From Bench to BedsideSpecial Section Editor: Alfredo Alberti

Insulin resistance, adiponectin, cytokines in NASH: Which is the best target to treat?

The occurrence of obesity has increased across the whole world. Many epidemiological studies have indicated that obesity strongly contributes to the development of cancer, cardiovascular diseases, type 2 diabetes, liver diseases and other disorders, accounting for a heavy burden on the public and on health-care systems every year. Excess energy uptake induces adipocyte hypertrophy, hyperplasia and formation of visceral fat in other non-adipose tissues to evoke cardiovascular disease, liver diseases. Adipose tissue can also secrete adipokines and inflammatory cytokines to affect the local microenvironment, induce insulin resistance, hyperglycemia, and activate associated inflammatory signaling pathways. This further exacerbates the development and progression of obesity-associated diseases. Although some progress in the treatment of obesity has been achieved in preclinical and clinical studies, the progression and pathogenesis of obesity-induced diseases are complex and unclear. We still need to understand their links to better guide the treatment of obesity and associated diseases. In this review, we review the links between obesity and other diseases, with a view to improve the future management and treatment of obesity and its co-morbidities.

Diabetes is a highly common metabolic disorder in advanced societies. One of the causes of diabetes is insulin resistance, which is associated with a loss of sensitivity to insulin-sensitive cells. Insulin resistance develops in the body of a person prone to diabetes many years before diabetes development. Insulin resistance is associated with complications such as hyperglycemia, hyperlipidemia, and compensatory hyperinsulinemia and causes liver inflammation, which, if left untreated, can lead to cirrhosis, fibrosis, and even liver cancer. Metformin is the first line of treatment for patients with diabetes, which lowers blood sugar and increases insulin sensitivity by inhibiting gluconeogenesis in liver cells. The use of metformin has side effects, including a metallic taste in the mouth, vomiting, nausea, diarrhea, and upset stomach. For this reason, other treatments, along with metformin, are being developed. Considering the anti-inflammatory role of mesenchymal stem cells (MSCs) derived exosomes, their use seems to help improve liver tissue function and prevent damage caused by inflammation. This study investigated the anti-inflammatory effect of Wharton's jelly MSCs derived exosomes in combination with metformin in the HepG2 cells insulin resistance model induced by high glucose. This study showed that MSCs derived exosomes as an anti-inflammatory agent in combination with metformin could increase the therapeutic efficacy of metformin without needing to change metformin doses by decreasing inflammatory cytokines production, including IL-1, IL-6, and TNF-α and apoptosis in HepG2 cells.

The present study was carried out to explore a novel strategy with the hypothesis that the combined treatment with standard antidiabetic drug metformin (MET) and chitosan stabilized nanoparticles (CTS-Se-NPs) may have a potential role on insulin level, hepatic damage and apoptosis, and cardiac injury markers of type 2 diabetes mellitus (T2DM) in rat model. T2DM was induced by a high fat diet (HFD) for 8 weeks and a single injection of a low dose streptozotocin (STZ) (35 mg/kg) in Sprague Dawley rats. A total number of one hundred rats were divided into five groups; the first served as a control (non-diabetic) group and the other four groups served as diabetic rats. The treatments were even mono or combined therapy by CTS-Se-NPs and/or MET for 8 weeks. A group was given only MET (500 mg/kg bw/day), another was administered only CTS-Se-NPs at a dose of 2 mg se/kg/day, while the last group was given both of them (co-treated group). Biochemical, molecular and histopathological analyses were conducted to figure out the efficiency of the treatment by the monotherapeutic mode or combination therapy on the insulin level, oxidants/antioxidants status, inflammatory mediators, hepatic and cardiac injury biomarkers and apoptotic/anti-apoptotic gene expressions. Our results indicated that HFD/STZ-induced toxic effects on the serum, hepatic and cardiac tissues including a remarkable elevation of the oxidative and inflammatory mediators, and up-regulation of the apoptotic genes (Bax, Caspase-3, Fas, Fas-L) expression. Histologically, the heart tissue revealed various degenerative, vascular and inflammatory alterations characteristic to murine cardiomyopathy. Besides, livers from HFD-STZ-treated rats showed numerous cytotoxic, circulatory and inflammatory alterations. Combined therapy with MET and CTS-Se-NPs resulted in a better remarkable anti-diabetic effect demonstrated by substantial decreases in fasting blood glucose and insulin levels, and elevated with up-regulation of anti-apoptotic gene (BCL-2) and down-regulation of apoptotic genes after 8 weeks of treatment than that revealed in the monotherapeutic strategy. In addition, it ameliorated the damage of cardiac and hepatic tissues and reduced lipid accumulation, and pro-inflammatory cytokines levels and restored the antioxidant capacity. It could be concluded that, the combined strategy applied in the current study have a potential role to limit the diabetic complications and restore insulin resistance to a higher extent than monotherapeutic strategy and could be considered a promising therapeutic alternative in T2DM rat model.

Nonalcoholic fatty liver disease (NAFLD) is defined as the most common liver disorder that encompasses a wide spectrum of liver pathologies, including simple hepatic steatosis (defined as hepatic triglyceride > 5% by liver weight) to inflammatory nonalcoholic steatohepatitis, fibrosis, subsequently progressed to cirrhosis and ultimately becoming a leading cause of end-stage liver failure or hepatocellular carcinoma. Almost all nutrients and foods with antioxidant and antiinflammatory properties can help in management of NAFLD; however, the most acceptable treatment is weight management. In this chapter, we review current evidence on dietary interventions in NAFLD.

Progressive insulin resistance in a prediabetic state has been reported to be the predominant causative factor for the development of nonalcoholic fatty liver disease. The combination of dietary modification and pharmacotherapy has been recommended to manage diabetic liver complications. However, poor patient compliance and toxicity of current drug therapy on liver function still results; thus, newer alternative drugs are required.

This study sought to investigate the hepatoprotective effects of the ruthenium(II) Schiff base complex in the presence and absence of dietary intervention in a diet-induced pre-diabetic rat model.

Prediabetic rats were randomly allocated to respective treatment groups. The ruthenium-based compound (15 mg/kg) was administered to the prediabetic rats in both the presence and absence of dietary intervention once a day every third day for 12 weeks.

The administration of the ruthenium compound in both the presence and absence of dietary intervention resulted in the restoration of liver and body weights. This treatment also reduced liver damage enzyme biomarkers, bilirubin, and sterol regulatory element binding protein 1c concentrations in the plasma.

The ruthenium(II) complex showed beneficial effects as it ameliorated and prevented the progression of diabetes-related liver derangements while eliminating the hepatotoxicity associated with the use of metal compounds. However, further studies are still required to further determine the physiological mechanisms behind this effect.

The pathogenesis of nonalcoholic fatty liver disease (NAFLD) is multifactorial and difficult to unify. The progression of benign nonalcoholic fatty liver (NAFL) to progressive nonalcoholic steatohepatitis (NASH) is acknowledged to be a multiple parallel hit process. Oxidative stress is one of the main factors that drives progression of NAFL to NASH, although it is also essential for vital cellular processes. Overaccumulation of long chain fatty acid results in mitochondrial β-oxidation pathway activation followed by reactive oxygen species (ROS) production. ROS can mediate the oxidative stress response in hepatocytes, Kupffer cells, or hepatic stellate cells resulting in hepatocyte damage, and in proinflammatory and profibrogenic responses that should be well balanced. ROS detoxification pathway signaling is often damaged in NAFLD following ROS accumulation. Inactivation of pro-oxidant production pathways and activation of detoxifying signaling pathways are the required treatment approach.