Protease inhibitors do not interfere with prohormone processing

Alteration in pancreatic islet function in human immunodeficiency virus

Molecular mechanisms behind the defects in insulin production and secretion associated with antihuman immunodeficiency virus (anti-HIV) therapy and the development of HIV-associated lipodystrophy syndrome (HALS) are discussed in this article. Data suggesting insulin resistance on the beta cell and defects in first-phase insulin release of HALS patients are presented. Hepatic extraction of insulin, nonglucose insulin secretagogues and insulin-like growth factor release may exert influence on the demand of circulating insulin and on insulin secretion in HIV-infected patients. Finally, the paucity in understanding the incretin effects in HIV and HIV therapy in relation to insulin secretion is highlighted.

Impaired proinsulin secretion before and during oral glucose stimulation in HIV-infected patients who display fat redistribution

The beta-cell function of HIV-infected patients on highly active antiretroviral therapy who display lipodystrophy may be impaired. An early defect in beta-cell function may be characterized by an increase in secretion of 32-33 split proinsulin (SP) and intact proinsulin (IP). To address this issue, the secretion patterns of SP and IP of 16 HIV-infected men with lipodystrophy (LIPO) and 15 HIV-infected men without lipodystrophy (NONLIPO) were studied during an oral glucose tolerance test (OGTT). All patients received highly active antiretroviral therapy. Insulin secretion rates were determined by deconvolution of plasma C-peptide concentrations. More LIPO than NONLIPO patients displayed diabetes mellitus and impaired glucose tolerance than normal glucose tolerance (LIPO 2/8/6 vs NONLIPO 1/2/12, P = .05). LIPO patients had increased fasting levels of SP and IP, ratio of SP/IP, and area under the curve of SP and IP during the early phase (0, 10, and 20 minutes) and during the late phase (45, 75, and 105 minutes) of the OGTT compared with NONLIPO patients (Ps < .05). LIPO patients exhibited significantly increased fasting SP/IP ratio, fasting SP/insulin ratio, and total proinsulin to C-peptide ratio during the OGTT. LIPO patients displayed increased incremental secretion of IP during the first 10 minutes of the OGTT (P < .05), although the incremental insulin secretion during this period did not differ between LIPO and NONLIPO patients. These data suggest that HIV-infected patients with lipodystrophy display major perturbations of proinsulin secretion in the fasting state and during an OGTT, which is compatible with the notion of a beta-cell dysfunction of such patients.

Hyperproinsulinaemia in normoglycaemic lipodystrophic HIV-infected patients

BACKGROUND

We aimed to investigate whether the insulin precursors, intact (IP) and 32-33 split proinsulin (SP), which are elevated in states of insulin resistance and predict type 2 diabetes, would be elevated in human immunodeficiency virus (HIV)-infected patients with lipodystrophy (LIPO).

MATERIALS AND METHODS

Forty-three normoglycaemic HIV-infected patients [18 LIPO and 18 without lipodystrophy (NONLIPO) receiving antiretroviral drugs, and seven patients naïve to antiretroviral drugs (NAIVE)] were examined. Insulin precursors were measured during fasting, during an intravenous glucose tolerance test and during a hyperinsulinaemic-euglycaemic clamp, respectively. Insulin secretion rates (ISR) were determined by deconvolution of C-peptide concentrations. Disposition index (DI) was calculated as insulin sensitivity (Si(RD)) multiplied by the first-phase insulin response to intravenous glucose.

RESULTS

LIPO exhibited increased fasting IP and SP (P < 0.05), a higher proportion of elevated fasting IP (3.1 pmol L(-1), 66% vs. 33% and 28%, P < 0.05) and SP (7.2 pmol L(-1), 50%, 11% and 0%, P < 0.01), reduced Si(RD) (> 50%, P < 0.001) and increased ISR (P < 0.001) compared with NONLIPO and NAIVE. Fasting SP and IP correlated positively with ISR (P < 0.001) and inversely and hyperbolically with Si(RD) (P < 0.001). Fasting SP/insulin ratio correlated inversely with Si(RD) (P < 0.05). Incremental IP + SP/insulin ratio after an intravenous glucose bolus correlated inversely with DI (P < 0.01), but did not differ between study groups.

CONCLUSIONS

Proinsulin appeared to be increased in HIV-lipodystrophy, but no more than caused by the increased ISR. Nevertheless, the inverse correlations between SP/insulin ratio versus Si(RD) and incremental total proinsulin/insulin ratio versus DI may argue for a subtle beta-cell dysfunction in those patients with insulin resistance and low DI.

Oral Glucose Tolerance and Insulin Sensitivity Are Unaffected by HIV Infection or Antiretroviral Therapy in Overweight Women

OBJECTIVE

To assess the frequency of diabetes, prediabetes, and insulin resistance among a subset of participants in the Women's Interagency HIV Study (WIHS).

DESIGN

Cross-sectional substudy nested within a prospective multicenter cohort study. Women underwent 75 g oral glucose tolerance testing. Diagnoses of diabetes and prediabetes were made according to the American Diabetes Association criteria, and insulin resistance was determined by area under the curve insulin and homeostasis model assessment values.

SETTING

Six urban clinical sites in the United States (Brooklyn, NY; Bronx, NY; Washington, DC; Chicago, IL; San Francisco, CA; Los Angeles, CA) participate in the entire WIHS. The Bronx, NY, and San Francisco, CA, WIHS sites participated in this substudy.

PARTICIPANTS

A total of 258 women, 88 HIV negative, 74 HIV positive not on highly active antiretroviral therapy (HAART), and 96 HIV positive taking HAART were enrolled in the study.

MAIN OUTCOMES

Prevalence of diabetes, prediabetes, and insulin resistance was compared among the HIV-uninfected and HIV-infected women.

RESULTS

The frequency of diabetes, prediabetes, or insulin resistance was unrelated to HIV status or antiretroviral treatment. Increasing body mass index was the only characteristic associated with the combined endpoints of diabetes and prediabetes (odds ratio = 1.104, P = 0.0002).

CONCLUSIONS

Routine oral glucose tolerance testing of HIV-infected women is not supported by these findings. Elucidation of putative perturbations from HIV or antiretroviral medications requires direct studies of insulin resistance and beta-cell function.

Mechanisms for the deterioration in glucose tolerance associated with HIV protease inhibitor regimens

The mechanisms responsible for the deterioration in glucose tolerance associated with protease inhibitor-containing regimens in HIV infection are unclear. Insulin resistance has been implicated as a major factor, but the affected tissues have not been identified. Furthermore, beta-cell function has not been evaluated in detail. The present study was therefore undertaken to assess the effects of protease inhibitor-containing regimens on hepatic, muscle, and adipose tissue insulin sensitivity as well as pancreatic beta-cell function. We evaluated beta-cell function in addition to glucose production, glucose disposal, and free fatty acid (FFA) turnover using the hyperglycemic clamp technique in combination with isotopic measurements in 13 HIV-infected patients before and after 12 weeks of treatment and in 14 normal healthy volunteers. beta-Cell function and insulin sensitivity were also assessed by homeostasis model assessment (HOMA). Treatment increased fasting plasma glucose concentrations in all subjects (P < 0.001). Insulin sensitivity as assessed by HOMA and clamp experiments decreased by approximately 50% (P < 0.003). Postabsorptive glucose production was appropriately suppressed for the prevailing hyperinsulinemia, whereas glucose clearance was reduced (P < 0.001). beta-Cell function decreased by approximately 50% (P = 0.002), as assessed by HOMA, and first-phase insulin release decreased by approximately 25%, as assessed by clamp data (P = 0.002). Plasma FFA turnover and clearance both increased significantly (P < 0.001). No differences at baseline or in responses after treatment were observed between drug naïve patients who were started on a nucleoside reverse transcriptase inhibitor (NRTI) plus a protease inhibitor and patients who had been on long-term NRTI treatment and had a protease inhibitor added. The present study indicates that protease inhibitor-containing regimens impair glucose tolerance in HIV-infected patients by two mechanisms: 1) inducement of peripheral insulin resistance in skeletal muscle and adipose tissue and 2) impairment of the ability of the beta-cell to compensate.

Lipodystrophy, insulin resistance, diabetes mellitus, dyslipidemia, and cardiovascular disease in human immunodeficiency virus infection

The introduction of highly active antiretroviral therapy has significantly reduced morbidity and mortality in patients infected with the human immunodeficiency virus. Treatment with antiretroviral agents--protease inhibitors in particular--has uncovered a syndrome of abnormal fat redistribution, dyslipidemia, and impaired glucose metabolism, collectively termed lipodystrophy syndrome. The cause of the syndrome seems to be multifactorial; however, its exact mechanisms have yet to be elucidated. Accelerated risk for cardiovascular disease is likely to be a major concern in these patients in the future. At this time, no clinical guidelines are available for the prevention and/or the treatment of lipodystrophy syndrome. The available treatment options range from switching the different antiretroviral drugs and lifestyle modifications to the use of pharmacologic agents to treat patients with dyslipidemia, impaired glucose tolerance and/or diabetes, and changes in body composition. This review emphasizes the clinical features, potential molecular mechanisms, and treatment options for patients infected with human immunodeficiency virus who have lipodystrophy syndrome.

Lipodystrophy syndrome in HIV infection: what is it, what causes it and how can it be managed?

Since the introduction of HIV-1 protease inhibitors as components of antiretroviral drug combination regimens, the clinical course of HIV disease and opportunistic infections has changed dramatically. Besides the favourable virological, immunological and clinical impact of highly active antiretroviral therapy (HAART), several adverse drug reactions have been observed in patients with HIV receiving therapy. Particularly, peripheral lipodystrophy, central adiposity, dyslipidaemia and insulin resistance have been described with a prevalence of up to 80% in patients infected with HIV, and attributed to almost all components of HAART. Hyperlipidaemia is characterised by an increase of low and very low density lipoprotein-cholesterol as well as apolipoproteins B and E. Several studies strongly suggest that there are either multiple syndromes or a variety of factors inducing different changes that influence the ultimate phenotype. Similarities between HIV-associated fat redistribution and metabolic abnormalities with both inherited lipodystrophies and benign symmetric lipomatosis suggest the pathophysiological involvement of, for example, nuclear factors like lamin A/C and drug-induced mitochondrial dysfunction. Moreover, there is some evidence that cytokines and hormones impair fat and glucose homeostasis in patients with HIV receiving HAART. Three years after the first description of HIV therapy-associated abnormal fat redistribution, there is still an ongoing discussion about the case definition, diagnostic procedure and treatment options for both body shape changes and metabolic disturbances. Regarding therapy, there is a major concern about possible complex pharmacological interactions and overlapping adverse effects between HAART and, for example, lipid-lowering therapy. In addition, the likely contribution of both nucleoside analogue reverse transcriptase inhibitors and protease inhibitors to the development of abnormal fat redistribution in patients with HIV limits options of changing to alternative effective antiretroviral drug combinations. Thus, the occurrence of hyperlipidaemia, maturity onset diabetes mellitus, and marked changes in body habitus resulted in important social and clinical consequences such as an increased risk of atherosclerosis. It also sheds new light on the use of protease inhibitors regarding risk factors for the initial treatment decision. In this article, we discuss the features, pathogenesis and treatment options for body fat redistribution and metabolic disturbances associated with HAART in HIV-1 infection.

Lipodystrophy syndrome in HIV infection: what is it, what causes it and how can it be managed?

Since the introduction of HIV-1 protease inhibitors as components of antiretroviral drug combination regimens, the clinical course of HIV disease and opportunistic infections has changed dramatically. Besides the favourable virological, immunological and clinical impact of highly active antiretroviral therapy (HAART), several adverse drug reactions have been observed in patients with HIV receiving therapy. Particularly, peripheral lipodystrophy, central adiposity, dyslipidaemia and insulin resistance have been described with a prevalence of up to 80% in patients infected with HIV, and attributed to almost all components of HAART. Hyperlipidaemia is characterised by an increase of low and very low density lipoprotein-cholesterol as well as apolipoproteins B and E. Several studies strongly suggest that there are either multiple syndromes or a variety of factors inducing different changes that influence the ultimate phenotype. Similarities between HIV-associated fat redistribution and metabolic abnormalities with both inherited lipodystrophies and benign symmetric lipomatosis suggest the pathophysiological involvement of, for example, nuclear factors like lamin A/C and drug-induced mitochondrial dysfunction. Moreover, there is some evidence that cytokines and hormones impair fat and glucose homeostasis in patients with HIV receiving HAART. Three years after the first description of HIV therapy-associated abnormal fat redistribution, there is still an ongoing discussion about the case definition, diagnostic procedure and treatment options for both body shape changes and metabolic disturbances. Regarding therapy, there is a major concern about possible complex pharmacological interactions and overlapping adverse effects between HAART and, for example, lipid-lowering therapy. In addition, the likely contribution of both nucleoside analogue reverse transcriptase inhibitors and protease inhibitors to the development of abnormal fat redistribution in patients with HIV limits options of changing to alternative effective antiretroviral drug combinations. Thus, the occurrence of hyperlipidaemia, maturity onset diabetes mellitus, and marked changes in body habitus resulted in important social and clinical consequences such as an increased risk of atherosclerosis. It also sheds new light on the use of protease inhibitors regarding risk factors for the initial treatment decision. In this article, we discuss the features, pathogenesis and treatment options for body fat redistribution and metabolic disturbances associated with HAART in HIV-1 infection.