The impact of poor fetal growth and chronic hyperpalatable diet exposure in adulthood on hippocampal function and feeding patterns in male rats

Poor fetal growth affects eating behavior and the mesocorticolimbic system; however, its influence on the hippocampus has been less explored. Brain insulin sensitivity has been linked to developmental plasticity in response to fetal adversity and to cognitive performance following high-fat diet intake. We investigated whether poor fetal growth and exposure to chronic hyperpalatable food in adulthood could influence the recognition of environmental and food cues, eating behavior patterns, and hippocampal insulin signaling. At 60 days of life, we assigned male offspring from a prenatal animal model of 50% food restriction (FR) to receive either a high-fat and -sugar (HFS) diet or standard chow (CON) diet. Behavioral tests were conducted at 140 days, then tissues were collected. HFS groups showed a diminished hippocampal pAkt/Akt ratio. FR-CON and FR-HFS groups had higher levels of suppressor of cytokine signaling 3, compared to control groups. FR groups showed increased exploration of a novel hyperpalatable food, independent of their diet, and HFS groups exhibited overall lower entropy (less random, more predictable eating behavior) when the environment changed. Poor fetal growth and chronic HFS diet in adulthood altered hippocampal insulin signaling and eating patterns, diminishing the flexibility associated with eating behavior in response to extrinsic changes in food availability in the environment.

Brain structural abnormalities in six major psychiatric disorders: shared variation and network perspectives

Common brain abnormalities are a possible explanation for comorbidities in psychiatric disorders. Challenges in understanding these conditions are likely due to the paucity of studies able to analyze the extent and regional distribution of shared morphometric abnormalities between disorders. Recently, Opeal et al. presented an elegant rationale to investigate shared and specific morphometric measures of cortical thickness and subcortical gray matter volume between healthy individuals and subjects across six major psychiatric disorders. Although their approach has the potential to systematically portray shared brain alterations, the chosen principal component analysis solution may not address the central question of the observed shared versus specific brain alterations due to misspecification of the number of components. Given how this misspecification can lead to different conclusions, we reanalyzed Opel et al. data to thoroughly determine the number of factors to be considered, explore the alternative solution, and visualize the patterns of shared brain matter correlations using network analysis. Our approach suggests that a unidimensional solution was appropriate in this situation. The unidimensional solution indicated that brain alterations in autism spectrum disorder (ASD) had a significant negative component loading, suggesting that brain abnormalities found in ASD covaried with major depressive disorder (MDD), bipolar disorder (BD), schizophrenia (SCZ), and obsessive-compulsive disorder (OCD), a finding not demonstrated by the original work. Network analysis indicated that SCZ had the highest strength, BD the highest closeness, and BD and MDD had the highest betweenness in the network. This work highlights how different component solutions can lead to different conclusions, with important implications for the understanding of overlapped patterns of symptoms among six major psychiatric diseases. The network approach is complementary in indicating central markers of specific psychopathology domains. Investigations using shared-variation and network perspectives are promising for the study of pathophysiological patterns of common brain alterations.

Brain structural abnormalities in six major psychiatric disorders: shared variation and network perspectives

Common brain abnormalities are a possible explanation for comorbidities in psychiatric disorders. Challenges in understanding these conditions are likely due to the paucity of studies able to analyze the extent and regional distribution of shared morphometric abnormalities between disorders. Recently, Opeal et al. presented an elegant rationale to investigate shared and specific morphometric measures of cortical thickness and subcortical gray matter volume between healthy individuals and subjects across six major psychiatric disorders. Although their approach has the potential to systematically portrait shared brain alterations, the chosen principal component analysis solution may not address the central question of the observed shared versus specific brain alterations due to misspecification of the number of components. Given how this misspecification can lead to different conclusions, we reanalyzed Opel et al. data to thoroughly determine the number of factors to be considered, explore the alternative solution, and visualize the patterns of shared brain matter correlations using network analysis. Our approach suggests that a unidimensional solution was appropriate in this situation. The unidimensional solution indicated that brain alterations in autism spectrum disorder (ASD) had a significant negative component loading, suggesting that brain abnormalities found in ASD carry more similarities with major depressive disorder (MDD), bipolar disorder (BD), schizophrenia (SCZ), and obsessive-compulsive disorder (OCD) than demonstrated by the original work. Network analysis indicated that SCZ had the highest strength, BD the highest closeness, and BD and MDD had the highest betweenness in the network. This work highlights how different component solutions can lead to different conclusions, with important implications for the understanding of overlapped patterns of symptoms among six major psychiatric diseases. The network approach is complementary in indicating central markers of specific psychopathology domains. Investigations using shared-variation and network perspectives are promising for the study of pathophysiological patterns of common brain alterations.

Intrauterine growth restriction increases impulsive behavior and is associated with altered dopamine transmission in both medial prefrontal and orbitofrontal cortex in female rats

Recent studies have implicated a role for impulsivity in the altered eating behaviors and the increased risk for obesity consistently associated with intrauterine growth restriction (IUGR). Changes in dopamine transmission within prefrontal areas are believed to contribute to these adverse outcomes. Here we investigated the impulsive behavior toward a delayed reward and evaluated dopamine levels and its receptors in the medial prefrontal (mPFC) and orbitofrontal (OFC) cortex of female adult rats exposed to IUGR. From day 10 of pregnancy and until birth, Sprague-Dawley dams received either an ad libitum (Adlib) or a 50% food-restricted (FR) diet. At birth, all pups were adopted by Adlib mothers, generating the groups Adlib/Adlib (control) and FR/Adlib (intrauterine growth-restricted). Adult impulsive behavior was evaluated using a Tolerance to Delay of Reward Task. In vivo dopamine responses to sweet food intake were measured by voltammetry, and D1, D2 and DAT levels were accessed by Western Blot. Animals from FR group showed a pronounced aversion to delayed rewards. DA response to sweet food was found to be blunted in the mPFC of FR animals, whereas in the OFC, the DA levels appear to be unaffected by reward consumption. Moreover, FR animals presented reduced D1 receptors in the OFC and a later increase in the mPFC D2 levels. These findings suggest that IUGR female rats are more impulsive and that the associated mechanism involves changes in the dopamine signaling in both the mPFC and OFC.

Intrauterine growth restriction modifies the hedonic response to sweet taste in newborn pups - Role of the accumbal μ-opioid receptors

Intrauterine growth restriction (IUGR) is associated with increased preference for palatable foods. The hedonic response to sweet taste, modulated by the nucleus accumbens μ-opioid-receptors, may be involved. We investigated hedonic responses and receptor levels in IUGR and Control animals. From pregnancy day 10, Sprague-Dawley dams received either an ad libitum (Control), or a 50% food restricted (FR) diet. At birth, pups were cross-fostered, and nursed by Adlib fed dams. The hedonic response was evaluated at 1 day after birth and at 90 days of life, by giving sucrose solution or water and analyzing the hedonic facial responses (within 60s). Control pups exposed either to water or sucrose resolved their hedonic responses after 16 and 18s, respectively, while FR hedonic responses to sucrose persisted over 20s. FR pups had deceased phospho-μ-opioid-receptor (p=0.009) and reduced phosphor:total mu opioid receptor ratio compared to controls pups (p=0.003). In adults, there was an interaction between group and solution at the end of the evaluation (p=0.044): Control decreased the response after sucrose solution, FR did not change over time. There were no differences in phosphorylation of μ-opioid-receptor in adults. These results demonstrate IUGR newborn rats exhibit alterations in hedonic response accompanied by a decrease in μ-opioid-receptor phosphorylation, though these alterations do not persist at 3 months of age. Opioid system alterations in early life may contribute to the development of preference for highly palatable foods and contribute to rapid weight gain and obesity in IUGR offspring.

Intrauterine growth restriction increases the preference for palatable foods and affects sensitivity to food rewards in male and female adult rats

Clinical evidence suggests that intrauterine growth restriction (IUGR) can cause persistent changes in the preference for palatable foods. In this study, we compared food preferences, the response to food rewards, and the role of the mesolimbic dopaminergic system in feeding behavior, between IUGR and control rats. Time-mated pregnant Sprague-Dawley rats were randomly allocated to a control group (standard chow ad libitum) or a 50% food restriction (FR) group, which received 50% of the control dams׳ habitual intake. These diets were provided from gestation day 10 to the 21st day of lactation. Within 24h of birth, pups were cross-fostered and divided into four groups: Adlib/Adlib, FR/Adlib, FR/FR, Adlib/FR. Standard chow consumption was compared between all groups. Food preferences, conditioned place preference to a palatable diet, and the levels of tyrosine hydroxylase (TH) phosphorylation and D2 receptors in the nucleus accumbens were analyzed and compared between the two groups of interest: Adlib/Adlib (control) and FR/Adlib (exposed to growth restriction during the fetal period only). IUGR adult rats had a stronger preference for palatable foods, but showed less conditioned place preference to a palatable diet than controls. D2 receptors levels were lower in IUGR rats. At baseline, TH and pTH levels were higher in FR/Adlib than control males. Measurements taken after exposure to sweet foods revealed higher levels of TH and pTH in FR/Adlib than control females. These data showed that IUGR rats exhibited a preference for palatable foods, potentially due to alterations in their mesolimbic reward pathway. Additionally, the changes observed in the mesolimbic dopaminergic system of IUGR rats proved to be sex-specific. This article is part of a Special Issue entitled 1618.

Effect of AV3V lesion on the cardiovascular, fluid, and electrolytic changes induced by activation of the lateral preoptic area

In this study we investigated the effect of the anteroventral third ventricle (AV3V) lesion on the pressor, bradycardic, natriuretic, kaliuretic, and dipsogenic responses induced by the injection of the cholinergic agonist carbachol into the lateral preoptic area (LPOA) in rats. Male Holtzman rats with sham or electrolytic AV3V lesion were implanted with stainless steel cannula directly into the LPOA. Injection of carbachol (7.5 nmol) into the LPOA of sham rats induced natriuresis (405 +/- 66 microEq/120 min), kaliuresis (234 +/- 44 microEq/120 min), water intake (9.5 +/- 1.7 ml/60 min), bradycardia (-47 +/- 11 bpm), and increase in mean arterial pressure (28 +/- 3 mmHg). Acute AV3V lesion (1-5 days) reduced the natriuresis (12 +/- 4 microEq/120 min), kaliuresis (128 +/- 27 microEq/120 min), water intake (1.7 +/- 0.9 ml/60 min), and pressor responses (14 +/- 4 mmHg) produced by carbachol into the LPOA. Tachycardia instead of bradycardia was also observed. Chronic (14-18 days) AV3V lesion reduced only the pressor response (10 +/- 2 mmHg) induced by carbachol. These results showed that acute, but not chronic, AV3V lesion reduced the natriuretic, kaliuretic, and dipsogenic responses to carbachol injection into the LPOA. The pressor response was reduced in acute or chronic AV3V-lesioned rats. The results suggest that the lateral areas may control the fluid and electrolyte balance independently from the AV3V region in chronic AV3V-lesioned rats.