The human immunodeficiency virus (HIV) is one of the most prevalent diseases globally. The highly active antiretroviral therapy (HAART) involves combining various types of antiretroviral drugs that are dependent on the infected person’s viral load. HAART helps regulate the viral load and prevents its associated symptoms from progressing into acquired immune deficiency syndrome (AIDS). Despite its success in prolonging HIV-infected patients’ lifespans, the use of HAART promotes metabolic syndrome (MetS) through an inflammatory pathway, excess production of reactive oxygen species (ROS), and mitochondrial dysfunction. Interestingly, Spirulina platensis (SP), a blue-green microalgae commonly used as a traditional food by Mexican and African people, has been demonstrated to mitigate MetS by regulating oxidative and inflammatory pathways. SP is also a potent antioxidant that has been shown to exhibit immunological, anticancer, anti-inflammatory, anti-aging, antidiabetic, antibacterial, and antiviral properties.
1. Introduction
The human immunodeficiency virus (HIV) has continued to be a global public concern due to its widespread infection rate and alarming mortality rate
[1]. The Joint United Nations Programme on HIV/AIDS (UNAIDS), in its most recent report in November 2021, estimated that 37.7 million people globally are living with HIV. It was also reported that about 1.5 million new HIV infections and 680,000 AIDS-related deaths have occurred in the year 2020
[1][2][3][4]. In South Africa, approximately 8.2 million people were living with HIV in the year 2021
[4]. According to the South African mid-year population statistics 2021, there has been an unprecedented increase from 79,420 to 85,154 HIV-AIDS-related deaths in 2021
[4]. Recently, the easy availability of antiretrovirals (ARVs) has tremendously changed the pattern of death. ARVs have also helped prolong the lifespan of HIV-infected people in South Africa. Globally, about 27.5 million HIV-infected persons had access to ARVs in 2020, while approximately 5.6 million infected South Africans accessed ARVs in 2020
[1][4][5].
The highly active antiretroviral therapy (HAART) entails combining three or more antiretroviral drugs that are subject to the HIV-infected person’s viral load. HAART assists in regulating viral loads and preventing the progression to AIDS. Despite its success in prolonging HIV-infected patients’ lifespans, the use of HAART promotes metabolic syndrome (MetS) through an inflammatory pathway, excess production of reactive oxygen species (ROS), and mitochondrial dysfunction. Over three decades since its discovery, HAART has significantly improved the diagnosis and management of persons with HIV
[6][7][8][9][10][11][12]. The persistence of MetS before and during HAART treatment further highlights the need for more studies on MetS inhibitory compounds, such as
Spirulina platensis (SP)
[13],
Moringa oleifera [14][15], Curcumin
[16], and Mangiferin
[17]. However, there are other alternatives to combat MetS and these include exercise training
[18], life style changes, and properly balanced healthy food choices
[19][20].
SP is a blue-green microalgae commonly used as a traditional food by some Mexican and African people
[21][22]. SP is mostly found in the alkaline water of volcanic lakes. In addition to its popular nutritional value, SP possesses various medicinal properties. It can induce both the humoral and cellular mechanisms of the immune system when consumed
[22]. Interestingly, SP was linked with MetS-lowering properties, such as hypoglycemia
[23], hypolipidemia
[24], and hypotension
[13]. Studies in rodents suggested that SP is particularly useful in preventing MetS
[13]. SP contains oxidative stress inhibitors, phycocyanin and phycocyanobilin
[25][26][27]. Previous studies have also demonstrated that SP inhibits oxidative stress
[21][25][28][29] and promotes mitochondrial health
[30][31][32][33], thereby inhibiting inflammation
[25][34]. Furthermore, SP can prevent the development of atherosclerosis
[28] and diabetes
[25]. The Food and Agriculture Organization (FAO) of the United Nations recommends
Spirulina as a daily dietary supplement
[35]. Microalgaes including
Spirulina are environmentally friendly and have a high rate of yield in large-scale production under controlled conditions
[36].
Spirulina, in addition to its nutritional and medicinal security, has the potential to eliminate poverty. The considerable potential for sustainable financial development in a small-scale crop for nutritional enhancement was evident in China, where the production increase resulted in a dramatic increase in profit from USD 7.6 million to USD 16.6 million.
Spirulina production is possible for small and marginal farmers as well as enthusiastic urban gardeners; this makes it easily accessible to the population
[37]. Moreover, the health system can provide SP as medication to control adverse effects in people living with HIV on HAART with minimal costs.
2. The Roles of HIV and HAART in MetS
HIV has often been associated with MetS
[38], which results in cardiovascular diseases. Recent reports have linked some HIV-related features to MetS. These characteristic features include escalated cases of cardiovascular diseases, type 2 diabetes mellitus, dyslipidemia, immunodeficiency, high viral load, and atherosclerosis
[7]. Recently, studies have suggested that HAART, in addition to the above-mentioned HIV-related features, actively induces MetS in persons with HIV
[7][39][40][41]. Earlier studies by Palios et al. (2011) on arterial stiffness, displayed by pulse wave velocity (PWV), and markers of MetS, reported that persons with HIV exhibited an increased degree of PWV when compared with the healthy controls. Subsequently, persons on HAART have been shown to exhibit a similar PWV as persons with hypertension
[39][40]. The prevalence of MetS in HIV-infected people receiving antiretroviral (ARV) treatment was higher when compared to the general population. This prevalence was attributed to age, physical inactivity, and a low cluster of differentiation 4 (CD4) count
[42][43][44]. The patient response to HAART varies; some antiviral drugs can successfully suppress the plasma viral load without increasing the CD4 count; this allows the risks of opportunistic infections and abnormalities. Failure to increase the CD4 count during HAART may be due to several factors, including drug resistance, low CD4+ T-cell count at the initiation of HAART, the advanced stage of the disease, and a low adherence to HAART
[45].
3. Spirulina Species
Spirulina has three commonly investigated species due to their potential therapeutic nature and high nutritional content. These Spirulina species include Spirulina platensis (SP) (otherwise known as Arthrospira platensis), Spirulina maxima (Arthrospira maxima), and Spirulina fusiformis (Arthrospira fusiformis). These Spirulina species are also classified as oxygenic photosynthetic bacteria under Cyanobacteria and Prochlorales [46][47][48][49][50][51]. SP is found in alkaline water with abundant bicarbonate and saline [22][52]. Spirulina species are generally three-dimensional helix microstructures [53] protected by a cell wall composed of complex sugars and proteins [22]; however, helical transformation results after mature trichomes divide into hormogonia, binary fission, and undergo length elongation [54]. SP is considered an antioxidant and anti-inflammatory agent [55].
SP contains several vital antioxidant and anti-inflammatory compounds as mentioned above, such as chlorophyll, phycocyanin, and carotenoids (β-carotene). The antioxidant and anti-inflammatory properties of phycocyanin have been determined in numerous studies
[28][56][57][58][59][60][61][62][63][64][65][66][67]. Phycocyanin is responsible for reducing oxidative stress and NADPH oxidase
[28]. It scavenges free radicals, such as alkoxy, hydroxyl, and peroxyl radicals, and decreases nitrite production and inducible nitric oxide synthase (iNOS) expression. Phycocyanin also inhibits liver microsomal lipid peroxidation
[28][56][57][58][59][60][61][62][63][64][65][66][67].
Phycocyanin has been proven to inhibit the formation of the pro-inflammatory cytokine TNF-α and cyclooxygenase-2 (COX-2) expression. Additionally, it decreases prostaglandin E(2) production
[28][56][57][58][59]. Phycocyanin prevents the degradation of cytosolic IκB-α, which suppresses the activation of nuclear factor-κB (NF-κB)
[28]. Furthermore, the inhibitory activity of phycocyanin is associated with the suppression of TNF-α formation in the macrophages
[59]. In addition, phycocyanin exerts regulatory effects on mitogen-activated protein kinase (MAPK) activation pathways, such as the p38, c-Jun N-terminal kinase (JNK), and extracellular-signal-regulated kinase (ERK1/2) pathways
[68][69][70]. The second compound of SP, carotenoids, β-carotene to be specific, is an antioxidant that has anti-carcinogenic, antioxidant, and anti-inflammatory activities
[71][72][73]. As a membrane antioxidant, β-carotene protects against singlet oxygen-mediated lipid peroxidation
[71]. Beta carotene inhibits the production of nitric oxide and prostaglandin E(2) and suppresses the expression of inducible nitric oxide synthase (iNOS), COX-2, TNF-α, and IL-1β. The suppression of inflammatory mediators by β-carotene results from its’ ability to inhibit NF-κB activation by preventing nuclear translocation of the NF-κB p65 subunit
[72][74][75]. Studies have shown that β-carotene suppressed the transcription of inflammatory cytokines such as IL-1β, IL-6, and IL-12 in vitro
[73]; this takes place in the macrophages. The third compound of
spirulina, chlorophyll, can perform antioxidant and antimutagenic activities
[76][77].
Spirulina’s mechanism of action is a concert of compounds, but it is not clear whether they all act simultaneously during demanding events.
4. Common Highly Active Antiretroviral Therapy (HAART) Combinations
HAART has several classes: nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs)
[78][79][80][81][82][83][84][85][86], protease inhibitors (PIs)
[86][87][88][89], integrase strand transfer inhibitors (INSTIs)
[90][91][92][93][94][95], fusion inhibitors (FIs)
[96], and chemokine receptor antagonists (CCR5 antagonists)
[97][98][99]. HAART is a specifically selected combination of NRTI and NNRTI, PI, or INSTI drugs responsible for the inhibition of viral replication by multiple virus targets
[85][100][101][102][103][104][105][106][107][108]. However, HAART can cause adverse drug reactions. Furthermore, 2′,3′-dideoxy-3′-thiacytidine (3TC), 2′,3′-dideoxy-5-fluoro-3′-thiacytidine (FTC), TDF (Tenofovir Disoproxil Fumarate), ZDV (Zidovudine), and d4T (Stavudine) are associated with mitochondrial toxicity and oxidative stress
[109][110][111][112]. Additionally, NNRTIs are linked to toxic hepatitis, and PIs are implicated in insulin resistance and hyperlipidemia
[86]. Chronic side effects linked to HAART include ROS-induced insulin resistance
[113][114], lipodystrophy, gastrointestinal disorders
[115], and cardiovascular disease
[11][116]. Primarily, HAART is used for the treatment and prevention of HIV-1. These primary functions of HAART are achieved by attacking different components of the virus lifecycle which ensures inhibition regardless of the virus being resistant to one of the drugs
[85][100][101][102][103][104][105][106][107][108]. A combination of two NRTIs (mostly FTC and TDF) and one NNRTI (e.g., EFV; Efavirenz) is a more favorable choice due to the convenience to dose, effectiveness, and less toxic effects compared to other drug combinations
[86][117][118]. A combination of three NRTIs is less effective than two NRTIs with an NNRTI
[119]. The d4T/ddI combination is associated with high toxicity and hence it is not often recommended
[120]. The most popular NRTIs are cytidine analogs (XTC), FTC, 3TC, and TDF, which form part of the first-line therapy
[121][122][123][124][125]. FTC and 3TC are similar in chemical structures with different pharmacokinetic and pharmacodynamic properties, and they have required deoxynucleosides for HIV DNA synthesis. They undergo phosphorylation through intracellular kinases to become FTC 50 -triphosphate (FTC-TP) and 3TC-TP; triphosphate metabolites with FTC-TP are more efficiently incorporated during HIV DNA synthesis than 3TC-TP
[117][126][127][128][129]. Moreover, 3TC-TP has a shorter intracellular half-life compared to FTC-TP
[127]. The TDF and FTC combination has a synergistic effect, increasing intracellular metabolites, and they are recommended for pre-exposure prophylaxis (PrEP)
[127][130][131][132][133].
5. Mechanism of HAART-Induced Oxidative Stress, Inflammation, and Mitochondrial Dysfunction
The exact mechanism of HAART-induced oxidative stress has not been completely explored; however, studies have demonstrated the link between HAART use and oxidative stress. HAART is linked with lipid metabolism dysfunction through the induction of peripheral lipodystrophy. Lipodystrophy results from the impaired cytoplasmic retinoic-acid binding protein type 1 (CRABP1)-mediated cis-9-retinoic acid stimulation of peroxisome proliferator-activated receptor type gamma (PPAR-γ), leading to impaired differentiation and increased apoptosis of peripheral adipocytes. HIV-1 protease-inhibitors further inhibit the cytochrome P450 3A-mediated synthesis of cis-9-retinoic acid, one of the key activators of PPAR-γ
[134]. Insulin resistance occurs following impaired fat storage and lipid release
[113][114][134], which impacts the oxidant profile. The depletion of ATP production and mitochondrial dysfunction
[8][9], and the depletion of mitochondrial DNA
[135][136][137], are some of the ways HAART induces oxidative stress. HIV increases oxidative stress, and HAART increases lipid oxidation, which amplifies the ROS imbalance leading to increased oxidative stress complications
[10][138].
6. Combined and Synergistic Therapeutic Actions of HAART and SP
Studies have shown that the possible therapeutic effects of antioxidants may provide strategies in suppressing oxidative stress-induced comorbidities that emerge with the use of HAART therapy in HIV-infected individuals
[12]. The combination of HIV and HAART has been associated with increased oxidative stress and lipid peroxidation. Furthermore, HIV or HAART induces ROS by inducing NADPH oxidase
[139][140]. Interestingly, SP is a potent antioxidant
[26][27] with anti-inflammatory activities
[34], which makes it a potential supplement in the mitigation of oxidative stress induced by HAART adverse drug reactions. Moreover, SP can inhibit NADPH oxidase which is considered one of the main sources of ROS and free radicals in HIV-infected persons on HAART
[34][139][140], resulting in reduced oxidative stress
[28]. Moreover, β-carotene from SP protects against singlet oxygen-mediated lipid peroxidation
[71]. Among HAART complications, TDF and lopinavir cause acute and chronic renal dysfunction
[141][142][143][144][145]. Herein, phycocyanin from SP can normalize urinary and renal oxidative stress markers and inhibit NADPH-dependent superoxide production in renal mesangial cells
[25], ameliorating renal dysfunction. Lately, SP has been an effective therapeutic approach to preventing diabetic nephropathy through the inhibition of oxidative stress
[25]. These properties indicate SP as a potential agent to mitigate renal dysfunction caused by HAART. As mentioned above, NRTIs can inhibit mitochondrial DNA polymerase
[146][147]. Studies in vitro showed that SP can enhance cell nucleus enzyme function, repair DNA synthesis
[54], and enhance mitochondrial health
[30][31][32][33][148]. Mitochondrial toxicity presented as peripheral neuropathy and lactic acidosis can be corrected by SP through providing trace minerals for the synthesis of antioxidant enzymes
[149] and reducing chronic inflammatory conditions
[150].
NNRTIs are associated with life-threatening skin reactions and toxic hepatitis
[86], these conditions may be ameliorated by SP. Phycocyanin from SP can inhibit liver microsomal lipid peroxidation
[28][56][57][58][59][60][61][62][63][64][65][66][67], and hence reducing toxic hepatitis. Moreso, SP incorporated into skin creams showed promising results as an anti-inflammatory and a wound-healing agent
[151]; this can be beneficial in the mitigation of NNRTI-induced skin reactions. PI therapy induces insulin resistance and hyperlipidemia
[7]. Additionally, HAART may be associated with a higher risk of myocardial infarction
[86][152][153]. SP has a therapeutic effect against vascular diseases, cancer, diabetes, and neurodegenerative diseases
[154]. In addition, the
Spirulina family has also shown central neuroprotective effects in rodents
[155] and may exert its neuroprotective activities through antioxidant and anti-inflammatory effects
[156]. Therefore, SP is a recommended antioxidant to use as a supplement; the list of benefits is evident. It also has antiallergic effects
[51], prevents cellular aging and infectious diseases, and promotes a strong immune system
[54]. Herein, promotion of a strong immune system by SP can help increase CD4 cell counts, lower HIV viral loads, and slow down the progression to AIDS. Moreover, SP prevents FR-induced apoptotic cell death
[157]; this may help decrease apoptosis of peripheral adipocytes induced by HAART. Chemically, SP is a recommended source of proteins, vitamins, and minerals
[54], important nutrients for individuals on the HAART program. Finally, SP can assist HAART in the inhibition of HIV-1 replication because it has been shown to inhibit viral production in PBMCs.