SGLT2 Inhibitor-Induced Sympathoinhibition: A Novel Mechanism for Cardiorenal Protection.

Recent clinical trial data suggest a cardiorenal protective effect of sodium glucose cotransporter 2 (SGLT2) inhibition. We demonstrate that chemical denervation in neurogenic hypertensive Schlager (BPH/2J) mice reduced blood pressure, improved glucose homeostasis, and reduced renal SGLT2 protein expression. Inhibition of SGLT2 prevented weight gain, reduced blood pressure, significantly reduced elevations of tyrosine hydroxylase and norepinephrine, and protects against endothelial dysfunction. These findings provide evidence for significant crosstalk between activation of the sympathetic nervous system and SGLT2 regulation and possible ancillary effects on endothelial function, which may contribute to the observed cardiorenal protective effects of SGLT2 inhibition.

Shining LIGHT on the metabolic role of the cytokine TNFSF14 and the implications on hepatic IL-6 production.

The cytokine Tumor Necrosis Factor Superfamily member 14, TNFSF14 (or LIGHT), is a controversial player in numerous diseases. We investigated the role of endogenously expressed TNFSF14 in diet-induced obesity in vivo. Firstly, we studied the effects of Tnfsf14 ablation on the development of obesity, glucose intolerance, insulin resistance, steatosis, tissue inflammation, and mitochondrial respiration in the liver. Secondly, we examined the role of TNFSF14 expression in hematopoietic cells on obesity and insulin sensitivity. Male Tnfsf14 knockout (KO) and wild type mice were fed chow or high fat diet (HFD) for 12 weeks and were assessed for weight gain, glucose intolerance, insulin resistance, hepatosteatosis, mitochondrial dysfunction, and cytokine expression. Wild-type mice were also reconstituted with bone marrow cells from Tnfsf14 knockout mice and were fed chow or HFD for 12 weeks. These mice were examined for weight gain and insulin resistance. HFD fed mice had elevated circulating levels of serum TNFSF14. Liver and white adipose tissue are potential sources of this elevated TNFSF14. Tnfsf14 deficient mice displayed increased obesity, glucose intolerance, insulin resistance, hepatosteatosis, and mitochondrial dysfunction compared to control mice on a HFD. Hepatic cytokine profiling pointed to a potential novel role of decreased IL-6 in the metabolic disturbances in obesogenic Tnfsf14 knockout mice. Bone marrow cells from Tnfsf14 deficient mice appeared to promote diet-induced obesity, insulin resistance and reduced FGF21 levels in white adipose tissue and liver. Our novel data suggest that Tnfsf14 ablation exacerbates parameters of the metabolic syndrome under high fat feeding conditions and provides evidence to support the development of TNFSF14 agonists as potential therapeutics in diet-induced obesity.

Role of the sympathetic nervous system in regulation of the sodium glucose cotransporter 2.

BACKGROUND: The sympathetic nervous system (SNS) regulates glucose metabolism in various organs including the kidneys. The sodium glucose cotransporter 2 (SGLT2) mediates glucose reabsorption in renal proximal tubules and its inhibition has been shown to improve glucose control, cardiovascular and renal outcomes. We hypothesized that SNS-induced alterations of glucose metabolism may be mediated via regulation of SGLT2. METHOD: We used human renal proximal tubule cells to investigate the effects of noradrenaline on SGLT2 regulation. Mice fed a high-fat diet were oral gavaged with dapagliflozin and the expression of noradrenaline and tyrosine hydroxylase was measured in the kidney and heart. RESULTS: Noradrenaline treatment resulted in a pronounced increase in SGLT2 and interleukin (IL)-6 expression in HK2 cells and promoted translocation of SGLT2 to the cell surface. In vivo, dapagliflozin treatment resulted in marked glucosuria in high-fat diet-fed mice. SGLT2 inhibition significantly reduced high-fat diet-induced elevations of tyrosine hydroxylase and noradrenaline in the kidney and heart. We also aimed to assess the levels of hypertension-related cytokines in the kidneys of our mice treated with and without dapagliflozin. Excitingly, we demonstrate that SGLT2 inhibition with dapagliflozin promoted a trend towards reduced tumour necrosis factor-alpha and elevated IL-1ß protein levels in the kidney. CONCLUSION: Our in-vitro and in-vivo studies provide first evidence for an important cross-talk between the SNS and SGLT2 regulation that may not only account for SNS-induced alterations of glucose metabolism but potentially contribute to cardiovascular and renal protection observed with SGLT2 inhibitors.

ADAM19: A Novel Target for Metabolic Syndrome in Humans and Mice.

Obesity is one of the most prevalent metabolic diseases in the Western world and correlates directly with insulin resistance, which may ultimately culminate in type 2 diabetes (T2D). We sought to ascertain whether the human metalloproteinase A Disintegrin and Metalloproteinase 19 (ADAM19) correlates with parameters of the metabolic syndrome in humans and mice. To determine the potential novel role of ADAM19 in the metabolic syndrome, we first conducted microarray studies on peripheral blood mononuclear cells from a well-characterised human cohort. Secondly, we examined the expression of ADAM19 in liver and gonadal white adipose tissue using an in vivo diet induced obesity mouse model. Finally, we investigated the effect of neutralising ADAM19 on diet induced weight gain, insulin resistance in vivo, and liver TNF-α levels. Significantly, we show that, in humans, ADAM19 strongly correlates with parameters of the metabolic syndrome, particularly BMI, relative fat, HOMA-IR, and triglycerides. Furthermore, we identified that ADAM19 expression was markedly increased in the liver and gonadal white adipose tissue of obese and T2D mice. Excitingly, we demonstrate in our diet induced obesity mouse model that neutralising ADAM19 therapy results in weight loss, improves insulin sensitivity, and reduces liver TNF-α levels. Our novel data suggest that ADAM19 is pro-obesogenic and enhances insulin resistance. Therefore, neutralisation of ADAM19 may be a potential therapeutic approach to treat obesity and T2D.