To begin the search for alternative anti-obesity agents, we exploited a hen immunization model to produce Anti-lipase IgY, a novel antibody that recognizes porcine pancreatic lipase. The lipolytic activity was strongly inhibited in a concentration-dependent manner upon addition of Anti-lipase IgY when compared with Control IgY (Figure 1). These results suggest that Anti-lipase IgY reacts specifically with pancreatic lipase. Surprisingly, the IC50 of Anti-lipase IgY (0.49 μM) that elicits an anti-obesity effect is approximately half that of Orlistat, which has an IC 50 of 0.96 μM . Both of these treatments are in turn superior to the green tea polyphenol, (−)-epigallocatechin gallate (EGCG), which has an IC50 of 7.5 μM  accompanying an anti-obesity action in mice fed a high fat diet. Interestingly, as the effective dose of IgY is 0.2% (w/w) in animal study, it is the lowest value among functional food components such as EGCG [3, 4].
Recently, the availability of lipase inhibitor agent for preventing metabolic syndrome has received much attention. Orlistat, an anti-obesity drug used in the clinic, is a potent and specific covalent inhibitor of digestive lipase [2, 23], which leads to reduced intestinal absorption of lipolysis products. However, the use of Orlistat is frequently associated with gastrointestinal adverse effects, such as oily stools, diarrhea, cholelithiasis and cholestatic hepatitis [2, 24]. But, judging from our observation and the data of liver lipids analysis, there is no side effect by the treatment of anti-lipase IgY as observed by Orlistat.
The effects of Anti-lipase IgY and Control IgY on obesity were evaluated in mice fed a high-fat diet containing 0.2% (w/w) IgY, respectively. Anti-lipase IgY supplementation significantly decreased adipose tissue weights and hepatic lipid levels and also significantly increased the fecal excretion of triglyceride compared with Control IgY feeding (Table 2). These results suggest an anti-obesity function of Anti-lipase IgY: it inhibits the hydrolysis of dietary fat in the small intestine and reduces intestinal absorption of dietary fat, which is then excreted into the feces.
To investigate the effect of anti-lipase IgY on the absorption of triglyceride in the diet, we analyzed fecal lipids contents. Previous study showed that lipase inhibition by synthetic lipase inhibitor Orlistat was extremely fast (half-inhibition time < 1 min) . Moreover, in our preliminary study, single anti-lipase IgY administration tended to decrease in plasma triglyceride levels after single gavage of olive oil. These results indicate that the treatment with anti-lipase IgY for short term is effective for the increase in fecal triglyceride content. Thus, we performed fecal collection during day 7 through 9. On the other hand, it seemed to need longer time before the treatment with anti-lipase IgY become effective against the other measurements, such as adiposity and hepatic lipid accumulation. Thus, in this study, we investigated the effects of anti-lipase IgY treatment for longer period (35 days) on these parameters. Unfortunately, we have no data about a timing effect on fecal lipid excretion, and further investigation on it is important in future study. However, to our knowledge, there is no report about the tolerant to pancreatic lipase inhibitor, such as Orlistat. Moreover, Moreno et al. reported that dietary supplementation with peanuts shell extracts, which inhibit pancreatic lipase, significantly increased the excretion of fecal lipids in rats fed a high fat diet at 3 weeks of the study and the increase continued until the end of the study, 12 weeks . In addition, Desmarchelier et al. reported that feeding mice a high fat Western diet containing cholesterol remarkably increased the excretion of fecal neutral sterol during day 4–11 of the experiment and the increase was kept until late in the experiments, day 74–81 . These findings in the literatures suggest that diet-, nutrient- and food ingredient-stimulated enhancement of fecal lipid excretion observed in early experimental stage could be sustained even in late stage. Therefore, we determined fecal lipids during the relatively early stage and found a significant increase in the fecal triglyceride of mice treated with anti-lipase IgY, which is predicted to be kept until the late stage.
The aim of this study is to determine whether the anti-lipase IgY has the preventive effects on early obesity development. Obesity is defined as excessive fat accumulation . Thus, in this study, we mainly investigated the effects of relatively short term treatment (35 days) with the anti-lipase IgY on the high-fat diet-induced development of white adipose tissues (WAT). Although the treatment with anti-lipase IgY didn’t affect body weight (tended to decrease but not significantly), we demonstrated that the anti-lipase IgY inhibited visceral WAT accumulation, and we evaluated that the anti-lipase IgY has an anti-obesity effect. A similar claim was made in the study done by Foucault AS et al. . The reason why anti-lipase IgY didn’t affect body weight gain in this study may be due to the experimental period because circular triglyceride level in mice fed control HFD in this study is not higher than those in mice fed HFD for prolonged period in previous studies [30, 31]. Therefore, further investigation is needed about the effects of anti-lipase IgY treatment for longer period on the body weight gain and obesity-induced metabolic disorders, in future. However, a specific pancreatic lipase inhibitor, Orlistat, has been used in clinics for the prevention of obesity , and Orlistat has been shown not only to prevent body weight gain but also to improve obesity-induced metabolic disorders, such as glucose intolerance and diabetes . Our results showed that anti-lipase IgY has more potent inhibitory effect on the pancreatic lipase than Orlistat (IC50 values: 0.49 μM vs 0.96 μM) . Thus, we think we can expect that anti-lipase IgY has useful effect on body weight gain and obesity-induced metabolic disorders in the prolonged treatment.
Taken all together, the data from our study show that Anti-lipase IgY is a promising new lead biologic agent for the development of functional foods and medicines expected to prevent and improve obesity.