Effect of starvation and insulin-induced hypoglycemia on oxidative stress scavenger system and electron transport chain complexes from rat brain, liver, and kidney

The Antioxidant Activity of Mistletoes (Viscum album and Other Species)

In addition to the European mistletoe, Viscum album, which is the most known and utilized one, there are several species commonly known as mistletoe. They are spread in various regions of the planet and are all characterized by hemiparasitism and epiphytic behaviour. The published studies evidence other similarities, including the sharing of important biological properties, with the common presence of antioxidant effects. However, whereas the European mistletoe is largely utilized in medical treatments, although with controversial aspects, the scientific knowledge and medical uses of other mistletoes are still insufficient. This review focuses on the controversial medical story of European mistletoe regarding its antioxidant activity and the potentiality of the other species named mistletoe pertaining to botanical families and genera different from Viscum.

Flying on empty: Reduced mitochondrial function and flight capacity in food-deprived monarch butterflies

Mitochondrial function is fundamental to organismal performance, health, and fitness - especially during energetically challenging events, such as migration. With this investigation, we evaluated mitochondrial sensitivity to ecologically relevant stressors. We focused on an iconic migrant, the North American monarch butterfly (Danaus plexippus), and examined the effects of two stressors: seven days of food deprivation, and infection by the protozoan parasite Ophryocystis elektroscirrha (known to reduce survival and flight performance). We measured whole-animal resting (RMR) and peak flight metabolic rate, and mitochondrial respiration of isolated mitochondria from the flight muscles. Food deprivation reduced mass-independent RMR and peak flight metabolic rate, whereas infection did not. Fed monarchs used mainly lipids in flight (respiratory quotient 0.73), but the respiratory quotient dropped in food-deprived individuals, possibly indicating switching to alternative energy sources, such as ketone bodies. Food deprivation decreased mitochondrial maximum oxygen consumption but not basal respiration, resulting in lower respiratory control ratio (RCR). Furthermore, food deprivation decreased mitochondrial complex III activity, but increased complex IV activity. Infection did not result in any changes in these mitochondrial variables. Mitochondrial maximum respiration rate correlated positively with mass-independent RMR and flight metabolic rate, suggesting a link between mitochondria and whole-animal performance. In conclusion, low food availability negatively affects mitochondrial function and flight performance, with potential implications on migration, fitness, and population dynamics. Although previous studies have reported poor flight performance in infected monarchs, we found no differences in physiological performance, suggesting that reduced flight capacity may be due to structural differences or low energy stores.

Role of carnitine in regulation of blood pressure (MAP/SBP) and gene expression of cardiac hypertrophy markers (α/β-MHC) during insulin-induced hypoglycaemia: Role of oxidative stress

Cardiovascular disease is a leading cause of death in diabetic patients. Hyperglycaemia and iatrogenic hypoglycaemia exacerbate several pathogenic mechanisms underlying hypertension and heart diseases. Carnitine is a potent endogenous antioxidant and cellular fatty acid transporter for antioxidative stress and energy production in the cardiovascular system. The current study aimed to find the role of carnitine in the regulation of hypoglycaemia-induced hypertension and cardiac hypertrophy. Male rats received insulin glargine (InG) to induce hypoglycaemia followed by D-carnitine or acetyl-L-carnitine for carnitine depletion or carnitine supplementation, respectively. The obtained results showed that carnitine deficiency provoked hypoglycaemia-induced hypertension. Mean arterial pressure was elevated from 78.16 ± 11.4 to 100 ± 5.11 mm Hg in InG treated group, and from 78.2 ± 8.5 to 123.4 ± 28.2 mm Hg in InG + D-carnitine treated group. Acetyl-L-carnitine resisted the elevation in blood pressure in all hypoglycaemic animals and kept it within the normal values (68.33 ± 6.7 mm Hg). Acetyl-L-carnitine increased myocardial carnitine content leading to the attenuation of hypoglycaemia-induced oxidative stress, which was evaluated through measurement of the oxidative stress biomarkers such as inducible nitric oxide synthase, NAD(P)H quinone dehydrogenase-1, heme oxygenase-I, and glutathione S-transferase. Moreover, acetyl-L-carnitine prevented induction of gene expression of cardiac hypertrophy markers during hypoglycaemic conditions, which was assessed via the evaluation of mRNA expression of α-myosin heavy chain and β-myosin heavy chain. These findings demonstrate that carnitine might play an essential role in prevention of hypoglycaemia-induced hypertension and cardiac hypertrophy through providing energy and antioxidants to the cardiovascular system.

Hypoglycemia increases endothelial-dependent vasodilation through suppressing phosphorylation at Threonine 495/497 site of endothelial nitric oxide synthase

OBJECTIVE

Phosphorylation plays an essential role in the regulation of endothelial nitric oxide synthase (eNOS) activity. However, the phosphorylation of eNOS under hypoglycemia and whether hypoglycemia changes eNOS activity is unknown. This paper aims to clarify the regulation of eNOS phosphorylation and its activity change under hypoglycemia.

METHODS

Bovine aortic endothelial cells (BAECs) and Sprague-Dawley rats were treated with hypoglycemia, and the phosphorylation of eNOS was subjected to western blot. Blood nitric oxide (NO) concentration was determined by NO kit and endothelial-dependent vasodilation was detected by multi-wire myograph.

RESULTS

In both BAECs and rats' thoracic aorta, hypoglycemia induced eNOS phosphorylation decrease specifically on Threonine (Thr) 497. Inhibition of ubiquitination of protein kinase C α subunit (PKCα) reverses the decrease of eNOS phosphorylation in hypoglycemia. Ubiquitinated PKCα can be reversed by AMPK knockdown. In rats, insulin induced hypoglycemia increased the concentration of NO in arterial blood, and progressively enhanced the endothelium-dependent vasodilation of the thoracic and mesenteric aorta.

CONCLUSIONS

In vitro, the activation of AMPK may lead to the expression of PKCα by regulating ubiquitination, resulting in a decrease in the level of P-eNOS Thr497 phosphorylation under hypoglycemia. In vivo, insulin-induced hypoglycemia produces a beneficial cardiovascular effect on rats.

Glycemic Variability and CNS Inflammation: Reviewing the Connection

Glucose is the primary energy source for the brain, and exposure to both high and low levels of glucose has been associated with numerous adverse central nervous system (CNS) outcomes. While a large body of work has highlighted the impact of hyperglycemia on peripheral and central measures of oxidative stress, cognitive deficits, and vascular complications in Type 1 and Type 2 diabetes, there is growing evidence that glycemic variability significantly drives increased oxidative stress, leading to neuroinflammation and cognitive dysfunction. In this review, the latest data on the impact of glycemic variability on brain function and neuroinflammation will be presented. Because high levels of oxidative stress have been linked to dysfunction of the blood-brain barrier (BBB), special emphasis will be placed on studies investigating the impact of glycemic variability on endothelial and vascular inflammation. The latest clinical and preclinical/in vitro data will be reviewed, and clinical/therapeutic implications will be discussed.

Development of malignancies and changes in time-dependent hemoglobin A1c among a nondiabetic population: longitudinal analysis

BACKGROUND

The fluctuation of hemoglobin A1c (HbA1c) and changes in health habits over time was not considered in previous studies. The aim of this study was to evaluate the time-sequenced association between malignancy incidence and HbA1c with a longitudinal study design using repeated measurements of HbA1c.

METHODS

A retrospective longitudinal study was conducted at a large teaching hospital in Tokyo, Japan, from 2005 to 2016. All participants who underwent voluntary health check-ups at the hospital were included. Our outcomes were the development of malignancy. We compared these outcomes using HbA1c categories. Longitudinal analyses were conducted with a mixed effects model in which time-dependent HbA1c measurements were applied to consider fluctuations in HbA1c levels, adjusted for covariates.

RESULTS

A total of 77,385 nondiabetic participants were included in the study; the mean age was 44.7 and 49.4% of participants were male. During a median follow-up of 1588 (interquartile range 730-2946) days, 4506 (5.8%) participants developed malignancies. The relationship between future malignancies and HbA1c was U-shaped; both the lower HbA1c groups (OR 1.31, 95% CI 1.17-1.46 for < 5.0%) and the higher HbA1c group (OR 1.87, 95% CI 1.03-3.39 for ≥ 7.5%) had significantly higher odds ratios compared to the 5.5-5.9%. The lowest HbA1c was associated with higher odds of breast cancer (OR 1.5, 95% CI 1.21-1.86) and female genital cancer (OR 1.57, 95% CI 1.04-2.37).

CONCLUSIONS

Our study found a U-shaped association between HbA1c and future malignancies among nondiabetic people but did not find additional risk at the prediabetic level. Low HbA1c may be associated with the incidence of breast cancer and female genital cancer.

Glycemic variability and subsequent malignancies among the population without diabetes

BACKGROUND

Glycemic variability has been suggested to be related to some unfavorable outcomes, but malignancy development has not been evaluated. The aim of this study was to evaluate the association of glycemic variability with malignancy development among the population without diabetes.

METHODS

We conducted a retrospective cohort study at a large teaching hospital in Tokyo, Japan, from 2005 to 2016. We included all participants without diabetes who underwent voluntary health check-ups. Our outcome was the development of any malignancy. As a measure of glycemic variability, we calculated the quotient of CV in HbA1c and categorized subjects into quartile groups. A Cox proportional hazard model was applied, adjusting for patient demographics and social and family histories.

RESULTS

A total of 42,731 participants were included in this study; the mean age was 53.8 and 48.3% were male. During the median follow up of 2639 (interquartile range (IQR):1787-3662) days, 2435 participants (5.7%) developed malignancies. Participants who had larger glycemic variability (CV in HbA1c; hazard ratio (HR) 1.15, 95%confidence interval (CI):1.02-0.31 for the second quartile group; HR 2.20, 95%CI:1.95-2.48 for the third quartile group, HR 4.66, 95%CI:4.16-5.21 for the fourth quartile group, compared to first quartile group) had a significantly higher risk of malignancies.

CONCLUSION

We found an association between large glycemic variability and a high risk of future malignancies in a dose-dependent manner among people without diabetes. This finding suggests that maintaining a constant level of glucose may have favorable effects on cancer prevention in people without diabetes.

Quantitative Proteomics Reveals the Beneficial Effects of Low Glucose on Neuronal Cell Survival in an in vitro Ischemic Penumbral Model

Understanding proteomic changes in the ischemic penumbra are crucial to rescue those salvageable cells and reduce the damage of an ischemic stroke. Since the penumbra region is dynamic with heterogeneous cells/tissues, tissue sampling from animal models of stroke for the molecular study is a challenge. In this study, cultured hippocampal HT22 cells under hypoxia treatment for 17.5 h with 0.69 mM low glucose (H+LG) could mimic ischemic penumbral cells since they had much higher cell viability and viable cell number compared to hypoxia without glucose (H-G) treatment. To validate established cell-based ischemic penumbral model and understand the beneficial effects of low glucose (LG), quantitative proteomics analysis was performed on H+LG, H-G, and normoxia with normal 22 mM glucose (N+G) treated cells. We identified 427 differentially abundant proteins (DAPs) between H-G and N+G and further identified 105 DAPs between H+LG and H-G. Analysis of 105 DAPs revealed that LG promotes cell survival by activating HIF1α to enhance glycolysis; preventing the dysregulations of extracellular matrix remodeling, cell cycle and division, and antioxidant and detoxification; as well as attenuating inflammatory reaction response, protein synthesis and neurotransmission activity. Our results demonstrated that this established cell-based system could mimic penumbral conditions and can be used for molecular studies.

Glutathione "Redox Homeostasis" and Its Relation to Cardiovascular Disease

More people die from cardiovascular diseases (CVD) than from any other cause. Cardiovascular complications are thought to arise from enhanced levels of free radicals causing impaired "redox homeostasis," which represents the interplay between oxidative stress (OS) and reductive stress (RS). In this review, we compile several experimental research findings that show sustained shifts towards OS will alter the homeostatic redox mechanism to cause cardiovascular complications, as well as findings that show a prolonged antioxidant state or RS can similarly lead to such cardiovascular complications. This experimental evidence is specifically focused on the role of glutathione, the most abundant antioxidant in the heart, in a redox homeostatic mechanism that has been shifted towards OS or RS. This may lead to impairment of cellular signaling mechanisms and elevated pools of proteotoxicity associated with cardiac dysfunction.

Visit-to-Visit Hemoglobin A1c Variability Is Associated With Later Cancer Development in Patients With Diabetes Mellitus

PURPOSE

Recent studies have shown that patients with diabetes mellitus have a higher risk of tumorigenesis. However, the effect of glycemic variability on tumorigenesis among diabetic patients has not been well investigated. Hence, we performed a retrospective cohort study to analyze the effect of visit-to-visit hemoglobin A1c (HbA1c) variability and later onset of malignancies.

METHODS

This study included 2640 patients with diabetes mellitus 50 years or older. To analyze visit-to-visit glycemic activity, we calculated intrapersonal SD of all recorded HbA1c and used SD-HbA1c as a measure of glycemic variability. Because the number of individual visits varied, we divided SD-HbA1c by visit times in order to adjust for the potential influence of visit time difference between individuals. Patients were divided into quartiles according to their HbA1c variability, and Cox regression models were used to evaluate the association between glycemic variability and later onset of tumorigenesis.

RESULTS

Three hundred thirty patients (12.5%) developed malignancy during follow-up. The median follow-up period was 1511 days (4.1 years; interquartile range, 2487.5 days). Relative to the group with the lowest glycemic variability (first quartile), the groups with higher glycemic variability showed a dose-dependent association with tumorigenesis. The odds ratios for the second, third, and fourth quartiles were 1.20 (95% confidence interval, 0.88-1.65), 1.43 (1.02-2.00), and 2.19 (1.52-3.17), respectively. The mean HbA1c and diabetes mellitus duration periods were not significantly associated with tumorigenesis. This result was consistent when limiting the number of covariates.

CONCLUSIONS

These results demonstrated that visit-to-visit HbA1c variability is a potential risk factor for later tumorigenesis. The association may be mediated by oxidative stress or hormone variability. Routine cancer screening may be suggested for diabetic patients with unstable glycemic control.

Inverse relationship between human erythrocyte fructose-6-phosphate and short-chain fatty acid levels

In muscle cells, fructose is initially metabolised to fructose-6-phosphate. In the liver, fructose is metabolised to fructose-1-phosphate and thence to glyceraldehydes, which in turn can either enter glycogenolysis via pyruvate or gluconeogenesis via fructose-1,6-bisphosphate and fructose-6-phosphate. High levels of fructose-1-phosphate inhibit both glycogenolysis and gluconeogenesis. We hypothesised that, if systemically absorbed short-chain fatty acids constitute a major metabolic fate of unabsorbed dietary fructose, then levels of erythrocyte fructose-6-phosphate would be inversely correlated with plasma levels of short-chain fatty acids. The aim of this study was to test this hypothesis in respect of the three main short-chain fatty acids acetate, propionate and butyrate. Venous blood samples from 39 patients (16 male, 23 female, mean (standard error) age 42.4 (3.3) years) were analysed. Erythrocyte fructose-6-phosphate was measured using quantitative Fourier transform infrared spectrometry following gel electrophoresis, while plasma acetate, propionate and butyrate levels were measured using gas-liquid chromatography. The erythrocyte fructose-6-phosphate level was inversely correlated with the plasma acetate (r = -0.30, p = 0.06), propionate (r = -0.31, p = 0.05) and butyrate (r = -0.40, p = 0.01). These results support our hypothesis. The conversion of unabsorbed dietary fructose into short-chain fatty acids may represent a protective mechanism against the adverse effects of hypoglycaemia.

Food deprivation and social inequality may lead to oxidative damage: a study on the preventive role of melatonin in the male rat reproductive system

Spermatogenic cells are susceptible to oxidative stress and apoptosis. Food deprivation (FD) has been reported as a stressor that could increase reactive oxygen species. In the present study, FD-induced oxidative stress and apoptosis, as well as the protective effects of melatonin, were evaluated in the testes. Wistar rats in the control group were fed a standard diet, whereas a sham group was administered saline as the melatonin vehicle. A third group received daily injections of melatonin (5mgkg-1 bodyweight). These rats were further divided into four groups of rats that were either subjected to FD, FD + isolation, FD + melatonin injection and FD + melatonin injection + isolation. Testicular tissues were evaluated for malondialdehyde (MDA) and reduced glutathione (GSH) concentrations, as well as and DNA damage. FD increased MDA and reduced GSH concentrations, whereas melatonin treatment improved these parameters. Immunohistochemistry for capsase-3 and terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling revealed that the number of apoptotic cells was increased in rats subjected to FD alone. Melatonin treatment offset the number of apoptotic cells following FD. The results provide evidence that FD can increase oxidative stress, leading to activation of apoptosis, and that melatonin has the ability to protect the testes against oxidative damage induced by FD.

Differential production of reactive oxygen species in distinct brain regions of hypoglycemic mice

Hypoglycemia is a serious complication of insulin therapy in patients suffering from type 1 Diabetes Mellitus. Severe hypoglycemia leading to coma (isoelectricity) induces massive neuronal death in vulnerable brain regions such as the hippocampus, the striatum and the cerebral cortex. It has been suggested that the production of reactive oxygen species (ROS) and oxidative stress is involved in hypoglycemic brain damage, and that ROS generation is stimulated by glucose reintroduction (GR) after the hypoglycemic coma. However, the distribution of ROS in discrete brain regions has not been studied in detail. Using the oxidation sensitive marker dihydroethidium (DHE) we have investigated the distribution of ROS in different regions of the mouse brain during prolonged severe hypoglycemia without isoelectricity, as well as the effect of GR on ROS levels. Results show that ROS generation increases in the hippocampus, the cerebral cortex and the striatum after prolonged severe hypoglycemia before the coma. The hippocampus showed the largest increases in ROS levels. GR further stimulated ROS production in the hippocampus and the striatum while in the cerebral cortex, only the somatosensory and parietal areas were significantly affected by GR. Results suggest that ROS are differentially produced during the hypoglycemic insult and that a different response to GR is present among distinct brain regions.

Neuronal damage and cognitive impairment associated with hypoglycemia: An integrated view

The aim of the present review is to offer a current perspective about the consequences of hypoglycemia and its impact on the diabetic disorder due to the increasing incidence of diabetes around the world. The main consequence of insulin treatment in type 1 diabetic patients is the occurrence of repetitive periods of hypoglycemia and even episodes of severe hypoglycemia leading to coma. In the latter, selective neuronal death is observed in brain vulnerable regions both in humans and animal models, such as the cortex and the hippocampus. Cognitive damage subsequent to hypoglycemic coma has been associated with neuronal death in the hippocampus. The mechanisms implicated in selective damage are not completely understood but many factors have been identified including excitotoxicity, oxidative stress, zinc release, PARP-1 activation and mitochondrial dysfunction. Importantly, the diabetic condition aggravates neuronal damage and cognitive failure induced by hypoglycemia. In the absence of coma prolonged and severe hypoglycemia leads to increased oxidative stress and discrete neuronal death mainly in the cerebral cortex. The mechanisms responsible for cell damage in this condition are still unknown. Recurrent moderate hypoglycemia is far more common in diabetic patients than severe hypoglycemia and currently important efforts are being done in order to elucidate the relationship between cognitive deficits and recurrent hypoglycemia in diabetics. Human studies suggest impaired performance mainly in memory and attention tasks in healthy and diabetic individuals under the hypoglycemic condition. Only scarce neuronal death has been observed under moderate repetitive hypoglycemia but studies suggest that impaired hippocampal synaptic function might be one of the causes of cognitive failure. Recent studies have also implicated altered mitochondrial function and mitochondrial oxidative stress.

Moderate recurrent hypoglycemia during early development leads to persistent changes in affective behavior in the rat

Recurrent hypoglycemia is a common problem among infants and children that is associated with several metabolic disorders and insulin-dependent diabetes mellitus. Although studies have reported a relationship between a history of juvenile hypoglycemia and psychological health problems, the direct effects of recurrent moderate hypoglycemia have not been fully determined. Thus, in this study, we used an animal model to examine the effects of recurrent hypoglycemia during the juvenile period on affective, social, and motor function (assessed under euglycemic conditions) across development. To model recurrent hypoglycemia, rats were administered 5 U/kg of insulin or saline twice per day from postnatal day (P)10 to P19. Body weight gain was retarded in insulin-treated rats during the treatment period, but recovered by the end of treatment. However, insulin-treated rats displayed increases in affective reactivity that emerged early during treatment and persisted after treatment into early adulthood. Specifically, insulin-treated pups showed increased maternal separation-induced vocalizations as infants, and an exaggerated acoustic startle reflex as juveniles and young adults. Moreover, young adult rats with a history of recurrent juvenile hypoglycemia exhibited increased fear-potentiated startle and increases in behavioral and hormonal responses to restraint stress. Some of these effects were sex-dependent. The changes in affective behavior in insulin-exposed pups were accompanied by decreases in adolescent social play behavior. These results provide evidence that recurrent, transient hypoglycemia during juvenile development can lead to increases in fear-related behavior and stress reactivity. Importantly, these phenotypes are not reversed with normalization of blood glucose and may persist into adulthood.

The mobile phone decreases fructose but not citrate in rabbit semen: a longitudinal study

The negative impact of mobile phones on sperm motility has been previously described. Both fructose and citrate are important components in semen that facilitate sperm motility. To date, no studies have investigated the effect of exposure to electromagnetic radiation emitted from the mobile phone on their levels.. Therefore, a longitudinal study using the adult rabbit as a model was undertaken. A total of 30 adult male rabbits were randomly divided into three groups. The first (phone) group was placed in specially designed cages, and exposed to radio frequency emitted from a mobile phone (900 MHz) kept in standby mode and positioned adjacent to the genitalia for 8 h daily for 12 weeks. The other two groups served as controls; the stress group which was housed in the same kind of cages to evaluate any cage-induced anxiety, and the control group which was housed in the conventional roomy cages. Semen samples were retrieved weekly. Sperm motility and viability, semen fructose and citrate, and serum testosterone were measured. Histological sections from the prostatic complex, ampulla, and vesicular gland were evaluated. A significant drop in both fructose levels (257 +/-11.6 vs. 489 +/- 8.4 mg %, the baseline level) and number of motile sperms (50 vs. 72%) was observedin the phone group at the 10th week. However, no correlation was found between the two values. The stress control animals showed a similar but significantly less decline in motility No significant changes in citrate levels or other study parameters were seen in the three animal groups throughout the study. In conclusion, the pulsed radio frequency emitted by the mobile phone kept in the standby position longitudinally affected sperm motility and fructose but not citrate levels in rabbit semen.

Selective vulnerability of brain regions to oxidative stress in a non-coma model of insulin-induced hypoglycemia

Insulin-induced hypoglycemia causes the death of neurons in particular brain regions including the cerebral cortex, the striatum and the hippocampus, while the cerebellum and the brain stem are more resistant. The mechanisms underlying this selective vulnerability to hypoglycemic damage are unknown. In the present study we have analyzed the presence of lipoperoxidation products and nitrosilated protein residues in different rat brain regions during and after the induction of hypoglycemia. Insulin-injected hypoglycemic rats were sacrificed before the onset of the isoelectric period or infused with glucose to end hypoglycemia, and then sacrificed at different times. Increased lipoperoxidation levels were observed before the onset of the isoelectric period, while 3-nitrotyrosine (NT) residues in proteins and NT-positive cells were only observed after glucose reperfusion. These changes were found only in vulnerable brain regions, while none of them was evident in the cerebellum, suggesting a correlation between oxidative damage and vulnerability to hypoglycemic neuronal death in selective brain regions. Results suggest that a pro-oxidant state is promoted in certain brain regions during hypoglycemia and after the glucose reperfusion phase, which might result from the activation of several oxidative stress pathways and may be related to subsequent cell death.

Lifelong consumption of sodium selenite: gender differences on blood-brain barrier permeability in convulsive, hypoglycemic rats

The aim of this study was to compare the effects of hypoglycemia and induced convulsions on the blood-brain barrier permeability in rats with or without lifelong administration of sodium selenite. There is a significant decrease of the blood-brain barrier permeability in three brain regions of convulsive, hypoglycemic male rats treated with sodium selenite when compared to sex-matched untreated rats (p<0.05), but the decrease was not significant in female rats (p>0.05). The blood-brain barrier permeability of the left and right hemispheres of untreated, moderately hypoglycemic convulsive rats of both genders was better than their untreated counterparts (p<0.05). Our results suggest that moderate hypoglycemia and lifelong treatment with sodium selenite have a protective effect against blood-brain barrier permeability during convulsions and that the effects of sodium selenite are gender-dependent.

L-carnitine inhibits hypoglycemia-induced brain damage in the rat

Hypoglycemia sometimes occurs in patients with diabetes mellitus who receive excessive doses of insulin. Severe hypoglycemia has been known to induce mitochondrial swelling followed by neuronal death in the brain. Since L-carnitine effectively preserves mitochondrial function in various cells both in vitro and in vivo, we investigated its effects on the neuronal damage induced by hypoglycemic insult in male Wistar rats. Animals were given L-carnitine-containing water (0.1%) for 1 week and then received insulin (20 U/kg, i.p.) to induce hypoglycemia. Although L-carnitine did not affect the mortality of animals that developed hypoglycemic shock, it improved the cognitive function of the survived animals as assessed by the Morris water-maze test. L-carnitine effectively inhibited the increase in oxidized glutathione and mitochondrial dysfunction in the hippocampus and prevented neuronal injury. L-carnitine also inhibited the decrease in mitochondrial membrane potential and the generation of reactive oxygen species in hippocampal neuronal cells cultured in glucose-deprived medium. These results suggest that L-carnitine prevents hypoglycemia-induced neuronal damage in the hippocampus, presumably by preserving mitochondrial functions. Thus, L-carnitine may have therapeutic potential in patients with hypoglycemia induced by insulin overdose.

Prolonged glutamate excitotoxicity: effects on mitochondrial antioxidants and antioxidant enzymes

Glutamate, a major excitatory amino acid neurotransmitter is also an endogenous excitotoxin. The present study examined the prolonged and delayed effects of glutamate excitotoxicity on mitochondrial lipid peroxidation and antioxidant parameters in different brain regions, namely, cerebral hemisphere, cerebellum, brain stem and diencephalon. Wistar rats (male) were exposed to monosodium glutamate (MSG) (4 mg x g body wt(-1), i.p.) for 6 consecutive days and sacrificed on 30th and 45th day after last MSG dose. MSG treatment markedly decreased the mitochondrial manganese superoxide-dismutase (Mn-SOD), catalase and reduced glutathione (GSH) content, and increased the lipid peroxidation (LPx), uric acid and glutathione peroxidase (GPx) activity. These results indicate that oxidative stress produced by glutamate in vulnerable brain regions may persist for longer periods and mitochondrial function impairment is an important mechanism of excitatory amino acid mediated neurotoxicity in chronic neurodegeneration.

Effect of nutritional status and ozone exposure on rat brain serotonin

BACKGROUND

Ozone is an environmental pollutant that has widely documented deleterious effects on exposed organisms. In Mexico City, this pollutant frequently reaches concentrations that surpass safe health limits. In addition, it has been reported that the prevalence of malnutrition remains high in our childhood population. This experiment was carried out to determine whether malnutrition is a factor contributing to an increase in the risk of damage associated with ozone exposure.

METHODS

Using an experimental animal model, 21-day-old rats fed normally or with induced malnutrition were subchronically exposed to 0.5 ppm of ozone or fresh air, respectively, for 30 days. At the end of this period and using HPLC, serotonin concentrations were measured in four areas of the brain: cortex, hemispheres, cerebellum, and medulla oblongata.

RESULTS

Malnourished animals had a significant weight deficit beginning at 28 days with respect to well-fed animals. Among the well-fed animals, this phenomenon is seen at 35 days in exposed and non-exposed animals. In the four regions of the brain, malnourished animals show low serotonin concentrations with respect to well-nourished animals. In the cerebellum, there was an interaction between the nutritional factor and ozone exposure, while in the medulla oblongata both factors acted independently.

CONCLUSIONS

Our results suggest a multiplicative effect from the nutritional factor and ozone exposure in the changes observed concerning serotonergic metabolism.

Alterations in free radical scavenger system profile of type I diabetic rat brain

The activities of the enzymes related to glutathione synthesis, degradation, and functions as well as reactive oxygen scavenging enzymes were analyzed in different brain regions, such as cerebral hemisphere, cerebellum, brainstem, thalamus, and hypothalamus after 1 and 3 mo of streptozotocin-induced diabetes in rats. Parallel studies were also made in age-matched control rats and insulin-treated diabetic rats. The content of glutathione (GSH) and its synthesizing enzyme gamma-glutamylcystein synthetase and also superoxide dismutase (SOD) and catalase activities (reactive oxygen scavenging enzymes) were significantly decreased from almost all the brain regions studied. However, glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), gamma-glutamyl transpeptidase (gamma-GTP), and glutamine synthetase (GS) activities were increased in the diabetic rat brain. Insulin treatment to the diabetic rats resulted in partial to full recovery in these enzymes activities. The present results emphasize the potentially serious alterations of brain free radical scavenger system in uncontrolled Type I diabetes.