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)

Differential effects of fish-oil and cocoa-butter based high-fat/high-sucrose diets on endocrine pancreas morphology and function in mice

Introduction

A high-fat/high-sucrose diet leads to adverse metabolic changes that affect insulin sensitivity, function, and secretion. The source of fat in the diet might inhibit or increase this adverse effect. Fish oil and cocoa butter are a significant part of our diets. Yet comparisons of these commonly used fat sources with high sucrose on pancreas morphology and function are not made. This study investigated the comparative effects of a fish oil-based high-fat/high-sucrose diet (Fish-HFDS) versus a cocoa butter-based high-fat/high-sucrose diet (Cocoa-HFDS) on endocrine pancreas morphology and function in mice.

Methods

C57BL/6 male mice (n=12) were randomly assigned to dietary intervention either Fish-HFDS (n=6) or Cocoa-HFDS (n=6) for 22 weeks. Intraperitoneal glucose and insulin tolerance tests (IP-GTT and IP-ITT) were performed after 20-21 weeks of dietary intervention. Plasma concentrations of c-peptide, insulin, glucagon, GLP-1, and leptin were measured by Milliplex kit. Pancreatic tissues were collected for immunohistochemistry to measure islet number and composition. Tissues were multi-labelled with antibodies against insulin and glucagon, also including expression on Pdx1-positive cells.

Results and discussion

Fish-HFDS-fed mice showed significantly reduced food intake and body weight gain compared to Cocoa-HFDS-fed mice. Fish-HFDS group had lower fasting blood glucose concentration and area under the curve (AUC) for both GTT and ITT. Plasma c-peptide, insulin, glucagon, and GLP-1 concentrations were increased in the Fish-HFDS group. Interestingly, mice fed the Fish-HFDS diet displayed higher plasma leptin concentration. Histochemical analysis revealed a significant increase in endocrine pancreas β-cells and islet numbers in mice fed Fish-HFDS compared to the Cocoa-HFDS group. Taken together, these findings suggest that in a high-fat/high-sucrose dietary setting, the source of the fat, especially fish oil, can ameliorate the effect of sucrose on glucose homeostasis and endocrine pancreas morphology and function.

Pathophysiological Mechanisms and Clinical Associations of Non-Alcoholic Fatty Pancreas Disease

Non-Alcoholic Fatty Pancreas disease (NAFPD), characterized by fat accumulation in pancreatic tissue, is an emerging clinical entity. However, the clinical associations, the underlying molecular drivers, and the pathophysiological mechanisms of NAFPD have not yet been characterized in detail. The NAFPD spectrum not only includes infiltration and accumulation of fat within and between pancreatic cells but also involves several inflammatory processes, dysregulation of physiological metabolic pathways, and hormonal defects. A deeper understanding of the underlying molecular mechanisms is key to correlate NAFPD with clinical entities including non-alcoholic fatty liver disease, metabolic syndrome, diabetes mellitus, atherosclerosis, as well as pancreatic cancer and pancreatitis. The aim of this review is to examine the pathophysiological mechanisms of NAFPD and to assess the possible causative/predictive risk factors of NAFPD-related clinical syndromes.

Capybara Oil Improves Renal Pathophysiology and Inflammation in Obese Mice

Obesity is an inflammatory disease associated with secondary diseases such as kidney disease, which can cause lipotoxicity, inflammation and loss of organ function. Polyunsaturated fatty acids act in the production of lipid mediators and have anti-inflammatory characteristics. In this work, the objective was to evaluate renal histopathology in obese mice and the effects of treatment with capybara oil (CO) (5000 mg/kg/day for 4 weeks). Parameters such as body mass, lipid profile, systolic blood pressure, urinary creatinine and protein excretion, structure and ultrastructure of the renal cortex, fibrosis, tissue inflammation and oxidative stress were analyzed. CO treatment in obese mice showed improvement in the lipid profile and reduction in systolic blood pressure levels, in addition to beneficial remodeling of the renal cortex. Our data demonstrated that CO decreased inflammation, oxidative stress and renal fibrosis, as evidenced by quantifying the expression of TNF-α, IL-10, CAT, SOD, α-SMA and TGF-β. Although treatment with CO did not show improvement in renal function, ultrastructural analysis showed that the treatment was effective in restoring podocytes and pedicels, with restructuring of the glomerular filtration barrier. These results demonstrate, for the first time, that treatment with CO is effective in reducing kidney damage, being considered a promising treatment for obesity.

Effects of dietary n-3 PUFA levels in early life on susceptibility to high-fat-diet-induced metabolic syndrome in adult mice

The maternal nutritional status during pregnancy and lactation was closely related to the growth and development of the fetus and infants, which had a profound impact on the health of the offspring. N-3 polyunsaturated fatty acid (PUFA) had been proved to have beneficial effects on glucolipid metabolism. However, the effects of dietary different n-3 PUFA levels for mother during pregnancy and lactation on susceptibility to high-fat-diet-induced metabolic syndrome for offspring in adulthood are still unclear. The maternal mice were fed with control, n-3 PUFA-deficient or fish oil-contained n-3 PUFA-rich diets during pregnancy and lactation, and the weaned offspring were fed with high-fat or low-fat diet for 13 weeks, then were subjected to oral glucose tolerance tests. The results showed that dietary n-3 PUFA-deficiency in early life could aggravate the high-fat-diet-induced glucolipid metabolism disorders, including glucose intolerance, insulin resistance, obesity, and dyslipidemia, thus increased the susceptibility to metabolic syndrome of adult mice. Notably, nutritional supplementation with n-3 PUFA in early life could significantly alleviate the glucose metabolism disorders by increasing insulin sensitivity, inhibiting gluconeogenesis and promoting glycogenesis. In addition, administration with n-3 PUFA in early life remarkably reduced serum and hepatic lipid profiles by mediating the expression of genes related to lipogenesis and β-oxidation of fatty acids. Dietary n-3 PUFA-deficiency in early life increases the susceptibility to metabolic syndrome of adult offspring, and nutritional supplementation with n-3 PUFA enhances the tolerance to a high-fat diet of adult offspring.

Alcohol Intoxication and the Postburn Gastrointestinal Hormonal Response

Gastrointestinal hormones are essential in postburn metabolism. Since near 50% of burn victims test positive for blood alcohol levels at hospital admission and have inferior outcomes compared to nonintoxicated burn patients; we hypothesized that the gastrointestinal hormone secretion is compromised in intoxicated burn victims. To test our theory, we quantified gastrointestinal hormones serum levels in a combine ethanol intoxication and burn injury mouse model. Thus, mice received a daily dose of ethanol for 3 days, rested 4 days, and were given ethanol 3 additional days. Mice underwent 15% TBSA scald burn 30 minutes after their last ethanol dose. Serum samples were collected 24 hours after burn injury. Nonintoxicated burned mice exhibited an increase in glucose, insulin, ghrelin, plasminogen activator inhibitor-1, leptin, and resistin by 1.4-, 3-, 13.5-, 6.2-, 9.4-, and 2.4-fold, respectively, compared to sham vehicle mice (P < .05). Burn injury also reduced serum gastric inhibitory polypeptide (GIP) by 32% compared to sham-injured, vehicle-treated mice. Leptin, resistin, glucagon-like peptide-1, as well as insulin, were not different from sham groups when intoxication preceded burn injury. Nevertheless, in burned mice treated with ethanol, gastric inhibitory polypeptide and glucagon serum levels exhibited a significant fold increase of 3.5 and 4.7, respectively. With these results, we conclude that 24 hours after burn injury, mice developed significant changes in gastrointestinal hormones, along with hyperglycemia. Moreover, the combined insult of burn and ethanol intoxication led to additional hormonal changes that may be attributed to a potential pancreatic dysfunction. Further multiday studies are required to investigate the etiology, behavior, and clinical significance of these hormonal changes.

Hesperidin ameliorates signs of the metabolic syndrome and cardiac dysfunction via IRS/Akt/GLUT4 signaling pathway in a rat model of diet-induced metabolic syndrome

BACKGROUND

Hesperidin has been reported to have biological activities such as antihypertensive, hypoglycemic, and antioxidant effects. This study investigated whether hesperidin could improve signs of the metabolic syndrome and cardiac function in a high-fat diet (HFD) induced metabolic syndrome (MS) in rats.

METHODS

Male Sprague-Dawley rats were fed HFD and 15% fructose for 16 weeks and treated with hesperidin (15 or 30 mg/kg, based on signs of MS from a preliminary study) or metformin, a positive control agent, (100 mg/kg) for the final four weeks. Cardiac function, blood pressure, fasting blood glucose, oral glucose tolerance, serum insulin, and lipid profiles were measured. Histomorphometrics of left ventricles, epidydimal fat pads and liver were evaluated. Expressions of phosphorylate insulin receptor substrate1(p-IRS1), p-Akt and GLUT4 in cardiac tissue were determined.

RESULTS

Hesperidin and metformin attenuated MS in HFD rats (p < 0.05). The accumulation of visceral fat pads and fatty liver associated with increases in liver lipid contents and liver enzymes were found in MS rats that were alleviated in hesperidin or metformin-treated groups (p < 0.05). Hesperidin and metformin improved cardiac dysfunction and hypertrophy observed in MS rats (p < 0.05). Restoration of the insulin signaling pathway, IRS/Akt/GLUT4 protein expression, was demonstrated in hesperidin and metformin-treated groups (p < 0.05). Hesperidin (30 mg/kg) was more effective than the lower dose.

CONCLUSION

Hesperidin was effective in reducing signs of MS and alterations of LV hypertrophy and function. These beneficial effects on the heart were associated with the restoration of the cardiac insulin signaling pathway in MS rats.

Maternal and Postnatal Supplementation of Fish Oil Improves Metabolic Health of Mouse Male Offspring

OBJECTIVE

Over half of American women of childbearing age have either obesity or overweight. Hence, maternal programming through diet is critical for prevention of diseases in the offspring. Clinical trials with fish oil (FO) report various health benefits; however, it remains unclear whether maternal and postnatal consumption of FO protects offspring from adverse effects of consuming a high-fat (HF) diet.

METHODS

Female mice were fed HF diets supplemented without (HF) or with FO from 8 weeks before pregnancy through lactation. A low-fat (LF) diet was included as a control diet. After weaning, male offspring from HF or FO dams were either continued on their respective diet (HF-HF and FO-FO) or switched to the other diet (HF-FO and FO-HF) and compared with LF. Phenotypic and mechanistic studies were performed.

RESULTS

FO-FO offspring demonstrated significantly higher glucose clearance and insulin sensitivity compared with other pups fed the HF diet (P < 0.05). Furthermore, FO-FO pups had lower adiposity, inflammation, and fat deposition in the liver, consistent with reduced markers of hepatic lipogenesis and increased hepatic lipid oxidation.

CONCLUSIONS

Supplementation of FO during pregnancy and early life is more beneficial than treating with FO either during pregnancy or in pups.

Capybara Oil Improves Hepatic Mitochondrial Dysfunction, Steatosis, and Inflammation in a Murine Model of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is recognized as the most common cause of liver dysfunction worldwide and is commonly associated with obesity. Evidences suggest that NAFLD might be a mitochondrial disease, which contributes to the hepatic steatosis, oxidative stress, cytokine release, and cell death. Capybara oil (CO) is a rich source of polyunsaturated fatty acids (PUFA), which is known to improve inflammation and oxidative stress. In order to determine the effects of CO on NAFLD, C57Bl/6 mice were divided into 3 groups and fed a high-fat diet (HFD) (NAFLD group and NAFLD + CO group) or a control diet (CG group) during 16 weeks. The CO (1.5 g/kg/daily) was administered by gavage during the last 4 weeks of the diet protocol. We evaluated plasma liver enzymes, hepatic steatosis, and cytokine expression in liver as well as hepatocyte ultrastructural morphology and mitochondrial function. CO treatment suppressed hepatic steatosis, attenuated inflammatory response, and decreased plasma alanine aminotransferase (ALT) in mice with NAFLD. CO was also capable of restoring mitochondrial ultrastructure and function as well as balance superoxide dismutase and catalase levels. Our findings indicate that CO treatment has positive effects on NAFLD improving mitochondrial dysfunction, steatosis, acute inflammation, and oxidative stress.

Modulation of the gut microbiota by the mixture of fish oil and krill oil in high-fat diet-induced obesity mice

Previous studies confirmed that dietary supplements of fish oil and krill oil can alleviate obesity in mice, but the underlying mechanism remains unclear. This study aims to discern whether oil treatment change the structure of the gut microbiota during the obesity alleviation. The ICR mice received high-fat diet (HFD) continuously for 12 weeks after two weeks of acclimatization with a standard chow diet, and the mice fed with a standard chow diet were used as the control. In the groups that received HFD with oil supplementation, the weight gains were attenuated and the liver index, total cholesterol, triglyceride and low-density lipoprotein cholesterol were reduced stepwise compared with the HFD group, and the overall structure of the gut microbiota, which was modulated in the HFD group, was shifted toward the structure found in the control group. Moreover, eighty-two altered operational taxonomic units responsive to oil treatment were identified and nineteen of them differing in one or more parameters associated with obesity. In conclusion, this study confirmed the effect of oil treatment on obesity alleviation, as well as on the microbiota structure alterations. We proposed that further researches are needed to elucidate the causal relationship between obesity alleviation and gut microbiota modulation.

Protective effects of fish oil and pioglitazone on pancreatic tissue in obese KK mice with type 2 diabetes

n-3 Polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have protective effects against the pancreatic β-cell dysfunction through several mechanisms. Thiazolidines are insulin sensitizers and are used in treating patients with type 2 diabetes. Our previous study demonstrated that a combination of fish oil, which is rich with EPA and DHA, and pioglitazone exerts beneficial effects on obesity and diabetes through their actions on the liver and adipose tissue. However, it remains largely unknown whether such combination therapy affects the pancreas. To answer this question, KK mice, which serve as a model for obesity and type 2 diabetes, were treated for 8 weeks with fish oil and pioglitazone. The combined regimen suppressed pancreatic islet hypertrophy (mean islet area decreased by an average of 49% vs. control) compared with mice treated with fish oil or pioglitazone alone (decreased by an average of 21% and 32% vs. control, respectively). Compared with the controls, individual or combined treatment significantly increased the percentage of β-cell area in the pancreatic islets, significantly decreased endoplasmic reticulum stress, and reduced the percentage of apoptotic cell death in the pancreatic islets. These findings suggest that fish oil and/or pioglitazone prevents β-cell dysfunction by improving the insulin resistance and decreasing the ER stress.

Olive oil-induced reduction of oxidative damage and inflammation promotes wound healing of pressure ulcers in mice

BACKGROUND

The overproduction of reactive oxygen species (ROS) and exacerbated inflammatory response are the main events that impair healing of pressure ulcers. Therefore, olive oil may be a good alternative to improve the healing of these chronic lesions due to its anti-inflammatory and antioxidant properties.

OBJECTIVE

This study investigated the effect of olive oil administration on wound healing of pressure ulcers in mice.

METHODS

Male Swiss mice were daily treated with olive oil or water until euthanasia. One day after the beginning of treatment, two cycles of ischemia-reperfusion by external application of two magnetic plates were performed in skin to induced pressure ulcer formation.

RESULTS

The olive oil administration accelerated ROS and nitric oxide (NO) synthesis and reduced oxidative damage in proteins and lipids when compared to water group. The inflammatory cell infiltration, gene tumor necrosis factor-α (TNF-α) expression and protein neutrophil elastase expression were reduced by olive oil administration when compared to water group. The re-epithelialization and blood vessel number were higher in the olive oil group than in the water group. The olive oil administration accelerated protein expression of TNF-α, active transforming growth factor-β1 and vascular endothelial growth factor-A when compared to water group. The collagen deposition, myofibroblastic differentiation and wound contraction were accelerated by olive oil administration when compared to water group.

CONCLUSION

Olive oil administration improves cutaneous wound healing of pressure ulcers in mice through the acceleration of the ROS and NO synthesis, which reduces oxidative damage and inflammation and promotes dermal reconstruction and wound closure.

Metabolic and testicular effects of the long-term administration of different high-fat diets in adult rats

Purpose:

To evaluate the effects of different high-fat diets on body mass, carbohydrate metabolism and testicular morphology in rats seven months old.

Materials and Methods:

Male Wistar rats were divided into four groups: SC (standard chow), HF-S (high fat diet rich in saturated fatty acids), HF-P (high fat diet rich in polyunsaturated fatty acids), HF-SP (high fat diet rich in saturated and polyunsaturated fatty acids). The rats were fed for 16 weeks. Blood samples, testes and genital fat deposits were collected for analysis. Data were analyzed by one-way ANOVA and Bonferroni post hoc test, considering p<0.05 as statistically significant.

Results:

Different high-fat diets promoted an increase in the body mass (p<0.0001). The genital fat deposits were higher in the high-fat groups (HF-S, HF-P, HF-SP) (p=0.0004). Regarding serum parameters, the animals in the HF-S and HF-SP groups presented hyperglycemia (p=0.0060), hyperinsulinemia (p=0.0030) and hypercholesterolemia (p=0.0021). All of the hyperlipidemic groups showed hyperleptinemia (p=0.0019). Concerning the testis, the HF-S group showed a reduction on the seminiferous epithelium height (p=0.0003) and cell proliferation (p=0.0450). Seminiferous tubule diameter was lower in the HF-SP than in the SC group (p=0.0010).

Conclusions:

The high fat diet administration, independent of the lipid quality, promotes overweight. Diet rich in saturated fatty acids (lard) alters the carbohydrate metabolism and the testicular morphology with reductions of seminiferous epithelium height, seminiferous tubule diameter and cell proliferation which could be related to a disturbance of spermatogenesis.

Supplementation with omega-3 fatty acids during gestation and lactation to a vitamin B12-deficient or -supplemented diet improves pregnancy outcome and metabolic variables in Wistar rats

Maternal vitamin B12 deficiency leads to an adverse pregnancy outcome and increases the risk for developing diabetes and metabolic syndrome in mothers in later life. Our earlier studies have demonstrated that vitamin B12 and n-3 polyunsaturated fatty acids (PUFA) are interlinked in the one carbon cycle. The present study for the first time examines the effect of maternal n-3 PUFA supplementation to vitamin B12 deficient or supplemented diets on pregnancy outcome, fatty-acid status and metabolic variables in Wistar rats. Pregnant dams were assigned to one of the following groups: control, vitamin B12 deficient, vitamin B12 supplemented, vitamin B12 deficient + n-3 PUFA or vitamin B12 supplemented + n-3 PUFA. The amount of vitamin B12 in the supplemented group was 0.50 μg kg–1 diet and n-3 PUFA was alpha linolenic acid (ALA) 1.68, eicosapentaenoic acid 5.64, docosahexaenoic acid (DHA) 3.15 (g per 100 g fatty acids per kg diet). Our findings indicate that maternal vitamin B12 supplementation did not affect the weight gain of dams during pregnancy but reduced litter size and weight and was ameliorated by n-3 PUFA supplementation. Vitamin B12 deficiency or supplementation resulted in a low percentage distribution of plasma arachidonic acid and DHA. n-3 PUFA supplementation to these diets improved the fatty-acid status. Vitamin B12 deficiency resulted in higher homocysteine and insulin levels, which were normalised by supplementation with either vitamin B12 or n-3 PUFA. Our study suggests that maternal vitamin B12 status is critical in determining pregnancy outcome and metabolic variables in dams and that supplementation with n-3 PUFA is beneficial.

Fish oil ameliorates trimethylamine N-oxide-exacerbated glucose intolerance in high-fat diet-fed mice

Dietary fish oil could ameliorate trimethylamineN-oxide (TMAO)-induced impaired glucose tolerance in HFD-fed mice.

Adverse association between obesity and menopause in mice treated with bezafibrate, a pan peroxisome proliferator-activated receptor agonist

OBJECTIVE

The goal of this study was to investigate the combined effects of ovariectomy (OVX) and high-fat diet (HF) on insulin sensitivity and pancreatic remodeling in C57BL/6 mice treated with bezafibrate.

METHODS

Female C57BL/6 mice were subjected to OVX or surgical procedure without removal of the ovary (SHAM). Animals received standard chow (SC; 10% lipids) or HF (60% lipids). After 13 weeks on the diets, the animals were subdivided into six groups based on diet, bezafibrate treatment, or both: SHAM-SC, SHAM-HF, SHAM-HFBz, OVX-SC, OVX-HF, and OVX-HFBz. After treatment for 5 weeks, the pancreas was removed and analyzed using morphometry, stereological tools, immunostaining, and multiplex assay kits.

RESULTS

SHAM-HF and OVX-HF mice showed increased fasting glucose levels, plasma insulin levels, homeostasis model of assessment for insulin resistance index, body mass, islet hypertrophy, β-cell mass, and insulin immunostaining, but decreased GLUT2 immunostaining. Bezafibrate treatment prevented islet hypertrophy and reduced body mass, plasma insulin levels, and homeostasis model of assessment for insulin resistance index.

CONCLUSIONS

OVX combined with HF accentuates the effects of menopause, leading to the development of insulin resistance. Bezafibrate treatment reduces body mass, plasma insulin levels, and pancreatic islet hypertrophy in mice fed HF.

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.

Long-term intake of rice improves insulin sensitivity in mice fed a high-fat diet

OBJECTIVE

The aim of this study was to evaluate the effects of rice as a carbohydrate source and its molecular mechanisms on insulin resistance induced by a high-fat diet (HFD).

METHODS

C57 BL/6 J mice were divided into three groups and were fed a low-fat diet (LFD); a HFD (with 18% fat, 0.5% cholesterol, 51.5% w/w cornstarch and sucrose); or a HFD with rice (HFD-CR, with 18% fat, 0.5% cholesterol and 51.5% w/w rice powder) for 12 wk. In the HFD-CR diet, cooked rice powder was substituted for cornstarch and sucrose in the HFD as a carbohydrate source.

RESULTS

HFD-CR-fed mice had significantly lower body weight, blood glucose, insulin and leptin levels and ameliorated glucose responses with decreased homeostasis model assessment-insulin resistance compared with HFD-fed mice. Hepatic mRNA levels of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase were down-regulated in the HFD-CR group. The hypertrophied islet size and the decreased pancreatic mRNA expression of glucose transporter 2 in the HFD group were normalized with cooked rice consumption. Rice promoted glucose uptake by activating AMP-activated protein kinase and downstream glucose transporter 4 in the skeletal muscle.

CONCLUSION

Rice consumption as a carbohydrate source might potentiate improvements in glucose uptake via AMP-activated protein kinase activation and glucose transporter 4 expression in the skeletal muscles, thereby improving insulin sensitivity.

Lipid-induced toxicity stimulates hepatocytes to release angiogenic microparticles that require Vanin-1 for uptake by endothelial cells

Angiogenesis is a key pathological feature of experimental and human steatohepatitis, a common chronic liver disease that is associated with obesity. We demonstrated that hepatocytes generated a type of membrane-bound vesicle, microparticles, in response to conditions that mimicked the lipid accumulation that occurs in the liver in some forms of steatohepatitis and that these microparticles promoted angiogenesis. When applied to an endothelial cell line, medium conditioned by murine hepatocytes or a human hepatocyte cell line exposed to saturated free fatty acids induced migration and tube formation, two processes required for angiogenesis. Medium from hepatocytes in which caspase 3 was inhibited or medium in which the microparticles were removed by ultracentrifugation lacked proangiogenic activity. Isolated hepatocyte-derived microparticles induced migration and tube formation of an endothelial cell line in vitro and angiogenesis in mice, processes that depended on internalization of microparticles. Microparticle internalization required the interaction of the ectoenzyme Vanin-1 (VNN1), an abundant surface protein on the microparticles, with lipid raft domains of endothelial cells. Large quantities of hepatocyte-derived microparticles were detected in the blood of mice with diet-induced steatohepatitis, and microparticle quantity correlated with disease severity. Genetic ablation of caspase 3 or RNA interference directed against VNN1 protected mice from steatohepatitis-induced pathological angiogenesis in the liver and resulted in a loss of the proangiogenic effects of microparticles. Our data identify hepatocyte-derived microparticles as critical signals that contribute to angiogenesis and liver damage in steatohepatitis and suggest a therapeutic target for this condition.

Dietary fish oil normalized glucose-stimulated insulin secretion in isolated pancreatic islets of dyslipemic rats through mechanisms involving glucose phosphorylation, peroxisome proliferator-activated receptor γ and uncoupling protein 2

This study evaluates some possible mechanisms behind the beneficial effects of dietary fish oil (FO) on β cell dysfunction in rats fed a sucrose-rich diet (SRD). Rats were fed a SRD for 6 months. Thereafter, half the rats received a SRD in which corn oil was partially replaced by FO up to 8 months. The other half continued consuming the SRD up to 8 months. A control group was fed a control diet throughout the experimental period. In isolated islets of SRD-fed rats dietary FO normalized the reduced glucose phosphorylation, the altered glucose oxidation, the triglyceride content, the increased protein mass levels of peroxisome proliferator-activated receptor γ (PPARγ) and uncoupling protein 2 without changes in GLUT2 and PPARα. These finding suggest that the changes mentioned above could be involved in the normalization of the altered glucose-stimulated insulin secretion pattern in this nutritional model of dyslipidemia and insulin resistance.

Fish oil supplementation for two generations increases insulin sensitivity in rats

We investigated the effect of fish oil supplementation for two consecutive generations on insulin sensitivity in rats. After the nursing period (21 days), female rats from the same prole were divided into two groups: (a) control group and (b) fish oil group. Female rats were supplemented with water (control) or fish oil at 1 g/kg body weight as a single bolus for 3 months. After this period, female rats were mated with male Wistar rats fed on a balanced chow diet (not supplemented). Female rats continued to receive supplementation throughout gestation and lactation periods. The same treatment was performed for the next two generations (G1 and G2). At 75 days of age, male offspring from G1 and G2 generations from both groups were used in the experiments. G1 rats did not present any difference with control rats. However, G2 rats presented reduction in glycemia and lipidemia and improvement in in vivo insulin sensitivity (model assessment of insulin resistance, insulin tolerance test) as well as in vitro insulin sensitivity in soleus muscle (glucose uptake and metabolism). This effect was associated with increased insulin-stimulated p38 MAP kinase phosphorylation and lower n-6/n-3 fatty acid ratio, but not with activation of proteins from insulin signaling (IR, IRS-1 and Akt). Global DNA methylation was decreased in liver but not in soleus muscle. These results suggest that long-term fish oil supplementation improves insulin sensitivity in association with increased insulin-stimulated p38 activation and decreased n-6:n-3 ratio in skeletal muscle and decreased global DNA methylation in liver.

The effect of cocoa, soy, oats and fish oil on metabolic syndrome in rats

BACKGROUND

The effect of functional foods alone or in combination (cocoa + soy + oats + fish oil) on hepatic damage in rats affected with metabolic syndrome was investigated.

RESULTS

Rats that were given cocoa showed a decrease in the levels of triglycerides (TGs) and glucose (63 and 32% respectively) as well as a decrease in blood pressure (15%). Animals fed with soy showed a reduction of 21% in total cholesterol, 15% in blood pressure and 44% in TGs, while feeding oats reduced the concentration of TGs by 53% (P < 0.5). Fish oil caused a reduction in TGs (56%) and glucose (26%). The effect on blood pressure was statistically significant for the groups supplemented with cocoa, soy, cocoa + oats and the total mix. The main finding was a reduction in liver steatosis in animals supplemented with cocoa + oats (from 30 to 4.7% steatosis). Cocoa or fish oil alone did not protect the liver from damage, while cocoa + fish oil did.

CONCLUSION

The most relevant effects were that the cocoa + oats mix decreased steatosis by a very large percentage, as did the cocoa + fish oil mix and the mix of all four functional foods.

Effects of high-fat diet on plasma lipids, adiposity, and inflammatory markers in ovariectomized C57BL/6 mice

OBJECTIVE

We hypothesized that a high-fat (HF) diet aggravates ovariectomy-related complications. To test this hypothesis, ovariectomized (OVX) mice were fed a HF diet, and we investigated the lipid metabolism, adipose tissue remodeling, adipokines, and inflammatory cytokines.

METHODS

To investigate the situation in a mouse model of ovariectomy, OVX and SHAM C57BL/6 mice fed a HF diet (60% fat) or standard chow (SC, 10% fat) were monitored for 18 wk. We evaluated daily food intake and weekly body weight. Mice were killed at 30 wk of age. Blood samples and adipose tissue were collected for biochemical, histologic, and molecular analysis.

RESULTS

OVX groups showed atrophied uterus compared to the SHAM groups, ensuring the success of surgically induced menopause. Despite lower food intake, OVX-HF mice gained about 52% more weight and had heavier total body fats, especially in relation to ovarian fat pad (372%)-a visceral fat which is associated with increased pathogenicity in obesity, and showed larger adipocytes (30%) when compared to OVX-SC mice. Biochemical analysis showed that the OVX-HF mice had increased levels of serum total cholesterol (51%), greater serum triglycerides (158%), lower serum adiponectin (40%), and higher plasma leptin (323%) than OVX-SC mice. The obese group (OVX-HF) also had higher IL-6 levels than both SHAM-HF (241%) and OVX-SC mice (870%).

CONCLUSION

OVX C57BL/6 mice fed HF diet had greater adipose fat pad, larger adipocytes, and increased inflammatory markers, reinforcing the idea that a HF diet aggravates the complications of ovariectomy-associated inflammation.

Ω3-Polyunsaturated fatty acids prevent lipoperoxidation, modulate antioxidant enzymes, and reduce lipid content but do not alter glycogen metabolism in the livers of diabetic rats fed on a high fat thermolyzed diet

Ω3-Polyunsaturated fatty acids (Ω3-PUFAs) are known to act as hypolipidaemics, but the literature is unclear about the effects that Ω3-PUFAs have on oxidative stress in obese and diabetic patients. In this study, our aim was to investigate the effects of Ω3-PUFAs on oxidative stress, including antioxidant enzyme activity and hepatic lipid and glycogen metabolism in the livers of diabetic and non-diabetic rats fed on a high fat thermolyzed diet. Rats were divided into six groups: (1) the control group (C), (2) the control diabetic group (D), (3) the high fat thermolyzed diet group (HFTD), which were fed a diet that was enriched in fat that was heated for 60 min at 180°C, (4) the high fat thermolyzed diet diabetic group (D + HFTD), (5) the high fat thermolyzed diet + Ω3 polyunsaturated fatty acid group (HFTD + Ω3), and (6) the high fat thermolyzed diet + Ω3 polyunsaturated fatty acid diabetic group (D + HFTD + Ω3). The most important finding of this study was that Ω3-PUFAs are able to reduce triglycerides, non-esterified fatty acid, lipoperoxidation levels, advanced glycation end products, SOD/CAT enzymatic ratio, and CAT immunocontent and increase SOD2 levels in the livers of diabetic rats fed with a HFTD. However, Ω3-PUFAs did not alter the observed levels of protein damage, blood glucose, or glycogen metabolism in the liver. These findings suggest that Ω3-PUFAs may represent an important auxiliary adjuvant in combating some diseases like diabetes mellitus, insulin resistance, and non-alcoholic fatty liver disease.

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.

Nonalcoholic Fatty liver disease: focus on lipoprotein and lipid deregulation

Obesity with associated comorbidities is currently a worldwide epidemic and among the most challenging health conditions in the 21st century. A major metabolic consequence of obesity is insulin resistance which underlies the pathogenesis of the metabolic syndrome. Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of obesity and metabolic syndrome. It comprises a disease spectrum ranging from simple steatosis (fatty liver), through nonalcoholic steatohepatitis (NASH) to fibrosis, and ultimately liver cirrhosis. Abnormality in lipid and lipoprotein metabolism accompanied by chronic inflammation is the central pathway for the development of metabolic syndrome-related diseases, such as atherosclerosis, cardiovascular disease (CVD), and NAFLD. This paper focuses on pathogenic aspect of lipid and lipoprotein metabolism in NAFLD and the relevant mouse models of this complex multifactorial disease.

New approach to modulate retinal cellular toxic effects of high glucose using marine epa and dha

Background

Protective effects of omega-3 fatty acids against cellular damages of high glucose were studied on retinal pigmented epithelial (RPE) cells.

Methods

Retinal epithelial cells were incubated with omega-3 marine oils rich in EPA and DHA and then with high glucose (25 mM) for 48 hours. Cellular responses were compared to normal glucose (5 mM): intracellular redox status, reactive oxygen species (ROS), mitochondrial succinate deshydrogenase activity, inflammatory cytokines release and caveolin-1 expression were evaluated using microplate cytometry, ELISA and flow cytometry techniques. Fatty acids incorporation in retinal cell membranes was analysed using chromatography.

Results

Preincubation of the cells with fish oil decreased ROS overproduction, mitochondrial alterations and TNFα release. These protective effects could be attributed to an increase in caveolin-1 expression induced by marine oil.

Conclusion

Marine formulations rich in omega-3 fatty acids represent a promising therapeutic approach for diabetic retinopathy.

The role of adipose tissue in mediating the beneficial effects of dietary fish oil

Fish oil improves several features of metabolic syndrome (MetS), such as dyslipidemia, insulin resistance and hepatic steatosis. Fish oil may mediate some of its beneficial effects by modulating the storage and/or secretory functions of adipose tissue (AT). The storage of triglycerides in AT is regulated by the availability of free fatty acids and the degree of lipolysis in AT. Fish oil has been shown to reduce lipolysis in several studies, indicating improved triglyceride storage. Importantly, AT secretes a variety of adipokines and fish oil feeding is associated with remarkable changes in the plasma levels of two key adipokines, adiponectin and leptin. Much attention has been focused on the contribution of adiponectin in fish oil-mediated improvements in MetS. However, emerging evidence also indicates a role of leptin in modulating the components of the MetS upon fish oil feeding. In addition to improving the storage and secretory functions of AT, fish oil, and the n-3 fatty acids found in fish oil, has been shown to reduce inflammation in AT. These effects may be in part a result of activation of peroxisome proliferator-activated receptor γ or inhibition of Toll-like receptor 4. Thus, there is compelling evidence that fish oil mediates its beneficial effects on MetS by improving AT storage and secretory functions and by reducing inflammation.

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.

Peroxisome proliferator-activated receptors (PPARs)-independent functions of fish oil on glucose and lipid metabolism in diet-induced obese mice

Background

Fish oil is known to improve lifestyle-related diseases. These effects occur partly via activation of PPARs by the n-3 polyunsaturated fatty acids included abundantly in fish oil. We investigated fish oil functions on glucose and lipid metabolism that are both dependent on and independent of PPARs pathway.

Methods

Mice were fed a diet containing 30 en% beef tallow (B diet) for twelve weeks to induce obesity. The mice were then divided into two groups which were fed either a B diet or a diet containing 30 en% fish oil (F diet). Each group was further divided into two groups which were administered PPARα and γ antagonists or vehicle once a day for three weeks.

Results

The F diet groups showed lower triglyceride levels in plasma and liver than the B diet groups, but PPARs antagonists did not affect the triglyceride levels in either diet groups. The F diet groups also showed improvement of glucose tolerance compared with the B diet groups. However, PPARs antagonists made glucose tolerance worse in the F diet group but improved it in the B diet group. Therefore, by the administration of antagonists, glucose tolerance was inversely regulated between the B and F diets, and hypolipidemic action in the plasma and liver of the F diet group was not affected.

Conclusion

These results suggest that fish oil decreases lipid levels in plasma and liver via PPARs pathway-independent mechanism, and that glucose tolerance is inversely regulated by PPARs antagonists under diets containing different oils.

A Mouse Model of Metabolic Syndrome: Insulin Resistance, Fatty Liver and Non-Alcoholic Fatty Pancreas Disease (NAFPD) in C57BL/6 Mice Fed a High Fat Diet

Diet-induced obesity in C57BL/6 mice triggers common features of human metabolic syndrome (MetS). The purpose is to assess the suitability of a diet-induced obesity model for investigating non-alcoholic fatty pancreatic disease (NAFPD), fatty liver and insulin resistance. Adult C57BL/6 mice were fed either high-fat chow (HFC, 60% fat) or standard chow (SC, 10% fat) during a 16-week period. We evaluated in both groups: hepatopancreatic injuries, pancreatic islets size, alpha and beta-cell immunodensities, intraperitoneal insulin tolerance test (IPITT) and oral glucose tolerance test (OGTT). The HFC mice displayed greater mass gain (p<0.0001) and total visceral fat pads (p<0.001). OGTT showed impairment of glucose clearance in HFC mice (p<0.0001). IPITT revealed insulin resistance in HFC mice (p<0.0001). The HFC mice showed larger pancreatic islet size and significantly greater alpha and beta-cell immunodensities than SC mice. Pancreas and liver from HFC were heavier and contained higher fat concentration. In conclusion, C57BL/6 mice fed a high-fat diet develop features of NAFPD. Insulin resistance and ectopic accumulation of hepatic fat are well known to occur in MetS. Additionally, the importance of fat accumulation in the pancreas has been recently highlighted. Therefore, this model could help to elucidate target organ alterations associated with metabolic syndrome.