Andreas Plagemann

Altered responses to orexigenic (AGRP, MCH) and anorexigenic (alpha-MSH, CART) neuropeptides of paraventricular hypothalamic neurons in early postnatally overfed rats.

Food intake and energy expenditure are regulated by neuropeptides in the hypothalamus. While cocaine‐ and amphetamine‐regulated transcript (CART) peptide and melanocortins such as α‐melanocyte‐stimulating hormone (α‐MSH) are anorexigenic and increase energy expenditure, the endogenous melanocortin receptor antagonist agouti gene‐related protein (AGRP), melanin‐concentrating hormone (MCH) and neuropeptideu2003Y (NPY) are orexigenic, anabolic peptides. Alterations in the regulatory balance may promote excessive weight gain. The action of these peptides on paraventricular hypothalamic neurons was studied in brain slices of overweight, adult rats previously subjected to early postnatal overfeeding in small litters of only three pups per mother, compared to 12 pups per dam in control litters. CART, melanocortins and NPY significantly excited paraventricular neurons of controls, whereas neurons of small‐litter rats were mainly inhibited. Inhibition was dominant following administration of AGRP, MCH and NPY. The altered responses of paraventricular neurons in adult small‐litter rats might reflect a general mechanism of neurochemical plasticity and ‘malprogramming’ of hypothalamic neuropeptidergic systems acquired during the postnatal critical differentiation period, thus leading to permanently altered function of these regulatory systems of body weight.

Different responses of ventromedial hypothalamic neurons to leptin in normal and early postnatally overfed rats

Leptin is crucially involved in the central nervous regulation of body weight. Neurons of the ventromedial hypothalamic nucleus (VMH) express leptin receptors and signal satiety with increase in their firing. Normally, leptin mainly activates VMH neurons. Rats grown up in small litters (SL) develop persistent hyperphagia and obesity throughout life. We studied single unit activity in hypothalamic brain slices of juvenile SL rats overweight due to early postnatal overfeeding (Mann-Whitney U-test, P < 0.001). VMH neurons of normal rats were mainly activated by leptin (Wilcoxon test, P < 0.05, n = 39), whereas neurons of overweight SL rats were mainly inhibited (Wt, P < 0.001, n = 33). This clearly altered response to leptin in neonatally overnourished rats might contribute to their persistent overweight throughout life.

Increased inhibition by agouti-related peptide of ventromedial hypothalamic neurons in rats overweight due to early postnatal overfeeding.

Melanocortins, e.g. alpha-melanocyte stimulating hormone, are involved in the central nervous regulation of body weight. Agouti-related peptide (AGRP) as an endogenous melanocortin receptor antagonist induces feeding. Overexpression leads to obesity. Rats that grow up in small litters develop persistent hyperphagia and are overweight throughout life. Changes in the neuronal activity of the ventromedial hypothalamic nucleus (VMH) that signals satiety with activation might be involved. We studied single unit activity in hypothalamic brain slices. Melanocortins activated or inhibited similarly in control and small litter rats. AGRP mainly inhibited VMH neurons of overweight rats (t-test, P < 0.005, n = 33), whereas it also activated neurons of controls. This increased inhibition of VMH neurons by AGRP in early postnatally overnourished rats might contribute to the changed regulation leading to a persistent overweight condition throughout life.

Hypothalamic ventromedial and arcuate neurons of normal and postnatally overnourished rats differ in their responses to melanin-concentrating hormone

Melanin-concentrating hormone (MCH) is a neuropeptide involved in regulation of food intake and body weight. The study aimed to detect possible differences in responses of hypothalamic ventromedial and arcuate neurons to MCH, depending on the short-term nutritional state (fed versus food-deprived) and on the long-term state in overweight rats due to early postnatal overnutrition. The effect of MCH on a single-unit activity was studied in brain slices of normal and overweight rats. The latter (n=16) were raised till weaning in small litters (SL) of 3 pups compared to 10 pups in control litters (CL) and gained significantly greater body mass. Whereas MCH in effective concentrations in the pico- to nanomolar range could increase or suppress the activity of ventromedial or arcuate neurons studied in male normal fed or food-deprived (24 h) rats, its action became shaped in an unidirectional way in overweight, hyperphagic rats. Medial arcuate neurons (n=25) from hyperphagic rats were predominantly activated by MCH (p<0.05, paired t-test). This effect differed significantly from that induced on neurons (n=27) of control rats. Ventromedial neurons (n=34) of overweight rats were predominantly inhibited. Activation of arcuate neurons may induce feeding in particular through release of neuropeptide Y (NPY). Inhibition of ventromedial neurons may contribute to reduced energy expenditure. The increased expression of one response type to MCH by a neuronal population in overweight, hyperphagic rats might reflect a general mechanism of neurochemical plasticity and also suggest a participation of the peptide in long-term regulation of food intake and body weight in this model of obesity.

Obesity induced by unspecific early postnatal overfeeding in male and female rats: hypophagic effect of CCK-8S

The response to cholecystokinin (CCK) as a satiety peptide in obesity or anorexia has been tested mainly in extreme models of food intake control. In the present study, the effect of CCK-8S on food intake was investigated in a nongenetic and less-stressful model of obesity due to unspecific early postnatal overfeeding in male and female rats. Reducing the normal litter size of ten to three newborn rats on day 3 of life led to an enhanced food intake resulting in an increased body weight until adulthood. Freely fed male and female, normal and obese rats were given 10 μg/kg CCK-8S i.p. on day 41 and 40 μg/kg CCK-8S on day 91 of life and food intake was measured for 24 h. Compared with treatment with saline (i.p.) 1 day before the test, the lower dose of 10 μg/kg CCK-8S reduced food intake for 2 h in normal, but not in obese rats. Conversely, the higher dose of 40 μg/kg CCK-8S reduced food intake in both normal and obese rats for 2 h, but this effect was more evident in the obese rats. Moreover, the satiating effect of CCK-8S was more pronounced and longer lasting in male than in female rats. In summary, the data suggest that the response to CCK-8S differs in normal and obese rats and depends on sex.

Differential involvement of dopamine D1 and D2 receptors and inhibition by dopamine of hypothalamic VMN neurons in early postnatally overfed juvenile rats.

Dopamine is among the neurotransmitters involved in central regulation of food intake and body weight control. To study possible changes in neuronal responses to dopamine, single unit activity of the ventromedial hypothalamic nucleus (VMN) was recorded in brain slices of normal and obese rats. The latter had developed overweight throughout juvenile life (p < 0.05) by early postnatal over-nourishment due to a reduction of litter size from 3rd to 21st day of life (small litters, SL). With effective concentrations of about 100–500 nM/1 dopamine inhibited significantly more VMN neurons in obese than normal rats (Chi-square p < 0.05). While D2 receptors in the VMN are reported to mediate inhibition of food intake, the responses to dopamine were blocked by D2 receptor antagonists in significantly fewer neurons of SL than normal rats (p < 0.05). Furthermore, including results of action of D1receptor agonists we found that significantly more neurons in SL than NL rats seem to express D1 receptors. Thus, increased suppression by dopamine of firing of VMN neurons that signal satiety with a rise in the discharge rate, and changed expression or activity of dopamine receptors might contribute to increased feeding behavior in juvenile rats hyperphagic and overweight due to early postnatal overfeeding.

Action of CCK and 5-HT on lateral hypothalamic neurons depends on early postnatal nutrition.

Wistar rats grown up during the early postnatal life (321 days after birth) in artificially built normal, small or large litters developed a significantly different body weight. This difference persisted also during adulthood when they had free access to food and water. The influence of iontophoretically administered cholecystokinin (CCK8S), serotonin (5-HT) or co-ejection of both on firing of lateral hypothalamic neurons was investigated in adult, urethane anesthetized rats of the three groups. The responsiveness to CCK8S was significantly higher in large- and small-litter rats than in the normal control group. The differences were greater in males than in females. They resulted in the male large-litter group from an increase of excitatory responses, whereas in the male small-litter group the proportion of inhibitory responses was augmented. Co-administration of 5-HT generally reduced the neuronal responsiveness. Especially in the large-litter group excitatory responses were significantly reduced. It may be speculated that the availability of food in the early postnatal life influences the development of the hypothalamic regulatory network in such a way that it stabilizes the high or low food ingestion all the life. At least in males, a changed responsiveness and type of response to cholecystokinin of lateral hypothalamic neurons might be involved in this altered regulation.

Maternal overweight is not an independent risk factor for increased birth weight, leptin and insulin in newborns of gestational diabetic women: observations from the prospective ‘EaCH’ cohort study

BackgroundBoth gestational diabetes mellitus (GDM) as well as overweight/obesity during pregnancy are risk factors for detrimental anthropometric and hormonal neonatal outcomes, identified to ‘program’ adverse health predispositions later on. While overweight/obesity are major determinants of GDM, independent effects on critical birth outcomes remain unclear. Thus, the aim of the present study was to evaluate, in women with GDM, the relative/independent impact of overweight/obesity vs. altered glucose metabolism on newborn parameters.MethodsThe prospective observational ‘Early CHARITÉ (EaCH)’ cohort study primarily focuses on early developmental origins of unfavorable health outcomes through pre- and/or early postnatal exposure to a ‘diabetogenic/adipogenic’ environment. It includes 205 mother-child dyads, recruited between 2007 and 2010, from women with treated GDM and delivery at the Clinic of Obstetrics, Charité – Universitätsmedizin Berlin, Germany. Recruitment, therapy, metabolite/hormone analyses, and data evaluation were performed according to standardized guidelines and protocols. This report specifically aimed to identify maternal anthropometric and metabolic determinants of anthropometric and critical hormonal birth outcomes in ‘EaCH’.ResultsGroup comparisons, Spearman’s correlations and unadjusted linear regression analyses initially confirmed that increased maternal prepregnancy body-mass-index (BMI) is a significant factor for elevated birth weight, cord-blood insulin and leptin (all Pu2009<u20090.05). However, consideration of and adjustment for maternal glucose during late pregnancy showed that no maternal anthropometric parameter (weight, BMI, gestational weight gain) remained significant (all n.s.). In contrast, even after adjustment for maternal anthropometrics, third trimester glucose values (fasting and postprandial glucose at 32nd and 36th weeks’ gestation, HbA1c in 3rd trimester and at delivery), were clearly positively associated with critical birth outcomes (all Pu2009<u20090.05).ConclusionsNeither overweight/obesity nor gestational weight gain appear to be independent determinants of increased birth weight, insulin and leptin. Rather, 3rd trimester glycemia seems to be crucial for respective neonatal outcomes. Thus, gestational care and future research studies should greatly consider late pregnancy glucose in overweight/obese women with or without GDM, for evaluation of critical causes and interventional strategies against ‘perinatal programming of diabesity’ in the offspring.

Effect of L364.718 during suckling on the sensitivity to the hypophagic effect of cholecystokinin in adult rats

1. In the present study it was investigated whether drugs acting at the cholecystokinin (CCK)-A receptor given to rat pups may result in long-lasting changes in body weight or regulation of food intake controlled by CCK. 2. From day 3 to day 10 of life, male and female Wistar rat pups were treated with the CCK-A receptor antagonist L-364.718 and the CCK-A + B agonist CCK-8S. 3. In adult rats, treated with L364.718 during suckling, the sensitivity to the acute hypophagic action of CCK-8S was weaker or abolished compared to adults treated with saline during suckling. In adult rats given CCK-8S during suckling acute treatment with CCK-8S reduced food intake to the same extent as in the group treated with saline postnatally. 4. These data show that early postnatal treatment with the CCK-A receptor antagonist L364.718 has an impact on the hypophagic response to CCK-8S in later life.

DNA methylation and expression of proopiomelanocortin (POMC) gene in the hypothalamus of three‐week‐old chickens show sex‐specific differences

Increased availability and improved sequence annotation of the chicken (Gallus gallus f. domestica) genome have sparked interest in the bird as a model system to investigate translational embryonic development and health/disease outcomes. However, the epigenetics of this bird genome remain unclear. The aim of this study was to determine the levels of gene expression and DNA methylation at the proopiomelanocortin (POMC) gene in the hypothalamus of 3‐week‐old chickens. POMC is a key player in the control of the stress response, food intake, and metabolism. DNA methylation of the promoter, CpG island, and gene body regions of POMC were measured. Our data illustrate the pattern, variability, and functionality of DNA methylation for POMC expression in the chicken. Our findings show correlation of methylation pattern and gene expression along with sex‐specific differences in POMC. Overall, these novel data highlight the promising potential of the chicken as a model and also the need for breeders and researchers to consider sex ratios in their studies.