小野 啓

Hypsyzigus marmoreus (HM), an edible mushroom, has several effects, including antitumor, antioxidant and anti-allergy properties. On the other hand, the possibly useful effect of HM in diabetic mice has not as yet been elucidated. In this study, we showed treatment with a water soluble extract from HM (EHM) to reduce fat deposits without affecting body weight loss in KK-Ay mice. EHM treatment also abolished the expressions of proinflammatory adipokines, such as tumor necrosis factor α and monocyte chemoattractant protein 1, as compared with vehicle treatment. The expressions of uncoupling protein 3 and peroxisome proliferator-activated receptor gamma coactivator 1 α in the soleus muscles of EHM treatment groups were significantly elevated as compared to those in vehicle-treated muscle tissues. These results raise the possibility that EHM can regulate both obesity and insulin resistance.

Phosphatase and tensin homolog (PTEN) dephosphorylates phosphatidylinositol (PI) 3,4,5-triphosphate and antagonizes PI 3-kinase. Insulin acts in the mediobasal hypothalamus (MBH) to not only suppress food intake and weight gain but also improve glucose metabolism via PI 3-kinase activation. Thus, the blocking of hypothalamic PTEN is a potential target for treating obesity as well as diabetes. However, genetic modification of PTEN in specific neuronal populations in the MBH yielded complex results, and no postnatal intervention for hypothalamic PTEN has been reported yet. To elucidate how postnatal modification of hypothalamic PTEN influences food intake as well as glucose metabolism, we bidirectionally altered PTEN activity in the MBH of rats by adenoviral gene delivery. Inhibition of MBH PTEN activity reduced food intake and weight gain, whereas constitutive activation of PTEN tended to induce the opposite effects. Interestingly, the effects of MBH PTEN intervention on food intake and body weight were blunted by high-fat feeding. However, MBH PTEN blockade improved hepatic insulin sensitivity even under high-fat-fed conditions. On the other hand, constitutive activation of MBH PTEN induced hepatic insulin resistance. Hepatic Akt phosphorylation and the G6Pase expression level were modulated bidirectionally by MBH PTEN intervention. These results demonstrate that PTEN in the MBH regulates hepatic insulin sensitivity independently of the effects on food intake and weight gain. Therefore, hypothalamic PTEN is a promising target for treating insulin resistance even in states of overnutrition.

The effect of biphasic insulin aspart 30 (aspart 30) and insulin lispro 50 (lispro 50) was evaluated by continuous glucose monitoring. Hospitalized ten Japanese type 2 diabetes patients were enrolled in each of two groups receiving twice-daily (2D) or thrice-daily (3D) regimens. The glucose levels were low when using aspart 30 from midnight to dawn in both groups. Both groups showed several significantly lower blood glucose levels after dinner when using lispro 50. A sub-group analysis revealed the mean glucose level in the nocturnal period of the 2D group and that in daytime period of the 3D group to be significantly lower when using aspart 30 in patients with a high fasting serum C-peptide level, and that the increases in the postprandial glucose (PPG) peak from a pre-meal level at breakfast and the AUC of PPG excursions above a pre-meal level at dinner of the 2D group were significantly lower when using lispro 50 in patients with a low post-breakfast serum C-peptide level. In conclusion, this study demonstrated that aspart 30 is more advantageous in nocturnal glycemic control, while lispro 50 demonstrated excellent postprandial glycemic control. However, the results also suggested that the efficacy of these premix analogues was influenced by the individual endogenous insulin secretion capacity.

A 32-year-old man presented in a coma |GCS (El, V2, M2) | due to hypoglycemic encephalopathy. Diffusion-weighted MRI (DWI), performed immediately after the patient lapsed into a coma, demonstrated high-intensity signal areas in the bilateral subcortex, including the corona radiata and caudate nucleus. While these signals, observed on MRI, transiently increased on day 3, they had decreased by day 7. On day 20, he showed recovery of consciousness, and the signals, observed on DWI, had completely disappeared by day 20. Three months later, he was discharged after activities of daily living, such as walking and conversation, had greatly improved. Herein, we present this diabetic patient with hypoglycemic encephalopathy, showing sequential DWI findings, i.e. the restricted high-intensity signal areas in the bilateral subcortex and their extinctions, to be very useful for predicting the functional outcomes of patients with severe hypoglycemia.

Insulin glargine (glargine) and insulin detemir (detemir) are long-acting insulin analogs manufactured in the completely different concepts. Detemir lowers the risk of nocturnal hypoglycemia and shows better improvement in fasting plasma glucose levels than conventional intermediate-acting NPH insulin in patients with type 1 diabetes. Due to small variation of the hypoglycemic effect in each administration, stable glycemic control can be expected with detemir, which has been shown to improve the patients' quality of life (QOL). However, only few reports regarding direct comparison between glargine with detemir have been published in Japan. We compared the efficacy and safety of two basal insulin analogs. Ten patients with type 1 diabetes treated with basal-bolus therapy using glargine and rapid-acting insulin analog were observed. At 24-week after switching from glargine to detemir, HbA1c levels improved from 7.76 ± 1.53% to 7.64 ± 1.47%, l,5-anhydroglucitol(1, 5-AG) levels improved from 3.63 ± 1.23 μg/mLto 4.49 ± 3.12 μg/mL, the insulin dose increased from 39.0 ± 14.4 units to 40.9 ± 15.7 units, and the body weight decreased from 57.0 ± 11.2 kg to 55.9 ± 11.5 kg. By the switching of basal insulin from glargine to detemir, the insulin dose could be increased without causing weight gain, and HbA1c and 1,5-AG levels improved at 24 weeks. In the insulin replacement therapy in Japanese type 1 diabetics, detemir was shown to be non-inferior to glargine.

Recent studies have shown colestimide, a bile acid-binding resin, to also exert a glucose-lowering effect via amelioration of insulin resistance. To evaluate the effects of colestimide on glucose metabolism and to elucidate the underlying mechanism, we conducted a 6-month, open-label pilot study on 43 type 2 diabetic patients with obesity (BMI ≥ 25). The subjects were randomized to either treatment with colestimide 4g/day (T group, n=23) or continuation of their current therapy (C group, n=20). In the T group patients, mean hemoglobin A1c (HbA1c) and fasting glucose improved markedly (from 7.71 ± 0.32% to 6.97 ± 0.20% from 147.4 ± 7.3mg/dL to 127.0 ± 5.0mg/dL, respectively), while obesityrelated parameters, i.e. body weight, waist circumference, and visceral fat and subcutaneous fat as determined by umbilical slice abdominal CT, showed no significant changes. Fractionation analyses of serum bile acids revealed significantly increased cholic acids (CA) and decreased chenodeoxycholic acids (CDCA) in the T group patients. However, no correlation was observed between these changes and ΔHbA1c. According to logistic regression analysis, baseline HbA1c was the only variable predicting the decrease of HbA1c (&gt 0.5%) among sex, age, BMI, total cholesterol, ΔCA and ΔCDCA. The index of insulin resistance, i.e. homeostasis model assessment of insulin resistance (HOMA-R), did not improve, and the index of β cell function, i.e. homeostasis model assessment of β-cell function (HOMA-β), actually increased significantly. These results suggests that, in obese patients with type 2 diabetes, the mechanism underlying improved glycemic control with colestimide treatment involves enhanced β cell activity rather than improved insulin resistance. © The Japan Endocrine Society.

PGC-1 alpha is a transcriptional coactivator that powerfully regulates many pathways linked to energy homeostasis. Specifically, PGC-1 alpha controls mitochondrial biogenesis in most tissues but also initiates important tissue-specific functions, including fiber type switching in skeletal muscle and gluconeogenesis and fatty acid oxidation in the liver. We show here that S6 kinase, activated in the liver upon feeding, can phosphorylate PGC-1 alpha directly on two sites within its arginine/serine-rich (RS) domain. This phosphorylation significantly attenuates the ability of PGC-1 alpha to turn on genes of gluconeogenesis in cultured hepatocytes and in vivo, while leaving the functions of PGC-1 alpha as an activator of mitochondrial and fatty acid oxidation genes completely intact. These phosphorylations interfere with the ability of PGC-1 alpha to bind to HNF4 alpha, a transcription factor required for gluconeogenesis, while leaving undisturbed the interactions of PGC-1 alpha with ERR alpha and PPAR alpha, factors important for mitochondrial biogenesis and fatty acid oxidation. These data illustrate that S6 kinase can modify PGC-1 alpha and thus allow molecular dissection of its functions, providing metabolic flexibility needed for dietary adaptation.

Peptidyl-prolyl cis/trans isomerase NIMA-interacting 1 (Pin1) is a unique enzyme that associates with the pSer/Thr-Pro motif and catalyzes cis-trans isomerization. We identified Pin1 in the immunoprecipitates of overexpressed IRS-1 with myc and FLAG tags in mouse livers and confirmed the association between IRS-1 and Pin1 by not only overexpression experiments but also endogenously in the mouse liver. The analysis using deletion-and point-mutated Pin1 and IRS-1 constructs revealed the WW domain located in the N terminus of Pin1 and Ser-434 in the SAIN (Shc and IRS-1 NPXY binding) domain of IRS-1 to be involved in their association. Subsequently, we investigated the role of Pin1 in IRS-1 mediation of insulin signaling. The overexpression of Pin1 in HepG2 cells markedly enhanced insulin-induced IRS-1 phosphorylation and its downstream events: phosphatidylinositol 3-kinase binding with IRS-1 and Akt phosphorylation. In contrast, the treatment of HepG2 cells with Pin1 siRNA or the Pin1 inhibitor Juglone suppressed these events. In good agreement with these in vitro data, Pin1 knock-out mice exhibited impaired insulin signaling with glucose intolerance, whereas adenoviral gene transfer of Pin1 into the ob/ob mouse liver mostly normalized insulin signaling and restored glucose tolerance. In addition, it was also demonstrated that Pin1 plays a critical role in adipose differentiation, making Pin1 knock-out mice resistant to diet-induced obesity. Importantly, Pin1 expression was shown to be up-regulated in accordance with nutrient conditions such as food intake or a high-fat diet. Taken together, these observations indicate that Pin1 binds to IRS-1 and thereby markedly enhances insulin action, essential for adipogenesis.

Ohno H, Nakatsu Y, Sakoda H, Kushiyama A, Ono H, Fujishiro M, Otani Y, Okubo H, Yoneda M, Fukushima T, Tsuchiya Y, Kamata H, Nishimura F, Kurihara H, Katagiri H, Oka Y, Asano T. 4F2hc stabilizes GLUT1 protein and increases glucose transport activity. Am J Physiol Cell Physiol 300: C1047-C1054, 2011. First published January 26, 2011; doi:10.1152/ajpcell.00416.2010.-Glucose transporter 1 (GLUT1) is widely distributed throughout various tissues and contributes to insulin-independent basal glucose uptake. Using a split-ubiquitin membrane yeast two-hybrid system, we newly identified 4F2 heavy chain (4F2hc) as a membrane protein interacting with GLUT1. Though 4F2hc reportedly forms heterodimeric complexes between amino acid transporters, such as LAT1 and LAT2, and regulates amino acid uptake, we investigated the effects of 4F2hc on GLUT1 expression and the associated glucose uptake. First, FLAG-tagged 4F2hc and hemagglutinin-tagged GLUT1 were overexpressed in human embryonic kidney 293 cells and their association was confirmed by coimmunoprecipitation. The green fluorescent protein-tagged 4F2hc and DsRed-tagged GLUT1 showed significant, but incomplete, colocalization at the plasma membrane. In addition, an endogenous association between GLUT1 and 4F2hc was demonstrated using mouse brain tissue and HeLa cells. Interestingly, overexpression of 4F2hc increased the amount of GLUT1 protein in HeLa and HepG2 cells with increased glucose uptake. In contrast, small interfering RNA (siRNA)-mediated 4F2hc gene suppression markedly reduced GLUT1 protein in both cell types, with reduced glucose uptake. While GLUT1 mRNA levels were not affected by overexpression or gene silencing of 4F2hc, GLUT1 degradation after the addition of cycloheximide was significantly suppressed by 4F2hc overexpression and increased by 4F2hc siRNA treatment. Taken together, these observations indicate that 4F2hc is likely to be involved in GLUT1 stabilization and to contribute to the regulation of not only amino acid but also glucose metabolism.

Pin1 is a unique regulator, which catalyzes the conversion of a specific phospho-Ser/Thr-Pro-containing motif in target proteins. Herein, we identified CRTC2 as a Pin1-binding protein by overexpressing Pin1 with Myc and FLAG tags in mouse livers and subsequent purification of the complex containing Pin1. The association between Pin1 and CRTC2 was observed not only in overexpression experiments but also endogenously in the mouse liver. Interestingly, Ser(136) in the nuclear localization signal of CRTC2 was shown to be involved in the association with Pin1. Pin1 overexpression in HepG2 cells attenuated forskolin- induced nuclear localization of CRTC2 and cAMP-responsive element (CRE) transcriptional activity, whereas gene knockdown of Pin1 by siRNA enhanced both. Pin1 also associated with CRTC1, leading to their cytosol localization, essentially similar to the action of CRTC2. Furthermore, it was shown that CRTC2 associated with Pin1 did not bind to CREB. Taken together, these observations indicate the association of Pin1 with CRTC2 to decrease the nuclear CBP.CRTC.CREB complex. Indeed, adenoviral gene transfer of Pin1 into diabetic mice improved hyperglycemia in conjunction with normalizing phosphoenolpyruvate carboxykinase mRNA expression levels, which is regulated by CRE transcriptional activity. In conclusion, Pin1 regulates CRE transcriptional activity, by associating with CRTC1 or CRTC2.

OBJECTIVE-The sites of insulin action in the central nervous system that regulate glucose metabolism and energy expenditure are incompletely characterized. We have shown that mice with hypothalamic deficiency (L1) of insulin receptors (InsRs) fail to regulate hepatic glucose production (HGP) in response to insulin. RESEARCH DESIGN AND METHODS-To distinguish neurons that mediate insulin's effects on HGP from those that regulate energy homeostasis, we used targeted knock-ins to express InsRs in agouti-related protein (AgRP) or proopiomelanocortin (POMC) neurons of L1 mice. RESULTS-Restoration of insulin action in AgRP neurons normalized insulin suppression of HGP. Surprisingly, POMC-specific InsR knock-in increased energy expenditure and locomotor activity, exacerbated insulin resistance and increased HGP, associated with decreased expression of the ATP-sensitive K(+) channel (K(ATP) channel) sulfonylurea receptor 1 subunit, and decreased inhibitory synaptic contacts on POMC neurons. CONCLUSIONS-The contrasting phenotypes of InSR knock-ins in POMC and AgRP neurons suggest a branched-pathway model of hypothalamic insulin signaling in which InsR signaling in AgRP neurons decreases HGP, whereas InsR activation in POMC neurons promotes HGP and activates the melanocortinergic energy expenditure program. Diabetes 59:337-346, 2010

The differentiation of macrophages into cytokine-secreting foam cells plays a critical role in the development of diabetic angiopathy. J774.1, a murine macrophage cell line, reportedly differentiates into foam cells when incubated with oxidized LDL, ApoE-rich VLDL or WHHLMI (myocardial infarction-prone Watanabe heritable hyperlipidemic) rabbit serum. In this study, serum samples from Type 2 diabetic patients were added to the medium with J774.1 cells and the degree of foam cell induction was quantified by measuring lipid accumulation. These values were calculated relative to the activities of normal and WHHLMI rabbit sera as 0% and 100%, respectively, and termed the MMI (Macrophage Maturation Index). These MMI values reflected intracellular lipids, including cholesteryl ester assayed by GC/MS. Statistical analysis revealed MMI to correlate positively and independently with serum triglycerides, the state of diabetic retinopathy, nephropathy and obesity, but negatively with administration of alpha-glucosidase inhibitors or thiazolidinediones. Taken together, our results suggest that this novel assay may be applicable to the identification of patients at risk for rapidly progressive angiopathic disorders. (C) 2009 Elsevier Ireland Ltd. All rights reserved.

Objective PPAR. agonists are widely used in type 2 diabetic patients to reduce insulin resistance. Recently, telmisartan, an AT1 receptor antagonist, was reported to function as a partial agonist of PPAR. based on in vitro experiments. The aim of the present study was to investigate whether the PPAR. enhancing activity of telmisartan is exerted clinically in diabetic patients. Methods We compared the effects of telmisartan with those of candesartan, on insulin sensitivity, the serum levels of various adipocytokines and oxidative stress. Patients In total, 85 Japanese type 2 diabetic patients with hypertension, maintained on 8 mg per day of candesartan, were randomly assigned to the TM group (candesartan switched to 40 mg of telmisartan, n=38) or the CD group (no treatment change, n=47). Results After 3 months, oxidized lipids were significantly decreased only in the TM group. Although the homeostasis assessment model of insulin resistance (HOMA-R) tended to be improved and serum concentrations of HDL-cholesterol and HMW adiponectin tended to be increased only in the TM group, these alterations were too small to be significant by unpaired t-test. Interestingly, in subgroup analysis, the alterations of HOMA-R, serum concentrations of oxidized lipids, and HMW adiponectin were more apparent in obese TM group subjects and the changes reached statistical significance. Conclusion Switching from candesartan to telmisartan in obese subjects increases serum adiponectin and improves both insulin resistance and oxidative stress, while these effects were not statistically apparent in the total patient population. These results support the idea that telmisartan exerts its PPAR. enhancing activity clinically in obese type 2 diabetic patients.

AMP-activated protein kinase (AMPK) activation reportedly suppresses transcriptional activity of the cAMP-responsive element (CRE) in the phosphoenolpyruvate carboxykinase C (PEPCK-C) promoter and reduces hepatic PEPCK-C expression. Although a previous study found TORC2 phosphorylation to be involved in the suppression of AMPK-mediated CRE transcriptional activity, we herein present evidence that glycogen synthase kinase 3 beta (GSK3 beta) phosphorylation induced by AMPK also plays an important role. We initially found that injecting fasted mice with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) markedly increased Ser-9 phosphorylation of hepatic GSK3 beta within 15 min. Stimulation with AICAR or the GSK3 beta inhibitor SB-415286 strongly inhibited CRE-containing promoter activity in HepG2 cells. Using the Gal4-based transactivation assay system, the transcriptional activity of cAMP-response element-binding protein (CREB) was suppressed by both AICAR and SB415286, whereas that of TORC2 was repressed significantly by AICAR but very slightly by SB415286. These results show inactivation of GSK3 beta to directly inhibit CREB but not TORC2. Importantly, the AICAR-induced suppres

Prolonged activation of p70 S6 kinase (S6K) by insulin and nutrients leads to inhibition of insuhn signaling via negative feedback input to the signaling factor IRS-1. Systemic deletion of S6K protects against diet-induced obesity and enhances insulin sensitivity in mice. Herein, we present evidence suggesting that hypothalamic S6K activation is involved in the pathogenesis of diet-induced hepatic insulin resistance. Extending previous findings that insulin suppresses hepatic glucose production (HGP) partly via its effect in the hypothalamus, we report that this effect was blunted by short-term high-fat diet (HFD) feeding, with concomitant suppression of insulin signaling and activation of S6K in the mediobasal hypothalamus (MBH). Constitutive activation of S6K in the MBH mimicked the effect of the HFD in normal chow-fed animals, while suppression of S6K by overexpression of dominant-negative S6K or dominant-negative raptor in the MBH restored the ability of MBH insulin to suppress HGP after HFD feeding. These results suggest that activation of hypothalamic S6K contributes to hepatic insulin resistance in response to short-term nutrient excess.

Several serine/threonine kinases reportedly phosphorylate serine residues of IRS-1 and thereby induce insulin resistance. In this study, to investigate the effect of mTOR/raptor on insulin signaling and metabolism in K/KAy mice with genetic obesity-associated insulin resistance, a dominant negative raptor, COOH-terminally deleted raptor (raptor-Delta C-T), was overexpressed in the liver via injection of its adenovirus into the circulation. Hepatic raptor-Delta C-T expression levels were 1.5- to 4-fold that of endogenously expressed raptor. Glucose tolerance in raptor-Delta C-T-overexpressing mice improved significantly compared with that of LacZ-overexpressing mice. Insulin-induced activation of p70S6 kinase (p70(S6k)) was significantly suppressed in the livers of raptor-Delta C-T overexpressing mice. In addition, insulin-induced IRS-1, Ser(307), and Ser636/639 phosphorylations were significantly suppressed in the raptor-Delta C-T-overexpressing liver, whereas tyrosine phosphorylation of IRS-1 was increased. PI 3-kinase activation in response to insulin stimulation was increased approximately twofold, and Akt phosphorylation was clearly enhanced under both basal and insulin-stimula

To elucidate the role of AMPK in hepatic glucose metabolism, dominant negative (DN), constitutively active (CA) forms of the AMPK alpha 1 subunit and control vector LacZ were overexpressed by means of adenovirus-mediated gene transfer. Five days after virus injection, hepatic AMPK activity was five-fold higher in CA mice than in DN mice. DN mice were apparently glucose intolerant with a higher fasting plasma glucose level (DN 82.3 +/- 0.7 mg/dl, CA 42.5 +/- 4.8 mg/dl and LacZ 54.3 +/- 2.4 mg/dl). PEPCK, a gluconeogenic key enzyme, mRNA was increased 131.54% and 48.92% in DN mice compared to that of CA and LacZ, respectively. Thus, hepatic AMPK activation plays a role in the suppression of gluconeogenesis and this might be the cause of decreased fasting plasma glucose level in CA mice. We also investigated the effects of dexamethasone on hepatic AMPK expression and activity in rat liver, mice liver, as well as primary cultured hepatocytes. Subcutaneously injecting mice with dexamethasone (1 mg/day) for 5 days significantly upregulated hepatic AMPK alpha 1 and alpha 2 expressions. Similarly, the treatment of primary cultured rat hepatocytes with dexamethasone (I mu M) increased expression of the AMPK alpha 1 subunit, AICAR-induced AMPK phosphorylation and kinase activity. Although increased AMPK expression cannot be attributed to dexamethasone-induced glucose intolerance, taken together our results raise the possibility that AMPK control liver glucose output and its expression in, liver might be modulated by various hormones and growth factors. (c) 2006 Elsevier Ireland Ltd. All rights reserved.

AMP-activated protein kinase (AMPK) regulates both glycogen and lipid metabolism functioning as an intracellular energy sensor. In this study, we identified a 160-kDa protein in mouse skeletal muscle lysate by using a glutathione-S-transferase (GST)-AMPK fusion protein pull-down assay. Mass spectrometry and a Mascot search revealed this protein to be a glycogen debranching enzyme (GDE). The association between AMPK and GDE was observed not only in the overexpression system but also endogenously. Next, we showed the β1-subunit of AMPK to be responsible for the association with GDE. Furthermore, experiments using deletion mutants of the β1-subunit of AMPK revealed amino acids 68-123 of the β1-subunit to be sufficient for GDE binding. W100G and K128Q, both β1-subunit mutants, are reportedly incapable of binding to glycogen, but both bound GDE, indicating that the association between AMPK and GDE does not involve glycogen. Rather, the AMPK-GDE association is likely to be direct. Overexpression of amino acids 68-123 of the β1-subunit inhibited the association between endogenous AMPK and GDE. Although GDE activity was unaffected, basal phosphorylation and kinase activity of AMPK, as well as phosphorylation of acetyl-CoA carboxylase, were significantly increased. Thus it is likely that the AMPK-GDE association is a novel mechanism regulating AMPK activity and the resultant fatty acid oxidation and glucose uptake. Copyright © 2005 the American Physiological Society.

Aims/hypothesis: Resistin and the resistin-like molecules (RELMs) comprise a novel class of cysteine-rich proteins. Among the RELMs, RELMβ and RELMγ are produced in non-adipocyte tissues, but the regulation of their expression and their physiological roles are largely unknown. We investigated in mice the tissue distribution and dimer formation of RELMβ and RELMγ and then examined whether their serum concentrations and tissue expression levels are related to insulin resistance. Methods: Specific antibodies against RELMβ and RELMγ were generated. Dimer formation was examined using COS cells and the colon. RELMβ and RELMγ tissue localisation and expression levels were analysed by an RNase protection assay, immunoblotting and immunohistochemical study. Serum concentrations in high-fat-fed and db/db mice were also measured using the specific antibodies. Results: The intestinal tract produces RELMβ and RELMγ, and colonic epithelial cells in particular express both RELMβ and RELMγ. In addition, RELMβ and RELMγ were shown to form a homodimer and a heterodimer with each other, in an overexpression system using cultured cells, and in mouse colon and serum. Serum RELMβ and RELMγ levels in high-fat-fed mice were markedly higher than those in mice fed normal chow. Serum RELMβ and RELMγ concentrations were also clearly higher in db/db mice than in lean littermates. Tissue expression levels revealed that elevated serum concentrations of RELMβ and RELMγ are attributable to increased production in the colon and bone marrow. Conclusions/interpretation: RELMβ and RELMγ form homo/heterodimers, which are secreted into the circulation. Serum concentrations of RELMβ and RELMγ may be a novel intestinal-tract-mediating regulator of insulin sensitivity, possibly involved in insulin resistance induced by obesity and a high-fat diet. © Springer-Verlag 2005.

Disruption of histamine H2 receptor and gastrin receptor had different effects growth of gastric mucosa: hypertrophy and atrophy, respectively. To clarify the roles of gastrin and histamine H2 receptors in gastric mucosa, mice deficient in both (double-null mice) were generated and analyzed. Double-null mice exhibited atrophy of gastric mucosae, marked hypergastrinemia and higher gastric pH than gastrin receptor-null mice, which were unresponsive even to carbachol. Comparison of gastric mucosae from 10-week-old wild-type, histamine H2 receptor-null, gastrin receptor-null and double-null mice revealed unique roles of these receptors in gastric mucosal homeostasis. While small parietal cells and increases in the number and mucin contents of mucous neck cells were secondary to impaired acid production, the histamine H2 receptor was responsible for chief cell maturation in terms of pepsinogen expression and type III mucin. In double-null and gastrin receptor-null mice, despite gastric mucosal atrophy, surface mucous cells were significantly increased, in contrast to gastrin-null mice. Thus, it is conceivable that gastrin-gene product(s) other than gastrin-17, in the stimulated state, may exert proliferative actions on surface mucous cells independently of the histamine H2 receptor. These findings provide evidence that different G-protein coupled-receptors affect differentiation into different cell lineages derived from common stem cells in gastric mucosa.

Aims/hypothesis. Oxidative stress is associated with diabetes, hypertension and atherosclerosis. Insulin resistance is implicated in the development of these disorders. We tested the hypothesis that oxidative stress induces insulin resistance in rats, and endeavoured to identify mechanisms linking the two. Methods. Buthionine sulfoximine (BSO), an inhibitor of glutathione synthase, was administered to Sprague-Dawley rats and 3T3-L1 adipocytes. Glucose metabolism and insulin signalling both in vivo and in 3T3-L1 adipocytes were examined. In 3T3-L1 adipocytes, the effects of overexpression of a dominant negative mutant of inhibitory κB (IκB), one role of which is to block oxidative-stress-induced nuclear factor (NF)-κB activation, were investigated. Results. In rats given BSO for 2 weeks, the plasma lipid hydroperoxide level doubled, indicating increased oxidative stress. A hyperinsulinaemic-euglycaemic clamp study and a glucose transport assay using isolated muscle and adipocytes revealed insulin resistance in BSO-treated rats. BSO treatment also impaired insulin-induced glucose uptake and GLUT4 translocation in 3T3-L1 adipocytes. In BSO-treated rat muscle, adipose tissue and 3T3-L1 adipocytes, insulin-induced IRS-1 phosphorylation in the low-density microsome (LDM) fraction was specifically decreased, while that in whole cell lysates was not altered, and subsequent translocation of phosphatidylinositol (PI) 3-kinase from the cytosol and the LDM fraction was disrupted. BSO-induced impairments of insulin action and insulin signalling were reversed by overexpressing the dominant negative mutant of IκB, thereby suppressing NF-κB activation. Conclusions/interpretation. Oxidative stress induces insulin resistance by impairing IRS-1 phosphorylation and PI 3-kinase activation in the LDM fraction, and NF-κB activation is likely to be involved in this process.

A high-salt diet, which is known to contribute to the pathogenesis of hypertension, is also reportedly associated with insulin resistance. We investigated the effects of a high-salt diet on insulin sensitivity and insulin signaling in salt-sensitive (Dahl-S) and salt resistant (Dahl-R) strains of the Dahl rat. Evaluation of hyperinsulinemic-euglycemic clamp studies and glucose uptake into the isolated soleus muscle revealed that salt loading (8% NaCl) for 4 weeks induced hypertension and significant insulin resistance in Dahl-S rats, whereas no significant effects were observed in Dahl-R rats. Despite the presence of insulin resistance, insulin-induced tyrosine phosphorylation of the insulin receptor and insulin receptor substrates, activation of phosphatidylinositol 3-kinase, and phosphorylation of Akt were all enhanced in Dahl-S rats fed a high-salt diet. The mechanism underlying this form of insulin resistance thus differs from that previously associated with obesity and dexamethasone and is likely due to the impairment of one or more metabolic steps situated downstream of phosphatidylinositol 3-kinase and Akt activation. Interestingly, supplementation of potassium (8% KCl) ameliorated the changes in insulin sensitivity in Dahl-S rats fed a high-salt diet; this was associated with a slight but significant decrease in blood pressure. Evidence presented suggest that there is an interdependent relationship between insulin sensitivity and salt sensitivity of blood pressure in Dahl-S rats, and it is suggested that supplementing the diet with potassium may exert a protective effect against both hypertension and insulin resistance in salt-sensitive individuals.