Increased expression of receptors for orexigenic factors in nodose ganglion of diet-induced obese rats - PubMed (original) (raw)

Increased expression of receptors for orexigenic factors in nodose ganglion of diet-induced obese rats

Gabriel Paulino et al. Am J Physiol Endocrinol Metab. 2009 Apr.

Abstract

The vagal afferent pathway is important in short-term regulation of food intake, and decreased activation of this neural pathway with long-term ingestion of a high-fat diet may contribute to hyperphagic weight gain. We tested the hypothesis that expression of genes encoding receptors for orexigenic factors in vagal afferent neurons are increased by long-term ingestion of a high-fat diet, thus supporting orexigenic signals from the gut. Obesity-prone (DIO-P) rats fed a high-fat diet showed increased body weight and hyperleptinemia compared with low-fat diet-fed controls and high-fat diet-induced obesity-resistant (DIO-R) rats. Expression of the type I cannabinoid receptor and growth hormone secretagogue receptor 1a in the nodose ganglia was increased in DIO-P compared with low-fat diet-fed controls or DIO-R rats. Shifts in the balance between orexigenic and anorexigenic signals within the vagal afferent pathway may influence food intake and body weight gain induced by high fat diets.

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Figures

Fig. 1.

Fig. 1.

Effect of ingestion of a high-fat (HF) diet on body weight gain, adiposity, and fat pad mass in low-fat (LF) and HF rats after 1 and 8 wk on respective diets. A: diet-induced obesity-prone (DIO-P) rats had a significant increase in body weight (expressed as a percentage of initial body weight) at 3–8 wk compared with diet-induced obesity-resistant (DIO-R) or LF rats (LF or DIO-R vs. DIO-P, P < 0.05). B: adiposity index calculated as the sum of fat pads expressed as a percentage of body weight. Note that at week 1, rats divided into 2 groups, either LF or HF, as cannot be discriminated into DIO-R and DIO-P groups. There was a significant increase in adiposity in DIO-R and DIO-P rats compared with rats maintained on LF diet (LF vs. DIO-R or DIO-P, P < 0.05). C: mass of different fat pads. There was a significant difference in mesenteric fat pad mass between DIO-R and DIO-P rats after 8 wk on a HF diet (P < 0.05). Data are means ± SE (LF, n = 10; DIO-R, n = 7; and DIO-P, n = 8). a,b,cDifferent letters denote significant differences between groups.

Fig. 2.

Fig. 2.

The increase in plasma leptin concentration between fasted state and 2 h after oral lipid gavage was significantly higher in DIO-P than in LF or DIO-R rats after 8 wk on a HF diet. Data are means ± SE (week 1: LF, n = 5; HF, n = 5; week 8: LF, n = 4; DIO-R and DIO-P, n = 5). a,b_P_ < 0.05, different letters denote significant differences between groups.

Fig. 3.

Fig. 3.

Cholecystokinin receptor (CCK1R), growth hormone secretagogue receptor (GHSR), cannabinoid type 1 receptor (CB1), and fatty acid amide hydrolase (FAAH) expression in the nodose ganglia are significantly increased in DIO-P but not DIO-R rats. No change was observed for Y2 receptor and leptin receptor (Ob1R). Receptor expression was expressed relative to LF rats at week 1 as a control group. Data are means ± SE (week 1: LF, n = 5; HF, n = 5; week 8: LF, n = 4; DIO-R, n = 5; DIO-P, n = 5).

Fig. 4.

Fig. 4.

Principle component analysis of all measured parameters from all rat groups after vast scale transformation of the data reveals the phenotypic shifts responsible for group changes in a single evaluation. Within-group variance was equivalent after transformation, and experimental groups are clearly discriminated. The first 2 principle components accounted for 86% of the variance in the data set. The 8-wk HF DIO-R animals differed from the 8-wk LF group in PC2 (P = 0.03) but not PC1 (P = 0.6), whereas the 8-wk HF DIO-P group differed from the LF group in both components (P < 0.001).

Fig. 5.

Fig. 5.

Correlations between variables were assessed in a Pearson's correlation matrix with all measured variables. Notably, fasting leptin was strongly correlated with epididymal fat mass but weakly correlated with other adipose depots measured. Also of specific interest, the change in CCK1R expression in nodose ganglion was strongly correlated with the fasting to 2-h post-lipid challenge leptin.

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