Pedro González-Muniesa

Lipoic Acid Improves Mitochondrial Function in Nonalcoholic Steatosis through the Stimulation of Sirtuin 1 and Sirtuin 3

Nonalcoholic steatosis is an important hepatic complication of obesity linked to mitochondrial dysfunction and oxidative stress. Lipoic acid (LA) has been reported to have beneficial effects on mitochondrial function and to attenuate oxidative stress. The sirtuin (SIRT) family has been demonstrated to play an important role in the regulation of mitochondrial function and in the activation of antioxidant defenses. In this study, we analyzed the potential protective effect of LA supplementation, via the modulation of mitochondrial defenses through the SIRT pathway, against oxidative stress associated with high‐fat feeding. Wistar rats were fed a standard diet (control group (C), n = 10), a high‐fat diet (obese group (OB), n = 10) and a high‐fat diet supplemented with LA (OLIP, n = 10). A group pair‐fed to the latter group (pair‐fed OLIP group (PFO), n = 6) was also included. LA prevented hepatic triglyceride (TG) accumulation (−68.2%) and liver oxidative damage (P < 0.01) through the inhibition of hydroperoxide (H2O2) production (P < 0.001) and the stimulation of mitochondrial antioxidant defenses. LA treatment upregulated manganese superoxide dismutase (SOD2) (60.6%) and glutathione peroxidase (GPx) (100.2%) activities, and increased the reduced glutathione (GSH): oxidized glutathione (GSSG) ratio and UCP2 mRNA levels (P < 0.001–P < 0.01). Moreover, this molecule reduced oxidative damage in mitochondrial DNA (mtDNA) and increased mitochondrial copy number (P < 0.001– P < 0.01). LA treatment decreased the acetylation levels of Forkhead transcription factor 3a (Foxo3a) and PGC1β (P < 0.001–P < 0.01) through the stimulation of SIRT3 and SIRT1 (P < 0.001). In summary, our results demonstrate that the beneficial effects of LA supplementation on hepatic steatosis could be mediated by its ability to restore the oxidative balance by increasing antioxidant defenses through the deacetylation of Foxo3a and PGC1β by SIRT1 and SIRT3.

Lipoic acid administration prevents nonalcoholic steatosis linked to long-term high-fat feeding by modulating mitochondrial function

Nonalcoholic steatosis is an important hepatic complication of obesity linked to mitochondrial dysfunction and insulin resistance. Furthermore, lipoic acid has been reported to have beneficial effects on mitochondrial function. In this study, we analyzed the potential protective effect of lipoic acid supplementation against the development of nonalcoholic steatosis associated with a long-term high-fat diet feeding and the potential mechanism of this effect. Wistar rats were fed on a standard diet (n=10), a high-fat diet (n=10) and a high-fat diet supplemented with lipoic acid (n=10). A group pair-fed to the latter group (n=6) was also included. Lipoic acid prevented hepatic triglyceride accumulation and liver damage in rats fed a high-fat diet (-68%±11.3% vs. obese group) through the modulation of genes involved in lipogenesis and mitochondrial β-oxidation and by improving insulin sensitivity. Moreover, this molecule showed an inhibitory action on electron transport chain complexes activities (P<.01-P<.001) and adenosine triphosphate synthesis (P<.05), and reduced significantly energy efficiency. By contrast, lipoic acid induced an increase in mitochondrial copy number and in Ucp2 gene expression (P<.001 vs. obese). In summary, this investigation demonstrated the ability of lipoic acid to prevent nonalcoholic steatosis induced by a high-fat intake. Finally, the novelty and importance of this study are the finding of how lipoic acid modulates some of the mitochondrial processes involved in energy homeostasis. The reduction in mitochondrial energy efficiency could also explain, at least in part, the beneficial effects of lipoic acid not only in fatty liver but also in preventing excessive body weight gain.

Regulation by chronic-mild stress of glucocorticoids, monocyte chemoattractant protein-1 and adiposity in rats fed on a high-fat diet

Stress has been reported as a widespread problem and several studies have linked obesity and inflammation-related diseases. Moreover, the combination of suffering from chronic stress and high energy intake might be related to the onset of some metabolic diseases. To study the possible relationships between stress, inflammatory status and obesity, a chronic-mild stress (CMS) paradigm with a high-fat dietary intake model (Cafeteria diet) was implemented on male Wistar rats for 11 weeks. Stress and dietary intake effects on animal adiposity, serum biochemical as well as glucocorticoids and inflammation markers were all analyzed. As expected, consuming a high-fat diet increased body weight, adiposity and insulin resistance in non-stressed animals. A decrease of total white adipose tissue (WAT) and an increase of fecal glucocorticoids, as well as angiotensinogen, and monocyte chemoattractant protein-1 (MCP-1) expression level in retroperitoneal WAT were found only on control-stressed rats. Regarding the serum MCP-1, a decrease was observed on animals under CMS while being fed Cafeteria diet. Furthermore, 11β-hydroxysteroid dehydrogenase activity, a glucocorticoid and obesity biomarker in the liver, was influenced by high-fat diet intake but not by stress. Finally, statistical analysis showed a strong relation between MCP-1 expression levels in retroperitoneal WAT, fecal corticosterone and total WAT. This trial proved that CMS induced a glucocorticoid-mediated response, which was reduced by the intake of a Cafeteria diet. These findings suggest that a high-fat diet could protect against a stress condition and revealed a different behavior to a stressful environment depending on the nutritional status.

A Dysregulation in CES1, APOE and Other Lipid Metabolism-Related Genes Is Associated to Cardiovascular Risk Factors Linked to Obesity

Objective: The aim of the present study was to investigate the relationship between the differential expression of genes related to lipid metabolism in subcutaneous adipose tissue and metabolic syndrome features in lean and obese subjects with habitual high fat intake. Methods: Microarray and RT-PCR analysis were used to analyze and validate differential gene expression in subcutaneous abdominal adipose tissue samples from lean and obese phenotype subjects. Results: Several genes and transcripts involved in lipolysis were down-regulated, such as AKAP1, PRKAR2B, Gi and CIDEA, whereas NPY1R and CES1 were up-regulated, when comparing obese to lean subjects. Similarly, transcripts associated with cholesterol and lipoprotein metabolism showed a differential expression, with APOE and ABCA being decreased and VLDLR being increased in obese versus lean subjects. In addition, positive correlations were found between different markers of the metabolic syndrome and CES1 and NPY1R mRNA expressions, while APOE showed an inverse association with some of them. Conclusion: Different expression patterns in transcripts encoding for proteins involved in lipolysis and lipoprotein metabolism were found between lean and obese subjects. Moreover, the dysregulation of genes such as CES1 and APOE seems to be associated with some physiopathological markers of insulin resistance and cardiovascular risk factors in obesity.

Impact of intermittent hypoxia and exercise on blood pressure and metabolic features from obese subjects suffering sleep apnea-hypopnea syndrome.

Strategies designed to reduce adiposity and cardiovascular-accompanying manifestations have been based on nutritional interventions conjointly with physical activity programs. The aim of this 13-week study was to investigate the putative benefits associated to hypoxia plus exercise on weight loss and relevant metabolic and cardiorespiratory variables, when prescribed to obese subjects with sleep apnea syndrome following dietary advice. The participants were randomly distributed in the following three groups: control, normoxia, and hypoxia. All the subjects received dietary advice while, additionally, normoxia group was trained under normal oxygen concentration and Hypoxia group under hypoxic conditions. There was a statistically significant decrease in fat-free mass (Kg) and water (%) on the control compared to normoxia group (p < 0.05 and p < 0.01, respectively). Body weight, body mass index, and waist circumference decreased in all the groups after the study. Moreover, leukocyte count was increased after the intervention in hypoxia compared to control group (p < 0.05). There were no statistically significant variations within groups in other variables, although changes in appetite were found after the 13-week period. In addition, associations between the variations in the leukocyte count and fat mass have been found. The hypoxia group showed some specific benefits concerning appetite and cardiometabolic-related measurements as exertion time and diastolic blood pressure, with a therapeutical potential.

Differential Proinflammatory and Oxidative Stress Response and Vulnerability to Metabolic Syndrome in Habitual High-Fat Young Male Consumers Putatively Predisposed by Their Genetic Background

The current nutritional habits and lifestyles of modern societies favor energy overloads and a diminished physical activity, which may produce serious clinical disturbances and excessive weight gain. In order to investigate the mechanisms by which the environmental factors interact with molecular mechanisms in obesity, a pathway analysis was performed to identify genes differentially expressed in subcutaneous abdominal adipose tissue (SCAAT) from obese compared to lean male (21–35 year-old) subjects living in similar obesogenic conditions: habitual high fat dietary intake and moderate physical activity. Genes involved in inflammation (ALCAM, CTSB, C1S, YKL-40, MIF, SAA2), extracellular matrix remodeling (MMP9, PALLD), angiogenesis (EGFL6, leptin) and oxidative stress (AKR1C3, UCHL1, HSPB7 and NQO1) were upregulated; whereas apoptosis, signal transcription (CITED 2 and NR3C1), cell control and cell cycle-related genes were downregulated. Interestingly, the expression of some of these genes (C1S, SAA2, ALCAM, CTSB, YKL-40 and tenomodulin) was found to be associated with some relevant metabolic syndrome features. The obese group showed a general upregulation in the expression of inflammatory, oxidative stress, extracellular remodeling and angiogenic genes compared to lean subjects, suggesting that a given genetic background in an obesogenic environment could underlie the resistance to gaining weight and obesity-associated manifestations.

The facilitative glucose transporter GLUT12: what do we know and what would we like to know?

Glucose, one of the most abundant molecules in nature, is used by most of the mammalian cells as their main energy source. Obtained from the diet, glucose is absorbed in the small intestine, incorporated into the circulating blood and stored as glycogen, mainly in the liver and muscle. Due to its hydrophilic nature, glucose cannot cross the plasma membrane by simple diffusion; instead, glucose enters the cell by specific membrane transporters. There are two families of glucose transporters, distinguished by their functional and structural properties: the Na/glucose cotransporter family SGLT/SLC5A [47] and the facilitative glucose transporter family GLUT/SLC2A [11, 22]. GLUT protein family members transport monosaccharides across the plasma membrane without energetic requirement, using the favourable concentration gradient of the hexose generated in some physiological situations. GLUTs share a common structural feature of 12 transmembrane domains, with both amino and carboxy terminal domains located on the cytosolic side, and an N-linked oligosaccharide site present either on the first or on the fifth extracellular loop [37]. At present, 14 different members of this family, divided in three classes according to its sequence homology, have been identified [11]. Class I is constituted by the well-characterized GLUT1, GLUT2, GLUT3, GLUT4 and GLUT14 (gene duplication of GLUT3); class II comprises the fructose transporter GLUT5, and GLUT7, GLUT9 and GLUT11; and class III includes GLUT6, GLUT8, GLUT10, GLUT12 and GLUT13 (HMIT) [12]. In relation to this classification, a recent phylogenetic analysis proposes that the proteins belonging to class III could be separated into three different groups and, therefore, suggests five structurally and/or functionally distinct GLUT classes (Fig. 1) [43]. Location, expression and regulation of the GLUT transporters are specific for each tissue and cellular type and are related to the cell metabolic needs. Inmany cases, the upor downregulation of the GLUT proteins is directly linked to the development of diseases (Table 1). GLUT1, 2, 3, 4 and 5 were the first members of the GLUT family cloned and their physiological function has been well characterized. GLUT9 seems to be a urate transporter, newly described as electrogenic [44], while GLUT13 (HMIT) is a H-dependent myoinositol cotransporter [36]. However, the physiological significance of the rest of GLUT transporters of class II and III still needs to be elucidated. Therefore, it is important to continue investigating the location and cellular function of recently discovered GLUT transporters, not only to determine their function in the organism, but also to J Physiol Biochem (2013) 69:325–333 DOI 10.1007/s13105-012-0213-8

Ectopic UCP1 gene expression in HepG2 cells affects ATP production

The UCP1 is an uncoupling protein located in the inner mitochondrial membrane of brown adipocytes, which has a well-documented role in diet-induced thermogenesis. The current study assessed whether UCP1 transfected liver cells demand more fuel substrates in the oxidative phosphorylation processes. Therefore, the purpose of this experiment was to achieve an ectopic expression of UCP1 in HepG2 cells to significantly decrease the production of ATP. The UCP1 gene was transferred into the hepatic cells by using a calcium phosphate precipitation protocol. The efficiency of the transfection was tested, 48 hours later, by bioluminescence of luciferase previously transfected, while the expression of mRNA of UCP1 was demonstrated by RT-PCR. In addition, measuring the production of ATP by using a bioluminescence procedure assessed the functionality of this protein. Transfected liver cells with UCP1 showed a decrease of 23% in ATP production in comparison with control cells without expression of UCP1 (2.23 vs. 2.90 RLU/pg protein, p=0.015). In conclusion, the ectopic expression of UCP1 decreased the production of ATP, possibly uncoupling the oxidative phosphorylation, which could be a novel approach for understanding thermogenic processes and eventually for energy metabolism and body weight management.ResumenLa UCP1 es una proteína desacoplante localizada en la membrana interna mitocondrial del adipocito pardo, que tiene un papel importante en la termogénesis inducida por la dieta. El presente estudio fue diseñado para verificar si las células hepáticas transfectadas con el gen de la proteína UCP1 utilizan más substratos energéticos en los procesos de fosforilación oxidativa. Así, el propósito del experimento era lograr una expresión ectópica de la proteína UCP1 en células HepG2 para disminuir significativamente la producción de ATP. El gen de la UCP1 fue transferido a las células hepáticas usando un protocolo de precipitación del fosfato cálcico. La eficiencia de la transfección se demostraba 48 horas más tarde por bioluminiscencia de la luciferasa previamente transfectada, y la expresión del RNA mensajero de la UCP1, por RT-PCR. Además, la funcionalidad de la proteína se comprobaba mediante la medida de la producción de ATP usando un procedimiento de bioluminiscencia. Los resultados demuestran un descenso en la producción de ATP del 23% en las células hepáticas transfectadas con UCP1 respecto de las células control (2,23 frente a 2,90 RLU/pg proteína, p=0,015). En suma, la expresión ectópica de la UCP1 redujo la producción de ATP, posiblemente por desacoplamiento de la fosforilación oxidativa, lo cuál puede ser de interés para estudiar la importancia de los procesos termogénicos implicados en la regulación del metabolismo energético y el peso corporal.

Living at Higher Altitude and Incidence of Overweight/Obesity: Prospective Analysis of the SUN Cohort.

Background Residence at high altitude has been associated with lower obesity rates probably due to hypoxia conditions. However, there is no evidence of this association in a free-living population. Objectives We assessed the association between the altitude where each participant of a Spanish cohort (the SUN Project) was living and the incidence of overweight/obesity. Methods The SUN Project is a dynamic, prospective, multipurpose cohort of Spanish university graduates with a retention rate of 89%. We included in the analysis 9 365 participants free of overweight/obesity at baseline. At the baseline questionnaire, participants reported their postal code and the time they had been living in their city/village. We imputed the altitude of each postal code according to the data of the Spanish National Cartographic Institute and categorized participants in tertiles. We used Cox regression models to adjust for potential confounding variables. Results During a median follow-up of 10 years, we identified 2 156 incident cases of overweight/obesity. After adjusting for sex, age, time of residence at current city, baseline body mass index, physical activity, sedentarism and years of education (≤ 3 years, ≥ 4 years, Master/PhD), those participants in the third tertile (>456 m) exhibited a statistically significant 14% reduction in the risk of developing overweight/obesity in comparison to those in the first tertile (<124 m) (adjusted HR = 0.86; 95% CI: 0.77, 0.96). Conclusions Living in cities of higher altitude was inversely associated with the risk of developing overweight/obesity in a cohort of Spanish university graduates.

Perinatal maternal feeding with an energy dense diet and/or micronutrient mixture drives offspring fat distribution depending on the sex and growth stage

Maternal nutrition during pregnancy and lactation influences offspring development and health. Novel studies have described the effects on next generation obesity-related features depending on maternal macro- and micro-nutrient perinatal feeding. We hypothesized that the maternal obesogenic diet during pregnancy and lactation programs an obese phenotype, while maternal micronutrient supplementation at these stages could partially prevent these features. Thus, the aim was to assess the influence of a perinatal maternal feeding with an obesogenic diet enriched in fat and sucrose and a micronutrient supplementation during pregnancy and lactation on offspring growth and obese phenotypical features during life course. Female Wistar rats were assigned to four dietary groups during pregnancy and lactation: control, control supplemented with micronutrients (choline, betaine, folic acid and vitamin B12 ), high-fat sucrose (HFS) and HFS supplemented. At weaning, the offspring were transferred to a chow diet, and weight and fat mass were measured at weeks 3, 12 and 20. At birth, both male and female offspring from mothers fed the obesogenic diet showed lower body weight (-5 and -6%, respectively), while only female offspring weight decreased by maternal micronutrient supplementation (-5%). During lactation, maternal HFS diet was associated with increased body weight, while micronutrient supplementation protected against body weight gain. Whole body fat mass content increased at weeks 3, 12 and 20 (from 16 to 65%) due to maternal HFS diet. Maternal micronutrient supplementation decreased offspring fat mass content at week 3 (-8%). Male offspring showed higher adiposity than females at weeks 12 and 20. In conclusion, maternal HFS feeding during pregnancy and lactation was associated with a low offspring weight at birth and obese phenotypical features during adult life in a sex- and time-dependent manner. Furthermore, maternal methyl donor supplementation protected against body weight gain in male offspring during lactation and in female offspring also during juvenile period.