Protective Effect Of [Gly14]-humanin On β-cell Apoptosis And Related Modulation On Glucose And Lipid Metabolism

Humanin (HN) has been reported to be a24-amino acid endogenous peptidethat exerts highly selective neuroprotection against cell death induced by varioustypes of Alzheimer’s disease-related insults. The replacement of the amino acidserine with a glycine at position14increases its potency up to a thousand-fold.This new humanin homologous is named as [Gly14]-Humanin (HNG).A recentreport suggests humanin reduced apoptosis induced by serum starvation in NIT-1cells and decreased apoptosis induced by cytokine treatment; Humanin improvesimpaired metabolic activity and prolongs the survival of serum-deprived humanlymphocytes. The metabolic activities of the cells was significantly enhanced byHN, but HN cannot induce cell proliferation but inhibit apoptosis. The resultsshowed that HNG protects β-cells from apoptosis induced by serum starvation andimproves insulin secretion with dose-dependency. The optimum concentration ofHNG is100nM. Palmitic acid (PA) is the main lipotoxicity component of islet βcells used to research glucolipotoxicity currently. It has been reported that thelipotoxicity of fatty acids with increasing concentration has an effect oninsulin-secreting cells and induces the apoptosis of separation in pancreatic β cellsin vitro. It is the first time demonstrated that HNG can significantly reduce theapoptosis induced by PA.T1MD is a chronic autoimmune disease, during this time, pancreatic β cellwere destroyed by autoimmune cells selectively, leading them to be unable tosynthesize and secrete insulin themselves, T lymphocytes play an important role inmediating these immune responses. NOD mice spontaneously develop type1diabetes as a result of islet antigen-specific T cell-mediated destruction ofpancreatic β-cells. The T1DM pathological process of NOD mice is very similar tothe pathological course of human, and female NOD mice develop T1D at a higherincidence than male NOD mice. HN and its analogues are a novel central regulatorof peripheral insulin action. HN inhibits β-cell apoptosis via a signal transducerand activator of transcription3activation and so delays and ameliorates diabetes innonobese diabetic mice. However the effect of HNG on lymphocyte has not yetbeen reported, so in this research in vivo, NOD mice were intraperitoneallyadministered for six weeks (0.2mg/[kg d]). At mice14weeks old,18weeks and22weeks old, respectively, spleens were harvested from each groups and thisresearch showed that HNG inhibited diabetogenic lymphocyte (CD4+T cells andCD8+Ｔcells,CD19B cells, CD20B cells) abnormal activation. This reduced thefrequency of Treg cells CD4+CD25+T cells experiencing apoptosis; similarly,lymphocytes were extracted. H&E: The majority of the pancreata innormoglycemic control animals had destructive insulitis,whereas insulitis wassignificantly reduced in HNG treated animals; Immunofluorescence resulted fromtreatment with HNG significantly increased the levels of insulin secretion anddecreased the levels of glucagon secretion in NOD mice. HNG inhibitedauto-reactive T cell activation effectively, and recovered tolerance of T cells to islet β cell antigens, significantly improved islets function, to ameliorates theprogression of diabetes in NOD mice. We studied the effects of HNG on glucosemetabolism, lipid metabolism, body weight and survival rate in mice. In atolerance test, HNG-administered-groups blood-glucose levels were significantlylower than control group; the body weight of HNG group mice was significantlylower than the control group and the survival rate was higher than control group.Differentiation fat cells co-cultured with HNG after six days and compared withthe control group, which only added the medium. To measure the concentration ofUCP-1, HSL, PPAR with RT-PCR, the expression of them impact directly on theformation and deposition of fat. The final results showed that their expressionlevels are higher than control, which indicated that HNG can reduce blood glucoselevel and enhanced the expression of proteins which are related to lipidmetabolism in NOD mice to accelerate the lipid metabolism.To our knowledge there are no directly reported results about HNGaccelerating fat metabolism. This new role of HNG for treatment various typesobesity of patients has a good prospect.