Gestational weight gain by reduced brain melanocortin activity affects offspring energy balance in rats

Maternal and Early Childhood Determinants of Women's Body Size in Midlife: Overall Cohort and Sibling Analyses

Observational evidence suggests that adult body size has its roots earlier in life, yet few life-course studies have data on siblings with which to control for family-level confounding. Using prospective data from the Early Determinants of Mammographic Density Study (n = 1,108; 1959-2008), we examined the association of maternal prepregnancy body mass index (BMI; weight (kg)/height (m)2), gestational weight gain (GWG), birth size, and childhood growth factors with adult BMI in daughters at midlife using quantile, linear, and logistic regression models. We compared overall cohort findings (n = 1,108) with sibling differences (n = 246 sibling sets). Results derived by all 3 regression methods supported positive and independent associations of prepregnancy BMI, GWG, and percentile change in early childhood growth with BMI in daughters at midlife. Sibling analyses demonstrated that higher GWG was independently related to a higher adult BMI in daughters, particularly for the highest 90th quantile of adult BMI (β = 0.64 (standard error, 0.26) BMI units). Greater increases in weight percentiles between 1 and 4 years of age within siblings were also associated with higher adult BMI in the 75th quantile (β = 0.06 (standard error, 0.03) kg). Thus, even after consideration of the role of family-level fixed effects, maternal GWG and childhood weight gain are associated with adult body size in midlife.

Attenuated hypothalamic responses to α-melanocyte stimulating hormone during pregnancy in the rat

KEY POINTS

Increased appetite and weight gain occurs during pregnancy, associated with development of leptin resistance, and satiety responses to the anorectic peptide α-melanocyte stimulating hormone (α-MSH) are suppressed. This study investigated hypothalamic responses to α-MSH during pregnancy, using c-fos expression in specific hypothalamic nuclei as a marker of neuronal signalling, and in vivo electrophysiology in supraoptic nucleus (SON) oxytocin neurons, as a representative α-MSH-responsive neuronal population that shows a well-characterised α-MSH-induced inhibition of firing. While icv injection of α-MSH significantly increased the number of c-fos-positive cells in the paraventricular, supraoptic, arcuate and ventromedial hypothalamic nuclei in non-pregnant rats, this response was suppressed in pregnant rats. Similarly, SON oxytocin neurons in pregnant rats did not demonstrate characteristic α-MSH-induced inhibition of firing that was observed in non-pregnant animals. Given the known functions of α-MSH in the hypothalamus, the attenuated responses are likely to facilitate adaptive changes in appetite regulation and oxytocin secretion during pregnancy.

ABSTRACT

During pregnancy, a state of positive energy balance develops to support the growing fetus and to deposit fat in preparation for the subsequent metabolic demands of lactation. As part of this maternal adaptation, the satiety response to the anorectic peptide α-melanocyte stimulating hormone (α-MSH) is suppressed. To investigate whether pregnancy is associated with changes in the response of hypothalamic α-MSH target neurons, non-pregnant and pregnant rats were treated with α-MSH or vehicle and c-fos expression in hypothalamic nuclei was then examined. Furthermore, the firing rate of supraoptic nucleus (SON) oxytocin neurons, a known α-MSH responsive neuronal population, was examined in non-pregnant and pregnant rats following α-MSH treatment. Intracerebroventricular injection of α-MSH significantly increased the number of c-fos-positive cells in the paraventricular, arcuate and ventromedial hypothalamic nuclei in non-pregnant rats, but no significant increase was observed in any of these regions in pregnant rats. In the SON, α-MSH did induce expression of c-fos during pregnancy, but this was significantly reduced compared to that observed in the non-pregnant group. Furthermore, during pregnancy, SON oxytocin neurons did not demonstrate the characteristic α-MSH-induced inhibition of firing rate that was observed in non-pregnant animals. Melanocortin receptor mRNA levels during pregnancy were similar to non-pregnant animals, suggesting that receptor down-regulation is unlikely to be a mechanism underlying the attenuated responses to α-MSH during pregnancy. Given the known functions of α-MSH in the hypothalamus, the attenuated responses will facilitate adaptive changes in appetite regulation and oxytocin secretion during pregnancy.

Maternal high fat feeding and gestational dietary restriction: effects on offspring body weight, food intake and hypothalamic gene expression over three generations in mice

Excessive gestational weight gain and maternal obesity have both been associated with increased incidence of obesity and metabolic disorder in offspring in both humans and animal models. The objectives of this study were to determine (1) whether mild gestational food restriction during the third trimester (GFR) would alter food intake and growth parameters of offspring, (2) whether effects of GFR depended on diet (high fat [HF] vs chow), (3) whether effects of excessive gestational weight gain (WG) would become magnified across generations, and (4) whether diet and GFR would alter hypothalamic gene expression in adult offspring. Three generations of female C57BL/6 mice were fed chow or HF diet, mated at 11 weeks of age and assigned to ad libitum feeding or 25% GFR. Offspring were fed the same diet as their mothers. Results showed (1) maternal gestational WG was positively correlated with offspring WG. (2) HF offspring weighed less (p<0.01) at weaning (WWT) but gained more during the 8 weeks after weaning than chow-fed offspring (p<0.05), resulting in higher final body weights (BW) (p<0.01). (3) HF males from GFR mothers had higher WWT (p<0.05), but subsequent WG and final BW were less (p<0.05) compared to males from ad lib mothers. (4) In the HF group, GFR also resulted in decreased FI (p<0.05) and FE (p<0.07) in offspring, compared to offspring from ad lib mothers. (5) In generation 3, hypothalamic expression of tyrosine hydroxylase was lower in HF males from GFR mothers compared to HF males from ad lib mothers (p<0.05). In conclusion, gender and maternal GFR had independent effects on growth and FI, and hypothalamic gene expression was dependent on both gender and maternal GFR in HF offspring. Even mild food restriction of obese mothers during pregnancy may have beneficial effects in reducing the risk or degree of obesity in offspring.

Early life influences on obesity risk: maternal overnutrition and programming of obesity

While adult lifestyle factors undoubtedly contribute to the incidence of obesity and its attendant disorders, mounting evidence suggests that programming of obesity may occur following over-nutrition during development. As hypothalamic control of appetite and energy expenditure is set early in life and can be perturbed by certain exposures, such as undernutrition and altered metabolic and hormonal signals, in utero exposure to maternal obesity-related changes may contribute to programming of obesity in offspring. Data from animal studies indicate both intrauterine and postnatal environments are critical determinants of the development of pathways regulating energy homeostasis. This review summarizes recent evidence of the impact of maternal obesity on subsequent obesity risk, paying particular attention to the hypothalamic regulation of appetite and markers of metabolic control. The extraordinary rise in the rates of maternal obesity underlines an urgent need to investigate the mechanisms contributing to its transgenerational effects.