Role of SREBP-1 in the Development of Parasympathetic Dysfunction in the Hearts of Type 1 Diabetic Akita Mice
- 31 July 2009
- journal article
- research article
- Published by Ovid Technologies (Wolters Kluwer Health) in Circulation Research
- Vol. 105 (3), 287-294
- https://doi.org/10.1161/circresaha.109.193995
Abstract
Rationale: Diabetic autonomic neuropathy (DAN), a major complication of diabetes mellitus, is characterized, in part, by impaired cardiac parasympathetic responsiveness. Parasympathetic stimulation of the heart involves activation of an acetylcholine-gated K+ current, IKAch, via a (GIRK1)2/(GIRK4)2 K+ channel. Sterol regulatory element binding protein-1 (SREBP-1) is a lipid-sensitive transcription factor. Objective: We describe a unique SREBP-1–dependent mechanism for insulin regulation of cardiac parasympathetic response in a mouse model for DAN. Methods and Results: Using implantable EKG transmitters, we demonstrated that compared with wild-type, Ins2Akita type I diabetic mice demonstrated a decrease in the negative chronotropic response to carbamylcholine characterized by a 2.4-fold decrease in the duration of bradycardia, a 52±8% decrease in atrial expression of GIRK1 (PPKAch with a peak value of −181±31 pA/pF compared with −451±62 pA/pF (PKAch activity in atrial myocytes from these mice to levels in wild-type mice. Insulin treatment of cultured atrial myocytes stimulated GIRK1 expression 2.68±0.12-fold (PKAch to levels in cells from wild-type mice. Conclusions: These results support a unique molecular mechanism for insulin regulation of GIRK1 expression and parasympathetic response via SREBP-1, which might play a role in the pathogenesis of DAN in response to insulin deficiency in the diabetic heart.Keywords
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