PPARgamma agonists inhibit cell growth and suppress the expression of cyclin D1 and EGF-like growth factors in ras-transformed rat intestinal epithelial cells

Peroxisome proliferator-activated receptor gamma (PPARgamma) inhibits the growth of several types of cancer cells. However, the mechanisms by which this occurs are poorly understood. The goal of the present study was to investigate the effects of PPARgamma on mutated ras-induced cell growth, activation of transcription factors and expression of genes associated with cellular transformation in rat intestinal epithelial cells. A human PPARgamma cDNA was introduced to the activated H-ras-transfected IEC-6 cells (IECras) and 1 clone (IECrasPR82) that stably expresses both activated ras and PPARgamma was obtained. Thiazolidinedione derivatives such as troglitazone and rosiglitazone, selective ligands for PPARgamma, inhibited the cellular growth of IECrasPR82 cells in a time-dependent manner and induced G1 cell cycle arrest. Treatment with troglitazone (20 microM) decreased the expression of cyclin D1, heparin-binding epidermal growth factor-like growth factor (HB-EGF) and amphiregulin and suppressed the promoter activities of cyclin D1 and HB-EGF. Furthermore, a luciferase assay and an electrophoretic mobility shift assay showed that thiazolidinedione derivatives suppressed the transcriptional activities of AP-1 and Ets, both of which play crucial roles in the expression of cyclin D1 and HB-EGF. These findings suggest that reduction of EGF-like growth factors and cyclin D1 through the suppression of AP-1 and Ets may be 1 mechanism whereby PPARgamma inhibits their growth.

Expression of cholesteryl ester transfer protein in human atherosclerotic lesions and its implication in reverse cholesterol transport

Reverse cholesterol transport (RCT) is the major protective system against atherosclerosis. In this system, cholesteryl ester transfer protein (CETP) is known to facilitate the transfer of neutral lipids between lipoproteins in plasma. We reported the pathophysiological significance of CETP by clinical studies with genetic CETP deficiency, showing that this protein plays a crucial role in the RCT system. However, information about the expression of this protein in the initial step of RCT, macrophages (Mphi) in the blood vessels, is still very limited. In the present study, we have performed immunohistochemical analyses on the expression of CETP in human atherosclerotic lesions. The immunoreactive mass of CETP was abundantly detected in foam cells in human aortic and coronary atherosclerotic lesions, but not in the normal arterial wall. A double immunostaining showed that the majority of CETP-positive foam cells were derived from Mphi and a minor population appeared to derive from smooth muscle cells. Transient transfection of CETP cDNA into COS-7 cells showed that high density lipoprotein (HDL)-mediated efflux of free cholesterol from the cells expressing CETP was much higher than that from mock-transfected cells, while uptake of HDL-lipids was not affected in cells transfected with CETP cDNA. Efflux of free cholesterol from the Mphi obtained from CETP deficiency was significantly decreased compared with that from normal subjects. These data indicate that CETP is expressed in Mphi in the atherosclerotic lesions and may possess an anti-atherogenic function to remove cholesterol from the cells, suggesting another role of CETP at the initial step of RCT.

Reference intervals for serum apolipoproteins A-I, A-II, B, C-II, C-III, and E in healthy Japanese determined with a commercial immunoturbidimetric assay and effects of sex, age, smoking, drinking, and Lp(a) level

BACKGROUND

Apolipoproteins, which are contained in lipoprotein particles, play important roles in the transport of lipids.

METHODS

Serum levels of apolipoproteins (apo) A-I, A-II, B, C-II, C-III, and E were determined by immunoturbidimetry in a healthy Japanese study population (1018 men and 1167 women, age 20-69 years) to establish reference intervals.

RESULTS

Among the 2185 subjects examined, the mean serum value for apoA-I was 1.42 +/- 0.20 g/l, for apoA-II was 0.30 +/- 0.05 g/l, for apoB was 0.87 +/- 0.18 g/l, for apoC-II was 29 +/- 13 mg/l, for apoC-III was 75 +/- 20 mg/l, and for apoE was 36 +/- 9 mg/l. A sex difference was detected in the mean serum concentrations of all six apolipoproteins. Alcohol consumption and cigarette use had a slight effect on serum apolipoprotein concentrations. Age effects were observed among women in apoB, apoC-II, and apoC-III concentrations. Moreover, individuals with elevated serum lipoprotein (a) [Lp(a), >300 mg/l] also displayed increased serum apoB and apoC-II levels and an increased apoB/apoA-I ratio.

CONCLUSION

The reference intervals for apolipoproteins in Japanese adults that we established, using commercially available reagents for automated analyzers, will be helpful for assessing risk of coronary heart disease and pathological conditions of patients with hyperlipidemia. We recommend use of these reference intervals for the clinical interpretation of serum apolipoprotein concentrations.

Increased expression of a nucleolar Nop5/Sik family member in metastatic melanoma cells: evidence for its role in nucleolar sizing and function

F10 and BL6 cells of B16 mouse melanoma cells are metastatic after intravenous injection, but only BL6 cells can metastasize to lungs after subcutaneous injection. Differences in gene expression between the two cell lines were examined, and a greater expression of the Sik-similar protein (Sik-SP) gene was found in BL6 cells. Structurally, Sik-SP belongs to the nucleolar Nop5/Sik family whose members play central roles in ribosome biogenesis; however, the function of Sik-SP has not been examined. Cytology with green fluorescent protein-fused proteins showed that Sik-SP was localized to the nucleolus. To examine whether Sik-SP is involved in ribosome biogenesis, two parameters were measured: magnitude of ribosomal RNA synthesis per nucleus and magnitude of protein production from the same amount of mRNA of an exogenous luciferase gene. Both values and, in addition, nucleolar size were larger in COS-7 monkey kidney cells overexpressing Sik-SP and BL6 cells than in mock-transfected COS-7 and F10 cells, respectively. Sik-SP seemed to promote ribosome biogenesis in the nucleolus. Furthermore, the expression of Sik-SP seemed to confer a greater cell growth response to serum, because such a response was greater in BL6 cells and F10 cells overexpressing Sik-SP than in untreated and mock-transfected F10 cells. Sik-SP may render melanoma cells more competent to survive through augmenting the activity of nucleolus.

Analysis of a non-functional HNF-1alpha (TCF1) mutation in Japanese subjects with familial type 1 diabetes

Mutations in the transcription factor hepatocyte nuclear factor-1alpha (HNF-1alpha; gene symbol TCF1) cause maturity-onset diabetes of the young type 3 (MODY3), a form of diabetes mellitus characterized by autosomal dominant inheritance, early onset, and pancreatic beta-cell dysfunction. Recent genetic studies, however, also found mutations in patients diagnosed with idiopathic (non-autoimmune based) type 1 diabetes. We identified a novel frameshift mutation (142delG) in the TCF1 gene in a family with a strong family history of type 1 diabetes and examined the functional properties of the mutant HNF 1alpha. The expression of the mutant protein was not detected in COS-7 cells by Western blot analysis after transfection of the mutant cDNA. This is the first case of an unstable mutant HNF-1alpha protein. Reporter gene analysis indicated that the mutant HNF-1alpha had no transactivation activity in HeLa and MIN6 cells. Haploinsufficiency for HNF-1alpha may lead to severe forms of diabetes like type 1 diabetes.

ATP-binding cassette transporter-1 induces rearrangement of actin cytoskeletons possibly through Cdc42/N-WASP

Positional cloning approaches revealed that Tangier disease (TD), a genetic high density lipoprotein deficiency, is associated with mutations in the ATP-binding cassette transporter-1 (ABCA1) gene. However, the biological function of ABCA1 is still not fully investigated. Recently, we have reported that the cells from the patients with TD had abnormal actin cytoskeletons in association with decreased expression of Cdc42, a member of RhoGTPases family. In the present study, we have found that actin cytoskeletons were altered in HEK293 cells transfected with human ABCA1 (hABCA1) cDNA. Cells expressing hABCA1 were divided into the following two groups by the distinct morphology with altered actin cytoskeletons: one had increased formation of filopodia (designated as Type I) and the other had long protrusions (designated as Type II). Type I cells had morphology similar to that of cells transfected with dominant active form of Cdc42 (Cdc42-DA, V12Cdc42Hs-DA). Type II cells had morphology similar to that of cells transfected with neural Wiskott-Aldrich Syndrome Protein (N-WASP),one of the established downstream effector molecules of Cdc42. We have obtained the data showing a possible pathway of ABCA1/Cdc42/N-WASP by the following experiments. Introduction of mutant of Cdc42 (dominant negative form of Cdc42, N17Cdc42Hs-DN) and N-WASP (N-WASP lacking verprolin homology domain, N-WASPDeltaVPH), both of which are supposed to have potential to inhibit rearrangement of actin cytoskeletons, significantly inhibited the morphological changes induced by expression of hABCA1. Immunoprecipitation study with FLAG-tagged ABCA1 (hABCA1-FLAG) revealed that Cdc42 was coimmunoprecipitated with hABCA1-FLAG. In addition, we have demonstrated possible intracellular colocalization of these two molecules in the overexpressing cells by the confocal laser microscopy. These results may suggest that hABCA1 regulates actin organization through the possible interaction with Cdc42Hs.

Genomic structure and insulin-mediated repression of the aquaporin adipose (AQPap), adipose-specific glycerol channel

Aquaporin adipose (AQPap) is a putative glycerol channel in adipocytes (Kishida, K., Kuriyama, H., Funahashi, T., Shimomura, I., Kihara, S., Ouchi, N., Nishida, M., Nishizawa, H., Matsuda, M., Takahashi, M., Hotta, K., Nakamura, T., Yamashita, S., Tochino, Y., and Matsuzawa, Y. (2000) J. Biol. Chem. 275, 20896-20902). In the current study, we examined the genomic structure of the mouse AQPap gene and its regulation by insulin. The mouse AQPap gene spanned 12 kilobase pairs in chromosome 4 and consisted of 8 exons and 7 introns. The first two exons, designated exon 1 and exon 1', are alternatively spliced to common exon 2, and thus the AQPap gene possessed two potential promoters. The exon 1-derived transcript is dominant in both adipose tissues and adipocytes on the basis of RNase protection assay and promoter analysis. The mRNA increased after fasting and decreased with refeeding. Insulin deficiency generated by streptozotocin enhanced the mRNA in adipose tissue. Insulin down-regulated AQPap mRNA in 3T3-L1 adipocytes. The AQPap promoter contained heptanucleotide sequences, TGTTTTT at -443/-437, similar to the insulin-response element identified previously in the promoters of insulin-repressed genes. Deletion and single base pair substitution analysis of the promoter revealed that these sequences were required for insulin-mediated repression of AQPap gene transcription. The phosphatidylinositol 3-kinase pathway was involved in this inhibition. We conclude that insulin represses the transcription of AQPap gene via insulin response element in its promoter. Sustained up-regulation of AQPap mRNA in adipose tissue in the insulin-resistant condition may disturb glucose homeostasis by increasing plasma glycerol.

A new IFN-like cytokine, limitin, modulates the immune response without influencing thymocyte development

A novel IFN-like molecule, limitin, was recently identified and revealed to suppress B lymphopoiesis through the IFN-alphabeta receptor, although it lacked growth suppression on myeloid and erythroid progenitors. Here we have studied diverse effects of limitin on T lymphocytes and compared limitin with previously known IFNs. Like IFN-alpha and -beta, limitin modified immunity in the following responses. It suppressed mitogen- and Ag-induced T cell proliferation through inhibiting the responsiveness to exogenous IL-2 rather than suppressing the production of IL-2. In contrast, limitin enhanced cytotoxic T lymphocyte activity associated with the perforin-granzyme pathway. To evaluate the effect of limitin in vivo, a lethal graft-versus-host disease assay was established. Limitin-treatment of host mice resulted in the enhancement of graft-versus-host disease. Limitin did not influence thymocyte development either in fetal thymus organ cultures or in newborn mice injected with limitin-Ig, suggesting that limitin is distinguishable from IFN-alpha and -beta. From these findings, it can be speculated that the human homolog of limitin may be applicable for clinical usage because of its IFN-like activities with low adverse effects on, for example, T lymphopoiesis, erythropoiesis, and myelopoiesis.

Platelet-associated anti-GPIIb-IIIa autoantibodies in chronic immune thrombocytopenic purpura recognizing epitopes close to the ligand-binding site of glycoprotein (GP) IIb

Localization of epitopes for platelet-associated (PA) anti-GPIIb-IIIa (alpha(IIb)beta(3)) autoantibodies in chronic immune thrombocytopenic purpura remains elusive. Previous studies suggest that PA antibodies recognize the tertiary structure of intact glycoprotein (GP) IIb-IIIa. To localize their epitopes using antigen-capture enzyme-linked immunosorbent assay (ELISA), the reactivity of 34 PA anti-GPIIb-IIIa antibodies was examined with recombinant GPIIb-IIIa having a defect in ligand-binding sites in either GPIIb or GPIIIa, and no major conformational change was induced: KO variant GPIIb-IIIa was attributed to a 2-amino acid insertion between residues 160 and 161 in the W3 4-1 loop in GPIIb, and CAM variant GPIIb-IIIa was attributed to D119Y in GPIIIa. In one third (11 of 34) of the patients, PA antibodies showed a marked decrease (less than 50%) in reactivity with KO compared with wild-type GPIIb-IIIa. Their reactivity was also impaired against GPIIbD163A-IIIa. In sharp contrast, they reacted normally with CAM GPIIb-IIIa. OP-G2, a ligand-mimetic monoclonal antibody, markedly inhibited their binding to GPIIb-IIIa in patients with impaired binding to KO GPIIb-IIIa, but small GPIIb-IIIa antagonists did not. In addition, a newly developed sensitive ELISA indicated that autoantibodies showing impaired binding to KO are more potent inhibitors for fibrinogen binding. The present data suggest that certain PA anti-GPIIb-IIIa autoantibodies recognize epitopes close to the ligand-binding site in GPIIb, but not in GPIIIa.

Galectin-12, an Adipose-expressed Galectin-like Molecule Possessing Apoptosis-inducing Activity

Galectins constitute a family of proteins that bind to beta-galactoside residues and have diverse physiological functions. Here we report on the identification of a galectin-like molecule, galectin-12, in a human adipose tissue cDNA library. The protein contained two potential carbohydrate-recognition domains with the second carbohydrate-recognition domain being less conserved compared with other galectins. In vitro translated galectin-12 bound to a lactosyl-agarose column far less efficiently than galectin-8. Galectin-12 mRNA was predominantly expressed in adipose tissue of human and mouse and in differentiated 3T3-L1 adipocytes. Caloric restriction and treatment of obese animals with troglitazone increased galectin-12 mRNA levels and decreased the average size of the cells in adipose tissue. The induction of galectin-12 expression by the thiazolidinedione, troglitazone, was paralleled by an increase in the number of apoptotic cells in adipose tissue. Immunocytochemical analysis revealed that galectin-12 was localized in the nucleus of adipocytes, and transfection with galectin-12 cDNA induced apoptosis of COS-1 cells. These results suggest that galectin-12, an adipose-expressed galectin-like molecule, may participate in the apoptosis of adipocytes.

Weight reduction increases plasma levels of an adipose-derived anti-inflammatory protein, adiponectin

Adiponectin, an adipose tissue-specific plasma protein, was recently revealed to have anti-inflammatory effects on the cellular components of vascular wall. Its plasma levels were significantly lower in men than in women and lower in human subjects with obesity, type 2 diabetes mellitus, or coronary artery disease. Therefore, it may provide a biological link between obesity and obesity-related disorders such as atherosclerosis, against which it may confer protection. In this study, we observed the changes of plasma adiponectin levels with body weight reduction among 22 obese patients who received gastric partition surgery. A 46% increase of mean plasma adiponectin level was accompanied by a 21% reduction in mean body mass index. The change in plasma adiponectin levels was significantly correlated with the changes in body mass index (r = -0.5, P = 0.01), waist (r = -0.4, P = 0.04) and hip (r = -0.6, P = 0.0007) circumferences, and steady state plasma glucose levels (r = -0.5, P = 0.04). In multivariate linear regression models, the increase in adiponectin as a dependent variable was significantly related to the decrease in hip circumference (beta = -0.16, P = 0.028), after adjusting body mass index and waist circumference. The change in steady state plasma glucose levels as a dependent variable was related to the increase of adiponectin with a marginal significance (beta = -0.92, P = 0.053), after adjusting body mass index and waist and hip circumferences. In conclusion, body weight reduction increased the plasma levels of a protective adipocytokine, adiponectin. In addition, the increase in plasma adiponectin despite the reduction of the only tissue of its own synthesis suggests that the expression of adiponectin is under feedback inhibition in obesity.

Gastrin induces CXC chemokine expression in gastric epithelial cells through activation of NF-kappaB

Although hypergastrinemia is frequently observed in individuals with a chronic Helicobacter pylori infection, its pathophysiological significance in gastric mucosal inflammation is unclear. The present study was designed to determine if gastrin induces the expression of CXC chemokines in gastric epithelial cells. Human and rat gastric epithelial cells, transfected with gastrin receptor, were stimulated with gastrin. The expression of mRNAs for human interleukin-8 (IL-8) and rat cytokine-induced neutrophil chemoattractant-1 and release of human IL-8 protein were then determined by Northern blot analysis and ELISA, respectively. Gastrin not only induced the expression of mRNAs for these chemokines but also stimulated IL-8 protein release. A luciferase assay using IL-8 promoter genes showed that nuclear factor (NF)-kappaB is absolutely required and activator protein-1 (AP-1) is partly required for the maximum induction of IL-8 by gastrin. An electrophoretic mobility shift assay revealed that gastrin is capable of activating both NF-kappaB and AP-1. In addition, the inhibition of NF-kappaB abrogated gastrin-induced chemokine expression. These results suggest that gastrin is capable of upregulating CXC chemokines in gastric epithelial cells and therefore may contribute to the progression of the inflammatory process in the stomach.

The genetic basis of plasma variation in adiponectin, a global endophenotype for obesity and the metabolic syndrome

Here we present the first genetic analysis of adiponectin levels, a newly identified adipocyte-derived protein. Recent work has suggested that adiponectin may play a role in mediating the effects of body weight as a risk factor for coronary artery disease. For this analysis we assayed serum levels of adiponectin in 1100 adults of predominantly northern European ancestry distributed across 170 families. Quantitative genetic analysis of adiponectin levels detected an additive genetic heritability of 46%. The maximum LOD score detected in a genome wide scan for adiponectin levels was 4.06 (P = 7.7 x 10(-6)), 35 cM from pter on chromosome 5. The second largest LOD score (LOD = 3.2; P = 6.2 x 10(-5)) was detected on chromosome 14, 29 cM from pter. The detection of a significant linkage with a quantitative trait locus on chromosome 5 provides strong evidence for a replication of a previously reported quantitative trait locus for obesity-related phenotypes. In addition, several secondary signals offer potential evidence of replications for additional previously reported obesity-related quantitative trait loci on chromosomes 2 and 10. Not only do these results identify quantitative trait loci with significant effects on a newly described, and potentially very important, adipocyte-derived protein, they also reveal the emergence of a consistent pattern of linkage results for obesity-related traits across a number of human populations.

PPARgamma ligands increase expression and plasma concentrations of adiponectin, an adipose-derived protein

Insulin resistance and its dreaded consequence, type 2 diabetes, are major causes of atherosclerosis. Adiponectin is an adipose-specific plasma protein that possesses anti-atherogenic properties, such as the suppression of adhesion molecule expression in vascular endothelial cells and cytokine production from macrophages. Plasma adiponectin concentrations are decreased in obese and type 2 diabetic subjects with insulin resistance. A regimen that normalizes or increases the plasma adiponectin might prevent atherosclerosis in patients with insulin resistance. In this study, we demonstrate the inducing effects of thiazolidinediones (TZDs), which are synthetic PPARgamma ligands, on the expression and secretion of adiponectin in humans and rodents in vivo and in vitro. The administration of TZDs significantly increased the plasma adiponectin concentrations in insulin resistant humans and rodents without affecting their body weight. Adiponectin mRNA expression was normalized or increased by TZDs in the adipose tissues of obese mice. In cultured 3T3-L1 adipocytes, TZD derivatives enhanced the mRNA expression and secretion of adiponectin in a dose- and time-dependent manner. Furthermore, these effects were mediated through the activation of the promoter by the TZDs. On the other hand, TNF-alpha, which is produced more in an insulin-resistant condition, dose-dependently reduced the expression of adiponectin in adipocytes by suppressing its promoter activity. TZDs restored this inhibitory effect by TNF-alpha. TZDs might prevent atherosclerotic vascular disease in insulin-resistant patients by inducing the production of adiponectin through direct effect on its promoter and antagonizing the effect of TNF-alpha on the adiponectin promoter.

Vascular endothelial dysfunction resulting from L-arginine deficiency in a patient with lysinuric protein intolerance

Although L-arginine is the only substrate for nitric oxide (NO) production, no studies have yet been reported on the effect of an L-arginine deficiency on vascular function in humans. Lysinuric protein intolerance (LPI) is a rare autosomal recessive defect of dibasic amino acid transport caused by mutations in the SLC7A7 gene, resulting in an L-arginine deficiency. Vascular endothelial function was examined in an LPI patient who was shown to be a compound heterozygote for two mutations in the gene (5.3-kbp Alu-mediated deletion, IVS3+1G-->A). The lumen diameter of the brachial artery was measured in this patient and in healthy controls at rest, during reactive hyperemia (endothelium-dependent vasodilation [EDV]), and after sublingual nitroglycerin administration (endothelium-independent vasodilation [EIV]) using ultrasonography. Both EDV and NO(x) concentrations were markedly reduced in the patient compared with those for the controls. They became normal after an L-arginine infusion. EIV was not significantly different between the patient and controls. Positron emission tomography of the heart and a treadmill test revealed ischemic changes in the patient, which were improved by the L-arginine infusion. Thus, in the LPI patient, L-arginine deficiency caused vascular endothelial dysfunction via a decrease in NO production.

[Efficacy and toxicity of lenograstim (glycosylated recombinant human granulocyte-colony stimulating factor) on peripheral blood stem cell harvest in healthy donors]

Peripheral blood stem cell harvest with lenograstim (glycosylated rhG-CSF) was performed 12 times from 10 normal donors. Five micrograms/kg of lenograstim was administered subcutaneously twice a day (10 micrograms/kg/day) for 4 to 6 days, and apheresis was performed on day 5 to 7 depending on the collected CD 34+ cell counts. We collected a sufficient number of CD 34+ cells in 9 mobilizations from 7 donors less than 50 years of age, with a total number of collected CD 34+ cells in each mobilization of 22.1 +/- 6.5 x 10(7). In contrast, we could not obtain a sufficient number of CD 34+ cells in 2 mobilizations from 3 donors above 50 years of age, with a total number of collected CD 34+ cells of 9.8 +/- 3.3 x 10(7). Although all donors had adverse events in response to lenograstim administration, all of them were grade 2 or less toxicity. These results indicate that peripheral blood stem cell mobilization and apheresis by lenograstim is safe and well tolerated, but the risk of poor mobilization may become higher in donors more than 50 years of age.

Weight reduction increases plasma levels of an adipose-derived anti-inflammatory protein, adiponectin

Adiponectin, an adipose tissue-specific plasma protein, was recently revealed to have anti-inflammatory effects on the cellular components of vascular wall. Its plasma levels were significantly lower in men than in women and lower in human subjects with obesity, type 2 diabetes mellitus, or coronary artery disease. Therefore, it may provide a biological link between obesity and obesity-related disorders such as atherosclerosis, against which it may confer protection. In this study, we observed the changes of plasma adiponectin levels with body weight reduction among 22 obese patients who received gastric partition surgery. A 46% increase of mean plasma adiponectin level was accompanied by a 21% reduction in mean body mass index. The change in plasma adiponectin levels was significantly correlated with the changes in body mass index (r = -0.5, P = 0.01), waist (r = -0.4, P = 0.04) and hip (r = -0.6, P = 0.0007) circumferences, and steady state plasma glucose levels (r = -0.5, P = 0.04). In multivariate linear regression models, the increase in adiponectin as a dependent variable was significantly related to the decrease in hip circumference (beta = -0.16, P = 0.028), after adjusting body mass index and waist circumference. The change in steady state plasma glucose levels as a dependent variable was related to the increase of adiponectin with a marginal significance (beta = -0.92, P = 0.053), after adjusting body mass index and waist and hip circumferences. In conclusion, body weight reduction increased the plasma levels of a protective adipocytokine, adiponectin. In addition, the increase in plasma adiponectin despite the reduction of the only tissue of its own synthesis suggests that the expression of adiponectin is under feedback inhibition in obesity.

The expression of SPARC in adipose tissue and its increased plasma concentration in patients with coronary artery disease

OBJECTIVE

Adipocytes secrete various cytokines and matrix proteins. Several of them precipitate in obesity-associated diseases, including atherosclerosis. In the current study, we have examined the expression of secreted protein, acidic and rich in cysteine (SPARC) in adipose tissue and its significance in obesity and coronary artery disease (CAD).

RESEARCH METHODS AND PROCEDURES

The SPARC mRNA expressions both in vivo and in vitro were detected by Northern blot analysis. Plasma SPARC concentrations were measured by enzyme immunosorbent assay. First, we investigated the plasma SPARC levels of 88 unrelated adult Japanese subjects (62 men and 26 women; average age: [+/- SD] 50 +/- 12 years; body mass index [BMI]: 16 to 46 kg/m(2)). Additionally 31 subjects with CAD diagnosed by coronary angiography (20 men and 11 women) were also investigated.

RESULTS

Human adipose tissues expressed abundant SPARC mRNA. SPARC expression in adipose tissues was upregulated in obese db/db mice. Markedly enhanced expression of SPARC mRNA was observed in 3T3-L1 fibroblasts during adipocyte differentiation. Consistent with these results, plasma SPARC levels proved a positive correlation with BMI in humans (r = 0.27; p < 0.01). Interestingly, plasma SPARC concentrations were significantly elevated in age- and BMI-matched subjects with CAD (p < 0.05).

DISCUSSION

SPARC was expressed in adipose tissues and its expression was enhanced in obese mice. In human, plasma SPARC levels were elevated in obesity and CAD patients. This elevated SPARC may be involved in the progression of CAD.

Mutation screening of the hepatocyte nuclear factor (HNF)-6 gene in Japanese subjects with diabetes mellitus

Heterozygous mutations in the genes encoding transcription factors (HNF-1alpha, HNF-1beta and HNF-4alpha) in the hepatocyte nuclear factor (HNF) network are associated with maturity-onset diabetes of the young (MODY). We screened HNF-6 gene for mutations in 34 Japanese subjects with MODY/early-onset diabetes mellitus and 56 subjects with late-onset diabetes mellitus. One single nucleotide polymorphism (SNP) at codon 287 (GGG to GGT) was found in the gene and the frequency was similar among MODY/early-onset diabetes, late-onset diabetes and control subjects. Genetic variations in the HNF-6 gene are not likely to contribute to the susceptibility to diabetes mellitus in Japanese.

Pancreatic biopsy as a procedure for detecting in situ autoimmune phenomena in type 1 diabetes: close correlation between serological markers and histological evidence of cellular autoimmunity

To better understand the pathogenesis of type 1 diabetes, we have developed pancreatic biopsy under laparoscope for recent-onset type 1 diabetic patients. The patients included 29 acute-onset type 1 diabetic patients, 5 latent-onset type 1 diabetic patients, and 1 type 2 diabetic patient. Their median age was 28 years, and the duration of diabetes at the time of biopsy was approximately 3 months. In 31 of 35 patients, we could obtain the pancreas tissue by punching. No serious complications, such as heavy bleeding, peritonitis, or pancreatitis, have been experienced. Pneumoderma was observed in two patients, and abdominal dull pain had continued for 2 days in two patients. However, special treatment was not necessary for these complications. T-cell-predominant infiltration to islets (insulitis) and hyperexpression of major histocompatibility complex class I antigens on islet cells were the two major findings and were observed in 17 of 29 recent-onset type 1 diabetic patients. These findings could be regarded as evidence of immune attack against beta-cells, and their presence was closely correlated with the presence of either anti-GAD or anti-IA-2 antibodies (P = 0.02). In conclusion, pancreatic biopsy under laparoscope is a safe procedure without serious complications, according to our findings, for detecting in situ autoimmune phenomenon in recent-onset type 1 diabetic patients.

Analyses of genetic abnormalities in type I CD36 deficiency in Japan: identification and cell biological characterization of two novel mutations that cause CD36 deficiency in man

To elucidate genetic abnormalities in type I CD36 deficiency, we analyzed 28 Japanese subjects whose platelets and monocytes/macrophages lacked CD36 on their surface. We identified two novel mutations in the CD36 gene. One was a complex deletion/insertion mutation, in which 3 bp, GAG, were deleted at nucleotide (nt) 839-841, and 5 bp, AAAAC, were inserted at the same position (839-841del-->insAAAAC). Mutation 839-841del-->insAAAAC led to a frameshift and appearance of a premature stop codon; it was also accompanied with a marked reduction in the amount of CD36 mRNA. The other was a 12-bp deletion at nt 1438-1449 (1438-1449del) accompanied with or without skipping of exon 9 (nt 959-1028). Mutation 1438-1449del led to an inframe 4-amino-acid deletion, whereas exon 9 skipping led to a frameshift and the appearance of a premature stop codon. Expression assay revealed that both 1438-1449del and exon 9 skipping directly caused impairment of the surface expression of CD36. A survey of the five known mutations including 839-841del-->insAAAAC and 1438-1449del in type I CD36-deficient subjects demonstrated that the five mutations covered more than 90% of genetic defects among them and that the substitution of T for C at nt 478 (478C-->T) was the most common mutation with more than 50% frequency. However, none of the four subjects that possessed isoantibodies against CD36 had 478C-->T, suggesting that 478C-->T prevents the production of isoantibodies against CD36.

Localization of CD36 and scavenger receptor class A in human coronary arteries--a possible difference in the contribution of both receptors to plaque formation

CD36 and scavenger receptor class A types I and II (SR-AI/II) are major receptors for oxidized low density lipoproteins (OxLDL) expressed on macrophages. To elucidate the role of these two macrophage scavenger receptors in the development of coronary atherosclerosis, we examined the localization of CD36 and SR-AI/II in human coronary atherosclerotic lesions. Serial cryostat sections of 49 coronary arteries obtained from 43 autopsied cases were examined immunohistochemically. Regarding the relationship between the severity of atherosclerosis and immunoreactivities to CD36, there was almost no immunoreactivity to CD36 in regions with diffuse intimal thickening, while the expression of CD36 was accelerated in parallel with the progression of atherosclerosis. In contrast, SR-AI/II was expressed persistently from regions with diffuse intimal thickening to atherosclerotic plaques. We also clarified the differential distribution of CD36 and SR-AI/II in atheromatous plaques. Close to the luminal surface of the intima, macrophages were relatively small in size, contained lesser lipids, and expressed SR-AI/II more abundantly than CD36. In contrast, macrophages in the core region were larger in size, contained more lipids, were strongly positive for CD36 and showed a weaker immunoreactivity to SR-AI/II than those in the luminal surface of the intima. In conclusion, the expression of CD36 and SR-AI/II on macrophages may be regulated differently in the process of coronary atherogenesis.

Point mutation (-69 G-->A) in the promoter region of cholesteryl ester transfer protein gene in Japanese hyperalphalipoproteinemic subjects

Cholesteryl ester transfer protein (CETP) transfers cholesteryl ester (CE) from HDL to apolipoprotein (apo) B-containing lipoproteins and plays a crucial role in reverse cholesterol transport, which is a major protective system against atherosclerosis. Genetic CETP deficiency is the most common cause of a marked hyperalphalipoproteinemia (HALP) in the Japanese, and various mutations have been identified in the coding region as well as in the exon/intron boundaries in the CETP gene. In the present study, we identified a novel mutation in the promoter region of the CETP gene. This mutation was a G-to-A substitution at the -69 nucleotide of the promoter region (-69 G-->A), corresponding to the second nucleotide of the PEA3/ETS binding site (CGGAA) located upstream of the putative TATA box. Four (2.0%) of 196 unrelated subjects with a marked HALP (HDL cholesterol >/=2.59 mmol/L=100 mg/dL) were revealed to be heterozygous for the -69 G-->A mutation, and the allelic frequency of the mutant was 0.0102 in the subjects with a marked HALP. The subjects with the -69 G-->A mutation had low plasma CETP levels. Reporter gene assay showed that this mutation markedly reduced the transcriptional activities in HepG2 cells (8% of wild type). These results suggested that this mutation would be dominant negative. In conclusion, a novel -69 G-->A mutation in the CETP gene causes the decreased transcriptional activity leading to HALP.

Hypoadiponectinemia in obesity and type 2 diabetes: close association with insulin resistance and hyperinsulinemia

Plasma concentrations of adiponectin, a novel adipose-specific protein with putative antiatherogenic and antiinflammatory effects, were found to be decreased in Japanese individuals with obesity, type 2 diabetes, and cardiovascular disease, conditions commonly associated with insulin resistance and hyperinsulinemia. To further characterize the relationship between adiponectinemia and adiposity, insulin sensitivity, insulinemia, and glucose tolerance, we measured plasma adiponectin concentrations, body composition (dual-energy x-ray absorptiometry), insulin sensitivity (M, hyperinsulinemic clamp), and glucose tolerance (75-g oral glucose tolerance test) in 23 Caucasians and 121 Pima Indians, a population with a high propensity for obesity and type 2 diabetes. Plasma adiponectin concentration was negatively correlated with percent body fat (r = -0.43), waist-to-thigh ratio (r = -0.46), fasting plasma insulin concentration (r = -0.63), and 2-h glucose concentration (r = -0.38), and positively correlated with M (r = 0.59) (all P < 0.001); all relations were evident in both ethnic groups. In a multivariate analysis, fasting plasma insulin concentration, M, and waist-to-thigh ratio, but not percent body fat or 2-h glucose concentration, were significant independent determinates of adiponectinemia, explaining 47% of the variance (r(2) = 0.47). Differences in adiponectinemia between Pima Indians and Caucasians (7.2 +/- 2.6 vs. 10.2 +/- 4.3 microg/ml, P < 0.0001) and between Pima Indians with normal, impaired, and diabetic glucose tolerance (7.5 +/- 2.7, 6.1 +/- 2.0, 5.5 +/- 1.6 microg/ml, P < 0.0001) remained significant after adjustment for adiposity, but not after additional adjustment for M or fasting insulin concentration. These results confirm that obesity and type 2 diabetes are associated with low plasma adiponectin concentrations in different ethnic groups and indicate that the degree of hypoadiponectinemia is more closely related to the degree of insulin resistance and hyperinsulinemia than to the degree of adiposity and glucose intolerance.