Protein malnutrition increases plasma adrenocorticotropin and anterior pituitary proopiomelanocortin messenger ribonucleic acid in the rat

Early renal impairment is associated with in-hospital death of patients with COVID-19

Introduction

Renal impairment is a common complication in coronavirus disease 2019 (COVID‐19), although its prognostic significance remains unknown.

Objectives

This study determines the impact of early renal impairment on the clinical outcome of COVID‐19.

Methods

Patients diagnosed with COVID‐19 and hospitalized in Xiaogan Central Hospital from 20 January to 29 February 2020 were retrospectively included and grouped into two cohorts (cohort with normal renal function and cohort with renal insufficiency) based on the renal function detected on admission. Records of clinical manifestation, laboratory findings and clinical outcome were collected and compared between these two cohorts.

Results

A total 543 COVID‐19 patients were included. Among these patients, 70 patients developed early renal impairment, with an incidence of 12.89%. A significantly higher white blood cell (WBC) count, C‐reactive protein (CRP), erythrocyte sedimentation rate (ESR), serum creatine (Cr), blood urine nitrogen (BUN) and brain natriuretic peptide (BNP) and a significantly lower blood platelet (PLT), lymphocyte count, prealbumin and albumin (ALB) were detected in the cohort with renal insufficiency (P < 0.05). Patients with early renal impairment were also associated with higher incidences of haematuria/proteinuria, higher incidences of mortality and prolonged hospitalization duration. The independent risk factors for in‐hospital death included age >65 years old, complication of diabetes, renal impairment on admission (Cr > 73 μmol/L and eGFR < 60 ml/min 1.73 m²), WBC > 9.5 × 10⁹/L and ALB < 35 g/L.

Conclusion

Early renal impairment is associated with higher risk of in‐hospital death for patients with COVID‐19. Risk stratification according to renal function can better guide the clinical management of COVID‐19.

Low-protein diet decreased the adrenal function and spontaneous activity of mice during chronic heat stress

Protein restriction is a well-known risk factor that induces the deterioration of various biological functions. However, little is known about the effects of protein restriction on behavioral markers and the adrenal function of mice exposed to chronic stress. Here we evaluated the effects of a low-protein diet on the spontaneous activity and adrenal function of chronic heat-stressed mice. ICR mice were fed a control diet (20% protein) or a low-protein diet (10% protein) for 14 consecutive days. From the 10th day of the diet period, the mice were repeatedly exposed to a temperature condition of 35 ± 1 °C for 2 hr/day for four consecutive days. The spontaneous activities of the mice were estimated for the behavioral analysis. On the last day, we performed a blood collection test and an ACTH stimulation test for adrenal function analysis. For the blood collection test, mice were exposed to heat stress again for 2 hr, and blood was collected immediately after this heat stress. We measured the plasma levels of corticotropin releasing hormone, adrenocorticotropin (ACTH), and corticosterone. For the ACTH stimulation test, cosyntropin was intraperitoneally administered, and the plasma corticosterone levels were measured. The spontaneous activity of the low-protein mice was significantly lower than that of the control mice during the dark period of heat stress. The plasma corticosterone levels were greatly increased by heat stress, with no significant difference between the control and low-protein groups. The ACTH stimulation test revealed that the plasma corticosterone concentration of the heat-stressed low-protein mice was significantly lower than that of the heat-stressed controls. In conclusion, the low-protein diet decreased the spontaneous activity and the adrenal function of mice during heat stress, which implies that protein restriction during chronic heat stress induces fatigue by reducing the adrenal function.

Impact of malnutrition on cardiac autonomic modulation in children

OBJECTIVE

To compare the autonomic behavior between malnourished children and a control group using analysis of heart rate variability (HRV).

METHOD

Data were analyzed from 70 children who were divided into two groups: malnourished and eutrophic, according to the Z-score nutritional status for height and age. For analysis of HRV indices, heart rate was recorded beat to beat with the child in the supine position for 20min. The analysis of these indices was performed using linear methods, analyzed in the time and frequency domains. Student's t-test for unpaired data and the Mann-Whitney test were used to compare variables between groups, with a significance level of 5%.

RESULTS

A reduction in systolic and diastolic blood pressure and an increase in heart rate were found in malnourished children compared to eutrophic children. The HRV indices suggested that malnourished children present reductions in both sympathetic and parasympathetic autonomic nervous system activity. The SDNN, rMSSD, NN50, pNN50, SD1, SD2, TINN, LF (ms²), and HF (ms²) indices were lower in malnourished children.

CONCLUSION

Malnourished children present changes in cardiac autonomic modulation, characterized by reductions in both sympathetic and parasympathetic activity, as well as increased heart rate and decreased blood pressure.

Late-Pregnancy Salivary Cortisol Concentrations of Ghanaian Women Participating in a Randomized Controlled Trial of Prenatal Lipid-Based Nutrient Supplements

BACKGROUND

High circulating cortisol is associated with miscarriage, preterm birth, and low birth weight. Research in nonpregnant individuals suggests that improved nutrition may lower cortisol concentrations. It is unknown whether nutritional supplementation during pregnancy lowers cortisol.

OBJECTIVE

Our objective was to determine whether women receiving a lipid-based nutrient supplement (LNS) throughout pregnancy would have lower salivary cortisol at 36 wk gestation compared with women receiving other nutrient supplements.

METHODS

We conducted a randomized controlled trial in 1320 pregnant Ghanaian women at ≤20 wk gestation who were assigned to receive daily throughout pregnancy: 1) 60 mg iron + 400 μg folic acid (IFA), 2) multiple micronutrients (MMNs), or 3) 20 g LNS (containing 118 kcal, 22 micronutrients, and protein). Morning salivary cortisol was collected from a subsample at baseline and at 28 and 36 wk gestation.

RESULTS

A total of 758 women had cortisol measurements at 28 or 36 wk gestation. Salivary cortisol at 36 wk gestation did not differ between groups and was (mean ± SE) 7.97 ± 0.199 in the IFA group, 7.84 ± 0.191 in the MMN group, and 7.77 ± 0.199 nmol/L in the LNS group, when adjusted for baseline cortisol, time of waking, and time between waking and saliva collection (P = 0.67). There was an interaction between supplementation group and women's age (continuous variable, P-interaction = 0.03); and when age was dichotomized by the median, significant differences in salivary cortisol concentrations between groups were seen in women ≤26 y of age (IFA = 8.23 ± 0.284 nmol/L, MMN = 8.20 ± 0.274 nmol/L, and LNS = 7.44 ± 0.284 nmol/L; P = 0.03) but not in women >26 y old (IFA = 7.71 ± 0.281 nmol/L, MMN = 7.50 ± 0.274 nmol/L, and LNS = 8.08 ± 0.281 nmol/L; P = 0.13).

CONCLUSIONS

We conclude that supplementation with LNSs or MMNs during pregnancy did not affect the cortisol concentration in the study population as a whole, in comparison with IFA, but that LNS consumption among younger women may lead to lower cortisol at 36 wk gestation. This trial was registered at clinicaltrials.gov as NCT00970866.

Forebrain glucocorticoid receptor gene deletion attenuates behavioral changes and antidepressant responsiveness during chronic stress

Stress is an important risk factor for mood disorders. Stress also stimulates the secretion of glucocorticoids, which have been found to influence mood. To determine the role of forebrain glucocorticoid receptors (GR) in behavioral responses to chronic stress, the present experiments compared behavioral effects of repeated social defeat in mice with forebrain GR deletion and in floxed GR littermate controls. Repeated defeat produced alterations in forced swim and tail suspension immobility in floxed GR mice that did not occur in mice with forebrain GR deletion. Defeat-induced changes in immobility in floxed GR mice were prevented by chronic antidepressant treatment, indicating that these behaviors were dysphoria-related. In contrast, although mice with forebrain GR deletion exhibited antidepressant-induced decreases in tail suspension immobility in the absence of stress, this response did not occur in mice with forebrain GR deletion after defeat. There were no marked differences in plasma corticosterone between genotypes, suggesting that behavioral differences depended on forebrain GR rather than on abnormal glucocorticoid secretion. Defeat-induced gene expression of the neuronal activity marker c-fos in the ventral hippocampus, paraventricular thalamus and lateral septum correlated with genotype-related differences in behavioral effects of defeat, whereas c-fos induction in the nucleus accumbens and central and basolateral amygdala correlated with genotype-related differences in behavioral responses to antidepressant treatment. The dependence of both negative (dysphoria-related) and positive (antidepressant-induced) behaviors on forebrain GR is consistent with the contradictory effects of glucocorticoids on mood, and implicates these or other forebrain regions in these effects.

Effects of low and high protein:carbohydrate ratios in the diet of pregnant gilts on maternal cortisol concentrations and the adrenocortical and sympathoadrenal reactivity in their offspring

Inadequate maternal nutrition during gestation may cause an adverse environment for the fetus leading to alterations of the hypothalamic-pituitary-adrenal (HPA) and sympatho-adrenomedullary (SAM) systems later in life. In the present study, we investigated the effects of diets with low and high protein:carbohydrate ratios on cortisol concentrations of pregnant gilts as well as the long-term effects on the function of the HPA and SAM axes in their offspring. Throughout gestation, 33 German Landrace gilts were fed high (HP, 30%), low (LP, 6.5%), or adequate (AP, 12.1%) protein diets, which were made isocaloric by adjusting the carbohydrate content. The salivary cortisol concentrations of the sows were measured in the course of the gestation period. The offspring were cross-fostered, and the plasma cortisol and catecholamine concentrations of the offspring were determined on postnatal d (PND) 1 and 27 and under specific challenging conditions: after weaning (PND 29) and after ACTH and insulin challenges (PND 68 and 70, respectively). Glucocorticoid receptor (GR) binding and neurotransmitter concentrations were measured in stress-related brain regions, and histological analyses of the adrenal were performed. Maternal salivary cortisol concentrations increased throughout gestation (P < 0.001) and the LP gilts had greater salivary cortisol compared with the AP and HP gilts (P < 0.05). No differences between diets were found for cortisol, corticosteroid-binding globulin, and catecholamine concentrations in plasma and for GR binding in hippocampus and hypothalamus in piglets at PND 1 and 27. However, the cortisol response to weaning was increased in LP piglets (P < 0.05), and in HP offspring the basal plasma noradrenaline concentrations were increased (P < 0.05). The cortisol response to the ACTH and the insulin challenge did not differ between diets. On PND 81, an increased adrenal medulla area was observed in LP offspring compared with the AP offspring (P < 0.05). Our results show that maternal diets with aberrant protein:carbohydrate ratios during gestation have moderate long-term effects on the function of the HPA and SAM system in the offspring, which indicates that pigs show a considerable plasticity to cope with maternal malnutrition.

High and low protein∶ carbohydrate dietary ratios during gestation alter maternal-fetal cortisol regulation in pigs

Imbalanced maternal nutrition during gestation can cause alterations of the hypothalamic-pituitary-adrenal (HPA) system in offspring. The present study investigated the effects of maternal low- and high-protein diets during gestation in pigs on the maternal-fetal HPA regulation and expression of the glucocorticoid receptor (GR), mineralocorticoid receptor (MR), 11β-hydroxysteroid dehydrogenase 1 and 2 (11β-HSD1 and 11β-HSD2) and c-fos mRNAs in the placenta and fetal brain. Twenty-seven German Landrace sows were fed diets with high (HP, 30%), low (LP, 6.5%) or adequate (AP, 12.1%) protein levels made isoenergetic by varying the carbohydrate levels. On gestational day 94, fetuses were recovered under general anesthesia for the collection of blood, brain and placenta samples. The LP diet in sows increased salivary cortisol levels during gestation compared to the HP and AP sows and caused an increase of placental GR and c-fos mRNA expression. However, the diurnal rhythm of plasma cortisol was disturbed in both LP and HP sows. Total plasma cortisol concentrations in the umbilical cord vessels were elevated in fetuses from HP sows, whereas corticosteroid-binding globulin levels were decreased in LP fetuses. In the hypothalamus, LP fetuses displayed an enhanced mRNA expression of 11β-HSD1 and a reduced expression of c-fos. Additionally, the 11β-HSD2 mRNA expression was decreased in both LP and HP fetuses. The present results suggest that both low and high protein∶carbohydrate dietary ratios during gestation may alter the expression of genes encoding key determinants of glucocorticoid hormone action in the fetus with potential long-lasting consequences for stress adaptation and health.

Serum albumin as a determinant of cortisol release in patients with acute ischemic stroke

OBJECTIVE

Animal studies demonstrated that protein malnutrition increases pituitary-adrenorcortical activity and leads to excessive cortisol release. The aim of our study was to determine the association between serum albumin and cortisol level in patients with acute ischemic stroke.

METHODS

Fifty-nine patients with first-ever ischemic stroke were included. Serum albumin level was measured within 36 h after stroke symptoms onset. Serum cortisol was measured between 36 and 72 h after stroke onset at 6 a.m., 10 a.m., 6 p.m. and 10 p.m.

RESULTS

The patients in upper tertile of serum albumin had significantly lower cortisol level measured at 6 a.m. (median with interquartiles: 549.0 [430.4-667.7] nmol/L vs 590.4 [482.8-918.7] nmol/L, P=0.047) and 10 a.m. (402.8 [344.9-510.4] nmol/L vs 634.6 [482.8-827.7] nmol/L, P<0.01) than patients in lower and middle tertiles. On logistic regression analysis adjusted for age and stroke severity, patients in lower and middle tertile of serum albumin had about 7-times higher risk of hypercortisolemia than patients in upper tertile (P<0.01).

CONCLUSIONS

Low serum albumin level in patients with ischemic stroke is associated with higher serum cortisol level and predisposes to hypercortisolemia.

The chronic ingestion of diets containing different proteins produces marked variations in brain tryptophan levels and serotonin synthesis in the rat

Serotonin (5HT) synthesis in brain is influenced by precursor (tryptophan (TRP)) concentrations, which are modified by food ingestion. Hence, in rats, a carbohydrate meal raises brain TRP and 5HT; a protein-containing meal does not, but little attention has focused on differences among dietary proteins. Recently, single meals containing different proteins have been shown to produce marked changes in TRP and 5HT. The present studies evaluate if such differences persist when rats ingest such diets chronically. Male rats were studied that ingested diets for 9 days containing zein, wheat gluten, soy protein, casein, or α-lactalbumin (17% dry weight). Brain TRP varied up to eightfold, and 5HT synthesis fivefold among the different protein groups. TYR and LEU concentrations, and catecholamine synthesis rate in brain varied much less. The effects of dietary protein on brain TRP and 5HT previously noted after single meals thus continue undiminished when such diets are consumed chronically.

Corticosterone and related receptor expression are associated with increased beta-amyloid plaques in isolated Tg2576 mice

Previously, we reported that the stress associated with chronic isolation was associated with increased beta-amyloid (Abeta) plaque deposition and memory deficits in the Tg2576 transgenic animal model of Alzheimer's disease (AD) [Dong H, Goico B, Martin M, Csernansky CA, Bertchume A, Csernansky JG (2004) Effects of isolation stress on hippocampal neurogenesis, memory, and amyloid plaque deposition in APP (Tg2576) mutant mice. Neuroscience 127:601-609]. In this study, we investigated the potential mechanisms of stress-accelerated Abeta plaque deposition in this Tg2576 mice by examining the relationship between plasma corticosterone levels, expression of glucocorticoid receptor (GR) and corticotropin-releasing factor receptor-1 (CRFR1) in the brain, brain tissue Abeta levels and Abeta plaque deposition during isolation or group housing from weaning (i.e. 3 weeks of age) until 27 weeks of age. We found that isolation housing significantly increased plasma corticosterone levels as compared with group-housing in both Tg+ mice (which contain and overexpress human amyloid precursor protein (hAPP) gene) and Tg- mice (which do not contain hAPP gene as control). Also, isolated, but not group-housed animals showed increases in the expression of GR in the cortex. Furthermore, the expression of CRFR1 was increased in isolated Tg+ mice, but decreased in isolated Tg- mice in both cortex and hippocampus. Changes in the components of hypothalamic-pituitary-adrenal (HPA) axis were accompanied by increases in brain tissue Abeta levels and Abeta plaque deposition in the hippocampus and overlying cortex in isolated Tg+ mice. These results suggest that isolation stress increases corticosterone levels and GR and CRFR1 expression in conjunction with increases in brain tissue Abeta levels and Abeta plaque deposition in the Tg2576 mouse model of AD.

Glucocorticoid feedback control of corticotropin in the hypoxic neonatal rat

The objective of this study was to determine the effects of manipulating glucocorticoid negative feedback on acute ACTH and corticosterone responses to corticotropin-releasing hormone (CRH) injection in 7-day-old rats exposed to normoxia or hypoxia from birth. Chemical adrenalectomy was achieved with aminoglutethimide, and glucocorticoids were replaced with a low dose of dexamethasone. Hypoxia per se increased basal plasma corticosterone and attenuated the plasma ACTH response to CRH. Aminoglutethimide per se decreased plasma corticosterone and strongly increased basal plasma ACTH and anterior pituitary POMC gene expression. Dexamethasone partially attenuated elevations in basal plasma ACTH due to aminoglutethimide in both normoxic and hypoxic pups, but inhibited anterior pituitary POMC expression and CRH-induced plasma ACTH only in hypoxic pups. Despite this inhibition, hypoxic pups treated with both dexamethasone and aminoglutethimide still exhibited a significant CRH-induced increment in plasma ACTH, which was lacking in hypoxic pups not treated with either dexamethasone or aminoglutethimide. We conclude that ACTH responses to acute stimuli in hypoxic neonatal rats are prevented by ACTH-independent increases in corticosterone, rather than by intrinsic hypothalamic-pituitary hypoactivity.

Perinatal maternal undernutrition programs the offspring hypothalamo-pituitary-adrenal (HPA) axis

There is now compelling evidence, coming both from animal and human studies that an early exposure to undernutrition is frequently associated with low birth weight and programs HPA axis alterations throughout the lifespan. Although animal models have reported conflicting findings arising from differences in experimental paradigms and species, they have clearly demonstrated that such programming not only affects the brain but also the pituitary corticotrophs and the adrenal cortex. In fetuses, maternal undernutrition reduces HPA axis function and implicates a reduction of placental 11beta-HSD2 activity and a greater transplacental transfer of glucocorticoids (GRs). In young adults, usually only fine HPA axis alterations were observed, whereas in older ones, maternal undernutrition was frequently associated with chronic hyperactivity of this neuroendocrine axis. In humans, evidence of HPA axis dysregulation in people who were small at birth has recently emerged. Thus, we suggest that such alterations in adults may be implicated in the aetiology of several disorders related to the metabolic syndrome as well as to immune or inflammatory diseases. To reverse such programming, recent experimental reports have shown that postnatal environmental interventions, dietary modifications and the use of agents modulating the epigenomic state could partly restore physiological functions and thus open new therapeutic strategies.

Association between chronic undernutrition and hypertension

In developing countries nutritional deficit during prenatal and continuing in post-natal life is very common. This condition leads to stunting and important metabolic changes. Over 30% of children in the world are stunted. The metabolic resultants of nutritional deficit during growth are classically known to aim at energy conservation. This review summarizes data from Brazil, a developing country undergoing the double burden of obesity and undernutrition, especially among the poor, and suggests that stunting or chronic undernutrition increases the risk of obesity and hypertension later in life. Around 60 million people are under the poverty line in Brazil. In São Paulo, the richest city of the country, 20% of the population live in slums and in Maceió, the capital of one of the poorest states, this percentage reaches 50%. Undernutrition in this population is around 20% among children, with high frequency of infections, anemia, and parasitic infestations, associated with poor sanitation. Among stunted adolescents, we found a high prevalence of hypertension (21%) that is a considerably higher estimate compared to non-stunted adolescents (less than 10%). The prevalence of hypertension in undernourished pre-school children, or in those who recovered from undernutrition, was higher than that in controls (29%, 20% and 2%, respectively, P < 0.001). Among stunted adults eating no more than 66% of the requirements (adjusted for stature), overweight/obesity was 35% in women and 25% in men. The prevalence of hypertension was 44% among stunted women and 18% among stunted men. Fifty per cent of stunted and obese women had hypertension. These data reinforce the important association between undernutrition and hypertension from childhood through adulthood. Health policies for preventing and combating childhood undernutrition should have an impact on the morbidity and mortality related to hypertension during adulthood.

Tumor necrosis factor-α and malnutrition-induced inhibition of diaphragm fiber growth in young rats

Tumor necrosis factor (TNF)-α has been implicated in several muscle-wasting disorders, with increased levels of the cytokine reported in malnourished children. The role of TNF-α in mediating malnutrition-induced inhibition of diaphragm (DIA) muscle growth in young growing rats was evaluated. Three groups of rats were studied: 1) control (CTL); 2) nutritional deprivation (ND; 50% of normal food intake for 7 days); and 3) ND + rat specific anti-TNF-α antibody. DIA fiber cross-sectional areas were determined. Serum and muscle TNF-α levels were measured by real-time PCR, ELISA, and immunohistochemistry. Body weights decreased 20% in ND rats and increased 46% in CTL animals. Anti-TNF-α had no effect on body weight or on DIA mass in ND animals. ND significantly reduced cross-sectional areas of all fiber types (33–46%). Anti-TNF-α failed to attenuate ND-induced inhibition of DIA fiber growth. Serum TNF-α levels increased 2.6-fold in ND animals, with levels suppressed to below CTL values with anti-TNF-α. DIA TNF-α mRNA and protein levels increased two- to threefold in ND rats. Anti-TNF-α antibodies suppressed muscle levels of the cytokine in ND animals to near CTL values. TNF-α immunoreactivity in all DIA fibers revealed similar directions of change in both ND groups. Direction and magnitude of change in DIA phosphorylated p38 MAPK (a likely second messenger of TNF-α) tracked those of TNF-α. Muscle levels of IGF-I mRNA and phosphorylated Akt were markedly reduced in ND animals with no change following anti-TNF-α therapy. Thus rat anti-TNF-α at a dose known to neutralize the cytokine failed to attenuate or reverse ND-induced inhibition of DIA fiber growth in our model.

Plasma leptin and ghrelin in the neonatal rat: interaction of dexamethasone and hypoxia

Ghrelin, leptin, and endogenous glucocorticoids play a role in appetite regulation, energy balance, and growth. The present study assessed the effects of dexamethasone (DEX) on these hormones, and on ACTH and pituitary proopiomelanocortin (POMC) and corticotropin-releasing hormone receptor-1 (CRHR1) mRNA expression, during a common metabolic stress - neonatal hypoxia. Newborn rats were raised in room air (21% O2) or under normobaric hypoxia (12% O2) from birth to postnatal day (PD) 7. DEX was administered on PD3 (0.5 mg/kg), PD4 (0.25 mg/kg), PD5 (0.125 mg/kg), and PD6 (0.05 mg/kg). Pups were studied on PD7 (24 h after the last dose of DEX). DEX significantly increased plasma leptin and ghrelin in normoxic pups, but only increased ghrelin in hypoxic pups. Hypoxia alone resulted in a small increase in plasma leptin. Plasma corticosterone and pituitary POMC mRNA expression were decreased 24 h following the last dose of DEX, whereas plasma ACTH and pituitary CRHR1 mRNA expression had already increased (normoxia and hypoxia). Hypoxia alone increased corticosterone, but had no effect on ACTH or pituitary POMC and CRHR1 mRNA expression. Neonatal DEX treatment, hypoxia, and the combination of both affect hormones involved in energy homeostasis. Pituitary function in the neonate was quickly restored following DEX-induced suppression of the hypothalamic-pituitary-adrenal axis. The changes in ghrelin, leptin, and corticosterone may be beneficial to the hypoxic neonate through the maintenance of appetite and shifts in intermediary metabolism.

Elevated corticosterone and inhibition of ACTH responses to CRH and ether in the neonatal rat: effect of hypoxia from birth

Hypoxia is a common cause of neonatal morbidity and mortality. We have previously demonstrated a dramatic ACTH-independent activation of adrenal steroidogenesis in hypoxic neonatal rats, leading to increases in circulating corticosterone levels. The purpose of the present study was to determine if this ACTH-independent increase in corticosterone inhibits the ACTH response to acute stimuli. Neonatal rats were exposed to normoxia (control) or hypoxia from birth to 5 or 7 days of age. At the end of the exposure, plasma ACTH and corticosterone were measured before and after either ether vapors were administered for 3 min or CRH (10 microg/kg) was given intraperitoneally. Thyroid function, pituitary pro-opiomelanocortin (POMC) mRNA and ACTH content, and hypothalamic corticotropin-releasing hormone (CRH), neuropeptide Y (NPY), and AVP mRNA were also assessed. Hypoxia led to a significant increase in corticosterone without a large increase in ACTH, confirming previous studies. The ACTH responses to ether or CRH administration were almost completely inhibited in hypoxic pups. Hypoxia did not affect the established regulators of the neonatal hypothalamic-pituitary-adrenal axis, including pituitary POMC or ACTH content, hypothalamic CRH, NPY, or AVP mRNA (parvo- or magnocellular), or thyroid function. We conclude that hypoxia from birth to 5 or 7 days of age leads to an attenuated ACTH response to acute stimuli, most likely due to glucocorticoid negative feedback. The neural and biochemical mechanism of this effect has yet to be elucidated.

COX-2 inhibition attenuates anorexia during systemic inflammation without impairing cytokine production

Anorexia and weight loss are frequent complications of acute and chronic infections and result from induction of cytokines, prostaglandins, and other inflammatory mediators that are critical for pathogen elimination. Selective attenuation of the hypophagic response to infection and maintenance of the production of factors essential for infection control would be a useful addition to antimicrobial therapy in the treatment of human disease. Here, we evaluate the relative contribution of cyclooxygenase (COX)-1- and COX-2-derived prostaglandins to anorexia and weight loss precipitated by systemic immune activation by lipopolysaccharide (LPS). Using COX isoform-selective pharmacological inhibitors and gene knockout mice, we found that COX-2 inhibition during LPS-induced inflammation results in preserved food intake and maintenance of body weight, whereas COX-1 inhibition results in augmented and prolonged weight loss. Regulation of neuropeptide Y, corticotropin-releasing hormone, leptin, and interleukin-6 does not change as a function of COX-2 inhibition after LPS administration. Our data implicate COX-2 inhibition as a therapeutic target to maintain nutritional status while still allowing a normal cytokine response during infection.

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.

Endogenous corticosteroids modulate Clostridium difficile toxin A-induced enteritis in rats

We examined the role of glucocorticoids in acute inflammatory diarrhea mediated by Clostridium difficile toxin A. Toxin A (5 microg) or buffer was injected in rat ileal loops, and intestinal responses were measured after 30 min to 4 h. Ileal toxin A administration increased plasma glucocorticoids after 1 h, at which time the toxin-stimulated secretion was not significant. Administration of the glucocorticoid analog dexamethasone inhibited toxin A-induced intestinal secretion and inflammation and downregulated toxin A-mediated increase of macrophage inflammatory protein-2. Adrenalectomy followed by replacement with glucocorticoids at various doses suggested that intestinal responses to toxin A were related to circulating levels of glucocorticoids. Administration of the glucocorticoid receptor antagonist RU-486 enhanced toxin A-mediated intestinal secretion and inflammation. We conclude that C. difficile toxin A causes increased secretion of endogenous glucocorticoids, which diminish the intestinal secretory and inflammatory effects of toxin A.

Interleukin-6 is an essential, corticotropin-releasing hormone-independent stimulator of the adrenal axis during immune system activation

Glucocorticoids play a critical role in control of the cytokine response after immune challenge. Conversely, cytokines modulate glucocorticoid production by the hypothalamic-pituitary-adrenal axis. To define the potency and mechanism of interleukin-6 (IL-6) for augmentation of adrenal function, we exploited mice deficient in corticotropin-releasing hormone (CRH), IL-6, or both. Mice deficient in CRH action demonstrate severely impaired glucocorticoid production in response to psychological and metabolic challenge, but near normal responses to stressors that activate the immune system. In this paper, we demonstrate that IL-6 is essential for activation of the hypothalamic-pituitary-adrenal axis during immunological challenge in the absence of hypothalamic input from CRH. IL-6 receptors are present on pituitary corticotrophs and adrenocortical cells, consistent with the ability of IL-6 to bypass CRH in augmentation of adrenal function. Plasma corticosterone levels after bacterial lipopolysaccharide injection in mice deficient in CRH or IL-6 were significantly lower than in wild-type mice but significantly greater than in mice deficient in both CRH and IL-6. A second model of immune system activation using 2C11, an antibody to the T cell receptor, demonstrated a normal corticosterone response in mice deficient in CRH or IL-6, but a markedly decreased response in mice deficient in both CRH and IL-6. Surprisingly, the relative contribution of IL-6 for modulation of the adrenal response to stress is greater in female than in male mice. This gender-specific difference in IL-6 action in mice suggests the utility of further analysis of IL-6 in determining the female predominance seen in many human inflammatory/autoimmune diseases.

Corticotropin-releasing hormone links pituitary adrenocorticotropin gene expression and release during adrenal insufficiency

Corticotropin-releasing hormone (CRH)-deficient (KO) mice provide a unique system to define the role of CRH in regulation of the hypothalamic-pituitary-adrenal (HPA) axis. Despite several manifestations of chronic glucocorticoid insufficiency, basal pituitary proopiomelanocortin (POMC) mRNA, adrenocorticotrophic hormone (ACTH) peptide content within the pituitary, and plasma ACTH concentrations are not elevated in CRH KO mice. The normal POMC mRNA content in KO mice is dependent upon residual glucocorticoid secretion, as it increases in both KO and WT mice after adrenalectomy; this increase is reversed by glucocorticoid, but not aldosterone, replacement. However, the normal plasma levels of ACTH in CRH KO mice are not dependent upon residual glucocorticoid secretion, because, after adrenalectomy, these levels do not undergo the normal increase seen in KO mice despite the increase in POMC mRNA content. Administration of CRH restores ACTH secretion to its expected high level in adrenalectomized CRH KO mice. Thus, in adrenal insufficiency, loss of glucocorticoid feedback by itself can increase POMC gene expression in the pituitary; but CRH action is essential for this to result in increased secretion of ACTH. This may explain why, after withdrawal of chronic glucocorticoid treatment, reactivation of CRH secretion is a necessary prerequisite for recovery from suppression of the HPA axis.

POMC-derived peptides and their biological action

It has long been known that a large number of POMC-related peptides are found in skin. In this introduction I describe the formation of POMC-derived peptides in various tissues to indicate that processing is largely tissue-dependent. I focus on the peptides from the N-terminal fragment, such as gamma-MSH, ACTH and alpha-MSH, and beta-lipopropin as well as beta-endorphin. I touch on the factors that control the synthesis of the various peptides, which are now numerous and varied, and again are tissue specific. The biologic activity of the peptides generated from POMC are described in relation to their possible action in skin. In addition, I describe a new class of peptides induced in skin following injury and which are of great interest.

Glucocorticoids reverse leptin effects on food intake and body fat in mice without increasing NPY mRNA

Glucocorticoid stimulation of appetite and leptin expression conflicts with leptin inhibition of food intake and suggests that glucocorticoids reduce sensitivity to leptin. To determine if glucocorticoids impair feeding and metabolic responses to leptin, we measured leptin-induced changes in food intake, body weight, hormones, carcass fat, and hypothalamic neuropeptide Y (NPY) mRNA in adrenalectomized mice with and without corticosterone replacement. Leptin infusion (0.5 microgram/h) significantly decreased food intake and body weight in adrenalectomized mice. Corticosterone replacement approximating normal 24-h mean levels restored food intake but did not permit weight gain equivalent to PBS-infused controls. Corticosterone levels comparable to stress-induced production completely reversed leptin-induced reductions in weight gain and body fat, despite significant attenuation by leptin of corticosterone-induced increases in plasma insulin levels. Glucocorticoid replacement increased food intake without reversing leptin inhibition of hypothalamic NPY mRNA levels. We conclude that glucocorticoid levels within the physiological range can interfere with leptin action and that glucocorticoid effects are at least partly independent of NPY.

Glucocorticoid replacement, but not corticotropin-releasing hormone deficiency, prevents adrenalectomy-induced anorexia in mice

There is considerable evidence that CRH can suppress food intake. As hypothalamic CRH, a main site of CRH expression, is also negatively regulated by glucocorticoids, it is unclear whether anorexia and weight loss in adrenal insufficiency are attributable to elevated CRH or to decreased glucocorticoid levels. To distinguish these possibilities, we have measured food intake and body weight in wild-type and CRH-deficient mice after sham adrenalectomy (Sham ADX) or adrenalectomy (ADX) with and without corticosterone (B) replacement. CRH deficiency neither increased basal food intake and body weight nor attenuated decreases in food intake after ADX or Sham ADX. B replacement producing plasma levels above the circadian peak completely blocked ADX-induced decreases in feeding and body weight in all mice and frequently stimulated food intake in CRH-deficient mice. Plasma levels of insulin and leptin, two other hormones involved in appetite regulation, did not differ between genotypes; however, the relationship between food intake and circulating leptin was significantly less negative at B doses that preserved appetite. B replacement levels slightly below circadian peak concentrations did not prevent hypophagia after ADX. We conclude that factors other than or in addition to CRH are more important in mediating appetite responses to adrenalectomy.

Impaired diurnal adrenal rhythmicity restored by constant infusion of corticotropin-releasing hormone in corticotropin-releasing hormone-deficient mice

The normal pattern of daily glucocorticoid production in mammals requires circadian modulation of hypothalamicpituitary-adrenal axis activity. To assess both the factors responsible for imparting this diurnal profile and its physiologic importance, we have exploited corticotropin-releasing hormone (CRH)-deficient mice generated by homologous recombination in embryonic stem cells. CRH-deficient mice have lost normal circadian variations in plasma ACTH and glucocorticoid while maintaining normal circadian locomotor activity. Constant peripheral infusion of CRH produced marked diurnal excursions of plasma glucocorticoid, indicating that CRH acts in part as a permissive factor for other circadian modulators of adrenocortical activity. The presence of atrophic adrenals in CRH-deficient mice without an overt deficit in basal plasma ACTH concentration suggests that the diurnal increase in ACTH is essential to maintain normal adrenal function.