Tau Protein Alterations Induced by Hypobaric Hypoxia Exposure

Tauopathies are a group of neurodegenerative diseases whose central feature is dysfunction of the microtubule-associated protein tau (MAPT). Although the exact etiology of tauopathies is still unknown, it has been hypothesized that their onset may occur up to twenty years before the clear emergence of symptoms, which has led to questions about whether the prognosis of these diseases can be improved by, for instance, targeting the factors that influence tauopathy development. One such factor is hypoxia, which is strongly linked to Alzheimer's disease because of its association with obstructive sleep apnea and has been reported to affect molecular pathways related to the dysfunction and aggregation of tau proteins and other biomarkers of neurological damage. In particular, hypobaric hypoxia exposure increases the activation of several kinases related to the hyperphosphorylation of tau in neuronal cells, such as ERK, GSK3β, and CDK5. In addition, hypoxia also increases the levels of inflammatory molecules (IL-β1, IL-6, and TNF-α), which are also associated with neurodegeneration. This review discusses the many remaining questions regarding the influence of hypoxia on tauopathies and the contribution of high-altitude exposure to the development of these diseases.

POS0845 ASSESSING FRAILTY IN SYSTEMIC SCLEROSIS: A CROSS-SECTIONAL STUDY COMPARING FRAIL AND EDMONTON FRAILTY SCALES WITH PHYSICAL FRAILTY PHENOTYPE

Background

Systemic sclerosis (SSc) is a chronic disease characterized by autoimmunity, vasculopathy and fibrosis. During the disease course, patients with SSc are prone to accumulate multiple organ damage, increasing their vulnerability to adverse outcomes in comparison with individuals of the same age: a phenomenon called frailty. One of the most used definitions of frailty is the physical frailty phenotype (PFP) by Fried, et al. The PFP consists of 5 components: unintentional weight loss, exhaustion, muscle weakness, slow walking speed, and low physical activity. There is scarce data about frailty in patients with SSc.

Objectives

To study the prevalence and clinical aspects of PFP in a sample of patients with SSc. Also, we aim to investigate the diagnostic accuracy of the Fatigue, Resistance, Ambulation, Illness and Loss of weight (FRAIL) scale and the Edmonton frailty scale (EFS) using the PFP as the reference standard.

Methods

Cross-sectional study, including patients with SSc according to the 2013 ACR-EULAR classification criteria or the criteria suggested by Le Roy and Medsger for early disease. PFP assessment was according to the original definition, except for physical activity domain, assessed with the International Physical Activity Questionnaire (IPAQ). Patients were classified according to Fried’s criteria in robust (0), pre-frail (1-2), and frail (≥3). FRAIL scale and EFS were also applied to the same individuals. The FRAIL score ranges from 0 to 5 and patients were classified as robust (0), pre-frail (1-2), or frail (≥3). The EFS score ranges from 0–17 and categorizes patients as not frail (0–4), vulnerable (5–6), mild frailty (7–8), moderate frailty (9–10), and severe frailty (≥11). For the diagnostic assessment of FRAIL scale and EFS, we estimated the area under the receiver operating characteristic curve (AUC), considering PFP as the reference standard and dichotomizing the results in frail vs. non-frail.

Results

Between March and December 2019, 82 SSc patients were consecutively included. The mean age and disease duration were 60.4 (±10.6) and 13.4 (±8.2) years, respectively; 91.5% were women, and 19.5% with diffuse cutaneous SSc. The PFP distribution was: 8 (9.8%) robust, 47 (57.3%) pre-frail and 27 (32.9%) frail patients. The PFP domains´ frequencies were: low physical activity in 57 (69.5%), muscle weakness in 41 (50%), exhaustion in 34 (41.5%), unintentional weight loss in 15 (18.3%) and slow walking speed in 8 (9.8%) patients. Using the FRAIL scale, 44 (53.7%) patients were considered pre-frail and 25 (30.5%) frail. According to the EFS, 26 patients (31.7%) were classified as vulnerable and 12 (14.6%) as frail: mild in 6 (7.3%), moderate in 4 (4.9%) and severe in 2 (2.4%). The AUC against PFP was: 0.871 (95% CI 0.789-0.954, p<0.001) for FRAIL scale and 0.870 (95% CI 0.791-0.948, p<0.001) for EFS (Figure 1).

Conclusion

Frailty is prevalent in patients with long-standing SSc, and most of them are considered pre-frail or vulnerable. Low physical activity, muscle weakness and exhaustion are among the most frequent clinical aspects of the frailty phenotype. Both FRAIL scale and EFS showed overlapping diagnostic accuracy against PFP as the reference standard, and FRAIL scale seems to be more feasible than EFS.

References

[1]Rockwood MR, MacDonald E, Sutton E, Rockwood K, Baron M. Frailty index to measure health status in people with systemic sclerosis. J Rheumatol. 2014;41(4):698-705.

[2]Morley JE, Vellas B, Abellan van Kan G, et al. Frailty consensus: a call to action. J Am Med Dir Association. 2014;14(6):392-7.

[3]Fried LP, Tangen CM, Walston J, et al. Frailty in older adults: evidence for a phenotype. J Gerontol A Biol Sci Med Sci. 2001;56(3):M146-56.

[4]van Kan GA, Rolland YM, Morley JE, Vellas B. Frailty: Toward a Clinical Definition. J Am Med Dir Assoc. 2008;9(2):71-2.

[5]Rolfson DB, Majumdar SR, Tsuyuki RT, Tahir A, Rockwood K. Validity and reliability of the Edmonton Frail Scale. Age Ageing. 2006;35(5):526-9.

Disclosure of Interests

None declared

Oxidative Stress and Diseases Associated with High-Altitude Exposure

Several diseases associated with high-altitude exposure affect unacclimated individuals. These diseases include acute mountain sickness (AMS), high-altitude cerebral edema (HACE), high-altitude pulmonary edema (HAPE), chronic mountain sickness (CMS), and, notably, high-altitude pulmonary hypertension (HAPH), which can eventually lead to right ventricle hypertrophy and heart failure. The development of these pathologies involves different molecules and molecular pathways that might be related to oxidative stress. Studies have shown that acute, intermittent, and chronic exposure to hypobaric hypoxia induce oxidative stress, causing alterations to molecular pathways and cellular components (lipids, proteins, and DNA). Therefore, the aim of this review is to discuss the oxidative molecules and pathways involved in the development of high-altitude diseases. In summary, all high-altitude pathologies are related to oxidative stress, as indicated by increases in the malondialdehyde (MDA) biomarker and decreases in superoxide dismutase (SOD) and glutathione peroxidase (GPx) antioxidant activity. In addition, in CMS, the levels of 8-iso-PGF2α and H₂O₂ are increased, and evidence strongly indicates an increase in Nox4 activity in HAPH. Therefore, antioxidant treatments seem to be a promising approach to mitigating high-altitude pathologies.

Oxidative Stress, Kinase Activation, and Inflammatory Pathways Involved in Effects on Smooth Muscle Cells During Pulmonary Artery Hypertension Under Hypobaric Hypoxia Exposure

High-altitude exposure results in hypobaric hypoxia, which affects organisms by activating several mechanisms at the physiological, cellular, and molecular levels and triggering the development of several pathologies. One such pathology is high-altitude pulmonary hypertension (HAPH), which is initiated through hypoxic pulmonary vasoconstriction to distribute blood to more adequately ventilated areas of the lungs. Importantly, all layers of the pulmonary artery (adventitia, smooth muscle, and endothelium) contribute to or are involved in the development of HAPH. However, the principal action sites of HAPH are pulmonary artery smooth muscle cells (PASMCs), which interact with several extracellular and intracellular molecules and participate in mechanisms leading to proliferation, apoptosis, and fibrosis. This review summarizes the alterations in molecular pathways related to oxidative stress, inflammation, kinase activation, and other processes that occur in PASMCs during pulmonary hypertension under hypobaric hypoxia and proposes updates to pharmacological treatments to mitigate the pathological changes in PASMCs under such conditions. In general, PASMCs exposed to hypobaric hypoxia undergo oxidative stress mediated by Nox4, inflammation mediated by increases in interleukin-6 levels and inflammatory cell infiltration, and activation of the protein kinase ERK1/2, which lead to the proliferation of PASMCs and contribute to the development of hypobaric hypoxia-induced pulmonary hypertension.

Involvement of overweight and lipid metabolism in the development of pulmonary hypertension under conditions of chronic intermittent hypoxia

There is growing evidence that exposure to hypoxia, regardless of the source, elicits several metabolic responses in individuals. These responses are constitutive and are usually observed under hypoxia but vary according to the type of exposure. The aim of this review was to describe the involvement of obesity and lipid metabolism in the development of high-altitude pulmonary hypertension and in the development of acute mountain sickness under chronic intermittent hypoxia. Overweight or obesity, which are common in individuals with long-term chronic intermittent hypoxia exposure (high-altitude miners, shift workers, and soldiers), are thought to play a major role in the development of acute mountain sickness and high-altitude pulmonary hypertension. This association may be rooted in the interactions between obesity-related metabolic and physical alterations, such as increased waist circumference and neck circumference, among others, which lead to critical ventilation impairments; these impairments aggravate hypoxemia at high altitude, thereby triggering high-altitude diseases. Overweight and obesity are strongly associated with higher mean pulmonary artery pressure in the context of long-term chronic intermittent hypoxia. Remarkably, de novo synthesis of triglycerides by the sterol regulatory element-binding protein-1c pathway has been demonstrated, mainly due to the upregulation of stearoyl-CoA desaturase-1, which is also associated with the same outcomes. Therefore, overweight, obesity, and other metabolic conditions may hinder proper acclimatization. The involved mechanisms include respiratory impairment, alteration of the nitric oxide pathways, inflammatory status, reactive oxygen species imbalance, and other metabolic changes; however, further studies are required.

Long-term chronic intermittent hypoxia: a particular form of chronic high-altitude pulmonary hypertension

In some subjects, high-altitude hypobaric hypoxia leads to high-altitude pulmonary hypertension. The threshold for the diagnosis of high-altitude pulmonary hypertension is a mean pulmonary artery pressure of 30 mmHg, even though for general pulmonary hypertension is ≥25 mmHg. High-altitude pulmonary hypertension has been associated with high hematocrit findings (chronic mountain sickness), and although these are two separate entities, they have a synergistic effect that should be considered. In recent years, a new condition associated with high altitude was described in South America named long-term chronic intermittent hypoxia and has appeared in individuals who commute to work at high altitude but live and rest at sea level. In this review, we discuss the initial epidemiological pattern from the early studies done in Chile, the clinical presentation and possible molecular mechanism and a discussion of the potential management of this condition.

A prospective, single arm study of intraosseous basivertebral nerve ablation for the treatment of chronic low back pain: 12-month results

Background

The basivertebral nerve (BVN) has been a recently discovered target as a potential source for vertebrogenic chronic low back pain (CLBP). Prior randomized controlled trials have demonstrated safety and efficacy of BVN ablation for vertebrogenic CLBP, but minimal data exists regarding BVN ablation’s clinical effectiveness with broader application outside of strict trial inclusion criteria.

Methods

Prospective, single arm, open label effectiveness trial of 48 patients from community spine and pain practices treated with BVN ablation. Inclusion criteria required more than 6 months of CLBP and type 1 or 2 Modic changes on MRI to be enrolled. Patients were followed post procedure for 12 months using ODI, VAS, EQ-5D-5L and SF-36 patient reported outcome metrics.Results: 47 patients successfully received BVN ablation and 45 patients completed 12 months of follow up. Mean reduction in ODI at 12 months was 32.31 +/- 14.07 (p<0.001) with 88.89% (40/45) patients reporting a ≥15 point ODI decrease at 12 months. Mean VAS pain score decrease was 4.31+/-2.51 at 12 months (p<0.001) and more than 69% reported a 50% reduction in VAS pain scale. Similarly, SF-36 and EQ-5D-5L scores improved 26.27+/-17.19 and 0.22+/-0.15 (each p<0.001).

Conclusions

This data supports the clinical effectiveness of BVN ablation in the community practice setting, with similar 12 month improvements in patient reported outcomes as seen in previously published randomized control trials.

FRI0243 SARCOPENIA IS ASSOCIATED WITH MALNUTRITION IN PATIENTS WITH SYSTEMIC SCLEROSIS

Background:

Sarcopenia is one of the major health problems in older patients and is defined as a progressive decrease in muscle mass and function1. Sarcopenia has only rarely been studied in systemic sclerosis (SSc) and its impact in clinical characteristics of SSc is poorly investigated.

Objectives:

To evaluate the associations between sarcopenia and clinical features in SSc patients.

Methods:

Cross-sectional study, including 82 patients who met the ACR/EULAR 2013 classification criteria for SSc. Dual-energy X-ray absorptiometry, handgrip strength, and short physical performance battery were used to assess sarcopenia according the European Working Group on Sarcopenia in Older People’s (EWGSOP) diagnostic criteria updated in 20191. Malnutrition was evaluated according to the European Society of Clinical Nutrition and Metabolism (ESPEN)2, using the Malnutrition Universal Screening Tool (MUST) to screen risk for malnutrition.

Results:

The mean age was 60.4 years and 91.5% were women (table 1). Sarcopenia was identified in 15 (18.3%) SSc patients. Malnutrition was diagnosed in 12 (14.6%) and was more common in patients with sarcopenia (P=0.038). Also, there were significant differences between patients with and without sarcopenia regarding Body Mass Index (P=0.001), Fat Free Mass Index (P<0.001), knee extension strength (P=0.049), and Timed Up and Go test (P=0.041). There were no differences regarding age, disease duration, Rodnan skin score (mRSS), FVC and DLCO.

Table 1.

Clinical characteristics of SSc patients with and without sarcopenia. Data presented as number (%) of patients, except when indicated otherwise.

Patients featuresWhole(n=82)SSc patients without sarcopenia(n=67)SSc patients with sarcopenia(n=15)PvalueFemales75 (91.5)62 (92.5)13 (86.6)0.606Caucasian68 (82.9)53 (79.1)15 (100)0.258Age (years)b60.4 (10.6)60.2 (10.3)61.5 (12.3)0.678Diffuse skin involvement16 (19.5)16 (23.8)0 (0)0.082Disease duration (years)a12.8 (7.5, 19.2)12.7 (7.1,19.2)13.4 (8.9, 19.8)0.324Rodnan skin scorea4.0 (2.0, 10.0)5.0 (2.0, 10.0)2.0 (2.0,10.0)0.076Interstitial lung disease on HRCT32 (39.5)25 (37.3)7 (10.4)0.737FVC (% predicted)b88.4 (16.6)88.4 (16.9)88.3 (15.3)0.991DLCO (% predicted)b63.7 (11.9)63.6 (12.2)64.2 (11.2)0.855BMI (kg/m2)b25.6 (4.6)26.5 (4.4)21.8 (4.1)0.001FFMI (kg/m2)b15.6 (1.7)16.1 (1.6)13.8 (1.2)<0.001FMI (kg/m2)b9.5 (3.7)9.9 (3.6)7.5 (3.5)0.023Malnutrition12 (14.6)7 (10.4)5 (33.3)0.038MUST - Low risk58 (70.7)51 (76.1)7 (46.7)0.046Moderate and high risk24 (29.3)16 (23.9)8 (53.3)HAQb0.778 (0.591)0.797 (0.575)0.833 (0.576)0.825Timed Up and Go test (s)a8.41 (7.41, 10.59)8.39 (7.5, 9.4)10.23 (7, 14)0.041Knee extension strength (kgf)a21.40 (15.65, 27.52)21.70 (18.05, 28.35)14.82 (9.5, 24)0.049

aMedian (25, 75thpercentiles)

bMean (standard deviation)

Abbreviations: BMI: body mass Index; DLCO: diffusion capacity of carbon monoxide; FFMI: fat free mass index; FMI: fat mass index; FVC: forced vital capacity; HAQ: Health Assessment Questionnaire; HRCT: high-resolution computed tomography; MUST: Malnutrition Universal Screening Tool; SSc: systemic sclerosis.

Conclusion:

Sarcopenia is relatively common and is associated with malnutrition in patients with SSc. In our population, sarcopenia was not associated with other features related to a more severe disease. The role of sarcopenia in the prognosis of SSc needs to be better understood in longitudinal studies.

References:

[1]Cruz-Jentoft AJ, Bahat G, Bauer J, et al. Sarcopenia: Revised European consensus on definition and diagnosis. Age Ageing. 2019;48(1):16-31.

[2]Cederholm T, Bosaeus I, Barazzoni R, et al. Diagnostic criteria for malnutrition - An ESPEN Consensus Statement. Clin Nutr. 2015;34(3):335-40

Disclosure of Interests:

Vanessa Hax: None declared, Rafaela Cavalheiro do Espírito Santo: None declared, Emerson Pena: None declared, Luísa Rodrigues: None declared, Renata Ternus Pedo: None declared, Jordana Miranda de Souza Silva: None declared, Nicole Pamplona Bueno de Andrade: None declared, Andrese Aline Gasparin: None declared, Ricardo Xavier Consultant of: AbbVie, Pfizer, Novartis, Janssen, Eli Lilly, Roche, Rafael Mendonça da Silva Chakr: None declared

Lower Body Weight in Rats Under Hypobaric Hypoxia Exposure Would Lead to Reduced Right Ventricular Hypertrophy and Increased AMPK Activation

Background

Both chronic hypoxia (CH) and long-term chronic intermittent hypoxia (CIH) exposure lead to right ventricular hypertrophy (RVH). Weight loss is an effective intervention to improve cardiac function and energy metabolism in cardiac hypertrophy. Likewise, caloric restriction (CR) also plays an important role in this cardioprotection through AMPK activation. We aimed to determine the influence of body weight (BW) on RVH, AMPK and related variables by comparing rats exposed to both hypoxic conditions.

Methods

Sixty male adult rats were separated into two groups (n = 30 per group) according to their previous diet: a caloric restriction (CR) group and an ad libitum (AL) group. Rats in both groups were randomly assigned to 3 groups: a normoxic group (NX, n = 10), a CIH group (2 days hypoxia/2 days normoxia; n = 10) and a CH group (n = 10). The CR group was previously fed 10 g daily, and the other was fed ad libitum. Rats were exposed to simulated hypobaric hypoxia in a hypobaric chamber set to 428 Torr (the equivalent pressure to that at an altitude of 4,600 m above sea level) for 30 days. Measurements included body weight; hematocrit; serum insulin; glycemia; the degree of RVH (Fulton's index and histology); and AMPK, mTOR, and PP2C expression levels in the right ventricle determined by western blotting.

Results

A lower degree of RVH, higher AMPK activation, and no activation of mTOR were found in the CR groups exposed to hypobaric hypoxia compared to the AL groups (p < 0.05). Additionally, decreased glycemia and serum insulin levels were observed. Interestingly, PP2C expression showed an increase in the AL groups but not in the CR groups (p < 0.05).

Conclusion

Maintaining a low weight before and during exposure to high-altitude hypoxia, during either CH or CIH, could prevent a major degree of RVH. This cardioprotection would likely be due to the activation of AMPK. Thus, body weight is a factor that might contribute to RVH at high altitudes.

P6480Asymmetric dimethylarginine (ADMA) predicts altitude-associated hypoxic pulmonary arterial hypertension

Acknowledgement/Funding

CONICYT/FONDEF/FONIS Sa 09I20007; FIC Tarapaca BIP 30477541-0; BMBF grant 01DN17046 (DECIPHER); Georg & Jürgen Rickertsen Foundation, Hamburg

Asymmetric Dimethylarginine at Sea Level Is a Predictive Marker of Hypoxic Pulmonary Arterial Hypertension at High Altitude

Background: Prolonged exposure to altitude-associated chronic hypoxia (CH) may cause high-altitude pulmonary hypertension (HAPH). Chronic intermittent hypobaric hypoxia (CIH) occurs in individuals who commute between sea level and high altitude. CIH is associated with repetitive acute hypoxic acclimatization and conveys the long-term risk of HAPH. As nitric oxide (NO) regulates pulmonary vascular tone and asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NO synthesis, we investigated whether ADMA concentration at sea level predicts HAPH among Chilean frontiers personnel exposed to 6 months of CIH.

Methods: In this prospective study, 123 healthy army draftees were subjected to CIH (5 days at 3,550 m, 2 days at sea level) for 6 months. In 100 study participants with complete data, ADMA, symmetric dimethylarginine (SDMA), L-arginine, arterial oxygen saturation (SaO₂), systemic blood pressure, and hematocrit were assessed at months 0 (sea level), 1, 4, and 6. Acclimatization to altitude was determined using the Lake Louise Score (LLS) and the presence of acute mountain sickness (AMS). Echocardiography was performed after 6 months of CIH in 43 individuals with either good (n = 23) or poor (n = 20) acclimatization.

Results: SaO₂ acutely decreased at altitude and plateaued at 90% thereafter. ADMA increased and SDMA decreased during the study course. The incidence of AMS and the LLS was high after the first ascent (53 and 3.1 ± 2.4) and at 1 month of CIH (47 and 3.0 ± 2.6), but decreased to 20 and 1.4 ± 2.0 at month 6 (both p < 0.001). Eighteen participants (42%) showed a mean pulmonary arterial pressure (mPAP) >25 mm Hg, out of which 9 (21%) were classified as HAPH (mPAP ≥ 30 mm Hg). ADMA at sea level was significantly associated with mPAP at high altitude in month 6 (R = 0.413; p = 0.007). In ROC analysis, a cutoff for baseline ADMA of 0.665 μmol/L was determined to predict HAPH (mPAP > 30 mm Hg) with a sensitivity of 100% and a specificity of 63.6%.

Conclusions: ADMA concentration increases during CIH. ADMA at sea level is an independent predictive biomarker of HAPH. SDMA concentration decreases during CIH and shows no association with HAPH. Our data support a role of impaired NO-mediated pulmonary vasodilation in the pathogenesis of HAPH.

Effects of practice change on outcomes of extremely preterm infants with patent ductus arteriosus

AIM

To determine whether a decrease in patent ductus arteriosus (PDA) treatment or ligation in extremely preterm (EP) infants was associated with changes in rates of mortality and/or morbidities.

METHODS

Observational study on EP infants admitted from 2008 to 2015. The small baby guidelines do not mandate ligation, however, in late 2010 the guidelines were amended based on new literature suggested that ligation may increase rates of morbidities.

RESULTS

There were 717 EP infants admitted during the study period. There were no significant changes in gestational age, birthweight or annual admissions during the study period. The annual rate of PDA medical treatment declined significantly (R = 0.83, p = 0.01), while the annual rate of PDA ligation declined substantially (R = 0.88, p = 0.004). The annual mortality rate also declined significantly (R = 0.81, p = 0.014). The annual rates of bronchopulmonary dysplasia (BPD), necrotising enterocolitis and intraventricular haemorrhage did not change significantly.

CONCLUSION

In this cohort of EP patients, the rate of PDA ligation decreased substantially since 2010, with no apparent adverse effects on mortality or rates of BPD. These data are consistent with the concept that ligation does not improve outcomes in EP infants.

Reactive Oxygen Species and Pulmonary Vasculature During Hypobaric Hypoxia

An increasing number of people are living or working at high altitudes (hypobaric hypoxia) and therefore suffering several physiological, biochemical, and molecular changes. Pulmonary vasculature is one of the main and first responses to hypoxia. These responses imply hypoxic pulmonary vasoconstriction (HPV), remodeling, and eventually pulmonary hypertension (PH). These events occur according to the type and extension of the exposure. There is also increasing evidence that these changes in the pulmonary vascular bed could be mainly attributed to a homeostatic imbalance as a result of increased levels of reactive oxygen species (ROS). The increase in ROS production during hypobaric hypoxia has been attributed to an enhanced activity and expression of nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase), though there is some dispute about which subunit is involved. This enzymatic complex may be directly induced by hypoxia-inducible factor-1α (HIF-1α). ROS has been found to be related to several pathways, cells, enzymes, and molecules in hypoxic pulmonary vasculature responses, from HPV to inflammation, and structural changes, such as remodeling and, ultimately, PH. Therefore, we performed a comprehensive review of the current evidence on the role of ROS in the development of pulmonary vasculature changes under hypoxic conditions, with a focus on hypobaric hypoxia. This review provides information supporting the role of oxidative stress (mainly ROS) in the pulmonary vasculature’s responses under hypobaric hypoxia and depicting possible future therapeutics or research targets. NADPH oxidase-produced oxidative stress is highlighted as a major source of ROS. Moreover, new molecules, such as asymmetric dimethylarginine, and critical inflammatory cells as fibroblasts, could be also involved. Several controversies remain regarding the role of ROS and the mechanisms involved in hypoxic responses that need to be elucidated.

Long-Term Chronic Intermittent Hypobaric Hypoxia Induces Glucose Transporter (GLUT4) Translocation Through AMP-Activated Protein Kinase (AMPK) in the Soleus Muscle in Lean Rats

Background: In chronic hypoxia (CH) and short-term chronic intermittent hypoxia (CIH) exposure, glycemia and insulin levels decrease and insulin sensitivity increases, which can be explained by changes in glucose transport at skeletal muscles involving GLUT1, GLUT4, Akt, and AMPK, as well as GLUT4 translocation to cell membranes. However, during long-term CIH, there is no information regarding whether these changes occur similarly or differently than in other types of hypoxia exposure. This study evaluated the levels of AMPK and Akt and the location of GLUT4 in the soleus muscles of lean rats exposed to long-term CIH, CH, and normoxia (NX) and compared the findings.

Methods: Thirty male adult rats were randomly assigned to three groups: a NX (760 Torr) group (n = 10), a CIH group (2 days hypoxia/2 days NX; n = 10) and a CH group (n = 10). Rats were exposed to hypoxia for 30 days in a hypobaric chamber set at 428 Torr (4,600 m). Feeding (10 g daily) and fasting times were accurately controlled. Measurements included food intake (every 4 days), weight, hematocrit, hemoglobin, glycemia, serum insulin (by ELISA), and insulin sensitivity at days 0 and 30. GLUT1, GLUT4, AMPK levels and Akt activation in rat soleus muscles were determined by western blot. GLUT4 translocation was measured with confocal microscopy at day 30.

Results: (1) Weight loss and increases in hematocrit and hemoglobin were found in both hypoxic groups (p < 0.05). (2) A moderate decrease in glycemia and plasma insulin was found. (3) Insulin sensitivity was greater in the CIH group (p < 0.05). (4) There were no changes in GLUT1, GLUT4 levels or in Akt activation. (5) The level of activated AMPK was increased only in the CIH group (p < 0.05). (6) Increased GLUT4 translocation to the plasma membrane of soleus muscle cells was observed in the CIH group (p < 0.05).

Conclusion: In lean rats experiencing long-term CIH, glycemia and insulin levels decrease and insulin sensitivity increases. Interestingly, there is no increase of GLUT1 or GLUT4 levels or in Akt activation. Therefore, cellular regulation of glucose seems to primarily involve GLUT4 translocation to the cell membrane in response to hypoxia-mediated AMPK activation.

[Prevalence of overweight and obesity in 9 and 10 year-old children in the Principality of Asturias: evaluation bias by parents]

INTRODUCTION

Overweight and obesity in children is a very important issue in the field of health. The aim of this study was to determine the prevalence of overweight and obesity in pre-adolescent children aged 9 to 10 years old in the Principality of Asturias, and to assess the reliability of the measurements of weight and height reported by parents.

MATERIAL AND METHOD

A sample of 291 subjects, 142 girls and 149 boys were chosen at random from the network of schools in the Principality of Asturias. They were weighed and measured individually at the school. All participants brought the signed consent of their parents, which also contained the anthropometric measurements of they made of their children.

RESULTS

The results showed that 28.17% of children aged 9 and 10 years old in the Principality of Asturias were overweight and 15.80% obese. This means that 44% of the sample had some degree of overweight. Data reported by parents underestimated the weight of both the boys and girls by an average of 2.07kg.

CONCLUSIONS

The high percentage of excess weight observed is due to the categorisation system used (IOFT) and the age of the sample. The results call into question the research with data indirectly recorded data.

Efficacy, safety, and tolerance of two types of intragastric balloons placed in obese subjects: a double-blind comparative study

The intragastric balloon is a temporary treatment for obese patients. Fluid-filled devices have shown efficacy and safety, and are widely used. Recently, although there are no comparative studies between them, an air-filled balloon, Heliosphere® bag, has been proposed. Prospective, double-blind study in 33 patients with morbid and type 2 obesity: 23 female, 43.9±10 years, 120.3±17 kg, and body mass index (BMI) of 44.2±5 kg/m2, placing 18 gastric balloons filled with 960 cm3 of air (Heliosphere® bag) or 15 balloons filled with 700 ml of saline (Bioenterics-BIB®). Both balloons were placed with conscious sedation and removed under general anesthesia 6 months later. Intravenous drugs were given to control symptoms for 48 h. Patients were sent home on a 1000-kcal diet, multivitamin supplements, and oral proton pump inhibitors, and were followed monthly. Complications, symptoms, weight, and quality of life evaluated by the Gastrointestinal Quality of Life Index (GIQLI) scale were recorded. At 6 months, mean weight loss (12.8±8 vs 14.1±8 kg), BMI loss (4.6±3 vs 5.5±3 kg/m2) and percent excess weight loss (27±16 vs.30.2±17) showed no significant differences between both groups. At removal, two Heliosphere® bags were not found in the stomach, and four patients required extraction of the balloon by rigid esophagoscopy or surgery (p=0.02). Tolerance was good in both groups, but early removal occurred in three BIB® (20%) due to vomits and dehydration. The GIQLI total scores remained unchanged. Both balloons achieve a significant weight loss with good tolerance in obese patients. Nevertheless, Heliosphere® bag has severe technical problems that need to be solved before recommending it.

Nuclear organization and dynamics of transcription sites in rat sensory ganglia neurons detected by incorporation of 5'-fluorouridine into nascent RNA

In this study we have used the transcription assay with 5'-fluorouridine incorporation into nascent RNA to analyze the nuclear organization and dynamics of transcription sites in rat trigeminal ganglia neurons. The 5'-FU administrated by i.p. injection was successfully incorporated into nuclear domains containing actively transcribing genes of trigeminal neurons. 5'-Fluorouridine RNA-labeling was detected with immunocytochemistry at light and electron microscopy levels. The 5'-fluorouridine incorporation sites were detected in the nucleolus, particularly on the dense fibrillar component, and in numerous transcription foci spread throughout the euchromatin regions, without preferential positioning at the nuclear periphery or in the nuclear interior. Double labeling experiments to combine 5'-fluorouridine incorporation with molecular markers of nuclear compartments showed the absence of transcription sites in Cajal bodies and nuclear speckles of splicing factors. Similarly, no 5'-fluorouridine labeling was detected in well-characterized chromatin silencing domain, the telomeric heterochromatin. The specificity and sensitivity of the run-on transcription assay in trigeminal ganglia neurons was verified by the i.p. administration of the transcription inhibitor actinomycin D. The dramatic reduction in RNA synthesis upon actinomycin D treatment was associated with two important cellular events, heterochromatin silencing and formation of DNA damage/repair nuclear foci, demonstrated by the expression of tri-methylated histone H4 and phosphorylated H2AX, respectively. 5'-Fluorouridine incorporation in animal models provides a useful tool to investigate the organization of gene expression in mammalian neurons in both normal physiology and experimental pathology systems.

Neuronal body size correlates with the number of nucleoli and Cajal bodies, and with the organization of the splicing machinery in rat trigeminal ganglion neurons

Trigeminal ganglion neurons comprise three main cell body-size types. This cell size heterogeneity provides an excellent neuronal model to study the cell size-dependent organization and dynamics of the nucleoli, Cajal (coiled) bodies (CBs), and nuclear speckles of pre-mRNA splicing factors, nuclear structures that play a key role in the normal neuronal physiology. We have analyzed the number of nucleoli and CBs and the structural and molecular organization of CBs and nuclear speckles in the three neuronal types by using immunofluorescence with antibodies that recognize nucleoli (fibrillarin), CBs (coilin), and nuclear speckles (snRNPs), confocal microscopy, and electron microscopy. Whereas the mean number of nucleoli per neuron decreases as a function of cell size, the number of CBs per cell significantly increases in large neurons in comparison with the small ones. In addition, large neurons have a higher proportion of CBs associated with the nucleolus. In all neuronal types, CBs concentrate coilin, fibrillarin, snRNPs, and the survival motor neuron protein (SMN). Immunostaining for snRNPs shows small speckle domains and extensive areas of diffuse nucleoplasmic signal in large neurons, in contrast with the large nuclear speckles found in small neurons. Furthermore, flow cytometric analysis shows that all neurons are in the range of diploid cells. These findings indicate that the fusion behavior of nucleoli, the formation of CBs and their relationships with the nucleolus, as well as the compartmentalization of the pre-mRNA splicing machinery, is related to cell body size in the trigeminal ganglion neurons. Because transcriptional activity is a basic determinant mechanism of cell size in diploid cells, we suggest that our findings reflect a distinct transcription-dependent organization of the nucleolus and splicing machinery in the three cell types of trigeminal ganglion neurons.

Stress-induced activation of c-Jun N-terminal kinase in sensory ganglion neurons: accumulation in nuclear domains enriched in splicing factors and distribution in perichromatin fibrils

In response to cellular stress, the activation of the JNK cascade mediates phosphorylation of c-Jun that promotes its transactivation, which in turn activates the transcription of specific genes. In an experimental model of neuronal stress in vivo, by means of immunofluorescence and kinase assays we have found a reversible activation of JNK induced by the administration of the anti-cancer drug Adriamycin. In control neurons, a considerable basal level of the active, phosphorylated JNK was detected in neuronal nuclei, with a speckled distribution in addition to a diffuse nucleoplasmic signal. Adriamycin-induced neuronal stress was associated with a notable increase of this nuclear immunostaining, indicating activation of the JNK pathway which was confirmed by the increase of JNK enzymatic activity, while no changes in the total JNK were detected by Western blots. The JNK neuronal response to stress was also accompanied by an increase in the nuclear immunoreactivity for c-Jun and also by the de novo appearance of a strong nuclear phospho-c-Jun signal. These effects tend to revert to the control situation after 24 h of Adriamycin treatment. The nuclear compartmentalization of phospho-JNK and its substrate c-Jun was analyzed by confocal laser microscopy. Phospho-JNK strongly colocalizes with snRNPs in nuclear speckles, while the former was not concentrated in the coiled bodies. Upon stress induction, both c-Jun and phospho-c-Jun show a nucleoplasmic distribution in euchromatin domains, with the nucleoli free of immunolabeling. Furthermore, the nuclear speckles enriched in phospho-JNK exhibit a very low or undetectable signal with both c-Jun antibodies. Immunogold electron microscopy confirms the accumulation of phospho-JNK in interchromatin granule clusters (nuclear speckles), while in the nucleoplasm this kinase is mainly localized in perichromatin fibrils. Both c-Jun and phospho-c-Jun were also detected in perichromatin fibrils. Double labeling experiments show the colocalization of phospho-JNK and phospho-c-Jun in certain perichromatin fibrils. These results indicate that the neuronal response to the Adriamycin-induced stress is mediated by the activation of the JNK pathway. The accumulation of phospho-JNK in nuclear speckles raises the possibility that this kinase may be involved in the phosphorylation of an unknown splicing factor. Moreover, the colocalization of phospho-JNK and c-Jun in perichromatin fibrils, which are associated with sites of active transcription, suggests that these nuclear structures may be putative sites for the phosphorylation of JNK substrates.

Formation of intranuclear crystalloids and proliferation of the smooth endoplasmic reticulum in schwann cells induced by tellurium treatment: association with overexpression of HMG CoA reductase and HMG CoA synthase mRNA

Administration of tellurium (Te) in weaning rats causes a well-established demyelinating neuropathy induced by the inhibition in myelinating Schwann cells (SC) of the synthesis of cholesterol, a major component of the myelin sheath, at the level of squalene epoxidase. We have used this experimental model of Te neuropathy to study the biogenesis and reorganization of the endomembranes of the nuclear envelope and endoplasmic reticulum (ER) in response to Te treatment by ultrastructural analysis and in situ hybridization for the detection of HMG CoA reductase and synthase mRNA, which encode key enzymes in cholesterol synthesis. The adaptive response of myelinating SC to cholesterol depletion includes cell hypertrophy, the formation of tubular invaginations of proliferating nuclear membranes giving rise to peculiar nuclear inclusions termed crystalloids, and, at the cytoplasmic level, the formation of lamellar bodies of rough ER, proliferation of the smooth ER, and overexpression of HMG CoA reductase and synthase mRNAs. The changes revert after withdrawal of Te treatment. Our results show that the biogenesis and structural organization of both endomembrane systems change dynamically upon Te-induced cholesterol depletion, indicating that this constituent plays a critical role in the organization of nuclear envelope and ER compartments in SC. The results also suggest that the HMG CoA reductase, an integral membrane protein of ER, provides the signal for the extensive membrane assembly. While the physiological meaning of crystalloid remains to be clarified, the hypertrophy of the smooth ER may represent a cytoprotective mechanism involved in detoxification of the neurotoxic agent or its metabolic derivates.

Necrosis of schwann cells during tellurium-induced primary demyelination: DNA fragmentation, reorganization of splicing machinery, and formation of intranuclear rods of actin

We present a cytological, immunocytochemical, and biochemical study of the cell death of mature myelinating Schwann cells (SCs) in the primary demyelinating neuropathy induced by tellurium (Te). Weaned rats were fed a diet containing 1.1% elemental Te. The animals were killed daily within the first week of Te diet. After 4 to 6 days of Te treatment some SCs underwent degeneration and necrosis. By electron microscopy analysis, degenerating SCs showed chromatin condensation, detachment from the nuclear envelope of condensed chromatin clumps, aggregation of interchromatin granule clusters, formation of intranuclear bundles of microfilaments, and cytoplasmic vesiculation. By confocal laser fluorescence microscopy, chromatin regions were stained with the TUNEL method for in situ labeling of DNA fragmentation and exhibited a progressive reduction of histone signal. In addition, splicing small nuclear ribonucleoprotein (snRNP) factors were redistributed in a few large nuclear domains and bright foci of intranuclear actin were observed. DNA electrophoresis revealed a smear pattern of DNA fragmentation in sciatic nerve samples from Te-treated animals. Upon Te treatment, no degradation of the caspase substrates poly (ADP-ribose) polymerase and lamin B was detected by Western blots or immunocytochemistry, respectively. The peculiar structural rearrangement of the transcription and splicing machinery as well as the vesicular degeneration of the cytoplasm in degenerating SCs support an autophagic cell death of the necrotic type. Unlike the apoptosis of pre-remyelinating SCs (11), this caspase independent cell death of necrotic type involves mature pre-demyelinating SCs and eliminates SCs injured by the neurotoxic effect of Te.

[Antigenic diversity of Plasmodium falciparum and serodiagnosis of tropical malaria]

The importance of antigenic diversity in immunogenicity of population of P. falciparum was studied in regard of immunodiagnosis of tropical malaria. The sera from 42 adult non-immune persons with confirmed infection by P. falciparum and from 30 persons from Africa with confirmed infection by P. falciparum were examined with three antigens differing in geographic origin. Antigen A2 Gambia, M94 Thailand, FCQ2 Papua New Guinea were checked. The following results were obtained: 1) In the quantity of polyclonal antibodies detected higher frequency of higher titres and higher GMRT (statistically significant differences) were demonstrated with three antigens in the persons from the endemic areas of malaria. 2) Higher variation (antigenic diversity) in the quantity of polyclonal antibodies (difference up to 6 dilutions) in the non-immune population in contrast to semi-immune population where the differences were only at the level of two fold dilutions. 3) The correspondence of titres of polyclonal antibodies to all three geographically different antigens was statistically significantly (P less than 0.05) more frequent in the sera of semi-immune persons in contrast to non-immune individuals. 4) The results have shown that repeated infections in endemic areas of malaria with antigenically diverse strains induce the formation of polyclonal antibodies against all antigenic varieties and are better detectable by antigen of any antigenic variety.(ABSTRACT TRUNCATED AT 250 WORDS)