Anti-obesity effect of intranasal administration of galanin-like peptide (GALP) in obese mice

Abstract

Galanin-like peptide (GALP) has an anti-obesity effect in rats and mice. It has been reported that the uptake of GALP by the brain is higher after intranasal administration than with intravenous injection. This study therefore aimed to clarify the effect of intranasal administration of GALP on the feeding behavior of lean and obese mice. Autoradiography revealed the presence of (125)I-GALP in the olfactory bulb and the brain microcirculation. The body weights of ob/ob mice gradually increased during vehicle treatment, but remained unchanged in response to repeated intranasal administration of GALP, with both ob/ob and diet-induced obese mice displaying significantly decreased food intake, water intake and locomotor activity when treated with GALP. These results suggest that intranasal administration is an effective route whereby GALP can exert its effect as an anti-obesity drug.

Figure 1. Autoradiographs of sagittal sections of brains 5 min after ¹²⁵I-GALP administration.

(a) Autoradiography of the brain +1.40 mm lateral to the median plane (left) and light microscopic image of the same section (right). (b) Autoradiography of the nasal region +1.40 mm lateral to the median plane (left), and light microscopic image of the same section (right).

Figure 2. Change in food intake and body weight in response to intranasal administration of GALP.

(a) Food intake and (b) body weight gain 24 h after the intranasal administration of vehicle (no fill, n = 3) or GALP (1 (horizontal lines), 2 (hash pattern) or 4 nmol (filled), n = 4 per group). The data are expressed as mean ± s.e.m., and analyzed by applying an ANOVA followed by Dunnett’s test, with comparison versus the vehicle group. *p < 0.05 vs. vehicle-treated mice.

Figure 3. c-Fos expression in the hypothalamus 90 min post-injection, and food intake, water intake and locomotor activity.

(a) Immunohistochemical staining of the hypothalamic region from vehicle- and GALP-treated mice. Scale bar in the lateral hypothalamus (LH) dorsomedial hypothalamus (DMH), and arcuate nucleus (ARC), 100 μm. Scale bar in the ventromedial hypothalamus (VMH), 200 μm. (b) Semi-quantitative scoring of c-Fos staining in the lateral hypothalamus (LH), dorsomedial hypothalamus (DMH), arcuate nucleus (ARC) and ventromedial hypothalamus (VMH) 90 min after intranasal administration of vehicle or GALP. The data are expressed as mean ± s.e.m., and analyzed by Student’s t-test. *p < 0.05 vs. vehicle treatment; **p < 0.005 vs. vehicle treatment. Locomotor activity (c), water intake (d) and food intake (e) 60 min after intranasal administration of vehicle (n = 4) or GALP (n = 4). The data are expressed as mean ± s.e.m., and analyzed by Student’s t-test was used. *p < 0.05 vs. vehicle-treated mice.

Figure 4. Effect of repeated intranasal GALP treatment in young ob/ob mice.

(a,c,e,g) Show results from lean mice. (b,d,f,h) Show results from ob/ob mice. The effects of repeated intranasal administration of GALP on body weight gain (a,b), daily food intake (c,d), cumulative water intake (e,f) and cumulative locomotor activity (g,h) in lean (n = 4) and ob/ob (n = 4) mice at 13 weeks of age. The first GALP injection occurred on day 0. The data are expressed as mean ± s.e.m., and were analyzed by repeated two-way ANOVA followed by Bonferroni’s test. *p < 0.05 vs. vehicle-treated group; **p < 0.01 vs. vehicle-treated group; **p < 0.001 vs. vehicle-treated group; ****p < 0.0001 vs. vehicle-treated group.

Figure 5. Effect of repeated intranasal GALP treatment in old ob/ob mice.

Effects of repeated intranasal administration of GALP on body weight gain, daily food intake, cumulative water intake and cumulative locomotor activity in lean and ob/ob mice at 20 weeks of age. (a) Body weight gain in lean mice (n = 4). (b) Body weight gain, (c) cumulative food intake, (d) cumulative water intake, and (e) cumulative locomotor activity in ob/ob mice with hyperglycemia (n = 6). The first injection of GALP occurred on day 0. (f) Relationship between body weight gain 24 h after the 14^th intranasal administration of GALP and blood glucose level in ob/ob mice with hyperglycemia or normoglycemia (n = 8). The data are expressed as mean ± s.e.m., and analyzed by repeated two-way ANOVA followed by Bonfferoni’s test. The correlation analysis was performed using the Pearson’s product moment correlation coefficient. *p < 0.05 vs. vehicle-treated group; **p < 0.01 vs. vehicle-treated group; **p < 0.001 vs. vehicle-treated group; ****p < 0.0001 vs. vehicle-treated group.

Figure 6. Effect of repeated intranasal GALP treatment in DIO mice.

(a) Body weight gain, (b) cumulative food intake, (c) cumulative water intake, and (d) cumulative locomotor activity during 7 days of intranasal vehicle or GALP administration (n = 7 in both cases). The first injection of GALP occurred on day 0. The data are expressed as mean ± s.e.m., and were analyzed repeated two-way ANOVA followed by Bonferroni’s test. *p < 0.05 vs. vehicle-treated group; **p < 0.01 vs. vehicle-treated group; **p < 0.001 vs. vehicle-treated group; ****p < 0.0001 vs. vehicle-treated group.

Figure 7. Conditioned taste aversion and food intake.

Two-hour saccharin preference ratio (saccharin intake/total fluid intake (saccharin intake + water intake) %) in mice treated 48 h earlier with vehicle (intranasal administration, n = 4 (no fill)), GALP (2 nmol, intranasal administration, n = 4 (black fill)) or LiCl (0.15 M, intraperitoneal injection, n = 4 (grey fill)). The data are expressed as mean ± s.e.m. Differences between groups were assessed by one-way ANOVA, followed by Bonferroni’s test for multiple comparisons. *p < 0.05 vs. vehicle-treated mice.