Applied nutritional investigationTomato juice supplementation in young women reduces inflammatory adipokine levels independently of body fat reduction
Introduction
A Mediterranean diet is widely accepted as healthy, and one of its signature components is tomato, a main dietary source of lycopene [1]. Lycopene is a carotenoid containing a long conjugated chain of double bonds arranged in a linear structure that is responsible for its antioxidant activity by scavenging free radicals and quenching singlet molecular oxygen. Many studies have reported the anticancer, antiosteoporosis, and antiatherogenic activities of lycopene [1], [2], [3]. Recently, potential functions of lycopene in ameliorating metabolic diseases have been noted. Metabolic derangements such as insulin resistance, central obesity, hypertension, and dyslipidemia increase the risk of developing cardiovascular disease and type 2 diabetes mellitus [4].
An epidemiologic study showed a significant negative correlation between metabolic syndrome morbidity and carotenoid or lycopene intake [5]. Healthy human volunteers given tomato juice or lycopene supplements showed a significant reduction in serum cholesterol and low-density lipoprotein (LDL)-C levels [6], [7]. Significant reductions in inflammation and increases in serum antioxidant levels were also observed [6], [8], [9]. Animal studies have demonstrated that hepatic steatosis induced by a high-fat diet is alleviated by lycopene through mechanisms involving antioxidation and antiinflammatory effects, sirtuin1 (SIRT1) activation, and microRNA [10], [11], [12]. Moreover, lycopene has been shown to reduce levels of the adipokines leptin, resistin, and interleukin-6 in white adipose tissue and in the circulation in high-fat diet-fed mice [13]. Lycopene treatment of cultures of adipose tissue or adipocytes results in decreased expression of tumor necrosis factor (TNF)-α-induced expression of the inflammatory adipokines interleukin-6, monocyte chemoattractant protein-1 (MCP-1), and interleukin-1β [14]. Thus, if lycopene has effects in preventing metabolic disease, as suggested by the previously mentioned epidemiological and intervention studies [5], [6], [7], [8], [9], [10], [11], [12], this may be because, at least in part, of its ability to alter the adipokine profile.
Adipokines, such as leptin, adiponectin, resistin, MCP-1, and visfatin, are chemical mediators produced by adipose tissue. Leptin acts on the hypothalamus to counteract obesity, though high leptin levels are seen in most obese subjects because of leptin resistance [15]. Serum adiponectin levels increase with weight loss and with insulin-sensitizing drugs [16]. By suppressing the NF-κB pathway, adiponectin inhibits expression of TNF-α and interferon-γ, resulting in antiinflammatory and insulin sensitizing effects [17]. MCP-1 (also known as CCL2) is a proinflammatory mediator that increases macrophage and monocyte infiltration into adipose tissue, especially omental adipose tissue [18], thus linking obesity with the metabolic disturbances associated with inflammation. Circulating levels of MCP-1 are increased in overweight and obese individuals [19].
Most human intervention trials of lycopene or tomato juice have focused on blood levels of lipids, antioxidants and inflammation [6], [7], [8], [9], whereas the effects on adiposity and adipokines have rarely been investigated. In this study, we tried to show the metabolic benefits of consuming tomato juice in generally healthy people with tomato juice as a daily supplement to young healthy Taiwanese women. Effects on adiposity and serum levels of glucose, lipids, antioxidants, and adipokines were evaluated. Because improvement in biomarkers associated with metabolic health, especially adipokine profiles, might be secondary to a reduction in adiposity [15], [16], [19], direct effects of lycopene were analyzed using statistical approaches.
Section snippets
Subjects
A total of 30 young (20- to 30-year-old) female students with a body mass index (BMI) ≥ 20 were recruited from the China Medical University in reply to an advertisement. The exclusion criteria included diabetes, endocrine disease, liver, kidney, or cardiovascular disease, gastrointestinal disease, psychological disease, eating disorders, pregnancy or lactation, asthma and allergies, smoking, and use of any drugs or dietary supplements that could potentially affect body weight, blood lipid,
Results
Thirty eligible female Taiwanese students from the China Medical University were enrolled in the study. However, three had body weight changes ≥0.5 kg during the run-in period, as they were assumed to be unable to maintain their usual diet and physical activity constantly, and another two disliked the taste of tomato juice, so only 25 completed the study (Fig. 1). The baseline (day −14) characteristics of the 25 subjects were age 22.5 ± 0.6 y, height 161.5 ± 0.9 cm, body weight 59.0 ± 1.3 kg,
Discussion
Adipose tissue is an active endocrine tissue and increased secretion of inflammatory adipokines has been shown to be involved in the pathology of insulin resistance and atherosclerosis [24]. In this study, we showed that, in young healthy Taiwanese women, tomato juice supplementation resulted in a decrease not only in adiposity indices, peroxidative stress, and serum cholesterol levels, but also in levels of the inflammatory adipokine MCP-1, and an increase in levels of the antiinflammatory
Conclusions
Daily supplementation for 8 wks with tomato juice containing 32.5 mg of lycopene in young healthy Taiwanese women has antiobesity, antioxidation, and antiinflammatory effects. The tomato juice-induced reductions in waist circumference, serum levels of cholesterol and the inflammatory adipokine MCP-1, and increase in serum levels of the antiinflammatory adipokine adiponectin are unrelated to body fat changes.
Acknowledgments
This study was supported by the Taiwan Ministry of Health and Welfare Clinical Trial and Research Center of Excellence (DOH102-TD-B-111-004), the National Science Council, Taiwan (NSC 102-2815-C-039-122-B), and, Taiwan Kagome Co. Ltd.
The authors' contributions are as follows: P. M. C. and M. D. Y. designed the study; Y. F. L. carried out the data analysis and participated in the draft preparation; Y. Y. C. was responsible for recruiting the participants and carried out the measurements; H. C.
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