Research Paper
Lycopene ameliorates insulin resistance and increases muscle capillary density in aging via activation of SIRT1

https://doi.org/10.1016/j.jnutbio.2021.108862Get rights and content

Abstract

Lycopene (Ly) is a kind of hydrocarbon, which belongs to the family of tetraterpene carotene and exists in red fruits and vegetables. The decrease of capillary density and blood flow with age is a significant reason for the increase of mortality and morbidity. Herein, our study aims to explore the effects of Ly (a bioactive food compound) on vascular aging in vitro and in vivo and its potential mechanisms. The cytological results showed that Ly could promote the proliferation of human umbilical vein endothelial cell (HUVECs) and enhance the ability of HUVECs to form capillary-like structures. Furthermore, the expression of SIRT1 in aged HUVECs was up-regulated. In vivo, aging rats showed signs of insulin resistance and blood vessel damage. Additionally, the capillary density and blood flow were reduced during the vascular aging process in both D‐gal‐induced and naturally aging muscle. However, when Ly was given, these conditions could be reversed. Simultaneously, the contents of ATP, lactic acid and pyruvic acid were determined, and it was found that Ly could promote angiogenesis by increasing the utilization rate of glucose and promoting energy metabolism. Finally, in the insulin resistance cell model, we knocked down the SIRT1 and administrated with Ly, and found that it couldn't restore insulin transdution. In conclusion, all the data in this study demonstrate that Ly could reactivate SIRT1 and improve insulin resistance, which was a reversible cause of vascular aging.

Introduction

Aging refers to the phenonmenon in which the function, adaptability and resistance of organisms decline with the passage of time [1]. Vascular aging begins early in our lives [2], which is an inevitable biological process in the aging process. At the macro level, the decrease of capillary density and the slowness of local blood flow will lead to the deterioration of peripheral circulation. Elevated blood glucose and insulin resistance are also of characteristics of aging [3]. Skeletal muscle is the main organ of the human body to make use of sugar. With the increase of age, blood glucose tolerance decreased gradually, diaphragm ATP and vascular atrophy in skeletal muscle. Vascular aging leads to the reduction of blood flow and vascular damage, making the body vulnerable to Alzheimer's disease [4], osteoporosis, atherosclerosis and sarcopenia [5], [6], [7]. Therefore, solving the problem of insulin resistance and vascular aging has become a new research direction.

Impaired glucose tolerance is mainly due to the dysfunction of the classical insulin signaling pathway [8]. Insulin-stimulated transport of glucose into muscle is mediated by the Glut4 [9]. Studies have shown that activation of PI3K/Akt pathway through the insulin receptor substrate is key to the activation of Glut4 [10]. Impaired insulin pathway function leads to changes in the activities of Glut4, PI3K and Akt [11]. SIRT1 is the essential convergence point that contact with the insulin sensitivity [12]. Previous studies have shown that promoting SIRT1 in endothelial cells can increase capillary density and blood flow [13]. In essence, the role of SIRT1 in vascular aging is to regulate angiogenic function and vascular function [14]. Similarly, a study showed that the expression of SIRT1 is decreased with age in HUVECs [15]. VEGF is a crucial regulator of angiogenesis, which can maintain the stability and permeability of vessels [16]. It has been reported that insulin-induced VEGF expression is mediated by activating the PI3K/Akt pathway [17]. These data suggest that improving insulin resistance and SIRT1 expression can reverse vascular aging.

Aging is a lifelong process, and relying on drugs is not a long-term solution. Long-term use of drugs can cause side effects and complications. Due to the safety and convenience of food, it has a broad application prospect in health maintenance and disease treatment. Thus, it is necessary to study effective substances from dietary sources to reverse the development of vascular aging.

Ly is a kind of carotenoid, which belongs to isoprene compounds, mainly from tomato. Ly has been shown to prevent elevated fasting blood glucose and insulin levels [18]. Moreover, as one of the carotenoids, Ly has a protective effect on vascular cells and can maintain vasomotor function [19]. Ly is a recognized antioxidant [20], and it also has anti-inflammatory activities [21] and anti-aging effects [22]. However, Ly's anti-aging role in vascular aging has not been well elucidated, and its specific mechanisms remain to be further explored. Luvizotto et al. [23] demonstrated that Ly could up-regulate the expression of SIRT1mRNA. As SIRT1 plays an important role in insulin function and vascular function, we speculate that Ly may be used to reverse vascular aging.

In order to explore the vascular protection of Ly, we tested whether Ly could delay aging by improving insulin resistance and regulating SIRT1 expression. As far as we know, this is the first study to deeply assess the underlying mechanisms of Ly in improving vascular aging.

Section snippets

Chemicals and Reagents

D-gal was purchased from Sigma Aldrich, USA. Ly was bought from Schulkbetta, China. Selisistat was from MedChemExpress, China. HUVECs and rat primary vascular endothelial cells (RPVECs) were purchased from China Centre for Type Culture Collection.

Drug concentration and time screening by MTT

To confirm the cell proliferation of Ly on HUVECs, HUVECs were exposed to various concentrations Ly. Cell viability was measured by tetrazolium (MTT) assay. Briefly, HUVECs were inoculated into the 96-well culture plates (1 × 105 cells/well). Then,

Drug concentration and time screening by MTT

As shown in Fig. S1, the cell proliferation of Ly was maximized at a concentration of 100 μM at different time (P<.05). However, the results showed that concentration of 400 μM reduced the survival rate and had a toxic effect on HUVECs. In addition, we found that Ly has the best proliferation effect on cells for 24 hours. Therefore, we chose the concentration of 100 μM to study its pharmacological effect within 24 h.

Ly promoted the proliferation and migration of HUVECs via up-regulation SIRT1

HUVECs were treated with the H2O2 and Ly at diverse groups for 24 h,

Discussion

Aging is characterized by the gradual accumulation of molecular, cellular and organ damage, leading to many abnormal metabolic processes or dysfunction, as well as general physiological decline. If this decline is uncompensated, it may result in the development of age-related diseases, such as neurodegenerative diseases, Alzheimer's and Parkinson's disease, metabolic disorders, type 2 diabetes and atherosclerosis, or cancer. Despite the complexity of the aging process, in the past 20 years,

Ethics statement

All experiments in this study were in accordance with NIH Guide for the Care and Use of Laboratory Animals, maximum efforts were made to minimize animal suffering and the number of animals necessary for the capture of reliable data.

Author's contributions

Hong Ding and Xiaolong Yang conceived and designed the research. Jing Li, Yingjiang Zhang and Xin Zeng performed the experiments and analyzed the data. Yahong Cheng and Liu Tang contributed to the experimental materials. Jing Li wrote the paper. Yingjiang Zhang revised the paper. All authors read and approved the final manuscript.

Acknowledgements

We thank School of basic Medical Sciences of Wuhan University for the help with cells experiment.

Declaration of competing interests

The authors declare that there are no conflicts of interest.

Funding

None.

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