Exercise training prevents diastolic dysfunction induced by metabolic syndrome in rats

OBJECTIVE: High fructose consumption contributes to the incidence of metabolic syndrome and, consequently, to cardiovascular outcomes. We investigated whether exercise training prevents high fructose diet-induced metabolic and cardiac morphofunctional alterations. METHODS: Wistar rats receiving fructose overload (F) in drinking water (100 g/l) were concomitantly trained on a treadmill (FT) for 10 weeks or kept sedentary. These rats were compared with a control group (C). Obesity was evaluated by the Lee index, and glycemia and insulin tolerance tests constituted the metabolic evaluation. Blood pressure was measured directly (Windaq, 2 kHz), and echocardiography was performed to determine left ventricular morphology and function. Statistical significance was determined by one-way ANOVA, with significance set at p<0.05. RESULTS: Fructose overload induced a metabolic syndrome state, as confirmed by insulin resistance (F: 3.6 +/- 0.2 vs. C: 4.5 +/- 0.2 mg/dl/min), hypertension (mean blood pressure, F: 118 +/- 3 vs. C: 104 +/- 4 mmHg) and obesity (F: 0.31 +/- 0.001 vs. C: 0.29 +/- 0.001 g/mm). Interestingly, fructose overload rats also exhibited diastolic dysfunction. Exercise training performed during the period of high fructose intake eliminated all of these derangements. The improvements in metabolic parameters were correlated with the maintenance of diastolic function. CONCLUSION: The role of exercise training in the prevention of metabolic and hemodynamic parameter alterations is of great importance in decreasing the cardiac morbidity and mortality related to metabolic syndrome.

Association of arterial events with the coexistence of metabolic syndrome and primary antiphospholipid syndrome

Objective Metabolic syndrome (MetS) is highly prevalent in rheumatic diseases and is recognized as a new independent cardiovascular risk factor. This study was undertaken to determine the clinical significance of MetS in patients with primary antiphospholipid syndrome (APS). Methods Seventy-one primary APS patients and 73 age- and sex-matched healthy controls were included. Serum samples were tested for lipid profile, Lp(a), glucose, insulin, thyroid-stimulating hormone, free T4, erythrocyte sedimentation rate, C-reactive protein level, and uric acid. MetS was defined by the International Diabetes Federation criteria, and insulin resistance was established using the homeostasis model assessment index. Results The prevalence of MetS was 33.8%, and further comparison between primary APS patients with and without MetS revealed that the former had a higher frequency of arterial events (79.2% versus 42.6%; P = 0.003), angina (29.2% versus 2.1%; P = 0.002), and positive lupus anticoagulant antibody (95.8% versus 76.6%; P = 0.049). In addition, primary APS patients with MetS, as expected, had a higher prevalence of cardiovascular risk factors. On multivariate analysis, only MetS was independently associated with arterial events in primary APS. Conclusion Coexistence of primary APS and MetS seems to identify a subgroup of patients with higher risk of arterial events, suggesting that MetS may aggravate existing endothelial abnormalities of primary APS.

Cardiometabolic benefits of exercise training in an experimental model of metabolic syndrome and menopause

Objective: The aim of this study was to investigate the cardiometabolic effects of exercise training in ovariectomized hypertensive rats both submitted and not submitted to fructose overload. Methods: Spontaneously hypertensive ovariectomized rats were divided into sedentary and trained (THO) groups submitted to normal chow and sedentary and trained groups submitted to fructose overload (100 g/L in drinking water for 19 wk). Exercise training was performed on a treadmill (8 wk). Arterial pressure (AP) was directly recorded. Cardiovascular autonomic control was evaluated through pharmacological blockade (atropine and propranolol) and in the time and frequency domains by spectral analysis. Results: The THO group presented reduced AP (approximately 16 mm Hg) and enhanced cardiac vagal tonus (approximately 49%) and baroreflex sensitivity (approximately 43%) compared with the sedentary hypertensive ovariectomized group. Exercise training attenuated metabolic impairment, resting tachycardia, cardiac and vascular sympathetic increases, and baroreflex sensitivity decrease induced by fructose overload in hypertensive rats. However, the trained hypertensive ovariectomized group submitted to fructose overload presented higher AP (approximately 32 mm Hg), associated with baroreflex sensitivity (approximately 69%) and parasympathetic dysfunctions compared with the THO group. Conclusions: These data suggest that the metabolic disorders in hypertensive rats after ovarian hormone deprivation could blunt and/or attenuate some exercise training benefits.

Birth weight, current body mass index, and insulin sensitivity and secretion in young adults in two Latin American populations

Background and aims: Although studies have shown association of birth weight (BW) and adult body mass index (BMI) with insulin sensitivity in adults, there is limited evidence that BW is associated with insulin secretion. We assessed the associations between BW and current BMI with insulin sensitivity and secretion in young Latin American adults. Methods and results: Two birth cohorts, one from Ribeirao Preto, Brazil, based on 1984 participants aged 23-25 years, and another from Limache, Chile, based on 965 participants aged 22-28 years were studied. Weight and height at birth, and current fasting plasma glucose and insulin levels were measured. Insulin sensitivity (HOMA%S) and secretion (HOMA%beta) were estimated using the Homeostatic Model Assessment (HOMA2). Multiple linear regression analyses were carried out to test the associations between BW and adult BMI z-scores on log HOMA%S and log HOMA%beta. BW z-score was associated with HOMA%S in the two populations and HOMA%beta in Ribeirao Preto when adult BMI z-score was included in the model. BW z-score was associated with decreasing insulin secretion even without adjusting for adult BMI, but only in Ribeirao Preto. BMI z-score was associated with low HOMA%S and high HOMA%beta. No interactions between BW and BMI z-scores on insulin sensitivity were shown. Conclusions: This study supports the finding that BW may affect insulin sensitivity and secretion in young adults. The effect size of BW on insulin status is small in comparison to current BMI. (C) 2010 Elsevier B.V. All rights reserved.

Relationship between Vitamin D Receptor gene polymorphisms and the components of metabolic syndrome

Abstract Background The Vitamin D Receptor gene (VDR) is expressed in many tissues and modulates the expression of several other genes. The purpose of this study was to investigate the association between metabolic syndrome (MetSyn) with the presence of VDR 2228570 C > T and VDR 1544410 A > G polymorphisms in Brazilian adults. Methods Two hundred forty three (243) individuals were included in a cross-sectional study. MetSyn was classified using the criteria proposed by National Cholesterol Educational Program - Adult Treatment Panel III. Insulin resistance and β cell secretion were estimated by the mathematical models of HOMA IR and β, respectively. The VDR 2228570 C > T and VDR 1544410 A > G polymorphisms were detected by enzymatic digestion and confirmed by allele specific PCR or amplification of refractory mutation. Results Individuals with MetSyn and heterozygosis for VDR 2228570 C > T have higher concentrations of iPTH and HOMA β than those without this polymorphism, and subjects with recessive homozygosis for the same polymorphisms presented higher insulin resistance than those with the heterozygous genotype. There is no association among VDR 1544410 A > G and components of MetSyn, HOMA IR and β, serum vitamin D (25(OH)D3) and intact parathormone (iPTH) levels in patients with MetSyn. A significant lower concentration of 25(OH)D3 was observed only in individuals without MetSyn in the VDR 1544410 A > G genotype. Additionally, individuals without MetSyn and heterozygosis for VDR 2228570 C > T presented higher concentration of triglycerides and lower HDL than those without this polymorphism. Conclusions Using two common VDR polymorphism data suggests they may influence insulin secretion, insulin resistance an serum HDL-cholesterol in our highly heterogeneous population. Whether VDR polymorphism may influence the severity of MetSyn component disorder, warrants examination in larger cohorts used for genome-wide association studies.

Metabolic syndrome, dyslipidemia, hypertension and type 2 diabetes in youth: from diagnosis to treatment

Overweight and obesity in youth is a worldwide public health problem. Overweight and obesity in childhood and adolescents have a substantial effect upon many systems, resulting in clinical conditions such as metabolic syndrome, early atherosclerosis, dyslipidemia, hypertension and type 2 diabetes (T2D). Obesity and the type of body fat distribution are still the core aspects of insulin resistance and seem to be the physiopathologic links common to metabolic syndrome, cardiovascular disease and T2D. The earlier the appearance of the clustering of risk factors and the higher the time of exposure, the greater will be the chance of developing coronary disease with a more severe endpoint. The age when the event may occur seems to be related to the presence and aggregation of risk factors throughout life.

Metabolic, hemodynamic and structural adjustments to low intensity exercise training in a metabolic syndrome model

Background The increase in fructose consumption is paralleled by a higher incidence of metabolic syndrome, and consequently, cardiovascular disease mortality. We examined the effects of 8 weeks of low intensity exercise training (LET) on metabolic, hemodynamic, ventricular and vascular morphological changes induced by fructose drinking in male rats. Methods Male Wistar rats were divided into (n = 8 each) control (C), sedentary fructose (F) and ET fructose (FT) groups. Fructose-drinking rats received D-fructose (100 g/l). FT rats were assigned to a treadmill training protocol at low intensity (30% of maximal running speed) during 1 h/day, 5 days/week for 8 weeks. Measurements of triglyceride concentrations, white adipose tissue (WAT) and glycemia were carried out together with insulin tolerance test to evaluate metabolic profile. Arterial pressure (AP) signals were directly recorded. Baroreflex sensitivity (BS) was evaluated by the tachycardic and bradycardic responses. Right atria, left ventricle (LV) and ascending aorta were prepared to morphoquantitative analysis. Results LET reduced WAT (−37.7%), triglyceride levels (−33%), systolic AP (−6%), heart weight/body weight (−20.5%), LV (−36%) and aortic (−76%) collagen fibers, aortic intima-media thickness and circumferential wall tension in FT when compared to F rats. Additionally, FT group presented improve of BS, numerical density of atrial natriuretic peptide granules (+42%) and LV capillaries (+25%), as well as the number of elastic lamellae in aorta compared with F group. Conclusions Our data suggest that LET, a widely recommended practice, seems to be particularly effective for preventing metabolic, hemodynamic and morphological disorders triggered by MS.

Changes in renal glucose transporters in an animal model of metabolic syndrome

Considering the similarity between structural, hemodynamic, and functional changes of obesity-related renal disease and diabetic nephropathy, we hypothesized that renal glucose transporter changes occur in obesity as in diabetes. The aim of the work was to evaluate GLUT1 and GLUT2 in kidneys of an animal model of metabolic syndrome. Neonate spontaneously hypertensive rats (SHR), n=15/group, were treated with monosodium glutamate (5 mg/g) (MetS) for 9 days and compared with saline-treated Wistar-Kyoto (C) and SHR (H) rats. Lee index, systolic arterial pressure (SAP), glycemia, insulin resistance, triglycerides, and HDL cholesterol were evaluated at 3 and 6 months. Medullar GLUT1 and cortical GLUT2 were analyzed by Western blot. MetS vs. C and H rats had the highest Lee index (p<0.001) and insulin resistance (3-months C: 4.3±0.7, H: 3.9±0.9, MetS: 2.7±0.6; 6-months C: 4.2±0.6, H: 3.8±0.5, MetS: 2.4±0.6% • min−1, p<0.001), similar glycemia, and the lowest HDL-cholesterol at 6-months (p<0.001). In the MetS and H rats, SAP was higher vs. C at 3-months (p<0.001) and 6-months (C: 151±15, H: 190±11, MetS: 185±13 mm Hg, p<0.001) of age. GLUT1 was ̴ 13× lower (p<0.001) at 3-months, reestablishing its content at 6-months in MetS group, while GLUT2 was 2× higher (p<0.001) in this group at 6-months of age. Renal GLUT1 and GLUT2 are modulated in kidney of rats with metabolic syndrome, where obesity, insulin resistance and hypertension coexist, despite normoglycemia. Like in diabetes, cortical GLUT2 overexpression may contribute to the development of kidney disease

Is the metabolic syndrome a new childhood disease?

Overweight and obesity in children and adolescents have become a major public health problem in recent years throughout the world. The medical consequences of obesity may manifest as an increase in the prevalence of the metabolic syndrome in children and adolescents putting them at increased risk for future cardiovascular diseases. Obesity can cause insulin resistance and might disturb glucose homeostasis eventually leading to type 2 diabetes in susceptible patients. Insulin resistance is also involved in the pathogenesis of dyslipidemia in obese children characteristically presenting as hypertriglyceridemia and low HDL cholesterol. Even elevated blood pressure might be present in obese kids. Here we present a 12-year-old boy diagnosed with the metabolic syndrome. The diagnostic criteria of the metabolic syndrome in children and adolescents are discussed. Thoughts about pathophysiology and therapeutic options are offered.

Cardiovascular risk factors and the metabolic syndrome in pediatric nonalcoholic fatty liver disease

BACKGROUND: Nonalcoholic fatty liver disease (NAFLD), the most common cause of liver disease in children, is associated with obesity and insulin resistance. However, the relationship between NAFLD and cardiovascular risk factors in children is not fully understood. The objective of this study was to determine the association between NAFLD and the presence of metabolic syndrome in overweight and obese children. METHODS AND RESULTS: This case-control study of 150 overweight children with biopsy-proven NAFLD and 150 overweight children without NAFLD compared rates of metabolic syndrome using Adult Treatment Panel III criteria. Cases and controls were well matched in age, sex, and severity of obesity. Children with NAFLD had significantly higher fasting glucose, insulin, total cholesterol, low-density lipoprotein cholesterol, triglycerides, systolic blood pressure, and diastolic blood pressure than overweight and obese children without NAFLD. Subjects with NAFLD also had significantly lower high-density lipoprotein cholesterol than controls. After adjustment for age, sex, race, ethnicity, body mass index, and hyperinsulinemia, children with metabolic syndrome had 5.0 (95% confidence interval, 2.6 to 9.7) times the odds of having NAFLD as overweight and obese children without metabolic syndrome. CONCLUSIONS: NAFLD in overweight and obese children is strongly associated with multiple cardiovascular risk factors. The identification of NAFLD in a child should prompt global counseling to address nutrition, physical activity, and avoidance of smoking to prevent the development of cardiovascular disease and type 2 diabetes.

ATM-dependent expression of the insulin-like growth factor-I receptor in a pathway regulating radiation response

The ATM gene is mutated in the syndrome of ataxia telangiectasia (AT), associated with neurologic dysfunction, growth abnormalities, and extreme radiosensitivity. Insulin-like growth factor-I receptor (IGF-IR) is a cell surface receptor with tyrosine kinase activity that can mediate mitogenesis, cell transformation, and inhibition of apoptosis. We report here that AT cells express low levels of IGF-IR and show decreased IGF-IR promoter activity compared with wild-type cells. Complementation of AT cells with the ATM cDNA results in increased IGF-IR promoter activity and elevated IGF-IR levels, whereas expression in wild-type cells of a dominant negative fragment of ATM specifically reduces IGF-IR expression, results consistent with a role for ATM in regulating IGF-IR expression at the level of transcription. When expression of IGF-IR cDNA is forced in AT cells via a heterologous viral promoter, near normal radioresistance is conferred on the cells. Conversely, in ATM cells complemented with the ATM cDNA, specific inhibition of the IGF-IR pathway prevents correction of the radiosensitivity. Taken together, these results establish a fundamental link between ATM function and IGF-IR expression and suggest that reduced expression of IGF-IR contributes to the radiosensitivity of AT cells. In addition, because IGF-I plays a major role in human growth and metabolism and serves as a survival and differentiation factor for developing neuronal tissue, these results may provide a basis for understanding other aspects of the AT syndrome, including the growth abnormalities, insulin resistance, and neurodegeneration.

Serine phosphorylation of human P450c17 increases 17,20-lyase activity: implications for adrenarche and the polycystic ovary syndrome.

Microsomal cytochrome P450c17 catalyzes both steroid 17 alpha-hydroxylase activity and scission of the C17-C20 steroid bond (17,20-lyase) on the same active site. Adrenal 17 alpha-hydroxylase activity is needed to produce cortisol throughout life, but 17,20-lyase activity appears to be controlled independently in a complex, age-dependent pattern. We show that human P450c17 is phosphorylated on serine and threonine residues by a cAMP-dependent protein kinase. Phosphorylation of P450c17 increases 17,20-lyase activity, while dephosphorylation virtually eliminates this activity. Hormonally regulated serine phosphorylation of human P450c17 suggests a possible mechanism for human adrenarche and may be a unifying etiologic link between the hyperandrogenism and insulin resistance that characterize the polycystic ovary syndrome.

Myocardial and vascular dysfunction and exercise capacity in the metabolic syndrome

The metabolic syndrome (MS) is associated with cardiovascular risk exceeding that expected from atherosclerotic risk factors, but the mechanism of this association is unclear. We sought to determine the effects of the MS on myocardial and vascular function and cardiorespiratory fitness in 393 subjects with significant risk factors but no cardiovascular disease and negative stress echocardiographic findings. Myocardial function was assessed by global strain rate, strain, and regional systolic velocity (s(m)) and diastolic velocity (e(m)) using tissue Doppler imaging. Arterial compliance was assessed using the pulse pressure method, involving simultaneous radial applanation tonometry and echocardiographic measurement of stroke volume. Exercise capacity was measured by expired gas analysis. Significant and incremental variations in left ventricular systolic (s(m), global strain, and strain rate) and diastolic (e(m)) function were found according to the number of components of MS (p <0.001). MS contributed to reduced systolic and diastolic function even in those without left ventricular hypertrophy (p <0.01). A similar dose-response association was present between the number of components of the MS and exercise capacity (p <0.001) and arterial compliance. The global strain rate and em were independent predictors of exercise capacity. In conclusion, subclinical left ventricular dysfunction corresponded to the degree of metabolic burden, and these myocardial changes were associated with reduced cardiorespiratory fitness.' Subjects with MS who also have subclinical myocardial abnormalities and reduced cardiorespiratory fitness may have a higher risk of cardiovascular disease events and heart failure. (C) 2005 Elsevier Inc. All rights reserved.

Fat as an endocrine organ: Relationship to the metabolic syndrome

Obesity and the metabolic syndrome have both reached pandemic proportions. Together they have the potential to impact on the incidence and severity of cardiovascular pathologies, with grave implications for worldwide health care systems. The metabolic syndrome is characterized by visceral obesity, insulin resistance, hypertension, chronic inflammation, and thrombotic disorders contributing to endothelial dysfunction and, subsequently, to accelerated atherosclerosis. Obesity is a key component in development of the metabolic syndrome and it is becoming increasingly clear that a central factor in this is the production by adipose cells of bioactive substances that directly influence insulin sensitivity and vascular injury. In this paper, we review advances in the understanding of biologically active molecules collectively referred to as adipokines and how dysregulated production of these factors in obese states mediates the pathogenesis of obesity associated metabolic syndrome.