Postnatal overfeeding in rodents by litter size reduction induces major short- and long-term pathophysiological consequences

Neonatal overfeeding promotes anxiety, impairs episodic-like memory, and disrupts transcriptional regulation of hippocampal steroidogenic enzymes

The objective of our study was to investigate the impact of neonatal overfeeding on cognitive functions and neurosteroidogenesis in male rats. Offspring were assigned to either small litters (SL; 4 pups/mother), resulting in increased milk intake and body weight gain, or normal litters (NL; 10 pups/mother). On postnatal day (PND) 21, half of the male rats were euthanized, while the remaining were kept under standard conditions (4 rats/cage) until PND70. At this stage, subjects underwent assessments for locomotor activity, anxiety levels via the elevated plus maze, and episodic-like memory (ELM) tests. By PND90, the rats were euthanized for brain dissection. Utilizing micropunch techniques, dentate gyrus (DG), CA1, and CA3 regions were extracted for analysis of mRNA expression and methylation patterns. At PND21, SL rats exhibited increased body and adipose tissue weights, alongside elevated cholesterol, glucose, and triglyceride levels compared to NL counterparts. By PND90, although metabolic disparities were no longer evident, SL rats demonstrated heightened anxiety-like behavior and diminished performance in ELM tests. Early life changes included a decreased expression of aromatase (P450arom) and 3α-HSD in CA1, with increased levels in CA3 and DG among SL rats. Additionally, PND90 rats from SL exhibited increased P450arom and decreased 5α-reductase 1 (5αR-1) expression in DG. Notably, some of these variations were correlated with changes in methylation patterns of their promoter regions. Our findings reveal that neonatal overfeeding exerts a long-term adverse effect on cognitive abilities and neurosteroidogenic pathways, underscoring the lasting impact of nutritional experiences during critical early postnatal development periods.

Gut microbiome and inflammation in response to increasing intermittent hypoxia in the neonatal rat

BACKGROUND

Intermittent hypoxia (IH) and oxidative stress play key roles in gut dysbiosis and inflammation. We tested the hypothesis that increasing numbers of daily IH episodes cause microbiome dysbiosis and severe gut injury.

METHODS

Neonatal rats were exposed to hyperoxia (Hx), growth restriction, and IH. For IH, pups were exposed to 2-12 daily episodes from birth (P0) to postnatal day 7 (7D) or P0-P14 (14D), with or without recovery in room air (RA) until P21. Animals raised in RA from P0 to P21 served as normoxia controls. Stool was expressed from the large intestines for microbiome analysis, and tissue samples were assessed for histopathology and biomarkers of inflammation.

RESULTS

Hx and IH caused a significant reduction in the number and diversity of organisms. The severity of gut injury and levels of inflammatory cytokines and TLR4 increased, while total glutathione (tGSH) declined, with increasing daily IH episodes. The number of organisms correlated with the villi number (p < 0.05) and tGSH depletion (p < 0.001).

CONCLUSIONS

The critical number of daily IH episodes that the newborn gut may sustain is 6, beyond which irreversible damage occurs. The immature gut is highly susceptible to IH-induced injury, and IH may contribute to pathological outcomes in the immature gut.

IMPACT STATEMENT

1. The neonatal gut at birth is highly susceptible to intermittent hypoxia (IH) injury. 2. IH causes gut dysbiosis, inflammation, and glutathione depletion. 3. The severity of gut injury worsens as a function of increasing daily IH episodes. 4. The critical number of daily IH episodes that the newborn gut may sustain is 6, beyond which irreversible damage occurs.

Postnatally overfed mice display cardiac function alteration following myocardial infarction

BACKGROUND

Cardiovascular (CV) pathologies remain a leading cause of death worldwide, often associated with common comorbidities such as overweight, obesity, type 2 diabetes or hypertension. An innovative mouse model of metabolic syndrome induced by postnatal overfeeding (PNOF) through litter size reduction after birth was developed experimentally. This study aimed to evaluate the impact of PNOF on cardiac remodelling and the development of heart failure following myocardial infarction.

METHODS

C57BL/6 male mice were raised in litter adjusted to 9 or 3 pups for normally-fed (NF) control and PNOF group respectively. After weaning, all mice had free access to standard diet and water. At 4 months, mice were subjected to myocardial infarction (MI). Echocardiographic follows-up were performed up to 6-months post-surgery and biomolecular analyses were carried-out after heart collection.

FINDINGS

At 4 months, PNOF mice exhibited a significant increase in body weight, along with a basal reduction in left ventricular ejection fraction (LVEF) and an increase in left ventricular end-systolic area (LVESA), compared to NF mice. Following MI, PNOF mice demonstrated a significant decrease in stroke volume and an increased heart rate compared to their respective initial values, as well as a notable reduction in cardiac output 4-months after MI. After 6-months, left ventricle and lung masses, fibrosis staining, and mRNA expression were all similar in the NF-MI and PNOF-MI groups.

INTERPRETATION

After MI, PNOF mice display signs of cardiac function worsening as evidenced by a decrease in cardiac output, which could indicate an early sign of heart failure decompensation.

Impact of early postnatal overnutrition on cardiac mitochondrial dysfunction in adult mice with ischemia/reperfusion

BACKGROUND AND AIMS

Nutritional imbalance at the beginning of life, a critical window period, leads to the development of obesity, overweight, dyslipidemia, diabetes, and cardiovascular disease in adulthood. In this study, the effects and associations of overnutrition during lactation on energy metabolism and oxidative stress in cardiomyocytes of adult male Swiss mice were examined.

METHODS AND RESULTS

Animals were divided into two groups (control and overfed) subjected to baseline and ischemia/reperfusion conditions, forming four groups: control baseline (CBL), control ischemia/reperfusion (CIR), overfed baseline (OBL), and overfed ischemia/reperfusion (OIR). The hearts were analyzed for hemodynamics using the Langendorff technique, mitochondrial energy metabolism using the Oroboros apparatus, ATP production, oxidative stress, and SIRT1, pSTAT3 and STAT3 protein content by Western blotting. Hemodynamic abnormalities in the cardiovascular system were associated with mitochondrial dysfunction, as demonstrated by impaired carbohydrate and fatty acid oxidation capacity, decreased mitochondrial coupling in the OG, and reduced ATP production in the OIR group. Alteration in pSTAT3 and SIRT1 proteins expression in overfed mice reinforce energy metabolism impairment. Lipid and/or protein degradation is altered in the heart of OG, suggesting increased oxidative stress.

CONCLUSION

Overnutrition during lactation associated with heart ischemia leads to molecular cardiac alterations in STAT3 and SIRT1 proteins, compromising energy metabolism via reduced mitochondrial oxidation capacity, ATP production and increased lipid peroxidation.

Swimming training prevents obesity installation and normalizes hypothalamic expressions of GLP1 and leptin receptors in adult offspring born in small litters

OBJECTIVE

Glucagon-like peptide-1 (GLP1) and leptin (Lep) are afferent signals that regulate energy metabolism. Lactational hypernutrition results in hyperphagia and adiposity in adult life, and these events can be prevented by exercise. We evaluated the effects of swimming training on hypothalamic (GLP1-R) and Lep receptor (Lep-R) gene expressions in lactational hypernutrition-induced obesity.

METHODS

On the 3rd postnatal day, the litter sizes of lactating dams were adjusted to small litters (SL; 3 pups/dams) or normal litters (NL; 9 pups/dams). After weaning (21 days), NL and SL male rats were randomly distributed to sedentary (Sed) and exercised (Exe) groups. Exercised mice swam (30 min/3 times/week) for 68 days. Food intake and body weight gain were registered. At 92 days, intraperitoneal glucose and insulin tolerance tests were performed and rats were euthanized at 93 days; adipose tissue depots were weighed, and blood counts and plasma biochemical analyses performed. Hypothalamus were isolated to evaluate Lep-R and GLP1-R gene expressions.

RESULTS

Small litters sedentary rats presented increased body weight gain, adiposity, insulin sensibility and higher fasting values of glucose and triglycerides, besides higher hypothalamic gene expressions of Lep-R and GLP1-R, compared to NLSed animals. SLExe rats did not develop obesity or metabolic abnormalities and Lep-R and GLP1-R hypothalamic gene expressions were normalized.

CONCLUSION

Lactational hypernutrition induces obesity and metabolic dysfunction in adult life, in association with higher hypothalamic expressions of the Lep-R and GLP1-R genes. Exercise prevented obesity and improved metabolic state in SL overnourished rats, and normalized their hypothalamic Lep-R and GLP1-R gene expressions.

Neonatal overfeeding alters the functioning of the mesolimbic dopaminergic circuitry involving changes in DNA methylation and effects on feeding behavior

Mesolimbic dopaminergic circuit is essential for food reward and motivational behaviors and can contribute to weight gain and obesity. Litter reduction is a classical model for studying the effects of neonatal overfeeding and overweight. Litters of Wistar rats were reduced to 4 pups/dam for small litter (SL) and 10 pups/dam for normal litter at postnatal day (PND) 4. Immediately after performing the feeding behavior tests, the animals were sacrificed in PND21 and PND90. The ventral tegmental area (VTA), Nucleus Accumbens Core (NAcC) and Shell (NAcSh) were isolated from frozen brain sections using the Palkovits micropunch technique. RNA and DNA were extracted from these areas, gene expression was measured by RT-qPCR and DNA methylation levels were measured by MSRM-qPCR technique. SL-PND21 animals presented increased expression levels of Tyrosine Hydroxylase and Dopamine Receptor D2 in VTA, decreased expression levels of dopamine active transporter (DAT) in VTA, and higher expression levels of DAT in NAcC. On the other hand, SL-PND90 animals showed decreased expression levels of Dopamine Receptor D1 and higher expression of DAT in NAcSh. These animals also evidenced impaired sensory-specific satiety. In addition, altered promoter methylation was observed at weaning, and remained in adulthood. This work demonstrates that neonatal overfeeding induces disruptions in the mesolimbic dopaminergic circuitry and causes alterations in feeding behavior from weaning to adulthood, suggesting that the neonatal period is critical for the normal development of dopaminergic circuit that impact on feeding behavior.

Postnatal Overfeeding during Lactation Induces Endothelial Dysfunction and Cardiac Insulin Resistance in Adult Rats

Early overnutrition is associated with cardiometabolic alterations in adulthood, likely attributed to reduced insulin sensitivity due to its crucial role in the cardiovascular system. This study aimed to assess the long-term effects of early overnutrition on the development of cardiovascular insulin resistance. An experimental childhood obesity model was established using male Sprague Dawley rats. Rats were organized into litters of 12 pups/mother (L12-Controls) or 3 pups/mother (L3-Overfed) at birth. After weaning, animals from L12 and L3 were housed three per cage and provided ad libitum access to food for 6 months. L3 rats exhibited elevated body weight, along with increased visceral, subcutaneous, and perivascular fat accumulation. However, heart weight at sacrifice was reduced in L3 rats. Furthermore, L3 rats displayed elevated serum levels of glucose, leptin, adiponectin, total lipids, and triglycerides compared to control rats. In the myocardium, overfed rats showed decreased IL-10 mRNA levels and alterations in contractility and heart rate in response to insulin. Similarly, aortic tissue exhibited modified gene expression of TNFα, iNOS, and IL-6. Additionally, L3 aortas exhibited endothelial dysfunction in response to acetylcholine, although insulin-induced relaxation remained unchanged compared to controls. At the molecular level, L3 rats displayed reduced Akt phosphorylation in response to insulin, both in myocardial and aortic tissues, whereas MAPK phosphorylation was elevated solely in the myocardium. Overfeeding during lactation in rats induces endothelial dysfunction and cardiac insulin resistance in adulthood, potentially contributing to the cardiovascular alterations observed in this experimental model.

Postnatal Overfeeding in Rodents Induces a Neurodevelopment Delay and Anxious-like Behaviour Accompanied by Sex- and Brain-Region-Specific Synaptic and Metabolic Changes

Nutritional disturbances during the early postnatal period can have long-lasting effects on neurodevelopment and may be related to behavioural changes at adulthood. While such neuronal connection disruption can contribute to social and behaviour alterations, the dysregulation of the neuroendocrine pathways involved in nutrient-sensing balance may also cause such impairments, although the underlying mechanisms are still unclear. We aimed to evaluate sex-specific neurodevelopmental and behavioural changes upon postnatal overfeeding and determine the potential underpinning mechanisms at the central nervous system level, with a focus on the interconnection between synaptic and neuroendocrine molecular alterations. At postnatal day 3 (PND3) litters were culled to three animals (small litter procedure). Neurodevelopmental tests were conducted at infancy, whereas behavioural tests to assess locomotion, anxiety, and memory were performed at adolescence, together with molecular analysis of the hippocampus, hypothalamus, and prefrontal cortex. At infancy, females presented impaired acquisition of an auditory response, eye opening, olfactory discrimination, and vestibular system development, suggesting that female offspring neurodevelopment/maturation was deeply affected. Male offspring presented a transitory delay in locomotor performance., while both offspring had lower upper limb strength. At adolescence, both sexes presented anxious-like behaviour without alterations in short-term memory retention. Both males and females presented lower NPY1R levels in a region-specific manner. Furthermore, both sexes presented synaptic changes in the hippocampus (lower GABAA in females and higher GABAA levels in males), while, in the prefrontal cortex, similar higher GABAA receptor levels were observed. At the hypothalamus, females presented synaptic changes, namely higher vGLUT1 and PSD95 levels. Thus, we demonstrate that postnatal overfeeding modulates offspring behaviour and dysregulates nutrient-sensing mechanisms such as NPY and GABA in a sex- and brain-region-specific manner.

AMPK Activation as a Protective Mechanism to Restrain Oxidative Stress in the Insulin-Resistant State in Skeletal Muscle of Rat Model of PCOS Subjected to Postnatal Overfeeding

Polycystic ovary syndrome (PCOS) is a common endocrinopathy in women of reproductive age, often associated with obesity and insulin resistance. Childhood obesity is an important predisposing factor for the development of PCOS later in life. Being particularly interested in the interplay between prepubertal obesity and hyperandrogenemia, we investigated the effects of early postnatal overfeeding, accomplished by reducing litter size during the period of suckling, on energy sensing and insulin signaling pathways in the gastrocnemius muscle of a rat model of PCOS-induced by 5α-dihydrotestosterone (DHT). The combination of overfeeding and DHT treatment caused hyperinsulinemia and decreased systemic insulin sensitivity. Early postnatal overfeeding induced defects at critical nodes of the insulin signaling pathway in skeletal muscle, which was associated with reduced glucose uptake in the presence of hyperandrogenemia. In this setting, under a combination of overfeeding and DHT treatment, skeletal muscle switched to mitochondrial β-oxidation of fatty acids, resulting in oxidative stress and inflammation that stimulated AMP-activated protein kinase (AMPK) activity and its downstream targets involved in mitochondrial biogenesis and antioxidant protection. Overall, a combination of overfeeding and hyperandrogenemia resulted in a prooxidative and insulin-resistant state in skeletal muscle. This was accompanied by the activation of AMPK, which could represent a potential therapeutic target in insulin-resistant PCOS patients.

Exposure to Obesogenic Environments during Perinatal Development Modulates Offspring Energy Balance Pathways in Adipose Tissue and Liver of Rodent Models

Obesogenic environments such as Westernized diets, overnutrition, and exposure to glycation during gestation and lactation can alter peripheral neuroendocrine factors in offspring, predisposing for metabolic diseases in adulthood. Thus, we hypothesized that exposure to obesogenic environments during the perinatal period reprograms offspring energy balance mechanisms. Four rat obesogenic models were studied: maternal diet-induced obesity (DIO); early-life obesity induced by postnatal overfeeding; maternal glycation; and postnatal overfeeding combined with maternal glycation. Metabolic parameters, energy expenditure, and storage pathways in visceral adipose tissue (VAT) and the liver were analyzed. Maternal DIO increased VAT lipogenic [NPY receptor-1 (NPY1R), NPY receptor-2 (NPY2R), and ghrelin receptor], but also lipolytic/catabolic mechanisms [dopamine-1 receptor (D1R) and p-AMP-activated protein kinase (AMPK)] in male offspring, while reducing NPY1R in females. Postnatally overfed male animals only exhibited higher NPY2R levels in VAT, while females also presented NPY1R and NPY2R downregulation. Maternal glycation reduces VAT expandability by decreasing NPY2R in overfed animals. Regarding the liver, D1R was decreased in all obesogenic models, while overfeeding induced fat accumulation in both sexes and glycation the inflammatory infiltration. The VAT response to maternal DIO and overfeeding showed a sexual dysmorphism, and exposure to glycotoxins led to a thin-outside-fat-inside phenotype in overfeeding conditions and impaired energy balance, increasing the metabolic risk in adulthood.

Infant Growth Trajectories and Lipid Levels in Adolescence: Evidence From a Chilean Infancy Cohort

Growth in early infancy is hypothesized to affect chronic disease risk factors later in life. To date, most reports draw on European-ancestry cohorts with few repeated observations in early infancy. We investigated the association between infant growth before 6 months and lipid levels in adolescents in a Hispanic/Latino cohort. We characterized infant growth from birth to 5 months in male (n = 311) and female (n = 285) infants from the Santiago Longitudinal Study (1991-1996) using 3 metrics: weight (kg), length (cm), and weight-for-length (g/cm). Superimposition by translation and rotation (SITAR) and latent growth mixture models (LGMMs) were used to estimate the association between infant growth characteristics and lipid levels at age 17 years. We found a positive relationship between the SITAR length velocity parameter before 6 months of age and high-density lipoprotein cholesterol levels in adolescence (11.5, 95% confidence interval; 3.4, 19.5), indicating higher high-density lipoprotein cholesterol levels occurring with faster length growth. The strongest associations from the LGMMs were between higher low-density lipoprotein cholesterol and slower weight-for-length growth, following a pattern of associations between slower growth and adverse lipid profiles. Further research in this window of time can confirm the association between early infant growth as an exposure and adolescent cardiovascular disease risk factors.

AMPK Activation Is Important for the Preservation of Insulin Sensitivity in Visceral, but Not in Subcutaneous Adipose Tissue of Postnatally Overfed Rat Model of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a well-known reproductive syndrome usually associated with obesity, insulin resistance, and hyperinsulinemia. Although the first signs of PCOS begin early in adolescence, it is underexplored whether peripubertal obesity predisposes women to PCOS metabolic disturbances. To highlight that, we examined the impact of postnatal overfeeding-induced obesity, achieved by litter size reduction during the suckling period, on metabolic disturbances associated with visceral and subcutaneous adipose tissue (VAT and SAT) function in the 5α-dihydrotestosterone (5α-DHT)-induced animal model of PCOS. We analyzed markers of insulin signaling, lipid metabolism, and energy sensing in the VAT and SAT. Our results showed that postnatally overfed DHT-treated Wistar rats had increased VAT mass with hypertrophic adipocytes, together with hyperinsulinemia and increased HOMA index. In the VAT of these animals, insulin signaling remained unchanged while lipogenic markers decreased, which was accompanied by increased AMPK activation. In the SAT of the same animals, markers of lipogenesis and lipolysis increased, while the activity of AMPK decreased. Taken together, obtained results showed that postnatal overfeeding predisposes development of PCOS systemic insulin resistance, most likely as a result of worsened metabolic function of SAT, while VAT preserved its tissue insulin sensitivity through increased activity of AMPK.

Hyperphagia and hyperleptinemia induced by low-protein, high-carbohydrate diet is reversed at a later stage of development in rats

This study investigated whether increased food intake after 15 days of low-protein, high-carbohydrate (LPHC) and its normalization in the later period of development change the content of key proteins related to leptin or adiponectin signaling in the hypothalamus. Male rats were divided into five groups: Control groups received a control diet (17% protein, 63% carbohydrate) for 15 (C15) or 45 (C45) days; LPHC groups received an LPHC diet (6% protein, 74% carbohydrate) for 15 (LPHC15) or 45 (LPHC45) days; and Reverse group (R): received LPHC diet for 15 days followed by control diet for another 30 days. The LPHC15 group showed increased adiposity index, leptin level, and adiponectin level, as well as decreased the leptin receptor (ObRb) and pro-opiomelanocortin (POMC) content in the hypothalamus compared with the C15 group. LPHC diet for 45 days or diet reversion (R group) rescued these alterations, except the adiponectin level in LPHC45 rats, which was higher. In summary, LPHC diet reduced hypothalamic leptin action by diminishing ObRb and POMC levels, leading to hyperphagia and adiposity body. Medium-term administration of LPHC diet or reverting to control diet restored the levels of these proteins, thereby improving body lipid mass rearrangement in adulthood.

Fecal Microbiota Transplantation During Lactation Programs the Metabolism of Adult Wistar Rats in a Sex-specific Way

BACKGROUND

The intestinal microbiota is involved in many physiological processes. However, the effects of microbiota in metabolic programming still unknow. We evaluated whether the transplantation of fecal microbiota during early life can program health or disease during adulthood in a model of lean and obese male and female Wistar rats.

METHODS

Parental obesity were induced using a small litter (SL, 3 pups/dam) model. At 90 d old, normal litter (NL, 9 pups/dam) and SL males and females (parents) from different litters were mated: NL male vs. NL female; SL male vs. SL female. After birth, male and female offspring rats were also standardized in normal litters or small litters . From the 10^th until 25^th d of life, the NL and SL male and female offspring received via gavage of a solution containing the diluted feces of the opposite dam (fecal microbiota, M) or saline solution (S). At 90 d of age, biometric and biochemical parameters were assessed.

RESULTS

NLM male rats transplanted with obese microbiota showed increased body weight, and fat pad deposition, hyperinsulinemia, glucose intolerance and dyslipidemia. SLM male rats transplanted with lean microbiota had decreased retroperitoneal and mesenteric fat, triglycerides and VLDL levels and improvement of glucose tolerance. Despite SLM female rats showed higher visceral fat, microbiota transplantation in female rats caused no changes in these parameters compared with control groups.

CONCLUSION

Fecal microbiota transplantation during lactation induces long-term effects on the metabolism of male Wistar rats. However, female rats were resistant to metabolic alterations caused by the treatment.

Litter Size Reduction as a Model of Overfeeding during Lactation and Its Consequences for the Development of Metabolic Diseases in the Offspring

Overfeeding during lactation has a deleterious impact on the baby’s health throughout life. In humans, early overnutrition has been associated with higher susceptibility to obesity and metabolic disorders in childhood and adulthood. In rodents, using a rodent litter size reduction model (small litter) to mimic early overfeeding, the same metabolic profile has been described. Therefore, the rodent small litter model is an efficient tool to investigate the adaptive mechanisms involved in obesogenesis. Besides central and metabolic dysfunctions, studies have pointed to the contribution of the endocrine system to the small litter phenotype. Hormones, especially leptin, insulin, and adrenal hormones, have been associated with satiety, glucose homeostasis, and adipogenesis, while hypothyroidism impairs energy metabolism, favoring obesity. Behavioral modifications, hepatic metabolism changes, and reproductive dysfunctions have also been reported. In this review, we update these findings, highlighting the interaction of early nutrition and the adaptive features of the endocrine system. We also report the sex-related differences and epigenetic mechanisms. This model highlights the intense plasticity during lactation triggering many adaptive responses, which are the basis of the developmental origins of health and disease (DOHaD) concept. Our review demonstrates the complexity of the adaptive mechanisms involved in the obesity phenotype promoted by early overnutrition, reinforcing the necessity of adequate nutritional habits during lactation.

Neonatal leptin antagonism improves metabolic programming of postnatally overnourished mice

BACKGROUND/OBJECTIVES

Alteration of the perinatal nutritional environment is an important risk factor for the development of metabolic diseases in later life. The hormone leptin plays a critical role in growth and development. Previous studies reported that postnatal overnutrition increases leptin secretion during the pre-weaning period. However, a direct link between leptin, neonatal overnutrition, and lifelong metabolic regulation has not been investigated.

METHODS

We used the small litter mouse model combined with neonatal leptin antagonist injections to examine whether attenuating leptin during early life improves lifelong metabolic regulation in postnatally overnourished mice.

RESULTS

Postnatally overnourished mice displayed rapid weight gain during lactation and remained overweight as adults. These mice also showed increased adiposity and perturbations in glucose homeostasis in adulthood. Neonatal administration of a leptin antagonist normalized fat mass and insulin sensitivity in postnatally overnourished mice. These metabolic improvements were associated with enhanced sensitivity of hypothalamic neurons to leptin.

CONCLUSIONS

Early postnatal overnutrition causes metabolic alterations that can be permanently attenuated with the administration of a leptin antagonist during a restricted developmental window.

Curcumin alleviates hepatic steatosis by improving mitochondrial function in postnatal overfed rats and fatty L02 cells through the SIRT3 pathway

Postnatal overfeeding could increase the risk of non-alcoholic fatty liver disease (NAFLD) in adulthood. This study investigated the effects of curcumin (CUR) on hepatic steatosis in postnatal overfed rats and elucidated potential mechanisms in mitochondrial functions. Male rats were adjusted to ten (normal litter, NL) or three (small litter, SL) at postnatal day 3. After weaning, NL rats were fed with normal diet (NL) or a high-fat diet (NH) for 10 weeks. SL rats were fed with normal diet (SL), a high-fat diet (SH), a normal diet supplemented with 2% CUR (SL-CUR) or a high-fat diet supplemented with 2% CUR (SH-CUR). At week 13, compared with NL rats, SL and NH rats showed increased body weight, glucose intolerance, dyslipidemia and hepatic lipid accumulation, and these changes were more obvious in SH rats. The opposite trends were observed in SL-CUR and SH-CUR rats. Moreover, CUR could preserve mitochondrial biogenesis and antioxidant response in postnatal overfed rats, and upregulated the mRNA and protein levels of SIRT3. In vitro, L02 cells were exposed to free fatty acids and/or CUR. CUR decreased the levels of cellular lipids and mitochondrial reactive oxygen species, and increased the mitochondrial DNA copy number and superoxide dismutase activity in fatty L02 cells. However, these effects were blocked after SIRT3 silencing. It was concluded that postnatal overfeeding damaged mitochondrial biogenesis and antioxidant response, and increased hepatic lipids and the severity of high-fat-induced NAFLD, while CUR alleviated hepatic steatosis, at least partially, by enhancing mitochondrial function through SIRT3.

Kefir modulates gut microbiota and reduces DMH-associated colorectal cancer via regulation of intestinal inflammation in adulthood offsprings programmed by neonatal overfeeding

Obesity is associated with chronic inflammation, intestinal dysbiosis, and colorectal cancer risk. The anti-cancer effects of kefir are highlighted. Here, lactating Wistar rats were divided into: Normal litter (NL); Kefir normal litter (KNL); Small litter (SL); Kefir small litter (KSL). The NL and SL groups received 1 mL of water/day; KNL and KSL received kefir milk daily (10⁸ CFU/mL) during lactation. After weaning, the pups continued to receive the same treatments until 60 days. At 67 days old, colorectal carcinogenesis was induced through intraperitoneal injection of 1,2-dimethylhydrazine. At 240 days, visceral adipose tissue was higher in SL compared to NL, KNL, and KSL. Kefir intake was found to suppress the number of tumors in both KNL and KSL groups (-100% and -71.43%; p < 0.01, respectively). IL-1β, IL-6, TNF-α, and NO levels in the colon were higher in the NL and SL compared to the KNL and KSL. The gut microbiota in cecal samples of SL was enriched with Alloprevotella, Acinetobacter, and Bacteroides. In contrast, the cecal contents of KSL and KNL were higher Romboutsia. Thus, neonatal overfeeding leads to greater adiposity, inflammation and number of colon tumors in adulthood. Early-life nutrition based on kefir reverted these alterations.

Preclinical models versus clinical renal ischemia reperfusion injury: A systematic review based on metabolic signatures

Despite decennia of research and numerous successful interventions in the preclinical setting, renal ischemia reperfusion (IR) injury remains a major problem in clinical practice, pointing toward a translational gap. Recently, two clinical studies on renal IR injury (manifested either as acute kidney injury or as delayed graft function) identified metabolic derailment as a key driver of renal IR injury. It was reasoned that these unambiguous metabolic findings enable direct alignment of clinical with preclinical data, thereby providing the opportunity to elaborate potential translational hurdles between preclinical research and the clinical context. A systematic review of studies that reported metabolic data in the context of renal IR was performed according to the PRISMA guidelines. The search (December 2020) identified 35 heterogeneous preclinical studies. The applied methodologies were compared, and metabolic outcomes were semi-quantified and aligned with the clinical data. This review identifies profound methodological challenges, such as the definition of IR injury, the follow-up time, and sampling techniques, as well as shortcomings in the reported metabolic information. In light of these findings, recommendations are provided in order to improve the translatability of preclinical models of renal IR injury.

The model of litter size reduction induces long-term disruption of the gut-brain axis: An explanation for the hyperphagia of Wistar rats of both sexes

The gut microbiota affects the host's metabolic phenotype, impacting health and disease. The gut-brain axis unites the intestine with the centers of hunger and satiety, affecting the eating behavior. Deregulation of this axis can lead to obesity onset. Litter size reduction is a well-studied model for infant obesity because it causes overnutrition and programs for obesity. We hypothesize that animals raised in small litters (SL) have altered circuitry between the intestine and brain, causing hyperphagia. We investigated vagus nerve activity, the expression of c-Fos, brain-derived neurotrophic factor (BDNF), gastrointestinal (GI) hormone receptors, and content of bacterial phyla and short-chain fatty acids (SCFAs) in the feces of adult male and female Wistar rats overfed during lactation. On the 3rd day after birth, litter size was reduced to 3 pups/litter (SL males or SL females) until weaning. Controls had normal litter size (10 pups/litter: 5 males and 5 females). The rats were killed at 5 months of age. The male and female offspring were analyzed separately. The SL group of both sexes showed higher food consumption and body adiposity than the respective controls. SL animals presented dysbiosis (increased Firmicutes, decreased Bacteroidetes) and had increased vagus nerve activity. Only the SL males had decreased hypothalamic GLP-1 receptor expression, while only the SL females had lower acetate and propionate in the feces and higher CCK receptor expression in the hypothalamus. Thus, overfeeding during lactation differentially changes the gut-brain axis, contributing to hyperphagia of the offspring of both sexes.

Pre-Weaning Exposure to Maternal High-Fat Diet Is a Critical Developmental Window for Programming the Metabolic System of Offspring in Mice

BACKGROUND

Maternal high-fat diet (HFD) during pregnancy and lactation exerts long-term effects on the health of offspring. However, the critical developmental window for metabolic programming of maternal exposure to HFD on pathogenesis of obesity in offspring needs further clarification.

MATERIALS & METHODS

Female ICR mice were fed low-fat diet (LFD) or HFD for 8 weeks until delivery. During lactation, half of LFD dams received HFD while the other half of LFD dams and HFD dams maintained the previous diet. Male offspring were weaned at postnatal day 21 (P21) and fed LFD or HFD for 7 weeks. Metabolic parameters, biochemical, and histological indicators of thermogenesis, rectal temperature, and sympathetic nerve tone were detected at P21 and 10 weeks old.

RESULTS

At P21, LH (maternal LFD before delivery but HFD during lactation) and HH (maternal HFD before delivery and during lactation) offspring gained more body weight and showed higher serum glucose and triglyceride levels as compared with LL (maternal LFD before delivery and during lactation), and the metabolic characters were maintained until 10 weeks age when fed with LFD after weaning. However, LH offspring exhibited a greater degree of metabolic abnormalities compared to HH offspring, with increased body weight, as well as lower norepinephrine (NE)-stimulated rectal temperature rise when fed with HFD after weaning. The lower UCP1 levels and HSL phosphorylation in LH offspring further suggested that brown adipose tissue (BAT) thermogenic function was impaired.

CONCLUSION

Exposure to maternal HFD feeding during pre-weaning period alone showed similar detrimental effects on programming metabolic system of offspring as those of both prenatal and early postnatal HFD feeding. Early postnatal stage is a critical time window for metabolic programming and has profound and long-lasting effects on BAT development and function through sympathetic nerve-mediated thermogenesis.

Lean in one way, in obesity another: effects of moderate exercise in brown adipose tissue of early overfed male Wistar rats

BACKGROUND

Early postnatal overfeeding (PO) induces long-term overweight and reduces brown adipose tissue (BAT) thermogenesis. Exercise has been suggested as a possible intervention to increase BAT function. In this study, we investigated chronical effects of moderate-intensity exercise in BAT function in postnatal overfed male Wistar rats METHODS: Litters' delivery was on postnatal-day 0 - PN0. At PN2, litters were adjusted to nine (normal litter - NL) or three pups (small litter - SL) per dam. Animals were weaned on PN21 and in PN30 randomly divided into sedentary (NL-Sed and SL-Sed) or exercised (NL-Exe and SL-Exe), N of 14 litters per group. Exercise protocol started (PN30) with an effort test; training sessions were performed three times weekly at 60% of the VO2max achieved in effort test, until PN80. On PN81, a temperature transponder was implanted beneath the interscapular BAT, whose temperature was assessed in periods of lights-on and -off from PN87 to PN90. Sympathetic nerve activation of BAT was registered at PN90. Animals were euthanized at PN91 and tissues collected RESULTS: PO impaired BAT thermogenesis in lights-on (pPO < 0.0001) and -off (pPO < 0.01). Exercise increased BAT temperature in lights-on (pExe < 0.0001). In NL-Exe, increased BAT activity was associated with higher sympathetic activity (pExe < 0.05), β3-AR (pExe < 0.001), and UCP1 (pExe < 0.001) content. In SL-Exe, increasing BAT thermogenesis is driven by a combination of tissue morphology remodeling (pExe < 0.0001) with greater effect in increasing UCP1 (pExe < 0.001) and increased β3-AR (pExe < 0.001) content.

CONCLUSION

Moderate exercise chronically increased BAT thermogenesis in both, NL and SL groups. In NL-Exe by increasing Sympathetic activity, and in SL-Exe by a combination of increased β3-AR and UCP1 content with morphologic remodeling of BAT. Chronically increasing BAT thermogenesis in obese subjects may lead to higher overall energy expenditure, favoring the reduction of obesity and related comorbidities.

Can breastfeeding affect the rest of our life?

The breastfeeding period is one of the most important critical windows in our development, since milk, our first food after birth, contains several compounds, such as macronutrients, micronutrients, antibodies, growth factors and hormones that benefit human health. Indeed, nutritional, and environmental alterations during lactation, change the composition of breast milk and induce alterations in the child's development, such as obesity, leading to the metabolic dysfunctions, cardiovascular diseases and neurobehavioral disorders. This review is based on experimental animal models, most of them in rodents, and summarizes the impact of an adequate breast milk supply in view of the developmental origins of health and disease (DOHaD) concept, which has been proposed by researchers in the areas of epidemiology and basic science from around the world. Here, experimental advances in understanding the programming during breastfeeding were compiled with the purpose of generating knowledge about the genesis of chronic noncommunicable diseases and to guide the development of public policies to deal with and prevent the problems arising from this phenomenon. This review article is part of the special issue on "Cross talk between periphery and brain".

ω3PUFAs improve hepatic steatosis in postnatal overfed rats and HepG2 cells by inhibiting acetyl-CoA carboxylase

Postnatal overfeeding can lead to persistent increases in hepatic lipid synthesis and the risk of nonalcoholic fatty liver disease (NAFLD) in adulthood. The ω3 polyunsaturated fatty acids (ω3PUFAs) exhibit beneficial effects on NAFLD. Here, we employed a rat model and an in vitro HepG2 cell model to investigate whether fish oil (FO) affects hepatic lipid synthesis due to postnatal overfeeding. Male Sprague-Dawley were divided into litter sizes of three (small litters, SLs) or 10 (normal litters, NLs) on postnatal day 3 and were fed standard chow or FO diet beginning on postnatal week 3 to generate NL, SL, NL-FO, and SL-FO groups. The results indicated that the FO diet reduced the postnatal overfeeding-induced body weight gain and NAFLD characteristics (such as serum and liver triglyceride (TG) and hepatic steatosis). In addition, FO restored the expression of hepatic lipid metabolism-related genes (including SCD1, FASN, CPT1, LPL, ACC, and SREBP-1c) in SL-FO rats. Specifically, the activity and expression pattern of ACC were consistent with SREBP-1c. Furthermore, HepG2 cells were treated with oleic acid (OA), followed by eicosapentenoic acid (EPA), with or without SREBP-1c siRNA. The cellular lipid droplets, TG content, and the expression of ACC (by 75%) and SREBP-1c (by 45%) were increased by OA stimulation (p < .05), which was inhibited by EPA treatment. However, the effect of EPA treatment was abolished when SREBP-1c was silenced. In conclusion, ω3PUFAs-rich diet may be an effective way to reverse the developmental programming of hepatic lipid synthesis, at least partially, by inhibiting ACC through modulating SREBP-1c.

The epigenetic role of breastfeeding in mammary differentiation

Maternal milk consumption can cause changes in the mammary epithelium of the offspring that result in the expression of molecules involved in the induction of differentiation, reducing the risk of developing mammary cancer later in life. We previously showed that animals that maintained a higher intake of maternal milk had a lower incidence of mammary cancer. In the present study, we evaluated one of the possible mechanisms by which the consumption of maternal milk could modify the susceptibility to mammary carcinogenesis. We used Sprague Dawley rats reared in litters of 3 (L3), 8 (L8), or 12 (L12) pups per mother in order to generate a differential consumption of milk. Whole mounts of mammary glands were performed to analyze the changes in morphology. Using real-time polymerase chain reaction (PCR), we analyzed the expression of mammary Pinc, Tbx3, Stat6, and Gata3 genes. We use the real-time methylation-specific polymerase chain reaction method to assess the methylation status of Stat6 and Gata3 CpG sites. Our findings show an increase in the size of the epithelial tree and a smaller number of ducts called terminal end buds in L3 vs. L12. We observed an increased expression of mRNA of Stat6, Gata3, Tbx3, and a lower expression of Pinc in L3 with respect to L12. Stat6 and Gata3 are more methylated in the CpG islands of the promoter analyzed in L12 vs. L3. In conclusion, the increased consumption of maternal milk during the postnatal stage generates epigenetic and morphological changes associated with the differentiation of the mammary gland.

Early postnatal overnutrition impairs VO2max gains with moderate exercise and increase post-exercise muscle damage in adult male rats

Exercise counteracts obesity effects, but information on how early-life obesity may affect long-term adaptation to exercise is lacking. This study investigates the impact of early-life postnatal overfeeding (PO) on animals' adaptation to exercise. Only male Wistar rats were used. On postnatal day (PN) 30, rats from control (NL-9 pups) or PO (SL-3 pups) litters were separated into four groups: NL-sedentary (NL-Se), NL-exercised (NL-Ex), SL-sedentary (SL-Se), and SL-exercised (SL-Ex). Exercised groups performed moderate-intensity exercise, running on a treadmill, from PN30 to PN90. Further experiments were carried out between PN90 and PN92. PO promoted obesity in SL versus NL rats (P < 0.05). Exercise reduced body weight (P < 0.001), body fat (P < 0.01), and improved glucose homeostasis in SL-Ex versus SL-Se. SL-Ex presented lower VO2max (P < 0.01) and higher post-exercise LDH (P < 0.05) compared to NL-Ex rats. Although moderate exercise counteracted obesity in SL rats, early-life overnutrition restricts fitness gains in adulthood, indicating that early obesity may impair animals' adaptation to exercise.

Maternal-infant nutrition and development programming of offspring appetite and obesity

In the United States and Mexico, the obesity epidemic represents a significant public health problem. Although obesity is often attributed to a Western-style, high-fat diet and decreased activity, there is now compelling evidence that this, in part, occurs because of the developmental programming effects resulting from exposure to maternal overnutrition. Human and animal studies demonstrate that maternal obesity and high-fat diet result in an increased risk for childhood and adult obesity. The potential programming effects of obesity have been partly attributed to hyperphagia, which occurs as a result of increased appetite with reduced satiety neuropeptides or neurons. However, depending on maternal nutritional status during the nursing period, the programmed hyperphagia and obesity can be exacerbated or prevented in offspring born to obese mothers. The underlying mechanism of this phenomenon likely involves the plasticity of the appetite regulatory center and thus presents an opportunity to modulate feeding and satiety regulation and break the obesity cycle.

Maternal overweight induced by reduced litter size impairs the behavioral neurodevelopment of offspring

AIMS

We assessed the influence of maternal overweight on the behavioral neurodevelopment of male and female offspring in prepubertal age by reducing the litter size.

MAIN METHODS

To reduce litter size in Wistar rats, the offspring of generation 0 (G0) were culled for 12 pups (6 males and 6 females: normal litter, NL-G1) or 4 pups (2 males and 2 females: small litter, SL-G1). In G1 dams, overweight was characterized, maternal behavior and locomotor activity were assessed. At G2, we quantified the ultrasonic vocalizations in post-natal day 5 (PND5); we evaluated olfactory discrimination in the homing behavior test on PND13; and in PND28-32 (prepubertal age), we performed the following tests: social play behavior, hole board, object recognition, and open field. At the end of the experiments, hippocampus and prefrontal cortex were dissected to quantify the synaptophysin by western blotting.

KEY FINDINGS

Our data demonstrated that a reduction in litter size was able to induce maternal overweight without altering the parameters related to overweight in the offspring. The SL-G2 offspring showed deficits in early social communication, olfactory discrimination, social play behavior, and the exploration of objects, in addition to increasing repetitive and stereotyped movements. There were also changes in the synaptophysin levels in the hippocampus and prefrontal cortex of the offspring from reduced litter dams. In conclusion, maternal overweight caused by litter reduction impairs behavioral neurodevelopment, inducing autism-like symptoms in the offspring.

SIGNIFICANCE

This study alerts the public about the negative consequences of maternal overweight in the descendants.

Effects of moderate intensity endurance training and high-intensity interval training on the reproductive parameters of wistar rats overfed in infancy

Studies indicate that rapid weight gain at critical development stages, such as the lactation period, is associated with the development of obesity, cardiovascular diseases, and diabetes in the long term. In addition to metabolic changes during adulthood, overweight/obesity may influence reproductive function. Human and animal studies suggest that lifestyle changes through exercise and/or controlled diet result in improved semen quality in obese individuals. However, the relationship between exercise volume/intensity and reproductive capacity effects remains inconclusive. The present study aimed to evaluate the effects of moderate intensity endurance training and high-intensity interval training (HIIT) on the reproductive parameters of lactating overfed male Wistar rats. Postnatal overfeeding was induced by applying the litter size reduction method. Forty males Wistar rats were used, divided into four groups: one with control litters (CLs) (10 animals/litter-sedentary) and three with small litters (SLs) (4 animals/litter), divided into sedentary, moderate endurance training, and HIIT. Morphologic, metabolic, and reproductive variables were analyzed. SL sedentary group showed increased body weight, adiposity, and decreased relative weight of the seminal vesicle, prostate, and epididymis as well as changes in the insulin tolerance and oral glucose tolerance tests glycemic tests compared to CL sedentary group. Endurance and HIIT protocols were efficient in improving the glycemic metabolism, central fat accumulation of trained groups and did not affect reproductive parameters. Endurance and HIIT protocols proved to be effective in reversing these metabolic changes without impairing the evaluated reproductive parameters.

Mapping of Microglial Brain Region, Sex and Age Heterogeneity in Obesity

The prevalence of obesity has increased rapidly in recent years and has put a huge burden on healthcare worldwide. Obesity is associated with an increased risk for many comorbidities, such as cardiovascular diseases, type 2 diabetes and hypertension. The hypothalamus is a key brain region involved in the regulation of food intake and energy expenditure. Research on experimental animals has shown neuronal loss, as well as microglial activation in the hypothalamus, due to dietary-induced obesity. Microglia, the resident immune cells in the brain, are responsible for maintaining the brain homeostasis and, thus, providing an optimal environment for neuronal function. Interestingly, in obesity, microglial cells not only get activated in the hypothalamus but in other brain regions as well. Obesity is also highly associated with changes in hippocampal function, which could ultimately result in cognitive decline and dementia. Moreover, changes have also been reported in the striatum and cortex. Microglial heterogeneity is still poorly understood, not only in the context of brain region but, also, age and sex. This review will provide an overview of the currently available data on the phenotypic differences of microglial innate immunity in obesity, dependent on brain region, sex and age.

Temporary effects of neonatal overfeeding on homeostatic control of food intake involve alterations in POMC promoter methylation in male rats

A small litter (SL) model was used to determine how neonatal overfeeding affects the homeostatic control of food intake in male rats at weaning and postnatal day (PND) 90. At PND4, litters were reduced to small (4 pups/dam) or normal (10 pups/dam) litters. At weaning, SL rats showed higher body weight and characteristic features of the metabolic syndrome. Gene expression of pro-opiomelanocortin (POMC), cocaine and amphetamine regulated transcript, neuropeptide Y (NPY) and leptin and ghrelin (GHSR) receptors were increased and POMC promoter was hypomethylated in arcuate nucleus, indicating that the early development of obesity may involve the GHSR/NPY system and changes in POMC methylation state. At PND90, body weight, metabolic parameters and gene expression were restored; however, POMC methylation state remained altered. This work provides insight into the effects of neonatal overfeeding, showing the importance of developmental plasticity in restoring early changes in central pathways involved in metabolic programming.

Influence of gestational exercise practice and litter size reduction on maternal care

Mother-pup interactions are extremely important to offspring survival and growth. The goal of this study was to evaluate the influence of prenatal and neonatal interventions on maternal care, analyzing the effect of maternal exercise, as a healthy intervention, and also the litter size reduction, a model that has been widely used to study early overfeeding in rats. Female Wistar rats were divided into 1) sedentary, and 2) swimming exercise for four weeks, starting one week before mating (5 days/week, 30 min/session). One day after birth, the litter was culled to 8 pups (normal) or 3 pups (small) per dam, yielding control and overfed subgroups for each maternal group, respectively. From postnatal days 2-9 the litter was observed 5 periods a day, to evaluate maternal behavior. Litter reduction caused important alterations in maternal behavior, reducing the total time out of the nest and increasing the frequency of maternal care and lactation in several observation periods, justifying the increased pup's weight gain already demonstrated by this animal model. The practice of maternal exercise did not prevent, but cause the less intensive frequency of non-maternal behavior and lactation in arched-back position, induced by the reduction of litter size. These data demonstrated that small litter size altered maternal behavior, and gestational exercise does not influence significantly these changes.

Neonatal overfeeding during lactation rapidly and permanently misaligns the hepatic circadian rhythm and programmes adult NAFLD

Childhood obesity is a strong risk factor for adult obesity, type 2 diabetes, and cardiovascular disease. The mechanisms that link early adiposity with late-onset chronic diseases are poorly characterised. We developed a mouse model of early adiposity through litter size reduction. Mice reared in small litters (SLs) developed obesity, insulin resistance, and hepatic steatosis during adulthood. The liver played a major role in the development of the disease.

OBJECTIVE

To gain insight into the molecular mechanisms that link early development and childhood obesity with adult hepatic steatosis and insulin resistance.

METHODS

We analysed the hepatic transcriptome (Affymetrix) of control and SL mice to uncover potential pathways involved in the long-term programming of disease in our model.

RESULTS

The circadian rhythm was the most significantly deregulated Gene Ontology term in the liver of adult SL mice. Several core clock genes, such as period 1-3 and cryptochrome 1-2, were altered in two-week-old SL mice and remained altered throughout their life course until they reached 4-6 months of age. Defective circadian rhythm was restricted to the periphery since the expression of clock genes in the hypothalamus, the central pacemaker, was normal. The period-cryptochrome genes were primarily entrained by dietary signals. Hence, restricting food availability during the light cycle only uncoupled the central rhythm from the peripheral and completely normalised hepatic triglyceride content in adult SL mice. This effect was accompanied by better re-alignment of the hepatic period genes, suggesting that they might have played a causal role in mediating hepatic steatosis in the adult SL mice. Functional downregulation of Per2 in hepatocytes in vitro confirmed that the period genes regulated lipid-related genes in part through peroxisome proliferator-activated receptor alpha (Ppara).

CONCLUSIONS

The hepatic circadian rhythm matures during early development, from birth to postnatal day 30. Hence, nutritional challenges during early life may misalign the hepatic circadian rhythm and secondarily lead to metabolic derangements. Specific time-restricted feeding interventions improve metabolic health in the context of childhood obesity by partially re-aligning the peripheral circadian rhythm.

Postnatal overfeeding induces hepatic microRNA-221 expression and impairs the PI3K/AKT pathway in adult male rats

BACKGROUND

Increasing evidence suggests that postnatal overfeeding induces childhood obesity, which is strongly associated with metabolic syndrome. Insulin resistance is a risk factor for metabolic syndrome. MicroRNA-221 (miR-221) is involved in the development of obesity and has been reported to negatively regulate insulin sensitivity. However, the underlying mechanism remains unclear.

METHODS

Rats raised in small litters (SLs, three pups/dam, n = 10) and normal litters (NLs, 10 pups/dam, n = 10) were used to model early postnatal overfeeding and act as controls, respectively. miR-221 and proteins related to the phosphoinositide 3-kinases (PI3K)/protein kinase B (AKT) pathway were assessed in the liver.

RESULTS

Early postnatal overfeeding significantly increased body weight, visceral fat index, blood glucose, serum triglycerides, and the homeostasis model assessment of insulin resistance at 9 weeks. Real-time polymerase chain reaction (PCR) and western blot analysis revealed that postnatal overfeeding induced insulin receptor and insulin receptor substrate 2 expression, but decreased PI3K and AKT phosphorylation in the liver. Quantitative real-time PCR showed that hepatic miR-221 was significantly overexpressed in the SL group.

CONCLUSIONS

These results indicate that postnatal overfeeding induces hepatic miR-221 overexpression and impairs the PI3K/AKT signal pathway, which may cause insulin resistance.

IMPACT

We first report postnatal overfeeding induces hepatic miR-221 expression. Postnatal overfeeding impairs PI3K/AKT pathway in the liver of adult rats. Postnatal overfeeding induces obesity and high blood glucose. Avoidance of overfeeding during early postnatal life may prevent obesity and T2DM.

Programming of Cardiovascular Dysfunction by Postnatal Overfeeding in Rodents

Nutritional environment in the perinatal period has a great influence on health and diseases in adulthood. In rodents, litter size reduction reproduces the effects of postnatal overnutrition in infants and reveals that postnatal overfeeding (PNOF) not only permanently increases body weight but also affects the cardiovascular function in the short- and long-term. In addition to increased adiposity, the metabolic status of PNOF rodents is altered, with increased plasma insulin and leptin levels, associated with resistance to these hormones, changed profiles and levels of circulating lipids. PNOF animals present elevated arterial blood pressure with altered vascular responsiveness to vasoactive substances. The hearts of overfed rodents exhibit hypertrophy and elevated collagen content. PNOF also induces a disturbance of cardiac mitochondrial respiration and produces an imbalance between oxidants and antioxidants. A modification of the expression of crucial genes and epigenetic alterations is reported in hearts of PNOF animals. In vivo, a decreased ventricular contractile function is observed during adulthood in PNOF hearts. All these alterations ultimately lead to an increased sensitivity to cardiac pathologic challenges such as ischemia-reperfusion injury. Nevertheless, caloric restriction and physical exercise were shown to improve PNOF-induced cardiac dysfunction and metabolic abnormalities, drawing a path to the potential therapeutic correction of early nutritional programming.

Early metformin treatment improves pancreatic function and prevents metabolic dysfunction in early overfeeding male rats at adulthood

NEW FINDINGS

What is the central question of this study? Studies reported the efficacy of metformin as a promising drug for preventing or treating of metabolic diseases. Nutrient stresses during neonatal life increase long-term risk for cardiometabolic diseases. Can early metformin treatment prevent the malprogramming effects of early overfeeding? What is the main finding and its importance? Neonatal metformin treatment prevented early overfeeding-induced metabolic dysfunction in adult rats. Inhibition of early hyperinsulinaemia and adult hyperphagia might be associated with decreased metabolic disease risk in these animals. Therefore, interventions during infant development offer a key area for future research to identify potential strategies to prevent the long-term metabolic diseases. We suggest that metformin is a potential tool for intervention.

ABSTRACT

Given the need for studies investigating the possible long-term effects of metformin use at crucial stages of development, and taking into account the concept of metabolic programming, the present work aimed to evaluate whether early metformin treatment might program rats to resist the development of adult metabolic dysfunctions caused by overnutrition during the neonatal suckling phase. Wistar rats raised in small litters (SLs, three pups per dam) and normal litters (NLs, nine pups per dam) were used as models of early overfeeding and normal feeding, respectively. During the first 12 days of suckling, animals from SL and NL groups received metformin, whereas the controls received saline injections. Food intake and body weight were monitored from weaning until 90 days of age, when biometric and biochemical parameters were assessed. The metformin treatment decreased insulin concentrations in pups from SL groups, and as adults, these animals showed improvements in glucose tolerance, insulin sensitivity, body weight gain, white fat pad stores and food intake. Low-glucose insulinotrophic effects were observed in pancreatic islets from both NL and SL groups. These results indicate that early postnatal treatment with metformin inhibits early overfeeding-induced metabolic dysfunctions in adult rats.

Impact of experimental obesity on diaphragm structure, function, and bioenergetics

Obesity is associated with bioenergetic dysfunction of peripheral muscles; however, little is known regarding the impact of obesity on the diaphragm. We hypothesized that obesity would be associated with diaphragm dysfunction attributable to mitochondrial oxygen consumption and structural and ultrastructural changes. Wistar rat litters were culled to 3 pups to induce early postnatal overfeeding and consequent obesity. Control animals were obtained from unculled litters. From postnatal day 150, diaphragm ultrasound, computed tomography, high-resolution respirometry, immunohistochemical, biomolecular, and ultrastructural histological analyses were performed. The diaphragms of obese animals, compared with those of controls, presented changes in morphology as increased thickening fraction, diaphragm excursion, and diaphragm dome height, as well as increased mitochondrial respiratory capacity coupled to ATP synthesis and maximal respiratory capacity. Fatty acid synthase gene expression was also higher in obese animals, suggesting a source of energy for the respiratory chain. Myosin heavy chain-IIA was increased, indicating shift from glycolytic toward oxidative muscle fiber profile. Diaphragm tissue also exhibited ultrastructural changes, such as compact, round, and swollen mitochondria with fainter cristae and more lysosomal bodies. Dynamin-1 expression in the diaphragm was reduced in obese rats, suggesting decreased mitochondrial fission. Furthermore, gene expressions of peroxisome γ proliferator-activated receptor coactivator-1α and superoxide dismutase-2 were lower in obese animals than in controls, which may indicate a predisposition to oxidative injury. In conclusion, in the obesity model used herein, muscle fiber phenotype was altered in a manner likely associated with increased mitochondrial respiratory capability, suggesting respiratory adaptation to increased metabolic demand.NEW & NOTEWORTHY Obesity has been associated with peripheral muscle dysfunction; however, little is known about its impact on the diaphragm. In the current study, we found high oxygen consumption in diaphragm tissue and changes in muscle fiber phenotypes toward a more oxidative profile in experimental obesity.

Size Does Matter: Litter Size Strongly Determines Adult Metabolism in Rodents

In this essay, we highlight how litter size in rodents is a strong determinant of neonatal growth and long-term metabolic health. Based on these effects, we strongly advise that scientific articles that utilize rodent models for obesity and metabolic research should include information on the litter sizes in the study to increase the data transparency of such reports.

Extracellular vesicles of MSCs and cardiomyoblasts are vehicles for lipid mediators

Recent works reported the relevance of cellular exosomes in the evolution of different pathologies. However, most of these studies focused on the ability of exosomes to convey mi-RNA from cell to cell. The level of knowledge concerning the transport of lipid mediators by these nanovesicles is more than fragmented. The role of lipid mediators in the inflammatory signaling is fairly well described, in particular concerning the derivatives of the arachidonic acid (AA), called eicosanoïds or lipid mediators. The aim of the present work was to study the transport of these lipids within the extracellular vesicles of rat bone marrow mesenchymal stem cells (BM-MSC) and the cardiomyoblast cell line H9c2. We were able to characterize, for the first time, complete profiles of oxilipins within these nanovesicles. We studied also the impact on these profiles, of the polyunsaturated fatty acids (PUFAs) know to be precursors of the inflammatory signaling molecules (AA, eicosapentaenoic acid EPA and Docosahexaenoic acid DHA), at physiological concentrations. By growing the progenitor cells under PUFAs supplementation, we provide a comprehensive assessment of the beneficial effect of ω-3 PUFA therapy. Actually, our results tend to support the resolving role of the inflammation that stromal cell-derived extracellular vesicles can have within the cardiac microenvironment.

Early overnutrition sensitizes the growth hormone axis to the impact of diet-induced obesity via sex-divergent mechanisms

In addition to its essential role in the physiological control of longitudinal growth, growth-hormone (GH) is endowed with relevant metabolic functions, including anabolic actions in muscle, lipolysis in adipose-tissue and glycemic modulation. Adult obesity is known to negatively impact GH-axis, thereby promoting a vicious circle that may contribute to the exacerbation of the metabolic complications of overweight. Yet, to what extent early-overnutrition sensitizes the somatotropic-axis to the deleterious effects of obesity remains largely unexplored. Using a rat-model of sequential exposure to obesogenic insults, namely postnatal-overfeeding during lactation and high-fat diet (HFD) after weaning, we evaluated in both sexes the individual and combined impact of these nutritional challenges upon key elements of the somatotropic-axis. While feeding HFD per se had a modest impact on the adult GH-axis, early overnutrition had durable effects on key elements of the somatotropic-system, which were sexually different, with a significant inhibition of pituitary gene expression of GH-releasing hormone-receptor (GHRH-R) and somatostatin receptor-5 (SST5) in males, but an increase in pituitary GHRH-R, SST2, SST5, GH secretagogue-receptor (GHS-R) and ghrelin expression in females. Notably, early-overnutrition sensitized the GH-axis to the deleterious impact of HFD, with a significant suppression of pituitary GH expression in both sexes and lowering of circulating GH levels in females. Yet, despite their similar metabolic perturbations, males and females displayed rather distinct alterations of key somatotropic-regulators/ mediators. Our data document a synergistic effect of postnatal-overnutrition on the detrimental impact of HFD-induced obesity on key elements of the adult GH-axis, which is conducted via mechanisms that are sexually-divergent.

Characterization of a Swine Model of Birth Weight and Neonatal Nutrient Restriction

Background

Evidence indicates that birth weight and neonatal nutrition have lifelong effects. Animal models are required to improve our understanding of these factors.

Objectives

We aimed to develop and validate a swine model of birth weight and neonatal undernutrition.

Methods

At birth, a total of 112 piglets were identified as low (LBW; 1.22 ± 0.28 kg SEM) or normal birth weight (NBW; 1.70 ± 0.27 kg). From day 3 to weaning (day 28), piglets received normal nutrition (NN) or restricted nutrition (RN) via intermittent suckling, where piglets were isolated from the sow for 6 h/d. After weaning, pigs were fed a common diet for 28 d. Body weight (BW) was determined for the duration of the study. On days 28 and 56, empty carcass, viscera, and individual organ weights were determined in 8 pigs/treatment.

Results

LBW pigs remained smaller than NBW pigs, regardless of nutrient restriction (P &lt; 0.05). Within birth weight category, RN reduced BW by day 7 after birth, which was maintained until weaning (P &lt; 0.05); however, at 7 d postweaning there was no difference in BW due to RN (P &gt; 0.05). At weaning, empty carcass, viscera, heart, liver, and lung weights were lower in LBW than in NBW pigs, whereas empty carcass, heart, small intestine, liver, kidneys, lung, and spleen weights were lower in RN than in NN pigs (P &lt; 0.05). Brain weight was highest in NBW-NN and lowest in NBW-RN, with LBW intermediate, regardless of nutrient restriction (P &lt; 0.05). Postweaning, LBW had lower empty carcass, viscera, heart, stomach, large intestine, liver, and kidney weights than NBW, whereas RN had a higher small intestine weight than NN (P &lt; 0.05).

Conclusions

Intermittent suckling is an effective means of inducing nutrient restriction in a swine model.

Overweight during lactation and its implications for biometric, nutritional and cardiovascular parameters of young and adult male and female rats

Litter size reduction can induce early overnourishment, being an attractive experimental model to study short- and long-term consequences of childhood obesity. Epidemiological data indicate sex differences regarding cardiometabolic disorders and hypertrophic cardiomyopathy. The present study aimed to describe biometric, nutritional and cardiovascular changes related to neonatal overweight promoted by litter size reduction in young and adult Wistar rats of both sexes. Litter adjustment to eight or four pups/mother (1:1 male-to-female ratio) gave, respectively, control and overweight groups. Body mass, food intake, haemodynamic and echocardiographic parameters and cardiorespiratory capacity were evaluated at postnatal days 30 and 150. Diminished litters were correlated with higher body mass and weight gain (12 %) during lactation, validating the experimental model of neonatal overweight. Soon after weaning male (16 %) and female (25 %) offspring of these litters presented a lower food intake than their respective control, without differences in body mass. Adult males from reduced litters presented higher abdominal circumference (7 %), systolic blood pressure (10 %), interventricular septum thickness (15 %) and relative wall thickness (15 %) compared with their respective control. Rats' performance on the maximal effort ergometer test was not affected by neonatal overweight. Data suggest the occurrence of catch-down growth and hypophagia in male and female rats submitted to neonatal overweight. However, only male rats presented haemodynamic and cardiac structural changes. These findings are crucial to personalised/gender medicine.

Long-term effects of early overfeeding and food restriction during puberty on cardiac remodeling in adult rats

Nutritional disorders during the perinatal period cause cardiometabolic dysfunction, which is observable in the early overfeeding (EO) experimental model. Therefore, severe caloric restriction has the potential of affecting homeostasis through the same epigenetic mechanisms, and its effects need elucidation. This work aims to determine the impact of food restriction (FR) during puberty in early overfed obese and non-obese animals in adult life. Three days after delivery (PN3), Wistar rats were separated into two groups: normal litter (NL; 9 pups) and small litter (SL; 3 pups). At PN30, some offspring were subjected to FR (50%) until PN60, or maintained with free access to standard chow. NL and SL animals submitted to food restriction (NLFR and SLFR groups) were kept in recovery with free access to standard chow from PN60 until PN120. Body weight and food intake were monitored throughout the experimental period. At PN120 cardiovascular parameters were analyzed and the animals were euthanized for sample collection. SLNF and SLFR offspring were overweight and had increased adiposity. Differences in blood pressure were observed only between obese and non-obese animals. Obese and FR animals have cardiac remodeling showing cardiomyocyte hypertrophy and the presence of interstitial and perivascular fibrosis. FR animals also show increased expression of AT1 and AT2 receptors and of total ERK and p-ERK. The present study showed that EO leads to the obese phenotype and cardiovascular disruptions. Interestingly, we demonstrated that severe FR during puberty leads to cardiac remodeling.

Renal Programming by Transient Postnatal Overfeeding: The Role of Senescence Pathways

Background

Early nutrition influences the risk of chronic kidney diseases (CKDs) development in adulthood. Mechanisms underlying the early programming of altered renal function remain incompletely understood. This study aims at characterizing the role of cell senescence pathways in early programming of CKD after transient postnatal overfeeding.

Materials and Methods

Reduced litters of 3 mice pups and standard litters of 9 mice pups were obtained to induce overfed animals during lactation and control animals, respectively. Animals were sacrificed at 24 days (weaning) or at 7 months of life (adulthood). Body weight, blood pressure, kidney weight, and glomerular count were assessed in both groups. Senescence pathways were investigated using β-Galactosidase staining and Western blotting of P16, P21, P53, P-Rb/Rb, and Sirtuin 1 (Sirt1) proteins.

Results

Early overfed animals had a higher body weight, a higher blood pressure at adulthood, and a higher glomerular number endowment compared to the control group. A higher β-Galactosidase activity, a significant increase in P53 protein expression (p = 0.0045) and a significant decrease in P-Rb/Rb ratio (p = 0.02), were observed at weaning in animals who underwent early postnatal overfeeding. Protein expression of Sirt1, a protective factor against accelerated stress-induced senescence, was significantly decreased (p = 0.03) at weaning in early overfed animals.

Conclusion

Early postnatal overfeeding by litter size reduction is associated with increased expression of factors involved in cellular senescence pathways, and decreased expression of Sirt 1 in the mouse kidney at weaning. These alterations may contribute to CKD programming after early postnatal overfeeding.

Fluoxetine administration in juvenile overfed rats improves hypothalamic mitochondrial respiration and REDOX status and induces mitochondrial biogenesis transcriptional expression

Nutritional imbalance in early life may disrupt the hypothalamic control of energy homeostasis and increase the risk of metabolic disease. The hypothalamic serotonin (5-hydroxytryptamine; 5-HT) system based in the hypothalamus plays an important role in the homeostatic control of energy balance, however the mechanisms underlying the regulation of energy metabolism by 5-HT remain poorly described. Several crucial mitochondrial functions are altered by mitochondrial stress. Adaptations to this stress include changes in mitochondrial multiplication (i.e, mitochondrial biogenesis). Due to the scarcity of evidence regarding the effects of serotonin reuptake inhibitors (SSRI) such as fluoxetine (FLX) on mitochondrial function, we sought to investigate the potential contribution of FLX on changes in mitochondrial function and biogenesis occurring in overfed rats. Using a neonatal overfeeding model, male Wistar rats were divided into 4 groups between 39 and 59 days of age based on nutrition and FLX administration: normofed + vehicle (NV), normofed + FLX (NF), overfed + vehicle (OV) and overfed + FLX (OF). We found that neonatal overfeeding impaired mitochondrial respiration and increased oxidative stress biomarkers in the hypothalamus. FLX administration in overfed rats reestablished mitochondrial oxygen consumption, increased mitochondrial uncoupling protein 2 (Ucp2) expression, reduced total reactive species (RS) production and oxidative stress biomarkers, and up-regulated mitochondrial biogenesis-related genes. Taken together our results suggest that FLX administration in overfed rats improves mitochondrial respiratory chain activity and oxidative balance and increases the transcription of genes employed in mitochondrial biogenesis favoring mitochondrial energy efficiency in response to early nutritional imbalance.

Maternal Nicotinamide Riboside Enhances Postpartum Weight Loss, Juvenile Offspring Development, and Neurogenesis of Adult Offspring

Conditions of metabolic stress dysregulate the NAD metabolome. By restoring NAD, nicotinamide riboside (NR) provides resistance to such conditions. We tested the hypotheses that postpartum might dysregulate maternal NAD and that increasing systemic NAD with NR might benefit mothers and offspring. In postpartum mothers, the liver NAD metabolome is depressed while blood increases circulation of NAD metabolites to enable a >20-fold increase in mammary NAD⁺ and NADP⁺. Lactation and NR synergize in stimulating prolactin synthesis and mammary biosynthetic programs. NR supplementation of new mothers increases lactation and nursing behaviors and stimulates maternal transmission of macronutrients, micronutrients, and BDNF into milk. Pups of NR-supplemented mothers are advantaged in glycemic control, size at weaning, and synaptic pruning. Adult offspring of mothers supplemented during nursing retain advantages in physical performance, anti-anxiety, spatial memory, delayed onset of behavioral immobility, and promotion of adult hippocampal neurogenesis. Thus, postgestational maternal micronutrition confers lasting advantages to offspring.

Differential effects of leptin administration on feeding and HPT axis function in early-life overfed adult rats

Early-life overfeeding (OF) disrupts neuroendocrine systems, energy homeostasis and food intake regulation inducing overeating and overweight in adults. Adult rats raised in small litters during lactation, display hyperphagia and overweight since weaning and exhibit a decrease in thyrotropin-releasing hormone (TRH) mRNA expression in hypothalamic paraventricular nucleus (PVN). This is counterintuitive because TRH expression should increase to activate the hypothalamic-pituitary-thyroid (HPT) axis and promote energy expenditure, thus, HPT axis seems inhibited in OF rats. Leptin, an adipocyte-synthesized hormone that stimulates hypothalamic TRH expression, enhances both TRH anorectic effects and HPT axis-induced metabolic rate. To evaluate hypothalamic resistance to the anorectic and HPT axis stimulatory actions of leptin, we injected leptin i.p. to ad libitum fed and to 48-h fasted adult control (reared in normal litters) and to small-litter reared (OF) male Wistar rats. Findings showed that HPT axis was still responsive to leptin, since PVN TRH mRNA levels, median eminence TRH release and T4 serum concentration increased in both, ad libitum and fasted OF rats after leptin administrations. Leptin was ineffective to reduce feeding of OF animals. By comparing leptin receptor (ObRb) expression changes between arcuate and PVN nuclei, we observed that arcuate ObRb was not modified in response to leptin administrations in OF rats, likely accounting for the differential effects in feeding and HPT axis function. Nevertheless, ObRb expression was modified by leptin in the PVN of OF rats to the same extent as controls; this supports the hormone's role as a therapeutic agent for early onset obesity in adults.

Overfeeding During Lactation in Rats is Associated with Cardiovascular Insulin Resistance in the Short-Term

Childhood obesity is associated with metabolic and cardiovascular comorbidities. The development of these alterations may have its origin in early life stages such as the lactation period through metabolic programming. Insulin resistance is a common complication in obese patients and may be responsible for the cardiovascular alterations associated with this condition. This study analyzed the development of cardiovascular insulin resistance in a rat model of childhood overweight induced by overfeeding during the lactation period. On birth day, litters were divided into twelve (L12) or three pups per mother (L3). Overfed rats showed a lower increase in myocardial contractility in response to insulin perfusion and a reduced insulin-induced vasodilation, suggesting a state of cardiovascular insulin resistance. Vascular insulin resistance was due to decreased activation of phosphoinositide 3-kinase (PI3K)/Akt pathway, whereas cardiac insulin resistance was associated with mitogen-activated protein kinase (MAPK) hyperactivity. Early overfeeding was also associated with a proinflammatory and pro-oxidant state; endothelial dysfunction; decreased release of nitrites and nitrates; and decreased gene expression of insulin receptor (IR), glucose transporter-4 (GLUT-4), and endothelial nitric oxide synthase (eNOS) in response to insulin. In conclusion, overweight induced by lactational overnutrition in rat pups is associated with cardiovascular insulin resistance that could be related to the cardiovascular alterations associated with this condition.

Treatment with cinnamaldehyde reduces the visceral adiposity and regulates lipid metabolism, autophagy and endoplasmic reticulum stress in the liver of a rat model of early obesity

Nutrition at early stages of life contributes to the alarming incidence of childhood obesity, insulin resistance and hepatoesteatosis. Cinnamaldehyde, major component of cinnamon, increases insulin sensitivity and modulates adiposity and lipid metabolism. The aim of this study was to analyze the impact of cinnamaldehyde treatment during adolescence in a rat model of early obesity. Litter size reduction was used to induce overfeeding and early obesity. At postnatal day 30 (adolescence), the male Wistar rats received cinnamaldehyde by gavage (40 mg/kg of body weight/day) for 29 days and were studied at the end of treatment at 60 days old or 4 months thereafter (180 days old). At 60 days of age, the treatment with cinnamaldehyde promoted reduced visceral adiposity, serum triacylglycerol, and attenuation of energy efficiency and insulin resistance. In the liver, it reduced lipid synthesis, stimulated autophagy and reduced ER stress. At 180 days of age, animals treated with cinnamaldehyde during the adolescence exhibited normalization of visceral adiposity and energy efficiency, and attenuation of hyperphagia, serum hypertriglyceridemia and hepatic triacylglycerol content, with molecular markers indicative of reduced hepatic synthesis. However, the beneficial effect observed at 60 days of age on glucose homeostasis, autophagy and ER stress was lost. Therefore, the cinnamaldehyde supplementation during the adolescence has short- and long-term metabolic beneficial effects, highlighting its potential as an adjuvant in the treatment of early obesity.