Canagliflozin ameliorates obesity by improving mitochondrial function and fatty acid oxidation via PPARα in vivo and in vitro

SGLT2i and GLP-1RA in Cardiometabolic and Renal Diseases: From Glycemic Control to Adipose Tissue Inflammation and Senescence

Background. Over the last few years, the use of sodium-glucose cotransporter 2 inhibitors (SGLT2i) and glucagon-like peptide 1 receptor agonists (GLP-1RA) has increased substantially in medical practice due to their documented benefits in cardiorenal and metabolic health. In this sense, and in addition to being used for glycemic control in diabetic patients, these drugs also have other favorable effects such as weight loss and lowering blood pressure, and more recently, they have been shown to have cardio and renoprotective effects with anti-inflammatory properties. Concerning the latter, the individual or associated use of these antihyperglycemic agents has been linked with a decrease in proinflammatory cytokines and with an improvement in the inflammatory profile in chronic endocrine-metabolic diseases. Hence, these drugs have been positioned as first-line therapy in the management of diabetes and its multiple comorbidities, such as obesity, which has been associated with persistent inflammatory states that induce dysfunction of the adipose tissue. Moreover, other frequent comorbidities in long-standing diabetic patients are chronic complications such as diabetic kidney disease, whose progression can be slowed by SGLT2i and/or GLP-1RA. The neuroendocrine and immunometabolism mechanisms underlying adipose tissue inflammation in individuals with diabetes and cardiometabolic and renal diseases are complex and not fully understood. Summary. This review intends to expose the probable molecular mechanisms and compile evidence of the synergistic or additive anti-inflammatory effects of SGLT2i and GLP-1RA and their potential impact on the management of patients with obesity and cardiorenal compromise.

SGLT2 Inhibitor-Induced Sympathoexcitation in White Adipose Tissue: A Novel Mechanism for Beiging

Recent preclinical data show that sodium glucose cotransporter 2 (SGLT2) inhibitors are able to reduce weight gain and induce beiging in white adipose tissue (WAT). We have previously shown that in neurogenic hypertensive Schlager (BPH/2J) mice, treatment with the SGLT2 inhibitor, Dapagliflozin, reduced blood pressure and prevented weight gain. Here we show that chemical sympathetic denervation achieved by systemic administration of 6-hydroxy-dopamine (6-OHDA) reduces body weight and the heightened sympathetic nervous system (SNS) innervation in WAT. Furthermore, we demonstrate that 2 weeks of Dapagliflozin treatment increases SNS innervation in WAT of hypertensive mice. This increase is accompanied by a non-significant elevation in mRNA levels of the Ucp1 and Pgc-1α genes, which are markers of beiging. No significant difference in the mRNA levels of the inflammatory mediators Il-6 and Tnf-α were detected in WAT of Dapagliflozin treated mice. These findings suggest that SGLT-2 inhibitor-associated prevention of weight gain may be mediated, at least in part, by inducing the beiging of WAT.

Cardiotrophin-1 contributes to metabolic adaptations through the regulation of lipid metabolism and to the fasting-induced fatty acid mobilization

It is becoming clear that several human pathologies are caused by altered metabolic adaptations. During liver development, there are physiological changes, from the predominant utilization of glucose (fetal life) to the use of lipids (postnatal life). Fasting is another physiological stress that elicits well-known metabolic adjustments. We have reported the metabolic properties of cardiotrophin-1 (CT-1), a member of the interleukin-6 family of cytokines. Here, we aimed at analyzing the role of CT-1 in response to these metabolic changes. We used different in vivo models. Furthermore, a differential study was carried out with wild-type and CT-1 null mice in fed (ad libitum) and food-restricted conditions. We demonstrated that Ct-1 is a metabolic gene induced in the liver via PPARα in response to lipids in mice (neonates- and food-restricted adults). We found that Ct-1 mRNA expression in white adipose tissue directly involved PPARα and PPARγ. Finally, the physiological role of CT-1 in fasting is confirmed by the impaired food restriction-induced adipose tissue lipid mobilization in CT-1 null mice. Our findings support a previously unrecognized physiological role of CT-1 in metabolic adaptations, through the regulation of lipid metabolism and contributes to fasting-induced free fatty acid mobilization.

Cardioprotective Effects of Sirtuin-1 and Its Downstream Effectors: Potential Role in Mediating the Heart Failure Benefits of SGLT2 (Sodium-Glucose Cotransporter 2) Inhibitors

The cardioprotective effects of SGLT2 (sodium-glucose cotransporter 2) inhibitors may be related to their ability to induce a fasting-like paradigm, which triggers the activation of nutrient deprivation pathways to promote cellular homeostasis. The most distinctive metabolic manifestations of this fasting mimicry are enhanced gluconeogenesis and ketogenesis, which are not seen with other antihyperglycemic drugs. The principal molecular stimulus to gluconeogenesis and ketogenesis is activation of SIRT1 (sirtuin-1) and its downstream mediators: PGC-1α (proliferator-activated receptor gamma coactivator 1-alpha) and FGF21 (fibroblast growth factor 21). These three nutrient deprivation sensors exert striking cardioprotective effects in a broad range of experimental models. This benefit appears to be related to their actions to alleviate oxidative stress and promote autophagy-a lysosome-dependent degradative pathway that disposes of dysfunctional organelles that are major sources of cellular injury. Nutrient deprivation sensors are suppressed in states of perceived energy surplus (ie, type 2 diabetes mellitus and chronic heart failure), but SGLT2 inhibitors activate SIRT1/PGC-1α/FGF21 signaling and promote autophagy. This effect may be related to their action to trigger the perception of a system-wide decrease in environmental nutrients, but SGLT2 inhibitors may also upregulate SIRT1, PGC-1α, and FGF21 by a direct effect on the heart. Interestingly, metformin-induced stimulation of AMP-activated protein kinase (a nutrient deprivation sensor that does not promote ketogenesis) has not been shown to reduce heart failure events in clinical trials. Therefore, promotion of ketogenic nutrient deprivation signaling by SGLT2 inhibitors may explain their cardioprotective effects, even though SGLT2 is not expressed in the heart.

Role of ketogenic starvation sensors in mediating the renal protective effects of SGLT2 inhibitors in type 2 diabetes

Sodium-glucose cotransporter 2 (SGLT2) inhibitors ameliorate the progression of diabetic chronic kidney disease, but the mechanisms underlying this nephroprotective effect have not been fully elucidated. These drugs induce a fasting-like transcriptional paradigm, which includes activation of sirtuin-1 (SIRT1) and its downstream effectors, peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and fibroblast growth factor 21 (FGF21). This triad of enzymes and transcription factors serve as master regulators of nutrient and cellular homeostasis, and each acts to enhance gluconeogenesis, fatty acid oxidation and ketogenesis, the hallmarks of treatment with SGLT2 inhibitors. At the same time, SIRT1/PGC-1α/FGF21 signaling also promotes autophagy, a lysosome-dependent degradative pathway that cleanses the cytosol of dysfunctional organelles. This action alleviates cellular stress, ameliorates inflammation, and is strikingly nephroprotective. Interestingly, type 2 diabetes is characterized by both a deficiency of SIRT1/PGC-1α signaling and an impairment of autophagic flux, thus explaining the high levels of oxidative stress in the diabetic kidney. SIRT1 gene polymorphisms have been linked with an increased risk of diabetic nephropathy in several epidemiological studies. Importantly, there is an inverse relationship between the activity of SGLT2 and signaling through the SIRT1/PGC-1α/FGF21 pathway, and SGLT2 inhibition leads to activation of these ketogenic nutrient deprivation sensors. Therefore, activation of SIRT1/PGC-1α/FGF21 may explain the effect of SGLT2 inhibitors not only to promote ketogenesis, but also to preserve renal function in type 2 diabetes.

Sodium-Glucose Cotransporter 2 Inhibitors Potentially Prevent Atrial Fibrillation by Ameliorating Ion Handling and Mitochondrial Dysfunction

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are a novel class of glucose-lowering agents that significantly improve the prognosis of patients with type 2 diabetes (T2D) and heart failure. SGLT2i has recently been implicated in the treatment of atrial fibrillation (AF) with clinical data demonstrating that these agents decrease the incidence of AF events in patients with T2D. Fundamental findings have suggested that SGLT2i may alleviate atrial electrical and structural remodeling. The underlying mechanisms of SGLT2i are likely associated with balancing the sodium and calcium handling disorders and mitigating the mitochondrial dysfunction in atrial myocytes. This review illustrates the advances in understanding the underlying mechanisms of SGLT2i as an evolving treatment modality for AF.

SGL 121 Attenuates Nonalcoholic Fatty Liver Disease through Adjusting Lipid Metabolism Through AMPK Signaling Pathway

A ginsenoside F2-enhanced mixture (SGL 121) increases the content of ginsenoside F2 by biotransformation. In the present study, we investigated the effect of SGL 121 on nonalcoholic fatty liver disease (NAFLD) in vitro and in vivo. High-fat, high-carbohydrate-diet (HFHC)-fed mice were administered SGL 121 for 12 weeks to assess its effect on improving NAFLD. In HepG2 cells, SGL 121 acted as an antioxidant, a hepatoprotectant, and had an anti-lipogenic effect. In NAFLD mice, SGL 121 significantly improved body fat mass; levels of hepatic triglyceride (TG), hepatic malondialdehyde (MDA), serum total cholesterol (TC), high-density lipoprotein (HDL), and low-density lipoprotein (LDL); and activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). In HepG2 cells, induced by oxidative stress, SGL 121 increased cytoprotection, inhibited reactive oxygen species (ROS) production, and increased antioxidant enzyme activity. SGL 121 activated the Nrf2/HO-1 signaling pathway and improved lipid accumulation induced by free fatty acids (FFA). Sterol regulatory element-binding protein-1 (SREBP-1) and fatty acid synthase (FAS) expression was significantly reduced in NAFLD-induced liver and HepG2 cells treated with SGL 121. Moreover, SGL 121 activated adenosine monophosphate-activated protein kinase (AMPK), which plays an important role in the regulation of lipid metabolism. The effect of SGL 121 on the improvement of NAFLD seems to be related to its antioxidant effects and activation of AMPK. In conclusion, SGL 121 can be potentially used for the treatment of NAFLD.

Autophagy-dependent and -independent modulation of oxidative and organellar stress in the diabetic heart by glucose-lowering drugs

Autophagy is a lysosome-dependent intracellular degradative pathway, which mediates the cellular adaptation to nutrient and oxygen depletion as well as to oxidative and endoplasmic reticulum stress. The molecular mechanisms that stimulate autophagy include the activation of energy deprivation sensors, sirtuin-1 (SIRT1) and adenosine monophosphate-activated protein kinase (AMPK). These enzymes not only promote organellar integrity directly, but they also enhance autophagic flux, which leads to the removal of dysfunctional mitochondria and peroxisomes. Type 2 diabetes is characterized by suppression of SIRT1 and AMPK signaling as well as an impairment of autophagy; these derangements contribute to an increase in oxidative stress and the development of cardiomyopathy. Antihyperglycemic drugs that signal through insulin may further suppress autophagy and worsen heart failure. In contrast, metformin and SGLT2 inhibitors activate SIRT1 and/or AMPK and promote autophagic flux to varying degrees in cardiomyocytes, which may explain their benefits in experimental cardiomyopathy. However, metformin and SGLT2 inhibitors differ meaningfully in the molecular mechanisms that underlie their effects on the heart. Whereas metformin primarily acts as an agonist of AMPK, SGLT2 inhibitors induce a fasting-like state that is accompanied by ketogenesis, a biomarker of enhanced SIRT1 signaling. Preferential SIRT1 activation may also explain the ability of SGLT2 inhibitors to stimulate erythropoiesis and reduce uric acid (a biomarker of oxidative stress)—effects that are not seen with metformin. Changes in both hematocrit and serum urate are the most important predictors of the ability of SGLT2 inhibitors to reduce the risk of cardiovascular death and hospitalization for heart failure in large-scale trials. Metformin and SGLT2 inhibitors may also differ in their ability to mitigate diabetes-related increases in intracellular sodium concentration and its adverse effects on mitochondrial functional integrity. Differences in the actions of SGLT2 inhibitors and metformin may reflect the distinctive molecular pathways that explain differences in the cardioprotective effects of these drugs.