Journal of Nutritional Health & Food Science

Background: In order to evaluate the regulational role of adiponectin and leptin on obesity, we examined the significance of daily adherence to the Sticky Japanese Diet (SJD) on the preventions of obesity and metabolic syndrome by assessing the fat adiponectin/leptin and plasma leptin levels using normal and high-fat diet (HFD) mice.

Methods: Five-week-old male ICR strain mice were placed in individual cages and randomly divided into eight groups based on feeding of SJD or not. At the end of each treatment period, plasma triglyceride, cholesterol, and leptin levels were measured by biochemical analysis. The adiponectin and leptin levels in adipose tissue were measured using RT-PCR.

Results: In normal mice, an eight-week treatment of SJD increased adiponectin levels in adipose tissue. However, four weeks after discontinuing the SJD, these levels decreased. Furthermore, continuous feeding of the SJD for eight weeks increased plasma leptin levels but not that of adipose tissue. And then, discontinuing the SJD for more than eight days resulted in a decrease in plasma leptin levels. In HFD mice, an increase in body weight and visceral fat was seen at eight days after discontinuing the SJD which was undertaken for a total of eight weeks. At this time, the plasma leptin levels in these mice were substantially higher than in normal mice, although these levels were getting to be decreased over four weeks.

Conclusion: This study revealed that discontinuous adherence to the SJD induced decreases in both adiponectin and leptin levels. Together with our previous publication, this paper suggests that daily adherence to the SJD might be essential for maintaining good health.

Keywords: NuruNeba (Sticky Japanese Diet); Washoku (Japanese foods); normal diet; high-fat diet; leptin; adiponectin; obesity; mice

Abbreviations: SJD: Sticky Japanese Diet; HFD: High-Fat Diet; CE-2: CLEA Rodent Diet CE-2; TG: Triglyceride; UCP1: Uncoupling Protein-1; BAT: Brown Adipose Tissue

It has been reported that the daily consumption of commercially available Japanese food products (Sticky Japanese Diet; SJD) containing ten kinds of sticky and slimy food components, which include a root kelp (Laminariaceae), wakame (Undaria pinnatifida), agar (generic name of raw material- Gelidiaceae), white cloud ear (Tremella fuciformis), shiitake (Lentinula edodes), nameko (Pholiota nameko), okra (Abelmoschus esculentus), mekabu (root of Undaria pinnatifida), cut tororo (Dioscorea japonica), and shimeji (Hypsizygus tessellatus). Significantly reduced the gain of body weight and visceral fat mass in high-fat diet (HFD; High Fat Diet 32: Japan CLEA, Tokyo) mice. The anti-obesity effects of SJD relate to the regulation of leptin levels in the adipose tissue of HFD mice [1]. These results indicated that adherence to SJD might play a preventative role against metabolic syndrome. Moreover, we reported that SJD in normal diet (CE-2; Japan CLEA, Tokyo) mice significantly increased adiponectin levels; however, leptin levels in the adipose tissue did not increase. Two independent reports by Tawara et al. and Hirokawa et al. suggest that increased adiponectin levels, under normal conditions, may be more effective in preventing obesity rather than impeding leptin-resistance in adipose tissue [1, 2].

In order to clarify the mechanism of SJD activity on obesity and other related diseases, we investigated the anti-obesity effects of continuous SJD consumption on normal mice, which were fed either the CE-2 or HFD. Furthermore, normal mice were continuously fed SJD until an increase in the adiponectin levels of the adipose tissue was detected, and the changes in body weight were measured.Additionally, normal mice continuously consumed SJD for two months and, subsequently, the presence or absence of an increase in adiponectin was elaborated. Once SJD feeding was stopped, either the CE-2 or HFD was continuously given to mice for an additional four weeks. Lastly, body weight, visceral fat, blood cholesterol, blood triglyceride (TG), plasma leptin, and fat adiponectin/leptin levels were measured. In this study, we discussed the impact of dailyadhering to the SJD for maintaining healthy conditions and preventing the development of metabolic syndrome.

Five-week-old ICR strain male mice were purchased from SLC (Shizuoka, Japan) and individually housed in stainless steel cages with mesh bottoms at 25 °C with 40–70% humidity on a 12 h light (7:00 AM-7:00 PM) and dark (7:00 PM-7:00 AM) cycle. All groups were pair-fed an isoenergetic diet based on the SJD group. CE-2 was administered orally to all mice for 1 week before being divided into 8 groups:

① CE-2 (3,500 mg/ mouse/ day) for 8 weeks (C: n = 4) ② CE-2 (3,150 mg/ mouse/ day) + SJD (350 mg/ mouse/ day) for 8 weeks (C+S: n = 4) ③ CE-2 (3,150 mg/ mouse/ day) + SJD (350 mg/ mouse/ day) for 8 weeks →* CE-2 (3,500 mg/ mouse/ day) for 8 days (C+S→C8d: n = 3) ④ CE-2 (3,150 mg/ mouse/ day) + SJD (350 mg/ mouse/ day) for 8 weeks →* HFD (3,500 mg/ mouse/ day) for 8 days (C+S→H8d: n = 3) ⑤ CE-2 (3,500 mg/ mouse/ day) for 8 weeks →* CE-2 (3,500 mg/ mouse/ day) for 4 weeks(C→C: n = 6) ⑥ CE-2 (3,500 mg/ mouse/ day) for 8 weeks →* HFD 32 (3,500 mg/ mouse/ day) for 4 weeks (C→H: n = 6)

1. Mora L, Reig M, Toldrá F. Bioactive peptides generated from meat industry by-products. Food Research International. 2014;65(C):344‑349.