Glyoxalase 1 and its Role in Metabolic Syndrome

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Abstract The overall goal of this proposal is to determine the role of glyoxalase 1 (GLO1) in the pathogenesis of obesity, Type 2 diabetes (T2D), and non-alcoholic fatty liver disease (NAFLD). Greater than 34 million Americans have diabetes, and another 88 million are considered pre-diabetic. This is largely attributed to the prevalence of obesity, with 72% of American adults currently classified as overweight or obese. Among the comorbidities associated with T2D, over 70% of patients have NAFLD. Epidemiological studies have linked high fructose consumption with obesity, T2D, and NAFLD. This proposal identifies GLO1 as pro-NAFLD/obesogenic gene. Using CRISPR-Cas9, we have generated GLO1 knockout mice. When fed a high-fat high sucrose diet, these mice display significantly blunted weight gain, restored glucose tolerance, and reduced hepatic steatosis compared to wild-type counterparts. GLO1 is a ubiquitously expressed enzyme that detoxifies the glycolytic by- product, methylglyoxal (MGO). When GLO1 activity is disrupted, MGO levels increase, resulting in long-lived protein post-translational modifications. We have shown that MGO serves as a metabolic sensor for nutrient flux, regulating glycolytic output and transcriptional responses to sugar. Thus, we hypothesize that GLO1 is a pro- NAFLD/obesogenic gene, reducing MGO and removing the brakes on metabolism. We will test this hypothesis by addressing the following three Specific Aims: In Specific Aim 1 we will quantify the impact of Glo1 on whole- body energetics and hepatic lipid metabolism using a 16-week chow- or high-fat high-sucrose diet. We will quantify lean vs. fat mass, energy expenditure, and total activity. Hepatic fatty acid oxidation and mitochondrial respiration will be quantified in primary hepatocytes. Lastly, lipogeneic genes will be assessed using RNA-seq. In Specific Aim 2 we will determine the impact of Glo1 on intestinal fructose metabolism. The intestine is a primary site of fructose metabolism. Stable isotope labeling via 13C6-fructose oral gavage will be used to quantify intestinal, hepatic, muscle, adipose, and circulating fructose metabolites. This approach will quantitatively determine how Glo1 regulates intestinal carbohydrate metabolism, a previously unexplored area of research. Finally, in Specific Aim 3, we will confirm that MGO-derived histone PTMs regulate transcriptional responses to metabolism in vivo. Site-specific canonical and MGO-derived PTMs will be quantified in each tissue/cohort. Putative reader domains will be identified for MG-H1 histone modifications. Lastly, liver, intestine, muscle, adipose, and pancreas will be subjected to RNA-seq and ATAC-seq. This approach will determine the global epigenomic landscape across multiple tissues in a physiologically relevant model for obesity, T2D and NAFLD. Collectively, this proposal will combine mechanistic biochemistry with a multi-omics approach to determine the mechanisms by which GLO1 propagates disease progression.