Liver mitochondrial dysfunction and oxidative stress in the pathogenesis of experimental nonalcoholic fatty liver disease

Oxidative stress and hepatic mitochondria play a role in the pathogenesis of nonalcoholic fatty liver disease. The aim of the present study was to evaluate the role of hepatic mitochondrial dysfunction and oxidative stress in the pathogenesis of the disease. Fatty liver was induced in Wistar rats with a choline-deficient diet (CD; N = 7) or a high-fat diet enriched with PUFAs-omega-3 (H; N = 7) for 4 weeks. The control group (N = 7) was fed a standard diet. Liver mitochondrial oxidation and phosphorylation were measured polarographically and oxidative stress was estimated on the basis of malondialdehyde and glutathione concentrations. Moderate macrovacuolar liver steatosis was observed in the CD group and mild liver steatosis was observed in the periportal area in the H group. There was an increase in the oxygen consumption rate by liver mitochondria in respiratory state 4 (S4) and a decrease in respiratory control rate (RCR) in the CD group (S4: 32.70 ± 3.35; RCR: 2.55 ± 0.15 ng atoms of O2 min-1 mg protein-1) when compared to the H and control groups (S4: 23.09 ± 1.53, 17.04 ± 2.03, RCR: 3.15 ± 0.15, 3.68 ± 0.15 ng atoms of O2 min-1 mg protein-1, respectively), P < 0.05. Hepatic lipoperoxide concentrations were significantly increased and the concentration of reduced glutathione was significantly reduced in the CD group. A choline-deficient diet causes moderate steatosis with disruption of liver mitochondrial function and increased oxidative stress. These data suggest that lipid peroxidation products can impair the flow of electrons along the respiratory chain, causing overreduction of respiratory chain components and enhanced mitochondrial reactive oxygen species. These findings are important in the pathogenesis of nonalcoholic fatty liver disease.

Obesity induces upregulation of genes involved in myocardial Ca2+ handling

Obesity is a complex multifactorial disorder that is often associated with cardiovascular diseases. Research on experimental models has suggested that cardiac dysfunction in obesity might be related to alterations in myocardial intracellular calcium (Ca2+) handling. However, information about the expression of Ca2+-related genes that lead to this abnormality is scarce. We evaluated the effects of obesity induced by a high-fat diet in the expression of Ca2+-related genes, focusing the L-type Ca2+ channel (Cacna1c), sarcolemmal Na+/Ca2+ exchanger (NCX), sarcoplasmic reticulum Ca2+ ATPase (SERCA2a), ryanodine receptor (RyR2), and phospholamban (PLB) mRNA in rat myocardium. Male 30-day-old Wistar rats were fed a standard (control) or high-fat diet (obese) for 15 weeks. Obesity was defined as increased percent of body fat in carcass. The mRNA expression of Ca2+-related genes in the left ventricle was measured by RT-PCR. Compared with control rats, the obese rats had increased percent of body fat, area under the curve for glucose, and leptin and insulin plasma concentrations. Obesity also caused an increase in the levels of SERCA2a, RyR2 and PLB mRNA (P < 0.05) but did not modify the mRNA levels of Cacna1c and NCX. These findings show that obesity induced by high-fat diet causes cardiac upregulation of Ca2+ transport_related genes in the sarcoplasmic reticulum.

Parasympathetic dysfunction is associated with insulin resistance in fructose-fed female rats

The objective of the present study was to identify metabolic, cardiovascular and autonomic changes induced by fructose overload administered in the drinking water of rats for 8 weeks. Female Wistar rats (200-220 g) were divided into 2 groups: control (N = 8) and fructose-fed rats (N = 5; 100 mg/L fructose in drinking water for 8 weeks). The autonomic control of heart rate was evaluated by pharmacological blockade using atropine (3 mg/kg) and propranolol (4 mg/kg). The animals were submitted to an intravenous insulin tolerance test (ITT) and to blood glucose measurement. The fructose overload induced a significant increase in body weight (~10%) and in fasting glycemia (~28%). The rate constant of glucose disappearance (KITT) during ITT was lower in fructose-fed rats (3.25 ± 0.7%/min) compared with controls (4.95 ± 0.3%/min, P < 0.05) indicating insulin resistance. The fructose-fed group presented increased arterial pressure compared to controls (122 ± 3 vs 108 ± 1 mmHg, P < 0.05) and a reduction in vagal tonus (31 ± 9 vs 55 ± 5 bpm in controls, P < 0.05). No changes in sympathetic tonus were observed. A positive correlation, tested by the Pearson correlation, was demonstrable between cardiac vagal tonus and KITT (r = 0.8, P = 0.02). These data provided new information regarding the role of parasympathetic dysfunction associated with insulin resistance in the development of early metabolic and cardiovascular alterations induced by a high fructose diet.

Effect and the probable mechanisms of silibinin in regulating insulin resistance in the liver of rats with non-alcoholic fatty liver

Our previous study has shown that reduced insulin resistance (IR) was one of the possible mechanisms for the therapeutic effect of silibinin on non-alcoholic fatty liver disease (NAFLD) in rats. In the present study, we investigated the pathways of silibinin in regulating hepatic glucose production and IR amelioration. Forty-five 4- to 6-week-old male Sprague Dawley rats were divided into a control group, an HFD group (high-fat diet for 6 weeks) and an HFD + silibinin group (high-fat diet + 0.5 mg kg-1·day-1 silibinin, starting at the beginning of the protocol). Both subcutaneous and visceral fat was measured. Homeostasis model assessment-IR index (HOMA-IR), intraperitoneal glucose tolerance test and insulin tolerance test (ITT) were performed. The expression of adipose triglyceride lipase (ATGL) and of genes associated with hepatic gluconeogenesis was evaluated. Silibinin intervention significantly protected liver function, down-regulated serum fat, and improved IR, as shown by decreased HOMA-IR and increased ITT slope. Silibinin markedly prevented visceral obesity by reducing visceral fat, enhanced lipolysis by up-regulating ATGL expression and inhibited gluconeogenesis by down-regulating associated genes such as Forkhead box O1, phosphoenolpyruvate carboxykinase and glucose-6-phosphatase. Silibinin was effective in ameliorating IR in NAFLD rats. Reduction of visceral obesity, enhancement of lipolysis and inhibition of gluconeogenesis might be the underlying mechanisms.

Early detection of metabolic and energy disorders by thermal time series stochastic complexity analysis

Maintenance of thermal homeostasis in rats fed a high-fat diet (HFD) is associated with changes in their thermal balance. The thermodynamic relationship between heat dissipation and energy storage is altered by the ingestion of high-energy diet content. Observation of thermal registers of core temperature behavior, in humans and rodents, permits identification of some characteristics of time series, such as autoreference and stationarity that fit adequately to a stochastic analysis. To identify this change, we used, for the first time, a stochastic autoregressive model, the concepts of which match those associated with physiological systems involved and applied in male HFD rats compared with their appropriate standard food intake age-matched male controls (n=7 per group). By analyzing a recorded temperature time series, we were able to identify when thermal homeostasis would be affected by a new diet. The autoregressive time series model (AR model) was used to predict the occurrence of thermal homeostasis, and this model proved to be very effective in distinguishing such a physiological disorder. Thus, we infer from the results of our study that maximum entropy distribution as a means for stochastic characterization of temperature time series registers may be established as an important and early tool to aid in the diagnosis and prevention of metabolic diseases due to their ability to detect small variations in thermal profile.

Salt-induced epithelial-to-mesenchymal transition in Dahl salt-sensitive rats is dependent on elevated blood pressure

Dietary salt intake has been linked to hypertension and cardiovascular disease. Accumulating evidence has indicated that salt-sensitive individuals on high salt intake are more likely to develop renal fibrosis. Epithelial-to-mesenchymal transition (EMT) participates in the development and progression of renal fibrosis in humans and animals. The objective of this study was to investigate the impact of a high-salt diet on EMT in Dahl salt-sensitive (SS) rats. Twenty-four male SS and consomic SS-13BN rats were randomized to a normal diet or a high-salt diet. After 4 weeks, systolic blood pressure (SBP) and albuminuria were analyzed, and renal fibrosis was histopathologically evaluated. Tubular EMT was evaluated using immunohistochemistry and real-time PCR with E-cadherin and alpha smooth muscle actin (α-SMA). After 4 weeks, SBP and albuminuria were significantly increased in the SS high-salt group compared with the normal diet group. Dietary salt intake induced renal fibrosis and tubular EMT as identified by reduced expression of E-cadherin and enhanced expression of α-SMA in SS rats. Both blood pressure and renal interstitial fibrosis were negatively correlated with E-cadherin but positively correlated with α-SMA. Salt intake induced tubular EMT and renal injury in SS rats, and this relationship might depend on the increase in blood pressure.

Effect of physical training on liver expression of activin A and follistatin in a nonalcoholic fatty liver disease model in rats

Nonalcoholic fatty liver disease (NAFLD) is characterized by fat accumulation in the liver and is associated with obesity and insulin resistance. Activin A is a member of the transforming growth factor beta (TGF)-β superfamily and inhibits hepatocyte growth. Follistatin antagonizes the biological actions of activin. Exercise is an important therapeutic strategy to reduce the metabolic effects of obesity. We evaluated the pattern of activin A and follistatin liver expression in obese rats subjected to swimming exercise. Control rats (C) and high-fat (HF) diet-fed rats were randomly assigned to a swimming training group (C-Swim and HF-Swim) or a sedentary group (C-Sed and HF-Sed). Activin βA subunit mRNA expression was significantly higher in HF-Swim than in HF-Sed rats. Follistatin mRNA expression was significantly lower in C-Swim and HF-Swim than in either C-Sed or HF-Sed animals. There was no evidence of steatosis or inflammation in C rats. In contrast, in HF animals the severity of steatosis ranged from grade 1 to grade 3. The extent of liver parenchyma damage was less in HF-Swim animals, with the severity of steatosis ranging from grade 0 to grade 1. These data showed that exercise may reduce the deleterious effects of a high-fat diet on the liver, suggesting that the local expression of activin-follistatin may be involved.

Effect of salt intake and potassium supplementation on brachial-ankle pulse wave velocity in Chinese subjects: an interventional study

Accumulating evidence has suggested that high salt and potassium might be associated with vascular function. The aim of this study was to investigate the effect of salt intake and potassium supplementation on brachial-ankle pulse wave velocity (PWV) in Chinese subjects. Forty-nine subjects (28-65 years of age) were selected from a rural community of northern China. All subjects were sequentially maintained on a low-salt diet for 7 days (3.0 g/day NaCl), a high-salt diet for an additional 7 days (18.0 g/day NaCl), and a high-salt diet with potassium supplementation for a final 7 days (18.0 g/day NaCl+4.5 g/day KCl). Brachial-ankle PWV was measured at baseline and on the last day of each intervention. Blood pressure levels were significantly increased from the low-salt to high-salt diet, and decreased from the high-salt diet to high-salt plus potassium supplementation. Baseline brachial-ankle PWV in salt-sensitive subjects was significantly higher than in salt-resistant subjects. There was no significant change in brachial-ankle PWV among the 3 intervention periods in salt-sensitive, salt-resistant, or total subjects. No significant correlations were found between brachial-ankle PWV and 24-h sodium and potassium excretions. Our study indicates that dietary salt intake and potassium supplementation, at least in the short term, had no significant effect on brachial-ankle PWV in Chinese subjects.

Exercise training prevents increased intraocular pressure and sympathetic vascular modulation in an experimental model of metabolic syndrome

The present study aimed to study the effects of exercise training (ET) performed by rats on a 10-week high-fructose diet on metabolic, hemodynamic, and autonomic changes, as well as intraocular pressure (IOP). Male Wistar rats receiving fructose overload in drinking water (100 g/L) were concomitantly trained on a treadmill for 10 weeks (FT group) or kept sedentary (F group), and a control group (C) was kept in normal laboratory conditions. The metabolic evaluation comprised the Lee index, glycemia, and insulin tolerance test (KITT). Arterial pressure (AP) was measured directly, and systolic AP variability was performed to determine peripheral autonomic modulation. ET attenuated impaired metabolic parameters, AP, IOP, and ocular perfusion pressure (OPP) induced by fructose overload (FT vs F). The increase in peripheral sympathetic modulation in F rats, demonstrated by systolic AP variance and low frequency (LF) band (F: 37±2, 6.6±0.3 vs C: 26±3, 3.6±0.5 mmHg2), was prevented by ET (FT: 29±3, 3.4±0.7 mmHg2). Positive correlations were found between the LF band and right IOP (r=0.57, P=0.01) and left IOP (r=0.64, P=0.003). Negative correlations were noted between KITT values and right IOP (r=-0.55, P=0.01) and left IOP (r=-0.62, P=0.005). ET in rats effectively prevented metabolic abnormalities and AP and IOP increases promoted by a high-fructose diet. In addition, ocular benefits triggered by exercise training were associated with peripheral autonomic improvement.

Sorafenib prevents liver fibrosis in a non-alcoholic steatohepatitis (NASH) rodent model

Liver fibrosis occurring as an outcome of non-alcoholic steatohepatitis (NASH) can precede the development of cirrhosis. We investigated the effects of sorafenib in preventing liver fibrosis in a rodent model of NASH. Adult Sprague-Dawley rats were fed a choline-deficient high-fat diet and exposed to diethylnitrosamine for 6 weeks. The NASH group (n=10) received vehicle and the sorafenib group (n=10) received 2.5 mg·kg-1·day-1 by gavage. A control group (n=4) received only standard diet and vehicle. Following treatment, animals were sacrificed and liver tissue was collected for histologic examination, mRNA isolation, and analysis of mitochondrial function. Genes related to fibrosis (MMP9, TIMP1, TIMP2), oxidative stress (HSP60, HSP90, GST), and mitochondrial biogenesis (PGC1α) were evaluated by real-time quantitative polymerase chain reaction (RT-qPCR). Liver mitochondrial oxidation activity was measured by a polarographic method, and cytokines by enzyme-linked immunosorbent assay (ELISA). Sorafenib treatment restored mitochondrial function and reduced collagen deposition by nearly 63% compared to the NASH group. Sorafenib upregulated PGC1α and MMP9 and reduced TIMP1 and TIMP2 mRNA and IL-6 and IL-10 protein expression. There were no differences in HSP60, HSP90 and GST expression. Sorafenib modulated PGC1α expression, improved mitochondrial respiration and prevented collagen deposition. It may, therefore, be useful in the treatment of liver fibrosis in NASH.

Combined treatment with caffeic and ferulic acid from Baccharis uncinella C. DC. (Asteraceae) protects against metabolic syndrome in mice

Fractionation of the EtOH extract from aerial parts of Baccharis uncinella C. DC. (Asteraceae) led to isolation of caffeic and ferulic acids, which were identified from spectroscopic and spectrometric evidence. These compounds exhibit antioxidant and anti-inflammatory properties and have been shown to be effective in the prevention/treatment of metabolic syndrome. This study investigated whether the combined treatment of caffeic and ferulic acids exhibits a more significant beneficial effect in a mouse model with metabolic syndrome. The combination treatment with caffeic and ferulic acids was tested for 60 days in C57 mice kept on a high-fat (40%) diet. The data obtained indicated that treatment with caffeic and ferulic acids prevented gain in body weight induced by the high-fat diet and improved hyperglycemia, hypercholesterolemia and hypertriglyceridemia. The expression of a number of metabolically relevant genes was affected in the liver of these animals, showing that caffeic and ferulic acid treatment results in increased cholesterol uptake and reduced hepatic triglyceride synthesis in the liver, which is a likely explanation for the prevention of hepatic steatosis. In conclusion, the combined treatment of caffeic and ferulic acids displayed major positive effects towards prevention of multiple aspects of the metabolic syndrome and liver steatosis in an obese mouse model.

Classification of different degrees of adiposity in sedentary rats

In experimental studies, several parameters, such as body weight, body mass index, adiposity index, and dual-energy X-ray absorptiometry, have commonly been used to demonstrate increased adiposity and investigate the mechanisms underlying obesity and sedentary lifestyles. However, these investigations have not classified the degree of adiposity nor defined adiposity categories for rats, such as normal, overweight, and obese. The aim of the study was to characterize the degree of adiposity in rats fed a high-fat diet using cluster analysis and to create adiposity intervals in an experimental model of obesity. Thirty-day-old male Wistar rats were fed a normal (n=41) or a high-fat (n=43) diet for 15 weeks. Obesity was defined based on the adiposity index; and the degree of adiposity was evaluated using cluster analysis. Cluster analysis allowed the rats to be classified into two groups (overweight and obese). The obese group displayed significantly higher total body fat and a higher adiposity index compared with those of the overweight group. No differences in systolic blood pressure or nonesterified fatty acid, glucose, total cholesterol, or triglyceride levels were observed between the obese and overweight groups. The adiposity index of the obese group was positively correlated with final body weight, total body fat, and leptin levels. Despite the classification of sedentary rats into overweight and obese groups, it was not possible to identify differences in the comorbidities between the two groups.

Glycemic profile and prebiotic potential "in vitro" of bread with yacon (Smallanthus sonchifolius) flour

The purpose of this study was to elaborate bread with yacon flour at two different levels (6% and 11%) and to analyze their proximate composition, their glycemic indices and their prebiotic potentials in vitro. Bread with 6% and 11% of yacon flour presented, simultaneously, low and moderate glycemic index. As for the prebiotic potentials, it was evident the presence of probiotic bacteria, particularly Lactobacillus. The results showed that, the addition of yacon flour on bread rendered products from low to moderate GI, with prebiotic potential, low fat and high fiber contents, according to the Brazilian food legislation.

Application of roasted rice bran in cereal bars

The objective of this study was to evaluate the viability of using microwave-roasted rice bran as an ingredient in high-fiber cereal bars to obtain a product with good acceptability. The influence of the rice flakes, corn flakes, and roasted rice bran levels on the physical and chemical characteristics of the cereal bars was studied. The overall acceptability of three selected formulations was also evaluated. An increase in the roasted rice bran level in the formulation reduced the force of rupture and water activity, resulted in intermediate density, and caused darkening of the bars. The contents of lipid and total dietary fiber were higher in the formulation with the highest rice bran content, which was therefore classified as functional food. The formulation containing 0.34; 0.32; and 0.34 roasted rice bran, rice flakes, and corn flakes, respectively, seemed to be the best outcome. Cereal bars with roasted rice bran levels between 10 and 20% were accepted by consumers.

White tea (Camellia sinensis) extract reduces oxidative stress and triacylglycerols in obese mice

White tea is an unfermented tea made from young shoots of Camellia sinensis protected from sunlight to avoid polyphenol degradation. Although its levels of catechins are higher than those of green tea (derived from the same plant), there are no studies addressing the relationship between this tea and obesity associated with oxidative stress.The objective of this study was to evaluate the effect of white tea on obesity and its complications using a diet induced obesity model. Forty male C57BL/6 mice were fed a high-fat diet to induce obesity (Obese group) or the same diet supplemented with 0.5% white tea extract (Obese + WTE) for 8 weeks. Adipose tissue, serum lipid profile, and oxidative stress were studied. White tea supplementation was not able to reduce food intake, body weight, or visceral adiposity. Similarly, there were no changes in cholesterol rich lipoprotein profile between the groups. A reduction in blood triacylglycerols associated with increased cecal lipids was observed in the group fed the diet supplemented with white tea. White tea supplementation also reduced oxidative stress in liver and adipose tissue. In conclusion, white tea extract supplementation (0.5%) does not influence body weight or adiposity in obese mice. Its benefits are restricted to the reduction in oxidative stress associated with obesity and improvement of hypertriacylglycerolemia.