Background
Diabetes mellitus is characterized by hyperglycemia resulting from a relative or absolute insulin deficiency［1］.The prevalence of diabetes has risen dramatically during recent decades，and it is now a serious global health burden［2］.It is reported that more than 371 million people have diabetes(IDF Diabetes Atlas 5th Edition 2012 Update)with the biggest population in China，soaring to 92.3million，9.42% of adults(http：//www.worlddiabetesday.org/).Insulin deficiency is the consequence of compromised insulin secretion perβ-cell and/or reduction in totalβ-cell mass［3］.Prolonged exposure to high glucose concentrations exerts toxic effects onβ-cell，resulting inβ-cell dysfunction and ultimately apoptosis［4］.
Evidences from both human disease and mouse models have shown that apoptosis is the main form ofβ-cell death in diabetes mellitus［3］.Beta-cell apoptosis is mainly mediated by three pathways，namely，death receptor signal pathway，mitochondrial pathway and endoplasmic reticulum(ER)stress pathway［5，6］.The death receptor signal pathway is activated upon ligation of the cell surface death receptors，including Fas receptor and tumor necrosis factor receptor-1(TNFR-1)，which in turn activates downstream effector of Caspase family［7］.The assembly of the death inducing signaling complex(DISC)，a multi-protein complex consisting of Fas receptor，the adaptor protein Fasassociated death domain，and pro-Caspase-8(pro-cysteinyl aspartate specific proteinase-8)，is the initiating signal for the processing of pro-Caspase-8 to its active form［7］.TNF forms the DISCin the similar way［8］.Depending upon the activity of Caspase-8，the ensuing signal can activate either downstream Caspase cascade or the mitochondrial death pathway or Nuclear Factor-kappa B(NF-kB)for efficient execution［9- 11］.
Mitochondrial pathway could be activated by the unbalance of the proportion of pro-/anti-apoptotic proteins(such as Bax，Bad，Bcl-2，Bcl-x L)，then release several apoptotic factors to cytoplasm，such as cytochrome-c，apoptotic protease-activating factor 1，apoptosis inducing factor，second mitochondria-derived activator of Caspase/direct inhibitor of apoptosis-binding protein with low PI，endonuclease G to induce apoptosis［12- 18］.
In the processing of ER stress pathway，some pro-apoptotic effectors are activated under ER stress，such as C/EBP homologous protein，c-Jun N-terminal kinase(JNK)，activating transcription factor-3(ATF-3)［19- 21］.ER stress could also activate p38 through Ca2+signal way and induce apoptosis［20，22］.Besides，under ER stress，Akt gene could promote cell survival［23］.(https://www.daowen.com)
Finally，these three pathways converge to activate Caspase-3 to execute cell apoptosis［24- 26］.In addition to the three pathway aforementioned，i NOS(inducible nitric oxide synthase)could be induced by environmental exposure leading to NO(Nitric Oxide)formation，which have a direct deleterious effects onβ-cells［27，28］.
Free fatty acids are important to pancreaticβ-cell for glucose-stimulated insulin secretion［29，30］.It is reported that unsaturated fatty acids(UFAs)usually protectβ-cell from glucose-induced apoptosis and impairedβ-cell proliferation［31，32］.In vivo research showed that UFA could alleviate insulin resistance and promote insulin secretion，while in vitro studies have revealed that omega-6 polyunsaturated fatty acid(PUFA)can prevent chemically induced diabetes and attenuate the oxidant stress that occurs in diabetes mellitus［33，34］.
Thorn grape(Vitis davidii Foex.)，one of characteristic plants in Hunan province，P.R.China，has been used to treat diabetes in Traditional Chinese medicine for centuries.It is rich in UFA，resveratrol，oligomeric proantho cyanidins，squalene and superoxide dismutase，et al.In thorn grape seed oil(TGSO)，UFA is mainly composed of linoleic acid(ω-6 PUFA)and oleic acid(monounsaturated fatty acid，MUFA)［35，36］.In our previous research，TGSO showed remarkable anti-diabetic effects in animal models［37］.However，its anti-diabetic mechanism has not been clarified.
This study aimed to evaluate the effects of TGSO on high glucose-induced rattus pancreaticβ-cell apoptosis by detecting the cell apoptotic rate and insulin levels，and reveal its mechanisms regarding signal transduction pathway by measuring related genes expression.