Central Obesity and Insulin Resistance in the Cardiometabolic Syndrome: Pathways to Preclinical Cardiovascular Structure and Function

The effects of gender and country of origin on acculturation, psychological factors, lifestyle factors, and diabetes-related physiological outcomes among Mexican Americans: The Starr County diabetes prevention initiative

OBJECTIVES

Examine acculturation and psychological, lifestyle, and physiological factors based on gender and country of origin (U.S. vs. Mexico).

METHODS

Baseline data from the Starr County diabetes prevention study (N = 300) were analyzed - acculturation (language), psychological factors (depression), lifestyle factors (sedentary behaviors), and diabetes-related physiological outcomes (insulin resistance). MANOVA and linear regression were used to examine variable relationships based on gender and country of origin and identify predictors of depression and insulin resistance.

RESULTS

Participants were: predominantly female (73%); 51 years of age, on average; born in Mexico (71%); and Spanish-speaking. Individuals spent 11 of their waking hours (range = 0-18 h) in sedentary activities. Compared to females, more males spoke English and reported fewer hours in sedentary activities. Compared to participants born in Mexico, those born in the U.S. were more likely to: speak English; report depressive symptoms; and exhibit elevated BMI and insulin resistance rates. Two distinct models significantly predicted depression (R² = 14.5%) and insulin resistance (R² = 26.8%), with acculturation-language entering into both models.

DISCUSSION

Significant gender and country-of-origin differences were found. Future research on diabetes prevention should examine other Hispanic subgroups and strategies for addressing individual differences, while employing cost-effective group interventions that incorporate these differences and reach more at-risk individuals.

Inhibition of transglutaminase 2 (TG2) ameliorates ventricular fibrosis in isoproterenol-induced heart failure in rats

AIMS

Transglutaminase (TG) inhibitors represent promising therapeutic interventions in cardiac fibrosis and related dysfunctions. However, it remains unknown how TG inhibition, TG2 in particular, affects the signaling systems that drive pathological fibrosis. This study aimed to examine the effect TG inhibition by cystamine on the progression of isoproterenol (ISO)-induced cardiac fibrosis and dysfunction in rats.

MATERIALS AND METHODS

Cardiac fibrosis was established by intraperitoneal injection of ISO to rats (ISO group), followed by 6 weeks of cystamine injection (ISO + Cys group). The control groups were administered normal saline alone or with cystamine. Hemodynamics, lipid profile, liver enzymes, urea, and creatinine were assessed in conjunction with heart failure markers (serum NT-proANP and cTnI). Left ventricular (LV) and atrial (LA) fibrosis, total collagen content, and mRNA expression of profibrotic markers including TG2 were quantified by Masson's trichrome staining, LC-MS/MS and quantitative PCR, respectively.

KEY FINDINGS

Cystamine administration to ISO rats significantly decreased diastolic and mean arterial pressures, total cholesterol, triglycerides, LDL, liver enzymes, urea, and creatinine levels, while increasing HDL. NT-proANP and cTnI serum levels remained unchanged. In LV tissues, significant reductions in ISO-induced fibrosis and elevated total collagen content were achieved after cystamine treatment, together with a reduction in TG2 concentration. Reduced mRNA expression of several profibrotic genes (COL1A1, FN1, MMP-2, CTGF, periostin, CX43) was also evidenced in LV tissues of ISO rats upon cystamine administration, whereas TGF-β1 expression was depressed in LA tissues. Cystamine decreased TG2 mRNA expression in the LV of control rats, while LV expression of TG2 was relatively low in ISO rats irrespective of cystamine treatment.

SIGNIFICANCE

TG2 inhibition by cystamine in vivo exerted cardioprotective effects against ISO-induced cardiac fibrosis in rats decreasing the LV abundance of several profibrotic markers and the content of TG2 and collagen, suggesting that TG2 pharmacological inhibition could be beneficial to alleviate cardiac fibrosis.

Acculturation, Dietary Behaviors, and Macronutrient Intake Among Mexican Americans With Prediabetes: The Starr County Diabetes Prevention Initiative

PURPOSE

The purpose of the study was to examine the influences of sex and acculturation on dietary behaviors, macronutrient intake, and dietary quality in participants enrolled in a diabetes prevention initiative in Starr County, Texas.

METHODS

Baseline data from the Starr County diabetes prevention study (N = 300) were analyzed-acculturation (country of origin, years in Starr County, language and food preferences), depressive symptoms (Patient Health Questionnaire-9), healthy eating self-efficacy (Weight Efficacy Lifestyle Questionnaire-Short Form), diet quality (USDA Healthy Eating Index), fat avoidance (Fat Avoidance Scale, Spanish version), and macronutrients. Descriptive statistics and univariate analysis of covariance were used to examine differences based on acculturation, controlling for sex.

RESULTS

Participants were predominantly female (73%) and, on average, 51 years of age. Language and food preferences favored Spanish language and Hispanic foods, respectively. The majority (71%) was born in Mexico but had resided in Starr County for 33 years, on average. Depressive symptoms were moderate, and eating self-efficacy scores suggested low confidence in making healthy food choices, particularly for saturated fats. Spanish language preference was associated with worse dietary habits. The mean dietary quality score was lower than the national average (54 vs 59 nationally); females had slightly higher dietary quality than males and a higher mean fat avoidance score, although differences were not clinically significant. Intakes of carbohydrate, saturated fats, and cholesterol were higher than recommended daily allowances.

CONCLUSIONS

The overall preference for speaking Spanish and the influence of language on dietary intake should inform future dietary interventions. Accommodating cultural norms and food preferences remain major challenges to improving dietary quality among the diverse Hispanic ethnic groups.

Sex differences in the association of vital exhaustion with regional fat deposition and subclinical cardiovascular disease risk

OBJECTIVE

Vital exhaustion (VE) is more strongly associated with cardiovascular disease (CVD) risk for women than men. This study examined whether sex differences in associations of VE with CVD risk markers are accounted for by unique associations of VE with regional adiposity.

METHODS

The study enrolled 143 persons (18-55 years) without diagnosed conditions. VE was assessed by the Maastricht questionnaire. CVD indices were measured using the euglycemic-hyperinsulinemia clamp, resting blood pressure, and blood draws. Regional adiposity was measured using computed tomography and 2-D echocardiography. This cross-sectional study employed a path analysis approach, including relevant covariates.

RESULTS

Of the cohort, aged 38.7 ± 8.4 years, 65% were men, and 41% were obese. The final model had excellent fit (χ2(36) = 36.5, p = .45; RMSEA = 0.009, CFI = 0.999). For women, but not men, the model indicated paths from VE to: 1) lower insulin sensitivity (B = -0.10, p = .04), and higher total cholesterol to HDL ratio (B = 0.12, p = .09), triglycerides (B = 0.10, p = .08), and C-reactive protein (B = 0.08, p = .09) through visceral adiposity; 2) higher mean arterial pressure (B = 0.14, p = .04), lower insulin sensitivity (B = -0.09, p = .08), and higher C-reactive protein (B = 0.12, p = .07) through subcutaneous adiposity; 3) lower insulin sensitivity (B = -0.07, p = .08) and higher total cholesterol to HDL ratio (B = 0.16, p = .03) through liver adiposity; and 4) higher C-reactive protein (B = 0.08, p = .09) through epicardial adiposity.

CONCLUSION

Results extend prior evidence by showing that the association of VE with CVD risk in women is linked with specific regional adiposity elevation. Further study of adiposity-related mechanisms in women who experience early decline in vitality may inform clinical targets for CVD prevention.

Pathophysiological Consequences of At-Risk Alcohol Use; Implications for Comorbidity Risk in Persons Living With Human Immunodeficiency Virus

At-risk alcohol use is a significant risk factor associated with multisystemic pathophysiological effects leading to multiorgan injury and contributing to 5.3% of all deaths worldwide. The alcohol-mediated cellular and molecular alterations are particularly salient in vulnerable populations, such as people living with HIV (PLWH), diminishing their physiological reserve, and accelerating the aging process. This review presents salient alcohol-associated mechanisms involved in exacerbation of cardiometabolic and neuropathological comorbidities and their implications in the context of HIV disease. The review integrates consideration of environmental factors, such as consumption of a Western diet and its interactions with alcohol-induced metabolic and neurocognitive dyshomeostasis. Major alcohol-mediated mechanisms that contribute to cardiometabolic comorbidity include impaired substrate utilization and storage, endothelial dysfunction, dysregulation of the renin-angiotensin-aldosterone system, and hypertension. Neuroinflammation and loss of neurotrophic support in vulnerable brain regions significantly contribute to alcohol-associated development of neurological deficits and alcohol use disorder risk. Collectively, evidence suggests that at-risk alcohol use exacerbates cardiometabolic and neurocognitive pathologies and accelerates biological aging leading to the development of geriatric comorbidities manifested as frailty in PLWH.

Effectiveness of workplace diabetes prevention programs: A systematic review of the evidence

PURPOSE

The primary purpose is to review diabetes workplace interventions and the degree to which they improve diabetes-related outcomes in employees diagnosed with or at risk for T2DM.

METHODS

Three electronic databases and ancestry searches were used to identify peer reviewed articles published in English from 2000 to June 2017.

RESULTS

The number of participants represented by the 22 selected studies, excluding one large outlier, was 4243. On average, the samples were 57% female and ethnically diverse. Interventions-healthy eating behaviors, physical activity, and/or monitoring and self-managing diabetes and cardiovascular risk factors-were delivered in group sessions of fewer than 20 employees. Programs involved 1-h weekly sessions held during lunch hour or at other times during the workday for 12 to 24 weeks. Study outcomes, commonly measured at 6 and/or 12 months, were consistently positive.

CONCLUSION

The literature search uncovered beginning evidence that workplace interventions hold promise for preventing diabetes and/or its complications. More rigorous, creatively designed, workplace studies, are needed for employees at high-risk for developing diabetes.

PRACTICE IMPLICATIONS

Implications include the need for employer education about the benefits of employer support for such programs and attention to motivational strategies so employees will take full advantage of programs that are offered.

In Search of New Therapeutic Targets in Obesity Treatment: Sirtuins

Most of the available non-invasive medical therapies for obesity are non-efficient in a long-term evaluation; therefore there is a constant need for new methods of treatment. Research on calorie restriction has led to the discovery of sirtuins (silent information regulators, SIRTs), enzymes regulating different cellular pathways that may constitute potential targets in the treatment of obesity. This review paper presents the role of SIRTs in the regulation of glucose and lipid metabolism as well as in the differentiation of adipocytes. How disturbances of SIRTs’ expression and activity may lead to the development of obesity and related complications is discussed. A special emphasis is placed on polymorphisms in genes encoding SIRTs and their possible association with susceptibility to obesity and metabolic complications, as well as on data regarding altered expression of SIRTs in human obesity. Finally, the therapeutic potential of SIRTs-targeted strategies in the treatment of obesity and related disorders is discussed.

The impact of oral contraceptives on cardiometabolic parameters

PURPOSE

There is much controversy regarding the use of oral contraceptive pills (OCPs) on cardiometabolic parameters, which is why this longitudinal population-based study was conducted to assess the impact of OCP use and its duration on cardiometabolic factors.

METHODS

Of 5532 reproductive-aged participants of the Tehran lipid and glucose study, 3160 women who met our inclusion criteria were subdivided according to the duration of OCPs consumption into four sub-groups: (1) Non-users; (2) <11 month users; (3) 12-35 month users, and (4) ≥36 month users, and their cardiometabolic parameters were compared.

RESULTS

No statistical significant differences were observed between the cardiometabolic parameters of these sub-groups, after further adjustment for confounding factors including age, parity, and education, except for mean low-density lipoprotein-cholesterol which was significantly higher in women who used OCPs for >36 months in comparison to non-OCP users. The odds ratio of hypercholesterolemia was significantly higher in women who used OCPs for >36 months in comparison to non-OCP users; being 1.5 times higher than non-users (95 % CI 1.01-2.2).

CONCLUSION

Results showed that if used for less than 3 years, OCPs have no cardiometabolic effects.

Culturally tailored diabetes prevention in the workplace: focus group interviews with Hispanic employees

PURPOSE

The purpose was to conduct focus groups with Hispanic employees to obtain input into adaptation of previous DSME interventions for use as a workplace diabetes prevention program.

METHODS

From a list of interested Hispanic employees who attended a local health fair (n = 68), 36 were randomly selected to participate in focus groups held during supper mealtime breaks. An experienced bilingual moderator directed the sessions, using interview guidelines developed by the research team.

RESULTS

Participants' ages ranged from 22 to 65 years (mean = 50.4, n = 36, SD = 10.7), 7 males and 29 females attended, and 53% had type 2 diabetes mellitus (T2DM). Employees expressed a keen interest in diabetes classes and recommended a focus on preparing healthier Hispanic foods. Primary barriers to promoting healthier lifestyles were work schedules; many employees worked 2 part-time or full-time jobs. Administrators and direct supervisors of the employees were highly supportive of a workplace diabetes prevention program.

CONCLUSIONS

The consistent message was that a workplace program would be the ideal solution for Hispanic employees to learn about diabetes and healthy behaviors, given their busy schedules, family responsibilities, and limited resources. If found to be effective, such a workplace program would be generalizable to other service employees who have disproportionate diabetes rates.

Modeling metabolic syndrome through structural equations of metabolic traits, comorbid diseases, and GWAS variants

OBJECTIVE

To provide a quantitative map of relationships between metabolic traits, genome-wide association studies (GWAS) variants, metabolic syndrome (MetS), and metabolic diseases through factor analysis and structural equation modeling (SEM).

DESIGN AND METHODS

Cross-sectional data were collected on 1,300 individuals from an eastern Adriatic Croatian island, including 14 anthropometric and biochemical traits, and diagnoses of type 2 diabetes, coronary heart disease, gout, kidney disease, and stroke. MetS was defined based on Adult Treatment Panel III criteria. Forty widely replicated GWAS variants were genotyped. Correlated quantitative traits were reduced through factor analysis; relationships between factors, genetic variants, MetS, and metabolic diseases were determined through SEM.

RESULTS

MetS was associated with obesity (P < 0.0001), dyslipidemia (P < 0.0001), glycated hemoglobin (HbA1c; P = 0.0013), hypertension (P < 0.0001), and hyperuricemia (P < 0.0001). Of metabolic diseases, MetS was associated with gout (P = 0.024), coronary heart disease was associated with HbA1c (P < 0.0001), and type 2 diabetes was associated with HbA1c (P < 0.0001) and obesity (P = 0.008). Eleven GWAS variants predicted metabolic variables, MetS, and metabolic diseases. Notably, rs7100623 in HHEX/IDE was associated with HbA1c (β = 0.03; P < 0.0001) and type 2 diabetes (β = 0.326; P = 0.0002), underscoring substantial impact on glucose control.

CONCLUSIONS

Although MetS was associated with obesity, dyslipidemia, glucose control, hypertension, and hyperuricemia, limited ability of MetS to indicate metabolic disease risk is suggested.

Metabolic syndrome as an underlying disease entity and its relationship to subclinical atherosclerosis in Andean Hispanics

BACKGROUND

The question of whether the metabolic syndrome truly reflects a single disease entity with a common underlying pathology remains unclear. In this study, we assess whether metabolic syndrome represents an underlying disease construct in a large population-based sample of Andean Hispanic adults and examine its relationship to subclinical atherosclerosis.

METHODS

The study sample was comprised of 2513 participants. Confirmatory factor analysis (CFA) was used to identify a metabolic syndrome latent factor using waist circumference, systolic and diastolic blood pressure, high-density lipoprotein cholesterol (HDL-C), triglycerides (TGs), and glucose levels as indicators. The relationship with subclinical atherosclerosis, measured by carotid intima media thickness (cIMT), was assessed using structural equation modeling.

RESULTS

Results supported the proposed structure of the metabolic syndrome latent factor evidenced by adequate fit indexes. HDL-C did not significantly load on the metabolic syndrome latent factor (standardized factor loading=0.01, P=0.88). The metabolic syndrome latent factor was significantly associated with cIMT in women (B=0.007, P<0.001) and men (B=0.008, P<0.001) after controlling for age, low-density lipoprotein cholesterol and smoking.

CONCLUSIONS

Our findings suggest that metabolic syndrome components, such as waist circumference, blood pressure, TGs, and glucose levels, but not HDL-C, share a common underlying pathophysiology that may contribute to the progression of atherosclerosis in Andean Hispanics. Its longitudinal association with cardiovascular disease should be the focus of future research.

Inflammatory stress exacerbates the progression of cardiac fibrosis in high-fat-fed apolipoprotein E knockout mice via endothelial-mesenchymal transition

Background Chronic inflammation plays a crucial role in the progression of cardiac fibrosis. This study investigated whether inflammation exacerbated the progression of cardiac fibrosis in high-fat-fed apolipoprotein E knockout (ApoE KO) mice via endothelial-mesenchymal transition (EndMT). Methods Twenty-four male ApoE KO mice were divided into normal chow diet (Control), high-fat diet (HFD), or high-fat diet plus 10% casein injection (inflamed) groups for 8 weeks. The body weight of ApoE KO mice was measured at each week. The lipid profile and serum amyloid A (SAA) levels were examined using clinical biochemistry and enzyme-linked immunosorbent assays, respectively. Cardiac lipid and collagen accumulation was visualised with haematoxylin-eosin (HE) and Masson's trichrome staining. EndMT-related molecule expression was examined by immunohistochemistry and Western blotting. Results SAA levels were increased in the inflamed group compared with the HFD and control groups, suggesting that inflammation was successfully induced. There were no differences in body weight among three groups at each week. Interestingly, inflammation significantly reduced serum total cholesterol, triglyceride, and low-density lipoprotein (LDL) levels compared with the HFD mice. However, both foam cell formation in cardiac blood vessels and cardiac collagen deposition were increased in the inflamed group, as demonstrated by HE and Masson trichrome staining. Furthermore, inflammation reduced protein expression of CD31 and increased protein expression of alpha-smooth muscle actin (α-SMA) and collagen I, which contribute to cardiac EndMT. Conclusions Inflammatory stress exacerbates the progression of cardiac fibrosis in high-fat-fed ApoE KO mice via EndMT, suggesting that hyperlipidaemia and inflammation act synergistically to redistribute plasma lipids to cardiac tissues and accelerate the progression of cardiac fibrosis.

Diet-induced swine model with obesity/leptin resistance for the study of metabolic syndrome and type 2 diabetes

The objective of the present study was to determine the suitability of a swine breed with leptin resistance and predisposition to obesity (the Iberian pig) as model for studies on metabolic syndrome and type 2 diabetes. Thus, six Iberian sows had ad libitum access to food enriched with saturated fat (SFAD group; food consumption was estimated to be 4.5 kg/animal/day) whilst four females acted as controls and were fed with 2 kg/animal/day of a commercial maintenance diet. After three months of differential feeding, SFAD animals developed central obesity, dyslipidemia, insulin resistance and impaired glucose tolerance, and elevated blood pressure; the five parameters associated with the metabolic syndrome. Thus, the current study characterizes the Iberian pig as a robust, amenable, and reliable translational model for studies on nutrition-associated diseases.

Short-term sprint interval training increases insulin sensitivity in healthy adults but does not affect the thermogenic response to beta-adrenergic stimulation

Sprint interval training (SIT) and traditional endurance training elicit similar physiological adaptations. From the perspective of metabolic function, superior glucose regulation is a common characteristic of endurance-trained adults. Accordingly, we have investigated the hypothesis that short-term SIT will increase insulin sensitivity in sedentary/recreationally active humans. Thirty one healthy adults were randomly assigned to one of three conditions: (1) SIT (n = 12): six sessions of repeated (4-7) 30 s bouts of very high-intensity cycle ergometer exercise over 14 days; (2) sedentary control (n = 10); (3) single-bout SIT (n = 9): one session of 4 x 30 s cycle ergometer sprints. Insulin sensitivity was determined (hyperinsulinaemic euglycaemic clamp) prior to and 72 h following each intervention. Compared with baseline, and sedentary and single-bout controls, SIT increased insulin sensitivity (glucose infusion rate: 6.3 +/- 0.6 vs. 8.0 +/- 0.8 mg kg(1) min(1); mean +/- s.e.m.; P = 0.04). In a separate study, we investigated the effect of SIT on the thermogenic response to beta-adrenergic receptor (beta-AR) stimulation, an important determinant of energy balance. Compared with baseline, and sedentary and single-bout control groups, SIT did not affect resting energy expenditure (EE: ventilated hood technique; 6274 +/- 226 vs. 6079 +/- 297 kJ day(1); P = 0.51) or the thermogenic response to isoproterenol (6, 12 and 24 ng (kg fat-free mass)(1) min(1): %EE 11 +/- 2, 14 +/- 3, 23 +/- 2 vs. 11 +/- 1, 16 +/- 2, 25 +/- 3; P = 0.79). Combined data from both studies revealed no effect of SIT on fasted circulating concentrations of glucose, insulin, adiponectin, pigment epithelial-derived factor, non-esterified fatty acids or noradrenaline (all P > 0.05). Sixteen minutes of high-intensity exercise over 14 days augments insulin sensitivity but does not affect the thermogenic response to beta-AR stimulation.

Short-term sprint interval training increases insulin sensitivity in healthy adults but does not affect the thermogenic response to beta-adrenergic stimulation

Sprint interval training (SIT) and traditional endurance training elicit similar physiological adaptations. From the perspective of metabolic function, superior glucose regulation is a common characteristic of endurance-trained adults. Accordingly, we have investigated the hypothesis that short-term SIT will increase insulin sensitivity in sedentary/recreationally active humans. Thirty one healthy adults were randomly assigned to one of three conditions: (1) SIT (n = 12): six sessions of repeated (4-7) 30 s bouts of very high-intensity cycle ergometer exercise over 14 days; (2) sedentary control (n = 10); (3) single-bout SIT (n = 9): one session of 4 x 30 s cycle ergometer sprints. Insulin sensitivity was determined (hyperinsulinaemic euglycaemic clamp) prior to and 72 h following each intervention. Compared with baseline, and sedentary and single-bout controls, SIT increased insulin sensitivity (glucose infusion rate: 6.3 +/- 0.6 vs. 8.0 +/- 0.8 mg kg(1) min(1); mean +/- s.e.m.; P = 0.04). In a separate study, we investigated the effect of SIT on the thermogenic response to beta-adrenergic receptor (beta-AR) stimulation, an important determinant of energy balance. Compared with baseline, and sedentary and single-bout control groups, SIT did not affect resting energy expenditure (EE: ventilated hood technique; 6274 +/- 226 vs. 6079 +/- 297 kJ day(1); P = 0.51) or the thermogenic response to isoproterenol (6, 12 and 24 ng (kg fat-free mass)(1) min(1): %EE 11 +/- 2, 14 +/- 3, 23 +/- 2 vs. 11 +/- 1, 16 +/- 2, 25 +/- 3; P = 0.79). Combined data from both studies revealed no effect of SIT on fasted circulating concentrations of glucose, insulin, adiponectin, pigment epithelial-derived factor, non-esterified fatty acids or noradrenaline (all P > 0.05). Sixteen minutes of high-intensity exercise over 14 days augments insulin sensitivity but does not affect the thermogenic response to beta-AR stimulation.

Chronic fatigue syndrome: illness severity, sedentary lifestyle, blood volume and evidence of diminished cardiac function

The study examined whether deficits in cardiac output and blood volume in a CFS (chronic fatigue syndrome) cohort were present and linked to illness severity and sedentary lifestyle. Follow-up analyses assessed whether differences in cardiac output levels between CFS and control groups were corrected by controlling for cardiac contractility and TBV (total blood volume). The 146 participants were subdivided into two CFS groups based on symptom severity data, severe (n=30) and non-severe (n=26), and two healthy non-CFS control groups based on physical activity, sedentary (n=58) and non-sedentary (n=32). Controls were matched to CFS participants using age, gender, ethnicity and body mass. Echocardiographic measures indicated that the severe CFS participants had 10.2% lower cardiac volume (i.e. stroke index and end-diastolic volume) and 25.1% lower contractility (velocity of circumferential shortening corrected by heart rate) than the control groups. Dual tag blood volume assessments indicated that the CFS groups had lower TBV, PV (plasma volume) and RBCV (red blood cell volume) than control groups. Of the CFS subjects with a TBV deficit (i.e. > or = 8% below ideal levels), the mean+/-S.D. percentage deficit in TBV, PV and RBCV were -15.4+/-4.0, -13.2+/-5.0 and -19.1+/-6.3% respectively. Lower cardiac volume levels in CFS were substantially corrected by controlling for prevailing TBV deficits, but were not affected by controlling for cardiac contractility levels. Analyses indicated that the TBV deficit explained 91-94% of the group differences in cardiac volume indices. Group differences in cardiac structure were offsetting and, hence, no differences emerged for left ventricular mass index. Therefore the findings indicate that lower cardiac volume levels, displayed primarily by subjects with severe CFS, were not linked to diminished cardiac contractility levels, but were probably a consequence of a co-morbid hypovolaemic condition. Further study is needed to address the extent to which the cardiac and blood volume alterations in CFS have physiological and clinical significance.