Sabine Wagnerberger

Toll‐like receptor 4 is involved in the development of fructose‐induced hepatic steatosis in mice

A link between dietary fructose intake, gut‐derived endotoxemia, and nonalcoholic fatty liver disease (NAFLD) has been suggested by the results of human and animal studies. To further investigate the role of gut‐derived endotoxin in the onset of fructose‐induced NAFLD, Toll‐like receptor (TLR‐) 4‐mutant (C3H/HeJ) mice and wildtype (C3H/HouJ) mice were either fed plain water or water enriched with 30% fructose for 8 weeks. Hepatic steatosis, plasma alanine aminotransferase (ALT), and markers of insulin resistance as well as portal endotoxin levels were determined. Hepatic levels of myeloid differentiation factor 88 (MyD88), interferon regulatory factor (IRF) 3 and 7, and tumor necrosis factor alpha (TNFα) as well as markers of lipid peroxidation were assessed. Chronic intake of 30% fructose solution caused a significant increase in hepatic steatosis and plasma ALT levels in wildtype animals in comparison to water controls. In fructose‐fed TLR‐4 mutant mice, hepatic triglyceride accumulation was significantly reduced by ≈40% in comparison to fructose‐fed wildtype mice and plasma ALT levels were at the level of water‐fed controls. No difference in portal endotoxin concentration between fructose‐fed wildtype and TLR‐4‐mutant animals was detected. In contrast, hepatic lipid peroxidation, MyD88, and TNFα levels were significantly decreased in fructose‐fed TLR‐4‐mutant mice in comparison to fructose‐fed wildtype mice, whereas IRF3 and IRF7 expression remained unchanged. Markers of insulin resistance (e.g., plasma TNFα, retinol binding protein 4, and hepatic phospho‐AKT) were only altered in fructose‐fed wildtype animals. Conclusion: Taken together, these data further support the hypothesis that in mice the onset of fructose‐induced NAFLD is associated with intestinal bacterial overgrowth and increased intestinal permeability, subsequently leading to an endotoxin‐dependent activation of hepatic Kupffer cells. (HEPATOLOGY 2009.)

Nutrition, Intestinal Permeability, and Blood Ethanol Levels Are Altered in Patients with Nonalcoholic Fatty Liver Disease (NAFLD)

BackgroundA role of an altered dietary pattern (e.g., a diet rich in sugar) but also alterations at the level of the intestinal barrier have repeatedly been discussed to be involved in the development and progression of nonalcoholic fatty liver disease (NAFLD).AimsTo determine if the nutritional intake, intestinal flora, and permeability and the development of NAFLD are related in humans.MethodsTen controls and 20 patients with NAFLD ranging from simple steatosis to steatohepatitis were included in the study. Bacterial overgrowth, orocecal transit time, and intestinal permeability were assessed. Alcohol, endotoxin, and plasminogen activator inhibitor (PAI-) 1 concentration were determined in plasma. Nutritional intake was assessed using a dietary history.ResultsDespite no differences in the prevalence of bacterial overgrowth and in the orocecal transit time, intestinal permeability, alcohol, and endotoxin levels in plasma were significantly higher in patients with NAFLD than in controls. Similar results were also found for PAI-1 plasma concentrations. Patients with NAFLD had a significantly higher intake of protein, total carbohydrates, and mono- as well as disaccharides than controls. PAI-1, endotoxin, and ALT plasma levels were positively related to total protein and carbohydrate intake.ConclusionsTaken together, our results indicate that intestinal permeability, endogenous alcohol synthesis, and nutritional intake are markedly altered in patients with NAFLD.

Role of tumor necrosis factor α (TNFα) in the onset of fructose-induced nonalcoholic fatty liver disease in mice

Tumor necrosis factor α (TNFα) is known to be involved in dysregulation of hepatic lipid metabolism and insulin signaling. However, whether TNFα also plays a casual role in the onset of fructose-induced nonalcoholic fatty liver disease (NAFLD) has not yet been determined. Therefore, wild-type and TNFα receptor 1 (TNFR1)-/- mice were fed with either 30% fructose solution or plain tap water. Hepatic triglycerides, markers of inflammation and ATP concentration as well as plasma ALT levels were determined. Hepatic PAI-1, SREBP-1, FAS mRNA expression was assessed by real-time RT-PCR. Furthermore, lipid peroxidation and indices of insulin resistance were determined in liver tissue and plasma. In comparison to water controls, chronic intake of 30% fructose solution caused a significant ∼5-fold increase in triglyceride accumulation and neutrophil infiltration in livers of wild-type mice and a ∼8-fold increase in plasma ALT levels. In TNFR1-/- mice, hepatic steatosis was attenuated and neutrophil infiltration in the liver as well as plasma ALT levels was similar to water controls. The protective effect of the TNFR1 deletion against the onset of fructose-induced steatosis was associated with increased phospho AMPK and Akt levels, decreased SREBP-1 and FAS expression in the liver and decreased RBP4 plasma levels, whereas hepatic lipid peroxidation, iNOS protein and ATP levels were similar between wild-type and TNFR1-/- mice fed fructose. Taken together, these data suggest that TNFα plays a casual role in the onset of fructose-induced liver damage as well as insulin resistance in mice through signaling cascades downstream of TNFR1.

Toll-like receptors 1–9 are elevated in livers with fructose-induced hepatic steatosis

Studies in animals and human subjects indicate that gut-derived bacterial endotoxins may play a critical role in the development of non-alcoholic fatty liver disease (NAFLD). In the present study, we investigated if the liver is also sensitised by other microbial components during the onset of fructose-induced steatosis in a mouse model. C57BL/6 mice were either fed with 30 % fructose solution or tap water (control) with or without antibiotics for 8 weeks. Expression of toll-like receptors (TLR)1-9, TNF-α, inducible NO synthase (iNOS), myeloid differentiation factor 88 (MyD88) and number of F4/80 positive cells in the liver were assessed. Occludin protein, DNA of microbiota in the small and large intestine and retinol binding protein 4 (RBP4) in plasma were analysed using Western blot, DNA fingerprinting and ELISA, respectively. F4/80 positive cells were determined by immunohistochemistry. The accumulation of TAG found in the livers of fructose-fed mice was associated with a significant induction of TLR 1-4 and 6-8. Plasma RBP4 concentration and hepatic mRNA expression levels of TNF-α, iNOS, MyD88 and number of F4/80 positive cells of fructose-fed animals were significantly higher than those of controls; however, these effects of fructose were attenuated in antibiotic-treated mice. Whereas protein concentration of occludin was lower in the duodenum of fructose-treated mice, no systematic alterations of microbiota were found in this part of the intestine. Taken together, these data support the hypothesis that (1) an increased intestinal translocation of microbial components and (2) an increased number of F4/80 positive cells and induction of several TLR and dependent pathways (e.g. MyD88 and iNOS) may be involved in the onset of fructose-induced NAFLD.

Lactobacillus casei Shirota protects from fructose-induced liver steatosis: a mouse model.

To test the hypothesis that Lactobacillus casei Shirota (Lcs) protects against the onset of non-alcoholic fatty liver disease (NAFLD) in a mouse model of fructose-induced steatosis, C57BL/6J mice were either fed tap water or 30% fructose solution +/- Lcs for 8 weeks. Chronic consumption of 30% fructose solution led to a significant increase in hepatic steatosis as well as plasma alanine-aminotransferase (ALT) levels, which was attenuated by treatment with Lcs. Protein levels of the tight junction protein occludin were found to be markedly lower in both fructose treated groups in the duodenum, whereas microbiota composition in this part of the intestine was not affected. Lcs treatment markedly attenuated the activation of the Toll-like receptor (TLR) 4 signalling cascade found in the livers of mice only treated with fructose. Moreover, in livers of fructose fed mice treated with Lcs peroxisome proliferator-activated receptor (PPAR)-γ activity was markedly higher than in mice only fed fructose. Taken together, the results of the present study suggest that the dietary intake of Lcs protects against the onset of fructose-induced NAFLD through mechanisms involving an attenuation of the TLR-4-signalling cascade in the liver.

Fructose-induced steatosis in mice: role of plasminogen activator inhibitor-1, microsomal triglyceride transfer protein and NKT cells.

Plasminogen activator inhibitor-1 (PAI-1) is an acute-phase protein known to be involved in alcoholic liver disease and hepatic fibrosis. In the present study, the hypothesis that PAI-1 is causally involved in the onset of fructose-induced hepatic steatosis was tested in a mouse model. Wild-type C57BL/6J and PAI-1−/− mice were fed with 30% fructose solution or water for 8 weeks. Markers of hepatic steatosis, expression of PAI-1, apolipoprotein B (ApoB), cluster of differentiation 1d (CD1d), markers of natural killer T (NKT) cells, protein levels of phospho-c-Met and tumor necrosis factor-α (TNF-α) were determined. Activity of the microsomal triglyceride transfer protein (MTTP) was measured in liver tissue. In comparison with water controls, chronic intake of 30% fructose solution caused a significant increase in hepatic triglycerides, PAI-1 expression and plasma alanine aminotransferase levels in wild-type mice. This effect of fructose feeding was markedly attenuated in PAI-1−/− mice. Despite no differences in portal endotoxin levels and hepatic TNF-α protein levels between fructose-fed groups, the protective effect of the loss of PAI-1 against the onset of fructose-induced steatosis was associated with a significant increase in phospho-c-Met, phospho Akt, expression of ApoB and activity of MTTP in livers of PAI-1−/− mice in comparison with fructose-fed wild types. Moreover, in PAI-1−/− mice, expressions of CD1d and markers of CD1d-reactive NKT cells were markedly higher than in wild-type mice; however, expression of markers of activation of CD1d-reactive NKT cells (eg, interleukin-15 and interferon-γ) were only found to be increased in livers of fructose-fed PAI-1−/− mice. Taken together, these data suggest that PAI-1 has a causal role in mediating the early phase of fructose-induced liver damage in mice through signaling cascades downstream of Kupffer cells and TNF-α.

Protective effect of bile acids on the onset of fructose-induced hepatic steatosis in mice.

Fructose intake is being discussed as a key dietary factor in the development of nonalcoholic fatty liver disease (NAFLD). Bile acids have been shown to modulate energy metabolism. We tested the effects of bile acids on fructose-induced hepatic steatosis. In C57BL/6J mice treated with a combination of chenodeoxycholic acid and cholic acid (100 mg/kg body weight each) while drinking water or a 30% fructose solution for eight weeks and appropriate controls, markers of hepatic steatosis, portal endotoxin levels, and markers of hepatic lipogenesis were determined. In mice concomitantly treated with bile acids, the onset of fructose-induced hepatic steatosis was markedly attenuated compared to mice only fed fructose. The protective effects of the bile acid treatment were associated with a downregulation of tumor necrosis factor (TNF)α, sterol regulatory element-binding protein (SREBP)1, FAS mRNA expression, and lipid peroxidation in the liver, whereas hepatic farnesoid X receptor (FXR) or short heterodimer partner (SHP) protein concentration did not differ between groups fed fructose. Rather, bile acid treatment normalized occludin protein concentration in the duodenum, portal endotoxin levels, and markers of Kupffer cell activation to the level of water controls. Taken together, these data suggest that bile acids prevent fructose-induced hepatic steatosis in mice through mechanisms involving protection against the fructose-induced translocation of intestinal bacterial endotoxin.

Dietary pattern and leisure time activity of overweight and normal weight children in Germany: sex-specific differences

BackgroundSeveral studies indicate that dietary pattern and leisure time activities of adults not only differ between sexes but also between overweight and normal weight individuals. The aim of the present study was to determine if sex-specific differences in dietary pattern and leisure time activity already exist and are associated with weight status in young childhood.MethodsNutritional intake, anthropometric parameters, leisure time activities and socio- demographical factors were assessed in 100 overweight and 51 normal weight children (81 girls and 70 boys), aged 5–8 years.ResultsIn general, independent of body weight, boys ate more cheese while girls consumed more vegetables and spent more time with sedentary activities. Moreover, regardless of sex, total energy and macronutrient intake did not differ between normal weight and overweight children. Also, time spent with sportive activities did not differ between groups; however, overweight boys spent significantly more leisure time with sedentary activities than normal weight boys. Furthermore, BMI of mothers and time spent with sedentary activities were identified as independent risk factors for the development of overweight when performing multiple regression analyses.ConclusionsTaken together, results of our study suggest that already at young age sex influences dietary pattern independent of body weight. Furthermore, an increased time spent with sedentary activities and an elevated maternal BMI were found to be associated with an elevated body weight in children. (Trial registration: NCT01306396)

Sex-Specific Differences in the Development of Acute Alcohol-Induced Liver Steatosis in Mice

AIMS Results of several animal studies suggest that similar to humans, female rodents are more susceptible to chronic alcohol-induced liver disease (ALD). The aim of the present study was to determine whether female mice are more susceptible to acute alcohol-induced steatosis than male mice and to investigate possible mechanisms involved. METHODS Male and female C57BL/6J mice received one single dose of ethanol (6 g/kg bodyweight) or isocaloric maltose-dextrin solution intragastrically. Plasma alcohol concentration, markers of hepatic steatosis, activation of the TLR-4 signaling cascade and triglyceride export as well as lipid peroxidation and of iron metabolism were measured 12 h after acute alcohol intake. RESULTS In male and female ethanol-treated mice, plasma alcohol concentrations were still markedly increased 12 h after the alcohol challenge, which was associated with a significant accumulation of lipids in the liver and increase of transaminases in plasma; however, lipid accumulation was ∼3-fold higher in females in comparison with male animals. Expression of MyD88 was only found to be significantly induced in livers of female alcohol-exposed mice, whereas protein levels of ApoB were found to be significantly lower only in livers of female mice exposed to ethanol. Levels of 4-HNE protein adducts and ferritin were induced in livers of male and female ethanol-treated mice. CONCLUSION Taken together, these data suggest that female mice are also more susceptible to acute alcohol-induced liver steatosis and that this involves an increased activation of TLR-4-dependent signaling pathways in the liver.

A low fructose diet in the treatment of pediatric obesity : A pilot study

Background:  Over the last three decades the prevalence of overweight and obesity has increased dramatically among children and adolescents worldwide. As the results of animal and human studies suggest that a diet rich in fructose may be a risk factor for the development of overweight, the aim of the pilot study was to evaluate if a dietary counseling aimed at a moderate reduction of dietary fructose intake (−50% in comparison to intake at baseline) has a positive effect on the body mass index (BMI) of overweight and obese children.