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Riessen, R.

Publications and source records attributed to Riessen, R..

2 recordsLinked to original sources
bioRxiv2020

Bile acid excess impairs thermogenic function in brown adipose tissue

Bile acids (BAs) not only facilitate fat digestion but also protect against obesity. Here, we show that a genetic mouse model for BA overload (Farnesoid X receptor; Small heterodimer double knockout (DKO)) exhibits mitochondrial dysfunction resulting in a thermogenic defect. By housing DKO mice at thermoneutrality, the poor mitochondrial function in brown fat protects them from diet-induced obesity. Compared to control, we find higher adipose BA levels with excess accumulation of taurocholic acid in the DKO mice. We report that the expression of genes responsible for BA de novo synthesis, conjugation and transporters and accumulation of BAs are present in both brown and white adipocytes. We determine that BA overload is sufficient to cause adipocyte mitochondrial dysfunction and induce the expression of cellular senescence genes in vitro. Taken together, we uncover that BA levels within the adipose tissue may modulate its overall function. HighlightsO_LIMouse model of BA overload exhibits adipose defects, which is partially restored by housing at thermoneutrality. C_LIO_LIBAs are present in detectable concentrations in both BAT and WAT. C_LIO_LIAdipocytes express genes responsible for de novo synthesis, conjugation and transport of BAs, and accumulate BAs. C_LIO_LIPathological accumulation of BAs impairs mitochondrial function leading to thermogenic defect. C_LI

physiology↗
bioRxiv2020

Deletion of intestinal SHP impairs short-term response to cholic acid challenge in mice.

Small heterodimer partner (SHP) is a crucial regulator of bile acid (BA) transport and synthesis; however, its intestine-specific role is not fully understood. Here, we report that Intestine-specific Shp knockout (IShpKO) mice have higher intestinal and hepatic BAs, but not serum BAs when challenged with an acute (5-day) 1% cholic acid (CA) diet. Consistent with this finding, BA synthetic genes Cyp7A1 and Cyp8b1 are not repressed to the same extent in IShpKO compared to control mice post-CA challenge. Loss of intestinal SHP did not alter Fxr mRNA but increased Asbt (BA ileal uptake transporter) and Ost (BA ileal efflux transporter) expression even under chow-fed conditions. Surprisingly, the acute CA diet in IShpKO did not elicit the expected induction of Fgf15 but was able to maintain the suppression of Asbt, and Ost/{beta} mRNA levels. At the protein level, ASBT was downregulated, while OST/{beta} expression was induced and maintained regardless of diet. Examination of ileal histology in IShpKO mice challenged with acute CA diet revealed reduced villus length and goblet cell numbers. However, no difference in goblet cell number, villus morphology, crypt depth, and the expression of BA regulator and transporter genes was seen between f/f Shp and IShpKO mice after chronic (14-day) CA diet suggesting an adaptive response. We found the upregulation of the Ppar-Ugt axis, which can reduce the BA burden and compensate for the ileal SHP function. Thus, our study reveals that ileal SHP expression contributes to both overall intestinal structure and BA homeostasis.

physiology↗