1. Introduction
Aging is a natural process during an individual’s lifetime that leads to a decline in natural body functions [
1,
2]. The functional changes associated with aging have been identified as risk factors for various health problems, including hypertension, osteoporosis, diabetes, cataracts, heart failure, and neurodegenerative diseases [
3].
According to the World Health Organization (WHO), global life expectancy is increasing, and it is projected that the elderly population will reach 1.4 billion people by 2030 and exceed 2.1 billion by 2050 [
4]. With this demographic shift, it is imperative to seek solutions that address the detrimental effects of aging, ensuring that individuals can maintain their independence and experience healthy aging [
2,
5].
Pharmacological interventions aimed at prolonging human longevity and preventing age-related diseases are under investigation. The nematode
Caenorhabditis elegans has emerged as a promising model for studying the determinants of longevity.
C. elegans has a short lifespan, compact size, and conserved genetic pathways that regulate aging, such as insulin signaling, oxidative stress response, and longevity-related genes [
6].
In this study, we employed the C. elegans model to investigate the effects of Terasen®, nutraceutical formulation composed of standardized extracts of Euterpe oleracea, Myrciaria dubia, and purified oil of Bixa orellana and Astrocaryum aculeatum. The phytochemical markers of Terasen® include anthocyanins, quercetin, ellagic acid, gallic acid, carotenoids, geranylgeraniol, and tocotrienols, which have been extensively studied for their pharmacological properties and their potential impact on longevity.
4. Discussion
With aging, there is an imbalance of reactive species. Hence, we assessed the radical scavenging of Terasen® through DPPH and ABTS methods. Although the radical scavenging in the DPPH assay was low compared to the positive control gallic acid, it was high in the ABTS assay. This could be explained by the presence of the phenolic compounds from the formulation with a higher affinity for radical scavenging of ABST [
13,
14].
Then, the potential of Terasen® on longevity was evaluated in vivo using
C. elegans as a model organism. This tiny nematode, which measures only 1 mm in length as an adult, is cultured in Petri dishes using solid and liquid culture media, and its primary food source is Escherichia coli. With its two types of sex, hermaphrodite (XX) and male (XO), the hermaphrodite can generate 300 to 1400 offspring, facilitating the creation of a uniform genetic lineage [
15].
Despite its simple anatomy with few tissues and organs, the nervous system, gastrointestinal tract, gonads, and muscles of
C. elegans are comparable to those of more complex animals [
16]. Although it lacks adipose tissue or a liver, its intestine can perform similar functions, such as lipid synthesis and lipoprotein secretion [
17]. The genetic sequence of
C. elegans is well known, and genomic research has revealed that its genome has 60 to 80% of genes similar to those of human diseases and metabolic pathways [
18].
C. elegans has proven to be a valuable organism for studying aging, as it undergoes noticeable changes over time, such as alterations in body movement, pharyngeal pumping, egg-laying posture, and body size, among others [
19,
20].
The pharynx of
C. elegans has rhythmic contractions that occur at high frequencies in young adults, reaching 200-300 contractions per minute. However, with aging, there is a progressive decrease in the frequency of pharyngeal contractions [
21]. This study observed that the pharyngeal pumping rate of Terasen®-treated groups was decreased compared to the control group, indicating that Terasen® likely decreased the nematode’s feeding behavior.
Caloric restriction has been widely studied and is associated with increased longevity in various organisms, including
C. elegans, because reducing calorie intake promotes metabolic changes that stimulate stress resistance and cellular protection [
22]. This was observed in the study conducted by (Lakowski and Hekimi, 1998), where the authors reported that caloric restriction extended the lifespan of
C. elegans.
During this study, the production of eggs in
C. elegans was monitored daily, revealing a decrease in the number of progenies in animals treated with Terasen® compared to the control group. Monitoring reproductive capacity is essential to age research, as several interventions that prolong adult lifespan impact progeny production. Dietary restrictions also have been associated with reductions in progeny production during the early life phase of animals and a reduction in the total number of progenies produced by self-fertile hermaphrodites [
22].
The results showed that after 4 days of Terasen® treatment, there were significant changes in the body length of the nematodes compared to the control, although this difference mitigates on the eighth day. As for the body movements, there were no statistically significant changes in the animals treated (p > 0.05; Two-Way ANOVA), although a trend was observed of decreased movement. Usually, young adult hermaphrodites exhibit fluid and synchronized body movement. However, their motor coordination deteriorates as they age, becoming increasingly uncoordinated and unpredictable until they stop moving [
19].
Finally, we observed that the treatment increased the average and maximum lifespan of the nematodes. As observed, other effects were seen, including decreased pharyngeal contractions, reduced body length, and decreased laid eggs. Notably, all these effects are also observed during caloric restriction [
24]. Hence, it appears that Terasen® may activate the same pathways triggered by caloric restriction, even if food is normally provided.
Caloric restriction is a non-genetic intervention that can increase the lifespan and decrease the incidence of age-related diseases. Hence, a body of research has been aiming to test the mechanisms beneath this process to achieve healthy aging. Some of the core components involved in the beneficial effects of caloric restriction are the mTOR [
25,
26] and the insulin/insulin-like growth factor-1 signaling (IIS) pathway in humans [
27,
28]. Accordingly, in
C. elegans, the IGF-1 receptor is codified by the gene daf-2 in worms (igf1 in humans); reduction of this pathway will cause activation of DAF-16 (orthologue of the human FOXO), a transcription factor that will synthesize products involved in longevity and stress resilience [
9,
29]. The gene daf-16 is related to increased life expectancy in
C. elegans [
9,
30]. Another important player involved in life expectancy in
C. elegans is SKN-1 (orthologue of the human Nrf2), which is involved in the resistance to oxidative stress (
Figure 6) [
31].
Finally, we observed that the treatment increased the average and maximum lifespan of the nematodes. As observed, other effects were seen, including decreased pharyngeal contractions, reduced body length, and decreased laid eggs. Notably, all these effects are also observed during caloric restriction [
24]. Hence, it appears that Terasen® may activate the same pathways triggered by caloric restriction, even if food is normally provided.
Caloric restriction is a non-genetic intervention that can increase the lifespan and decrease the incidence of age-related diseases. Hence, a body of research has been aiming to test the mechanisms beneath this process to achieve healthy aging. Some of the core components involved in the beneficial effects of caloric restriction are the mTOR [
25,
26] and the insulin/insulin-like growth factor-1 signaling (IGF-1) pathway in humans [
27,
28,
32]. Accordingly, in
C. elegans, the IGF-1 receptor is codified by the gene daf-2 in worms (IGF-1 in humans); reduction of this pathway will cause activation of DAF-16 (orthologue of the human FOXO), a transcription factor that will synthesize products involved in longevity and stress resilience [
9,
29]. The gene daf-16 is related to increased life expectancy in
C. elegans [
9,
30]. Another important player involved in life expectancy in
C. elegans is SKN-1 (orthologue of the human Nrf2), which is involved in the resistance to oxidative stress (
Figure 6) [
31,
33].
Studies in the literature report that some plant secondary metabolites can aid in longevity by acting in these pathways. In line with the results observed here, some phytochemical compounds present in Terasen® have been reported to increase C. elegan’s lifespan, including anthocyanins, which are found in E. oleracea, quercetin, which is a marker from M. dubia, and tocotrienols, abundantly found in B. orellana.
[
29] reported that the extract of black rice, which is a rich source of anthocyanins (representing 43% of the extract), extended the lifespan, enhanced stress resistance, increased antioxidant enzymes activity, and reduced the accumulation of lipofuscin, ROS, and MDA. The treatment downregulated the expression of age-1 and daf-2 mRNA while upregulated daf-16 mRNA and upregulated protein expression of SOD-3, CTL-1, and GST. The major anthocyanins found were cyanidin-3-O-glucoside (76.15 %) and peonidin-3-O-glucoside (22.11 %).
The increased lifespan and stress resistance in
C. elegans induced by cyanidin-3-O-glucoside (the most abundant anthocyanin from
E. oleracea) was also reported by [
34]. Other anthocyanin-rich sources that were reported to increase
C. elegans’ lifespan were
Prunus cerasus [
35],
Paeonia suffruticosa [
36],
Eugenia uniflora [
37], and
Euterpe precatoria [
38].
E. oleracea also increased longevity in
Drosophila melanogaster [
39].
M. dubia has quercetin as marker. [
40] reported that quercetin increased the mean lifespan of
C. elegans by 15%, and increased the translocation of DAF-16 to the nucleus, a mechanism correlated with stress response and longevity. This was also reported by [
41], who also showed that quercetin is safer than its glycosylated forms.
The phytochemical markers of
A. aculeatum include gallic acid, ellagic acid, and carotenoids. Cocoa beans, derived from
Theobroma cacao, are commonly used to produce chocolate and cocoa powder. A single serving of cocoa powder (about 2 tablespoons) contains high levels of gallic acid [
42]. In a study conducted by [
43], the effects of cocoa powder enriched with polyphenols were evaluated on resistance to oxidative stress in biological models such as the yeast
Saccharomyces cerevisiae and the nematode
C. elegans. The results showed that cocoa enriched with polyphenols increased resistance to oxidative stress in both models, as well as life expectancy in the nematode. These effects were attributed to the presence of polyphenols in cocoa and the sirtuins Hst3 and SIR-2.1, in addition to the insulin/IGF-1 signaling pathway in the nematode.
A recent study [
44] delved into the impact of extracts from
Glochidion zeylanicum leaves on
C. elegans, specifically examining their anti-aging and oxidative stress resistance properties. The study employed HPLC analysis to identify oxyresveratrol and quercetin, as well as high levels of gallic acid and catechin within the extracts. Findings revealed that these leaf extracts from
G. zeylanicum provided protection against oxidative stress, regulated stress response genes like SOD-3 and GST-4, and involved transcription factors DAF-16/FoxO and SKN-1/Nrf-2 in the oxidative stress resistance properties. Additionally, the extracts improved pharyngeal pumping function and increased the life expectancy of worms, suggesting anti-aging benefits.
The impact of raspberry extracts (RE), which consist of various phytochemical compounds such as ellagic acid, salicylic acid, chlorogenic acid, p-coumaric acid, quercitrin, catechin, and luteolin, on the lifespan of
C. elegans and the underlying mechanisms were studied [
33]. The findings demonstrate that RE enhances resistance to oxidative stress, increases the activity of antioxidant enzymes, and decreases the excessive production of reactive oxygen species. Nevertheless, in certain mutants, the administration of RE had disparate effects, indicating that the SKN-1/Nrf2 pathway is vital in regulating RE-induced longevity and response to oxidative stress.
A study by [
45] evaluated the effects of ß-carotene and fucoxanthin on the lifespans of
D. melanogaster and
C. elegans. The findings indicated that both carotenoids extended the lifespan of fruit flies, while only fucoxanthin exhibited beneficial effects on nematodes. The activation of the FOXO transcription factor by carotenoids initiated a series of events that triggered the activation of stress response genes, culminating in heightened resistance to stressors and an increase in lifespan.
According to research conducted by [
46], mamey carotenoids were analyzed for their antioxidant properties on nematodes. The study found that both pure β-carotene and mamey pulp extract (MPCE) enhanced resistance to oxidative stress and increased the survival rate of the nematodes. However, it was observed that mamey skin extract (MSCE) had adverse effects due to the degradation of β-carotene. Even though high concentrations of MSCE were toxic, they still managed to improve survival, likely due to antioxidant mechanisms and the phenomenon of hormesis.
Finally, Terasen® has the oil of
B. orellana in its composition, a rich source of tocotrienols. Tocotrienols are another group of compounds that potentially increase lifespan. [
47] showed that
C. elegans subjected to oxidative stress with hydrogen peroxide had decreased lifespan and increased lipofuscin accumulation. On the other hand, animals treated with a tocotrienols-rich fraction had restored lifespan and reduced lipofuscin accumulation. [
48] reported that the lipophilic extract of
B. orellana increased the median and maximum lifespan by 35% and 27%, increasing oxidative and thermal stress without affecting the fertility (which is different from what was observed here). According to the authors, the effect depended on the insulin/insulin growth factor-1 pathway.