Hypothalamic Nuclei Nitric Oxide Synthase Expression in Rats Malnourished During Early Lactation Period

Malnourishment during early lactation disrupts the ontogenetic distribution of the CART and α-MSH anorexigenic molecules in the arcuate/paraventricular pathway and lateral hypothalamus in male rats

Developmental malnourishment impacts the energetic metabolism control throughout life. In rat offspring, a 0% protein diet during the first 10 days of lactation results in leptin resistance and in alterations in: feeding behavior, serum leptin and neuropeptide Y (NPY) levels in the hypothalamic arcuate nucleus (ARC)/paraventricular (PVN) pathway. Here, the distributions of alpha-melanocyte stimulating hormone (α-MSH) and cocaine and amphetamine regulated transcript (CART), anorexigenic molecules, were immunohistochemically assessed in the ARC, PVN and lateral hypothalamus (LH) nuclei. Rat dams were subjected to one of the following diet protocols from postnatal day (P) 1-10: 1) Protein-free (PFG, 0% protein chow); 2) Pair-fed (UFG, normoprotein chow); 3) Control group (CG, normoprotein chow). PFG, UFG and CG male offspring were analyzed at different time points, from P5 to P180. In the ARC, PFG α-MSH and CART were increased from P10 to P45 when compared to CG and UFG. In the PVN, α-MSH and CART peaks in PFG animals were delayed from P20 to P30 when compared to CG. In the LH, CART was more intense in PFG animals than in UFG and CG ones by P20, and, by P30, UFG immunostaining became less intense than in CG. In conclusion, aproteic diet altered the ontogenetic distribution of both anorexigenic molecules. In the PVN, the peak was delayed to P30, which coincides with the leptin peak and follows the previously described NPY (orexigenic) peak in this model. The permanent LH CART and α-MSH increase may be associated with the previously observed PFG hypophagia.

Detraining in pregnancy and/or lactation modulates neuropeptidergic hypothalamic systems in offspring mice

Manipulations in metabolic parameters during pregnancy/lactation can impact the development of short- and long-term energy control mechanisms, which are mainly modulated by neural and hormonal inputs to the hypothalamus. Thus, we tested how mice training and detraining during pregnancy and lactation affect hypothalamus gene expression and change biometric and metabolic profiles of the offspring. Three-month-old female Swiss mice were submitted to an 8-week exercise program (swimming 5 times/week, 1 h/day). Following this physical exercise protocol, these conditioned animals and the control group were submitted to matting. After pregnancy verification, the animals were distributed into four groups: training during pregnancy and lactation (T); detraining after pregnancy confirmation (DP); detraining during lactation (DL); and control (CT), without interventions. After weaning, the offspring of the four groups were derived into these as follows: TO, DPO, DLO, and CTO, respectively. The body weight was lower in conditioned females compared to control at weeks 4-8 of the exercise regimen. No statistical difference in dam's body weight was observed during pregnancy. Related to offspring, at post-natal day 90, the animals were euthanized and DPO and DLO showed decrease in Npy and Cart expression in hypothalamus, and DLO also had increased Lep gene expression in white adipose tissue. Additionally, DPO showed increase in plasma triglycerides levels, total liver weight, and decrease in brown adipose tissue compared to CTO. Together, these results support that detraining during critical periods of development leads to altered gene expression in hypothalamic neuropeptidergic systems.

Protein restriction during lactation alters the autonomic nervous system control on glucose-induced insulin secretion in adult rats

Involvement of autonomic nervous system (ANS) neurotransmitters on insulin secretion in rats submitted to protein malnutrition during lactation was studied. During the first 2/3 of lactation, mothers received a 4% protein diet (LP). Control group received normal diet (23% protein) (NP). After protein restriction, mothers received normal diets. At 81 days rats were submitted to intravenous glucose tolerance tests (ivGTT). Plasma glucose and insulin concentration (PIC) were measured. Glucose-induced insulin secretion (GIIS) was tested in pancreatic islets. Fasting normoglycemia and hypoinsulinemia were observed in LP rats. Glucose intolerance and low PIC in LP group were detected during ivGTT. Acetylcholine (Ach) or blockage of alpha-adrenoceptors induced high PIC increment in LP rats; atropine or stimulation of alpha-adrenoceptors did not change PIC. Insulin secretion of LP rat islets showed low glucose and carbachol responses. Epinephrine-inhibited GIIS in both islet groups. Hypoinsulinemia observed in lactation-malnourished rats might be caused by alterations in GIIS regulation, including ANS modulation.

Myelin basic protein accumulation is impaired in a model of protein deficiency during development

During the development of the central nervous system (CNS) there is a great possibility of permanent effects in consequence of environmental disturbances. Nutritional deficiency is one of the factors that impair the normal CNS formation. In general, the protein deficiency evokes, beyond the damages in the maturation of nervous system, several consequences in body growth, biochemical maturation, motor function and the major cognitive functions. These effects were observed in undernourished children all over the world. Even in a restricted period, the malnutrition status may evoke permanent impairments in feeding behavior and in metabolism. Rats submitted to malnutrition during development, showed a marked decrease in the number of myelinated fibers. This condition may reflect a failure in the beginning of the wrapping of axons by oligodendroglial processes and/or a delay in the myelin synthesis. Myelin basic protein (MBP) is an intracellular oligodendrocyte protein that is directly related to the formation of the myelin sheath. In this study we verified the temporal pattern of MBP expression, by immunohistochemical and immunoblotting analyses, in a model of protein malnutrition induced during the first half of the lactation period. We showed that MBP expression was impaired in our malnutrition model and that some of the effects were maintained in adulthood, with possible consequences in the maturation of myelin sheath.

Glycogen stores are impaired in hypothalamic nuclei of rats malnourished during early life

Perinatal nutrition has persistent influences on neural development and cognition. In humans and other animals, protein malnutrition during the perinatal period causes permanent changes, inducing to adulthood metabolic syndrome. Feeding is mainly modulated by neural and hormonal inputs to the hypothalamus. Hypothalamic glycogen stores are a source of glucose in high energetic demands, as during development of neural circuits. As some hypothalamic circuits are formed during lactation, we studied the effects of malnutrition, during the first 10 days of lactation, on glycogen stores in hypothalamic nuclei involved in the control of energy metabolism. Female pregnant rats were fed ad libitum with a normal protein diet (22% protein). After delivery, each dam was kept with 6 male pups. During the first 10 days of lactation, dams from the experimental group received a protein-free diet and the control group a normoprotein diet. By post-natal day 10 (P10), glycogen stores were very high in the arcuate nucleus and median eminence of control group. Glycogen stores decreased during development. In P20 control animals, glycogen stores were lower when compared to P10 control animals. Animals submitted to malnutrition presented a staining even lower than control ones. After P45, it was difficult to determine differences between control and diet groups because glycogen stores were reduced. We also showed that tanycytes were the cells presenting glycogen stores. Our data reinforce the concept that maternal nutritional state during lactation may be critical for neurodevelopment since it resulted in a low hypothalamic glycogen store, which may be critical for establishment of neuronal circuitry.

Exercise and food ad libitum reduce the impact of early in life nutritional inbalances on nitrergic activity of hippocampus and striatum

Nutritional imbalances were produced by varying litter size pups per dam: 3 (small), 6 (medium), and 12 (large). On the 21st day, 4 subjects of each litter, were sacrificed and the remaining were grouped, 2 per cage, with or without running wheels, with food and water ad libitum. Adult subjects were tested in water maze, their brains processed for NADPH-diaphorase histochemistry and quantified by densitometry. No differences were detected in water maze. At 21st day, S and L compared with M presented reduced NADPH-d in the stratum molecular of dentate gyrus (DG), stratum lacunosum of CA1 and in all CA3 layers but not in the striatum. On the 58th day, actvity remained low in S and L in CA3 and striatum and L in CA1 and DG. Voluntary exercise increased NADPH-d in DG, CA1, CA3, and striatum in S, and in the stratum lacunosum of CA1 and CA3 in L.