The pathways that impact longevity in the wake of dietary restriction (DR) remain still ill-defined. Most studies have focused on nutrient limitation and perturbations of energy metabolism. We showed that the L-threonine was elevated in Caenorhabditis elegans under DR, and that L-threonine supplementation increased its healthspan. Using metabolic and transcriptomic profiling in worms that were fed with RNAi to induce loss of key candidate mediators. L-threonine supplementation and loss-of-threonine dehydrogenaseincreased the healthspan by attenuating ferroptosis in a ferritin-dependent manner. Transcriptomic analysis showed that FTN-1 encoding ferritin was elevated, implying FTN-1 is an essential mediator of longevity promotion. Organismal ferritin levels were positively correlated with chronological aging and L-threonine supplementation protected against age-associated ferroptosis through the DAF-16 and HSF-1 pathways. Our investigation uncovered the role of a distinct and universal metabolite, L-threonine, in DR-mediated improvement in organismal healthspan, suggesting it could be an effective intervention for preventing senescence progression and age-induced ferroptosis.

Korean ginseng has been widely evaluated to treat human diseases; however, most studies on Korean ginseng have focused on its root. In this study, polysaccharides [acidic-polysaccharide-linked glycopeptide (APGP) extracted with 90% ethanol and hot water] were prepared from Korean ginseng berries, and their effect on immunosenescence was explored. The effect of APGP on thymic involution was evaluated by measuring the size of thymi dissected from aged mice. The effect of APGP on populations of immune cells, including natural killer (NK) cells, dendritic cells, age-correlated CD11c-positive B cells, and several subtypes of T cells [CD4-positive, CD8-positive, and regulatory (Treg) T cells] in the thymi and spleens of aged mice was analyzed by fluorescence-activated cell sorting analysis. Serum levels of interleukin (IL)-2 and IL-6 were evaluated by enzyme-linked immunosorbent assay analysis. Profiles of APGP components were evaluated by high-performance liquid chromatography (HPLC) analysis. APGP suppressed thymic involution by increasing the weight and areas of thymi in aged mice. APGP increased the population of NK cells, but showed no effect on the population of dendritic cells in the thymi and spleens of aged mice. APGP decreased the population of age-correlated CD11c-positive B cells in the spleens of aged mice. APGP showed no effect on the populations of CD4- and CD8-positive T cells in the thymi of aged mice, whereas it increased the population of Treg cells in the spleens of aged mice. APGP further decreased the reduced serum levels of IL-2 in aged mice, but serum levels of IL-6 were not statistically changed by APGP in aged mice. Finally, HPLC analysis showed that APGP had one major peak at 15 min (a main type of polysaccharide) and a long tail up to 35 min (a mixture of a variety of types of polysaccharides). These results suggested that APGP exerted an anti-immunosenescent effect by suppressing thymic involution and modulating several types of immune cells.

The skin of an organism is affected by various environmental factors and fights against aging stress via mechanical and biochemical responses. Photoaging induced by ultraviolet B (UVB) irradiation is common and is the most vital factor in the senescence phenotype of skin, and so, suppression of UVB stress-induced damage is critical. To lessen the UVB-induced hyperimmune response and hyperpigmentation, we investigated the ameliorative effects of intense pulsed light (IPL) treatment on the photoaged phenotype of skin cells. Normal human epidermal keratinocytes and human epidermal melanocytes were exposed to 20 mJ/cm² of UVB. After UVB irradiation, the cells were treated with green (525–530 nm) and yellow (585–592 nm) IPL at various time points prior to the harvest step. Subsequently, various signs of excessive immune response, including expression of proinflammatory and melanogenic genes and proteins, cellular oxidative stress level, and antioxidative enzyme activity, were examined. We found that IPL treatment reduced excessive cutaneous immune reactions by suppressing UVB-induced proinflammatory cytokine expression. IPL treatment prevented hyperpigmentation, and combined treatment with green and yellow IPL synergistically attenuated both processes. IPL treatment may exert protective effects against UVB injury in skin cells by attenuating inflammatory cytokine and melanogenic gene overexpression, possibly by reducing intracellular oxidative stress. IPL treatment also preserves antioxidative enzyme activity under UVB irradiation. This study suggests that IPL treatment is a useful strategy against photoaging, and provides evidence supporting clinical approaches with non-invasive light therapy.

Skin aging is a major risk factor for the dermal diseases, and interventions to attenuate cellular senescence are expected to reduce the risk for age-related diseases involving skin atrophy. However, blocking cell death or extending proliferation causally results in side effects and an increased cancer risk. For identification of a safer approach, we focused on PDK1 inhibition, which could revert cellular senescence and reduce senescence factors in skin in vitro, in a human skin equivalent model and in an exploratory, placebo-controlled, interventional trial. Natural phytochemical kaempferol tetrasaccharides resulted in a significant reduction in cellular senescence, and an increase in collagen fiber was observed in the skin cell and human skin equivalent. Clinical enhancement in skin appearance was noted in multiple participants, and an immunohistochemical study revealed improvement in the histological appearance of skin tissue and extracellular matrix. This change was associated with relative improvement in histological markers of senescence and clinical appearance of the aged skin and an increase in collagen fiber, an essential factor for preventing skin atrophy and consistency of the basement membrane. These results indicate that PDK1 inhibition is a potentially effective antiaging intervention, suggesting a diagnostic role and preventive actions of PDK1 in senescence-associated skin atrophy.

Demands for safe depigmentation compounds are constantly increasing in the pharmaceutical and cosmetic industry, since the numerous relevant compounds reported to date have shown undesirable side effects or low anti-melanogenic effects. In this study, we reported three novel inhibitors of tyrosinase, which is the key enzyme in melanogenesis, identified using docking-based high throughput virtual screening of an in-house natural compound library followed by mushroom tyrosinase inhibition assay. Of the three compounds, gallacetophenone showed high anti-melanogenic effect in both human epidermal melanocytes and a 3D human skin model, MelanoDerm. The inhibitory effect of gallacetophenone on tyrosinase was elucidated by computational molecular modeling at the atomic level. Binding of gallacetophenone to the active site of tyrosinase was found to be stabilized by hydrophobic interactions with His367, Ile368, and Val377; hydrogen bonding with Ser380 and a water molecule bridging the copper ions. Thus, our results strongly suggested gallacetophenone as an anti-melanogenic ingredient that inhibits tyrosinase.