Abstract 20340: Defect of Ca2+-activated Cl- Channel in Intestinal Nodose Neurons Contributes to Impaired Satiety Signal in High-Fat Diet Induced Obesity
High fat diet inhibits the cholecystokinin (CCK) induced satiety signal in vagal afferents, which may contribute to the associated increased food intake. We hypothesized that a defect of Ca2+-activated chloride channel (CaCC) in high fat (HFD) fed mice leads to the reduction of CCK responses in intestinal vagal afferent nodose neurons. By using the whole cell patch-clamp in cultured nodose ganglia neurons isolated from C57BL/6 mice, we found that CCK (10nM) induced large inward chloride (Cl-) currents (36.0±11pA/pF) that were eliminated with the fast Ca2+ chelator BAPTA (1.0±0.5pA/pF, n=7), and reduced significantly by the CaCC channel inhibitor niflumic acid (100 μM, 13.6±2.0pA/pF, p<0.05, n=8). The response to CCK in DiI-labeled proximal intestinal nodose neurons from obese mice fed a 60% HFD for 10 weeks was reduced significantly (6.1±2.9pA/pF, n=7, p<0.01) relative to control lean mice (24.8±4.9pA/pF, n=7). The underlying molecular mechanism of the reduced CCK response in mice fed a HFD did not involve altered expression of CCK receptors in nodose neurons. We found that the relative mRNA (qPCR) of CCK receptor B was not significantly changed (1.01±0.13 in control vs. 1.18±0.31 in HFD nodose ganglia, n=4, p>0.05) and the mRNA of CCK receptor A was even increased from 1.06±0.37 in control to 1.54±0.41 in HFD ganglia (n=4, p<0.05). In contrast, the CaCC channel mRNA (Ano I) was decreased to 0.61±0.09 relative to 1.01±0.20 (n=4, p<0.001), and Ano II mRNA was decreased to 0.31±0.07 relative to 1.02±0.22 (n=4, p<0.001) in nodose ganglia from HFD fed vs. control lean mice. Since the maximum current induced by a saturation level of ligand reflects the level of protein expressed on the cytoplasmic membrane, we tested the CaCC current induced by a high level of intracellular Ca2+ (20μM). We found that the maximum current was smaller in DiI labeled intestinal nodose neurons from HFD fed mice (13.7±2.9 pA/pF vs. 26.9±3.6 pA/pF in control mice, n=10, p<0.05).
Our results indicate that CCK-activated currents recorded from intestinal vagal afferent nodose neurons are reduced in mice fed a HFD, and are associated with reduced expression of a CCK-activated Ca2+-dependent Cl- channel. This mechanism may contribute significantly to HFD-induced suppression of the satiety reflex.
Author Disclosures: R. Wang: None. Y. Lu: None. M.Z. Cicha: None. K. Rahmouni: None. M.W. Chapleau: None. C.J. Benson: None. F.M. Abboud: None.
- © 2014 by American Heart Association, Inc.