Richard N. Pierson

Hypertriglyceridemia in the Acquired Immunodeficiency Syndrome

PURPOSE A relationship between the induction of hypertriglyceridemia by cytokines and the cachexia seen in chronic infection has been proposed by other investigators. Since patients with the acquired immunodeficiency syndrome (AIDS) often experience progressive tissue wasting, we decided to examine serum lipid levels and body cell mass in patients with AIDS. PATIENTS AND METHODS Serum lipid levels and body cell mass were measured in 32 patients with the acquired immunodeficiency syndrome (AIDS), eight asymptomatic subjects who were anti-human immunodeficiency virus (HIV) antibody positive, and 17 heterosexual and homosexual control subjects who did not have antibodies to HIV. RESULTS Mean triglyceride concentrations and the prevalence of hypertriglyceridemia (50 percent) were significantly increased in patients with AIDS compared with control subjects (p less than 0.002 and p less than 0.005, respectively), whereas the mean triglyceride levels of HIV-positive subjects were intermediate. There were no differences in cholesterol levels among the three groups. Using total body potassium adjusted for height and age (KHT) as a measure of body cell mass, 16 of 32 patients with AIDS but none of the HIV-positive or control subjects had significant depletion of body cell mass. There was no direct relationship between triglyceride levels and KHT among AIDS or HIV-positive subjects. In patients with AIDS, mean triglyceride levels and the prevalence of hypertriglyceridemia were similar in the presence and absence of wasting. CONCLUSION Hypertriglyceridemia is a common finding in AIDS and is independent of the degree of wasting.

Prediction of body cell mass, fat-free mass, and total body water with bioelectrical impedance analysis: effects of race, sex, and disease.

The inability to precisely estimate body composition with simple, inexpensive, and easily applied techniques is an impediment to clinical investigations in nutrition. In this study, predictive equations for body cell mass (BCM), fat-free mass (FFM), and total body water (TBW) were derived from direct measurements through use of single-frequency bioelectrical impedance analysis (BIA) in 332 subjects, including white, black, and Hispanic men and women, who were both healthy control subjects and patients infected with the human immunodeficiency virus (HIV). Preliminary studies showed more accurate predictions of BCM when parallel-transformed values of reactance were used rather than the values reported by the bioelectrical impedance analyzer. Modeling equations derived after logarithmic transformation of height, reactance, and impedance were more accurate predictors than equations using height2/resistance, and the use of sex-specific equations further improved accuracy. The effect of adding weight to the modeling equation was less important than the BIA measurements. The resulting equations were validated internally, and race and disease (HIV infection) were shown not to affect the predictions. The equation for FFM was validated externally against results derived from hydrodensitometry in 440 healthy individuals; the SEE was < 5%. These results indicate that body composition can be estimated with simple and easily applied techniques, and that the estimates are sufficiently precise for use in clinical investigation and practice.

Relation of BMI to fat and fat-free mass among children and adolescents

OBJECTIVE:Although the body mass index (BMI, kg/m2) is widely used as a surrogate measure of adiposity, it is a measure of excess weight, rather than excess body fat, relative to height. We examined the relation of BMI to levels of fat mass and fat-free mass among healthy 5- to 18-y-olds.METHODS AND PROCEDURES:Dual-energy X-ray absorptiometry was used to measure fat and fat-free mass among 1196 subjects. These measures were standardized for height by calculating the fat mass index (FMI, fat mass/ht2) and the fat-free mass index (FFMI, fat-free mass/ht2).RESULTS:The variability in FFMI was about 50% of that in FMI, and the accuracy of BMI as a measure of adiposity varied greatly according to the degree of fatness. Among children with a BMI-for-age ≥85th P, BMI levels were strongly associated with FMI (r=0.85–0.96 across sex–age categories). In contrast, among children with a BMI-for-age <50th P, levels of BMI were more strongly associated with FFMI (r=0.56–0.83) than with FMI (r=0.22–0.65). The relation of BMI to fat mass was markedly nonlinear, and substantial differences in fat mass were seen only at BMI levels ≥85th P.DISCUSSION:BMI levels among children should be interpreted with caution. Although a high BMI-for-age is a good indicator of excess fat mass, BMI differences among thinner children can be largely due to fat-free mass.

Studies of body composition and fat distribution in HIV-infected and control subjects.

OBJECTIVE Recent studies have documented alterations in body fat distribution that have been associated with protease inhibitor therapy. We compared body composition, including measurements of fat distribution, in 96 HIV-infected subjects studied since January 1996 (current HIV), subjects seen prior to January 1996 (previous HIV), and healthy controls. DESIGN Retrospective cross-sectional studies of subjects matched by gender, race, age, and height. METHODS Body weight, height, body cell mass by whole-body counting of 40K plus fat, fat-free mass, and body fat distribution by anthropometry were measured. RESULTS Current HIV men weighed more (p = .025) and had more body cell mass than previous HIV men, but less than controls (p < .001). In women, the between group differences in fat were greater than the differences in body cell mass. Current and previous HIV study subjects had lower indices of subcutaneous and higher indices of visceral fat than controls. In current HIV subjects, body fat distribution was significantly associated with log plasma HIV RNA content but not with antiretroviral or protease inhibitor usage, nor with CD4+ lymphocyte counts. In 7 of 9 current HIV subjects studied, 24-hour urinary free cortisol excretion was abnormally high. CONCLUSIONS Alterations in body fat distribution are a characteristic feature in HIV infection. The occurrence of increased visceral fat content and decreased subcutaneous fat content preceded the era of combination antiretroviral therapy. The alteration in fat distribution may be affected by plasma HIV RNA content rather than antiretroviral or protease-inhibitor therapy. The body composition alterations might be associated with endogenous hypercortisolism.

Effect of Home Total Parenteral Nutrition on Body Composition in Patients with Acquired Immunodeficiency Syndrome

Malnutrition occurs commonly in patients with acquired immunodeficiency syndrome (AIDS). The efficacy of nutritional support is unknown. A prospective, longitudinal study was conducted to determine the effect of prolonged total parenteral nutrition on body composition in 12 AIDS patients. Five patients were malnourished because of problems with food intake or absorption, while seven had systemic infections, with or without a malabsorption syndrome. The AIDS patients gained body weight and body fat content in response to total parenteral nutrition, while mean body cell mass, estimated as total body potassium content, was unchanged. However, all five patients with altered intake or absorption had significant repletion of body cell mass which was significantly different from the patients with systemic infections. Calorie and nitrogen intake did not differ between the two groups. It is concluded that body mass repletion is possible in AIDS patients in whom malabsorption is the major pathogenetic factor in producing malnutrition and is less successful in patients with serious ongoing systemic diseases. Thus, the response to nutritional support is dependent on the particular clinical circumstances.

Anthropometry in Body Composition: An Overview

Abstract: Anthropometry is a simple reliable method for quantifying body size and proportions by measuring body length, width, circumference (C), and skinfold thickness (SF). More than 19 sites for SF, 17 for C, 11 for width, and 9 for length have been included in equations to predict body fat percent with a standard error of estimate (SEE) range of ±3% to ±11% of the mean of the criterion measurement. Recent studies indicate that not only total body fat, but also regional fat and skeletal muscle, can be predicted from anthropometrics. Our Rosetta database supports the thesis that sex, age, ethnicity, and site influence anthropometric predictions; the prediction reliabilities are consistently higher for Whites than for other ethnic groups, and also by axial than by peripheral sites (biceps and calf). The reliability of anthropometrics depends on standardizing the caliper and site of measurement, and upon the measuring skill of the anthropometrist. A reproducibility of ± 2% for C and ± 10% for SF measurements usually is required to certify the anthropometrist.

Resting metabolic rate and energy balance in amenorrheic and eumenorrheic runners

This study investigated metabolic and nutritional factors in association with athletic menstrual dysfunction (AMD). Three groups of women were studied: amenorrheic runners (amenorrheic), eumenorrheic runners (eumenorrheic), and eumenorrheic sedentary controls (sedentary). Amenorrheic and eumenorrheic were similar in age, weight, percent body fat by hydrodensitometry, training pace and mileage, best 10 km race time, years running, and maximal oxygen consumption. When adjusted for body weight or for fat-free mass by analysis of covariance, RMR was significantly lower in amenorrheic than in eumenorrheic and sedentary. The daily caloric intakes of the groups did not differ significantly, but the amenorrheic scored significantly higher than the eumenorrheic and sedentary on a scale of aberrant eating patterns. Amenorrheic high mileage runners seem to have a less adequate diet than eumenorrheic runners but appear to maintain energy balance and stable weight through a reduction in RMR.

Hemodynamic Exercise Testing A Valuable Tool in the Selection of Cardiac Transplantation Candidates

BACKGROUND Peak exercise oxygen consumption (Vo2), a noninvasive index of peak exercise cardiac output (CO), is widely used to select candidates for heart transplantation. However, peak exercise Vo2 can be influenced by noncardiac factors such as deconditioning, motivation, or body composition and may yield misleading prognostic information. Direct measurement of the CO response to exercise may avoid this problem and more accurately predict prognosis. METHODS AND RESULTS Hemodynamic and ventilatory responses to maximal treadmill exercise were measured in 185 ambulatory patients with chronic heart failure who had been referred for cardiac transplantation (mean left ventricular ejection fraction, 22 +/- 7%; mean peak Vo2, 12.9 +/- 3.0 mL. min-1.kg-1). CO response to exercise was normal in 83 patients and reduced in 102. By univariate analysis, patients with normal CO responses had a better 1-year survival rate (95%) than did those with reduced CO responses (72%) (P < .0001). Survival in patients with peak Vo2 of > 14 mL.min-1.kg-1 (88%) was not different from that of patients with peak Vo2 of < or = 14 mL.min-1.kg-1 (79%) (P = NS). However, survival was worse in patients with peak Vo2 of < or = 10 mL.min-1.kg-1 (52%) versus those with peak Vo2 of > 10 mL.min-1.kg-1 (89%) (P < .0001). By Cox regression analysis, exercise CO response was the strongest independent predictor of survival (risk ratio, 4.3), with peak Vo2 dichotomized at 10 mL. min-1.kg-1 (risk ratio, 3.3) as the only other independent predictor. Patients with reduced CO responses and peak Vo2 of < or = 10 mL.min-1.kg-1 had an extremely poor 1-year survival rate (38%). CONCLUSIONS Both CO response to exercise and peak exercise Vo2 provide valuable independent prognostic information in ambulatory patients with heart failure. These variables should be used in combination to select potential heart transplantation candidates.

Six-compartment body composition model: inter-method comparisons of total body fat measurement.

OBJECTIVE: To compare 16 currently used total body fat methods to a six-compartment criterion model based on in vivo neutron activation analysis.DESIGN: Observational, inter-method comparison study.SUBJECTS: Twenty-three healthy subjects (17 male and 6 female).MEASUREMENTS: Total body water (TBW) was measured by tritium dilution; body volume by underwater weighing (UWW); total body fat and bone mineral by dual-energy X-ray absorptiometry (DXA), total body potassium (TBK) by whole-body 40K counting; total body carbon, nitrogen, calcium, phosphorus, sodium and chlorine by in vivo neutron activation analysis; skinfolds/circumferences by anthropometry (Anth); and resistance by single-frequency bioimpedance analysis (BIA).RESULTS: The average of total body fat mass measurements by the six-compartment neutron activation model was 19.7±10.2 kg (mean±s.d.) and comparable estimates by other methods ranged from 17.4–24.3 kg. Although all 16 methods were highly correlated with the six-compartment criterion model, three groups emerged based on their comparative characteristics (technical error, coefficient of reliability, Bland-Altman analysis) relative to criterion fat estimates, in decreasing order of agreement: 1. multi-compartment model methods of Baumgartner (19.5±9.9 kg), Heymsfield (19.6±9.9 kg), Selinger (19.7±10.2 kg) and Siri-3C (19.6±9.9 kg); 2. DXA (20.0±10.8 kg), Pace-TBW (18.8±10.1 kg), Siri-2C (20.0±9.9 kg), and Brozek-UWW (19.4±9.2 kg) methods; and 3. Segal-BIA (17.4±7.2 kg), Forbes-TBN (21.8±10.5 kg), Durnin-Anth (22.1±9.5 kg), Forbes-TBK (22.9±11.9 kg), and Steinkamp-Anth (24.3±9.5 kg) methods.CONCLUSION: Relative to criterion fat estimates, body composition methods can be organized into three groups based on inter-method comparisons including technical error, coefficient of reliability and Bland-Altman analysis. These initial groupings may prove useful in establishing the clinical and research role of the many available fat estimation methods.

Continuous Loss of Bone During Chronic Immobilization: A Monozygotic Twin Study

Abstract: Acute immobilization is associated with rapid loss of bone. Prevailing opinion, based on population cross-sectional data, assumes that bone mass stabilizes thereafter. In order to address whole-body and regional skeletal mass in long-term immobilization, monozygotic twins were studied, one of each twin pair having chronic spinal cord injury (SCI) of a duration ranging from 3 to 26 years. The research design consisted of the co-twin control method using 8 pairs of identical male twins (mean ± SD age, 40 ± 10 years; range 25–58 years), one of each set with SCI. The twins were compared by paired t-tests for total and regional bone mineral content (BMC) and bone mineral density (BMD) measured by dual-energy X-ray absorptiometry. Linear regression analyses were performed to determine the associations of age or duration of injury with the differences between twin pairs for total and regional skeletal bone values. In the SCI twins, total-body BMC was significantly reduced (22%± 9%, p<0.001), with the predominant sites of reduction for BMC and BMD being the legs (42%± 14% 35%± 10%, p<0.0001), and pelvis (50%± 10% and 29%± 9%, p<0.0001). Duration of SCI, not age, was found to be linearly related to the degree of leg bone loss in SCI twins (BMC: r2= 0.60, p<0.05; BMD: r2= 0.70, p<0.01). Our findings suggest that pelvic and leg bone mass continues to decline throughout the chronic phase of immobilization in the individual with SCI, and this bone loss appears to be independent of age.