Publications

BACKGROUND

Some HIV protease inhibitors (PIs) have been shown to induce insulin resistance in vitro but the degree to which specific PIs affect insulin sensitivity in humans is less well understood.

METHODS

In two separate double-blind, randomized, cross-over studies, we assessed the effects of a single dose of ritonavir (800 mg) and amprenavir (1200 mg) on insulin sensitivity (euglycemic hyperglycemic clamp) in healthy normal volunteers.

RESULTS

Ritonavir decreased insulin sensitivity (-15%; P = 0.008 versus placebo) and non-oxidative glucose disposal (-30%; P = 0.0004), whereas neither were affected by amprenavir administration.

CONCLUSION

Compared to previously performed studies of identical design using single doses of indinavir and lopinavir/ritonavir, a hierarchy of insulin resistance was observed with the greatest effect seen with indinavir followed by ritonavir and lopinavir/ritonavir, with little effect of amprenavir.

Inflammation can produce abnormalities that could increase the risk for atherosclerosis including alterations in lipid and lipoprotein metabolism. Apolipoprotein M is a recently described HDL-associated apoprotein expressed mainly in the liver and kidney with protective effects against atherosclerosis. In this study, we describe the regulation of apolipoprotein M during the acute phase response. Stimuli that produce systemic inflammation, LPS, zymosan, or turpentine, decrease apolipoprotein M mRNA levels in the liver and kidney. Treatment of Hep3B hepatoma cells with TNF or IL-1 also decreased apolipoprotein M mRNA levels. The decrease in apolipoprotein M mRNA leads to a decrease in apolipoprotein M secretion into the media in Hep3B cells and a decrease in mouse serum following LPS administration. Moreover, in humans with acute bacterial infections or chronic HIV infection, serum apolipoprotein M levels are decreased. Apolipoprotein M is a negative acute response protein that decreases during infection and inflammation. These results are consistent with the finding that infections and inflammatory disorders accompanied by systemic inflammation are associated with an increased risk of atherosclerosis.

People with HIV infection have metabolic abnormalities that resemble metabolic syndrome (hypertriglyceridemia, low high-density lipoprotein cholesterol, and insulin resistance), which is known to predict increased risk of cardiovascular disease (CVD). However, there is not one underlying cause for these abnormalities and they are not linked to each other. Rather, individual abnormalities can be affected by the host response to HIV itself, specific HIV drugs, classes of HIV drugs, HIV-associated lipoatrophy, or restoration to health. Furthermore, one component of metabolic syndrome, increased waist circumference, occurs less frequently in HIV infection. Thus, HIV infection supports the concept that metabolic syndrome does not represent a syndrome based on a common underlying pathophysiology. As might be predicted from these findings, the prevalence of CVD is higher in people with HIV infection. It remains to be determined whether CVD rates in HIV infection are higher than might be predicted from traditional risk factors, including smoking.

BACKGROUND

HIV infection and antiretroviral therapy are associated with dyslipidemia, but the association between regional adipose tissue depots and lipid levels is not defined.

METHODS

The association of magnetic resonance imaging-measured visceral adipose tissue (VAT) and regional subcutaneous adipose tissue (SAT) volume with fasting lipid parameters was analyzed by multivariable linear regression in 737 HIV-infected and 145 control men from the study of Fat Redistribution and Metabolic Change in HIV Infection.

RESULTS

HIV-infected men had higher median triglycerides (170 mg/dL vs. 107 mg/dL; P < 0.0001), lower high-density lipoprotein cholesterol (HDL-C; 38 mg/dL vs. 46 mg/dL; P < 0.0001), and lower low-density lipoprotein cholesterol (LDL-C; 105 mg/dL vs. 125 mg/dL; P < 0.0001) than controls. After adjustment, greater VAT was associated with higher triglycerides and lower HDL-C in HIV-infected and control men, whereas greater leg SAT was associated with lower triglycerides in HIV-infected men with a similar trend in controls. More upper trunk SAT was associated with higher LDL-C and lower HDL-C in controls, whereas more lower trunk SAT was associated with higher triglycerides in controls. After adjustment, HIV infection remained strongly associated (P < 0.0001) with higher triglycerides (+76%, 95% confidence interval [CI]: 53 to 103), lower LDL-C (-19%, 95% CI: -25 to -12), and lower HDL-C (-18%, 95% CI: -22 to -12).

CONCLUSIONS

HIV-infected men are more likely than controls to have higher triglycerides and lower HDL-C, which promote atherosclerosis, but also lower LDL-C. Less leg SAT and more VAT are important factors associated with high triglycerides and low HDL-C in HIV-infected men. The reduced leg SAT in HIV-infected men with lipoatrophy places them at increased risk for proatherogenic dyslipidemia.

OBJECTIVES

To assess long-term changes in subcutaneous tissue among antiretroviral-naive persons initiating 1 of 3 nucleoside reverse transcriptase inhibitor (NRTI)-containing regimens.

METHODS

We compared changes in 308 participants initiating stavudine plus lamivudine (d4T+3TC; N = 63), zidovudine plus lamivudine (ZDV+3TC; N = 192), and abacavir plus lamivudine (ABC+3TC; N = 53), along with protease inhibitors and/or non-NRTIs. Anthropometric measurements (skinfolds) were performed at baseline and 4-month intervals. Rates of change (mm/y) over 36 months, for the early period (months 4 through 12) and late period (months 16 through 36), were calculated.

RESULTS

The rates were negative (tissue loss) for the abdomen and thigh (d4T+3TC, ZDV+3TC) and triceps (ZDV+3TC) skinfolds. For ABC+3TC, most rates were positive (tissue gain). No differences among regimens were seen for the rates of change in the subscapular or suprascapular skinfolds. Rates in the early period were generally positive. The late period rates were negative for d4T+3TC and ZDV+3TC and significantly different from 0 for the abdomen and thigh (d4T+3TC, ZDV+3TC) and triceps (ZDV+3TC) skinfolds, whereas ABC+3TC had less loss in the late period. Most early versus late differences were significant for d4T+3TC and ZDV+3TC; only the triceps skinfold was significant for ABC+3TC.

CONCLUSIONS

In this prospective nonrandomized evaluation, subcutaneous tissue changes varied by regimen. Similar losses were demonstrated for d4T+3TC and ZDV+3TC, whereas ABC+3TC had gains. Temporal differences in rates for d4T+3TC and ZDV+3TC suggest initial recovery followed by long-term treatment effect.

Protease inhibitors (PIs) are widely assumed to be associated with a syndrome of insulin resistance accompanied by hyperlipidemia and fat redistribution. Insulin resistance in HIV infection has numerous other causes, however, which include not only the direct effects of antiretroviral drugs but also factors such as aging and restoration to health accompanied by fat accumulation. Studies of PIs in HIV-infected and noninfected patients indicate that some of these drugs are associated with reduced insulin sensitivity (greater acute versus chronic effects) that may be due to direct blockade of the insulin-sensitive glucose transporter in muscle and fat cells. Other studies have shown that insulin levels increase over time with antiretroviral therapy, likely the result of improved health, fat accumulation, and aging, and that increases in visceral fat and upper trunk fat are associated with a higher risk of insulin resistance in HIV-infected and -uninfected individuals alike. This article summarizes a presentation on insulin resistance in HIV infection made by Carl Grunfeld, MD, PhD, at the 10th Annual Ryan White HIV/AIDS Program Clinical Update in Phoenix in June 2007.

Inflammation produces marked changes in lipid metabolism, including increased serum fatty acids (FAs) and triglycerides (TGs), increased hepatic TG production and VLDL secretion, increased adipose tissue lipolysis, and decreased FA oxidation in liver and heart. Lipopolysaccharide (LPS) also increases TG and cholesteryl ester levels in kidneys. Here we confirm these findings and define potential mechanisms. LPS decreases renal FA oxidation by 40% and the expression of key proteins required for oxidation of FAs, including FA transport protein-2, fatty acyl-CoA synthase, carnitine palmitoyltransferase-1, medium-chain acyl-CoA dehydrogenase, and acyl-CoA oxidase. Similar decreases were observed in peroxisome proliferator-activated receptor alpha (PPARalpha)-deficient mice. LPS also caused a reduction in renal mRNA levels of PPARalpha (75% decrease), thyroid hormone receptor alpha (TRalpha) (92% decrease), and TRbeta (84% decrease), whereas PPARbeta/delta and gamma were not altered. Expression of PGC1 alpha and beta, coactivators required for PPARs and TR, was also decreased in kidneys of LPS-treated mice, as were mitochondrial genes regulated by PGC1 (Atp5g1, COX5a, Idh3a, and Ndufs8). Decreased renal FA oxidation could be a by-product of the systemic coordinated host response to increase FAs and TGs available for host defense and/or tissue repair. However, the kidney requires energy to support its transport functions, and the inability to generate energy via FA oxidation might contribute to the renal failure seen in severe sepsis.