Mitochondrial dysfunction in the liver of type 2 diabetic Goto-Kakizaki rats: improvement by a combination of nutrients

Central and Peripheral Metabolic Defects Contribute to the Pathogenesis of Alzheimer's Disease: Targeting Mitochondria for Diagnosis and Prevention

Significance: Epidemiological studies indicate that metabolic disorders are associated with an increased risk for Alzheimer's disease (AD). Metabolic remodeling occurs in the central nervous system (CNS) and periphery, even in the early stages of AD. Mitochondrial dysfunction has been widely accepted as a molecular mechanism underlying metabolic disorders. Therefore, focusing on early metabolic changes, especially from the perspective of mitochondria, could be of interest for early AD diagnosis and intervention. Recent Advances: We and others have identified that the levels of several metabolites are fluctuated in the periphery before their accumulation in the CNS, which plays an important role in the pathogenesis of AD. Mitochondrial remodeling is likely one of the earliest signs of AD, linking nutritional imbalance to cognitive deficits. Notably, by improving mitochondrial function, mitochondrial nutrients efficiently rescue cellular metabolic dysfunction in the CNS and periphery in individuals with AD. Critical Issues: Peripheral metabolic disorders should be intensively explored and evaluated for the early diagnosis of AD. The circulating metabolites derived from mitochondrial remodeling represent novel potential diagnostic biomarkers for AD that are more readily detected than CNS-oriented biomarkers. Moreover, mitochondrial nutrients provide a promising approach to preventing and delaying AD progression. Future Directions: Abnormal mitochondrial metabolism in the CNS and periphery is involved in AD pathogenesis. More clinical studies provide evidence for the suitability and reliability of circulating metabolites and cytokines for the early diagnosis of AD. Targeting mitochondria to rewire cellular metabolism is a promising approach to preventing AD and ameliorating AD-related metabolic disorders.

Mitoprotective Clinical Strategies in Type 2 Diabetes and Fanconi Anemia Patients: Suggestions for Clinical Management of Mitochondrial Dysfunction

Oxidative stress (OS) and mitochondrial dysfunction (MDF) occur in a number of disorders, and several clinical studies have attempted to counteract OS and MDF by providing adjuvant treatments against disease progression. The present review is aimed at focusing on two apparently distant diseases, namely type 2 diabetes (T2D) and a rare genetic disease, Fanconi anemia (FA). The pathogenetic links between T2D and FA include the high T2D prevalence among FA patients and the recognized evidence for OS and MDF in both disorders. This latter phenotypic/pathogenetic feature-namely MDF-may be regarded as a mechanistic ground both accounting for the clinical outcomes in both diseases, and as a premise to clinical studies aimed at counteracting MDF. In the case for T2D, the working hypothesis is raised of evaluating any in vivo decrease of mitochondrial cofactors, or mitochondrial nutrients (MNs) such as α-lipoic acid, coenzyme Q10, and l-carnitine, with possibly combined MN-based treatments. As for FA, the established knowledge of MDF, as yet only obtained from in vitro or molecular studies, prompts the requirement to ascertain in vivo MDF, and to design clinical studies aimed at utilizing MNs toward mitigating or delaying FA's clinical progression. Altogether, this paper may contribute to building hypotheses for clinical studies in a number of OS/MDF-related diseases.

Alpha-lipoic acid suppresses Nε-(carboxymethyl) lysine-induced epithelial mesenchymal transition in HK-2 human renal proximal tubule cells

N^ε-(carboxymethyl) lysine (CML) plays causal roles in diabetic complications. In the present study, we investigated whether CML-induced HIF-1α accumulation and epithelial-mesenchymal transition (EMT) in HK-2 renal proximal tubular epithelial cells. Treatment with CML-BSA increased reactive oxygen species (ROS) production reduced the mitochondrial membrane potential and induced mitochondrial fragmentation. Pre-treatment of cells with antioxidant, α-lipoic acid, normalised the ROS production and restored the mitochondrial membrane potential. These changes were accompanied with morphological changes of epithelial mesenchymal transition. CML-BSA increased the protein level of hypoxia-inducible factor-1α (HIF-1α), and the EMT-associated transcription factor, TWIST. These effects were reversed by α-lipoic acid. CML-BSA increased the protein levels of mesenchymal-specific markers, including vimentin, α-smooth muscle actin, which were alleviated by pre-treatment with α-lipoic acid. Our data suggest that CML-BSA induces EMT through a ROS/HIF-1α/TWIST-dependent mechanism, and that α-lipoic acid may alleviate the CML-induced EMT in renal tubular cells.

Ellagic Acid Alleviates Hepatic Oxidative Stress and Insulin Resistance in Diabetic Female Rats

Non-alcoholic fatty liver disease (NAFLD) affects more than 70% of patients with type 2 diabetes mellitus (T2DM) and has become one of the most common metabolic liver diseases worldwide. To date, treatments specifically targeting NAFLD do not exist. Oxidative stress and insulin resistance have been implicated in the pathogenesis of NAFLD in diabetes. Accordingly, the goal of this present study was to determine whether Ellagic acid (EA), a natural antioxidant polyphenol found in berries and nuts, mitigates hepatic oxidative stress and insulin resistance in T2DM rats, and thus alleviates NAFLD. Using adult female Goto Kakizaki (GK) rats, a non-obese and spontaneous model of T2DM, we found that EA treatment significantly lowered fasting blood glucose and reduced insulin resistance, as shown by a 21.8% reduction in the homeostasis model assessment index of insulin resistance (HOMA-IR), while triglyceride and total cholesterol levels remained unchanged. Increased hepatic lipid accumulation and oxidative stress present in diabetic GK rats was markedly reduced with EA treatment. This effect was associated with a downregulation of the NADPH oxidase subunit, p47-phox, and overexpression of NF-E2-related factor-2 (NRF2). Moreover, EA was able to decrease the hepatic expression of hypoxia-inducible factor (HIF-α), a transcription factor linked to hypoxia and hepatic steatosis. We further showed that EA treatment activated an insulin signaling pathway in the liver, as evidenced by increased levels of phosphorylated Akt (Ser 473). In conclusion, our results demonstrate that EA diminishes blood glucose levels and potently suppress NAFLD in diabetic rats via mechanisms that involve reductions in p47-phox and HIF-α, upregulation of NRF2 and enhancement of the Akt signaling pathway in the liver. Together, these results reveal that EA improves hepatic insulin sensitivity and lipid metabolism as a result of its antioxidant effects. This implies an anti-diabetic effect of EA with beneficial effects for the treatment of hepatic complications in T2DM.

A pilot trial of l-carnitine in patients with traumatic brain injury: Effects on biomarkers of injury

OBJECTIVE

To investigate the effects of l-Carnitine on neuron specific enolase (NSE) as a marker of inflammation in patients with traumatic brain injury (TBI).

METHODS

Forty patients with severe TBI were randomized into 2 groups. The (LCA-) group received standard treatment with placebo while the (LCA+) group received l-Carnitine 2g/day for one week. NSE was measured on days 1, 3 and 7 after the initiation of the study. Neurocognitive and neurobehavioral disorders were recorded on the first and third months.

RESULTS

Neurocognitive function and NSE significantly improved within one week in both groups. Patient mortality was similar in LCA+ and LCA- groups (P value: 0.76). Brain edema was present in 7 patients in LCA+ group and 13 patients in LCA-group (P value: 0.044). While there was no difference in NSE levels between the two groups. Neurological function was preserved in the LCA+ group with an exception of attention deficit, which was frequent in the LCA+ group.

CONCLUSION

We concluded that despite improvements in neurobehavioral function and the degree of cerebral edema, 7-days of treatment with l-Carnitine failed to reduce serum NSE levels or improve mortality rate at 90days in patients with TBI.

Avocado Oil Improves Mitochondrial Function and Decreases Oxidative Stress in Brain of Diabetic Rats

Diabetic encephalopathy is a diabetic complication related to the metabolic alterations featuring diabetes. Diabetes is characterized by increased lipid peroxidation, altered glutathione redox status, exacerbated levels of ROS, and mitochondrial dysfunction. Although the pathophysiology of diabetic encephalopathy remains to be clarified, oxidative stress and mitochondrial dysfunction play a crucial role in the pathogenesis of chronic diabetic complications. Taking this into consideration, the aim of this work was to evaluate the effects of 90-day avocado oil intake in brain mitochondrial function and oxidative status in streptozotocin-induced diabetic rats (STZ rats). Avocado oil improves brain mitochondrial function in diabetic rats preventing impairment of mitochondrial respiration and mitochondrial membrane potential (ΔΨ m ), besides increasing complex III activity. Avocado oil also decreased ROS levels and lipid peroxidation and improved the GSH/GSSG ratio as well. These results demonstrate that avocado oil supplementation prevents brain mitochondrial dysfunction induced by diabetes in association with decreased oxidative stress.

The role of antioxidants and other agents in alleviating hyperglycemia mediated oxidative stress and injury in liver

Several antioxidants and agents having similar antioxidant effects are known to exert beneficial effects in ameliorating the injurious effects of hyperglycemia on liver in different diabetic in vitro and in vivo models. The review deals with some of the agents which have been shown to exert protective effects on liver against hyperglycemic insult and the various mechanisms involved. The different classes of agents which protect the diabetic liver or decrease the severity of hyperglycemia mediated injury include flavonoids, catechins, and other polyphenolic compounds, curcumin and its derivatives, certain vitamins, hormones and drugs, trace elements, prototypical antioxidants and amino acids. Some of the pronounced changes mediated by the antioxidants in liver exposed to hyperglycemia include decreased oxidative stress, and alterations in carbohydrate and lipid metabolism. Other mechanisms through which the agents ameliorate hyperglycemia mediated liver injury include decrease in oxidative DNA and protein damage, restoration of mitochondrial structural and functional integrity, decrease in inflammation and improved insulin signaling. Thus, antioxidants may prove to be an important mode of defense in maintaining normal hepatic functions in diabetes.

Expression of hepatic antioxidant enzymes in non-obese type-2 diabetic Goto-Kakizaki rats

Diabetes mellitus and its complications have been attributed in part to oxidative stress, against which antioxidant enzymes constitute a major protective mechanism. The present study was performed to investigate the effects of early stage type 2 diabetes in the absence of obesity and liver damage on hepatic antioxidant enzyme expression and oxidative stress using 9-week-old Goto-Kakizaki (GK) rats. Hepatic total antioxidant capacity determined by total oxygen radical scavenging capacity and lipid peroxidation determined by malondialdehyde in plasma and liver were not significantly different between normal Wistar rats and GK rats. These results indicated that oxidative stress is not evident in these type 2 diabetic rats. Hepatic expression levels of antioxidant enzymes, including superoxide dismutase-1, catalase, glutathione peroxidase and reductase, thioredoxin-1, mu- and pi-class glutathione S-transferase (GST), and the gamma-glutamylcysteine ligase catalytic subunit, were not different between normal rats and GK rats. But, hepatic level and activity of alpha-class GST were decreased and peroxiredoxin-1 level was increased in GK rats, suggesting that upregulation of peroxiredoxin-1 compensates for downregulation of alpha-class GST. These results suggest that alpha-class GST and peroxiredoxin-1 in liver can be altered during the early stages of type 2 diabetes in the absence of obesity and severe oxidative stress.

Effects of sesame oil on the reproductive parameters of diabetes mellitus-induced male rats

PURPOSE

The purpose of the present study was to investigate the effect of sesame oil on the reproductive parameters of diabetic male Wistar rats.

MATERIALS AND METHODS

The adult male rats in a split plot design were divided into normal (n=10), normal 5% (n=5; 5% sesame oil enriched diet), diabetic (Streptozocin induced diabetes; n=9), diabetic 5% (n=9; 5% sesame oil enriched diet), and diabetic 10% (n=9; 10% sesame oil enriched diet) groups. Diet supplementation continued for 56 days.

RESULTS

Sesame oil supplementation did not reduce the plasma glucose concentration of rats in the diabetic groups (p>0.05). The total spermatogonia, spermatocytes, Leydig cells/tubule, and the germ cell to Sertoli cell ratio were lower in the diabetic rats than the normal ones (p<0.05), and with the exception of spermatogonia counts, these values improved by the addition of sesame oil to the diet (p<0.05). The sperm progressive motility and viability were lower in the diabetic rats (p<0.05) and sesame oil supplementation did not improve them. Incorporation of sesame oil into the diet improved the plasma testosterone concentration of the diabetic rats in a dose-dependent manner (p<0.05).

CONCLUSIONS

In summary, sesame oil supplementation improved the reproductive parameters of diabetic rats at the levels of the testicular microstructure and function, but was not effective in protecting the epididymal sperm.

Progression of type 2 diabetes in GK rats affects muscle and liver mitochondria differently: pronounced reduction of complex II flux is observed in liver only

Impaired mitochondrial function is implicated in the development of type 2 diabetes mellitus (T2DM). This was investigated in mitochondria from skeletal muscle and liver of the Goto-Kakizaki (GK) rat, which spontaneously develops T2DM with age. The early and the manifest stage of T2DM was studied in 6- and 16-wk-old GK rats, respectively. In GK16 compared with GK6 animals, a decrease in state 3 respiration with palmitoyl carnitine (PC) as substrate was observed in muscle. Yet an increase was seen in liver. To test the complex II contribution to the state 3 respiration, succinate was added together with PC. In liver mitochondria, this resulted in an ∼50% smaller respiratory increase in the GK6 group compared with control and no respiratory increase at all in the GK16 animals. Yet no difference between groups was seen in muscle mitochondria. RCR and P/O ratio was increased (P < 0.05) in liver but unchanged in muscle in both GK groups. We observed increased lipid peroxidation and decreased Akt phosphorylation in liver with the progression of T2DM but no change in muscle. We conclude that, during the progression of T2DM in GK rats, liver mitochondria are affected earlier and/or more severely than muscle mitochondria. Succinate dehydrogenase flux in the presence of fatty acids was reduced severely in liver but not in muscle mitochondria during manifest T2DM. The observations support the notion that T2DM pathogenesis is initiated in the liver and that only later are muscle mitochondria affected.

Alfa-lipoic acid controls tumor growth and modulates hepatic redox state in Ehrlich-ascites-carcinoma-bearing mice

The effect of oral supplementation of α-lipoic (LA) on growth of Ehrlich ascites carcinoma cells (EACs) and hepatic antioxidant state in mice was investigated. The results revealed that α-lipoic (LA) acid at 50 mg/kg body wt reduced the viability and volume of EAC cells and increased the survival of the treated animals. In addition, LA normalized oxidative stress in liver of mice-bearing EAC cells evidenced by increasing the levels of total thiols, glutathione, glutathione-S-transferase, superoxide dismutase, and catalyse. On the other hand, significant decreases in the levels of malondialdehyde and protein carbonyl were demonstrated in liver indicating controlled oxidative stress in these animals. As a consequence, LA regulated liver enzymes, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyl transferase. The data also indicated the efficiency of LA as cancer inhibitor and therapeutic influence. In conclusion, the present data suggest LA as a potential therapeutic complement in the treatment or prevention of different pathologies that may be related to an imbalance of the cellular oxidoreductive status associated with malignancy.

Acetyl-L-carnitine treatment following spinal cord injury improves mitochondrial function correlated with remarkable tissue sparing and functional recovery

We have recently documented that treatment with the alternative biofuel, acetyl-L-carnitine (ALC, 300 mg/kg), as late as 1 h after T10 contusion spinal cord injury (SCI), significantly maintained mitochondrial function 24 h after injury. Here we report that after more severe contusion SCI centered on the L1/L2 segments that are postulated to contain lamina X neurons critical for locomotion (the "central pattern generator"), ALC treatment resulted in significant improvements in acute mitochondrial bioenergetics and long-term hind limb function. Although control-injured rats were only able to achieve slight movements of hind limb joints, ALC-treated animals produced consistent weight-supported plantar steps 1 month after injury. Such landmark behavioral improvements were significantly correlated with increased tissue sparing of both gray and white matter proximal to the injury, as well as preservation of choline acetyltransferase (ChAT)-positive neurons in lamina X rostral to the injury site. These findings signify that functional improvements with ALC treatment are mediated, in part, by preserved locomotor circuitry rostral to upper lumbar contusion SCI. Based on beneficial effects of ALC on mitochondrial bioenergetics after injury, our collective evidence demonstrate that preventing mitochondrial dysfunction acutely "promotes" neuroprotection that may be associated with the milestone recovery of plantar, weight-supported stepping.

The protection role of heat shock protein 70 (HSP-70) in the testes of cadmium-exposed rats

Cadmium (Cd) is an environmental carcinogenic pollutant known to inactivate several proteins involved in DNA repair systems while at the same time creating an oxidative stress that can result in additional DNA lesions. The testis and the lung are the target organs for cadmium carcinogenesis. Increased production of oxidants in vivo can cause damage to intracellular macromolecules such as DNA, proteins and lipids, which in turn lead to oxidative injury. So, this investigation aimed to evaluate the protective role of L-Carnitine through up regulation of HSPs against DNA damage induced by cadmium chloride. The current study was carried out on forty adult male rats, each with average weight 220-250g., were divided into 4 equal groups. 1(st) group was received saline solution (0.5 ml/100 g body weight) and kept as control. 2(nd) group was received 500mg / kg body weight L-Carnitine intraperitoneally (IP). 3(rd) group was administered 1.2 mg cadmium chloride IP. 4(th) group was received both cadmium chloride and L-Carnitine simultaneously. The comet assay parameters showed significantly increased HSP70 and DNA damage in testis cells after 10 and 56 days in the third group. Meanwhile, HSP70 showed significantly decreased levels after 10 days and 56 days in the fourth group after L-Carnitine treatment simultaneously with cadmium chloride. The results of the present study demonstrate a damaging effect of cadmium chloride on DNA of the testis cells (with low stress response). This damaging effect increases the synthesis of HSP70 that upregulated by L-Carnitine treatment and showed ameliorative effect of the cells for recovery.

Non-alcoholic fatty liver disease and cardiovascular risk: metabolic aspects and novel treatments

Non-alcoholic fatty liver disease (NAFLD) is usually a silent disease that occurs in a very high proportion of people with features of the metabolic syndrome, including overweight, insulin resistance and type 2 diabetes. Because obesity and type 2 diabetes are now extremely common in Westernised societies, it is likely that the prevalence of NAFLD increases markedly in the future. Although previously it was thought that NAFLD was harmless, it is now recognised that NAFLD can be a progressive liver condition that increases risk of cirrhosis, end-stage liver disease and hepatocellular carcinoma. Additionally, liver fat accumulation causes insulin resistance and increases risk of type 2 diabetes. Increasing evidence now shows NAFLD is a risk factor for cardiovascular disease (CVD). The purpose of this review is to briefly discuss the pathogenesis of NAFLD, to describe the relationship between NAFLD and CVD and the mechanisms linking both conditions and to discuss some of the treatment options (including lifestyle, nutrition and drugs) that may influence both NAFLD and risk of CVD.

L-carnitine ameliorated fatty liver in high-calorie diet/STZ-induced type 2 diabetic mice by improving mitochondrial function

BACKGROUND

There are an increasing number of patients suffering from fatty liver caused by type 2 diabetes. We intended to study the preventive and therapeutic effect of L-carnitine (LC) on nonalcoholic fatty liver disease (NAFLD) in streptozotocin (STZ)-induced type 2 diabetic mice and to explore its possible mechanism.

METHODS

Thirty male Kungming mice were randomly divided into five groups: control group, diabetic group, pre-treatment group (125 mg/kg BW), low-dose (125 mg/kg BW) therapeutic group and high-dose (250 mg/kg BW) therapeutic group. The morphology of hepatocytes was observed by light and electron microscopy. LC and ALC (acetyl L-carnitine) concentrations in the liver were determined by high-performance liquid chromatography (HPLC). Moreover, liver weight, insulin levels and free fatty acid (FFA) and triglyceride (TG) levels in the liver and plasma were measured.

RESULTS

Average liver LC and ALC levels were 33.7% and 20% lower, respectively, in diabetic mice compared to control mice (P < 0.05). After preventive and therapeutic treatment with LC, less hepatocyte steatosis, clearer crista and fewer glycogen granules in the mitochondria were observed. Decreased liver weight, TG levels, and FFA concentrations (P < 0.05) in the liver were also observed after treatment with LC in diabetic mice. Moreover, liver LC and ALC levels increased upon treatment with LC, whereas the ratio of LC and ALC decreased significantly (P < 0.01).

CONCLUSION

LC supplements ameliorated fatty liver in type 2 diabetic mice by increasing fatty acid oxidation and decreasing the LC/ALC ratio in the liver. Therefore, oral administration of LC protected mitochondrial function in liver.