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.

Frecuencia de aparición y validez predictiva de la disfunción olfatoria y del gusto en pacientes con infección por SARS-CoV-2 / Frequency and predictive validity of olfactory and taste dysfunction in patients with SARS-CoV-2 infection

Antecedentes y objetivo: La disfunción olfatoria (DO) y gustativa (DG) han demostrado ser síntomas de la infección por SARS-CoV-2. Sin embargo, su presencia en determinadas poblaciones, sobre todo en aquellas con cuadros clínicos leves, aún debe aclararse. El objetivo fue estimar la frecuencia de DO y DG, y su validez predictiva en pacientes detectados en Atención Primaria.Pacientes y métodosSe realizó un estudio transversal en el Sistema Nacional de Salud español. Se administró una encuesta epidemiológica dirigida a pacientes a los que se les solicitó la prueba PCR para SARS-CoV-2. Se estimaron las odds ratio (OR) para medir la magnitud de la asociación entre la DO y DG y la existencia de infección por SARS-CoV-2. Se calculó la sensibilidad, la especificidad y los valores predictivos positivos (VPP) y negativos (VPN) de estos síntomas en la infección por SARS-CoV-2.ResultadosSe captaron 1.038 pacientes, de los cuales el 20,1% presentaban infección por SARS-CoV-2. Las DO y DG estuvieron presentes en el 64,4% (IC 95% 56,0-72,1) y el 56,2% (IC 95% 47,9-64,2) de los sujetos con infección, respectivamente. La OR para la DO fue de 12,2 (IC 95% 8,26-18,06) y para la DG de 7,95 (IC 95% 5,48-11.53). La DG presentó una sensibilidad del 41,1% (IC 95% 34,4-46,1), una especificidad del 91,9% (IC 95% 89,8-93,7), un VPP del 56,2% (IC 95% 48,0-64,2) y un VPN de 86,1% (IC 95% 83,6-88,3), mientras que la DO mostró una sensibilidad del 45,0% (IC 95% 37,6-51,5), una especificidad del 93,7% (IC 95% 91,8-95,0), un VPP del 64,4% (IC 95% 56,0-72,1) y un VPN del 87,1% (IC 95% 84,7-89,2).ConclusionesMás de la mitad de los sujetos con infección por SARS-CoV-2 presentan DO o DG. La presencia de DO o de DG podría ser de utilidad diagnostica por su capacidad para predecir la infección en más de la mitad de las ocasiones. (AU)

Background and objective: Olfactory and taste dysfunction (OD, TD) have been considered symptoms of SARS-CoV-2 infection. However, its presence in certain populations, especially those with mild clinical symptoms, has not been clarified. The objective was to estimate the frequency of OD and TD, and its predictive validity in patients detected in Primary Care.Patients and methodsA cross-sectional study was carried out in the Spanish National Health System. An epidemiological survey was administered to patients who were requested the PCR test for SARS-CoV-2. Odds ratio (OR) were estimated to measure the magnitude of the association between OD and TD and the existence of SARS-CoV-2 infection. The sensitivity, specificity, and positive and negative predictive values (PPV, NPV) of these symptoms in SARS-CoV-2 infection were calculated.ResultsOf 1,038 patients screened, 20.1% had SARS-CoV-2 infection. OD and DG were present in 64.4% (95% CI 56.0-72.1) and 56.2% (95% CI 47.9-64.2) of the subjects with infection, respectively. The OR for OD was 12.2 (95% CI 8.26-18.06) and for TD was 7.95 (95% CI 5.48-11.53). TD presented a sensitivity of 41.1% (95% CI 34.4-46.1), a specificity of 91.9% (95% CI 89.8-93.7), a PPV of 56.2% (95% CI48.0-64.2) and a NPV of 86.1% (95% CI 83.6-88.3), while the OD showed a sensitivity of 45.0% (95% CI 37.6-51.5), a specificity of 93.7% (95% CI 91.8-95.0), a PPV of 64.4% (95% CI 56.0-72.1) and a NPV of 87.1% (95% CI 84.7-89.2).ConclusionsMore than half of the subjects with SARS-CoV-2 infection have OD or TD. The presence of OD or TD could be of diagnostic utility due to its ability to predict infection in more than half of the cases. (AU)

Frequency and predictive validity of olfactory and taste dysfunction in patients with SARS-CoV-2 infection.

BACKGROUND AND OBJECTIVE: Olfactory and taste dysfunction (OD, TD) have been considered symptoms of SARS-CoV-2 infection. However, its presence in certain populations, especially those with mild clinical symptoms, has not been clarified. The objective was to estimate the frequency of OD and TD, and its predictive validity in patients detected in Primary Care. PATIENTS AND METHODS: A cross-sectional study was carried out in the Spanish National Health System. An epidemiological survey was administered to patients who were requested the PCR test for SARS-CoV-2. Odds ratio (OR) were estimated to measure the magnitude of the association between OD and TD and the existence of SARS-CoV-2 infection. The sensitivity, specificity, and positive and negative predictive values (PPV, NPV) of these symptoms in SARS-CoV-2 infection were calculated. RESULTS: Of 1038 patients screened, 20.1% had SARS-CoV-2 infection. OD and DG were present in 64.4% (95% CI 56.0-72.1) and 56.2% (95% CI 47.9-64.2) of the subjects with infection, respectively. The OR for OD was 12.2 (95% CI 8.26-18.06) and for TD was 7.95 (95% CI 5.48-11.53). TD presented a sensitivity of 41.1% (95% CI 34.4-46.1), a specificity of 91.9% (95% CI 89.8-93.7), a PPV of 56.2% (95% CI48.0-64.2) and a NPV of 86.1% (95% CI 83.6-88.3), while the OD showed a sensitivity of 45.0% (95% CI 37.6-51.5), a specificity of 93.7% (95% CI 91.8-95.0), a PPV of 64.4% (95% CI 56.0-72.1) and a NPV of 87.1% (95% CI 84.7-89.2). CONCLUSIONS: More than half of the subjects with SARS-CoV-2 infection have OD or TD. The presence of OD or TD could be of diagnostic utility due to its ability to predict infection in more than half of the cases.

ANTECEDENTES Y OBJETIVO: La disfunción olfatoria (DO) y gustativa (DG) han demostrado ser síntomas de la infección por SARS-CoV-2. Sin embargo, su presencia en determinadas poblaciones, sobre todo en aquellas con cuadros clínicos leves, aún debe aclararse. El objetivo fue estimar la frecuencia de DO y DG, y su validez predictiva en pacientes detectados en Atención Primaria. PACIENTES Y MÉTODOS: Se realizó un estudio transversal en el Sistema Nacional de Salud español. Se administró una encuesta epidemiológica dirigida a pacientes a los que se les solicitó la prueba PCR para SARS-CoV-2. Se estimaron las odds ratio (OR) para medir la magnitud de la asociación entre la DO y DG y la existencia de infección por SARS-CoV-2. Se calculó la sensibilidad, la especificidad y los valores predictivos positivos (VPP) y negativos (VPN) de estos síntomas en la infección por SARS-CoV-2. RESULTADOS: Se captaron 1.038 pacientes, de los cuales el 20,1% presentaban infección por SARS-CoV-2. Las DO y DG estuvieron presentes en el 64,4% (IC 95% 56,0­72,1) y el 56,2% (IC 95% 47,9­64,2) de los sujetos con infección, respectivamente. La OR para la DO fue de 12,2 (IC 95% 8,26−18,06) y para la DG de 7,95 (IC 95% 5,48−11.53). La DG presentó una sensibilidad del 41,1% (IC 95% 34,4­46,1), una especificidad del 91,9% (IC 95% 89,8­93,7), un VPP del 56,2% (IC 95% 48,0­64,2) y un VPN de 86,1% (IC 95% 83,6­88,3), mientras que la DO mostró una sensibilidad del 45,0% (IC 95% 37,6­51,5), una especificidad del 93,7% (IC 95% 91,8­95,0), un VPP del 64,4% (IC 95% 56,0­72,1) y un VPN del 87,1% (IC 95% 84,7­89,2). CONCLUSIONES: Más de la mitad de los sujetos con infección por SARS-CoV-2 presentan DO o DG. La presencia de DO o de DG podría ser de utilidad diagnostica por su capacidad para predecir la infección en más de la mitad de las ocasiones.

[Frequency and predictive validity of olfactory and taste dysfunction in patients with SARS-CoV-2 infection]. / Frecuencia de aparición y validez predictiva de la disfunción olfatoria y del gusto en pacientes con infección por SARS-CoV-2.

BACKGROUND AND OBJECTIVE: Olfactory and taste dysfunction (OD, TD) have been considered symptoms of SARS-CoV-2 infection. However, its presence in certain populations, especially those with mild clinical symptoms, has not been clarified. The objective was to estimate the frequency of OD and TD, and its predictive validity in patients detected in Primary Care. PATIENTS AND METHODS: A cross-sectional study was carried out in the Spanish National Health System. An epidemiological survey was administered to patients who were requested the PCR test for SARS-CoV-2. Odds ratio (OR) were estimated to measure the magnitude of the association between OD and TD and the existence of SARS-CoV-2 infection. The sensitivity, specificity, and positive and negative predictive values (PPV, NPV) of these symptoms in SARS-CoV-2 infection were calculated. RESULTS: Of 1,038 patients screened, 20.1% had SARS-CoV-2 infection. OD and DG were present in 64.4% (95% CI 56.0-72.1) and 56.2% (95% CI 47.9-64.2) of the subjects with infection, respectively. The OR for OD was 12.2 (95% CI 8.26-18.06) and for TD was 7.95 (95% CI 5.48-11.53). TD presented a sensitivity of 41.1% (95% CI 34.4-46.1), a specificity of 91.9% (95% CI 89.8-93.7), a PPV of 56.2% (95% CI48.0-64.2) and a NPV of 86.1% (95% CI 83.6-88.3), while the OD showed a sensitivity of 45.0% (95% CI 37.6-51.5), a specificity of 93.7% (95% CI 91.8-95.0), a PPV of 64.4% (95% CI 56.0-72.1) and a NPV of 87.1% (95% CI 84.7-89.2). CONCLUSIONS: More than half of the subjects with SARS-CoV-2 infection have OD or TD. The presence of OD or TD could be of diagnostic utility due to its ability to predict infection in more than half of the cases.

Sensing of nutrients by CPT1C regulates late endosome/lysosome anterograde transport and axon growth.

Anterograde transport of late endosomes or lysosomes (LE/Lys) is crucial for proper axon growth. However, the role of energetic nutrients has been poorly explored. Malonyl-CoA is a precursor of fatty acids, and its intracellular levels highly fluctuate depending on glucose availability or the energy sensor AMP-activated protein kinase (AMPK). We demonstrate in HeLa cells that carnitine palmitoyltransferase 1C (CPT1C) senses malonyl-CoA and enhances LE/Lys anterograde transport by interacting with the endoplasmic reticulum protein protrudin and facilitating the transfer of Kinesin-1 from protrudin to LE/Lys. In cultured mouse cortical neurons, glucose deprivation, pharmacological activation of AMPK or inhibition of malonyl-CoA synthesis decreases LE/Lys abundance at the axon terminal, and shortens axon length in a CPT1C-dependent manner. These results identify CPT1C as a new regulator of anterograde LE/Lys transport in response to malonyl-CoA changes, and give insight into how axon growth is controlled by nutrients.

Hypothalamic endocannabinoids inversely correlate with the development of diet-induced obesity in male and female mice.

The endocannabinoid (eCB) system regulates energy homeostasis and is linked to obesity development. However, the exact dynamic and regulation of eCBs in the hypothalamus during obesity progression remain incompletely described and understood. Our study examined the time course of responses in two hypothalamic eCBs, 2-arachidonoylglycerol (2-AG) and arachidonoylethanolamine (AEA), in male and female mice during diet-induced obesity and explored the association of eCB levels with changes in brown adipose tissue (BAT) thermogenesis and body weight. We fed mice a high-fat diet (HFD), which induced a transient increase (substantial at 7 days) in hypothalamic eCBs, followed by a progressive decrease to basal levels with a long-term HFD. This transient rise at early stages of obesity is considered a physiologic compensatory response to BAT thermogenesis, which is activated by diet surplus. The eCB dynamic was sexually dimorphic: hypothalamic eCBs levels were higher in female mice, who became obese at later time points than males. The hypothalamic eCBs time course positively correlated with thermogenesis activation, but negatively matched body weight, leptinemia, and circulating eCB levels. Increased expression of eCB-synthetizing enzymes accompanied the transient hypothalamic eCB elevation. Icv injection of eCB did not promote BAT thermogenesis; however, administration of thermogenic molecules, such as central leptin or a peripheral ß3-adrenoreceptor agonist, induced a significant increase in hypothalamic eCBs, suggesting a directional link from BAT thermogenesis to hypothalamic eCBs. This study contributes to the understanding of hypothalamic regulation of obesity.

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.

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.

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.

IFN gamma regulates proliferation and neuronal differentiation by STAT1 in adult SVZ niche.

The adult subventricular zone (SVZ) is the main neurogenic niche in normal adult brains of mice and rats. Interferon gamma (IFNγ) has somewhat controversially been associated with SVZ progenitor proliferation and neurogenesis. The in vivo involvement of IFNγ in the physiology of the adult SVZ niche is not fully understood and its intracellular mediators are unknown. Here we show that IFNγ, through activation of its canonical signal transducer and activator of transcription 1 (STAT1) pathway, acts specifically on Nestin+ progenitors by decreasing both progenitor proliferation and the number of cycling cells. In addition, IFNγ increases the number of neuroblasts generated without shifting glial fate determination. The final result is deficient recruitment of newborn neurons to the olfactory bulb (OB), indicating that IFNγ-induced stimulation of neuronal differentiation does not compensate for its antiproliferative effect. We conclude that IFNγ signaling via STAT1 in the SVZ acts dually as an antiproliferative and proneurogenic factor, and thereby regulates neurogenesis in normal adult brains.

Fructose supplementation impairs rat liver autophagy through mTORC activation without inducing endoplasmic reticulum stress.

Supplementation with 10% liquid fructose to female rats for 2weeks caused hepatic steatosis through increased lipogenesis and reduced peroxisome proliferator activated receptor (PPAR) α activity and fatty acid catabolism, together with increased expression of the spliced form of X-binding protein-1 (Rebollo et al., 2014). In the present study, we show that some of these effects are preserved after sub-chronic (8weeks) fructose supplementation, specifically increased hepatic expression of lipid synthesis-related genes (stearoyl-CoA desaturase, ×6.7-fold; acetyl-CoA carboxylase, ×1.6-fold; glycerol-3-phosphate acyltransferase, ×1.65-fold), and reduced fatty acid ß-oxidation (×0.77-fold), resulting in increased liver triglyceride content (×1.69-fold) and hepatic steatosis. However, hepatic expression of PPARα and its target genes was not modified and, further, livers of 8-week fructose-supplemented rats showed no sign of unfolded protein response activation, except for an increase in p-IRE1 levels. Hepatic mTOR phosphorylation was enhanced (×1.74-fold), causing an increase in the phosphorylation of UNC-51-like kinase 1 (ULK-1) (×2.8-fold), leading to a decrease in the ratio of LC3B-II/LC3B-I protein expression (×0.39-fold) and an increase in the amount of the autophagic substrate p62, indicative of decreased autophagy activity. A harmful cycle may be established in the liver of 8-week fructose-supplemented rats where lipid accumulation may cause defective autophagy, and reduced autophagy may result in decreased free fatty acid formation from triglyceride depots, thus reducing the substrates for ß-oxidation and further increasing hepatic steatosis. In summary, the length of supplementation is a key factor in the metabolic disturbances induced by fructose: in short-term studies, PPARα inhibition and ER stress induction are critical events, whereas after sub-chronic supplementation, mTOR activation and autophagy inhibition are crucial.

Liquid fructose downregulates Sirt1 expression and activity and impairs the oxidation of fatty acids in rat and human liver cells.

Fructose ingestion is associated with the production of hepatic steatosis and hypertriglyceridemia. For fructose to attain these effects in rats, simultaneous induction of fatty acid synthesis and inhibition of fatty acid oxidation is required. We aimed to determine the mechanism involved in the inhibition of fatty acid oxidation by fructose and whether this effect occurs also in human liver cells. Female rats were supplemented or not with liquid fructose (10% w/v) for 7 or 14 days; rat (FaO) and human (HepG2) hepatoma cells, and human hepatocytes were incubated with fructose 25mM for 24h. The expression and activity of the enzymes and transcription factors relating to fatty acid ß-oxidation were evaluated. Fructose inhibited the activity of fatty acid ß-oxidation only in livers of 14-day fructose-supplemented rats, as well as the expression and activity of peroxisome proliferator activated receptor α (PPARα). Similar results were observed in FaO and HepG2 cells and human hepatocytes. PPARα downregulation was not due to an osmotic effect or to an increase in protein-phosphatase 2A activity caused by fructose. Rather, it was related to increased content in liver of inactive and acetylated peroxisome proliferator activated receptor gamma coactivator 1α, due to a reduction in sirtuin 1 expression and activity. In conclusion, fructose inhibits liver fatty acid oxidation by reducing PPARα expression and activity, both in rat and human liver cells, by a mechanism involving sirtuin 1 down-regulation.

Liquid fructose down-regulates liver insulin receptor substrate 2 and gluconeogenic enzymes by modifying nutrient sensing factors in rats.

High consumption of fructose-sweetened beverages has been linked to a high prevalence of chronic metabolic diseases. We have previously shown that a short course of fructose supplementation as a liquid solution induces glucose intolerance in female rats. In the present work, we characterized the fructose-driven changes in the liver and the molecular pathways involved. To this end, female rats were supplemented or not with liquid fructose (10%, w/v) for 7 or 14 days. Glucose and pyruvate tolerance tests were performed, and the expression of genes related to insulin signaling, gluconeogenesis and nutrient sensing pathways was evaluated. Fructose-supplemented rats showed increased plasma glucose excursions in glucose and pyruvate tolerance tests and reduced hepatic expression of several genes related to insulin signaling, including insulin receptor substrate 2 (IRS-2). However, the expression of key gluconeogenic enzymes, glucose-6-phosphatase and phosphoenolpyruvate carboxykinase, was reduced. These effects were caused by an inactivation of hepatic forkhead box O1 (FoxO1) due to an increase in its acetylation state driven by a reduced expression and activity of sirtuin 1 (SIRT1). Further contributing to FoxO1 inactivation, fructose consumption elevated liver expression of the spliced form of X-box-binding-protein-1 as a consequence of an increase in the activity of the mammalian target of rapamycin 1 and protein 38-mitogen activated protein kinase (p38-MAPK). Liquid fructose affects both insulin signaling (IRS-2 and FoxO1) and nutrient sensing pathways (p38-MAPK, mTOR and SIRT1), thus disrupting hepatic insulin signaling without increasing the expression of key gluconeogenic enzymes.

Metabolic alterations and increased liver mTOR expression precede the development of autoimmune disease in a murine model of lupus erythematosus.

Although metabolic syndrome (MS) and systemic lupus erythematosus (SLE) are often associated, a common link has not been identified. Using the BWF1 mouse, which develops MS and SLE, we sought a molecular connection to explain the prevalence of these two diseases in the same individuals. We determined SLE- markers (plasma anti-ds-DNA antibodies, splenic regulatory T cells (Tregs) and cytokines, proteinuria and renal histology) and MS-markers (plasma glucose, non-esterified fatty acids, triglycerides, insulin and leptin, liver triglycerides, visceral adipose tissue, liver and adipose tissue expression of 86 insulin signaling-related genes) in 8-, 16-, 24-, and 36-week old BWF1 and control New-Zealand-White female mice. Up to week 16, BWF1 mice showed MS-markers (hyperleptinemia, hyperinsulinemia, fatty liver and visceral adipose tissue) that disappeared at week 36, when plasma anti-dsDNA antibodies, lupus nephritis and a pro-autoimmune cytokine profile were detected. BWF1 mice had hyperleptinemia and high splenic Tregs till week 16, thereby pointing to leptin resistance, as confirmed by the lack of increased liver P-Tyr-STAT-3. Hyperinsulinemia was associated with a down-regulation of insulin related-genes only in adipose tissue, whereas expression of liver mammalian target of rapamicyn (mTOR) was increased. Although leptin resistance presented early in BWF1 mice can slow-down the progression of autoimmunity, our results suggest that sustained insulin stimulation of organs, such as liver and probably kidneys, facilitates the over-expression and activity of mTOR and the development of SLE.

Hepatic biomarkers of xenobiotic metabolism in eighteen marine fish from NW Mediterranean shelf and slope waters in relation to some of their biological and ecological variables.

A suite of hepatic biomarkers currently used in pollution monitoring were measured in eighteen common fish species, comprising five orders, eleven families of teleosts and two elasmobranchs. The sampling was carried out seasonally in front of the Barcelona coast (NW Mediterranean) during 2007. The hepatic enzymes considered were the activities of catalase, glutathione reductase, ethoxyresorufin O-deethylase, carboxylesterase and glutathione S-transferase. As markers at higher levels of biological organization, feeding preferences (on benthic, suprabenthic or zooplanktonic species), swimming capability, stomach fullness and trophic level were considered. Significant species differences were found among all the biochemical parameters analysed, although no relationships among the biomarkers themselves were evidenced. In general enzymatic activities were much higher in teleosts than in elasmobranchs, and in perciforms than in gadiforms. Seasonality was observed in some species with higher activities usually corresponding to the winter period. No site related differences were observed in the two selected sites, which differ over a small pollution gradient. A multivariate canonical Correspondence analysis (CCA) was performed on shelf and slope species separately to relate biochemical markers with ecological variables. CCA revealed that for shelf species, EROD was positively related to benthos feeding as well as trophic level, while on the slope the clearest association was between suprabenthos feeders and trophic level. Our present results, including seasonality, slightly differ from former observations (Solé et al., 2009a) and reveal a more significant role of the ecological variables in controlling biomarkers expression in fish from the shelf.

Muscular cholinesterase activities and lipid peroxidation levels as biomarkers in several Mediterranean marine fish species and their relationship with ecological variables.

Muscular cholinesterase activities, as potential markers of neurotoxic exposure, and lipid peroxidation levels, indicative of oxidative stress damage, both currently used in early-warning pollution monitoring, were characterised in eighteen fish species of ecologic and/or economic importance. These species comprise five orders and eleven families of teleosts and two species of elasmobranchs, feed using different strategies (benthic, epibenthic, endobenthic and pelagic), belong to different trophic levels and express different swimming behaviour. Their habitat ranges from 50 to 60 m (shallow or continental shelf) and 600 to 850 m (middle continental slope). Sampling took place in front of the Barcelona coast (NW Mediterranean) during four seasonal cruises in 2007. In the summer sampling, another site potentially exposed to a different pollution load (Vilanova) was included for comparison. Species, seasonal and site differences were tested and discussed in relation to chemical analysis of the local sediment, systematic position, habitat depth, feeding strategy, trophic level and swimming activity. Greater inter species differences rather than seasonal or site trends were seen in accordance to little pollution fluctuations. Higher cholinesterase activities were recorded in suprabenthos feeders, regardless of depth habitat, whereas LP levels were similar in all species except for the shark Scyliorhinus canicula in which they were consistently elevated. This study confirms and broadens former observations carried out with a more reduced number of fish species (Solé et al., 2008a).