Although MOS supplementation has been reported to reduce body weight gain, body fat and visceral adipose tissue (18
), this was not observed in the current study. Specifically, there were no significant differences in body weight, total body fat or individual fat depots in male C57Bl/6J mice when fed a high-fat diet supplemented with 1% MOS. There are several aspects of this study that contrast with previous reports. This study utilized a purified MOS compound of measured chemical structure and substance. Previous studies have utilized a coffee-based MOS, derived from a galactomannan (18
). Although the konjac-derived MOS used in this study has a different composition of monosaccharides constituents (mannose and glucose), the similar chemical structures of the mannan backbones should retain the undigestible β-1,4 glycoside linkages and produce similar fiber-like metabolic effects based on the proposed mechanism of action of MOS. However, the different monosaccharide composition of the MOS oligos was not directly tested and cannot be excluded as a contributor to the difference in observed results. Additionally, the purity of the MOS used in previous studies has not been disclosed. The amount used in this study should provide at least an equivalent amount of MOS in the diet that has been previously demonstrated as beneficial in mice (20
Another point of contrast regards the mice used. This study utilized male C57Bl/6J strain, contrasted with the ICR female mice previously reported (20
), raising the possibility that sex or strain differences contribute to the difference in results. However, C57Bl/6J mice are commonly used for diet-induced obesity conditions, as well as CR studies, and should serve as a useful model for this type of analysis.
Of particular note, an earlier study utilized a higher fat diet (63% of calories from fat) that was not reported to contain any fiber (20
), compared with the normal fiber percentage (5% by weight) included in rodent diets. In contrast, the additional 1% MOS supplementation in this study provided a relative fiber increase of only 20% (from 5 g/100g diet to 6g/100g). This, in combination with a lower fat content in the current study (45% vs. 63%), may reduce any basic fiber effects previously observed. However, the results presented here should be relevant to more “normal” diets that contain at least some amount of fiber.
The food allotment of 95% AL
was chosen to reduce variability in food intake values between animals and across groups in order to better assess the influence of MOS supplementation in the absence of confounding differences in food intake amounts (12
). This was of particular interest in assessing the future use of MOS as a CR mimetic. Although increased food intake would not be measurable with this feeding paradigm, previous research reported significantly reduced body weight and body fat despite greater food intake with MOS supplementation (20
). Therefore, any potential effect on body weight or body fat reduction would be larger when increased food intake is not permitted. In addition, multiple mice in both the CON and MOS groups did not fully consume their daily allotment during the progression of the study, suggesting compensatory feeding was not elevated with MOS supplementation or stimulated with advancing age and increasing body weight.
Despite the lack of a significant difference in body weight (), MOS is proposed to reduce body fat accumulation that could be offset by gains in lean mass (20
). However, body composition was measured every three weeks during the study and no significant differences were observed with MOS supplementation (). MOS supplementation has also been reported to selectively reduce visceral adipose depots (18
). To address the potential that visceral adipose depots had been reduced while other depots increased, resulting in no difference in body weight or total body fat, individual fat pads were dissected and wet weights measured. There were no significant differences in individual, visceral or total fat pad weights (), dismissing the possibility that MOS supplementation had selectively altered fat accumulation in this study. In addition to lean and fat, no significant differences were observed in the amount or density of bone between the groups. Although other types of non-digestible oligosaccharides have been shown to increase mineral absorption and promote bone production (32
), the MOS utilized in the current study did not.
During the study the mice seemed to tolerate the MOS supplementation, gaining similar amounts of body weight as the control group, with no adverse events observed. However, the lack of any reduction in body weight, body fat or visceral fat challenges the potential use of MOS as a CR mimetic or body composition enhancer.