No substudy participant changed protease inhibitor therapy or was diagnosed with diabetes through week 48. Four of 140 (3%) participants, two in each TPV/r group, received lipid-lowering therapy (gemfibrozil) when on-study.
Baseline median limb fat mass in the TPV/r groups was non-significantly higher than in the LPV/r group (Kruskal–Wallis test, P = 0.91). The median increase in limb fat mass at week 48 was higher with LPV/r (1.17 kg) than with TPV/r200 (0.83 kg) or TPV/r100 (0.41 kg), although the difference was not significant (Table 2). After adjusting for baseline CD4+ stratum, the median limb fat increase with LPV/r was marginally higher than with TPV/r100 (P = 0.03) or TPV/r200 (P = 0.05). The within-group change in limb fat mass from baseline to week 48 was significant for all groups: TPV/r200 (P = 0.0024), TPV/r100 (P = 0.012) and LPV/r (P < 0.0001).
Generally, the median of each subcutaneous fat variable and hip circumference increased in all three groups. Overall, higher increases were observed with LPV/r. There were significant differences between both TPV/r groups and the LPV/r group with respect to the increase from baseline for trunk fat mass and percentage, and between the TPV/r100 and LPV/r groups with respect to the increase from baseline for arm, leg, limb and total fat percentage, but not for hip circumference. The increase in SAT for LPV/r group was higher than for either TPV/r group though this was not statistically significant. The sensitivity analysis for these variables adjusted for baseline CD4+ stratum showed similar results (data not shown).
The two factors significantly associated with a greater increase in limb fat mass were a higher baseline HIV viral load (a 1.0 log10 higher baseline viral load was associated with 0.6 kg greater increase in limb fat; P = 0.02) and a lower baseline insulin 2 h after an OGTT (a 1 μU/ml lower insulin value was associated with 0.008 kg greater increase in limb fat; P = 0.037).
Visceral and truncal fat
VAT did not increase but rather declined modestly in all groups, despite the increases in limb fat mass and weight. The most prominent change was observed for the TPV/r200 group (P = 0.04 for comparison with LPV/r group).
Notably, the change in VAT correlated positively with change in limb fat mass (r = 0.25, P = 0.004). Baseline factors associated with a greater decline in VAT were higher VAT (each 10 cm2 higher VAT was associated with 1.7 cm2 greater decrease in VAT; P < 0.0001) and higher insulin levels 2 h after an OGTT (each 1 μU/ml higher insulin level was associated with 0.14 cm2 greater decrease in VAT; P = 0.014).
Waist circumference increased most with LPV/r, although none of the between-group differences was significant.
Overall body composition
The increases in BMI were comparable across groups. Overall body fat distribution did not appear to change significantly, with minimal changes in trunk:limb fat percentage, VAT:SAT, and waist:hip ratios. Nevertheless, there was a significant increase in waist:hip ratio in the LPV/r group relative to the TPV/r200 group. Also of note, the total fat and total fat percentage increase for LPV/r group was higher than for either TPV/r group.
When analysed using the Lipodystrophy Case Definition, there was a relatively small change in lipodystrophy severity score in all three groups. The prevalence of lipodystrophy increased by 11% with LPV/r compared with an 8% decrease with TPV/r200 (P = 0.006) and a 2% increase with TPV/r100 (P = 0.20).
Subjective changes in body composition
Physicians and participants identified only small changes in fat accumulation or fat wasting to week 48 in any group, with most finding no limb fat gain or loss (data not shown).
At baseline, approximately 90% of the physicians found normal waist size compared with approximately 74–87% of participants for the three treatment groups. On the basis of physician assessment, the proportion of participants with no gain in waist size decreased to 80% in the TPV/r100, 65% in the TPV/r200, and 60% in the LPV/r group on physical examination, and to 74, 65 and 52%, respectively, on participant report after 48 weeks.
Changes over 48 weeks in fasting glucose, insulin, HOMA-IR and HOMA-IS, and 2-h glucose and 2-h insulin values were modest and not significantly different between groups (Table 3). For all three treatments, the within-group changes at week 48 were not significant, except for a significant decline in fasting insulin in the TPV/r100 group (P = 0.012) and a significant (P = 0.003) increase in fasting glucose with LPV/r (although both insulin and HOMA-IR declined slightly with LPV/r).
Plasma adiponectin levels increased significantly (P < 0.0001) within all groups from baseline, but significantly more in both TPV/r groups compared with LPV/r (Table 3). Nevertheless, median values in all groups at week 48 remained within the reference range.
Factors associated with the change in adiponectin levels were sex, baseline triglyceride levels and treatment with TPV/r. The greater increase in adiponectin levels was associated significantly with TPV/r100 (P = 0.015) or TPV/r200 (P < 0.0001) treatment compared with LPV/r. Women had a 4030 ng/ml greater increase in adiponectin than men (P = 0.004). Each 10 mg/dl higher baseline triglyceride level was also associated with a 155 ng/ml greater decrease in adiponectin (P = 0.005).
Leptin concentrations increased with LPV/r and TPV/r200 but the increase in the LPV/r group was significant compared with the observed decrease in the TPV/r100 group (P = 0.015). A strong correlation between the changes in leptin and limb fat mass was observed (r = 0.67; P < 0.0001). The within-group change for leptin from baseline to week 48 was significant only for LPV/r (P = 0.001).
Total cholesterol and triglycerides increased in all groups, although the effects were greater in both TPV/r groups. The increase in HDL cholesterol was comparable in all groups. The ratio of total cholesterol:HDL cholesterol increased in both TPV groups (+0.3) but declined slightly (−0.1) in the LPV/r group. The within-group changes to week 48 were significant for all three parameters and all three treatments (P < 0.0001).
Over 48 weeks, TPV/r or LPV/r, each with TDF–3TC, increased limb fat mass, did not increase visceral abdominal fat, and was not associated with significant onset of insulin resistance or type 2 diabetes mellitus. A positive correlation was found between changes in limb fat and VAT, as would be expected in a wasted person who gains weight.
The median increases in limb fat were somewhat lower in both TPV/r groups, especially after adjustment for baseline CD4+ lymphocyte counts as patients on LPV/r had a higher CD4+ count at baseline. Even though the LPV/r group had lower limb fat at baseline, the week-48 values were very similar for all treatments. Therefore, it is possible that the greater increase in limb fat seen in the LPV/r group after 48 weeks may be due to greater HIV-related fat wasting prior to baseline in these patients. The findings for limb fat were similar to those of recent, unpublished studies that evaluated initial ART that included a ritonavir-boosted protease inhibitor but excluded a NRTI [26,27]. Nevertheless, our data should be interpreted cautiously, as limb fat was only measured at week 48. It is possible that limb fat may fall with more prolonged exposure, although treatment with LPV/r without a tNRTI for up to 24 months was also not associated with an overall loss of limb fat .
One possible reason for the subcutaneous fat outcome in the present study is the use of low-dose ritonavir. In a randomized trial in which ritonavir-boosted atazanavir (AZV/r) was compared with unboosted AZV over 96 weeks, there was less lipoatrophy with AZV/r . In keeping with these data, ritonavir can promote adipogenesis in vitro .
The outcomes for VAT were unexpected, given the longstanding perception that protease inhibitor therapy is associated with intra-abdominal fat accumulation. The data should be interpreted with care, however, as VAT was only measured once after baseline. Nevertheless, previous prospective studies found that central abdominal fat increased over 24 weeks and thereafter remained stable for up to 3 years in patients receiving therapy including a tNRTI, whereas we observed a decline in VAT .
There was no evidence that any regimen induced insulin resistance, including when assessed by OGTT, from the first postbaseline assessment at week 12 through week 48. This does not exclude the possibility that protease inhibitors might transiently induce insulin resistance or induce sustained insulin resistance in a minority of patients, but it does suggest that any acute effects seen with some protease inhibitors and with low-dose ritonavir are transient in most patients. The lack of insulin resistance seen in the present study may also stem from the lack of lipoatrophy through week 48, as both congenital and HIV-associated lipodystrophy are strongly associated with insulin resistance. Another likely reason is the avoidance of tNRTI therapy, which can rapidly induce insulin resistance before any measurable change in body fat [27,31].
As we did not observe limb fat loss, VAT increase or insulin resistance, the present data suggest that patients initiating TPV/r or LPV/r-based ART and who do not become lipodystrophic, will not develop insulin resistance. This possibility requires further evaluation.
Plasma adiponectin levels increased in all groups, particularly with TPV/r and in women. This finding is somewhat unexpected as adiponectin levels generally fall with weight gain . Recent studies have shown, however, that adiponectin levels are lower in HIV-infected patients than in healthy controls and that the levels decrease further with non-NRTI-based ART [16,33,34]. The increase we observed may reflect improvement in a perturbation induced by HIV infection; this seems unlikely, however, as the antiretroviral effects of the three regimens were very similar. Another possibility is that the increase was a compensatory response to antiretroviral-induced insulin resistance, in which case the increase appeared to be effective as insulin sensitivity did not appreciably change. Four weeks of LPV/r or indinavir in healthy volunteers increased plasma adiponectin and lipid levels, but insulin resistance was only observed with indinavir . The increases in adiponectin levels we observed may, therefore, be a compensatory response to the dyslipidaemic effects of both regimens rather than to insulin resistance. This may explain the significant association between baseline triglyceride levels and change in adiponectin levels at week 48. This possibility is supported by a study that showed adiponectin administered to mice receiving ritonavir significantly reduced lipid levels . Lastly, it is important to note that adiponectin levels tended to remain within the physiological range. The clinical implications of these changes, therefore, are uncertain.
Total cholesterol and triglyceride levels increased more in the TPV/r200 group than in the LPV/r group, however, the ratio of total to HDL cholesterol, a predictor of cardiovascular disease , does not suggest a clinically meaningful difference between these protease inhibitors.
Although there was a relatively small change in the lipodystrophy severity score in all three groups, patients in the LPV/r group had an increase in lipodystrophy prevalence compared with both TPV/r groups.
Our study has limitations. It only recruited adults and mostly white men. We only recorded body composition at two timepoints, and so a rise followed by a fall in limb fat mass that has been observed with tNRTI-based regimens remains a possibility, although treatment with lipoatrophic drugs such as stavudine and zidovudine for 1 year generally reduces limb fat mass to levels that are lower than at baseline, whereas in the present study limb fat was significantly higher. Lastly, we did not study adults with abnormal glucose tolerance, who might be less able to compensate for any drug-induced metabolic disturbance.
Our study suggests that TPV/r or LPV/r, coadministered with TDF-3TC, does not incur a significant risk of diabetes and do not significantly induce visceral fat accumulation, a complication that is both disfiguring and associated with cardiovascular disease. Lastly, the lack of lipoatrophy observed with these combinations will make these options attractive to patients, for whom lipoatrophy can be stigmatizing and can lead to poor ART adherence.
We would like to thank all sub-study investigators and staff, and especially the participants for their time.
Author contributions: The substudy was designed by Andrew Carr and Ricardo Chaves. The statistical analyses were performed by Armin Ritzhaupt and Wei Zhang. All authors contributed to the analysis plan and the manuscript.
Disclosure statement: Andrew Carr has received research funding from Abbott, Merck and Roche; consultancy fees from Bristol-Myers Squibb, Gilead Sciences, GlaxoSmithKline, Merck and Roche; lecture sponsorships from Abbott, Boehringer-Ingelheim, Bristol-Myers Squibb, Gilead Sciences, GlaxoSmithKline, and Merck; and has served on advisory boards for Abbott, Bristol-Myers Squibb, GlaxoSmithKline, Merck and Roche.
Armin Ritzhaupt, Wei Zhang, and Ricardo Chaves were all employees of Boehringer-Ingelheim, which wholly funded the study. Roberto Zajdenverg declares no conflict of interest.
Cassy Workman has served on advisory boards for Abbott, GlaxoSmithKline, Gilead, Janssen-Cilag, Merck and Roche; and has received speaker fees from Abbott, GlaxoSmithKline, Gilead, Janssen-Cilag, and Roche.
Pedro Cahn has served as advisor or speaker for: Avexa, Abbott, BMS, Boehringer-Ingelheim, GlaxoSmithKline, Merck Sharp & Dohme, Pfizer, Pharmasset, Schering Plough, and Tibotec. Jose M. Gatell has received research grants or honoraria for lectures or advisory boards from: Abbott, Boehringer-Ingelheim, Bristol-Myers Squibb, Gilead, GlaxoSmithKline, Janssen-Cilag, Merck, Roche, Tibotec, and Virco.
Data presented previously at the 9th International Workshop on Adverse Events and Lipodystrophy in HIV, Sydney, July, 2007 and published as abstract 7.
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Keywords:Copyright © 2008 Wolters Kluwer Health, Inc.
adiponectin; HIV; insulin resistance; lipoatrophy; protease inhibitors; visceral adiposity