Structures of cobalt(III)-pepleomycin and cobalt(III)-deglycopepleomycin (green forms) determined by NMR studies

Pepleomycin (PEP) is a metalloglycopeptide that has stronger anticancer activity and less pulmonary toxicity than bleomycin (BLM). PEP, like BLM, exerts its action by binding to and degrading DNA in the presence of oxygen and certain metals. Obtaining detailed structural information of PEP and PEP-DNA complexes is crucial to understanding its anticancer activity. The structures of two green forms of cobalt-PEP species, HO2-Co(III)-PEP (denoted CoPEP) and deglycosylated HO2-Co(III)-PEP (denoted CodPEP) have been obtained by NOE restrained refinements. Earlier studies of the related HO2-Co(III)-BLM A2 proposed that two chiral conformers (form A or B) could exist with either the beta-aminoalanine primary amine (A,NH2) or the mannose carbamoyl nitrogen (M,NH2) as the axial ligand. Analysis of our NOESY data shows convincingly that form A is the most probable conformer with the mannose carbamoyl M,NH2 and the beta-aminoalanine primary amine A,NH2 as the axial ligands in CoPEP and CodPEP, respectively. The NOE cross-peaks resulting from the interactions between the N-terminus (i.e., the metal-binding domain) and the C-terminus of CoPEP and CodPEP have similar patterns, suggesting that they both adopt compact structures with the bithiazole group folded back over the N-terminus.

Retrovirus in salivary glands from patients with Sjögren's syndrome

AIMS

To investigate the possibility of an immune response to retroviral antigens or of detecting retrovirus in Sjögren's syndrome.

METHODS

Retroviruses were sought in labial salivary glands and peripheral blood mononuclear cells from patients with Sjögren's syndrome by immunoblotting assay, immunohistochemical assay, polymerase chain reaction (PCR), reverse transcriptase (RT) activity assay, and transmission electron microscopy.

RESULTS

Sera from five of 15 patients with Sjögren's syndrome (33%) reacted against p24 group specific antigen (gag) of human immunodeficiency virus (HIV). Labial salivary gland biopsy specimens from seven of the 15 patients with Sjögren's syndrome (47%) contained an epithelial cytoplasmic protein reactive with a monoclonal antibody to p24 of HIV. PCR was performed to detect HIV and human T lymphotropic virus type I (HTLV-I) genes from salivary gland tissues and peripheral blood mononuclear cells from patients with Sjögren's syndrome. Mn2+ dependent, Mg2+ independent RT activity was detected in the salivary gland tissues in three of 10 patients. A-type-like retroviral particles were observed in epithelial cells of salivary glands by transmission electron microscopy. Target genes for HIV and HTLV-I were not found in any of the salivary gland tissues or peripheral blood mononuclear cells from Sjögren's syndrome patients.

CONCLUSIONS

The data suggest the presence of an unknown retrovirus similar to HIV in the salivary gland which might be involved in the pathogenesis of a subpopulation in Sjögren's syndrome.

Treatment of branch retinal arterial occlusion with sodium ozagrel, a thromboxane A2 synthetase inhibitor

A 47-year-old woman with branch retinal arterial occlusion treated with sodium ozagrel is described. The patient presented with acute visual field loss in her right eye. Blood tests demonstrated the elevation of beta-thromboglobulin and platelet factor 4. Sodium ozagrel, a thromboxane A2 synthetase inhibitor, 160 mg daily was administered for 14 days. This treatment prevented exacerbation of retinal arterial thrombosis and produced a marked improvement in the visual field loss. Sodium ozagrel may be a useful drug in the treatment of acute retinal arterial occlusion thought to be caused by thrombosis.

[Expression of HGF and c-met/HGF receptor mRNA in brains of normal rats and in phaeochromocytoma cells PC-12 of rats treated with NGF]

Gene expression of HGF and c-met proto-oncogene was examined during rat brain development and in cultured PC-12 cells, using reverse-transcriptase (RT)-polymerase chain reaction (PCR) technique. The both mRNAs of HGF and c-met proto-oncogene were remained at low levels in the middle and late stages of gestation (E-13 and E-18). After birth, and the level of both mRNA expression suddenly increased. During P-1 and P-12, their high level of expression continued and then decreased in P-20 and adult brain. Both HGF mRNA and c-met photo-oncogene mRNA were transiently expressed between day 2 and day 5, and disappeared in cultured PC-12 cells treated with NGF. The neurites of PC-12 cells that were treated with anti-sense oligonucleotides of HGF and c-met proto-oncogene, were shorter and fewer in number than untreated control cells. We conclude that neurite extension of PC-12 cells treated with NGF may ensue by way of c-MET protein activation and signal transduction pathways. Thus, c-MET protein activation and up-regulation of the two mRNAs may also play an important role in neuronal maturation in the developing rat brain.

Expression of aquaporins in the rat ocular tissue

The aquaporins (AQPs) are a rapid growing family of water channel proteins found in animals, plants and microorganisms that raise plasma membrane water permeability required for efficient isosmotic fluid transport. Five homologs of aquaporins (AQP1, AQP2, AQP3, AQP4 and AQP5) have been identified from various mammalian tissues; the expression of these aquaporins in ocular tissues was studied. Semiquantitative expression levels of these aquaporins were determined in ciliary body, cornea, lens, retina, iris and choroid using RT-PCR. Expression levels of AQP1 are highest among the known aquaporins in each rat ocular tissue examined. In cornea, AQP1 is expressed approximately three-fold higher than AQP3 and 2.5 fold higher than AQP5. However, the highest intraocular expressions of AQP3 and AQP5 are in the cornea. In the iris, expression levels of AQP1 are approximately 600-700 fold higher than AQP4 and AQP5. In the ciliary body, the expression levels of AQP1 are approximately ten-fold higher than AQP4, the only other aquaporin expressed. In the lens, the major water channel is AQP1 with detectable levels of AQP4 and AQP5 that are approximately 1000-fold lower than AQP1. In choroid, AQP1 is the only water channel expressed. In retin, AQP1 is expressed approximately six-fold higher than AQP4, the only other aquaporin expressed. However, the highest ocular expression of AQP4 is in retina. AQP2 is not detected in the eye. Finally, the possible physiological roles of aquaporins in maintaining and regulating the aqueous flow, and corneal and lens transparency are discussed.

Antimicrobial activity of a new fluoroquinolone, DU-6859a, against quinolone-resistant clinical isolates of Neisseria gonorrhoeae with genetic alterations in the GyrA subunit of DNA gyrase and the ParC subunit of topoisomerase IV

The in-vitro antimicrobial activity of DU-6859a, a new fluoroquinolone, was tested against 55 clinical isolates of Neisseria gonorrhoeae. The MIC of DU-6859a inhibiting 90% (MIC90) of the isolates with genetic alterations of both the GyrA subunit of DNA gyrase and the ParC subunit of topoisomerase IV was 0.125 mg/L. The MIC90 for isolates with alterations of GyrA alone or without alterations of GyrA or ParC was 0.03 mg/L and 0.004 mg/L, respectively. The potency of DU-6859a against clinical isolates bearing genetic alterations associated with quinolone resistance was significantly greater than that of currently available fluoroquinolones.

Cooperative alkylation by duocarmycin A-distamycin A heterodimer

Duo A (Duo) normally alkylates adenine N3 at the 3' end of A + T-rich sequence in DNA. The addition of another minor groove binder, dist A (Dist), dramatically modulate the site of DNA alkylation by Duo with great acceleration of the reaction rate. In order to examine the mode of alkylation, the kinetics of the reaction under various conditions were examined. Based on the simulation of experimental data, a new reaction pathway was proposed.

Increased blood plasminogen activator inhibitor-1 and intercellular adhesion molecule-1 as possible risk factors of atherosclerosis in Werner syndrome

Werner syndrome is a rare premature aging syndrome accompanied by severe atherosclerosis. The etiology of atherosclerosis is suspected to be due to its complications, namely diabetes mellitus, hyperinsulinemia and hyperlipidemia. But from an autopsy case we found that some other risk factors may be involved in the mechanism of atherosclerosis in this syndrome. Previously we revealed that the plasminogen activator inhibitor-1 (PAI-1) gene was being overexpressed in skin fibroblasts from a patient with this syndrome. PAI-1 is a potent inhibitor of tissue plasminogen activator and a possible risk factor of atherosclerosis. This led us to assess the plasma concentration of PAI-1. Our working hypothesis was that the PAI-1 gene was upregulated or not fully suppressed in cells responsible for the production of PAI-1 in plasma as well as in fibroblasts. The results show a high concentration of plasma PAI-1. One of the well-known physiological substances that induce the PAI-1 gene is tumor necrosis factor-alpha, which also induces other possible risk factors of atherosclerosis, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1. We found the serum concentrations of ICAM-1 to be elevated in patients with this syndrome. We conclude that high concentrations of PAI-1 and ICAM-1 in blood may be one of the potent causes of severe atherosclerosis in Werner syndrome.

Interleukin-2 gene transduction into freshly isolated lung adenocarcinoma cells with adenoviral vectors

We evaluated the efficiency of gene transduction and of gene expression by adenoviral vectors in human lung adenocarcinoma cells. Freshly isolated cancer cells were collected from pleural effusions in adenocarcinoma patients by centrifugation with a Percoll gradient. Adenoviral vectors resulted in effective gene transduction into human lung cancer cell lines and into freshly isolated lung adenocarcinoma cells. In an experiment using the beta-galactosidase (LacZ) gene, the Adex1CA vector with a regulatory sequence of chicken beta-actin as promoter and an enhancer derived from cytomegalovirus produced a higher transduction ratio and greater expression levels than adenoviral vectors with other promoter systems. Transduction with Adex1CA vectors containing the human interleukin-2 (IL-2) gene (Adex1CAhIL-2) resulted in enhanced secretion of IL-2 from gene-modified lung cancer cells. Treatment with normal human serum inhibited gene transduction by Adex1CAhIL-2 but did not inhibit gene expression after transduction by Adex1CAhIL-2. The secretion of IL-2 from the gene-modified cells, which were irradiated at 100 Gy before transduction, continued for 8 days. In a mouse model, the intrapleural injection of IL-2 gene-modified 3LL cells transduced by Adex1CAhIL-2 could cure the pre-existing lung tumours with malignant pleural effusions to induce tumor-specific immunity. But these therapies did not show any therapeutic benefit on the pre-existing tumor in subcutaneous region. These data suggest a potentially useful but limited clinical role of Adex1CAhIL-2 in gene therapy for lung cancer patients.

Transplantation of genetically marked cardiac muscle cells

We examined the possibility that cardiomyocytes could be genetically marked or modified before being grafted to the heart under conditions applicable to the clinical setting. We used a replication-defective recombinant adenovirus carrying the beta-galactosidase reporter gene, and delivered it to cultured murine fetal cardiac myocytes. Virtually all fetal cardiomyocytes in a primary culture expressed beta-galactosidase 24 hours after recombinant adenovirus infection. These cells were transplanted to the hearts of syngenic adult recipient mice. Expression of the beta-galactosidase gene in the grafted cells was demonstrated by staining with 5-bromo-4-chloro-3-indoyl-beta-D-galactosidase, resulting in a blue color at the histochemical level and an electron-dense deposit on transmission electron microscopic analysis. Gene expression was recognized from 7 days to 12 weeks after transplantation. Implanted cardiomyocytes aligned themselves along the layers of the host myocardium. Formation of gap junctions was demonstrated by transmission electron microscopy. Neither inflammation nor fibrous scar tissue was detectable by histologic analysis. This study demonstrates that ex vivo gene transfer to the heart by means of the adenoviral vector is possible.

In vivo correction with recombinant adenovirus of 4-hydroxyphenylpyruvic acid dioxygenase deficiencies in strain III mice

Tyrosinemia type 3, caused by a genetic deficiency of 4-hydroxyphenylpyruvic acid dioxygenase (HPD) in tyrosine catabolism, is characterized by convulsion, ataxia, and mental retardation. The III mouse is a model of tyrosinemia type 3. HPD activity and protein are defective in the liver and its blood tyrosine levels are elevated, the range being between 1,100 and 1,656 microM. We constructed a recombinant adenoviral vector bearing the human HPD cDNA (AdexCAGhHPD), which is expressed under the control of a potent CAG promoter. III mice were injected with 1.0 x 10(8) to 1.0 x 10(9) pfu of AdexCAGhHPD through the tail vein. When 3.0 x 10(8) - 1.0 x 10(9) pfu were injected, blood tyrosine levels decreased within 3 hr, reached a normal range (under 300 microM), and remained at a low level for 2-6 weeks. Hepatic HPD activities also increased as early as 3 hr after the injection of 5.0 x 10(8) pfu, reached the levels comparable to the control mice in 3-7 days, and then decreased, and correlated well to blood tyrosine. Hepatic HPD expression was confirmed by Northern blot and immunoblot analyses. Histology revealed no difference (gross or microscopic) between the liver injected with AdexCAGhHPD and the control. No significant changes in blood tyrosine levels were noted after the second injection of 5.0 x 10(8) pfu of AdexCAGhHPD. Thus, the intravenous administration of the adenoviral vector bearing a foreign gene seems suitable for transient, early gene transfer into the liver.

Distamycin A modulates the sequence specificity of DNA alkylation by duocarmycin A

Duocarmycin A (Duo) normally alkylates adenine N3 at the 3' end of A + T-rich sequences in DNA. The efficient adenine alkylation by Duo is achieved by its monomeric binding to the DNA minor groove. The addition of another minor groove binder, distamycin A (Dist), dramatically modulates the site of DNA alkylation by Duo, and the alkylation switches preferentially to G residues in G + C-rich sequences. HPLC product analysis using oligonucleotides revealed a highly efficient G-N3 alkylation via the cooperative binding of a heterodimer between Duo and Dist to the minor groove. The three-dimensional structure of the ternary alkylated complex of Duo/Dist/d(CAGGTGGT).d(ACCACCTG) has been determined by nuclear Overhauser effect (NOE)-restrained refinement using 750 MHz two-dimensional NOE spectroscopy data. The refined NMR structure fully explains the sequence requirement of such modulated alkylations. This is the first demonstration of Duo DNA alkylation through cooperative binding with another structurally different natural product, and it suggests a promising new way to alter or modify the DNA alkylation selectivity in a predictable manner.

Soluble CD14 mediates lipopolysaccharide-induced intercellular adhesion molecule 1 expression in cultured human gingival fibroblasts

Intercellular adhesion molecule 1 (ICAM-1) is involved in the accumulation and activation of leukocytes in inflammatory diseases such as periodontitis. As reported previously, ICAM-1 is up-regulated on cultured human gingival fibroblasts (HGF) by exposure to lipopolysaccharide (LPS), suggesting a specific LPS recognition mechanism. We therefore investigated the role of CD14, an LPS receptor, in stimulation of HGF by LPS. Cell surface CD14 antigen was not observed on HGF by flow cytometric analysis. In addition, expression of CD14 mRNA in HGF was not detected by reverse transcription-PCR analysis. Since HGF did not express endogenous CD14, we investigated the role of human serum-derived soluble CD14 (sCD14) in ICAM-1 induction on HGF by LPS. The serum-dependent ICAM-1 induction by LPS was observed in HGF. In medium containing human serum, anti-CD14 antibody inhibited ICAM-1 induction on HGF by LPS. Depletion of sCD14 from human serum markedly reduced ICAM-1 expression on HGF in response to LPS. Supplementation of the serum-free medium with sCD14 alone restored the capacity of HGF to respond to LPS. These results show that induction of ICAM-1 in HGF by LPS does not involve binding to cell surface CD14 but is mediated by serum-derived sCD14.

Efficient gene activation system on mammalian cell chromosomes using recombinant adenovirus producing Cre recombinase

To develop a method for activating genes located on cell chromosomes, an on/off switching unit regulated by the site-specific recombinase Cre was constructed. The switching unit was designed to express firstly the neo gene and secondly the reporter lacZ gene by Cre-mediated excisional deletion of the neo gene. CV1 cell lines bearing the switching unit on a cell chromosome were isolated and activation of the lacZ gene was examined after infection with a Cre-producing recombinant adenovirus. In one cell line virtually 100% of the cells stably expressed the lacZ gene, whereas in another cell line lacZ-expressing cell populations reached only to about 90% and decreased after cell divisions. The Southern blot analyses showed that the latter type of cells contained a head-to-tail array of the switching units, and that consequently the lacZ-expressing units were excised from a cell chromosome and present as extrachromosomal circular DNAs. These results showed that the system offers efficient activation of genes introduced into cell chromosomes and that the organization of the reporter units are important for efficiency and duration of the activated gene expression.

Risk of clot formation with ionic and nonionic contrast media in cerebral angiography. Tama Contrast Media Study Group

RATIONALE AND OBJECTIVES

The introduction of low-osmolality contrast media has improved patient tolerance to angiographic procedures. However, nonionic contrast media may be associated with an increase in the risk of clot formation. The objective of this study was to test whether there is more clotting with nonionic agents than with ionic agents.

METHODS

Ninety-eight patients undergoing transfemoral cerebral angiography were randomly assigned to receive ionic (ioxaglate) (n = 62) or nonionic (iopamidol or iohexol) (n = 36) contrast material. Incidence of clot formation was examined by observation of catheters.

RESULTS

Clot formation was found in 4.8% of patients in the ionic contrast material group and 22.2% of patients in the nonionic contrast material group (P < .05).

CONCLUSION

Nonionic contrast media resulted in a statistically significantly higher incidence of clot formation than ionic media during cerebral catheter angiography. These results suggest that ionic contrast media are preferable in patients with risk of thrombosis.

[Atherosclerosis and clinical examination: epidemiology of stroke and ischemic heart disease]

We discussed the risk factors for stroke and ischemic heart disease (IHD) as a main atherosclerotic disease. We showed that hypertension was the most principal risk factor for both cerebral hemorrhage and cerebral infarction, and the increase of total cholesterol (TCH) was inversely related with the incidence of cerebral hemorrhage. Many of the cerebral infarctions occurred where a large number of the cerebral hemorrhages did. We indicated that the mechanism of occurrence was different between stroke and IHD. In Japan, TCH has been recognized as a risk factor for IHD as same as western countries, but there are not many IHD. The mean of TCH was lower before one or two decade. But, it has increased in the last decade, and recently is nearing the level of American people in the thirties and forties. Death statistics of IHD became more accurate in Japan by reason for revision of the death certificate form from ICD-9 to ICD-10. The recognition of IHD death statistics will be changed. Incidence of stroke has been decreasing because of the decrease of hypertension. However, we will have to reconsider a preventive measure of IHD.

Identification of two Xenopus laevis genes, xMCM2 and xCDC46, with sequence homology to MCM genes involved in DNA replication

The Schizosaccharomyces pombe genes, nda1 and nda4, are essential for the normal regulation of DNA replication and belong to the MCM gene family. This gene family includes Saccharomyces cerevisiae MCM2, MCM3, MCM5/CDC46 and CDC47, S. pombe nda1, nda4, cdc21 and mis5, and genes encoding human BM28, P1MCM3 and P1.1MCM3 and mouse P1MCM3, most of which are considered to be required for the initiation of DNA replication. We isolated two homologues of the MCM genes, xMCM2 and xCDC46, from a Xenopus laevis cDNA library using the polymerase chain reaction (PCR) method. The predicted amino acid (aa) sequences of xMCM2 and xCDC46 are most similar to those of human BM28 (78% identity) and S. pombe Nda4 (48% identity), respectively. By Western blot analysis using anti-xMCM2 and anti-xCDC46 polyclonal antibodies (Ab) raised against glutathione S-transferase (GST)::xMCM2 or GST::xCDC46 fusion proteins, xMCM2 and xCDC46 were identified as 120- and 95-kDa proteins, respectively. When either xMCM2 or xCDC46 was immunoprecipitated with the specific Ab, the other was also co-precipitated. These results suggest that xMCM2 and xCDC46 physically interact with each other.

Prevalence of Mycoplasma genitalium in men with gonococcal urethritis

A significant association of Mycoplasma genitalium with non-gonococcal urethritis has been reported, but the prevalence of this mycoplasma in men with gonococcal urethritis has not been so well studied. In this study, we examined urethral swab specimens from 45 Japanese male patients with gonococcal urethritis for the presence of M. genitalium by using a polymerase chain reaction-based assay. We also sought Chlamydia trachomatis by an enzyme immunoassay (Chlamydiazyme). Of the 45 specimens, 2 (4.4%) were positive for the mycoplasma and 12 (26.7%) were positive for C. trachomatis. The findings suggest that M. genitalium may be a cause not only of non-gonococcal urethritis but also of postgonococcal urethritis.

Catalytic activities of hammerhead ribozymes with a triterpenoid linker instead of stem/loop II

A minizyme is a hammerhead ribozyme with short oligonucleotide linkers instead of stem/loop II. In a previous study we demonstrated that a minizyme with high-level activity forms a dimeric structure with a common stem II (Amontov and Taira, J. Am. Chem. Soc., 118 (1996) 1624-1628). As a continuation of this study, we recently examined whether a short oligonucleotide linker at stem/loop II could be replaced by a triterpenoid linker and whether the resulting minizymes with bulky hydrophobic groups would form dimeric structures. In contrast to the minizyme with high-level activity that we characterized in the previous study, minizymes that contained a triterpenoid group had low cleavage activities. The nature of the dependence of the activity on the concentration of ribozyme revealed that these minizymes with a triterpenoid group do not form dimeric structures. Thus, the low activities of these structures can be attributed to their failure to form dimers.

Rapid detection of point mutations of the Neisseria gonorrhoeae gyrA gene associated with decreased susceptibilities to quinolones

Mutations in the gyrA gene resulting in amino acid changes at Ser-91 and Asp-95 are significantly associated with decreased susceptibilities to quinolones in Neisseria gonorrhoeae. To detect these mutations, we developed a rapid and simple assay based on amplification of the region of the gyrA gene containing the mutation sites by PCR and digestion of the PCR product with a restriction enzyme. A naturally occurring HinfI restriction site was present in the region containing the Ser-91 codon, and an artificial HinfI restriction site was created in the region containing the Asp-95 codon by the method of primer-specified restriction site modification. The mutations generating alterations at Ser-91 and Asp-95 were detected as restriction fragment length polymorphisms of the PCR products digested with HinfI. Fifty-five clinical strains of N. gonorrhoeae were examined for mutations in the gyrA gene by this method. Mutations at Ser-91 and/or Asp-95 were detected in all the 31 strains in which the mutations had been confirmed by DNA sequencing. Our method allows simultaneous testing of a large number of strains and provides results within 8 h. This rapid and simple assay could be a useful screening device for genetic alterations associated with decreased susceptibilities to quinolones in N. gonorrhoeae and could facilitate epidemiological studies on clinical isolates of N. gonorrhoeae with decreased susceptibilities to quinolones.

Effect of mitochondrial and/or cytosolic glycerol 3-phosphate dehydrogenase overexpression on glucose-stimulated insulin secretion from MIN6 and HIT cells

The glycerol phosphate shuttle consists of FAD-linked mitochondrial glycerol 3-phosphate dehydrogenase (mGPDH) and its cytosolic NAD-linked isoform (cGPDH). Impaired mGPDH activity has recently been suggested to be one of the primary causes of insulin secretory defects in beta-cells. We found that mGPDH and cGPDH activities in MIN6 cells are comparable to those of isolated islets and higher than those in HIT cells by eightfold and threefold, respectively. Therefore, we selected the MIN6 cell line as a beta-cell model with normally regulated insulin secretion and normal shuttle enzyme activities and the HIT cell line as a beta-cell model with impaired insulin secretion and lower activities of these enzymes. The role of these dehydrogenases in glucose-stimulated insulin secretion was addressed by examining the effects of overexpression of mGPDH and/or cGPDH via recombinant adenoviruses in these cells. Infection with recombinant adenovirus with a cDNA encoding the Escherichia coli beta-galactosidase gene resulted in expression of its gene in 90% of MIN6 and HIT cells. Infection with a recombinant adenovirus with mGPDH cDNA (Adex1CAmGPDH) caused 2.1-fold and 5.7-fold increases in dehydrogenase activity as compared with those of control MIN6 and HIT cells, respectively. Infection with a recombinant adenovirus with cGPDH cDNA (Adex1CAcGPDH) caused a more than 50-fold increase in activity in both cell lines. Glycerol phosphate shuttle flux, as estimated by [2-3H]glycerol conversion to [3H]H2O, was increased to 120-130% by infection with Adex1CAmGPDH, but not with Adex1CAcGPDH infection, in both MIN6 and HIT cells. No further increase in flux through the glycerol phosphate shuttle was detected when the cells were infected with Adex1CAmGPDH together with Adex1CAcGPDH. Furthermore, neither [U-14C]glucose oxidation nor the insulin secretory response to glucose was affected in either cell line. Thus, mGPDH abundance in MIN6 and HIT cells is not directly related to their insulin secretory capacity in response to glucose, and reduced expression of mGPDH is not the primary cause of abnormal insulin secretory responses in HIT cells. The present data indicate that the emerging hypothesis pointing to mGPDH deficiency as a possible cause of NIDDM needs to be carefully evaluated.