Self-reported fatigue common among optimally treated HIV patients: no correlation with cerebral FDG-PET scanning abnormalities

Neurologic Complications of Human Immunodeficiency Virus

PURPOSE OF REVIEW

This article reviews the neurologic complications associated with human immunodeficiency virus (HIV) infection.

RECENT FINDINGS

Neurologic complications of HIV may be caused by direct virally mediated pathology, immune-mediated phenomena in response to viral infection, or opportunistic infections secondary to depletion of lymphocytes. These neurologic disorders may be influenced by the degree of immunosuppression (ie, CD4+ T-cell lymphocyte count) and stage of infection (early versus late), as well as use of antiretroviral therapy, and may manifest as a variety of central and peripheral neurologic syndromes, including the more commonly encountered HIV-associated cognitive disorders and length-dependent sensorimotor polyneuropathy, respectively. Immune dysregulation underlies the majority of these neurologic phenomena, as well as other HIV-associated conditions including immune reconstitution inflammatory syndrome (IRIS), CD8 lymphocytosis, and potentially the development of compartmentalized infection within the CSF, also referred to as CSF escape.

SUMMARY

This article reviews a spectrum of clinical syndromes and related neuropathologic states associated with HIV infection.

Brain 18F-FDG PET of SIV-infected macaques after treatment interruption or initiation

BACKGROUND

Although rates of severe HIV-associated neurocognitive disorders have declined in the post-antiretroviral treatment (ART) era, subtle deficits persist, possibly exacerbated by treatment non-adherence. The actual effects of ART interruption/initiation on brain glucose metabolism as a reflection of viral replication and neuroinflammation remain unclear. Our study investigates how treatment initiation and interruption alter brain glucose metabolism in SIV-infected macaques, using 18F-FDG PET in correlation with plasma and CSF viral loads (VL) and cytokine levels.

METHODS

SIV-infected macaques (n = 7) underwent ART initiation only, ART interruption only, or both. Five uninfected animals served as controls. 18F-FDG PET imaging was performed at baseline and 1, 3, and 6 months after treatment modification. Mean and maximum standardized uptake values (SUV) for the whole-brain and subregions were calculated. Plasma and CSF VL and cytokine levels were measured. Paired t tests evaluated acute changes in whole-brain SUV from baseline to 1 month, while mixed-effect linear regression models evaluated changes over multiple timepoints and correlated SUV values with disease markers.

RESULTS

ART interruption was associated with increased SUVmean and SUVmax acutely, after 1 month (SUVmean 95% CI [0.044-0.786 g/ml], p = 0.037; SUVmax 95% CI [0.122-3.167 g/ml], p = 0.041). The correlation between SUV and time, however, was not significant when evaluated across all timepoints. Increased SUVmean and SUVmax correlated with decreased CD4+ and CD8+ T-cell counts and increased plasma VL. SUVmax was positively associated with increases in CSF VL, and there were borderline positive associations between SUVmax and IL-2, and between SUVmean and IL-15. The treatment initiation group showed no associations between imaging and disease biomarkers despite viral suppression, reduced cytokine levels, and increased CD4+ and CD8+ T-cell counts.

CONCLUSIONS

ART interruption is associated with increased brain glucose metabolism within 1 month of treatment cessation, which, in concert with increased levels of pro-inflammatory cytokines in the CSF, may reflect neuroinflammation in the setting of viral rebound. Although we cannot assert neurologic damage in association with cerebral hypermetabolism, it is a concerning outcome of ART non-adherence. Treatment initiation, meanwhile, did not result in significant changes in brain metabolism. HIV-induced neuroinflammation may require a longer period to abate than our follow-up period allowed.

Neuroimaging of HIV-associated neurocognitive disorders (HAND)

PURPOSE OF REVIEW

HIV enters the brain after initial infection, and with time can lead to HIV-associated neurocognitive disorders (HAND). Although the introduction of combination antiretroviral therapy has reduced the more severe forms of HAND, milder forms are still highly prevalent. The 'gold standard' for HAND diagnosis remains detailed neuropsychological performance testing but additional biomarkers (including neuroimaging) may assist in early detection of HAND.

RECENT FINDINGS

We review the application of recently developed noninvasive MRI and PET techniques in HIV+ individuals. In particular, magnetic resonance spectroscopy may be more sensitive than conventional MRI alone in detecting HIV associated changes. Diffusion tensor imaging has become increasingly popular for assessing changes in white matter structural integrity due to HIV. Both functional MRI and PET have been limitedly performed but could provide keys for characterizing neuropathophysiologic changes due to HIV.

SUMMARY

It is hoped that continued progress will allow novel neuroimaging methods to be included in future HAND management guidelines.

Soluble urokinase plasminogen activator receptor as a marker for use of antidepressants

Objectives

Inflammation is involved in the pathogenesis of depression. A few cross-sectional population-based studies have found that depression is associated with increased levels of inflammatory markers. Soluble urokinase plasminogen activation receptor (suPAR) is known to be a stable marker for inflammation. We investigated the bidirectional association between suPAR levels and use of antidepressants.

Methods

suPAR level was measured in 9305 blood donors and analysed in relation to 5-years follow-up data on purchase of antidepressants and hospital diagnoses of depression from a nationwide Danish register.

Results

For men and women without prior use of antidepressants we found a significantly higher risk for incident use of antidepressants with higher suPAR values. For men, the risk of first use of antidepressants increased by 72% from the 1^st to the 4^th quartile (HR = 1.72, 95% CI: 1.11–2.69). For women, it increased by 108% from the 1^st to the 4^th quartile (HR = 2.08, 95% CI: 1.45–2.98). Previous use of antidepressants was also significantly associated with higher suPAR levels (p = 0.002).

Conclusions

High suPAR levels are associated with an increased risk for both previous and future use of antidepressants in healthy men and women. High suPAR are also associated with increased risk for a hospital diagnosis of depression.

Predictors and treatment strategies of HIV-related fatigue in the combined antiretroviral therapy era

OBJECTIVE

To assess predictors and reported treatment strategies of HIV-related fatigue in the combined antiretroviral (cART) era.

METHOD

Five databases were searched and reference lists of pertinent articles were checked. Studies published since 1996 on predictors or therapy of HIV-related fatigue measured by a validated instrument were selected.

RESULTS

A total of 42 studies met the inclusion criteria. The reported HIV-related fatigue prevalence in the selected studies varied from 33 to 88%. The strongest predictors for sociodemographic variables were unemployment and inadequate income. Concerning HIV-associated factors, the use of cART was the strongest predictor. Comorbidity and sleeping difficulties were important factors when assessing physiological influences. Laboratory parameters were not predictive of fatigue. The strongest and most uniform associations were observed between fatigue and psychological factors such as depression and anxiety. Reported therapeutic interventions for HIV-related fatigue include testosterone, psycho-stimulants (dextroamphetamine, methylphenidate hydrochloride, pemoline, modafinil), dehydroepiandrosterone, fluoxetine and cognitive behavioural or relaxation therapy.

CONCLUSION

HIV-related fatigue has a high prevalence and is strongly associated with psychological factors such as depression and anxiety. A validated instrument should be used to measure intensity and consequences of fatigue in HIV-infected individuals. In the case of fatigue, clinicians should not only search for physical mechanisms, but should question depression and anxiety in detail. There is a need for intervention studies comparing the effect of medication (antidepressants, anxiolytics) and behavioural interventions (cognitive-behavioural therapy, relaxation therapy, graded exercise therapy) to direct the best treatment strategy. Treatment of HIV-related fatigue is important in the care for HIV-infected patients and requires a multidisciplinary approach.

Cerebral FDG-PET scanning abnormalities in optimally treated HIV patients

Background

The long-term neurological consequences of HIV infection and treatment are not yet completely understood. In this study we examined the prevalence of cerebral metabolic abnormalities among a cohort of neurologically intact HIV patients with fully suppressed HIV viral loads. Concomitant analyses of circulating brain derived neurotrophic factor (BDNF) were performed to correlate these abnormalities with potential signs of neuro-regenerating/protective activity, and concomitant analyses of circulating tumour necrosis factor (TNF) α, interleukin (IL) 6, and soluble urokinase plasminogen activator receptor (suPAR) were performed to correlate these abnormalities with potential signs of neurodegenerative processes.

Methods

The study population consisted of HIV-positive patients known to be infected for more than 5 years and on antiretroviral (ARV) treatment for a minimum of three years with no history of virological failure, a CD4 count above 200 × 10⁶ cells/l and no other co-morbidities. The distribution of the regional cerebral metabolic rate of glucose metabolism was measured using fluorine-18-flourodeoxyglucose positron emission tomography (FDG-PET) scanning. The PET scans were evaluated for individual pathology using Neurostat software and for group pathology using statistical parametric mapping (SPM). Circulating levels of BDNF, TNF α, IL-6 and suPAR were measured by ELISA techniques.

Results

More than half (55%) of the patients exhibited varying severities of mesial frontal reduction in the relative metabolic rate of glucose. Compared to healthy subjects, the patients with abnormal FDG-PET scanning results had a shorter history of known HIV infection, fewer years on antiretroviral therapy and higher levels of circulating TNF α and IL-6 (p = 0.08).

Conclusion

A large proportion of optimally treated HIV patients exhibit cerebral FDG-PET scanning abnormalities and elevated TNF α and IL-6 levels, which may indicate imminent neuronal damage. The neuroprotective effect of early ARV treatment should be considered in future prospective follow-up studies.

Functional neuroimaging of fatigue

Clearly, the use of functional neuroimaging for the study of fatigue is in its infancy. Relatively few studies focusing on fatigue using functional neuroimaging techniques have been published, and the few that exist focus primarily on persons with MS and CFS. The vast majority of these studies have examined self-reported fatigue, an approach that benefits from ease of administration but suffers from significant difficulties in interpretation. For example, we know that self-reported fatigue most often correlates with the degree of psychopathology.1 We also know that with more than 100 years of inquiry, self-reported fatigue does not correlate with objective measures of fatigue. As such, when functional imaging studies show a relationship between self-reported fatigue and activities in distinct areas of the brain, one must remain cautious about the interpretation of these results. A more recent approach in the functional imaging literature is to assess fatigue behaviorally during scanning and relate such objective measures of fatigue with cerebral activation. Although this is a new and novel approach, it remains unclear if this approach of operationally defining fatigue behaviorally will be a more valid paradigm in understanding the elusive construct of fatigue. Although fatigue is extraordinarily common as a symptom in many neurologic and psychiatric diseases, little is known about its precise mechanism. Chaudhuri and Behan hypothesized that the nonmotor functions of the basal ganglia play a key role in central fatigue. Specifically, they posit that fatigue is due to "alterations in the normal flow of sequential activation within the basal ganglia system affecting the neural integrator and the cortical feedback by the associated loop of the striato-thalamo-cortical fibers is a possible mechanism of central fatigue ." (p40). Therefore, other regions interacting with the basal ganglia may also contribute to fatigue, including the frontal cortex, thalamus, and the amygdala. In general, the functional imaging studies reviewed in this article tend to generally support the suggestion that damage to cortical-subcortical circuitry might be to blame for fatigue as well. If indeed fatigue is associated with functional impairment in a cortical-subcortical circuitry, it might be that studies that have examined structural damage (eg, total lesion load throughout the brain) may simply not provide the sensitivity required to detect a relationship between fatigue and pathology. After more than 100 years of frustration, it appears that functional neuroimaging techniques promise to provide an exciting potential for significant advances in our elusive understanding of the brain mechanisms associated with fatigue in clinical populations.

Physiological correlates of HIV-related fatigue

Our primary aim is to describe the relationship of multiple physiological variables and HIV-related fatigue. We report baseline data collected from 128 human immunodeficiency virus (HIV)-positive individuals. The HIV-Related Fatigue Scale was used to measure several aspects of fatigue. Blood was drawn for the following physiological variables: hepatic function, thyroid function, HIV viral load, immunologic function, gonadal function, hematologic function, serum cortisol, and cellular injury. In bivariable analyses, free testosterone (p=0.03) and CD8 (p=0.07) were negatively correlated with fatigue intensity, and nonlinear relationships were observed between fatigue intensity and total testosterone (p=0.02), thyroxine (p=0.01), hematocrit (p=0.06), and total bilirubin (p=0.06). However, none of these associations persisted in multivariable models. It is possible that fatigue suffered by seropositive people is better predicted by other variables, which must be better understood to develop interventions to successfully ameliorate HIV-related fatigue.