Review article: fructose in non-alcoholic fatty liver disease

A selective hybrid fluorescent sensor for fructose detection based on a phenylboronic acid and BODIPY-based hydrophobicity probe

Fructose is widely used in the food industry. However, it may be involved in diseases by generating harmful advanced glycation end-products. We have designed and synthesized a novel fluorescent probe for fructose detection by combining a phenylboronic acid group with a BODIPY-based hydrophobicity probe. This probe showed a linear fluorescence response to d-fructose concentration in the range of 100-1000 μM, with a detection limit of 32 μM, which is advantageous for the simple and sensitive determination of fructose.

Dietary Counseling Aimed at Reducing Sugar Intake Yields the Greatest Improvement in Management of Weight and Metabolic Dysfunction in Children with Obesity

Pediatric obesity is a significant public health problem, the negative outcomes of which will challenge individual well-being and societal resources for decades to come. The objective of this study was to determine the effects of dietary counseling on weight management and metabolic abnormalities in children with obesity. One hundred and sixty-five patients aged 2−18 years old were studied over a two and a half year period. Data collected included demographic information, anthropometric assessment, laboratory measurements, and self-reported eating behaviors. Dietary counseling was provided at each visit. The data was analyzed from the first and last visits and the subjects were retrospectively divided into responders and non-responders based on a decrease in their BMI. After receiving dietary guidance, BMI decreased in 44% of the children, and these participants were classified as responders (BMI-R; n = 72). However, BMI did not improve in 56% of the participants, and these were classified as non-responders (BMI-NR; n = 93). At the initial visit, anthropometric measurements and dietary habits were similar between the groups. At the time of the last visit, mean change in BMI was −1.47 (SD 1.31) for BMI-R and +2.40 (SD 9.79) for BMI-NR. Analysis of food intake revealed that BMI-R significantly improved their dietary habits (p = 0.002) by reducing the intake of sugar-sweetened beverages (p = 0.019), processed foods (p = 0.002), sweets (p < 0.001), and unhealthy snacks (p = 0.009), as compared with BMI-NR. There was no change in the intake of second helpings, portion sizes, skipping meals, frequency of meals eaten at school, condiment use, intake of fruits and vegetables and consumption of whole grains between the groups. BMI-R also achieved an improvement in fasted glucose (p = 0.021), triglycerides (p < 0.001), and total cholesterol (p = 0.023), as compared to BMI-NR. In conclusion, children with obesity who were able to decrease their BMI implemented a significant reduction in consumption of foods with high sugar content. Focusing on reducing sugar intake may yield the biggest impact in terms of weight management and the improvement of metabolic abnormalities.

Reversion to regular diet with alternate day fasting can cure grade-I non-alcoholic fatty liver disease (NAFLD) in high-fructose-intake-associated metabolic syndrome

Background

Non-alcoholic fatty liver disease (NAFLD) is an emerging global health problem that accompanied the obesity epidemic and is considered as the hepatic component of metabolic syndrome (MetS). Modification of lifestyle of MetS patients remains the focus to reverse and prevent progression of hepatic steatosis to NAFLD and its worsening to severe forms. The present study investigates the possible curability of metabolic syndrome -associated grade-1 NAFLD merely by alternate day fasting with or without reversion to regular diet in adult male rats. The present study was performed on 66 local strain male rats aged (6–10 m.) distributed randomly into C group (n = 12), on regular rat diet; and M group (n = 54) on high fructose- intake. On the 8th week, then rats were subjected to measurement of BW, BMI, WC, FBG, IPGTT, HDL-C, TGs, and liver histopathology, to include MetS rats randomly into four experimental groups for 4 weeks as follows: MS (n = 14); MSRD (n = 12); MSF (n = 13); and MSRDF (n = 12). On the 12th week, all rats were subjected to measurements of BW, BMI, WC, LW, LW/BW, VFW, VFW/BW, FBG, IPGTT, Ins., HOMA-IR, HbA1C, TGs, TC, LDL-C, HDL-C, CRP, Alb., bilirubin, ALT, L-MDA, and liver histopathology.

Results

On the 8th week, M group developed MerS and grade-I NAFLD with score-4 hepatosteatosis (69%). On the 12th week, MS group had grade-1 NAFLD with score-4 hepatosteatosis (82%) with significantly increased Ins., HOMA-IR, HDL-C, LW, LW/BW, L-MDA, ALT, CRP, and significantly decreased Alb. than C rats. Both MSRD and MSF groups had grade-1 NAFLD with score-3 hepatosteatosis (42%) with significantly decreased Ins., HOMA-IR, TC, LDL-C, LW, LW/BW, L-MDA, ALT, CRP, and significantly increased HDL-C and Alb. than MS group. MSRDF rats showed cure of grade-1 NAFLD and significantly decreased LW than other groups and normalized HOMA-IR, HbA1C TC, LDL-C, ALT, and CRP.

Conclusion

One month of alternate-day fasting and regular rat diet could cure grade-I NAFLD associated with Mets due to high fructose intake possibly by attenuating metabolic disorders. These two interventions might be recommended in the management of MetS patients with grade 1-NAFLD disease.

Tissue-Specific Fructose Metabolism in Obesity and Diabetes

PURPOSE OF REVIEW

The objective of this review is to provide up-to-date and comprehensive discussion of tissue-specific fructose metabolism in the context of diabetes, dyslipidemia, and nonalcoholic fatty liver disease (NAFLD).

RECENT FINDINGS

Increased intake of dietary fructose is a risk factor for a myriad of metabolic complications. Tissue-specific fructose metabolism has not been well delineated in terms of its contribution to detrimental health effects associated with fructose intake. Since inhibitors targeting fructose metabolism are being developed for the management of NAFLD and diabetes, it is essential to recognize how inability of one tissue to metabolize fructose may affect metabolism in the other tissues. The primary sites of fructose metabolism are the liver, intestine, and kidney. Skeletal muscle and adipose tissue can also metabolize a large portion of fructose load, especially in the setting of ketohexokinase deficiency, the rate-limiting enzyme of fructose metabolism. Fructose can also be sensed by the pancreas and the brain, where it can influence essential functions involved in energy homeostasis. Lastly, fructose is metabolized by the testes, red blood cells, and lens of the eye where it may contribute to infertility, advanced glycation end products, and cataracts, respectively. An increase in sugar intake, particularly fructose, has been associated with the development of obesity and its complications. Inhibition of fructose utilization in tissues primary responsible for its metabolism alters consumption in other tissues, which have not been traditionally regarded as important depots of fructose metabolism.

Oil and extract of safflower seed improve fructose induced metabolic syndrome through modulating the homeostasis of trace elements, TNF-α and fatty acids metabolism

ETHNOPHARMACOLOGICAL RELEVANCE

Safflower (Carthamus tinctorius) has many applications in folk medicine. Its oil is used traditionally to treat obesity and other metabolic disorders. The anti-hypercholesterolemic and antioxidant effects of this plant have been well documented, but the anti-inflammatory effects and its role on fatty acid oxidation and homeostasis of trace elements are not fully understood.

OBJECTIVE

The aim of this study was to evaluate the protective effects of different doses of oil and extract of safflower seed against fructose induced metabolic syndrome by investigating the homeostasis of trace elements, TNF-α, and fatty acids metabolism.

METHODS

Eighty adult male Sprague-Dawley rats were randomly divided into ten groups and treated daily for 16 weeks. At the end of the study, plasma levels of liver enzymes, lipid profiles, blood glucose, insulin and TNF-α were measured. The levels of antioxidant enzymes and lipid peroxidation were also measured along with the expression of CD36, fatty acyl-CoA synthetase (FAS), and Carnitine palmitoyl transferase I (CPT-1) beta genes in the liver.

RESULTS

The antioxidant enzymes activity significantly decreased and lipid peroxidation, lipid profiles, liver enzymes, and TNF-α significantly increased in fructose-induced metabolic syndrome compared to the control groups, as well as the level of some trace elements significantly changed (p < 0.05). Treatment with oil and safflower seed extract in a dose dependent manner could improve biochemical parameters in groups of metabolic syndrome treated with oil and extract compared to metabolic syndrome (p < 0.05). The results also showed that the expression of above mentioned genes significantly increased in groups of metabolic syndrome treated with oil and extract compared to control and metabolic syndrome groups (p < 0.05).

CONCLUSION

It can be concluded that safflower seed extract and its oil can improve fructose-induced metabolic syndrome through antioxidant and anti-inflammatory effects, adjustment of homeostasis of trace elements, and enhancing the beta-oxidation capacity of the liver by increasing the expression of CD36, FAS, and CPT-1beta genes.

Glycation With Fructose: The Bitter Side of Nature's Own Sweetener

Fructose is a ketohexose and sweetest among all the natural sugars. Like other reducing sugars, it reacts readily with the amino- and nucleophilic groups of proteins, nucleic acids and other biomolecules resulting in glycation reactions. The non-enzymatic glycation reactions comprise Schiff base formation, their Amadori rearrangement followed by complex and partly incompletely understood reactions culminating in the formation of Advance Glycation End products (AGEs). The AGEs are implicated in complications associated with diabetes, cardiovascular disorders, Parkinson's disease, etc. Fructose is highly reactive and forms glycation products that differ both in structure and reactivity as compared to those formed from glucose. Nearly all tissues of higher organisms utilize fructose but only a few like the ocular lens, peripheral nerves erythrocytes and testis have polyol pathway active for the synthesis of fructose. Fructose levels rarely exceed those of glucose but, in tissues that operate the polyol pathway, its concentration may rise remarkably during diabetes and related disorders. Diet contributes significantly to the body fructose levels however, availability of technologies for the large scale and inexpensive production of fructose, popularity of high fructose syrups as well as the promotion of vegetarianism have resulted in a remarkable increase in the consumption of fructose. In vivo glycation reactions by fructose, therefore, assume remarkable significance. The review, therefore, aims to highlight the uniqueness of glycation reactions with fructose and its role in some pathophysiological situations.

Copper modulates sex-specific fructose hepatoxicity in nonalcoholic fatty liver disease (NALFD) Wistar rat models

This study aimed to characterize the impact of dietary copper on the biochemical and hepatic metabolite changes associated with fructose toxicity in a Wistar rat model of fructose-induced liver disease. Twenty-four male and 24 female, 6-week-old, Wister rats were separated into four experimental dietary treatment groups (6 males and 6 females per group), as follows: (1) a control diet: containing no fructose with adequate copper (i.e., CuA/0% Fruct); (2) a diet regimen identical to the control and supplemented with 30% w/v fructose in the animals' drinking water (CuA/30% Fruct); (3) a diet identical to the control diet but deficient in copper content (CuD/0% Fruct) and (4) a diet identical to the control diet but deficient in copper content and supplemented with 30% w/v fructose in the drinking water (CuD/30% Fruct). The animals were fed the four diet regimens for 5 weeks, followed by euthanization and assessment of histology, elemental profiles and identification and quantitation of liver metabolites. Results from ¹H nuclear magnetic resonance metabolomics revealed mechanistic insights into copper modulation of fructose hepatotoxicity through identification of distinct metabolic phenotypes that were highly correlated with diet and sex. This study also identified previously unknown sex-specific responses to both fructose supplementation and restricted copper intake, while the presence of adequate dietary copper promoted most pronounced fructose-induced metabolite changes.

Vitamin E Ameliorates Lipid Metabolism in Mice with Nonalcoholic Fatty Liver Disease via Nrf2/CES1 Signaling Pathway

BACKGROUND

Vitamin E has been reported to have a beneficial effect on nonalcoholic fatty liver disease (NAFLD); however, the underlying mechanism of action has not yet been clearly defined.

AIM

We aimed to evaluate the effects and mechanisms of vitamin E on lipid and glucose homeostasis both in vivo and in vitro.

METHODS

An NAFLD model was established in C57BL/6 mice fed a 30% fructose solution for 8 weeks. Subsequently, NAFLD mice were given vitamin E (70 mg/kg) for 2 weeks. In addition, L02 cells were treated with 5 mM fructose and 100 nM vitamin E to explore the potential mechanisms of action.

RESULTS

Vitamin E reversed the impaired glucose tolerance of fructose-treated mice. Histopathological examination showed that liver steatosis was significantly relieved in vitamin E-treated mice. These effects may be attributed to the upregulation of nuclear factor erythroid-2-related factor 2 (Nrf2), carboxylesterase 1 (CES1), and downregulated proteins involved in lipid synthesis by vitamin E treatment. In vivo, vitamin E also significantly reduced lipid accumulation in fructose-treated L02 cells, and the Nrf2 inhibitor ML385 reversed the protective effects of vitamin E.

CONCLUSION

These data indicated that the therapeutic effects of vitamin E on lipid and glucose homeostasis may be associated with activation of the Nrf2/CES1 signaling pathway.

Obesity and Metabolic Syndrome in Kidney Transplantation: The Role of Dietary Fructose and Systemic Endotoxemia

BACKGROUND

The concepts that obesity is merely a consequence of overeating, and that metabolic health then reflects obesity, may be insufficient and potentially flawed. The role of fructose intake and metabolic endotoxemia has gained attention recently, but data in kidney transplantation are lacking. This study evaluated the risk factors for metabolic syndrome (MS), its components, and other associated markers in kidney transplant recipients (KTRs), focusing particularly on fructose intake and systemic endotoxemia.

METHODS

This cross-sectional observational study enrolled 128 KTRs longer than 1 year posttransplantation. Clinical, biochemical, anthropometric, and questionnaire assessments were undertaken.

RESULTS

Obesity (body mass index, ≥30 kg/m) and MS (International Diabetes Federation Definition) were found in 36.7% and 50% of KTRs, respectively. Both increased fructose intake (P = 0.01) and endotoxin level (P = 0.02) were independently associated with MS; and higher fructose intake was independently associated with obesity (P < 0.001). Specifically, increased fructose intake was associated with the central obesity (P = 0.01) and hyperglycemia (P < 0.001) criteria of MS, whereas higher endotoxin level was associated with the hypertriglyceridemia (P = 0.003) and low HDL cholesterol concentration (P = 0.002) criteria of MS. Neither saturated fat nor total caloric intakes were independently associated with obesity and MS; and neither obesity nor central obesity were independently associated with the dyslipidemia and hyperglycemia criteria of MS. Principal component analysis demonstrated relationships between higher levels of endotoxin, soluble endothelial selectin, triglycerides, and insulin resistance (r > 0.6), as well as relationships between increased fructose intake, inflammation, and blood glucose (r > 0.6).

CONCLUSIONS

Dietary modifications through decreasing fructose intake and addressing systemic endotoxemia are plausible targets for improving metabolic health of KTRs.

A study on hepatopathic, dyslipidemic and immunogenic properties of fructosylated-HSA-AGE and binding of autoantibodies in sera of obese and overweight patients with fructosylated-HSA-AGE

Over consumption of fructose may lead to obesity and dyslipidemia and cause fructosylation-induced alterations in the structure and function of proteins. The aim of this study was to investigate the role of fructosylated-HSA-AGE in the pathogenesis of fatty liver (NAFLD and NASH) by biochemical, immunological and histological studies. Immunogenicity of fructosylated-HSA-AGE was probed by inducing antibodies in rabbits. Fructosylated-HSA-AGE was found to be highly immunogenic. Furthermore, fructosylated-HSA-AGE caused mild fibrosis with steatosis and portal inflammation of hepatocytes in experimental animals. Liver function test and dyslipidemic parameters in immunized animals were also found to be raised. Ultrasonography, which should form part of the assessment of chronically raised transaminases, shows fatty infiltration. Interestingly, alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin, total cholesterol (TC) and triglyceride (TG) profiles confirms USG images of overweight, obese patients. Thus, present study demonstrates that fructosylated-HSA-AGE is hepatotoxic, immunologically active and may cause dyslipidemia.

Hepatoprotective effect of calculus bovis sativus on nonalcoholic fatty liver disease in mice by inhibiting oxidative stress and apoptosis of hepatocytes

Calculus bovis (CB, niu-huang) is a high-class therapeutic drug that is often used in traditional Chinese medicine. CB helps to eliminate heat and toxic components, and prevents the accumulation of phlegm and blood stasis in the liver. In Asian countries, CB Sativus (CBS), an ideal substitute for natural CB, is presently extensively used for long-term treatment of chronic liver diseases. The present study aimed to evaluate the effects and potential mechanism(s) of action of CBS on mice with fructose-induced nonalcoholic fatty liver disease (NAFLD). The NAFLD model was established in C57BL/6 mice by exclusively feeding fluids containing 30% fructose for 8 consecutive weeks. After these 8 weeks, mice were given CBS (50 mg/kg/day or 100 mg/kg/day) for 2 consecutive weeks. Treatment with CBS reversed the fructose-induced impaired glucose tolerance. Compared with the model group, in which mice received 8 weeks of high-fructose diet and 2 weeks of 0.5% sodium carboxymethyl cellulose, CBS treatment significantly decreased the levels of fasting serum glucose, fasting insulin, triglyceride, and total cholesterol, and increased levels of high-density lipoprotein-cholesterol. CBS treatment also significantly decreased the levels of triglyceride, total cholesterol, and free fatty acid in the liver. The activity of superoxide dismutase in the liver was increased after treatment with CBS, however, levels of malondialdehyde and reactive oxygen species decreased. Histopathological examination showed that liver steatosis and injury were significantly reduced in CBS-treated mice. The expression of fatty acid synthase, nuclear factor kappa-light-chain-enhancer of activated B cells, Cysteinyl aspartate-specific proteinase-3, and synonyms B-cell leukemia/lymphoma-2 gene-associated X protein were downregulated after treatment with CBS, whereas the expression of nuclear factor erythroid-2-related factor 2 was upregulated. In conclusion, CBS treatment exerted therapeutic effects in the liver of mice with NAFLD, which may be associated with amelioration of metabolic disorders, enhanced antioxidant effects, and alleviation of apoptosis.

The Associations of Endotoxemia With Systemic Inflammation, Endothelial Activation, and Cardiovascular Outcome in Kidney Transplantation

OBJECTIVE

Cardiovascular disease is the leading cause of death in kidney transplant recipients (KTRs), yet incompletely accountable by traditional risk factors. Inflammation is an unconventional cardiovascular risk factor, with gut-derived endotoxemia potentially driving inflammation and endothelial disease. Comparable data are lacking in kidney transplantation. This study investigated the associations of endotoxemia with inflammation, endothelial activation, and 5-year cardiovascular events in KTRs. Determinants of endotoxemia were also explored.

DESIGN AND METHODS

This is a single-center cross-sectional study with prospective follow-up from a prevalent cohort of 128 KTRs.

MAIN OUTCOME MEASURES

Demographic, nutritional and clinical predictors of inflammation (high-sensitivity C-reactive protein [hsCRP]), endothelial activation (sE-selectin), and endotoxemia (endotoxin) were assessed. Follow-up data on 5-year cardiovascular event rates were collected.

RESULTS

Endotoxemia (P = .03), reduced 25-hydroxyvitamin D (P = .04), high fructose intake (P < .001), decreased fiber intake (P < .001), and abdominal obesity (P = .002) were independently associated with elevated hsCRP. In turn, endotoxemia (P = .007) and increasing hsCRP (P = .02) were both independently associated with raised sE-selectin. Furthermore, endotoxemia predicted increased cardiovascular event rate (P = .02), independent of hsCRP and a global measure of cardiovascular risk estimated by a validated algorithm of 7-year risk for major adverse cardiac events in kidney transplantation. Determinants of endotoxemia included reduced 25-hydroxyvitamin D (P < .001), hypertriglyceridemia (P < .001), increased fructose intake (P = .01), and abdominal obesity (P = .01).

CONCLUSIONS

Endotoxemia in KTRs contributes to inflammation, endothelial activation, and increased cardiovascular events. This study highlights the clinical relevance of endotoxemia in KTRs, suggesting future interventional targets.

Development of hepatocellular cancer induced by long term low fat-high carbohydrate diet in a NAFLD/NASH mouse model

Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease. It can progress to nonalcoholic steatohepatitis (NASH) and, in a percentage of cases, to hepatocarcinogenesis. The strong incidence in western countries of obesity and metabolic syndrome, whose NAFLD is the hepatic expression, is thought to be correlated to consumption of diets characterized by processed food and sweet beverages. Previous studies described high-fat diet-induced liver tumors. Conversely, the involvement of low-fat/high-carbohydrate diet in the progression of liver disease or cancer initiation has not been described yet. Here we show for the first time hepatic cancer formation in low-fat/high-carbohydrate diet fed NAFLD/NASH mouse model. Animals were long term high-fat, low-fat/high-carbohydrate or standard diet fed. We observed progressive liver damage in low-fat/high-carbohydrate and high-fat animals after 12 and, more, 18 months. Tumors were detected in 20% and 50% of high-fat diet fed mice after 12 and 18 months and, interestingly, in 30% of low-fat/high-carbohydrate fed animals after 18 months. No tumors were detected in standard diet fed mice. Global increase of hepatic interleukin-1β, interleukin-6, tumor necrosis factor-α and hepatocyte growth factor was detected in low-fat/high-carbohydrate and high-fat with respect to standard diet fed mice as well as in tumor with respect to non-tumor bearing mice. A panel of 15 microRNAs was analyzed: some of them revealed differential expression in low-fat/high-carbohydrate with respect to high-fat diet fed groups and in tumors. Data here shown provide the first evidence of the involvement of low-fat/high-carbohydrate diet in hepatic damage leading to tumorigenesis.

Microbiome and NAFLD: potential influence of aerobic fitness and lifestyle modification

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease with prevalence rates that are on the rise in the US and worldwide. NAFLD encompasses a spectrum of liver pathologies including simple steatosis to nonalcoholic steatohepatitis (NASH) with inflammation and fibrosis. The gut microbiome has emerged as a potential therapeutic target in combating metabolic diseases including obesity, Type 2 diabetes, and NAFLD/NASH. Diet-induced obesity/Western style diet feeding causes severe microbial dysbiosis initiating a microbiome signature that promotes metabolite production that directly impacts hepatic metabolism. Changes in lifestyle (i.e., diet, exercise, and aerobic fitness) improve NAFLD outcomes and can significantly influence the microbiome. However, directly linking lifestyle-induced remodeling of the microbiome to NAFLD pathogenesis is not well understood. Understanding the reshaping of the microbiome and the metabolites produced and their subsequent actions on hepatic metabolism are vital in understanding the gut-liver axis. In this review, we 1) discuss microbiome-derived metabolites that significantly contribute to the gut-liver axis and are directly linked to NAFLD/NASH and 2) present evidence on lifestyle modifications reshaping the microbiome and the potential therapeutic aspects in combating the disease.

The Acute Effects of Simple Sugar Ingestion on Appetite, Gut-Derived Hormone Response, and Metabolic Markers in Men

This pilot study aimed to investigate the effect of simple sugar ingestion, in amounts typical of common ingestion, on appetite and the gut-derived hormone response. Seven healthy men ingested water (W) and equicaloric solutions containing 39.6 g glucose monohydrate (G), 36 g fructose (F), 36 g sucrose (S), and 19.8 g glucose monohydrate + 18 g fructose (C), in a randomised order. Serum concentrations of ghrelin, glucose dependent insulinotropic polypeptide (GIP), glucagon like peptide-1 (GLP-1), insulin, lactate, triglycerides, non-esterified fatty acids (NEFA), and d-3 hydroxybutyrate, were measured for 60 min. Appetite was measured using visual analogue scales (VAS). The ingestion of F and S resulted in a lower GIP incremental area under the curve (iAUC) compared to the ingestion of G (p < 0.05). No differences in the iAUC for GLP-1 or ghrelin were present between the trials, nor for insulin between the sugars. No differences in appetite ratings or hepatic metabolism measures were found, except for lactate, which was greater following the ingestion of F, S, and C, when compared to W and G (p < 0.05). The acute ingestion of typical amounts of fructose, in a variety of forms, results in marked differences in circulating GIP and lactate concentration, but no differences in appetite ratings, triglyceride concentration, indicative lipolysis, or NEFA metabolism, when compared to glucose.

Formation of Fructose-Mediated Advanced Glycation End Products and Their Roles in Metabolic and Inflammatory Diseases

Fructose is associated with the biochemical alterations that promote the development of metabolic syndrome (MetS), nonalcoholic fatty liver disease, and type 2 diabetes. Its consumption has increased in parallel with MetS. It is metabolized by the liver, where it stimulates de novo lipogenesis. The triglycerides synthesized lead to hepatic insulin resistance and dyslipidemia. Fructose-derived advanced glycation end products (AGEs) may be involved via the Maillard reaction. Fructose has not been a main focus of glycation research because of the difficulty in measuring its adducts, and, more importantly, because although it is 10 times more reactive than glucose, its plasma concentration is only 1% of that of glucose. In this focused review, I summarize exogenous and endogenous fructose metabolism, fructose glycation, and in vitro, animal, and human data. Fructose is elevated in several tissues of diabetic patients where the polyol pathway is active, reaching the same order of magnitude as glucose. It is plausible that the high reactivity of fructose, directly or via its metabolites, may contribute to the formation of intracellular AGEs and to vascular complications. The evidence, however, is still unconvincing. Two areas that have been overlooked so far and should be actively explored include the following: 1) enteral formation of fructose AGEs, generating an inflammatory response to the receptor for AGEs (which may explain the strong association between fructose consumption and asthma, chronic bronchitis, and arthritis); and 2) inactivation of hepatic AMP-activated protein kinase by a fructose-mediated increase in methylglyoxal flux (perpetuating lipogenesis, fatty liver, and insulin resistance). If proven correct, these mechanisms would put the fructose-mediated Maillard reaction in the limelight again as a contributing factor in chronic inflammatory diseases and MetS.

High-fructose diet in pregnancy leads to fetal programming of hypertension, insulin resistance, and obesity in adult offspring

BACKGROUND

Consumption of fructose-rich diets in the United States is on the rise and thought to be associated with obesity and cardiometabolic diseases.

OBJECTIVE

We sought to determine the effects of antenatal exposure to high-fructose diet on offspring's development of metabolic syndrome-like phenotype and other cardiovascular disease risk factors later in life.

STUDY DESIGN

Pregnant C57BL/6J dams were randomly allocated to fructose solution (10% wt/vol, n = 10) or water (n = 10) as the only drinking fluid from day 1 of pregnancy until delivery. After weaning, pups were started on regular chow, and evaluated at 1 year of life. We measured percent visceral adipose tissue and liver fat infiltrates using computed tomography, and blood pressure using CODA nonivasive monitor. Intraperitoneal glucose tolerance testing with corresponding insulin concentrations were obtained. Serum concentrations of glucose, insulin, triglycerides, total cholesterol, leptin, and adiponectin were measured in duplicate using standardized assays. Fasting homeostatic model assessment was also calculated to assess insulin resistance. P values <.05 were considered statistically significant.

RESULTS

Maternal weight, pup number, and average weight at birth were similar between the 2 groups. Male and female fructose group offspring had higher peak glucose and area under the intraperitoneal glucose tolerance testing curve compared with control, and higher mean arterial pressure compared to control. Female fructose group offspring were heavier and had higher percent visceral adipose tissue, liver fat infiltrates, homeostatic model assessment of insulin resistance scores, insulin area under the intraperitoneal glucose tolerance testing curve, and serum concentrations of leptin, and lower concentrations of adiponectin compared to female control offspring. No significant differences in these parameters were noted in male offspring. Serum concentrations of triglycerides or total cholesterol were not different between the 2 groups for either gender.

CONCLUSION

Maternal intake of high fructose leads to fetal programming of adult obesity, hypertension, and metabolic dysfunction, all risk factors for cardiovascular disease. This fetal programming is more pronounced in female offspring. Limiting intake of high fructose-enriched diets in pregnancy may have significant impact on long-term health.

An Accessible and Pragmatic Experimental Model of Nonalcoholic Fatty Liver Disease

BACKGROUND

There is no convenient cheap pragmatic experimental model for Nonalcoholic Fatty Liver Disease (NAFLD)/Nonalcoholic Steatohepatitis (NASH). Objective: Our objective was to create a pragmatic model of NAFLD/NASH.

METHODS

Sprague-Dawley rats were fed a high-fat, high sugar homemade diet ad libitum for seven weeks. The high-fat, high sugar diet included 59% of energy derived from fat, 30% from carbohydrates, and 11% from protein. Serum levels of fasting glucose, triglyceride, cholesterol, liver enzymes, insulin, and hepatic tumor necrosis factor-alpha (TNF-α) gene expression were determined. Hepatic histology was examined by H&E stain.

RESULTS

Rats fed the high-fat, high sugar diet developed hepatic steatosis, and a moderate inflammation, which was associated with increased serum levels of liver enzymes, glucose, insulin, triglyceride, cholesterol, and hepatic TNF-α gene expression.

CONCLUSION

This rat model resembles the key features of human NAFLD/NASH and provides a simple pragmatic experimental model for elucidating the disease prevention and treatment.

A "systems medicine" approach to the study of non-alcoholic fatty liver disease

The prevalence of fatty liver (steatosis) in the general population is rapidly increasing worldwide. The progress of knowledge in the physiopathology of fatty liver is based on the systems biology approach to studying the complex interactions among different physiological systems. Similarly, translational and clinical research should address the complex interplay between these systems impacting on fatty liver. The clinical needs drive the applications of systems medicine to re-define clinical phenotypes, assessing the multiple nature of disease susceptibility and progression (e.g. the definition of risk, prognosis, diagnosis criteria, and new endpoints of clinical trials). Based on this premise and in light of recent findings, the complex mechanisms involved in the pathology of fatty liver and their impact on the short- and long-term clinical outcomes of cardiovascular, metabolic liver diseases associated with steatosis are presented in this review using a new "systems medicine" approach. A new data set is proposed for studying the impairments of different physiological systems that have an impact on fatty liver in different subsets of subjects and patients.

A High-Fat, High-Fructose Diet Induces Antioxidant Imbalance and Increases the Risk and Progression of Nonalcoholic Fatty Liver Disease in Mice

Excessive fat liver is an important manifestation of nonalcoholic fatty liver disease (NAFLD), associated with obesity, insulin resistance, and oxidative stress. In the present study, the effects of a high-fat, high-fructose diet (HFFD) on mRNA levels and activities of the antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), were determined in mouse livers and brains. The histomorphology of the livers was examined and the state of nonenzymatic reducing system was evaluated by measuring the glutathione system and the lipid peroxidation. Histopathology of the liver showed that fat accumulation and inflammation depended on the period of the HFFD-consumption. The levels of mRNA and enzymatic activities of SOD, CAT, and GPx were raised, followed by the increases in malondialdehyde levels in livers and brains of the HFFD mice. The oxidized GSSG content was increased while the total GSH and the reduced GSH were decreased, resulting in the increase in the GSH/GSSG ratio in both livers and brains of the HFFD mice. These observations suggested that liver damage and oxidative stress in the significant organs were generated by continuous HFFD-consumption. Imbalance of antioxidant condition induced by long-term HFFD-consumption might increase the risk and progression of NAFLD.

Potential link between excess added sugar intake and ectopic fat: a systematic review of randomized controlled trials

CONTEXT

The effect of added sugar intake on ectopic fat accumulation is a subject of debate.

OBJECTIVE

A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to examine the potential effect of added sugar intake on ectopic fat depots.

DATA SOURCES

MEDLINE, CAB Abstracts, CAB Global Health, and EBM (Evidence-Based Medicine) Reviews - Cochrane Central Register of Controlled Trials databases were searched for studies published from 1973 to September 2014.

DATA EXTRACTION

RCTs with a minimum of 6 days' duration of added sugar exposure in the intervention group were selected. The dosage of added sugar intake as a percentage of total energy was extracted or calculated. Means and standard deviations of pre- and post-test measurements or changes in ectopic fat depots were collected.

DATA SYNTHESIS

Fourteen RCTs were included. Most of the studies had a medium to high risk of bias. Meta-analysis showed that, compared with eucaloric controls, subjects who consumed added sugar under hypercaloric conditions likely increased ectopic fat, particularly in the liver (pooled standardized mean difference = 0.9 [95%CI, 0.6-1.2], n = 6) and muscles (pooled SMD = 0.6 [95%CI, 0.2-1.0], n = 4). No significant difference was observed in liver fat, visceral adipose tissue, or muscle fat when isocaloric intakes of different sources of added sugars were compared.

CONCLUSIONS

Data from a limited number of RCTs suggest that excess added sugar intake under hypercaloric diet conditions likely increases ectopic fat depots, particularly in the liver and in muscle fat. There are insufficient data to compare the effect of different sources of added sugars on ectopic fat deposition or to compare intake of added sugar with intakes of other macronutrients. Future well-designed RCTs with sufficient power and duration are needed to address the role of sugars on ectopic fat deposition.

Advanced glycation end product accumulation: a new enemy to target in chronic kidney disease?

PURPOSE OF REVIEW

The critical role of advanced glycation end products (AGEs) in the progression of chronic diseases and their complications has recently become more apparent. This review summarizes the recent contributions to the field of AGEs in chronic kidney disease (CKD).

RECENT FINDINGS

Over the past 3 decades, AGEs have been implicated in the progression of CKD, and specifically diabetic nephropathy. Although numerous in-vitro and in-vivo studies highlight the detrimental role of AGEs accumulation in tissue injury, few prospective human studies or clinical trials show that inhibiting this process ameliorates disease. Nonetheless, recent studies have focused on the novel mechanisms that contribute to end-organ injury as a result of AGEs accumulation, as well as novel targets of therapy in kidney disease.

SUMMARY

As the prevalence and the incidence of CKD rises in the United States, it is essential to identify therapeutic strategies that either delay the progression of CKD or improve mortality in this population. The focus of this review is on highlighting the recent studies that advance our current understanding of the mechanisms mediating AGEs-induced CKD progression, as well as novel treatment strategies that have the potential to abrogate this disease process.

VIDEO ABSTRACT

http://links.lww.com/CONH/A12.

Nutrigenomics analysis reveals that copper deficiency and dietary sucrose up-regulate inflammation, fibrosis and lipogenic pathways in a mature rat model of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) prevalence is increasing worldwide, with the affected US population estimated near 30%. Diet is a recognized risk factor in the NAFLD spectrum, which includes nonalcoholic steatohepatitis (NASH) and fibrosis. Low hepatic copper (Cu) was recently linked to clinical NAFLD/NASH severity. Simple sugar consumption including sucrose and fructose is implicated in NAFLD, while consumption of these macronutrients also decreases liver Cu levels. Though dietary sugar and low Cu are implicated in NAFLD, transcript-level responses that connect diet and pathology are not established. We have developed a mature rat model of NAFLD induced by dietary Cu deficiency, human-relevant high sucrose intake (30% w/w) or both factors in combination. Compared to the control diet with adequate Cu and 10% (w/w) sucrose, rats fed either high-sucrose or low-Cu diet had increased hepatic expression of genes involved in inflammation and fibrogenesis, including hepatic stellate cell activation, while the combination of diet factors also increased ATP citrate lyase and fatty acid synthase gene transcription (fold change > 2, P < 0.02). Low dietary Cu decreased hepatic and serum Cu (P ≤ 0.05), promoted lipid peroxidation and induced NAFLD-like histopathology, while the combined factors also induced fasting hepatic insulin resistance and liver damage. Neither low Cu nor 30% sucrose in the diet led to enhanced weight gain. Taken together, transcript profiles, histological and biochemical data indicate that low Cu and high sucrose promote hepatic gene expression and physiological responses associated with NAFLD and NASH, even in the absence of obesity or severe steatosis.

Role of the diet as a link between oxidative stress and liver diseases

Oxidative stress is caused by an imbalance between the production of reactive oxygen (free radicals) and the body's ability (antioxidant capacity) to readily detoxify the reactive intermediates or easily repair the resulting damage. An adequate diet, characterized by daily intake of foods associated with improvements in the total antioxidant capacity of individuals and reduced incidence of diseases related to oxidation, can modulate the degree of oxidative stress. In fact, diet-derived micronutrients may be direct antioxidants, or are components of antioxidant enzymes, leading to improvement of some indicators of hepatic function. However, although their increased dietary intake might be beneficial, literature data are still controversial. This review summarizes what is known about the effects of diet nutrients on oxidative stress, inflammation and liver function. Moreover, we have analyzed: (1) the main nutritional components involved in the production and/or removal of free radicals; and (2) the role of free radicals in the pathogenesis of several hepatic diseases and related comorbidities.

Involvement of the TAGE-RAGE system in non-alcoholic steatohepatitis: Novel treatment strategies

Non-alcoholic fatty liver disease (NAFLD) is a major cause of liver disease around the world. It includes a spectrum of conditions from simple steatosis to non-alcoholic steatohepatitis (NASH) and can lead to fibrosis, cirrhosis, liver failure, and/or hepatocellular carcinoma. NAFLD is also associated with other medical conditions such as obesity, diabetes mellitus (DM), metabolic syndrome, hypertension, insulin resistance, hyperlipidemia, and cardiovascular disease (CVD). In diabetes, chronic hyperglycemia contributes to the development of both macro- and microvascular conditions through a variety of metabolic pathways. Thus, it can cause a variety of metabolic and hemodynamic conditions, including upregulated advanced glycation end-products (AGEs) synthesis. In our previous study, the most abundant type of toxic AGEs (TAGE); i.e., glyceraldehyde-derived AGEs, were found to make a significant contribution to the pathogenesis of DM-induced angiopathy. Furthermore, accumulating evidence suggests that the binding of TAGE with their receptor (RAGE) induces oxidative damage, promotes inflammation, and causes changes in intracellular signaling and the expression levels of certain genes in various cell populations including hepatocytes and hepatic stellate cells. All of these effects could facilitate the pathogenesis of hypertension, cancer, diabetic vascular complications, CVD, dementia, and NASH. Thus, inhibiting TAGE synthesis, preventing TAGE from binding to RAGE, and downregulating RAGE expression and/or the expression of associated effector molecules all have potential as therapeutic strategies against NASH. Here, we examine the contributions of RAGE and TAGE to various conditions and novel treatments that target them in order to prevent the development and/or progression of NASH.

Involvement of the TAGE-RAGE system in non-alcoholic steatohepatitis: Novel treatment strategies

Non-alcoholic fatty liver disease (NAFLD) is a major cause of liver disease around the world. It includes a spectrum of conditions from simple steatosis to non-alcoholic steatohepatitis (NASH) and can lead to fibrosis, cirrhosis, liver failure, and/or hepatocellular carcinoma. NAFLD is also associated with other medical conditions such as obesity, diabetes mellitus (DM), metabolic syndrome, hypertension, insulin resistance, hyperlipidemia, and cardiovascular disease (CVD). In diabetes, chronic hyperglycemia contributes to the development of both macro- and microvascular conditions through a variety of metabolic pathways. Thus, it can cause a variety of metabolic and hemodynamic conditions, including upregulated advanced glycation end-products (AGEs) synthesis. In our previous study, the most abundant type of toxic AGEs (TAGE); i.e., glyceraldehyde-derived AGEs, were found to make a significant contribution to the pathogenesis of DM-induced angiopathy. Furthermore, accumulating evidence suggests that the binding of TAGE with their receptor (RAGE) induces oxidative damage, promotes inflammation, and causes changes in intracellular signaling and the expression levels of certain genes in various cell populations including hepatocytes and hepatic stellate cells. All of these effects could facilitate the pathogenesis of hypertension, cancer, diabetic vascular complications, CVD, dementia, and NASH. Thus, inhibiting TAGE synthesis, preventing TAGE from binding to RAGE, and downregulating RAGE expression and/or the expression of associated effector molecules all have potential as therapeutic strategies against NASH. Here, we examine the contributions of RAGE and TAGE to various conditions and novel treatments that target them in order to prevent the development and/or progression of NASH.

Focus on emerging drugs for the treatment of patients with non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) has become the most common liver disorder in Western countries and is increasingly being recognized in developing nations. Fatty liver disease encompasses a spectrum of hepatic pathology, ranging from simple steatosis to non-alcoholic steatohepatitis, cirrhosis, hepatocellular carcinoma and end-stage liver disease. Moreover, NAFLD is often associated with other metabolic conditions, such as diabetes mellitus type 2, dyslipidemia and visceral obesity. The most recent guidelines suggest the management and treatment of patients with NAFLD considering both the liver disease and the associated metabolic co-morbidities. Diet and physical exercise are considered the first line of treatment for patients with NAFLD, but their results on therapeutic efficacy are often contrasting. Behavior therapy is necessary most of the time to achieve a sufficient result. Pharmacological therapy includes a wide variety of classes of molecules with different therapeutic targets and, often, little evidence supporting the real efficacy. Despite the abundance of clinical trials, NAFLD therapy remains a challenge for the scientific community, and there are no licensed therapies for NAFLD. Urgently, new pharmacological approaches are needed. Here, we will focus on the challenges facing actual therapeutic strategies and the most recent investigated molecules.

Fibroblast growth factor 21 limits lipotoxicity by promoting hepatic fatty acid activation in mice on methionine and choline-deficient diets

BACKGROUND & AIMS

Nonalcoholic fatty liver disease is a common consequence of human and rodent obesity. Disruptions in lipid metabolism lead to accumulation of triglycerides and fatty acids, which can promote inflammation and fibrosis and lead to nonalcoholic steatohepatitis. Circulating levels of fibroblast growth factor (FGF)21 increase in patients with nonalcoholic fatty liver disease or nonalcoholic steatohepatitis; therefore, we assessed the role of FGF21 in the progression of murine fatty liver disease, independent of obesity, caused by methionine and choline deficiency.

METHODS

C57BL/6 wild-type and FGF21-knockout (FGF21-KO) mice were placed on methionine- and choline-deficient (MCD), high-fat, or control diets for 8-16 weeks. Mice were weighed, and serum and liver tissues were collected and analyzed for histology, levels of malondialdehyde and liver enzymes, gene expression, and lipid content.

RESULTS

The MCD diet increased hepatic levels of FGF21 messenger RNA more than 50-fold and serum levels 16-fold, compared with the control diet. FGF21-KO mice had more severe steatosis, fibrosis, inflammation, and peroxidative damage than wild-type C57BL/6 mice. FGF21-KO mice had reduced hepatic fatty acid activation and β-oxidation, resulting in increased levels of free fatty acid. FGF21-KO mice given continuous subcutaneous infusions of FGF21 for 4 weeks while on an MCD diet had reduced steatosis and peroxidative damage, compared with mice not receiving FGF21. The expression of genes that regulate inflammation and fibrosis were reduced in FGF21-KO mice given FGF21, similar to those of wild-type mice.

CONCLUSIONS

FGF21 regulates fatty acid activation and oxidation in livers of mice. In the absence of FGF21, accumulation of inactivated fatty acids results in lipotoxic damage and increased steatosis.

Activation of farnesoid X receptor (FXR) protects against fructose-induced liver steatosis via inflammatory inhibition and ADRP reduction

Fructose is a key dietary factor in the development of nonalcoholic fatty liver disease (NAFLD). Here we investigated whether WAY-362450 (WAY), a potent synthetic and orally active FXR agonist, protects against fructose-induced steatosis and the underlying mechanisms. C57BL/6J mice, fed 30% fructose for 8 weeks, were treated with or without WAY, 30 mg/kg, for 20 days. The elevation of serum and hepatic triglyceride in mice fed 30% fructose was reversed by WAY treatment. Histologically, WAY significantly reduced triglyceride accumulation in liver, attenuated microphage infiltration and protected the junction integrity in intestine. Moreover, WAY remarkably decreased portal endotoxin level, and lowered serum TNFα concentration. In lipopolysaccharide (LPS)-induced NAFLD model, WAY attenuated serum TNFα level. Moreover, WAY suppressed LPS-induced expression of hepatic lipid droplet protein adipose differentiation-related protein (ADRP), down-regulation of it in mice fed 30% fructose. Furthermore, WAY repressed lipid accumulation and ADRP expression in a dose-dependent manner in palmitic acid (PA)-treated HepG2 and Huh7 cells. WAY suppressed TNFα-induced ADRP up-regulation via competing with AP-1 for ADRP promoter binding region. Together, our findings suggest that WAY, an FXR agonist, attenuates liver steatosis through multiple mechanisms critically involved in the development of hepatosteatosis, and represents a candidate for NAFLD treatment.

Diet macronutrients composition in nonalcoholic Fatty liver disease: a review on the related documents

CONTEXT

Non-alcoholic fatty liver disease (NAFLD) is a growing health problem in both developed and developing countries. Metabolic abnormalities, specially insulin resistance and hyperglycemia are highly correlated with NAFLD. Lifestyle modifications including physical activity and promoting nutrient intakes are critical in prevention and treatment of NAFLD. Hence, in this article we aimed to review the evidence regarding the effects of various macronutrients on fat accumulation in hepatic cells as well as the level of liver enzymes.

EVIDENCE ACQUISITIONS

The relevant English and non-English published papers were searched using online databases of PubMed, ISI Web of Science, SCOPUS, Science Direct and EMBASE from January 2000 to January 2013. We summarized the findings of 40 relevant studies in this review.

RESULTS

Although a hypocaloric diet could prevent the progression of fat accumulation in liver, the diet composition is another aspect which should be considered in diet therapy of patients with NAFLD.

CONCLUSIONS

Several studies assessed the effects of dietary composition on fat storage in liver; however, their findings are inconsistent. Most studies focused on the quantity of carbohydrate and dietary fat; whilst there is very limited information regarding the role of protein intake.

Pathophysiology of NASH: perspectives for a targeted treatment

Non alcoholic steatohepatitis (NASH) is the more severe form of nonalcoholic fatty liver disease. In NASH, fatty liver, hepatic inflammation, hepatocyte injury and fibrogenesis are associated, and this condition may eventually lead to cirrhosis. Current treatment of NASH relies on the reduction of body weight and increase in physical activity, but there is no pharmacologic treatment approved as yet. Emerging data indicate that NASH progression results from parallel events originating from the liver as well as from the adipose tissue, the gut and the gastrointestinal tract. Thus, dysfunction of the adipose tissue through enhanced flow of free fatty acids and release of adipocytokines, and alterations in the gut microbiome generate proinflammatory signals that underlie NASH progression. Additional 'extrahepatic hits' include dietary factors and gastrointestinal hormones. Within the liver, hepatocyte apoptosis, ER stress and oxidative stress are key contributors to hepatocellular injury. In addition, lipotoxic mediators and danger signals activate Kupffer cells which initiate and perpetuate the inflammatory response by releasing inflammatory mediators that contribute to inflammatory cell recruitment and development of fibrosis. Inflammatory and fibrogenic mediators include chemokines, the cannabinoid system, the inflammasome and activation of pattern-recognition receptors. Here we review the major mechanisms leading to appearance and progression of NASH, focusing on both extrahepatic signals and local inflammatory mechanisms, in an effort to identify the most promising molecular targets for the treatment of this condition.

Pathophysiology of NASH: perspectives for a targeted treatment

Non alcoholic steatohepatitis (NASH) is the more severe form of nonalcoholic fatty liver disease. In NASH, fatty liver, hepatic inflammation, hepatocyte injury and fibrogenesis are associated, and this condition may eventually lead to cirrhosis. Current treatment of NASH relies on the reduction of body weight and increase in physical activity, but there is no pharmacologic treatment approved as yet. Emerging data indicate that NASH progression results from parallel events originating from the liver as well as from the adipose tissue, the gut and the gastrointestinal tract. Thus, dysfunction of the adipose tissue through enhanced flow of free fatty acids and release of adipocytokines, and alterations in the gut microbiome generate proinflammatory signals that underlie NASH progression. Additional 'extrahepatic hits' include dietary factors and gastrointestinal hormones. Within the liver, hepatocyte apoptosis, ER stress and oxidative stress are key contributors to hepatocellular injury. In addition, lipotoxic mediators and danger signals activate Kupffer cells which initiate and perpetuate the inflammatory response by releasing inflammatory mediators that contribute to inflammatory cell recruitment and development of fibrosis. Inflammatory and fibrogenic mediators include chemokines, the cannabinoid system, the inflammasome and activation of pattern-recognition receptors. Here we review the major mechanisms leading to appearance and progression of NASH, focusing on both extrahepatic signals and local inflammatory mechanisms, in an effort to identify the most promising molecular targets for the treatment of this condition.

Glucose transporter 8 (GLUT8) mediates fructose-induced de novo lipogenesis and macrosteatosis

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in the world, and it is thought to be the hepatic manifestation of the metabolic syndrome. Excess dietary fructose causes both metabolic syndrome and NAFLD in rodents and humans, but the pathogenic mechanisms of fructose-induced metabolic syndrome and NAFLD are poorly understood. GLUT8 (Slc2A8) is a facilitative glucose and fructose transporter that is highly expressed in liver, heart, and other oxidative tissues. We previously demonstrated that female mice lacking GLUT8 exhibit impaired first-pass hepatic fructose metabolism, suggesting that fructose transport into the hepatocyte, the primary site of fructose metabolism, is in part mediated by GLUT8. Here, we tested the hypothesis that GLUT8 is required for hepatocyte fructose uptake and for the development of fructose-induced NAFLD. We demonstrate that GLUT8 is a cell surface-localized transporter and that GLUT8 overexpression or GLUT8 shRNA-mediated gene silencing significantly induces and blocks radiolabeled fructose uptake in cultured hepatocytes. We further show diminished fructose uptake and de novo lipogenesis in fructose-challenged GLUT8-deficient hepatocytes. Finally, livers from long term high-fructose diet-fed GLUT8-deficient mice exhibited attenuated fructose-induced hepatic triglyceride and cholesterol accumulation without changes in hepatocyte insulin-stimulated Akt phosphorylation. GLUT8 is thus essential for hepatocyte fructose transport and fructose-induced macrosteatosis. Fructose delivery across the hepatocyte membrane is thus a proximal, modifiable disease mechanism that may be exploited to prevent NAFLD.

Obesity-associated nonalcoholic fatty liver disease

Obesity is strongly associated with the prevalence of nonalcoholic fatty liver disease (NAFLD) in adult and pediatric populations. Nutrition, physical activity, and behavioral modifications are critical components of the treatment regimen for all obese patients with NAFLD. Bariatric surgeries that affect or restrict the flow of food through the gastrointestinal tract may improve liver histology in morbidly obese patients with nonalcoholic steatohepatitis (NASH), although randomized clinical trials and quasi-randomized clinical studies are lacking. Early detection of NASH and hepatic fibrosis using noninvasive biochemical and imaging markers that may replace liver biopsy is the current challenge.

Industrial, not fruit fructose intake is associated with the severity of liver fibrosis in genotype 1 chronic hepatitis C patients

BACKGROUND & AIMS

Unhealthy food intake, specifically fructose, has been associated with metabolic alterations and with the severity of liver fibrosis in patients with non-alcoholic fatty liver disease. In a cohort of patients with genotype 1 chronic hepatitis C (G1 CHC), we tested the association of fructose intake with the severity of liver histology.

METHODS

Anthropometric and metabolic factors, including waist circumference (WC), waist-to-hip ratio (WHR), dorso-cervical lipohypertrophy and HOMA were assessed in 147 consecutive biopsy-proven G1 CHC patients. Food intake, namely industrial and fruit fructose, was investigated by a three-day structured interview and a computed database. All biopsies were scored by an experienced pathologist for staging and grading (Scheuer classification), and graded for steatosis, which was considered moderate-severe if ≥ 20%. Features of non-alcoholic steatohepatitis (NASH) in CHC were also assessed (Bedossa classification).

RESULTS

Mean daily intake of total, industrial and fruit fructose was 18.0±8.7g, 6.0±4.7g, and 11.9±7.2g, respectively. Intake of industrial, not fruit fructose, was independently associated with higher WHR (p=0.02) and hypercaloric diet (p<0.001). CHC patients with severe liver fibrosis (⩾F3) reported a significantly higher intake of total (20.8±10.2 vs. 17.2±8.1g/day; p=0.04) and industrial fructose (7.8±6.0 vs. 5.5±4.2; p=0.01), not fruit fructose (12.9±8.0 vs. 11.6±7.0; p=0.34). Multivariate logistic regression analysis showed that older age (OR 1.048, 95% CI 1.004-1.094, p=0.03), severe necroinflammatory activity (OR 3.325, 95% CI 1.347-8.209, p=0.009), moderate-severe steatosis (OR 2.421, 95% CI 1.017-6.415, p=0.04), and industrial fructose intake (OR 1.147, 95% CI 1.047-1.257, p=0.003) were independently linked to severe fibrosis. No association was found between fructose intake and liver necroinflammatory activity, steatosis, and the features of NASH.

CONCLUSIONS

The daily intake of industrial, not fruit fructose is a risk factor for metabolic alterations and the severity of liver fibrosis in patients with G1 CHC.

Bone quality and strength are greater in growing male rats fed fructose compared with glucose

Optimization of peak bone mass during adolescence is important for osteoporosis prevention. Studies in rodents and humans have demonstrated the harmful effects of sugar intake on bone health. With the high levels of sucrose in the diets of adolescents, it is necessary to understand the influence of glucose and fructose on growing bones. This study compared the effects of dietary glucose and fructose on bone formation, microarchitecture, and strength. Because of the different metabolic effects of glucose and fructose, we hypothesized that their individual effects on bone would be different. Eighteen male Sprague-Dawley rats (age, 60 days) were randomly assigned to high-fructose (n = 9; 40% fructose, 10% glucose) or high-glucose diet (n = 9; 50% glucose) for 12 weeks. Bone measurements included histology and histomorphometry of trabecular bone in the distal femur and a 3-point bending test of the whole tibia. Whole liver mass and postprandial serum glucose, insulin, and triglycerides were used to assess differences in energy metabolism between the diets. There were no differences in food intake, body weight, or visceral adiposity between groups, but fructose consumption led to heavier livers (P = .001) and elevated serum triglycerides (P = .00). The distal femurs of fructose-fed rats had greater bone volume (bone volume/total volume; P = .03), lower bone surface (bone surface/bone volume; P = .02), and thicker trabeculae (trabecular thickness; P = .01). The tibias of the fructose-fed rats also withstood a greater maximum flexure load (P = .032). These results indicate that consumption of the high-fructose diet resulted in stronger bones with enhanced microarchitecture than consumption of the high-glucose diet.

Long term metabolic syndrome induced by a high fat high fructose diet leads to minimal renal injury in C57BL/6 mice

Metabolic syndrome can induce chronic kidney disease in humans. Genetically engineered mice on a C57BL/6 background are highly used for mechanistic studies. Although it has been shown that metabolic syndrome induces cardiovascular lesions in C57BL/6 mice, in depth renal phenotyping has never been performed. Therefore in this study we characterized renal function and injury in C57BL/6 mice with long-term metabolic syndrome induced by a high fat and fructose diet (HFFD). C57BL/6 mice received an 8 months HFFD diet enriched with fat (45% energy from fat) and drinking water enriched with fructose (30%). Body weight, food/water consumption, energy intake, fat/lean mass ratio, plasma glucose, HDL, LDL, triglycerides and cholesterol levels were monitored. At 3, 6 and 8 months, renal function was determined by inulin clearance and measure of albuminuria. At sacrifice, kidneys and liver were collected. Metabolic syndrome in C57BL/6 mice fed a HFFD was observed as early 4 weeks with development of type 2 diabetes at 8 weeks after initiation of diet. However, detailed analysis of kidney structure and function showed only minimal renal injury after 8 months of HFFD. HFFD induced moderate glomerular hyperfiltration (436,4 µL/min vs 289,8 µL/min; p-value=0.0418) together with a 2-fold increase in albuminuria only after 8 months of HFFD. This was accompanied by a 2-fold increase in renal inflammation (p-value=0.0217) but without renal fibrosis or mesangial matrix expansion. In addition, electron microscopy did not show alterations in glomeruli such as basal membrane thickening and foot process effacement. Finally, comparison of the urinary peptidome of these mice with the urinary peptidome from humans with diabetic nephropathy also suggested absence of diabetic nephropathy in this model. This study provides evidence that the HFFD C57BL/6 model is not the optimal model to study the effects of metabolic syndrome on the development of diabetic kidney disease.

The chemical chaperon 4-phenylbutyric acid ameliorates hepatic steatosis through inhibition of de novo lipogenesis in high-fructose-fed rats

Non-alcoholic fatty liver disease caused by dietary factors such as a high fructose intake is a growing global concern. The aim of this study was to investigate the intervention effects of an endoplasmic reticulum stress (ERS) inhibitor 4-phenylbutyric acid (PBA) on liver steatosis induced by high-fructose feeding in rats and the possible underlying mechanisms. Wistar rats were divided into the control, high-fructose group (HFru) and PBA intervention (HFru-PBA) groups. PBA intervention was initiated following 4 weeks of high-fructose feeding. After 8 weeks of feeding, the ERS markers p-PERK, p-eIF2α, p-IRE-1, spliced XBP-1, ATF-6 were measured by western blotting. Liver triglyceride contents and morphological changes were examined. The protein expression of lipogenic key enzymes (ACC, FAS and SCD-1) and upstream transcriptional factors (SREBP-1c and ChREBP) were measured. The ERS-related cell events, oxidative stress and apoptosis, were evaluated by standard methods. Results demonstrated that PBA intervention significantly resolved hepatic ERS and improved liver steatosis induced by high-fructose feeding in rats. The protein expression of ACC, FAS, SCD-1 and SREBP-1c was upregulated in high-fructose-fed rats, whereas it decreased following PBA intervention. Oxidative stress and apoptosis were observed in livers of high-fructose-fed rats, but were alleviated by PBA intervention. ERS is involved in the development of fatty liver induced by a high fructose intake. ERS inhibition by PBA can therefore ameliorate liver steatosis through inhibition of hepatic lipogenesis.

Liver disease and malnutrition

Patients with hepatic disorders are exceptionally vulnerable to developing malnutrition because of the key role played by the liver in regulating the nutritional state and the energy balance. Moreover, the presence of chronic liver disorders could reduce the appetite and thus influence the nutrient intake. Poor nutritional status has been shown in various patient groups with hepatic disorders, and particularly in patients with alcoholic cirrhosis who are at high nutritional risk. It is well established that malnourished patients with liver diseases generally have a higher risk of developing adverse clinical outcomes and increased healthcare costs. Nutrition screening with the Subjective Global Assessment and anthropometric measurements are an important first step in the early identification of malnutrition and initiates the whole nutrition care process. It is therefore important for appropriate nutrition policies and protocols to be implemented so that all patients with chronic liver diseases are monitored closely from a nutritional standpoint. Early and evidence-based nutritional interventions are eagerly needed to minimize the nutritional decline associated with chronic liver disorders and ultimately improve the prognosis of such patients. This review includes a comprehensive analysis of methods to identify malnutrition in patients with chronic liver diseases as well as the extent and impact of the malnutrition problem in selected patient populations.

Non-alcoholic fatty liver disease (NAFLD): a tale of fat and sugar?

The global diffusion of the so-called Western diet, which is enriched in fat and carbohydrates, such as fructose, has been proposed to be an underlying cause of the increased prevalence of metabolic conditions, including non-alcoholic fatty liver disease (NAFLD). This Smart Card summarizes the main metabolic and hepatic histological features of rodent models fed with diets combining high fat and fructose.

Therapeutic approaches to non-alcoholic fatty liver disease: past achievements and future challenges

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a leading cause of chronic liver injury and mortality in Western countries and China. However, as to date, there is no direct and effective therapy for this disease. The aim of this review is to analyze the key progress and challenges of main current therapeutic approaches in NAFLD.

DATA SOURCE

We carried out a PubMed search of English-language articles relevant to NAFLD therapy.

RESULTS

There are two major therapeutic strategies for NAFLD treatment: (1) lifestyle interventions (including weight reduction, dietary modification and physical exercise) and (2) pharmaceutical therapies. Lifestyle interventions, particularly chronic and moderate intensity exercise, are the most effective and recognized clinical therapies for NAFLD. For pharmaceutical therapies, although their effects and mechanisms have been extensively investigated in laboratory studies, they still need further tests and investigations in clinical human trials.

CONCLUSION

Future advancement of NAFLD therapy should focus on the mechanistic studies on cell based and animal models and human clinical trials of exercise, as well as the combination of lifestyle intervention and pharmaceutical therapy specifically targeting main signaling pathways related to lipid metabolism, oxidative stress and inflammation.

High fat diets and pathology in the guinea pig. Atherosclerosis or liver damage?

Animal models have been widely used to investigate the relationship between diet and atherosclerosis and also to study disease etiology and possible interventions. Guinea pigs have been suggested to be a more "realistic" model for atherosclerosis due to their many similarities to humans. However, few published studies actually reported observations of characteristic atherosclerotic lesions and even fewer of advanced lesions. Studies, by our group, of guinea pigs fed on a high-fat diet revealed similar observations, with indications primarily of fatty streaks but little evidence of atherosclerotic plaques. This review discusses the feasibility of the guinea pig as a model for dietary-induced atherosclerosis. As it stands, current evidence raises doubt as to whether guinea pigs could serve as a realistic model for atherosclerosis. However, our own data and the literature suggest that they could be useful models for studying lipoprotein metabolism, non-alcoholic fatty liver disease, and dietary interventions which may help regulate these conditions.

Oral xylose isomerase decreases breath hydrogen excretion and improves gastrointestinal symptoms in fructose malabsorption - a double-blind, placebo-controlled study

BACKGROUND

Incomplete resorption of fructose results in increased colonic hydrogen production and is a frequent cause of abdominal symptoms. The only treatment available is diet.

AIM

To study whether orally administered xylose isomerase (XI), an enzyme that catalyses the reversible isomerisation of glucose and fructose, can decrease breath hydrogen excretion in patients with fructose malabsorption.

METHODS

Patients received 25 g fructose in 100 mL water together with either placebo or XI capsules. Primary endpoint was the reduction in breath hydrogen excretion, as assessed by the area under the breath hydrogen curve over 4 h (AUC). A secondary endpoint was the reduction in abdominal pain, bloating and nausea assessed on a visual analogue scale (VAS, range: 0-10). A P value <0.05 was considered statistically significant.

RESULTS

Sixty-five patients in whom fructose malabsorption had been diagnosed by positive breath hydrogen test within the previous year, were included in the study [15 males, 50 females; mean age 43.3 (s.d. = 14.4), range: 21-73 years]. The median AUC was 885 ppm/240 min in the XI group compared to 2071 ppm/240 min in the placebo group (P = 0.00). Median scores for abdominal pain (0.7 vs. 1.3) and nausea (0.2 vs. 0.6), but not for bloating (P = 0.053), were significantly improved after XI (P = 0.009 and P = 0.005) as compared with placebo.

CONCLUSIONS

Oral administration of xylose isomerase significantly decreased breath hydrogen excretion after ingestion of a watery fructose solution. Nausea and abdominal pain were significantly improved by xylose isomerase.