Patricia Cristina Lisboa

Maternal low-protein diet during lactation programmes body composition and glucose homeostasis in the adult rat offspring

Previously we have reported that maternal malnutrition during lactation programmes body weight and thyroid function in the adult offspring. In the present study we evaluated the effect of maternal protein restriction during lactation upon body composition and hormones related to glucose homeostasis in adult rats. During lactation, Wistar lactating rats and their pups were divided into two experimental groups: control (fed a normal diet; 23% protein) and protein-restricted (PR; fed a diet containing 8% protein). At weaning, offspring received a normal diet until they were 180 d old. Body weight (BW) and food intake were monitored. Serum, adrenal glands, visceral fat mass (VFM) and carcasses were collected. PR rats showed lower BW (-13%; P < 0.05), VFM (-33%; P < 0.05), total body fat (-33%; P < 0.05), serum glucose (-7%; P < 0.05), serum insulin (-26%, P < 0.05), homeostasis model assessment index (-20%), but higher total adrenal catecholamine content (+90%; P < 0.05) and serum corticosterone concentration (+51%; P < 0.05). No change was observed in food intake, protein mass or total body water. The lower BW of PR rats is due to a reduction of white fat tissue, probably caused by an increase in lipolysis or impairment of lipogenesis; both effects could be related to higher catecholaminergic status, as well as to hypoinsulinaemia. To conclude, changes in key hormones which control intermediary metabolism are programmed by maternal protein restriction during lactation, resulting in BW alterations in adult rats.

Maternal high‐fat diet induces obesity and adrenal and thyroid dysfunction in male rat offspring at weaning

•  Perinatal maternal high‐fat diet changes milk composition, resulting in obesity and hyperglycaemia in male offspring at weaning. •  Offspring obesity is associated with hyperleptinaemia and changes in the central leptin signalling pathway in the hypothalamic arcuate nucleus. •  Maternal high‐fat diet increased adrenal catecholamines in offspring but reduced liver and adipose tissue adrenoreceptors, thereby contributing to increased adiposity in these animals. •  Early obesity and hyperleptinaemia in offspring may have a stimulatory effect on the hypothalamus–pituitary–thyroid axis as an adaptive response to the positive energy balance. •  Both catecholamines and thyroid hormones may impact cardiovascular function, thereby contributing to the development of hypertension.

Postnatal early overnutrition changes the leptin signalling pathway in the hypothalamic–pituitary–thyroid axis of young and adult rats

Postnatal early overnutrition (EO) is a risk factor for obesity in adult life. Rats raised in a small litter can develop hyperinsulinaemia, hyperphagia, hyperleptinaemia and hypertension as adults. Since leptin regulates the hypothalamic–pituitary–thyroid axis and the metabolism of thyroid hormones, we studied the leptin signalling pathway in pituitary and thyroid glands of the postnatal EO model. To induce EO, at the third day of lactation the litter size was reduced to three pups per litter (SL group). In control litters (NL group), the litter size was adjusted to 10 pups per litter. Body weight and food intake were monitored. Rat offspring were killed at 21 (weaning) and 180 days old (adulthood). Plasma thyroid hormones, thyroid‐stimulating hormone (TSH) and leptin were measured by radioimmunoassay. Proteins of the leptin signalling pathway were analysed by Western blotting. Body weight of offspring in the SL group was higher from the seventh day of lactation (+33%, P < 0.05) until 180 days old (+18%, P < 0.05). Offspring in the SL group showed higher visceral fat mass at 21 and 180 days old (+176 and +52%, respectively, P < 0.05), but plasma leptin was higher only at 21 days (+88%, P < 0.05). The SL offspring showed higher plasma TSH, 3,5,3′‐triiodothronine (T3) and thyroxine (T4) at 21 days (+60, +91 and +68%, respectively, P < 0.05), while the opposite was observed at 180 days regarding thyroid hormones (T3, −10%; and T4, −30%, P < 0.05), with no difference in TSH levels. In hypothalamus, no change was observed in the leptin signalling pathway at 21 days. However, lower janus thyrosine kinase 2 (JAK2) and phosphorilated‐signal transducer and activator of transcription‐3 (p‐STAT3) content were detected in adulthood. In pituitary, the SL group presented higher leptin receptors (Ob‐R), JAK2 and p‐STAT3 content at 21 days and lower JAK2 and STAT3 content at 180 days old. In contrast, in thyroid, the Ob‐R expression was lower in young SL rats, while the adult SL group presented higher Ob‐R and JAK2 content. We showed that postnatal EO induces short‐ and long‐term effects upon the hypothalamic–pituitary–thyroid axis. These changes may help to explain future development of metabolic and endocrine dysfunctions, such as metabolic syndrome and hypothyroidism.

Short- and long-term effects of maternal nicotine exposure during lactation on body adiposity, lipid profile, and thyroid function of rat offspring

Epidemiological studies show a higher prevalence of obesity in children from smoking mothers and smoking may affect human thyroid function. To evaluate the mechanism of smoking as an imprinting factor for these dysfunctions, we evaluated the programming effects of maternal nicotine (NIC) exposure during lactation. Two days after birth, osmotic minipumps were implanted in lactating rats, divided into: NIC (6 mg/kg per day s.c.) for 14 days; Control - saline. All the significant data were P<0.05 or less. Body weight was increased from 165 days old onwards in NIC offspring. Both during exposure (at 15 days old) and in adulthood (180 days old), NIC group showed higher total fat (27 and 33%). In addition, NIC offspring presented increased visceral fat and total body protein. Lipid profile was not changed in adulthood. Leptinemia was higher at 15 and 180 days old (36 and 113%), with no changes in food intake. Concerning the thyroid status, the 15-days-old NIC offspring showed lower serum-free tri-iodothyronine (FT(3)) and thyroxine (FT(4)) with higher TSH. The 180-days-old NIC offspring exhibited lower TSH, FT(3), and FT(4)). In both periods, liver type 1 deiodinase was lower (26 and 55%). We evidenced that NIC imprints a neonatal thyroid dysfunction and programs for a higher adiposity, hyperleptinemia, and secondary hypothyroidism in adulthood. Our study identifies lactation as a critical period to NIC programming for obesity, with hypothyroidism being a possible contributing factor.

Postnatal early overfeeding induces hypothalamic higher SOCS3 expression and lower STAT3 activity in adult rats

Postnatal early overnutrition (EO) is a risk factor for future obesity and metabolic disorders. Rats raised in small litters (SLs) develop overweight, hyperphagia, hyperleptinemia, hyperinsulinemia and hypertension when adults. As obesity is related to hyperleptinemia, leptin resistance and metabolic syndrome, we aimed to investigate body composition, plasma hormone levels, glucose tolerance and the leptin signaling pathway in hypothalamus from early overfed animals at weaning and adulthood. To induce postnatal EO, we reduced litter size to three pups/litter (SL), and the groups with normal litter size (10 pups/litter) were used as control. Rats had free access to standard diet and water postweaning. Body weight and food intake were monitored daily, and offspring were killed at 21 (weaning) and 180 days old (adulthood). Postnatal EO group had higher body weight and total and visceral fat mass at both periods. Lean mass and serum high-density lipoprotein cholesterol (HDL-C) were higher at 21 days and lower at 180 days. Small litter rats presented higher levels of globulins at both periods, while albumin levels were higher at weaning and lower at adulthood. There was higher leptin, insulin and glucose serum concentrations at 21 days old, while no glucose intolerance was observed in adulthood. Leptin signaling pathway was unaffected at weaning. However, postnatal EO induced lower JAK2 and p-STAT3, and higher SOCS3 expression in adult animals, indicating central leptin resistance in adulthood. In conclusion, postnatal EO induces obesity, higher total and visceral fat mass, lower HDL-C and central leptin resistance in adult life.

Nicotine exposure affects mother's and pup's nutritional, biochemical, and hormonal profiles during lactation in rats

We have shown that maternal nicotine exposure during lactation has long-lasting effects on body adiposity and hormonal status of rat offspring. Here, we studied the nutritional and hormonal profiles in this experimental model. Two days after birth, osmotic minipumps were implanted in lactating rats divided into two groups: NIC - continuous s.c. infusions of nicotine (6 mg/kg per day) for 14 days and C - saline. Dams and pups were killed at 15 and 21 days of lactation. Body weight and food intake were evaluated. Milk, blood, visceral fat, carcass, and adrenal gland were collected. All the significant data were P<0.05. At the end of nicotine exposure (15 days), dams presented higher milk production, hyperprolactinemia, and higher serum high-density lipoprotein cholesterol (HDL-C). Milk from NIC dams had higher lactose concentration and energy content. After nicotine withdrawal (21 days), dams showed lower food intake and hyperleptinemia. The 15-day-old NIC pups presented higher total body fat, higher HDL-C, serum leptin, serum corticosterone, and adrenal catecholamine content, but lower tyrosine hydroxylase protein levels. The 21-day-old NIC pups had higher body protein content and serum globulin. Thus, maternal nicotine exposure during lactation results in important changes in nutritional, biochemical, and hormonal parameters in dams and offspring. The pattern of these effects is clearly distinct when comparing the nicotine-exposed group to the withdrawal group, which could be important for the programming effects observed previously.

Resveratrol attenuates oxidative stress and prevents steatosis and hypertension in obese rats programmed by early weaning.

We hypothesized that resveratrol, a natural phytoalexin found in grapes, can prevent oxidative stress, obesity and its related disturbances in obese rats programmed by early weaning. Lactating Wistar rats were separated into two groups: early weaning (EW) - dams who were wrapped with a bandage to interrupt the lactation in the last 3 days of lactation; control - dams whose pups had free access to milk during all lactation. At the 150th day, EW offspring were randomly subdivided into EW+resveratrol (EW+Res) - resveratrol (30 mg/kg/day); EW+vehicle (EW) - rats that received 0.5% (w/v) aqueous methylcellulose. The control group received vehicle. Rats were treated by gavage daily for 30 days. EW offspring developed hyperphagia, higher body weight, visceral obesity, higher systolic (SBP) and diastolic blood pressure (DBP) (+15% and +20%, respectively; P<.05) and higher serum triglycerides (TG) and low-density lipoprotein but lower high-density lipoprotein (+55%, +33% and -13%, respectively; P<.05). Resveratrol normalized food intake, SBP and DBP and prevented obesity and dyslipidemia in EW+Res. EW rats had higher plasma and liver thiobarbituric-acid-reactive substances (TBARS) and lower plasma superoxide dismutase (SOD) and liver glutathione peroxidase activities (+51%, +18%, -58%, -31%, respectively; P<.05), and resveratrol normalized both plasma and liver TBARS and increased the activity of SOD and catalase in plasma. EW rats presented liver steatosis and higher liver TG, and resveratrol prevented these hepatic alterations. In conclusion, this study demonstrated a potential therapeutic use of resveratrol in preventing obesity and oxidative stress and reducing the risk of hypertension, dyslipidemia and steatosis in adult rats programmed by early weaning.

Oxidative stress programming in a rat model of postnatal early overnutrition — role of insulin resistance ☆ ☆☆

Postnatal early overfeeding (EO) is related to later development of overweight and other metabolic disorders. As oxidative stress is implicated in most human diseases, as obesity and diabetes, we decided to study some parameters related to oxidative stress and insulin signaling in liver from EO animals in adult life. To induce EO, litter size was reduced to three pups per litter (SL: small litter) and groups with normal litter size (NL:10 pups per litter) were used as control. After weaning, rats had free access to standard diet and water. Body weight and food intake were monitored daily and offspring were killed at 180 days-old. Significant differences had P<.05 or less. As expected, SL rats had hyperphagia, higher body weight and higher visceral fat mass at weaning and adulthood. In liver, postnatal EO programmed for lower catalase (-42%), superoxide dismutase (-45%) and glutathione peroxidase (-65%) activities. The evaluation of liver injury in adult SL group showed lower nitrite content (-10%), higher liver and plasma malondialdehyde content (+25% and 1.1-fold increase, respectively). No changes of total protein bound carbonyl or Cu/Zn superoxide dismutase protein expression in liver were detected between the groups. Regarding insulin signaling pathway in liver, SL offspring showed lower IRβ (-66%), IRS1 (-50%), phospho-IRS1 (-73%), PI3-K (-30%) and Akt1 (-58%). Indeed, morphological analysis showed that SL rats presented focal areas of inflammatory cell infiltrate and lipid drops in their cytoplasm characterizing a microsteatosis. Thus, we evidenced that postnatal EO can program the oxidative stress in liver, maybe contributing for impairment of the insulin signaling.

Prolactin inhibition at the end of lactation programs for a central hypothyroidism in adult rat

Malnutrition during lactation is associated with hypoprolactinemia and failure in milk production. Adult rats whose mothers were malnourished presented higher body weight and serum tri-iodothyronine (T(3)). Maternal hypoprolactinemia at the end of lactation caused higher body weight in adult life, suggesting an association between maternal prolactin (PRL) level and programming of the offsprings adult body weight. Here, we studied the consequences of the maternal PRL inhibition at the end of lactation by bromocriptine (BRO) injection, a dopaminergic agonist, upon serum TSH and thyroid hormones, thyroid iodide uptake, liver mitochondrial alpha-glycerophosphate dehydrogenase (mGPD), liver and pituitary de-iodinase activities (D1 and/or D2), and in vitro post-TRH TSH release in the adult offspring. Wistar lactating rats were divided into BRO - injected with 1 mg/twice a day, daily for the last 3 days of lactation, and C - control, saline-injected with the same frequency. At 180 days of age, the offspring were injected with (125)I i.p. and after 2 h, they were killed. Adult animals whose mothers were treated with BRO at the end of lactation presented lower serum TSH (-51%), T(3) (-23%), and thyroxine (-21%), lower thyroid (125)I uptake (-41%), liver mGPD (-55%), and pituitary D2 (-51%) activities, without changes in the in vitro post-TRH TSH release. We show that maternal PRL suppression at the end of lactation programs a hypometabolic state in adulthood, in part due to a thyroid hypofunction, caused by a central hypothyroidism, probably due to decreased TRH secretion. We suggest that PRL during lactation can regulate the hypothalamus-pituitary-thyroid axis and programs its function.

Neonatal hyperleptinaemia programmes adrenal medullary function in adult rats: effects on cardiovascular parameters

Epidemiological studies have shown a strong correlation between stressful events (nutritional, hormonal or environmental) in early life and development of adult diseases such as obesity, diabetes and cardiovascular failure. It is known that gestation and lactation are crucial periods for healthy growth in mammals and that the sympathoadrenal system is markedly influenced by environmental conditions during these periods. We previously demonstrated that neonatal hyperleptinaemia in rats programmes higher body weight, higher food intake and hypothalamic leptin resistance in adulthood. Using this model of programming, we investigated adrenal medullary function and effects on cardiovascular parameters in male rats in adulthood. Leptin treatment during the first 10 days of lactation (8μg 100 g−1 day−1, s.c.) resulted in lower body weight (6.5%, P < 0.05), hyperleptinaemia (10‐fold, P < 0.05) and higher catecholamine content in adrenal glands (18.5%, P < 0.05) on the last day of treatment. In adulthood (150 days), the rats presented higher body weight (5%, P < 0.05), adrenal catecholamine content (3‐fold, P < 0.05), tyrosine hydroxylase expression (35%, P < 0.05) and basal and caffeine‐stimulated catecholamine release (53% and 100%, respectively, P < 0.05). Systolic blood pressure and heart rate were also higher in adult rats (7% and 6%, respectively, P < 0.05). Our results show that hyperleptinaemia in early life increases adrenal medullary function in adulthood and that this may alter cardiovascular parameters. Thus, we suggest that imprinting factors which increase leptin and catecholamine levels during the neonatal period could be involved in development of adult chronic diseases.