Bombyxin II Regulates Glucose Absorption and Glycogen Synthesis through the PI3K Signaling Pathway in HepG2 Cells.

Hongliang Yang,Yujie Sui,Zhenwu Du,Yang Song,Guizhen Zhang,Hongxia Li,Jane Hanrahan

doi:10.1155/2021/6639232

Abstract

Bombyxin, as an insulin-like insect hormone, was discovered in the silkmoth Bombyx mori. It can regulate the metabolism of trehalose and glycogen in Bombyx mori, but whether it has glucose absorption and glycogen synthesis effect on mammalian cells was not clear. BombyxinII (BbxII) and mutant BbxII (mBbxII) genes were cloned into pcDNA3.1(+) vector, respectively; then, gene vectors were transfected into 293FT cells using Lipofectamine 2000. Levels of mRNA and protein expression of BbxII and mBbxII were detected by PCR and Western blot in 293FT cells, respectively. Glucose consumption and glycogenesis were determined by glucose oxidase-peroxidase (GOD-POD) and periodic acid-Schiff (PAS) staining in HepG2 cells; the PI3K signaling pathway was inhibited with wortmannin S1952 in HepG2 cells. Result showed that BbxII and mBbxII genes were being successfully expressed in 293FT cells, respectively. The expression protein of BbxII gene is 10kd pre-bombyxinII, and yet, the expression protein of mBbxII gene is 4kd mature bombyxinII. Only the 4kd bombyxinII showed increased glucose uptake and glycogenesis in HepG2 cells, and the ability of increasing glucose uptake was equal to the human insulin (10 nM). PI3K-wortmannin S1952 inhibitor can decrease the glycogen synthesis induced by bombyxin II protein in HepG2 cells. In conclusion, mature bombyxin II may adjust glucose absorption and glycogen synthesis in HepG2 cells through the PI3K signaling pathway.

Highlights

Diabetes mellitus (DM) as a chronic metabolic disease has already become one of the major diseases threatening human health in the world
The results showed that the glycogen synthesis of HepG2 cells was inhibited, and the number of glycogen-positive cells and the staining intensity in HepG2 cells decreased with the increase of I3K inhibitor concentration
Bombyxin II genes encode polypeptides similar to human, which consist of the signal peptide, B-chain, C-peptide, and A-chain; the expression of bombyxin II has the same mechanism as that of insulin: first, the gene is transcribed, the bombyxin precursor is translated, and the structure is signal peptide (S57)-B chain (b84)-2 basic amino acid residues-C peptide (C63)-2 basic amino acid residues-a chain (A60)

Summary

Introduction

Diabetes mellitus (DM) as a chronic metabolic disease has already become one of the major diseases threatening human health in the world. In China, it is reported that the prevalence of diabetes in adults was 10.9%, and the prevalence of prediabetes was 35.7% in 2013 [1]. The first insulin-like peptide, was discovered in the silkmoth Bombyx mori since 1984 [2]. Bombyxin was called 4K-prothoracicotropic hormone (4KPTTH), because its MW is about 4400 and can stimulate the prothoracic glands (PGs) to release ecdysone [5]. By analyzing 4K-PTTH purified from Bombyx adult heads revealed an abundance of molecular forms of bombyxin. According to different N-terminal amino acid sequences, bombyxin is divided into three forms, namely, 4K-PTTH-I, II, III; these forms were similar to each other [5]

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Discussion

Conclusion