1. Introduction

Childhood obesity is a serious health concern in many countries in the world ^{[1, 3, 4]}. In developed countries, between 20% and 25% of children are overweight or obese ^[1]. In addition, childhood obesity is a leading cause of childhood chronic liver disease, and 22.5% to 38% of obese children have fatty liver compared with 2.6% to 9.6% of the general pediatric population ^{[5, 6]}. Obese children are likely to remain obese into adulthood ^[2], and therefore will be at increased risk of developing non-alcoholic fatty liver disease, hypertension, hyperlipidemia, and diabetes mellitus ^{[16, 17, 18, 19]}. Lifestyle education during primary care visits to emphasize the need for an appropriate diet and exercise routine is an important basic strategy to treat childhood obesity ^{[7, 8, 9, 10]}; however, the success of these efforts is often hampered by the limited contact the child has with their primary care facility ^{[8, 9, 10]}. Thus, there is interest in using drugs or functional foods and beverages that are easily taken at home and could help prevent or reduce childhood obesity ^{[11, 12, 13, 21, 22, 23]}.

Obesity occurs most often as a consequence of excessive caloric intake resulting in increased storage of triglycerides in adipose tissue ^[20]; therefore, pharmacological inhibition of triglyceride (TG) synthesis or absorption is a potential therapeutic strategy to reduce obesity ^{[11, 12, 13, 22, 23]}. Previously, globin digest (GD), an oligopeptide mixture derived from edible globin proteins, was developed as a functional food or beverage and has been shown to be effective at reducing hyperlipidemia and to have hepatoprotective effects in humans and other mammals ^{[12, 13, 14]}. The amino acid residue contained in GD, Val-Val-Tyr-Pro, inhibits the absorption of fat in the digestive tract and enhances the activity of hepatic triglyceride lipase in mice ^[12]. Furthermore, a clinical study has shown that postprandial serum TG and chylomicron levels are suppressed after intake of GD in healthy individuals ^[13]. Although GD is a promising means of reducing obesity, the efficacy and long-term safety of GD in both children and adults with obesity remains unknown. Here we evaluated the efficacy and safety of GD in obese Japanese children.

2. Materials and Methods

The GD (MG Pharma Incorporation, Osaka, Japan) used in the present study was produced from the enzymatic hydrolysis of globin protein in bovine or swine hemoglobin, as previously described ^[13]. The GD was manufactured as a 50-mL beverage containing 6 mg of the amino acid residue Val-Val-Tyr-Pro. A placebo beverage with a similar taste and appearance was produced at the same factory that produced the GD beverage.

Twenty-eight Japanese obese children (median, 12.4 years; range, 6.0–17.3 years; 18 males) were enrolled in the study between November 2012 and April 2013. For each child, percentage overweight (POW) based on the Japanese age-, sex-, and height-specific bodyweight standards was calculated and obesity was diagnosed if POW was greater than or equal to 20%, which is the definition that has been adopted by the Ministry of Health, Labor and Welfare of Japan ^[15]. Because body fat percentage is not required for the diagnosis of obesity ^[15], we used POW (>20%) for the inclusion criteria which is modified after trial commencement. Children without obesity, or with chronic intestinal diseases associated with absorption or digestion failure, severe liver disorder, kidney disease, other known severe underlying disease or past history of severe illness, or females who are pregnant, breastfeeding or intended to become pregnant during study were excluded. To analyze the baseline biochemical characteristics of the subjects, blood was drawn before the start of GD intake and serum concentrations of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and TG were determined by means of standard laboratory blood tests. Serum concentrations of total cholesterol, high-density lipoprotein, low-density lipoprotein, glucose and insulin were not evaluated in some of participants because of lack of enough amount of blood sample thus excluded from the baseline characteristics determination after trial commencement.

This study was a randomized, double-blind, placebo-controlled trial conducted at Osaka City University Hospital. Participants are randomly allocated to one of the two study groups (GD or placebo) by using dynamic allocation that minimizes the differences between groups as participants enter the study. Balancing factors were sex, age, and body weight. The trial conformed to the Helsinki Declaration and was approved by the ethical committees of Osaka City University Graduate School of Medicine (the approved number, 2394; UMIN trial ID, UMIN000021826). Written informed consent was obtained from each child’ s parent or legal guardian, and written assent was obtained from children who were at least 6 years old, after children and each child’ s parent or legal guardian were given, in writing, a full explanation of the aims of the study, its possible hazards, discomfort, and inconvenience.

Fourteen subjects were randomly assigned to orally receive GD beverage, and 14 subjects were randomly assigned to receive placebo beverage within 1 h of dinner daily for 3 months. Children under 12 years were given 25 mL of placebo or GD beverage; children 12 to 18 years old were given 50 mL of placebo or GD beverage. It was difficult for patients and legal guardians to have regular medical visits every 4 weeks during research period described in the approved study protocol, thus patients were evaluated after 3 and 6 months of GD or placebo intake. Patients were blinded, and all clinical assessments were performed without knowledge of the assigned treatment. In both groups, brief lifestyle counseling was provided.

Changes in body weight, POW, and body mass index (BMI) percentile for age were compared between the groups at 3 and 6 months after study initiation. Patients were asked to report adverse events such as vomiting, diarrhea, abdominal pain, or skin eruption.

Comparisons of patient baseline characteristics and outcomes between the GD group and the placebo group were performed by using the Mann–Whitney U test. P values < 0.05 were considered statistically significant.

3. Results

There were no significant differences in the baseline characteristics of sex, age, height, body weight, POW, and BMI percentile between the GD and placebo groups (Table 1). Serum levels of TG, AST, and ALT at the start of the study were also not significantly different between the two groups.

Table 1. Baseline patient demographics and biochemical parameters

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All of the subjects finished the 3-month course of daily oral placebo or GD beverage. During the trial period, no adverse events related to GD intake were reported.

There were no significant differences in change in body weight, BMI percentile, or POW between the two groups at 3 months and at 6 months after the start of GD intake (Table 2). Furthermore, when the numbers of patients with a reduction in body weight, POW, or BMI percentile were compared between the groups, there were no significant differences: body weight (8 in GD group vs. 8 in placebo group), POW (6 vs. 5), and BMI percentile (5 vs. 4), suggesting that GD may induce a placebo effect that results in weight loss.

Table 2. Outcome of globin digest (GD) beverage intake

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Table 3. Number of patients who showed a reduction in body weight (BW), percent overweight (POW), or body mass index (BMI) percentile at 3 months after the end of treatment

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4. Discussion

Functional foods and beverages may be useful to treat obesity in children. Here we found that a GD beverage did not produce any side effects and was safe and had good compliance in the obese Japanese pediatric population. However, we found that the GD beverage did not have a significant effect on the body weight between the GD and the placebo group.

The present study had several limitations. The first was that it was difficult to standardize fat intake among the subjects. A previous study demonstrated that GD effectively reduced hyperlipidemia in healthy adults that were ingesting standardized amounts of fat and calories ^[13]. However, in the present study it was difficult to standardize fat intake because the age, gender, and lifestyle, including favorite foods, varied widely among the children. Therefore, in future studies, it may be necessary to compare the fat and caloric intake between the two groups based on diet records.

The second limitation was that there have been no previous studies demonstrating the effects of GD in obese children, so it was not easy to determine suitable dosages and timing of GD intake. Because obese children ingest excessive amounts of calories or fat, or both, at each meal, and GD is expected to reduce the postprandial absorption of fat, it may be necessary to give the GD beverage not once daily but three times daily after each meal. The third limitation concerns the lifestyle education the children received. Encouragement was provided to the children to improve their lifestyle at each medical visit; therefore, this lifestyle education may have contributed to the suspected placebo effect of the GD beverage.

In conclusion, although we did not show a difference between the GD and placebo groups in the current study design, the limitations of the study mean that we are unable to conclude that the GD beverage had no effect on the body weight of the subjects. Since we did show that the GD beverage used in the present study was safe and had good compliance in obese Japanese children, we recommend that a large group study be conducted to further clarify whether or not GD beverages are effective for reducing obesity in the pediatric population.

Acknowledgements

The globin digest and placebo beverages used in this study were provided by MG Pharma Incorporation (Osaka, Japan). The authors have no other competing interests.

Abbreviations

TG, triglyceride; GD, globin digest; POW, percentage overweight; AST, aspartate aminotransferase; ALT, alanine aminotransferase; BMI, body mass index; BW, body weight

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