Lymphocyte protein synthesis is increased with the progression of HIV-associated disease to AIDS.

HIV infection has been shown to affect lymphocyte function and to reduce lymphocyte responsiveness in vitro to mitogenic stimulation, but little is known about lymphocyte metabolism in vivo and how it is affected during the course of the disease. This study investigated the metabolic activity of lymphocytes in vivo through the progression of HIV-associated disease. Lymphocyte protein synthesis was measured with L-[(2)H(5)]phenylalanine (45 mg/kg body weight) in healthy volunteers (n=7), in patients who were HIV-positive (n=7) but asymptomatic, and in patients with AIDS (n=8). The rates of lymphocyte protein synthesis [expressed as a percentage of lymphocyte protein, i.e. fractional synthesis rate (FSR)] were not altered in HIV-positive patients compared with healthy controls (7.9+/-1.28% and 9.1+/-0.53%/day respectively), but were significantly elevated in AIDS patients (14.0+/-1.16%/day; P<0.05). The serum concentration of the cytokine tumour necrosis factor-alpha (TNF-alpha) increased with the progression of the disease, and TNF-alpha levels were significantly higher in AIDS patients (6.81+/-0.88 ng/l) than in healthy controls (3.09+/-0.27 ng/l; P<0.05). Lymphocyte protein FSR was positively correlated with serum TNF-alpha concentration (r=0.55, P=0.009) and negatively correlated with CD4(+) lymphocyte count (r=-0.70, P=0.004). The elevation of lymphocyte protein synthesis in AIDS patients suggests a higher rate of turnover of lymphocytes. This may be associated with a generalized activation of the immune system, which is also reflected by the elevated serum TNF-alpha concentration in the late stages of HIV-associated disease.

Increased concentration of tracee affects estimates of muscle protein synthesis.

Muscle protein synthesis was measured by infusion of L-[2H(5)]phenylalanine in two groups of anesthetized dogs, before and during infusion of insulin with euaminoacidemia, and with differing concentrations of unlabeled phenylalanine (tracee). With the infusion of insulin, muscle protein synthesis increased 39 +/- 12% based on phenylalanyl-tRNA. Calculation with plasma phenylalanine enrichment overestimated insulin stimulation by 40% (56 +/- 12 vs. 39 +/- 12%). Raising the concentration of plasma phenylalanine twofold during infusion of insulin further increased the apparent stimulation of muscle protein synthesis based on plasma relative to phenylalanyl-tRNA by 225% (65 +/- 19 vs. 20 +/- 14%, P < 0.001). In both experiments, the stimulation of synthesis rates calculated from phenylalanine enrichment within the muscle was closer to that from phenylalanyl-tRNA (48 +/- 19%, experiment 1; 30 +/- 14%, experiment 2). Results indicate that the enrichment of a labeled amino acid within plasma and tissue amino acid pools is affected by the concentration of tracee infused. Increasing the concentration of tracee overestimates the insulin-mediated stimulation of muscle protein synthesis when amino acid pools other than aminoacyl-tRNA are used as the precursor enrichment.

The prediction of basal metabolic rate in female patients with anorexia nervosa.

OBJECTIVE: To evaluate in female patients with anorexia nervosa the accuracy of a specific predictive formula for basal metabolic rate (BMR) already proposed in the literature and to derive a new disease-specific equation with the same purpose. DESIGN: Cross-sectional study. SUBJECTS: One-hundred and twenty adolescent girls (<18 y) and young-adult women (18-30 y) with anorexia nervosa. MEASUREMENTS: BMR was determined by indirect calorimetry or predicted according to the Schebendach formula, which was specifically derived for anorexia nervosa. RESULTS: On average the Schebendach formula performed well in the adolescent group but not in the young-adult group. The range including 95% of the predicted-measured differences was in both cases wider than 2000 kJ/day. In the young-adult patients the accuracy of the prediction was also related to age and body mass index. Weight and age (but not height or body mass index) emerged as predictors of BMR in the sample as a whole, and only weight when the two age groups were considered separately, thus leading to three different equations. The intercepts of these regression lines were very close and not significantly different from zero while their standard error of estimate was 500-550 kJ/day. CONCLUSION: The Schebendach formula is not very accurate in estimating the BMR of female anorectic patients. Moreover, in this group the relationship between BMR and weight was altered. The predictive formulas proposed by the present study have a reasonable prediction power.

Albumin synthesis is diminished in men consuming a predominantly vegetarian diet.

Albumin synthesis was calculated in healthy male volunteers consuming diets differing in the relative contribution of protein from animal or vegetable sources. In one study (Study 1, n = 4) two isoenergetic and isonitrogenous diets were consumed for a period of 10 d each. One diet (diet A) was animal protein rich (74%), the other one (diet V) contained 67% of vegetable protein. Albumin synthesis rate was measured from L-[(2)H(5)]phenylalanine incorporation (43 mg/kg) at the end of each dietary period. Both albumin fractional synthesis rate (FSR) (5.7 +/- 0.6 vs. 6.7 +/- 0. 8%/d, P = 0.04) and absolute synthesis rate (ASR) (123 +/- 6 vs. 143 +/- 8 mg. kg(-1). d(-1), P = 0.05) were reduced after diet V. In a second study (Study 2, n = 8) a third dietary treatment was added (Diet VS). This was similar to diet V but supplemented with soy protein (18g/d). The results of study 2 confirmed that albumin synthesis was reduced after diet V (FSR: 5.9 +/- 0.3 vs. 6.7 +/- 0. 5%/d, P = 0.015; ASR: 126 +/- 7 vs. 146 +/- 9 mg. kg(-1). d(-1), P = 0.007), but it also showed that the drop could be prevented by adding supplemental protein to the predominantly vegetarian diet (Diet VS) (FSR: 6.4 +/- 0.3%/d, P = 0.08; ASR: 140 +/- 7 mg. kg(-1). d(-1), P = 0.03). Albumin synthesis appears to be modulated by changes in the proportion of animal vs. vegetable protein occurring in the diet. The mechanism might be related to differences in digestibility and consequently in net amino acid availability between diets.

Determination of protein synthesis in lymphocytes in vivo after surgery.

1. The stimulation and depression of peripheral blood lymphocytes has previously been studied in vitro, showing an immune depression postoperatively; however, it is difficult to interpret these in vitro findings. Therefore, an in vivo technique has been established for determination of the fractional protein synthesis rate, as an index of metabolic activity in human peripheral blood lymphocytes, by using a stable isotope technique. 2. The rate of protein synthesis was calculated from the increase in enrichment of L-[2H5]phenylalanine in protein of a mixed population of mononuclear leucocytes, isolated by density gradient, after an intravenous flooding dose of L-[2H5]phenylalanine. A linear time course of isotopic incorporation into the cells was demonstrated. 3. The fractional rate of protein synthesis of a mixed population of mononuclear leucocytes was studied in relation to surgical interventions and to potential modifiers of the response. The fractional synthesis rate increased 24 h after open and laparoscopic cholecystectomy (49 +/- 19% and 40 +/- 14% respectively, P < 0.02), irrespective of postoperative total parenteral nutrition or preoperative glucose infusion. In contrast to surgery, insulin did not stimulate protein synthesis in peripheral mononuclear leucocytes.

Familial and environmental influences on body composition and body fat distribution in childhood in southern Italy.

The aim of this paper was to evaluate the factors affecting body fat excess and distribution in prepubertal age. A cross-sectional survey was carried out on children attending the 4th grade of a primary school in Naples. Eighty-eight per cent of the total sample was examined: 52 girls, 58 boys; mean age = 9.6 yrs (s.e. +/- 0.10). Each child underwent a medical examination, anthropometric measurements and bio-impedance analysis of body composition. The parents were asked to fill in a questionnaire that included demographic data, family history, parent's weight and height, child's perinatal history and his or her involvement in sports activities. Data were analyzed by multiple linear regression. The results showed a direct correlation between parental BMI and children's anthropometric measurements: the children's BMI correlated with the fathers' (P = 0.02) and mothers' BMI (P = 0.027); the children's waist/hip ratio correlated with the fathers' BMI (P = 0.07); the children's subscapular skinfolds correlated with the father's (P = 0.07) and mothers' BMI (P = 0.02); the children's triceps skinfolds correlated with the fathers' BMI (P = 0.004). Among congenital factors, sex was shown to be correlated with the children's waist/hip ratio (P = 0.05) with a lower ratio in the female, indicating a sex influence on body fat distribution even in prepubertal age. The children's BMI correlated with their waist/hip ratio (P = 0.001). Children's systolic blood pressure showed a positive correlation with triceps (P = 0.04) and subscapular (P = 0.05) skinfolds thickness % FAT-PLI (P = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

[Basal metabolism and postprandial thermogenesis in anorexia nervosa and constitutional leanness]. / Metabolismo basale e termogenesi postprandiale nell'anoressia nervosa e nella magrezza costituzionale.

Body composition and energy expenditure (basal metabolic rate--BMR--and postprandial thermogenesis--PPT) were evaluated in 11 anorectic patients, 16 very lean young women and 26 control female subjects. BMR in absolute terms was severely depressed in the anorectics when compared to the other two groups (p less than 0.01). After adjustment for fat free mass BMR was significantly higher in the lean subjects than the controls (p less than 0.05). PTT was studied for 240 minutes after the ingestion of a 3.56 MJ mixed meal (16% Prot, 50% CHO and 34% Fat) in 7 anorectics, 7 lean and 8 control women. PPT was similar in the anorectics and in the controls, but lower in the lean subjects (p less than 0.05) than in the other two groups. This study shows that a sharp decline in BMR occurs in severely undernourished anorectic patients who, however, have a normal PPT. On the other hand, very lean healthy women tend to have higher BMR but a decreased thermic response to a mixed test meal.