Insulin-induced GLUT4 movements in C2C12 myoblasts: evidence against a role of conventional kinesin motor proteins

Insulin induces translocation of the glucose transporter GLUT4 from intracellular storage compartment to the plasma membrane via complex mechanisms that require intact cytoskeletal networks. In cultured adipocytes, conventional kinesin motor proteins have been proposed to mediate GLUT4 movements on microtubules. It remains, however, unclear whether kinesin motor system plays a similar regulatory role in myocytes. We addressed this issue using C2C12 myoblasts, which have now been shown to express both heavy and light chains of conventional kinesin. In these cells, overexpression of either wild-type kinesin light chain 2 (KLC2) or its phosphorylation-defective mutant did not significantly affect insulin-stimulated translocation of exofacial Myc-tagged GLUT4-green fluorescent protein to the cell surface and its subsequent externalization. Likewise, a dominant-negative mutant of KLC2 had no marked effect on GLUT4 movements in this cell type. These results suggest that conventional kinesin is dispensable for insulin-induced GLUT4 translocation in cultured myoblasts and may thus reveal a cell-type specific role of the microtubules-based cytoskeleton in glucose transport in response to insulin.

PDK1 regulates cell proliferation and cell cycle progression through control of cyclin D1 and p27Kip1 expression

PDK1 (3-phosphoinositide-dependent protein kinase 1) is a key mediator of signaling by phosphoinositide 3-kinase. To gain insight into the physiological importance of PDK1 in cell proliferation and cell cycle control, we established immortalized mouse embryonic fibroblasts (MEFs) from mice homozygous for a "floxed" allele of Pdk1 and from wild-type mice. Introduction of Cre recombinase by retrovirus-mediated gene transfer resulted in the depletion of PDK1 in Pdk1(lox/lox) MEFs but not in Pdk1(+/+) MEFs. The insulin-like growth factor-1-induced phosphorylation of various downstream effectors of PDK1, including Akt, glycogen synthase kinase 3, ribosomal protein S6, and p70 S6 kinase, was markedly inhibited in the PDK1-depleted (Pdk1-KO) MEFs. The rate of serum-induced cell proliferation was reduced; progression of the cell cycle from the G(0)-G(1) phase to the S phase was delayed, and cell cycle progression at G(2)-M phase was impaired in Pdk1-KO MEFs. These cells also manifested an increased level of p27(Kip1) expression and a reduced level of cyclin D1 expression during cell cycle progression. The defect in cell cycle progression from the G(0)-G(1) to the S phase in Pdk1-KO MEFs was rescued by forced expression of cyclin D1, whereas rescue of the defect in G(2)-M progression in these cells required both overexpression of cyclin D1 and depletion of p27(Kip1) by RNA interference. These data indicate that PDK1 plays an important role in cell proliferation and cell cycle progression by controlling the expression of both cyclin D1 and p27(Kip1).

VEGF T-1498C polymorphism, a predictive marker of differentiation of colorectal adenocarcinomas in Japanese

BACKGROUND

Previously, MDR1 T-129C polymorphism, encoding multidrug resistant transporter MDR1/P-glycoprotein, was reported to be predictive of poorly-differentiated colorectal adenocarcinomas. Here, VEGF T-1498C, C-634G and C-7T polymorphisms, encoding vascular endothelial growth factor (VEGF), were investigated in terms of their association with differentiation grade.

METHODS

VEGF genotypes were determined by TaqMan(R) MGB probe based polymerase chain reaction and evaluated were confirmed by direct sequencing in 36 Japanese patients.

RESULTS

VEGF T-1498C, but not C-634G or C-7T, was predictive of poorly-differentiated ones, and thereby a poor prognosis (p = 0.064 for genotype, p = 0.037 for allele), and this effect can be explained by that on VEGF expression. Treatment of a colorectal adenocarcinoma cell line, HCT-15, with sodium butyrate, a typical differentiating agent, resulted in an increase of alkaline phosphatase activity and MDR1 mRNA expression, but in a decrease of VEGF mRNA expression. The transfection of VEGF small interfering RNA (siRNA) induced the expression of MDR1 mRNA to 288-332% of the control level, whereas MDR1 siRNA had no effect on VEGF mRNA expression.

CONCLUSIONS

VEGF T-1498C polymorphism is also a candidate marker predictive of poorly-differentiated colorectal adenocarcinomas, but further investigations with a large number of patients should be addressed to draw a conclusion.

Cdx2 transcription factor regulates claudin-3 and claudin-4 expression during intestinal differentiation of gastric carcinoma

According to the expression of gastric (claudin-18) and intestinal claudins (claudin-3 and claudin-4), the authors have previously proposed a new phenotypic classification of gastric carcinoma (GC): the gastric (G-CLDN), intestinal (I-CLDN) and unclassified claudin (U-CLDN) phenotypes. The aim of the present study was to examine the role of Cdx2, the caudal-related transcription factor, on the regulation of intestinal claudins expression in vitro and in vivo. It was confirmed on immunohistochemistry that non-neoplastic gastric mucosa with intestinal metaplasia (IM) expressed Cdx2 with increased levels of intestinal claudin expression. In addition, Cdx2 expression was detected in 28 (30%) of 94 GC at the invasive front. Interestingly, Cdx2 expression had a significant association with the I-CLDN phenotype (P < 0.001), which was almost identical to the established gastric and intestinal mucin-based GC classification. Furthermore, the transfection of a recombinant human CDX2-expressing vector into TMK-1 (Cdx2-negative) GC cells specifically elevated the expression of claudin-3 and claudin-4 at the mRNA (CLDN3, 3.9-fold; CLDN4, 2.8-fold) and protein levels (claudin-3, 8.6-fold; claudin-4, 9.8-fold), whereas no induction of the other claudins was detected. These findings suggest that Cdx2 plays an important role in the regulation of intestinal claudin expression not only in gastric mucosa with IM but also GC.

Methylglyoxal induces prostaglandin E2 production in rat mesangial cells

The formation of methylglyoxal (MG), a reactive dicarbonyl compound, is accelerated under hyperglycemia, presumably contributing to tissue injury in diabetes. On the other hand, prostaglandin E2 (PGE2) has been implicated in glomerular hyperfiltration, a characteristic change in the early stage of diabetic nephropathy. We therefore examined whether MG was capable of inducing PGE2 production in rat mesangial cells (RMC) to address a possible mechanism by which hyperglycemia-derived dicarbonyls accelerated the development of diabetic nephropathy. RMC were incubated with 0 - 200 microM of MG, followed by determination of secreted PGE2 by enzyme immunoassay (EIA). We further investigated the intracellular mechanisms mediating the MG-induced PGE2 synthesis, focusing particularly on cyclooxygenase-2 (COX-2) and the MAPK superfamily. Our results indicated that MG induced PGE2 production in a dose-dependent manner, accompanied by augmentation of COX-2 mRNA expression. This MG-induced PGE2 production was significantly suppressed by inhibiting either ERK1/2 or p38 MAPK, implicating involvement of the MAPK superfamily. Our results suggest a potential role of MG in the development of diabetic nephropathy through PGE2 production, and may serve as a novel insight into the therapeutic strategies for diabetic nephropathy.

Association of serum MCP-1 concentration and MCP-1 polymorphism with insulin resistance in Japanese individuals with obese type 2 diabetes

Monocyte chemoattractant protein-1 (MCP-1, also known as CCL2) secreted by adipocytes is a member of the CC chemokine family and plays a pivotal role in the inflammatory process. A polymorphism, the -2518 A/G of MCP-1 gene, has been associated with type 2 diabetes, type 1 diabetes, parameters of insulin resistance and obesity. Therefore, we investigated the effects of MCP-1 single nucleotide polymorphisms (SNPs) on the susceptibility to type 2 diabetes or insulin resistance in the Japanese population. We also assessed the correlation between serum MCP-1 concentration and other clinical characteristics in Japanese type 2 diabetic subjects. The serum MCP-1 concentration was significantly correlated with HOMA-IR and the visceral fat area, but not with BMI. Although there was no association between this SNP and type 2 diabetes, the -2518A/G polymorphism was associated with the serum MCP-1 concentration. In subgroup analysis, Japanese obese diabetic -2518AA carriers had a higher MCP-1 concentration and increased insulin resistance than obese diabetic -2518G carriers. These data indicated that the MCP-1 polymorphism was associated with insulin resistance in Japanese obese diabetic subjects and that MCP-1 was implicated in the pathogenesis of insulin resistance, especially associated with obesity, in humans.

Relationship of BRAF mutation, morphology, and apoptosis in early colorectal cancer

BACKGROUND AND AIMS

Many investigators have reported flat and depressed lesions as a new type of precursor of colorectal cancer. In our previous study, we determined that mutations in the BRAF gene may contribute to colorectal carcinogenesis by inhibiting apoptosis. However, the relationship among BRAF mutations, morphology and apoptosis in early colorectal cancer has not been clear. Therefore, gene alternation, morphology, and apoptosis in early colorectal cancer were investigated.

MATERIALS AND METHODS

Forty-five flat and depressed early colorectal cancer samples and 43 polypoid early colorectal cancer samples were analyzed. Mutations in the BRAF gene and the K-ras gene were examined by direct sequence analysis, and proliferative activity and induction of apoptosis were evaluated using immunohistochemical examination. RESULTS FINDINGS: BRAF mutations were found in 5 (11.1%) of 45 flat and depressed early colorectal cancer samples. No BRAF alteration was found in polypoid early colorectal cancer samples. Mutations in the K-ras gene were detected in 13 (30.2%) of 43 polypoid early colorectal cancer samples. The rate of submucosal invasion of the samples with BRAF mutations was significantly higher than that of the samples with K-ras mutations (p<0.05).

INTERPRETATION/CONCLUSIONS

BRAF and K-ras mutations were independent factors that influenced morphology in early colorectal cancer. In this study, the relationship between BRAF mutation and apoptosis is not so clear, but BRAF mutations and inhibition in apoptosis may play an important role in the developmental process of flat and depressed early colorectal cancer.

Japanese case of hepatitis B virus genotypes C/D hybrid

Hepatitis B virus (HBV) is classified into eight genotypes based on complete genome sequence. Each genotype is related to geographic distribution and race. In Japan, most of the genotypes are B and C. In the present study, we report the first Japanese strain of HBV having a recombination between genotypes C and D. A 30-year-old woman was admitted to Kobe Medical Center because of liver dysfunction. She was diagnosed with spontaneous reactivation of chronic hepatitis B. She had no history of blood transfusion and her parents were negative for HBV. The phylogenetic analysis based on the complete genome sequences revealed that this strain was classified into genotype C, whereas the analysis based on Sgene sequence showed that this strain was genotype D. By using a SimPlot program, this strain was confirmed as a recombinant strain between genotypes C and D. Compared with previous recombinant strains in China, the breakpoint was the same and the difference was only 0.8% of the complete genome sequence. It was unclear whether or not this strain was transmitted from China, but the recombinant strains and intergenotypes of HBV have already existed in Japan.

Frequency of the G/G genotype of resistin single nucleotide polymorphism at -420 appears to be increased in younger-onset type 2 diabetes

OBJECTIVE

Resistin is an adipocyte-secreted cytokine associated with insulin resistance in mice. We previously reported that the G/G genotype of a resistin single nucleotide polymorphism (SNP) at -420 increases type 2 diabetes susceptibility by enhancing its promoter activity. The aim of the present study was to determine the relevance of SNP -120 in a large number of subjects.

RESEARCH DESIGN AND METHODS

We examined 2,610 type 2 diabetic case and 2,502 control subjects. The relation between SNP -420 and the age of type 2 diabetes onset was further analyzed by adding 237 type 2 diabetic subjects with age of onset <or=40 years.

RESULTS

When analyzed without considering subject age, the SNP -420 genotype was not associated with type 2 diabetes. Since we reported that the onset of type 2 diabetes was earlier in G/G genotype, we analyzed the data using a trend test for age intervals of 10 years. The frequency of G/G genotype differed among age grades in type 2 diabetes (P = 0.037) and appeared to be higher in younger grades. In type 2 diabetes, G/G genotype was more frequent in subjects aged <40 years than in those aged >or=40 years (G/G vs. C/C, P = 0.003). In a total of 2,430 type 2 diabetic subjects with age of onset <60 years, the trend test showed that the G/G genotype had an increasing linear trend as the age grade of type 2 diabetes onset became younger (P = 0.0379). In control subjects, the frequency of C/G genotype showed an increasing linear trend with increasing age (P = 0.010).

CONCLUSIONS

The G/G genotype frequency of resistin SNP -420 appears to be increased in younger-onset type 2 diabetic subjects.

Effects of pioglitazone and metformin on intracellular lipid content in liver and skeletal muscle of individuals with type 2 diabetes mellitus

Both ectopic fat accumulation and changes of the amount of several adipocyte secreting proteins (adipokines) are thought to contribute to the development of insulin resistance associated with obesity and type 2 diabetes mellitus. We have now investigated the effects of 2 insulin-sensitizing drugs, pioglitazone and metformin, on body fat composition and serum adipokine concentrations in individuals with type 2 diabetes mellitus. A total of 41 diabetic patients were treated with pioglitazone (n =21) or metformin (n =20) for 6 months. Intramyocellular lipid content (IMCL) and hepatic lipid content as well as the areas of subcutaneous and visceral fat deposits in the abdomen were determined by nuclear magnetic resonance spectroscopy before and after drug treatment. The serum concentrations of adiponectin and retinol binding protein 4 were also determined by enzyme-linked immunosorbent assays. Pioglitazone treatment reduced both hepatic lipid content (12.0 +/- 6.1 vs 8.4 +/- 3.7 arbitrary units [AU], P < .01) and IMCL (8.4 +/- 3.6 vs 6.3 +/- 2.4 AU/creatine, P < .01), whereas metformin reduced only IMCL (7.0 +/- 3.6 vs 5.8 +/- 2.0 AU/creatine, P < .05). Although the areas of visceral and subcutaneous fat were not significantly affected by treatment with either drug, pioglitazone induced a significant reduction in the ratio of visceral to subcutaneous fat area (0.92 +/- 0.41 vs 0.85 +/- 0.41, P < .05). Pioglitazone treatment also resulted in a marked increase in serum adiponectin concentration (5.6 +/- 4.1 vs 16.2 +/- 9.9 microg/mL, P < .0001) and a small but significant decrease in serum retinol binding protein 4 concentration (73.4 +/- 25.1 vs 65.1 +/- 23.7 microg/mL, P < .05). These results suggest that pioglitazone may improve insulin sensitivity both by affecting serum adipokine concentrations and by reducing the intracellular triglyceride content of liver and skeletal muscle in individuals with type 2 diabetes mellitus.

Variations in the core promoter/pre-core region in HBV genotype C in Japanese and Northern Vietnamese patients

Hepatitis B virus (HBV) subgenotypes Cs (C1) and Ce (C2) are common in East Asia. To investigate the genomic difference of HBV genotype C between two separated regions, 50 subgenotype Cs-infected Vietnamese and 70 subgenotype Ce-infected Japanese patients were enrolled for analysis. The patients were categorized to either a hepatocellular carcinoma group (HCC) or a non-HCC group including liver cirrhosis, chronic hepatitis, and asymptomatic carriers. HBV serology, HBV-DNA level, and variations in core promoter/pre-core region were examined. Phylogenetic analysis based on the full genome sequences and nucleotide sequences partly in the S gene and in the P gene revealed that all Japanese strains (70/70) were subgenotype Ce, and nearly all of the Vietnamese strains (50/51) were subgenotype Cs, excluding one subgenotype C5. C1858 and G1775 were common in the Vietnamese (64% and 40%) but not in the Japanese (0%). The prevalence of C/A1753 in Vietnamese was higher than that in the Japanese (32% vs. 17.1%), however the frequency of A1896 in the Japanese was significantly higher (32.9% vs. 12%, P < 0.05). Most of the Vietnamese patients with HCC had a high level of HBV-DNA, the Japanese HCC had a relatively low level. In the Vietnamese, C/A1753 and C1858 were associated closely with T1762A1764, higher HBV-DNA levels and higher HCC incidence. The multivariate analysis revealed that male, T1653 and C/A1753 were independent risk factors for HCC. The subgenotypes and unique mutations of HBV genotype C in the Vietnamese and Japanese differed, and C/A1753 and C1858 variants might play a role in the pathogenesis of liver disease in Vietnamese patients.

Neuroepithelial cells supply an initial transient wave of MSC differentiation

Mesenchymal stem cells (MSCs) are defined as cells that undergo sustained in vitro growth and are able to give rise to multiple mesenchymal lineages. Although MSCs are already used in regenerative medicine little is known about their in vivo behavior and developmental derivation. Here, we show that the earliest wave of MSC in the embryonic trunk is generated from Sox1+ neuroepithelium but not from mesoderm. Using lineage marking by direct gfp knock-in and Cre-recombinase mediated lineage tracing, we provide evidence that Sox1+ neuroepithelium gives rise to MSCs in part through a neural crest intermediate stage. This pathway can be distinguished from the pathway through which Sox1+ cells give rise to oligodendrocytes by expression of PDGFRbeta and A2B5. MSC recruitment from this pathway, however, is transient and is replaced by MSCs from unknown sources. We conclude that MSC can be defined as a definite in vivo entity recruited from multiple developmental origins.

Molecular epidemiological study of hepatitis B virus infection in two different ethnic populations from the Solomon Islands

The Solomon Islands is a multi-ethnic nation with a high rate of hepatitis B virus (HBV) infection. The prevalence relative to ethnicity was examined in relation to HBV infection, genotypes, and mutations. Asymptomatic populations (n = 564, 308 Melanesian and 118 Micronesian) from the Western Province were enrolled. Positive samples for Hepatitis B surface antigen (HBsAg) were examined for serological status, genotyping, viral load, and mutations of the basic core promoter (BCP) and pre-core (Pre-C) regions. The positive rate for HBsAg was 21.5%. The major Melanesian genotype was C (HBV/C), whereas the major Micronesian genotype was D (HBV/D). The prevalence of Hepatitis B e antigen (HBeAg) in serum was lower in carriers of HBV/D than of HBV/C. While the prevalence of the BCP mutation (T(1762)A(1764)) tended to be higher in HBV/C, that of the Pre-C mutation (T(1846)) was significantly higher in HBV/D (P < 0.0001). Genetic distance and phylogenetic analyses based on complete genome sequences were also carried out for two strains of HBV/C and two strains of HBV/D, and the findings were compared with those in the DDBJ/EMBL/GenBank database. The full-length sequence revealed that strains from the Solomon Islands were classified into subgenotype C3 (HBV/C3) and D4 (HBV/D4), and that the HBV/D strains were related closely to those from Papua New Guinea. HBV infection in the Solomon Islands is hyperendemic, and the genotype is ethnicity-specific. HBeAg appears to clear from the serum in young adulthood in HBV/D infection, which may be influenced by genotype-dependent features in relation to viral mutations.

Favorable genetic polymorphisms predictive of clinical outcome of chemoradiotherapy for stage II/III esophageal squamous cell carcinoma in Japanese

OBJECTIVES

This study was performed to find the genetic factors predictive of clinical outcome to a 5-fluorouracil (5-FU)/cisplatin (CDDP)-based chemoradiotherapy (CRT) in Japanese patients with locally advanced esophageal squamous cell carcinoma (ESCC).

MATERIALS AND METHODS

Thirty-one patients with stage I-IVa ESCC (I/II/III/IVa = 7/7/14/3) were enrolled in this study. One course of treatment consisted of protracted venous infusions (PVIs) of 5-FU (400 mg/m2/24 hours for days 1-5 and 8-12), CDDP (40 mg/m2/3 hours on days 1 and 8) and radiation (2 Gy/d on days 1-5, 8-12, and 15-19), and a 2nd course was successively repeated after a 2-week interval. A total of 8 measurements of the plasma concentration of 5-FU were made using high performance liquid chromatography. Genetic polymorphisms examined herein included those in the genes coding thymidylate synthase (TS), glutathione S-transferase P1 (GSTP1), multidrug resistant transporter MDR1/P-glycoprotein, and intercellular adhesion molecule-1, and in a circadian rhythm-relating gene, CLOCK.

RESULTS

The CR rate depended on stage (P = 0.001), but the analysis was not sufficiently powered to reach a level of statistical significance for the 2-year survival rate (P = 0.061). For stage II/III patients, to have 2 or 3 polymorphisms of 3R/3R of 5'-TSER, a 6 bp of 3'-TSUTR, and GSTP1-Ile105Val resulted in an extensively longer survival (P = 0.020), although no difference was found between 2 groups, with respect to the plasma concentrations of 5-FU and clinicopathologic characteristics.

CONCLUSIONS

The prognostic index may allow predictions of the clinical outcome of a 5-FU/CDDP-based CRT in stage II/III ESCC patients.

Favorable genetic polymorphisms predictive of clinical outcome of chemoradiotherapy for stage II/III esophageal squamous cell carcinoma in Japanese

15088

Background: A 5-fluorouracil (5-FU)/cisplatin (CDDP)-based chemoradiotherapy (CRT) was proposed for esophageal cancer patients. Currently, there is an urgent need to establish a methodology to decide which is preferable for a patient, i.e., surgical treatment or CRT, especially for Stage II to III tumors defined as resectable. This study was performed to find the genetic factors predictive of clinical outcome to a 5-FU/ CDDP-based CRT in Japanese patients with locally advanced esophageal squamous cell carcinoma (ESCC). Methods: Thirty-one patients with Stage I-IVa ESCC (I/II/III/IVa = 7/7/14/3) were enrolled in this study. One course of treatment consisted of protracted venous infusions of 5-FU (400 mg/m2/24 h for day 1–5 and 8–12), CDDP (40 mg/m2/3 h on day 1 and 8) and radiation (2 Gy/day on day 1–5, 8–12 and 15–19), and a 2nd course was successively repeated after a 2-week interval. A total of 8 measurements of the plasma concentration of 5-FU were made using high performance liquid chromatography. Genetic polymorphisms examined herein included those in the genes coding thymidylate synthase (TS), glutathione S-transferase P1 (GSTP1) and multi-drug resistant transporter MDR1/P-glycoprotein. Results: The complete response rate depended on Stage (p = 0.001), but the analysis was not sufficiently powered to reach a level of statistical significance for the 2-year survival rate (p = 0.061). For Stage II/III patients, to have 2 or 3 polymorphisms of 3R/3R of 5’-TSER, a 6bp of 3’-TSUTR, and GSTP1-Leu105Val resulted in an extensively longer survival (p =0.0197), although no difference was found between 2 groups, with respect to the plasma concentrations of 5-FU and clinical or pathological characteristics. Conclusions: The genetic prognostic index may allow predictions of the clinical outcome of a 5- FU/CDDP-based CRT in Stage II/III ESCC patients. Now, we are analyzing the contribution of genetic polymorphisms of cytokines, including tumor necrosis factor a.

No significant financial relationships to disclose.

Heterogeneous Expression of Claudin-4 in Human Colorectal Cancer: Decreased Claudin-4 Expression at the Invasive Front Correlates Cancer Invasion and Metastasis

OBJECTIVE

Claudin-4 plays a key role in constructing the tight junction (TJ), and altered claudin-4 expression has been documented in various human malignancies; however, little is known about the biological significance of claudin-4 in colorectal cancers (CRCs). The aim of this study is to investigate the significance of claudin-4 expression in CRC and its association with clinicopathological factors.

METHODS

The levels of claudin-4 expression in a total of 129 CRCs and 44 metastatic tumors were examined by immunohistochemistry. A small interfering RNA (siRNA)-mediated claudin-4 knockdown examination was also conducted to assess the biological role(s) of claudin-4 in cultured cells.

RESULTS

Expression of claudin-4 at the intercellular membrane was well preserved at the surface of the tumor; however, decreased claudin-4 expression was detected in 57% of CRCs, particularly at the invasive front. Interestingly, decreased claudin-4 expression was detected in metastatic lesions of CRC. The siRNA-mediated claudin-4 knockdown in SW480 claudin-4-positive CRC cells upregulated cell motility, whereas no significant change was detected in cell proliferation.

CONCLUSIONS

These observations suggested that disruption of claudin-4-mediated TJ construction enhances cancer cell invasion and metastasis in human CRC. Claudin-4 might be a good biomarker for diagnosing the risk of distant metastasis.

Histomorphometric analysis of diabetic osteopenia in streptozotocin-induced diabetic mice: a possible role of oxidative stress

Diabetic osteopenia causes an increase in bone fracture and a delay in healing of fractures, and affects the quality of life. However, the mechanisms responsible for the disease have not been clearly identified. Oxidative stress may be a potential candidate for the pathogenesis, since it is increased under diabetic conditions and is known to induce cellular dysfunction in a wide variety of cell types. Although in vitro studies have shown that oxidative stress inhibits osteoblastic differentiation and induces osteoblast insults and apoptosis, the relationship between diabetic osteopenia and oxidative stress remains unclear. To explore these issues, analysis of a mouse model that represents the diabetic osteopenia as seen in patients with diabetes is necessary. However, there are few reports of such a model. Therefore, we focused on the streptozotocin (STZ)-induced diabetic mouse, one of the most common animal models of type 1 diabetes. Eight-week-old male C57BL/6 mice were randomly assigned to the following three groups: 1) control group, 2) diabetic group, and 3) insulin-treated diabetic group. After 12 weeks of STZ treatment, the physical properties of the femora, and the static and dynamic parameters of bone histomorphometry of the tibiae from STZ-induced diabetic mice (STZ-mice) were assessed, and oxidative stress in the whole body and bone of the mice was evaluated. Renal function was comparable in all three groups at the end of the experimental period. In addition, no significant difference in serum PTH, Ca, and P was found among the three groups. In contrast, radiological analysis demonstrated a significant decrease in trabecular bone volume, and histomorphometric analyses confirmed that parameters for both bone formation (OV/BV, OS/BS, and BFR/BS) and bone resorption (ES/BS and Oc.S/BS) were also significantly lower in STZ-mice. In addition, urinary excretion of 8-hydroxydeoxyguanosine, a marker of oxidative DNA damage, was elevated in STZ-mice. Further immunohistological studies showed intensified immunostaining of an oxidative stress marker in bone tissue including the osteoblasts of diabetic mice. Here, we demonstrated that STZ-mice exhibit low-turnover osteopenia associated with increased oxidative stress.

Lack of association of CPT1A polymorphisms or haplotypes on hepatic lipid content or insulin resistance in Japanese individuals with type 2 diabetes mellitus

Accumulation of fat in the liver is associated with insulin resistance and type 2 diabetes mellitus. The carnitine palmitoyltransferase (CPT) enzyme system facilitates the transport of long-chain fatty acids into mitochondria, and the gene for the hepatic isoform of CPT1 (CPT1A) is a candidate gene for metabolic disorders such as insulin resistance associated with fatty liver. We have now investigated the contribution of the CPT1A locus to hepatic lipid content (HLC), insulin resistance, and susceptibility to type 2 diabetes mellitus. A total of 324 type 2 diabetic patients and 300 nondiabetic individuals were enrolled in the study. Eighty-seven of the type 2 diabetic patients who had not been treated with insulin or lipid-lowering drugs were evaluated by homeostasis model assessment for insulin resistance and were subjected to nuclear magnetic resonance for determination of HLC. A total of 19 single nucleotide polymorphisms (SNPs) were identified at the CPT1A locus, and linkage disequilibrium analysis revealed a strong linkage disequilibrium block between SNP8 (intron 5) and SNP17 (intron 14). Neither haplotypes nor SNPs of CPT1A were found to be associated either with susceptibility to type 2 diabetes mellitus or with HLC or insulin resistance in type 2 diabetic patients.