The Effect of Long-Term Inorganic Iodine on Intrathyroidal Iodothyronine Content and Gene Expression in Mice with Graves' Hyperthyroidism.

Background: The main molecular mechanism underlying acute suppression of iodine organification in normal thyroids after an excessive iodine load, that is, the Wolff-Chaikoff effect, is assumed to be suppression of iodine oxidation and iodothyronine synthesis. However, the mechanism underlying chronic antithyroid action of inorganic iodine in Graves' disease is not fully understood. Using a mouse model of Graves' hyperthyroidism, we examined changes in iodothyronine content and gene expression profiles in the thyroid glands after inorganic iodine loading. Materials and Methods: Graves' hyperthyroidism was induced and maintained in BALB/c mice by repeated immunizations of recombinant adenovirus expressing the human thyrotropin (TSH) receptor A-subunit. Hyperthyroid mice were left untreated (GD-C; n = 8) or treated with inorganic iodine for 12 weeks (GD-NaI; n = 8). We used unimmunized BALB/c mice as a control group (n = 10). In each mouse, serum thyroxine (T4) levels were measured with enzyme-linked immunosorbent assay (ELISA) at 4-week intervals. The intrathyroidal iodothyronine content and gene expression levels were, respectively, evaluated by mass spectrometry and RNA sequencing (RNA-seq) at the end of the experimental period. Results: Serum T4 levels in the GD-C group remained higher than in the control group, whereas those in the GD-NaI group declined to normal levels during the experimental period. Intrathyroidal triiodothyronine (T3), reverse T3 (rT3), and T4 contents in the GD-C group were higher than the control group, and rT3 and T4 were further increased in the GD-NaI group. The observed alterations in iodothyronine levels in the thyroid and sera may be explained by altered expression levels of genes for iodothyronine biosynthetic molecules, their transporter, and deiodinases. Conclusion: In this mouse model of hyperthyroidism, higher intrathyroidal accumulation of T4 and reduced gene expression data of iodothyronine transporters in the GD-NaI group suggest that chronic antithyroid action of iodine in Graves' disease involves suppression of hormone secretion.

GH-induced LH hyporesponsiveness as a potential mechanism for hypogonadism in male patients with acromegaly.

Male patients with acromegaly frequently have hypogonadism. However, whether excess GH affects gonadal function remains unclear. We retrospectively compared clinical features affecting total testosterone (TT) and free testosterone (FT) levels between 112 male patients with acromegaly and 100 male patients with non-functioning pituitary adenoma (NFPA) without hyperprolactinemia. Median maximum tumor diameter (14.4 vs. 26.5 mm) and suprasellar extension rate (33 vs. 100%) were lower in acromegaly, but LH, FSH, TT, and FT were not significantly different. In acromegaly, TT was less than 300 ng/dL in 57%, and FT was below the age-specific reference range in 77%. TT and FT were negatively correlated with GH, IGF-1, and the tumor size, and positively correlated with LH. In NFPA, they were positively correlated with IGF-1, LH, FSH, ACTH, cortisol, and free T4, reflecting hypopituitarism. Multiple regression analysis showed that TT and FT had the strongest correlation with GH in acromegaly, and with LH in NFPA. Surgical remission was achieved in 87.5% of 56 follow-up patients with acromegaly. TT and FT increased in 80.4 and 87.5%, respectively, with a significant increase in LH. In acromegaly, the degree of postoperative increase in TT(FT) correlated with the fold increase of TT(FT)/LH ratio, a potential parameter of LH responsiveness, but not with fold increase of LH, whereas in NFPA it correlated with both. These results suggest that excessive GH is the most relevant factor for hypogonadism in male acromegaly, and may cause impaired LH responsiveness as well as the suppression of LH secretion.

Influence of Short-Term Dietary and Therapeutic Iodine Restriction on the Therapeutic Effects of Radioactive Iodine Therapy in Patients with Graves' Disease.

Background: Several studies have investigated the factors affecting the effects of radioactive iodine (131I) treatment (RAIT) in patients with Graves' disease. However, the influence of dietary or therapeutic iodine on the effect of RAIT has not been fully elucidated yet. The aim of this study was to investigate whether dietary or therapeutic iodine before RAIT influences the therapeutic effects of RAIT with a fixed-dose regimen and a short-term restriction of iodine intake in an iodine-sufficient area. Materials and Methods: We retrospectively analyzed 81 Japanese patients with Graves' disease treated with the following RAIT regimen: dietary iodine restriction for 7 days as well as discontinuation of antithyroid drugs (ATDs), potassium iodine (KI), or both for 5 days before RAIT. On the day of RAIT, we measured urinary iodine content to estimate daily iodine intake. After RAIT, we adjusted the dose of ATDs, KI, or both according to serum thyroid hormone levels every 1-2 months. Using the data from these patients, we investigated the effect of dietary and therapeutic iodine on the therapeutic effects of RAIT. The therapeutic effects at 1 year after RAIT were evaluated based on the necessity of ATDs, KI, or both. Results: Dietary iodine intake was weakly correlated with 131I uptake (RAIU), but the dose of therapeutic iodine was not correlated with RAIU. The therapeutic effects of RAIT were strongly negatively associated with estimated thyroid volume before RAIT. Neither dietary iodine intake nor therapeutic iodine before RAIT affected this association. Conclusion: This study did not find an association between short-term dietary or therapeutic iodine restriction before RAIT and the therapeutic effects of RAIT in an iodine-sufficient area.

Analysis of the risk factors and treatment for repeated implantation failure: OPtimization of Thyroid function, IMmunity, and Uterine Milieu (OPTIMUM) treatment strategy.

PROBLEM: What are the pregnancy outcomes after the OPtimization of Thyroid function, Immunity, and Uterine Milieu (OPTIMUM) treatment strategy in patients with repeated implantation failure (RIF)? METHOD OF STUDY: Infertile women with a history of RIF after more than three embryo transfer (ET) cycles underwent implantation testing, including a hysteroscopy, endometrial biopsy for CD138 immunostaining and bacterial culture, and serum 25-hydroxyvitamin D3 , interferon-γ-producing helper T (Th1) cell, IL-4-producing helper T (Th2) cell, thyroid-stimulating hormone, thyroid peroxidase antibody, and thrombophilia screening between April 2017 and August 2018. We treated chronic endometritis with antibiotics, aberrant high Th1/Th2 cell ratios with vitamin D and/or tacrolimus intake, overt/subclinical hypothyroidism with levothyroxine, and thrombophilia with low-dose aspirin. Of the 116 RIF women, 88 women with 133 ET cycles were recruited from a questionnaire-based survey regarding pregnancy outcomes. Fifty-nine consecutive RIF patients without the OPTIMUM treatment strategy were also recruited as a control. RESULTS: The 116 women with RIF after the OPTIMUM treatment strategy were 38.3 ± 3.8 years old and had an implantation failure history over 5 (3-19) ET cycles. Implantation testing identified impaired intrauterine circumstances in 75 women (64.7%), an aberrant elevated Th1/Th2 cell ratio in 56 women (48.3%), and thyroid abnormalities in 33 women (28.4%). Cumulative ongoing pregnancy rates including spontaneous pregnancy in the patients aged < 40 and ≥ 40 years were 72.7% and 45.5% within two ET cycles, respectively. The pregnancy outcomes in the OPTIMUM group were significantly higher than those in the control. CONCLUSIONS: The OPTIMUM treatment strategy improved pregnancy outcomes in patients with RIF.

Everolimus Directly Suppresses Insulin Secretion Independently of Cell Growth Inhibition.

Everolimus, an orally administered mammalian target of rapamycin inhibitor, has been widely used as an immunosuppressant and an anticancer agent. Whereas everolimus can control recurrent hypoglycemia in patients with insulinoma, possibly through tumor regression and/or the direct inhibition of insulin secretion, time-dependent changes in serum insulin levels caused by everolimus still remain unclear. Here we report a clinical case of a patient with metastatic insulinoma, in which frequent monitoring of serum insulin levels demonstrated rapid and substantial changes in insulin secretion levels, a few days after the discontinuation as well as the readministration of everolimus. To further confirm the direct effect of everolimus on ß-cell function, we performed in vitro experiments using mouse insulinoma cells (MIN6) and human induced pluripotent stem cell (hiPSC)-derived insulin-producing cells and found that everolimus significantly suppressed glucose-stimulated insulin secretion in both MIN6 cells and hiPSC-derived insulin-producing cells. Thus, both a patient with metastatic insulinoma and in vitro experiments demonstrated that everolimus directly suppresses insulin secretion, independently of its tumor regression effect.

Disorganized Steroidogenesis in Adrenocortical Carcinoma, a Case Study.

Most adrenocortical carcinomas (ACCs) produce excessive amounts of steroid hormones including aldosterone, cortisol, and steroid precursors. However, aldosterone- and cortisol-producing cells in ACCs have not yet been immunohistochemically described. We present a case of ACC causing mild primary aldosteronism and subclinical Cushing's syndrome. Removal of the tumor cured both conditions. In order to examine the expression patterns of the steroidogenic enzymes responsible for adrenocortical hormone production, 10 tumor portions were immunohistochemically analyzed for aldosterone synthase (CYP11B2), 11ß-hydroxylase (CYP11B1, cortisol-synthesizing enzyme), 3ß-hydroxysteroid dehydrogenase (3ßHSD, upstream enzyme for both CYP11B2 and CYP11B1), and 17α-hydroxylase/C17-20 lyase (CYP17, upstream enzyme for CYP11B1, but not for CYP11B1). CYP11B2, CYP11B1, and 3ßHSD were expressed sporadically, and their expression patterns varied significantly among the different tumor portions examined. The expression of these enzymes was random and not associated with each other. CYP17 was expressed throughout the tumor, even in CYP11B2-positive cells. Small tumor cell populations were aldosterone- or cortisol-producing cells, as judged by 3ßHSD coinciding with either CYP11B2 or CYP11B1, respectively. These results suggest that the tumor produced limited amounts of aldosterone and cortisol due to the lack of the coordinated expression of steroidogenic enzymes, which led to mild clinical expression in this case. We delineated the expression patterns of steroidogenic enzymes in ACC. The coordinated expression of steroidogenic enzymes in normal and adenoma cells was disturbed in ACC cells, resulting in the inefficient production of steroid hormones in relation to the large tumor volume.

High prevalence of anti-TSH receptor antibody in fibromyalgia syndrome.

AIM: Fibromyalgia syndrome (FMS) is defined as chronic widespread pain that cannot be accounted for by any other medical disorder. Our aim was to explore the prevalence of thyroid autoimmunity in patients with FMS. METHODS: For determining thyroid function in 207 FMS patients, we tested for the titers of free tri-iodothyronine, free thyroxine, thyroid-stimulating hormone (TSH), anti-thyroid peroxidase antibody (TPOAb), anti-thyroglobulin antibody (TgAb) and anti-TSH receptor antibody (TRAb). RESULTS: Twenty-five patients who had either subclinical hyper- or hypothyroidism, or overt hypothyroidism were excluded. Sixty-nine FMS patients with autoimmune thyroid diseases (AITD) (37.9%, 69/182) were identified. The prevalence of positivity for TRAb, TgAb and TPOAb was 20.3% (n = 37), 16.5% (n = 30) and 13.2% (n = 24), respectively. Compared to control populations in previous studies, the prevalence of TRAb positivity was high, and titers of TRAb were low (1.0-1.5 IU/L). The prevalence of TPOAb and TgAb positivity was not significantly higher than that reported in FMS patients in previous studies. Clinical symptom profiles were identical for FMS patients with and without AITD. CONCLUSION: We found a high prevalence of AITD among 207 patients with clinically defined FMS, with TRAb being especially prominent among these patients. Further study is needed to evaluate changes in thyroid function among FMS patients with AITD.

Comparison of the therapeutic effects of prednisolone and nonsteroidal anti-inflammatory drugs in patients with subacute thyroiditis.

Subacute thyroiditis is a transient inflammatory thyroid disease of unknown etiology. The primary goal for treatment is to mitigate inflammation. The aim of this retrospective study was to compare the therapeutic effects of prednisolone and nonsteroidal anti-inflammation drugs in patients with subacute thyroiditis. In this study, 53 consecutive Japanese patients who had been diagnosed with were referred to our hospital for further management. After excluding 11 patients (9 did not need treatment, 2 did not meet the criteria for diagnosis of subacute thyroiditis), the remaining 42 patients were treated either with prednisolone (n = 25) or loxoprofen (n = 17). We compared the time periods required for resolution of clinical symptoms and signs and normalization of thyroid function between the two groups. The mean dose of prednisolone was 15.0 (range, 14-16) mg/day and that of loxoprofen was 180 mg/day. The time period to normalization of thyroid function was comparable between the prednisolone and loxoprofen groups (25, 18-36, vs 32, 21-39 days, p = 0.388). However, the time period for resolution of symptoms was shorter under prednisolone than loxoprofen (7, 7-12 days, vs 21, 14-32 days, p < 0.001). Prednisolone treatment of patients with subacute thyroiditis was superior to nonsteroidal anti-inflammation drugs with regard to resolution of symptoms.

Evanescent Hyperechoic Changes After Fine-Needle Aspiration Biopsy of the Thyroid in a Series With a Low Overall Prevalence of Complications.

OBJECTIVES: The purpose of this study was to assess the frequency of and risk factors for fine-needle aspiration biopsy (FNAB)-related complications in Japanese patients with thyroid nodules evaluated by standard FNAB techniques. METHODS: Six hundred fifty-three consecutive Japanese patients with 742 nodules who had undergone FNAB were enrolled. Nodule characteristics were evaluated, and thyroid volumes were measured. Fine-needle aspiration biopsy-related complications were identified on the basis of sonographic findings and patients' conditions after undergoing FNAB. Comparisons of patients' backgrounds and nodule characteristics were made between those with and without complications. RESULTS: The prevalence rates for FNAB-related complications, including acute transient thyroid swelling after FNAB and appearance of anechoic lesions, were 0.13% and 0.94%. In this study, we could not identify risk factors for FNAB-related complications. The sudden appearance of bright hyperechoic foci within the thyroid immediately after biopsy was reported as an FNAB-related unfamiliar appearance in 5 cases. Experimental FNA using resected porcine thyroid tissue suggested that the etiology of the hyperechoic appearance may be artificial air bubbles or reversed flow of aspirated fluid. CONCLUSIONS: Fine-needle aspiration biopsy-related complications are rare if preventive measures are performed and are not specific to Japanese patients with thyroid nodules. The sudden appearance of bright hyperechoic foci may be cause by contamination from air or fluid.

Human IAPP-induced pancreatic ß cell toxicity and its regulation by autophagy.

Pancreatic islets in patients with type 2 diabetes mellitus (T2DM) are characterized by loss of ß cells and formation of amyloid deposits derived from islet amyloid polypeptide (IAPP). Here we demonstrated that treatment of INS-1 cells with human IAPP (hIAPP) enhances cell death, inhibits cytoproliferation, and increases autophagosome formation. Furthermore, inhibition of autophagy increased the vulnerability of ß cells to the cytotoxic effects of hIAPP. Based on these in vitro findings, we examined the pathogenic role of hIAPP and its relation to autophagy in hIAPP-knockin mice. In animals fed a standard diet, hIAPP had no toxic effects on ß cell function; however, hIAPP-knockin mice did not exhibit a high-fat-diet-induced compensatory increase in ß cell mass, which was due to limited ß cell proliferation and enhanced ß cell apoptosis. Importantly, expression of hIAPP in mice with a ß cell-specific autophagy defect resulted in substantial deterioration of glucose tolerance and dispersed cytoplasmic expression of p62-associated toxic oligomers, which were otherwise sequestrated within p62-positive inclusions. Together, our results indicate that increased insulin resistance in combination with reduced autophagy may enhance the toxic potential of hIAPP and enhance ß cell dysfunction and progression of T2DM.

FFA-induced hepatic insulin resistance in vivo is mediated by PKCδ, NADPH oxidase, and oxidative stress.

Fat-induced hepatic insulin resistance plays a key role in the pathogenesis of type 2 diabetes in obese individuals. Although PKC and inflammatory pathways have been implicated in fat-induced hepatic insulin resistance, the sequence of events leading to impaired insulin signaling is unknown. We used Wistar rats to investigate whether PKCδ and oxidative stress play causal roles in this process and whether this occurs via IKKß- and JNK-dependent pathways. Rats received a 7-h infusion of Intralipid plus heparin (IH) to elevate circulating free fatty acids (FFA). During the last 2 h of the infusion, a hyperinsulinemic-euglycemic clamp with tracer was performed to assess hepatic and peripheral insulin sensitivity. An antioxidant, N-acetyl-L-cysteine (NAC), prevented IH-induced hepatic insulin resistance in parallel with prevention of decreased IκBα content, increased JNK phosphorylation (markers of IKKß and JNK activation, respectively), increased serine phosphorylation of IRS-1 and IRS-2, and impaired insulin signaling in the liver without affecting IH-induced hepatic PKCδ activation. Furthermore, an antisense oligonucleotide against PKCδ prevented IH-induced phosphorylation of p47(phox) (marker of NADPH oxidase activation) and hepatic insulin resistance. Apocynin, an NADPH oxidase inhibitor, prevented IH-induced hepatic and peripheral insulin resistance similarly to NAC. These results demonstrate that PKCδ, NADPH oxidase, and oxidative stress play a causal role in FFA-induced hepatic insulin resistance in vivo and suggest that the pathway of FFA-induced hepatic insulin resistance is FFA → PKCδ → NADPH oxidase and oxidative stress → IKKß/JNK → impaired hepatic insulin signaling.

Exendin-4 improves ß-cell function in autophagy-deficient ß-cells.

Autophagy is cellular machinery for maintenance of ß-cell function and mass. The implication of autophagy failure in ß-cells on the pathophysiology of type 2 diabetes and its relation to the effect of treatment of diabetes remains elusive. Here, we found increased expression of p62 in islets of db/db mice and patients with type 2 diabetes mellitus. Treatment with exendin-4, a glucagon like peptide-1 receptor agonist, improved glucose tolerance in db/db mice without significant changes in p62 expression in ß-cells. Also in ß-cell-specific Atg7-deficient mice, exendin-4 efficiently improved blood glucose level and glucose tolerance mainly by enhanced insulin secretion. In addition, we found that exendin-4 reduced apoptotic cell death and increased proliferating cells in the Atg7-deficient islets, and that exendin-4 counteracted thapsigargin-induced cell death of isolated islets augmented by autophagy deficiency. Our results suggest the potential involvement of reduced autophagy in ß-cell dysfunction in type 2 diabetes. Without altering the autophagic state in ß-cells, exendin-4 improves glucose tolerance associated with autophagy deficiency in ß-cells. This is mainly achieved through augmentation of insulin secretion. In addition, exendin-4 prevents apoptosis and increases the proliferation of ß-cells associated with autophagy deficiency, also without altering the autophagic machinery in ß-cells.

The diabetes-susceptible gene SLC30A8/ZnT8 regulates hepatic insulin clearance.

Recent genome-wide association studies demonstrated that common variants of solute carrier family 30 member 8 gene (SLC30A8) increase susceptibility to type 2 diabetes. SLC30A8 encodes zinc transporter-8 (ZnT8), which delivers zinc ion from the cytoplasm into insulin granules. Although it is well known that insulin granules contain high amounts of zinc, the physiological role of secreted zinc remains elusive. In this study, we generated mice with ß cell-specific Slc30a8 deficiency (ZnT8KO mice) and demonstrated an unexpected functional linkage between Slc30a8 deletion and hepatic insulin clearance. The ZnT8KO mice had low peripheral blood insulin levels, despite insulin hypersecretion from pancreatic ß cells. We also demonstrated that a substantial amount of the hypersecreted insulin was degraded during its first passage through the liver. Consistent with these findings, ZnT8KO mice and human individuals carrying rs13266634, a major risk allele of SLC30A8, exhibited increased insulin clearance, as assessed by c-peptide/insulin ratio. Furthermore, we demonstrated that zinc secreted in concert with insulin suppressed hepatic insulin clearance by inhibiting clathrin-dependent insulin endocytosis. Our results indicate that SLC30A8 regulates hepatic insulin clearance and that genetic dysregulation of this system may play a role in the pathogenesis of type 2 diabetes.

2-Methoxyestradiol ameliorates glucose tolerance with the increase in ß-cell mass in db/db mice.

UNLABELLED: Aims/Introduction: 2-Methoxyestradiol (2ME) is an estradiol metabolite with little estrogenic activity. Previous data identified its anti-carcinogenic properties and possible cardiovascular benefits. However, its effect on diabetes mellitus has not been fully elucidated. The aim of the present study was to determine the effects of 2ME on glucose metabolism in the diabetic state. MATERIALS AND METHODS: To evaluate the effects of 2ME, pellets of two different doses of the drug were implanted into female db/db mice at the age of 5 weeks. Intraperitoneal glucose tolerance test and insulin tolerance test were carried out at the age of 8 weeks. The pancreas was harvested for morphological analysis and ß-cell function at the age of 9 weeks. RESULTS: 2ME improved random blood glucose levels and glucose tolerance with increases in insulin levels during an intraperitoneal glucose tolerance test. Insulin sensitivity judged by an insulin tolerance test was comparable in the low- and high-dose 2ME groups and the control group. Although glucose-stimulated insulin secretion in isolated islets was comparable among the three groups, ß-cell mass in 2ME-treated groups was higher than the control group. In the 2ME-treated groups, the number of Ki67-positive cells in islets was higher, whereas the number of cleaved caspase-3-positive cells was comparable with the control. CONCLUSIONS: 2ME ameliorates glucose tolerance by promoting the proliferation of ß-cell mass in db/db mice. Our data suggests its potential clinical usefulness as a disease-modifying drug for type 2 diabetes mellitus. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2010.00087.x, 2011).

Normal islet vascularization is dispensable for expansion of beta-cell mass in response to high-fat diet induced insulin resistance.

The inability to increase of islet mass adequately to compensate for the demand of insulin due to insulin resistance is an important pathophysiological feature of type 2 diabetes. Previous studies suggested a relationship between pancreatic beta-cell mass and islet vascularization, although no evidence has confirmed this association in response to insulin resistance. Vascular endothelial growth factor-A (VEGF-A) in islets is essential for maintaining normal islet blood vessels. Here, insulin resistance was induced in mice carrying a beta-cell-specific VEGF-A gene mutation (RIP-Cre:Vegf(fl/fl)) by 20-week feeding of high-fat diet as a model of impaired islet vascularization. These mice showed only a modest decrease in glucose tolerance, compared with control mice. In addition, although the endothelial cell area in the islets of high-fat-fed RIP-Cre:Vegf(fl/fl) mice remained diminished, the pancreatic beta-cell area was modestly more than in high-fat-fed control mice. Thus, normal islet vascularization does not seem to be essential for expansion of beta cell mass in response to insulin resistance.

Combined expression of transcription factors induces AR42J-B13 cells to differentiate into insulin-producing cells.

Neurogenin 3 (Ngn3) is a transcription factor that regulates an initial step of differentiation from uncommitted pancreatic progenitors into endocrine cells. Additional transcription factors are required for complete differentiation into mature pancreatic beta cells. In this study, we established an in vitro model system of beta-cell differentiation by adenovirus-mediated expression of several transcription factors in AR42J-B13 cells, a pancreatic progenitor-like cell line derived from exocrine pancreas. Exogenous expression of Ngn3 in AR42J-B13 cells induced expression of Nkx2.2, Pax4, and Pax6, which are all essential for beta-cell differentiation in mouse embryos. However, Ngn3 did not induce more downstream regulators of beta-cell differentiation, Nkx6.1 and Maf A. Coexpression of Nkx6.1 and Ngn3 induced endogenous expression of the insulin 2 gene, while coexpression of Maf A and Ngn3 induced both insulin 1 and 2 genes in AR42J-B13 cells. Our data demonstrated that Ngn3 expressed together with Nkx6.1 or MafA induces AR42J-B13 cells to differentiate into insulin-producing cells, supporting the use of these cells as a model system for studying beta-cell differentiation in vitro.

Impact of oxidative stress and peroxisome proliferator-activated receptor gamma coactivator-1alpha in hepatic insulin resistance.

OBJECTIVE: Recent studies identified accumulation of reactive oxygen species (ROS) as a common pathway causing insulin resistance. However, whether and how the reduction of ROS levels improves insulin resistance remains to be elucidated. The present study was designed to define this mechanism. RESEARCH DESIGN AND METHODS: We investigated the effect of overexpression of superoxide dismutase (SOD)1 in liver of obese diabetic model (db/db) mice by adenoviral injection. RESULTS: db/db mice had high ROS levels in liver. Overexpression of SOD1 in liver of db/db mice reduced hepatic ROS and blood glucose level. These changes were accompanied by improvement in insulin resistance and reduction of hepatic gene expression of phosphoenol-pyruvate carboxykinase and peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha), which is the main regulator of gluconeogenic genes. The inhibition of hepatic insulin resistance was accompanied by attenuation of phosphorylation of cAMP-responsive element-binding protein (CREB), which is a main regulator of PGC-1alpha expression, and attenuation of Jun NH(2)-terminal kinase (JNK) phosphorylation. Simultaneously, overexpression of SOD1 in db/db mice enhanced the inactivation of forkhead box class O1, another regulator of PGC-1alpha expression, without the changes of insulin-induced Akt phosphorylation in liver. In hepatocyte cell lines, ROS induced phosphorylation of JNK and CREB, and the latter, together with PGC-1alpha expression, was inhibited by a JNK inhibitor. CONCLUSIONS: Our results indicate that the reduction of ROS is a potential therapeutic target of liver insulin resistance, at least partly by the reduced expression of PGC-1alpha.

Swings in blood glucose levels accelerate atherogenesis in apolipoprotein E-deficient mice.

The aim of this study was to investigate the effect of fluctuations in blood glucose levels on atherogenesis. Apolipoprotein (apo) E-deficient mice fed maltose twice daily were used as a model of repetitive postprandial glucose spikes. We investigated the number of macrophages adherent to the endothelium and the area of fibrotic arteriosclerotic lesions, with and without administration of miglitol, an alpha-glucosidase inhibitor. Macrophage adhesion to endothelial cells in thoracic aorta was quantitated by the en face method for optimal observation of endothelial surface after immunohistochemical staining for Mac-2. The area of arteriosclerotic lesions was measured in elastica van Giesson-stained proximal aorta. The number of adherent macrophages increased at 1 week after commencement of maltose feeding and the size of arteriosclerotic lesion increased at 5 weeks after such feeding. These increases were prevented by simultaneous use of miglitol. Our data demonstrated that glucose fluctuations accelerate atherogenesis. This was independent of changes in serum cholesterol level in vivo. Reduction of glucose fluctuation by alpha-glucosidase inhibitor efficiently controlled the progression of atherosclerosis.