the two in critically ill older patients. Therefore, we aim to investigate the association of the AST/ALT ratio with hospital mortality in this special population.

METHODS

In this retrospective cohort study, we extracted elderly patients (age ≥ 65 years) from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. The primary outcome was in-hospital mortality. The association between the AST/ALT ratio and hospital mortality was studied using univariable and multivariable Cox regression analysis, as well as restricted cubic splines (RCS). Survival analysis was performed using the Kaplan-Meier (KM) method according to the AST/ALT ratio.

RESULTS

Among the 13,358 eligible patients, the mean age was 77.6 years, 7,077 patients (52.9%) were male, and 2,511 patients (18.8%) died in hospital. The AST/ALT ratio was found to be independently associated with in-hospital mortality (HR = 1.05, 95% CI: 1.01-1.09, P = 0.022) after adjusting for potential confounders. Furthermore, a non-linear relationship and saturation effect were observed between them, with the inflection point being 1.80. When the AST/ALT ratio was less than 1.80, we found that every 1 unit increase in the AST/ALT ratio resulted in a 39% increased risk of in-hospital mortality (HR = 1.39, 95% CI: 1.18-1.64, P < 0.001). However, when the AST/ALT ratio was greater than 1.80, the association became saturated (HR = 1.01, 95% CI: 0.96-1.07, P = 0.609). Sensitivity and subgroup analyses showed the results were robust.

CONCLUSION

In critically ill older patients, the association between the AST/ALT ratio and in-hospital mortality was non-linear and showed a saturation effect. An elevated AST/ALT ratio was significantly associated with increased in-hospital mortality when the AST/ALT ratio was less than 1.80.

The Role of High-Fructose Diet in Liver Function of Rodent Models: A Systematic Review of Molecular Analysis

The present systematic review of animal studies on long-term fructose intake in rodents revealed a significant decrease in the activities of antioxidant enzymes due to a fructose-rich diet. The reduced activity of these enzymes led to an increase in oxidative stress, which can cause liver damage in rodents. Of eight studies analyzed, 5 (62.5%) and 1 (12.5%) used male and female rats, respectively, while 2 studies (25%) used female mice. Moreover, half of the studies used HFCS, but the other half employed fructose in the diet. Hence, it is essential to monitor dietary habits to ensure public health and nutrition research outcomes.

Increased transferase ratio is associated with adverse cardio-cerebral events in patients with unstable angina: A retrospective cohort study

To investigate the prognostic role of the elevated aspartate and alanine aminotransferase (AST/ALT) ratio in patients with unstable angina (UA). In this observational study, all patients with UA undergoing percutaneous coronary intervention at our center from January 2019 to December 2020 were examined. Clinical presentations, laboratory parameters, and procedural characteristics were collected. The primary endpoint was a composite of major adverse cardio-cerebral events (MACCE), such as death, nonfatal myocardial infarction, nonfatal stroke, and target vessel revascularization. In total, 1123 eligible UA patients were enrolled in the present study (mean age 62.3 years; 54.5% of male). Patients in the upper tertile of the AST/ALT ratio were older, had more extensive coronary stenosis, and had poor nutritional status (P < .05). Meanwhile, the cumulative incidence of MACCE at 13 months of follow-up increased in a stepwise manner and across the tertile of the AST/ALT ratio, predominantly driven by target vessel revascularization (both log-rank P < .001). Importantly, the AST/ALT ratio was associated with MACCE in a multivariate analysis that was adjusted for potential covariates (hazard ratio 1.72, 95% confidence interval 1.48-1.99, P < .01). The optimal cutoff point of the AST/ALT ratio to predict MACCE was 1.29 (area under the curve 0.77, 95% confidence interval 0.69-0.84, P < .001), with sensitivity and specificity of 77.5% and 65.1%, respectively. The increased AST/ALT ratio, especially when above 1.29, is associated with MACCE in patients with UA undergoing percutaneous coronary intervention.

De Ritis Ratio is Associated with Contrast-Associated Acute Kidney Injury Prediction and Long-Term Clinical Outcomes in Patients Undergoing Emergency Percutaneous Coronary Intervention

Contrast-associated acute kidney injury (CA-AKI) is a familiar complication following percutaneous coronary intervention (PCI). The present study evaluated the predictive value of the De Ritis ratio for CA-AKI and its association with long-term clinical outcomes in patients undergoing emergency PCI. Overall, 546 patients were included in this study. The De Ritis ratio was calculated by aspartate aminotransferase/alanine aminotransferase activity. The De Ritis ratios in the CA-AKI patients were significantly higher than the non-CA-AKI patients [3.74 (2.32, 4.90) vs 1.61 (1.02, 2.53); P < .001]. The De Ritis ratio was an independent risk factor for CA-AKI [odds ratio, 2.243; 95% confidence interval (CI), 1.823-2.759; P < .001]. The area under the ROC curve was .813 (95% CI, .763-.862; P < .001), and the sensitivity and specificity were 67.0% and 82.4%, respectively, when the optimum cut-off value was 2.97. Furthermore, patients in the high De Ritis ratio group (≥1.76) had a significantly greater incidence of primary endpoints [26.7% (73/273) vs 13.2% (36/273); P < .001], and the high De Ritis ratio was an independent predictor for primary endpoints (hazard ratio, 1.888, 95% CI, 1.235-2.887; P = .003). In conclusion, the De Ritis Ratio is associated with CA-AKI prediction and long-term clinical outcomes in patients undergoing emergency PCI.

Aspartate aminotransferase to alanine aminotransferase ratio and the risk of diabetic nephropathy progression in patients with type 2 diabetes mellitus: A biopsy-based study

PURPOSE

To study the relationship between baseline serum aspartate aminotransferase (AST) to alanine aminotransferase (ALT) ratio (AAR) in both clinicopathological features and renal outcome among type 2 diabetes mellitus (T2DM) patients with biopsy-confirmed diabetic nephropathy (DN).

METHODS

As a retrospective cohort study, we included 253 patients with T2DM and biopsy-confirmed DN. For receiver operating characteristic (ROC) curve showed that the optimal cut-off for AAR to predict end stage renal disease (ESRD) was 1.22. So, patients were divided into two groups according to their AAR at the time of renal biopsy: high AAR Group (those with AAR > 1.22); low AAR Group (those with AAR ≤1.22). Association between AAR and clinicopathological features as well as renal outcome were analyzed.

RESULTS

Patients with higher AAR presented elder, more hypertensive, more insulin use, higher serum cholesterol, more proteinuria and lower estimated glomerular filtration rate (eGFR). Compared with low AAR group, patients with high AAR had more severe glomerular pathological lesions and interstitial fibrosis and tubular atrophy. For prognostic analysis, high AAR Group was associated with a higher risk of progression to ESRD in univariate analysis. No matter treated with continuous or categorical variate, higher AAR remained an independent predictor for ESRD after adjusted for various confounding factors: gender, age, the duration of diabetes, serum glucose level, hypertension, serum lipid level, smoking, insulin use, eGFR and proteinuria.

CONCLUSION

High AAR was associated with more severe renal pathologic lesions and worse renal function in patients with T2DM and DN, which might be a novel noninvasive predictor for ESRD.

CLINICAL RELEVANCE

To our knowledge, there was no biopsy-based cohort study. In our study, high AAR was associated with more severe renal pathologic lesions and worse renal function in patients with T2DM and DN, which might be a novel noninvasive predictor of ESRD for patients with DN.

Hippocampal Endoplasmic Reticulum Stress Hastens Motor and Cognitive Decline in Adult Male Rats Sustainedly Exposed to High-Sucrose Diet

Metabolic dysfunctions, such as hyperglycemia and insulin resistance, have been associated to cognitive impairment and dementia regardless of advanced age, although the underlying mechanisms are still elusive. Thus, this study investigates the deleterious effects of metabolic syndrome (MetS) induced by long-term exposure to a high-sucrose diet on motor and cognitive functions of male adult rats and its relationship with hippocampal endoplasmic reticulum (ER) stress. Weaned Wistar male rats were fed a high-sucrose diet until adulthood (HSD; 6 months old) and compared to both age-matched (CTR; 6 months old) and middle-aged chow-fed rats (OLD; 20 months old). MetS development, serum redox profile, behavioral, motor, and cognitive functions, and hippocampal gene/protein expressions for ER stress pro-adaptive and pro-apoptotic pathways, as well as senescence markers were assessed. Prolonged exposure to HSD induced MetS hallmarked by body weight gain associated to central obesity, hypertriglyceridemia, insulin resistance, and oxidative stress. Furthermore, HSD rats showed motor and cognitive decline similar to that in OLD animals. Noteworthy, HSD rats presented marked hippocampal ER stress characterized by failure of pro-adaptive signaling and increased expression of Chop, p21, and Parp-1 cleavage, markers of cell death and aging. This panorama resembles that found in OLD rats. In toto, our data showed that early and sustained exposure to a high-sucrose diet induced MetS, which subsequently led to hippocampus homeostasis disruption and premature impairment of motor and cognitive functions in adult rats.

Biochemical Mechanisms of Sirtuin-Directed Protein Acylation in Hepatic Pathologies of Mitochondrial Dysfunction

Mitochondrial protein acetylation is associated with a host of diseases including cancer, Alzheimer’s, and metabolic syndrome. Deciphering the mechanisms regarding how protein acetylation contributes to disease pathologies remains difficult due to the complex diversity of pathways targeted by lysine acetylation. Specifically, protein acetylation is thought to direct feedback from metabolism, whereby nutritional status influences mitochondrial pathways including beta-oxidation, the citric acid cycle, and the electron transport chain. Acetylation provides a crucial connection between hepatic metabolism and mitochondrial function. Dysregulation of protein acetylation throughout the cell can alter mitochondrial function and is associated with numerous liver diseases, including non-alcoholic and alcoholic fatty liver disease, steatohepatitis, and hepatocellular carcinoma. This review introduces biochemical mechanisms of protein acetylation in the regulation of mitochondrial function and hepatic diseases and offers a viewpoint on the potential for targeted therapies.

Evaluation of the relationship between aspartate aminotransferase/alanine aminotransferase ratio and coronary slow-flow phenomenon

Aim: To assess the correlation between the ratio of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) and slow coronary flow (SCF). Methods: A total of 119 patients with SCF and 121 age- and sex-matched patients with normal coronary flow were included in this retrospective cross-sectional study. Thrombolysis in myocardial infarction frame count of angiography images was marked by two interventionalists. In addition to AST and ALT levels, complete blood count; kidney, liver and thyroid function tests; age; sex; medication and medical history were recorded. Results: Significant spikes in AST/ALT ratio were discovered in the SCF group compared with the normal coronary flow group (p < 0.001). Thrombolysis in myocardial infarction frame count values were significantly higher in all coronaries for the SCF group compared with the normal coronary flow group (p < 0.001). Thrombolysis in myocardial infarction frame count values of the left anterior descending artery (r = 0.258; p < 0.001), left circumflex artery (r = 0.297; p < 0.001) and right coronary artery (r = 0.195; p = 0.002) were positively correlated with AST/ALT ratio. Conclusion: AST/ALT ratio is significantly correlated with SCF; therefore, this ratio may have predictive value.

Salvia hispanica L. (chia) seed ameliorates liver injury and oxidative stress by modulating NrF2 and NFκB expression in sucrose-rich diet-fed rats

The aim of this study was to analyze the liver injury and oxidative stress in an experimental model of Metabolic Syndrome (MS) induced by chronic administration of a sucrose-rich diet (SRD) and to evaluate the effects of chia seed as a therapeutic strategy. Male Wistar rats were fed with a reference diet (RD) -6 months- or a SRD -3 months. Then, the latter group was randomly divided into two subgroups. One subgroup continued receiving the SRD for up to 6 months and the other was fed with a SRD where whole chia seed was incorporated as a source of dietary fat for the next 3 months (SRD+CHIA). The results showed that rats fed with a SRD for a long period of time developed dyslipidemia, hyperglycemia, hepatic lipid accumulation, liver injury, hepatic lipid peroxidation and oxidative stress. Hepatic NrF2 expression was significantly decreased. In addition, a significant increase in hepatic NFκB p65 expression and a positive correlation of this with plasma TNFα levels were found. The administration of chia seed for 3 months reversed dyslipidemia, hyperglycemia, lipid accumulation, liver injury, lipid peroxidation and oxidative stress. In the liver tissue, NrF2 expression was normalized and NFκB p65 expression was decreased, the latter was associated with a decrease in plasma TNFα levels. The present study showed new aspects of liver damage, lipid peroxidation and oxidative stress in dyslipidemic insulin resistant rats chronically fed with a sucrose-rich diet. However, we demonstrated new properties and molecular mechanisms associated with the beneficial anti-oxidant effects of chia seed consumption.

The association between AST/ALT ratio and all-cause and cardiovascular mortality in patients with hypertension

Previous studies had shown that an increased aspartate aminotransferase to alanine aminotransferase ratio (AST/ALT ratio) was associated with cardiovascular disease. This study aimed to assess the relationship between AST/ALT ratio and all-cause and cardiovascular mortality in patients with hypertension.By March 31, 2020, a cohort of 14,220 Chinese hypertensive patients was followed up. The end point was all-cause and cardiovascular death. Hazard ratios (HRs) and 95% CIs were calculated for mortality associated with AST/ALT ratio, using Cox proportional hazards models and competing risk model.In an average of 1.7 years of follow-up, 1.39% (n = 198) of patients died, 55.5% (n = 110) of whom from cardiovascular disease. AST/ALT ratio was associated with increased risk of all-cause death (HR:1.37, 95% CI:1.15-1.63) and cardiovascular death (HR:1.32, 95% CI:1.03-1.68) after adjustment for other potential confounders. Compared with low AST/ALT ratio (Tertile 1), high AST/ALT ratio was associated with high cause mortality (Tertile 2: HR:1.35, 95% CI:0.86-2.10; Tertile 3: HR:2.10, 95% CI:1.37-3.21; P for trend <.001). Compared with low AST/ALT ratio (Tertile 1), a statistically significant increased risk of cardiovascular mortality was also observed (Tertile 2: HR:1.27, 95% CI:0.70-2.29; Tertile 3: HR:1.92, 95% CI:1.09-3.37; P for trend <.001). High AST/ALT ratio was also associated with high cardiovascular mortality (Tertile 2: HR:1.27, 95% CI:0.70-2.29; Tertile 3: HR:1.92, 95% CI:1.09-3.37; P for trend <.001).Present study indicated that increased AST/ALT ratio levels were predictive of all-cause and cardiovascular mortality among Chinese hypertensive patients.Trial registration: CHICTR, CHiCTR1800017274. Registered 20 July 2018.

Morin alleviates fructose-induced metabolic syndrome in rats via ameliorating oxidative stress, inflammatory and fibrotic markers

Metabolic syndrome (MBS) is a widespread disease that has strongly related to unhealthy diet and low physical activity, which initiate more serious conditions such as obesity, cardiovascular diseases and type 2 diabetes mellitus. This study aimed to examine the therapeutic effects of morin, as one of the flavonoids constituents, which widely exists in many herbs and fruits, against some metabolic and hepatic manifestations observed in MBS rats and the feasible related mechanisms. MBS was induced in rats by high fructose diet feeding for 12 weeks. Morin (30 mg/kg) was administered orally to both normal and MBS rats for 4 weeks. Liver tissues were used for determination of liver index, hepatic expression of glucose transporter 2 (GLUT2) as well as both inflammatory and fibrotic markers. The fat/muscle ratio, metabolic parameters, systolic blood pressure, and oxidative stress markers were also determined. Our data confirmed that the administration of morin in fructose diet rats significantly reduced the elevated systolic blood pressure. The altered levels of metabolic parameters such as blood glucose, serum insulin, serum lipid profile, and oxidative stress markers were also reversed approximately to the normal values. In addition, morin treatment decreased liver index, serum liver enzyme activities, and fat/muscle ratio. Furthermore, morin relatively up-regulated GLUT2 expression, however, down-regulated NF-κB, TNF-α, and TGF-β expressions in the hepatic tissues. Here, we revealed that morin has an exquisite effect against metabolic disorders in the experimental model through, at least in part, antioxidant, anti-inflammatory, and anti-fibrotic mechanisms.

Four weeks exercise training enhanced the hepatic insulin sensitivity in high fat- and high carbohydrate-diet fed hyperinsulinemic rats

Aim

Hyperinsulinemia is considered the primary defect underlying the development of type 2 diabetes. The liver is essential for the regular glucose homeostasis. In this study, we examined the effect of physical training on the insulin signaling, oxidative stress enzymes and Glucose-6-phosphatase(G6Pase) activity in the liver of Wistar rats.

Methods

Adult male Wistar rats were divided into Control diet group(C), High carbohydrate diet(HCD), High fat diet(HFD), HCD and HFD with training(HCD Ex & HFD Ex). HFD Ex and HCD Ex were trained on a small animal treadmill running at 20 m/min for 30 min, 5 days/wk. The present work investigated the effect of training on hepatic insulin receptor(InsR) signaling events, oxidative stress marker expressions and G6Pase activity in hyperinsulinemic rats.

Results

High carbohydrate and fat feeding led to hyperinsulinemic status with increased hepatic G6Pase activity and impaired phosphorylation of insulin receptor substrate 1(IRS1) and reduced expression of antioxidant enzymes.Training significantly reduced hepatic G6Pase activity, upregulated phosphoinositide 3 kinase(PI3K) docking site phosphorylation and downregulated the negative IRS1 phosphorylations thereby increasing the glucose transporter(GLUT) expressions (aa(P < 0.001) when compared to HFD, b(P < 0.01),bb (P < 0.001 when compared to HCD). Anti oxidant enzymes like CAT, SOD, eNOS expression were increased with reduction in the expression of inflammatory enzymes like TNF-α and COX-2 (*(P < 0.05),**(P < 0.01),***(P < 0.001) when compared to control, †(P < 0.05),††(P < 0.01),†††(P < 0.001) when compared to HFD and HCD).

Conclusion

Thus, our study shows that four weeks training enhanced the hepatic insulin sensitivity in high fat and high carbohydrate-diet fed hyperinsulinemic rats.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-020-00694-y.

Fructose Consumption Affects Glucocorticoid Signaling in the Liver of Young Female Rats

The effects of early-life fructose consumption on hepatic signaling pathways and their relation to the development of metabolic disorders in later life are not fully understood. To investigate whether fructose overconsumption at a young age induces alterations in glucocorticoid signaling that might contribute to development of metabolic disturbances, we analysed glucocorticoid receptor hormone-binding parameters and expression of its target genes involved in gluconeogenesis (phosphoenolpyruvate carboxykinase and glucose-6-phosphatase) and lipid metabolism (lipin-1), as well as redox and inflammatory status in the liver of female rats subjected to a fructose-rich diet immediately after weaning. The fructose diet increased hepatic corticosterone concentration, 11β-hydroxysteroid dehydrogenase type 1 level, glucocorticoid receptor protein level and hormone-binding activity, as well as lipin-1 level. The expression of glucose-6-phosphatase was reduced in fructose-fed rats, while phosphoenolpyruvate carboxykinase remained unaltered. The fructose-rich diet increased the level of fructose transporter GLUT2, while the expression of fructolytic enzymes fructokinase and aldolase B remained unaltered. The diet also affected pro-inflammatory pathways, but had no effect on the antioxidant defence system. In conclusion, a fructose-rich diet applied immediately after weaning promoted lipogenesis and enhanced hepatic glucocorticoid signaling, possibly to protect against inflammatory damage, but without an effect on gluconeogenesis and antioxidant enzymes. Yet, prolonged treatment might ultimately lead to more pronounced metabolic disturbances.

Suppression of uric acid and lactate production by sodium acetate ameliorates hepatic triglyceride accumulation in fructose-insulin resistant pregnant rats

High fructose intake has been associated with perturbed lipid, uric acid and lactate homeostasis. However, consumption of fructose-sweetened beverages is not usually regulated during pregnancy. The effect of short-chain fatty acid (acetate) on the metabolic effects of high fructose intake during pregnancy is not known. We hypothesized that acetate prevents gestational fructose-induced hepatic triglyceride (TG) accumulation by suppressing uric acid and lactate production. Pregnant Wistar rats were randomly separated into three groups (n = 6/group) receiving drinking water (CON), 10 % (w/v) fructose drink (FRU) and 10 % (w/v) fructose with 200 mg/kg (w/w; p.o.) sodium acetate (FRU + ACE) daily for nineteen days. Fructose intake resulted in increased body weight gain, liver weight, fluid intake, visceral fat, insulin resistance, fasting blood glucose, insulin, plasma and hepatic TG, total cholesterol, free fatty acid, lipid peroxidation, adenosine deaminase, xanthine oxidase, uric acid, lactate, lactate dehydrogenase, and liver injury marker enzymes. However, gestational high fructose intake led to depressed plasma and hepatic glucose-6-phosphate dehydrogenase (G6PD)-dependent antioxidant barrier, adenosine and food intake. All these effects except water intake and food intake were abated by sodium acetate. These results demonstrate that maternal fructose-enriched drink would cause hepatic TG accumulation that is associated with perturbed glucose, uric acid, lactate homeostasis, and G6PD-dependent antioxidant barrier. These results also demonstrate that acetate protects the liver against gestational fructose-induced TG accumulation by inhibiting uric acid and lactate production. Thus, acetate may be useful in the treatment of hyperuricemia- and hyperlactatemia-related disorders.

Dietary high calories from sunflower oil, sucrose and fructose sources alters lipogenic genes expression levels in liver and skeletal muscle in rats

INTRODUCTION AND OBJECTIVES

The objectives of this study were to investigate the underlying mechanism of PPARα, LXRα, ChREBP, and SREBP-1c at the level of gene and protein expression with high-energy diets in liver and skeletal muscle.

MATERIALS AND METHODS

Metabolic changes with consumption of high fat (Hfat), high sucrose (Hsuc) and high fructose (Hfru) diets were assessed. Levels of mRNA and protein of PPARα, LXRα, ChREBP, and SREBP-1c were investigated. Body weight changes, histological structure of liver and plasma levels of some parameters were also examined.

RESULTS

In Hfru group, body weights were higher than other groups (P<0.05). In liver, LXRα levels of Hsuc and Hfru groups were upregulated as 1.87±0.30 (P<0.05) and 2.01±0.29 (P<0.01). SREBP-1c levels were upregulated as 4.52±1.25 (P<0.05); 4.05±1.11 (P<0.05) and 3.85±1.04 (P<0.05) in Hfat, Hsuc, and Hfru groups, respectively. In skeletal muscle, LXRα and SREBP-1c were upregulated as 1.77±0.30 (P<0.05) and 2.71±0.56 (P<0.05), in the Hfru group. Protein levels of ChREBP (33.92±8.84ng/mg protein (P<0.05)) and SREBP-1c (135.16±15.57ng/mg protein (P<0.001)) in liver were higher in Hfru group. In skeletal muscle, LXRα, ChREBP and SREBP-1c in Hfru group were 6.67±0.60, 7.11±1.29 and 43.17±6.37ng/mg, respectively (P<0.05; P<0.01; P<0.05). The rats in Hfru group had the most damaged livers.

CONCLUSION

Besides liver, fructose consumption significantly effects skeletal muscle and leads to weight gain, triggers lipogenesis and metabolic disorders.

β-Sitosterol mitigates the development of high-fructose diet-induced nonalcoholic fatty liver disease in growing male Sprague–Dawley rats

Fructose contributes to the development of nonalcoholic fatty liver disease (NAFLD). β-Sitosterol (Bst), a naturally occurring phytosterol, has antihyperlipidaemic and hepatoprotective properties. This study interrogated the potential protective effect of β-sitosterol against NAFLD in growing rats fed a high-fructose diet, modelling children fed obesogenic diets. Forty-four 21 day old male rat pups were randomly allocated to and administered the following treatments for 12 weeks: group I, standard rat chow (SRC) + plain drinking water (PW) + plain gelatine cube (PC); group II, SRC + 20% w/v fructose solution (FS) as drinking fluid + PC; group III, SRC + FS + 100 mg/kg fenofibrate in a gelatine cube; group IV, SRC + FS + 20 mg/kg β-sitosterol gelatine cube (Bst); group V, SRC + PW + Bst. Terminally, the livers were dissected out, weighed, total liver lipid content determined, and histological analyses done. Harvested plasma was used to determine the surrogate biomarkers of liver function. The high-fructose diet caused increased (p < 0.05) hepatic lipid (total) accretion (>10% liver mass), micro- and macrovesicular hepatic steatosis, and hepatic inflammation. β-Sitosterol and fenofibrate prevented the high-fructose diet-induced macrovesicular steatosis and prevented the progression of NAFLD to steatohepatitis. β-Sitosterol can prospectively be used to mitigate diet-induced NAFLD.

Assessment of fructose overload in the metabolic profile and oxidative/nitrosative stress in the kidney of senescent female rats

The aging process is a complex phenomenon that leads the body to several changes, affecting its integrity and resulting in chronic pathologies, which compromises health and quality of life of elderly people. Animals supplemented with fructose have been used as an experimental model for induction of insulin resistance. The objective of this study was to evaluate the metabolic effects and the levels of oxidative/nitrosative stress in the kidney of senescent rats with a high fructose intake. The animals were allocated into 4 groups: young control (Y), aged control (A), young fructose (YF) and aged fructose (AF). Groups Y and A received water and groups YF and AF received fructose (100g/L) in the water, both ad libitum. After 12weeks of high fructose intake, the animals were sacrificed to collect their kidneys, blood and the thoracic aorta. The results are presented as mean±SE, analyzed by the One-Way ANOVA test with Newman-Keuls post-test; significant at p<0.05. The fructose overload caused metabolic dysfunctions and insulin resistance, confirming the efficacy of the chosen model. In this study, we observed a body weight gain in the studied groups (except in the elderly fructose group), and an increase in general caloric intake, diuresis and adipose tissue; insulin resistance, increased fasting glucose, triglycerides and cholesterol in the fructose groups. We also found a loss of renal function, increased oxidative/nitrosative stress and inflammation, and a reduction of antioxidants and a lower vasodepressor response in the studied groups, especially those who consumed fructose. In summary, our data showed that aging or high fructose intake contributed to the increase of oxidative/nitrosative stress in animals, demonstrating that at the dose and the period of fructose treatment utilized in this study, fructose was not able to aggravate several aspects which were already altered by aging. We believe that the high fructose intake simulates most of the effects of aging, and this understanding would be useful to prevent or minimize many of the alterations caused by this condition.

Exercise training modulates the hepatic renin-angiotensin system in fructose-fed rats

NEW FINDINGS

What is the central question of this study? What are the effects of exercise training on the hepatic renin-angiotensin system and their contribution to damage resulting from fructose overload in rats? What is the main finding and its importance? Exercise training attenuated the deleterious actions of the angiotensin-converting enzyme/angiotensin II/angiotensin II type 1 receptor axis and increased expression of the counter-regulatory (angiotensin-converting enzyme 2/angiotensin (1-7)/Mas receptor) axis in the liver. Therefore, our study provides evidence that exercise training modulates the hepatic renin-angiotensin system, which contributes to reducing the progression of metabolic dysfunction and non-alcoholic fatty liver disease in fructose-fed rats. The renin-angiotensin system (RAS) has been implicated in the development of metabolic syndrome. We investigated whether the hepatic RAS is modulated by exercise training and whether this modulation improves the deleterious effects of fructose overload in rats. Male Wistar rats were divided into (n = 8 each) control (CT), exercise control (CT-Ex), high-fructose (HFr) and exercise high-fructose (HFr-Ex) groups. Fructose-drinking rats received d-fructose (100 g l^-1 ). After 2 weeks, CT-Ex and HFr-Ex rats were assigned to a treadmill training protocol at moderate intensity for 8 weeks (60 min day^-1 , 4 days per week). We assessed body mass, glucose and lipid metabolism, hepatic histopathology, angiotensin-converting enzyme (ACE) and angiotensin-converting enzyme 2 (ACE2) activity, the angiotensin concentration and the expression profile of proteins affecting the hepatic RAS, gluconeogenesis and inflammation. Neither fructose overload nor exercise training influenced body mass gain and serum ACE and ACE2 activity. The HFr group showed hyperinsulinaemia, but exercise training normalized this parameter. Exercise training was effective in preventing hepatic steatosis and in preventing triacylglycerol and glycogen accumulation. Furthermore, exercise improved the response to the deleterious effects of HFr overload by normalizing the gluconeogenesis pathway and the protein levels of interleukin-6 and tumour necrosis factor-α. The HFr rats displayed increased hepatic ACE activity and protein expression and angiotensin II concentration, which were attenuated by exercise training. Exercise training restored the ACE2/angiotensin-(1-7)/Mas receptor axis. Exercise training may favour the counter-regulatory ACE2/angiotensin-(1-7)/Mas receptor axis over the classical RAS (ACE/angiotensin II/angiotensin II type 1 receptor axis), which could be responsible for the reduction of metabolic dysfunction and the prevention of non-alcoholic fatty liver disease.

Fructose Consumption in the Development of Obesity and the Effects of Different Protocols of Physical Exercise on the Hepatic Metabolism

Fructose consumption has been growing exponentially and, concomitant with this, the increase in the incidence of obesity and associated complications has followed the same behavior. Studies indicate that fructose may be a carbohydrate with greater obesogenic potential than other sugars. In this context, the liver seems to be a key organ for understanding the deleterious health effects promoted by fructose consumption. Fructose promotes complications in glucose metabolism, accumulation of triacylglycerol in the hepatocytes, and alterations in the lipid profile, which, associated with an inflammatory response and alterations in the redox state, will imply a systemic picture of insulin resistance. However, physical exercise has been indicated for the treatment of several chronic diseases. In this review, we show how each exercise protocol (aerobic, strength, or a combination of both) promote improvements in the obesogenic state created by fructose consumption as an improvement in the serum and liver lipid profile (high-density lipoprotein (HDL) increase and decrease triglyceride (TG) and low-density lipoprotein (LDL) levels) and a reduction of markers of inflammation caused by an excess of fructose. Therefore, it is concluded that the practice of aerobic physical exercise, strength training, or a combination of both is essential for attenuating the complications developed by the consumption of fructose.

Liver and Metformin: Lessons of a fructose diet in mice

Studies show that the continuous consumption of fructose can lead to nonalcoholic fatty liver disease (NAFLD) and steatohepatitis. We aimed to investigate the role of Metformin in an animal model of liver injury caused by fructose intake, focusing on the molecular markers of lipogenesis, beta-oxidation, and antioxidant defenses. Male three months old C57BL/6 mice were divided into control group (C) and fructose group (F, 47% fructose), maintained for ten weeks. After, the groups received Metformin or vehicle for a further eight weeks: control (C), control + Metformin (CM), fructose (F), and fructose + Metformin (FM). Fructose resulted in hepatic steatosis, insulin resistance and lower insulin sensitivity in association with higher mRNA levels of proteins linked with de novo lipogenesis and increased lipid peroxidation. Fructose diminished mRNA expression of antioxidant enzymes, and of proteins responsible for mitochondrial biogenesis. Metformin reduced de novo lipogenesis and increased the expression of proteins related to mitochondrial biogenesis, thereby increasing beta-oxidation and decreasing lipid peroxidation. Also, Metformin upregulated the expression and activity of antioxidant enzymes, providing a defense against increased reactive oxygen species generation. Therefore, a significant reduction in triglyceride accumulation in the liver, steatosis and lipid peroxidation was observed in the FM group. In conclusion, fructose increases de novo lipogenesis, reduces the antioxidant defenses, and diminishes mitochondrial biogenesis. After an extended period of fructose intake, Metformin treatment, even in continuing the fructose intake, can reverse, at least partially, the liver injury and prevents NAFLD progression to more severe states.

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Fructose increases lipogenesis and lipid peroxidation, reduces the antioxidant defenses, and mitochondrial biogenesis.

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Metformin mechanism of action remains partially understood and controversial.

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Metformin can reverse the liver injury preventing the progression to more severe states.

Catalase deletion promotes prediabetic phenotype in mice

Hydrogen peroxide is produced endogenously and can be toxic to living organisms by inducing oxidative stress and cell damage. However, it has also been identified as a signal transduction molecule. By metabolizing hydrogen peroxide, catalase protects cells and tissues against oxidative damage and may also influence signal transduction mechanisms. Studies suggest that acatalasemic individuals (i.e., those with very low catalase activity) have a higher risk for the development of diabetes. We now report catalase knockout (Cat-/-) mice, when fed a normal (6.5% lipid) chow, exhibit an obese phenotype that manifests as an increase in body weight that becomes more pronounced with age. The mice demonstrate altered hepatic and muscle lipid deposition, as well as increases in serum and hepatic triglycerides (TGs), and increased hepatic transcription and protein expression of PPARγ. Liver morphology revealed steatosis with inflammation. Cat-/- mice also exhibited pancreatic morphological changes that correlated with impaired glucose tolerance and increased fasting serum insulin levels, conditions consistent with pre-diabetic status. RNA-seq analyses revealed a differential expression of pathways and genes in Cat-/- mice, many of which are related to metabolic syndrome, diabetes, and obesity, such as Pparg and Cidec. In conclusion, the results of the present study show mice devoid of catalase develop an obese, pre-diabetic phenotype and provide compelling evidence for catalase (or its products) being integral in metabolic regulation.

Fructose: Toxic effect on cardiorenal risk factors and redox state

AIM

To investigate the effects of fructose consumption on the antioxidant capacity in heart and kidney, cardiovascular disease risk factors, and evaluation of these variables after its removal.

METHODS

Male Wistar rats (n = 36) were divided into control group (n = 12): standard chow + water or F group: standard chow + fructose in drinking water (30%) for 15 weeks. After, F group was divided to continue receiving standard chow + fructose in drinking water (30%) (n = 12) or standard chow + water (Ex group, n = 12) for 9 weeks. Water, chow and caloric diaries intake, final body weight, adiposity index, plasma glucose and triacylglycerol, systolic blood pressure, and cardiac and renal hydrophilic antioxidant capacity were analyzed.

RESULTS

Control and Ex groups consumed less chow and water compared to F group. Caloric intake was higher in control group. There was no difference in final body weight and adiposity index. Systolic blood pressure and cardiac and renal hydrophilic antioxidant capacity were worst in F group.

CONCLUSION

Prolonged exposure to fructose induces oxidative stress, systolic blood pressure, and increase in triacylglycerol. When stopped fructose consumption, Ex group presented improvement in these variables, suggesting the toxicity effect of fructose when consumed in high amounts and prolonged exposure.

Divergent outcomes of fructose consumption on exercise capacity of rats: friend or foe

To test the hypothesis that high fructose (HF) consumption divergently affects exercise capability as a function of feeding duration, rats were fed a normal (as control) diet or a normal caloric diet with HF for 3, 6, 10, and 30 days, respectively, and then were run on a treadmill. Results show that running distance and work were significantly increased, which was associated with greater exercise oxygen consumption in rats fed HF for 3 (HF-3D) and 6 days, but were decreased in rats fed HF for 30 days (HF-30D) compared with rats in their respective control groups. Shear stress-induced vasodilation (SSID) in isolated plantaris muscle arterioles was significantly greater in the HF-3D group than the control group. The difference in SSID between the two groups was abolished by N^ω-nitro-l-arginine methyl ester (L-NAME), suggesting a nitric oxide (NO)-mediated response. Expression of phosphorylated/activated endothelial NO synthase (eNOS) and release of nitrite/NO were significantly increased in vessels of animals in the HF-3D group than controls. In contrast, arterioles isolated from the hypertensive rats in the HF-30D group displayed significantly attenuated NO-mediated SSID accompanied with greater production of superoxide compared with vessels of control animals. Additionally, the NO-dependent modulation of myocardial oxygen consumption (MV̇o₂) was also impaired in the HF-30D group, and was prevented by blocking superoxide production with apocynin, an inhibitor that also normalized the reduced SSID in the HF-30D group. In conclusion, short-term (3-6 days) HF feeding enhances exercise potential via an increase in endothelial sensitivity to shear stress, which stimulates eNOS to release NO, leading to better tissue perfusion and utilization of oxygen. However, long-term (30 days) HF feeding initiates endothelial dysfunction by superoxide-dependent mechanisms to compromise exercise performance.NEW & NOTEWORTHY The evidence that short-term fructose intake potentiates exercise capacity by nitric oxide-mediated mechanisms yields an optimal fructose feeding frame in which beneficial effects of fructose have been acquired while detrimental effects have not yet been manifested. This highlights the significance of exercise physiology in providing constructive regimens to improve physical performance.

The aspartate aminotransferase-to-alanine aminotransferase ratio predicts all-cause and cardiovascular mortality in patients with type 2 diabetes

An increased aspartate aminotransferase-to-alanine aminotransferase ratio (AAR) has been widely used as a marker of advanced hepatic fibrosis. Increased AAR was also shown to be significantly associated with the risk of developing cardiovascular (CV) disease. The aim of this study was to assess the relationship between the AAR and mortality risk in a well-characterized cohort of patients with type 2 diabetes.A cohort of 2529 type 2 diabetic outpatients was followed-up for 6 years to collect cause-specific mortality. Cox regression analyses were modeled to estimate the independent association between AAR and the risk of all-cause and CV mortality.Over the 6-year follow-up period, 12.1% of patients died, 47.5% of whom from CV causes. An increased AAR, but not its individual components, was significantly associated with an increased risk of all-cause (adjusted-hazard risk 1.83, confidence interval [CI] 95% 1.14-2.93, P = 0.012) and CV (adjusted-hazard risk 2.60, CI 95% 1.38-4.90, P < 0.003) mortality after adjustment for multiple clinical risk factors and potential confounding variables.The AAR was independently associated with an increased risk of both all-cause and CV mortality in patients with type 2 diabetes. These findings suggest that an increased AAR may reflect more systemic derangements that are not simply limited to liver damage. Further studies are needed to elucidate the pathophysiological implications of an increased AAR.

Strength Training Prevents Hyperinsulinemia, Insulin Resistance, and Inflammation Independent of Weight Loss in Fructose-Fed Animals

The aim of this study was to compare the effects of aerobic, strength, and combined training on metabolic disorders induced by a fructose-rich diet. Wistar rats (120 days old) were randomized into five groups (n = 8-14): C (control diet and sedentary), F (fed the fructose-rich diet and sedentary), FA (fed the fructose-rich diet and subject to aerobic exercise), FS (fed the fructose-rich diet and subject to strength exercise), and FAS (fed the fructose-rich diet and subject to combined aerobic and strength exercises). After the 8-week experiment, glucose homeostasis, blood biochemistry, tissue triglycerides, and inflammation were evaluated and analyzed. The strength protocol exerted greater effects on glucose homeostasis, insulin sensitivity, and liver lipid contents than other protocols (all P < 0.05). All three exercise protocols induced a remarkable reduction in inflammation, tissue triglyceride content, and inflammatory pathways, which was achieved through c-Jun NH2-terminal kinase (JNK) phosphorylation and factor nuclear kappa B (NFkB) activation in both the liver and the muscle. Our data suggest that strength training reduced the severity of most of the metabolic disorders induced by a fructose-rich diet and could be the most effective strategy to prevent or treat fructose-induced metabolic diseases.

The expression and activity of antioxidant enzymes in the liver of rats exposed to high-fructose diet in the period from weaning to adulthood

BACKGROUND

Increased fructose consumption correlates with rising prevalence of various metabolic disorders, some of which were linked to oxidative stress. The relationship between fructose consumption and oxidative stress is complex and effects of a fructose-rich diet on the young population have not been fully elucidated. The aim of this study was to investigate whether high-fructose diet applied in the period from weaning to adulthood induces oxidative stress in the liver, thus contributing to induction or aggravation of metabolic disturbances in later adulthood. To that end we examined the effects of high-fructose diet on expression and activity of antioxidant enzymes, markers of lipid peroxidation and protein damage in the liver as the main fructose metabolizing tissue.

RESULTS

High-fructose diet increased only SOD2 (mitochondrial manganese superoxide dismutase) activity, with no effect on other antioxidant enzymes, lipid peroxidation or accumulation of damaged proteins in the liver.

CONCLUSION

The results show that fructose-induced metabolic disturbances could not be attributed to oxidative stress, at least not at young age. The absence of oxidative stress in the liver observed herein implies that young organisms are capable of maintaining redox homeostasis when challenged by fructose-derived energy overload.

Inhibitory effects of eucalyptus and banaba leaf extracts on nonalcoholic steatohepatitis induced by a high-fructose/high-glucose diet in rats

Nonalcoholic steatohepatitis (NASH) is a liver disease associated with metabolic syndrome. The aim of this work was to examine whether eucalyptus (Eucalyptus globulus) leaf extract (ELE) and banaba (Lagerstroemia speciosa L.) leaf extract (BLE) inhibited NASH induced by excessive ingestion of fructose in rats. Wistar rats were divided into four groups according to four distinct diets: starch diet (ST), high-fructose/high-glucose diet (FG), FG diet supplemented with ELE, or FG diet supplemented with BLE. All rats were killed after 5 weeks of treatment. Serum alanine aminotransferase and total cholesterol levels were significantly lower in the BLE group than in the FG group. Liver histopathology, including steatosis, lipogranulomas, and perisinusoidal fibrosis, was significantly attenuated in the ELE and BLE groups compared with the FG group. Levels of 2-thiobarbituric acid reactive substances (TBARS), which reflect oxidative injury to the liver, were significantly suppressed by ELE and BLE. Western blotting analysis indicated that interleukin-6 expression levels were significantly lower in the ELE and BLE groups than in the FG group. These results suggest that ELE and BLE reduced lipogenesis, oxidative stress, and inflammatory cytokine expression and thus inhibited NASH induced by excessive ingestion of fructose in rats.

Comparative effects of Aliskiren and Telmisartan in high fructose diet-induced metabolic syndrome in rats

Fructose is a commonly used sweetener associated with diets that increase the prevalence of metabolic syndrome (MS). Inhibition of the renin-angiotensin system (RAS) has been consistently demonstrated to reduce MS. However, there has been no direct comparison among different pharmacological modes of inhibiting the RAS concerning their effects on MS. This study investigated the effect of aliskiren, a direct renin inhibitor, versus telmisartan, an angiotensin II-receptor blocker, in the treatment of fructose-induced MS in rats. MS was induced by high fructose (FRC) diet feeding for 12 weeks. Oral administrations of telmisartan (TEL, 5 mg/kg), aliskiren (ALS, 30 mg/kg) or vehicle were started in the last 4 weeks. Results showed that administration of either TEL or ALS with FRC diet equally ameliorated the metabolic parameters (glucose level, oral glucose tolerance test, insulin resistance and serum lipids profile), systolic blood pressure and oxidative stress markers (malondialdehyde, nitric oxide, reduced glutathione levels and catalase activity). Additionally, the effects of TEL and ALS were associated with a decrease in body composition index and attenuation of liver index, serum liver enzyme activities and hepatic expressions of inflammatory and fibrotic markers (tumor necrosis factor-α, nuclear factor kappa-B and transforming growth factor-β) with a significant increase in hepatic glucose transporter-2 and peroxisome proliferator-activated receptors-alpha and gamma expressions. The results suggested that, at indicated dosage, ALS has ameliorative effect equal to that of TEL against FRC-induced metabolic and hepatic disorders; implying that drugs which inhibit the RAS, by different mode of inhibition, profoundly affect fructose-induced MS in rats.

Standard short-term diet ameliorates the lipid profile altered by a fructose-rich diet in rats

Markers of metabolic abnormalities are commonly found in rodents fed a fructose-rich diet. The purpose of this study was to determine whether the administration of a short-term standard diet to rats is able to improve the lipid profile altered by a fructose-rich diet. The male pups, immediately after birth, were divided in three groups according to the diet for 90 days. Standard diet: a standard diet for the whole experimental period; fructose (60% fructose-rich diet): fructose-rich diet during the entire experimental period; fructose/standard (FS): fructose-rich diet from the neonatal period up to 60 days of age and standard diet from 60 to 90 days of age. A fructose-rich diet from the neonatal period to 60 days reduced weight gain (P<0.05), as well as the weight of adipose tissues in all the regions analyzed (epididymal, mesenteric, retroperitoneal and posterior subcutaneous), and it altered the lipid profile (elevation of triglycerides, total cholesterol, low density lipoprotein (LDL) cholesterol and very low density lipoprotein (VLDL) cholesterol; P<0.05). When a standard diet was administered after the fructose-rich diet, it was able to partially reverse changes to the lipid profile, as total cholesterol levels were significantly different in all the groups (P<0.05), and triglyceride and VLDL cholesterol levels were similar between the control and FS group. In summary, a fructose-rich diet altered the lipid profile, and a standard diet can partially reverse the changed parameters in short term.

Differences and similarities in hepatic lipogenesis, gluconeogenesis and oxidative imbalance in mice fed diets rich in fructose or sucrose

Changes in feeding habits are the primary environmental factors (though modifiable) commonly correlated with increase in diseases such as obesity and associated comorbidities.

Muscle glycogen metabolism changes in rats fed early postnatal a fructose-rich diet after maternal protein malnutrition: effects of acute physical exercise at the maximal lactate steady-state intensity

BACKGROUND

The objective was to evaluate the muscle glucose metabolism in rats fed a fructose-rich diet after fetal protein malnutrition, at rest and after acute physical exercise at maximal lactate steady-state intensity.

METHODS

The male offspring born of mothers fed on a balanced or low-protein diet were split in four groups until 60 days: Balanced (B): balanced diet during the whole period; Balanced/Fructose (BF): balanced diet in utero and fructose-rich diet after birth; Low protein/Balanced (LB): low-protein diet in utero and balanced diet after birth; Low protein/Fructose (LF): low protein diet in utero and fructose-rich diet after birth.

RESULTS

Acute physical exercise reduced the muscle glycogen concentrations in all groups, although the LF group showed higher concentrations at rest. There was no difference among the groups in the glucose uptake and oxidation rates in the isolated soleus muscle neither at rest nor after acute exercise. However, glycogen synthesis was higher in the LF muscle than in the others at rest. Acute physical exercise increased glycogen synthesis in all groups, and the LF group showed the highest values.

CONCLUSION

The fructose-rich diet administered in rats after fetal protein malnutrition alters muscle glycogen concentrations and glycogen synthesis in the rest and after acute exercise at maximal lactate steady-state intensity.

Long-term fructose-enriched diet introduced immediately after weaning does not induce oxidative stress in the rat liver

Increased fructose consumption is correlated with the rising prevalence of obesity, metabolic syndrome, and type 2 diabetes. It is believed that reactive oxygen species contribute to the development and progression of metabolic disturbances, especially those associated with insulin resistance. Dietary fructose produces both pro-oxidative and antioxidative effects, depending upon the experimental conditions, dosage, duration of treatment, and pathophysiological milieu. The effects of fructose overconsumption on young populations, which have an increased risk of developing metabolic disorders in adulthood, have not been fully elucidated. We have previously shown that rats subjected to a long-term fructose-enriched diet immediately after weaning display impaired hepatic insulin sensitivity. In this study, we tested the hypothesis that long-term fructose consumption induces alterations in the redox setting of the liver. Starting from the 21st day after birth, male Wistar rats were maintained for 9 weeks on a standard diet (control) or a fructose-enriched diet that consisted of standard food and 10% fructose solution instead of drinking water. The expression and activity of antioxidant enzymes as well as lipid peroxidation and protein damage markers were measured. The results showed that a fructose-enriched diet led to an increased expression of mitochondrial manganese superoxide dismutase but did not affect antioxidant enzymes activity, lipid peroxidation, thiol content, and the level of protein oxidation. Therefore, our results suggest that the decrease in hepatic insulin sensitivity that was previously observed in rats that were kept on the same diet regime might be attributed to molecular mechanisms other than redox disbalance. A possible fructose-related micronutrient deficiency should be examined.

Mitoneet mediates TNFα-induced necroptosis promoted by exposure to fructose and ethanol

Fructose and ethanol are metabolized principally in the liver and are both known to contribute to the development of hepatic steatosis that can progress to hepatic steatohepatitis. The present study indentifies a synergistic interaction between fructose and ethanol in promoting hepatocyte sensitivity to TNFα-induced necroptosis. Concurrent exposure to fructose and ethanol induces the overexpression of the CDGSH iron-sulfur domain-containing protein 1 (CISD1 or mitoneet), which is localized to the outer mitochondrial membrane. The increased expression of mitoneet primes the hepatocyte for TNFα-induced cytotoxicity. Treatment with TNFα induces the translocation of a Stat3-Grim-19 complex to the mitochondria, which binds to mitoneet and promotes the rapid release of its 2Fe-2S cluster, causing an accumulation of mitochondrial iron. The dramatic increase of mitochondrial iron provokes a surge in formation of reactive oxygen species, resulting in mitochondrial injury and cell death. Additionally, mitoneet is constitutively expressed at high levels in L929 fibrosarcoma cells and is required for L929 cells to undergo TNFα-induced necroptosis in the presence of caspase inhibition, indicating the importance of mitoneet to the necroptotic form of cell death.