Programming of Adiposity in Childhood and Adolescence: Associations With Birth Weight and Cord Blood Adipokines.

Context: Exposure to maternal adiposity during pregnancy is associated with higher offspring birth weight and greater adiposity through childhood and adult life. As birth weight reflects the summation of lean and fat mass, the extent to which fat mass at birth tracks into later life is unknown. Objective: To determine whether fat mass at birth is associated with child and adolescent adiposity. Design, Setting, and Participants: UK birth cohort with markers of neonatal fat mass; cord blood leptin, adiponectin, and birth weight and adiposity outcomes at age 9 (n = 2775) and 17 years (n = 2138). Main Outcomes: Offspring body mass index (BMI), waist circumference, dual-energy X-ray absorptiometry-determined fat mass, and obesity at age 9 and 17 years. Results: Higher cord blood leptin was associated with higher z scores of fat mass [difference in mean per 10 pg/mL: 0.03 standard deviation (SD); 95% confidence interval (CI), 0.00 to 0.06], waist circumference (0.04 SD; 95% CI, 0.00 to 0.07), and BMI (0.04 SD; 95% CI, 0.00 to 0.08) at age 9. However, by age 17 the adjusted results were attenuated to the null. Cord blood adiponectin was not associated with measures of adiposity at age 9. At age 17, cord blood adiponectin was positively associated with fat mass (0.02 SD per 10 µg/mL; 95% CI, 0.02 to 0.03) and waist circumference (0.04 SD per 10 µg/mL; 95% CI, 0.03 to 0.05). Birth weight was positively associated with waist circumference (0.03 SD per 100 g; 95% CI, 0.02 to 0.04) and BMI (0.02 SD per 100 g; 95% CI, 0.00 to 0.03), but not fat mass or odds of obesity. Cord blood leptin and adiponectin were not associated with obesity at either age. Conclusions: Increased cord blood leptin and adiponectin, known surrogates of fetal fat mass, were weakly associated with increased fat mass in late childhood and adolescence, respectively.

Cord Blood Adipokines and Lipids and Adolescent Nonalcoholic Fatty Liver Disease.

CONTEXT: Maternal adiposity in pregnancy is associated with offspring adiposity and metabolic dysfunction postnatally, including greater risk of nonalcoholic fatty liver disease (NAFLD). Recent genetic analyses suggest a causal effect of greater maternal body mass index on offspring birth weight and ponderal index, but the relative roles of the environment in utero or later in life remains unclear. OBJECTIVE: We sought to determine whether markers of infant adiposity (birth weight, umbilical cord blood leptin, adiponectin, and lipids) were associated with markers of NAFLD in adolescence. DESIGN, SETTING, AND PARTICIPANTS: This was a UK prospective birth cohort with 17 years of follow-up with liver function tests (aspartate aminotransferase, alanine aminotransferase, gamma-glutamyltransferase) (n = 1037 participants), and ultrasound scan assessed liver fat, volume, and sheer velocity at age 17 (n = 541 participants). Missing covariate data were imputed. MAIN OUTCOMES: Ultrasound and biochemical measures of NAFLD were measured. RESULTS: Birth weight, cord blood leptin, and adiponectin were not associated with a diagnosis of NAFLD. In adjusted analyses, 2 of 42 associations attained conventional 5% levels of significance. Birth weight was positively associated with liver volume (1.0% greater per 100 g [95% confidence interval 0.5%-2.0%]). Cord high-density lipoprotein-cholesterol was positively associated with alanine aminotransferase (11.6% higher per 1 mmol/L [95% confidence interval 0.3, 23.4]); however, this association was primarily mediated via offspring adiposity. CONCLUSIONS: In this extensive analysis, we found little evidence measurements of infant fat mass and birth size were related to adolescent markers of NAFLD. The association between birth weight and adolescent liver volume may indicate the contribution of greater organ size to birth weight and tracking of organ size.

Hippocampal volume and total cell numbers in major depressive disorder.

Neuroimaging consistently reveals smaller hippocampal volume in recurrent or chronic major depressive disorder (MDD). The underlying cellular correlates of the smaller volume are not clearly known. Postmortem tissues from 17 pairs of depressed and control subjects were obtained at autopsy, and informant-based retrospective psychiatric assessment was performed. Formalin-fixed left temporal lobes were sectioned (40 µm), stained for Nissl substance, and every 60th section selected throughout the entire hippocampus. Total volume of the hippocampal formation was calculated, and total numbers of pyramidal neurons (in hippocampal fields CA1, CA2/3, hilus), dentate gyrus (DG) granule cells, and glial cells were estimated stereologically. While hippocampal volume in all MDD subjects was not significantly smaller versus control subjects, in recurrent/chronic MDD, total volume decreased with duration of depressive illness (r = -0.696, p < 0.026). There was no significant difference between MDD and controls in total number or density of pyramidal neurons/granule cells or glial cells in CA1, CA2/3, hilus, or DG. However, CA1 pyramidal neuron density increased with duration of illness in recurrent/chronic MDD (r = 0.840, p < 0.002). Granule cell (r = 0.971, p < 0.002) and glial cell numbers (r = 0.980, p < 0.001) increased with age in those taking antidepressant medication (n = 6). Increasing DG granule cell and glial cell numbers with age in antidepressant-treated subjects may reflect proliferative effects of antidepressant medications. Decreasing total volume and increasing CA1 pyramidal neuron density with duration of illness in recurrent/chronic MDD lends support to the neuropil hypothesis of MDD.

The effects of isolated and enriched housing conditions on baseline and drug-induced behavioural responses in the male rat.

Environmental enrichment (EE) involves enhancing an animal's environment, with the goal of improving animal welfare. Though a well-established discipline, the consequences of EE on behavioural pharmacological tests have not been extensively examined. The purpose of this study was to examine the consequences of EE (or isolation) housing on a range of behavioural pharmacological tests in the rat. Male Sprague-Dawley rats were randomly assigned to the 3 housing conditions; IC (isolation) and SC (standard group-housed, 4/cage) were housed in standard cages (42 cm×25.5 cm×20 cm), while the EE group was housed in groups of 4 in larger cages (54 cm×38 cm×19 cm) enriched with a variety of wooden, cardboard and plastic toys/objects. After 4 weeks, housing effects were examined in the following pharmacological tests: diazepam (DZP) effects on anxiolytic behaviour in the elevated plus maze (EPM); desipramine (DMI) effects on immobility time in the forced swim test (FST) and amphetamine (AMP) effects on homecage activity. Dose-response assessments demonstrated that rats housed in EE showed reduced sensitivity to the behavioural effects of DZP and DMI but increased sensitivity to the locomotor-enhancing effects of AMP compared to SC and IC; while IC animals exhibited the clearest dose-response effects to increasing doses of DMI. It may be concluded that environmental manipulation can vary along a continuum and its intensity may be crucial to observable effects. Nonetheless, environmental factors can influence sensitivity to psychotropic drugs and should be considered when implementing EE protocols in such evaluations.

Effect of early life housing manipulation on baseline and drug-induced behavioural responses on neurochemistry in the male rat.

Employing environmental enrichment (EE) provides continual sources of dynamic interaction for animals. Though an established discipline in behavioural science, the consequences of EE on behavioural pharmacological tests have not been extensively examined. The purpose of this study was to examine the consequences of EE (or isolation housing) on a range of behavioural pharmacological tests and brain monoamine and brain-derived neurotrophic factor (BDNF) expression in the rat. Male rats were randomly assigned to IC (isolation), SC (standard group-housed) or EE conditions. IC and SC animals were housed singly or in groups of four in standard cages, whilst the EE group were housed in groups of four in larger cages enriched with a variety of wooden, cardboard and plastic objects. After 5weeks of housing, its impact on the effects of diazepam (DZP) in the elevated plus maze (EPM); desipramine (DMI) in the forced swim test (FST) and amphetamine (AMP) effects on homecage activity were assessed. Post-mortem monoamine and BDNF levels were analysed using HPLC and ELISA. EE rats displayed reduced activity in the OFT, however no other differences were found in baseline behaviours. DMI reduced immobility time in the FST, but only for rats housed in IC, while AMP effects were somewhat greater for socially-housed animals than those in IC. There were no housing effects on monoamine or BDNF levels in discreet brain regions. The results suggest that post-weaning enrichment had no significant effect on baseline behaviours or monoamine and BDNF levels, thus it is suitable to implement as a commonplace husbandry practice, however, caution must be taken when investigating responsiveness to psychotropic drugs.

Sex differences in baseline and drug-induced behavioural responses in classical behavioural tests.

Behavioural pharmacology relies on animal models which are primarily validated using the male laboratory rat. Many researchers solely employ male animals in studies; this is primarily due to concerns about the impact of variations in the female estrous cycle on behavioural responses. The objective of the present study therefore was to examine whether sex has any effect in some commonly employed behavioural pharmacology tests. Male and female Sprague Dawley rats were examined in the following behavioural pharmacology tests: diazepam (DZP) effects on anxiolytic behaviour in the elevated plus maze (EPM); desipramine (DMI) effects on immobility time in the forced swim test (FST); amphetamine (AMP) and apomorphine (APO) effects on locomotor activity in the homecage monitoring apparatus (HCMA). Baseline investigations revealed that females were more active than males in all three tests. DZP increased open arm time and entries for males but not for females. Similarly, significant reduction in immobility time with DMI was found for males in the FST, with no effect observed in females. There was a significant effect of AMP dose on distance moved for both sexes; the peak locomotor stimulating effects were seen following 1-2 mg kg⁻¹ AMP doses for males, while 0.5 mg kg⁻¹ produced the greatest effect in females. APO impaired locomotor activity in both sexes. These results demonstrate that male and female rats respond differently to psychotropic drugs. The absence of female responses to the effects of DZP and DMI in the EPM and FST respectively was due to the high baseline activity levels seen with females; thus behavioural tests must be designed to account for sex differences in baseline behaviours to allow for unambiguous extrapolation of the results.

An investigation of whether there are sex differences in certain behavioural and neurochemical parameters in the rat.

In clinical populations, sex differences in disease prevalence, symptoms and outcome have been established. Despite this, female rats are frequently omitted from preclinical research; growing preclinical evidence, however, illustrates meaningful sex differences in behavioural, neurochemical and neuroanatomical endpoints. This review outlines the effects of sex on tests of depression- and anxiety-like symptoms, learning and memory, and responses to stress in rats. In addition, sexual dimorphisms in monoamine neurotransmitter and neurotrophic factor levels, neurogenesis and plasticity, and responsiveness to drugs of abuse are reviewed. Female rats display greater baseline activity levels compared to males, test-specific sex differences also exist in learning and memory protocols as females respond more actively in conditioning paradigms and are somewhat impaired in tests of spatial memory compared to males. Differential baseline and stress-induced hypothalamic-pituitary-adrenal axis responses between male and female rats depend on the nature of the stressor. Females are more responsive to the effects of psychomotor stimulant drugs; sexual dimorphisms in response to psychotropic drugs are likely mediated by neurochemical differences between male and female rats. Differences exist in neurotransmitter activity, transporter and receptor expression between the sexes. Studies of ovariectomised and intact female rats demonstrate a potent impact of elevated estrogen during the estrous cycle on behaviour, neurochemistry, dendritic growth and drug response. Sex differences in baseline behaviours and the methodological procedures employed can influence behavioural pharmacology result interpretation. In addition, the inclusion of both male and female rats in studies investigating neurochemistry and neuromorphology may enhance the validity of drug or rehabilitative treatments.

The impact of environmental enrichment in laboratory rats--behavioural and neurochemical aspects.

The provision of environmental enrichment (EE) for laboratory rats is recommended in European guidelines governing laboratory animal welfare. It is believed the EE implementation can improve animals' well-being and EE has been used to demonstrate learning and plasticity of the brain in response to the environment. This review suggests that the definition and duration of EE varies considerably across laboratories. Notwithstanding this, some EE protocols have revealed profound effects on brain neurochemistry and resulting behaviour, suggesting that EE can have the potential to significantly modify these parameters in rats. For this review, a literature search was conducted using PubMed and the search terms "Environmental Enrichment" and "rats". From the results of this search the most important variables for consideration in the implementation of EE are identified and summarised, and include cage size and housing density; rat age, sex and strain; duration of EE; the EE protocol and enrichment items employed; and the use of appropriate controls. The effects of EE in a number of behavioural tests and its effects on neurotransmitters, neurotrophic factors, stress hormones and neurogenesis and proliferation are outlined. The findings summarised in the present review show the range of EE protocols employed and their effects in tests of activity, learning and affect, as well neurochemical effects which mediate enhanced plasticity in the brain. EE, as is provided in many laboratories, may be of benefit to the animals, however it is important that future work aims to provide a better understanding of EE effects on research outcomes.