Isoquercitrin attenuates the progression of non-alcoholic steatohepatitis in mice by modulating galectin-3-mediated insulin resistance and lipid metabolism.

BACKGROUND: Non-alcoholic steatohepatitis (NASH) is a global health problem with no effective treatment. Isoquercitrin (IQ) alters hepatic lipid metabolism and inhibits adipocyte differentiation. The underlying regulatory mechanisms of IQ in regulating insulin resistance (IR) and lipid metabolism remain unclear. PURPOSE: This study was aimed at investigating the effects of IQ on NASH and deciphering whether the underlying mechanisms are via modulation of galectin-3 mediated IR and lipid metabolism. METHODS: IR-HepG2 cell lines were used to demonstrate the ability of IQ to modulate galectin-3-mediated glucose disposal and lipid metabolism. A 20-week high-fat diet (HFD)-induced NASH model was established in C57BL/6J mice, and the protective effect of IQ on lipid disposal in the liver was verified. Further, the mRNA and protein levels of glucose and lipid metabolism were investigated, and lysophosphatidylcholine (LPC) and acylcarnitine (AC) profiling were performed to characterize the changes in endogenous substances associated with mitochondrial function and lipid metabolism in serum and cells. Furthermore, the pharmacokinetic features of IQ were explored in a rat model of NASH. RESULTS: IQ restored liver function and ameliorated inflammation and lipid accumulationin NASH model mice. Notably, significant regulation of the proteins included fatty acid-generating and transporting, cholesterol metabolism enzymes, nuclear transcription factors, mitochondrial metabolism, and IR-related enzymes was noted to be responsible for the therapeutic mechanisms of IQ against experimental NASH. Serum lipid metabolism-related metabolomic assay confirmed that LPC and AC biosynthesis mostly accounted for the therapeutic effect of IQ in mice with NASH and that IQ maintained the homeostasis of LPC and AC levels. CONCLUSION: This is the first study showing that IQ protects against of NASH by modulating galectin-3-mediated IR and lipid metabolism. The mechanisms responsible for liver protection and improved lipid metabolic disorder by IQ may be related to the suppression of IR and regulation of mitochondrial function and lipid metabolism. Galectin-3 down-regulation represents a potentially novel approach for the treatment and prevention of NASH.

Modified Citrus Pectin Prevents Blood-Brain Barrier Disruption in Mouse Subarachnoid Hemorrhage by Inhibiting Galectin-3.

Background and Purpose- Plasma levels of galectin-3-a matricellular protein-are increased after aneurysmal subarachnoid hemorrhage (SAH), but the functional significance remains undetermined. This study was conducted to evaluate whether modified citrus pectin (MCP; galectin-3 inhibitor) prevents post-SAH early brain injury, focusing on blood-brain barrier disruption. Methods- C57BL/6 male adult mice (n=251) underwent sham or filament perforation SAH modeling, followed by a random intracerebroventricular injection of vehicle or drug at 30 minutes post-modeling. First, vehicle-treated and 0.8, 4, 16, or 32 µg MCP-treated mice were assessed by neuroscore and brain water content at 24 and 48 hours post-modeling. Second, Evans blue extravasation, Western blotting, coimmunoprecipitation and immunostaining were performed in vehicle-treated or 4 µg MCP-treated mice at 24 hours post-modeling. Third, vehicle or R-galectin-3 (recombinant galectin-3) was administered to SAH mice simultaneously with vehicle or MCP, and neuroscore and Evans blue extravasation were evaluated at 24 hours post-modeling. Fourth, vehicle or R-galectin-3 was administered to MCP-treated SAH mice at 24 hours, and neuroscore and IgG immunostaining were evaluated at 48 hours post-SAH. Results- Among tested dosages, 4 µg MCP showed the best neuroprotective effects as to preventing neurological impairments and brain edema at 24 to 48 hours post-SAH. Four micrograms MCP attenuated post-SAH blood-brain barrier disruption and galectin-3 upregulation in brain capillary endothelial cells, associated with inactivation of ERK (extracellular signal-related kinase) 1/2, STAT (signal transducer and activator of transcription)-3, and MMP (matrix metalloproteinase)-9, and the consequent preservation of a tight junction protein ZO-1 (zonula occludens-1). Coimmunoprecipitation assay demonstrated physical interactions between galectin-3 and TLR (Toll-like receptor) 4. R-galectin-3 blocked the neuroprotective effects of MCP. Conclusions- MCP prevents post-SAH blood-brain barrier disruption possibly by inhibiting galectin-3, of which the mechanisms may include binding to TLR4 and activating ERK1/2, STAT-3, and MMP-9. This study suggests galectin-3 to be a novel therapeutic target against post-SAH early brain injury.

Role for Galectin-3 in Calcific Aortic Valve Stenosis.

BACKGROUND: Aortic stenosis (AS) is a chronic inflammatory disease, and calcification plays an important role in the progression of the disease. Galectin-3 (Gal-3) is a proinflammatory molecule involved in vascular osteogenesis in atherosclerosis. Therefore, we hypothesized that Gal-3 could mediate valve calcification in AS. METHODS AND RESULTS: Blood samples and aortic valves (AVs) from 77 patients undergoing AV replacement were analyzed. As controls, noncalcified human AVs were obtained at autopsy (n=11). Gal-3 was spontaneously expressed in valvular interstitial cells (VICs) from AVs and increased in AS as compared to control AVs. Positive correlations were found between circulating and valvular Gal-3 levels. Valvular Gal-3 colocalized with the VICs markers, alpha-smooth muscle actin and vimentin, and with the osteogenic markers, osteopontin, bone morphogenetic protein 2, runt-related transcription factor 2, and SRY (sex-determining region Y)-box 9. Gal-3 also colocalized with the inflammatory markers cd68, cd80 and tumor necrosis factor alpha. In vitro, in VICs isolated from AVs, Gal-3 induced expression of inflammatory, fibrotic, and osteogenic markers through the extracellular signal-regulated kinase 1 and 2 pathway. Gal-3 expression was blocked in VICs undergoing osteoblastic differentiation using its pharmacological inhibitor, modified citrus pectin, or the clustered regularly interspaced short palindromic repeats/Cas9 knockout system. Gal-3 blockade and knockdown decreased the expression of inflammatory, fibrotic, and osteogenic markers in differentiated VICs. CONCLUSIONS: Gal-3, which is overexpressed in AVs from AS patients, appears to play a central role in calcification in AS. Gal-3 could be a new therapeutic approach to delay the progression of AV calcification in AS.