Nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM) remain as one of the most global problematic metabolic diseases with rapidly increasing prevalence and incidence. Epidemiological studies noted that T2DM patients have by two-fold increase to develop NAFLD, and vice versa. This complex and intricate association is supported and mediated by insulin resistance (IR). In this review, we discuss the NAFLD immunopathogenesis, connection with IR and T2DM, the role of screening and noninvasive tools, and mostly the impact of the current antidiabetic drugs on steatosis liver and new potential therapeutic targets.

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The Intricate Relationship between Type 2 Diabetes Mellitus (T2DM), Insulin Resistance (IR), and Nonalcoholic Fatty Liver Disease (NAFLD).

Nonalcoholic Fatty Liver Disease (NAFLD) represents the leading cause of liver disease in developed countries but its diffusion is currently also emerging in Asian countries, in South America and in other developing countries. It is progressively becoming one of the main diseases responsible for hepatic insufficiency, hepatocarcinoma and the need for orthotopic liver transplantation. NAFLD is linked with metabolic syndrome in a close and bidirectional relationship. To date, NAFLD is a diagnosis of exclusion, and liver biopsy is the gold standard for diagnosis. NAFLD pathogenesis is complex and multifactorial, mainly involving genetic, metabolic and environmental factors. New concepts are constantly arising in the literature promising new diagnostic and therapeutic tools. One of the challenges will be to better characterize not only NAFLD development but overall NAFLD progression, in order to better identify NAFLD patients at higher risk of metabolic, cardiovascular and neoplastic complications. This review analyses NAFLD epidemiology and the different prevalence of the disease in distinct groups, particularly according to sex, age, body mass index, type 2 diabetes and dyslipidemia. Furthermore, the work expands on the pathophysiology of NAFLD, examining multiple-hit pathogenesis and the role of different factors in hepatic steatosis development and progression: genetics, metabolic factors and insulin resistance, diet, adipose tissue, gut microbiota, iron deposits, bile acids and circadian clock. In conclusion, the current available therapies for NAFLD will be discussed.

https://www.mdpi.com/1422-0067/20/8/1948/pdf

Pathophysiological, Molecular and Therapeutic Issues of Nonalcoholic Fatty Liver Disease: An Overview.

Oxidative stress (OxS) is considered a major factor in the pathophysiology of inflammatory chronic liver diseases, including non-alcoholic liver disease (NAFLD). Chronic impairment of lipid metabolism is closely related to alterations of the oxidant/antioxidant balance, which affect metabolism-related organelles, leading to cellular lipotoxicity, lipid peroxidation, chronic endoplasmic reticulum (ER) stress, and mitochondrial dysfunction. Increased OxS also triggers hepatocytes stress pathways, leading to inflammation and fibrogenesis, contributing to the progression of non-alcoholic steatohepatitis (NASH). The antioxidant response, regulated by the Nrf2/ARE pathway, is a key component in this process and counteracts oxidative stress-induced damage, contributing to the restoration of normal lipid metabolism. Therefore, modulation of the antioxidant response emerges as an interesting target to prevent NAFLD development and progression. This review highlights the link between disturbed lipid metabolism and oxidative stress in the context of NAFLD. In addition, emerging potential therapies based on antioxidant effects and their likely molecular targets are discussed.

Role of Oxidative Stress in the Pathogenesis of Non-Alcoholic Fatty Liver Disease: Implications for Prevention and Therapy

OBJECTIVE Assess the prevalence of nonalcoholic fatty liver disease (NAFLD) and of liver fibrosis associated with nonalcoholic steatohepatitis in unselected patients with type 2 diabetes mellitus (T2DM). RESEARCH DESIGN AND METHODS A total of 561 patients with T2DM (age: 60 ± 11 years; BMI: 33.4 ± 6.2 kg/m2; and HbA1c: 7.5 ± 1.8%) attending primary care or endocrinology outpatient clinics and unaware of having NAFLD. At the visit, volunteers were invited to be screened by elastography for steatosis and fibrosis by controlled attenuation parameter (≥274 dB/m) and liver stiffness measurement (LSM; ≥7.0 kPa), respectively. Secondary causes of liver disease were ruled out. Diagnostic panels for prediction of advanced fibrosis, such as AST-to-platelet ratio index (APRI) and Fibrosis-4 (FIB-4) index, were also measured. A liver biopsy was performed if results were suggestive of fibrosis. RESULTS The prevalence of steatosis was 70% and of fibrosis 21% (LSM ≥7.0 kPa). Moderate fibrosis (F2: LSM ≥8.2 kPa) was present in 6% and severe fibrosis or cirrhosis (F3–4: LSM ≥9.7 kPa) in 9%, similar to that estimated by FIB-4 and APRI panels. Noninvasive testing was consistent with liver biopsy results. Elevated AST or ALT ≥40 units/L was present in a minority of patients with steatosis (8% and 13%, respectively) or with liver fibrosis (18% and 28%, respectively). This suggests that AST/ALT alone are insufficient as initial screening. However, performance may be enhanced by imaging (e.g., transient elastography) and plasma diagnostic panels (e.g., FIB-4 and APRI). CONCLUSIONS Moderate-to-advanced fibrosis (F2 or higher), an established risk factor for cirrhosis and overall mortality, affects at least one out of six (15%) patients with T2DM. These results support the American Diabetes Association guidelines to screen for clinically significant fibrosis in patients with T2DM with steatosis or elevated ALT.

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Advanced Liver Fibrosis Is Common in Patients With Type 2 Diabetes Followed in the Outpatient Setting: The Need for Systematic Screening.

Gut-Resident Lactobacilli Activate Hepatic Nrf2 and Protect Against Oxidative Liver Injury.

There has been a growing interest in the role of vitamin E supplementation in the treatment and/or prevention of nonalcoholic fatty liver (NAFLD). We performed a systematic review of the medical literature from inception through 15 June 2018 by utilizing PubMed and searching for key terms such as NAFLD, vitamin E, alpha-tocopherol, and nonalcoholic steatohepatitis (NASH). Data from studies and medical literature focusing on the role of vitamin E therapy in patients with NAFLD and nonalcoholic steatohepatitis (NASH) were reviewed. Most studies assessing the impact of vitamin E in NAFLD were designed to evaluate patients with NASH with documented biochemical and histological abnormalities. These studies demonstrated improvement in biochemical profiles, with a decline in or normalization of liver enzymes. Furthermore, histological assessment showed favorable outcomes in lobular inflammation and hepatic steatosis following treatment with vitamin E. Current guidelines regarding the use of vitamin E in the setting of NAFLD recommend that vitamin E-based treatment be restricted to biopsy-proven nondiabetic patients with NASH only. However, some concerns have been raised regarding the use of vitamin E in patients with NASH due to its adverse effects profile and lack of significant improvement in hepatic fibrosis. In conclusion, the antioxidant, anti-inflammatory, and anti-apoptotic properties of vitamin E accompanied by ease-of-use and exceptional tolerability have made vitamin E a pragmatic therapeutic choice in non-diabetic patients with histologic evidence of NASH. Future clinical trials with study design to assess vitamin E in combination with other anti-fibrotic agents may yield an additive or synergistic therapeutic effect.

https://www.mdpi.com/2079-9721/6/4/86/pdf

The Role of Vitamin E in the Treatment of NAFLD

Our aim is to review the efficacy of various herbs and supplements as a possible therapeutic option in the treatment and/or prevention of nonalcoholic fatty liver disease (NAFLD). We performed a systematic review of medical literature using the PubMed Database by searching the chemical names of many common herbs and supplements with “AND (NAFLD or NASH)”. Studies and medical literature that discussed the roles and usage of herbs and supplements in NAFLD and nonalcoholic steatohepatitis (NASH) from inception until 20 June 2018 were reviewed. Many studies have claimed that the use of various herbs and supplements may improve disease endpoints and outcomes related to NAFLD and/or NASH. Improvement in liver function tests were noted. Amelioration or reduction of lobular inflammation, hepatic steatosis, and fibrosis were also noted. However, well-designed studies demonstrating improved clinical outcomes are lacking. Furthermore, experts remain concerned about the lack of regulation of herbs/supplements and the need for further research on potential adverse effects and herb–drug interactions. In conclusion, preliminary data on several herbs have demonstrated promising antioxidant, anti-inflammatory, anti-apoptotic, and anti-adipogenic properties that may help curtail the progression of NAFLD/NASH. Clinical trials testing the safety and efficacy must be completed before widespread use can be recommended.

https://www.mdpi.com/2079-9721/6/3/80/pdf

Potential Therapeutic Benefits of Herbs and Supplements in Patients with NAFLD

Recent breakthrough in our understanding pertaining to the pathogenesis of nonalcoholic fatty liver disease (NAFLD) has pointed to dysregulation or derangement of the gut microbiome, also known as dysbiosis. This has led to growing interest in probiotic supplementation as a potential treatment method for NAFLD due to its ability to retard and/or reverse dysbiosis and restore normal gut flora. A thorough review of medical literature was completed from inception through July 10, 2018 on the PubMed database by searching for key terms such as NAFLD, probiotics, dysbiosis, synbiotics, and nonalcoholic steatohepatitis (NASH). All studies reviewed indicate that probiotics had a beneficial effect in patients with NAFLD and its subset NASH. Results varied between studies, but there was evidence demonstrating improvement in liver enzymes, hepatic inflammation, hepatic steatosis, and hepatic fibrosis. No major adverse effects were noted. Currently, there are no guidelines addressing the use of probiotics in the setting of NAFLD. In conclusion, probiotics appear to be a promising option in the treatment of NAFLD. Future research is necessary to assess the efficacy of probiotics in patients with NAFLD.

https://www.mdpi.com/2079-9721/7/1/27/pdf

The Therapeutic Implications of the Gut Microbiome and Probiotics in Patients with NAFLD

The two main subsets of nonalcoholic fatty liver disease (NAFLD) include: (1) nonalcoholic fatty liver (NAFL), the more common and non-progressive subtype; and (2) nonalcoholic steatohepatitis (NASH), the less common subtype, which has the potential to progress to advanced liver damage. Current treatment strategies have focused on lifestyle management of modifiable risk factors, namely weight, and on the optimization of the management of individual components of metabolic syndrome. Various hypothetical pathogenic mechanisms have been proposed, leading to the development of novel drugs with the potential to effectively treat patients with NASH. Numerous clinical trials are ongoing, utilizing these experimental drugs and molecules targeting specific mechanistic pathway(s) to effectively treat NASH. Some of these mechanistic pathways targeted by experimental pharmacologic agents include chemokine receptor 2 and 5 antagonism, inhibition of galectin-3 protein, antagonism of toll-like receptor 4, variation of fibroblast growth factor 19, agonism of selective thyroid hormone receptor-beta, inhibition of apoptosis signal-regulating kinase 1, inhibition of acetyl-coenzyme A carboxylase, agonism of farnesoid X receptor, antibodies against lysl oxidase-like-2, and inhibition of inflammasomes. Emerging data are promising and further updates from ongoing clinical trials are eagerly awaited.

https://www.mdpi.com/2079-9721/6/3/83/pdf

Emerging Therapeutic Targets and Experimental Drugs for the Treatment of NAFLD

As a chronic disease encompassing a wide spectrum of liver-related histologic damage, nonalcoholic fatty liver disease (NAFLD) is becoming a global epidemic with significant impacts on all-cause morbidity and mortality. Insulin resistance and type 2 diabetes mellitus predispose individuals to NAFLD and related complications. Therefore, timely intervention with anti-diabetic medications may prevent and delay the development of NAFLD or have a therapeutic implication. The focus of this review is to evaluate the evidence supporting the efficacy of anti-diabetic medications in the treatment of NAFLD. While many of these anti-diabetic agents have shown to improve biochemical parameters, their effect on hepatic histology is limited. Among anti-diabetic medications, only thiazolidinediones and glucagon-like peptide-1 receptor agonists demonstrate significant improvement in hepatic histology.

https://www.mdpi.com/2079-9721/6/4/93/pdf

Waiyee Kwong

Papers

The Role of Vitamin E in the Treatment of NAFLD

Potential Therapeutic Benefits of Herbs and Supplements in Patients with NAFLD

The Therapeutic Implications of the Gut Microbiome and Probiotics in Patients with NAFLD

Emerging Therapeutic Targets and Experimental Drugs for the Treatment of NAFLD

Anti-Diabetic Medications for the Pharmacologic Management of NAFLD.