Dietary effect of different high-fat diet on rat liver stereology

Intrauterine exposure to a high-fat diet, with different levels of lipids, and its gastrointestinal repercussions: a model of fetal programming in rats

It is known that adverse stimuli, such as altered diets during pregnancy and lactation, can result in deleterious effects on the progeny. The aim of this study was to evaluate the possible gastrointestinal repercussions in the offspring of Wistar rats exposed to high-fat diets. Pregnant rats were divided into three groups: normolipidic diet (3.5% lipids), a diet containing 28% lipids, and a diet with 40% lipids. Body weight and food, water, daily caloric, and macronutrient intake were evaluated in the pregnant rats. Structural and functional gastrointestinal parameters were assessed in 30-day-old male pups. Depending on the lipid content of the maternal diet, the pups may exhibit gastric mucosal thickening, an increase in the relative weight of the small intestine, a reduction in the jejunal and ileal mucosa, and a decrease in the total thickness of the ileum. Additionally, there may be a reduction in the number of villi per area in these organs and a thinning of the muscular layer in the large intestine. The structural changes induced by the maternal high-fat diet seem to reduce the stomach's sensitivity to ethanol-induced ulcers, which is the only functional alteration observed. Therefore, the offspring of dams exposed to high-fat diets during pregnancy and lactation exhibits impaired gastrointestinal development, with alterations depending on dietary fat content and specific gastrointestinal regions. Structural changes did not always result in functional abnormalities and, in some cases, appeared protective. The long-term consequences of the observed morphological alterations require further investigation.

Fat augments leptin-induced uterine contractions by decreasing JAK2 and BKCa channel expressions in late pregnant rats

Altered lipid metabolism in obesity causes pregnancy complications in humans and animals. Leptin levels increase in pregnancy, as well as obesity. However, the effect of obesity on uterine leptin receptors and its distal signaling is not clear. The present study aimed to understand the effect of increased fat on leptin signaling in rat uterus. Wistar female rats were fed with an HF diet (40% Fat, 17% Sucrose, 1.25% Cholesterol, 0.75% Cholic acid) for 6 weeks before the mating and during pregnancy. HF diet significantly increased the fat depots, liver weight, serum, and tissue cholesterol levels. It produced fatty degeneration in the liver and caused infiltration of inflammatory cells, cystic endometrial glands, and sub endometrial fibrosis of the uterus. In isometric tension experiments, leptin caused a significant increase in uterine contractions in high fat-fed animals compared to control animals. Analysis of receptor expressions revealed no significant difference between the groups. However, a significant decrease in the JAK2 and BKCaα mRNA expression was observed in the uterus of high fat-fed rats. No change in the BKCaβ, eNOS, iNOS, MLCP, and MLCK mRNA expressions was noticed in the HF group compared to the control. The findings of the present study suggest that the contractile response to leptin in the uterus of high fat-fed rats may be attributed to reduced signaling through JAK2 and, lowered expressions of BKCa channel α subunits.

The mTORC1/AMPK pathway plays a role in the beneficial effects of semaglutide (GLP-1 receptor agonist) on the liver of obese mice

PURPOSE

The liver regulates lipid metabolism. Decreasing mTOR (mechanistic target of rapamycin complex 1) and enhancing AMPK (AMP-activated protein kinase) help degrade hepatic diet-induced accumulated lipids. Therefore, the glucagon-like peptide type 1 receptor agonist (GLP-1) is indicated to treat obesity-related liver metabolic alterations. Then, we investigated the effects of semaglutide (recent GLP-1) by analyzing the liver mTORC1/AMPK pathway genes in obese mice.

BASIC PROCEDURES

C57BL/6 male mice were separated into two groups and submitted for 16 weeks of obesity induction. Then they were treated for an additional four weeks with semaglutide (subcutaneous, 40 μg/kg once every three days). The groups formed were: C, control group; CS, control group plus semaglutide; HF, high-fat group; HFS, high-fat group plus semaglutide. Next, the livers were dissected, and rapidly fragments of all lobes were kept and frozen at -80° C for analysis (RT-qPCR).

MAIN FINDINGS

Liver markers for the mTOR pathway associated with anabolism and lipogenesis de novo were increased in the HF group compared to the C group but comparatively attenuated by semaglutide. Also, liver markers for the AMPK pathway, which regulates chemical pathways involving the cell's primary energy source, were impaired in the HF group than in the C group but partly restored by semaglutide.

CONCLUSION

the mTOR pathway was attenuated, and the insulin signaling and the AMPK pathway were enhanced by semaglutide, ameliorating the liver gene expressions related to the metabolism of obese mice. These findings are promising in delaying the progression of nonalcoholic fatty liver disease.

Diet-induced rodent models of obesity-related metabolic disorders-A guide to a translational perspective

Diet is a critical element determining human health and diseases, and unbalanced food habits are major risk factors for the development of obesity and related metabolic disorders. Despite technological and pharmacological advances, as well as intensification of awareness campaigns, the prevalence of metabolic disorders worldwide is still increasing. Thus, novel therapeutic approaches with increased efficacy are urgently required, which often depends on cellular and molecular investigations using robust animal models. In the absence of perfect rodent models, those induced by excessive consumption of fat and sugars better replicate the key aspects that are the root causes of human metabolic diseases. However, the results obtained using these models cannot be directly compared, particularly because of the use of different dietary protocols, and animal species and strains, among other confounding factors. This review article revisits diet-induced models of obesity and related metabolic disorders, namely, metabolic syndrome, prediabetes, diabetes and nonalcoholic fatty liver disease. A critical analysis focused on the main pathophysiological features of rodent models, as opposed to the criteria defined for humans, is provided as a practical guide with a translational perspective for the establishment of animal models of obesity-related metabolic diseases.

Anti-steatotic linagliptin pleiotropic effects encompasses suppression of de novo lipogenesis and ER stress in high-fat-fed mice

AIM

To investigate the effects of linagliptin treatment on hepatic energy metabolism and ER stress in high-fat-fed C57BL/6 mice.

METHODS

Forty male C57BL/6 mice, three months of age, received a control diet (C, 10% of lipids as energy, n = 20) or high-fat diet (HF, 50% of lipids as energy, n = 20) for 10 weeks. The groups were randomly subdivided into four groups to receive linagliptin, for five weeks, at a dose of 30 mg/kg/day added to the diets: C, C-L, HF, and HF-L groups.

RESULTS

The HF group showed higher body mass, total and hepatic cholesterol levels and total and hepatic triacylglycerol levels than the C group, all of which were significantly diminished by linagliptin in the HF-L group. The HF group had higher hepatic steatosis than the C group, whereas linagliptin markedly reduced the hepatic steatosis (less 52%, P < 0.001). The expression of Sirt1 and Pgc1a was more significant in the HF-L group than in the HF group. Linagliptin also elicited enhanced GLP-1 concentrations and a reduction in the expression of the lipogenic genes Fas and Srebp1c. Besides, HF-L showed a reduction in the genes related to endoplasmic reticulum stress Chop, Atf4, and Gadd45 coupled with reduced apoptotic nuclei immunostaining.

CONCLUSION

Linagliptin caused a marked reduction in hepatic steatosis as a secondary effect of its glucose-lowering property. NAFLD countering involved reduced lipogenesis, increased beta-oxidation, and relief in endoplasmic reticulum stress, leading to reduced apoptosis and better preservation of the hepatic structure. Therefore, linagliptin may be used, preferably in diabetic patients, to avoid the progression of hepatic steatosis.

Protective Effect of α-Linolenic Acid on Non-Alcoholic Hepatic Steatosis and Interleukin-6 and -10 in Wistar Rats

Consumption of omega-3 (n-3) polyunsaturated fatty acids (PUFA) is related to improvement in the inflammatory response associated with decreases in metabolic disorders of obesity, such as low-grade inflammation and hepatic steatosis. Linseed (Linum usitatissimum) oil is a primary source of n-3 fatty acids (FAs) of plant origin, particularly α-linolenic acid, and provides an alternative for the ingestion of n-3 PUFA by persons allergic to, or wishing to avoid, animal sources. In our study, we evaluated the effect of the consumption of different lipidic sources on metabolic and inflammatory parameters in Wistar rats. We split 56 male rats into four groups that were fed for 60 days with the following diets: sesame oil, (SO, Sesamum indicum), linseed oil (LO), SO + LO (SLO), and a control group (CG) fed with animal fat. Our results reveal that the use of LO or SLO produced improvements in the hepatic tissue, such as lower values of aspartate aminotransferase, liver weight, and hepatic steatosis. LO and SLO reduced the weight of visceral fats, weight gain, and mediated the inflammation through a decrease in interleukin (IL)-6 and increase in IL-10. Though we did not detect any significant differences in the intestine histology and the purinergic system enzymes, the consumption of α-linolenic acid appears to contribute to the inflammatory and hepatic modulation of animals compared with a diet rich in saturated FAs and or unbalanced in n-6/n-3 PUFAs, inferring possible use in treatment of metabolic disorders associated with obesity and cardiovascular diseases.

Long-term metabolic effects of malnutrition: Liver steatosis and insulin resistance following early-life protein restriction

Early postnatal-life malnutrition remains prevalent globally, and about 45% of all child deaths are linked to malnutrition. It is not clear whether survivors of childhood malnutrition suffer from long-term metabolic effects, especially when they are later in life exposed to a fat and carbohydrate rich obesogenic diet. The lack of knowledge around this dietary “double burden” warrants studies to understand the long-term consequences of children previously exposed to malnutrition. We hypothesized that an early-life nutritional insult of low protein consumption in mice would lead to long-term metabolic disturbances that would exacerbate the development of diet-induced insulin resistance and non-alcoholic fatty liver disease (NAFLD). We investigated the effects of feeding a low protein diet (4% wt/wt) immediately after weaning for four weeks and subsequent feeding of a high carbohydrate high fat feeding for 16 weeks on metabolic function and development of NAFLD. Mice exposed to early-life protein restriction demonstrated a transient glucose intolerance upon recovery by regular chow diet feeding. However, protein restriction after weaning in mice did not exacerbate an obesogenic diet-induced insulin resistance or progression to NAFLD. These data suggest that transient protein restriction in early-life does not exacerbate an obesogenic diet-induced NAFLD and insulin resistance.

Adipocytes and intestinal epithelium dysfunctions linking obesity to inflammation induced by high glycemic index pellet-diet in Wistar rats

We investigated the inflammatory effect of a pellet-diet with high glycemic index and load (HGLI) on the histological organization of adipocytes, intestinal epithelium, and fat in liver and pancreas in adult male Wistar rats. Two groups (n=10) received for 17 weeks: (1) HGLI diet or (2) Standard diet (Labina®). Histological analyses of adipose tissue, jejunum, liver, and pancreas were performed. Stereology analysis, visceral adiposity index, gene expression, and immunohistochemistry of tumor necrosis factor-α (TNF-α) in visceral adipose tissue and plasma TNF-α were also assessed. The HGLI diet-induced hypertrophy of adipocytes with adipocyte volume density equal to 97.0%, cross-sectional area of adipocytes equivalent to 1387 µm² and a total volume of adipocytes of 6.97 cm³ an elevation of 8%, 25%, and 58%, respectively. Furthermore, the HGLI diet increased liver and pancreatic fat deposition, altered and inflamed the intestinal epithelia, and increased TNF-α gene expression (P=0.014) with a positive immunostaining in visceral adipose tissue and high plasma TNF-α in comparison with standard diet. The results suggest that this diet was able to generate changes commonly caused to solid diets with high fat or fructose-rich beverages. To the best of our knowledge, this is the first report in the literature concerning the properties of low-cost, sucrose-rich pellet-diet presenting high glycemic index and high glycemic load efficient on the development of obesity complications in Wistar rats that were subjected to diet-induced obesity. Therefore, the HGLI pellet-diet may be considered an effective tool to be used by the scientific community in experimental research.

Rosuvastatin limits the activation of hepatic stellate cells in diet-induced obese mice

AIM

The aim of this study was to investigate the effects of rosuvastatin in a model of diet-induced obesity and non-alcoholic fatty liver disease, with attention to the activation of hepatic stellate cells (HSCs).

METHOD

Male C57BL/6 mice received a control diet (C; 10% energy as lipids) or a high-fat diet (HF; 50% energy as lipids) for 12 weeks, followed by 7 weeks of treatment. Group CR received control diet + rosuvastatin; group HFR received high-fat diet + rosuvastatin.

RESULTS

The HF group showed higher insulin, total cholesterol, triacylglycerol, and leptin levels than the C group, all of which were significantly diminished by rosuvastatin in the HFR group. The HF group had greater steatosis and activated HSCs than the C group, whereas rosuvastatin diminished the steatosis (less 21%, P < 0.001) and significantly inhibited the activation of the HSCs in the HFR group compared to the HF group. The sterol regulatory element-binding protein-1 and the peroxisome proliferator-activated receptor (PPAR)-γ protein expressions were increased in HF animals and reduced after treatment in the HFR group. By contrast, low PPAR-α and carnitine palmitoyltransferase-1 expressions were found in the HF group, and were restored by rosuvastatin treatment in the HFR group.

CONCLUSION

Rosuvastatin mitigated hepatic steatosis by modulating PPAR balance, favoring PPAR-α over PPAR-γ downstream effects. The effects were accompanied by a diminishing of insulin resistance, the anti-inflammatory adipokine profile, and HSC activation, avoiding non-alcoholic fatty liver disease progression and non-alcoholic steatohepatitis onset in this model.

Hormetic modulation of hepatic insulin sensitivity by advanced glycation end products

Because of the paucity of information regarding metabolic effects of advanced glycation end products (AGEs) on liver, we evaluated effects of AGEs chronic administration in (1) insulin sensitivity; (2) hepatic expression of genes involved in AGEs, glucose and fat metabolism, oxidative stress and inflammation and; (3) hepatic morphology and glycogen content. Rats received intraperitoneally albumin modified (AlbAGE) or not by advanced glycation for 12 weeks. AlbAGE induced whole-body insulin resistance concomitantly with increased hepatic insulin sensitivity, evidenced by activation of AKT, inactivation of GSK3, increased hepatic glycogen content, and decreased expression of gluconeogenesis genes. Additionally there was reduction in hepatic fat content, in expression of lipogenic, pro-inflamatory and pro-oxidative genes and increase in reactive oxygen species and in nuclear expression of NRF2, a transcription factor essential to cytoprotective response. Although considered toxic, AGEs become protective when administered chronically, stimulating AKT signaling, which is involved in cellular defense and insulin sensitivity.

Transcriptomic responses of the liver and adipose tissues to altered carbohydrate-fat ratio in diet: an isoenergetic study in young rats

Background

To elucidate the effects of altered dietary carbohydrate and fat balance on liver and adipose tissue transcriptomes, 3-week-old rats were fed three kinds of diets: low-, moderate-, and high-fat diets (L, M, and H) containing a different ratio of carbohydrate-fat (C-F) (65:15, 60:20, and 35:45 in energy percent, respectively).

Methods

The rats consumed the diets for 9 weeks and were subjected to biochemical and DNA microarray analyses.

Results

The rats in the H-group exhibited lower serum triacylglycerol (TG) levels but higher liver TG and cholesterol content than rats in the L-group. The analysis of differentially expressed genes (DEGs) between each group (L vs M, M vs H, and L vs H) in the liver revealed about 35% of L vs H DEGs that were regulated in the same way as M vs H DEGs, and most of the others were L- vs H-specific. Gene ontology analysis of these L vs H DEGs indicated that those related to fatty acid synthesis and circadian rhythm were enriched. Interestingly, about 30% of L vs M DEGs were regulated in a reverse way compared with L vs H and M vs H DEGs. These reversed liver DEGs included M-up/H-down genes (Sds for gluconeogenesis from amino acids) and M-down/H-up genes (Gpd2 for gluconeogenesis from glycerol, Agpat9 for TG synthesis, and Acot1 for beta-oxidation). We also analyzed L vs H DEGs in white (WAT) and brown (BAT) adipose tissues and found that both oxidation and synthesis of fatty acids were inhibited in these tissues.

Conclusions

These results indicate that the alteration of dietary C-F balance differentially affects the transcriptomes of metabolizing and energy-storing tissues.

Electronic supplementary material

The online version of this article (doi:10.1186/s12263-017-0558-2) contains supplementary material, which is available to authorized users.

Dietary Egg Yolk Supplementation Improves Low-Protein-Diet-Induced Fatty Liver in Rats

Egg yolk is an important source of nutrients and contains different bioactive substances. In the present study, we studied the benefits of egg yolk in preventing low-protein-diet-induced fatty liver in rats. Rats were fed the following diets, which were based on the AIN-76 formula, for 2 wk: an adequate-protein diet containing 20% casein (C), a low-protein diet containing 5% casein (LP-C), a low-protein diet supplemented with 12.5% egg yolk (LP-EY), and a low-protein diet supplemented with 4.1% egg yolk oil (LP-EYO). The low-protein diets were adjusted to contain 4.13% protein and 4.7% lipids. The LP-C diet resulted in a greater increase in the liver trigriceride (TG) and the vacuolation and a greater decrease in the serum TG and free fatty acid (FFA) than did the C diet. These deviations in the serum and liver TG, serum FFA levels and the liver histopathology were corrected in rats fed the LP-EY diet but not in those fed the LP-EYO diet. Compared to rats fed the LP-C diet, although the activities of lipogenesis-related enzymes (fatty acid synthase, glucose-6-phosphate dehydrogenase, and malic enzyme) decreased in rats fed both of the LP-EY and LP-EYO diets, the level of the microsomal TG transfer protein (MTP) increased only in rats fed the LP-EY diet. Collectively, these results suggest that dietary egg yolk supplementation decreases the LP diet-induced accumulation of TG in the liver by increasing transport of TG in the liver, and egg yolk oil alone is not sufficient enough to bring about these benefits.

Short-term administration of GW501516 improves inflammatory state in white adipose tissue and liver damage in high-fructose-fed mice through modulation of the renin-angiotensin system

High activation of the angiotensin-converting enzyme (ACE)/(angiotensin-II type 1 receptor) AT1r axis is closely linked to pro-inflammatory effects and liver damage. The aim of this study was to evaluate the effects of the short-term administration of GW501516 on pro-inflammatory markers in white adipose tissue (WAT) and hepatic stellate cells (HSCs), lipogenesis and insulin resistance in the liver upon high-fructose diet (HFru)-induced ACE/AT1r axis activation. Three-month-old male C57Bl/6 mice were fed a standard chow diet or a HFru for 8 weeks. Then, the animals were separated randomly into four groups and treated with GW501516 for 3 weeks. Morphological variables, systolic blood pressure, and plasma determinations were analyzed. In the WAT, the ACE/AT1r axis and pro-inflammatory cytokines were assessed, and in the liver, the ACE/AT1r axis, HSCs, fatty acid oxidation, insulin resistance, and AMPK activation were evaluated. The HFru group displayed a high activation of the ACE/AT1r axis in both the WAT and liver; consequently, we detected inflammation and liver damage. Although GW501516 abolished the increased activation of the ACE/AT1r axis in the WAT, no differences were found in the liver. GW501516 blunted the inflammatory state in the WAT and reduced HSC activation in the liver. In addition, GW501516 alleviates damage in the liver by increasing the expression of the genes that regulate beta-oxidation and decreasing the expression of the genes and proteins that are involved in lipogenesis and gluconeogenesis. We conclude that GW501516 may serve as a therapeutic option for the treatment of a highly activated ACE/AT1r axis in WAT and liver.

A Grape Seed Procyanidin Extract Ameliorates Fructose-Induced Hypertriglyceridemia in Rats via Enhanced Fecal Bile Acid and Cholesterol Excretion and Inhibition of Hepatic Lipogenesis

The objective of this study was to determine whether a grape seed procyanidin extract (GSPE) exerts a triglyceride-lowering effect in a hyperlipidemic state using the fructose-fed rat model and to elucidate the underlying molecular mechanisms. Rats were fed either a starch control diet or a diet containing 65% fructose for 8 weeks to induce hypertriglyceridemia. During the 9th week of the study, rats were maintained on their respective diet and administered vehicle or GSPE via oral gavage for 7 days. Fructose increased serum triglyceride levels by 171% after 9 weeks, compared to control, while GSPE administration attenuated this effect, resulting in a 41% decrease. GSPE inhibited hepatic lipogenesis via down-regulation of sterol regulatory element binding protein 1c and stearoyl-CoA desaturase 1 in the fructose-fed animals. GSPE increased fecal bile acid and total lipid excretion, decreased serum bile acid levels and increased the expression of genes involved in cholesterol synthesis. However, bile acid biosynthetic gene expression was not increased in the presence of GSPE and fructose. Serum cholesterol levels remained constant, while hepatic cholesterol levels decreased. GSPE did not modulate expression of genes responsible for esterification or biliary export of the newly synthesized cholesterol, but did increase fecal cholesterol excretion, suggesting that in the presence of GSPE and fructose, the liver may secrete more free cholesterol into the plasma which may then be shunted to the proximal small intestine for direct basolateral to apical secretion and subsequent fecal excretion. Our results demonstrate that GSPE effectively lowers serum triglyceride levels in fructose-fed rats after one week administration. This study provides novel insight into the mechanistic actions of GSPE in treating hypertriglyceridemia and demonstrates that it targets hepatic de novo lipogenesis, bile acid homeostasis and non-biliary cholesterol excretion as important mechanisms for reducing hypertriglyceridemia and hepatic lipid accumulation in the presence of fructose.

Programming of obesity and comorbidities in the progeny: lessons from a model of diet-induced obese parents

Aim

To determine the impact of paternal obesity, maternal obesity or the combination of two obese parents on markers of adult offspring metabolism, with a focus on body mass (BM), lipid and carbohydrate, components of lipogenesis and beta-oxidation in the liver, sex dimorphism in the offspring that received a SC diet during the postnatal period.

Materials and Methods

Male and female C57BL/6 mice were fed a high-fat diet (HF; 49% lipids) or standard chow (SC; 17% lipids) for 8 weeks before mating until lactation. The offspring were labeled according to sex, maternal diet (first letters), paternal diet (second letters), and received a SCdiet until 12-weeks of age when they were sacrificed. BM, eating behavior, glucose tolerance, plasma analysis, gene and protein expression of the components of lipogenesis and beta-oxidation in the liver of offspring were evaluated.

Results

HF diet-fed mothers and fathers were overweight, hyperglycemic and glucose intolerant and had a deteriorating lipid profile. The adult male and female offspring of HF-mothers were overweight, with an increased adiposity index, hyperphagic, had an impaired glucose metabolism, increased total cholesterol and triacylglycerol levels, increased lipogenesis concomitant with decreased beta-oxidation resulting in liver steatosis. The male and female offspring of HF-father had impaired glucose metabolism, exacerbated lipogenesis without influencing beta-oxidation and enhanced hepatic steatosis. These findings are independent of BM. Male and female offspring of a mother and father that received a HF diet demonstrated these effects most prominently in adult life.

Conclusion

Paternal obesity leads to alterations in glucose metabolism, increase in components of lipogenesis and liver steatosis. In contrast, maternal obesity leads to overweight and changes in the metabolic profile and liver resulting from activation of hepatic lipogenesis with impaired beta-oxidation. When both parents are obese, the effects observed in the male and female offspring are exacerbated.

Singular effects of PPAR agonists on nonalcoholic fatty liver disease of diet-induced obese mice

AIMS

To assess the effects of peroxisome proliferator-activated receptor (PPAR) agonists on glucose tolerance and hepatic lipid metabolism in diet-induced obese mice.

MAIN METHODS

Male C57BL/6 mice received a standard chow diet (SC, 10% energy as lipids) or high-fat diet (HF, 50% energy as lipids) for 10 weeks, after which treatment was initiated, forming the groups: SC group, HF group, HF-BZ group (HF + bezafibrate, pan-PPAR agonist), HF-WY group (HF + WY-14643, PPARalpha agonist) and HF-GW group (HF + GW1929, PPARgamma agonist). Treatments lasted for four weeks. Insulin resistance and liver remodeling were evaluated by biochemical and molecular approaches.

KEY FINDINGS

The HF and HF-GW mice were overweight. Conversely, the HF-BZ and HF-WY mice presented with body masses equal to those of the SC mice. All treatments restored insulin sensitivity and blood lipid and adiponectin levels. Hepatic steatosis was prevented in the HF-WY and HF-BZ mice as shown by the elevated mRNA levels of PPARalpha and Carnitine palmitoyl transferase-1a in both groups, which favored enhanced beta-oxidation. Marked decreases in liver triacylglycerol levels confirmed these findings. In contrast, the HF-GW mice exhibited increased PPARgamma and fatty acid translocase/CD136 mRNA levels, contributing to enhanced hepatic lipogenesis.

SIGNIFICANCE

The WY14643 and bezafibrate treatments most effectively improved the adverse metabolic and hepatic effects caused by obesity and IR. The results reinforce the central role of PPARalpha, as well as its contrary relationship to PPARgamma in the regulation of metabolic homeostasis and lipolytic pathways in the liver.

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

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

Early hepatic insult in the offspring of obese maternal mice

We hypothesized that the maternal obesity initiates metabolic disorders associated with oxidative stress in the liver of offspring since early life. Mouse's mothers were assigned into 2 groups according to the diet offered (n = 10 per group): standard chow (SC) or high-fat diet (HF). The results revealed that HF offspring had an increase in body mass at day 10 (+25%, P < .05) and in glucose levels (+25%, P < .0001). Hepatic triacylglycerol was increased in HF offspring at day 1 and day 10 compared with SC offspring (+30%, P < .01 and +40%, P < .01) as was hepatic steatosis (+110%, P < .001; +145%, P < .0001). Fatty acid synthase was increased in HF offspring at day 1 (+450%, P < .01) and peroxisome proliferator activator receptor-γ was elevated at day 1 and day 10 (+140%, P < .01; +2741%, P < .01). Peroxisome proliferator activator receptor-α was diminished in HF offspring at day 10 compared with SC offspring (-100%, P < .01). Moreover, carnitine palmitoyl-CoA transferase-1 was decreased in HF offspring at day 1 and day 10 (-80%, P < .01; -60%, P < .05). In the HF offspring (compared with the SC offspring), the catalase and the superoxide dismutase were significantly lower in both days 1 and 10 (P < .05). In 10-day-old offspring, glutathione peroxidase 1 and glutathione reductase were lower in HF offspring than in SC offspring (P < .0001). Our findings suggest that the maternal obesity in mice induces an early oxidative dysfunction coupled with hepatic steatosis and might contribute to progressive liver injury later in life.

Liver damage is not reversed during the lean period in diet-induced weight cycling in mice

AIM

Weight cycling (WC) is frequent in obesity treatment. We evaluated the degree of regression of the liver damage in WC.

METHODS

C57BL/6 male mice received standard chow (SC, 10% energy from lipids) or high-fat diet (HF, 60% energy from lipids) for 6 months (SC6 or HF6) or a diet that alternated every 2 months (SC2/HF2/SC2 or HF2/SC2/HF2).

RESULTS

The body mass gain followed the HF intake and induced WC in the animals. The liver alanine aminotransferase, triglyceride and cholesterol levels were higher in the groups receiving the HF diet for any period. The plasma insulin and glucose levels were the highest in the HF6 and HF2/SC2/HF2 groups. Any HF intake increased the liver mass. All the groups had some degree of liver steatosis, with the SC6 group exhibiting the lowest level (∼23% compared with 50-70%). The activated hepatic stellate cells were sparse throughout the liver sections from the HF6 and HF2/SC2/HF2 groups. The lowest sterol regulatory element-binding protein-1c (SREBP-1c) level was detected in the SC6 group. The peroxisome proliferator-activated receptor (PPAR)-α expression was higher in the SC6 and SC2/HF2/SC2 groups than in the HF6 and HF2/SC2/HF2 groups that showed reduced expression.

CONCLUSION

WC induced by diet leads to adverse response in the liver, including biochemical and molecular alterations that are not reversed during the lean period of the WC, which must be maintained for a long period to allow the liver to recover from the damage associated with obesity.

Effects of a diet rich in n-3 polyunsaturated fatty acids on hepatic lipogenesis and beta-oxidation in mice

Here, we investigate whether a diet rich in fish oil can lead to the development of hepatic alterations associated with non-alcoholic fatty liver disease (NAFLD). To achieve this goal, we provided, for 8 weeks, four different diets to 3-month-old C57BL/6 mice: (a) standard-chow diet (SC; 40 g soybean oil/kg diet, 10 % of the total energy content from lipids), (b) fish oil diet (FO; 4 g soybean oil and 36 g fish oil/kg diet, 10 % of the total energy content from lipids), (c) high-fat diet (HF; 40 g soybean oil and 238 g lard/kg diet, 50 % of the total energy content from lipids), and (d) high-fish oil diet (HFO; 40 g soybean oil and 238 g fish oil/kg diet, 50 % of the total energy content from lipids). Biochemical analyses, stereology, western-blotting and RT-qPCR were used. In the HF group, we found evidence of obesity, metabolic syndrome, and liver damage, along with hypertriglyceridemia, hepatic insulin resistance, and steatosis. On the other hand, the HFO group did not present these alterations and remained similar to the controls. The changes observed in the animals fed the HF diet were accompanied by an increase in hepatic lipogenesis and a decrease in beta-oxidation; meanwhile, in the HFO group, the opposite results were found, that is, reduced lipogenesis and elevated beta-oxidation, were most likely responsible for the prevention of deleterious hepatic alterations and liver damage. In conclusion, a diet rich in fish oil has beneficial effects on hepatic insulin resistance, lipogenesis and beta-oxidation and prevents hepatic tissue from liver damage and NAFLD.

The inflammatory profile and liver damage of a sucrose-rich diet in mice

It is still unclear if an isoenergetic, sucrose-rich diet leads to health consequences.

AIMS

To investigate the effects of excessive sucrose within an isoenergetic diet on metabolic parameters in male C57BL/6 mice.

METHODS

Animals were fed a control diet (10% fat, 8% sucrose - SC group), a high-sucrose diet (10% fat, 32% sucrose - HSu group), a high-fat diet (42% fat, 8% sucrose - HF group) or a high-fat/high-sucrose diet (42% fat, 32% sucrose - HF/HSu group) for 8 weeks.

RESULTS

Mice fed HF and HF/HSu diets gained more body mass (BM) and more body adiposity than SC- or Hsu-fed mice. Despite the unchanged BM and adiposity indices, HSu mice presented adipocyte hypertrophy, which was also observed in the HF and HF/HSu groups (P<.0001). The HF, HSu and HF/HSu mice were glucose intolerant and had elevated serum insulin levels (P<.05). The levels of leptin, resistin and monocyte chemotactic protein-1 increased, while the serum adiponectin decreased in the HF, HSu and HF/HSu groups (P<.05). In the adipose tissue, the HF, HSu and HF/HSu groups showed higher levels of leptin expression and lower levels of adiponectin expression in comparison with the SC group (P<.05). Liver steatosis was higher in the HF, HSu and HF/HSu groups than in the SC group (P<.0001). Hepatic cholesterol was higher in the HF and HF/HSu groups, while hepatic TG was higher in the HSu and HF/HSu groups (P<.05). In hepatic tissue, the sterol receptor element-binding protein-1c expression was increased in the HF, HSu and HF/HSu groups, unlike the peroxisome proliferator-activated receptor-alpha expression that decreased in the HF, HSu and HF/HSu groups in comparison with the SC group (P<.05).

CONCLUSION

A sucrose-rich diet does not lead to a state of obesity but has the potential to cause changes in the adipocytes (hypertrophy) as well as glucose intolerance, hyperinsulinemia, hyperlipidemia, hepatic steatosis and increases in the number of inflammatory cytokines. The deleterious effects of a sucrose-rich diet in an animal model, even when the sucrose replaces starch isocalorically in the feed, can have far-reaching consequences for health.

Hepatic adverse effects of fructose consumption independent of overweight/obesity

The chronic intake of fructose has been linked to insulin resistance, obesity, dyslipidemia and nonalcoholic fatty liver disease (NAFLD), which in turn, may progress to nonalcoholic steatohepatitis (NASH). We aimed to evaluate the magnitude of the effects of the chronic consumption of high-fructose (HFr) and high fat (HF) alone or combined. Four groups of male mice were fed different diets for 16 weeks: standard chow (9% fat: SC), HF diet (42% fat), HFr diet (34% fructose) and HF/HFr diet (42% fat, 34% fructose). The food intake was not different among the groups, and the body mass was not greater in the HFr group than in the SC group. The homeostasis model assessment for insulin resistance (HOMA-IR), as well as plasmatic total cholesterol and triglycerides were greater in the groups HF, HFr, and HF/HFr group than in the SC group. We observed in the groups HF, HFr and HF/HFr, compared to the group SC, nonalcoholic fatty liver disease (NAFLD) with a predominance of lipogenesis mediated by SREBP-1c and PPAR-γ, and a reduction of the oxidation mediated by PPAR-α. We also observed an increase in gluconeogenesis mediated by the GLUT-2 and the PEPCK. Importantly, we identified areas of necroinflammation indicating a transition from NAFLD to nonalcoholic steatohepatitis in the HFr and HF/HFr groups. This study is relevant in demonstrating that fructose consumption, even in the absence of obesity, causes serious and deleterious changes in the liver with the presence of the dyslipidemia, insulin resistance (IR), and NAFLD with areas of necroinflammation. These conditions are associated with a poor prognosis.

Role of choline deficiency in the Fatty liver phenotype of mice fed a low protein, very low carbohydrate ketogenic diet

Though widely employed for clinical intervention in obesity, metabolic syndrome, seizure disorders and other neurodegenerative diseases, the mechanisms through which low carbohydrate ketogenic diets exert their ameliorative effects still remain to be elucidated. Rodent models have been used to identify the metabolic and physiologic alterations provoked by ketogenic diets. A commonly used rodent ketogenic diet (Bio-Serv F3666) that is very high in fat (~94% kcal), very low in carbohydrate (~1% kcal), low in protein (~5% kcal), and choline restricted (~300 mg/kg) provokes robust ketosis and weight loss in mice, but through unknown mechanisms, also causes significant hepatic steatosis, inflammation, and cellular injury. To understand the independent and synergistic roles of protein restriction and choline deficiency on the pleiotropic effects of rodent ketogenic diets, we studied four custom diets that differ only in protein (5% kcal vs. 10% kcal) and choline contents (300 mg/kg vs. 5 g/kg). C57BL/6J mice maintained on the two 5% kcal protein diets induced the most significant ketoses, which was only partially diminished by choline replacement. Choline restriction in the setting of 10% kcal protein also caused moderate ketosis and hepatic fat accumulation, which were again attenuated when choline was replete. Key effects of the 5% kcal protein diet - weight loss, hepatic fat accumulation, and mitochondrial ultrastructural disarray and bioenergetic dysfunction - were mitigated by choline repletion. These studies indicate that synergistic effects of protein restriction and choline deficiency influence integrated metabolism and hepatic pathology in mice when nutritional fat content is very high, and support the consideration of dietary choline content in ketogenic diet studies in rodents to limit hepatic mitochondrial dysfunction and fat accumulation.

Adipocytes regulate the bone marrow microenvironment in a mouse model of obesity

Obesity is markedly associated with abnormal bone density indicating the importance of adipocytes in bone metabolism. However, the specific function of adipocytes remains unclear, with marked discrepancies in observations of previous studies. In the present study, the effect of adipocytes on osteoblasts/osteoclasts was analyzed. A mouse model of obesity was established and an in vitro co-culture system was utilized containing adipocyte and MC3T3/RAW 264.7 cells in a Transwell plate. Compared with control mice, obese mice exhibited low body weight and bone mineral density of the tibia and fat cells were observed to accumulate in bone marrow. MC3T3/RAW 264.7 cells were co-cultured with adipocytes and the mRNA and protein expression of alkaline phosphatase and osteocalcin was found to be decreased in MC3T3-E1 cells and mRNA and protein expression of tartrate-resistant acid phosphatase and cathepsin K was significantly increased in RAW 264.7 cells. In addition, the effect of adipocytes on the osteoprotegerin (OPG)/receptor activator of nuclear factor κB ligand (RANKL)/RANK system indicated that the RANKL/OPG ratio secreted by osteoblasts increased and RANK expression by osteoclasts increased, leading to increased osteoclastogenesis. These results indicate that bone metabolism is impaired in obese mice leading to decreased osteoblastogenesis and marked increases in osteoclastogenesis and low bone mass.

Pleiotropic effects of rosuvastatin on the glucose metabolism and the subcutaneous and visceral adipose tissue behavior in C57Bl/6 mice

The aim of this study was to evaluate whether rosuvastatin (HMG-CoA reductase inhibitor) modulates the carbohydrate and lipid metabolism, the development of non-alcoholic fatty liver disease (NAFLD), and the increase in body mass in a model of diet-induced obesity. Male C57Bl/6 mice (3-months-old) were fed a high-fat diet (HF, 60% lipids) or the standard chow (SC, 10% lipids) for 15 weeks. The animals were then treated with 10 mg/kg/day (HF-R10 group), 20 mg/kg/day (HF-R20), or 40 mg/kg/day (HF-R40) of rosuvastatin for five weeks. The HF diet led to glucose intolerance, insulin resistance, weight gain, increased visceral adiposity with adipocyte hypertrophy, and hepatic steatosis (micro and macrovesicular). The rosuvastatin treatment decreased the adiposity and the adipocyte size in the HF-R10 and HF-R20 groups. In addition, rosuvastatin changed the pattern of fat distribution in the HF-R40 group because more fat was stored subcutaneously than in visceral depots. This redistribution improved the fasting glucose and the glucose intolerance. Rosuvastatin also improved the liver morphology and ultrastructure in a dose-dependent manner. In conclusion, rosuvastatin exerts pleiotropic effects through a dose-dependent improvement of glucose intolerance, insulin sensitivity and NAFLD and changes the fat distribution from visceral to subcutaneous fat depots in a mouse model of diet-induced obesity.

Beneficial effects of rosuvastatin on insulin resistance, adiposity, inflammatory markers and non-alcoholic fatty liver disease in mice fed on a high-fat diet

The aim of the present study was to evaluate the effects of ST (rosuvastatin) and GZ (rosiglitazone) on IR (insulin resistance) and on liver as well as adipose tissue in mice fed on an HF (high-fat) diet. Our data show that treatment with ST resulted in a marked improvement in insulin sensitivity characterized by enhanced glucose clearance during the insulin tolerance test and a 70% decrease in the HOMA-IR (homoeostasis model assessment of insulin resistance) index level (P=0.0008). The ST-treated mice exhibited lower gains in BM (body mass; -8%; P<0.01) and visceral fat pad thickness (-60%; P<0.01) compared with the untreated HF group. In comparison with HF-diet-fed mice, HF+ST-treated mice showed a significant reduction in hepatomegaly and liver steatosis (-6%, P<0.05; and -21%, P<0.01 respectively). In HF+ST-treated mice, the hepatic TAG (triacylglycerol) levels were reduced by 58% compared with the HF group (P<0.01). In addition, the expression of SREBP-1c (sterol-regulatory-element-binding protein-1c) was decreased by 50% in the livers of HF+ST-treated mice (P<0.01) relative to the HF-diet-fed mice. The levels of resistin were lower in the HF+ST-treated group compared with the HF group (44% less, P< 0.01). In conclusion, we demonstrated that ST treatment improved insulin sensitivity and decreased liver steatosis in mice fed on an HF diet. Furthermore, ST reduced BM gains, improved the circulating levels of plasma cholesterol and TAG, and reduced hepatic TAG, which was concomitant with lower resistin levels.

The use of design-based stereology to evaluate volumes and numbers in the liver: a review with practical guidelines

Stereology offers a number of tools for the analysis of sections in microscopy (which usually provide only two-dimensional information) for the purpose of estimating geometric quantities, such as volume, surface area, length or number of particles (cells or other structures). The use of these tools enables recovery of the three-dimensional information that is inherent in biological tissues. This review uses the liver as a paradigm for summarizing the most commonly used state-of-the-art methods for quantitation in design-based stereology. Because it is often relevant to distinguish hyperplasia and hypertrophy in liver responses, we also focus on potential pitfalls in the sampling and processing of liver specimens for stereological purposes, and assess the existing methods for volume and number estimation. With respect to volume, we considered whole liver volume (V), volume density (V(V)) and so-called local volumes, including the number-weighted volume (V(N)) and the volume-weighted volume (V(V)). For number, we considered the total number (N) and the numerical density (N(V)). If correctly applied, current stereological methods guarantee that no bias is introduced in the estimates, which will be therefore accurate; additionally, methods can be tuned for obtaining precise quantitative estimates that can reveal subtle changes in the volume or number of selected hepatic cells. These methods have already detailed the effects of some substances and specific diets on the liver, and should be routinely included in the toolbox of liver research.

A critical analysis of three quantitative methods of assessment of hepatic steatosis in liver biopsies

The issue of adequately quantitatively evaluating hepatic steatosis is still unresolved. Therefore, we compared three methods of quantitative assessment. Two groups of mice (n = 10 each) were fed standard chow (10% fat, SC group) or a high-fat diet (60% fat, HF group) for 16 weeks, and hepatic triglyceride (HT) and liver tissue were then studied. Paraplast-embedded tissues stained by hematoxylin and eosin (H-E) were compared to frozen sections stained by Oil Red-O (ORO). In addition, the volume density of steatosis (Vv[steatosis, liver]) was measured by point counting (P-C, sections H-E or ORO) or by image analysis (I-A, sections ORO). HT was significantly higher in the HF group (104% greater, P = 0.0004) than in the SC group. With P-C and H-E, Vv[steatosis, liver] was 4.80 ± 0.90% in the SC group and 33.50 ± 3.17% in the HF group (600% greater, P < 0.0001). With P-C and ORO, Vv[steatosis, liver] was 4.86 ± 0.89% in the SC group and 25.21 ± 1.27% in the HF group (420% greater, P < 0.0001). With I-A and ORO, Vv[steatosis, liver] was 4.17 ± 0.85% in the SC group and 23.35 ± 1.58% in the HF group (460% greater, P < 0.0001). Correlations between Vv[steatosis, liver] and HT were strong and significant in all methods. In conclusion, all methods were appropriate and reproducible. In P-C and H-E, there is a slight overestimation of steatosis in the HF animals in comparison to frozen sections and ORO; in frozen sections, differences between P-C and I-A are insignificant.

Maternal high-fat intake predisposes nonalcoholic fatty liver disease in C57BL/6 offspring

OBJECTIVE

This work aimed to verify the hypothesis that maternal intake of high-fat diet in critical periods of pregnancy and/or suckling period predisposes nonalcoholic fatty liver disease in adult C57BL/6 mice offspring.

STUDY DESIGN

Male pups were divided into 5 groups: (1) SC, from standard chow-fed dams; (2) G, from high-fat chow (HF)-fed dams during the gestation (G) period; (3) L, from HF-fed dams during the lactation (L) period; (4) GL, from HF-fed dams during the gestation and lactation (GL) periods; and (5) GL/HF, from HF-fed dams during GL, maintaining an HF diet from postweaning to adulthood. We analyzed body mass, plasma blood, and liver structure.

RESULTS

The G offspring showed insulin resistance and lower glucose transporter-2 expression. Hepatic steatosis was present in the G, L, GL, and mainly in GL/HF offspring. Sterol regulatory element-binding protein-1c expression was higher in G, GL, and GL/HF offspring.

CONCLUSION

Programming by HF chow predisposes hepatic adverse remodeling in the liver of adult offspring.

Swimming training beneficial effects in a mice model of nonalcoholic fatty liver disease

The study aimed to investigate the effect of swimming training in reducing the nonalcoholic fatty liver disease (NAFLD) and associated comorbidities, including the hepatic expression of fatty acid synthesis and peroxisome proliferator receptor activity-alpha. Male C57BL/6 mice were separated into two major groups according to their nutrition and studied during 22 weeks: standard chow (10% fat, SC) or high-fat chow (60% fat, HF), characterizing the sedentary groups SC-Sed and HF-Sed. In the last 10 weeks of the experiment, half of the sedentary groups were submitted to a swimming training with a progressive increase in duration, characterizing the exercised groups: SC-Ex and HF-Ex. At the end of the experiment, considering the findings in the SC-Sed group, HF-Sed group had significantly higher body mass, hyperglycemia, hyperinsulinemia with insulin resistance, hypertrophy of the adipocytes (with inflammatory infiltrate), hypertrophy of the pancreatic islets, dyslipidemia, altered liver enzymes and inflammatory cytokines, and NAFLD with changes in gene expression of hepatic lipogenic and oxidative proteins. The swimming program, even concomitant with the high-fat diet, reduced overweight and all the other worst findings, especially NAFLD. In conclusion, the swimming training can attenuate the morbid effects of a high-fat diet combined with sedentary lifestyle in mice. These data reinforce the notion that swimming exercise can be considered an efficient nonpharmacologic therapy in the treatment of NAFLD, obesity and insulin resistance.

Comparative effects of telmisartan, sitagliptin and metformin alone or in combination on obesity, insulin resistance, and liver and pancreas remodelling in C57BL/6 mice fed on a very high-fat diet

The aim of the present study was to evaluate the effects of monotherapies and combinations of drugs on insulin sensitivity, adipose tissue morphology, and pancreatic and hepatic remodelling in C57BL/6 mice fed on a very HF (high-fat) diet. Male C57BL/6 mice were fed on an HF (60% lipids) diet or SC (standard chow; 10% lipids) diet for 10 weeks, after which time the following drug treatments began: HF-T (HF diet treated with telmisartan; 5.2 mg x kg-1 of body weight x day-1), HF-S (HF diet treated with sitagliptin; 1.08 g x kg-1 of body weight.day-1), HF-M (HF diet treated with metformin; 310.0 mg x kg-1 of body weight x day-1), HF-TM (HF diet treated with telmisartan+metformin), HF-TS (HF diet treated with telmisartan+sitagliptin) and HF-SM (HF diet treated with sitagliptin+metformin). Treated groups also had free access to the HF diet, and treatments lasted for 6 weeks. Morphometry, stereological tools, immunostaining, ELISA, Western blot analysis and electron microscopy were used. The HF diet yielded an overweight phenotype, an increase in oral glucose intolerance, hyperinsulinaemia, hypertrophied islets and adipocytes, stage 2 steatosis (>33%), and reduced liver PPAR-alpha (peroxisome-proliferator-activated receptor-alpha) and GLUT-2 (glucose transporter-2) levels, concomitant with enhanced SREBP-1 (sterol-regulatory-element-binding protein-1) expression (P<0.0001). Conversely, all drug treatments resulted in significant weight loss, a reversal of insulin resistance, islet and adipocyte hypertrophy, and alleviated hepatic steatosis. Only the HF-T and HF-TS groups had body weights similar to the SC group at the end of the experiment, and the latter treatment reversed hepatic steatosis. Increased PPAR-alpha immunostaining in parallel with higher GLUT-2 and reduced SREBP-1 expression may explain the favourable hepatic outcomes. Restoration of adipocyte size was consistent with higher adiponectin levels and lower TNF-alpha (tumour necrosis factor-alpha) levels (P<0.0001) in the drug-treated groups. In conclusion, all of the drug treatments were effective in controlling the metabolic syndrome. The best results were achieved using telmisartan and sitagliptin as monotherapies or as a dual treatment, combining partial PPAR-gamma agonism and PPAR-alpha activation in the liver with extended incretin action.

Adipose tissue, liver and pancreas structural alterations in C57BL/6 mice fed high-fat-high-sucrose diet supplemented with fish oil (n-3 fatty acid rich oil)

Fish oil treatment was used in reversing the morphological and metabolic changes of C57BL/6 mice fed high-fat-high-sucrose (HFHS) diet. Two-month-old male C57BL/6 mice were fed HFHS chow or standard chow (SC). At 3 months of age, HFHS mice were separated into an untreated group (HFHS) and a group treated with fish oil (HFHS-Fo, 1.5g/kg/day). At 4 months of age, HFHS fed mice had an increase in body mass (BM) and total body fat, when the animals were sacrificed. Both parameters were lower in HFHS-Fo than in HFHS mice. Plasma glucose and insulin levels were not affected among the groups, but HFHS and HFHS-Fo animals had higher homeostasis model assessment for insulin resistance HOMA-IR ratio. HFHS and HFHS-FO mice had increased plasma total cholesterol and LDL-C, HFHS-Fo increased plasma HDL-C and decreased triglycerides levels. The liver mass (LM) and the adipocytes' size were larger in HFHS mice, while HFHS-Fo mice had a lower LM and smaller adipocytes. The liver steatosis and hepatocyte binucleation were increased in HFHS mice, while HFHS-Fo mice had reduced liver steatosis and hepatocyte binucleation. HFHS-Fo mice had a lower pancreas mass, while HFHS animals had higher islet pancreatic diameter. The SC group showed strong expression for insulin, glucagon and a glucose transporter type 2 GLUT-2 in all pancreatic islets, while in HFHS mice there was less expression for GLUT-2. However, HFHS-Fo mice showed an increase of GLUT-2 expression. In conclusion, dietary fish oil treatment reduces body mass and fat pad adiposity, and also by reducing plasma TG and pancreatic islet hypertrophy in mice fed high-fat-high-sucrose diet. Furthermore, fish oil improves glucagon and GLUT-2 expressions when it is decreased in insulin, but in hepatocyte binucleation and hepatic steatosis where the effect is reduced.

Hepatic stereology of Schistosomiasis mansoni infected-mice fed a high-fat diet

High-fat diets induce weight gain and fatty liver in wild-type mice. Schistosomiasis mansoni infection also promotes hepatic injury. This study was designed to quantify hepatic alterations in schistosomiasis mansoni-infected mice fed a high fat-rich chow compared to mice fed a standard rodent chow, using stereology. Female SW mice fed each either high-fat diet (29% lipids) or standard chow (12% lipids) over 8 months, and then were infected with Schistosoma mansoni cercariae. Four experimental groups were studied: infected mice fed a high-fat diet (IHFC) or standard chow (ISC), uninfected mice fed a high-fat diet (HFC) or standard chow (SC). Mice were sacrificed during early infection (9 weeks from exposure). The following hepatic biometry and the stereology parameters were determined: volume density (hepatocytes [h], sinusoids [s], steatosis [st] and hepatic fibrosis [hf]); numerical density (hepatocyte nuclei - Nv[h]); absolute number of total hepatocyte N[h], normal hepatocyte N[nh], and binucleated hepatocyte N[bh], percentage of normal hepatocyte P[nh] and binucleated hepatocyte P[bh]. IHFC and HFC groups exhibited TC, HDL-C, LDL-C, and body mass significantly greater (p < 0.05) than control group. No significant differences were found regards liver volume (p = 0.07). Significant differences were observed regards P[nh] (p = 0.0045), P[bh] (p = 0.0045), Nv[h] (p = 0.0006), N[h] (p = 0.0125), N[bh] (p = 0.0164) and N[nh] (p = 0.0078). IHFC mice group presented 29% of binucleated hepatocytes compared to HFC group (19%), ISC group (17%) and SC (6%). Volume density was significantly different between groups: Vv[h] (p = 0.0052), Vv[s] (p = 0.0025), Vv[st] (p = 0.0004), and Vv[hf] (p = 0.0007). In conclusion, schistosomiasis mansoni infection with concurrent high-fat diet promotes intensive quantitative changes in hepatic structure, contributing to an increasing on hepatic regeneration.

Hepatic structural alteration in adult programmed offspring (severe maternal protein restriction) is aggravated by post-weaning high-fat diet

The present study aimed to evaluate the effects of a post-weaning high-fat (HF) diet upon hepatic morphology in rats subjected to perinatal protein restriction. Pregnant Wistar rats were assigned to a normal-protein diet (NP; with 19 % of protein) or a low-protein (LP) diet (with 5 % of protein). At weaning, the following groups were formed: NP and NP-HF, males and females, which were fed standard chow and an HF diet, respectively. Likewise, LP rat dams originated LP and LP-HF offspring, both sexes. Euthanasia was performed at 6 months of age. Three-way ANOVA disclosed a three-factor interaction among sex, perinatal diet and HF diet in relation to body mass, retroperitoneal fat pad, liver mass:tibia length ratio, binucleation rate and hepatocyte area at 6 months old (P < 0·05). The high-fat diet intensified the effects of perinatal protein restriction concerning systolic blood pressure, genital fat pad and hepatocyte number (P < 0·05; two-way ANOVA). Furthermore, higher steatosis rates and insulin and leptin concentrations were found in males fed on the HF diet, indicating a sex–post-weaning diet interaction (P < 0·05; two-way ANOVA). Fetal programming and HF diet as a single stimulus caused mild hypertension at 3 months, an important reduction in hepatocyte number as well as stage 1 steatosis at 6 months. However, hypertension and hepatocyte number deficit were worsened and grade 2 steatosis occurred after exposure to the HF diet. All of these serve to highlight the paramount importance of intra-uterine conditions and postnatal diet quality when it comes to the pathogenesis of chronic diseases.

Long-term feeding a high-fat diet causes histological and parasitological effects on murine schistosomiasis mansoni outcome

This study investigated whether long-term feeding a high-fat diet (HFC) has an effect on schistosomiasis mansoni outcome compared to standard chow diet (SC). Swiss Webster female mice (3 wk old) fed each diet over 5 months, and then were infected with 50 Schistosoma mansoni cercariae. Their nutritional status was assessed by monitoring growth rates twice a week and measuring serum levels of lipoproteins. Mice were euthanised 63 days after infection. Parasitological and liver histological analyses were performed. The levels of TC, HDL-C and LDL-C, fecal and tissue schistosome eggs were statistically different (p<0.05) between groups. Livers from HFC mice showed exudative, exudative/exudative-productive, exudative-productive and productive granulomas, some degree of hepatic steatosis and focal necrosis. Mice fed normal-chow did not present productive granulomas and hepatic steatosis. The morphometric evaluation of hepatic granulomas did not reach statistical significance (p>0.05) between diets assayed. The high-fat diet for long-term produces effects on schistosomiasis mansoni outcome.

Postprandial glycogen and lipid synthesis in prednisolone-treated rats maintained on high-protein diets with varied carbohydrate levels

OBJECTIVE

The present experiment was designed to study the effect of a high-protein, high-carbohydrate diet versus a high-protein, low-carbohydrate diet on in vivo postprandial glycogen and lipid synthesis of rats treated with prednisolone.

METHODS

Thirty-two 6-wk-old male Sprague-Dawley rats were randomly assigned to one of four equal groups: high-protein, high-carbohydrate; high-protein, high-carbohydrate with prednisolone; high-protein, low-carbohydrate; and high-protein, low-carbohydrate with prednisolone. Rats were sham operated or subcutaneously implanted with prednisolone pellets while being maintained on their respective diets (39% of energy from protein) for 6 wk. Food intake and body weight were monitored throughout the experiment. At the end of the feeding period, overnight-fasted rats were fed a test meal and injected with 3H2O to measure in vivo rates of glycogen and lipid synthesis. Final plasma glucose, insulin, and triacylglycerol concentrations and hepatic glycogen content were also measured.

RESULTS

Results showed that hepatic glycogen content (milligrams per gram of liver) was similar across all four experimental groups. Total hepatic glycogen synthesis and its percentage synthesis via pyruvate (indirect pathway) were higher in rats maintained on the high-protein, high-carbohydrate diet compared with those on the high-protein, low-carbohydrate diet and this was not substantially affected by prednisolone administration. Hepatic and epididymal fat pad lipid syntheses were not altered by diet or prednisolone treatments.

CONCLUSION

Under long-term high-protein conditions, prednisolone administration does not seem to affect hepatic glycogen synthesis, which was increased with the increased carbohydrate content of the diet.