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This Article Full Text Full Text (PDF) All Versions of this Article: 294/4/G1078    most recent 00591.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Stearns, A. T. Articles by Tavakkolizadeh, A. Search for Related Content PubMed PubMed Citation Articles by Stearns, A. T. Articles by Tavakkolizadeh, A.

MUCOSAL BIOLOGY

Capsaicin-sensitive vagal afferents modulate posttranscriptional regulation of the rat Na⁺/glucose cotransporter SGLT1

¹Department of Surgery, Brigham & Women's Hospital, Boston; ²Harvard Medical School, Boston; ³Department of Physiology, Anatomy, and Genetics, Oxford University, Oxford, United Kingdom; ⁴Pediatric Endocrine Unit, MassGeneral Hospital for Children, Boston, Massachusetts

Submitted 18 December 2007 ; accepted in final form 22 February 2008

Introduction: the intestinal Na⁺/glucose cotransporter (SGLT1) displays rapid anticipatory diurnal rhythms in mRNA and protein expression. The vagus nerve has been implicated in the entrainment of some transporters. We aimed to clarify the influence of the vagus nerve on the diurnal entrainment pathway for SGLT1 and examine the role of vagal afferent fibers. Methods: male Sprague-Dawley rats were randomized to three groups, total subdiaphragmatic vagotomy, selective deafferentation of the vagus with capsaicin, or sham laparotomy. Postoperatively, animals were maintained in a 12-h light-dark cycle with food access limited to night. On the ninth postoperative day, animals were euthanized to harvest jejunal mucosa at 6-h intervals starting at 10 AM. Whole cell SGLT1 protein was measured by semiquantitative densitometry of immunoblots. Sglt1 and regulatory subunit RS1 mRNA was assessed by quantitative PCR. Fluorogold tracer technique was used to confirm adequacy of the vagotomy. Results: the diurnal rhythm in intestinal SGLT1, with a 5.3-fold increase in Sglt1 mRNA at 4 PM, was preserved in both vagotomy and capsaicin groups. However, the rhythmicity in SGLT1 protein expression (2.3-fold peak at 10 PM; P = 0.041) was abolished following either total vagotomy or deafferentation. Lack of change in RS1 mRNA suggests this is independent of the RS1 regulatory pathway. Conclusion: SGLT1 transcription is independent of the vagus. However, dissociation of the protein rhythm from the underlying mRNA signal by vagotomy suggests the vagus may be involved in posttranscriptional regulation of SGLT1 in an RS1 independent pathway. Disruption following afferent ablation by capsaicin suggests this limb is specifically necessary.

glucose transport; vagus; vagotomy

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