D-galactose: a model of accelerated ageing sufficiently sensitive to reflect preventative efficacy of an antioxidant treatment

Reduced energy metabolism contributing to aging of skeletal muscle by serum metabolomics and gut microbiota analysis

AIMS

Sarcopenia is an age-related syndrome characterized by a gradual loss of the muscle mass, strength, and function. It is associated with a high risk of adverse consequences such as poorer quality of life, falls, disability and mortality among the elderly. The aim in this study is to investigate the pathological mechanism of sarcopenia.

MAIN METHODS

The aging of skeletal muscle was investigated by the D-galactose induced accelerated aging model combining with constrained motion. After 10 weeks, muscle function and gastrocnemius muscle index, and morphology of muscle fibers were evaluated, and myostatin, IGF-1 and ATP in skeletal muscle were also determined. Then the mechanism of aging-related skeletal muscle dysfunctions was investigated based on untargeted serum metabolomics and 16S rRNA gene sequencing. Four key metabolites were validated by the D-galactose-induced C2C12 senescent cell model in vitro.

KEY FINDINGS

Results showed that gastrocnemius muscle mass was decreased significantly, morphology of muscle fibers was altered, and muscle function was damaged in the aged group. Furthermore, increased MSTN, and decreased IGF-1 and ATP were also observed in the aging skeletal muscle. Importantly, alteration of the key pathways including riboflavin biosynthesis and energy metabolism contributed to the aging of skeletal muscle. Four key metabolites, including riboflavin, α-ketoglutaric acid and two dicarboxylic acids, which were involved in these metabolic pathways, could promote the proliferation of C2C12 cells.

SIGNIFICANCE

These findings provide novel insights into pathological mechanism of sarcopenia, and will facilitate the development of therapeutic and preventive strategies for sarcopenia.

Effects of Loofah cylindrica extract on learning and memory ability, brain tissue morphology, and immune function of aging mice

In this study, we aimed to observe the effects of Loofah cylindrica (LC) extract on learning and memory ability, brain tissue morphology, and immune function of aging mice. Kunming mice were selected and randomly divided into a control group, a positive control group, an aging group, and three dose groups. Three dose groups were administered 187.5, 375, and 750 mg/kg of LC extract, respectively. Except for the control group, the mice in any other group were continuously subcutaneously injected d-galactose on the back and neck. Platform tests and Morris water maze (MWM) were adopted to test the learning and memory ability of each group. The brain index, thymus index, and spleen index of each group were determined by the organ-to-body ratio method. The enzyme-linked immunosorbent assay was performed to measure the concentration of cytokines interleukin 2 and interferon gamma and the proliferation activity of T lymphocytes in mouse serum. In addition, the hematoxylin and eosin staining was employed to observe the morphological changes in mouse brain tissues of each group. The results show that the aging group made more errors in the platform test, had longer escape latency, shorter swimming time in the platform quadrant, and fewer platform crossings in the MWM; much fewer brain tissue cells; and smaller brain index, thymus index, and spleen index. The LC extracts (375 and 750 mg/kg) can significantly antagonize the changes in the above indices. It can be concluded that LC extract can improve the learning and memory of aging mice, enhance their immune activity, and delay the aging process.

Spermidine, a caloric restriction mimetic, provides neuroprotection against normal and D-galactose-induced oxidative stress and apoptosis through activation of autophagy in male rats during aging

Spermidine (SPD) is a natural polyamine present in all living organisms and is involved in the maintenance of cellular homeostasis by inducing autophagy in different model organisms. Its role as a caloric restriction mimetic (CRM) is still being investigated. We have undertaken this study to investigate whether SPD, acting as a CRM, can confer neuroprotection in D-galactose induced accelerated senescence model rat and naturally aged rats through modulation of autophagy and inflammation. Young male rats (4 months), D-gal induced (500 mg/kg b.w., subcutaneously) aging and naturally aged (22 months) male rats were supplemented with SPD (10 mg/kg b.w., orally) for 6 weeks. Standard protocols were employed to measure prooxidants, antioxidants, apoptotic cell death and electron transport chain complexes in brain tissues. Gene expression analysis with reverse transcriptase-polymerase chain reaction (RT-PCR) was performed to assess the expression of autophagy and inflammatory marker genes. Our data demonstrate that SPD significantly (p ≤ 0.05) decreased the level of pro-oxidants and increased the level of antioxidants. SPD supplementation also augmented the activities of electron transport chain complexes in aged brain mitochondria thus proving its antioxidant potential at the level of mitochondria. RT-PCR data revealed that SPD up-regulated the expression of autophagy genes (ATG-3, Beclin-1, ULK-1 and LC3B) and down-regulated the expression of the inflammatory gene (IL-6) in aging brain. Our results provide first line of evidence that SPD provides neuroprotection against aging-induced oxidative stress by regulating autophagy, antioxidants level and also reduces neuroinflammation. These results suggest that SPD may be beneficial for neuroprotection during aging and age-related disorders.