Inhibition of hsa_circ_0001313 (circCCDC66) induction enhances the radio-sensitivity of colon cancer cells via tumor suppressor miR-338-3p: Effects of cicr_0001313 on colon cancer radio-sensitivity.

Circular RNA_0001313 (circ_0001313), also known as circCCDC66, is a novel circRNA that recently found to be upregulated in colon cancer tissues and promote colon cancer progression. However, the role of circ_0001313 in regulating radio-sensitivity of colon cancer and its molecular mechanism remain undetermined. Here we found circ_0001313 was significantly upregulated and miR-338-3p was downregulated in radio-resistant colon cancer tissues compared to radio-sensitive tissues. Radiation treatment in colon cells triggered a remarkable upregulation of circ_0001313 and a downregulation of miR-338-3p. Knockdown of circ_0001313 reduced cell viability, colony formation rate and increased caspase-3 activity in colon cancer cells under irradiation. Moreover, circ_0001313 act as a sponge for miR-338-3p in colon cancer cells. Furthermore, miR-338-3p could reverse the effects of circ_0001313 knockdown on cell viability, colony formation, and caspase-3 activity. These findings revealed that knockdown of circ_0001313 could induce radio-sensitivity of colon cancer cells by negatively regulating miR-338-3p.

Phenotypic and molecular characteristics in eleven Chinese patients with 5α-reductase Type 2 deficiency.

CONTEXT: Steroid 5α-reductase type 2 deficiency (5α-RD2) is a male-limited, autosomal recessive inherited disease. Affected 46, XY individuals usually present with ambiguous genitalia at birth. An early and precise diagnosis is of great value to the long-term prognosis of the disease. OBJECTIVE: To describe the clinical features and molecular determinants in 11 Chinese patients with the SRD5A2 gene mutation and to investigate the functional alteration arising from a novel splicing site mutation identified in one of the patients. SUBJECTS AND METHODS: Eleven subjects born with abnormal external genitalia from 10 unrelated families were recruited. Among them, nine patients who were reared as girls underwent virilization and gender change after puberty. Genotyping analysis of the SRD5A2 gene was performed in each of the patients. Haplotype analysis was performed in five patients with a prevalent mutation of p.G203S to illustrate the founder effect in China. Functional impairment of the new variant was explored by an in vitro splicing study and enzymatic activity assay. RESULTS: Nine mutations in the SRD5A2 gene were detected in the eleven patients. In addition to the previously reported p.G203S, p.R227Q, p.N193S, p.R246Q, p.Q6X, p.A228V, c.655delT and IVS1-2 A>G, a novel splicing site mutation (IVS4 + 2 T>C) was identified. From an in vitro functional study, this mutation was found to result in a skipping of exon 4 in the course of mRNA splicing, leading to a truncated protein of 205 amino acids that lacks the catalysing activity. Two siblings with the same compound heterozygous mutation (IVS1-2A>G/p.G203S) exhibited differing phenotypes and opposite patterns of gender rearing. A prevalent variation p.V89L combined with c.655delT was revealed to cause a mild phenotype of 5α-RD2 with a micropenis. CONCLUSION: This cohort study describes the phenotypic, biochemical and long-term outcome in 11 Chinese patients with 5α-RD2 deficiency and defines the genotypic spectrum of SRD5A2 mutations in China.

A refined study of FCRL genes from a genome-wide association study for Graves' disease.

To pinpoint the exact location of the etiological variant/s present at 1q21.1 harboring FCRL1-5 and CD5L genes, we carried out a refined association study in the entire FCRL region in 1,536 patients with Graves' disease (GD) and 1,516 sex-matched controls by imputation analysis, logistic regression, and cis-eQTL analysis. Among 516 SNPs with P<0.05 in the initial GWAS scan, the strongest signals associated with GD and correlated to FCRL3 expression were located at a cluster of SNPs including rs7528684 and rs3761959. And the allele-specific effects for rs3761959 and rs7528684 on FCRL3 expression level revealed that the risk alleles A of rs3761959 and C of rs7528684 were correlated with the elevated expression level of FCRL3 whether in PBMCs or its subsets, especially in CD19(+) B cells and CD8(+) T subsets. Next, the combined analysis with 5,300 GD cases and 4,916 control individuals confirmed FCRL3 was a susceptibility gene of GD in Chinese Han populations, and rs3761959 and rs7528684 met the genome-wide association significance level (P(combined) = 2.27×10(-12) and 7.11×10(-13), respectively). Moreover, the haplotypes with the risk allele A of rs3761959 and risk allele C of rs7528684 were associated with GD risk. Finally, our epigenetic analysis suggested the disease-associated C allele of rs7528684 increased affinity for NF-KB transcription factor. Above data indicated that FCRL3 gene and its proxy SNP rs7528684 may be involved in the pathogenesis of GD by excessive inhibiting B cell receptor signaling and the impairment of suppressing function of Tregs.

Identifying a novel mutation of CYP17A1 gene from five Chinese 17α-hydroxylase/17, 20-lyase deficiency patients.

Mutations of CYP17A1 gene could cause complete or partial, combined or isolated 17α-hydroxylase/17,20-lyase enzyme deficiencies (17OHD). We intended to investigate the CYP17A1 mutation in five unrelated patients and analyze its possible influence on phenotype of an atypical 17OHD patient presented with micropenis, hypertension and intermittent hypokalemia. Steroid hormones were assayed in these patients. A novel missense mutation (c.1169C>G, p. Thr390Arg) located in exon 7 was detected in one of the patients. Homozygous c. 985_987delinsAA, p. Tyr329fs mutation was found in two patients, while compound heterozygous mutations (c. 985_987delinsAA, p. Tyr329fs/c. 932-939 del, p. Val311fs and c. 287G>A, p. Arg96Gln/c. 985_987delinsAA, p. Tyr329fs) were found in two other patients, respectively. Then, steric model analysis of CYP17A1 showed that the novel mutation T390R changed the local structure as well as the electrostatic potential of the nearby beta sheet. Finally, site-directed mutagenesis and in vitro expression were used to analyze the activity of novel mutant CYP17A1. It indicated the T390R mutant retained part of enzyme activity, which was consistent to the clinical features. In conclusion, we identified a novel missense mutation of CYP17A1 gene from a patient with micropenis, hypertension and intermittent hypokalemia, which varied from other four patients. It also expanded our understanding of genotype-phenotype correlation of the disease.

Identification of a novel mutation in CYP17A1 gene.

17α-hydroxylase/17,20-lyase deficiency (17OHD) is a rare autosomal recessive genetic disease that is characterized by low-renin hypertension, hypokalemia, and abnormal development of the genitalia. Mutations in the CYP17A1 gene account for this disease. We aim to investigate the CYP17A1 mutation and analyze its possible influence on phenotype in a Chinese patient with 17OHD. Steroid hormones were assayed. The 8 exons of the CYP17A1 gene were amplified and directly sequenced. Wild-type and mutant CYP17A1 cDNA were cloned into pcDNA3.1 expression vectors and transfected into 293T cells. Finally, 17-hydroxylase and 17,20-lyase activity were detected by using progesterone and 17-hydroxypregnenolone as the substrates. A novel missense mutation c.716 G>A located in exon 4 that changed the amino acid from arginine to glutamine (R239Q) was discovered in the patient. Steric model analysis of CYP17A1 showed that R239Q changed the local structure and the electrostatic potential. Functional study indicated that the R239Q mutant caused the complete loss of both 17α-hydroxylase and 17,20-lyase activities. Our study expanded the CYP17A1 mutation spectrum. With a functional study, we confirmed that the novel mutation caused the complete loss of both 17α-hydroxylase and 17,20-lyase activities.

Effects of C-reactive protein on adipokines genes expression in 3T3-L1 adipocytes.

Adipose tissue is now recognized to be an important endocrine organ, secreting a variety of adipokines that are involved in the regulation of energy metabolism, insulin resistance and metabolic syndrome. C-reactive protein (CRP) is considered as one of the most sensitive markers of inflammation. A number of studies have shown that elevation of CRP concentrations is an independent predictive parameter of type 2 diabetes mellitus, which is also strongly associated with various components of the metabolic syndrome. The aim of the present study is to investigate the effects of CRP on adipokines genes expression in 3T3-L1 adipocytes. Quantitative real-time PCR analysis revealed that CRP inhibited adiponectin, leptin and peroxisome proliferator-activated receptor-gamma (PPAR-γ) genes expression and raised tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) mRNA levels in matured 3T3-L1 adipocytes in a dose and time-dependent manner. Pharmacological inhibition of phosphatidylinositol (PI)-3 kinase by wortmannin partially reversed the effects of CRP on adiponectin, TNF-α and leptin genes expression. These results collectively suggest that CRP regulates adiponectin, TNF-α, leptin, IL-6 and PPAR-γ genes expression, and that might represent a mechanism by which CRP regulates insulin resistance, obesity and metabolic syndrome.

Mimecan in pituitary corticotroph cells may regulate ACTH secretion and the HPAA.

Mimecan is a protein of unknown function that is expressed in the pituitary tissues of mouse and human. In this study, we observed the function of mimecan on the proopiomelanocortin (POMC) gene in the pituitary and the hypothalamo-pituitary-adrenal axis (HPAA). Incubating pituitary corticotroph AtT-20 cells with recombinant mimecan protein stimulated adrenocorticotrophic hormone (ACTH) secretion without significantly up-regulating POMC gene expression. In addition, pituitary corticotroph AtT-20 cell corticotropin-releasing hormone receptor 1 (CRHR1) gene expression was induced by mimecan. Interestingly, long-term mimecan overexpression in corticotroph cells increased CRHR1 mRNA levels while slightly decreasing POMC mRNA expression and ACTH secretion. Using mimecan knockout mice, we found that, although the serum ACTH concentration was not significantly different between wild type and mimecan knockout mice under basal conditions, the serum ACTH level was relatively lower in mimecan knockout mice after treatment with corticotropin-releasing hormone (CRH). Meanwhile, we observed that POMC and CRHR1 gene expression decreased in primary cultured knockout mouse pituitary cells compared with wild type cells. Taken together, these data suggest that mimecan expressed in pituitary corticotroph cells mainly regulates ACTH secretion in the pituitary and coordinates the HPAA.

A unique exonic splicing mutation in the CYP17A1 gene as the cause for steroid 17{alpha}-hydroxylase deficiency.

BACKGROUND: 17α-Hydroxylase/17,20-lyase deficiency (17OHD) caused by a mutation in the CYP17A1 gene is characterized by hypertension, hypokalemia, and abnormal development of the genitalia. The majority of CYP17A1 mutations are located in the coding sequence, and several intronic splicing site mutations have been reported. OBJECTIVE: A 2.5-year-old girl with 46,XY disordered sex development exhibited a nearly normal basal cortisol level and reduced sexual steroids. This study is aimed to explore the molecular basis and analyze its possible influence on the phenotype of the patient. METHODS AND RESULTS: Mutation analysis revealed compound heterozygous CYP17A1 mutations, with c.985_987delinsAA in one allele and a synonymous substitution (c.1263G>A) in another allele. In vitro expression analysis of the allelic minigene showed that the novel nucleotide variation located in exon 8 induces a splicing signal, which results in an aberrant splicing of CYP17A1 mRNA and a missing portion of exon 8. The translation product includes the deletion of six or seven amino acids from residue position 415 without causing a frameshift. Consistent with the result of molecular modeling, functional studies in transiently transfected HEK-293T cells with the aberrantly spliced enzyme proteins showed that the deleted proteins completely abolished the enzyme activity. However, RT-PCR indicated the existence of a small fraction of normal, functionally intact enzyme, which may explain the partial masculinization of this patient. CONCLUSION: This is the first description of an exonic splicing mutation in CYP17A1 relevant to the 17OHD phenotype. It also demonstrates the importance of studying synonymous change in such patients with less severe phenotype.

Berberine attenuates cAMP-induced lipolysis via reducing the inhibition of phosphodiesterase in 3T3-L1 adipocytes.

Berberine, a hypoglycemic agent, has been shown to decrease plasma free fatty acids (FFAs) level in insulin-resistant rats. In the present study, we explored the mechanism responsible for the antilipolytic effect of berberine in 3T3-L1 adipocytes. It was shown that berberine attenuated lipolysis induced by catecholamines, cAMP-raising agents, and a hydrolyzable cAMP analog, but not by tumor necrosis factor α and a nonhydrolyzable cAMP analog. Unlike insulin, the inhibitory effect of berberine on lipolysis in response to isoproterenol was not abrogated by wortmannin, an inhibitor of phosphatidylinositol 3-kinase, but additive to that of PD98059, an extracellular signal-regulated kinase kinase inhibitor. Prior exposure of adipocytes to berberine decreased the intracellular cAMP production induced by isoproterenol, forskolin, and 3-isobutyl-1-methylxanthine (IBMX), along with hormone-sensitive lipase (HSL) Ser-563 and Ser-660 dephosphorylation, but had no effect on perilipin phosphorylation. Berberine stimulated HSL Ser-565 as well as adenosine monophosphate-activated protein kinase (AMPK) phosphorylation. However, compound C, an AMPK inhibitor, did not reverse the regulatory effect of berberine on HSL Ser-563, Ser-660, and Ser-565 phosphorylation, nor the antilipolytic effect of berberine. Knockdown of AMPK using RNA interference also failed to restore berberine-suppressed lipolysis. cAMP-raising agents increased AMPK activity, which was not additive to that of berberine. Stimulation of adipocytes with berberine increased phosphodiesterase (PDE) 3B and PDE4 activity measured by hydrolysis of (3)[H]cAMP. These results suggest that berberine exerts an antilipolytic effect mainly by reducing the inhibition of PDE, leading to a decrease in cAMP and HSL phosphorylation independent of AMPK pathway.

Glucocorticoid up-regulates mimecan expression in corticotroph cells.

Mimecan is a protein of unknown function that is expressed in the pituitary. The aim of this study is to clarify the regulation and intracellular localisation of mimecan gene expression in the pituitary. With immunohistochemistry, we observed that mimecan protein was co-expressed with ACTH in pituitary corticotroph cells. Northern and Western blot analyses revealed that mimecan expression and secretion in corticotroph cells were up-regulated by treating AtT-20 cells with glucocorticoid. Meanwhile, mimecan expression in rat primary culture pituitary cells was also promoted by glucocorticoid. Co-incubation of AtT-20 cells with RU486 and glucocorticoid completely reversed the induction of mimecan gene expression by glucocorticoid. In addition, luciferase reporter assays showed that the -1474/+43 promoter region of mimecan was sufficient for glucocorticoid-responsive mimecan expression. These data collectively suggest that mimecan expressed in pituitary corticotroph cells is increased by glucocorticoid and that the up-regulation may be mediated by the classical GR pathways.

Identification of steroid biosynthetic defects in genotype-proven heterozygous individuals for 17alpha-hydroxylase/17,20-lyase deficiency.

OBJECTIVE: P450c17 deficiency (17alpha-hydroxylase/17,20-lyase deficiency, 17OHD) is a rare form of congenital adrenal hyperplasia caused by CYP17A1 gene mutations. The D487_F489 deletion in exon 8 and Y329fs in exon 6 are relatively frequent mutations of the CYP17A1 gene in China that completely abolish the enzyme activity of P450c17. However, little remains known about steroid biosynthetic functions in carriers with these mutations in a single allele of the CYP17A1 gene, who are assumed to have 50% P450c17 activity. We investigated adrenal steroidogenic function in genotype-proven heterozygotes carrying such mutations in the CYP17A1 gene in vivo. PATIENTS AND DESIGN: Eight patients and fourteen family members from five families with 17OHD were recruited. The mutations of the CYP17A1 gene in these individuals were screened by sequencing. The hormonal response to cosyntropin (ACTH) was evaluated in the 14 genotype-proven carriers and 45 age- and gender-matched normal controls. RESULTS: Fourteen carriers of the CYP17A1 mutation - seven with the D487_F489 deletion, six with Y329fs and one with H373L - were identified from the five families with 17OHD. Compared with normal controls, carriers showed lower basal and ACTH-stimulated cortisol levels but higher ACTH-stimulated corticosterone levels. The ratios of corticosterone to cortisol in the genotype-proven heterozygotes were higher than those of the normal controls at the baseline and after cosyntropin stimulation. Similarly, the progesterone levels and the ratios of progesterone to 17-hydroxyprogesterone in the male heterozygotes were also higher than those of the normal controls, both before and after ACTH stimulation. CONCLUSION: Genotype-proven carriers of the CYP17A1 mutation who lack apparent clinical symptoms exhibit decreased adrenal 17alpha-hydroxylase activity and altered adrenal gland reserve for steroid biosynthesis.

Expression of adiponectin receptors in mouse adrenal glands and the adrenocortical Y-1 cell line: adiponectin regulates steroidogenesis.

Obesity is frequently associated with malfunctions of the hypothalamus-pituitary-adrenal (HPA) axis and hyperaldosteronism, but the mechanism underlying this association remains unclear. Since the adrenal glands are embedded in adipose tissue, direct cross-talk between adipose tissue and the adrenal gland has been proposed. A previous study found that adiponectin receptor mRNA was expressed in human adrenal glands and aldosterone-producing adenoma (APA). However, the expression of adiponectin receptors in adrenal glands has not been confirmed at the protein level or in other species. Furthermore, it is unclear whether adiponectin receptors expressed in adrenal cells are functional. We found, for the first time, that adiponectin receptor (AdipoR1 and AdipoR2) mRNA and protein were expressed in mouse adrenal and adrenocortical Y-1 cells. However, adiponectin itself was not expressed in mouse adrenal or Y-1 cells. Furthermore, adiponectin acutely reduced basal levels of corticosterone and aldosterone secretion. ACTH-induced steroid secretion was also inhibited by adiponectin, and this was accompanied by a parallel change in the expression of the key genes involved in steroidogenesis. These findings indicate that adiponectin may take part in the modulation of steroidogenesis. Thus, adiponectin is likely to have physiological and/or pathophysiological significance as an endocrine regulator of adrenocortical function.

[Clinical and molecular genetic analysis for 7 patients from 5 pedigrees with 17a-hydroxylase/17, 20 lyase deficiency].

OBJECTIVE: To investigate the clinical and genetic characteristics of 7 patients from 5 families with 17a-hydroxylase/17,20 lyase deficiency (17OHD) and the CYP17A1 mutation in Chinese. METHODS: Clinical features and laboratory data were collected from 5 families with 17OHD. PCR direct sequencing was performed to screen the mutation of CYP17A1 gene of the patients. Polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) and sequencing were performed to screen the mutations of CYP17A1 gene in 288 healthy individuals from Shandong province. RESULTS: Seven patients (5 of them were 46,XX; 2 were 46,XY) had typical clinical presentation of sexual infantilism, hypertension and hypokalemia. Hormone profile indicated decreased plasma cortisol and sex hormones, and elevated blood adrenocorticotrophic hormone (ACTH). TAC329AA and H373L in exon 6 and D487_F489del in exon 8 were identified from the patients. One heterozygote for D487_F489del was identified in 288 healthy controls. CONCLUSION: The TAC329AA and D487_F489del of the CYP17A1 gene were the most frequent mutations in Chinese with 17OHD.There might be certain frequency of heterozygotes for D487_F489del in Chinese population.

A splice site mutation combined with a novel missense mutation of LHCGR cause male pseudohermaphroditism.

Leydig cell hypoplasia (LCH) is a rare form of male pseudohermaphroditism caused by inactivating mutations in the luteinizing hormone receptor gene (LHCGR). The majority of LHCGR mutations are located in the coding sequence, resulting in impairment of either LH/CG binding or signal transduction. We report a Chinese family with two siblings (46, XY and 46, XX) carrying a missense mutation (c. 455 T>C, p. Ile152Thr) and a splice site mutation (c. 537-3 C>A). Computational analysis of the missense mutation in the three-dimensional structural model predicted it might influence the distribution of hydrogen bonds and intermolecular contacts between the hormone and receptor. Consistent with these findings, in vitro mutant analysis revealed a marked impairment of human chorionic gonadotropin binding and signal transduction. The splice-acceptor mutation (c. 537-3 C>A) resulted in abnormal splicing of LHCGR mRNA, skipping exon 7. This report expands the genotypic spectrum of LHCGR mutations, with relevant implications for the molecular analysis of this gene.

Functional SNPs in the SCGB3A2 promoter are associated with susceptibility to Graves' disease.

Graves' disease (GD) is one of the most common human autoimmune diseases, and recent data estimated a prevalence of clinical hyperthyroidism of 0.25-1.09% in the population. Several reports have linked GD to the region 5q12-q33; and a locus between markers D5s436 and D5s434 was specifically linked to GD susceptibility in the Chinese population. In the present study, association analysis was performed using a large number of single-nucleotide polymorphisms (SNPs) at this locus in 2811 patients with GD recruited from different geographic regions of China. The strongest associations with GD in the combined Chinese Han cohorts were mapped to two SNPs in the promoter (pSNP) of SCGB3A2 [SNP76, rs1368408, P = 1.43 x 10(-6), odds ratio (OR) = 1.28 and SNP75, -623 - -622, P = 7.62 x 10(-5), OR = 1.32, respectively], a gene implicated in immune regulation. On the other hand, pSNP haplotypes composed of the SNP76 (rs1368408)+SNP74 (rs6882292) or SNP76+SNP75 (-623 approximately -622, AG/T) variants are correlated with high disease susceptibility (P = 0.0007, and P = 0.0192, respectively) in this combined Chinese Han cohort. Furthermore, these haplotypes were associated with reduced SCGB3A2 gene expression levels in human thyroid tissue, while functional analysis revealed a relatively low efficiency of SCGB3A2 promoters of the SNP76+SNP75 and SNP76+SNP74 haplotypes in driving gene expression. These results suggest that the SCGB3A2 gene may contribute to GD susceptibility.

Influence of visceral adiposity on ghrelin secretion and expression in rats during fasting.

Although circulating ghrelin levels correlate inversely with adiposity at baseline, little is known about the effect of percent visceral adipose tissue value (PVATV) on ghrelin expression and secretion in response to fasting. Our study demonstrated that ghrelin increased with 24-h fasting in rats with the lowest PVATV (less than 6%), after 3 days in rats with intermediate PVATV (6-9%) and 5 days in rats with the highest PVATV (greater than 9%). Ghrelin mRNA in the stomach was increased after 3 days in low-PVATV (5.8+/-0.9%) rats but not in high-PVATV (14+/-1.6%) rats. Therefore, both ghrelin secretion and mRNA were delayed in response to fasting in rats with increased visceral fat. In rats matched for PVATV, but with different body weights, the fasting induced similar levels of increased ghrelin while in rats with different PVATV ghrelin secretion was different in response to fasting, even when body weights were matched in two groups. These data suggested that the initial PVATV, not lean mass, was related to the pattern of plasma ghrelin in response to fasting in rats.

Astragaloside IV attenuates lipolysis and improves insulin resistance induced by TNFalpha in 3T3-L1 adipocytes.

Increased circulating free fatty acid (FFA) concentrations have been demonstrated to potentially link obesity, insulin resistance and cardiovascular diseases. Astragaloside IV (AS-IV) is a saponin which is widely used in traditional Chinese medicine to treat type 2 diabetes and cardiovascular diseases. The purpose of the present study was to examine the effects of AS-IV on the lipolysis and insulin resistance induced by tumor necrosis factor-alpha (TNFalpha) in cultured 3T3-L1 adipocytes. TNFalpha promotes lipolysis in mammal adipocytes via the mitogen activated protein kinase (MAPK) family resulting in reduced expression/function of perilipin. Application of AS-IV inhibited TNFalpha-induced accelerated lipolysis in a dose-dependent manner, which was compatible with suppressed phosphorylation of ERK1/2 and reversed the downregulation of perilipin. Moreover, TNFalpha induced downregulation of key enzymes in lipogenesis, including LPL, FAS and GPAT, were also attenuated by AS-IV. Further studies showed that AS-IV improved TNFalpha-induced insulin resistance in 3T3-L1 adipocytes. This study provides the first direct evidence of the antilipolytic action of AS-IV in adipocytes, which may allow this agent to decrease the circulating FFA levels, thus increase insulin sensitivity and treat cardiovascular diseases.

Ginsenoside Rb1 stimulates glucose uptake through insulin-like signaling pathway in 3T3-L1 adipocytes.

A series of clinical trials and animal experiments have demonstrated that ginseng and its major active constituent, ginsenosides, possess glucose-lowering action. In our previous study, ginsenoside Rb(1) has been shown to regulate peroxisome proliferator-activated receptor gamma activity to facilitate adipogenesis of 3T3-L1 cells. However, the effect of Rb(1) on glucose transport in insulin-sensitive cells and its molecular mechanism need further elucidation. In this study, Rb(1) significantly stimulated basal and insulin-mediated glucose uptake in a time- and dose-dependent manner in 3T3-L1 adipocytes and C2C12 myotubes; the maximal effect was achieved at a concentration of 1 microM and a time of 3 h. In adipocytes, Rb(1) promoted GLUT1 and GLUT4 translocations to the cell surface, which was examined by analyzing their distribution in subcellular membrane fractions, and enhanced translocation of GLUT4 was confirmed using the transfection of GLUT4-green fluorescence protein in Chinese Hamster Ovary cells. Meanwhile, Rb(1) increased the phosphorylation of insulin receptor substrate-1 and protein kinase B (PKB), and stimulated phosphatidylinositol 3-kinase (PI3K) activity in the absence of the activation of the insulin receptor. Rb(1)-induced glucose uptake as well as GLUT1 and GLUT4 translocations was inhibited by the PI3K inhibitor. These results suggest that ginsenoside Rb(1) stimulates glucose transport in insulin-sensitive cells by promoting translocations of GLUT1 and GLUT4 by partially activating the insulin signaling pathway. These findings are useful in understanding the hypoglycemic and anti-diabetic properties of ginseng and ginsenosides.

Berberine acutely inhibits insulin secretion from beta-cells through 3',5'-cyclic adenosine 5'-monophosphate signaling pathway.

Berberine, a hypoglycemic agent, has recently been shown to activate AMP-activated protein kinase (AMPK) contributing to its beneficial metabolic effects in peripheral tissues. However, whether berberine exerts a regulatory effect on beta-cells via AMPK or other signaling pathways and counteracts glucolipotoxicity remains uncertain. In the present study, the impact of berberine on beta-cell function was investigated in vivo and in vitro. In high-fat-fed rats, berberine treatment for 6 wk significantly decreased plasma glucose and insulin levels before and after an oral glucose challenge along with the reduction of body weight and improvement of blood lipid profile. In accordance with the in vivo results, berberine acutely decreased glucose-stimulated insulin secretion (GSIS) and palmitate-potentiated insulin secretion in MIN6 cells and rat islets. However, pretreated with berberine for 24 h augmented the response of MIN6 cells and rat islets to glucose and attenuated the glucolipotoxicity. Berberine acutely increased AMPK activity in MIN6 cells. However, compound C, an AMPK inhibitor, completely reversed troglitazone-suppressed GSIS, not berberine-suppressed GSIS. Otherwise, berberine decreased cAMP-raising agent-potentiated insulin secretion in MIN6 cells and rat islets. These results suggest that the activation of AMPK is required for troglitazone-suppressed GSIS, whereas cAMP signaling pathway contributes, at least in part, to the regulatory effect of berberine on insulin secretion.

Serum visfatin concentrations in obese adolescents and its correlation with age and high-density lipoprotein cholesterol.

Visfatin was recently identified as an adipocytokine and has insulin mimetic properties, but its role in adolescents remains largely unknown. In this study, we examined the impact of adolescent obesity on circulating visfatin levels and the relationship between visfatin and anthropometric indices, insulin sensitivity, and blood lipids in Chinese adolescents (11-18 years). Serum visfatin, adiponectin, leptin, and blood lipids were measured in 76 non-obese and 72 obese adolescents. The medians of serum visfatin levels were significantly higher in obese subjects of 34.68ng/ml than in non-obese subjects of 28.67ng/ml (P=0.002). There were no significant correlations in the non-obese group between the serum visfatin concentration and the anthropometric indices or the lipid parameters. However, visfatin levels were negatively correlated with age, early insulin secretion index (EISI), Tanner stage, and positively correlated with HDL-c in the obese adolescents. These relationships, except that for EISI and Tanner stage, remained significant (P<0.05) after adjusting for age, gender, and body mass index. Moreover, unlike adiponectin and leptin, visfatin concentration did not correlate with testosterone in non-obese and obese boys. In conclusion, visfatin levels may decrease with age and be related to the HDL metabolism in obese adolescents.