Retrospective analysis of medical costs and resource utilization for severe hypoglycemic events in patients with type 2 diabetes in Japan.

AIMS/INTRODUCTION: The present study aimed to describe hospital utilization and examine actual medical costs for severe hypoglycemic events in patients with type 2 diabetes mellitus in Japan. MATERIALS AND METHODS: Medical resource utilization associated with severe hypoglycemia was evaluated using a receipt database of acute-care hospitals in Japan. Patients with type 2 diabetes treated with antihyperglycemic agents were included. Severe hypoglycemic events were identified and divided into two groups: with or without hospitalization. Total and attributable medical costs per event were calculated based on the actual medical treatment after severe hypoglycemic events. Attributable costs were estimated from the receipt codes directly associated with the treatment of severe hypoglycemia. RESULTS: In the hospitalized patients, the median length of hospital stay was 11 days, and the median total and attributable medical costs were ¥402,081 and ¥302,341, respectively. The majority of the hospitalized patients underwent a radiographic examination and general blood tests. Apart from the hospitalization costs, the costs associated with diagnosis accounted for 29.6% of the total medical costs. In the outpatients, 60.6% visited hospitals only once for the severe hypoglycemic event, whereas 11.4% visited hospitals daily for a week after the severe hypoglycemic event. The mean number of hospital visits of the outpatient after a severe hypoglycemic event was 2.7 ± 2.6 days. The median total and attributable medical costs were ¥265,432 and ¥4,628, respectively. CONCLUSIONS: Significant medical resources are used for the treatment of severe hypoglycemic events of patients with type 2 diabetes in Japan.

Incidence rate and patient characteristics of severe hypoglycemia in treated type 2 diabetes mellitus patients in Japan: Retrospective Diagnosis Procedure Combination database analysis.

AIMS/INTRODUCTION: To evaluate the incidence rate of and identify factors associated with severe hypoglycemic episodes in patients with treated type 2 diabetes mellitus. MATERIALS AND METHODS: Using Diagnosis Procedure Combination hospital-based medical database, we carried out a retrospective cohort study to assess the incidence rate of severe hypoglycemia in treated type 2 diabetes mellitus patients. We evaluated the associations between severe hypoglycemia and age, sex, complications, and current use of insulin or sulfonylurea (SU) in a nested case-control study. RESULTS: Of 166,806 eligible patients, 1,242 had episodes of severe hypoglycemia during the observational period. The incidence rate of the first hypoglycemic events was 3.70/1,000 patient years. Based on the nested case-control analysis, age was associated with hypoglycemic events with adjusted odds ratios (ORs) of 1.64 or 65-74-year-old patients and 3.79 for ≥75-year-old patients in comparison with 20-64-year-old patients. Comorbidities, such as cognitive impairment, cancer, macrovascular disease and diabetic complications (retinopathy, nephropathy and neuropathy), were associated with severe hypoglycemia, with adjusted ORs ranging from 1.25 to 3.80. Severe hypoglycemic events also increased in patients with current use of both SU and insulin, either SU or insulin, with adjusted ORs of 18.36, 6.31 or 14.07, respectively, compared with patients with other antihyperglycemic agents. In patients with an SU glimepiride, adjusted ORs increased dose-dependently from 3.65 (≤1 mg) to 13.34 (>2 mg). CONCLUSIONS: The incidence rate of severe hypoglycemia in this cohort was 3.70/1,000 patient years. Age, cognitive impairment, cancer, diabetic complications, current use of insulin + SU and SU dosage were identified as risk factors for severe hypoglycemia.

Analysis of development of lesions in mice with serine palmitoyltransferase (SPT) deficiency -Sptlc2 conditional knockout mice-.

Serine palmitoyltransferase (SPT) is the enzyme which catalyzes the first step of the biosynthesis of sphingolipids. However, the precise roles of SPT in vivo are not well understood, since complete knockout (KO) of genes which compose SPT results in a fetal lethal phenotype. A conditional KO (cKO) mouse of SPT long chain base 2 (Sptlc2) was therefore developed, and the effects of Sptlc2 deficiency were examined. Single cell necrosis in the epithelia of the crypts of the small and large intestines was observed as early as 24 h after induction of knockout. At 48 h after induction, decreases in spleen and thymus weights and decreases in numbers of reticulocytes and lymphocytes were observed in cKO mice, and single cell necrosis in the intestine became prominent. At 72 h after induction, decreases in body weight, spleen and thymus weights, and numbers of reticulocytes and lymphocytes became obvious in cKO mice. Histologically, atrophy of gastrointestinal mucosa and lymphoid necrosis as well as depletion of lymphoid and hematopoietic tissues were observed. These findings suggest that SPT plays important roles in the maintenance of the gastrointestinal mucosa, especially in the proliferation of the mucosal epithelial cells, and that deficiency of Sptlc2 induces necrotic lesions in gastrointestinal cells followed by atrophic change of the tissue in short term.

Direct interaction of nuclear liver X receptor-beta with ABCA1 modulates cholesterol efflux.

Cholesterol is an essential component of eukaryotic cells; at the same time, however, hyperaccumulation of cholesterol is harmful. Therefore, the ABCA1 gene, the product of which mediates secretion of cholesterol, is highly regulated at both the transcriptional and post-transcriptional levels. The transcription of ABCA1 is regulated by intracellular oxysterol concentration via the nuclear liver X receptor (LXR)/retinoid X receptor (RXR); once synthesized, ABCA1 protein turns over rapidly with a half-life of 1-2 h. Here, we show that the LXRbeta/RXR complex binds directly to ABCA1 on the plasma membrane of macrophages and modulates cholesterol secretion. When cholesterol does not accumulate, ABCA1-LXRbeta/RXR localizes on the plasma membrane, but is inert. When cholesterol accumulates, oxysterols bind to LXRbeta, and the LXRbeta/RXR complex dissociates from ABCA1, restoring ABCA1 activity and allowing apoA-I-dependent cholesterol secretion. LXRbeta can exert an immediate post-translational response, as well as a rather slow transcriptional response, to changes in cellular cholesterol accumulation. Thus, we provide the first demonstration that protein-protein interaction suppresses ABCA1 function. Furthermore, we show that LXRbeta is involved in both the transcriptional and post-transcriptional regulation of the ABCA1 transporter.

Hepatic de novo lipogenesis is present in liver-specific ACC1-deficient mice.

Acetyl coenzyme A (acetyl-CoA) carboxylase (ACC) catalyzes carboxylation of acetyl-CoA to form malonyl-CoA. In mammals, two isozymes exist with distinct physiological roles: cytosolic ACC1 participates in de novo lipogenesis (DNL), and mitochondrial ACC2 is involved in negative regulation of mitochondrial beta-oxidation. Since systemic ACC1 null mice were embryonic lethal, to clarify the physiological role of ACC1 in hepatic DNL, we generated the liver-specific ACC1 null mouse by crossbreeding of an Acc1(lox(ex46)) mouse, in which exon 46 of Acc1 was flanked by two loxP sequences and the liver-specific Cre transgenic mouse. In liver-specific ACC1 null mice, neither hepatic Acc1 mRNA nor protein was detected. However, to compensate for ACC1 function, hepatic ACC2 protein and activity were induced 1.4 and 2.2 times, respectively. Surprisingly, hepatic DNL and malonyl-CoA were maintained at the same physiological levels as in wild-type mice. Furthermore, hepatic DNL was completely inhibited by an ACC1/2 dual inhibitor, 5-tetradecyloxyl-2-furancarboxylic acid. These results strongly demonstrate that malonyl-CoA from ACC2 can access fatty acid synthase and become the substrate for the DNL pathway under the unphysiological circumstances that result with ACC1 disruption. Therefore, there does not appear to be strict compartmentalization of malonyl-CoA from either of the ACC isozymes in the liver.

Detection of ABCA7-positive cells in salivary glands from patients with Sjögren's syndrome.

ABCA7 is a member of the subfamily A of adenosine triphosphate-binding cassette (ABC) proteins, and highly homologous to ABCA1, which mediates the release of cellular cholesterol and phospholipid to form high-density lipoprotein. ABCA1 and ABCA7 contain two large extracellular domains, ECD1 and 2, which are thought to be important for their functions. Interestingly, part of ECD1 of ABCA7 is deposited as an autoantigen of Sjögren's syndrome. To determine the relationship between ABCA7 and Sjögren's syndrome, an immunohistochemical study was conducted with salivary gland biopsy samples from patients with Sjögren's syndrome. ECD1 of human ABCA7 (amino acids 45-549) was expressed in Escherichia coli as a protein fused with glutathione-S-transferase and a monoclonal antibody, KM3095, was generated. KM3095-immunoreactive cells were observed in salivary glands from 10 of 18 patients with Sjögren's syndrome. Immunostaining of serial sections with the plasma cell marker NCL-PC indicated that most of the plasma cells infiltrating salivary glands of patients with Sjögren's syndrome were KM3095-immunoreactive. Although the pathological or biological significance is not clear, it will be intriguing to further examine the relationship between ABCA7 and Sjögren's syndrome.

Human ABCA7 supports apolipoprotein-mediated release of cellular cholesterol and phospholipid to generate high density lipoprotein.

Apolipoprotein-mediated release of cellular cholesterol and phospholipids was induced in HEK293 cells by expressing human ATP-binding cassette transporter A7 (ABCA7) and ABC transporter A1 (ABCA1) proteins, whether transient or stable, to generate cholesterol-rich high density lipoprotein (HDL). Green fluorescent protein (GFP) attached at their C termini did not influence the lipid release reactions. Transfected ABCA7-GFP induced apolipoprotein-mediated assembly of cholesterol-containing HDL also in L929 cells, which otherwise generate only cholesterol-deficient HDL with their endogenous ABCA1. Time-dependent release of cholesterol and phospholipid by apolipoprotein A (apoA)-I was parallel both with ABCA1 and with ABCA7 when highly expressed in HEK293 cells, but dose-dependent profiles of lipid release on apoA-I and apoA-II were somewhat different between ABCA1 and ABCA7. Analyses of the stable clones with ABCA1-GFP (293/2c) and ABCA7-GFP (293/6c) by using the same vector indicated some differences in regulation of their activities by protein kinase modulators. Dibutyryl cyclic AMP increased ABCA1-GFP and the release of cholesterol and phospholipid in 293/2c but increased neither ABCA7-GFP nor the lipid release in 293/6c. Expression of ABCA1-GFP- and apoA-I-mediated lipid release were enhanced in parallel by phorbol 12-myristate 13-acetate (PMA) in 293/2c cells. In contrast, the same treatment of 293/6c increased ABCA7-GFP, but apoA-I-mediated lipid release was significantly suppressed. Despite these different responses to PMA, all of the effects of PMA were reversed by a specific protein kinase C inhibitor Gö6976, suggesting that the changes were in fact due to protein kinase C activation. A thiol protease inhibitor, N-acetyl-Leu-Leu-norleucinal, increased the protein levels of ABCA1-GFP in 293/2c and ABCA7-GFP in 293/6c, indicating their common degradation pathway. The data indicated that human ABCA7 would compensate the function of ABCA1 for release of cell cholesterol in a certain condition(s), but post-transcriptional regulation of their activity is different.

Posttranscriptional regulation of human ABCA7 and its function for the apoA-I-dependent lipid release.

ABCA7 is expressed predominantly in myelo-lymphatic tissues or reticuloendothelial cells. Physiological role and function of this protein are not fully understood. We isolated the full-length cDNA (type I) and a splicing variant cDNA (type II) of human ABCA7, and developed monoclonal antibodies against extracellular domain (ECD)1 of ABCA7. RT-PCR experiments suggested that human ABCA7 gene produced the type II mRNA in a tissue-specific manner. Immunostaining revealed that the type I ABCA7, expressed in HEK293 cells, was localized to the plasma membrane and ECD1 was exposed to the extracellular space as was the case for ABCA1. HEK293 cells expressing type I ABCA7 showed apoA-I-dependent cholesterol and phospholipid release. In contrast, type II ABCA7 appeared to be localized mainly in endoplasmic reticulum and did not show apoA-I-dependent cholesterol and phospholipid release. Alternative splicing could be involved in the post-transcriptional regulation of the expression and function of human ABCA7.

Effects of mutations of ABCA1 in the first extracellular domain on subcellular trafficking and ATP binding/hydrolysis.

ABCA1 mediates release of cellular cholesterol and phospholipid to form high density lipoprotein (HDL). The three different mutants in the first extracellular domain of human ABCA1 associated with Tangier disease, R587W, W590S, and Q597R, were examined for their subcellular localization and function by using ABCA1-GFP fusion protein stably expressed in HEK293 cells. ABCA1-GFP expressed in HEK293 was fully functional for apoA-I-mediated HDL assembly. Immunostaining and confocal microscopic analyses demonstrated that ABCA1-GFP was mainly localized to the plasma membrane (PM) but also substantially in intracellular compartments. All three mutant ABCA1-GFPs showed no or little apoA-I-mediated HDL assembly. R587W and Q597R were associated with impaired processing of oligosaccharide from high mannose type to complex type and failed to be localized to the PM, whereas W590S did not show such dysfunctions. Vanadate-induced nucleotide trapping was examined to elucidate the mechanism for the dysfunction in the W590S mutant. Photoaffinity labeling of W590S with 8-azido-[alpha-(32)P]ATP was stimulated by adding ortho-vanadate in the presence of Mn(2+) as much as in the presence of wild-type ABCA1. These results suggest that the defect of HDL assembly in R587W and Q597R is due to the impaired localization to the PM, whereas W590S has a functional defect other than the initial ATP binding and hydrolysis.