Growth hormone (GH) responses to GH-releasing hormone-arginine testing in human immunodeficiency virus lipodystrophy

Prior studies suggest reduced overnight GH secretion in association with excess visceral adiposity among patients with HIV lipodystrophy (LIPO, i.e. with fat redistribution). We now investigate GH responses to standardized GHRH-arginine in LIPO patients (n = 39) in comparison with body mass index- and age-matched control groups [HIV patients without fat distribution (NONLIPO, n = 17)] and healthy subjects (C, n = 16). IGF-I [242 +/- 17; 345 +/- 38; 291 +/- 27 ng/ml (P < 0.05 vs. NONLIPO)] was lowest in the LIPO group. Our data demonstrate failure rates of 18% for the LIPO group vs. 5.9% for the NONLIPO group and 0% for the C group, using a stringent criterion of 3.3 ng/ml for peak GH response to GHRH-arginine (P < 0.05 LIPO vs. C). Using less stringent cutoffs, the failure rate in the LIPO group rises to 38.5% at 7.5 ng/ml. Among the LIPO patients, the peak GH response to GHRH-arginine was significantly predicted by visceral adipose tissue (P = 0.008), free fatty acid (P = 0.04), and insulin level (P = 0.007) in regression modeling controlling for age, body mass index, sc fat area, and triglyceride level. These data demonstrate increased failure rates to standardized stimulation testing with GHRH-arginine in LIPO patients, in association with increased visceral adiposity. The effects of low-dose GH should be assessed in the large subset of LIPO patients with abnormal GH stimulation testing.     

Hyperandrogenemia in human immunodeficiency virus-infected women with the lipodystrophy syndrome

A novel lipodystrophy syndrome characterized by insulin resistance, hypertriglyceridemia, and fat redistribution has recently been described in human immunodeficiency virus (HIV)-infected men and women. Women with the HIV lipodystrophy syndrome exhibit a marked increase in waist-to-hip ratio and truncal adiposity; however, it is unknown whether androgen levels are increased in these patients. In this study, we assessed androgen levels in female patients with clinical lipodystrophy based on evidence of significant fat redistribution in the trunk, extremities, neck and/or face (LIPO: n = 9; age, 35.7+/-1.7 yr; BMI, 24.7+/-0.8 kg/m2) in comparison with age- and BMI-matched nonlipodystrophic HIV-infected females (NONLIPO: n = 14; age, 37.6+/-1.1 yr; BMI, 23.4+/-0.6 kg/m2) and healthy non-HIV-infected control subjects (C: n = 16; age, 35.8+/-0.9 yr; BMI, 23.1+/-0.4 kg/m2). Fasting insulin, lipid levels, virologic parameters, and regional body composition using dual energy x-ray absorptiometry were also assessed. Total testosterone [ LIPO, 33+/-6 ng/dL (1.1+/-0.2 nmol/L); NONLIPO, 17+/-2 ng/dL (0.6+/-0.1 nmol/L); C, 23+/-2 ng/dL (0.8+/-0.1 nmol/L); P < 0.05 LIPO vs. C and LIPO vs. NONLIPO] and free testosterone determined by equilibrium dialysis [LIPO, 4.5+/-0.9 pg/mL (16+/-3 pmol/L); NONLIPO, 1.7+/-0.2 pg/mL (6+/-1 pmol/L); C, 2.4+/-0.2 pg/mL (8+/-1 pmol/L); P < 0.05 LIPO vs. C and LIPO vs. NONLIPO] were increased in the lipodystrophic patients. Sex hormone-binding globulin levels were not significantly different between LIPO and C, but were significantly lower in the LIPO vs. NONLIPO patients (LIPO 84+/-7 vs. NONLIPO 149+/-17 nmol/L, P < 0.05). The LH/FSH ratio was significantly increased in the LIPO group compared with the NONLIPO and C subjects (LIPO, 2.0+/-0.6; NONLIPO, 1.1+/-0.1; C, 0.8+/-0.1; P < 0.05 LIPO vs. NONLIPO and LIPO vs. C). Body fat distribution was significantly different between LIPO and C subjects. Trunk to extremity fat ratio (1.46+/-0.17 vs. 0.75+/-0.05, LIPO vs. C, P < 0.05) was increased and extremity to total fat ratio decreased (0.40+/-0.03 vs. 0.55+/-0.01, LIPO vs. C, P < 0.05). In contrast, fat distribution was not different in the NONLIPO group vs. control subjects. Among the HIV-infected patients, free testosterone correlated with percent truncal fat (trunk fat/trunk mass) (r = 0.43, P = 0.04). These data suggest that hyperandrogenemia is another potentially important feature of the HIV-lipodystrophy syndrome in women. Additional studies are necessary to determine the clinical significance of increased androgen levels and the relationship of hyperandrogenism to fat redistribution and insulin resistance in this population of patients.     

Elevated concentrations of free fatty acids are associated with increased insulin response to standard glucose challenge in human immunodeficiency virus-infected subjects with fat redistribution

Fat redistribution, defined by both increased abdominal visceral fat and/or decreased abdominal, extremity, and facial subcutaneous fat, is increasingly recognized among human immunodeficiency virus (HIV)-infected patients treated with combination antiretroviral therapy. Fat redistribution in this population is associated with insulin resistance and dyslipidemia and is often referred to as the HIV lipodystrophy syndrome (LIPO). Fatty acids are known to modulate insulin resistance in other disease states, but a comprehensive evaluation of fatty acids has not been undertaken among HIV-infected patients with fat redistribution. In this study, we investigated fatty acid concentrations in 64 HIV-infected individuals (45 men and 19 women) with evidence of fat redistribution (LIPO) in comparison to 30 HIV-infected individuals (20 men and 10 women) without evidence of fat redistribution (NONLIPO) and 32 HIV-negative healthy control subjects (C) (21 males and 11 females) of similar age and body mass index (BMI). Glucose, insulin, and free fatty acid (FFA) levels were measured in response to a 75-g oral glucose tolerance test (OGTT) in the LIPO, NONLIPO, and C subjects. In addition, fasting lipids were obtained, and body composition was determined by anthropometric measurements and dual-energy x-ray absorptiometry (DXA). Fasting FFA concentrations were significantly increased in the LIPO group as compared with NONLIPO and C subjects (0.74 +/- 0.03 v 0.60 +/- 0.04 [mean +/- SEM] mmol/L, P =.002, LIPO v NONLIPO; 0.74 +/- 0.03 v 0.59 +/- 0.03 mmol/L, P =.001, LIPO v C). In contrast, fasting FFA concentrations were not increased in the NONLIPO group (0.60 +/- 0.04 v 0.59 +/- 0.03, P =.909, NONLIPO v C). Similarly, fasting triglycerides and 120-minute OGTT FFA were significantly increased in the LIPO group as compared with the NONLIPO and C group. FFA decreased in HIV-infected LIPO, NONLIPO, and C subjects in response to OGTT, but the 120-minute FFA concentrations remained significantly elevated in LIPO patients compared with NONLIPO and C subjects. In a multivariate regression model of LIPO patients, fasting FFA (P =.027) was a strong independent predictor of insulin area under the curve (AUC), controlling for age, BMI, gender, and body composition (r(2) for model =.31). No differences were observed in FFA concentrations in the LIPO group in an analysis based on current protease inhibitor (PI) use. These data suggest that FFA concentrations are increased in HIV-infected patients with fat redistribution. Increased fasting concentrations of fatty acids are associated with abnormal insulin responses to standard glucose challenge in HIV-infected patients with fat redistribution. Further studies are necessary to determine the mechanism of increased fatty acid concentrations and the role played by increased FFA in mediating insulin resistance in this population.     

Insulin-like growth factors, insulin-like growth factor-binding proteins, insulin-like growth factor-binding protein-3 protease, and growth hormone-binding protein in lipodystrophic human immunodeficiency virus-infected patients

Human immunodeficiency virus (HIV)-lipodystrophy is associated with impaired growth hormone (GH) secretion. It remains to be elucidated whether insulin-like growth factors (IGFs), IGF-binding proteins (IGFBPs), IGFBP-3 protease, and GH-binding protein (GHBP) are abnormal in HIV-lipodystrophy. These parameters were measured in overnight fasting serum samples from 16 Caucasian males with HIV-lipodystrophy (LIPO) and 15 Caucasian HIV-infected males without lipodystrophy (NONLIPO) matched for age, weight, duration of HIV infection, and antiretroviral therapy. In LIPO, abdominal fat mass and insulin concentration were increased (>90%, P < .01) and insulin sensitivity (Log10ISI(composite)) was decreased (-50%, P < .001). Total and free IGF-I, IGF-II, IGFBP-3, and IGFBP-3 protease were similar between groups (all P > .5), whereas, in LIPO, IGFBP-1 and IGFBP-2 were reduced (-36%, P < .05 and -50%, P < .01). In pooled groups, total IGF-I, free IGF-I, total IGF-II, and IGFBP-3, respectively, correlated inversely with age (all P < .01). In pooled groups, IGFBP-1 and IGFBP-2 correlated positively with insulin sensitivity (age-adjusted all P < .05). IGFBP-3 protease correlated with free IGF-I in pooled groups (r(p) = 0.47, P < .02), and in LIPO (r(p) = 0.71, P < .007) controlling for age, total IGF-I, and IGFBP-3. GHBP was increased, whereas GH was decreased in LIPO (all P < .05). GH correlated inversely with GHBP in pooled groups (P < .05). Taken together the similar IGFs and IGFBP-3 concentrations between study groups, including suppressed GH, and increased GHBP in LIPO, argue against GH resistance of GH-sensitive tissues in LIPO compared with NONLIPO; however, this notion awaits examination in dose-response studies. Furthermore, our data suggest that IGFBP-3 protease is a significant regulator of bioactive IGF-I in HIV-lipodystrophy.     

Different growth hormone sensitivity of target tissues and growth hormone response to glucose in HIV-infected patients with and without lipodystrophy

Growth hormone (GH)-secretion in HIV-lipodystrophy is impaired; however, GH-sensitivity of GH-target tissues remains to be evaluated. We measured overnight fasting concentrations of GH-sensitive insulin-like growth-factor-I (IGF-I) and IGF binding protein-3 (IGFBP-3) including GH binding protein (GHBP), a marker of GH-receptor sensitivity, in antiretroviral treated HIV-infected patients with (LIPO) and without lipodystrophy (NONLIPO) and antiretroviral naive HIV-infected patients (NAIVE). Three h GH-suppression tests using oral glucose were undertaken to determine dynamics of GH-secretion. IGF-I and IGFBP-3 were increased in LIPO compared with NONLIPO (p <0.05), but did not differ significantly between NONLIPO and NAIVE. Area under the curve of GH (AUC-GH) during the GH-suppression test was decreased in LIPO compared with NONLIPO (p <0.05). Ratio of limb to trunk fat, which was decreased in LIPO compared to NONLIPO and NAIVE (p <0.001), correlated positively with AUC-GH and rebound-GH (p <0.05). All groups displayed suppression of GH during the suppression test (p <0.05) and all groups, except LIPO, displayed a rebound of GH (p <0.05), which probably is explained by persistently increased plasma glucose in LIPO compared with NONLIPO and NAIVE (p <0.01). GHBP was inversely correlated with AUC-GH (p <0.01). Our data suggest that GH-target tissues in LIPO are at least as GH-sensitive as in HIV-infected patients without lipodystrophy.     

In vivo evidence of impaired peripheral fatty acid trapping in patients with human immunodeficiency virus-associated lipodystrophy

The use of antiretroviral combination therapy in HIV has been associated with lipodystrophy and several metabolic risk factors. We postulated that patients with HIV-lipodystrophy have impaired adipose tissue free fatty acid (FFA) trapping and, consequently, increased hepatic FFA delivery. We investigated FFA, hydroxybutyric acid (HBA; reflecting hepatic FFA oxidation), and triglyceride (TG) changes after a high fat meal in HIV-infected males with (LIPO; n = 26) and without (NONLIPO; n = 12) lipodystrophy and in healthy males (n = 35). Because defective peripheral FFA trapping has been associated with impaired action of complement component 3 (C3), we also determined postprandial C3 concentrations. The LIPO group had higher homeostasis model assessment scores compared with the other groups. Areas under the curve (AUCs) for FFA, HBA, and TG were higher in the LIPO group than in the NONLIPO group or the controls. No differences in TG-AUC, FFA-AUC, and HBA-AUC were observed between the NONLIPO group and controls. In HIV-infected patients, FFA-AUC and HBA-AUC were inversely related to sc adipose tissue area. Plasma C3 showed a postprandial increase in healthy controls, but not in the HIV-infected groups. C3 was not related to body fat distribution, postprandial FFA, or HBA. The present data suggest disturbed postprandial FFA metabolism in patients with HIV-lipodystrophy, most likely due to inadequate incorporation of FFA into TG in sc adipose tissue, but do not support a major role for C3 in these patients. The higher postprandial HBA levels reflect increased hepatic FFA delivery and may aggravate insulin resistance and dyslipidemia, leading to increased cardiovascular risk.     

Impaired proinsulin secretion before and during oral glucose stimulation in HIV-infected patients who display fat redistribution

The beta-cell function of HIV-infected patients on highly active antiretroviral therapy who display lipodystrophy may be impaired. An early defect in beta-cell function may be characterized by an increase in secretion of 32-33 split proinsulin (SP) and intact proinsulin (IP). To address this issue, the secretion patterns of SP and IP of 16 HIV-infected men with lipodystrophy (LIPO) and 15 HIV-infected men without lipodystrophy (NONLIPO) were studied during an oral glucose tolerance test (OGTT). All patients received highly active antiretroviral therapy. Insulin secretion rates were determined by deconvolution of plasma C-peptide concentrations. More LIPO than NONLIPO patients displayed diabetes mellitus and impaired glucose tolerance than normal glucose tolerance (LIPO 2/8/6 vs NONLIPO 1/2/12, P = .05). LIPO patients had increased fasting levels of SP and IP, ratio of SP/IP, and area under the curve of SP and IP during the early phase (0, 10, and 20 minutes) and during the late phase (45, 75, and 105 minutes) of the OGTT compared with NONLIPO patients (Ps < .05). LIPO patients exhibited significantly increased fasting SP/IP ratio, fasting SP/insulin ratio, and total proinsulin to C-peptide ratio during the OGTT. LIPO patients displayed increased incremental secretion of IP during the first 10 minutes of the OGTT (P < .05), although the incremental insulin secretion during this period did not differ between LIPO and NONLIPO patients. These data suggest that HIV-infected patients with lipodystrophy display major perturbations of proinsulin secretion in the fasting state and during an OGTT, which is compatible with the notion of a beta-cell dysfunction of such patients.     

Increased abdominal visceral fat is associated with reduced bone density in HIV-infected men with lipodystrophy

OBJECTIVE: To examine the relationship between bone density and changes in regional and whole body composition in HIV-infected men with and without lipodystrophy. DESIGN: Cross-sectional, observational study of HIV-infected men with and without lipodystrophy and matched HIV-negative controls. SETTING: Tertiary care academic medical institution. PATIENTS: A total of 59 men, belonging to three different groups: HIV-positive men with lipodystrophy (n = 21), HIV-positive men without lipodystrophy (n = 20), and age-matched and body mass index-matched HIV-negative controls (n = 18). METHODS: Bone density, markers of bone turnover and indices of calcium metabolism were measured in all subjects. Quantitative computed tomography was used both to determine volumetric bone density of the spine and to quantify abdominal visceral fat. Dual energy X-ray absorptiometry was used to determine whole body composition and bone density. Statistical comparisons were performed according to lipodystrophy categorization and protease inhibitor exposure. RESULTS: Men with HIV-associated lipodystrophy had reduced lumbar spine bone density compared with both HIV-infected non-lipodystrophic men [mean +/- SD, 132 +/- 29 versus 154 +/- 30 mg/cm(3); P = 0.02] and HIV-negative controls [mean +/- SD 132 +/- 29 versus 148 +/- 18) mg/cm(3); P = 0.04]. Lumbar spine bone density was reduced significantly in HIV lipodystrophy patients independently of protease inhibitor use. In an analysis among all HIV-infected subjects, increased visceral abdominal fat area was associated with decreased lumbar spine bone density (r, -0.47; P = 0.002). The association between visceral fat and bone density remained significant (P = 0.007) after controlling for age, body mass index, lowest body weight, protease inhibitor use, and extremity fat in a multivariate regression model. Markers of bone turnover were not related to bone density or lipodystrophy status. CONCLUSIONS: Lumbar spine bone density is reduced in association with increased visceral fat in HIV-infected men with lipodystrophy. Further studies are needed to determine the mechanisms of osteopenia in HIV lipodystrophy and whether increased marrow fat occurs in such patients and affects bone density.     

Relationship of fat distribution with adipokines in human immunodeficiency virus infection

BACKGROUND AND METHODS: HIV-infected patients receiving antiretroviral therapy often develop changes in body fat distribution; the dominant change is reduction in sc adipose tissue (SAT). Because adipose tissue makes important hormones involved in whole-body energy metabolism, including leptin and adiponectin, we examined plasma concentrations and their relationship to regional adiposity measured by magnetic resonance imaging in 1143 HIV-infected persons (803 men and 340 women) and 286 controls (151 men and 135 women) in a cross-sectional analysis of the FRAM study. RESULTS: Total and regional adiposity correlated positively with leptin levels in HIV-infected subjects and controls (P < 0.0001). In controls, total and regional adiposity correlated negatively with adiponectin. In HIV-infected subjects, adiponectin was not significantly correlated with total adiposity, but the normal negative correlation with visceral adipose tissue and upper trunk SAT was maintained. However, leg SAT was positively associated with adiponectin in HIV-infected subjects. Within the lower decile of leg SAT for controls, HIV-infected subjects had paradoxically lower adiponectin concentrations compared with controls (men: HIV 4.1 microg/ml vs. control 7.5 microg/ml, P = 0.009; women: HIV 7.8 microg/ml vs. control 11.6 microg/ml, P = 0.037). Even after controlling for leg SAT, exposure to stavudine was associated with lower adiponectin, predominantly in those with lipoatrophy. CONCLUSION: The normal relationships between adiponectin levels and total and leg adiposity are lost in HIV-infected subjects, possibly due to changes in adipocyte function associated with HIV lipodystrophy, whereas the inverse association of adiponectin and visceral adipose tissue is maintained. In contrast, the relationship between adiposity and leptin levels appears similar to controls and unaffected by HIV lipodystrophy.     

GH treatment reduces trunkal adiposity in HIV-infected patients with lipodystrophy: a randomized placebo-controlled study

OBJECTIVE: HIV lipodystrophy is a common complication of highly active anti-retroviral therapy, characterized by both metabolic and morphological features. The most feared morphological feature is body fat redistribution leading to HIV lipodystrophy. GH is known to induce reduction of visceral obesity and body fat redistribution in adults. DESIGN: A crossover, double-blind protocol of GH treatment (6 months of recombinant human GH (rhGH) at 0.2 IU/kg per week) vs placebo (6 months of placebo with a 2 month wash-out between periods) was performed. SUBJECTS AND SETTING: Thirty HIV-infected patients with lipodystrophy were recruited in the Outpatient Clinic of the Division of Infectious Diseases of San Raffaele Scientific Institute in Milan, Italy. MAIN OUTCOME AND RESULTS: Our data demonstrate an effect of low-dose rhGH administration in reducing trunk adiposity in HIV patients with lipodystrophy (Delta from basal: -394 +/- 814 g, P = 0.048 with respect to placebo. Data are given as mean +/- standard deviation). A trend to an increase of arm depots was also shown (Delta from basal: +43 +/- 384 g, P = NS with respect to placebo). Interestingly, no detrimental metabolic effects on glucose tolerance and lipid levels were found following the administration of 0.2 IU/kg per week of rhGH for 6 months. CONCLUSIONS: Low-dose GH administration is an effective treatment in reducing trunk obesity in HIV-infected patients with lipodystrophy.     

Regulation of adiponectin in human immunodeficiency virus-infected patients: relationship to body composition and metabolic indices

HIV-related lipodystrophy is characterized by adipose redistribution, dyslipidemia, and insulin resistance. Adiponectin is an adipose-derived peptide thought to act as a systemic regulator of glucose and lipid metabolism. We investigated adiponectin concentrations in 10 HIV-infected patients during acute HIV infection (viral load, 2.0 x 10(6) +/- 1.0 x 10(6) copies/ml) and then 6-8 months later, as well as cross-sectionally in 41 HIV-infected patients (21 with evidence of fat redistribution and 20 without evidence of fat redistribution) in comparison with 20 age- and body mass index-matched healthy control subjects. Circulating adiponectin concentrations did not change with treatment of acute HIV infection (5.8 +/- 0.4 vs. 5.9 +/- 0.7 micro g/ml, P = 0.96) but were reduced in patients with chronic HIV infection and fat redistribution (7.8 +/- 0.9 micro g/ml), compared with age- and body mass index-matched HIV-infected patients without fat redistribution (12.7 +/- 1.7 micro g/ml) and healthy control subjects (11.9 +/- 1.7 micro g/ml, P < 0.05 vs. HIV-infected patients without fat redistribution and vs. control subjects). Adiponectin concentrations correlated with body composition [correlation coefficient (r) = -0.47, P = 0.002 vs. trunk fat:total fat; r = 0.51, P < 0.001 vs. extremity fat:total fat], insulin response to glucose challenge (r = -0.36, P = 0.03), triglyceride (r = -0.39, P = 0.01), and high-density lipoprotein (r = 0.37, P = 0.02) among the HIV-infected patients. Adiponectin remained a significant correlate of insulin response to GTT, controlling for medication use and body composition changes in HIV-infected patients. These data suggest a strong relationship between adiponectin and body composition in HIV-infected patients. Changes in adiponectin may contribute to the metabolic dysregulation in this group of patients.     

The relationship of ghrelin to biochemical and anthropometric markers of adult growth hormone deficiency

INTRODUCTION: Ghrelin is the natural ligand of the growth hormone secretagogue receptor (GHS-R) and potently stimulates GH release in humans. Ghrelin is found in the hypothalamus, but most circulating ghrelin is derived from the stomach. Ghrelin stimulates food intake but circulating levels are low in obesity. We hypothesized that GH deficiency (GHD) might be associated with increased circulating ghrelin concentrations as a result of low GH levels. We therefore measured circulating ghrelin concentrations, leptin and body composition in subjects with GHD and healthy controls. METHODS: Subjects with GHD (n = 18) were compared to healthy control subjects (n = 18), matched for body mass index (BMI). They underwent assessment of body composition [waist circumference, BMI and percentage body fat (using bioimpedance)]. Plasma ghrelin, leptin, insulin, GH and IGF-1 were measured in the fasting state. Plasma ghrelin was measured using a specific radioimmunassay, and the other hormones using commercially available assays. RESULTS: The groups were well-matched for BMI (GHD vs. control; 32.9 +/- 10.8 vs. 31.3 +/- 11.7, P = ns) and waist circumference (GHD vs. control; 102.9 +/- 20.0 vs. 99.8 +/- 25.2, P = ns), but percentage body fat (GHD vs. control; 37.0 +/- 9.1 vs. 29.4 +/- 13.0, P = 0.06) tended to be higher in the GHD group. As expected, IGF-1 was lower in GHD (GHD vs. control; 12.5 +/- 6.8 vs. 19.2 +/- 5.8 nmol/l, P = 0.003). Ghrelin [GHD vs. controls; geometric mean (95% CI); 828.8 (95% CI 639.9-1074.2) vs. 487.9 (95% CI 297.2-800.2) pmol/l] and leptin [GHD vs. controls; 13.2 (95% CI 6.6-26.5) vs. 7.9 (95% CI 3.7-16.9) ng/ml] were similar in the two groups. Plasma ghrelin correlated inversely with waist circumference and waist hip ratio in GHD subjects (r = -0.6, P = 0.02) but not with IGF-1 or GH concentrations. There was no significant correlation in the control subjects. CONCLUSION: Circulating ghrelin concentrations are influenced by body fat distribution, but not by levels of either GH or IGF-1. However, given that obesity is associated with reduced ghrelin concentrations and that GHD is commonly associated with increased body fat, it is possible that these two opposing influences on circulating ghrelin levels result in normal concentrations in subjects with GHD.     

GH/GHRH axis in HIV lipodystrophy

Approximately half of patients with HIV-infection develop abnormal body fat distribution, characterized by increased abdominal, breast, and dorsocervical adiposity and decreased fat in the limbs and face in association with antiretroviral therapy. Changes in fat distribution are associated with dyslipidemia, insulin resistance, and increased cardiovascular risk in patients with HIV lipodystrophy. Growth hormone secretion is reduced and responses to standardized stimulation testing altered, suggesting relative growth hormone deficiency in this population. Growth hormone secretion is characterized by normal pulse frequency, but decreased pulse amplitude, pulse width, and trough GH levels compared to weight matched, non-HIV-infected patients. Abnormalities in GH secretion are strongly associated with body composition and metabolic abnormalities in patients with HIV lipodystrophy, particularly with increased visceral fat and elevated free fatty acids. Increased somatostatin tone and decreased ghrelin concentrations may also contribute to reduced GH levels. Administration of exogenous GH or growth hormone releasing hormone (GHRH) to normalize growth hormone concentrations is effective to reduce visceral fat and improve lipid parameters in HIV-infected patients. Treatment with supraphysiologic GH is limited by side effects and exacerbation of insulin resistance, whereas administration of physiologic doses of GH demonstrates more modest treatment effects but fewer adverse effects. Initial studies of GHRH also show significant reductions in visceral adipose tissue (VAT) with potentially fewer adverse effects. GHRH may be particularly useful to normalize GH dynamics in patients with HIV lipodystrophy by increasing endogenous GH pulse height, GH pulse width, and trough GH levels, while preserving the negative feedback of IGF-I on pituitary GH secretion.     

Growth hormone decreases visceral fat and improves cardiovascular risk markers in women with hypopituitarism: a randomized, placebo-controlled study

CONTEXT: Data regarding gender-specific efficacy of GH on critical endpoints are lacking. There are no randomized, placebo-controlled studies of physiological GH therapy solely in women. OBJECTIVE: Our objective was to determine the effects of physiological GH replacement on cardiovascular risk markers and body composition in women with GH deficiency (GHD). DESIGN: This was a 6-month, randomized, placebo-controlled, double-blind study. SETTING: The study was conducted at the General Clinical Research Center. STUDY PARTICIPANTS: 43 women with GHD due to hypopituitarism were included in the study. INTERVENTION: Study participants were randomized to receive GH (goal mid-normal serum IGF-1) or placebo. MAIN OUTCOME MEASURES: Cardiovascular risk markers, including high-sensitivity C-reactive protein, tissue plasminogen activator, and body composition, including visceral adipose tissue by cross-sectional computed tomography, were measured. RESULTS: Mean daily GH dose was 0.67 mg. The mean IGF-1 sd score increased from -2.5 +/- 0.3 to -1.4 +/- 0.9 (GH) (P < 0.0001 vs. placebo). High-sensitivity C-reactive protein decreased by 38.2 +/- 9.6% (GH) vs.18.2 +/- 6.0% (placebo) (P = 0.03). Tissue plasminogen activator and total cholesterol decreased, and high-density lipoprotein increased. Homeostasis model assessment-insulin resistance and other markers were unchanged. Body fat decreased [-5.1 +/- 2.0 (GH) vs. 1.9 +/- 1.0% (placebo); P = 0.002] as did visceral adipose tissue [-9.0 +/- 5.9 (GH) vs. 4.3 +/- 2.7% (placebo); P = 0.03]. Change in IGF-1 level was inversely associated with percent change in visceral adipose tissue (r = -0.61; P = 0.002), total body fat (r = -0.69; P < 0.0001), and high-sensitivity C-reactive protein (r = -0.51; P = 0.003). CONCLUSIONS: Low-dose GH replacement in women with GHD decreased total and visceral adipose tissue and improved cardiovascular markers, with a relatively modest increase in IGF-1 levels and without worsening insulin resistance.     

Increased PAI-1 and tPA antigen levels are reduced with metformin therapy in HIV-infected patients with fat redistribution and insulin resistance

Cardiovascular disease (CVD) risk associated with fat redistribution seen among HIV-infected individuals remains unknown, but may be increased due to hyperlipidemia, hyperinsulinemia, increased visceral adiposity, and a prothrombotic state associated with these metabolic abnormalities. In this study we characterized plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (tPA) antigen levels, markers of fibrinolysis and increased CVD risk, in HIV lipodystrophic patients compared to controls. Furthermore, we investigated the effect of treatment with metformin on PAI-1 and tPA antigen levels in patients with HIV-associated fat redistribution. Eighty-six patients (age 43 +/- 1 yr, BMI 26.1 +/- 0.5 kg/m(2)) with HIV and fat redistribution were compared to 258 age- and BMI-matched subjects from the Framingham Offspring study. In addition, 25 HIV-infected patients with fat redistribution and fasting insulin >15 microU/mL [104 pmol/L] or impaired glucose tolerance, but without diabetes mellitus were enrolled in a placebo-controlled treatment study of metformin 500 mg twice daily. PAI-1 and tPA antigen levels were significantly increased in patients with HIV related fat redistribution compared to Framingham control subjects (46.1 +/- 4 vs 18.9 +/- 0.9 microg/L PAI-1, 16.6 +/- 0.8 vs. 8.0 +/- 0.3 microg/L tPA, P = 0.0001). Among patients with HIV infection, a multivariate regression analysis including age, sex, waist-to-hip ratio, BMI, smoking status, protease inhibitor use and insulin area under the curve (AUC), found gender and insulin AUC were significant predictors of tPA antigen. Twelve weeks of metformin treatment resulted in decreased tPA antigen levels (-1.9 +/- 1.4 vs +1.4 +/- 1.0 microg/L in the placebo-treated group P = 0.02). Similarly, metformin resulted in improvement in PAI-1 levels (-8.7 +/- 2.3 vs +1.7 +/- 2.9 microg/L, P = 0.03). Change in insulin AUC correlated significantly with change in tPA antigen (r = 0.43, P = 0.03). PAI-1 and tPA antigen, markers of impaired fibrinolysis and increased CVD risk, are increased in association with hyperinsulinemia in patients with HIV and fat redistribution. Metformin reduces PAI-1 and tPA antigen concentrations in these patients and may ultimately improve associated CVD risk.     

Serum adiponectin and leptin levels in patients with lipodystrophies

Lipodystrophies are characterized by selective but variable loss of body fat and metabolic complications of insulin resistance. We hypothesized that reduced synthesis and secretion of adipocyte-specific proteins may be related to the metabolic complications of lipodystrophy. Therefore, we compared fasting serum concentrations of adiponectin and leptin, in 18 patients with congenital generalized lipodystrophy (CGL), 11 with acquired generalized lipodystrophy (AGL), 46 with familial partial lipodystrophy-Dunnigan variety (FPLD) and 18 with acquired partial lipodystrophy (APL) and studied their relationship to metabolic parameters. Patients with CGL and AGL had markedly reduced serum adiponectin levels compared to those with FPLD and APL (median [range]: 1.5 [0.4-7.5], 3.2 [0.6-7.7], 6.9 [1.9-23.2] and 7.9 [3.1-13.3] microg/mL, respectively, p < 0.0001); the same trend was noted for serum leptin levels (0.63 [0.05-3.7], 2.18 [0.05-11.30], 2.86 [0.23-9.00] and 6.24 [1.21-10.4] ng/mL, respectively, p < 0.0001). Serum adiponectin levels correlated negatively with fasting serum triglycerides (r = -0.6, p < 0.001) and insulin levels (r = -0.5, p < 0.0001) and positively with serum high-density lipoprotein cholesterol levels (r = 0.5, p < 0.001). Serum adiponectin levels were lower in patients with diabetes compared to non-diabetic subjects (3.0 vs. 7.1 microg/mL, p < 0.001). Our results indicate that serum adiponectin and leptin levels are extremely low in patients with generalized lipodystrophies and may be related to severe insulin resistance and its metabolic complications in lipodystrophies.     

Cafeteria diet-induced obesity is associated with a low spontaneous growth hormone secretion and normal plasma insulin-like growth factor-I concentrations.

Pituitary growth hormone (GH) secretion has been shown to be blunted in human and animal obesity. With respect to human obesity, cafeteria diet-induced obesity might be an appropriate model to study spontaneous GH secretion. In 6 cafeteria diet-overfed obese male Wistar rats and 6 control rats with chronically implanted catheters, GH levels were measured every 15 min over 6 h by standard RIA. A significantly lower GH secretion, reflected by the integrated GH concentration, was found in the obese rats (median 16.46, [range 10.55-19.13] ng/ml x 6 h vs 35.63 [range 21.90-41.50] ng/ml x 6 h, P < 0.05). The GH secretion in the obese rats was significantly negatively correlated with the body fat percentage, assessed by dual X-ray absorptiometry (Rho = -0.95, P < 0.05). Median plasma insulin-like growth factor-I (IGF-I) concentration was comparable between the two groups, while the median insulin concentration was significantly higher in the obese group (1.95 [range 1.76-3.55] ng/ml vs 1.21 [range 0.86-2.13] ng/ml, P < 0.05). No significant correlation existed between GH secretion and the plasma insulin concentration. In conclusion, cafeteria diet-induced obesity is associated with a low spontaneous GH secretion and normal plasma IGF-I concentration. The hyperinsulinemia present in this model probably explains the normal IGF-I concentrations, but not the GH hyposecretion.     

Pubertal alterations in growth and body composition: IX. Altered spontaneous secretion and metabolic clearance of growth hormone in overweight youth

Deconvolution analysis was used to determine 12-hour spontaneous nocturnal growth hormone (GH) secretion and GH half-life in lean (body mass index, <85th percentile; n = 39) and overweight (body mass index, > or =85th percentile; n = 18) youth. The integrated GH concentration, GH burst mass, and half-life were lower (P < .05) in overweight than in lean youth. For each unit increase in percentage of body fat, integrated serum GH concentrations, secretory burst mass, and half-life declined by 83.6 microg/L per minute (r = -0.39, P < .01), 0.22 microg/L (r = -0.28, P < .05), and 0.2 minute (r = -0.38, P < .01), respectively. The effect of overweight on GH secretion was independent of pubertal status. Hierarchical regression models tested the hypothesis that altered GH secretion in youth is more related to total adiposity than abdominal visceral fat. When age, sex, fat-free mass, testosterone, and estradiol were held constant, the sequential addition of abdominal visceral fat did not increase R2 for any GH secretion variable. Sequential addition of percentage of body fat increased R2 (P < .05) for integrated GH concentration, total secretory rate, secretory burst mass, and pulsatile production rate. We conclude that serum GH concentrations are reduced in overweight youth primarily because of reduced GH burst mass with no change in the number of secretory events and secondarily to reduced GH half-life. Based on the model that GH-releasing hormone predominantly increases GH pulse amplitude whereas somatostatin primarily controls GH pulse frequency, these results suggest that overweight in youth diminishes GH-releasing hormone stimulation resulting in truncated GH bursts but does not alter the number of somatostatin withdrawal intervals so that GH burst frequency is conserved.     

Recombinant human insulin-like growth factor I has significant anabolic effects in adults with growth hormone receptor deficiency: studies on protein, glucose, and lipid metabolism

The physiological effects of insulin-like growth factor I (IGF-I) on intermediate metabolism of substrates have been extensively studied in a variety of experimental situations in man, and its effects on linear growth of children with GH receptor mutations have proven beneficial. However, there is a paucity of data on the metabolic effects of IGF-I as replacement therapy in adults with GH receptor deficiency (Laron's syndrome). We designed these studies to investigate the in vivo effects of 8 weeks of therapy with recombinant human IGF-I (rhIGF-I) in a unique group of 10 adult subjects with profound IGF-I deficiency due to a mutation in the GH receptor gene (mean +/- SEM age, 29.2 +/- 2.0 yr; 4 males and 6 females). At baseline, patients had infusions of stable tracers, including L-[13C]leucine, [2H2]glucose, and d5-glycerol, as well as indirect calorimetry, assessment of body composition (dual energy x-ray absortiometry), and measurements of growth factor concentrations. Patients were then discharged to receive twice daily rhIGF-I (60 microg/kg, sc) for the next 8 weeks when the studies were repeated identically. Plasma IGF-I concentrations increased during rhIGF-I treatment from 9.3 +/- 1.5 microg/L to 153 +/- 23 (P = 0.0001). There was no change in weight during these studies, but a significant change in body composition was observed, with a decrease in percent fat mass (P = 0.003) and an increase in lean body mass (P = 0.001). These were accompanied by increased rates of protein turnover, decreased protein oxidation, and increased rates of whole body protein synthesis, as measured by leucine tracer methods (P < 0.01). These results are similar to those observed in GH-deficient subjects treated with GH. All measures of lipolytic activity and fat oxidation increased during treatment, with an 18% increase in the glycerol turnover rate (P = 0.04), an increase in free fatty acid and beta-hydroxybutyrate concentrations, and a significant increase in fat oxidation, as measured by indirect calorimetry (P = 0.04). There were significant decreases in insulin concentrations (P = 0.01) and a reciprocal increase in glucose production rates (P = 0.04) during rhIGF-I, yet plasma glucose concentrations remained constant, suggestive of a significant insulin-like action of this peptide. RhIGF-I was well tolerated by all patients. In conclusion, 8 weeks of treatment with rhIGF-I had significant positive effects on body composition and measures of intermediate metabolism independent of GH. These results suggest that, similar to GH treatment of adults with GH deficiency, rhIGF-I may be beneficial as long term replacement therapy for the adult patient with Laron's syndrome.