A maternal "junk-food" diet reduces sensitivity to the opioid antagonist naloxone in offspring postweaning.
ABSTRACT Perinatal exposure to a maternal "junk-food" diet has been demonstrated to increase the preference for palatable diets in adult offspring. We aimed to determine whether this increased preference could be attributed to changes in μ-opioid receptor expression within the mesolimbic reward pathway. We report here that mRNA expression of the μ-opioid receptor in the ventral tegmental area (VTA) at weaning was 1.4-fold (males) and 1.9-fold (females) lower in offspring of junk-food (JF)-fed rat dams than in offspring of dams fed a standard rodent diet (control) (P<0.05). Administration of the opioid antagonist naloxone to offspring given a palatable diet postweaning significantly reduced fat intake in control offspring (males: 7.7±0.7 vs. 5.4±0.6 g/kg/d; females: 6.9±0.3 vs. 3.9±0.5g/kg/d; P<0.05), but not in male JF offspring (8.6±0.6 vs. 7.1±0.5g/kg/d) and was less effective at reducing fat intake in JF females (42.2±6.0 vs. 23.1±4.1% reduction, P<0.05). Similar findings were observed for total energy intake. Naloxone treatment did not affect intake of standard rodent feed in control or JF offspring. These findings suggest that exposure to a maternal junk-food diet results in early desensitization of the opioid system which may explain the increased preference for junk food in these offspring.
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ABSTRACT: AIM: This study aimed to determine whether the negative effects of maternal 'junk food' feeding on food preferences and gene expression in the mesolimbic reward system could be reversed by weaning the offspring onto a low-fat diet. METHODS: Offspring of Control (n=11) and junk food-fed (JF, n=12) dams were weaned onto a standard rodent chow until 6 weeks (juvenile) or 3 months (adult). They were then given free access to both chow and junk food for 3 weeks and food preferences determined. mRNA expression of key components of the mesolimbic reward system were determined by qRT-PCR at 6 weeks, 3 and 6 months of age. RESULTS: In the juvenile group, both male and female JF offspring consumed more energy and carbohydrate during the junk food exposure at 6 weeks of age and had a higher body fat mass at 3 months (P<0.05). Female juvenile JF offspring had higher tyrosine hydroxylase, dopamine receptors, and dopamine active transporter expression in the ventral tegmental area (P<0.05). In the adult group, there was no difference between Control and JF offspring in energy and macronutrient intakes during exposure to junk food, however female JF offspring had a higher body fat mass at 6 months (P<0.05). CONCLUSION: These results suggest that the effects of perinatal junk food exposure on food preferences and fat mass can be reversed by consuming a low-fat diet from weaning to adulthood in males. Females, however, retain a higher propensity for diet-induced obesity even after consuming a low-fat diet for an extended period after weaning. This article is protected by copyright. All rights reserved.Acta Physiologica 06/2013; DOI:10.1111/apha.12132 · 4.25 Impact Factor
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ABSTRACT: Feeding behavior is closely regulated by neuroendocrine mechanisms that can be influenced by stressful life events. However, the feeding response to stress varies among individuals with some increasing and others decreasing food intake after stress. In addition to the impact of acute lifestyle and genetic backgrounds, the early life environment can have a life-long influence on neuroendocrine mechanisms connecting stress to feeding behavior and may partially explain these opposing feeding responses to stress. In this review I will discuss the perinatal programming of adult hypothalamic stress and feeding circuitry. Specifically I will address how early life (prenatal and postnatal) nutrition, early life stress, and the early life hormonal profile can program the hypothalamic-pituitary-adrenal (HPA) axis, the endocrine arm of the body's response to stress long-term and how these changes can, in turn, influence the hypothalamic circuitry responsible for regulating feeding behavior. Thus, over- or under-feeding and/or stressful events during critical windows of early development can alter glucocorticoid (GC) regulation of the HPA axis, leading to changes in the GC influence on energy storage and changes in GC negative feedback on HPA axis-derived satiety signals such as corticotropin-releasing-hormone. Furthermore, peripheral hormones controlling satiety, such as leptin and insulin are altered by early life events, and can be influenced, in early life and adulthood, by stress. Importantly, these neuroendocrine signals act as trophic factors during development to stimulate connectivity throughout the hypothalamus. The interplay between these neuroendocrine signals, the perinatal environment, and activation of the stress circuitry in adulthood thus strongly influences feeding behavior and may explain why individuals have unique feeding responses to similar stressors.Frontiers in Neuroscience 06/2013; 7:109. DOI:10.3389/fnins.2013.00109
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ABSTRACT: We have previously reported that the opioid receptor blocker, naloxone, is less effective at reducing palatable food intake in offspring exposed to a maternal cafeteria diet during the perinatal period, implicating a desensitization of the central opioid pathway in the programming of food preferences. The present study aimed to investigate the effect of a maternal cafeteria diet and naloxone treatment on the development of the mesolimbic reward pathway and food choices in adulthood. We measured mRNA expression of key components of the reward pathway (mu-opioid receptor, proenkephalin, tyrosine hydroxlase, D1 and D2 receptors and the dopamine active transporter (DAT)) in the nucleus accumbens (NAc) and ventral tegmental area (VTA) of the offspring of control and cafeteria fed (JF) dams at weaning and after a 10-day naloxone treatment post-weaning; and determined food preferences in adulthood in the remaining offspring. Naloxone treatment decreased the expression of DAT by 8.2 fold in female control offspring but increased it by 4.3 fold in female offspring of JF dams relative to the saline-injected reference groups. Proenkephalin mRNA expression was higher in the NAc of female JF offspring compared to controls, independent of naloxone treatment (P<0.05). There was no effect of naloxone treatment on food preferences in adulthood in either control or JF offspring. These data indicate that prenatal exposure to a cafeteria diet alters the impact of opioid signaling blockade in the early post-weaning period on gene expression in the central reward pathway in a sex specific manner, but that these changes in gene expression do not appear to have any persistent impact on food preferences in adulthood.Physiology & Behavior 04/2014; DOI:10.1016/j.physbeh.2014.04.007 · 3.03 Impact Factor