Pioglitazone inhibits the diabetogenic action of growth hormone, but not its ability to promote growth

Effects of growth hormone and pioglitazone in viscerally obese adults with impaired glucose tolerance: a factorial clinical trial

OBJECTIVE

Recombinant human growth hormone (GH) and pioglitazone (PIO) in abdominally obese adults with impaired glucose tolerance were evaluated under the hypothesis that the combination attenuates GH-induced increases in glucose concentrations, reduces visceral adipose tissue (VAT), and improves insulin sensitivity over time.

DESIGN

Randomized, double-blind, placebo-controlled, 2 x 2 factorial design.

SETTING

Veterans Affairs Palo Alto Health Care System, Palo Alto, California, United States.

PARTICIPANTS

62 abdominally obese adults aged 40-75 with impaired glucose tolerance.

INTERVENTIONS

GH (8 microg/kg/d, or placebo) and pioglitazone (30 mg/d, or placebo) for 40 wk.

OUTCOME MEASURES

Baseline and after 40 wk of treatment, VAT content was quantified by CT scan, glucose tolerance was assessed using a 75-g oral glucose tolerance test, and insulin sensitivity was measured using steady-state plasma glucose levels obtained during insulin suppression test.

RESULTS

BASELINE: body mass index (BMI), plasma glucose, and visceral fat content were similar. 40 wk: visceral fat area declined 23.9 +/- 7.4 cm(2) in GH group, mean difference from placebo: -28.1 cm(2) (95% CI -49.9 to -6.3 cm(2); p = 0.02). Insulin resistance declined 52 +/- 11.8 mg/dl with PIO, mean difference from placebo of -58.8 mg/dl (95% CI -99.7 to -18.0 mg/dl; p = 0.01). VAT and SSPG declined with GH and PIO combined, mean differences from placebo of -31.4 cm(2) (95% CI -56.5 cm(2) to -6.3 cm(2); p = 0.02) and -55.3 mg/dl (95% CI -103.9 to -6.7 mg/dl; p = 0.02), respectively. Fasting plasma glucose increased transiently in GH group. No significant changes in BMI were observed.

CONCLUSIONS

Addition of PIO to GH attenuated the short-term diabetogenic effect of GH; the drug combination reduced VAT and insulin resistance over time. GH plus PIO may have added benefit on body composition and insulin sensitivity in the metabolic syndrome.

Combined low-dose pioglitazone, flutamide, and metformin for women with androgen excess

CONTEXT AND OBJECTIVE

One of the treatments for hyperinsulinemic hyperandrogenism in nonobese women is combined androgen receptor blockade (with flutamide; Flu), insulin sensitization (with metformin; Met) plus an estroprogestagen contraceptive. We tested whether adding low-dose pioglitazone (Pio; 7.5 mg/d) confers more benefit.

SETTING

The study was conducted at a university hospital.

STUDY POPULATION AND DESIGN

This double-blind study enrolled 38 young women with hyperinsulinemic hyperandrogenism [mean body mass index (BMI) 24 kg/m(2)], all of whom started on Flu (62.5 mg/d) and Met (850 mg/d) plus a transdermal estroprogestagen, each for 21 of 28 d over 6 months. Patients were randomly assigned to receive, in addition, placebo (n=19) or Pio (n=19; 7.5 mg/d) for the same 21 of 28 d over 6 months.

MAIN OUTCOMES

BMI, waist to hip ratio, hirsutism score, fasting endocrine-metabolic markers, body composition, abdominal fat (visceral vs. sc), and carotid intima-media thickness were measured at study start and after 6 months.

RESULTS

PioFluMet reduced intima-media thickness more than FluMet and lowered glucose, IGF-I, and C-reactive protein more as well as the ratio of low-density lipoprotein to high-density lipoprotein cholesterol and the ratio of neutrophils to lymphocytes. PioFluMet treatment was followed by a leaner body composition and a loss of visceral fat (both P < 0.001). In the total group, the changes included not only decreases in waist to hip ratio, hirsutism score, and testosterone (all P < 0.001) but also minor drops in alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transpeptidase, and lactate dehydrogenase (all P < 0.005), indicating absence of hepatotoxicity; BMI remained unchanged. Clinical side effects were not detected.

CONCLUSION

In this proof-of-concept study, addition of Pio to FluMet plus an estroprogestagen led to improvements in the endocrine-metabolic condition, in low-grade inflammation, in total and visceral adiposity, and in markers of cardiovascular health.

Pioglitazone

Pioglitazone is an orally administered insulin sensitising thiazolidinedione agent that has been developed for the treatment of type 2 diabetes mellitus. Pioglitazone activates the nuclear peroxisome proliferator activated receptor-gamma (PPAR-gamma), which leads to the increased transcription of various proteins regulating glucose and lipid metabolism. These proteins amplify the post-receptor actions of insulin in the liver and peripheral tissues, which leads to improved glycaemic control with no increase in the endogenous secretion of insulin. In placebo-controlled clinical trials, monotherapy with pioglitazone 15 to 45 mg/day has been shown to decrease blood glycosylated haemoglobin (HbA1c) levels in patients with type 2 diabetes mellitus. The addition of pioglitazone 30 mg/day to preexisting therapy with metformin, or of pioglitazone 15 or 30 mg/day to sulphonylurea, insulin or voglibose therapy, has been shown to decrease HbA1c and fasting blood glucose levels significantly in patients with poorly controlled type 2 diabetes mellitus. Pioglitazone has also been associated with improvements in serum lipid profiles in randomised placebo-controlled clinical studies. The drug has been well tolerated by adult patients of all ages in clinical studies. Oedema has been reported with monotherapy, and pooled data have shown hypoglycaemia in 2 to 15% of patients after the addition of pioglitazone to sulphonylurea or insulin treatment. There have been no reports of hepatotoxicity.

Effects of troglitazone on hepatic and peripheral insulin resistance induced by growth hormone excess in rats

It is well known that short-term growth hormone (GH) administration in humans and animals induces insulin resistance and glucose intolerance. The purpose of the present study was to clarify whether troglitazone, a new insulin-sensitizing drug of the thiazolidinedione class, counteracts the insulin antagonistic effects of recombinant human (rh) GH on glucose metabolism in rats. Male Wistar rats weighing 184 to 226 g were treated either with rhGH (n = 8) or rhGH plus troglitazone (n = 8). rhGH (20 IU/kg body weight/d) was given by subcutaneous injection twice daily for 2 days. Troglitazone was given at 100 mg/kg/d orally for 5 days before and 2 days during rhGH. Saline was injected to the control rats (n = 7). Euglycemic clamp studies with an insulin infusion rate of 8 mU/kg/min were performed in these rats after an overnight fast. Hepatic glucose output (HGO), glucose infusion rate (GIR), and glucose disappearance rate (GDR) were measured. Fasting levels of plasma glucose (6.6 +/- 0.1, 6.1 +/- 0.3, 6.5 +/- 0.2 mmol/L), insulin (187.5 +/- 24.1, 206.4 +/- 24.1, 182.3 +/- 31.0 pmol/L), and serum free fatty acid (FFA) (1.58 +/- 0.18, 1.43 +/- 0.16, 1.61 +/- 0.25 mEq/L) were comparable among rats treated with rhGH, rhGH plus troglitazone, and controls, respectively. Basal HGO was also comparable among the three treatment groups. HGO was suppressed significantly during the hyperinsulinemic glucose clamp in control rats, but not in rhGH rats. When troglitazone was coadministered with rhGH, suppressibility of HGO during the glucose clamp was comparable to that of controls. GIR (13.5 +/- 4.5 v 24.1 +/- 4.1 mg/kg/min) and GDR (18.1 +/- 5.8 v 30.3 +/- 5.2 mg/kg/min) were decreased by rhGH treatment compared with control values. They returned to normal levels in rats treated with both rhGH and troglitazone (GIR, 22.4 +/- 5.9; GDR, 24.7 +/- 7.1). From these results, it is evident that rhGH treatment impaired insulin's ability to suppress HGO and stimulate peripheral glucose utilization. Troglitazone could block the insulin antagonistic effects of GH on hepatic glucose output and peripheral glucose utilization.