Peroxisome Proliferator-Activated Receptors and Their Novel Ligands as Candidates for the Treatment of Non-Alcoholic Fatty Liver Disease.

Non-alcoholic fatty liver disease (NAFLD) is a major health issue worldwide, frequently associated with obesity and type 2 diabetes. Steatosis is the initial stage of the disease, which is characterized by lipid accumulation in hepatocytes, which can progress to non-alcoholic steatohepatitis (NASH) with inflammation and various levels of fibrosis that further increase the risk of developing cirrhosis and hepatocellular carcinoma. The pathogenesis of NAFLD is influenced by interactions between genetic and environmental factors and involves several biological processes in multiple organs. No effective therapy is currently available for the treatment of NAFLD. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that regulate many functions that are disturbed in NAFLD, including glucose and lipid metabolism, as well as inflammation. Thus, they represent relevant clinical targets for NAFLD. In this review, we describe the determinants and mechanisms underlying the pathogenesis of NAFLD, its progression and complications, as well as the current therapeutic strategies that are employed. We also focus on the complementary and distinct roles of PPAR isotypes in many biological processes and on the effects of first-generation PPAR agonists. Finally, we review novel and safe PPAR agonists with improved efficacy and their potential use in the treatment of NAFLD

Role of Microbiome in Impacting Treatment of Obesity and Type 2 Diabetes

Metabolic Syndrome is a constellation of metabolic abnormalities associated with insulin resistance and obesity, including hyperglycemia and hypertension. Metabolic syndrome often progresses to type 2 diabetes, hypertension, cardiovascular disease, and liver disease. Metabolic syndrome is increasingly appreciated to be an inflammatory disease in that is associated with increased expression of pro-inflammatory genes and markers, remodeling of adipose tissue, and markedly increased incidence in the last 50 years. Additionally, both diseases alter the microbiota, specifically with alteration in gut microbiota composition. Metabolic syndrome requires a microbiota in that disease is not observed in germ- free mice, and some aspects of the disease can be transferred by fecal transplant. There is a probable correlation between metabolic disorder and gut microbiota. It’s also been shown that the efficacy of systemic medications can be affected by the gut microbiota and that some medications can alter the microbiota. Metformin is believed to be one of those medications. Accordingly, the results of the present study could be employed to develop novel methods for treating metabolic syndrome using medications such as metformin. Furthermore, this study can set the stage for further research towards the application of fecal transplantation as a treatment strategy for individuals with conditions like metabolic syndrome. The overall goal of my studies was to investigate this hypothesis. First, I comprehensively examined the existing gut microbiota literature to discern the range of treatment of type 2 diabetes mellitus that have been associated with, or attributed to, changes in microbiota composition. Chapter 1 outlines findings from this effort. Next, I performed experiments to investigate the extent to which metformin attenuates metabolic syndrome and inflammation by alternation of intestinal microbiota. My results support the notion that metformin induces changes in gut microbiota composition. However, such changes were not necessary for metformin to alleviate parameters of metabolic syndrome indicating that metformin can, at least in part act independently of gut microbiota. Rather Metformin reduced indices of inflammation in both conventional germ-free conditions. These results support a role for metformin’s anti-inflammatory effects rather than its direct action on microbiota for its beneficial metabolic impacts

New insights along the gut-liver axis in cardiometabolic disease

In this thesis we targeted the human gut microbiome for the development of therapeutic strategies in metabolic disorders. In chapter 3 we performed a randomized placebo-controlled cross-over study in individuals with the metabolic syndrome in which we showed that a single duodenal infusion of A. soehngenii improved peripheral glycemic control. In chapter 4 we studied the effect of a 2 weeks oral A. soehngenii treatment in individuals with T2D treated with metformin on their glycemic control.The second part of the thesis focused on MASLD, currently the most common cause of chronic liver dysfunction worldwide. In chapter 5 we reviewed the gut microbial and gut microbial-derived metabolite signatures associated with the development and disease progression of MASLD. To dissect causality of intestinal microbiota in MASLD, in chapter 6 we performed a single-center, double-blind, randomized controlled proof-of-principle pilot study comparing the effect of three 8-weekly lean vegan donor FMT versus autologous FMT on the severity of MASLD, using liver biopsies in individuals with hepatic steatosis on ultrasound. Moreover, we aimed to identify and validate noninvasive diagnostic methods in disease progression in MASLD. Hence, in chapter 7 we examined the diagnostic performance of multiparametric MRI for the assessment of disease severity along the MASLD disease spectrum with comparison to histological scores

On the Road to Accurate Biomarkers for Cardiometabolic Diseases by Integrating Precision and Gender Medicine Approaches

The need to facilitate the complex management of cardiometabolic diseases (CMD) has led to the detection of many biomarkers, however, there are no clear explanations of their role in the prevention, diagnosis or prognosis of these diseases. Molecules associated with disease pathways represent valid disease surrogates and well-fitted CMD biomarkers. To address this challenge, data from multi-omics types (genomics, epigenomics, transcriptomics, proteomics, metabolomics, microbiomics, and nutrigenomics), from human and animal models, have become available. However, individual omics types only provide data on a small part of molecules involved in the complex CMD mechanisms, whereas, here, we propose that their integration leads to multidimensional data. Such data provide a better understanding of molecules related to CMD mechanisms and, consequently, increase the possibility of identifying well-fitted biomarkers. In addition, the application of gender medicine also helps to identify accurate biomarkers according to gender, facilitating a differential CMD management. Accordingly, the impact of gender differences in CMD pathophysiology has been widely demonstrated, where gender is referred to the complex interrelation and integration of sex (as a biological and functional marker of the human body) and psychological and cultural behavior (due to ethnical, social, and religious background). In this review, all these aspects are described and discussed, as well as potential limitations and future directions in this incipient field

Genetic Deficiency of CD40 in Mice Exacerbates Metabolic Manifestations of Diet-induced Obesity: A Dissertation

The past two decades have seen an explosive increase of obesity rates worldwide, with more than one billion adults overweight and 300 million of them obese. Obesity and its associated complications have become leading causes of morbidity and mortality in the United States and major contributing factors to the rising costs of national health care. The pathophysiology of obesity and type 2 diabetes in rodents and humans is characterized by low-grade inflammation and chronic activation of immune pathways in adipose tissue and liver. The CD40 receptor and its ligand, CD40L, initiate immune cell signaling promoting inflammation, but conflicting data on CD40L-null mice confound its role in obesity-associated insulin resistance. A clear understanding of how CD40 and its ligand communicate to regulate and sustain the inflammatory environment of obesity is lacking. Here we demonstrate that CD40 receptor deficient mice on a high-fat diet display the expected decrease in hepatic cytokine levels, but paradoxically exhibit liver steatosis, insulin resistance and glucose intolerance compared with their age-matched wild-type controls. Hyperinsulinemic-euglycemic clamp studies also demonstrated insulin resistance in glucose utilization by the CD40-null mice compared with wild-type mice. In contrast to liver, visceral adipose tissue in CD40 deficient animals harbors elevated cytokine levels and infiltration of inflammatory cells, particularly macrophages and CD8+ effector T cells. In addition, ex vivo explants of epididymal adipose tissue from CD40-null mice display elevated basal and isoproterenol-stimulated lipolysis, suggesting a potential increase of lipid efflux from visceral fat to the liver. These findings reveal that 1) CD40-null mice represent an unusual model of hepatic steatosis with reduced hepatic inflammation, and 2) CD40 unexpectedly functions in adipose tissue to attenuate the chronic inflammation associated with obesity, thereby protecting against hepatic steatosis

Oxidative Stress in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a challenging disease caused by multiple factors, which may partly explain why it still remains an orphan of adequate therapies. This review highlights the interaction between oxidative stress (OS) and disturbed lipid metabolism. Several reactive oxygen species generators, including those produced in the gastrointestinal tract, contribute to the lipotoxic hepatic (and extrahepatic) damage by fatty acids and a great variety of their biologically active metabolites in a “multiple parallel-hit model”. This leads to inflammation and fibrogenesis and contributes to NAFLD progression. The alterations of the oxidant/antioxidant balance affect also metabolism-related organelles, leading to lipid peroxidation, mitochondrial dysfunction, and endoplasmic reticulum stress. This OS-induced damage is at least partially counteracted by the physiological antioxidant response. Therefore, modulation of this defense system emerges as an interesting target to prevent NAFLD development and progression. For instance, probiotics, prebiotics, diet, and fecal microbiota transplantation represent new therapeutic approaches targeting the gut microbiota dysbiosis. The OS and its counter-regulation are under the influence of individual genetic and epigenetic factors as well. In the near future, precision medicine taking into consideration genetic or environmental epigenetic risk factors, coupled with new OS biomarkers, will likely assist in noninvasive diagnosis and monitoring of NAFLD progression and in further personalizing treatments

Are we close to defining a metabolomic signature of human obesity? A systematic review of metabolomics studies

BPV is supported by a grant to postdoctoral researchers at foreign universities and research centers from the Alfonso Martín Escudero Foundation, Spain.Introduction Obesity is a disorder characterized by a disproportionate increase in body weight in relation to height, mainly due to the accumulation of fat, and is considered a pandemic of the present century by many international health institutions. It is associated with several non-communicable chronic diseases, namely, metabolic syndrome, type 2 diabetes mellitus (T2DM), cardiovascular diseases (CVD), and cancer. Metabolomics is a useful tool to evaluate changes in metabolites due to being overweight and obesity at the body fluid and cellular levels and to ascertain metabolic changes in metabolically unhealthy overweight and obese individuals (MUHO) compared to metabolically healthy individuals (MHO). Objectives We aimed to conduct a systematic review (SR) of human studies focused on identifying metabolomic signatures in obese individuals and obesity-related metabolic alterations, such as inflammation or oxidative stress. Methods We reviewed the literature to identify studies investigating the metabolomics profile of human obesity and that were published up to May 7th, 2019 in SCOPUS and PubMed through an SR. The quality of reporting was evaluated using an adapted of QUADOMICS. Results Thirty-three articles were included and classified according to four types of approaches. (i) studying the metabolic signature of obesity, (ii) studying the differential responses of obese and non-obese subjects to dietary challenges (iii) studies that used metabolomics to predict weight loss and aimed to assess the effects of weight loss interventions on the metabolomics profiles of overweight or obese human subjects (iv) articles that studied the effects of specific dietary patterns or dietary compounds on obesity-related metabolic alterations in humans. Conclusion The present SR provides state-of-the-art information about the use of metabolomics as an approach to understanding the dynamics of metabolic processes involved in human obesity and emphasizes metabolic signatures related to obesity phenotypes.ODRH has received funding from the European Union Seventh Framework Programme (FP7-PEOPLE-2013-COFUND) under grant agreement n° 609020 - Scientia Fellows

Ketogenic Diet : a New Light Shining on Old but Gold Biochemistry

Diets low in carbohydrates and proteins and enriched in fat stimulate the hepatic synthesis of ketone bodies (KB). These molecules are used as alternative fuel for energy production in target tissues. The synthesis and utilization of KB are tightly regulated both at transcriptional and hormonal levels. The nuclear receptor peroxisome proliferator activated receptor \u3b1 (PPAR\u3b1), currently recognized as one of the master regulators of ketogenesis, integrates nutritional signals to the activation of transcriptional networks regulating fatty acid \u3b2-oxidation and ketogenesis. New factors, such as circadian rhythms and paracrine signals, are emerging as important aspects of this metabolic regulation. However, KB are currently considered not only as energy substrates but also as signaling molecules. \u3b2-hydroxybutyrate has been identified as class I histone deacetylase inhibitor, thus establishing a connection between products of hepatic lipid metabolism and epigenetics. Ketogenic diets (KD) are currently used to treat different forms of infantile epilepsy, also caused by genetic defects such as Glut1 and Pyruvate Dehydrogenase Deficiency Syndromes. However, several researchers are now focusing on the possibility to use KD in other diseases, such as cancer, neurological and metabolic disorders. Nonetheless, clear-cut evidence of the efficacy of KD in other disorders remains to be provided in order to suggest the adoption of such diets to metabolic-related pathologies