Examination of methylglyoxal levels in an in vitro model of steatosis and serum from patients with non-alcoholic fatty liver disease

Abstract

This abstract was presented as the Cellular and Molecular Nutrition Theme highlight.Elevated levels of methylglyoxal (MG), a highly reactive glycating agent forming advanced glycation endproducts (AGEs), have been associated with diabetes, obesity and vascular disease (1) . However, its role in the hepatic manifestation of metabolic syndrome, nonalcoholic fatty liver disease (NAFLD), is still a novel inquiry. The objective of these experiments was to assess MG levels in response to lipid loading in the liver.Immortalised human hepatocytes (HepG2 cells) cultured in physiological levels of glucose (5 mM) were treated with either saturated (400 μM palmitic acid, PA) or mono-unsaturated (500 μM oleic acid, OA) fatty acids (n = 3). Fatty acid-induced lipid loading was confirmed by Nile red staining. MG content of cells and in culture medium was measured by stable isotopic dilution liquid chromatography-mass spectrometry (LC-MS/MS) (2) . The MG-derived major AGE, hydroimidazolone MG-H1, was assessed by competitive ELISA in serum samples from a cohort of biopsy-confirmed adult NAFLD patients (n = 62). Sample collection was under full NHS ethical approval and conducted in accordance with the Declaration of Helsinki. One-way ANOVA with Dunnett's test was used to analyse the in vitro data. Pearson or Spearman correlations were used to examine MG-H1 relationship to histological features and clinical biochemistries, followed by multiple linear regression analyses.Fatty acid treatment resulted in a 4-fold increase of intracellular lipid in the OA-treated cells ( Fig. 1; P < 0·01). MG increased by 44 % in OA-treated cells compared to vehicle ( Fig. 2; P < 0·05), while culture medium MG increased by 46 % and 45 % in PA-and OA-treated cells, respectively ( Fig. 3; P < 0·05). Serum MG-H1 (n = 59) was inversely correlated with alanine aminotransferase levels, lobular inflammation and hepatocyte ballooning (P < 0·001). MG-H1 was positively correlated with body mass index (BMI) (P < 0·0001) however, there was no correlation between MG-H1 and steatosis or fibrosis score and, surprisingly, in this cohort BMI was inversely correlated to inflammation and ballooning. The multiple regression analyses resulted in no conclusive relationships between MG-H1 and variables to predict NAFLD activity.Accumulation of MG, as measured by LC-MS/MS, in fatty acid-treated cells and their associated medium suggests lipid accumulation increases MG formation and/or decreases MG metabolism. In contrast, serum MG-H1 from patients with fatty liver measured by ELISA did not correlate with extent of steatosis. If these findings can be corroborated by robust measurement of MG-H1 by LC-MS/MS, increased MG and AGEs formation in hepatic steatosis in vivo may be localised to the liver where proteolysis likely releases increased MG-H1 free adduct into plasma.

Methylglyoxal induces ambience for cancer promotion in HepG2 cells via Warburg effect and promotes glycation

“…15 However, some studies have shown the involvement of MGO in liver diseases. [16][17][18] We were curious to know whether MGO creates an ambience for cancer in the liver cells. So, we put forth a hypothesis that MGO could trigger metabolic reprogramming to induce cancer development in the HepG2 cells through its multifaceted pathologies like the Warburg effect and glycation.…”

“…However, some studies have shown the involvement of MGO in liver diseases 16–18 . We were curious to know whether MGO creates an ambience for cancer in the liver cells.…”

Identification of a potent NAFLD drug candidate for controlling T2DM-mediated inflammation and secondary damage in vitro and in vivo

“…Despite various reports on MGO-AGE-mediated toxicity in different organs, its role in the liver system is yet to be reported. By using LC-MS/ MS, it was found that increased MG and MGO-AGEs formation in hepatic steatosis in vivo may be localized to the liver (Maldonado et al, 2015). Previous studies focused on the pathophysiology of NAFLD with special emphasis on the role of AGEs in NAFLD progression to non-alcoholic steatohepatitis and liver fibrosis.…”