Coagulopathy in Malnourished Mice Is Sexually Dimorphic and Regulated by Nutrient‐Sensing Nuclear Receptors

Abstract

Liver dysfunction, including coagulopathy, is a prominent feature of protein-energy malnutrition. To identify mechanisms underlying malnutrition-associated coagulopathy, we administered a low-protein low-fat diet to lactating dams and examined hepatic transcription and plasma coagulation parameters in young adult weanlings. Malnutrition impacted body composition to a greater extent in male versus female mice. Transcriptional profiles suggested opposing effects of nutrient-sensing nuclear receptors, namely induction of peroxisome proliferator-activated receptor α (PPARα) targets and repression of farnesoid-X-receptor (FXR) targets. Coagulopathy with decreased synthesis of fibrinogen-α (FGA) and factor 11 (F11) was observed in malnourished male animals but not female animals. In primary mouse hepatocytes, FXR agonist increased and PPARα agonist decreased Fga and F11 messenger RNA expression. Nuclear receptor DNA response elements were identified in the Fga and F11 gene regulatory regions, and opposing effects of FXR and PPARα were confirmed with luciferase assays. Unexpectedly, hepatic PPARα protein was markedly depleted in malnourished male liver and was not enriched on Fga or F11 response elements. Rather, there was loss of FXR binding at these response elements. Reduced PPARα protein was associated with loss of hepatocyte peroxisomes, which are necessary for bile acid biosynthesis, and with decreased concentrations of bile acids that function as FXR ligands, most notably the FXR agonist chenodeoxycholic acid. Conclusion: Malnutrition impairs growth and liver synthetic function more severely in male mice than in female mice. Malnourished male mice are coagulopathic and exhibit decreased hepatocyte peroxisomes, FXR agonist bile acids, FXR binding on Fga and F11 gene regulatory elements, and coagulation factor synthesis. These effects are absent in female mice, which have low baseline levels of PPARα, suggesting that nutrient-sensing nuclear receptors regulate coagulation factor synthesis in response to host nutritional status in a sex-specific manner. (Hepatology Communications 2020;0:1-16). M alnutrition remains one of the leading global health challenges, contributing to half of all child deaths. In developing countries, stunting is observed in 31% of children under 5 years of age. (1) Child malnutrition is difficult to treat and carries a high mortality rate, in part due to liver pathophysiology, which includes synthetic function impairment and coagulopathy. (2) Although coagulopathy in child malnutrition often is attributed to vitamin K deficiency, many cases of moderate to

Hepatic PPARα Is Destabilized by SIRT1 Deacetylase in Undernourished Male Mice

“…We first administered a single intraperitoneal injection of the proteasome inhibitor bortezomib, or vehicle, to healthy and undernourished male mice, then harvested livers 24 h later for western blot. PPARα was profoundly reduced in livers from vehicle-treated undernourished mice, confirming our previous findings ( 6 ). Strikingly, hepatic PPARα levels in undernourished mice were rescued completely by bortezomib ( Figure 4A ), confirming that proteasome mediated degradation is responsible for loss of hepatic PPARα in undernutrition.…”

“…It has been proposed that deacetylation might facilitate the release of corepressors or the recruitment of coactivators, or enhance clearing from the promoter for subsequent rounds of transcription ( 24 ). Congruent with this working model, transcriptional analysis of our undernourished mouse livers revealed marked upregulation in PPAR signaling, including induction of the positive PPARα target genes Fgf21, Acot1 , and Cyp4a14 ( 6 ). PPARα is strongly activated in the fasted state ( 2 ), and it remains to be determined whether similarly strong PPARα activation is detected during the initial phases of acute undernutrition.…”

“…We recently reported that undernutrition dramatically decreases hepatic concentrations of the nuclear receptor PPARα in male mice ( 6 ). This effect is not observed in female mice, which have low hepatic PPARα protein expression at baseline ( Figure 1 ).…”

“…The purpose of this study was to identify mechanisms contributing to the loss of hepatic PPARα protein in undernutrition. We employed a mouse model that reproduces key features of chronic undernutrition in humans, including decreased peroxisome abundance and impaired synthesis of bile acids and coagulation factors ( 6 ). After ruling out the possibility of transcriptional repression of PPARα, we found that SIRT1 expression was markedly increased in livers from undernourished mice, and we revealed in cultured hepatocytes that SIRT1 negatively regulates PPARα protein levels via deacetylation and subsequent ubiquitination and proteasomal degradation.…”

“…Steatosis, decreased hepatic peroxisome abundance, and impaired fatty acid oxidation are observed in rats chronically undernourished by a low-protein diet; these abnormalities are partially ameliorated by a PPARα agonist, suggesting a lack of PPARα signaling in chronic undernutrition ( 5 ). We recently confirmed that hepatic PPARα protein levels are dramatically reduced in chronically undernourished mice fed a low-protein, low-fat diet (LPLFD) ( 6 ). Mechanisms by which chronic undernutrition decreases hepatic PPARα protein levels have not been defined.…”