Very low-carbohydrate versus isocaloric high-carbohydrate diet in dietary obese rats

Enhancement of biochemical and genomic pathways through lycopene-loaded nano-liposomes: Alleviating insulin resistance, hepatic steatosis, and autophagy in obese rats with non-alcoholic fatty liver disease: Involvement of SMO, GLI-1, and PTCH-1 genes

Non-alcoholic fatty liver (NAFL) is a prevalent hepatic disorder of global significance that can give rise to severe complications. This research endeavor delves into the potential of nano-liposomal formulated Lycopene (Lip-Lyco) in averting the development of obesity and insulin resistance, both of which are major underlying factors contributing to NAFL. The investigation further scrutinizes the impact of Lip-Lyco on intricate cellular pathways within the liver tissue of rats induced with NAFL, specifically focusing on the progression of steatosis and fibrosis. To establish an obesity-NAFL model, twenty rats were subjected to a high-fat diet (HFD) for a duration of twelve weeks, after which they received an oral treatment of Lip-Lyco (10mg/kg) for an additional eight weeks. Another group of sixteen non-obese rats were subjected to treatment with or without Lip-Lyco, serving as a control for comparison. Results: The rats on a hypercaloric diet had high body mass index (BMI) and insulin resistance, reflected in disturbed serum adipokines and lipid profiles. Oxidative stress, inflammation, and apoptosis were evident in hepatic tissue, and the autophagic process in hepatocytes was inhibited. Additionally, the hedgehog pathway was activated in the liver tissue of NAFL group. Lip-Lyco was found to counteract all these aspects of NAFL pathogenesis. Lip-Lyco exhibited antioxidant, anti-inflammatory, hypoglycemic, antiapoptotic, autophagy-inducing, and Hedgehog signaling inhibitory effects. This study concludes that Lip-Lyco, a natural compound, has promising therapeutic potential in combating NAFLdisease. However, more experimental and clinical studies are required to confirm the effectiveness of lycopene in treating NAFLdisease.

Anti-Diabetic and Anti-Adipogenic Effect of Harmine in High-Fat-Diet-Induced Diabetes in Mice

One of the most important health issues facing the world today is obesity. It is an important independent risk factor for developing type 2 diabetes. Harmine offers various pharmacological effects, such as anti-inflammatory and anti-tumor effects. The current study aims to investigate Harmine's anti-diabetic and anti-adipogenic properties in albino mice after inducing low-grade inflammation with a high-fat diet (HFD). About forty-eight male albino mice were divided into four groups. Group 1: control mice were injected with daily saline and fed a normal chow diet of 21% protein for 5 months. Group 2: mice were treated daily with IP-injected Harmine (30 mg/kg body weight) and were fed a normal chow diet for 5 months. Group 3: mice were fed HFD to induce type 2 Diabetes Mellitus (T2DM) for 5 months. Group 4: mice were fed HFD for 14 weeks and treated with Harmine for the last 6 weeks. A figh-fat diet caused a significant increase in body and organ weight, lipid profiles, and destructive changes within the pancreas, kidney, and liver tissue. The administration of Harmine led to a remarkable improvement in the histological and ultrastructural changes induced by HFD. The findings indicate that mice cured using Harmine had lower oxidative stress, a higher total antioxidant capacity, and a reduced lipid profile compared to HFD mice. Harmine led to the hepatocytes partly restoring their ordinary configuration. Furthermore, it was noticed that the pathological incidence of damage in the structure of both the kidney and pancreas sections reduced in comparison with the diabetic group. Additional research will be required to fully understand Harmine and its preventive effects on the two forms of diabetes.

Macronutrient intake: Hormonal controls, pathological states, and methodological considerations

A plethora of studies to date has examined the roles of feeding-related peptides in the control of food intake. However, the influence of these peptides on the intake of particular macronutrient constituents of food - carbohydrate, fat, and protein - has not been as extensively addressed in the literature. Here, the roles of several feeding-related peptides in controlling macronutrient intake are reviewed. Next, the relationship between macronutrient intake and diseases including diabetes mellitus, obesity, and eating disorders are examined. Finally, some key considerations in macronutrient intake research are discussed. We hope that this review will shed light onto this underappreciated topic in ingestive behavior research and will help to guide further scientific investigation in this area.

The Effect of the Restrictive Ketogenic Diet on the Body Composition, Haematological and Biochemical Parameters, Oxidative Stress and Advanced Glycation End-Products in Young Wistar Rats with Diet-Induced Obesity

Over the past few years, the interest in the application of the ketogenic diet (KD) for obesity management is growing. Although many studies have been performed on the effects of KD, the metabolic and physiological impact of KD is still not fully understood. Therefore, this study aimed to evaluate the effect of calorie-restricted KD on the body weight and composition, oxidative stress, and advanced glycation end products (AGEs) assessed in an animal model with young Wistar rats. KD was followed for 4 weeks in maturity after an obesity-inducing high-fat diet during adolescence, resulting in a slowing down of the weight gain but higher adiposity compared to a standard diet. Increased adiposity resulted in an deterioration of liver parameters, suggesting negative changes in this organ. No adverse effects of KD were determined in haematological parameters in young rats. KD did not affect AGEs; however, a decrease in oxidative stress was observed. Based on the presented results, it can be concluded that KD applied for weight loss in obesity induced in adolescence may reduce oxidative stress without compromising the haematological status; however, caution may be required to control adiposity, glucose level and liver health. Thus, KD therapy should be carefully controlled, especially in young subjects.

Evaluating anti-obesity potential, active components, and antioxidant mechanisms of Moringa peregrina seeds extract on high-fat diet-induced obesity

There are no medical drugs that provide an acceptable weight loss with minimal adverse effects. This study evaluated the Moringa peregrina (MP) seed extract's anti-obesity effect. Twenty-four (6/each group) male Sprague Dawley rats were divided into group Ι (control), group ΙΙ (high-fat diet [HFD]), group ΙΙΙ (HFD+ MP [250 mg/kg b.wt]), and group ΙV (HFD+ MP [500 mg/kg b.wt]). MP administration significantly ameliorated body weight gains and HFD induced elevation in cholesterol, triglycerides, LDL, and reduced HDL. Moreover, MP seed oil showed high free radical-scavenging activity, delayed β-carotene bleaching and inhibited lipoprotein and pancreatic lipase enzymes. High-performance liquid chromatography (HPLC) revealed three major active components: crypto-chlorogenic acid, isoquercetin, and astragalin. Both quantitative Real-time PCR (RT-PCR) and western blotting revealed that MP seeds oil significantly decreased the expression of lipogenesis-associated genes such as peroxisome proliferator-activated receptors gamma (PPARγ) and fatty acid synthase (FAS) and significantly elevated the expression of lipolysis-associated genes (acetyl-CoA carboxylase1, ACCl). The oil also enhanced phosphorylation of AMP-activated protein kinase alpha (AMPK-α) and suppressed CCAAT/enhancer-binding protein β (C/EBPβ). In conclusion, administration of M. peregrina seeds oil has anti-obesity potential in HFD-induced obesity in rats. PRACTICAL APPLICATIONS: M. peregrina seeds oil had a potential anti-obesity activity that may be attributed to different mechanisms. These included decreasing body weight, and body mass index and improving lipid levels by decreasing total cholesterol, triglycerides and LDL-C, and increasing HDL-C. Also, M. peregrina seeds oil regulated adipogenesis-associated genes, such as downregulating the expression of (PPARγ, C/EBPα, and FAS) and improving and upregulating the expression and phosphorylation of AMPKα and ACCl. Despite that M. peregrina extract has reported clear anti-obesity potential through animal and laboratory studies, the available evidence-based on human clinical trials are very limited. Therefore, further studies are needed that could focus on clinical trials investigating anti-obesity potential different mechanisms of M. peregrina extract in humans.

The effect of a low carbohydrate ketogenic diet with or without exercise on postpartum weight retention, metabolic profile and physical activity performance in postpartum mice

OBJECTIVE

the present study examined the effect of the isocaloric low-carbohydrate ketogenic diet (LCKD) with or without exercise training for 6 weeks on postpartum weight retention (PPWR), body composition, metabolic profile and physical activity performance in postpartum mice.

METHODS

postpartum mice were assigned to 4 groups (n=8/group) as follows: (1) those on a control diet without aerobic exercise (CN); (2) those on a control diet with aerobic exercise (CN+EX), (3); those on a LCKD without aerobic exercise (LCKD); (4) those on a LCKD with aerobic exercise (LCKD+EX). CN+EX and LCKD+EX mice performed 6 weeks of exercise training on a treadmill. After the 6-week intervention, physical activity performance was determined.

RESULTS

postpartum mice in all groups experienced progressive reductions in body weight over the study period. The LCKD group had the smallest reduction in PPWR (p<0.05). The LCKD group had significantly higher total cholesterol, low-density lipoprotein cholesterol and lactate dehydrogenase levels, and liver lipid concentrations with a worsened glucose tolerance, compared to the CN group (p<0.05). The LCKD group showed significant reductions in physical activity performance, whilst the LCKD+EX group showed significantly improvement in endurance performance, and paralleled the concomitant elevation in blood ketone levels.

CONCLUSIONS

6-week LCKD feeding on its own was less effective for reducing PPWR, and more detrimental to postpartum metabolic outcomes and physical activity performance of the postpartum mice. The feasibility of a LCKD with or without exercise during the postpartum period as a strategy for managing PPWR and improving postpartum metabolic profiles should be carefully considered.

Obesity in C57BL/6J mice fed diets differing in carbohydrate and fat but not energy content

To investigate the contributions of carbohydrate and fat to obesity we measured the body weight, body composition and food intake of adult C57BL/6J mice fed ad libitum with various combinations of two semisynthetic diets that differed in carbohydrate and fat but not in protein, micronutrient or energy content. In Experiment 1, involving male mice, body weights were similar in groups fed diets comprised of (by energy) 20% protein, 75% carbohydrate and 5% fat (C75-F5) or 20% protein, 5% carbohydrate and 75% fat (C5-F75). However, mice fed a 50:50 composite mixture of the C75-F5 and C5-F75 diets (i.e., a C40-F40 diet) became substantially more obese. Mice that could choose between the C75-F5 and C5-F75 diets ate equal amounts of each diet and gained almost as much weight as did the group fed C40-F40 diet. Mice switched every day between the C75-F5 and C5-F75 diets gained no more weight than did those fed either diet exclusively. In Experiment 2, male and female mice were fed chow or one of 8 isocaloric diets that differed parametrically in carbohydrate and fat content. Groups fed diets in the middle of the range (i.e., C35-F45 or C45-F35) weighed significantly more and were significantly fatter than were those fed diets with more extreme proportions of carbohydrate and fat (e.g., C75-F5, C5-F75), an effect that was more pronounced in males than females. In Experiment 3 and 4, male mice fed versions of the C40-F40 formulation gained more weight than did those fed the C75-F5 or C5-F75 formulations irrespective of whether the carbohydrate was predominantly sucrose or predominantly starch, or whether the fat was vegetable shortening, corn oil, palm oil or canola oil; the type of carbohydrate or fat had little or no impact on body weight. In all four experiments, energy intakes differed among the diet groups but could not account for the differences in body weight. These results demonstrate that the proportion of carbohydrate and fat in the diet influences body weight independently of energy content, and that the type of carbohydrate or fat has little impact on body weight. Consuming carbohydrate and fat simultaneously or in close temporal proximity exacerbates obesity.

Caloric Restriction per se Rather Than Dietary Macronutrient Distribution Plays a Primary Role in Metabolic Health and Body Composition Improvements in Obese Mice

Caloric restriction (CR) is of key importance in combating obesity and its associated diseases. We aimed to examine effects of dietary macronutrient distribution on weight loss and metabolic health in obese mice exposed to CR. Male C57BL/6J mice underwent diet-induced obesity for 18 weeks. Thereafter mice were exposed to a 6-week CR for up to 40% on either low-fat diet (LFD; 20, 60, 20% kcal from protein, carbohydrate, fat), low-carb diet (LCD; 20, 20, 60% kcal, respectively) or high-pro diet (HPD; 35, 35, 30% kcal, respectively) (n = 16 each). Ten mice on the obesogenic diet served as age-matched controls. Body composition was evaluated by tissue dissections. Glucose tolerance, bloods lipids and energy metabolism were measured. CR-induced weight loss was similar for LFD and LCD while HPD was associated with a greater weight loss than LCD. The diet groups did not differ from obese controls in hindlimb muscle mass, but showed a substantial decrease in body fat without differences between them. Glucose tolerance and blood total cholesterol were weight-loss dependent and mostly improved in LFD and HPD groups during CR. Blood triacylglycerol was lowered only in LCD group compared to obese controls. Thus, CR rather than macronutrient distribution in the diet plays the major role for improvements in body composition and glucose control in obese mice. Low-carbohydrate-high-fat diet more successfully reduces triacylglycerol but not cholesterol levels compared to isocaloric high-carbohydrate-low-fat weight loss diets.

Anti-obesity potential of Moringa olifera seed extract and lycopene on high fat diet induced obesity in male Sprauge Dawely rats

Present research explored the anti-obesity effect of Moringa olifera seed oil extract and lycopene (LYC). Forty eight male Sprauge Dawely rats were divided equally into 6 groups. Group Ι (C) served as control, group ΙΙ (MC) was given Moringa olifera seed oil extract (800 mg/kg b.wt) for 8 weeks, group ΙΙΙ (LC) was given (20 mg/kg b.wt) LYC for 8 weeks, group ΙV (O) received high fat diet (HFD) for 20 weeks, group Ѵ (MO), was given HFD for 20 weeks and received (800 mg/kg b.wt) Moringa olifera seed oil extract for last 8 weeks and group ѴΙ (LO), received HFD for 20 weeks and was given (20 mg/kg b.wt) LYC for last 8 weeks. Hematology, lipid peroxidation and antioxidants, non-esterified fatty acids (NEFA), glucose, lipid profile, serum liver and kidney biomarkers, inflammatory markers, leptin, resistin and heart fatty acid binding protein (HFABP) were determined. Also histopathology for liver, kidney and aorta were performed besides immunohistochemistry (IHC) for aortic inducible nitric oxide synthase (iNOS). Administration of Moringa olifera seed oil extract and LYC significantly ameliorated the HFD induced hematological and metabolic perturbations as well as reduced leptin and resistin. Both treatments exerted these effects through promotion of antioxidant enzymes and reducing lipid peroxidation as well as inflammatory cytokines along with reduced iNOS protein expression. Administration of Moringa olifera seed oil extract and LYC have anti-obesity potential in HFD induced obesity in male Sprauge Dawely rats.

Low-Carbohydrate Diet Inhibits Different Advanced Glycation End Products in Kidney Depending on Lipid Composition but Causes Adverse Morphological Changes in a Non-Obese Model Mice

Low carbohydrate diets (LC diets) have been noted for adverse health effects. In addition, the effect of lipid composition on an LC diet is unclear. In this study, we used an LC diet containing two different lipids, lard (LC group) and medium-chain triglyceride oil (MCT-LC group), to examine the effect of an LC diet in non-obese mice. Male C57BL/6J mice were fed the control diet or one of the experimental diets ad libitum for 13 weeks. Increased renal weight and glomerular hypertrophy, as well as enlargement of intraglomerular small vessels with wall thickening, were seen in the LC and MCT-LC groups. Renal AMP-activated protein kinase activity was significantly decreased only in the LC diet group. On the other hand, epididymal adipose tissue weight and adipocyte area were markedly decreased only in the MCT-LC group. A positive effect was also observed in the kidney, where different advanced glycation end products, Nε-(carboxyethyl)-lysine and Nε-(carboxymethyl)-lysine, were inhibited depending on the lipid composition of the LC diet. Our findings suggest that, in non-obese conditions, low dietary intake of carbohydrates had both positive and negative impacts. The safety of diets low in carbohydrates, including the effects of fatty acid composition, requires further investigation.

The carbohydrate-insulin model does not explain the impact of varying dietary macronutrients on the body weight and adiposity of mice

Objectives

The carbohydrate-insulin model (CIM) predicts that increases in fasting and post-prandial insulin in response to dietary carbohydrates stimulate energy intake and lower energy expenditures, leading to positive energy balance and weight gain. The objective of the present study was to directly test the CIM's predictions using C57BL/6 mice.

Methods

Diets were designed by altering dietary carbohydrates with either fixed protein or fat content and were fed to C57BL/6 mice acutely or chronically for 12 weeks. The body weight, body composition, food intake, and energy expenditures of the mice were measured. Their fasting and post-prandial glucose and insulin levels were also measured. RNA-seq was performed on RNA from the hypothalamus and subcutaneous white adipose tissue. Pathway analysis was conducted using IPA.

Results

Only the post-prandial insulin and fasting glucose levels followed the CIM's predictions. The lipolysis and leptin signaling pathways in the sWAT were inhibited in relation to the elevated fasting insulin, supporting the CIM's predicted impact of high insulin. However, because higher fasting insulin was unrelated to carbohydrate intake, the overall pattern did not support the model. Moreover, the hypothalamic hunger pathways were inhibited in relation to the increased fasting insulin, and the energy intake was not increased. The browning pathway in the sWAT was inhibited at higher insulin levels, but the daily energy expenditure was not altered.

Conclusions

Two of the predictions were partially supported (and hence also partially not supported) and the other three predictions were not supported. We conclude that the CIM does not explain the impact of dietary macronutrients on adiposity in mice.

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Higher fasting insulin related to inhibited lipolysis and leptin pathways in sWAT, supporting CIM.

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Higher fasting insulin related to inhibited hypothalamic hunger pathway, contrasting CIM.

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Fasting insulin decreased with higher dietary carbohydrate, overall contrasting CIM.

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Higher dietary carbohydrate did not lead to greater EI/adiposity, or lowered EE.

Very low-carbohydrate, high-fat, weight reduction diet decreases hepatic gene response to glucose in obese rats

Background

Very low carbohydrate (VLC) diets are used to promote weight loss and improve insulin resistance (IR) in obesity. Since the high fat content of VLC diets may predispose to hepatic steatosis and hepatic insulin resistance, we investigated the effect of a VLC weight-reduction diet on measures of hepatic and whole body insulin resistance in obese rats.

Methods

In Phase 1, adult male Sprague-Dawley rats were made obese by ad libitum consumption of a high-fat (HF1, 60% of energy) diet; control rats ate a lower-fat (LF, 15%) diet for 10 weeks. In Phase 2, obese rats were fed energy-restricted amounts of a VLC (5%C, 65%F), LC (19%C, 55%F) or HC (55%C, 15%F) diet for 8 weeks while HF2 rats continued the HF diet ad libitum. In Phase 3, VLC rats were switched to the HC diet for 1 week. At the end of each phase, measurements of body composition and metabolic parameters were obtained. Hepatic insulin resistance was assessed by comparing expression of insulin-regulated genes following an oral glucose load,that increased plasma insulin levels, with the expression observed in the feed-deprived state.

Results

At the end of Phase 1, body weight, percent body fat, and hepatic lipid levels were greater in HF1 than LF rats (p < 0.05). At the end of Phase 2, percent body fat and intramuscular triglyceride decreased in LC and HC (p < 0.05), but not VLC rats, despite similar weight loss. VLC and HF2 rats had higher HOMA-IR and higher insulin at similar glucose levels following an ip glucose load than HC rats (p < 0.05). HC, but not VLC or HF2 rats, showed changes in Srebf1, Scd1, and Cpt1a expression (p < 0.05) in response to an oral glucose load. At the end of Phase 3, switching from the VLC to the HC diet mitigated differences in hepatic gene expression.

Conclusion

When compared with a high-carbohydrate, low-fat diet that produced similar weight loss, a commonly used VLC diet failed to improve whole body insulin resistance; it also reduced insulin’s effect on hepatic gene expression, which may reflect the development of hepatic insulin resistance.

Cardiac, Metabolic and Molecular Profiles of Sedentary Rats in the Initial Moment of Obesity

BACKGROUND

Different types of high-fat and/or high-energy diets have been used to induce obesity in rodents. However, few studies have reported on the effects observed at the initial stage of obesity induced by high-fat feeding on cardiac functional and structural remodelling.

OBJECTIVE

To characterize the initial moment of obesity and investigate both metabolic and cardiac parameters. In addition, the role of Ca2+ handling in short-term exposure to obesity was verified.

METHODS

Thirty-day-old male Wistar rats were randomized into two groups (n = 19 each): control (C; standard diet) and high-fat diet (HF, unsaturated high-fat diet). The initial moment of obesity was defined by weekly measurement of body weight (BW) complemented by adiposity index (AI). Cardiac remodelling was assessed by morphological, histological, echocardiographic and papillary muscle analysis. Ca2+ handling proteins were determined by Western Blot.

RESULTS

The initial moment of obesity occurred at the 3rd week. Compared with C rats, the HF rats had higher final BW (4%), body fat (20%), AI (14.5%), insulin levels (39.7%), leptin (62.4%) and low-density lipoprotein cholesterol (15.5%) but did not exhibit alterations in systolic blood pressure. Echocardiographic evaluation did not show alterations in cardiac parameters. In the HF group, muscles were observed to increase their +dT/dt (C: 52.6 ± 9.0 g/mm2/s and HF: 68.0 ± 17.0 g/mm2/s; p < 0.05). In addition, there was no changes in the cardiac expression of Ca2+ handling proteins.

CONCLUSION

The initial moment of obesity promotes alterations to hormonal and lipid profiles without cardiac damage or changes in Ca2+ handling.

Choline and Fructooligosaccharide: Non-alcoholic Fatty Liver Disease, Cardiac Fat Deposition, and Oxidative Stress Markers

This study investigates the treatment of non-alcoholic fatty liver disease (NAFLD) in rats with choline and fructooligosaccharide (FOS). The healthy control group received standard diet. The other three groups consisted of animals with NAFLD. Group E_str received standard diet; group E_cho received standard diet plus choline (3 g/100 g diet); and group E_fos received standard diet plus FOS (10 g/100 g diet). Food intake, weight, urinary nitrogen, urinary ammonia, total cholesterol, serum triacylglyceride, liver and heart weights, tissue nitrogen, tissue fat, vitamin E, TBARS, and reduced glutathione (GSH) were measured in hepatic and heart tissue. Choline and FOS treatments resulted in total mean fat reduction in liver and heart tissue of 0.2 and 1.7 g, respectively. Both treatments were equally effective in reducing hepatic and cardiac steatosis. There were no differences in the TBARS level among experimental and control groups, indicating that the proposed treatments had no added protection against free radicals. While all experimental groups had increased vitamin E and GSH levels, choline treatment led to a significant increase compared to control.

Dietary docosahexaenoic acid and eicosapentaenoic acid influence liver triacylglycerol and insulin resistance in rats fed a high-fructose diet

This study aimed to examine the benefits of different amounts of omega-3 (n-3) polyunsaturated fatty acids from fish oil (FO) on lipid metabolism, insulin resistance and gene expression in rats fed a high-fructose diet. Male Wistar rats were separated into two groups: Control (C, n = 6) and Fructose (Fr, n = 32), the latter receiving a diet containing 63% by weight fructose for 60 days. After this period, 24 animals from Fr group were allocated to three groups: FrFO2 (n = 8) receiving 63% fructose and 2% FO plus 5% soybean oil; FrFO5 (n = 8) receiving 63% fructose and 5% FO plus 2% soybean oil; and FrFO7 (n = 8) receiving 63% fructose and 7% FO. Animals were fed these diets for 30 days. Fructose led to an increase in liver weight, hepatic and serum triacylglycerol, serum alanine aminotransferase and HOMA1-IR index. These alterations were reversed by 5% and 7% FO. FO had a dose-dependent effect on expression of genes related to hepatic β-oxidation (increased) and hepatic lipogenesis (decreased). The group receiving the highest FO amount had increased markers of oxidative stress. It is concluded that n-3 fatty acids may be able to reverse the adverse metabolic effects induced by a high fructose diet.

Experimental induction of steatosis in different tissues after the ingestion of a carbohydrate-rich diet: effect on the liver, on the heart and on indicators of oxidation

CONTEXT

The western dietary pattern is characterized by a high calorie intake with a high proportion of simple sugars. This diet is associated with comorbidities such as hepatic fat deposition and is possibly related to non-alcoholic fatty liver disease.

OBJECTIVE

To evaluate the capacity of a hyperglucidic diet to induce steatosis in adult male Wistar rats. After the administration of a carbohydrate-rich diet, we also evaluated the presence of hepatic and cardiac steatosis and the levels of intrinsic antioxidants in the liver.

METHODS

Forty-six eutrophic adult male Wistar rats were used and 10 of them were chosen, at random, to serve as controls, while the remaining ones formed the experimental group. Control animals received the standard ration offered by the animal house and the experimental group received the hyperglucidic diet. The diets were offered for 21 days and, at the end of this period, tissue samples were collected for analysis of indicators of oxidative stress (malondialdehyde, and reduced glutathione) and of vitamin E. The animals were then sacrificed by decapitation and their viscera were removed for analysis of liver and heart fat.

RESULTS

The hyperglucidic diet used induced hepatic fat deposition, with lipid vacuoles being detected in 83% of the livers analyzed by histology. No lipid vacuoles were observed in the heart. Malondialdehyde and reduced glutathione levels remained unchanged when the animals were submitted to the hyperglucidic diet, probably because there was no liver development of fibrosis or inflammation. In contrast, the levels of vitamin E (antioxidant) were reduced, as confirmed in the literature for steatotic animals.

CONCLUSION

The hyperglucidic diet induced hepatic steatosis. In the heart there was an increase in fat content, although no histological changes were observed. These alterations cannot be explained by the presence of malondialdehyde or reduced glutathione (indicators of oxidation), since the values were similar in the groups studied. However, a significant reduction of vitamin E was observed in the experimental group.

Induction of ketosis in rats fed low-carbohydrate, high-fat diets depends on the relative abundance of dietary fat and protein

Low-carbohydrate/high-fat diets (LC-HFDs) in rodent models have been implicated with both weight loss and as a therapeutic approach to treat neurological diseases. LC-HFDs are known to induce ketosis; however, systematic studies analyzing the impact of the macronutrient composition on ketosis induction and weight loss success are lacking. Male Wistar rats were pair-fed for 4 wk either a standard chow diet or one of three different LC-HFDs, which only differed in the relative abundance of fat and protein (percentages of fat/protein in dry matter: LC-75/10; LC-65/20; LC-55/30). We subsequently measured body composition by nuclear magnetic resonance (NMR), analyzed blood chemistry and urine acetone content, evaluated gene expression changes of key ketogenic and gluconeogenic genes, and measured energy expenditure (EE) and locomotor activity (LA) during the first 4 days and after 3 wk on the respective diets. Compared with chow, rats fed with LC-75/10, LC-65/20, and LC-55/30 gained significantly less body weight. Reductions in body weight were mainly due to lower lean body mass and paralleled by significantly increased fat mass. Levels of β-hydroxybutyate were significantly elevated feeding LC-75/10 and LC-65/20 but decreased in parallel to reductions in dietary fat. Acetone was about 16-fold higher with LC-75/10 only (P < 0.001). In contrast, rats fed with LC-55/30 were not ketotic. Serum fibroblast growth factor-21, hepatic mRNA expression of hydroxymethylglutaryl-CoA-lyase, peroxisome proliferator-activated receptor-γ coactivator-1α, and peroxisome proliferator-activated receptor-γ coactivator-1β were increased with LC-75/10 only. Expression of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase was downregulated by 50-70% in LC-HF groups. Furthermore, EE and LA were significantly decreased in all groups fed with LC-HFDs after 3 wk on the diets. In rats, the absence of dietary carbohydrates per se does not induce ketosis. LC-HFDs must be high in fat, but also low in protein contents to be clearly ketogenic. Independent of the macronutrient composition, LC-HFD-induced weight loss is not due to increased EE and LA.

Fructose and NAFLD: metabolic implications and models of induction in rats

PURPOSE: The increase in fructose consumption is paralleled by a higher incidence of obesity worldwide. This monosaccharide is linked to metabolic syndrome, being associated with hypertriglyceridemia, hypertension, insulin resistance and diabetes mellitus. It is metabolized principally in the liver, where it can be converted into fatty acids, which are stored in the form of triglycerides leading to NAFLD. Several models of NAFLD use diets high in simple carbohydrates. Thus, this study aimed to describe the major metabolic changes caused by excessive consumption of fructose in humans and animals and to present liver abnormalities resulting from high intakes of fructose in different periods of consumption and experimental designs in Wistar rats. METHODS: Two groups of rats were fasted for 48 hours and reefed for 24 or 48 hours with a diet containing 63% fructose. Another group of rats was fed an diet with 63% fructose for 90 days. RESULTS: Refeeding for 24 hours caused accumulation of large amounts of fat, compromising 100% of the hepatocytes. The amount of liver fat in animals refed for 48 hours decreased, remaining mostly in zone 2 (medium-zonal). In liver plates of Wistar rats fed 63% fructose for 45, 60 and 90 days it's possible to see that there is an increase in hepatocytes with fat accumulation according to the increased time; hepatic steatosis, however, is mild, compromising about 20% of the hepatocytes. CONCLUSIONS: Fructose is highly lipogenic, however the induction of chronic models in NAFLD requires long periods of treatment. The acute supply for 24 or 48 hours, fasted rats can cause big changes, liver steatosis with macrovesicular in all lobular zones.

Longitudinal adaptations to very low-carbohydrate weight-reduction diet in obese rats: body composition and glucose tolerance

Longitudinal effects of a very low-carbohydrate (VLC) and a calorie-matched high-carbohydrate (HC) weight reduction diet were compared in dietary obese Sprague-Dawley rats exhibiting impaired glucose tolerance and insulin resistance. Obese rats were divided into weight-matched groups: (i) VLC rats consumed an energy-restricted 5% carbohydrate, 60% fat diet for 8 weeks, (ii) HC rats consumed an isocaloric 60% carbohydrate, 15% fat diet, and (iii) HF rats consumed a high-fat diet ad libitum. HC and VLC rats showed similar reductions in body fat and hepatic lipid at the midpoint of the weight-reduction program, indicating effects due to energy deficit. At the end point, however, HC rats showed greater reductions in total and percent body fat, hepatic lipid and intramuscular lipid than did VLC rats, suggesting that diet composition induced changes in the relative efficiencies of the HC and VLC diets over time. HC rats showed marked improvement in glucose tolerance at the midpoint and end point, whereas VLC rats showed no improvement. Impaired glucose tolerance in VLC rats at the end point was due to insulin resistance and an attenuated insulin secretory response. Glucose tolerance in energy-restricted rats correlated negatively with hepatic and intramuscular lipid levels, but not visceral or total fat mass. These findings demonstrate that adaptations to diet composition eventually enabled HC rats to lose more body fat than VLC rats even though energy intakes were equal, and suggest that the elevated levels of hepatic and intramuscular lipid associated with VLC diets might predispose to insulin resistance and impaired glucose tolerance despite weight loss.

Increasing the fat-to-carbohydrate ratio in a high-fat diet prevents the development of obesity but not a prediabetic state in rats

Metabolic disorders induced by high-fat feeding in rodents evoke some, if not all, of the features of human metabolic syndrome. The occurrence and severity of metabolic disorders, however, varies according to rodent species, and even strain, as well as the diet. Therefore, in the present study, we investigated the long-term obesogenic and diabetogenic effects of three high-fat diets differing by their fat/carbohydrate ratios. Sprague-Dawley rats were fed a control high-carbohydrate and low-fat diet [HCD; 3:16:6 ratio of fat/carbohydrate/protein; 15.48 kJ/g (3.7 kcal/g)], a high-fat and medium-carbohydrate diet [HFD1; 53:30:17 ratio of fat/carbohydrate/protein; 19.66 kJ/g (4.7 kcal/g)], a very-high-fat and low-carbohydrate diet [HFD2; 67:9:24 ratio of fat/carbohydrate/protein; 21.76 kJ/g (5.2 kcal/g)] or a very-high-fat and carbohydrate-free diet [HFD3; 75:0:25 ratio of fat/carbohydrate/protein; 24.69 kJ/g (5.9 kcal/g)] for 10 weeks. Compared with the control diet (HCD), rats fed with high-fat combined with more (HFD1) or less (HFD2) carbohydrate exhibited higher BMI (body mass index; +13 and +10% respectively; P<0.05) and abdominal fat (+70% in both HFD1 and HFD2; P<0.05), higher plasma leptin (+130 and +135% respectively; P<0.05), lower plasma adiponectin levels (-23 and -30% respectively; P<0.05) and impaired glucose tolerance. Only the HFD1 group had insulin resistance. By contrast, a very-high-fat diet devoid of carbohydrate (HFD3) led to impaired glucose tolerance, insulin resistance and hypoadiponectinaemia (-50%; P<0.05), whereas BMI, adiposity and plasma leptin did not differ from respective values in animals fed the control diet. We conclude that increasing the fat-to-carbohydrate ratio to the uppermost (i.e. carbohydrate-free) in a high-fat diet prevents the development of obesity, but not the prediabetic state (i.e. altered glucose tolerance and insulin sensitivity).