A rosiglitazone-induced increase in adiponectin does not improve glucose metabolism in HIV-infected patients with overt lipoatrophy

Lipodystrophies-Disorders of the Fatty Tissue

Lipodystrophies are a heterogeneous group of physiological changes characterized by a selective loss of fatty tissue. Here, no fat cells are present, either through lack of differentiation, loss of function or premature apoptosis. As a consequence, lipids can only be stored ectopically in non-adipocytes with the major health consequences as fatty liver and insulin resistance. This is a crucial difference to being slim where the fat cells are present and store lipids if needed. A simple clinical classification of lipodystrophies is based on congenital vs. acquired and generalized vs. partial disturbance of fat distribution. Complications in patients with lipodystrophy depend on the clinical manifestations. For example, in diabetes mellitus microangiopathic complications such as nephropathy, retinopathy and neuropathy may develop. In addition, due to ectopic lipid accumulation in the liver, fatty liver hepatitis may also develop, possibly with cirrhosis. The consequences of extreme hypertriglyceridemia are typically acute pancreatitis or eruptive xanthomas. The combination of severe hyperglycemia with dyslipidemia and signs of insulin resistance can lead to premature atherosclerosis with its associated complications of coronary heart disease, peripheral vascular disease and cerebrovascular changes. Overall, lipodystrophy is rare with an estimated incidence for congenital (<1/1.000.000) and acquired (1-9/100.000) forms. Due to the rarity of the syndrome and the phenotypic range of metabolic complications, only studies with limited patient numbers can be considered. Experimental animal models are therefore useful to understand the molecular mechanisms in lipodystrophy and to identify possible therapeutic approaches.

High Molecular Weight (HMW): total adiponectin ratio is low in hiv-infected women receiving protease inhibitors

Background

At the time of the study, the HIV-treatment policy in South Africa included highly active antiretroviral therapy (HAART) regimens 1 (nucleotide reverse transcriptase inhibitors (NRTIs) only), and 2 (protease inhibitors (PI) and NRTIs). HAART is associated with the lipodystrophy syndrome, insulin resistance and reduced total adiponectin (TA) levels. The high molecular weight (HMW):TA ratio is a superior marker of insulin resistance. The aim of this study was to establish whether HMW:TA ratios are low in patients on PIs and whether they correlate with insulin resistance.

Methods

This was a cross-sectional study undertaken in an antiretroviral clinic at a tertiary hospital. The participants were 66 HIV-infected females: 22 were on regimen 2 (PI group), 22 on regimen 1 (non-PI) and 22 treatment naïve (TN), matched for BMI and age. Patients with a history of diabetes or impaired glucose tolerance were excluded. Serum adiponectin multimers were analysed using the AlpcoTM Adiponectin (Multimeric) enzyme immunoassay. Waist hip ratios (WHR), glucose and insulin levels were assessed, and HOMA-IR and QUICKI calculated. Data were analysed non-parametrically and multivariate analysis was performed.

Results

TA and HMW levels were lower in the treatment groups than in the TN group. HMW:TA was lower in the PI than in the non-PI and TN groups, and in the non-PI than in the TN groups. HMW:TA correlated negatively with waist, insulin and HOMA-IR, independently of BMI and duration of therapy. HOMA-IR and QUICKI did not differ among the groups.

Conclusion

HMW:TA is significantly decreased with HAART (particularly with PIs, but also with non-PIs) and may be a more sensitive marker of insulin resistance in these patients than conventional markers or HMW and total adiponectin individually.

Exercise training augments the peripheral insulin-sensitizing effects of pioglitazone in HIV-infected adults with insulin resistance and central adiposity

The prevalence and incidence of insulin resistance and type 2 diabetes mellitus (DM) are higher in people treated for human immunodeficiency virus-1 (HIV) infection than in the general population. Identifying safe and effective interventions is a high priority. We evaluated whether the peroxisome proliferator-activated receptor-γ agonist pioglitazone with exercise training improves central and peripheral insulin sensitivity more than pioglitazone alone in HIV-infected adults with insulin resistance and central adiposity. Forty-four HIV-infected adults with baseline insulin resistance and central adiposity were randomly assigned to 4 mo of pioglitazone (30 mg/day) with or without supervised, progressive aerobic, and resistance exercise training (1.5-2 h/day, 3 days/wk). The hyperinsulinemic euglycemic clamp was used to evaluate alterations in central and peripheral insulin sensitivity. Thirty-nine participants completed the study. Hepatic insulin sensitivity improved similarly in both groups. Exercise training augmented the beneficial effects of pioglitazone on peripheral insulin sensitivity. Greater improvements in peripheral insulin sensitivity were associated with reductions in total body and limb adipose content rather than increases in limb adiposity or pioglitazone-induced increases in adiponectin concentration. We conclude that supplementing pioglitazone with increased physical activity improved insulin sensitivity more effectively than pioglitazone alone in HIV-infected adults with insulin resistance and central adiposity. Pioglitazone alone did not significantly increase limb adipose content. Potential cardiovascular benefits of these interventions in HIV need investigation.

The efficacy and safety of insulin-sensitizing drugs in HIV-associated lipodystrophy syndrome: a meta-analysis of randomized trials

Background

HIV-associated lipodystrophy syndrome (HALS) is characterized by insulin resistance, abnormal lipid metabolism and redistribution of body fat. To date, there has been no quantitative summary of the effects of insulin sensitizing-agents for the treatment of this challenging problem.

Methods

We searched MEDLINE, the Cochrane Library, clinical trial registries, conference proceedings and references for randomized trials evaluating rosiglitazone, pioglitazone or metformin in patients with evidence of HALS (last update December 2009). Two reviewers independently abstracted data and assessed quality using a standard form. We contacted authors for missing data and calculated weighted mean differences (WMD) and 95% confidence intervals (CI) for each outcome.

Results

Sixteen trials involving 920 patients met inclusion criteria. Rosiglitazone modestly improved fasting insulin (WMD -3.67 mU/L; CI -7.03, -0.31) but worsened triglycerides (WMD 32.5 mg/dL; CI 1.93, 63.1), LDL (WMD 11.33 mg/dL; CI 1.85, 20.82) and HDL (WMD -2.91 mg/dL; CI -4.56, -1.26) when compared to placebo or no treatment in seven trials. Conversely, pioglitazone had no impact on fasting insulin, triglycerides or LDL but improved HDL (WMD 7.60 mg/dL; CI 0.20, 15.0) when compared to placebo in two trials. Neither drug favorably impacted measures of fat redistribution. Based on six trials with placebo or no treatment controls, metformin reduced fasting insulin (WMD -8.94 mU/L; CI -13.0, -4.90), triglycerides (WMD -42.87 mg/dL; CI -73.3, -12.5), body mass index (WMD -0.70 kg/m²; CI -1.09, -0.31) and waist-to-hip ratio (WMD -0.02; CI -0.03, 0.00). Three trials directly compared metformin to rosiglitazone. While effects on insulin were comparable, lipid levels and measures of fat redistribution all favored metformin. Severe adverse events were uncommon in all 16 trials.

Conclusion

Based on our meta-analysis, rosiglitazone should not be used in HALS. While pioglitazone may be safer, any benefits appear small. Metformin was the only insulin-sensitizer to demonstrate beneficial effects on all three components of HALS.