Dried plum and chokeberry ameliorate d-galactose-induced aging in mice by regulation of Pl3k/Akt-mediated Nrf2 and Nf-kB pathways
Introduction
Aging is process which may be described as deterioration of the physiological system and impairment of the homeostatic condition. According to free radical theory, or the oxidative stress hypothesis, attack of free radicals on cells and tissues results in the accumulation of reactive oxygen species (ROS) (Harman, 1956). Excessive ROS levels bring about lipid peroxidation, specifically the formation of malondialdehyde (MDA) and accumulation of advanced glycation end product (AGE) (Cand and Verdetti, 1989, Munch et al., 1997). It also results in the deterioration of the antioxidative system, which acts as a crucial defense system in the aging process (Sohal and Weindruch, 1996). Many studies have investigated concrete process of aging and phosphoinositide 3-kinase (PI3K) / Akt, nuclear factor-erythroid 2-related factor 2 (Nrf2) and nuclear factor-kappa B (Nf-κB) are one of candidates to explain the process (Krasilnikov, 2000, Salminen and Kaarniranta, 2009, Chapple et al., 2012).
PI3K and its downstream factor, Akt pathway plays an important role in cell proliferation, survival, growth and responses to various nutrients (Liang and Slingerland, 2003). PI3K is in control of major functions related to aging such as regulation of the number and activities of various stem cells (Sahin and Depinho, 2010). There have been many attempts to investigate the involvement of the PI3K/Akt cascade pathway in the anti-apoptotic and aging (Krasilnikov, 2000).
Nrf2 is an important regulator of many antioxidants in organisms. Nrf2 exhibits a defense system against oxidative stress through association with Kelch-like ECH-associated protein 1 (KEAP1). Together with KEAP1, Nrf2 controls the activities of antioxidative enzymes such as heme oxygenase-1 (HO-1), catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) (Taguchi et al., 2011). Previous researches reported that Nrf2, which possesses antioxidative and protective functions, is related to the aging process provoked by oxidative stress (Sykiotis et al., 2011, Tomobe et al., 2012).
Nf-κB is located with other proteins, which suppress its translocation into the nucleus (Knight, 2000). Oxidants, several cytokines and viruses activate Nf-κB to enter the nucleus and diverse cytokines, chemokines and adhesion molecules are influenced (Tilstra et al., 2011, Knight, 2000). Among them, inducible nitric oxide synthetase (iNOS) is one of the isoforms of nitric oxide synthases (NOS) regulated by Nf-κB (Aktan, 2004). Taken together, Nf-κB and iNOS pathway is a crucial mechanism in inflammatory responses (Aktan, 2004). Previous studies have demonstrated that aging process and expression of Nf-κB are related (Salminen and Kaarniranta, 2009, Tilstra et al., 2011, Kim et al., 2002). Age-related change in the expression of Nf-κB is considered to be linked to increased oxidative stress during senescence (Kim et al., 2008).
In order to investigate the meticulous mechanism of aging, animal studies are implemented and provide detailed sources on process of aging. Especially, in previous studies, d-galactose has been proposed as an agent to induce senescence of animals because it provides mimetic condition to that of aging, such as increased oxidative stress level in lungs, livers, kidneys and brains (Yeh et al., 2014, Li et al., 2014, Hadzi-Petrushev et al., 2015, Yu et al., 2015a, Yu et al., 2015b). High level of d-galactose in the cell leads to reduction into galactitol, which may result in cell swelling (Ho et al., 2003). Consequently, ROS accumulates and AGE binds to AGE receptor, resulting in proinflammatory responses (Yeh et al., 2014). Also, d-galactose-induced aging has been reported to decrease activities of antioxidant enzymes and activate proinflammatory cytokines (Hadzi-Petrushev et al., 2015, Yu et al., 2015a, Yu et al., 2015b). However, more researches are needed to elucidate the concrete mechanism of how d-galactose influence antioxidant enzymes and proinflammatory cytokines. The present study investigated d-galactose-induced aging model and tried to address the underlying issues of the mimetic aging model.
A wide variety of foods and dietary methods that can delay the aging process or lead to healthy aging have been proposed in previous senescence studies (Willcox et al., 2007, Piper and Bartke, 2008) (Hallfrisch et al., 1990). Foods with high polyphenol contents, such as wine, walnuts, olive oil and wild blueberries, have received considerable attention and many studies have reported potential effectiveness in slowing the aging process (Valls-Pedret et al., 2012, Obrenovich et al., 2010, Papandreou et al., 2009).
Chokeberry is a member of the Rosaceae family and the black chokeberry (Aronia melanocarpa) is the main cultivar used for fruit production (Kulling and Rawel, 2008). Chokeberry is famous for high polyphenols such as anthocyanins, proanthocyanidins, hydroxycinnamic acids, flavonols, flavan-3-ols and chlorogenic acids (Denev et al., 2012). Chokeberry has been widely studied to prove its effectiveness against inflammation, atherosclerosis and liver damage (Appel et al., 2015, Kim et al., 2013; Valcheva-Kuzmanova et al., 2004). Although chokeberry exhibits protective effects in many physiological states, cultivation of the fruit increased originally for food coloring due to its distinctive bitter and astringent taste. For this reason, chokeberry was consumed in mixtures of sweet fruits such as apples, pears and currants and chokeberry products on the market nowadays still add sweetness to enhance the palate (Kulling and Rawel, 2008).
Dried plums, also known as prunes, have sweetness in the taste and are produced by dehydrating Prunus domestica L. at high temperatures for several hours (Shukitt-Hale et al., 2009). The dehydration process not only darkens the color of plums, but also increases total phenolic compounds and antioxidant capacity (Stacewicz-Sapuntzakis, 2013). The main components that contribute to antioxidative power of dried plums are nechlorogenic acid (3-O-caffeolyquinic acid), chlorogenic acid (5-O-caffeolyquinic acid) and cryptochlorogenic acid (4-O-caffeolyquinic acid) (Nakatani et al., 2000). Dried plums have been reported to have beneficial effects in osteoclast differentiation, inflammatory responses and lipid metabolism (Rendina et al., 2013, Hooshmand et al., 2015, Gallaher and Gallaher, 2009).
Precedent studies suggested that foods high in polyphenol content exhibit antioxidative power and delay senescence (Valls-Pedret et al., 2012, Obrenovich et al., 2010, Papandreou et al., 2009, Fernández and Fraga, 2011, Reinisalo et al., 2015). Dried plum and chokeberry are rich in polyphenols and shown to have beneficial effects in slowing aging process (Stacewicz-Sapuntzakis, 2013, Nakatani et al., 2000, Kulling and Rawel, 2008, Denev et al., 2012). Therefore, we aimed to investigate the effect of dried plum and chokeberry, both separately and combined, in d-galactose-induced aging model to suggest potential foods that can slow aging process. In specific, the influence of d-galactose injection in aging markers and the PI3K/Akt pathway along with Nrf2 and Nf-κB regulation were investigated in order to elucidate the detailed mechanism of d-galactose-induced aging. Consequently, mimetic aging model with d-galactose injection may be confirmed in more definite and concrete manner.
Section snippets
Preparation of diets
The normal diet was a modification of AIN-93 M diet (Research diet, New Brunswick, NJ, USA). Dried plum was purchased from E-mart (Seoul, Korea) and its composition, shown in Table 1, was investigated before making experimental diets. Chokeberry was purchased from San Deul Hae, Inc. (Hamyang-gun, Gyeongnam, Korea) and freeze-dried for 2 days (Bondiro MCFD 8508 Freeze Dryer, Ilshin, Seoul, Korea). Thereafter, dried chokeberry was grounded with mixer. Dried plum and chokeberry diets were adjusted
Body weight, organ coefficient and food intake
Body weight, organ weight and food intake of each group is presented in Table 3, Fig. 1. Initial body weights did not show significant difference among all groups. In addition, body weight changes during 8 weeks of study period did not show significant difference. Food intake per day in each group did not differ significantly among all 5 groups. Organ coefficients, presented in Table 4, Fig. 2, were calculated with livers, kidneys, hearts and lungs. Coefficients of aforementioned organs did not
Discussion
Accumulation of oxidative stress accelerates the aging process and lipid peroxidation, which results in the increased formation of MDA (Cand and Verdetti, 1989). Increased oxidative stress leads to the binding of AGE to AGE receptor (RAGE), which promotes oxidative stress and the formation of AGE (Peppa et al., 2008). d-galactose has been proposed as an agent to induce aging in animal studies. A high level of D-galactose is reduced to galactitol which accumulates in the cell, causing cell
Acknowledgement
This work was supported by the Medical Research Center Program (No. 2011-0030074) through National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP).
References (73)
iNOS-mediated nitric oxide production and its regulation
Life Sci.
(2004)- et al.
Chokeberry (Aronia melanocarpa (Michx.) Elliot) concentrate inhibits NF-κB and synergizes with selenium to inhibit the release of pro-inflammatory mediators in macrophages
Fitoterapia
(2015) - et al.
Superoxide dismutase, glutathione peroxidase, catalase, and lipid peroxidation in the major organs of the aging rats
Free Radic. Biol. Med.
(1989) - et al.
Crosstalk between Nrf2 and the proteasome: therapeutic potential of Nrf2 inducers in vascular disease and aging
Int. J. Biochem. Cell Biol.
(2012) - et al.
Inflammation, free radicals and antioxidants
Nutrition
(1996) - et al.
Antimutagenic activity of anthocyanins isolated from Aronia melanocarpa fruits
Cancer Lett.
(1997) - et al.
Aging-induced up-regulation of nuclear binding activities of oxidative stress responsive NF-kB transcription factor in mouse cardiac muscle
J. Mol. Cell. Cardiol.
(1996) - et al.
Anti-inflammatory effects of β-hydroxyisovalerylshikonin in BV2 microglia are mediated through suppression of the PI3K/Akt/NF-kB pathway and activation of the Nrf2/HO-1 pathway
Food Chem. Toxicol.
(2014) - et al.
Alterations of antioxidant enzymes and oxidative stress markers in aging
Exp. Gerontol.
(2001) - et al.
Influence of aging and calorie restriction on MAPKs activity in rat kidney
Exp. Gerontol.
(2002)