Lycium barbarum увеличивает калорийность расходы и уменьшает окружность талии у здоровых полных мужчин и женщин: пилотное исследование

4. Discussion

RPE is essential for neuroretina survival and, consequently, for visual function [43]. In response to damage caused by hyperglycemic condition, RPE cells migrate and proliferate, leading to a breakdown in adhesion between the RPE and the choroidal capillaries, followed by BRB breakdown, compromising blood flow within the RPE layer and leading to eventual retinal edema [37]. In addition, studies have shown that abnormalities in both the structural and secretory functions of RPE cells, followed by photoreceptor apoptosis are found in DR [43, 44].

An objective of the current study was to examine an extract of Goji berry and its major active component on protection of retinal epithelial cell against glucose-induced cytotoxicity as a model of diabetic retinopathy. Diabetes results in various metabolic and biochemical abnormalities in the retina, including increased oxidative stress, which has been shown to induce the expression of the proapoptotic molecules leading to apoptosis. Distinct members of the caspase family are involved in both the initiation and execution phases of apoptosis [45]. Among them, caspase-3 is the “executioner” caspase known to play an important role in the proteolytic cascade during apoptosis [46]. Moreover, the detection of activated caspase-3 is a very reliable tool to identify cells destined to die by apoptosis [47].

Our previous work has established that Gogi berry and its taurine component activate PPAR-γ [29]. PPAR-γ is heterogeneously expressed in the mammalian eye, prominently present in the retinal pigmented epithelium, photoreceptor outer segments, and choriocapillaris [48]. A recent study has shown that retinal expression of PPAR-γ was suppressed in experimental models of diabetes and in endothelial cells treated with high glucose [49]. Moreover, recent studies have suggested that PPAR-γ ligands, including 15d-PGJ₂ (PG) and rosiglitazone (RG), control apoptosis, contributing to tissue protection [50, 51]. Moreover, a screen of FDA-approved compounds identified RG as a novel anti-apoptotic agent in retinal cells both in vivo and in vitro [52]. Indeed, one recent study has shown that RG protects oxidative stress-induced apoptosis through upregulation of Bcl-2 and modulation of caspase-3 activation [17].

We have investigated the potential of Lycium barbarum (LB) as a natural medicine for management of diabetic retinopathy. LB is a traditional Chinese medicine used for centuries in the east and is believed to be beneficial for eye-related pathology [53]. Different biological activities of LB have been demonstrated, including antiaging and cytoprotection [54]. A recent study has shown that the aqueous extract of LB exhibits neuroprotective effects against β-amyloid peptide-induced apoptosis in cultured neurons by attenuating the caspase-3-like activity [55]. Moreover, it has been suggested that LB polysaccharides (LBPs) effectively protected the retina from neuronal death and apoptosis by inhibiting proapoptotic signaling pathways, such as c-Jun N-terminal protein kinase (JNK), dsRNA-dependent protein kinase (PKR), and caspase-3 activity in retinal ischemia/reperfusion injury, confirming a neuroprotective role in ocular diseases [56]. In addition, the study showed anti-apoptotic activity of LBP in cultured seminiferous epithelium against hyperthermia-induced damage through the inhibition of superoxide-induced cyt c [57].

In parallel with the studies on LB extract, we have investigated the effect of taurine on apoptotic cytotoxicity pathways in ARPE-19 cells. Taurine is one of the major components in LB present in retina in abundance, where it is essential for sustaining retinal structure and function [25]. Various studies have shown that plasma and tissue levels of taurine are reduced in diabetes [58–60]. Indeed, studies have shown the beneficial effect of taurine supplementation in preventing or ameliorating hyperglycemia-induced retinal defects [58, 59]. Moreover, recent studies have shown that diabetes or high-glucose-induced retinal glial cell apoptosis is inhibited by taurine, exhibiting effective prevention against DR [61]. Anti-apoptotic action of taurine has also been shown to occur by suppressing the Ca²⁺-dependent mitochondrial permeability transition (mPT) to prevent mitochondrial dysfunction and block activation of the cyt c/caspase-3 apoptotic pathway in rat retinal ganglion cells [62]. In addition, taurine exerts neuroprotective effects through an anti-apoptotic effect by increasing Bcl-2 levels, with a decrease in Bax and caspase-3 levels [15].

In previous work which formed the background leading to the present studies, we determined that LB extract and pure taurine, a major component in the LB extract, activated PPAR-γ by luciferase reporter gene analysis and by mRNA and western blotting measurement in human retinal pigment epithelial cells. At the same time, both LB extract and pure taurine inhibited a variety of PPAR-γ-dependent downstream effectors in the retinal cells [29]. In the present study, we hypothesised that taurine and the LB extract may have a modulating effect on high-glucose-induced apoptosis through PPAR-γ-mediated caspase-3 pathway, responsible for their effects in DR. In order to test this hypothesis, we first investigated the effect of taurine and LB extract on modulating cell viability and therefore apoptosis in high-glucose-treated ARPE-19 cells. Our results demonstrated that a methanol extract of LB dose dependently overcame the decreased cell viability in high-glucose-treated ARPE-19 cells (Figure 2). Taurine had a similar effect on overcoming decreased cell viability (Figure 2). The cytoprotective effect of taurine was associated with the attenuation of high-glucose-induced apoptosis, which was shown by characteristic morphological staining (Figure 3(b)) and Annexin V/PI double staining (Figure 4(b)), and a dose dependent decrease in the number of apoptotic cells (Figures 3(a) and 4(a)). Moreover, the results have shown that taurine and the LB extract dose-dependently downregulated caspase-3 protein expression (Figures 5(a) and 5(b)) and inhibited the enzymatic activity of caspase-3 (Figure 6). Therefore, the cytoprotective effect of LB extract parallels the profound suppression of high-glucose-induced apoptosis at the site of caspase-3 regulation. The effects of taurine closely mimicked the effects of the methanolic LB extract, since they occurred at concentrations 0.001–1.00 mM which we showed previously [29] were present in the range of methanolic extract used in the treatments (0.1 to 0.75 mg/mL). However, we cannot exclude the possibility that other components may also contribute to the cytoprotective effects of LB.

In summary, this study has demonstrated for the first time that the traditional Chinese medicine Lycium barbarum is cytoprotective against high-glucose cytotoxicity in retinal pigment epithelial cells, at least in part by regulating apoptosis as a result of caspase-3 modulation. This may occur through the initial PPAR-γ activation found in previous studies [29]. The effects of the extract are closely mimicked by taurine at concentrations present in the extracts. This pathway and demonstration of its major active component provide a rationale for the therapeutic use of taurine and the valuable medicinal herb LB for the prevention of DR. However, further investigation into their specific mechanisms is warranted to gather proof of efficacy and safety of taurine and LB for protection against DR in various preclinical and clinical settings.