Neonatal overfeeding causes higher adrenal catecholamine content and basal secretion and liver dysfunction in adult rats

Purpose

Rats that are overfed during lactation exhibit neonatal hyperleptinemia and higher visceral adiposity, hypertension, higher liver oxidative stress and insulin resistance in the liver as adults. Previously, we demonstrated that neonatal hyperleptinemia is associated with adrenal medullary hyperfunction, hypertension and liver steatosis in adulthood. Therefore, we hypothesised that adrenal and liver functions are altered in adult obese rats that were overfed during lactation, which would underlie their hypertension and liver alterations.

Methods

The litter size was reduced from ten to three male pups on the third day of lactation until weaning (SL) to induce early overfeeding in Wistar rats. The control group had ten rats per litter (NL). Rats had free access to standard diet, and water after weaning until the rats were 180 days old.

Results

The SL group exhibited higher adrenal catecholamine content (absolute: +35% and relative: +40%), tyrosine hydroxylase (+31%) and DOPA decarboxylase (+90%) protein contents and basal catecholamine secretion in vitro (+57%). However, the hormones of the hypothalamic-pituitary-adrenal cortex axis were unchanged. β₃-adrenergic receptor content in visceral adipose tissue was unchanged in SL rats, but the β₂-adrenergic receptor content in the liver was lower in this group (?45%). The SL group exhibited higher glycogen and triglycerides contents in the liver (+79 and +49%, respectively), which suggested microesteatosis.

Conclusions

Neonatal overfeeding led to higher adrenomedullary function, but the liver β₂-adrenergic receptor content was reduced. These results may contribute to the hepatic dysfunction characteristic of liver obesity complications.     

Protective effects of garlic extract on cardiac function,heart rate variability,and cardiac mitochondria in obese insulin-resistant rats

Purpose

Garlic has been shown to exhibit antioxidant effects and cardioprotective properties. However, the effects of garlic extract on the heart in insulin resistance induced by long-term high-fat-diet consumption are not well defined. Therefore, we sought to determine the effects of garlic extract in the obese insulin-resistant rats.

Methods

Male Wistar rats (180–200 g) were divided into two groups: normal-diet or high-fat-diet (n = 24/group) fed for 12 weeks. Rats in each groups were divided into three subgroups (n = 8 each): vehicle or garlic extract (250 or 500 mg/kg/day, respectively) treated for 28 days. At the end of the treatment, the metabolic parameters, heart rate variability (HRV), cardiac function, and cardiac mitochondrial function were determined.

Results

Rats that received a high-fat-diet for 12 weeks had increased body weight, visceral fat, plasma insulin levels, total cholesterol, oxidative stress levels, depressed HRV, and cardiac mitochondrial dysfunction. Garlic extract at both concentrations significantly decreased the plasma insulin, total cholesterol, homeostasis model assessment index, and oxidative stress levels. Furthermore, garlic extract at both doses restored the HRV, cardiac function, and cardiac mitochondrial function.

Conclusion

We concluded that garlic extract at both concentrations exerted cardioprotective effects against cardiac dysfunction and mitochondrial dysfunction in obese insulin-resistant rats.     

Nephroprotective effect of astaxanthin against trivalent inorganic arsenic-induced renal injury in wistar rats

Inorganic arsenic (iAs) is a toxic metalloid found ubiquitously in the environment. In humans, exposure to iAs can result in toxicity and cause toxicological manifestations. Arsenic trioxide (As₂O₃) has been used in the treatment for acute promyelocytic leukemia. The kidney is the critical target organ of trivalent inorganic As (iAs^III) toxicity. We examine if oral administration of astaxanthin (AST) has protective effects on nephrotoxicity and oxidative stress induced by As₂O₃ exposure (via intraperitoneal injection) in rats. Markers of renal function, histopathological changes, Na⁺-K⁺ ATPase, sulfydryl, oxidative stress, and As accumulation in kidneys were evaluated as indicators of As₂O₃ exposure. AST showed a significant protective effect against As₂O₃-induced nephrotoxicity. These results suggest that the mechanisms of action, by which AST reduces nephrotoxicity, may include antioxidant protection against oxidative injury and reduction of As accumulation. These findings might be of therapeutic benefit in humans or animals suffering from exposure to iAs^III from natural sources or cancer therapy.     

Protective effect of resveratrol on arsenic trioxide-induced nephrotoxicity in rats

BACKGROUD/OBEJECTIVES

Arsenic, which causes human carcinogenicity, is ubiquitous in the environment. This study was designed to evaluate modulation of arsenic induced cancer by resveratrol, a phytoalexin found in vegetal dietary sources that has antioxidant and chemopreventive properties, in arsenic trioxide (As₂O₃)-induced Male Wistar rats.

MATERIALS/METHODS

Adult rats received 3 mg/kg As₂O₃ (intravenous injection, iv.) on alternate days for 4 days. Resveratrol (8 mg/kg) was administered (iv.) 1 h before As₂O₃ treatment. The plasma and homogenization enzymes associated with oxidative stress of rat kidneys were measured, the kidneys were examined histologically and trace element contents were assessed.

RESULTS

Rats treated with As₂O₃ had significantly higher oxidative stress and kidney arsenic accumulation; however, pretreatment with resveratrol reversed these changes. In addition, prior to treatment with resveratrol resulted in lower blood urea nitrogen, creatinine and insignificant renal tubular epithelial cell necrosis. Furthermore, the presence of resveratrol preserved the selenium content (0.805 ± 0.059 µg/g) of kidneys in rats treated with As₂O₃. However, resveratrol had no effect on zinc level in the kidney relative to As₂O₃-treated groups.

CONCLUSIONS

Our data show that supplementation with resveratrol alleviated nephrotoxicity by improving antioxidant capacity and arsenic efflux. These findings suggest that resveratrol has the potential to protect against kidney damage in populations exposed to arsenic.     

L-Ascorbic Acid and α-Tocopherol Reduces Hepatotoxicity Associated with Arsenic Trioxide Chemotherapy by Modulating Nrf2 and Bcl2 Transcription Factors in Chang liver Cells

Arsenic trioxide (As₂O₃) is a promising new regimen for the treatment of acute promyelocytic leukemia (APL). The induction of oxidative stress mediated by reactive oxygen species (ROS) and excessive intracellular calcium influx are the main reasons behind As₂O₃ toxicity. Since liver is the major organ for xenobiotic metabolism, it is always under stress. Antioxidant vitamins such as L-Ascorbic acid (L-AA) and α-Tocopherol (α-TOC) have been proposed to have beneficial effects against a variety of pathological conditions and are known by their free radical scavenging properties. The present study evaluates the curative efficacy of L-AA and α-TOC against As₂O₃ toxicity using immortalized human Chang liver cells. Our results suggest that L-AA (100 µM) and α-TOC (50 µM) recovered As₂O₃ (10 µM) cytotoxicity. Furthermore, As₂O₃ treatment showed an increase in lipid peroxidation and depletion in antioxidant status, mitochondrial trans membrane potential and values of total antioxidant capacity. Cotreatment of antioxidant vitamins with As₂O₃ resulted in a significant reversal of oxidative stress markers. Our findings substantiate the effect of antioxidant vitamins in protecting the hepatocytes from oxidative stress which may be attributed through Nrf2 (Nuclear factor erythroid 2-related factor 2) mediated upregulation of Bcl2 (B-cell lymphoma 2) expression.     

Diets high in sugar, fat, and energy induce muscle type-specific adaptations in mitochondrial functions in rats

Obesity is often associated with insulin resistance and mitochondrial dysfunction within skeletal muscles, but the causative factors are not clearly identified. The present study examined the role of nutrition, both qualitatively and quantitatively, in the induction of muscle mitochondrial defects. Two experimental diets [high sucrose (SU) and high fat (F)] were provided for 6 wk to male Wistar rats at 2 levels of energy [standard (N) and high (H)] and compared with a standard energy cornstarch-based diet (C). Insulin sensitivity (intraperitoneal glucose tolerance test, IPGTT) and intramyocellular triglyceride (IMTG) content (1H MRS) were determined at wk 5. Mitochondrial oxidative phosphorylation and superoxide anion radical (MSR) production were assessed on soleus (oxidative) and tibialis (glycolytic) muscles. Experimental diets induced hyperinsulinemia during IPGTT (P < 0.01 vs. C). Rats in the HSU and HF groups were hyperglycemic relative to the C group, P < 0.05 vs. C. The severity of insulin resistance paralleled IMTG accumulation (P < 0.05). In soleus, mitochondrial respiration and ATP production rates were lower in HSU and HF than in C (P < 0.05). By contrast, respiration was unaffected by the diets in tibialis, whereas ATP production tended to be lower in rats fed the experimental diets compared with C (P = 0.09). Mitochondrial adaptations were associated with more than a 50% reduction in MSR production in HSU and HF compared with C in both soleus (P < 0.05) and tibialis (P < 0.01). Changes in mitochondrial functions in the NSU and NF groups were intermediate and not significantly different from C. Therefore, excess fat or sucrose and more importantly, excess energy intake by rats is associated with muscle type-specific mitochondrial adaptations, which contribute to decrease mitochondrial production of ATP and reactive oxygen species.     

An Integrated Imaging Approach to the Study of Oxidative Stress Generation by Mitochondrial Dysfunction in Living Cells

Background

The mechanisms of action of many environmental agents commonly involve oxidative stress resulting from mitochondrial dysfunction. Zinc is a common environmental metallic contaminant that has been implicated in a variety of oxidant-dependent toxicological responses. Unlike ions of other transition metals such as iron, copper, and vanadium, Zn²⁺ does not generate reactive oxygen species (ROS) through redox cycling.

Objective

To characterize the role of oxidative stress in zinc-induced toxicity.

Methods

We used an integrated imaging approach that employs the hydrogen peroxide (H₂O₂)-specific fluorophore Peroxy Green 1 (PG1), the mitochondrial potential sensor 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbocyanine iodide (JC-1), and the mitochondria-targeted form of the redox-sensitive genetically encoded fluorophore MTroGFP1 in living cells.

Results

Zinc treatment in the presence of the Zn²⁺ ionophore pyrithione of A431 skin carcinoma cells preloaded with the H₂O₂-specific indicator PG1 resulted in a significant increase in H₂O₂ production that could be significantly inhibited with the mitochondrial inhibitor carbonyl cyanide 3-chlorophenylhydrazone. Mitochondria were further implicated as the source of zinc-induced H₂O₂ formation by the observation that exposure to zinc caused a loss of mitochondrial membrane potential. Using MTroGFP1, we showed that zinc exposure of A431 cells induces a rapid loss of reducing redox potential in mitochondria. We also demonstrated that zinc exposure results in rapid swelling of mitochondria isolated from mouse hearts.

Conclusion

Taken together, these findings show a disruption of mitochondrial integrity, H₂O₂ formation, and a shift toward positive redox potential in cells exposed to zinc. These data demonstrate the utility of real-time, live-cell imaging to study the role of oxidative stress in toxicological responses.     

Effects of Arsenite Exposure during Fetal Development on Energy Metabolism and Susceptibility to Diet-Induced Fatty Liver Disease in Male Mice

Background

Chronic exposure to arsenicals at various life stages and across a range of exposures has been implicated in cardiometabolic and liver disease, but disease predisposition from developmental exposures remains unclear.

Objectives

In utero and post-weaning exposure to trivalent arsenic (As^III) was examined on the background of a Western-style diet to determine whether As^III exposure affects metabolic disease.

Methods

Male Swiss Webster mice were exposed to 100 ppb As^III in utero, after weaning, or both. Ad libitum access to a Western-style diet was provided after weaning, and the plasma metabolome, liver histopathology, liver enzyme activity, and gene expression were analyzed.

Results

Hepatic lipid composition and histopathology revealed that developmental As^III exposure exacerbated Western-style diet–induced fatty liver disease. Continuous As^III exposure increased cardiometabolic risk factors including increased body weight, insulin resistance, hyperglycemia, and plasma triglycerides. As^III exposure produced a decrease in the intermediates of glycolysis and the TCA cycle while increasing ketones. Hepatic isocitrate dehydrogenase activity was also decreased, which confirmed disruption of the TCA cycle. Developmental As^III exposure increased the expression of genes involved in fatty acid synthesis, lipogenesis, inflammation, and packaging of triglycerides, suggesting an increased acetyl coenzyme A (acetyl-CoA) load.

Conclusions

In utero and continuous early-life exposure to As^III disrupted normal metabolism and elevated the risk for fatty liver disease in mice maintained on a high-fat diet. Our findings suggest that individuals exposed to As^III during key developmental periods and who remain exposed to As^III on the background of a Western-style diet may be at increased risk for metabolic disease later in life.

Citation

Ditzel EJ, Nguyen T, Parker P, Camenisch TD. 2016. Effects of arsenite exposure during fetal development on energy metabolism and susceptibility to diet-induced fatty liver disease in male mice. Environ Health Perspect 124:201–209; http://dx.doi.org/10.1289/ehp.1409501     

Increased hepatic de novo lipogenesis and mitochondrial efficiency in a model of obesity induced by diets rich in fructose

Purpose

To assess hepatic de novo lipogenesis and mitochondrial energetics as well as whole-body energy homeostasis in sedentary rats fed a fructose-rich diet.

Methods

Male rats of 90 days of age were fed a high-fructose or control diet for 8 weeks. Body composition, energy balance, oxygen consumption, carbon dioxide production, non-protein respiratory quotient, de novo lipogenesis and insulin resistance were measured. Determination of specific activity of hepatic enzymes of de novo lipogenesis, mitochondrial mass, oxidative capacity and degree of coupling, together with parameters of oxidative stress and antioxidant defence, was also carried out.

Results

Body energy and lipid content as well as plasma insulin and non-esterified fatty acids were significantly higher in fructose-fed than in control rats. Significantly higher rates of net de novo lipogenesis and activities of hepatic lipogenic enzymes fatty acid synthase and stearoyl CoA desaturase-1 were found in fructose-fed rats compared to controls. Mitochondrial protein mass and degree of coupling were significantly higher in fructose-fed rats compared to controls. Hepatic mitochondria showed oxidative damage, both in the lipid and in the protein component, together with decreased activity of antioxidant defence.

Conclusion

Liver mitochondrial compartment is highly affected by fructose feeding. The increased mitochondrial efficiency allows liver cells to burn less substrates to produce ATP for de novo lipogenesis and gluconeogenesis. In addition, increased lipogenesis gives rise to whole body and ectopic lipid deposition, and higher mitochondrial coupling causes mitochondrial oxidative stress.     

Naringin Improves Diet-Induced Cardiovascular Dysfunction and Obesity in High Carbohydrate,High Fat Diet-Fed Rats

Obesity, insulin resistance, hypertension and fatty liver, together termed metabolic syndrome, are key risk factors for cardiovascular disease. Chronic feeding of a diet high in saturated fats and simple sugars, such as fructose and glucose, induces these changes in rats. Naturally occurring compounds could be a cost-effective intervention to reverse these changes. Flavonoids are ubiquitous secondary plant metabolites; naringin gives the bitter taste to grapefruit. This study has evaluated the effect of naringin on diet-induced obesity and cardiovascular dysfunction in high carbohydrate, high fat-fed rats. These rats developed increased body weight, glucose intolerance, increased plasma lipid concentrations, hypertension, left ventricular hypertrophy and fibrosis, liver inflammation and steatosis with compromised mitochondrial respiratory chain activity. Dietary supplementation with naringin (approximately 100 mg/kg/day) improved glucose intolerance and liver mitochondrial dysfunction, lowered plasma lipid concentrations and improved the structure and function of the heart and liver without decreasing total body weight. Naringin normalised systolic blood pressure and improved vascular dysfunction and ventricular diastolic dysfunction in high carbohydrate, high fat-fed rats. These beneficial effects of naringin may be mediated by reduced inflammatory cell infiltration, reduced oxidative stress, lowered plasma lipid concentrations and improved liver mitochondrial function in rats.