Adipose Tissue Protects against Hepatic Steatosis in Male Rats Fed a High-Fat Diet plus Liquid Fructose: Sex-Related Differences.

Non-alcoholic fatty liver disease is a sexual dimorphic disease, with adipose tissue playing an essential role. Our previous work showed that female rats fed a high-fat high-fructose diet devoid of cholesterol (HFHFr) developed simple hepatic steatosis dissociated from obesity. This study assessed the impact of the HFHFr diet on the male rat metabolism compared with data obtained for female rats. A total of 16 Sprague Dawley (SD) male rats were fed either a control (standard rodent chow and water) or HFHFr (high-fat diet devoid of cholesterol, plus 10% fructose in drinking water) diet for 3 months. Unlike female rats, and despite similar increases in energy consumption, HFHFr males showed increased adiposity and hyperleptinemia. The expression of hormone-sensitive lipase in the subcutaneous white adipose tissue was enhanced, leading to high free fatty acid and glycerol serum levels. HFHFr males presented hypertriglyceridemia, but not hepatic steatosis, partially due to enhanced liver PPARα-related fatty acid ß-oxidation and the VLDL-promoting effect of leptin. In conclusion, the SD rats showed a sex-related dimorphic response to the HFHFr diet. Contrary to previous results for HFHFr female rats, the male rats were able to expand the adipose tissue, increase fatty acid catabolism, or export it as VLDL, avoiding liver lipid deposition.

Bempedoic acid for nonalcoholic fatty liver disease: evidence and mechanisms of action.

PURPOSE OF REVIEW: Nonalcoholic fatty liver disease (NAFLD) is a highly prevalent progressive condition that lacks a specific pharmacological treatment. ATP-citrate lyase (ACLY) is one of the emergent targets for the treatment of NAFLD. This review aims to summarize the role of ACLY in NAFLD, provide evidence of the beneficial effects of the ACLY inhibitor bempedoic acid (BemA) in NAFLD and discuss the mechanisms involved. RECENT FINDINGS: BemA is effective in reducing hepatic steatosis in several animal models that recapitulate different stages of the disease. Thus, in a dietary model of simple hepatic steatosis in female rats, BemA abrogates the accumulation of liver fat. Apart from ACLY inhibition, BemA has several functions in the liver that contribute to the antisteatotic effect: inhibition of ketohexokinase, induction of patatin-like phospholipase domain-containing protein 3 and increases in both fatty acid ß-oxidation activity and hepatic H 2 S production. In models of the advanced phases of NAFLD, BemA reduces not only steatosis, but also ballooning, lobular inflammation and hepatic fibrosis, by mechanisms involving both hepatocytes and hepatic stellate cells. SUMMARY: BemA, an ACLY inhibitor currently approved for the treatment of hypercholesterolemia, may be a useful drug to treat NAFLD through its antisteatotic, anti-inflammatory and antifibrotic effects.

KHK, PNPLA3 and PPAR as Novel Targets for the Anti-Steatotic Action of Bempedoic Acid.

Bempedoic acid (BemA) is an ATP-citrate lyase (ACLY) inhibitor used to treat hypercholesterolemia. We studied the anti-steatotic effect of BemA, and the mechanisms involved, in a model of fatty liver in female rats obtained through the administration of a high-fat diet supplemented with liquid fructose (HFHFr) for three months. In the third month, a group of rats was treated with BemA (30 mg/kg/day) by gavage. Plasma analytes, liver histology, adiposity, and the expression of key genes controlling fatty acid metabolism were determined, and PPAR agonism was explored by using luciferase reporter assays. Our results showed that, compared to HFHFr, BemA-treated rats exhibited lower body weight, higher liver/body weight, and reduced hepatic steatosis. In addition to ACLY inhibition, we found three novel mechanisms that could account for the anti-steatotic effect: (1) reduction of liver ketohexokinase, leading to lower fructose intake and reduced de novo lipogenesis; (2) increased expression of patatin-like phospholipase domain-containing protein 3, a protein related to the export of liver triglycerides to blood; and (3) PPARα agonist activity, leading to increased hepatic fatty acid ß-oxidation. In conclusion, BemA may represent a novel approach to treat hepatic steatosis, and therefore to avoid progression to advanced stages of non-alcoholic fatty liver disease.

ChREBP-driven DNL and PNPLA3 Expression Induced by Liquid Fructose are Essential in the Production of Fatty Liver and Hypertriglyceridemia in a High-Fat Diet-Fed Rat Model.

SCOPE: The aim of this study is to delineate the contribution of dietary saturated fatty acids (FA) versus liquid fructose to fatty liver and hypertriglyceridemia. METHODS AND RESULTS: Three groups of female rats are maintained for 3 months in standard chow (CT); High-fat diet (46.9% of fat-derived calories, rich in palmitic and stearic FA, HFD); and HFD with 10% w/v fructose in drinking water (HFHFr). Zoometric parameters, plasma biochemistry, and liver Oil-Red O (ORO) staining, lipidomics, and expression of proteins involved in FA metabolism are analyzed. Both diets increase ingested calories without modifying body weight. Only the HFHFr diet increases liver triglycerides (x11.0), with hypertriglyceridemia (x1.7) and reduces FA ß-oxidation (x0.7), and increases liver FA markers of DNL (de novo lipogenesis). Whereas HFD livers show a high content of ceramides, HFHFr samples show unchanged ceramides, and an increase in diacylglycerols. Only the HFHFr diet leads to a marked increase in the expression of enzymes involved in DNL and triglyceride metabolism, such as carbohydrate response element binding protein ß (ChREBPß, x3.2), a transcription factor that regulates DNL, and patatin-like phospholipase domain-containing 3 (PNPLA3, x2.6), a lipase that mobilizes stored triglycerides for VLDL secretion. CONCLUSION: The addition of liquid-fructose to dietary FA is determinant in liver steatosis and hypertriglyceridemia production, through increased DNL and PNPLA3 expression, and reduced FA catabolism.

Bempedoic Acid Restores Liver H2S Production in a Female Sprague-Dawley Rat Dietary Model of Non-Alcoholic Fatty Liver.

We previously demonstrated that treatment with BemA (bempedoic acid), an inhibitor of ATP citrate lyase, significantly reduces fatty liver in a model of liver steatosis (HFHFr-female Sprague-Dawley rat fed a high-fat high-fructose diet). Since the hepatic production of the gasotransmitter H2S is impaired in liver disorders, we were interested in determining if the production of H2S was altered in our HFHFr model and whether the administration of BemA reversed these changes. We used stored liver samples from a previous study to determine the total and enzymatic H2S production, as well as the expression of CBS (cystathionine ß-synthase), CSE (cystathionine γ-lyase), and 3MST (3-mercaptopiruvate sulfurtransferase), and the expression/activity of FXR (farnesoid X receptor), a transcription factor involved in regulating CSE expression. Our data show that the HFHFr diet reduces the total and enzymatic production of liver H2S, mainly by decreasing the expression of CBS and CSE. Furthermore, BemA treatment restored H2S production, increasing the expression of CBS and CSE, providing evidence for the involvement of FXR transcriptional activity and the mTORC1 (mammalian target of rapamycin1)/S6K1 (ribosomal protein S6 kinase beta-1)/PGC1α (peroxisome proliferator receptor gamma coactivator1α) pathway.

Bempedoic acid as a PPARα activator: new perspectives for hepatic steatosis treatment in a female rat experimental model. / El ácido bempedoico como activador PPARα: Nuevas perspectivas para el tratamiento de la esteatosis hepática en un modelo experimental de rata hembra.

INTRODUCTION: In its initial stages, nonalcoholic fatty liver disease presents hypertriglyceridemia and accumulation of lipids in the liver (hepatic steatosis). Bempedoic acid is an ATP:citrate lyase inhibitor that promotes a dual inhibition of the synthesis of cholesterol and fatty acids. However, its effect in the prevention / treatment of hepatic steatosis and hypertriglyceridemia has not been investigated. The aim of our work has been to elucidate whether bempedoic acid, through a mechanism other than ATP:citrate lyase inhibition, reverses these metabolic alterations. EXPERIMENTAL DESIGN: The study was carried out in female Sprague-Dawley rats fed, for three months, with a high fat diet supplemented with fructose (10% w/v) in drinking water. During the last month, bempedoic acid (30mg/kg/day) was administered to a group of animals. Zoometric and plasmatic parameters were analyzed, gene and protein expression analysis were performed in liver samples and PPAR-PPRE binding activity was determined. RESULTS: Our interventional model developed hepatic steatosis and hypertriglyceridemia. Despite an increase in total caloric intake, there was no increase in body weight of the animals. The administration of bempedoic acid significantly reduced hepatic steatosis and promoted a marked hepatocyte hypertrophy. There was a 66% increase in the liver weight of the animals treated with the drug that was not accompanied by modifications in the markers of inflammation, oxidative stress, or endoplasmic reticulum stress. Bempedoic acid activated the peroxisome proliferator activated nuclear receptor (PPARα) and its target genes. CONCLUSIONS: Bempedoic acid could be an effective therapy for the treatment of fatty liver and associated cardiovascular risk. Bempedoic acid has other mechanisms of action besides the inhibition of ATP: citrate lyase, such as the activation of PPARα, which could explain the reduction in hepatic steatosis and the increase in liver weight observed in animals treated with the drug.

Chronic liquid fructose supplementation does not cause liver tumorigenesis but elicits clear sex differences in the metabolic response in Sprague-Dawley rats.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) has increased over the last decades and may evolve into hepatocellular carcinoma (HCC). As HCC is challenging to treat, knowledge on the modifiable risk factors for NAFLD/HCC (e.g. hyper caloric diets rich in fructose) is essential. OBJECTIVE AND DESIGN: We used a model of diethyl nitrosamine-induced hepatocarcinogenesis to investigate the liver cancer-promoting effects of a diet supplemented with 10% liquid fructose, administered to male and female rats for 11 months. A subset of the fructose-supplemented rats received resveratrol (RVT) in the last 4 months of treatment. RESULTS AND DISCUSSION: Rat livers showed no de visu or histological evidence of liver tumorigenesis. However, we observed metabolic abnormalities that could be related to cancer development mainly in the female fructose-supplemented rats, such as increases in weight, adiposity and hepatic triglyceride levels, as well as hyperglycaemia, hyperuricemia, hyperleptinemia and a reduced insulin sensitivity index, which were partially reversed by RVT. Therefore, we performed a targeted analysis of 84 cancer-related genes in the female liver samples, which revealed expression changes associated with cancer-related pathways. Analysis of individual genes indicated that some changes increased the risk of hepatocarcinogenesis (Sfrp2, Ccl5, Socs3, and Gstp1), while others exerted a protective/preventive effect (Bcl2 and Cdh1). CONCLUSION: Our data clearly demonstrate that chronic fructose supplementation, as the sole dietary intervention, does not cause HCC development in rats.

Simple sugar intake and cancer incidence, cancer mortality and all-cause mortality: A cohort study from the PREDIMED trial.

OBJECTIVE: To examine associations between intake of simple sugars and cancer incidence, cancer mortality, and total mortality in a prospective cohort study based on the PREDIMED trial conducted from 2003 to 2010. METHODS: Participants were older individuals at high cardiovascular risk. Exposures were total sugar, glucose and fructose from solid or liquid sources, and fructose from fruit and 100% fruit juice. Cancer incidence was the primary outcome; cancer mortality and all-cause mortality were secondary outcomes. Multivariable-adjusted, time-dependent Cox proportional hazard models were used. RESULTS: Of 7447 individuals enrolled, 7056 (94.7%) were included (57.6% women, aged 67.0 ± 6.2 years). 534 incident cancers with 152 cancer deaths and 409 all-cause deaths were recorded after a median follow-up of 6 years. Intake of simple sugars in solid form was unrelated to outcomes. Higher cancer incidence was found per 5 g/day increase in intake of liquid sugars, with multivariable-adjusted HR of 1.08 (95% CI, 1.03-1.13) for total liquid sugar, 1.19 (95% CI, 1.07-1.31) for liquid glucose, 1.14 (95% CI, 1.05-1.23) for liquid fructose, and 1.39 (95% CI, 1.10-1.74) for fructose from fruit juice. Cancer and all-cause mortality increased to a similar extent with intake of all sugars in liquid form. In categorical models, cancer risk was dose-related for all liquid sugars. CONCLUSIONS: Simple sugar intake in drinks and fruit juice was associated with an increased risk of overall cancer incidence and mortality and all-cause mortality. This suggests that sugary beverages are a modifiable risk factor for cancer and all-cause mortality.

Effects of a Low Dose of Caffeine Alone or as Part of a Green Coffee Extract, in a Rat Dietary Model of Lean Non-Alcoholic Fatty Liver Disease without Inflammation.

Non-alcoholic fatty liver disease is a highly prevalent condition without specific pharmacological treatment, characterized in the initial stages by hepatic steatosis. It was suggested that lipid infiltration in the liver might be reduced by caffeine through anti-inflammatory, antioxidative, and fatty acid metabolism-related mechanisms. We investigated the effects of caffeine (CAF) and green coffee extract (GCE) on hepatic lipids in lean female rats with steatosis. For three months, female Sprague-Dawley rats were fed a standard diet or a cocoa butter-based high-fat diet plus 10% liquid fructose. In the last month, the high-fat diet was supplemented or not with CAF or a GCE, providing 5 mg/kg of CAF. Plasma lipid levels and the hepatic expression of molecules involved in lipid metabolism were determined. Lipidomic analysis was performed in liver samples. The diet caused hepatic steatosis without obesity, inflammation, endoplasmic reticulum stress, or hepatic insulin resistance. Neither CAF nor GCE alleviated hepatic steatosis, but GCE-treated rats showed lower hepatic triglyceride levels compared to the CAF group. The GCE effects could be related to reductions of hepatic (i) mTOR phosphorylation, leading to higher nuclear lipin-1 levels and limiting lipogenic gene expression; (ii) diacylglycerol levels; (iii) hexosylceramide/ceramide ratios; and (iv) very-low-density lipoprotein receptor expression. In conclusion, a low dose of CAF did not reduce hepatic steatosis in lean female rats, but the same dose provided as a green coffee extract led to lower liver triglyceride levels.

Mesenteric arterial dysfunction in the UC Davis Type 2 Diabetes Mellitus rat model is dependent on pre-diabetic versus diabetic status and is sexually dimorphic.

Previous reports suggest that diabetes may differentially affect the vascular beds of females and males. However, there is insufficient evidence to establish the timeline of the vascular dysfunction in diabetes, specifically in relation to sex. Here, we determined whether mesenteric arterial function is altered in UC Davis Type-2 Diabetes Mellitus (UCD-T2DM) rats and if this occurs as early as the pre-diabetic stage of the disease. Specifically, we investigated whether vascular dysfunction differs between pre-diabetic or diabetic status and if this varies by sex. We measured the responses to endothelium-dependent and -independent vasorelaxant as well as vasoconstrictor agents and explored the potential mechanisms involved in sex-specific development of arterial dysfunction in UCD-T2DM rats. In addition, indices of insulin sensitivity were assessed. We report the reduced insulin sensitivity in pre-diabetic males and diabetic females. Vascular relaxation to acetylcholine was impaired to a greater extent in mesenteric artery from males in the pre-diabetic stage than in their female counterparts. In contrast, the arteries from females with diabetes exhibited a greater impairment to acetylcholine compared with diabetic males. Additionally, the sensitivity of mesenteric artery to contractile agents in females, but not in males, after the onset of diabetes was increased. Our data suggest that the reduced insulin sensitivity through AKT may predispose vessels to injury in the pre-diabetic stage in males. On the other hand, reduced insulin sensitivity as well as enhanced responsiveness to contractile agents may predispose arteries to injury in the diabetic stage in females.

mTOR is a Key Protein Involved in the Metabolic Effects of Simple Sugars.

One of the most important threats to global human health is the increasing incidences of metabolic pathologies (including obesity, type 2 diabetes and non-alcoholic fatty liver disease), which is paralleled by increasing consumptions of hypercaloric diets enriched in simple sugars. The challenge is to identify the metabolic pathways affected by the excessive consumption of these dietary components when they are consumed in excess, to unravel the molecular mechanisms leading to metabolic pathologies and identify novel therapeutic targets to manage them. Mechanistic (mammalian) target of rapamycin (mTOR) has emerged as one of the key molecular nodes that integrate extracellular signals, such as energy status and nutrient availability, to trigger cell responses that could lead to the above-mentioned diseases through the regulation of lipid and glucose metabolism. By activating mTOR signalling, excessive consumption of simple sugars (such as fructose and glucose), could modulate hepatic gluconeogenesis, lipogenesis and fatty acid uptake and catabolism and thus lipid deposition in the liver. In the present review we will discuss some of the most recent studies showing the central role of mTOR in the metabolic effects of excessive simple sugar consumption.

Chronic fructose intake does not induce liver steatosis and inflammation in female Sprague-Dawley rats, but causes hypertriglyceridemia related to decreased VLDL receptor expression.

PURPOSE: Sugar-sweetened beverage intake is a risk factor for insulin resistance, dyslipidemia, fatty liver, and steatohepatitis (NASH). Sub-chronic supplementation of liquid fructose, but not glucose, in female rats increases liver and plasma triglycerides without inflammation. We hypothesized that chronic supplementation of fructose would cause NASH and liver insulin resistance. METHODS: We supplemented female Sprague-Dawley rats with water or either fructose or glucose 10% w/v solutions under isocaloric conditions for 7 months. At the end, plasma analytes, insulin, and adiponectin were determined, as well as liver triglyceride content and the expression of key genes controlling inflammation, fatty acid synthesis and oxidation, endoplasmic reticulum stress, and plasma VLDL clearance, by biochemical and histological methods. RESULTS: Although sugar-supplemented rats increased their energy intake by 50-60%, we found no manifestation of liver steatosis, fibrosis or necrosis, unchanged plasma or tissue markers of inflammation or fibrosis, and reduced liver expression of gluconeogenic enzymes, despite both sugars increased fatty acid synthesis, mTORC1, and IRE1 activity, while decreasing fatty acid oxidation and PPARα activity. Only fructose-supplemented rats were hypertriglyceridemic, showing a reduced expression of VLDL receptor and lipoprotein lipase in skeletal muscle and vWAT. Glucose-supplemented rats showed increased adiponectinemia, which would explain the different metabolic outcomes of the two sugars. CONCLUSIONS: Chronic liquid simple sugar supplementation, as the sole risk factor, is not enough for female rats to develop NASH and increased liver gluconeogenesis. Nevertheless, under isocaloric conditions, only fructose induced hypertriglyceridemia, thus confirming that also the type of nutrient matters in the development of metabolic diseases.

Chronic Liquid Fructose, but not Glucose, Supplementation Selectively Induces Visceral Adipose Tissue Leptin Resistance and Hypertrophy in Female Sprague-Dawley Rats.

SCOPE: The effect of chronic supplementation with simple-sugar solutions on leptin signaling in liver, hypothalamus, and visceral white adipose tissue (vWAT) is studied, which is designed to mimic the temporal pattern of consumption by humans. METHODS AND RESULTS: Solutions of fructose or glucose are isocalorically supplemented (7 months) in female Sprague-Dawley rats consuming ad libitum rodent chow. After sacrifice, plasma and tissue samples (liver, hypothalamus, and vWAT) are collected. Zoometric parameters, plasma analytes, and the tissue expression and activity of markers of leptin signaling are determined by biochemical and molecular biological methods. The two sugars cause different types of adiposopathy. Both sugars induce increases in plasma nonesterified fatty acids, and leptin resistance in the liver and the hypothalamus. Only fructose-supplemented rats show hyperleptinemia, and increased body weight due to a hypertrophy of vWAT, with no signs of leptin-mediated lipolysis. Glucose-supplemented rats show no significant changes in these parameters but present elevated plasma adiponectin concentrations, lipolysis, and inflammatory markers in vWAT, indicating a shift to a nonexpandable adipose tissue phenotype. CONCLUSION: Chronic consumption of fructose places a greater burden on metabolic homeostasis than equivalent consumption of glucose, inducing hyperleptinemia, generalized leptin resistance, and increased body weight due to expanded, hypertrophic vWAT.

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

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

Impairment of Novel Object Recognition Memory and Brain Insulin Signaling in Fructose- but Not Glucose-Drinking Female Rats.

Excessive sugar intake has been related to cognitive alterations, but it remains unclear whether these effects are related exclusively to increased energy intake, and the molecular mechanisms involved are not fully understood. We supplemented Sprague-Dawley female rats with 10% w/v fructose in drinking water or with isocaloric glucose solution for 7 months. Cognitive function was assessed through the Morris water maze (MWM) and the novel object recognition (NOR) tests. Plasma parameters and protein/mRNA expression in the frontal cortex and hippocampus were determined. Results showed that only fructose-supplemented rats displayed postprandial and fasting hypertriglyceridemia (1.4 and 1.9-fold, p < 0.05) and a significant reduction in the discrimination index in the NOR test, whereas the results of the MWM test showed no differences between groups. Fructose-drinking rats displayed an abnormal glucose tolerance test and impaired insulin signaling in the frontal cortex, as revealed by significant reductions in insulin receptor substrate-2 protein levels (0.77-fold, p < 0.05) and Akt phosphorylation (0.72-fold, p < 0.05), and increased insulin-degrading enzyme levels (1.86-fold, p < 0.001). Fructose supplementation reduced the expression of antioxidant enzymes and altered the amount of proteins involved in mitochondrial fusion/fission in the frontal cortex. In conclusion, cognitive deficits induced by chronic liquid fructose consumption are not exclusively related to increased caloric intake and are correlated with hypertriglyceridemia, impaired insulin signaling, increased oxidative stress and altered mitochondrial dynamics, especially in the frontal cortex.

The Addition of Liquid Fructose to a Western-Type Diet in LDL-R-/- Mice Induces Liver Inflammation and Fibrogenesis Markers without Disrupting Insulin Receptor Signalling after an Insulin Challenge.

A high consumption of fat and simple sugars, especially fructose, has been related to the development of insulin resistance, but the mechanisms involved in the effects of these nutrients are not fully understood. This study investigates the effects of a Western-type diet and liquid fructose supplementation, alone and combined, on insulin signalling and inflammation in low-density lipoprotein (LDL) receptor-deficient mice (LDL-R-/-). LDL-R-/- mice were fed chow or Western diet ±15% fructose solution for 12 weeks. Plasma glucose and insulin, and the expression of genes related to inflammation in the liver and visceral white adipose tissue (vWAT), were analysed. V-akt murine thymoma viral oncogene homolog-2 (Akt) activation was measured in the liver of the mice after a single injection of saline or insulin. None of the dietary interventions caused inflammation in vWAT, whereas the Western diet induced hepatic inflammation, which was further enhanced by liquid fructose, leading also to a significant increase in fibrogenesis markers. However, there was no change in plasma glucose or insulin, or insulin-induced Akt phosphorylation. In conclusion, hepatic inflammation and fibrogenesis markers induced by a Western diet supplemented with liquid fructose in LDL-R-/- mice are not associated with a significant impairment of hepatic insulin signalling.

Type of supplemented simple sugar, not merely calorie intake, determines adverse effects on metabolism and aortic function in female rats.

High consumption of simple sugars causes adverse cardiometabolic effects. We investigated the mechanisms underlying the metabolic and vascular effects of glucose or fructose intake and determined whether these effects are exclusively related to increased calorie consumption. Female Sprague-Dawley rats were supplemented with 20% wt/vol glucose or fructose for 2 mo, and plasma analytes and aortic response to vasodilator and vasoconstrictor agents were determined. Expression of molecules associated with lipid metabolism, insulin signaling, and vascular response were evaluated in hepatic and/or aortic tissues. Caloric intake was increased in both sugar-supplemented groups vs. control and in glucose- vs. fructose-supplemented rats. Hepatic lipogenesis was induced in both groups. Plasma triglycerides were increased only in the fructose group, together with decreased expression of carnitine palmitoyltransferase-1A and increased microsomal triglyceride transfer protein expression in the liver. Plasma adiponectin and peroxisome proliferator-activated receptor (PPAR)-α expression was increased only by glucose supplementation. Insulin signaling in liver and aorta was impaired in both sugar-supplemented groups, but the effect was more pronounced in the fructose group. Fructose supplementation attenuated aortic relaxation response to a nitric oxide (NO) donor, whereas glucose potentiated it. Phenylephrine-induced maximal contractions were reduced in the glucose group, which could be related to increased endothelial NO synthase (eNOS) phosphorylation and subsequent elevated basal NO in the glucose group. In conclusion, despite higher caloric intake in glucose-supplemented rats, fructose caused worse metabolic and vascular responses. This may be because of the elevated adiponectin level and the subsequent enhancement of PPARα and eNOS phosphorylation in glucose-supplemented rats. NEW & NOTEWORTHY: This is the first study comparing the effects of glucose and fructose consumption on metabolic factors and aortic function in female rats. Our results show that, although total caloric consumption was higher in glucose-supplemented rats, fructose ingestion had a greater impact in inducing metabolic and aortic dysfunction.

Liquid fructose in Western-diet-fed mice impairs liver insulin signaling and causes cholesterol and triglyceride loading without changing calorie intake and body weight.

BACKGROUND/OBJECTIVES: Liquid fructose associates with prevalence of type 2 diabetes mellitus and obesity. Intervention studies suggest that metabolically unfit individuals are more responsive than healthy individuals to liquid fructose. We determined whether mice consuming an obesogenic Western diet were more responsive than chow-fed mice to the alterations induced by liquid fructose supplementation (LFS). METHODS: C57BL/6N mice were fed chow or Western diet±ad libitum 15% fructose solution for 12 weeks. Food and liquid intake and body weight were monitored. Plasma analytes and liver lipids, histology and the expression of genes related to lipid handling, endoplasmic reticulum stress, inflammation and insulin signaling were analyzed. RESULTS: Western diet increased energy intake, visceral adipose tissue (vWAT), body weight, plasma and liver triglycerides and cholesterol, and inflammatory markers in vWAT vs. chow-fed mice. LFS did not change energy intake, vWAT or body weight. LFS significantly increased plasma and liver triglycerides and cholesterol levels only in Western-diet-fed mice. These changes associated with a potentiation of the increased liver expression of PPARγ and CD36 that was observed in Western-fed mice and related to the increased liver mTOR phosphorylation induced by LFS. Furthermore, LFS in Western-diet-fed mice induced the largest reduction in liver IRS2 protein and a significant decrease in whole-body insulin sensitivity. CONCLUSIONS: LFS in mice, in a background of an unhealthy diet that already induces fatty liver visceral fat accretion and obesity, increases liver lipid burden, hinders hepatic insulin signaling and diminishes whole-body insulin sensitivity without changing energy intake.

Fructose, but not glucose, impairs insulin signaling in the three major insulin-sensitive tissues.

Human studies support the relationship between high intake of fructose-sweetened beverages and type 2 diabetes, but there is a debate on whether this effect is fructose-specific or it is merely associated to an excessive caloric intake. Here we investigate the effects of 2 months' supplementation to female rats of equicaloric 10% w/v fructose or glucose solutions on insulin sensitivity in target tissues. Fructose supplementation caused hepatic deposition of triglycerides and changed the fatty acid profile of this fraction, with an increase in monounsaturated and a decrease in polyunsaturated species, but did not cause inflammation and oxidative stress. Fructose but not glucose-supplemented rats displayed an abnormal glucose tolerance test, and did not show increased phosphorylation of V-akt murine thymoma viral oncogene homolog-2 (Akt) in white adipose tissue and liver after insulin administration. In skeletal muscle, phosphorylation of Akt and of Akt substrate of 160 kDA (AS160) was not impaired but the expression of the glucose transporter type 4 (GLUT4) in the plasma membrane was reduced only in fructose-fed rats. In conclusion, fructose but not glucose supplementation causes fatty liver without inflammation and oxidative stress and impairs insulin signaling in the three major insulin-responsive tissues independently from the increase in energy intake.

Hypercholesterolemia and neurodegeneration. Comparison of hippocampal phenotypes in LDLr knockout and APPswe/PS1dE9 mice.

Previous studies suggest that Alzheimer's disease (AD) neurobiology could not be explained solely by an increase in ß-amyloid levels. Recently, it has been proposed that alterations in brain cholesterol metabolism may contribute to the pathogenesis of AD. In the present work, we focus on early changes in the hippocampal phenotypes of two mouse models in which cognitive impairments were previously described: a) the hypercholesterolemic LDL receptor knockout (LDLr -/-) and b) the APPswe/PS1dE9 (APP/PS1) transgenic model of familial AD. Our initial analysis, subsequent validation and additional experiments at the mRNA and protein levels demonstrate some parallels between the hippocampal phenotypes of these 2 mouse models, however our data suggest that the molecular mechanisms leading to cognitive decline are distinct in LDLr -/- and APP/PS1 animals. Genes related to cytokine signaling were significantly down-regulated in LDLr -/- mice when compared to both the wild-type and APP/PS1 mice, and these include prostaglandin-endoperoxide synthases 1 and 2 (ptgs1 and 2) and nerve grow factor (ngf). We have also detected reduced expression of genes related to lipid metabolism in LDLr -/- mice: peroxisome proliferator activated receptor gamma (pparg), pro-opiomelanocortin-alpha (pomc) and of protein kinase, AMP-activated, alpha 1 catalytic subunit of AMPK (prkaa1). Our array data also indicate that transcriptional activity of early genes involved in memory process, such as FBJ osteosarcoma oncogene (Fos) and the activity regulated cytoskeletal-associated protein (Arc) gene, are increased in the hippocampus of LDLr -/- mice. Several proteins like insulin degrading enzyme (IDE), PGC-1α, OXPHOS 1, NMDAR1 and cyclic AMP response element binding protein (CREB) are up-regulated in the LDLr -/- mice, while in the APP/PS1 mouse model only OXPHOS complexes 2, 3 and 5 are slightly downregulated. Further studies are necessary to understand the molecular pathways involved in memory loss in hypercholesterolemic LDLr -/- mice.