Hyperlipidaemia is a lipid metabolism disorder that can lead to atherosclerosis, which is the underlying cause of heart attack, stroke, and peripheral vascular disease [1] - [3] . Hyperlipidaemia can disrupt oxidation-reduction balance and induce an imbalance in inflammatory factors or disorders in various organs [3] - [10] .

Various agents, such as statins, can be used to treat hyperlipidaemia by lowering lipid levels. However, these drugs may cause side effects, including myopathy and organ injury [5] [11] - [14] , and research on non-statin lipid-lowering therapies has recently advanced [15] . Consequently, the establishment of new anti-hyperlipidaemic strategies, including the identification of substances from natural resources, especially those that can improve blood lipid levels without side effects, is required. Thus, natural resources with anti-hyperlipidaemic activities have been reported [16] [17] .

Adequate water intake is essential for maintaining overall health and preventing disease. Recently, we reported a reduction in serum uric acid levels following the administration of lifeceramics (LC)-treated water (LC water) in hyperuricaemic rats [18] . LC is composed of zeolite and oyster shells under high temperature and pressure conditions [18] . We also reported the protective effects of LC water against oxidative stress in cultured human cells [19] [20] . In addition, in the livers of alcoholic rats, LC administration decreased and increased malondialdehyde (MDA) and glutathione (GSH) levels, respectively, suggesting an anti-oxidative effect of LC on alcoholic hepatic injury [21] .

In contrast, increased intake of a high-calorie diet (HCD) rich in fat and sugar may cause hyperlipidaemia [22] - [24] . This study aimed to investigate the effects of LC water consumption on hyperlipidaemia in rats by estimating serum lipid levels, anti-oxidant indices, and inflammatory factors.

Identifying and developing new substances, particularly those from natural

resources that can improve blood lipid profiles without side effects, are crucial. Interestingly, the intake of a natural zeolite-containing diet suppressed the increase in body weight, liver weight, and epididymal fat weight and decreased plasma lipid levels, such as those of TC, TG, and HDL-C, in mice with high-fat diet-induced obesity and type 2 diabetes mellitus [28] . In the future, zeolite is expected to be applied to functional foods aimed at preventing high blood sugar, hyperlipidaemia, and obesity associated with a high-fat diet. On the other hand, oyster shells are used for various products, such as fertilizers, interiors, and accessories, in groundbreaking ways that take advantage of their characteristics and main ingredients. However, most oyster shells were discarded. Therefore, LC was developed by using zeolite and oyster shells together for ceramicization to increase the zeolite efficacy. In particular, LC was manufactured with the idea of changing the size of the zeolite pores and increasing the mineral content [29] . In this study, we examined the effects of zeolite- and oyster shell-derived LC on hyperlipidaemia in rats. Notably, no changes in the physical condition of the rats were observed when they were fed only normal diet and LC water, as reported previously [18] [30] . However, the hyper-LP rats gavaged with the HCD rich in fat and sugar exhibited an increase in body weight and the liver and epididymal fat indices ( Figure 1 ), along with the serum lipid levels of TC, TG, and LDL-C ( Figure 2 ), indicating the induction of hyperlipidaemia, as previously reported [26] . However, the weight gain exhibited a decreasing trend in the HCD-gavaged rats following LC water administration ( Figure 1 ). Furthermore, the increased TC, TG, and LDL-C levels were reduced by LC water ( Figures 2(A) - (C) ). Therefore, LC water effectively inhibited the worsening of the blood lipid profile in rats with hyperlipidaemia, although the HDL-C levels did not differ significantly between the groups ( Figure 2(D) ).

Dyslipidaemia, including hyperlipidaemia, is characterised by the dysregulation of multiple systems, such as the oxidant/anti-oxidant balance [31] . CAT is an anti-oxidant enzyme that scavenges hydrogen peroxide (H₂O₂) and protects against the peroxidation of cell wall lipids and lipoproteins. In this study, serum CAT activity increased in the hyperlipidaemic rats ( Figure 3(A) ). In contrast, the increased CAT activity was reduced in the rats administered LC water as well as those administered ATS ( Figure 3(A) ). CAT activity has been reported to decrease in patients with hyperlipidaemia [32] , whereas another study reported no significant interaction between hyperlipidaemia and the activity of anti-oxidative enzymes, including CAT [33] . Further studies are warranted to clarify the causal relationship between hyperlipidaemia and CAT activity and its subsequent effect [33] .

GSH and SOD also exert anti-oxidant effects, and both GSH levels and enzymatic SOD activity decrease in hyperlipidaemia [34] [35] . Consistently, a decrease in the GSH levels was observed in the hyperlipidaemic rats in this study ( Figure 3(B) ). However, the decreased GSH levels that accompanied hyperlipidaemia were recovered to the control levels in the rats administered LC water and ATS ( Figure 3(B) ). SOD activity also seemed to decrease in the hyper-LP rats, but increased in the rats administered LC water ( Figure 3(C) ). In addition, estimation of oxidative stress-induced products is critical for elucidating the causal relationship between hyperlipidaemia and the antioxidant enzyme activity. An increase in serum MDA levels due to lipid peroxidation may occur because of hyperlipidaemia-associated changes in oxidative status [31] . Notably, the hyperlipidaemic rats exhibited an increase in the serum MDA levels; however, these levels recovered to the control levels following LC water and ATS administration ( Figure 3(D) ). Therefore, hyperlipidaemia in the rats in this study appears to be associated with the oxidative status, and drinking LC water may effectively improve it.

We also measured the levels of other remarkable factors, such as TNF-α and ADNP, which contribute to hyperlipidaemia. The levels of TNF-α and ADNP increased and decreased, respectively, in the hyperlipidaemic rats compared with the control levels, and both of these recovered to around the control levels following LC water and ATS administration ( Figure 4 ). TNF-α is a pleiotropic pro-inflammatory cytokine and is proposed to contribute to metabolic diseases [36] . Lower ADNP levels have been suggested to be linked to dyslipidaemia and high TG levels in humans [37] [38] . Therefore, fluctuations in their levels in this study may be associated with fluctuations in the blood lipid profile.

We found the anti-hyperuricaemic [18] [25] and anti-liver damage effects [21] in addition to the anti-hyperlipidaemic effect of LC water in rats, suggesting that LC water promotes human health. In addition, we reported that LC water mitigated stress conditions and suppressed renal function deterioration in human [39] . Recently, we started a metabolome analysis [40] to analyse the effect of LC water consumption in humans using low molecular weight metabolites in the blood. Thus, drinking LC water may be applicable for protecting human health against unhealthy conditions, although a more detailed dose-response analysis, such as testing a wider range of LC water concentrations and including pharmacokinetic data, could enable the establishment of a clear dose-response relationship and determine the optimal dosage for the maximal efficacy of LC water drinking.

We suggest that LC water has a multifaceted efficacy in the anti-hyperlipidaemic action reported here, including previously reported anti-oxidative [19] [20] , anti-inflammatory [21] , and anti-hyperuricemic [18] actions, although the mechanisms underlying its efficacy remain unclear. Our findings underscoring the beneficial effects of LC water in hyperlipidaemic rats may serve as a foundation for improving human health conditions.

This work was supported by the Non-Profit Organization Chiba Researchers Network for Health Care Promotion. We would like to thank Editage ( https://www.editage.jp/ ) for the English language editing.

This study was financially supported by the Scientific and Technological Research of Chengde Medical University (Xiaobo Tong, No. 201714; Kuihua Li, No. 201708).

During the research and preparation of the manuscript, Jingyao Yu (JY), Xiaobo Tong (XT), and Kuihua Li (KL) performed the experiments, and JY and XT prepared and analysed the experimental data. XT and Nobuo Suzuki designed the study and prepared the manuscript as corresponding authors, respectively. Atsushi Suzuki and Kazuko Kita (KK) revised, and KK submitted the manuscript. All the authors have read and agreed to publish this manuscript.

All experiments on rats were approved by Beijing Vital River Laboratory Animal Technology Co., Ltd. (Beijing, China) and were conducted in accordance with the institutional and ethical guidelines of the Animal Ethics Committee of Chengde Medical University.