Investigation of salicylate hepatic responses in comparison with chemical analogues of the drug

Abstract

Anti-hyperglycaemic effects of the hydroxybenzoic acid salicylate might stem from effects of the drug on mitochondrial uncoupling, activation of AMP-activated protein kinase, and inhibition of NF-κB signalling. Here, we have gauged the contribution of these effects to control of hepatocyte glucose production, comparing salicylate with inactive hydroxybenzoic acid analogues of the drug. In rat H4IIE hepatoma cells, salicylate was the only drug tested that activated AMPK. Salicylate also reduced mTOR signalling, but this property was observed widely among the analogues. In a sub-panel of analogues, salicylate alone reduced promoter activity of the key gluconeogenic enzyme glucose 6-phosphatase and suppressed basal glucose production in mouse primary hepatocytes. Both salicylate and 2,6 dihydroxybenzoic acid suppressed TNFα-induced IκB degradation, and in genetic knockout experiments, we found that the effect of salicylate on IκB degradation was AMPK-independent. Previous data also identified AMPK-independent regulation of glucose but we found that direct inhibition of neither NF-κB nor mTOR signalling suppressed glucose production, suggesting that other factors besides these cell signalling pathways may need to be considered to account for this response to salicylate. We found, for example, that H4IIE cells were exquisitely sensitive to uncoupling with modest doses of salicylate, which occurred on a similar time course to another anti-hyperglycaemic uncoupling agent 2,4-dinitrophenol, while there was no discernible effect at all of two salicylate analogues which are not anti-hyperglycaemic. This finding supports much earlier literature suggesting that salicylates exert anti-hyperglycaemic effects at least in part through uncoupling.

Salsalate (Salicylate) Uncouples Mitochondria, Improves Glucose Homeostasis, and Reduces Liver Lipids Independent of AMPK-β1

“…This is the first study to suggest that salicylate-driven mitochondrial uncoupling is the primary mechanism of action to explain the host of beneficial effects associated with salicylate (11,49,50) and salsalate (6)(7)(8)14,51,52). Data from the present study and previous investigations suggest that mitochondrial uncoupling resulting from the protonophoric properties of salicylate explains the consistently observed increases in energy expenditure in murine models and human subjects treated with salicylate-based compounds (6,10,11,14,15,(52)(53)(54)(55)(56)(57)(58).…”

Effects of sodium salicylate on glucose kinetics and insulin signaling in postpartum dairy cows

“…These experiments confirmed that SS activates AMPK, inhibits NFκB activation, and induces metabolic uncoupling simultaneously with inhibition of gluconeogenesis. Importantly, though, in dose-response experiments, none of these effects were observed at salicylate concentrations <1 mM (Cameron et al, 2016). Most in vivo and in vitro studies investigating salicylate inhibition of gluconeogenesis have used concentrations of 0.8 to 30 mM (Kim et al, 2001;Hawley et al, 2012;Smith et al, 2016), and to our knowledge, metabolic responses have not been reported at concentrations less than 0.25 mM (Smith et al, 2016).…”

“…The treatment protocol used in the current study resulted in a mean plasma salicylate concentration of just 34 µg/mL, which equates to 0.25 mM (Farney et al, 2013a). Based on the findings of Smith et al (2016) in comparison to dose-responses of Cameron et al (2016), perhaps the most likely mode of action for the effect of SS on hepatic metabolism is mitochondrial uncoupling, resulting in decreased ATP concentrations and AMPK activation, and in turn, enhanced insulin signaling. Nevertheless, other data directly contradict this model (Ford et al, 2015).…”

“…Recently, Cameron et al (2016) published an indepth investigation of several possible modes of action for salicylate's effect on hepatic function. These experiments confirmed that SS activates AMPK, inhibits NFκB activation, and induces metabolic uncoupling simultaneously with inhibition of gluconeogenesis.…”

β‐ RA reduces DMQ /CoQ ratio and rescues the encephalopathic phenotype in Coq9 R239X mice

“…Additionally, b-RA is a structural analogue of salicylic acid (2-hydroxybenzoic acid), an anti-inflammatory molecule that may be potentially valuable to reduce the neuroinflammation (Lan et al, 2011;Gomez-Guzman et al, 2014), a factor that has been recently postulated as an essential pathomechanism and a therapeutic target in mitochondrial encephalopathies (Ignatenko et al, 2018), leukoencephalopathy, and neurodegenerative diseases (Eto et al, 2002;Liddelow & Barres, 2015, 2017. Also salicylic derivate, known as salicylates, may act as mTOR inhibitors (Cameron et al, 2016), and this action may be therapeutic in mitochondrial diseases (Johnson et al, 2013).…”