Metabolic Mechanisms Of Silkworm Pupa Peptide Based Enteral Formula For Supporting Type 2 Diabetes Mellitus In Streptozotocin Induced Mice

The silkworm(Bombyx mori) is not only a very useful animal model for research but also a good nutritional insect source of protein. Silkworm pupa protein(SPP) contains 18 amino acids including 8 essential amino acids. The protein content of silkworm pupa is about 60% on a dry weight basis. The SPP powder can be easily digested and absorbed by human bodies. It also reported that it can promote the physiological functions of the gastrointestinal tract. The results of animal experiments showed that SPP powder could decrease blood-glucose contents rapidly without any side effects. Long-term consumption of SPP can improve immunity and does not cause glycopenia. Effects of the SPP and its hydrolysates on the blood glucose metabolism has been used for long time in the anti-diabetic medicinal preparations of traditional healers by Wayanad, but the potential of the SPP used in diabetes-specific enteral nutritional(EN) is still remained undefined. Therefore, considering the above issue, the present study was aimed to investigate the metabolic characteristic of silkworm pupa protein or peptide-based enteral formula in high- fat diets and streptozotocin induced type 2 diabetic mice.Enteral Formula preparation: The aim of this part is to elaborate enteral formula preparation of silkworm pupa peptide. The comparison of main ingredient and chemical composition between Abbott Glucerna SR and self-control enteral nutrition is given in the first section of this part. Amino acid composition of three types of silkworm pupae protein and peptide samples are analysised in the second section.Effects investigation: Objective:The present study was designed to investigate the silkworm pupa protein or peptide-based enteral formula for improving metabolic characteristic in streptozotocin-induced type 2 diabetic mice. Method:Type 2 diabetes mellitus(T2DM) was established in mice model by high fat chow for 3 weeks and then intraperitoneal injection of STZ(40mg/kg per body weight) for 3 times. T2 DM mice were randomly assigned to 5 groups(n=10/group). The 1st group, control group fed with Standard chow, the 2nd and 3rd group fed with Abbott Glucerna SR and silkworm pupae peptide sample 1-based EN(spp1), respectively. The 4th and 5th group fed with silkworm pupae peptide sample 2-based EN(spp2) and silkworm pupae protein sample 3-based EN(spp3). Normal mice(without any treatment) were assigned to 6th group, which feed with standard chow. The levels of fasting blood glucose(FBG) were estimated at 7 days interval and oral glucose tolerance test(OGTT) was performed in the 3rd week and other blood biochemical indices were determined after 4 weeks of administration. Results:The SPP Enteral Formula could significantly reduce blood glucose in T2 DM mice(P<0.01)compared with the model group. FBG of spp1, spp2 and spp3 was decreased with the value of 47.47%, 38.14% and 41.52%, respectively. The results of OGTT showed that two SPP groups were increased significantly(P<0.01). The level of blood biochemical indices including TC,TG and LDL were decreased in the 3rd and 4th group, which use SPP- based EN. However, the HDL in group 4 also gives a low level. Conclusion:SPP- based Enteral Formula marked decreased the levels of T2 DM mice blood glucose. It is also showed the actively effect of improving lipid metabolism.Mechanism investigation: Aim:The present study was designed to investigate the silkworm pupa peptide-based enteral formula for improving metabolic characteristics in streptozotocin-induced type 2 diabetic mice and its probable mechanisms. Methods:Type 2 diabetes mellitus(T2DM) mice model was established by high fat chow for 3 weeks along with intra-peritoneal injection of STZ(40mg/kg per body weight) for 3 times in C57 BL mice of either sex. T2 DM mice model of either sex was randomly divided into 5 groups(n=5/group). The 1st group(blank group) fed with purified diets(PD), the 2nd and 3rd group supported with silkworm pupa peptide(SPP)-based PD and treatment with metformin hydrochloride(125mg/kgbw d) and charantin(350mg/kgbw d), respectively. The 4th and 5th group supported with SPP-based enteral nutrition(EN) and SPP-based PD, respectively. Normal mice(without any treatment, control group) were assigned to 6th group, which fed with PD. The levels of fasting blood glucose(FBG) were estimated in every weekend and oral glucose tolerance test(OGTT) and starch tolerance test(OSTT) was performed in the 3rd weekend; and other blood biochemical indices were determined after 4 weeks of treatment. The activities of hexokinase(HK) and pyruvate kinase(PK) in liver, as well as those of α-glucosidase in intestinal mucosa of mice were observed. Organ index was calculated by following formula:Organ index = organ weight(mg) / body weight(g). The liver index, kidney index and spleen index will be calculated in this paper.Results:The SPP-based EN consumed DM mice were more active, feed and water intake as compared with PD consumed mice(blank group). After 4 weeks of support, body weight in mice received with SPP-EN and metformin give a gradually increased over time. The mice’s organs index(liver and kidney) raised by SPP-EN diet had an obviously change(P<0.01)compared with the blank group, while the spleen index decreased. At the end of 1st week, FBG levels of mice fed with silkworm pupa peptide-based enteral formula were significantly decreased when compared with DM mice in blank group. SPP-EN can significantly reduce T2 DM mice glucose as compared with the blank group after 4 weeks of treatment. FBG of metformin hydrochloride and SPP-EN was decreased with the value of 58.48% and 41.44%, respectively. The glucose tolerance test data were analyzed as glucose and total AUC from 0 to 120 min. After 30 min of glucose administered, mice blood glucose level was greatly increased in SPP-EN group compared to blank group. FBG of SPP-EN group was decreased with a value of 19.69% within one hour. When compared to blank group, the control group animal had lower level of TC, TG and LDL respectively. The activities of HK and PK in liver as well as those of α-glucosidase in intestinal mucosa of mice in all the SPP-EN support groups were significantly different to those in the model group(P < 0.05), and the blood glucose was significantly correlated with the activities of HK and PK in liver as well as those of α-glucosidase in intestinal mucosa of rats(P < 0.00 1).Conclusion:SPP- based Enteral Formula greatly decreased the levels of T2 DM mice blood glucose. Silkworm pupa peptide-based enteral formula could inhibit the blood glucose increase of T2 DM mice, and one of the mechanisms may be that it could restrain the activity of α-glucosidase and increase the activities of HK and PK. From the above results, it is concluded that the SPP- based Enteral Formula could influence the lipid metabolism as a result it may be useful drug to treat type II diabetes.