Neonatal IL-4 exposure decreases adipogenesis of male rats into adulthood

Type 2 Immunity Regulates Dermal White Adipose Tissue Function

Type 2 immune responses have been increasingly linked with tissue maintenance, regeneration, and metabolic homeostasis. The molecular basis of regulator and effector mechanisms of type 2 immunity in skin regeneration and homeostasis is still lacking. In this study, we analyzed the role of IL-4Rα signaling in the regeneration of diverse cellular compartments in the skin. Mutants with global IL-4Rα deficiency showed two major phenotypes: first, a pronounced atrophy of the interfollicular epidermis, and second, a significant increase in dermal white adipose tissue thickness in mice aged 3 weeks (postnatal day 21) compared with littermate controls. Notably, IL-4Rα deficiency decreased the activation of hormone-sensitive lipase, a rate-limiting step in lipolysis. Immunohistochemical and FACS analysis in IL-4/enhanced GFP reporter mice showed that IL-4 expression peaked on postnatal day 21 and that eosinophils are the predominant IL-4-expressing cells. Eosinophil-deficient mice recapitulated the lipolytic-defective dermal white adipose tissue phenotype of Il4ra-deficient mice, showing that eosinophils are necessary for dermal white adipose tissue lipolysis. Collectively, we provide mechanistic insights into the regulation of interfollicular epidermis and hormone-sensitive lipase-mediated lipolysis in dermal white adipose tissue in early life by IL-4Rα, and our findings show that eosinophils play a critical role in this process.

Slower Growth during Lactation Rescues Early Cardiovascular and Adipose Tissue Hypertrophy Induced by Fetal Undernutrition in Rats

Low birth weight (LBW) and accelerated growth during lactation are associated with cardiometabolic disease development. LBW offspring from rats exposed to undernutrition during gestation (MUN) develops hypertension. In this rat model, we tested if slower postnatal growth improves early cardiometabolic alterations. MUN dams were fed ad libitum during gestation days 1–10, with 50% of the daily intake during days 11–21 and ad libitum during lactation. Control dams were always fed ad libitum. Pups were maintained with their own mother or cross-fostered. Body weight and length were recorded weekly, and breastmilk was obtained. At weaning, the heart was evaluated by echocardiography, and aorta structure and adipocytes in white perivascular fat were studied by confocal microscopy (size, % beige-adipocytes by Mitotracker staining). Breastmilk protein and fat content were not significantly different between groups. Compared to controls, MUN males significantly accelerated body weight gain during the exclusive lactation period (days 1–14) while females accelerated during the last week; length growth was slower in MUN rats from both sexes. By weaning, MUN males, but not females, showed reduced diastolic function and hypertrophy in the heart, aorta, and adipocytes; the percentage of beige-type adipocytes was smaller in MUN males and females. Fostering MUN offspring on control dams significantly reduced weight gain rate, cardiovascular, and fat hypertrophy, increasing beige-adipocyte proportion. Control offspring nursed by MUN mothers reduced body growth gain, without cardiovascular modifications. In conclusion, slower growth during lactation can rescue early cardiovascular alterations induced by fetal undernutrition. Exclusive lactation was a key period, despite no modifications in breastmilk macronutrients, suggesting the role of bioactive components. Our data support that lactation is a key period to counteract cardiometabolic disease programming in LBW and a potential intervention window for the mother.