Mitochondrial dysfunction: maternal protein restriction as a trigger of reactive species overproduction and brainstem energy failure in male offspring brainstem.

Mitochondria are important organelles in eukaryotic organisms, wherein their capacity to produce energy vary among the tissues depending upon the amounts of oxygen consumed. Part of the oxygen consumed during ATP generation produces reactive oxygen species, which if not efficiently removed can trigger a systemic damage to molecular compounds characterized as oxidative stress. Several studies have demonstrated that mitochondrial dysfunction and oxidative stress in the central nervous system (CNS) are related to a plethora of neural disorders. Herein, we hypothesize that a late autonomic imbalance-induced hypertension might be related to long-lasting effects of protein restriction during the critical period of the CNS development on the mitochondrial function and oxidative stress in the brainstem of adult (i.e. 150 days of age) male Wistar rats. Maternal protein restriction was induced by offering a diet based on 8% of casein from first day of pregnancy until weaning, when the male pups started to receive laboratory chow up to 150 days of life. The protein restriction induced an extended detrimental modulation in mitochondria function, decreasing the phosphorylation capacity with concomitant decrease in the mitochondrial membrane potential, wherein the reactive species overproduction triggered a disruption in proton conductance, which may gradually compromise mitochondria energy conservation. Interestingly, the elevated activity of glutathione-S-transferase and the augmented expression of uncoupling protein 2 are likely protective mechanisms induced by lipid peroxidation products, being feasible molecular changes attempting to deal with oxidative stress-induced ageing.

Maternal low-protein diet in female rat heart: possible protective effect of estradiol.

Several studies have shown that maternal low-protein (LP) diet induces detrimental effects in cardiovascular system and oxidative stress in male animals. Additional studies suggested that female has lower incidence of cardiovascular disease. However until present data, the possible effects of estradiol on the undernutrition during gestational and lactation periods are not discussed. The present study was conducted to evaluate the effects of a maternal LP diet during gestational and lactation period on oxidative balance in the female rat hearts ventricles at two ages. Dams were fed with normal protein (NP) or a LP diet during the gestational and lactation period, and their female offspring were divided into age groups (22 or 122 days, corresponding to a low or high estrogen level) composing four experimental groups. Evaluating the nutritional effect showed an increase in oxidative stress biomarkers and decrease in enzymatic defense in LP-22D compared with NP-22D. In contrast, no changes were observed in malondialdehyde and carbonyls, but an increase in glutathione-S-transferase (GST) activity in the LP-122D compared with NP-122D. The global oxy-score in the LP-22D group indicated a predominance of oxidative damage when compared with NP-22D, while in LP-122D group the global oxy-score was restored to NP-122D levels. Evaluating the estradiol effect, our data show a significant decrease in oxidative stress with increase in CAT and GST activity, associated with increase in intracellular thiols. Our data suggest that in situation with low levels of estradiol, hypoproteic diet during gestation and lactation period has detrimental effects on heart, however when estradiol levels raise, the detrimental effects induced are mitigated.

Protein undernutrition during development and oxidative impairment in the central nervous system (CNS): potential factors in the occurrence of metabolic syndrome and CNS disease.

Mitochondria play a regulatory role in several essential cell processes including cell metabolism, calcium balance and cell viability. In recent years, it has been postulated that mitochondria participate in the pathogenesis of a number of chronic diseases, including central nervous system disorders. Thus, the concept of mitochondrial function now extends far beyond the common view of this organelle as the 'powerhouse' of the cell to a new appreciation of the mitochondrion as a transducer of early metabolic insult into chronic disease in later life. In this review, we have attempted to describe some of the associations between nutritional status and mitochondrial function (and dysfunction) during embryonic development with the occurrence of neural oxidative imbalance and neurogenic disease in adulthood.

Fluoxetine induces lean phenotype in rat by increasing the brown/white adipose tissue ratio and UCP1 expression.

The serotonergic system plays a crucial role in the energy balance regulation. Energy balance is mediated by food intake and caloric expenditure. Thus, the present study investigated the mechanisms that might be associated with fluoxetine treatment-induced weight reduction. Wistar male rat pups received daily injections with subcutaneous fluoxetine (Fx-group) or vehicle solution (Ct-group) from day 1 until 21 days of age. Several analyses were conducted to verify the involvement of mitochondria in weight reduction. We found that body weight in the Fx-group was lower compared to control. In association to lower fat mass in the Fx-group (25%). Neither neonatal caloric intake nor food intake reveals significant differences. Evaluating caloric expenditure (locomotor activity and temperature after stimulus), we did not observe differences in locomotor activity. However, we observed that the Fx group had a higher capacity to maintain body temperature in a cold environment compared with the Ct-group. Since brown adipose tissue-(BAT) is specialized for heat production and the rate of heat production is related to mitochondrial function, we found that Fx-treatment increases respiration by 36%, although after addition of GDP respiration returned to Ct-levels. Examining ROS production we observe that Fx-group produced less ROS than control group. Evaluating uncoupling protein (UCP) expression we found that Fx-treatment increases the expression by 23%. Taken together, our results suggest that modulation of serotonin system results in positive modulation of UCP and mitochondrial bioenergetics in brown fat tissue.

The effect of glutamine supplementation and physical exercise on neutrophil function.

Glutamine is the most abundant free amino acid in the body. Its primary source is skeletal muscle, from where it is released into the bloodstream and transported to a variety of tissues. Several studies have shown that glutamine is important for rat and human neutrophil function and that these cells utilize glutamine at high rates. Physical exercise has also been shown to induce considerable changes in neutrophil metabolism and function. As neutrophils represent 50-60% of the total circulating leukocyte pool and play a key role in inflammation, both physical exercise and glutamine might be expected to regulate the inflammatory process. In this review, the changes in neutrophil function induced by physical exercise and glutamine supplementation are compared.

Neutrophil fatty acid composition: effect of a single session of exercise and glutamine supplementation.

The fatty acid composition of immune cells appears to contribute to variations of cell function. The independent and combined effects of a single session of exercise (SSE) and glutamine supplementation (GS) on neutrophil fatty acid composition were investigated. Compared to control (no treatment given--i.e. neither SSE or GS), single session of exercise decreased myristic, palmitic and eicosapentaenoic (EPA) acids, and increased lauric, oleic, linoleic, arachidonic (AA) and docosahexaenoic (DHA) acids whereas glutamine supplementation combined with SSE (GS+SSE) increased oleic acid. Polyunsaturated/saturated fatty acid ratio and Unsaturation index were higher in neutrophils from the SSE and GS groups as compared with control. These findings support the proposition that SSE and GS may modulate neutrophil function through alterations in fatty acid composition.

Molecular mechanisms of glutamine action.

Glutamine is the most abundant free amino acid in the body and is known to play a regulatory role in several cell specific processes including metabolism (e.g., oxidative fuel, gluconeogenic precursor, and lipogenic precursor), cell integrity (apoptosis, cell proliferation), protein synthesis, and degradation, contractile protein mass, redox potential, respiratory burst, insulin resistance, insulin secretion, and extracellular matrix (ECM) synthesis. Glutamine has been shown to regulate the expression of many genes related to metabolism, signal transduction, cell defense and repair, and to activate intracellular signaling pathways. Thus, the function of glutamine goes beyond that of a simple metabolic fuel or protein precursor as previously assumed. In this review, we have attempted to identify some of the common mechanisms underlying the regulation of glutamine dependent cellular functions.

Glutamine-dependent changes in gene expression and protein activity.

The functions of glutamine are many and include, substrate for protein synthesis, anabolic precursor for muscle growth, acid-base balance in the kidney, substrate for ureogenesis in the liver, substrate for hepatic and renal gluconeogenesis, an oxidative fuel for intestine and cells of the immune system, inter-organ nitrogen transport, precursor for neurotransmitter synthesis, precursor for nucleotide and nucleic acid synthesis and precursor for glutathione production. In the present review information on the mechanism of glutamine action is presented. This amino acid has been shown to regulate the expression of several genes (such as p47phox, p22phox, gp91phox, alpha-actin and fibronectin) and activate several proteins (such as ASK1, c-myc, c-jun and p70s6k).

cAMP inhibits natriuretic peptide receptor-B activity and increases C-type natriuretic peptide in FRTL-5 rat thyroid cells.

C-type natriuretic peptide (CNP) and its cognate guanylyl cyclase receptor, the natriuretic peptide receptor B (NPR-B) together constitute a regulatory system that controls cell function via the generation of intracellular cyclic GMP. In this report we have examined the role of cAMP signaling in the regulation of CNP and NPR-B activity in the FRTL-5 rat thyroid follicular cell line. As had been observed earlier with TSH, the cAMP mimetic, dibutyryl cAMP (dbcAMP; 1 mM) induced a significant reduction in CNP-stimulated cGMP generation that was first apparent after 6 h of treatment. The inhibitory effect of dbcAMP on NPR-B was dose dependent, with an EC50 of 0.2 mM. Pretreatment of FRTL-5 cells with either of two protein kinase A (PKA) inhibitors, KT-5720 and H-89, failed to curtail the dbcAMP reduction in NPR-B activity, suggesting that the cAMP pathway leading to inhibition of NPR-B is PKA independent. Whereas either a 30-min or a 24-h treatment with the protein kinase C-activator phorbol myristate acetate failed to alter maximal levels of CNP-stimulated cGMP, a 24-h exposure to the calcium ionophore A23187 reduced CNP-stimulated cGMP to about one-third of control. Pretreatment of FRTL-5 cells with the cell-permeable calcium chelator 1,2 bis(2-aminophenoxy)ethane-N,N,N1,N1-tetraacetic acid, tetraacetoxymethyl ester completely abrogated the cAMP-induced reduction of CNP-stimulated cGMP. Real-time PCR showed no effect of dbcAMP on NPR-B transcript at 3 and 6 h, but indicated a 40% reduction in transcript by dbcAMP at 24 h. In contrast, real-time PCR indicated a 5-fold increase in CNP transcript at 3 h, reaching 15.4-fold above control at 6 h in cells treated with dbcAMP. In addition, immunofluorescence staining of FRTL-5 cells with a specific antibody for CNP-22 showed the presence of cytoplasmic CNP that was up-regulated by incubation with either TSH or dbcAMP. These results suggested that cAMP signaling regulates the natriuretic peptide system in rat thyroid cells by increasing CNP expression, and reducing NPR-B activity. This latter action of cAMP appears to be both PKA independent and calcium dependent, and provides support for a dominant role for calcium in the regulation of NPR-B in the rat thyroid.

Atrial natriuretic factor and C-type natriuretic peptide induce retraction of human thyrocytes in monolayer culture via guanylyl cyclase receptors.

The natriuretic peptides signal through three receptor subtypes, of which two (NPR-A and NPR-B) are membrane-bound guanylyl cyclases for which the principal ligands are respectively atrial natriuretic factor (ANF) and C-type natriuretic peptide (CNP). In the human thyroid cell, a third receptor, NPR-C, has been implicated in the regulation of thyroglobulin, but functional roles for NPR-A and NPR-B have not yet been defined. In the present study we used RT-PCR to identify transcripts of all three receptor subtypes, both in human thyroid and in HTU-5 cells, a long-term culture of thyroid-derived cells. Both ANF and CNP induced a twofold increase in intracellular cGMP content in HTU-5 cells. Morphologic changes (a significant increase in cells of the retracted phenotype) were observed in ANF- and CNP-treated cells within 3 and 5 h of treatment respectively. Significant increases in retracted cell number were induced by ANF and CNP, but not the NPR-C-specific ring-deleted ANF analog, C-ANF(4-23), during a 15-day treatment. All three natriuretic peptides, however, induced a small (15-20%) but significant (P<0 small middle dot001) increase in DNA content per well. The stable analog of cGMP, 8-bromo-cGMP (8-BrcGMP; 1 mM), also increased the number of retracted HTU-5 cells, and was equipotent with the cAMP analog, 8-BrcAMP, in this effect. The cGMP-dependent protein kinase inhibitor, KT5823, however, had no significant effect on the ANF-induced increase in numbers of retracted cells. These results suggest that the actions of NPR-A and NPR-B, functional receptors in the human thyroid cell, may in part be mediated by cGMP-induced alterations in the cytoskeleton.

Thyroglobulin increases cell proliferation and suppresses Pax-8 in mesangial cells.

Thyroglobulin (Tg), has recently been identified as a transcriptional regulator of thyroid-restricted genes. The extrathyroidal expression of several of these genes (including the transcription factor Pax-8) together with the occurrence of specific Tg binding sites suggests a secondary role for Tg as a circulating hormone. In this study, we demonstrate using Northern analysis that Pax-8 is expressed in the mouse mesangial cell, and that its transcript levels are suppressed by Tg. These cells also express an asialoglycoprotein receptor, a receptor involved in Tg endocytosis in the thyroid, and a Tg transcript smaller than the 8.3-kb thyroidal form. Reverse transcriptase PCR showed that suppression of Pax-8 by Tg is correlated with reduced expression of bcl-2 apoptosis suppressor. Tg, but not triiodothyronine (T(3)) significantly increased MC proliferation above control as determined by DNA content of MC cultures. The effect of Tg on proliferation was not duplicated by either bovine serum albumin, gamma-globulins, lactoferrin, or the ASGPR-specific ligand,orosomucoid. These results suggest a possible endocrine role for Tg in regulating both Pax-8 related gene transcription and cell division in the mesangial cell.