Can androgen therapy replete lean body mass and improve muscle function in wasting associated with human immunodeficiency virus infection?

A significant number of men who are infected with the human immunodeficiency virus (HIV) have low testosterone levels. Androgen deficiency in HIV-infected patients is associated with decreased muscle mass and function, and adverse disease outcome. Administration of replacement doses of testosterone to healthy hypogonadal men augments lean body mass, muscle size, and maximal voluntary strength. Recent studies have shown that physiologic testosterone replacement in HIV-infected men with weight loss who have low testosterone levels can also increase muscle mass and effort-dependent strength. However, further studies are needed to determine whether androgen therapy can improve physical function and health-related outcomes in HIV-infected men.

Insulin-like growth factor system in patients with HIV infection: effect of exogenous growth hormone administration

The purpose of this study was to characterize changes in the levels of insulin-like growth factor-I (IGF-I) and IGF binding proteins (BP) 1, 2, and 3 in HIV-infected adults throughout the course of their disease, and to assess the responsiveness of the IGF system components to growth hormone (GH) administration (6 mg/day) for 2 weeks. Healthy control study subjects (n = 10) were compared with patients who were either HIV-positive (n = 9), had AIDS without weight loss (n = 13), or had AIDS with >10% weight loss (n = 6), all of whom had been free of acute illness for at least 3 months. Under basal conditions, fasting serum concentrations of epinephrine, norepinephrine, cortisol, glucagon, insulin, IGF-I, and IGFBP-3 were not significantly different among the four groups. The serum concentrations of IGFBP-1 and IGFBP-2 were significantly higher in AIDS patients with wasting than in the other three groups (p < .05). In addition, there was a statistically significant positive correlation between the levels of IGFBP- 1 (p = .004) and IGFBP-2 (p = .03) and the stage of disease. Following GH administration, the serum concentrations of insulin and IGF-I were increased in all groups (p < .05). In addition, the increases in insulin levels correlated with stage of disease (p = .004). The responses of the IGFBPs were more variable. GH administration significantly increased the levels of IGFBP-3 in all groups except the patients with AIDS wasting, whereas the levels of IGFBP-1 were significantly decreased in controls and AIDS patients. These results demonstrate that there is a continuum of both elevations in the IGFBPs and altered metabolic responsiveness in patients infected with HIV that increases with the severity of the disease. These data also demonstrate that AIDS patients, who are free from secondary infection, respond to administration of GH by significantly increasing hepatic IGF-I production.

Sustained anabolic effects of long-term androgen administration in men with AIDS wasting

Fifty-one human immunodeficiency virus-positive men with hypogonadism and wasting were randomized to receive testosterone enanthate, 300 mg i.m. every 3 weeks, or placebo for 6 months, followed by open-label testosterone administration for 6 months. Subjects initially randomized to placebo gained lean body mass (LBM) only after crossover to testosterone administration (mean change +/- standard error of the mean, -0.6 +/- 0.7 kg [months 0-6] vs. 1.9 +/- 0.7 kg [months 6-12]; P = .03). In contrast, subjects initially randomized to testosterone continued to gain LBM during open-label administration (2.0 +/- 0.7 kg [months 0-6] vs. 1.6 +/- 0.6 kg [months 6-12]; P = .62) and had gained more LBM at 1 year than did subjects receiving testosterone for only the final 6 months of the study (3.7 +/- 0.8 kg vs. 1.0 +/- 1.0 kg; P = .05). Testosterone administration results in sustained increases in LBM during 1 year of therapy in hypogonadal men with AIDS wasting.

Wasting in HIV infection and AIDS

AIDS wasting is not characterized by a single pathophysiological process but by a variety of processes that operate at different times. Acute wasting tends to be associated with secondary infections; chronic wasting is associated with gastrointestinal disease. Although resting energy expenditure is increased, total energy expenditure is reduced in individuals who are losing weight and it is usually reduced intake that commonly drives wasting. However, reduced intake is not an adequate explanation for the metabolic abnormalities that are seen in HIV infection. In particular, protein metabolism and lipid metabolism are abnormal, possibly representing inappropriate utilization of substrates. The response to nutrition may be impaired, particularly in terms of accrual of lean tissue but nutritional support may prolong survival. The impact of protease inhibitors on wasting in HIV infection is yet to be fully ascertained but despite antiviral therapy it seems that wasting is likely to remain a problem at least in some patients.

Quantitative assessment of cross-sectional muscle area, functional status, and muscle strength in men with the acquired immunodeficiency syndrome wasting syndrome

The acquired immunodeficiency syndrome wasting syndrome (AWS) in men is characterized by the loss of lean body mass out of proportion to weight. Although the wasting syndrome has been thought to contribute to reduced functional capacity, the relationships among lean body mass, muscle size, functional status, and regional muscle strength have not previously been investigated in this population. In this study, 24 eugonadal men with the AWS (weight <90% of the ideal body weight or weight loss >10% from preillness maximum) underwent determination of body composition by dual energy x-ray absorptiometry (DXA), 40K isotope analysis, urinary creatinine excretion, and quantitative computed tomographic analysis of cross-sectional muscle areas of the midarm and thigh. Overall exercise functional capacity was evaluated using the 6-min walk test, and performance of upper and lower extremities was determined with the quantitative muscle function test. Subjects were 37 +/- 1 yr of age and weighed 95.5 +/- 3.0% of ideal body weight, with a body mass index of 21.9 +/- 0.7 kg/m2 and an average weight loss of 15 +/- 1%. The mean CD4 count among the subjects was 354 +/- 70 cells/mm3, and viral load was 58,561 +/- 32,205 copies. Sixty-two percent of subjects were receiving protease inhibitor therapy. The subjects demonstrated 90% of the expected muscle mass by the creatinine height index method. Overall performance status on the Karnofsky scale was highly correlated to weight (r = 0.51; P = 0.018; by body mass index), lean body mass (r = 0.46; P = 0.036; by DXA), and body cell mass (r = 0.47; P = 0.037; by 40K isotope analysis). Cross-sectional muscle area of the upper extremity was the best predictor (P < 0.001) of Karnofsky score, accounting for 52% of the variability in a stepwise regression analysis. Upper body muscle strength was most significantly predicted by lean body mass (by DXA; r2 = 0.78; P < 0.0001), whereas lower body strength and performance on the 6-min walk test were best predicted by lower extremity cross-sectional muscle area (r2 = 0.70; P < 0.0001 and r2 = 0.26; P = 0.030, respectively). These data demonstrate that cross-sectional muscle area is highly predictive of functional status and muscle strength in men with the AWS.

Organization of the human myostatin gene and expression in healthy men and HIV-infected men with muscle wasting

Myostatin, a member of the transforming growth factor-beta superfamily, is a genetic determinant of skeletal muscle growth. Mice and cattle with inactivating mutations of myostatin have marked muscle hypertrophy. However, it is not known whether myostatin regulates skeletal muscle growth in adult men and whether increased myostatin expression contributes to wasting in chronic illness. We examined the hypothesis that myostatin expression correlates inversely with fat-free mass in humans and that increased expression of the myostatin gene is associated with weight loss in men with AIDS wasting syndrome. We therefore cloned the human myostatin gene and cDNA and examined the gene's expression in the skeletal muscle and serum of healthy and HIV-infected men. The myostatin gene comprises three exons and two introns, maps to chromosomal region 2q33.2, has three putative transcription initiation sites, and is transcribed as a 3.1-kb mRNA species that encodes a 375-aa precursor protein. Myostatin is expressed uniquely in the human skeletal muscle as a 26-kDa mature glycoprotein (myostatin-immunoreactive protein) and secreted into the plasma. Myostatin immunoreactivity is detectable in human skeletal muscle in both type 1 and 2 fibers. The serum and intramuscular concentrations of myostatin-immunoreactive protein are increased in HIV-infected men with weight loss compared with healthy men and correlate inversely with fat-free mass index. These data support the hypothesis that myostatin is an attenuator of skeletal muscle growth in adult men and contributes to muscle wasting in HIV-infected men.

Role of cytokines in AIDS wasting

There is now a large literature implicating cytokines in the development of wasting and cachexia commonly observed in a variety of pathophysiologic conditions. In the acquired immunodeficiency syndrome (AIDS), cytokines elicited by primary and secondary infections seem to exert subtle and sustained effects on behavioral, hormonal, and metabolic axes, and their combined effects on appetite and metabolism have been postulated to drive wasting. However, correlations of increased blood levels of a particular cytokine with wasting in AIDS have not been consistent observations, perhaps because cytokines act principally as paracrine and autocrine hormones, as well as indirectly by activating other systems. A better understanding of the mechanisms underlying the catabolic effects of cytokines in clearly needed if more efficacious strategies are to be developed for the prevention and treatment of wasting in AIDS. In this review we first examine the interacting factors contributing to the AIDS wasting syndrome. We then analyze the complex and overlapping role of cytokines in the pathophysiology of this condition, and put forward a number of hypotheses to explain some of the most important features of this syndrome.

Increased plasma gln and Leu Ra and inappropriately low muscle protein synthesis rate in AIDS wasting

Muscle protein wasting occurs in human immunodeficiency virus (HIV)-infected individuals and is often the initial indication of acquired immunodeficiency syndrome (AIDS). Little is known about the alterations in muscle protein metabolism that occur with HIV infection. Nine subjects with AIDS wasting (CD4 < 200/mm3), chronic stable opportunistic infections (OI), and >/=10% weight loss, fourteen HIV-infected men and one woman (CD4 > 200/mm3) without wasting or OI (asymptomatic), and six HIV-seronegative lean men (control) received a constant intravenous infusion of [1-13C]leucine (Leu) and [2-15N]glutamine (Gln). Plasma Leu and Gln rate of appearance (Ra), whole body Leu turnover, disposal and oxidation rates, and [13C]Leu incorporation rate into mixed muscle protein were assessed. Total body muscle mass/fat-free mass was greater in controls (53%) than in AIDS wasting (43%; P = 0.04). Fasting whole body proteolysis and synthesis rates were increased above control in the HIV+ asymptomatic group and in the AIDS-wasting group (P = 0. 009). Whole body Leu oxidation rate was greater in the HIV+ asymptomatic group than in the control and AIDS-wasting groups (P < 0.05). Fasting mixed muscle protein synthesis rate was increased in the asymptomatic subjects (0.048%/h; P = 0.01) but was similar in AIDS-wasting and control subjects (0.035 vs. 0.037%/h). Plasma Gln Ra was increased in AIDS-wasting subjects but was similar in control and HIV+ asymptomatic subjects (P < 0.001). These findings suggest that AIDS wasting results from 1) a preferential reduction in muscle protein, 2) a failure to sustain an elevated rate of mixed muscle protein synthesis while whole body protein synthesis is increased, and 3) a significant increase in Gln release into the circulation, probably from muscle. Several interesting explanations for the increased Gln Ra in AIDS wasting exist.

Factors of weight loss in patients with HIV and chronic diarrhea

Weight loss is significant in patients with HIV and chronic diarrhea. The aim of our study was to test for the links between weight loss, the level of food intake, and the severity of diarrhea and nutrient malabsorption. One hundred and sixteen patients with HIV and chronic diarrhea underwent a standardized gastrointestinal and nutritional evaluation, which included a questionnaire on diarrhea, a prospective estimation of food intake, a measurement of blood parameters and fecal lipid and nitrogen outputs, a stool examination for bacteria and parasites, and upper and lower digestive tract endoscopy. Diarrhea resulted from an infection by Cryptosporidia, Microsporida, or other pathogens in 22%, 20%, and 13% of the patients, respectively. Diarrhea appeared idiopathic in 45% of the patients. A significant negative correlation existed between the severity of weight loss and the levels of nutrient intake (p < .005), and a significant positive correlation between the severity of weight loss and stool frequency (p < .01). Multiple linear regression identified low caloric intake and high stool frequency as predictive of weight loss. No significant correlation was found between weight loss and the parameters of malabsorption, either by bivariate study or multiple regression. These results suggest that, in patients with HIV and chronic diarrhea, the degree of wasting is significantly related to the levels of dietary intake and the clinical severity of diarrhea, but not to the extent of nutrient malabsorption.

Bioelectrical impedance analysis in human immunodeficiency virus-infected patients: comparison of single frequency with multifrequency, spectroscopy, and other novel approaches

Bioelectrical impedance (BIA), a prediction method for estimating body water compartments and body cell mass (BCM), is being increasingly used in studies of human immunodeficiency virus (HIV)-related wasting, but there are few validation studies of the method in this group. The aim of this study is to examine the relationship between impedance measurements and body water compartments in patients with advanced HIV disease, and to investigate whether the newer approaches of multifrequency BIA, BIA spectroscopy, logarithmic transformation using a parallel circuit model, and direct calculation from electrical theory offer any advantage over traditional single-frequency BIA. We measured total body water (TBW) by deuterium dilution and extracellular water by bromide dilution in 33 patients with advanced HIV disease. Intracellular water and BCM were calculated from these results. Impedance was measured over a range of frequencies using a multifrequency analyzer. The relationship between impedance index at various frequencies and body water compartments was assessed by correlation and linear regression. We found that impedance index at higher frequencies had a closer relationship to TBW (r = 0.86, standard error of the estimate [SEE] = 2.96 at 1000 kHz) and at lower frequencies a closer relationship to extracellular water (ECW) (r = 0.47, SEE = 3.13 at 0 kHz) than the traditional 50 kHz measurement (r = 0.84, SE = 3.11 for TBW; r = 0.44 SEE = 3.19 for ECW), but the differences were marginal and not statistically significant. None of the other novel approaches tested were significantly better than traditional single frequency measurement. The 50 kHz equation for BCM developed in this study [BCM (kg) = (0.360331 x Ht2/Z50) + (0.151123 x Wt)-2.95] may be useful to investigators using BIA for hIV-wasting studies.

Effects of androgen administration in men with the AIDS wasting syndrome. A randomized, double-blind, placebo-controlled trial

BACKGROUND

Development of successful anabolic strategies to reverse the loss of lean body mass is of critical importance to increase survival in men with the AIDS wasting syndrome. Hypogonadism, an acquired endocrine deficiency state characterized by loss of testosterone, occurs in more than half of all men with advanced HIV disease. It is unknown whether testosterone deficiency contributes to the profound catabolic state and loss of lean body mass associated with the AIDS wasting syndrome.

OBJECTIVE

To investigate the effects of physiologic testosterone administration on body composition, exercise functional capacity, and quality of life in androgen-deficient men with the AIDS wasting syndrome.

DESIGN

Randomized, double-blind, placebo-controlled study.

SETTING

University medical center.

PATIENTS

51 HIV-positive men (age 42 +/- 8 years) with wasting (body weight < 90% of ideal body weight or weight loss > 10% of baseline weight) and a free testosterone level less than 42 pmol/L (normal range for men 18 to 49 years of age, 42 to 121 pmol/L [12.0 to 35.0 pg/mL]).

INTERVENTION

Patients were randomly assigned to receive testosterone enanthate, 300 mg, or placebo intramuscularly every 3 weeks for 6 months.

MEASUREMENTS

Change in fat-free mass was the primary end point. Secondary clinical end points were weight, lean body mass, muscle mass, exercise functional capacity, and change in perceived quality of life. Virologic variables were assessed by CD4 count and viral load.

RESULTS

Compared with patients who received placebo, testosterone-treated patients gained fat-free mass (-0.6 kg and 2.0 kg; P = 0.036), lean body mass (0.0 kg and 1.9 kg; P = 0.041), and muscle mass (-0.8 kg and 2.4 kg; P = 0.005). The changes in weight, fat mass, total-body water content, and exercise functional capacity did not significantly differ between the groups. Patients who received testosterone reported benefit from the treatment (P = 0.036), feeling better (P = 0.033), improved quality of life (P = 0.040), and improved appearance (P = 0.021). Testosterone was well tolerated in all patients.

CONCLUSIONS

Physiologic testosterone administration increases lean body mass and improves quality of life among androgen-deficient men with the AIDS wasting syndrome.

Levels of HIV RNA are quantitatively related to prior weight loss in HIV-associated wasting

Thirty-three patients referred to a wasting clinic were evaluated to assess whether levels of HIV RNA were related to the magnitude of prior weight loss. Their median RNA level was 46,887 gene copies/ml (range, <200-510,070 gene copies/ml) at the time of referral. Patients had lost 10.5 +/- 6.4 kg over 461 +/- 304 days. RNA levels were correlated with the absolute amount and percentage of weight lost as well as the difference in body mass index (BMI) at the prior maximal and minimal recorded weights (r = 0.7, 0.67, 0.69; p = .0001 for the comparisons). The magnitude of these changes increased across strata of HIV RNA levels (p < or = .004), previously defined as associated with increasing risk for disease progression. The other parameter that could be associated with weight loss was the CD4 lymphocyte count (r = -0.43; p = .01). Low levels of testosterone and measures of body cell mass, fat free mass, or fat mass within 6 weeks of the RNA level could not be related to weight loss, change in BMI, or RNA levels. Thirty-two of the patients had chronic, relentless weight loss; in 15 of these subjects, no apparent secondary opportunistic complications were associated with weight loss or gastrointestinal symptoms to impair energy intake. Levels of HIV replication appear to be causally related to the magnitude of weight loss in some patients with wasting.

Human immunodeficiency virus-related wasting: malabsorption syndromes

Diarrhea and malabsorption are common findings in patients with the acquired immunodeficiency syndrome (AIDS). The pathogenesis and consequences of malabsorption in human immunodeficiency virus (HIV) infection are similar to those found in non-HIV-related conditions, and are related to both direct intestinal damage and alterations in the coordination of the body's response to feeding. The pathogenesis of malabsorption is multifactorial and includes primary enterocyte injury with partial villus atrophy and crypt hyperplasia, ileal dysfunction with bile salt wasting and fat malabsorption, and exudative enteropathy. Clinical studies show that intestinal cryptosporidiosis leads to excess fecal losses of about 20% for protein and fat. The consequences of malabsorption include decreased appetite; "enterogastrone" effects including dry mouth, decreased gastric acid secretion, decreased rate of gastric emptying, and slowed intestinal transit; anemia resulting from iron, folate, or vitamin B12 malabsorption; and metabolic effects including osteomalacia, gallstones, renal stones, and hypocholesterolemia. Few studies of nutritional therapy have been applied specifically to AIDS patients with malabsorption. Total parenteral nutrition promotes weight gain, although the response to this therapy depends on the underlying clinical problem, with body cell mass repletion noted in patients with malabsorption but predominantly fat gain in patients with systemic infections. Nutritional stabilization also was noted in response to oral administration of a semielemental diet.

HIV gp120 inhibits the somatotropic axis: a possible GH-releasing hormone receptor mechanism for the pathogenesis of AIDS wasting

AIDS is often associated with growth retardation in children and wasting in adults. The dissociated envelope protein of the HIV (HIV-1), gp120, can be found in significant concentrations in the parenchyma and cerebrospinal fluid of brains in infected individuals, even in the earliest stages of HIV-1 disease. On the basis of this and the fact that we observed pentapeptide sequence homology between GH-releasing hormone (GHRH) and the V2 receptor-binding region of gp120, we initiated experiments to determine whether gp120 could affect GH secretion and growth in vivo and/or interact with anterior pituitary GHRH receptors in vitro. Although acute IV administration of gp120 in conscious rats had no effect on plasma GH levels, acute administration of gp120 (400 ng) into the brain significantly suppressed pulsatile GH release over a 6-h period compared with saline-injected controls. Furthermore, the putative gp120 antagonist, Peptide T (DAPTA), prevented the suppression of GH by gp120. In support of these in vivo findings, gp120 also significantly (P < 0.05) suppressed GHRH-stimulated GH release in static cultures of dispersed pituitary cells and from cells undergoing perifusion with the peptides. DAPTA prevented the GH suppression by gp120 in both of the pituitary cell paradigms. Furthermore, chronic administration of gp120 into the third ventricle significantly reduced body weight in juvenile rats, compared with saline-injected controls. Thus, gp120 appears to act both at the hypothalamus and pituitary to suppress GH release, and its action at these two locations is associated with a significant loss in body weight in chronically treated young animals. These findings may suggest a specific mechanism for the pathogenesis of wasting in HIV-1 patients that involves blockade of endogenous GHRH receptors by gp120.

Bioelectrical impedance analysis (BIA) in HIV infection: principles and clinical applications

Wasting is a common manifestation of AIDS that diminishes quality of life and is predictive of death. Body composition changes can occur in asymptomatic HIV infection, suggesting that early detection and treatment could potentially prevent the downward spiral to serious wasting. Bioelectrical impedance analysis (BIA) is a method for estimating body composition that is gaining widespread use among HIV-infected populations. In this article, the principles underlying BIA and its appropriate applications and limitations in HIV/AIDS are described.

Role of cysteine and glutathione in HIV infection and other diseases associated with muscle wasting and immunological dysfunction

The combination of abnormally low plasma cystine and glutamine levels, low natural killer (NK) cell activity, skeletal muscle wasting or muscle fatigue, and increased rates of urea production defines a complex of abnormalities that is tentatively called "low CG syndrome." These symptoms are found in patients with HIV infection, cancer, major injuries, sepsis, Crohn's disease, ulcerative colitis, chronic fatigue syndrome, and to some extent in overtrained athletes. The coincidence of these symptoms in diseases of different etiological origin suggests a causal relationship. The low NK cell activity in most cases is not life-threatening, but may be disastrous in HIV infection because it may compromise the initially stable balance between the immune system and virus, and trigger disease progression. This hypothesis is supported by the coincidence observed between the decrease of CD4+ T cells and a decrease in the plasma cystine level. In addition, recent studies revealed important clues about the role of cysteine and glutathione in the development of skeletal muscle wasting. Evidence suggests that 1) the cystine level is regulated primarily by the normal postabsorptive skeletal muscle protein catabolism, 2) the cystine level itself is a physiological regulator of nitrogen balance and body cell mass, 3) the cyst(e)ine-mediated regulatory circuit is compromised in various catabolic conditions, including old age, and 4) cysteine supplementation may be a useful therapy if combined with disease-specific treatments such as antiviral therapy in HIV infection.

Altered concentrations of appetite regulators may contribute to the development and maintenance of HIV-associated wasting

OBJECTIVE

To examine the relation of circulating appetite neuropeptides, CCK-8 sulphate (CCK-8s) and beta-endorphin, and the tumour necrosis factor-alpha (TNF-alpha) and soluble TNF receptors (sTNFR) to the anorexia and wasting associated with HIV-infection.

DESIGN

Cross-sectional analysis.

SETTING

A university-based HIV/AIDS ambulatory clinic in Madrid, Spain.

PARTICIPANTS

Thirty-six randomly selected AIDS patients without concomitant diseases or secondary infections were classified into two groups: 19 patients with wasting and 17 with normal body weight, and 18 healthy controls.

MEASUREMENTS

Nutritional status was evaluated by anthropometry, laboratory parameters and self-report of appetite. Plasma levels of TNF-alpha and sTNFR proteins p55 (sTNFR-p55) and p75 (sTNFR-p75) were determined by enzyme immunoassay, whereas CCK-8s and beta-endorphin levels were measured by radioimmunoassay.

RESULTS

AIDS patients with wasting had significantly higher plasma concentrations of CCK-8s, but lower levels of beta-endorphin when compared to well-nourished AIDS patients (P < 0.01) or controls (P < 0.001). Mean levels of TNF-alpha, and sTNFR-p55 and sTNFR-p75 were greater in AIDS patients with wasting than in asymptomatic AIDS patients or in controls. No significant association was observed between any of these circulating peptides and the parameters of malnutrition.

CONCLUSIONS

An activation of the TNF system, together with reciprocal changes in plasma concentrations of two neuropeptides with opposing appetite regulation, that is increased concentrations of CCK-8s but lower levels of beta-endorphin, are associated with the presence of HIV wasting. We hypothesize that these changes may contribute to the development of HIV wasting by producing a pathological inhibition of appetite.