The metabolic syndrome is a cluster of disorders that includes obesity, hypertriglyceridemia, hypertension, non-alcoholic fatty liver disease and insulin resistance which predispose to the development of diabetes and cardiovascular disease. Excessive sugar consumption, predominantly in the form of sugar- sweetened beverages, can contribute to the development of the metabolic syndrome. The mechanisms by which excessive fructose consumption contributes to metabolic disease remain uncertain. Carbohydrate Responsive- Element Binding Protein (ChREBP) is a transcription factor which is activated by products of carbohydrate metabolism and regulates metabolic gene programs and systemic glucose and lipid homeostasis. SNPs in the ChREBP locus identified in genome-wide association studies predict features of the metabolic syndrome in human populations. Hepatic and intestinal ChREBP are highly responsive to fructose ingestion. Loss of intestinal ChREBP results in fructose-intolerance due to fructose malabsorption. In contrast, loss of hepatic ChREBP is well-tolerated and protects against fructose-induced metabolic disease. Some mouse strains are highly sensitive to fructose-induced disease whereas others are highly resistant. Preliminary data suggests that this susceptibility may be mediated by relative differences in intestinal fructose absorption and metabolism, which may affect delivery of fructose to the liver where it is deleterious. Understanding the molecular determinants of intestinal versus hepatic fructose metabolism may have important implications for the susceptibility to diet-induced disease. Through a combination of genetic and dietary models, we will investigate physiological, molecular, and genetic mechanisms by which ChREBP-mediated intestinal and hepatic fructose metabolism protect against or contribute to fructose-induced disease.
In Aim 1, using an intestine-specific, loss-of-function mouse model, we will explore the importance of intestinal fructose metabolism in regulating endogenous glucose production and mediating fructose-induced disease.
In Aim 2, we will determine whether the net beneficial versus adverse effects of hepatic ChREBP activation may be dependent on the metabolic hormone FGF21.
In Aim 3, using fructose sensitive and fructose resistant mice in combination with an intestinal organoid model, we will explore the molecular mechanisms giving rise to differences in intestinal fructose absorption, metabolism, and susceptibility to fructose-induced disease. We anticipate that these studies will provide fundamental insight into mechanisms of fructose-induced metabolic disease and lay the groundwork for novel strategies for the prevention and treatment of obesity and diabetes.
Increased sugar consumption contributes to the obesity and diabetes epidemics, and the fructose component of sugar appears to be particularly harmful. We have demonstrated that a key cellular factor called ChREBP plays an important role in intestinal and liver fructose metabolism and participates in fructose-induced disease. Using animal models, we will explore the mechanisms by which this factor and additional genetic factors participate in fructose-induced disease, which will provide the basic knowledge needed to develop rational strategies to prevent and treat obesity, diabetes, and associated metabolic diseases.
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