Growth factors, glucose and insulin kinetics after low dose growth hormone therapy in HIV-lipodystrophy

Sustained low-dose growth hormone therapy optimizes bioactive insulin-like growth factor-I level and may enhance CD4 T-cell number in HIV infection

High-dose recombinant human growth hormone (rhGH) (2-6 mg/day) regimes may facilitate T-cell restoration in patients infected with human immunodeficiency virus (HIV) on highly active antiretroviral therapy (HAART). However, high-dose rhGH regimens increase insulin-like growth factor-I (IGF-I) to supra-physiological levels associated with severe side effects. The present study investigated whether lower doses of rhGH may improve T-cell restoration in patients infected with HIV following an expedient response of total and bioactive (i.e., free) IGF-I. A previous 16-week pilot-study included six HIV-infected patients on stable HAART to receive rhGH 0.7 mg/day, which increased total (+117%, P < 0.01) and free (+155%, P < 0.01) IGF-I levels. The study was extended to examine whether continuous use of low-dose rhGH (0.7 mg/day until week 60; 0.4 mg/day from week 60 to week 140) would maintain expedient IGF-I levels and improve CD4 T-cell response. Total and free IGF-I increased at week 36 (+97%, P < 0.01 and +125%, P < 0.01, respectively) and week 60 (+77%, P = 0.01 and +125%, P < 0.01) compared to baseline levels (161 +/- 15 and 0.75 +/- 0.11 microg/L). CD4 T-cell number increased at week 36 (+15%, P < 0.05) and week 60 (+31%, P = 0.01) compared to baseline levels (456 +/- 55 cells/microL). Following rhGH dose reduction, total IGF-I and CD4 T-cell number remained increased at week 88 (+44%, P = 0.01 and +33%, P < 0.01) and week 140 (+46%, P = 0.07 and +36%, P = 0.02) compared to baseline levels. These data support the notion that low-dose rhGH regimens may increase expediently total and bioactive IGF-I and improve T-cell restoration in patients infected with HIV on HAART.

Long-term high-physiological-dose growth hormone reduces intra-abdominal fat in HIV-infected patients with a neutral effect on glucose metabolism

OBJECTIVES

The aim of the study was to investigate the effect of long-term high-physiological-dose recombinant human growth hormone (rhGH) therapy on fat distribution and glucose metabolism in HIV-infected patients.

METHODS

Forty-six HIV-infected Caucasian men on highly active antiretroviral therapy (HAART), with an age range of 21-60 years and no significant comorbidity, were included in this randomized, placebo-controlled, double-blind, single-centre trial. Twenty-eight subjects were randomized to 0.7 mg/day rhGH, and 18 subjects to placebo, administered as daily subcutaneous injections between 1 and 3 pm for 40 weeks. Endpoints included changes in visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), limb fat mass, percentage of limb fat, plasma lipids, insulin resistance and glucose tolerance.

RESULTS

VAT and trunk fat mass decreased significantly in the GH group compared with the placebo group [-19 cm(2) (-11%) vs. 12 cm(2) (6%), P=0.03, and -548 g (-9%) vs. 353 g (6%), P<0.01, respectively]. The beneficial fat redistribution in the GH group occurred without concomitant changes in subcutaneous fat at the abdomen or extremities. rhGH therapy was well tolerated. Insulin resistance, glucose tolerance, and total plasma cholesterol and triglycerides did not significantly change during intervention.

CONCLUSIONS

Daily 0.7 mg rhGH treatment for 40 weeks reduced abdominal visceral fat and trunk fat mass in HIV-infected patients. This treatment appeared to be safe with respect to glucose tolerance and insulin sensitivity.

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.

Recombinant human growth hormone: rationale for use in the treatment of HIV-associated lipodystrophy

The role of hormonal and metabolic alterations in HIV-associated lipodystrophy syndrome is not yet clear. In patients with HIV-1 undergoing antiretroviral treatment, lipodystrophy is associated with peripheral fat wasting and central adiposity, dyslipidemia, insulin resistance, and increased intramuscular fat accumulation. In HIV lipodystrophy, changes in fat distribution are heterogeneous and can include reduced subcutaneous fat as well as increased visceral fat. In the literature, there is evidence showing that overnight growth hormone (GH) secretion and pulse amplitude decrease in patients with HIV lipodystrophy, with rates of response to standardized GH stimulation being abnormal in at least 20% of these patients. Excess accumulation of visceral fat, central obesity, and increased intra-abdominal adiposity are also typical features of patients with GH deficiency. Recombinant human GH (rhGH) is a potential treatment to diminish excess visceral fat. Our group recently demonstrated that GH therapy in HIV-infected patients with syndromes of fat accumulation produced a significant decrease in body fat and a gain in lean tissue. In this article, we discuss the origin of lipodystrophy in HIV patients, and the use of rhGH treatment (benefits and adverse effects) in HIV-related lipodystrophy.