High-fat diet causes an imbalance in the colonic serotonergic system promoting adipose tissue enlargement and dysplasia in rats

A high-fat (HF) diet, the serotonergic system and stromal elements have all been implicated in colon carcinogenesis. We investigated whether the colonic serotonergic system could play a main role in the development of colonic dysplasia and stromal reactivity in carcinogen-treated rats under HF diet. For this, dimethylhydrazine-treated rats were fed with standard diet and a HF diet. Fat distribution was quantified by computerized tomography exam, serotonergic activity was analyzed by high-performance liquid chromatography, gene expression, and immunohistochemistry, which along with histopathological technique enabled us to enumerate dysplasia, microvessels density, cell proliferation and COX-2 expression. We found that the HF diet induced an increase in the amount of viscera! adipose tissue, even without expressive changes in the average body weight. This was correlated with a loss of serotonergic balance in colon tissue. Moreover, the HF diet promoted dysplasia and microvessel density in association with increased proliferation and COX-2 expression within pericryptal colonic stroma. Our current findings suggest that a HF diet promotes the enlargement of adipose tissue via loss of control in colon serotonergic activity, which enhances colonic dysplasia by supporting microvessel development. (C) 2012 Elsevier Ireland Ltd. All rights reserved.

High-Fat Diet Obesity Associated With Insulin Resistance Increases Cell Proliferation, Estrogen Receptor, and PI3K Proteins in Rat Ventral Prostate

In this study, we evaluated the effects of obesity and insulin resistance induced by a high-fat diet on prostate morphophysiology, focusing on cell proliferation, expression of androgen (AR) and estrogen receptors (ER) and proteins of the insulin signaling pathway. Adult male Wistar rats were fed a high-fat diet (20% fat) for 15 weeks, whereas control animals received a balanced diet (4% fat). Both groups were then divided and treated for 2 weeks with 1 mg/kg body weight/day of the aromatase inhibitor letrozole or vehicle only. The ventral prostate was analyzed with immunohistochemical, histopathological, stereological, and Western blotting methods. Obese rats showed insulin resistance, hyperinsulinemia, and reduced plasma testosterone levels. The incidence of prostatic intraepithelial neoplasia (PIN) was 2.7 times higher in obese rats and affected 0.4% of the gland compared with 0.1% PIN areas found in control rats. Obesity doubled cell proliferation in both prostate epithelium and stroma. AR content decreased in the prostate of obese rats and estrogen receptor beta (ER beta) increased in this group. Protein levels of insulin receptor substrate 1 and protein kinase B diminished in the obese group, whereas phosphatidylinositol 3-kinase (PI3K) increased significantly. Most structural changes observed in the prostate of obese rats normalized after letrozole treatment, except for increased stromal cell proliferation and ER beta expression, which might be associated with insulin resistance. This experimental model of obesity and insulin resistance induced by a high-fat diet increases cell proliferation in rat prostate. Such alterations are associated with decreased levels of AR and increased ER beta and PI3K proteins. This change can facilitate the establishment of proliferative lesions in rat prostate.

Time sequence of the intensification of the liver glucose production induced by high-fat diet in mice

It is well established that the development of insulin resistance shows a temporal sequence in different organs and tissues. Moreover, considering that the main aspect of insulin resistance in liver is a process of glucose overproduction from gluconeogenesis, we investigated if this metabolic change also shows temporal sequence. For this purpose, a well-established experimental model of insulin resistance induced by high-fat diet (HFD) was used. The mice received HFD (HFD group) or standard diet (COG group) for 1, 7, 14 or 56?days. The HFD group showed increased (P?<?0.05 versus COG) epididymal, retroperitoneal and inguinal fat weight from days 1 to 56. In agreement with these results, the HFD group also showed higher body weight (P?<?0.05 versus COG) from days 7 to 56. Moreover, the changes induced by HFD on liver gluconeogenesis were progressive because the increment (P?<?0.05 versus COG) in glucose production from l-lactate, glycerol, l-alanine and l-glutamine occurred 7, 14, 56 and 56 days after the introduction of the HFD schedule, respectively. Furthermore, glycaemia and cholesterolemia increased (P?<?0.05 versus COG) 14?days after starting the HFD schedule. Taken together, the results suggest that the intensification of liver gluconeogenesis induced by an HFD is not a synchronous all-or-nothing process but is specific for each gluconeogenic substrate and is integrated in a temporal manner with the progressive augmentation of fasting glycaemia. Copyright (c) 2012 John Wiley & Sons, Ltd.

Caffeic acid phenethyl ester reduces the activation of the nuclear factor kappa B pathway by high-fat diet-induced obesity in mice

Objective. The aim of this study was to investigate the effect of CAPE on the insulin signaling and inflammatory pathway in the liver of mice with high fat diet induced obesity. Material/Methods. Swiss mice were fed with standard chow or high-fat diet for 12-week. After the eighth week, animals in the HFD group with serum glucose levels higher than 200 mg/dL were divided into two groups, HFD and HFD receiving 30 mg/kg of CAPE for 4 weeks. After 12 weeks, the blood samples could be collected and liver tissue extracted for hormonal and biochemical measurements, and insulin signaling and inflammatory pathway analyzes. Results. The high-fat diet group exhibited more weight gain, glucose intolerance, and hepatic steatosis compared with standard diet group. The CAPE treatment showed improvement in glucose sensitivity characterized by an area under glucose curve similar to the control group in an oral glucose tolerance test Furthermore, CAPE treatment promoted amelioration in hepatic steatosis compared with the high-fat diet group. The increase in glucose sensitivity was associated with the improvement in insulin-stimulated phosphorylation of the insulin receptor substrate-2, followed by an increase in Akt phosphorylation. In addition, it was observed that CAPE reduced the induction of the inflammatory pathway, c-jun-N- terminal kinase, the nuclear factor kappa B, and cyclooxygenase-2 expression, respectively. Conclusions. Overall, these findings indicate that CAPE exhibited anti-inflammatory activity that partly restores normal metabolism, reduces the molecular changes observed in obesity and insulin resistance, and therefore has a potential as a therapeutic agent in obesity. (C) 2012 Elsevier Inc. All rights reserved.

Exercise and caloric restriction alter the immune system of mice submitted to a high-fat diet

As the size of adipocytes increases during obesity, the establishment of resident immune cells in adipose tissue becomes an important source of proinflammatory mediators. Exercise and caloric restriction are two important, nonpharmacological tools against body mass increase. To date, their effects on the immune cells of adipose tissue in obese organisms, specifically when a high-fat diet is consumed, have been poorly investigated. Thus, after consuming a high-fat diet, mice were submitted to chronic swimming training or a 30% caloric restriction in order to investigate the effects of both interventions on resident immune cells in adipose tissue. These strategies were able to reduce body mass and resulted in changes in the number of resident immune cells in the adipose tissue and levels of cytokines/chemokines in serum. While exercise increased the number of NK cells in adipose tissue and serum levels of IL-6 and RANTES, caloric restriction increased the CD4+/CD8+ cell ratio and MCP-1 levels. Together, these data demonstrated that exercise and caloric restriction modulate resident immune cells in adipose tissues differently in spite of an equivalent body weight reduction. Additionally, the results also reinforce the idea that a combination of both strategies is better than either individually for combating obesity

Metformin attenuates the exacerbation of the allergic eosinophilic inflammation in high fat-diet-induced obesity in mice

A positive relationship between obesity and asthma has been well documented. The AMP-activated protein kinase (AMPK) activator metformin reverses obesity-associated insulin resistance (IR) and inhibits different types of inflammatory responses. This study aimed to evaluate the effects of metformin on the exacerbation of allergic eosinophilic inflammation in obese mice. Male C57BL6/J mice were fed for 10 weeks with high-fat diet (HFD) to induce obesity. The cell infiltration and inflammatory markers in bronchoalveolar lavage (BAL) fluid and lung tissue were evaluated at 48 h after ovalbumin (OVA) challenge. HFD obese mice displayed peripheral IR that was fully reversed by metformin (300 mg/kg/day, two weeks). OVA-challenge resulted in higher influx of total cell and eosinophils in lung tissue of obese mice compared with lean group. As opposed, the cell number in BAL fluid of obese mice was reduced compared with lean group. Metformin significantly reduced the tissue eosinophil infiltration and prevented the reduction of cell counts in BAL fluid. In obese mice, greater levels of eotaxin, TNF-α and NOx, together with increased iNOS protein expression were observed, all of which were normalized by metformin. In addition, metformin nearly abrogated the binding of NF-κB subunit p65 to the iNOS promoter gene in lung tissue of obese mice. Lower levels of phosphorylated AMPK and its downstream target acetyl CoA carboxylase (ACC) were found in lung tissue of obese mice, which were restored by metformin. In separate experiments, the selective iNOS inhibitor aminoguanidine (20 mg/kg, 3 weeks) and the anti-TNF-α mAb (2 mg/kg) significantly attenuated the aggravation of eosinophilic inflammation in obese mice. In conclusion, metformin inhibits the TNF-α-induced inflammatory signaling and NF-κB-mediated iNOS expression in lung tissue of obese mice. Metformin may be a good pharmacological strategy to control the asthma exacerbation in obese individuals.

A new model of interactive effects of alcohol and high-fat diet on hepatic fibrosis

Alcoholic steatohepatitis (ASH) and nonalcoholic steatohepatitis (NASH) are the most frequent conditions leading to elevated liver enzymes and liver cirrhosis, respectively, in the Western world. However, despite strong epidemiological evidence for combined effects on the progression of liver injury, the mutual interaction of the pathophysiological mechanisms is incompletely understood. The aim of this study was to establish and analyze an experimental murine model, where we combined chronic alcohol administration with a NASH-inducing high-fat (HF) diet.

Increased myocardial susceptibility to repetitive ischemia with high-fat diet-induced obesity.

Obesity and diabetes are frequently associated with cardiovascular disease. When a normal heart is subjected to brief/sublethal repetitive ischemia and reperfusion (I/R), adaptive responses are activated to preserve cardiac structure and function. These responses include but are not limited to alterations in cardiac metabolism, reduced calcium responsiveness, and induction of antioxidant enzymes. In a model of ischemic cardiomyopathy inducible by brief repetitive I/R, we hypothesized that dysregulation of these adaptive responses in diet-induced obese (DIO) mice would contribute to enhanced myocardial injury. DIO C57BL/6J mice were subjected to 15 min of daily repetitive I/R while under short-acting anesthesia, a protocol that results in the development of fibrotic cardiomyopathy. Cardiac lipids and candidate gene expression were analyzed at 3 days, and histology at 5 days of repetitive I/R. Total free fatty acids (FFAs) in the cardiac extracts of DIO mice were significantly elevated, reflecting primarily the dietary fatty acid (FA) composition. Compared with lean controls, cardiac FA oxidation (FAO) capacity of DIO mice was significantly higher, concurrent with increased expression of FA metabolism gene transcripts. Following 15 min of daily repetitive I/R for 3 or 5 days, DIO mice exhibited increased susceptibility to I/R and, in contrast to lean mice, developed microinfarction, which was associated with an exaggerated inflammatory response. Repetitive I/R in DIO mice was associated with more profound significant downregulation of FA metabolism gene transcripts and elevated FFAs and triglycerides. Maladaptive metabolic changes of FA metabolism contribute to enhanced myocardial injury in diet-induced obesity.

Western diet, but not high fat diet, causes derangements of fatty acid metabolism and contractile dysfunction in the heart of Wistar rats.

Obesity and diabetes are associated with increased fatty acid availability in excess of muscle fatty acid oxidation capacity. This mismatch is implicated in the pathogenesis of cardiac contractile dysfunction and also in the development of skeletal-muscle insulin resistance. We tested the hypothesis that 'Western' and high fat diets differentially cause maladaptation of cardiac- and skeletal-muscle fatty acid oxidation, resulting in cardiac contractile dysfunction. Wistar rats were fed on low fat, 'Western' or high fat (10, 45 or 60% calories from fat respectively) diet for acute (1 day to 1 week), short (4-8 weeks), intermediate (16-24 weeks) or long (32-48 weeks) term. Oleate oxidation in heart muscle ex vivo increased with high fat diet at all time points investigated. In contrast, cardiac oleate oxidation increased with Western diet in the acute, short and intermediate term, but not in the long term. Consistent with fatty acid oxidation maladaptation, cardiac power decreased with long-term Western diet only. In contrast, soleus muscle oleate oxidation (ex vivo) increased only in the acute and short term with either Western or high fat feeding. Fatty acid-responsive genes, including PDHK4 (pyruvate dehydrogenase kinase 4) and CTE1 (cytosolic thioesterase 1), increased in heart and soleus muscle to a greater extent with feeding a high fat diet compared with a Western diet. In conclusion, we implicate inadequate induction of a cassette of fatty acid-responsive genes, and impaired activation of fatty acid oxidation, in the development of cardiac dysfunction with Western diet.

Acceleration of the PanIN Development in Mice Expressing Oncogenic K-Ras Due to a High Fat Diet

Obesity is postulated to be one of the major risk factors for pancreatic cancer, and recently it was indicated that an elevated body mass index (BMI correlates strongly with a decrease in patient survival. Despite the evident relationship, the molecular mechanisms involved are unclear. Oncogenic mutation of K-Ras is found early and is universal in pancreatic cancer. Extensive evidence indicates oncogenic K-Ras is not entirely active and it requires a triggering event to surpass the activity of Ras beyond the threshold necessary for a Ras-inflammation feed-forward loop. We hypothesize that high fat intake induces a persistent low level inflammatory response triggering increased K-Ras activity and that Cox-2 is essential for this inflammatory reaction. To determine this, LSL-K-Ras mice were crossed with Ela-CreER (Acinar-specific) or Pdx-1-Cre (Pancreas-specific) to “knock-in” oncogenic K-Ras. Additionally, these animals were crossed with Cox-2 conditional knockout mice to access the importance of Cox-2 in the inflammatory loop present. The mice were fed isocaloric diets containing 60% energy or 10% energy from fat. We found that a high fat diet increased K-Ras activity, PanIN formation, and fibrotic stroma significantly compared to a control diet. Genetic deletion of Cox-2 prevented high fat diet induced fibrosis and PanIN formation in oncogenic K-Ras expressing mice. Additionally, long term consumption of high fat diet, increased the progression of PanIN lesions leading to invasive cancer and decreased overall survival rate. These findings indicate that a high fat diet can stimulate the activation of oncogenic K-Ras and initiate an inflammatory feed forward loop requiring Cox-2 leading to inflammation, fibrosis, and PanINs. This mechanism could explain the relationship between a high fat diet and elevated risk for pancreatic cancer.

Effects of Dietary Fibre (Pectin) and/or Increased Protein (Casein or Pea) on Satiety, Body Weight, Adiposity and Caecal Fermentation in High Fat Diet-Induced Obese Rats

Funding: This work was funded by the Scottish Government Rural and Environment Science and Analytical Services Division. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

High fat diet-induced hyperglycemia: prevention by low level expression of a glucose transporter (GLUT4) minigene in transgenic mice.

High-fat intake leading to obesity contributes to the development of non-insulin-dependent diabetes mellitus (NIDDM, type 2). Similarly, mice fed a high-fat (safflower oil) diet develop defective glycemic control, hyperglycemia, and obesity. To assess the effect of a modest increase in the expression of GLUT4 (the insulin-responsive glucose transporter) on impaired glycemic control caused by fat feeding, transgenic mice harboring a GLUT4 minigene were fed a high-fat diet. Low-level tissue-specific (heart, skeletal muscle, and adipose tissue) expression of the GLUT4 minigene in transgenic mice prevented the impairment of glycemic control and accompanying hyperglycemia, but not obesity, caused by fat feeding. Thus, a small increase (< or = 2-fold) in the tissue level of GLUT4 prevents a primary symptom of the diabetic state in a mouse model, suggesting a possible target for intervention in the treatment of NIDDM.

White Adipose Tissue Re-growth after Partial Lipectomy in High Fat Diet Induced Obese Wistar Rats

The effects of partial removal of epididymal (EPI) and retroperitoneal (RET) adipose tissues (partial lipectomy) on the triacylglycerol deposition of high fat diet induced obese rats were analyzed, aiming to challenge the hypothesized body fat regulatory system. Male 28-day-old wistar rats received a diet enriched with peanuts, milk chocolate and sweet biscuits during the experimental period. At the 90th day of life, rats were submitted to either lipectomy (L) or sham surgery. After 7 or 30 days, RET, EPI, liver, brown adipose tissue (BAT), blood and carcass were obtained and analyzed. Seven days following surgery, liver lipogenesis rate and EPI relative weight were increased in L. After 30 days, L, RET and EPI presented increased lipogenesis, lipolysis and percentage of small area adipocytes. L rats also presented increased liver malic enzyme activity, BAT lipogenesis, and triacylglycerol and corticosterone serum levels. The partial removal of visceral fat pads affected the metabolism of high fat diet obese rats, which leads to excised tissue re-growth and possibly compensatory growth of non-excised depots at a later time.

Effect of inulin supplementation in male mice fed with high fat diet on biochemical profile and α-amylase gene expression

Purpose: To evaluate the preventive and therapeutic effects of inulin supplementation in Naval Medical Research Institute (NMRI) male mice fed with high fat diet. Methods: NMRI male mice (n = 36) were divided into three groups. Control (C1), obese (O1) and experimental mice (E1) were fed during 8 weeks as follows: C1 with normal rodent pellet, O1 with high fat diet, and E1 with high fat diet plus 20 % inulin. C2, O2, and E2 were fed as follows: C2 with normal rodent pellets for 12 weeks; O2 with high fat diet during 8 weeks and switched to normal rodent pellet during next 4 weeks; and E2 with high fat diet over a period of 8 weeks and switched to normal rodent pellet plus 20 % inulin for 4 weeks. Body weight, serum glucose, triglycerides, total cholesterol, high density lipoprotein (HDL), low density lipoprotein (LDL), and hepatic α-amylase gene expression were measured. Results: Groups receiving high fat diet showed higher weight (30.71 ± 0.66 g in O2, p < 0.001), nonfasting blood glucose levels (257.69 ± 5.10 mg/dl in O2, p < 0.001), TG (282.15 ± 1.83 mg/dl in O2, (p < 0.001)), and cholesterol levels (335.72 ± 2.23 mg/dl in O2, (p < 0.001)), compared with control. In C2 group, mean body weight was 25.71 ± 0.54 g, non-fasting blood level 161.54 ± 4.48 mg/dl, TG level 214.29 ± 5.54 mg/dl, and cholesterol level 164.29 ±4.57 mg/dl. Compared to obese group, mice receiving inulin showed lower blood glucose levels (223.10 ± 8.7 mg/dl in E2, p < 0.001), body weight (27.86 ± 0.57 g in E2, p < 0.001), TG (232.14 ± 4.02 mg/dl in E2, p < 0.001) and cholesterol (249.97 ± 2.28 in E2, p < 0.001). A slight decrease in hepatic α-amylase gene expression was observed only in E1. Conclusion: Besides its sweetening properties, inulin may also find use as a potential anti-obesity compound.

In vitro antioxidative activity of moss extract, and effect of moss on serum lipid level of mice fed with high-fat diet

Purpose: To evaluate the potential of active compounds derived from moss in the prevention and treatment of various diseases. Methods: Three species of moss were extracted with deionized water at 95 °C, and with 70.5 % ethanol at 85 °C. Analysis of total phenolic contents (TPC) of the extracts were performed by FolinCiocalteu (FC) method. The antioxidant activity of the extracts were determined using three methods, namely, by 2,2\'-azino-bis(3-ethylbenzothiazoline-6-sulphonic) acid (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP). In vivo effects were evaluated in mice fed high fat diet (HFD) supplemented with 20 % ground moss. Cholesterol levels in HFD were evaluated by ophthalaldehyde method. Serum triglyceride levels were measured using triglyceride (TG) kit, while blood insulin level and leptin concentration were measured by enzyme-linked immunosorbent assay (ELISA) kit. Results: The moss extracts exhibited antioxidative effects, as evidenced of . TPC of 47.20 ± 11.20 to 119.87 ± 11.51 mg GAE/mg, respectively. ABTS scavenging activity was 1078.11 ± 18.95 to 2587.33 ± 46.19 μmol Trolox/mg, DPPH scavenging activity of were 42.11 ± 8.22 to 298.78 ± 20.02 μmol Trolox/mg, and FRAP value of 393.19 ± 24.64 to 1070.14 ± 17.92 μmol Trolox/mg, respectively. Mice fed with 20 % ground moss did not show any significant effect (p < 0.05) on visceral weight and blood lipid levels of HFD, while leptin concentrations reduced significantly to 4.74 ± 0.00 and 0.20 ± 0.00 ng/dL) relative to HFD alone (26.72 ± 6.53 ng/dL). Conclusion: Moss can potentially be used as an antioxidative ingredient, for the improvement of overall human health, suggesting that important medical benefits associated with moss consumption. However, further investigations are required to ascertain this.