Impact of maternal undernutrition on hypothalamo-pituitary-adrenal axis and adipocyte functions in male rat offspring.

Malnutrition induces profound deleterious effects on several metabolic and neuroendocrine functions. In the present study, we examined the impact of maternal food restriction, during gestation and lactation, on the metabolic-neuroendocrine function of their male offspring at 21 and 60 d of age. Well-nourished (WN) and undernourished (UN) pregnant rats were used, during gestation and lactation, until pups were weaned. Twenty-one-day-old WN and UN male pups were studied in basal and postinsulin conditions. Additional groups of weaned (WN and UN) male rats were fed either ad libitum (WN-WN and UN-WN) or in a restricted fashion (WN-UN and UN-UN) until experimentation at age 60 d. Body weights of mothers and their male offspring were monitored. Basal and postinsulin plasma concentrations of several metabolic fuels were evaluated. Our results indicate that 21-d-old UN male rats exhibited (vs their WN counterparts), decreased body weights, similar basal and postinsulin glycemia, similar basal plasma adrenocorticotropic hormone (ACTH) and corticosterone levels but diminished ACTH response to insulin treatment, and basal hypoleptinemia and significant insulin-induced leptin release. Finally, at 60 d of age, long-term UN (WN-UN and UN-UN) rats showed lower plasma (basal and postinsulin) glucose, and basal triglyceride levels than their counterparts (WN-WN and UN-WN). Sixty-day-old rats submitted to either food restriction protocol also showed a reduced hypothalamo-pituitary-adrenal axis response to insulin-induced hypoglycemia and basal hypoleptinemia, in spite of restoration of normal body weights. These results further indicate a clear metabolic-neuroendocrine dysfunction in male pups of UN mothers, with the abnormality partially present at weaning and deteriorated by adulthood, even after the recovery of normal body weight. Our study strongly supports the importance of the irreversibility of a deleterious allostatic state resulting from fetal and early postnatal undernutrition.

Maternal undernutrition induces neuroendocrine immune dysfunction in male pups at weaning.

The present study was designed to assess the effect of maternal undernutrition, during gestation and lactation, on the neuroendocrine [hypothalamo-pituitary-adrenal (HPA)]-immune axis response to endotoxin (LPS) administration. For this purpose, 21-day-old male rats from both well-nourished (WN) and undernourished (UN) mothers were examined 2 h after injection (i.p.) of vehicle alone (VEH) or containing LPS (130 microg/kg BW). Circulating levels of glucose (GLU), ACTH, corticosterone (B), tumor necrosis factor-alpha (TNFalpha) and leptin were explored. The results indicate that: (a) mother body weight was significantly (p < 0.05) reduced, as a consequence of UN, at the second and third weeks of pregnancy; (b) no differences in basal glycemia were found in the two groups of pups, and LPS treatment did not induce hypoglycemia, in either group; (c) basal plasma ACTH, B and TNFalpha levels were similar in the two groups, and LPS-induced ACTH, B and TNFalpha secretions, although severalfold higher than respective VEH values (p < 0.05) in pups from WN mothers, were fully (ACTH and B) and partially (TNFalpha) abolished in products from UN mothers; (d) both mean body weights and basal plasma leptin levels were significantly (p < 0.05) lower in pups from UN than from WN mothers, and LPS administration did not modify plasma leptin values in products from both groups. In addition, results of dispersed total adrenal cells incubated in vitro indicate that: (a) both basal and ACTH (22 pM)-induced B secretion were significantly (p < 0.05) lower in cells from UN than WN pups, and (b) leptin (100 nM) was able to inhibit partially ACTH-stimulated B output by adrenal gland (AG) cells from WN pups; however, it failed to inhibit ACTH-stimulated glucocorticoid release by AG cells from UN pups. The present results indicate that undernutrition in mothers, during the very critical periods of gestation and lactation, induces in their male pups at weaning: (a) reduced circulating leptin levels and body weight values; (b) metabolic adaptation to normal carbohydrate metabolism; (c) hyporesponsiveness of the HPA and immune (TNFalpha) axes during endotoxemia, and (d) leptin resistance at the adrenocortical level. This study strongly supports that undernutrition of mothers results in neuroendocrine immune dysfunction of their pups; however, adrenal resistance to the inhibitory effect of leptin on glucocorticoid output is developed, probably as an adaptive mechanism to counteract unfavorable metabolic conditions.

Sexual dimorphism in the hypothalamo-pituitary-adrenal (HPA) axis and TNFalpha responses to phospholipase A2-related neurotoxin (from crotalus durissus terrifcus) challenge.

Neuroendocrine-immune interactions are vital for the individual's survival in certain physiopathological conditions such as sepsis and tissular injury. It is known that several snake venoms (SV) are potent neurotoxic compounds and that their main component is a specific phospholipase type 2 (PLA2). It has been recently described that the venom from crotalus durissus terrificus (SV) possesses a cytotoxic effect in different in vitro and in vivo animal models. In the present study we investigated whether SV is able to stimulate both TNFalpha and neuroendocrine functions in a sexual dimorphic fashion. For this purpose the modulatory role of endogenous sex steroids during neurotoxemia was evaluated. Our results indicate that SV (25 microg/animal) stimulates the hypothalamo-pituitary-adrenal axis and TNFalpha secretion when administered (ip) to adult male mice, such responses were characterized by a time-related enhance in plasma glucose, ACTH, corticosterone and TNFalpha levels. SV-stimulated glycemia, corticosteronemia and adrenal glucocorticoid were sexually dimorphic. Twenty-day gonadectomized mice showed a similar sexual dimorphism to that found in intact animals, however, they additionally showed a sexual dimorphic pattern in cytokine release in plasma 30 min post-SV. Estradiol (E2) treatment, in gonadectomized mice, abolished some characteristics of the sexual dimorphism, such as hyperglycemia, hypercorticosteronemia and hypercytokinemia. Finally, in vitro experiments indicate that: a) gonadectomy increased spontaneous and SV-stimulated cytokine output by incubated peripheral mononuclear cells (PMNC), regardless of the sex; and b) despite E2 treatment, in gonadectomized, did not modify the pattern of basal and SV-elicited TNFalpha secretion induced by orchidectomy, fully reversed the enhance in basal and SV-stimulated cytokine release found after ovariectomy alone. Our results further indicate that neurotoxemia, due to SV challenge, induces several symptoms common to those of inflammatory stress; they also strongly support that both gender and endogenous sex steroids are responsible for neuroendocrine-immunological sexual dimorphism.

Modulatory role of the epinergic system in the neuroendocrine-immune system function.

It is well recognized that the reciprocal interaction established between the immune and neuroendocrine systems is crucial for the homeostatic adaptation of individuals during septicemia. In the present study, using an in vivo rat model, we investigated the degree of participation of central and peripheral epinergic systems in the modulation of the hypothalamic-pituitary-adrenal and immune axes' functions during endotoxemia. For this purpose, acute endotoxemia was induced in adult male rats pretreated intraperitoneally with either different inhibitors of phenylethanolamine-N-methyltransferase (PNMT) [which are active either peripherally (SKF 29661) or both peripherally and centrally (SKF 64139), thus lowering epinephrine (EPI) synthesis] or vehicle only (CTRL). Twelve hours after pretreatment, animals were intraperitoneally injected with vehicle alone (basal) or vehicle containing bacterial lipopolysaccharide (LPS) and sacrificed 2 h later. A significant (p < 0.05 vs. the respective basal value) hypoglycemia was found in all groups studied. No pretreatment modified basal plasma adrenocorticotropic hormone (ACTH), glucocorticoid and cytokine concentrations. Endotoxin-stimulated ACTH secretion was severalfold (p < 0.05) higher than the respective basal value in CTRL and in SKFs-pretreated rats; however, the plasma ACTH levels after LPS were significantly (p < 0.05 vs. CTRL and SKF-29661 values) reduced in SKF-64139-pretreated rats. All groups studied showed an appropriate adrenal response to endotoxin challenge. Although no differences were found in basal anterior pituitary (AP) ACTH content among groups, LPS treatment significantly (p < 0.05 versus the respective basal value) decreased AP ACTH in CTRL and SKF 29661 groups. No pretreatment modified the basal medial basal hypothalamus (MBH) corticotropin-releasing hormone (CRH) content. Conversely, SKF 64139 pretreatment significantly (p < 0.05 vs. CTRL and SKF 29661 values) reduced basal median eminence (ME) CRH content, and LPS administration significantly (p < 0.05) decreased ME CRH in CTRL and SKF-29661-pretreated rats. SKF 64139 pretreatment significantly (p < 0.05) enhanced basal MBH and ME arginine vasopressin (AVP) contents. LPS administration significantly (p < 0.05) decreased MBH AVP in CTRL and SKF-29661-pretreated rats and diminished (p < 0.05 vs. basal values) ME AVP in all groups. The plasma tumor necrosis factor alpha (TNFalpha) concentrations were enhanced severalfold (p < 0.05 vs. basal values) after LPS treatment in CTRL rats, but not in SKFs-treated animals. In order to explore the reduced cytokine release after LPS in PNMT-inhibited rats, additional ex vivo experiments were performed by using peripheral mononuclear cells (PMNC) from both CTRL and SKF-29661-pretreated rats. The results of these experiments confirmed an immune dysfunction after inhibition of peripheral EPI synthesis; in fact, basal and concanavalin-A-stimulated TNFalpha secretions were significantly (p < 0.05) lower in SKF-29661-treated than in CTRL PMNC, while, interestingly, addition of EPI (10(-7) M) to the medium fully restored these effects. These data demonstrate that: (1) the mechanism whereby LPS-induced hypoglycemia was independent of epinergic activity; (2) selective central inhibition of epinergic function reduced endotoxin-stimulated ACTH secretion, an effect that could mainly be due to a decrease in CRH-ergic activity; (3) the central epinergic system positively and negatively modulates CRH- and AVPergic functions, respectively, and (4) inhibition of peripheral PNMT activity reduced immune system function in vivo and ex vivo. It is further suggested that low peripheral levels of EPI could be beneficial for the body's defense mechanisms during endotoxic shock.

Metabolic, neuroendocrine and immune functions in basal conditions and during the acute-phase response to endotoxic shock in undernourished rats.

Chronic malnutrition is one of the most important causes of several metabolic, immune and neuroendocrine dysfunctions. The aim of the present study was to determine the influence of chronic food restriction on basal neuroendocrine, immune and adipocyte functions and during the acute-phase response to endotoxic shock in female rats. The effect of refeeding of undernourished rats on the above-mentioned functions was also investigated. For these purposes, plasma total protein, glucose, triglycerides, ACTH, corticosterone, tumor necrosis factor-alpha (TNF) and leptin (LEP) levels were determined in basal condition and 2 h after endotoxin (LPS; 180 microgram/kg body weight, i.p.) administration in 3 different groups: (1) well-nourished (WN) controls; (2) undernourished (UN) rats as a consequence of chronic food restriction, and (3) UN rats re-fed to restoration of their body weights in the WN rat range. The results indicate that UN rats, in comparison with WN controls, developed an arrest in body weight gain as well as in basal hypoglycemia, hypotriglyceridemia, hypoleptinemia, hypercorticosteronemia and enhanced adrenal glucocorticoid content; however, no changes in basal total protein, ACTH and TNF plasma levels and in anterior pituitary ACTH concentrations were found. When endotoxic shock was induced, the LPS-induced hypoglycemia developed in WN rats was abolished in UN animals, and both ACTH and TNF plasma concentrations after endotoxin, albeit significantly (p < 0.05) higher than the respective basal values, were significantly (p < 0.05) lower in UN than in WN control rats. Despite the high basal plasma corticosterone concentration in UN vs. WN rats, the LPS-induced glucocorticoid release was similar in WN and UN rats. Additionally, LPS treatment did not modify basal plasma LEP levels, regardless of the group. Interestingly, UN rats fed ad libitum for 15 days restored their body weight to WN rat range values, and the various metabolic dysfunctions seen in UN rats in both basal and post-LPS conditions were fully normalized. Our results clearly indicate that chronic undernutrition not only affects, as earlier described, reproductive function but also metabolic, neuroendocrine, immune and adipocyte functions, and that the effects induced by undernutrition can be fully reversed after recovery of normal body weight. The present study strongly supports the involvement of the metabolic status in the effectiveness of the defense mechanisms developed in patients in inflammatory stress conditions.

Food intake-induced leptin secretion modulates hypothalamo-pituitary-adrenal axis response and hypothalamic Ob-Rb expression to insulin administration.

The mutation of the ob gene is known to induce a phenotype of obesity accompanied by symptoms including enhanced production of glucocorticoid. Chronic administration to ob/ob mice of leptin, the ob gene product, reverses hypercorticosteronemia. This establishes a clear relation between adipocyte and hypothalamo-pituitary-adrenal (HPA) axis functions. In the present study we investigated the acute modulatory effects of food intake-stimulated leptin secretion on HPA axis activity and hypothalamic leptin receptor (Ob-Rb) expression in 24-hour fasting, adult female, BALB/c mice after insulin-induced hypoglycemia. Our results indicate that: (1) food supply for 45 min to 24-hour fasting mice increased plasma glucose levels and reversed both hypercorticosteronemia and hypoleptinemia; (2) the insulin-induced hypoglycemia produced a marked HPA axis activation in animals with no access to food but this response was fully prevented by food intake and the consecutive increase in plasma leptin levels; (3) the inhibitory effect of leptin on the HPA axis response to insulin-induced hypoglycemia was corroborated by i.p. administration of murine leptin, and (4) fasting-induced hypothalamic Ob-Rb overexpression is not modulated by insulin itself but by leptin, since increase in leptin levels by food intake or by administration of exogenous leptin completely reversed this Ob-Rb overexpression. These results confirm the inhibitory effect of leptin on the HPA axis response to various stress stimuli. They clearly demonstrate that acute food intake in 24-hour fasting mice: (a) rapidly reduced fasting-induced hypercorticosteronemia by enhancing both spontaneous and insulin-elicited endogenous leptin secretion; (b) fully prevented HPA axis response to insulin administration, by rapidly increasing endogenous leptin secretion and probably also by diminishing the extent and the duration of insulin-induced hypoglycemia, and (c) abolished hypothalamic Ob-Rb overexpression induced by fasting itself combined with insulin treatment. The present data strongly suggests an inhibitory effect of endogenous leptin on insulin-induced HPA axis response, an interaction relevant to the physiological adaptation to starvation and caloric excess, and further supports the pivotal role played by the hypothalamus in restoring homeostasis in different allostatic states.

Gender-dependent characteristics of the hypothalamo-corticotrope axis function in glucocorticoid-replete and glucocorticoid-depleted rats.

The aim of the present study was to determine the role of the endogenous sex steroid environment in the hypothalamo-corticotrope (HC) function in both sham-operated (SHAM) and bilaterally adrenalectomized (ADX) rats. For this purpose adult rats of both sexes were used 3 and 6 weeks after either SHAM or ADX. The results indicate that: a) in SHAM animals, basal plasma ACTH levels were significantly higher in females than in males, and this sexual dimorphism was overridden by ADX, regardless of the time post-surgery; b) although basal anterior pituitary (AP) ACTH content was similar in SHAM animals of both sexes, 3- and 6-week ADX induced higher AP ACTH in males than in females; c) at 3- and 6-weeks, ADX rats of hoth sexes had an AVP:CRH ratio (r), in the median eminence (ME) and medial basal hypothalamus (MBH), increased several fold over the respective SHAM-value and, although no sexual dimorphism was found at week 3 post-ADX, by 6-weeks post ADX, these ratios were significantly higher in both brain tissues of females than in those of males; and d) the in vitro ME CRH and AVP output in response to high potassium concentrations (hK+; 28 and 56 mmol/I), was concentration-related, regardless of sex and surgery, and was characterized by enhanced secretion of neuropeptides by MEs from ADX in comparison to SHAM rats of both sexes, and a sexual dimorphism was found in this parameter, consisting in general, in greater neuropeptide output from tissues of female than of male animals. Our results indicate that: 1) there is a gender-dependent characteristic of the HC axis function in glucocorticoid-replete rats and 2) the absence of the glucocorticoid negative feedback mechanism is responsible for either the expression or for the override of the sexual dimorphism in different parameters, a phenomenon which dependent on the time elapsed after ADX.

Bilateral adrenal enucleation-induced changes in adenohypophyseal pro-opiomelanocortin (POMC)-related peptides synthesis and secretion: a comparative study with adrenalectomized rats.

The aim of the present study was to elucidate the modulatory effect of transient changes in endogenous glucocorticoids, occurring after bilateral adrenal enucleation (ENUC), on anterior pituitary (AP) proopiomelanocortin (POMC)-derived peptides synthesis and output in rats. For this purpose, adult female rats were either bilaterally ENUC, adrenalectomized (ADX), or sham-operated (SHAM) and killed by decapitation 2, 7, 14, and 21 days after surgery. Trunk blood was collected for measurements of ACTH, beta-endorphin (beta-END) and corticosterone (B) concentrations; APs were quickly dissected for the determination of ACTH, beta-endorphin (beta-END)-like (beta-END-LI) and gamma 3-MSH contents and adrenal glands were removed and submitted to histological study. The results indicate that ENUC and ADX increased AP POMC-related peptides synthesis and release in association with changes in the AP processing of peptides belonging to the N-terminal (gamma 3-MSH), mid (ACTH) and C-terminal (beta-LPH/ENDs) portions of POMC. While ADX abolished plasma B levels, ENUC induced a transient (day 2) decrease in plasma B concentrations which returned to SHAM levels at 7 days after surgery. These data tallied with the histological observations carried out, indicating a time-dependent regenerative process of the adrenal which was completed by three weeks after ENUC. There was a different pattern in plasma ACTH and beta-END levels between ENUC and ADX; maximal plasma peptide levels were found 7-14 days after ENUC, then falling down to SHAM values at 21 days post ENUC. Conversely, there was a constant increment in plasma peptide levels up to 21 days after ADX. At 2 days after both ENUC and ADX all peptides measured in the AP were lower than SHAM values, thus reflecting a rapid corticotrope secretion. Thereafter, 7 or more days after surgery, AP peptide content in ADX rats increased, in a time-related fashion, up to 21 days after surgery. Only beta-END-LI showed a similar AP content to that of the SHAM group, thereafter indicating a preferential cleavage of POMC to beta-END long after ADX (21 days). ENUC rats showed increased AP POMC peptides content throughout the whole time, and it was significantly different from SHAM and ADX values 14 days post-surgery. Interestingly, we found an increment in AP gamma 3-MSH, a peptide which is preferentially synthesized in the intermediate lobe of the rat pituitary, in both ENUC and ADX situations. Our results further indicate that: 1) glucocorticoids, from regenerating adrenal origin, induce a fast negative feedback mechanism on AP secretion, and 2) there might be a delayed inhibitory action of newly synthesized corticosteroids on higher levels of the central nervous system. The lack of glucocorticoids (ADX) clearly corroborates a persistent enhancement of AP POMC-related peptides synthesis and secretion. The differences in AP processing of POMC between ENUC and ADX might be due to qualitative/quantitative changes in hypothalamic ACTH secretagogues output.

Participation of the central serotonergic pathway in the endotoxin-stimulated hypothalamo-pituitary-adrenal axis function.

The aim of the present study was to determine whether the central serotoninergic pathway (5HT) plays any stimulatory/inhibitory role in endotoxin-stimulated hypothalamo-pituitary-adrenal (HPA) axis function in the male rat. For this purpose, animals inhibited or not of central 5HT synthesis were injected with vehicle alone or containing endotoxin (LPS) and killed 2 h later. The results indicate that the inhibition of the 5HT pathway did not modify the LPS-induced hypoglycemia but that it significantly reduced ACTH release in plasma. Although the inhibition of 5HT did not modify the CRH-ergic system, it diminished hypothalamic vasopressin (AVP) content in basal condition. After LPS injection, rats inhibited of 5HT synthesis showed a significant activation of the hypothalamic AVP-ergic system whereas control rats did not. These data clearly indicate that decreased HPA axis function after 5HT inhibition could be partially compensated by the facilitation of the AVP neuronal activity.

Sex steroid regulation of the hypothalamo-pituitary-adrenal axis activity in middle-aged mice during endotoxic shock.

Many studies have documented the presence of a sexually dimorphic response of neuroendocrine functions in response to immune signals. The aims of the present study were to evaluate the hypothalamopituitary-adrenal (HPA) axis response to inflammatory stress stimulus in 15-month-old mice, and to determine whether such a response depends on circulating sex steroids. Our results indicate that in the 15-month-old mice: (1) there is a sexual dimorphism in the HPA axis activity in basal condition and after endotoxin treatment with generally higher levels of several parameters of this axis in female than in male mice, (2) gonadectomy alone, followed by sex steroid therapy, modulates HPA axis function in both basal and stress conditions, and (3) whereas estradiol plays a stimulatory role on adrenal function, testosterone inhibits adrenal glucocorticoid production. This study further suggests a clear sexual dimorphism in middle-aged mice injected with endotoxin. These results may be relevant for the treatment of sepsis in aged patients.