Relation of cumulative weight burden to vascular endothelial dysfunction in obesity

Impact of excess body weight on arterial structure, function, and blood pressure in firefighters

Cardiovascular disease is the leading cause of death among firefighters. The purpose of the present study was to examine the effect of excess body weight on arterial structure and function and blood pressure (BP) in relatively young, apparently healthy, firefighters. The body mass index, brachial BP, carotid BP, aortic BP, radial augmentation index, central pulse wave velocity, forearm blood flow, forearm vasodilatory capacity, carotid arterial compliance, carotid intima-media thickness, and brachial flow-mediated dilation were assessed in 110 firefighters (aged 29.7 +/- 8.0 years). The group was divided into equal tertiles according to the body mass index (<25.9, 25.9 to 29.4, and >or=29.5 kg/m(2)). Group differences in hemodynamics, anthropometrics, microvascular function, and macrovascular structure and function were tested using multivariate analysis of variance. The obese group was older, heavier, and had a larger waist circumference compared to the lean and overweight groups (p <0.05). The overweight group was also older, heavier, and had a larger waist circumference than the lean group (p <0.05). Compared to the lean group, the overweight and obese groups had a greater systolic BP (p <0.05). The obese group also had a significantly greater mean arterial BP and carotid systolic BP than the lean group (p <0.05). The obese group had greater beta stiffness and elastic modulus compared to the lean and overweight groups (p <0.05), but no group differences were found in endothelial function. In conclusion, in a population of relatively young firefighters, an increased body mass index was associated with elevated peripheral BP and arterial stiffness, with no apparent decrements in endothelial function.

Endothelial dysfunction and specific inflammation in obesity hypoventilation syndrome

Background

Obesity hypoventilation syndrome (OHS) is associated with increased cardiovascular morbidity. What moderate chronic hypoventilation adds to obesity on systemic inflammation and endothelial dysfunction remains unknown.

Question

To compare inflammatory status and endothelial function in OHS versus eucapnic obese patients.

Methodology

14 OHS and 39 eucapnic obese patients matched for BMI and age were compared. Diurnal blood gazes, overnight polysomnography and endothelial function, measured by reactive hyperemia peripheral arterial tonometry (RH-PAT), were assessed. Inflammatory (Leptin, RANTES, MCP-1, IL-6, IL-8, TNFα, Resistin) and anti-inflammatory (adiponectin, IL-1Ra) cytokines were measured by multiplex beads immunoassays.

Principal Findings

OHS exhibited a higher PaCO₂, a lower forced vital capacity (FVC) and tended to have a lower PaO₂ than eucapnic obese patients. _HS-CRP, RANTES levels and glycated haemoglobin (HbA1c) were significantly increased in OHS (respectively 11.1±10.9 vs. 5.7±5.5 mg.l⁻¹ for _HS-CRP, 55.9±55.3 vs 23.3±15.8 ng/ml for RANTES and 7.3±4.3 vs 6.1±1.7 for HbA1c). Serum adiponectin was reduced in OHS (7606±2977 vs 13660±7854 ng/ml). Endothelial function was significantly more impaired in OHS (RH-PAT index: 0.22±0.06 vs 0.51±0.11).

Conclusions

Compared to eucapnic obesity, OHS is associated with a specific increase in the pro-atherosclerotic RANTES chemokine, a decrease in the anti-inflammatory adipokine adiponectin and impaired endothelial function. These three conditions are known to be strongly associated with an increased cardiovascular risk.

Trial Registration

ClinicalTrials.gov NCT00603096

Modifiers of cognitive function and brain structure in middle-aged and elderly individuals with type 2 diabetes mellitus

Cognitive deficits and hippocampal atrophy, features that are shared with aging and dementia, have been described in type 2 diabetes mellitus (T2DM). T2DM is associated with obesity, hypertension, dyslipidemia, hypothalamic pituitary adrenocortical (HPA) axis abnormalities and inflammation, all of which have been shown to negatively impact the brain. However, since most reports in T2DM focused on glycemic control, the relative contribution of these modifying factors to the impairments observed in T2DM remains unclear. We contrasted 41 middle-aged dementia-free volunteers with T2DM (on average 7 years since diagnosis) with 47 age-, education-, and gender-matched non-insulin resistant controls on cognition and brain volumes. HPA axis activity and other modifiers that accompany T2DM were assessed to determine their impact on brain and cognition. Individuals with T2DM had specific verbal declarative memory deficits, reduced hippocampal and prefrontal volumes, and impaired HPA axis feedback control. Diminished cortisol suppression after dexamethasone and dyslipidemia were associated with decreased cognitive performance, whereas obesity was negatively related to hippocampal volume. Moreover, prefrontal volume was influenced by worse glycemic control. Thus, obesity and altered cortisol levels may contribute to the impact of T2DM on the hippocampal formation, resulting in decreased verbal declarative memory performance.

Psychological Factors Associated With Weight Loss in Obese and Severely Obese Women in a Behavioral Physical Activity Intervention

The behavioral processes of weight reduction are poorly understood, and responses to treatments based primarily on caloric restriction have been unfavorable. A theory-based path derived from proposed relations of physical activity, changes in psychological factors, and weight loss was separately tested with women with Class I and Class II obesity (body mass index [BMI] from 30 to 39.9 kg/m2; n = 116), and Class III (BMI ≥ 40.0 kg/m2; n = 57) obesity. Participation in a cognitive-behavioral exercise support treatment along with nutrition education was significantly associated with changes in measures of self-efficacy, body satisfaction, and mood. Changes did not significantly differ by BMI group. Multiple regression analyses indicated that changes in the psychological factors explained 14% (Class I/II obesity group) and 22% (Class III obesity group) of the variance in exercise session attendance, and attendance was strongly related to weight loss. Implications for weight loss theory and treatment are discussed.

Cardiovascular Risks Associated With Obesity in Children and Adolescents

Introduction: The aim of this paper is to review the cardiovascular (CVS) risks associated with obesity in children and adolescents. Both short-term and long-term CVS consequences, the mechanisms of how these develop and the measures that can alter or reverse these CVS events are reviewed. Materials and Methods:Selected publications include original articles and review papers that report on studies of CVS risks and consequences related to childhood obesity. Some papers that contain data from adults studies are also included if the contents help to explain some underlying mechanisms or illustrate the continuation of related CVS changes into adulthood. Results: Obese children and adolescents have an increased risk for CVS complications that include elevation of blood pressure, clustering of CVS risk factors (Metabolic Syndrome), changes to arterial wall thickness, elasticity and endothelium, as well as changes in left ventricular structure and function. Some of these cardiovascular problems may be initiated or potentiated by obstructive sleep apnoea that can accompany obesity in children. Many of such changes have been noted to reverse or improve with weight reduction. Conclusions:Early development of CVS risks in obese children and the possible continuation of CVS complications into adulthood have been observed. Obstructive sleep apnoea in obese children can further contribute to such CVS risks. These findings underscore the importance of prevention of childhood obesity as a priority over management of obesity in children. The prevalence of obesity has risen by three-folds or more in many countries since 1980. In 2005, it was estimated that globally there are about 1.6 billion overweight adults and at least 400 million of them are obese. This increase in the prevalence of adults being overweight and obese comes with a heavy price. The cost of healthcare has significantly increased and is expected to increase even more because of the close association between obesity and various chronic diseases. Key words: Endothelial function, Hypertension, Metabolic syndrome, Obstructive sleep apnoea

Association of central obesity with early Carotid intima-media thickening is independent of that from other risk factors

AIM

We investigated whether anthropometric measurements or metabolic risk factors correlated more with vascular changes associated with obesity.

METHODS

One hundred never smoking subjects (71 women, 29 men) without vascular events, with blood pressure (BP) <140/90 mm Hg, LDL cholesterol <4 mmol/l, glucose <6.2 mmol/l participated. Anthropometric measurements (body mass index (BMI), waist/hip ratio (WHR), waist circumference (WC) and Waist/height ratio WHTR) and metabolic risk factors (glucose, insulin, lipid and uric acid levels plus BP) were assessed. Subjects underwent vascular measurements (Carotid intima-media thickness (IMT) using duplex ultrasonography, vascular stiffness assessment (Augmentation Index) by applanation tonometry and brachial artery reactivity tests).

RESULTS

Risk factors were in the 'normal distribution'. BMI, WHR, WC, WHTR correlated significantly with triglyceride, HDL, LDL, insulin, glucose, uric acid and systolic BP levels (P<0.001). IMT correlated with WHTR, BMI, WC, Glucose (P<0.001), Homoeostasis Model Assessment (HOMA) and cholesterol levels (P<0.05). Only Age, WHTR or BMI were significant correlates of IMT in a multivariate analysis (P<0.01) including WHTR or BMI, with age, sex, systolic BP, HDLc and HOMA. Augmentation Index correlated with age (P<0.0001), WHTR and WC (P<0.0005) but with age only in a multivariate analysis. Brachial reactivity did not correlate with any anthropometric or metabolic parameters. Anthropometric cutoff points, (BMI > or =25, WC > or =102 cm men, > or =88 cm women, WHR > or =0.9 men, > or =0.8 women and WHTR > or =0.5 men and women) significantly differentiated normal from abnormal metabolic and vascular measurements. The WHTR ratio > or =0.5 was as reliable as the BMI cutoff > or =25 in determining metabolic and vascular abnormalities. BMI and WHTR were strongly associated with 89% agreement (P<0.0001).

CONCLUSION

These results demonstrated that in 'healthy individuals', anthropometric parameters and metabolic risk factors correlated with each other, but anthropometric parameters were the only significant correlates of carotid IMT. A waist/height ratio > or =0.5 predicts both early vascular and metabolic changes. These data support a risk factor independent vasculotrophic effect of obesity.

The effects of body mass index on cerebral blood flow velocity

OBJECTIVE

Obesity is a risk factor for cerebrovascular disease. We aimed to determine the effects of high body mass index (BMI) on cerebral blood flow regulation in patients with type-2 diabetes mellitus, hypertension, and stroke.

METHODS

We analyzed data from 90 controls, 30 diabetics, 45 hypertensives, and 32 ischemic stroke patients who underwent transcranial Doppler for evaluation of blood flow velocities (BFV) in the middle cerebral arteries (MCA) and cerebrovascular resistance (CVR) during supine rest and head-up tilt. This study was a cross-sectional analysis. We used a structural equation multiple indicators modeling to determine the effects of BMI and other background variables (age, sex, race, smoking, alcohol use, and systolic blood pressure) on cerebral BFV.

RESULTS

Higher BMI (P = 0.02) and age (P = 0.004) were associated with lower mean BFV during baseline, independent of diagnosis of diabetes mellitus, hypertension or stroke, and after adjusting for all background variables and vessel diameters. Men, especially those with stroke, had a lower mean BFV than women (P = 0.01). CVR increased with BMI (P = 0.001) at baseline and during head-up tilt (P = 0.02), and was elevated in obese subjects (P = 0.004) compared to normal weight subjects across all groups.

INTERPRETATION

High BMI is associated with a reduction in cerebral BFV and increased CVR. These findings indicate that obesity can adversely affect cerebral blood flow and resistance in the cerebrovascular bed, independent of diagnosis of type-2 diabetes, hypertension or stroke. Obesity may contribute to cerebromicrovascular disease, and affect clinical functional outcomes of the older population.