Physical activity, cardiorespiratory fitness, and the metabolic syndrome in youth.

The metabolic syndrome is defined as the coexistence of multiple cardiovascular and diabetes risk factors, the prevalence of which has increased dramatically in adult populations in the last decades. More recently, the same cluster of metabolic risk factors has also been recognized in children and adolescents. Epidemiological evidence suggests that high levels of cardiorespiratory fitness (CRF) and physical activity are associated with a favorable metabolic risk profile in adults. However, in youth the role of these factors is less clear. Therefore, the purpose of this mini-review is to examine the recent evidence between objectively measured habitual physical activity and CRF with clustered metabolic risk in youth. In general, it appears that both physical activity and CRF are separately and independently associated with metabolic risk factors in youth, possibly through different causal pathways. Further research is necessary to quantify how much physical activity is needed to prevent the metabolic syndrome and the diseases with which it is associated. Public health approaches that encourage increased physical activity and reduce sedentary behaviors may prove useful in reducing the population burden associated with metabolic risk.     

Decreased skin function may be a risk factor for metabolic syndrome

The metabolic syndrome, a cluster of risk factors for cardiovascular disease, is closely related to environmental and lifestyle risk factors. Increasing evidence suggests that environmental risk factors may involve an increase in xenobiotic exposure, for example due to environmental toxins, medications, high meat intake, food additives and supplements; while lifestyle risk factors, such as sedentary lifestyles, may involve a decrease in the detoxification and elimination of xenobiotics. The skin, the body's largest organ, plays a distinct role in the detoxification and elimination of xenobiotics and the body lipid homeostasis, which is affected by sedentary lifestyle and physical activity, as well as by ambient temperature. Thus, it seems that decreased skin biotransformation and excretion, for example due to low ambient temperature and sedentary lifestyle, may be an important risk factor for metabolic syndrome. This review aims to provide insight into the role of the skin in the development of metabolic syndrome.     

Epidemiological evidence for the role of physical activity in reducing risk of type 2 diabetes and cardiovascular disease.

Epidemiological studies suggest that physically active individuals have a 30-50% lower risk of developing type 2 diabetes than do sedentary persons and that physical activity confers a similar risk reduction for coronary heart disease. Risk reductions are observed with as little as 30 min of moderate-intensity activity per day. Protective mechanisms of physical activity include the regulation of body weight; the reduction of insulin resistance, hypertension, atherogenic dyslipidemia, and inflammation; and the enhancement of insulin sensitivity, glycemic control, and fibrinolytic and endothelial function. Public health initiatives promoting moderate increases in physical activity may offer the best balance between efficacy and feasibility to improve metabolic and cardiovascular health in largely sedentary populations.     

A major health hazard: the metabolic syndrome

The clustering of several metabolic and cardiovascular disease risk factors has been termed the metabolic syndrome. The metabolic syndrome seems to result from a collision between susceptible "thrifty genes" and a society characterized by an increased prevalence of obesity and a sedentary lifestyle. The typical patient is characterized by abdominal obesity, a varying degree of glucose intolerance, dyslipidemia and often hypertension. The components of the metabolic syndrome are associated with insulin resistance, disturbances of coagulation and fibrinolysis, endothelial dysfunction and elevated markers of sub-clinical inflammation. The current review focuses mainly on the new definitions of the syndrome, the results of recent epidemiological studies and the consequences of the metabolic syndrome as an important risk factor for cardiovascular disease, premature death and diabetes. The metabolic syndrome constitutes a major challenge for public health professionals in the field of preventive medicine since more than 40 million U.S. adults seem to be affected by the syndrome. Lifestyle changes could have a profound influence on the syndrome and its development.     

Cardiac Health in Women With Metabolic Syndrome: Clinical Aspects and Pathophysiology

Although the classical cardiovascular risk factors (e.g., smoking and hypertension) are becoming more effectively managed, a continuous increase of the so‐called “cardiometabolic risk” is noted. Starting from this century, the nomenclature “metabolic syndrome” has become more popular to identify a cluster of disorders including obesity, dyslipidemia, hypertension, and insulin resistance. It is a primary risk factor for diabetes and cardiovascular disease in both genders. Interestingly, the metabolic diseases display a distinct gender disparity with an apparent “female advantage” in the premenopausal women compared with age‐matched men. However, women usually lose such “sex protection” following menopause or affliction of metabolic syndrome especially insulin resistance. A controversy exists in the medical literature concerning whether metabolic syndrome is a real syndrome or simply a cluster of risk factors. Several scenarios are speculated to contribute to the gender dimorphism in the cardiovascular sequelae in patients with metabolic syndrome including sex hormones, intrinsic organ function, and the risk factor profile (e.g., hypertension, dyslipidemia, obesity, sedentary lifestyle, and atherogenic diet). With the alarming rise of obesity prevalence, heart problems in metabolic syndrome continue to rise with a distinct gender dimorphism. Although female hearts seem to better tolerate the stress insults compared with the male counterparts, the female sex hormones such as estrogen can interact with certain risk factors to precipitate myopathic changes in the hearts. This synthetic review of recent literature suggests a role of gender disparity in myopathic factors and risk attributable to each metabolic component in the different prevalence of metabolic syndrome.     

Epidemiology,risk factors across the spectrum of age-related metabolic diseases

BackgroundPopulation aging is dynamic process of increasing proportion of older adults in the total population, which is an inescapable result of decline in fertility rate and extension in life expectancy. Inevitably, age-related metabolic diseases, for example obesity, type 2 diabetes, metabolic syndrome, dyslipidemia, and nonalcoholic fatty liver disease, are becoming epidemic globally along with the demographic transition.ContentThe review examines the literatures related to: 1) the epidemiology of age related metabolic diseases including obesity, type 2 diabetes, metabolic syndrome, dyslipidemia, and nonalcoholic fatty liver disease; and 2) the risk factors of age related metabolic diseases including genetic factors, diet, smoking, Physical activity, intestinal microbiota and environmental factors.ConclusionPopulation aging is becoming epidemic worldwide, resulting in increasing incidence and prevalence of a serious of age-related metabolic diseases. Both genetic and environmental factors contribute to the diseases, thus interventions targeting on these factors may have beneficial effect on the development of age-related metabolic diseases.     

Mitochondrial dysfunction in metabolic syndrome

Metabolic syndrome is co-occurrence of obesity, insulin resistance, atherogenic dyslipidemia (high triglyceride, low high density lipoprotein cholesterol), and hypertension. It is a global health problem. An estimated 20%–30% of adults of the world have metabolic syndrome. Metabolic syndrome is associated with increased risk of type 2 diabetes mellitus, nonalcoholic fatty liver disease, myocardial infarction, and stroke. Thus, it is a major cause of morbidity and mortality worldwide. However, molecular pathogenesis of metabolic syndrome is not well known. Recently, there has been interest in the role of mitochondria in pathogenesis of metabolic problems such as obesity, metabolic syndrome, and type 2 diabetes mellitus. Mitochondrial dysfunction contributes to the oxidative stress and systemic inflammation seen in metabolic syndrome. Role of mitochondria in the pathogenesis of metabolic syndrome is intriguing but far from completely understood. However, a better understanding will be very rewarding as it may lead to novel approaches to control this major public health problem. This brief review explores pathogenesis of metabolic syndrome from a mitochondrial perspective.     

Physical inactivity as the culprit of metabolic inflexibility: evidence from bed-rest studies

Although it is no longer debatable that sedentary behaviors are an actual cause of many metabolic diseases, the physiology of physical inactivity has been poorly investigated for this purpose. Along with microgravity, the physiological adaptations to spaceflights require metabolic adaptations to physical inactivity, and that is exceedingly well-simulated during the ground-based microgravity bed-rest analogs. Bed rest thus represents a unique model to investigate the mechanisms by which physical inactivity leads to the development of current societal chronic diseases. For decades, however, clinicians and physiologists working in space research have worked separately without taking full awareness of potential strong mutual questioning. This review summarizes the data collected over the last 60 years on metabolic adaptations to bed rest in healthy subjects. Our aim is to provide evidence that supports the hypothesis that physical inactivity per se is one of the primary causes in the development of metabolic inflexibility. This evidence will focus on four main tenants of metabolic inflexiblity: 1) insulin resistance, 2) impaired lipid trafficking and hyperlipidemia, 3) a shift in substrate use toward glucose, and 4) a shift in muscle fiber type and ectopic fat storage. Altogether, this hypothesis places sedentary behaviors upstream on the list of factors involved in metabolic inflexibility, which is considered to be a primary impairment in several metabolic disorders such as obesity, insulin resistance, and type 2 diabetes mellitus.     

Inference of Cross-Level Interaction between Genes and Contextual Factors in a Matched Case-Control Metabolic Syndrome Study: A Bayesian Approach

Genes, environment, and the interaction between them are each known to play an important role in the risk for developing complex diseases such as metabolic syndrome. For environmental factors, most studies focused on the measurements observed at the individual level, and therefore can only consider the gene-environment interaction at the same individual scale. Indeed the group-level (called contextual) environmental variables, such as community factors and the degree of local area development, may modify the genetic effect as well. To examine such cross-level interaction between genes and contextual factors, a flexible statistical model quantifying the variability of the genetic effects across different categories of the contextual variable is in need. With a Bayesian generalized linear mixed-effects model with an unconditional likelihood, we investigate whether the individual genetic effect is modified by the group-level residential environment factor in a matched case-control metabolic syndrome study. Such cross-level interaction is evaluated by examining the heterogeneity in allelic effects under various contextual categories, based on posterior samples from Markov chain Monte Carlo methods. The Bayesian analysis indicates that the effect of rs1801282 on metabolic syndrome development is modified by the contextual environmental factor. That is, even among individuals with the same genetic component of PPARG_Pro12Ala, living in a residential area with low availability of exercise facilities may result in higher risk. The modification of the group-level environment factors on the individual genetic attributes can be essential, and this Bayesian model is able to provide a quantitative assessment for such cross-level interaction. The Bayesian inference based on the full likelihood is flexible with any phenotype, and easy to implement computationally. This model has a wide applicability and may help unravel the complexity in development of complex diseases.     

Girls' perception of neighborhood factors on physical activity, sedentary behavior, and BMI

Objective: The purpose of this study was to examine the association of perceived physical neighborhood factors with physical activity, sedentary behavior, and BMI among adolescent girls. Research Methods and Procedures: Sixth grade girls (n = 1554) completed a questionnaire on neighborhood factors (e.g., safety, esthetics, access to physical activity resources). The dependent variables included non‐school metabolic equivalent weighted moderate to vigorous physical activity (MW‐MVPA) and non‐school sedentary behavior, both measured using accelerometry, and BMI. Results: The following neighborhood factors were associated with lower BMI: seeing walkers and bikers on neighborhood streets, not having a lot of crime in the neighborhood, seeing other children playing outdoors, having bicycle or walking trails in the neighborhood, and access to physical activity facilities. The absolute contribution for the average girl for each of these neighborhood factors was relatively small, with none of these factors exceeding 0.8 kg/m² BMI units. The following neighborhood factors were associated with higher MW‐MVPA: having well‐lit streets at night, having a lot of traffic in the neighborhood, having bicycle or walking trails in the neighborhood, and access to physical activity facilities. Girls with ≥9 places to go for physical activity had 14.0% higher non‐school MW‐MVPA than girls with ≤4 places. Discussion: This study identified several neighborhood factors associated with non‐school MW‐MVPA and BMI, but none of the factors explored were associated with non‐school sedentary behavior. Of all of the neighborhood factors we examined, reporting more physically active destinations contributed the largest absolute amount to the average girl's non‐school MW‐MVPA, according to this cross‐sectional study.     

Prevention and treatment of type 2 diabetes in youth

Parallel to the increase in obesity worldwide, there has been a rise in the prevalence of type 2 diabetes mellitus (T2DM) in children and adolescents. The etiology of T2DM in youth, similar to adults, is multifactorial including genetic and environmental factors, among them obesity, sedentary lifestyle, family history of the disease, high-risk ethnicity and insulin resistance phenotype playing major roles. Treatment of T2DM should not have a glucocentric approach; it should rather target improving glycemia, dyslipidemia, hypertension, weight management and the prevention of short- and long-term complications. Prevention strategies, especially in high-risk groups, should focus on environmental change involving participation of families, schools, the food and entertainment industries and governmental agencies. Presently, limited pharmacotherapeutic options need to be expanded both for childhood T2DM and obesity. The coming decades will prove very challenging for healthcare providers battling socioeconomic waves conducive to obesity and T2DM. Evidence-based research and clinical experience in pediatrics, possibly modeled after adult trials, need to be developed if this public health threat is to be contained.     

2型糖尿病肠道菌群研究进展

2型糖尿病是一种常见的慢性消耗性疾病,其发病机制十分复杂,流行病学研究表明,肥胖、高热量饮食、体力活动不足及年龄增大是2型糖尿病最主要的环境因素。它是一种以胰岛素抵抗和胰岛素分泌不足为特征的代谢性疾病。肠道菌群作为进入人体的一个重要环境因素,肠道微生物的菌群变化影响宿主能量物质的吸收,调节肠道的分泌功能和非特异性免疫功能,从营养、代谢、疾病等各方面与我们生命活动相关。肠道菌群已成为我们身体的一部分,影响宿主的免疫,在肥胖、糖尿病、代谢综合征等疾病中都具有非常重要的作用。     

Metabolic syndrome in rheumatic diseases: epidemiology,pathophysiology, and clinical implications

Subjects with metabolic syndrome–a constellation of cardiovascular risk factors of which central obesity and insulin resistance are the most characteristic–are at increased risk for developing diabetes mellitus and cardiovascular disease. In these subjects, abdominal adipose tissue is a source of inflammatory cytokines such as tumor necrosis factor-alpha, known to promote insulin resistance. The presence of inflammatory cytokines together with the well-documented increased risk for cardiovascular diseases in patients with inflammatory arthritides and systemic lupus erythematosus has prompted studies to examine the prevalence of the metabolic syndrome in an effort to identify subjects at risk in addition to that conferred by traditional cardiovascular risk factors. These studies have documented a high prevalence of metabolic syndrome which correlates with disease activity and markers of atherosclerosis. The correlation of inflammatory disease activity with metabolic syndrome provides additional evidence for a link between inflammation and metabolic disturbances/vascular morbidity.     

Anti-obesity effects of gut microbiota are associated with lactic acid bacteria

The prevalence of obesity is rapidly becoming endemic in industrialized countries and continues to increase in developing countries worldwide. Obesity predisposes people to an increased risk of developing metabolic syndrome. Recent studies have described an association between obesity and certain gut microbiota, suggesting that gut microbiota might play a critical role in the development of obesity. Although probiotics have many beneficial health effects in humans and animals, attention has only recently been drawn to manipulating the gut microbiota, such as lactic acid bacteria (LAB), to influence the development of obesity. In this review, we first describe the causes of obesity, including the genetic and environmental factors. We then describe the relationship between the gut microbiota and obesity, and the mechanisms by which the gut microbiota influence energy metabolism and inflammation in obesity. Lastly, we focus on the potential role of LAB in mediating the effects of the gut microbiota in the development of obesity.     

Obesity in rhesus and cynomolgus macaques: a comparative review of the condition and its implications for research

Obesity is an increasingly important health issue in both humans and animals and has been highly correlated as a risk factor for hyperglycemic conditions in humans. Naturally occurring obesity has been extensively studied in nonhuman primates with a focus on the development of biomarkers for characterizing overweight individuals and tracking the progression of obesity to conditions such as type 2 diabetes mellitus. Animal models have provided a basic understanding of metabolism and carbohydrate physiology, and continue to contribute to ongoing research of obesity and its adverse health effects. This review focuses on spontaneous obesity in rhesus and cynomolgus macaques as a model for human obesity and type 2 diabetes mellitus, including associated risk factors for the development of obesity and obesity-related health conditions. Little is known about preventive measures to minimize obesity while maintaining a healthy colony of macaques, and numerous complexities such as social status, feeding behaviors, timing of feeding, food distribution, and stress have been identified as contributing factors to overweight body condition in both single and group housed nonhuman primates. As in humans, increased body weight and obesity in macaques affect their overall health status. These conditions may interfere with the suitability of some animals in various studies unrelated to obesity.     

Diagnosis of the metabolic syndrome in children

PURPOSE OF REVIEW: The metabolic syndrome, a cluster of potent risk factors for atherosclerotic cardiovascular disease and type 2 diabetes mellitus in adults, is composed of insulin resistance, obesity, hypertension and hyperlipidemia. Of significant impact in the adult population, atherosclerotic cardiovascular disease and death are rarely seen in the young, but the pathologic processes and risk factors associated with its development have been shown to begin during childhood. The current review summarizes the work published during the past year in the following areas: childhood obesity, insulin resistance, dyslipidemia, hypertension and type 2 diabetes mellitus. RECENT FINDINGS: Recent studies have revealed the presence of components of the metabolic syndrome in children and adolescents. Obesity has a central role in the syndrome. There is an increasing amount of data to show that being overweight during childhood and adolescence is significantly associated with insulin resistance, abnormal lipids, and elevated blood pressure in young adulthood. Weight loss in these situations results in a decrease in insulin concentration and an increase in insulin sensitivity toward normalcy. With cardiovascular disease, obesity, and type 2 diabetes reaching epidemic proportions, it is of great importance to understand and control the risk factors at an early age. SUMMARY: The information obtained during the past year has improved our understanding of the pathogenesis, diagnosis and treatment of components of the metabolic syndrome in children, and potentially could improve the risk profiles for cardiovascular disease as children make the transition toward adolescence and young adulthood.     

Oxidative stress and metabolic syndrome

Metabolic syndrome is a collection of cardiometabolic risk factors that includes obesity, insulin resistance, hypertension and dyslipidemia. Although there has been significant debate regarding the criteria and concept of the syndrome, this clustering of risk factors is unequivocally linked to an increased risk of developing type 2 diabetes and cardiovascular disease. Metabolic syndrome is often characterized by oxidative stress, a condition in which an imbalance results between the production and inactivation of reactive oxygen species. Reactive oxygen species can best be described as double-edged swords; while they play an essential role in multiple physiological systems, under conditions of oxidative stress, they contribute to cellular dysfunction. Oxidative stress is thought to play a major role in the pathogenesis of a variety of human diseases, including atherosclerosis, diabetes, hypertension, aging, Alzheimer's disease, kidney disease and cancer. The purpose of this review is to discuss the role of oxidative stress in metabolic syndrome and its major clinical manifestations (namely coronary artery disease, hypertension and diabetes). It will also highlight the effects of lifestyle modification in ameliorating oxidative stress in metabolic syndrome. Discussion will be limited to human data.     

Sex differences in risk factors for cardiovascular disease: the PERU MIGRANT study

Introduction

Although men and women have similar risk factors for cardiovascular disease, many social behaviors in developing countries differ by sex. Rural-to-urban migrants have different cardiovascular risk profiles than rural or urban dwellers. The objective of this study was to evaluate the sex differences with specific cardiovascular risk factors in rural-to-urban migrants.

Methods and Results

We used the rural-to-urban migrant group of the PERU MIGRANT cross-sectional study to investigate the sex differences in specific cardiovascular risk factors: obesity, hypertension, metabolic syndrome, as well as exposures of socioeconomic status, acculturation surrogates and behavioral characteristics. Logistic regression analysis was used to characterize strength of association between sex and our outcomes adjusting for potential confounders. The sample of migrants was 589 (mean age 46.5 years) and 52.4% were female. In the adjusted models, women were more likely to be obese (OR=5.97; 95%CI: 3.21–11) and have metabolic syndrome (OR=2.22; 95%CI: 1.39–3.55) than men, explaining the greatest variability for obesity and metabolic syndrome but not for hypertension.

Conclusions

Our results suggest that interventions for CVD in Peru should be sex-specific and address the unique health needs of migrant populations living in urban shantytowns since the risk factors for obesity and metabolic syndrome differ between males and females.     

Dietary carbohydrates, physical inactivity, obesity, and the 'metabolic syndrome' as predictors of coronary heart disease

Several decades of epidemiological and clinical research have identified physical inactivity, excessive calorie consumption, and excess weight as common risk factors for both type 2 diabetes mellitus and coronary heart disease. This trio forms the environmental substrate for a now well-recognized metabolic phenotype called the insulin resistance syndrome. Recent data suggest that a high intake of rapidly absorbed carbohydrates, which is characterized by a high glycemic load (a measure of carbohydrate quality and quantity), may increase the risk of coronary heart disease by aggravating glucose intolerance and dyslipidemia. These data also suggest that individuals who are obese and insulin resistant are particularly prone to the adverse effects of a high dietary glycemic load. In addition, data continue to accumulate suggesting the important beneficial effects of physical activity, even at moderate levels, and weight reduction on improving insulin sensitivity and reducing the risk of coronary heart disease. Future metabolic studies should continue to quantify the physiological impact of different foods on serum glucose and insulin, and such information should routinely be incorporated into large-scale and long-term prospective studies, in which the possible interaction effects between diet and other metabolic determinants such as physical activity and obesity can be examined. Until more definitive data are available, replacing refined grain products and potatoes with minimally processed plant-based foods such as whole grains, fruits, and vegetables, and reducing the intake of high glycemic load beverages may offer a simple strategy for reducing the incidence of coronary heart disease.