👤 Ludivine Doridot

Carbohydrate response element-binding protein (ChREBP) is a carbohydrate-sensing transcription factor that regulates both adaptive and maladaptive genomic responses in coordination of systemic fuel homeostasis. Genetic variants in the ChREBP locus associate with diverse metabolic traits in humans, including circulating lipids. To identify novel ChREBP-regulated hepatokines that contribute to its systemic metabolic effects, we integrated ChREBP ChIP-Seq analysis in mouse liver with human genetic and genomic data for lipid traits and identified hepatocyte growth factor activator (HGFAC) as a promising ChREBP-regulated candidate in mice and humans. HGFAC is a protease that activates the pleiotropic hormone hepatocyte growth factor. We demonstrate that HGFAC-KO mice had phenotypes concordant with putative loss-of-function variants in human HGFAC. Moreover, in gain- and loss-of-function genetic mouse models, we demonstrate that HGFAC enhanced lipid and glucose homeostasis, which may be mediated in part through actions to activate hepatic PPARγ activity. Together, our studies show that ChREBP mediated an adaptive response to overnutrition via activation of HGFAC in the liver to preserve glucose and lipid homeostasis. Show less

The epithelial to mesenchymal transition (EMT) has been implicated in the development of adenomyosis, along with dysregulated immune responses. Inflammation potentially induces Notch signaling, which could promote this EMT. The objective of this study was to investigate the involvement of immune cells and Notch1-mediated EMT in the development of adenomyosis. Adenomyosis was induced in 18 CD-1 mice by neonatal oral administration of tamoxifen (TAM group), while 18 neonates received vehicle only (Control group). Their uteri were sampled at 30, 60 or 90 days of age. Immune cell markers (Cd45, Ly6c1, Cd86, Arginine1, Cd19, Cd4, Cd8), Notch1 and its target genes (Hey1, Hey2, Hes1, Hes5) and biomarkers of EMT (E-Cadherin, Vimentin, Tgfb, Snail1, Slug, Snail3) were analyzed by quantitative RT-PCR and immunohistochemistry. Activated-Notch1 protein was measured by western blot. Aberrant expression of immune cell markers was observed in the uteri of mice as they developed adenomyosis. The expression of inflammatory cell markers, notably M1 macrophages and natural killer cells, was increased from Day 30 in the TAM group compared to controls, followed by an increase in the Cd4 marker (T cells) at Day 60. Conversely, expression of the Cd19 marker (B cells) was significantly reduced at all of the stages studied. Notch1 signaling was also highly activated compared to controls at Day 30 and Day 60. Concomitantly, the levels of several markers for EMT were also higher. Therefore, the activation of Notch1 coincides with aberrant expression of immune and EMT markers in the early development of adenomyosis. Show less

Increased sugar consumption is a risk factor for the metabolic syndrome including obesity, hypertriglyceridemia, insulin resistance, diabetes, and nonalcoholic fatty liver disease (NAFLD). Carbohydrate responsive element-binding protein (ChREBP) is a transcription factor that responds to sugar consumption to regulate adaptive metabolic programs. Hepatic ChREBP is particularly responsive to fructose and global ChREBP-KO mice are intolerant to diets containing fructose. It has recently been suggested that ChREBP protects the liver from hepatotoxicity following high-fructose diets (HFrDs). We directly tested this hypothesis using tissue-specific ChREBP deletion. HFrD increased adiposity and impaired glucose homeostasis in control mice, responses that were prevented in liver-specific ChREBP-KO (LiChKO) mice. Moreover, LiChKO mice tolerated chronic HFrD without marked weight loss or hepatotoxicity. In contrast, intestine-specific ChREBP-KO (IChKO) mice rapidly lost weight after transition to HFrD, and this was associated with dilation of the small intestine and cecum, suggestive of malabsorption. These findings were associated with downregulation of the intestinal fructose transporter, Slc2a5, which is essential for fructose tolerance. Altogether, these results establish an essential role for intestinal, but not hepatic, ChREBP in fructose tolerance. Show less

Increased fructose consumption is a contributor to the burgeoning epidemic of non-alcoholic fatty liver disease (NAFLD). Recent evidence indicates that the metabolic hormone FGF21 is regulated by fructose consumption in humans and rodents and may play a functional role in this nutritional context. Here, we sought to define the mechanism by which fructose ingestion regulates FGF21 and determine whether FGF21 contributes to an adaptive metabolic response to fructose consumption. We tested the role of the transcription factor carbohydrate responsive-element binding protein (ChREBP) in fructose-mediated regulation of FGF21 using ChREBP knockout mice. Using FGF21 knockout mice, we investigated whether FGF21 has a metabolic function in the context of fructose consumption. Additionally, we tested whether a ChREBP-FGF21 interaction is likely conserved in human subjects. Hepatic expression of In summary, ChREBP and FGF21 constitute a signaling axis likely conserved in humans that mediates an essential adaptive response to fructose ingestion that may participate in the pathogenesis of NAFLD and liver fibrosis. Show less

Obese, insulin-resistant states are characterized by a paradoxical pathogenic condition in which the liver appears to be selectively insulin resistant. Specifically, insulin fails to suppress glucose production, yet successfully stimulates de novo lipogenesis. The mechanisms underlying this dysregulation remain controversial. Here, we hypothesized that carbohydrate-responsive element-binding protein (ChREBP), a transcriptional activator of glycolytic and lipogenic genes, plays a central role in this paradox. Administration of fructose increased hepatic hexose-phosphate levels, activated ChREBP, and caused glucose intolerance, hyperinsulinemia, hypertriglyceridemia, and hepatic steatosis in mice. Activation of ChREBP was required for the increased expression of glycolytic and lipogenic genes as well as glucose-6-phosphatase (G6pc) that was associated with the effects of fructose administration. We found that fructose-induced G6PC activity is a major determinant of hepatic glucose production and reduces hepatic glucose-6-phosphate levels to complete a homeostatic loop. Moreover, fructose activated ChREBP and induced G6pc in the absence of Foxo1a, indicating that carbohydrate-induced activation of ChREBP and G6PC dominates over the suppressive effects of insulin to enhance glucose production. This ChREBP/G6PC signaling axis is conserved in humans. Together, these findings support a carbohydrate-mediated, ChREBP-driven mechanism that contributes to hepatic insulin resistance. Show less