PPARs in obesity-induced T2DM, dyslipidaemia and NAFLD

PPARs: regulators of metabolism and as therapeutic targets in cardiovascular disease. Part I: PPAR-α

This article provides a comprehensive review about the molecular and metabolic actions of PPAR-α. It describes its structural features, ligand specificity, gene transcription mechanisms, functional characteristics and target genes. In addition, recent progress with the use of loss of function and gain of function mouse models in the discovery of diverse biological functions of PPAR-α, particularly in the vascular system and the status of the development of new single, dual, pan and partial PPAR agonists (PPAR modulators) in the clinical management of metabolic diseases are presented. This review also summarizes the clinical outcomes from a large number of clinical trials aimed at evaluating the atheroprotective actions of current clinically used PPAR-α agonists, fibrates and statin-fibrate combination therapy.

PPARs: regulators of metabolism and as therapeutic targets in cardiovascular disease. Part II: PPAR-β/δ and PPAR-γ

The PPARs are a subfamily of three ligand-inducible transcription factors, which belong to the superfamily of nuclear hormone receptors. In mammals, the PPAR subfamily consists of three members: PPAR-α, PPAR-β/δ and PPAR-γ. PPARs control the expression of a large number of genes involved in metabolic homeostasis, lipid, glucose and energy metabolism, adipogenesis and inflammation. PPARs regulate a large number of metabolic pathways that are implicated in the pathogenesis of metabolic diseases such as metabolic syndrome, Type 2 diabetes mellitus, nonalcoholic fatty liver disease and cardiovascular disease. The aim of this review is to provide up-to-date information about the biochemical and metabolic actions of PPAR-β/δ and PPAR-γ, the therapeutic potential of their agonists currently under clinical development and the cardiovascular disease outcome of clinical trials of PPAR-γ agonists, pioglitazone and rosiglitazone.

Protective effect of Hua Tan Qu Shi decoction against liver injury in rats with nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD), is currently a worldwide health problem. None of the existing treatment medications had got a satisfactory effect. Hua Tan Qu Shi (HTQS) decoction is a Chinese herbal formula, which has been used clinically to treat NAFLD for years. However, the underlying mechanisms are still unclear.

METHODS

High-fat diet (HFD) induced non-alcoholic fatty liver disease rats treated with or without HTQS decoction by gavage for 10 weeks and examined by serology, 24-h albuminuria, histology, immunohistochemistry, and molecular analyses.

Distinct but complementary contributions of PPAR isotypes to energy homeostasis

Peroxisome proliferator-activated receptors (PPARs) regulate energy metabolism and hence are therapeutic targets in metabolic diseases such as type 2 diabetes and non-alcoholic fatty liver disease. While they share anti-inflammatory activities, the PPAR isotypes distinguish themselves by differential actions on lipid and glucose homeostasis. In this Review we discuss the complementary and distinct metabolic effects of the PPAR isotypes together with the underlying cellular and molecular mechanisms, as well as the synthetic PPAR ligands that are used in the clinic or under development. We highlight the potential of new PPAR ligands with improved efficacy and safety profiles in the treatment of complex metabolic disorders.

Sanggenol F exerts anti-diabetic effects via promoting adipocyte differentiation and modifying adipokines expression

Adipose tissue is not only a lipid storage site, but also a well-known endocrine organ. Dysfunction of adipose tissue is associated with irregular lipid metabolism, ectopic lipid accumulation and insulin resistance. It is proposed that modulating on adipose tissue is a reasonable way to ameliorate glucose and lipid metabolism. (±)-sanggenol F (SGF, purity >98.5%) was synthesized as a racemic mixture of natural (+)-sanggenol F. In this study, SGF was found to promote adipocyte differentiation, enhance insulin sensitivity, and upregulate beneficial adipokines expression in 3T3-L1 cells. Furthermore, in vivo study showed that treatment with SGF for 4 weeks improved glucose metabolism, by decreasing fasting blood glucose and enhancing insulin sensitivity. It also improved lipid metabolism, with reduced serum lipid level and ameliorated hepatic steatosis in db/db mice. During the process of target finding, we found that SGF had multiple activities of protein tyrosine phosphatase 1B inhibition, peroxisome proliferator-activated receptor γ and peroxisome proliferator-activated receptor α agonism. These results showed the potential of SGF as a candidate for the therapy of type 2 diabetes.

Pharmacological management of nonalcoholic fatty liver disease in type 2 diabetes

INTRODUCTION

The prevalence of nonalcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes (T2D) is high and it is associated with poor prognosis. Hepatic steatosis results as a consequence of excessive hepatic lipid accumulation which correlates with insulin resistance and lipotoxicity, with subsequent oxidative stress, inflammation, apoptosis and fibrosis. Areas covered: This article presents the main pathophysiologic mechanisms and currently available drugs evaluated for their therapeutic effects on NAFLD/nonalcoholic steatohepatitis (NASH) and drugs under development that target relevant pathogenetic pathways. However, to date there is no particular drug approved for treatment of NAFLD in patients with T2D. Expert commentary: Early recognition and intervention are essential to ameliorate disease progression. Specific recommendations are still needed for NAFLD/NASH screening and diagnosis and therapeutic algorithm in patients with T2D. Lifestyle optimization with significant weight loss is a key intervention in patients with NAFLD and T2D. Pioglitazone, liraglutide, vitamin E, OCA and pentoxifylline have proven some histological improvements in NASH and omega 3-PUFAs were shown to decrease liver fat, but no specific recommendation can be made for treatment of NASH. Perhaps a combination of agents that target different pathogenic pathways are needed to better control disease progression, but more robust evidence for these agents is still needed.

Molecular implications of adenosine in obesity

Adenosine has broad activities in organisms due to the existence of multiple receptors, the differential adenosine concentrations necessary to activate these receptors and the presence of proteins able to synthetize, degrade or transport this nucleoside. All adenosine receptors have been reported to be involved in glucose homeostasis, inflammation, adipogenesis, insulin resistance, and thermogenesis, indicating that adenosine could participate in the process of obesity. Since adenosine seems to be associated with several effects, it is plausible that adenosine participates in the initiation and development of obesity or may function to prevent it. Thus, the purpose of this review was to explore the involvement of adenosine in adipogenesis, insulin resistance and thermogenesis, with the aim of understanding how adenosine could be used to avoid, treat or improve the metabolic state of obesity. Treatment with specific agonists and/or antagonists of adenosine receptors could reverse the obesity state, since adenosine receptors normalizes several mechanisms involved in obesity, such as lipolysis, insulin sensitivity and thermogenesis. Furthermore, obesity is a preventable state, and the specific activation of adenosine receptors could aid in the prevention of obesity. Nevertheless, for the treatment of obesity and its consequences, more studies and therapeutic strategies in addition to adenosine are necessary.

MicroRNAs-Dependent Regulation of PPARs in Metabolic Diseases and Cancers

Peroxisome proliferator-activated receptors (PPARs) are a family of ligand-dependent nuclear receptors, which control the transcription of genes involved in energy homeostasis and inflammation and cell proliferation/differentiation. Alterations of PPARs' expression and/or activity are commonly associated with metabolic disorders occurring with obesity, type 2 diabetes, and fatty liver disease, as well as with inflammation and cancer. Emerging evidence now indicates that microRNAs (miRNAs), a family of small noncoding RNAs, which fine-tune gene expression, play a significant role in the pathophysiological mechanisms regulating the expression and activity of PPARs. Herein, the regulation of PPARs by miRNAs is reviewed in the context of metabolic disorders, inflammation, and cancer. The reciprocal control of miRNAs expression by PPARs, as well as the therapeutic potential of modulating PPAR expression/activity by pharmacological compounds targeting miRNA, is also discussed.