Relationship between basal metabolic rate and cortisol secretion throughout pregnancy

Impact of Ghrelin on Islet Size in Nonpregnant and Pregnant Female Mice

Reducing ghrelin by ghrelin gene knockout (GKO), ghrelin-cell ablation, or high-fat diet feeding increases islet size and β-cell mass in male mice. Here we determined if reducing ghrelin also enlarges islets in females and if pregnancy-associated changes in islet size are related to reduced ghrelin. Islet size and β-cell mass were larger (P = .057 for β-cell mass) in female GKO mice. Pregnancy was associated with reduced ghrelin and increased liver-expressed antimicrobial peptide-2 (LEAP2; a ghrelin receptor antagonist) in wild-type mice. Ghrelin deletion and pregnancy each increased islet size (by ∼19.9-30.2% and ∼34.9-46.4%, respectively), percentage of large islets (>25 µm2×103, by ∼21.8-42% and ∼21.2-41.2%, respectively), and β-cell mass (by ∼15.7-23.8% and ∼65.2-76.8%, respectively). Neither islet cross-sectional area, β-cell cross-sectional area, nor β-cell mass correlated with plasma ghrelin, although all positively correlated with LEAP2 (P = .081 for islet cross-sectional area). In ad lib-fed mice, there was an effect of pregnancy, but not ghrelin deletion, to change (raise) plasma insulin without impacting blood glucose. Similarly, there was an effect of pregnancy, but not ghrelin deletion, to change (lower) blood glucose area under the curve during a glucose tolerance test. Thus, genetic deletion of ghrelin increases islet size and β-cell cross-sectional area in female mice, similar to males. Yet, despite pregnancy-associated reductions in ghrelin, other factors appear to govern islet enlargement and changes to insulin sensitivity and glucose tolerance in the setting of pregnancy. In the case of islet size and β-cell mass, one of those factors may be the pregnancy-associated increase in LEAP2.

Metabolic rates in female guinea pigs during different reproductive stages

Reproduction in female mammals is characterized by major changes in steroid hormone concentrations, which can be linked to fluctuations in energy expenditure (EE). Estradiol and cortisol can increase EE and metabolic rates (MRs), but knowledge on MR changes during the estrous cycle and gestation is scarce for many species. This also applies to the domestic guinea pig, a species exhibiting an exceptional estrous cycle among rodents. In this study, MRs were measured through oxygen (O2) consumption in female guinea pigs during different reproductive stages. Mean O2 consumption over 2.5 h, resting metabolic rate (RMR, lowest and most stable O2 consumption over 3 min), body mass, fecal estrogen and progesterone, and saliva cortisol concentrations were measured in twelve female guinea pigs in a repeated measurements design during diestrus, estrus, and the second trimester of gestation. In estrus, body mass was significantly lower and estrogen and cortisol concentrations were significantly higher compared to diestrus and gestation. Mean O2 consumption and RMR both were significantly increased in estrus compared to diestrus. Additionally, a positive effect of body mass on MRs detected during diestrus and gestation was not found during estrus. Mean O2 consumption was also higher during gestation compared to diestrus, and a significant increase in cortisol concentrations during the 2.5-h MR measurement was recorded. The results indicate that estrus in guinea pigs is energetically demanding, which probably reflects catabolic effects of estrogens and cortisol that uncoupled MRs from body mass. Knowledge on the energetic requirements associated with different reproductive stages is important for future physiological and behavioral studies on female guinea pigs.

Co-administration of bromocriptine and corticosterone produces short- and long-lasting reduction in intake of high-fat food in male rats

Dopaminergic and glucocorticoid activity has been associated with reduced food consumption; however, their possible synergic action has not yet been studied. With the aim of examining the effect of the co-administration of the dopamine receptor D2 agonist bromocriptine and corticosterone on palatable food intake, male Wistar rats were administered either bromocriptine (1 mg/kg), corticosterone (2 mg/kg), bromocriptine + corticosterone (1 mg + 2 mg/kg) or a vehicle, with a fifth group used as a control. In all cases, substances were administered 30 min before exposure to standard food or palatable food, the latter high in carbohydrates [high carbohydrate food (HCF), 75%] or high-fat food (HFF, 67%). Food consumption and body weight were recorded daily. Results showed higher consumption of standard food but lower consumption of HCF and HFF in the groups that received bromocriptine, alone or in combination. In general, lower total kcal intake was observed in the bromocriptine and bromocriptine + corticosterone groups during the period of pharmacological treatment and following re-exposure to palatable food. The low HFF intake in the bromocriptine + corticosterone group persisted 10 days after the pharmacological treatment was interrupted. This effect suggests plastic changes in either the mechanisms involved in the incentive value of palatable food - particularly foods with high-fat content - or those that regulate lipid metabolism. Our findings suggest that homeostatic and reward mechanisms could be influenced by the co-participation of the dopaminergic and hypothalamic-pituitary-adrenal systems, and the macronutrient content of food.

The energetic cost of allostasis and allostatic load

Chronic psychosocial stress increases disease risk and mortality, but the underlying mechanisms remain largely unclear. Here we outline an energy-based model for the transduction of chronic stress into disease over time. The energetic model of allostatic load (EMAL) emphasizes the energetic cost of allostasis and allostatic load, where the "load" is the additional energetic burden required to support allostasis and stress-induced energy needs. Living organisms have a limited capacity to consume energy. Overconsumption of energy by allostatic brain-body processes leads to hypermetabolism, defined as excess energy expenditure above the organism's optimum. In turn, hypermetabolism accelerates physiological decline in cells, laboratory animals, and humans, and may drive biological aging. Therefore, we propose that the transition from adaptive allostasis to maladaptive allostatic states, allostatic load, and allostatic overload arises when the added energetic cost of stress competes with longevity-promoting growth, maintenance, and repair. Mechanistically, the energetic restriction of growth, maintenance and repair processes leads to the progressive wear-and-tear of molecular and organ systems. The proposed model makes testable predictions around the physiological, cellular, and sub-cellular energetic mechanisms that transduce chronic stress into disease risk and mortality. We also highlight new avenues to quantify allostatic load and its link to health across the lifespan, via the integration of systemic and cellular energy expenditure measurements together with classic allostatic load biomarkers.

Energy expenditure during pregnancy: a systematic review

CONTEXT

Contrary to nutritional guidelines, accumulating evidence shows that pregnant women's energy intakes remain stable throughout trimesters. Although pregnant women may eat below their needs or underreport their energy intakes, it is also relevant to question how energy requirements - estimated through measurements of energy expenditure (EE) - change throughout pregnancy.

OBJECTIVE

This review examined prospective studies that measured EE during pregnancy, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

DATA SOURCES

PubMed/MEDLINE, Web of Science, Embase, and CINAHL databases were searched to identify relevant publications up to November 14, 2019.

STUDY SELECTION

All studies that measured EE prospectively and objectively during pregnancy were included in this systematic review. Two authors independently screened 4852 references. A total of 32 studies were included in the final analysis.

DATA EXTRACTION

One author extracted data and assessed the risk of bias and a second author did so for a random sample of studies (n = 7; 22%).

DATA ANALYSIS

Increases in resting EE ranged from 0.5% to 18.3% (8-239 kcal), from 3.0% to 24.1% (45-327 kcal), and from 6.4% to 29.6% (93-416 kcal) between early and mid-, mid- and late, and early and late pregnancy, respectively. Increases in total EE ranged from 4.0% to 17.7% (84-363 kcal), from 0.2% to 30.2% (5-694 kcal), and from 7.9% to 33.2% (179-682 kcal) between early and mid-, mid- and late, and early and late pregnancy, respectively. Participants were mainly of normal weight, although many studies did not report important covariates such as prepregnancy body mass index and gestational weight gain adequacy.

CONCLUSIONS

Additional high-quality longitudinal studies (ie, with multiple objective measurements of EE in all periods of pregnancy while considering important confounding variables, like gestational weight gain) are required.

Estradiol and body weight during temporally targeted food restriction: Central pathways and peripheral metabolic factors

We used temporally-targeted food restriction (TTFR), in which ovariectomized rats had chow only for 2 h/day, to test the hypothesis that estradiol benzoate (EB) suppresses feeding and decreases body weight during brief (4 day) TTFR, as it does during ad libitum feeding. All rats lost weight during TTFR, but the loss was greater with EB treatment. However, OIL and EB-treated rats ate comparable amounts of chow during TTFR. We next investigated central nervous system pathways and peripheral hormonal and metabolic changes that accompany the effects of TTFR to determine the mechanism for this effect. Immunolabeling for fos in the nucleus of the solitary tract, the terminal site of vagal afferents from the gastrointestinal tract, was increased when rats on TTFR had access to chow for 1 h on the test day, indicating neuronal activation associated with consumption of the meal. However, fos immunolabeling was not affected by EB treatment, nor were numbers of the α subtype of estrogen receptors. TTFR had the expected effects on carbohydrate and lipid metabolites and metabolic hormones, with only slight differences in plasma glucose, triglycerides, and free fatty acids attributable to EB treatment. Interestingly, plasma corticosterone levels were greater in EB-treated rats on TTFR, and increased further after eating. Given that corticosterone affects metabolism, these findings suggest that elevated corticosterone may explain the persistence of EB-induced differences in body weight during TTFR despite the lack of effect on food intake.

A decade in female reproduction: an endocrine view of the past and into the future

Over the last decade, huge achievements have been made in the fields of neurophysiology, molecular endocrinology, and biochemistry, as well as in the successful translation of clinical research into diseases into clinical practice. As regards female reproduction, most of the advances made in this area were achieved in gonadal axis regulation, regulation of behavior through sex steroids, reproductive genetics, preservation of ovarian reproductive function, steroid profiling, and metabolic and overall reproductive outcomes. The coming years are expected to bring further understanding of the relationships between nutrition, energy metabolism, and reproductive function and to succeed in identifying new genetic markers linked to adverse metabolic and unfavorable cardiovascular outcomes in women. From our perspective, future research in the field of female reproduction should be directed toward doing research into genetic reproductive abnormalities and neuroendocrine diseases, pathophysiology, long-term health outcomes for oligo/amenorrhea, hyperandrogenism, and ovulatory dysfunction. It is additionally expected that a better understanding will be gained of the endocrinology of the placenta and of pregnancy, the role of the microbiome in female reproduction, the role of insulin sensitizers, anti-obesity and anti-diabetic drugs, and various advances in the prevention of ovarian damage caused by various oncology therapies, while new therapeutic options for the treatment of infertility, including kisspeptin, will be developed.

Maternal stress alters the phenotype of the mother, her eggs and her offspring in a wild-caught lizard

While biomedical researchers have long appreciated the influence of maternally derived glucocorticoids (GCs) on offspring phenotype, ecologists have only recently begun exploring its impact in wild animals. Interpreting biomedical findings within an ecological context has posited that maternal stress, mediated by elevations of maternal GCs, may play an adaptive role preparing offspring for a stressful or rigorous environment. Yet, the influence of maternal stress on offspring phenotype has been little studied in wild animals. We experimentally elevated GCs to ecologically relevant levels (mimicking increases in maternal stress hormones following a nonlethal predator encounter, a heat challenge, or a chasing or confinement stressor) in female eastern fence lizards Sceloporus undulatus during gestation. We tested the hypothesis that maternally derived stress hormones themselves are sufficient to alter offspring phenotype. Specifically, we examined the effects of experimentally elevated maternal GCs on fitness-relevant traits of the mother, her eggs and her subsequent offspring. We found that daily maternal GC elevation: (a) increased maternal antipredator behaviours and postlaying glucose levels; (b) had no effect on egg morphology or caloric value, but altered yolk hormone (elevated GC) and nutrient content; and (c) altered offspring phenotype including stress-relevant physiology, morphology and behaviour. These findings reveal that maternally derived GCs alone can alter offspring phenotype in a wild animal, changes that may be mediated via maternal behaviour, and egg hormone and nutrient content. Understanding the ecological consequences of these effects under different environmental conditions will be critical for determining the adaptive significance of elevated maternal GCs for offspring.

First trimester depression scores predict development of gestational diabetes mellitus in pregnant rural Appalachian women

Gestational diabetes (GDM) occurs in up to 9% of pregnancies. Perinatal depression affects up to 20% of women during pregnancy, and can extend into the postpartum period. A number of studies have linked depression and diabetes, however, whether this applies to GDM or which might come first is less understood. The purpose of this study was to examine the potential relationship between depression identified in the first trimester of pregnancy and the subsequent development of GDM. Women without pre-existing Type I/II diabetes (n = 1021) were evaluated for depression during the first trimester of pregnancy, and medical records were reviewed to identify a positive history of diabetes. Women identified as depressed during the first trimester were more likely to have GDM compared to those not depressed. After controlling for demographic factors and weight-related variables level of depression in the first trimester still predicted later GDM development. Depression identified in early pregnancy may predict increased risk of subsequent GDM development. Due to the numerous maternal, fetal and neonatal complications associated with GDM, early recognition is essential to promote the best possible outcomes for mother and infant. Recognizing depression as a possible risk factor for GDM development could lead to earlier screening and preventative measures.

Variation in maternal urinary cortisol profiles across the peri-conceptional period: a longitudinal description and evaluation of potential functions

STUDY QUESTION

How do women's first morning urinary cortisol levels, a marker of stress axis activity, vary during the peri-conceptional period (the 12 weeks around conception)?

SUMMARY ANSWER

First morning urinary cortisol follows an overall increasing trajectory across the peri-conceptional period, interrupted by 2 week-long decreases during the week preceding conception and the fifth week following conception.

WHAT IS KNOWN ALREADY

Later gestational stages (i.e. second and third trimesters) are characterized by increasing levels of circulating cortisol. This increase is hypothesized to constitute a response to the energy demands imposed by fetal growth, and the development of energy reserves in preparation for nursing and performing regular activities while carrying pregnancy's extra weight and volume.

STUDY DESIGN, SIZE, DURATION

This study is based on a data set collected as part of a longitudinal, naturalistic investigation into the interactions between the stress (hypothalamic-pituitary-adrenal axis (HPAA)) and reproductive (hypothalamic-pituitary-gonadal axis (HPGA)) axes. Biomarkers of HPAA and HPGA function were quantified in first morning urinary specimens collected every other day from 22 healthy women who conceived a pregnancy during the study. We analyzed the longitudinal within- and between-individual variation in first morning urinary cortisol levels across the 12-week peri-conceptional period.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants were recruited from two rural, aboriginal, neighboring communities in Guatemala. Cortisol, estradiol and progesterone metabolites (estrone-3-glucuronide and pregnanediol glucuronide, respectively) and hCG levels were quantified in first morning urinary specimens using immunoassays to determine time of conception and confirm pregnancy maintenance. Linear mixed-effects models with regression splines were used to evaluate the magnitude and significance of changes in cortisol trajectories.

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, maternal first morning urinary cortisol increased from 6 weeks prior to conception (geometric mean ± SD = 58.14 ± 36.00 ng/ml) to 6 weeks post-conception (89.29 ± 46.76 ng/ml). The magnitude of the increase between the pre- and post-conception periods varied significantly between women (likelihood ratio test statistic = 8.0017, P = 0.005). The peri-conceptional period is characterized by an increasing cortisol trajectory (+1.36% per day; P = 0.007) interrupted by a week-long decline immediately prior to conception (-4.02% per day; P = 0.0013). After conception cortisol increased again (+1.73% per day; P = 0.0008) for 4 weeks, fell in the fifth week (-6.60% per day; P = 0.0002) and increased again in post-conceptional week 6 (+8.86% per day; P = 0.002). Maternal urinary cortisol levels varied with sex of the gestating embryo. During gestational week 2, mothers carrying female embryos (N = 10) had higher mean cortisol levels than those carrying male embryos (N = 9) (t(17) = 2.28, P = 0.04).

LIMITATIONS, REASONS FOR CAUTION

Our results are based on a relatively small sample (n = 22) of women. However, our repeated-measures design with an average of 27 ± 8 (mean ± SD) data points per woman strengthens the precision of estimates resulting in high statistical power. Additionally, our study population's high degree of ethnic and cultural homogeneity reduces the effects of confounders compared with those found in industrialized populations. This higher level of homogeneity also increases our statistical power. However, since there may be small differences in absolute cortisol values among ethnic groups, the social and biological background of our sample may affect the generalizability of our results. General patterns of HPAA activity, however, are expected to be universal across women. Finally, as there is, to the best of our knowledge, no evidence to the contrary, we assumed that urinary cortisol levels reflect HPAA activity and that changes in gonadal steroids across the menstrual cycle do not affect the levels of free cortisol measured in urine.

WIDER IMPLICATIONS OF THE FINDINGS

To our knowledge, this is the first longitudinal profile of basal maternal HPAA activity across the peri-conceptional period. A basic understanding of the normative (basal as opposed to stress-induced) changes in HPAA activity across this period is needed to accurately assess women's stress at this juncture. Importantly, changes in HPAA activity are likely to play a critical role in ovulation, fertilization, implantation, placentation and embryonic programing. Thus, this novel information should aid in the development of interventions aimed at preventing or moderating undesired effects of maternal physiological stress during the peri-conceptional period on reproductive outcomes as well as embryonic development.

STUDY FUNDING/COMPETING INTERESTS

This research was funded by a CIHR IGH Open Operating grant (CIHR 106705) to P.A.N. and L.Z.; a Simon Fraser University (SFU) President's Start-up grant, a Community Trust Endowment Fund grant through SFU's Human Evolutionary Studies Program and a Michael Smith Foundation for Health Research Career Investigator Scholar Award to P.A.N.; an NSERC Discovery grant to L.Z.; a CIHR Post-Doctoral Fellowship to C.K.B. and an NSERC Undergraduate Student Research Award to H.M. and J.C.B. The funding agencies had no role in the design, analysis, interpretation or reporting of the findings. There are no competing interests.

TRIAL REGISTRATION NUMBER

Not applicable.

Differential regulation of placental amino acid transport by saturated and unsaturated fatty acids

Fatty acids are critical for normal fetal development but may also influence placental function. We have previously reported that oleic acid (OA) stimulates amino acid transport in primary human trophoblasts (PHTs). In other tissues, saturated and unsaturated fatty acids have distinct effects on cellular signaling, for instance, palmitic acid (PA) but not OA reduces IκBα expression. We hypothesized that saturated and unsaturated fatty acids differentially affect trophoblast amino acid transport and cellular signaling. To test this hypothesis, PHTs were cultured in docosahexaenoic acid (DHA; 50 μM), OA (100 μM), or PA (100 μM). DHA and OA were also combined to test whether DHA could counteract the OA stimulatory effect on amino acid transport. The effects of fatty acids were compared against a vehicle control. Amino acid transport was measured by isotope-labeled tracers. Activation of inflammatory-related signaling pathways and the mechanistic target of rapamycin (mTOR) pathway were determined by Western blot analysis. Exposure of PHTs to DHA for 24 h reduced amino acid transport and phosphorylation of p38 MAPK, STAT3, mTOR, eukaryotic initiation factor 4E-binding protein 1, and ribosomal protein (rp)S6. In contrast, OA increased amino acid transport and phosphorylation of ERK, mTOR, S6 kinase 1, and rpS6. The combination of DHA with OA increased amino acid transport and rpS6 phosphorylation. PA did not affect amino acid transport but reduced IκBα expression. In conclusion, these fatty acids differentially regulated placental amino acid transport and cellular signaling. Taken together, these findings suggest that dietary fatty acids could alter the intrauterine environment by modifying placental function, thereby having long-lasting effects on the developing fetus.

The effects of childhood sexual abuse on cortisol trajectories in pregnancy are moderated by current family functioning

The goal of this study was to understand the roles of maternal history of childhood sexual abuse (CSA) and current family functioning on the cortisol awakening response (CAR) in pregnancy. Participants were 185 pregnant women (ages 18-40) who completed items from the Adverse Childhood Experiences scale to measure child maltreatment history and the Family Assessment Device to measure current family functioning. Participants provided saliva samples at wake-up and 30min after wake-up at 25, 29, and 35 weeks gestation to measure CAR. A moderation effect was found such that participants with more severe CSA histories and poorer perceived family functioning had increasing CAR in pregnancy compared to participants with less severe CSA histories and better family functioning. These findings highlight the importance of considering stress in both childhood and current environments in predicting maternal cortisol in pregnancy.

[Basal metabolism during pregnancy: a systematic review]

Gestational energy expenditure (EE) is the basis for nutritional counseling and body weight control. The objective of this study was to systematically review the behavior of the basal metabolic rate (BMR), the major component of EE, during non gemelar pregnancy of healthy women. Based on the inclusion criteria, 37 articles were identified (24 cohort and 13 cross-sectional studies). Increases in BMR (between 8% and 35%) were observed in most cohort studies and it was related to the duration of follow-up and nutritional status. In the cross-sectionals, the increase in BMR varied from 8% to 28% close to delivery in comparison with the first trimester or post-partum. Lack of information on maternal age, loss of follow-up and short duration of follow-up during the pregnancy were serious limitations in the identified studies. In conclusion, BMR increases during pregnancy, and the increase is more intense after the second trimester. The most reliable data come from the few cohort studies that initiated before pregnancy.

The association between a medical history of depression and gestational diabetes in a large multi-ethnic cohort in the United States

BACKGROUND

Both major depression and gestational diabetes mellitus (GDM) are prevalent among women of reproductive age. Our objective was to determine whether a medical history of depression is related to subsequent development of GDM.

METHODS

The Consortium on Safe Labor was a US retrospective cohort study of 228,562 births between 2002 and 2008. Exclusion criteria for the present analysis included multiple gestation pregnancies (n = 5059), pre-existing diabetes (n = 12,771), deliveries <24 weeks (n = 395), site GDM prevalence (<1%) (n = 20, 721) and missing data on pre-pregnancy body mass index (BMI) (n = 61,321). Using generalised estimating equations, we estimated the association between a history of depression and a pregnancy complicated by GDM.

RESULTS

The final analytic population included 121, 260 women contributing 128 295 pregnancies, of which 5606 were affected by GDM. A history of depression was significantly associated with an increased risk of developing GDM (multivariate odds ratio [aOR] = 1.42 [95% confidence interval (CI) 1.26, 1.60]). Adjusting for pre-pregnancy BMI and weight gain during pregnancy attenuated the association, although it remained statistically significant (aOR = 1.17 [95% CI 1.03, 1.33]).

CONCLUSIONS

A history of depression was significantly associated with an increased GDM risk among a large multi-ethnic US cohort of women. If the association is confirmed, depression presents a potentially modifiable risk factor of GDM and provides additional clues to the underlying pathophysiology of GDM.

On the function of placental corticotropin-releasing hormone: a role in maternal-fetal conflicts over blood glucose concentrations

Throughout the second and third trimesters, the human placenta (and the placenta in other anthropoid primates) produces substantial quantities of corticotropin-releasing hormone (placental CRH), most of which is secreted into the maternal bloodstream. During pregnancy, CRH concentrations rise over 1000-fold. The advantages that led selection to favour placental CRH production and secretion are not yet fully understood. Placental CRH stimulates the production of maternal adrenocorticotropin hormone (ACTH) and cortisol, leading to substantial increases in maternal serum cortisol levels during the third trimester. These effects are puzzling in light of widespread theory that cortisol has harmful effects on the fetus. The maternal hypothalamic-pituitary-adrenal (HPA) axis becomes less sensitive to cortisol during pregnancy, purportedly to protect the fetus from cortisol exposure. Researchers, then, have often looked for beneficial effects of placental CRH that involve receptors outside the HPA system, such as the uterine myometrium (e.g. the placental clock hypothesis). An alternative view is proposed here: the beneficial effect of placental CRH to the fetus lies in the fact that it does stimulate the production of cortisol, which, in turn, leads to greater concentrations of glucose in the maternal bloodstream available for fetal consumption. In this view, maternal HPA insensitivity to placental CRH likely reflects counter-adaptation, as the optimal rate of cortisol production for the fetus exceeds that for the mother. Evidence pertaining to this proposal is reviewed.

Differences in preterm and term milk fatty acid compositions may be caused by the different hormonal milieu of early parturition

INTRODUCTION

The hormonal milieus of pregnancy and lactation are driving forces of nutrient fluxes supporting infant growth and development. The decrease of insulin sensitivity with compensatory hyperinsulinemia with advancing gestation, causes adipose tissue lipolysis and hepatic de novo lipogenesis (DNL).

SUBJECTS AND METHODS

We compared fatty acid (FA) contents and FA-indices for enzyme activities between preterm (28-36 weeks) and term (37-42) milks, and between colostrum (2-5 days), transitional (6-15) and mature (16-56) milks. We interpreted FA differences between preterm and term milks, and their changes with lactation, in terms of the well known decrease of insulin sensitivity during gestation and its subsequent postpartum restoration, respectively.

RESULTS

Compared with term colostrum, preterm colostrum contained higher indices of DNL in the breast (DNL-breast) and medium chain saturated-FA (MCSAFA), and lower DNL-liver and monounsaturated-FA (MUFA). Preterm milk also had higher docosahexaenoic acid (DHA) in colostrum and transitional milk and higher arachidonic acid (AA) in mature milk. Most preterm-term differences vanished with advancing lactation. In both preterm and term milks, DNL-breast and MCSAFA increased with advancing lactation, while DNL-liver, MUFA, long chain SAFA and AA decreased. DHA decreased in term milk. MUFA was inversely related to MCSAFA in all samples, correlated inversely with PUFA in colostrum and transitional milks, but positively in mature milk. MCSAFA correlated inversely with PUFA in mature milk.

CONCLUSION

Higher maternal insulin sensitivity at preterm birth may be the cause of lower MUFA (a proxy for DNL-liver) and higher MCSAFA (a proxy for DNL-breast) in preterm colostrum, compared with term colostrum. Restoring insulin sensitivity after delivery may be an important driving force for milk FA-changes in early lactation.

Chronic stress in pregnant guinea pigs (Cavia aperea f. porcellus) attenuates long-term stress hormone levels and body weight gain, but not reproductive output

Stress, when extreme or chronic, can have a negative impact on health and survival of mammals. This is especially true for females during reproduction when self-maintenance and investment in offspring simultaneously challenge energy turnover. Therefore, we investigated the effects of repeated stress during early- and mid-gestation on the maternal stress axis, body weight gain and reproductive output. Female guinea pigs (Cavia aperea f. porcellus, n = 14) were either stressed (treatment: exposure to strobe light in an unfamiliar environment on gestational day -7, 0, 7, 14, 21, 28, 35, 42) or left completely undisturbed (control) throughout pregnancy. Females of both groups received the same respective diets, and reproductive parameters were evaluated upon parturition. Additionally, hormonal data were obtained from blood and feces. The stress exposure induced a significant increase in plasma cortisol concentrations during the afternoon. In contrast to this short-term response in plasma cortisol concentrations, we found no significant differences in the levels of cortisol metabolites in feces collected after stress exposure between groups and even significantly decreased levels of fecal cortisol metabolites on non-stress days over time in treatment females. Among treatment females, gain in body weight was attenuated over gestation and body weight was lower compared to control females during lactation, especially in cases of large litter sizes. No differences could be seen in the reproductive parameters. We conclude that repeated stress exposure with strobe light during early- and mid-gestation results in a down-regulation of the hypothalamic-pituitary-adrenal axis and lower weight gain in treatment females, but has no effect on reproductive output.

Effect of insulin and dexamethasone on fetal assimilation of maternal glucose

The growing fetus depends upon transfer of glucose from maternal blood to fetal tissues. Insulin and glucocorticoid impact maternal glucose metabolism, but the effects of these hormones on fetal glucose assimilation in vivo are understudied. We thus used positron emission tomography imaging to determine the disposition of [(18)F]fluorodeoxyglucose (FDG) in rats on gestational d 20, quantifying the kinetic competition of maternal tissues and fetus for glucose. Three fasting maternal states were studied: after 2-d dexamethasone (DEX), during euglycemic hyperinsulinemic clamp insulin receiving (INS), and control (CON). In CON and DEX mothers, FDG accumulation in fetuses and placentae was substantial, rivaling that of maternal brain. By contrast, FDG accumulation was reduced in INS fetuses, placentae, and maternal brain by approximately 2-fold, despite no diminution in FDG extraction kinetics from maternal blood into these structures. The reduced FDG accumulation was due to more rapid clearance of FDG from the circulation in INS mothers, related to increased FDG avidity in INS select maternal tissues, including skeletal muscle, brown adipose tissue, and heart. DEX treatment of mothers reduced fetal weight by nearly 10%. Nonetheless, the accumulation of FDG into placentae and fetuses was similar in DEX and CON mothers. In our rat model, fetal growth restriction induced by DEX does not involve diminished glucose transport to the fetus. Maternal insulin action has little effect on the inherent avidity of the fetal-placental unit for glucose but increases glucose utilization by maternal tissues, thus indirectly reducing the glucose available to the fetus.

Pattern of maternal circulating CRH in laboratory-housed squirrel and owl monkeys

The anthropoid primate placenta appears to be unique in producing corticotropin-releasing hormone (CRH). Placental CRH is involved in an endocrine circuit key to the production of estrogens during pregnancy. CRH induces cortisol production by the maternal and fetal adrenal glands, leading to further placental CRH production. CRH also stimulates the fetal adrenal glands to produce dehydroepiandrostendione sulfate (DHEAS), which the placenta converts into estrogens. There are at least two patterns of maternal circulating CRH across gestation among anthropoids. Monkeys examined to date (Papio and Callithrix) have an early-to-mid gestational peak of circulating CRH, followed by a steady decline to a plateau level, with a possible rise near parturition. In contrast, humans and great apes have an exponential rise in circulating CRH peaking at parturition. To further document and compare patterns of maternal circulating CRH in anthropoid primates, we collected monthly blood samples from 14 squirrel monkeys (Saimiri boliviensis) and ten owl monkeys (Aotus nancymaae) during pregnancy. CRH immunoreactivity was measured from extracted plasma by using solid-phase radioimmunoassay. Both squirrel and owl monkeys displayed a mid-gestational peak in circulating CRH: days 45-65 of the 152-day gestation for squirrel monkeys (mean±SEM CRH=2,694±276 pg/ml) and days 60-80 of the 133-day gestation for owl monkeys (9,871±974 pg/ml). In squirrel monkeys, circulating CRH declined to 36% of mean peak value by 2 weeks before parturition and then appeared to increase; the best model for circulating CRH over gestation in squirrel monkeys was a cubic function, similar to previous results for baboons and marmosets. In owl monkeys, circulating CRH appeared to reach plateau with no subsequent significant decline approaching parturition, although a cubic function was the best fit. This study provides additional evidence for a mid-gestational peak of maternal circulating CRH in ancestral anthropoids that has been lost in the hominoid lineage.