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Exp Clin Endocrinol Diabetes. 2015 Feb;123(2):80-7. doi: 10.1055/s-0034-1398502. Epub 2015 Feb 5.

Impact of toll-like-receptor-9 (TLR9) deficiency on visceral adipose tissue adipokine expression during chronic DSS-induced colitis in mice.

Author information

1
Department of Internal Medicine III, Giessen University Hospital, Germany.
2
Department of Internal Medicine I, Regensburg University Hospital, Germany.

Abstract

BACKGROUND:

Studies postulate an involvement of adipokines in inflammatory gastrointestinal diseases. Leptin-deficient ob/ob mice as well as TLR9-deficient mice have a more moderate course of chronic DSS-induced colitis (DSS-CC) and adipocytes do express functional TLR9 molecules.

MATERIAL AND METHODS:

Adipokine mRNA expression in visceral adipose tissue of mice before and after the induction of DSS-CC was investigated. Experiments were performed in both TLR9(wt/wt) and TLR9(-/-) mice. In vitro, the effect of TLR9 blocking peptide on leptin and visfatin protein secretion was studied in 3T3-L1 adipocytes.

RESULTS:

Induction of DSS-CC led to an upregulation of leptin mRNA expression in TLR9(wt/wt) mice, while TLR9(-/-) animals showed a significant reduction of leptin expression even below baseline. While visfatin expression remained unchanged in TLR9(wt/wt) animals, TLR9(-/-) mice exhibited a significant induction during DSS-CC. CTRP-3 expression was reduced after colitis induction only in TLR9(-/-) animals. Of note, IL-6 expression levels remained unchanged, while CXCL1/KC and cyclophilin A expression was reduced in DSS-CC. Inhibition of TLR9 signaling by using TLR9 blocking peptide led to reduced leptin protein secretion into cell culture supernatants in 3T3-L1 adipocytes, while visfatin protein secretion was enhanced.

CONCLUSIONS:

DSS-CC leads to differential adipokine expression profiles in the visceral fat pad in TLR9(wt/wt) vs. TLR9(-/-) mice. In vitro, inhibition of TLR9 signaling induces visfatin secretion while inhibiting leptin secretion in adipocytes. Thus, visceral adipokines are regulated by intact TLR9 signaling pathway and a specific interplay between the leptin- and the TLR9-pathways might be of pathophysiological importance in chronic intestinal inflammation.

PMID:
25654671
DOI:
10.1055/s-0034-1398502
[Indexed for MEDLINE]

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