Matching Items (3)

156088-Thumbnail Image.png

Effect of fatty acids and insulin on syncytin-1 and 4E-BP1 in skeletal muscle

Description

Obesity impairs skeletal muscle maintenance and regeneration, a condition that can progressively lead to muscle loss, but the mechanisms behind it are unknown. Muscle is primarily composed of multinucleated cells

Obesity impairs skeletal muscle maintenance and regeneration, a condition that can progressively lead to muscle loss, but the mechanisms behind it are unknown. Muscle is primarily composed of multinucleated cells called myotubes which are derived by the fusion of mononucleated myocytes. A key mediator in this process is the cellular fusion protein syncytin-1. This led to the hypothesis that syncytin-1 could be decreased in the muscle of obese/insulin resistant individuals. In contrast, it was found that obese/insulin resistant subjects had higher syncytin-1 expression in the muscle compared to that of the lean subjects. Across the subjects, syncytin-1 correlated significantly with body mass index, percent body fat, blood glucose and HbA1c levels, insulin sensitivity and muscle protein fractional synthesis rate. The concentrations of specific plasma fatty acids, such as the saturated fatty acid (palmitate) and monounsaturated fatty acid (oleate) are known to be altered in obese/insulin resistant humans, and also to influence the protein synthesis in muscle. Therefore, it was evaluated that the effects of palmitate and oleate on syncytin-1 expression, as well as 4E-BP1 phosphorylation, a key mechanism regulating muscle protein synthesis in insulin stimulated C2C12 myotubes. The results showed that treatment with 20 nM insulin, 300 µM oleate, 300 µM oleate +20 nM insulin and 300 µM palmitate + 300 µM oleate elevated 4E-BP1 phosphorylation. At the same time, 20 nM insulin, 300 µM palmitate, 300 µM oleate + 20 nM insulin and 300 µM palmitate + 300 µM oleate elevated syncytin-1 expression. Insulin stimulated muscle syncytin-1 expression and 4E-BP1 phosphorylation, and this effect was comparable to that observed in the presence of oleate alone. However, the presence of palmitate + oleate diminished the stimulatory effect of insulin on muscle syncytin-1 expression and 4E-BP1 phosphorylation. These findings indicate oleate but not palmitate increased total 4E-BP1 phosphorylation regardless of insulin and the presence of palmitate in insulin mediated C2C12 cells. The presence of palmitate inhibited the upregulation of total 4EB-P1 phosphorylation. Palmitate but not oleate increased syncytin-1 expression in insulin mediated C2C12 myotubes. It is possible that chronic hyperinsulinemia in obesity and/or elevated levels of fatty acids such as palmitate in plasma could have contributed to syncytin-1 overexpression and decreased muscle protein fractional synthesis rate in obese/insulin resistant human muscle.

Contributors

Agent

Created

Date Created
  • 2017

149300-Thumbnail Image.png

An ecological approach to investigating the influences of obesity

Description

"Globesity," as defined by the World Health Organization, describes obesity as a pandemic affecting at least 400 million people worldwide. The prevalence of obesity is higher among women than men;

"Globesity," as defined by the World Health Organization, describes obesity as a pandemic affecting at least 400 million people worldwide. The prevalence of obesity is higher among women than men; and in non-Hispanic black and Hispanic populations. Obesity has been significantly associated with increased all-cause mortality, and mortality from cardiovascular disease, obesity-related cancers, diabetes and kidney disease. Current strategies to curb obesity rates often use an ecological approach, suggesting three main factors: biological, behavioral, and environmental. This approach was used to develop four studies of obesity. The first study assessed dietary quality, using the Healthy Eating Index (HEI)-2005, among premenopausal Hispanic and non-Hispanic white women, and found that Hispanic women had lower total HEI-2005 scores, and lower scores for total vegetables, dark green and orange vegetables and legumes, and sodium. Markers of obesity were negatively correlated with total HEI-2005 scores. The second study examined the relationship between reported screen time and markers of obesity among premenopausal women and found that total screen time, TV, and computer use were positively associated with markers of obesity. Waist/height ratio, fat mass index, and leptin concentrations were significantly lower among those who reported the lowest screen time versus the moderate and high screen time categories. The third study examined the relationship between screen time and dietary intake and found no significant differences in absolute dietary intake by screen time category. The fourth study was designed to test a brief face-to-face healthy shopping intervention to determine whether food purchases of participants who received the intervention differed from those in the control group; and whether purchases differed by socioeconomic position. Participants in the intervention group purchased more servings of fruit when compared to the control group. High-income participants purchased more servings of dark green/deep yellow vegetables compared to those in the low-income group. Among those who received the intervention, low-income participants purchased foods of lower energy density, and middle-income participants purchased food of higher fat density. The findings of these studies support policy changes to address increasing access and availability of fruits and vegetables, and support guidelines to limit screen time among adults.

Contributors

Agent

Created

Date Created
  • 2010

150128-Thumbnail Image.png

Salud con Sabor Latino para los Niños: a feasibility study

Description

Obesity in Hispanic youth has reached alarmingly high levels, increasing the risk of type 2 diabetes, hyperlipidemia, hypertension, and cardiovascular disease. In Mexican American children ages 6-11 years, 41.7% are

Obesity in Hispanic youth has reached alarmingly high levels, increasing the risk of type 2 diabetes, hyperlipidemia, hypertension, and cardiovascular disease. In Mexican American children ages 6-11 years, 41.7% are overweight and obese, 24.7% are obese and 19.6% have a Body Mass Index (BMI) greater than the 97th percentile. While personal, behavioral, and environmental factors contribute to these high rates, emerging literature suggests acculturation, self-efficacy and social support are key influences. The one-group, pre- and post-test, quasi-experimental design used a community-based participatory research (CBPR) method to test the feasibility, acceptability, and preliminary efficacy of the 8-week intervention. Social Cognitive Theory (SCT) was used to guide the design. Measurements included an analysis of recruitment, retention, participant satisfaction, observation of intervention sessions, paired t-tests, effect sizes, and bivariate correlations between study variables (acculturation, nutrition and physical activity [PA] knowledge, attitude and behaviors, perceived confidence and social support) and outcome variables (BMI z-score, waist circumference and BP percentile) Findings showed the SSLN program was feasible and acceptable. Participants (n = 16) reported that the curriculum was fun and they learned about nutrition and PA. The retention rate was 94%. The preliminary effects on adolescent nutrition and PA behaviors showed mixed results with small-to-medium effect sizes for nutrition knowledge and attitude, PA and sedentary behavior. Correlation analysis among acculturation and study variables was not significant. Positive associations were found between perceived confidence in eating and nutrition attitude (r = .61, p < .05) and nutrition behavior (r = .62, p < .05), perceived confidence in exercise and nutrition behavior (r = .66, p < .05), social support from family for exercise and PA behavior (r = .67, p < .01) and social support from friends for exercise and PA behavior (r = .56, p < .05). These findings suggest a culturally specific healthy eating and activity program for adolescents was feasible and acceptable and warrants further investigation, since it may fill a gap in existing obesity programs designed for Hispanic youth. The positive correlations suggest further testing of the theoretical model.

Contributors

Agent

Created

Date Created
  • 2011