Gaetano Serviddio

Searching for an Operational Definition of Frailty: A Delphi Method Based Consensus Statement. The Frailty Operative Definition-Consensus Conference Project

BACKGROUND There is no consensus regarding the definition of frailty for clinical uses. METHODS A modified Delphi process was used to attempt to achieve consensus definition. Experts were selected from different fields and organized into five Focus Groups. A questionnaire was developed and sent to experts in the area of frailty. Responses and comments were analyzed using a pre-established strategy. Statements with an agreement more than or equal to 80% were accepted. RESULTS Overall, 44% of the statements regarding the concept of frailty and 18% of the statements regarding diagnostic criteria were accepted. There was consensus on the value of screening for frailty and about the identification of six domains of frailty for inclusion in a clinical definition, but no agreement was reached concerning a specific set of clinical/laboratory biomarkers useful for diagnosis. CONCLUSIONS There is agreement on the usefulness of defining frailty in clinical settings as well as on its main dimensions. However, additional research is needed before an operative definition of frailty can be established.

Uncoupling protein-2 (UCP2) induces mitochondrial proton leak and increases susceptibility of non-alcoholic steatohepatitis (NASH) liver to ischaemia–reperfusion injury

Background: The mechanisms of progression from fatty liver to steatohepatitis and cirrhosis are not well elucidated. Mitochondrial dysfunction represents a key factor in the progression of non-alcoholic steatohepatitis (NASH) as mitochondria are the main cellular site of fatty acid oxidation, ATP synthesis and reactive oxygen species (ROS) production. Aims: (1) To evaluate the role of the uncoupling protein 2 in controlling mitochondrial proton leak and ROS production in NASH rats and humans; and (2) to assess the acute liver damage induced by ischaemia–reperfusion in rats with NASH. Methods: Mitochondria were extracted from the livers of NASH humans and rats fed a methionine and choline deficient diet. Proton leak, H2O2 synthesis, reduced glutathione/oxidised glutathione, 4-hydroxy-2-nonenal (HNE)–protein adducts, uncoupling protein-2 (UCP2) expression and ATP homeostasis were evaluated before and after ischaemia–reperfusion injury. Results: NASH mitochondria exhibited an increased rate of proton leak due to upregulation of UCP2. These results correlated with increased production of mitochondrial hydrogen peroxide and HNE–protein adducts, and decreased hepatic ATP content that was not dependent on mitochondrial ATPase dysfunction. The application of an ischaemia–reperfusion protocol to these livers strongly depleted hepatic ATP stores, significantly increased mitochondrial ROS production and impaired ATPase activity. Livers from patients with NASH exhibited UCP2 over-expression and mitochondrial oxidative stress. Conclusions: Upregulation of UCP2 in human and rat NASH liver induces mitochondrial uncoupling, lowers the redox pressure on the mitochondrial respiratory chain and acts as a protective mechanism against damage progression but compromises the liver capacity to respond to additional acute energy demands, such as ischaemia–reperfusion. These findings suggest that UCP2-dependent mitochondria uncoupling is an important factor underlying events leading to NASH and cirrhosis.

Ursodeoxycholic acid protects against secondary biliary cirrhosis in rats by preventing mitochondrial oxidative stress

Ursodeoxycholic acid (UDCA) improves clinical and biochemical indices in primary biliary cirrhosis and prolongs survival free of liver transplantation. Recently, it was suggested that the cytoprotective mechanisms of UDCA may be mediated by protection against oxidative stress, which is involved in the development of cirrhosis induced by chronic cholestasis. The aims of the current study were 1) to identify the mechanisms involved in glutathione depletion, oxidative stress, and mitochondrial impairment during biliary cirrhosis induced by chronic cholestasis in rats; and 2) to determine the mechanisms associated with the protective effects of UDCA against secondary biliary cirrhosis. The findings of the current study indicate that UDCA partially prevents hepatic and mitochondrial glutathione depletion and oxidation resulting from chronic cholestasis. Impairment of biliary excretion was accompanied by decreased steady‐state hepatic levels of γ‐glutamyl cysteine synthetase and γ‐cystathionase messenger RNAs. UDCA treatment led to up‐regulation of γ‐glutamyl cysteine synthetase in animals with secondary biliary cirrhosis and prevented the marked increases in mitochondrial peroxide production and hydroxynonenal‐protein adduct production that are observed during chronic cholestasis. A population of damaged and primarily apoptotic hepatocytes characterized by dramatic decreases in mitochondrial cardiolipin levels and membrane potential as well as phosphatidylserine exposure evolves in secondary biliary cirrhosis. UDCA treatment prevents the growth of this population along with the decreases in mitochondrial cardiolipin levels and membrane potential that are induced by chronic cholestasis. In conclusion, UDCA treatment enhances the antioxidant defense mediated by glutathione; in doing so, this treatment prevents cardiolipin depletion and cell injury in animals with secondary biliary cirrhosis. (HEPATOLOGY 2004;39:711–720)

Free radical biology for medicine: learning from nonalcoholic fatty liver disease

Reactive oxygen species, when released under controlled conditions and limited amounts, contribute to cellular proliferation, senescence, and survival by acting as signaling intermediates. In past decades there has been an epidemic diffusion of nonalcoholic fatty liver disease (NAFLD) that represents the result of the impairment of lipid metabolism, redox imbalance, and insulin resistance in the liver. To date, most studies and reviews have been focused on the molecular mechanisms by which fatty liver progresses to steatohepatitis, but the processes leading toward the development of hepatic steatosis in NAFLD are not fully understood yet. Several nuclear receptors, such as peroxisome proliferator-activated receptors (PPARs) α/γ/δ, PPARγ coactivators 1α and 1β, sterol-regulatory element-binding proteins, AMP-activated protein kinase, liver-X-receptors, and farnesoid-X-receptor, play key roles in the regulation of lipid homeostasis during the pathogenesis of NAFLD. These nuclear receptors may act as redox sensors and may modulate various metabolic pathways in response to specific molecules that act as ligands. It is conceivable that a redox-dependent modulation of lipid metabolism, nuclear receptor-mediated, could cause the development of hepatic steatosis and insulin resistance. Thus, this network may represent a potential therapeutic target for the treatment and prevention of hepatic steatosis and its progression to steatohepatitis. This review summarizes the redox-dependent factors that contribute to metabolism alterations in fatty liver with a focus on the redox control of nuclear receptors in normal liver as well as in NAFLD.

Aberrant insulin signaling in Alzheimer's disease: current knowledge

Alzheimers disease (AD) is the most common form of dementia affecting elderly people. AD is a multifaceted pathology characterized by accumulation of extracellular neuritic plaques, intracellular neurofibrillary tangles (NFTs) and neuronal loss mainly in the cortex and hippocampus. AD etiology appears to be linked to a multitude of mechanisms that have not been yet completely elucidated. For long time, it was considered that insulin signaling has only peripheral actions but now it is widely accepted that insulin has neuromodulatory actions in the brain. Insulin signaling is involved in numerous brain functions including cognition and memory that are impaired in AD. Recent studies suggest that AD may be linked to brain insulin resistance and patients with diabetes have an increased risk of developing AD compared to healthy individuals. Indeed insulin resistance, increased inflammation and impaired metabolism are key pathological features of both AD and diabetes. However, the precise mechanisms involved in the development of AD in patients with diabetes are not yet fully understood. In this review we will discuss the role played by aberrant brain insulin signaling in AD. In detail, we will focus on the role of insulin signaling in the deposition of neuritic plaques and intracellular NFTs. Considering that insulin mitigates beta-amyloid deposition and phosphorylation of tau, pharmacological strategies restoring brain insulin signaling, such as intranasal delivery of insulin, could have significant therapeutic potential in AD treatment.

Alterations of hepatic ATP homeostasis and respiratory chain during development of non-alcoholic steatohepatitis in a rodent model

Background  Mitochondrial dysfunction is considered a key player in non‐alcoholic steatohepatitis (NASH) but no data are available on the mitochondrial function and ATP homeostasis in the liver during NASH progression. In the present paper we evaluated the hepatic mitochondrial respiratory chain activity and ATP synthesis in a rodent model of NASH development.

Mitochondrial function in liver disease.

Oxidative stress is involved in the pathogenesis and progression of different liver diseases, such as alcoholic liver disease and biliary cirrhosis. The increased mitochondrial production of O2(-) at complexes I and III, and consequently of H2O2 and other reactive oxygen species (ROS), triggered by NADH overproduction seems the major cause of mitochondrial and cellular oxidative stress and damage in chronic alcoholism. The mitochondrial oxidative stress renders hepatocytes susceptible to ethanol- or acetaldehyde-induced mitochondrial membrane permeability transition (MMPT) and apoptosis. Nitrosative stress contributes to cell death by peroxynitrite formation. The expression of the death receptor ligand CD95 is also up-regulated by acetaldehyde metabolism. Consequently, a dual mechanism, NADH-driven MMPT and CD95-mediated apoptosis, involving in both cases acetaldehyde metabolism and ROS production, operates in ethanol-induced apoptosis. In the biliary cirrhosis induced by chronic cholestasis, liver mitochondria show increased H2O2 production and GSH depletion and oxidation. Dysfunctional hepatocytes, with a loss in mitochondrial cardiolipin and decreased mitochondrial membrane potential evolve during cholestasis to apoptosis. Ursodeoxycholic acid prevents enlargement of this population as well as mitochondrial oxidative stress. Mitochondrial oxidative stress precedes the initiation and execution of hepatocyte apoptosis in chronic alcoholism and biliary cirrhosis. We suggest that overproduction of mitochondrial NADH is the primary cause for the development of alcoholic and non-alcoholic liver disease by a situation of chronic mitochondrial oxidative stress, which should be considered the second hit that renders hepatocytes susceptible to cell injury and apoptosis.

Oxidative stress in symptom-free HCV carriers : relation with ALT flare-up

The reason why some hepatitis C virus carriers with normal aminotransferase activity present, during time, an activation of the disease, is unknown. The aim of this study was to assess the oxidative balance in such patients and to evaluate its possible role on the severity of disease.

Associated changes of lipid peroxidation and transforming growth factor β1 levels in human colon cancer during tumour progression

Background: During neoplastic progression, alterations in transforming growth factor β1 (TGF-β1) dependent control of cell growth may be an important mechanism of selective proliferation of transformed cellular clones. Defective regulation of TGF-β1 receptors has been reported to occur in a number of human malignant tumours while little is known of the actual levels of this growth inhibitory cytokine in cancer. On the basis of the demonstrated ability of major lipid peroxidation products such as 4-hydroxynonenal to modulate TGF-β1 expression and synthesis, we speculated that decreased lipid oxidation, as frequently observed in neoplastic tissues, would contribute to the selective promotion of tumour growth through decreased expression of the cytokine within the tumour mass. Aims: To seek a possible association between steady state levels of major aldehydic end products of lipid peroxidation and TGF-β1 content in human colon cancer at different stages of growth. Patients and methods: Tissue biopsies from 15 adult patients with colon adenocarcinoma of different TNM and G stagings were compared with regard to lipid peroxidation aldehydes and net TGF-β1 levels. For a more comprehensive analysis, cytokine type I and II receptors were measured in tumour biopsies. In one set of experiments, to support the conclusions, the apoptotic effect of TGF-β1 was evaluated in a human colon cancer cell line, CaCo-2, retaining receptor changes consistent with those observed in cancer patients. Results: With the exception of two extremely advanced cases (T4/G3) in which tissue levels of lipid peroxidation were within the normal range, 4-hydroxynonenal was significantly decreased in all other cancer specimens. Consistent with lipid peroxidation levels, TGF-β1 protein was markedly decreased or even negligible compared with the corresponding normal tissue surrounding the tumour in all tested biopsies except for the two T4/G3 colon cancers in which cytokine content was again within the normal range. As regards TGF-β1 receptors, both in tumour sections and CaCo-2 cells, downregulation was greater for TGF-β1 receptor I than for receptor II. Of note, in CaCo-2 cells, incubation with appropriate doses of TGF-β1 led to marked nuclear fragmentation and apoptosis. Conclusions: Evasion of human colon cancer cells from TGF-β1 mediated growth inhibition appears to be due not only to downregulation of TGF-β1 receptors, which is inconsistent and unrelated to cancer development, but also to the constant low concentration of this cytokine in the tumour mass. The associated levels of lipid peroxidation aldehydes, much lower than in control tissue, probably represent a lower stimulus for TGF-β1 production in the neoplastic area and thus a favourable condition for neoplastic progression.

Targeting mitochondria: a new promising approach for the treatment of liver diseases.

Mitochondrial dysfunction acts as a common pathogenetic mechanism in several acute and chronic liver diseases, such as Alcoholic and Non-Alcoholic Fatty Liver Disease (NAFLD), drug-induced steatohepatitis, viral hepatitis, biliary cirrhosis, hepatocellular carcinoma, ischemia/reperfusion injury and transplant rejection. In particular mitochondrial uncoupling,has been recently identified to play a determinant role in the pathogenesis of liver diseases by causing decrease of mitochondrial proton motive force and ATP depletion. Damaged mitochondria present defects in lipid homeostasis, bioenergetics impairment and overproduction of Reactive Oxygen Species (ROS), leading to lipid accumulation and oxidative stress. Dysfunctional and/or uncoupled mitochondria enhance the susceptibility of hepatocytes to cell death by necrosis, via ATP depletion, or by apoptosis, via membrane permeabilization. Thus, prevention of mitochondrial alterations promises to be an effective strategy for treatment of liver diseases. However, no therapy has proven to be absolutely effective, whereas those that are beneficial present several side effects. The present review summarizes the recent approaches in mitochondrial drug deliver systems and focuses on mitochondria-targeted molecules application in liver disease. New selective molecules and nanocarriers technology are also considered as potentially effective in the targeting of mitochondrial dysfunction in liver pathology.