Chronic Tumor Necrosis Factor-α Infusion in Gravid C57BL6/J Mice Accelerates Adipose Tissue Development in Female Offspring

Bioavailability of the tumor necrosis factor alpha/regulated on activation, normal T cell expressed and secreted (RANTES) biosystem inside the gestational sac during the pre-immune stages of embryo development

OBJECTIVES

In-vivo studies of the bioavailability of major components of the tumor necrosis factor alpha (TNFα) biosystem inside the gestational sac during embryogenesis have not been reported. We sought to determine the concentration of TNFα, soluble (s) TNFα receptors (sTNFR1, sTNFR2), and RANTES in the primate extraembryonic celomic fluid (ECF).

METHODS

A validated timed-pregnant baboon animal model (N: 10) for experimental research in pregnancy was used to collect paired maternal blood and ECF samples in ongoing pregnancies. The concentrations (pg/dL) of TNFα, sTNFR1, sTNFR2, and RANTES were then determined by ELISA immunoassays.

RESULTS

All animals delivered at term healthy newborns. The differential concentration of TNFα, sTNFR1, sTNFR2, and RANTES between the maternal plasma and the ECF could be determined with ratios for TNFα (5.4), sTNFR2 (1.85) and RANTES (3.59) that contrasted with that of sTNFR1 (0.07), which favored the gestational sac compartment. No significant correlations were noted between maternal plasma and ECF TNFR1, sTNFR2 and RANTES. There was a trend for a correlation between TNFα in maternal plasma and ECF (R=0.74; p=0.07).

CONCLUSIONS

We report the physiological concentrations of TNFα, sTNFR1, sTNFR2, and RANTES in extraembryonic celomic fluid during embryogenesis in primates.

Role of adipose tissue in regulating fetal growth in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a global health issue with significant short and long-term complications for both mother and baby. There is a strong need to identify an effective therapeutic that can prevent the development of GDM. A better understanding of the pathophysiology of GDM and the relationship between the adipose tissue, the placenta and fetal growth is required. The placenta regulates fetal growth by modulating nutrient transfer of glucose, amino acids and fatty acids. Various factors secreted by the adipose tissue, such as adipokines, adipocytokines and more recently identified extracellular vesicles, can influence inflammation and interact with placental nutrient transport. In this review, the role of the placental nutrient transporters and the adipose-derived factors that can influence their function will be discussed. A better understanding of these factors and their relationship may make a potential target for therapeutic interventions to prevent the development of GDM and its consequences.

Toll-Like Receptor-4 Antagonist (+)-Naloxone Confers Sexually Dimorphic Protection From Inflammation-Induced Fetal Programming in Mice

Inflammation elicited by infection or noninfectious insults during gestation induces proinflammatory cytokines that can shift the trajectory of development to alter offspring phenotype, promote adiposity, and increase susceptibility to metabolic disease in later life. In this study, we use mice to investigate the utility of a small molecule Toll-like receptor (TLR)4 antagonist (+)-naloxone, the nonopioid isomer of the opioid receptor antagonist (-)-naloxone, for mitigating altered fetal metabolic programming induced by a modest systemic inflammatory challenge in late gestation. In adult progeny exposed to lipopolysaccharide (LPS) challenge in utero, male but not female offspring exhibited elevated adipose tissue, reduced muscle mass, and elevated plasma leptin at 20 weeks of age. Effects were largely reversed by coadministration of (+)-naloxone following LPS. When given alone without LPS, (+)-naloxone elicited accelerated postweaning growth and elevated muscle and fat mass in adult male but not female offspring. LPS induced expression of inflammatory cytokines Il1a, Il1b, Il6, Tnf, and Il10 in fetal brain, placental, and uterine tissues, and (+)-naloxone suppressed LPS-induced cytokine expression. Fetal sex-specific regulation of cytokine expression was evident, with higher Il1a, Il1b, Il6, and Il10 induced by LPS in tissues associated with male fetuses, and greater suppression by (+)-naloxone of Il6 in females. These data demonstrate that modulating TLR4 signaling with (+)-naloxone provides protection from inflammatory diversion of fetal developmental programming in utero, associated with attenuation of gestational tissue cytokine expression in a fetal sex-specific manner. The results suggest that pharmacologic interventions targeting TLR4 warrant evaluation for attenuating developmental programming effects of fetal exposure to maternal inflammatory mediators.

Chronic maternal inflammation or high-fat-feeding programs offspring obesity in a sex-dependent manner

BACKGROUND/OBJECTIVES

The current world-wide obesity epidemic partially results from a vicious circle whereby maternal obesity during pregnancy predisposes the offspring for accelerated weight gain and development of metabolic syndrome. Here we investigate whether low-grade inflammation, characteristic of the obese state, provides a causal role for this disastrous fetal programming in mice.

METHODS

We exposed pregnant and lactating C57BL/6JBom female mice to either high-fat diet (HFD), or continuous infusion of lipopolysaccharide (LPS), a potent trigger of innate immunity, and studied offspring phenotypes.

RESULTS

Both maternal LPS or HFD treatments rendered the offspring hyperphagic and inept of coping with a HFD challenge during adulthood, increasing their adiposity and weight gain. The metabolic effects were more pronounced in female offspring, while exposed male offspring mounted a larger inflammatory response to HFD at adulthood.

CONCLUSIONS

This supports our hypothesis and highlights the programming potential of inflammation in obese pregnancies.

Baseline TNFα operational capacity in fetal and maternal circulation prior to the onset of labor: "tuned for different purposes"

OBJECTIVE

In this study, we sought to characterize the tumor necrosis factor α (TNFα) baseline operational capacity in mature fetuses and their mothers prior to the onset of labor.

MATERIALS AND METHODS

We used an experimental pregnant nonhuman primate model to measure the plasma concentration of TNFα, TNF transmembrane receptor I (TNFRI), and TNFRII with validated enzyme-linked immunosorbent assays. Coefficients of correlations between the maternal and the fetal values and the soluble TNFα, TNFRI, or TNFRII concentrations and ratios were calculated.

RESULTS

The TNFα/TNFRI ratio was 3 times lower in fetal circulation than in maternal circulation. No correlations were noted between the maternal and the fetal TNFα, TNFRI, or TNFRII plasma concentrations.

CONCLUSIONS

These findings suggest that the fetal and maternal baseline circulatory operational capacities of TNFα are independent of each other and tuned differently. This differential regulation of TNFα in fetal and maternal circulation at the end of pregnancy may be guided to protect the fetus from the systemic inflammatory response that is essential for the mechanisms of labor to proceed in the mother.

Placental effects of systemic tumour necrosis factor-α in an animal model of gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) may adversely affect fetoplacental interaction. Numerous reports demonstrate that GDM women have increased circulating tumour necrosis factor-α (TNF), a pro-apoptotic peptide.

OBJECTIVE

To examine whether implantation site apoptosis is increased by exogenous TNF in mice heterozygous for a defective leptin receptor (db/+), a GDM animal model.

STUDY DESIGN

Implantation sites were studied at gestational day (gd)18.5 in 3 groups: saline-treated wild-type (wt) and db/+ mice, and TNF-treated db/+ mice. Saline or TNF (total dose 4 μg) was administered by miniosmotic pump from gd11.5. Immunostaining for cleaved caspase-3, PAS and cytokeratin was performed for quantification of apoptotic cells, uterine natural killer (uNK) cells, and trophoblast invasion, respectively. The mRNA expression of TNF and TNF-induced apoptotic markers in placenta and mesometrial triangle (MT) was measured by quantitative RT-PCR.

RESULTS

The implantation sites from saline-treated wt and db/+ mice showed comparable numbers of apoptotic cells and uNK cells. Compared with the saline-treated groups, TNF-treated db/+ dams had less fetuses; the placental labyrinth and trophospongium contained more apoptotic cells; and the MT contained a higher total number of uNK cells including more cells intensely stained for cleaved caspase-3 as well as cells with negative staining. Trophoblast invasion was shallower in db/+ than in wt mice (14% and 30% of total invasion into MT, respectively) but this was not affected by TNF. The mRNA expression of TNF and apoptotic markers was comparable in the 3 groups.

CONCLUSIONS

TNF treatment in db/+ mice raises the number of apoptotic cells in the placenta, and appears to increase the retention of uNK cells in the MT. Db/+ mice demonstrate shallower trophoblast invasion which is unaffected by exogenous TNF.

Left-sided cardiac valvulitis in tristetraprolin-deficient mice: the role of tumor necrosis factor alpha

Inflammation may play a role in the etiology of both degenerative and rheumatic cardiac valve diseases. We report here that mice deficient in tristetraprolin (TTP), a protein with known anti-inflammatory functions, develop severe left-sided cardiac valvulitis. TTP is an mRNA binding protein that inhibits inflammation by destabilizing the mRNA encoding tumor necrosis factor alpha (TNF). This leads in turn to a TNF-excess syndrome characterized by systemic inflammation. Evaluation of hearts from TTP-/- mice demonstrated gross thickening of the mitral and aortic but not the tricuspid or pulmonary valves, accompanied by inflammatory cell infiltrates. To determine whether TNF played a role in the development of this valvulitis, we examined mice deficient in both TNF receptors and in TTP; four of five of these mice exhibited no histological evidence of valvulitis, but one mouse had aortic valve leaflet thickening with a cellular infiltrate. Four additional mice had no external evidence of valvular thickening. Cardiac valves of transgenic mice expressing human TNF developed mild aortic valve leaflet edema without evidence of hypercellularity. Thus, TTP deficiency in mice leads to left-sided cardiac valvulitis with prominent inflammatory cell involvement, due, at least in part, to excess TNF. These findings support the potential involvement of TNF and inflammation in the development of cardiac valve disease in man.

Diet-induced obesity in gravid rats engenders early hyperadiposity in the offspring

Exposure to a dysmetabolic in utero environment may be one of the mechanisms to explain why individuals with high birth weight are more likely to remain overweight. We explored this hypothesis in an animal model of diet-induced obesity (DIO). We studied adipose tissue development and glucose tolerance in the offspring of rat dams fed a diet rich in milk and sugar from early adulthood until day (d) 2 postpartum. This diet promoted body weight (BW) gain and was previously shown to produce insulin resistance and gestational glucose intolerance. The DIO offspring showed a higher BW in early life (between d7 and d35), with a maximum of 1 SD above the mean BW of controls; however, BW in DIO offspring after d35 was comparable with that of controls. Neonatal DIO offspring also showed larger fat depots, adipocyte hypertrophy (P <or= .001), and more than 2-fold increased tumor necrosis factor alpha messenger RNA levels in subcutaneous adipose tissue (P < .05). In addition, they displayed a higher peak glucose response to a glucose challenge (P < .05). In postpubertal (d56) and adult (d98) offspring, we found differences in fat mass and distribution and glucose tolerance relating to the offspring's sex but not the maternal diet. In conclusion, DIO during pregnancy results in hyperadiposity and reduced glucose tolerance only in their neonatal/weanling but not postpubertal offspring. Future research should disclose whether these early-life effects are reactivated in conditions of heightened insulin resistance.