Selenoprotein S protects against high glucose-induced vascular endothelial apoptosis through the PKCßII/JNK/Bcl-2 pathway.

Vascular endothelial apoptosis is closely associated with the pathogenesis and progression of diabetic macrovascular diseases. Selenoprotein S (SelS) participates in the protection of vascular endothelial and smooth muscle cells from oxidative and endoplasmic reticulum stress-induced injury. However, whether SelS can protect vascular endothelium from high glucose (HG)-induced apoptosis and the underlying mechanism remains unclear. The present study preliminarily analyzed aortic endothelial apoptosis and SelS expression in diabetic rats in vivo and the effects of HG on human umbilical vein endothelial cell (HUVEC) apoptosis and SelS expression in vitro. Subsequently, SelS expression was up- or downregulated in HUVECs using the pcDNA3.1-SelS recombinant plasmid and SelS-specific small interfering RNAs, and the effects of high/low SelS expression on HG-induced HUVEC apoptosis and a possible molecular mechanism were analyzed. As expected, HG induced vascular endothelial apoptosis and upregulated endothelial SelS expression in vivo and in vitro. SelS overexpression in HUVECs suppressed HG-induced increase in apoptosis and cleaved caspase3 level, accompanied by reduced protein kinase CßII (PKCßII), c-JUN N-terminal kinase (JNK), and B-cell lymphoma/leukemia-2 (Bcl-2) phosphorylation. In contrast, inhibiting SelS expression in HUVECs further aggravated HG-induced increase in apoptosis and cleaved caspase3 level, which was accompanied by increased PKCßII, JNK, and Bcl-2 phosphorylation. Pretreatment with PKC activators blocked the protective effects of SelS and increased the apoptosis and cleaved caspase3 level in HUVECs. In summary, SelS protects vascular endothelium from HG-induced apoptosis, and this was achieved through the inhibition of PKCßII/JNK/Bcl-2 pathway to eventually inhibit caspase3 activation. SelS may be a promising target for the prevention and treatment of diabetic macrovascular complications.

The antagonist of CXCR1 and CXCR2 protects db/db mice from metabolic diseases through modulating inflammation.

Interleukin-8 (IL-8, also named CXCL8) binds to its receptors (CXCR1 and CXCR2) with subsequent recruitment of neutrophils and enhancement of their infiltration into inflamed sites, which exaggerates inflammation in many diseases. Recent studies have proposed that metabolic disorders can be attenuated by counteracting certain inflammatory signal pathways. In this study, we examined whether intervention with G31P, an antagonist of CXCL8, could attenuate tissue inflammation and development of metabolic disorders in db/db mice. The db/m and db/db mice were subcutaneously injected with G31P or equivalent normal saline once a day for 6 wk. The physical and metabolic parameters, glucose tolerance, insulin sensitivity, hepatic lipid accumulation, and inflammation markers were measured. G31P improved hepatic insulin sensitivity by modulating expression of genes related to gluconeogenesis and phosphorylated Akt levels. The expressions of several genes encoding proteins involved in de novo lipogenesis were decreased in G31P-treated db/db mice. Meanwhile, immune cell infiltration and cytokine release were attenuated in db/db mice with G31P treatment. G31P also improved the ratio of proinflammatory M1 and anti-inflammatory M2 macrophages. Furthermore, G31P ameliorates metabolic disturbances via inhibition of CXCR1 and CXCR2 pathways in db/db mice. These data suggest that the selective inhibition of CXC chemokines may have therapeutic effects on symptoms associated with obesity and diabetes.

Deficiency of VCP-Interacting Membrane Selenoprotein (VIMP) Leads to G1 Cell Cycle Arrest and Cell Death in MIN6 Insulinoma Cells.

BACKGROUND/AIMS: VCP-interacting membrane selenoprotein (VIMP), an ER resident selenoprotein, is highly expressed in ß-cells, however, the role of VIMP in ß-cells has not been characterized. In this study, we studied the relationship between VIMP deficiency and ß-cell survival in MIN6 insulinoma cells. METHODS: To determine the role of VIMP in ß-cells, lentiviral VIMP shRNAs were used to knock down (KD) expression of VIMP in MIN6 cells. Cell death was quantified by propidium iodide (PI) staining followed by flow cytometric analyses using a FACS Caliber and FlowJo software. Cell apoptosis and proliferation were determined by TUNEL assay and Ki67 staining, respectively. Cell cycle was analyzed after PI staining. RESULTS: The results show that 1) VIMP suppression induces ß-cell apoptosis, which is associated with a decrease in Bcl-xL, and the ß-cell apoptosis induced by VIMP suppression can be inhibited by overexpression of Bcl-xL; 2) VIMP knockdown (KD) decreases cell proliferation and G1 cell cycle arrest by accumulating p27 and decreasing E2F1; 3) VIMP KD suppresses unfolded protein response (UPR) activation by regulating the IRE1α and PERK pathways; 4) VIMP KD increases insulin secretion. CONCLUSION: These results suggest that VIMP may function as a novel regulator to modulate ß-cell survival, proliferation, cell cycle, UPR and insulin secretion in MIN6 cells.

Selenoprotein S protects against adipocyte death through mediation of the IRE1α-sXBP1 pathway.

As the most conserved branch of the unfolded protein response (UPR), the inositol-requiring enzyme 1a (IRE1a)/X-box binding protein 1 (XBP1) pathway plays crucial roles in cell survival and cell death by upregulating UPR-associated genes involved in protein entry into the endoplasmic reticulum (ER) and ER-associated degradation (ERAD). Selenoprotein S (SelS) is localized to the ER membrane and involved in ERAD. Although SelS plays an important role in restoring ER stress, the SelS-dependent protective mechanisms against cell death remain unclear. Here, using an inducible SelS knockdown (KD) 3T3-L1 cell model, we showed that SelS KD resulted adipocyte death, which was associated with imbalance of the Bcl-2 family members. Furthermore, SelS KD decreased spliced XBP1 (sXBP1), increased IRE1α and p-JNK, suggesting a role of SelS in the modulation of the IRE1α-sXBP1 pathway. Moreover, adipocyte death induced by SelS suppression can be inhibited by overexpression of sXBP1. Thus, it is proposed that SelS promotes cell survival through the IRE1α-XBP1 signaling pathway.

Selenoprotein S Attenuates Tumor Necrosis Factor-α-Induced Dysfunction in Endothelial Cells.

Endothelial dysfunction, partly induced by inflammatory mediators, is known to initiate and promote several cardiovascular diseases. Selenoprotein S (SelS) has been identified in endothelial cells and is associated with inflammation; however, its function in inflammation-induced endothelial dysfunction has not been described. We first demonstrated that the upregulation of SelS enhances the levels of nitric oxide and endothelial nitric oxide synthase in tumor necrosis factor- (TNF-) α-treated human umbilical vein endothelial cells (HUVECs). The levels of TNF-α-induced endothelin-1 and reactive oxygen species are also reduced by the upregulation of SelS. Furthermore, SelS overexpression blocks the TNF-α-induced adhesion of THP-1 cells to HUVECs and inhibits the increase in intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. Moreover, SelS overexpression regulates TNF-α-induced inflammatory factors including interleukin-1ß, interleukin-6, interleukin-8, and monocyte chemotactic protein-1 and attenuates the TNF-α-induced activation of p38 mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) pathways. Conversely, the knockdown of SelS with siRNA results in an enhancement of TNF-α-induced injury in HUVECs. These findings suggest that SelS protects endothelial cells against TNF-α-induced dysfunction by inhibiting the activation of p38 MAPK and NF-κB pathways and implicates it as a possible modulator of vascular inflammatory diseases.

The source of circulating selenoprotein S and its association with type 2 diabetes mellitus and atherosclerosis: a preliminary study.

BACKGROUND: Selenoprotein S (SelS) is a transmembrane protein that is expressed in the liver, skeletal muscle, adipose tissue, pancreatic islets, kidney, and blood vessels. In addition to its transmembrane localization, SelS is also secreted from hepatoma HepG2 cells (but not L6 skeletal muscle cells, 3T3-L1 adipocytes, Min6 pancreatic ß cells and human embryonic kidney 293 cells) and has been detected in the serum of some human subjects, with a detection rate of 31.1 %. These findings prove that serum SelS is secreted by hepatocytes. However, whether vascularly expressed SelS can be secreted has not been reported. Transmembrane SelS has been suggested to play different roles in the pathogenesis and progression of diabetes mellitus (DM) and atherosclerosis (AS), but the association of secreted SelS with DM and macroangiopathy remains unclear. RESEARCH DESIGN AND METHODS: Supernatants were collected from human umbilical vein endothelial cells (HUVECs), human aortic vascular smooth muscle cells (HA/VSMCs) and human hepatoma HepG2 cells that were untransfected or transfected with the indicated plasmid and concentrated for western blotting. Serum samples were collected from 158 human subjects with or without type 2 DM (T2DM) and/or AS. Serum SelS levels were measured using an enzyme-linked immunosorbent assay. RESULTS: Secreted SelS was only detected in the supernatants of hepatoma HepG2 cells. The SelS detection rate among the 158 human serum samples was 100 %, and the average SelS level was 64.81 ng/dl. The serum SelS level in the isolated DM subjects was lower than the level in the healthy control subjects (52.66 ± 20.53 vs 70.40 ± 21.38 ng/dl). The serum SelS levels in the DM complicated with SAS subjects (67.73 ± 21.41 ng/dl) and AS subjects (71.69 ± 27.00 ng/dl) were significantly increased compared with the serum SelS level in the isolated DM subjects. There was a positive interaction effect between T2DM and AS on the serum SelS level (P = 0.002). Spearman correlation analysis showed that the serum SelS level was negatively correlated with fasting plasma glucose. CONCLUSIONS: Vascular endothelial and vascular smooth muscle cells could not secrete SelS. Serum SelS was primarily secreted by hepatocytes. SelS was universally detected in human serum samples, and the serum SelS level was associated with T2DM and its macrovascular complications. Thus, regulating liver and serum SelS levels might become a new strategy for the prevention and treatment of DM and its macrovascular complications.

Effect of needle-free injection on psychological insulin resistance and insulin dosage in patients with type 2 diabetes.

Background and objective: Psychological insulin resistance (PIR), which refers to the reluctance of diabetic patients to use insulin, is a frequently encountered clinical issue. Needle-free injection (NFI) offers advantages in terms of expediting insulin absorption and mitigating adverse reactions related to injection. To evaluate the effects of subcutaneous injection of insulin aspart 30 with NFI on PIR and insulin dosage in patients with type 2 diabetes mellitus (T2DM). Methods: Sixty-four patients with T2DM participated in this randomized, prospective, open, crossover study. Insulin aspart 30 was administered subcutaneously to each subject via QS-P NFI and Novo Pen 5 (NP) successively. The effects of NFI on PIR were analyzed. Differences in insulin dosage, glycemic variability, and injection safety were compared at similar levels of glycemic control. Results: After the administration of NFI, the insulin treatment attitude scale score decreased (53.7 ± 7.3 vs. 58.9 ± 10.7, p<0.001), the insulin treatment adherence questionnaire score increased (46.3 ± 4.9 vs. 43.8 ± 7.1, p<0.001), and the insulin treatment satisfaction questionnaire score increased (66.6 ± 10.5 vs. 62.4 ± 16.5, p<0.001). At the same blood glucose level, NFI required a smaller dosage of insulin aspart 30 compared with that of NP (30.42 ± 8.70 vs. 33.66 ± 9.13 U/d, p<0.001). There were no differences in glycemic variability indices (standard deviation, mean amplitude of glycemic excursion or coefficient of variation) between the two injection methods. Compared with NP, NFI did not increase the incidence of hypoglycemia (17.2% vs. 14.1%, p=0.774), and it decreased the incidence of induration (4.7% vs. 23.4%, p=0.002) and leakage (6.3% vs. 20.3%, p=0.022) while decreasing the pain visual analog scale score (2.30 ± 1.58 vs. 3.11 ± 1.40, p<0.001). Conclusion: NFI can improve PIR in patients with T2DM and be used with a smaller dose of insulin aspart 30 while maintaining the same hypoglycemic effect. Clinical trial registration: https://www.chictr.org.cn/, identifier ChiCTR2400083658.

Oxidized Low-Density Lipoprotein Decreases the Survival of Bone Marrow Stem Cells via Inhibition of Bcl-2 Expression.

Therapy with mesenchymal stem cells (MSCs) is considered an attractive strategy for the repair or regeneration of damaged tissues. However, low survival of MSCs limits their applications clinically. Oxidized low-density lipoprotein (ox-LDL) is significantly increased in patients with hyperlipidemia and decreases the survival of MSCs. Bcl-2 is critically involved in important cell functions, including cell membrane integrity and cell survival. The present study was designed to test the hypothesis that ox-LDL attenuates the survival of MSCs through suppression of Bcl-2 expression. Bone marrow MSCs from C57BL/6 mice were cultured with ox-LDL at different concentrations (0-140 µg/mL) for 24 h with native LDL as control. Ox-LDL treatment substantially decreased the survival of MSCs dose-dependently and enhanced the release of intracellular lactate dehydrogenase (LDH) in association with a significant decrease in Bcl-2 protein level without change in BAX protein expression in MSCs. Bcl-2 overexpression effectively protected MSCs against ox-LDL-induced damages with preserved cell numbers without significant increase in LDH release. Treatment with N-acetylcysteine (NAC) (1 mM) effectively preserved Bcl-2 protein expression in MSCs and significantly attenuated ox-LDL-induced decrease of cell number and increase in the release of intracellular LDH. These data indicated that ox-LDL treatment resulted in a significant damage of cell membrane and dramatically decreased the survival of MSCs dose-dependently through inhibition of Bcl-2 expression. NAC treatment significantly protected MSCs against the damage of cell membrane by ox-LDL and promoted the survival of MSCs in association with preserved Bcl-2 expression.

Effects of selenoprotein S on oxidative injury in human endothelial cells.

BACKGROUND: Selenoprotein S (SelS) is an important endoplasmic reticulum and plasma membrane-located selenoprotein implicated in inflammatory responses and insulin resistance. However, the effects of SelS on endothelial cells (ECs) have not been reported. In the present study, the role of SelS in oxidative stress and the underlying mechanism were investigated in human ECs. METHODS: A SelS over-expression plasmid (pc-SelS) and a SelS-siRNA plasmid were transfected into human umbilical vein endothelial cells (American Type Culture Collection, USA). The cells were divided into four groups: control, SelS over-expression (transfected with pc-SelS), vector control, and SelS knockdown (transfected with siRNA-SelS). After treating the cells with H2O2, the effects of oxidative stress and the expression of caveolin-1 (Cav-1) and protein kinase Cα (PKCα) were investigated. RESULTS: Following treatment with H2O2, over-expression of SelS significantly increased cell viability and superoxide dismutase (SOD) activity, and decreased malondialdehyde (MDA) production and Cav-1 gene and protein expression. However, no effects on PKCα were observed. In contrast, knockdown of SelS significantly decreased cell viability, SOD activity, and PKCα gene and protein expression, and increased MDA production and Cav-1 gene and protein expression. CONCLUSIONS: SelS protects ECs from oxidative stress by inhibiting the expression of Cav-1 and PKCα.

[Relationship of amyloid-ß with vascular endothelial cell damage induced by diabetic serum].

OBJECTIVE: To explore the relationship of the impairment of human umbilical vein endothelial cell (HUVEC) with amyloid-ß. METHODS: HUVECs were cultured in the serum of patients with type 2 diabetes mellitus (DM) or serum of healthy control (HC), while fetal bovine serum (FBS) was used as a negative control. The proliferative activity of HUVEC were assessed by thiazolyl blue tetrazolium bromide (MTT) after 72 h. The supernatant concentrations of superoxide dismutase (SOD), maleic dialdehyde (MDA), nitric oxide (NO), amyloid-ß40 (Aß40) and Aß42 were measured after 0.5, 3 and 72 h respectively. RESULTS: Glycosylated hemoglobin values, fasting plasma glucose and fasting plasma Aß40 concentrations of diabetic patients were higher than those of healthy counterparts (P < 0.01). Proliferative activity of HUVECs in group DM were significantly lower than that of group HC. Both group and the time of intervention had crossover effects on the levels of MDA, SOD, NO and Aß40 ((163 ± 64), (207 ± 69), (286 ± 75) ng/L in group DM; (146 ± 76), (154 ± 75), (161 ± 72) ng/L in group HC after 0.5, 3 and 72 h, P < 0.05) and Aß42 ((48 ± 46), (54 ± 43), (79 ± 44) ng/L in group DM; (41 ± 12), (44 ± 16), (48 ± 12) ng/L in group HC after 0.5, 3 and 72 h, P < 0.05). With the elongating time of intervention, the levels of SOD and NO decreased significantly in group DM and reached the lowest after 72 h while increased significantly in groups HC and FBS and peaked after 72 h. The concentrations of MDA, Aß40 and Aß42 increased significantly in all three groups while the fastest and marked increments were found in group DM (P < 0.01). Pearson correlation analysis showed that SOD was negatively correlated with Aß40 (r = -0.482, P = 0.02) and Aß42 (r = -0.422, P = 0.02) while MDA positively with Aß40 (r = 0.418, P < 0.05) and Aß42 (r = 0.833, P < 0.05) after 72 h. CONCLUSION: Oxidative stress of vascular endothelial cells may be correlated with Aß40 and Aß42 in diabetes.

Hepatic deficiency of selenoprotein S exacerbates hepatic steatosis and insulin resistance.

Nonalcoholic fatty liver disease (NAFLD) is closely associated with insulin resistance (IR) and type 2 diabetes mellitus (T2DM), which are all complex metabolic disorders. Selenoprotein S (SelS) is an endoplasmic reticulum (ER) resident selenoprotein involved in regulating ER stress and has been found to participate in the occurrence and development of IR and T2DM. However, the potential role and mechanism of SelS in NAFLD remains unclear. Here, we analyzed SelS expression in the liver of high-fat diet (HFD)-fed mice and obese T2DM model (db/db) mice and generated hepatocyte-specific SelS knockout (SelSH-KO) mice using the Cre-loxP system. We showed that hepatic SelS expression levels were significantly downregulated in HFD-fed mice and db/db mice. Hepatic SelS deficiency markedly increased ER stress markers in the liver and caused hepatic steatosis via increased fatty acid uptake and reduced fatty acid oxidation. Impaired insulin signaling was detected in the liver of SelSH-KO mice with decreased phosphorylation levels of insulin receptor substrate 1 (IRS1) and protein kinase B (PKB/Akt), which ultimately led to disturbed glucose homeostasis. Meanwhile, our results showed hepatic protein kinase Cɛ (PKCɛ) activation participated in the negative regulation of insulin signaling in SelSH-KO mice. Moreover, the inhibitory effect of SelS on hepatic steatosis and IR was confirmed by SelS overexpression in primary hepatocytes in vitro. Thus, we conclude that hepatic SelS plays a key role in regulating hepatic lipid accumulation and insulin action, suggesting that SelS may be a potential intervention target for the prevention and treatment of NAFLD and T2DM.

Ubiquitinated gasdermin D mediates arsenic-induced pyroptosis and hepatic insulin resistance in rat liver.

As an environmental toxicant, arsenic exposure may cause insulin resistance (IR). Previous studies have shown that pyroptosis plays an important role in the occurrence and development of IR. Although gasdermin D (GSDMD) functions as an executor of pyroptosis, the relationship between GSDMD-mediated pyroptosis and hepatic IR remains unclear. Here, we observed that sodium arsenite (NaAsO2) activated NOD-like receptors containing pyrin domain 3 (NLRP3) inflammasomes, promoted GSDMD activation, induced pyroptosis and hepatic IR, while GSDMD knockdown attenuated pyroptosis and hepatic IR caused by NaAsO2. However, GSDMD interference did not affect NLRP3 activation. Ubiquitination modification is widely involved in protein regulation and intracellular signal transduction, and whether it regulates GSDMD and affects its degradation, and exerts effects on arsenic-induced pyroptosis remain unclear. We observed that NaAsO2 reduced the K48- and K63-linked ubiquitination of GSDMD, thereby inhibiting its degradation through the ubiquitin-proteasome system (UPS) and the autophagy-lysosome pathway (ALP), causing GSDMD to accumulate and lyse into GSDMD-N, which promoted pyroptosis. In summary, we demonstrated that GSDMD participated in arsenic-induced hepatic IR. Moreover, NaAsO2 reduced GSDMD ubiquitination and decreased its intracellular degradation, aggravating pyroptosis and hepatic IR. We have revealed the molecular mechanism underpinning arsenic-induced IR, and we provide potential solutions for the prevention and treatment of type 2 diabetes (T2D).

Selenoprotein S attenuates high glucose and/or ox-LDL-induced endothelium injury by regulating Akt/mTOR signaling and autophagy.

Glucolipid metabolism disorder in diabetes mellitus (DM) causes human endothelial injury and autophagy dysfunction is an important cause of endothelial dysfunction (ED). Selenoprotein S (SelS) could protect endothelium from oxidative stress, inflammatory responses, and apoptosis. This study assessed the effect of SelS on autophagy in glucolipid metabolic disorders and protection of the resulted vascular endothelial injury. The results showed that high glucose (HG), high oxidized low-density lipoprotein (HL), and HG combined with HL (HGL) could reduce viability of human aortic endothelial cells (HAECs), induce HAECs injury and increase SelS expression in a time-dependent manner. HG, HL, and HGL also initially induced autophagy but later reduced it in HAECs, while activity of the Akt/mTOR signaling was inhibited, especially in HGL culture of HAECs. SelS overexpression reduced the endothelial injury and autophagy and activated the Akt/mTOR signaling in HG, HL and HGL-cultured HAECs, compared to the control. Conversely, knockdown of SelS expression had the opposite effects on HAECs. In conclusion, SelS demonstrated a protective effect on endothelial injury induced by high glucose and/or ox-LDL and the underlying molecular events might be related to its regulation of HAECs autophagy by activating the Akt/mTOR signaling. SelS could be a potential intervention target in prevention and treatment of diabetic vascular complications.

Selenoprotein S attenuates endothelial dysfunction in a diabetic vascular chip.

Endothelial dysfunction (ED) is a critical and initiating factor in the genesis of diabetic vascular complications whose occurrence and development is closely related to the complex intravascular microenvironment. However, currently, there is no dynamic model simulating the diabetic vascular endothelial microenvironment that can be used to investigate the mechanism underlying multifactor-induced ED. Here, we developed an integrated microfluidic chip as a new methodological platform to study vascular ED. Selenoprotein S (SELENOS) was found to be involved in the defense against oxidative stress-induced vascular endothelial injury in our previous studies. However, the regulatory signaling pathway underlying this process has not been described. With this chip, we demonstrated that multifactor-induced oxidative stress injury in human aortic endothelial cells (HAECs) has a synergistic effects and upregulates SELENOS expression. Subsequently, SELENOS was found to protect HAECs against multifactor-induced oxidative stress injury by regulating the PKCα/PI3K/Akt/eNOS pathway in the diabetic vascular endothelial microenvironment. Based on these data, our diabetic vascular chip provides a promising tool for studying vascular endothelial function, and SELENOS may be a novel target for prevention and treatment of diabetic macrovascular complications.

Selenoprotein S regulates adipogenesis through IRE1α-XBP1 pathway.

The induction of endoplasmic reticulum (ER) stress is associated with adipogenesis, during which the inositol-requiring enzyme 1 alpha (IRE1α)-X-box-binding protein 1 (XBP1) pathway is involved. Selenoprotein S (SelS), which is an ER resident selenoprotein, is involved in ER homeostasis regulation; however, little is known about the role of SelS in regulating adipogenesis. In vivo studies showed that SelS protein levels in white adipose tissue were increased in obese subjects and high-fat diet (HFD)-fed mice. Moreover, we identified that SelS protein levels increased in the early phase of adipogenesis and then decreased in the late phase during adipogenesis. Overexpression of SelS promoted adipogenesis. Conversely, knockdown (KD) of SelS resulted in the inhibition of adipogenesis, which was related to increasing cell death, decreased mitotic clonal expansion, and cell cycle G1 arrest. In vivo studies also showed that ER stress markers (p-IRE1α/IRE1α, XBP1s, and Grp78) were significantly increased with upregulating of SelS expression in subcutaneous and visceral adipose tissues in the obese subjects and HFD-fed mice. Furthermore, in SelS KD cells, the levels of Grp78 were increased and the levels of p-IRE1α/IRE1α were unchanged , but mRNA levels of spliced XBP1 (XBP1s) produced by IRE1α-mediated splicing were decreased, suggesting a role of SelS in the modulation of IRE1α-XBP1 pathway. Moreover, inhibition of adipogenesis by SelS suppression can be rescued by overexpression of XBP1s. Thus, SelS appears to function as a novel regulator of adipogenesis through the IRE1α-XBP1 signaling pathway.

[Primary preventive effect of metformin upon atherosclerosis in patients with type 2 diabetes mellitus].

OBJECTIVE: To investigate the preventive action of metformin for atherosclerosis (AS) in patients with type 2 diabetes mellitus (T2DM). METHODS: A total of 140 cases with T2DM were assigned to 2 groups taking metformin (n = 75) or not (n = 65). All cases received intensive control of blood glucose, blood pressure and blood lipids for 100 weeks. The data before and after intensive control were recorded and statistically analyzed. Common carotid intima-media thickness (CC-IMT) was the efficacy endpoint of AS. RESULTS: Diastolic blood pressure (DBP), fasting blood glucose, post 2-hour blood glucose, glycated hemoglobin A1c, triglyceride (TG) and total cholesterol (TC) decreased in both groups after intensive metabolic control for 100 weeks (P < 0.05). Body mass index (BMI), HOMA insulin resistance index (HOMA-IR) and CC-IMT decreased in metformin group (P < 0.05) while high-density lipoprotein cholesterol (HDL-C) increased (P < 0.05). BMI (23.1 +/- 0.98) kg/m2, HOMA-IR (1.68 +/- 0.20) and CC-IMT (0.55 +/- 0.13) mm in metformin group were lower than those in non-metformin group [(24.1 +/- 0.05) kg/m2, 2.03 +/- 1.38, (0.70 +/- 0.15) mm)] at 100 week (P < 0.05). CC-IMT was positively correlated with BMI (r = 0.489, P < 0.05) , TC (r = 0.429, P < 0.05), low-density lipoprotein cholesterol (LDL-C) (r = 0.426, P < 0.05) and HOMA-IR (r = 0.428, P < 0.05). CONCLUSION: Metformin attenuates CC-IMT of patients with T2DM and it has the primary preventive effect upon AS in patients with T2DM.

Acute Deletion of METTL14 in ß-Cells of Adult Mice Results in Glucose Intolerance.

N6-Methyladenosine (m6A) is the most common and abundant mRNA modification that involves regulating the RNA metabolism. However, the role of m6A in regulating the ß-cell function is unclear. Methyltransferase-like 14 (METTL14) is a key component of the m6A methyltransferase complex. To define the role of m6A in regulating the ß-cell function, we generated ß-cell METTL14-specific knockout (ßKO) mice by tamoxifen administration. Acute deletion of Mettl14 in ß-cells results in glucose intolerance as a result of a reduction in insulin secretion in ß-cells even though ß-cell mass is increased, which is related to increased ß-cell proliferation. To define the molecular mechanism, we performed RNA sequencing to detect the gene expression in ßKO islets. The genes responsible for endoplasmic reticulum stress, such as Ire1α, were among the top upregulated genes. Both mRNA and protein levels of IRE1α and spliced X-box protein binding 1 (sXBP-1) were increased in ßKO islets. The protein levels of proinsulin and insulin were decreased in ßKO islets. These results suggest that acute METTL14 deficiency in ß-cells induces glucose intolerance by increasing the IRE1α/sXBP-1 pathway.

O-GlcNAcylation in immunity and inflammation: An intricate system (Review).

Chronic, low­grade inflammation associated with obesity and diabetes result from the infiltration of adipose and vascular tissue by immune cells and contributes to cardiovascular complications. Despite an incomplete understanding of the mechanistic underpinnings of immune cell differentiation and inflammation, O­GlcNAcylation, the addition of O­linked N­acetylglucosamine (O­GlcNAc) to cytoplasmic, nuclear and mitochondrial proteins by the two cycling enzymes, the O­linked N­acetylglucosamine transferase (OGT) and the O­GlcNAcase (OGA), may contribute to fine­tune immunity and inflammation in both physiological and pathological conditions. Early studies have indicated that O­GlcNAcylation of proteins play a pro­inflammatory role in diabetes and insulin resistance, whereas subsequent studies have demonstrated that this post­translational modification could also be protective against acute injuries. These studies suggest that diverse types of insults result in dynamic changes to O­GlcNAcylation patterns, which fluctuate with cellular metabolism to promote or inhibit inflammation. In this review, the current understanding of O­GlcNAcylation and its adaptive modulation in immune and inflammatory responses is summarized.

METTL14 is essential for ß-cell survival and insulin secretion.

Defects in the development, maintenance or expansion of ß-cell mass can result in impaired glucose metabolism and diabetes. N6-methyladenosine affects mRNA stability and translation efficiency, and impacts cell differentiation and stress response. To determine if there is a role for m6A in ß-cells, we investigated the effect of Mettl14, a key component of the m6A methyltransferase complex, on ß-cell survival and function using rat insulin-2 promoter-Cre-mediated deletion of Mettl14 mouse line (ßKO). We found that ßKO mice with normal chow exhibited glucose intolerance, lower levels of glucose-stimulated insulin secretion, increased ß-cell death and decreased ß-cell mass. In addition, HFD-fed ßKO mice developed glucose intolerance, decreased ß-cell mass and proliferation, exhibited lower body weight, increased adipose tissue mass, and enhanced insulin sensitivity due to enhanced AKT signaling and decreased gluconeogenesis in the liver. HFD-fed ßKO mice also showed a decrease in de novo lipogenesis, and an increase in lipolysis in the liver. RNA sequencing in islets revealed that Mettl14 deficiency in ß-cells altered mRNA expression levels of some genes related to cell death and inflammation. Together, we showed that Mettl14 in ß-cells plays a key role in ß-cell survival, insulin secretion and glucose homeostasis.

Association of SelS mRNA expression in omental adipose tissue with Homa-IR and serum amyloid A in patients with type 2 diabetes mellitus.

BACKGROUND: Tanis was reported as a putative receptor for serum amyloid A (SAA) involving glucose regulated protein in insulin regulated resistance. It was found to be dysregulated in diabetic rats (Psammomys obesus, Israeli sand rat) and its homologue for humans is SelS/AD-015. The present study analyzed mRNA expression of SelS in omental adipose tissue biopsies from patients with type 2 diabetes mellitus (T2DM), and age- and weight-matched nondiabetic patients, the relationship of SelS mRNA with Homa-IR and serum SAA level. METHODS: Human omental adipose tissues from ten cases of type 2 diabetic patients and twelve cases of nondiabetic individuals were analyzed for the expression level of SelS mRNA by semiquantitative polymerase chain reaction (PCR), Homa-IR estimated by standard formula and SAA level by enzyme-linked immunosorbent assay (ELISA). RESULTS: SelS mRNA expression, Homa-IR and serum SAA were higher in T2DM sufferers than in nondiabetic control group. SelS mRNA level was positively correlated with Homa-IR and SAA level in each group. CONCLUSIONS: SelS protein may be involved in insulin resistance in Chinese with T2DM by acting as the SAA receptor, thus playing an important role in the development of T2DM and atherosclerosis.