Highly active antiretroviral therapy dysregulates proliferation and differentiation of human pre-adipocytes

AIM

To investigate the mechanism(s) by which potential effects of multi-drug highly-active antiretroviral therapy contributes to lipodystrophy syndrome.

METHODS

Preadipocytes from healthy donors were assessed for proliferation and differentiation in the presence of nucleoside reverse transcriptase inhibitors (NRTIs), nonnucleoside reverse transcriptase inhibitors (NNRTIs), and protease inhibitors (PIs) individually and in combination. Effects on proliferation were assessed with a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide assay and effects on differentiation were assessed from glycerol-3-phosphate dehydrogenase (GP DH) activity and quantitation of Oil Red O staining for intracellular lipid. Data were analyzed with a randomized block ANOVA with post-hoc Fisher’s Least Significant Difference test.

RESULTS

Preadipocyte proliferation was inhibited by a combination of NNRTI + NRTI (14% at 48 h, P < 0.001) and PI + NRTI (19% at 48 h, P < 0.001) with additional suppression when ritonavir (RTV) was added (26% at 48 h). The drug combination of atazanavir (ATV) + RTV + emtricitabine (FTC) + tenofovir (TDF) had the greatest inhibitory effect on proliferation at 48 h. Preadipocyte differentiation was most significantly reduced by the efavirenz + FTC + TDF assessed either by GPDH activity (64%) or lipid accumulation (39%), P < 0.001. Combining NRTIs with a PI (ATV + FTC + TDF) significantly suppressed differentiation (GPDH activity reduced 29%, lipid accumulation reduced by 19%, P < 0.01). This effect was slightly greater when a boosting amount of RTV was added (ATV + FTC + TDF + RTV, P < 0.001).

CONCLUSION

Although combination antiretroviral therapy is clinically more efficacious than single drug regimens, it also has a much greater inhibitory effect on preadipocyte proliferation and differentiation.

Changes in diabetes medications in the Diabetes and Periodontal Therapy Trial and their effect on hemoglobin A1c (HbA1c)

OBJECTIVE

Evaluate the effect of medications and medication changes during the Diabetes and Periodontal Therapy Trial (DPTT) on the primary study outcome, namely, change in hemoglobin A1c (HbA1c) at 6months following baseline.

METHODS

The DPTT set strict criteria for changes in diabetes medications. Medication change was defined as: change in dose of any 1 oral hypoglycemic agent by more than two-fold, change in dose of insulin of >10% and/or addition or subtraction of an oral hypoglycemic agent, insulin or non-insulin injectable agents. Comparisons between the treatment (non- surgical periodontal therapy) and control (no therapy) groups used t-tests for continuous variables and chi-square tests for categorical variables, including DPTT defined diabetes medication changes between baseline (BL) and 3month visits and 3- and 6-month visits. Changes in HbA1c were compared across the four medication change categories using ANOVA models, overall and for each treatment group separately.

RESULTS

Baseline medication use was similar between the treatment groups (p>0.40), as were medication changes between BL- 3month visits and 3 and 6month visits (p=0.58). Participants with higher BL HbA1c (>8%) and those taking insulin at BL were more likely to have a change in medication (p=0.03).

CONCLUSIONS

The DPTT had the most rigorous definition of medication changes and medication monitoring of any trial in this field to date. The absence of a significant difference in medication changes between treatment groups may suggest that such changes did not play a role in the negative outcome of the DPTT.

The effect of nonsurgical periodontal therapy on hemoglobin A1c levels in persons with type 2 diabetes and chronic periodontitis: a randomized clinical trial

IMPORTANCE

Chronic periodontitis, a destructive inflammatory disorder of the supporting structures of the teeth, is prevalent in patients with diabetes. Limited evidence suggests that periodontal therapy may improve glycemic control.

OBJECTIVE

To determine if nonsurgical periodontal treatment reduces levels of glycated hemoglobin (HbA1c) in persons with type 2 diabetes and moderate to advanced chronic periodontitis.

DESIGN, SETTING, AND PARTICIPANTS

The Diabetes and Periodontal Therapy Trial (DPTT), a 6-month, single-masked, multicenter, randomized clinical trial. Participants had type 2 diabetes, were taking stable doses of medications, had HbA1c levels between 7% and less than 9%, and untreated chronic periodontitis. Five hundred fourteen participants were enrolled between November 2009 and March 2012 from diabetes and dental clinics and communities affiliated with 5 academic medical centers.

INTERVENTIONS

The treatment group (n = 257) received scaling and root planing plus chlorhexidine oral rinse at baseline and supportive periodontal therapy at 3 and 6 months. The control group (n = 257) received no treatment for 6 months.

MAIN OUTCOMES AND MEASURES

Difference in change in HbA1c level from baseline between groups at 6 months. Secondary outcomes included changes in probing pocket depths, clinical attachment loss, bleeding on probing, gingival index, fasting glucose level, and Homeostasis Model Assessment (HOMA2) score.

RESULTS

Enrollment was stopped early because of futility. At 6 months, mean HbA1c levels in the periodontal therapy group increased 0.17% (SD, 1.0), compared with 0.11% (SD, 1.0) in the control group, with no significant difference between groups based on a linear regression model adjusting for clinical site (mean difference, -0.05% [95% CI, -0.23% to 0.12%]; P = .55). Periodontal measures improved in the treatment group compared with the control group at 6 months, with adjusted between-group differences of 0.28 mm (95% CI, 0.18 to 0.37) for probing depth, 0.25 mm (95% CI, 0.14 to 0.36) for clinical attachment loss, 13.1% (95% CI, 8.1% to 18.1%) for bleeding on probing, and 0.27 (95% CI, 0.17 to 0.37) for gingival index (P < .001 for all).

CONCLUSIONS AND RELEVANCE

Nonsurgical periodontal therapy did not improve glycemic control in patients with type 2 diabetes and moderate to advanced chronic periodontitis. These findings do not support the use of nonsurgical periodontal treatment in patients with diabetes for the purpose of lowering levels of HbA1c.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00997178.

Peripheral fat loss and decline in adipogenesis in older humans

OBJECTIVE

Aging is associated with a redistribution of body fat including a relative loss of subcutaneous peripheral fat. These changes in body fat can have important clinical consequences since they are linked to increased risk of metabolic complications. The causes and mechanisms of loss of peripheral fat associated with aging are not clear. The aim of this study was to assess whether defects in adipogenesis contribute to fat loss in aging humans, as suggested from animal studies, and to evaluate the role of inflammation on pathogenesis of fat loss.

MATERIALS/METHODS

Preadipocytes isolated from subcutaneous peripheral fat of healthy young and elderly subjects were compared in their ability to replicate and differentiate.

RESULTS

The results show that both the rate of replication and differentiation of preadipocytes are reduced in older subjects. The reduction in adipogenesis is accompanied by a higher plasma level of the inflammatory marker, soluble tumor necrosis factor receptor 2, and greater release of tumor necrosis factor α from fat tissue.

CONCLUSIONS

Thus, the gradual relative loss of peripheral fat in aging humans may in part result from a defect in adipogenesis, which may be linked to inflammation and increased release of proinflammatory cytokines from fat tissue.

Rosiglitazone-Mediated Effects on Skeletal Muscle Gene Expression Correlate with Improvements in Insulin Sensitivity in Individuals with HIV-Insulin Resistance

Rosiglitazone, an agonist of peroxisome proliferator activated receptor (PPARγ), improves insulin sensitivity by increasing insulin-stimulated glucose uptake into muscle tissue. This study was undertaken to assess changes in expression of PPAR-regulated genes in muscle tissue following treatment of HIV-associated insulin resistance with rosiglitazone. Muscle gene expression was assessed in twenty-two seronegative HIV subjects (control), 21 HIV-infected individuals with normal insulin sensitivity (HIV-IS) and 19 HIV-infected individuals with insulin resistance (HIV-IR). A subset of the HIV-IR group (N=10) were re-evaluated 12 weeks after treatment with 8 mg/d of rosiglitazone. The HIV-IR group's rosiglitazone-mediated improvement in insulin sensitivity was highly correlated with increased expression of PPARγ and carnitine palmitoyl transferase-1 (CPT-1), (r=0.87, P<.001) and (r=0.95, P<.001), respectively. The changes in PPARγ expression were also correlated with the changes in CPT1 expression (r=0.75, P=.009). The results suggest that rosiglitazone; may have a direct effect on muscle tissue to improve insulin sensitivity.

Effect of ritonavir and atazanavir on human subcutaneous preadipocyte proliferation and differentiation

Protease inhibitors (PIs) have been implicated in the development of HIV-associated lipodystrophy through a reduction in the differentiation of preadipocytes. While atazanavir (ATV) is associated with fewer clinical metabolic abnormalities in the short-term, the effects of long-term exposure are not known. ATV effects on preadipocyte replication or differentiation would indicate the potential for long-term problems. This study compared ritonavir (RTV) and ATV effects on preadipocyte replication and differentiation in human primary cultures. Preadipocytes from subcutaneous fat were studied in the presence of therapeutic concentrations of RTV and ATV for replication, differentiation, and adipokine secretion. The effects of the drugs on the expression of PPARgamma and related genes during differentiation were also assessed by real-time quantitative PCR. RTV induced a significant inhibition of preadipocyte proliferation, differentiation and adiponectin secretion. ATV at concentrations within the range of therapeutic levels did not affect differentiation or adiponectin secretion, but did have inhibitory effects on preadipocyte proliferation. Inhibition of differentiation by PIs was associated with decreased expression of PPARgamma, C/EBPalpha, and aP2 genes. In summary, although ATV at therapeutic levels has a smaller impact on adipogenesis, alterations in preadipocyte proliferation suggest the potential for adverse effects with long-term use.

Feeding acutely stimulates fibrinogen synthesis in healthy young and elderly adults

Fibrinogen is a positive acute-phase protein and its hepatic synthesis is enhanced following inflammation and injury. However, it is not clear whether fibrinogen synthesis is also responsive to oral nutrients and whether the response to a meal may be affected by age. Our aim in this study was to investigate the acute effect of oral feeding on fibrinogen synthesis in both young and elderly men and women. Fibrinogen synthesis was determined in 3 separate occasions from the incorporation of l[(2)H(5)]phenylalanine (43 mg/kg body weight) in 8 young (21-35 y) and 8 elderly (>60 y) participants following the ingestion of water (control), a complete liquid meal (15% protein, 30% fat, and 55% carbohydrate), or only the protein component of the meal. The ingestion of the complete meal enhanced fibrinogen fractional synthesis rates (FSR) by 17 +/- 6% in the young and by 38 +/- 10% in the elderly participants compared with the water meal (P < 0.02). A comparable stimulation of FSR occurred with only the protein component of the meal in both young (29 +/- 7%) and elderly participants (41 +/- 9%) compared with the water meal (P < 0.005). Similar results were obtained when fibrinogen synthesis was expressed as absolute synthesis rates (i.e. mg.kg(-1).d(-1)). The results demonstrate that fibrinogen synthesis is acutely stimulated after ingestion of a meal and that this effect can be reproduced by the protein component of the meal alone, both in young and elderly adults.

Influence of age on the association of retinol-binding protein 4 with metabolic syndrome

OBJECTIVE

The relationships of retinol-binding protein 4 (RBP4) with insulin sensitivity and body fat distribution have been investigated in a few recent studies with conflicting results. This may have been due to differences in ages of the subjects in the different studies. The aim of this study was to investigate whether the association of RBP4 and insulin sensitivity and percent trunk fat are influenced by age.

METHODS AND PROCEDURES

Cross-sectional analyses of 48 young subjects and 55 elderly subjects. Insulin sensitivity was determined by a hyperinsulinemic-euglycemic clamp. Body fat distribution was determined by a dual-energy X-ray absorptiometry (DXA).

RESULTS

In the young subjects, RBP4 levels were associated with insulin sensitivity (r = -0.30, P = 0.04), percent trunk fat (r = 0.54, P < 0.001), triglycerides (r = 0.44, P = 0.003), low-density lipoprotein (r = 0.38, P = 0.01). In contrast, in the elderly subjects there was no correlation between RBP4 levels and insulin sensitivity (r = -0.18, P = 0.20), percent trunk fat (r = 0.00, P = 0.10), triglycerides (r = 0.25, P = 0.10), and low-density lipoprotein (r = -0.11, P = 0.47).

DISCUSSION

The associations of RBP4 with insulin sensitivity, percent trunk fat, and lipid levels are influenced by age.

Chromium picolinate for insulin resistance in subjects with HIV disease: a pilot study

AIM

Multidrug regimens in HIV disease are associated with an increased incidence of insulin resistance, by as much as 50%. Not only does insulin resistance predisposes subjects to diabetes but also it is associated with the metabolic syndrome and increased risk of cardiovascular disease. Previous studies suggest that chromium picolinate can improve insulin resistance in patients with type 2 diabetes. The objective was to study the efficacy and safety of chromium picolinate as a treatment of insulin resistance in subjects infected with HIV.

METHODS

The ability of chromium picolinate (1000 mug/day) to improve insulin sensitivity, determined with a hyperinsulinaemic-euglycaemic insulin clamp, was determined in eight HIV-positive subjects on highly active antiretroviral therapy.

RESULTS

The mean rate of glucose disposal during the clamp was 4.41 mg glucose/kg lean body mass (LBM)/min (range 2.67-5.50), which increased to 6.51 mg/kg LBM/min (range 3.19-12.78, p = .03), an increase of 25% after 8 weeks of treatment with chromium picolinate. There were no significant changes in blood parameters, HIV viral burden or CD4+ lymphocytes with chromium picolinate treatment. Two subjects experienced abnormalities of liver function during the study. Another subject experienced an elevation in blood urea nitrogen.

CONCLUSIONS

The study shows that chromium picolinate therapy improves insulin resistance in some HIV-positive subjects, but with some concerns about safety in this population.

Limb fat to trunk fat ratio in elderly persons is a strong determinant of insulin resistance and adiponectin levels

BACKGROUND

Similar to lipodystrophy syndromes, aging results in increased visceral adiposity with loss of subcutaneous adipose tissue in the extremities. The hypothesis of this study is that the distribution of limb fat to trunk fat (LF/TF) ratio in elderly persons has a stronger correlation than trunk fat alone to insulin resistance and adiponectin levels.

METHODS

Thirty-eight elderly participants were divided into an insulin-resistant (IR) group and an insulin-sensitive (IS) group. Limb fat and trunk fat were measured by dual-energy x-ray absorptiometry. Insulin resistance was measured by a hyperinsulinemic-euglycemic clamp.

RESULTS

There was no significant difference between the IS and IR groups with respect to body mass index, body fat index, absolute amount of trunk fat, or percent body fat. However, the difference in LF/TF ratio between the IS (1.02 +/- 0.05) and the IR groups (0.77 +/- 0.05) was highly significantly different (p <.001). Insulin resistance had a stronger correlation to the LF/TF ratio (r = 0.61, p <.001) than to absolute trunk fat (r = -0.32, p =.051). Adiponectin levels had a strong association with the LF/TF ratio (r = 0.63, p <.001), but did not correlate to absolute trunk fat (r = -0.24, p =.18).

CONCLUSIONS

The distribution of body fat (LF/TF ratio) in elderly persons is a stronger determinant of insulin resistance and adiponectin levels than is trunk fat alone. The LF/TF ratio can be a useful tool to assess insulin sensitivity in the elderly population.

Wall suction applied to needle muscle biopsy - a novel technique for increasing sample size

BACKGROUND

The needle biopsy technique described by Bergström is the most commonly used technique to obtain samples to assess muscle metabolism. Sampling of muscle, particularly the vastus lateralis, has become an essential tool in biomedical and clinical research. Optimal sample size is critical for availability of tissue for processing. To evaluate the effectiveness of a novel technique to obtain adequate sample size using wall suction applied to needle muscle biopsy, we collected samples from subjects in on-going clinical studies for gene expression.

MATERIALS AND METHODS

Muscle biopsy samples of the vastus lateralis using 6 mm Bergström needles under local anesthesia were obtained from 55 subjects who had volunteered to participate in this research project. The vastus lateralis was biopsied according to the methods described by Bergström with a 6 mm biopsy needle. Wall suction was applied to the inner bore of the biopsy needle after the needle was inserted into the muscle.

RESULTS

The mean sample of biopsy taken using the 6 mm was 233 mg (n = 55). The wall suction (200 mm Hg) applied to the needle pulled the surrounding tissue into the central bore of the needle. The quality of the samples was adequate for all biochemical assays. The biopsy technique did not result in any complications due to infection or bleeding.

CONCLUSIONS

Using a novel technique of connecting a 6 mm Bergström biopsy needle to wall suction, we have obtained 200 to 300 mg muscle biopsy specimens uniformly, with ease, and minimal discomfort. An increase in sample size allows for a wider variety of biochemical and histopathological analysis.

Retinol-binding protein 4 is associated with insulin resistance and body fat distribution in nonobese subjects without type 2 diabetes

BACKGROUND

Adipose tissue is responsible for releasing various adipokines that have been related to insulin resistance. Understanding the relationship of these adipokines to insulin resistance may foster the development of new treatments for diabetes.

OBJECTIVES

The primary objective of this study was to determine whether an association between retinol-binding protein 4 (RBP4) and insulin resistance exists in nonobese individuals without a family history or diagnosis of diabetes. The secondary objective was to determine by a dual energy x-ray absorptiometry scan which adipose tissue depot most closely relates to RBP4 levels.

DESIGN

Cross-sectional analysis of 92 study participants ranging in age from 20 to 83 yr was performed. The range of body mass index (BMI) was from 18 to 30 kg/m(2). Exclusion criteria were a BMI greater than 30 kg/m(2), family history of diabetes, or a diagnosis of diabetes. Insulin sensitivity was determined by a hyperinsulinemic euglycemic clamp. Body fat was measured by dual energy x-ray absorptiometry scan.

RESULTS

RBP4 values were lower in females (35.8 +/- 1.7 microg/ml) compared with males (39.9 +/- 1.4 microg/ml; P = 0.06). RBP4 levels were found to correlate negatively with insulin sensitivity (r = -0.32; P = 0.002) and positively with age (r = 0.38; P < 0.001). RBP4 levels did not correlate with BMI (r = -0.13; P = 0.22), trunk fat (r = 0.16; P = 0.22), or percent body fat (r = 0.07; P = 0.65). However, RBP4 levels did correlate with percent trunk fat (r = 0.36; P = 0.001).

CONCLUSION

These findings indicate a relationship between RBP4, insulin sensitivity, and percent trunk fat in individuals who may not have features of insulin resistance.

Response of albumin synthesis to oral nutrients in young and elderly subjects

BACKGROUND

The synthesis of albumin after oral ingestion of nutrients provides a means of storing amino acids, which can be made available during periods of fasting.

OBJECTIVE

This study was undertaken to see whether the response of albumin synthesis to the oral intake of nutrients is compromised in elderly subjects.

DESIGN

Albumin synthesis was determined from the incorporation of 43 mg l-[(2)H(5)]phenylalanine/kg body wt. Eight elderly subjects (aged >60 y) and 8 young subjects (aged 21-35 y) were studied on 3 separate occasions: after the intake of water, a liquid meal (with 15% of energy from protein, 30% of energy from fat, and 55% of energy from carbohydrate), or an isonitrogenous but not isocaloric meal containing only protein.

RESULTS

Mean (+/-SEM) albumin synthesis, expressed as an absolute rate (ie, the amount of albumin synthesized per day), was significantly lower in elderly subjects (108 +/- 7 mg . kg body wt(-1) . d(-1)) than in young subjects (141 +/- 7 mg . kg body wt(-1) . d(-1)). In response to the complete meal, albumin synthesis was significantly increased in both the elderly (144 +/- 7 mgkg body wt(-1) . d(-1)) and the young (187 +/- 11 mg . kg body wt(-1) . d(-1)) subjects. The protein component of the meal was sufficient to stimulate albumin synthesis in both the elderly (147 +/- 14 mg . kg body wt(-1) . d(-1)) and the young (182 +/- 6 mg . kg body wt(-1) . d(-1)) subjects.

CONCLUSIONS

Elderly subjects have lower rates of albumin synthesis than do young subjects during fasting, but they stimulate albumin synthesis proportionately in response to the oral ingestion of protein. The intakes of additional fat and carbohydrate do not stimulate albumin synthesis further.

The increase in human muscle protein synthesis induced by food intake is similar when assessed with the constant infusion and flooding techniques

Food intake is accompanied by a stimulation of muscle protein synthesis. However, the reported magnitude of the response differs with different methods of measurement. The aim of this study was to assess whether the response to feeding is dependent on the technique used for measurement when length and amount of feeding are controlled. Muscle protein fractional synthesis rates (FSRs) were measured both in the fasting and feeding states in 2 groups of healthy volunteers (n = 8). Two techniques were used to measure FSR: in one group, FSRs were assessed with a primed constant infusion of L-[2H5]phenylalanine, whereas in the other, a flooding amount of the same label was employed. The fasting FSRs assessed with the constant infusion method and estimated using the free amino acid in the tissue fluid to represent the precursor pool for protein synthesis were comparable to those obtained with the flooding method (1.94 +/- 0.15 vs. 1.86 +/- 0.13%/d). The degree of stimulation due to feeding (P < 0.02) did not differ between the constant infusion (+15%) and flooding (+22%) techniques. The stimulatory effect of feeding on muscle FSR was associated with enhanced phosphorylation of the Mr = 70,000 ribosomal protein S6 kinase, suggesting that it may involve activation of translation. This study demonstrates that human muscle FSRs obtained with the constant infusion technique are comparable to those obtained with the flooding method and that, in response to feeding, the 2 techniques give comparable estimates of stimulation.

Insulin and carbohydrate dysregulation

Patients with human immunodeficiency virus receiving highly active antiretroviral therapy (HAART) may experience abnormal body composition changes as well as metabolic abnormalities, including dyslipidemia, increases in triglycerides, low high-density lipoprotein cholesterol levels, and abnormal carbohydrate metabolism, ranging from insulin resistance with and without glucose intolerance to frank diabetes. Whether the body composition changes (i.e., increased visceral adiposity and fat wasting in the peripheral tissues) are linked to abnormalities in carbohydrate metabolism is unclear. The use of HAART with and without therapy with protease inhibitors (PIs) is related to carbohydrate abnormalities and changes in body composition. Regimens that include PIs appear to have a higher incidence of insulin resistance (up to 90%) and diabetes mellitus (up to 40%). The etiology of these abnormalities is not well understood; what is known about insulin and carbohydrate dysregulation with HAART is discussed.

Adiponectin and leptin levels in HIV-infected subjects with insulin resistance and body fat redistribution

In this study, we sought to determine the relationship between serum levels of leptin and adiponectin (Acrp30) in patients with HIV-associated lipodystrophy (HIV-LD). Three groups of subjects were studied; HIV-positive subjects with lipodystrophy (HIV-LD; n = 22), HIV-positive subjects without lipodystrophy (HIV; n = 17), and ethnicity- and body mass index-matched healthy control subjects (n = 20). Although total body fat from dual energy x-ray absorptiometry was similar in all three groups, the HIV-LD group had a significantly lower mean proportion of body fat in the limbs +/- SEM (37.2% +/- 2.2%) than either controls (49.8% +/- 1.5%) or HIV subjects (45.7% +/- 2.0%). The HIV-LD group also had the lowest mean insulin sensitivity +/- SEM (5.11 +/- 0.59 mg of glucose/[kg of lean body mass. min] vs. 10.2 +/- 0.72 mg of glucose/[kg of lean body mass. min] in controls and 8.64 +/- 0.69 mg of glucose/[kg of lean body mass. min] in the HIV group). Leptin levels were similar in all three groups and were significantly correlated to total body fat (r = 0.86; p <.001), but these levels did not correlate with either insulin sensitivity or limb fat. Mean Acrp30 levels +/- SEM were lowest in the HIV-LD group (5.43 +/- 0.44 microg/mL vs. 11.2 +/- 1.4 microg/mL in the HIV group and 14.9 +/- 1.8 microg/mL in control subjects). Further, Acrp30 levels were positively correlated with insulin sensitivity (r = 0.610; p <.001) and limb fat (r = 0.483; p <.001). However, the correlation between limb fat and insulin sensitivity disappeared when Acrp30 level and other potential mediators were removed from the association, suggesting that a deficiency in Acrp30 in subjects with HIV-LD may be part of the mechanism for the reduced insulin sensitivity.

Improved insulin sensitivity and body fat distribution in HIV-infected patients treated with rosiglitazone: a pilot study

The insulin-sensitizing drugs thiazolidinediones (TZDs), such as rosiglitazone, improve insulin sensitivity and also promote adipocyte differentiation in vitro. The authors hypothesized that TZDs might be beneficial to patients with HIV disease to improve insulin sensitivity and the distribution of body fat by increasing peripheral fat. The ability of rosiglitazone (8 mg/d) to improve insulin sensitivity (from hyperinsulinemic-euglycemic clamp) and to improve body fat distribution (determined from computed tomography measurements of visceral adipose tissue [VAT] and subcutaneous adipose tissue [SAT]) was determined in 8 HIV-positive patients. Before treatment, the insulin sensitivity of the patients was reduced to approximately 34% of that in control subjects. The rate of glucose disposal during a hyperinsulinemic-euglycemic clamp (Rd) was 3.8 +/-.4 (SEM) mg glucose/kg lean body mass/min compared with 11.08 +/- 1.1 (p<.001) in healthy age- and body mass index (BMI)-matched control subjects. After rosiglitazone treatment of 6 to 12 weeks, Rd increased to 5.99 +/-.9 (p=.02), an improvement of 59 +/- 22%. SAT increased by 23 +/- 10% (p=.05), and, surprisingly, VAT was decreased by 21 +/- 8% (p=.04) with a trend for increased SAT/VAT that failed to reach statistical significance. There were no significant changes in blood counts, viral loads, or CD4 counts with rosiglitazone treatment. The study demonstrates that rosiglitazone therapy improves insulin resistance and body fat distribution in some patients with HIV disease.

Cushing's disease after surgical resection and radiation therapy for nonfunctioning pituitary adenoma

OBJECTIVE

To describe a patient with an aggressive nonfunctioning pituitary adenoma in whom Cushing's disease developed after two resections of tumor and radiation therapy.

METHODS

We present a case report, with serial laboratory and immunohistochemical data, and summarize information about similar patients described in the medical literature.

RESULTS

A 48-year-old woman had irregular menstrual periods, decreased peripheral vision, headaches, and weight gain. Laboratory and radiologic investigation revealed a large nonfunctioning pituitary adenoma. Transsphenoidal subtotal resection of the tumor improved her vision. Results of immunohistochemical studies were positive for b-follicle-stimulating hormone and b-luteinizing hormone. She had radiation therapy 1 year postoperatively for rapidly enlarging residual tumor. Bifrontal craniotomy was done 3 months later because of worsening vision. The pituitary adenoma from the second surgical procedure stained negatively for all pituitary hormones. Postoperatively, she received tapering doses of prednisone for 4 months. Two months after the last dose of prednisone, she had signs and symptoms of hypercortisolism. Inferior petrosal sinus venous sampling studies for plasma corticotropin confirmed the presence of Cushing's disease. She did not tolerate medical therapy. Bilateral adrenalectomy led to remission of hypercortisolism.

CONCLUSION

Nonfunctioning pituitary tumors often come to clinical attention when they are large and cause symptoms associated with hypopituitarism or invasion of parasellar structures. In contrast, functioning pituitary tumors may have few compressive symptoms if they manifest with complaints attributable to excessive pituitary hormones.

Soluble tumour necrosis factor alpha receptor 2, a serum marker of resistance to the anabolic actions of growth hormone in subjects with HIV disease

Therapies are still being sought for the prevention of loss of body weight and lean body mass in HIV disease. The purpose of the present study was to identify a serum marker that would help in selecting patients who may be appropriate candidates for the use of anabolic agents, such as growth hormone, to restore lean body mass. This study included 26 HIV-infected patients and nine healthy controls, assessed previously for the effectiveness of 2 weeks of growth hormone administration in the stimulation of protein synthesis in skeletal muscle. Serum levels of interleukins-1beta, -6 and -10 were not useful predictors of the anabolic response to growth hormone. Serum concentrations of tumour necrosis factor alpha (TNFalpha) were significantly elevated (P<0.05) in patients with AIDS and AIDS-related weight loss, and there was a significant correlation between the serum concentration of interleukin-1 receptor antagonist and stage of disease (P=0.03). However, the serum concentration of the soluble TNFalpha receptor type 2 was most predictive of an inability of muscle protein synthesis to respond anabolically to growth hormone (r=-0.42, P=0.01). These data suggest that inflammation impacts on the responsiveness of muscle tissue to an anabolic stimulus, and that the soluble TNFalpha receptor type 2 provides a useful serum marker for metabolic dysfunction in HIV disease, which can be used to identify individuals likely to respond to growth hormone-based anabolic therapy.

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.

Association of severe insulin resistance with both loss of limb fat and elevated serum tumor necrosis factor receptor levels in HIV lipodystrophy

HIV-lipodystrophy (HIV-LD) is characterized by the loss of body fat from the limbs and face, an increase in truncal fat, insulin resistance, and hyperlipidemia, factors placing affected patients at increased risk for vascular disease. This study evaluated insulin sensitivity and inflammatory status associated with HIV-LD and provides suggestions about its etiology. Insulin sensitivity and immune activation markers were assessed in 12 control subjects and 2 HIV-positive groups, 14 without and 15 with LD syndrome. Peripheral insulin sensitivity (mostly skeletal muscle) was determined with the hyperinsulinemic-euglycemic clamp. Circulating insulin-like growth factor (IGF) binding protein-1 (IGFBP-1) and free fatty acid (FFA) levels, and their response to insulin infusion were indicative of insulin responsiveness of liver and adipose tissue, respectively. Serum levels of soluble type 2 tumor necrosis factor-alpha (TNF-alpha) receptor (sTNFR2) were used as an indicator of immune activation. HIV-LD study subjects had significantly reduced (twofold) peripheral insulin sensitivity, but normal levels of FFA and reduced levels of IGFBP-1, relative to the nonlipodystrophy groups, indicating that the loss of insulin sensitivity was more pronounced in skeletal muscle than in liver or fat. The significant loss of peripheral fat in the HIV-LD group (34%; p <.05) closely correlated with the reduced peripheral insulin sensitivity (p =. 0001). Levels of sTNFR2 were elevated in all HIV-infected study subjects, but they were significantly higher in those with lipodystrophy than without, and sTNFR2 levels strongly correlated with the reduction in insulin sensitivity (p =.0001). Loss of peripheral fat, normal levels of FFA, and reduced levels of IGFBP-1 indicate that insulin resistance in HIV-LD is distinct from type 2 diabetes and obesity. The relationship between the degree of insulin resistance and sTNFR2 levels suggests an inflammatory stimulus is contributing to the development of HIV-associated lipodystrophy.

The growth hormone/insulin-like growth factor axis in critical illness

Over the past several years, we have studied a variety of clinical conditions that are characterized by significant alterations in the GH/IGF system that might contribute to catabolism. Our studies have focused in detail on IGF-I and -II and the major IGFBPs in the circulation, IGFBP-3, -1, and -2; GH was also measured in some of these studies. In light of a recent study that has raised concerns about the use of GH in critically ill patients, we now review the changes in the GH/IGF axis during critical illness, the interaction between cytokines and the GH/IGF axis, and the safety and efficacy of GH therapy in critical illness. We conclude that it is premature to recommend interruption of GH therapy in patients with documented GH deficiency during periods of acute illness.

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.

Hormonal regulation of protein metabolism in relation to nutrition and disease

This paper examines the role of hormones in the normal responses of muscle protein synthesis to nutrient intake and the use of hormones to improve the effects of nutritional therapies in patients with protein-wasting conditions. In growing rats, the increase in muscle protein synthesis after feeding seems to be mediated by the rise in plasma insulin and also by an enhanced sensitivity of the muscle to insulin brought about by the amino acid leucine. In adult rats, however, the responsiveness of muscle to both feeding and insulin is much reduced, suggesting that changes in protein degradation play an important role in the response to feeding. Similarly, in adult humans, muscle protein synthesis is not affected by insulin, but is stimulated by insulin-like growth factor (IGF)-I and growth hormone (GH). The effect of GH treatment has been studied in a number of different groups of patients suffering from protein wasting, and improvements in nitrogen balance and lean body mass have been reported. In a study of patients with acquired immunodeficiency syndrome (AIDS), however, GH treatment for 2 wk caused a fall in muscle protein synthesis in the patients with wasting, despite an increase in healthy controls, suggesting that the responsiveness of muscle to the hormone may be altered by the stage of the disease.

Responsiveness of muscle protein synthesis to growth hormone administration in HIV-infected individuals declines with severity of disease

This study was undertaken to determine if human recombinant growth hormone (hrGH, 6 mg/d for 2 wk) would stimulate muscle protein synthesis in AIDS wasting. Healthy controls were compared with patients who were HIV+, had AIDS without weight loss, and had AIDS with > 10% weight loss. Before hrGH, rates of skeletal muscle protein synthesis, measured with l-[2H5]phenylalanine, were the same in controls and in all stages of disease. Rates of myofibrillar protein degradation, however, assessed from urinary excretion of 3-methyl histidine, were higher in AIDS and AIDS wasting than in HIV+ or healthy individuals. The group with weight loss had significantly higher TNFalpha levels but not higher HIV viral loads. Muscle function, as determined by isokinetic knee extension and shoulder flexion, was significantly higher in controls than all infected individuals. After GH, rates of protein synthesis were stimulated 27% in controls, with a smaller increase (11%) in HIV+, and a significant depression (42%) in AIDS with weight loss, despite fourfold elevation in insulin-like growth factor-I in all groups. There was a significant correlation of hrGH-induced changes in muscle protein synthesis with severity of disease (P = 0.002). The results indicate increased basal muscle protein degradation and decreased responsiveness of muscle protein synthesis to GH in the later stages of disease.

Transient exposure of human myoblasts to tumor necrosis factor-alpha inhibits serum and insulin-like growth factor-I stimulated protein synthesis

Tumor necrosis factor-alpha (TNF-alpha) induces cachexia and is postulated to be responsible for muscle wasting in several pathophysiological conditions. The purpose of the present study was to investigate whether exposure of human myoblasts to TNF-alpha could directly inhibit the ability of serum or insulin-like growth factor I (IGF-I) to stimulate protein synthesis as assessed by the incorporation of [3H]phenylalanine into protein. Serum and IGF-I stimulated protein synthesis dose dependently. Half-maximal stimulation of protein synthesis occurred at 05% serum and 8 ng/ml of IGF-I, respectively. TNF-alpha inhibited IGF-I-stimulated protein synthesis in a dose-dependent manner. Additionally, as little as 2 ng/ml of TNF-alpha impaired the ability of IGF-I to stimulate protein synthesis by 33% and, at a dose of 100 ng/ml, TNF-alpha completely prevented the increase in protein synthesis induced by either serum or a maximally stimulating dose of IGF-I. Inhibition of protein synthesis was independent of whether TNF-alpha and growth factors were added to cells simultaneously or if the cells were pretreated with growth factors. Exposure ofmyoblasts to TNF-alpha for 10 min completely inhibited serum-induced stimulation of protein synthesis. TNF-alpha inhibited protein synthesis up to 48 h after addition of the cytokine. TNF-alpha also inhibited serum-stimulated protein synthesis in human myoblasts that were differentiated into myotubes. In contrast, exposure of myoblasts to TNF-alpha had no effect on IGF-I binding and failed to alter the ability of either IGF-I or serum to stimulate [3H]thymidine uptake. These data indicate that transient exposure of myoblasts or myotubes to TNF-alpha inhibits protein synthesis. Thus, the anabolic actions of IGF-I on muscle protein synthesis may be impaired during catabolic conditions in which TNF-alpha is over expressed.

IGFBP-3. Functional and structural implications in aging and wasting syndromes

Over the last several years, the authors have studied the relationship of insulin-like growth factors (IGFs) and the insulin-like growth factor binding proteins (IGFBPs) in the circulation in a number of clinical settings. Patterns have emerged that seem to be characteristic of various conditions. In aging, there are marked decreases in IGF-I and -II, normal levels of IGFBP-3, and marked increases in IGFBP-1 in serum. Using ligand blotting and an IGFBP-3 proteolysis assay, BP-3 is intact. Based on native gel electrophoresis, IGFBP-1 is in its most highly phosphorylated state in those elders who have high IGFBP-1 levels. This pattern is slightly different in catabolic conditions such as AIDS (wasting in adults; failure to thrive in children), uncontrolled diabetes mellitus, trauma, and severe burns. In these conditions, serum levels of IGF-I and -II are markedly diminished, IGFBP-3 levels are also decreased, and IGFBP-1 levels are markedly increased. In addition, there is increased proteolysis of IGFBP-3 (AIDS failure to thrive, uncontrolled diabetes mellitus) and disruption of the ternary complex with decreased levels of ALS (AIDS wasting and burns). IGFBP-1 is in its most highly phosphorylated state in all catabolic conditions studied. Thus, the alterations in the circulating levels of IGFs and the changes in the physical state of the IGFBPs may lead to decreased anabolic activity and be a part of the mechanism of increased catabolism and wasting.

Acute alterations in growth hormone-insulin-like growth factor axis in humans injected with endotoxin

The purpose of the present study was to characterize the acute changes in the insulin-like growth factor (IGF) system in humans after administration of endotoxin (lipopolysaccharide; LPS). Escherichia coli LPS (4 ng/kg) was injected intravenously into healthy adults, and serial blood samples were collected for the next 5 h; subjects injected with saline served as time-matched controls. LPS administration resulted in a gradual decrease in the total extractable IGF-I concentration, which was reduced by approximately 20% over the final 2 h of the experiment; levels of free IGF-I were not significantly altered. LPS also produced a marked but transient elevation in growth hormone (GH) concentration. IGF-binding protein (BP)-1 levels were elevated more than fivefold 2 h after LPS injection, and thereafter levels gradually returned toward baseline. IGFBP-2 concentration also increased after LPS injection, but the maximal increase (approximately 50% above basal) was observed during the final 2 h of the protocol. In contrast, IGFBP-3 levels did not vary over the period examined in response to LPS, and there was no apparent increase in number of BP-3 proteolytic fragments. Cortisol levels were increased early and remained two- to threefold above baseline throughout the protocol. No significant alterations in serum concentration of glucose or insulin were noted. LPS also produced an early elevation in tumor necrosis factor and a later increase in interleukin-6. These data indicate that the acute changes in the GH-IGF axis in humans in response to LPS are comparable with those observed in humans in other traumatic conditions and in animal models of endotoxemia and infection.

Hypothalamic versus pituitary dysfunction in Down's syndrome as cause of growth retardation

We have found that some children with Down's syndrome (DS) have growth retardation secondary to growth hormone (GH) deficiency. To test the hypothesis that hypothalamic dysfunction is the primary cause for GH deficiency and growth retardation, hypothalamic-pituitary responses of serum GH concentrations to levodopa and clonidine as well as pituitary responses in serum GH concentrations to growth-hormone-releasing hormone (GHRH) were analysed in 14 prepubertal children with DS. Levodopa and clonidine were given, and blood was drawn for determining serum GH levels. Seven prepubertal control children had both levodopa and clonidine tests done. The delta serum GH during levodopa was 5.7 +/- 6.3 ng ml-1 in DS and 13.1 +/- 9.8 ng ml-1 in controls. The delta serum GH during clonidine administration was 3.0 +/- 3.2 ng ml-1 in DS and 17.3 +/- 5.6 ng ml-1 in controls. Children with DS had a significantly lower response to levodopa and clonidine, compared with controls by the Mann-Whitney U-test (P < 0.03 and P < 0.009, respectively). Growth-hormone-releasing hormone was given at 1 microgram kg-1 i.v. bolus and bloods for GH were drawn at-15, 0, 15, 30, 60, 90 and 120 min in 14 subjects with DS and 24 normal controls, both groups prepubertal. The mean delta serum GH concentration in DS was 53.6 +/- 38.3 ng ml-1, and it was 35.6 +/- 25.1 ng ml-1 in controls with P < 0.23 non-significant by the Mann-Whitney U-test. These results indicate that levodopa and clonidine (drugs stimulating hypothalamic GHRH release and secondary pituitary GH release in normal individuals) do not stimulate GH release in DS. Furthermore, normal GH response to GHRH in DS indicates normal pituitary function (normal somatotroph response to GHRH) and supports hypothalamic dysfunction in DS.

Effect of short-term fasting on free/dissociable insulin-like growth factor I concentrations in normal human serum

A small portion of circulating insulin-like growth factor I (IGF-I) is detected in the free or readily dissociable state, which is thought to be the metabolically active form. The amount of free/dissociable IGF-I in serum is dependent on a complex interplay between the production rate and the concentrations of IGF-I and IGF-binding proteins (IGFBPs). IGF availability is also influenced by posttranslational changes in IGFBPs that affect the affinity of IGFBPs for IGF-I. In the present study, we examined whether a short term fast (approximately 12 h) alters the serum concentration of free/dissociable IGF-I, and whether these changes are associated with alterations in IGFBP-1 and the proteolysis status of IGFBP-3. Circulating free/dissociable IGF-I concentrations, as assessed by a two-site immunoradiometric assay, did not differ between fasting and 4 h after a morning meal (1.48 +/- 0.07 vs. 1.50 +/- 0.07 microgram/L, respectively). Likewise, free/dissociable IGF-I levels measured by RIA after separation by centrifugal ultrafiltration were not different between the two groups (1.43 +/- 0.14 vs. 1.38 +/- 0.18 microgram/L, respectively). IGF-I bioactivity, as measured by thymidine incorporation by fibroblasts, did not differ in fasting and 4-h postprandial sera. There was no difference in IGFBP-3 and total acid-ethanol-extractable IGF-I concentrations in serum from fasted and fed subjects. In contrast, the concentration of IGFBP-1 in the serum was increased approximately 5-fold in the fasted state compared to fed values. IGFBP-1 existed in a highly phosphorylated form under fasting conditions. There was no change in IGFBP-3 proteolysis assessed either in vivo or in vitro between the fasting and fed states. The results indicate that a physiologically relevant short term overnight fast does not alter the circulating levels of free/dissociable IGF-I despite a marked elevation in IGFBP-1.

IL-6 stimulation of insulin-like growth factor binding protein (IGFBP)-1 production

TNF alpha and IL-1 beta have previously been shown to increase the IGFBP-1 concentration in plasma and liver under in vivo conditions. The present study demonstrates that another inflammatory cytokine, IL-6, also elevates a 30- to 32-kDa IGF binding protein in the plasma of mice. Moreover, IL-6 produced dose- and time-dependent increases in IGFBP-1 production by HepG2 cells. The maximal IL-6-induced increase in IGFBP-1 was comparable to that observed with dexamethasone, and this increase was attenuated by diltiazem or dantrolene, both of which are known to reduce the cytosolic Ca2+ concentration. Finally, incubation of HepG2 cells with TNF alpha or IL-1 beta also increased IGFBP-1 in a dose-dependent manner. These results demonstrate that IGFBP-1 production is mediated directly by proinflammatory cytokines and suggest that this mechanism may be important for the upregulation of IGFBP-1 seen in catabolic conditions associated with overexpression of these cytokines.

Proteolysis of insulin-like growth factor-binding protein-3 in human immunodeficiency virus-positive children who fail to thrive

Failure to thrive is a common manifestation of human immunodeficiency virus (HIV) infection in children. Given the role of insulin-like growth factor I (IGF-I) in stimulating postnatal growth, we have examined whether HIV-infected pediatric patients with growth failure have lower serum concentrations of IGF-I than age-matched control subjects. IGF-I was measured in 16 HIV-infected children and 13 HIV-negative controls. Ten of the HIV-infected children failed to thrive based on height and linear growth that was below the National Center for Health Statistics 10th percentile. IGF-I levels were significantly lower in children who failed to thrive compared to those in age-matched controls (20 vs. 60 micrograms/L; P < 0.001). Children who failed to thrive also displayed lower IGF-I levels than HIV-positive children, who exhibited normal growth velocity (20 vs. 91 micrograms/L; P < 0.001). Failure to thrive was associated with a significant reduction in circulating levels of IGF-binding protein-3 (IGFBP-3), as determined by ligand and Western blotting (P < 0.001), enhanced IGFBP-3 proteolysis (P < 0.001), and a decrease in the serum concentration of the acid-labile subunit of the IGFBP-3 ternary complex (P < 0.005). IGFBP-3 proteolysis was negatively correlated with IGF-I (r = 0.78) and IGFBP-3 levels (r = 0.70). Failure to thrive was associated with a reduction in the formation of the ternary complex, but the ternary complex could be restored by the addition of an excess of IGFBP-3 to serum. These results indicate that low levels of IGF-I, IGFBP-3, and acid-labile subunit are associated with a failure to thrive in HIV-infected children.

Regulation of the insulin-like growth factor system by insulin in burn patients

The aim of the present investigation was to determine whether there is a net uptake of insulin-like growth factor I (IGF-I) or IGF-binding proteins (IGFBPs) by the leg after burn injury and to elucidate the regulatory role of insulin exerted on this system under in vivo conditions in burn patients. Studies were performed on nine patients after burn injury (approximately 60% body surface area). Each patient was studied twice during a continuous infusion of a carbohydrate-rich enteral diet. Blood was collected simultaneously from the femoral artery and vein for the measurement of various elements of the IGF system after 7 days of enteral diet alone (basal period) and after 7 days of the enteral diet plus the infusion of insulin (insulin period). Data from these patients were compared to values in age-matched fed healthy volunteers. During the basal period, burn patients demonstrated a significant reduction in the venous concentration of IGF-I and an increase in both IGFBP-1 and -2 compared to control values. Insulin produced a significant 15% increase in the IGF-I concentration in burn patients, but decreased the circulating levels of IGFBP-1 by 50%. The IGF-I and IGFBP-1 concentrations at the end of the insulin period were still significantly different from those in control subjects. Burn patients also exhibited a marked reduction in intact IGFBP-3 and the acid-labile subunit under basal conditions, and these alterations were not reversed by insulin. Under basal conditions, all burn patients had a positive arterio-venous (A-V) difference for IGF-I across the leg. The A-V difference was increased 50% in response to insulin. The net uptake of IGF-I by the leg was 2.4 micrograms/min under basal conditions, and as leg blood flow also tended to increase in response to insulin, IGF-I uptake was elevated more than 3-fold during the insulin period. No A-V difference across the leg was detected for IGFBP-1, -2, or -3 in burn patients. In conclusion, burn injury in humans produces dramatic and sustained alterations in various components of the IGF system that persist despite adequate nutritional support. Our data indicate the presence of a net uptake of IGF-I by the leg in burn patients that may serve to counteract the catabolic state.

Wasting in the acquired immune deficiency syndrome is associated with multiple defects in the serum insulin-like growth factor system

OBJECTIVE

The aim of this investigation was to characterize the GH-IGF axis of patients with AIDS associated wasting. A special emphasis was placed on determining whether IGF binding proteins (IGFBPs) of patients who have lost more than 10% of their ideal body mass are structurally different from the IGFBPs of patients with no weight loss.

DESIGN AND PATIENTS

A cross-sectional study of 11 AIDS patients was performed to determine whether the IGF system is abnormal in AIDS patients with wasting. Seven additional AIDS patients were followed longitudinally to determine whether AIDS patients experience long-term changes to their IGF system.

MEASUREMENTS

Serum levels of GH and IGF-I were measured by radioimmunoassay, IGF-II was measured by radioreceptor assay, and IGFBP-1 was measured by an enzyme linked immunoassay. IGFBP-3 and IGFBP-3 protease activity were measured by ligand blotting and a BP-3 protease assay, respectively. IGFBP-3 ternary complex formation and IGFBP-1 phosphovariants were analysed by non-denaturing PAGE.

RESULTS

AIDS patients who had lost more than 10% of their ideal body mass demonstrated a 55% reduction in serum IGF-I (81 vs 179 micrograms/l) and a 70% reduction in IGF-II (226 vs 776 micrograms/l), compared to healthy HIV negative subjects. IGF-I levels were depressed, in some patients, despite high serum levels of GH. AIDS patients who had lost more than 10% of their ideal body mass had low levels of IGFBP-3 and a reduced ability to form the IGFBP-3 ternary complex. The IGFBP-3 ternary complex could be restored only upon addition of pure IGFBP-3 and acid labile subunit to serum. Serum IGFBP-1 was increased more than threefold compared to control subjects (90 vs 24 micrograms/l). IGFBP-1 was present as a free phosphoprotein in AIDS patients with low levels of IGF-I and in a bound form when serum IGF-I levels were normal. Changes in the GH-IGF axis were sustained for up to 25 months in AIDS patients with wasting.

CONCLUSIONS

AIDS wasting is associated with a GH resistant state that results in low levels of serum IGF-I, IGF-II and IGFBP-3, elevated levels of phosphorylated IGFBP-1, and a reduced ability to form the IGFBP-3 ternary complex.

Aging and immune function: a possible role for growth hormone

Elderly individuals have four to five times the case rate of cancer, tuberculosis and herpes zoster and six to seven times the fatality rate from pneumonia compared to young adults. This may be causally related to two changes that occur with aging, i.e. decreased growth hormone (GH)/insulin-like growth factor-1 (IGF-1) production and decreased immune function. Data from our laboratory as well as others have shown that, based on either GH secretory dynamics or IGF-1 levels, approximately 40% of adults aged 60 and older are GH deficient. In the same population of subjects, immune function decreases such that there is a decline in cell-mediated and humoral immune responsiveness. Some of these immune deficits have been shown to be reversed in humans and primates by GH and/or IGF-1 treatment. This paper will review some of these data.

Regulation of insulin-like growth factor-I (IGF-I) and IGF-binding proteins by tumor necrosis factor

The purpose of the present study was to determine 1) whether exogenous administration of tumor necrosis factor-alpha (TNF-alpha) alters insulin-like growth factor-I (IGF-I) and IGF-binding proteins (BPs) and 2) whether the enhanced endogenous production of TNF mediates the lipopolysaccharide (LPS)-induced changes in the IGF system. The overnight infusion of murine TNF-alpha reduced circulating concentrations of both growth hormone (GH) and IGF-I in fasted rats. Furthermore, TNF-alpha decreased IGF-I content in liver, gastrocnemius muscle, and pituitary. In contrast, TNF-alpha increased IGF-I content in kidney and brain. IGFBP-1 was increased in plasma, liver, and muscle in response to TNF-alpha. In a second study, rats were injected with LPS after treatment with a neutralizing anti-TNF antibody (Ab), and blood and tissues were collected 4 h later. In LPS-treated rats, plasma concentrations of GH and IGF-I were reduced. LPS also decreased the IGF-I content in liver and skeletal muscle and increased plasma, liver, and muscle concentrations of IGFBP-1. Pretreatment with anti-TNF Ab attenuated the LPS-induced reduction in IGF-I and the increased IGFBP-1 in plasma and liver and completely prevented the decrease in IGF-I observed in muscle. In contrast, the LPS-induced decrease in plasma GH and the increased IGFBP-1 observed in muscle were unaltered by the anti-TNF Ab.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in hepatic production and peripheral clearance of IGF-I after endotoxin

Lipopolysaccharide (LPS) produces a rapid and sustained reduction in the circulating concentration of insulin-like growth factor I (IGF-I), which may be responsible, in part, for the alterations in protein metabolism observed in these animals. The purpose of the present study was to determine whether this drop was due to a decreased hepatic production of IGF-I and/or an increased clearance of the peptide from the blood. Four hours after intravenous injection of LPS the plasma IGF-I concentration was decreased 50%. IGF-I release by in situ perfused livers from control rats was constant throughout the 60-min perfusion period and averaged 111 +/- 3 ng/min. In contrast, hepatic IGF-I output was decreased 46% by in vivo LPS. In contrast, livers from LPS-injected rats released more IGF binding proteins-1, -2 and -4 than did control livers. Hepatic cell isolation indicated that LPS decreased the IGF-I content in Kupffer and parenchymal cells, but not endothelial cells, by approximately 45%. Pharmacokinetic analysis of blood 125I-IGF-I decay curves indicated that the half-life for whole body clearance of 125I-IGF-I from the circulation was not altered by LPS. However, LPS increased 125I-IGF-I uptake by spleen, liver, lung, and kidney while decreasing uptake by the pancreas and gastrointestinal tract. These results indicate that the LPS-induced decrease in blood IGF-I concentration is primarily due to a reduction in hepatic production, not a change in whole body peptide clearance, and that a decreased production by both parenchymal and Kupffer cells contributes to this alteration.

Endocrine effects of erythropoietin

Uremic men may manifest a variety of hormonal abnormalities, including decreased serum concentrations of testosterone and thyroid hormones and increased serum levels of growth hormone and prolactin. Some previous investigations have reported that erythropoietin therapy may reverse these hormonal changes. To investigate this possibility further, we measured serum prolactin, testosterone, LH, FSH, TSH, free thyroxine, triiodothyronine, growth hormone and IGF-I in 21 generally elderly male hemodialysis patients before and during erythropoietin therapy; many of the patients also received an anabolic steroid or metoclopramide treatment. Despite a significant erythropoietic response in a majority of the subjects, no significant changes were seen in any of the hormonal parameters other than a small decrease in serum growth hormone concentrations. Advanced age and chronic illness in our patients may have played a role in limiting the hormonal response reported by others.

Alterations in the insulin-like growth factor system in trauma patients

The aim of the present study was to elucidate changes in the growth hormone (GH)-insulin-like growth factor (IGF) axis in trauma patients throughout their stay in the surgical intensive care unit (SICU). The first venous blood sample was obtained within 24 h after admission to the SICU and before the start of nutritional support; the last sample was obtained within 24 h of each patient's discharge from the SICU. All patients were receiving nutritional support at this later time. Control subjects were healthy volunteers, matched for age and sex and fasted approximately 18 h before blood sampling. GH in trauma patients was increased 25-fold on the first day and was still elevated > or = 5-fold on the last day. Trauma decreased circulating levels of both IGF-I (50-60%) and IGF-II (33-45%) throughout the duration of the patients' stay in the SICU. A sustained reduction in plasma IGF-binding protein (BP)-3 (55-75%) was observed in trauma patients throughout the protocol. In contrast, IGFBP-1 levels increased more than threefold during this same period. Furthermore, IGFBP-1 in these patients had undergone posttranslational modification and existed primarily in a highly phosphorylated form. Blood, collected from a cohort (n = 3) of these patients within 24 h of their discharge from the hospital, indicated that IGF-I and IGF-II were still reduced (30%) and that the decrease in IGFBP-3 and the elevation in IGFBP-1 were still evident at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of insulin on the insulin-like growth factor system in children with new-onset insulin-dependent diabetes mellitus

To further characterize the mechanism of impaired growth in children with insulin-dependent diabetes mellitus, we examined the serum components of the insulin-like growth factor (IGF) system in 11 children with new-onset insulin-dependent diabetes mellitus and followed the effect of insulinization on the IGF system longitudinally 1 day, 1 week, and 1 month after starting insulin treatment. Before insulin therapy, serum IGF-I, IGF-II, IGF-binding protein-3 (IGFBP-3), and GH-binding protein (GHBP) levels were significantly decreased, whereas IGFBP-1 and cortisol were significantly increased in diabetic children compared to those in an age-, sex-, and stage of puberty-matched control group. Random serum GH concentrations did not differ significantly. The alterations in the IGF system reversed with insulin therapy in a sequential manner. IGFBP-1 fell rapidly and was comparable to control values within 24 h after insulin treatment. IGF-I rose 1 week after treatment, reaching levels comparable to those in controls and continued to rise through 1 month of treatment. IGF-II, IGFBP-3, and GHBP showed a slower pattern of change, with their levels reaching control values only 1 month after the start of insulin treatment. Improvement in glycemic control, as determined by a change in hemoglobin-A1c, correlated positively with improvement in IGF-I, IGF-II, IGFBP-3, GHBP, and weight gain after 1 month of insulin therapy. These data are consistent with the hypothesis that changes in the IGF system in the insulinopenic state are similar to those during nutritional deprivation and may serve to minimize IGF's anabolic actions. The decreases in IGF-I, IGF-II, and IGFBP-3 may in part be due to a decrease in the GHBP/receptor. However, the observation that an increase in serum IGF-I was observed earlier than an increase in GHBP and without a significant change in serum GH suggests a direct stimulatory effect of insulin on liver IGF-I production or reversal by insulin of some postreceptor defect in GH action independent of GHBP.

Phosphorylation of insulin-like growth factor binding protein-1 in patients with insulin-dependent diabetes mellitus and severe trauma

We have determined the level of phosphorylated insulin-like growth factor binding protein-1 (pIGFBP-1) in serum during two catabolic states: diabetes mellitus and trauma. Human sera were incubated with [125I]IGF-I for 2 h followed by non-denaturing PAGE. [125I]IGF-I/IGFBP-1 complexes from serum co-migrated with a pure p4IGFBP-1 standard. Complex formation was specifically inhibited by unlabeled IGF-I. The migration of IGF-I/pIGFBP-1 complexes was retarded by IGFBP-1 antibodies, but not by antibodies against IGFBP-2 or IGFBP-3. Sera from three severely traumatized patients had up to 12-fold more pIGFBP-1 than sera from age-matched controls. The level of pIGFBP-1 was reduced in all three patients upon hospital discharge. Sera from three patients with insulin dependent diabetes mellitus (IDDM) and severe ketoacidosis (DKA) had more pIGFBP-1 than controls. Administration of insulin to DKA patients lowered the level of pIGFBP-1. The present study shows that IGFBP-1 exists as a free, high affinity, phosphorylated form in vivo during two catabolic states.