Canagliflozin, an SGLT2 inhibitor, attenuates the development of hepatocellular carcinoma in a mouse model of human NASH

SGLT-2 inhibitors as promising therapeutics for non-alcoholic fatty liver disease: pathophysiology, clinical outcomes, and future directions

Nonalcoholic fatty liver disease (NAFLD) is increasingly recognized as a major expanding national and international health problem. Despite numerous investigations using a variety of therapeutic agents, the positive result on any single medication has not been established enough to gain widespread approval. This is in part related to concerns regarding side effects of agents, but is also related to the complex etiology of NAFLD. An often discussed question has been whether insulin resistance that is frequently present in those with NAFLD is a cause of NAFLD or is merely associated with the condition. Nevertheless, it is clear that a very high proportion of patients with NAFLD are obese, have elements of metabolic syndrome, or have type 2 diabetes (T2DM). Also, much progress has been made toward a better understanding of the pathophysiology of NAFLD. Life-style interventions resulting in weight loss remain the foundation for the prevention and treatment of NAFLD. In addition, agents such as Vitamin E and pioglitazone as well as other glycemia-lowering agents including Glucagon Like Peptide-1 (GLP-1) receptor agonists and Sodium Glucose Contransporter-2 inhibitors (SGLT-2i(s)) exhibit positive effects on the clinical course of NAFLD. This narrative review summarizes the current understanding of the diagnosis, epidemiology, and pathophysiology of NAFLD and specifically focuses on the efficacy of SGLT2i(s) as a potentially promising group of agents for the management of patients with NAFLD.

Targeting Metabolism, Insulin Resistance, and Diabetes to Treat Nonalcoholic Steatohepatitis

Obesity, insulin resistance, and diabetes are strongly linked to the accumulation of excessive lipids in the liver parenchyma, a condition known as nonalcoholic fatty liver disease (NAFLD). Given its association with obesity and related metabolic diseases, it is not surprising that the prevalence of NAFLD has dramatically increased in the past few decades. NAFLD has become the most common liver disease in many areas of the world. The term, NAFLD, encompasses a spectrum of disorders that ranges from simple steatosis to steatosis with inflammatory lesions (nonalcoholic steatohepatitis [NASH]). Although simple steatosis might be relatively benign, epidemiologic studies have linked NASH to greatly increased risk of developing cirrhosis and hepatocellular carcinoma. Yet despite this, there are no approved treatments for the disease, and it remains a significant unmet medical need. This Perspective will review some of the relevant literature on the topic and examine approved and experimental NASH therapeutic concepts that target intermediary metabolism, insulin resistance, and diabetes to treat this emerging public health problem.

A reduced M1-like/M2-like ratio of macrophages in healthy adipose tissue expansion during SGLT2 inhibition

The adipose tissue includes various stromal cells, such as preadipocytes, endothelial cells, fibroblasts, and immune cells, which are involved in adipose tissue functions. We previously reported that, in obese mice, the sodium–glucose cotransporter 2 inhibitor ipragliflozin (Ipra) promoted the expansion of the epididymal adipose tissue (Epi) with increase of serum ketone body concentration. The Ipra-induced adipose tissue expansion did not deteriorate adipose inflammation, or systemic glucose/lipid metabolism, referred to as “healthy adipose tissue expansion.” Here we found that Ipra promoted healthy adipose tissue expansion with a reduced ratio of pro-inflammatory M1-like adipose tissue macrophages (ATMs) to anti-inflammatory M2-like ATMs. Ipra downregulated the gene expression of interleukin (IL)−15 (Il15) in stromal cells of Epi. IL-15 inhibited lipogenesis in 3T3-L1 cells associated with downregulation of the lipogenic gene. Ketone body β-hydroxybutyrate suppressed Il15 gene induction in M1-polarized cultured macrophages, and a ketogenic diet reproduced the adipose tissue expansion without deteriorating systemic glucose metabolism in mice. Our data indicate that the phenotypic switch of ATMs could mediate healthy adipose tissue expansion by treatment with Ipra, and it may offer new insights into the pathophysiological mechanisms of adipose tissue expansion.

Mouse models for investigating the underlying mechanisms of nonalcoholic steatohepatitis-derived hepatocellular carcinoma

As the incidence of hepatocellular carcinoma (HCC) caused by infection with the hepatotropic viruses hepatitis B and hepatitis C decreases, greater attention has become focused on HCC caused by nonalcoholic steatohepatitis (NASH), an advanced form of nonalcoholic fatty liver disease which has shown increasing prevalence in correspondence with the overall increase in metabolic syndrome over the recent decades. Several clinical population studies have shown a positive relationship between NASH and HCC, while also providing initial insights into the underlying mechanisms of HCC development from NASH. Research into the pathological progression of NASH to HCC has advanced by use of several beneficial rodent models. In this review, we summarize the established mouse models for preclinical research of NASH-associated HCC and discuss the underlying hepatic mechanisms of NASH-related tumorigenesis identified to date that could lead to new targets for treatment and prevention.

Exploring novel pharmacotherapeutic applications and repurposing potential of sodium glucose CoTransporter 2 inhibitors

Sodium glucose cotransporter 2 (SGLT2) inhibitors are a relatively new class of anti-hyperglycaemic drugs with a distinctive mechanism of action focusing on renal absorption of glucose. Apart from its anti-hyperglycaemic effects, a multitude of research studies on this class have revealed that these drugs have far more versatile and comprehensive pharmacological effects than previously believed. Approximately 30% of FDA approved drugs are repurposed and used for indications other than those for which they were initially intended. Repurposing already approved drugs leads to significant reduction in pre-clinical and clinical R&D costs as well as minimizing the burden with respect to obtaining regulatory approval. SGLT2 inhibitors have been found to exhibit cardioprotective, renoprotective, anti-hyperlipidaemic, anti-atherosclerotic, anti-obesity, anti-neoplastic, hepatoprotective, and renoprotective effects in in vitro, pre-clinical, and clinical studies. The pleiotropic effects of this class have been attributed to a variety of its pharmacodynamic actions such as natriuresis, haemoconcentration, deactivation of RAAS, ketone body formation, alterations in energy homeostasis, glycosuria, lipolysis, anti-inflammatory, and anti-oxidative actions. These favourable observations encourage further research on this multifaceted class in order to effectively explore and harness its full potential and consequently lead to clinical outcomes.

High Basolateral Glucose Increases Sodium-Glucose Cotransporter 2 and Reduces Sirtuin-1 in Renal Tubules through Glucose Transporter-2 Detection

Under diabetic conditions, sodium-glucose cotransporter 2 (SGLT2) for glucose uptake in proximal tubules (PTs) increases, whereas NAD⁺-dependent protein deacetylase silent mating type information regulation 2 homolog 1 (Sirtuin-1; SIRT1) for PT survival decreases. Therefore, we hypothesized that increased glucose influx by SGLT2 reduces SIRT1 expression. To test this hypothesis, db/db mice with diabetes and high-glucose (HG)-cultured porcine PT LLC-PK1 cells in a two-chamber system were treated with the SGLT2 inhibitor canagliflozin. We also examined SIRT1 and SGLT2 expression in human kidney biopsies. In db/db mice, SGLT2 expression increased with concomitant decreases in SIRT1, but was inhibited by canagliflozin. For determination of the polarity of SGLT2 and SIRT1 expression, LLC-PK1 cells were seeded into Transwell chambers (pore size, 0.4 µm; Becton Dickinson, Oxford, UK). HG medium was added to either or to both of the upper and lower chambers, which corresponded to the apical and basolateral sides of the cells, respectively. In this system, the lower chamber with HG showed increased SGLT2 and decreased SIRT1 expression. Canagliflozin reversed HG-induced SIRT1 downregulation. Gene silencing and inhibitors for glucose transporter 2 (GLUT2) blocked HG-induced SGLT2 expression upregulation. Gene silencing for the hepatic nuclear factor-1α (HNF-1α), whose nuclear translocation was enhanced by HG, blocked HG-induced SGLT2 expression upregulation. Similarly, gene silencing for importin-α1, a chaperone protein bound to GLUT2, blocked HG-induced HNF-1α nuclear translocation and SGLT2 expression upregulation. In human kidney, SIRT1 immunostaining was negatively correlated with SGLT2 immunostaining. Thus, under diabetic conditions, SIRT1 expression in PTs was downregulated by an increase in SGLT2 expression, which was stimulated by basolateral HG through activation of the GLUT2/importin-α1/HNF-1α pathway.