Perinatal Obesity Sensitizes for Premature Kidney Aging Signaling.

Chronic Kidney Disease (CKD), a global health burden, is strongly associated with age-related renal function decline, hypertension, and diabetes, which are all frequent consequences of obesity. Despite extensive studies, the mechanisms determining susceptibility to CKD remain insufficiently understood. Clinical evidence together with prior studies from our group showed that perinatal metabolic disorders after intrauterine growth restriction or maternal obesity adversely affect kidney structure and function throughout life. Since obesity and aging processes converge in similar pathways we tested if perinatal obesity caused by high-fat diet (HFD)-fed dams sensitizes aging-associated mechanisms in kidneys of newborn mice. The results showed a marked increase of γH2AX-positive cells with elevated 8-Oxo-dG (RNA/DNA damage), both indicative of DNA damage response and oxidative stress. Using unbiased comprehensive transcriptomics we identified compartment-specific differentially-regulated signaling pathways in kidneys after perinatal obesity. Comparison of these data to transcriptomic data of naturally aged kidneys and prematurely aged kidneys of genetic modified mice with a hypomorphic allele of Ercc1, revealed similar signatures, e.g., inflammatory signaling. In a biochemical approach we validated pathways of inflammaging in the kidneys after perinatal obesity. Collectively, our initial findings demonstrate premature aging-associated processes as a consequence of perinatal obesity that could determine the susceptibility for CKD early in life.

Maternal and perinatal obesity induce bronchial obstruction and pulmonary hypertension via IL-6-FoxO1-axis in later life.

Obesity is a pre-disposing condition for chronic obstructive pulmonary disease, asthma, and pulmonary arterial hypertension. Accumulating evidence suggests that metabolic influences during development can determine chronic lung diseases (CLD). We demonstrate that maternal obesity causes early metabolic disorder in the offspring. Here, interleukin-6 induced bronchial and microvascular smooth muscle cell (SMC) hyperproliferation and increased airway and pulmonary vascular resistance. The key anti-proliferative transcription factor FoxO1 was inactivated via nuclear exclusion. These findings were confirmed using primary SMC treated with interleukin-6 and pharmacological FoxO1 inhibition as well as genetic FoxO1 ablation and constitutive activation. In vivo, we reproduced the structural and functional alterations in offspring of obese dams via the SMC-specific ablation of FoxO1. The reconstitution of FoxO1 using IL-6-deficient mice and pharmacological treatment did not protect against metabolic disorder but prevented SMC hyperproliferation. In human observational studies, childhood obesity was associated with reduced forced expiratory volume in 1 s/forced vital capacity ratio Z-score (used as proxy for lung function) and asthma. We conclude that the interleukin-6-FoxO1 pathway in SMC is a molecular mechanism by which perinatal obesity programs the bronchial and vascular structure and function, thereby driving CLD development. Thus, FoxO1 reconstitution provides a potential therapeutic option for preventing this metabolic programming of CLD.

Macrophage-derived IL-6 trans-signalling as a novel target in the pathogenesis of bronchopulmonary dysplasia.

RATIONALE: Premature infants exposed to oxygen are at risk for bronchopulmonary dysplasia (BPD), which is characterised by lung growth arrest. Inflammation is important, but the mechanisms remain elusive. Here, we investigated inflammatory pathways and therapeutic targets in severe clinical and experimental BPD. METHODS AND RESULTS: First, transcriptomic analysis with in silico cellular deconvolution identified a lung-intrinsic M1-like-driven cytokine pattern in newborn mice after hyperoxia. These findings were confirmed by gene expression of macrophage-regulating chemokines (Ccl2, Ccl7, Cxcl5) and markers (Il6, Il17A, Mmp12). Secondly, hyperoxia-activated interleukin 6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) signalling was measured in vivo and related to loss of alveolar epithelial type II cells (ATII) as well as increased mesenchymal marker. Il6 null mice exhibited preserved ATII survival, reduced myofibroblasts and improved elastic fibre assembly, thus enabling lung growth and protecting lung function. Pharmacological inhibition of global IL-6 signalling and IL-6 trans-signalling promoted alveolarisation and ATII survival after hyperoxia. Third, hyperoxia triggered M1-like polarisation, possibly via Krüppel-like factor 4; hyperoxia-conditioned medium of macrophages and IL-6-impaired ATII proliferation. Finally, clinical data demonstrated elevated macrophage-related plasma cytokines as potential biomarkers that identify infants receiving oxygen at increased risk of developing BPD. Moreover, macrophage-derived IL6 and active STAT3 were related to loss of epithelial cells in BPD lungs. CONCLUSION: We present a novel IL-6-mediated mechanism by which hyperoxia activates macrophages in immature lungs, impairs ATII homeostasis and disrupts elastic fibre formation, thereby inhibiting lung growth. The data provide evidence that IL-6 trans-signalling could offer an innovative pharmacological target to enable lung growth in severe neonatal chronic lung disease.

Identification of Critical Windows of Metabolic Programming of Metabolism and Lung Function in Male Offspring of Obese Dams.

Perinatal nutritional determinants known as metabolic programming could be either detrimental or protective. Maternal obesity in the perinatal period determines susceptibility for diseases, such as obesity, metabolic disorders, and lung disease. Although this adverse metabolic programming is well-recognized, the critical developmental window for susceptibility risk remains elusive. Thus, we aimed to define the vulnerable window for impaired lung function after maternal obesity; and to test if dietary intervention protects. First, we studied the impact of high-fat diet (HFD)-induced maternal obesity during intrauterine (HFDiu ), postnatal (HFDpost ), or perinatal (i.e., intrauterine and postnatal (HFDperi ) phase on body weight, white adipose tissue (WAT), glucose tolerance, and airway resistance. Although HFDiu , HFDpost , and HFDperi induced overweight in the offspring, only HFDperi and HFDiu led to increased WAT in the offspring early in life. This early-onset adiposity was linked to impaired glucose tolerance in HFDperi -offspring. Interestingly, these metabolic findings in HFDperi -offspring, but not in HFDiu -offspring and HFDpost -offspring, were linked to persistent adiposity and increased airway resistance later in life. Second, we tested if the withdrawal of a HFD immediately after conception protects from early-onset metabolic changes by maternal obesity. Indeed, we found a protection from early-onset overweight, but not from impaired glucose tolerance and increased airway resistance. Our study identified critical windows for metabolic programming of susceptibility to impaired lung function, highlighting thereby windows of opportunity for prevention.

Maternal high-fat diet induces long-term obesity with sex-dependent metabolic programming of adipocyte differentiation, hypertrophy and dysfunction in the offspring.

Maternal obesity determines obesity and metabolic diseases in the offspring. The white adipose tissue (WAT) orchestrates metabolic pathways, and its dysfunction contributes to metabolic disorders in a sex-dependent manner. Here, we tested if sex differences influence the molecular mechanisms of metabolic programming of WAT in offspring of obese dams. To this end, maternal obesity was induced with high-fat diet (HFD) and the offspring were studied at an early phase [postnatal day 21 (P21)], a late phase (P70) and finally P120. In the early phase we found a sex-independent increase in WAT in offspring of obese dams using magnetic resonance imaging (MRI), which was more pronounced in females than males. While the adipocyte size increased in both sexes, the distribution of WAT differed in males and females. As mechanistic hints, we identified an inflammatory response in females and a senescence-associated reduction in the preadipocyte factor DLK in males. In the late phase, the obese body composition persisted in both sexes, with a partial reversal in females. Moreover, female offspring recovered completely from both the adipocyte hypertrophy and the inflammatory response. These findings were linked to a dysregulation of lipolytic, adipogenic and stemness-related markers as well as AMPKα and Akt signaling. Finally, the sex-dependent metabolic programming persisted with sex-specific differences in adipocyte size until P120. In conclusion, we do not only provide new insights into the molecular mechanisms of sex-dependent metabolic programming of WAT dysfunction, but also highlight the sex-dependent development of low- and high-grade pathogenic obesity.

Strain-dependent effects on lung structure, matrix remodeling, and Stat3/Smad2 signaling in C57BL/6N and C57BL/6J mice after neonatal hyperoxia.

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of preterm infants, characterized by lung growth arrest and matrix remodeling. Various animal models provide mechanistic insights in the pathogenesis of BPD. Since there is increasing evidence that genetic susceptibility modifies the response to lung injury, we investigated strain-dependent effects in hyperoxia (HYX)-induced lung injury of newborn mice. To this end, we exposed newborn C57BL/6N and C57BL/6J mice to 85% O2 (HYX) or normoxia (NOX; 21% O2) for 28 days, followed by lung excision for histological and molecular measurements. BL/6J-NOX mice exhibited a lower body and lung weight than BL/6N-NOX mice; hyperoxia reduced body weight in both strains and increased lung weight only in BL/6J-HYX mice. Quantitative histomorphometric analyses revealed reduced alveolar formation in lungs of both strains after HYX, but the effect was greater in BL/6J-HYX mice than BL/6N-HYX mice. Septal thickness was lower in BL/6J-NOX mice than BL/6N-NOX mice but increased in both strains after HYX. Elastic fiber density was significantly greater in BL/6J-HYX mice than BL/6N-HYX mice. Lungs of BL/6J-HYX mice were protected from changes in gene expression of fibrillin-1, fibrillin-2, fibulin-4, fibulin-5, and surfactant proteins seen in BL/6N-HYX mice. Finally, Stat3 was activated by HYX in both strains; in contrast, activation of Smad2 was markedly greater in lungs of BL/6N mice than BL/6J mice after HYX. In summary, we demonstrate strain-dependent differences in lung structure and matrix, alveolar epithelial cell markers, and Smad2 (transforming growth factor ß) signaling in neonatal HYX-induced lung injury. Strain-dependent effects and genetic susceptibility need be taken into consideration for reproducibility and reliability of results in animal models.

IL-6/Smad2 signaling mediates acute kidney injury and regeneration in a murine model of neonatal hyperoxia.

Prematurity is linked to incomplete nephrogenesis and risk of chronic kidney diseases (CKDs). Oxygen is life-saving in that context but induces injury in numerous organs. Here, we studied the structural and functional impact of hyperoxia on renal injury and its IL-6 dependency. Newborn wild-type (WT) and IL-6 knockout (IL-6-/-) mice were exposed to 85% O2 for 28 d, followed by room air until postnatal d (P) 70. Controls were in room air throughout life. At P28, hyperoxia reduced estimated kidney cortex area (KCA) in WT; at P70, KCA was greater, number of glomeruli was fewer, fractional potassium excretion was higher, and glomerular filtration rate was slightly lower than in controls. IL-6-/- mice were protected from these changes after hyperoxia. Mechanistically, the acute renal injury phase (P28) showed in WT but not in IL-6-/- mice an activation of IL-6 (signal transducer and activator of transcription 3) and TGF-ß [mothers against decapentaplegic homolog (Smad)2] signaling, increased inflammatory markers, disrupted mitochondrial biogenesis, and reduced tubular proliferation. Regenerative phase at P70 was characterized by tubular proliferation in WT but not in IL-6-/- mice. These data demonstrate that hyperoxia increases the risk of CKD through a novel IL-6-Smad2 axis. The amenability of these pathways to pharmacological approaches may offer new avenues to protect premature infants from CKD.-Mohr, J., Voggel, J., Vohlen, C., Dinger, K., Dafinger, C., Fink, G., Göbel, H., Liebau, M. C., Dötsch, J., Alejandre Alcazar, M. A. IL-6/Smad2 signaling mediates acute kidney injury and regeneration in a murine model of neonatal hyperoxia.

Novel functional role of GH/IGF-I in neonatal lung myofibroblasts and in rat lung growth after intrauterine growth restriction.

Intrauterine growth restriction (IUGR) is a risk factor for neonatal chronic lung disease (CLD) characterized by reduced alveoli and perturbed matrix remodeling. Previously, our group showed an activation of myofibroblasts and matrix remodeling in rat lungs after IUGR. Because growth hormone (GH) and insulin-like growth factor I (IGF-I) regulate development and growth, we queried 1) whether GH/IGF-I signaling is dysregulated in lungs after IUGR and 2) whether GH/IGF-I signaling is linked to neonatal lung myofibroblast function. IUGR was induced in Wistar rats by isocaloric low-protein diet during gestation. Lungs were obtained at embryonic day (E) 21, postnatal day (P) 3, P12, and P23. Murine embryonic fibroblasts (MEF) or primary neonatal myofibroblasts from rat lungs of control (pnFCo) and IUGR (pnFIUGR) were used for cell culture studies. In the intrauterine phase (E21), we found a reduction in GH receptor (GH-R), Stat5 signaling and IGF-I expression in lungs after IUGR. In the postnatal phase (P3-P23), catchup growth after IUGR was linked to increased GH mRNA, GH-R protein, activation of proliferative Stat5/Akt signaling, cyclin D1 and PCNA in rat lungs. On P23, a thickening of the alveolar septae was related to increased vimentin and matrix deposition, indicating fibrosis. In cell culture studies, nutrient deprivation blocked GH-R/IGF-IR signaling and proliferation in MEFs; this was reversed by IGF-I. Proliferation and Stat5 activation were increased in pnFIUGR. IGF-I and GH induced proliferation and migration of pnFCo; only IGF-I had these effects on pnFIUGR. Thus, we show a novel mechanism by which the GH/IGF-I axis in lung myofibroblasts could account for structural lung changes after IUGR.

Intraperitoneal Glucose Tolerance Test, Measurement of Lung Function, and Fixation of the Lung to Study the Impact of Obesity and Impaired Metabolism on Pulmonary Outcomes.

Obesity and respiratory disorders are major health problems. Obesity is becoming an emerging epidemic with an expected number of over 1 billion obese individuals worldwide by 2030, thus representing a growing socioeconomic burden. Simultaneously, obesity-related comorbidities, including diabetes as well as heart and chronic lung diseases, are continuously on the rise. Although obesity has been associated with increased risk for asthma exacerbations, worsening of respiratory symptoms, and poor control, the functional role of obesity and perturbed metabolism in the pathogenesis of chronic lung disease is often underestimated, and underlying molecular mechanisms remain elusive. This article aims to present methods to assess the effect of obesity on metabolism, as well as lung structure and function. Here, we describe three techniques for mice studies: (1) assessment of intraperitoneal glucose tolerance (ipGTT) to analyze the effect of obesity on glucose metabolism; (2) measurement of airway resistance (Res) and respiratory system compliance (Cdyn) to analyze the effect of obesity on lung function; and (3) preparation and fixation of the lung for subsequent quantitative histological assessment. Obesity-related lung diseases are probably multifactorial, stemming from systemic inflammatory and metabolic dysregulation that potentially adversely influence lung function and the response to therapy. Therefore, a standardized methodology to study molecular mechanisms and the effect of novel treatments is essential.

Renal Metabolic Programming Is Linked to the Dynamic Regulation of a Leptin-Klf15 Axis and Akt/AMPKα Signaling in Male Offspring of Obese Dams.

Childhood obesity is associated with renal diseases. Maternal obesity is a risk factor linked to increased adipocytokines and metabolic disorders in the offspring. Therefore, we studied the impact of maternal obesity on renal-intrinsic insulin and adipocytokine signaling and on renal function and structure. To induce maternal obesity, female mice were fed a high-fat diet (HFD) or a standard diet (SD; control group) prior to mating, during gestation, and throughout lactation. A third group of dams was fed HFD only during lactation (HFD-Lac). After weaning at postnatal day (P)21, offspring of all groups received SD. Clinically, HFD offspring were overweight and insulin resistant at P21. Although no metabolic changes were detected at P70, renal sodium excretion was reduced by 40%, and renal matrix deposition increased in the HFD group. Mechanistically, two stages were differentiated. In the early stage (P21), compared with the control group, HFD showed threefold increased white adipose tissue, impaired glucose tolerance, hyperleptinemia, and hyperinsulinemia. Renal leptin/Stat3-signaling was activated. In contrast, the Akt/ AMPKα cascade and Krüppel-like factor 15 expression were decreased. In the late stage (P70), although no metabolic differences were detected in HFD when compared with the control group, leptin/Stat3-signaling was reduced, and Akt/AMPKα was activated in the kidneys. This effect was linked to an increase of proliferative (cyclinD1/D2) and profibrotic (ctgf/collagen IIIα1) markers, similar to leptin-deficient mice. HFD-Lac mice exhibited metabolic changes at P21 similar to HFD, but no other persistent changes. This study shows a link between maternal obesity and metabolic programming of renal structure and function and intrinsic-renal Stat3/Akt/AMPKα signaling in the offspring.

Role of LTBP4 in alveolarization, angiogenesis, and fibrosis in lungs.

Deficiency of the extracellular matrix protein latent transforming growth factor-ß (TGF-ß)-binding protein-4 (LTBP4) results in lack of intact elastic fibers, which leads to disturbed pulmonary development and lack of normal alveolarization in humans and mice. Formation of alveoli and alveolar septation in pulmonary development requires the concerted interaction of extracellular matrix proteins, growth factors such as TGF-ß, fibroblasts, and myofibroblasts to promote elastogenesis as well as vascular formation in the alveolar septae. To investigate the role of LTBP4 in this context, lungs of LTBP4-deficient (Ltbp4-/-) mice were analyzed in close detail. We elucidate the role of LTBP4 in pulmonary alveolarization and show that three different, interacting mechanisms might contribute to alveolar septation defects in Ltbp4-/- lungs: 1) absence of an intact elastic fiber network, 2) reduced angiogenesis, and 3) upregulation of TGF-ß activity resulting in profibrotic processes in the lung.

Novel role of NPY in neuroimmune interaction and lung growth after intrauterine growth restriction.

Individuals with intrauterine growth restriction (IUGR) are at risk for chronic lung disease. Using a rat model, we showed in our previous studies that altered lung structure is related to IL-6/STAT3 signaling. As neuropeptide Y (NPY), a coneurotransmitter of the sympathetic nervous system, regulates proliferation and immune response, we hypothesized that dysregulated NPY after IUGR is linked to IL-6, impaired myofibroblast function, and alveolar growth. IUGR was induced in rats by isocaloric low-protein diet; lungs were analyzed on embryonic day (E) 21, postnatal day (P) 3, P12, and P23. Finally, primary neonatal lung myofibroblasts (pnF) and murine embryonic fibroblasts (MEF) were used to assess proliferation, apoptosis, migration, and IL-6 expression. At E21, NPY and IL-6 expression was decreased, and AKT/PKC and STAT3/AMPKα signaling was reduced. Early reduction of NPY/IL-6 was associated with increased chord length in lungs after IUGR at P3, indicating reduced alveolar formation. At P23, however, IUGR rats exhibited a catch-up of body weight and alveolar growth coupled with more proliferating myofibroblasts. These structural findings after IUGR were linked to activated NPY/PKC, IL-6/AMPKα signaling. Complementary, IUGR-pnF showed increased survival, impaired migration, and reduced IL-6 compared with control-pnF (Co-pnF). In contrast, NPY induced proliferation, migration, and increased IL-6 synthesis in fibroblasts. Additionally, NPY-/- mice showed reduced IL-6 signaling and less proliferation of lung fibroblasts. Our study presents a novel role of NPY during alveolarization: NPY regulates 1) IL-6 and lung STAT3/AMPKα signaling, and 2) proliferation and migration of myofibroblasts. These new insights in pulmonary neuroimmune interaction offer potential strategies to enable lung growth.

Dietary intervention in obese dams protects male offspring from WAT induction of TRPV4, adiposity, and hyperinsulinemia.

OBJECTIVE: One major risk factor for childhood overweight is maternal obesity. The underlying molecular mechanisms are ill-defined, and effective prevention strategies are missing. METHODS: Diet-induced obese mouse dams were changed to standard chow during pregnancy and lactation as an intervention against predisposition for obesity and metabolic sequelea in the offspring. Expression of adipokines and TRPV4, a regulator of adipose oxidative metabolism, inflammation, and energy homeostasis, in offspring's white adipose tissue (WAT) was assessed. RESULTS: Pathological effects on offspring's body weight, fat content, and serum insulin were fully reversed in intervention offspring on postnatal day 21. In WAT, a sixfold increase of Trpv4 mRNA expression in offspring consuming high-fat-containing diet was found, which was completely blunted in the intervention group. Simultaneously, WAT adipokine, interleukin-6, and peroxisome proliferator-activated receptor-γ mRNA and UCP1 protein expression were largely returned to control levels in intervention offspring. CONCLUSIONS: Improvement of maternal nutrition offers a powerful strategy to improve offspring's metabolic health. Targeting TRPV4-linked aspects of WAT metabolic function during early development might be a promising approach to prevent long-term adverse metabolic effects of maternal high-fat nutrition.

Early-onset obesity dysregulates pulmonary adipocytokine/insulin signaling and induces asthma-like disease in mice.

Childhood obesity is a risk factor for asthma, but the molecular mechanisms linking both remain elusive. Since obesity leads to chronic low-grade inflammation and affects metabolic signaling we hypothesized that postnatal hyperalimentation (pHA) induced by maternal high-fat-diet during lactation leads to early-onset obesity and dysregulates pulmonary adipocytokine/insulin signaling, resulting in metabolic programming of asthma-like disease in adult mice. Offspring with pHA showed at postnatal day 21 (P21): (1) early-onset obesity, greater fat-mass, increased expression of IL-1ß, IL-23, and Tnf-α, greater serum leptin and reduced glucose tolerance than Control (Ctrl); (2) less STAT3/AMPKα-activation, greater SOCS3 expression and reduced AKT/GSK3ß-activation in the lung, indicative of leptin resistance and insulin signaling, respectively; (3) increased lung mRNA of IL-6, IL-13, IL-17A and Tnf-α. At P70 body weight, fat-mass, and cytokine mRNA expression were similar in the pHA and Ctrl, but serum leptin and IL-6 were greater, and insulin signaling and glucose tolerance impaired. Peribronchial elastic fiber content, bronchial smooth muscle layer, and deposition of connective tissue were not different after pHA. Despite unaltered bronchial structure mice after pHA exhibited significantly increased airway reactivity. Our study does not only demonstrate that early-onset obesity transiently activates pulmonary adipocytokine/insulin signaling and induces airway hyperreactivity in mice, but also provides new insights into metabolic programming of childhood obesity-related asthma.

Running Exercise in Obese Pregnancies Prevents IL-6 Trans-signaling in Male Offspring.

PURPOSE: Maternal obesity is known to predispose the offspring to impaired glucose metabolism and obesity associated with low-grade inflammation and hypothalamic dysfunction. Because preventive approaches in this context are missing to date, we aimed to identify molecular mechanisms in the offspring that are affected by maternal exercise during pregnancy. METHODS: Diet-induced obese mouse dams were divided into a sedentary obese (high-fat diet [HFD]) group and an obese intervention (HFD-running intervention [RUN]) group, which performed voluntary wheel running throughout gestation. Male offspring were compared with the offspring of a sedentary lean control group at postnatal day 21. RESULTS: HFD and HFD-RUN offspring showed increased body weight and white adipose tissue mass. Glucose tolerance testing showed mild impairment only in HFD offspring. Serum interleukin-6 (IL-6) levels, hypothalamic and white adipose tissue IL-6 gene expressions, and phosphorylation of signal transducer and activator of transcription 3 in HFD offspring were significantly increased, whereas HFD-RUN was protected against these changes. The altered hypothalamic global gene expression in HFD offspring showed partial normalization in HFD-RUN offspring, especially with respect to IL-6 action. CONCLUSION: Maternal exercise in obese pregnancies effectively reduces IL-6 trans-signaling and might be the underlying mechanism for the amelioration of glucose metabolism at postnatal day 21 independent of body composition.

Modeling autosomal recessive cutis laxa type 1C in mice reveals distinct functions for Ltbp-4 isoforms.

Recent studies have revealed an important role for LTBP-4 in elastogenesis. Its mutational inactivation in humans causes autosomal recessive cutis laxa type 1C (ARCL1C), which is a severe disorder caused by defects of the elastic fiber network. Although the human gene involved in ARCL1C has been discovered based on similar elastic fiber abnormalities exhibited by mice lacking the short Ltbp-4 isoform (Ltbp4S(-/-)), the murine phenotype does not replicate ARCL1C. We therefore inactivated both Ltbp-4 isoforms in the mouse germline to model ARCL1C. Comparative analysis of Ltbp4S(-/-) and Ltbp4-null (Ltbp4(-/-)) mice identified Ltbp-4L as an important factor for elastogenesis and postnatal survival, and showed that it has distinct tissue expression patterns and specific molecular functions. We identified fibulin-4 as a previously unknown interaction partner of both Ltbp-4 isoforms and demonstrated that at least Ltbp-4L expression is essential for incorporation of fibulin-4 into the extracellular matrix (ECM). Overall, our results contribute to the current understanding of elastogenesis and provide an animal model of ARCL1C.

Prevention of early postnatal hyperalimentation protects against activation of transforming growth factor-ß/bone morphogenetic protein and interleukin-6 signaling in rat lungs after intrauterine growth restriction.

BACKGROUND: Intrauterine growth restriction (IUGR) is intimately linked with postnatal catch-up growth, leading to impaired lung structure and function. However, the impact of catch-up growth induced by early postnatal hyperalimentation (HA) on the lung has not been addressed to date. OBJECTIVE: The aim of this study was to investigate whether prevention of HA subsequent to IUGR protects the lung from 1) deregulation of the transforming growth factor-ß(TGF-ß)/bone morphogenetic protein (BMP) pathway, 2) activation of interleukin (IL)-6 signaling, and 3) profibrotic processes. METHODS: IUGR was induced in Wistar rats by isocaloric protein restriction during gestation by feeding a control (Co) or a low-protein diet with 17% or 8% casein, respectively. On postnatal day 1 (P1), litters from both groups were randomly reduced to 6 pups per dam to induce HA or adjusted to 10 pups and fed with standard diet: Co, Co with HA (Co-HA), IUGR, and IUGR with HA (IUGR-HA). RESULTS: Birth weights in rats after IUGR were lower than in Co rats (P < 0.05). HA during lactation led to accelerated body weight gain from P1 to P23 (Co vs. Co-HA, IUGR vs. IUGR-HA; P < 0.05). At P70, prevention of HA after IUGR protected against the following: 1) activation of both TGF-ß [phosphorylated SMAD (pSMAD) 2; plasminogen activator inhibitor 1 (Pai1)] and BMP signaling [pSMAD1; inhibitor of differentiation (Id1)] compared with Co (P < 0.05) and Co or IUGR (P < 0.05) rats, respectively; 2) greater mRNA expression of interleukin (Il) 6 and Il13 (P < 0.05) as well as activation of signal transducer and activator of transcription 3 (STAT3) signaling (P < 0.05) after IUGR-HA; and 3) greater gene expression of collagen Iα1 and osteopontin (P < 0.05) and increased deposition of bronchial subepithelial connective tissue in IUGR-HA compared with Co and IUGR rats. Moreover, HA had a significant additive effect (P < 0.05) on the increased enhanced pause (indicator of airway resistance) in the IUGR group (P < 0.05) at P70. CONCLUSIONS: This study demonstrates a dual mechanism in IUGR-associated lung disease that is 1) IUGR-dependent and 2) HA-mediated and thereby offers new avenues to develop innovative preventive strategies for perinatal programming of adult lung diseases.