3. Insulin resistance and atherosclerosis.
Explore the source record for details and available documents.
Arteriosclerosis↗
Biomedical subjects
Nobuhiro Yamada
Publications and source records attributed to Nobuhiro Yamada.
Cerebral hemorrhagic infarction after radiation for pituitary adenoma.
We report a case of cerebral hemorrhagic infarction after radiation for pituitary adenoma. A 55-year-old woman was hospitalized to check for aldosteronism, post-operative pituitary function, and recurrence of thyroid cancer. She had short-term memory disturbance beginning two months prior to admission. Brain MRI showed a T1 and T2 high intensity lesion of her left anterolateral thalamus. Brain MRA revealed a narrowing in her left middle cerebral artery. The abnormal brain lesion was diagnosed as cerebral hemorrhagic infarction. She had received radiation therapy for pituitary adenoma 20 years earlier. It was considered that her cerebral hemorrhagic infarction was caused by radiation therapy.
Adenoma↗
Lipolysis in the absence of hormone-sensitive lipase: evidence for a common mechanism regulating distinct lipases.
Hormone-sensitive lipase (HSL) is presumed to be essential for lipolysis, which is defined as the mobilization of free fatty acids from adipocytes. In the present study, we investigated the effects of various lipolytic hormones on the lipolysis in adipocytes derived from mouse embryonic fibroblasts (MEF adipocytes) prepared from HSL-deficient mice (HSL-/-). HSL-/- MEF differentiated into mature adipocytes in a manner indistinguishable from that of wild-type mice. Both isoproterenol (ISO) and tumor necrosis factor (TNF)-alpha stimulated the rate of lipolysis in HSL-/- MEF adipocytes, although to a lesser extent than in wild-type cells, and these lipolytic activities were inhibited by H-89, a cAMP-dependent protein kinase inhibitor, and troglitazone, respectively. Thus, the responses of the residual lipolytic activity to lipolytic hormones and TNF-alpha were well conserved in the absence of HSL. Extracts from HSL-/- MEF adipocytes hydrolyzed triacylglycerol (TG) but not cholesterol ester, indicating that the residual lipolytic activity was mediated by another TG-specific lipase. The TG lipase activity, which was decreased in cytosolic fraction in response to ISO, was increased in fat cake fraction. Therefore, translocation of the TG lipase may explain, at least partially, the ISO-stimulated lipolysis in HSL-/- adipocytes. In conclusion, lipolysis is mediated not only by HSL but also by the non-HSL TG lipase, whose responses to lipolytic hormones are similar to those of HSL. We propose that both lipases are regulated by common mechanism of lipolysis.
Adipocytes↗
The long-term effects of self-management education for patients with type 2 diabetes on glycemic control: response to Norris et al.
Explore the source record for details and available documents.
Adult↗
Report of the Japan Atherosclerosis Society (JAS) Guideline for Diagnosis and Treatment of Hyperlipidemia in Japanese adults.
This paper described the Guideline for Diagnosis and Management of Hyperlipidemias for Prevention of Atherosclerosis proposed by The Japan Atherosclerosis Society (JAS) Guideline Investigating Committee (1,995-2,000) under the auspices of the JAS Board of Directors. 1) The guideline defines the diagnostic criteria for serum total cholesterol (Table 1), LDL-cholesterol (Table 1), triglycerides (Table 4) and HDL-cholesterol (Table 7). It also indicates the desirable range (Table 1), the initiation levels of management (Table 2) and the target levels of treatment (Table 2) for total and LDL-cholesterol. 2) Though both total and LDL-cholesterol are shown as atherogenic parameter in the guideline, the use of LDL-cholesterol, rather than total cholesterol, is encouraged in daily medical practice and lipid-related studies, because LDL-cholesterol is more closely related to atherosclerosis. 3) Elevated triglycerides and low HDL-cholesterol are included in the risk factors, since no sufficient data have been accumulated to formulate the guideline for these two lipid disorders. 4) Emphasis is laid on evaluation of risk factors of each subject before starting any kind of treatment (Table 2). 5) This guideline is applied solely for adults (age 20-64). Lipid abnormalities in children or the youth under age 19, and the elderly with an age over 65 have to be evaluated by their own standard. 6) This part of the guideline gives only the diagnostic aspects of hyperlipidemias. The part of management and treatment will follow in the second section of the guideline that will be published in future.
Adult↗
Insulin sensitizers and atherosclerosis.
It is surprising that only about ten years after the concept of insulin resistance in diabetes mellitus was established, the role of insulin resistance in the development of atherosclerosis has been discussed and clarified. Insulin resistance predisposes the development of glucose intolerance, hyperlipidemia, and hypertension; the cluster of these abnormalities is referred to as multiple risk factor syndrome and it increases the risk of atherosclerosis. A few insulin sensitizers have recently begun to be used in the therapy for diabetic patients. However, the inhibitory effects of these insulin sensitizers against atherosclerosis have not been studied in large-scale clinical trials because these drugs were approved for clinical treatment only several years ago. Accordingly, this review presents a summary of the previous studies on the anti-atherogenic effects of insulin sensitizers by different strategies and provides information on why it is expected that insulin sensitizers will be used as anti-atherogenic drugs.
Animals↗
Clinical effects of rosuvastatin, a new HMG-CoA reductase inhibitor, in Japanese patients with primary hypercholesterolemia: an early phase II study.
The effects and tolerability of the new HMG-CoA reductase inhibitor rosuvastatin were assessed in 68 hypercholesterolemic Japanese patients (22 men and 46 postmenopausal women; age range 28-72 years) in a multicenter, double-blind, dose-ranging, early phase II study. Patients were randomized into three groups and received once-daily doses of 1, 2, or 4 mg rosuvastatin. Sixty evaluable patients (19 men and 41 women) with mean total cholesterol (TC) 294 mg/dl (7.60 mmol/l) and mean triglyceride (TG) 150 mg/dl (1.69 mmol/l) provided data in the efficacy analysis based on percentage changes in lipids at 4 and 8 weeks. All doses of rosuvastatin improved lipid parameters after both 4 and 8 weeks of therapy. On average, TC decreases were 22-29%, low-density lipoprotein cholesterol (LDL-C) decreases 32-42%, TG decreases 2% to 22%, and HDL-C increases 3-7%. There were no remarkable differences between efficacy at 4 and at 8 weeks, and dose-dependent reductions were noted for LDL-C, with 30, 39, and 42% decreases in the 1-, 2-, and 4-mg/ day dose groups, respectively, at 8 weeks. The drug was well tolerated over the 8 weeks of therapy. These preliminary results indicate that rosuvastatin is a potent cholesterol-lowering agent, capable of achieving marked reductions in LDL-C even at low doses.
Adult↗
Dual regulation of mouse Delta(5)- and Delta(6)-desaturase gene expression by SREBP-1 and PPARalpha.
In the process of seeking sterol regulatory element-binding protein 1a (SREBP-1a) target genes, we identified and cloned a cDNA clone encoding mouse Delta(5)-desaturase (D5D). The hepatic expression of D5D as well as Delta(6)-desaturase (D6D) was highly activated in transgenic mice overexpressing nuclear SREBP-1a, -1c, and -2. Disruption of the SREBP-1 gene significantly reduced the expression of both desaturases in the livers of SREBP-1-deficient mice refed after fasting. The hepatic expression of both desaturases was downregulated by dietary PUFA, which were reported to suppress SREBP-1c gene expression. Sustained expression of hepatic nuclear SREBP-1c protein in the transgenic mice abolished the PUFA suppression of both desaturases. Although these data suggested that SREBP-1c regulates D5D and D6D expression, there was no difference in either the D5D or D6D mRNA level between fasted and refed normal mouse livers, indicating a mechanism for fasting induction of both desaturases. Administration of fibrate, a pharmacological ligand for peroxisome proliferator activating receptor alpha (PPARalpha), caused a significant increase in expression of both desaturases. The data suggested that D5D and D6D expression is dually regulated by SREBP-1c and PPARalpha, two reciprocal transcription factors for fatty acid metabolism, and could be involved in lipogenic gene regulation by producing PUFA.
Amino Acid Sequence↗
[Fibrates].
Fibrates regulates not only plasma lipid metabolism but vascular biology by activating nuclear receptor peroxisome proliferating activated alpha (PPAR alpha). Major effects on plasma lipid levels are lowering plasma triglyceride level and elevating plasma HDL cholesterol level, whereas its effect on plasma cholesterol level is moderate compared to HMG-CoA reductase inhibitor. As a mechanism for its effects on plasma lipid levels and atherosclerosis, recent studies reported that fibrates activates various genes involved in metabolism of remnants and HDL such as lipoprotein lipase, apo AI, apo AII, and apo CIII genes through the interaction with PPAR alpha, lowering atherogenic lipoproteins and elevating anti-atherogenic lipoproteins. Furthermore, fibrates may influence the process of atherosclerosis by modifying inflammatory process in vascular wall. Recent clinical studies demonstrated that fibrates significantly reduce cardiovascular events in patients with either hypertriglyceridemia or low HDL cholesterol level.
Bezafibrate↗
Cloning and characterization of a mammalian fatty acyl-CoA elongase as a lipogenic enzyme regulated by SREBPs.
The mammalian enzyme involved in the final elongation of de novo fatty acid biosynthesis following the building of fatty acids to 16 carbons by fatty acid synthase has yet to be identified. In the process of searching for genes activated by sterol regulatory element-binding protein 1 (SREBP-1) by using DNA microarray, we identified and characterized a murine cDNA clone that is highly similar to a fatty acyl-CoA elongase gene family such as Cig30, Sscs, and yeast ELOs. Studies on the cells overexpressing the full-length cDNA indicate that the encoded protein, designated fatty acyl-CoA elongase (FACE), has a FACE activity specific for long-chains; C12-C16 saturated- and monosaturated-fatty acids. Hepatic expression of this identified gene was consistently activated in the livers of transgenic mice overexpressing nuclear SREBP-1a, -1c, or -2. FACE mRNA levels are markedly induced in a refed state after fasting in the liver and adipose tissue. This refeeding response is significantly reduced in SREBP-1 deficient mice. Dietary PUFAs caused a profound suppression of this gene expression, which could be restored by SREBP-1c overexpression. Hepatic FACE expression was also highly up-regulated in leptin-deficient ob/ob mice. Hepatic FACE mRNA was markedly increased by administration of a pharmacological agonist of liver X-activated receptor (LXR), a dominant activator for SREBP-1c expression. These data indicated that this elongase is a new member of mammalian lipogenic enzymes regulated by SREBP-1, playing an important role in de novo synthesis of long-chain saturated and monosaturated fatty acids in conjunction with fatty acid synthase and stearoyl-CoA desaturase.
Acyl Coenzyme A↗
Transcriptional activities of nuclear SREBP-1a, -1c, and -2 to different target promoters of lipogenic and cholesterogenic genes.
Recent studies on the in vivo roles of the sterol regulatory element binding protein (SREBP) family indicate that SREBP-2 is more specific to cholesterogenic gene expression whereas SREBP-1 targets lipogenic genes. To define the molecular mechanism involved in this differential regulation, luciferase-reporter gene assays were performed in HepG2 cells to compare the transactivities of nuclear SREBP-1a, -1c, and -2 on a battery of SREBP-target promoters containing sterol regulatory element (SRE), SRE-like, or E-box sequences. The results show first that cholesterogenic genes containing classic SREs in their promoters are strongly and efficiently activated by both SREBP-1a and SREBP-2, but not by SREBP-1c. Second, an E-box containing reporter gene is much less efficiently activated by SREBP-1a and -1c, and SREBP-2 was inactive in spite of its ability to bind to the E-box. Third, promoters of lipogenic enzymes containing variations of SRE (SRE-like sequences) are strongly activated by SREBP-1a, and only modestly and equally by both SREBP-1c and -2. Finally, substitution of the unique tyrosine residue within the basic helix-loop-helix (bHLH) portion of nuclear SREBPs with arginine, the conserved residue found in all other bHLH proteins, abolishes the transactivity of all SREBPs for SRE, and conversely results in markedly increased activity of SREBP-1 but not activity of SREBP-2 for E-boxes. These data demonstrate the different specificity and affinity of nuclear SREBP-1 and -2 for different target DNAs, explaining a part of the mechanism behind the differential in vivo regulation of cholesterogenic and lipogenic enzymes by SREBP-1 and -2, respectively.
ATP Citrate (pro-S)-Lyase↗
[Large-scale randomized intervention trial on diabetes in Japan].
Explore the source record for details and available documents.
Diabetes Mellitus↗
[Molecular mechanisms of diabetic atherosclerosis].
Explore the source record for details and available documents.
Arteriosclerosis↗
Polyunsaturated fatty acids suppress sterol regulatory element-binding protein 1c promoter activity by inhibition of liver X receptor (LXR) binding to LXR response elements.
Previous studies have demonstrated that polyunsaturated fatty acids (PUFAs) suppress sterol regulatory element-binding protein 1c (SREBP-1c) expression and, thus, lipogenesis. In the current study, the molecular mechanism for this suppressive effect was investigated with luciferase reporter gene assays using the SREBP-1c promoter in HEK293 cells. Consistent with previous data, the addition of PUFAs to the medium in the assays robustly inhibited the SREBP-1c promoter activity. Deletion and mutation of the two liver X receptor (LXR)-responsive elements (LXREs) in the SREBP-1c promoter region eliminated this suppressive effect, indicating that both LXREs are important PUFA-suppressive elements. The luciferase activities of both SREBP-1c promoter and LXRE enhancer constructs induced by co-expression of LXRalpha or -beta were strongly suppressed by the addition of various PUFAs (arachidonic acid > eicosapentaenoic acid > docosahexaenoic acid > linoleic acid), whereas saturated or mono-unsaturated fatty acids had minimal effects. Gel shift mobility and ligand binding domain activation assays demonstrated that PUFA suppression of SREBP-1c expression is mediated through its competition with LXR ligand in the activation of the ligand binding domain of LXR, thereby inhibiting binding of LXR/retinoid X receptor heterodimer to the LXREs in the SREBP-1c promoter. These data suggest that PUFAs could be deeply involved in nutritional regulation of cellular fatty acid levels by inhibiting an LXR-SREBP-1c system crucial for lipogenesis.
Animals↗
Antioxidants and an inhibitor of advanced glycation ameliorate death of retinal microvascular cells in diabetic retinopathy.
BACKGROUND: Pericyte ghosts and acellular capillaries are well known as early histological changes resulting from diabetic retinopathy. These histological changes mean that the cell death of retinal microvessels has accelerated. It was reported that apoptosis of retinal microvascular cells (RMCs) was increased in diabetic patients. Therefore, we investigated apoptosis of RMCs in Goto-Kakizaki (GK) rats, a type 2 diabetic model, and involvement with antioxidants (a combination of vitamins C and E) or a novel inhibitor of advanced glycation, OPB-9195. METHODS: GK rats were treated with the antioxidants combination or OPB-9195 for 36 weeks. We obtained isolated preparations of the vascular network from their retinas by trypsin digestion. Apoptosis of retinal vascular cells was detected with terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. RESULTS: We found that apoptosis of RMCs was increased in the diabetic GK rats. Furthermore, a combination of vitamins C and E and an advanced glycation end-products inhibitor mostly inhibited this increased apoptosis. CONCLUSIONS: We concluded that apoptosis of RMCs was a good marker that indicates the progression of diabetic retinopathy in GK rats. Both oxidative stress and the accumulation of advanced glycation end-products appears to promote the apoptosis of retinal microvascular cells, and antioxidants or advanced glycation end-products inhibitors might ameliorate diabetic retinopathy.
Animals↗
Erythrocytic sorbitol contents in diabetic patients correlate with blood aldose reductase protein contents and plasma glucose levels, and are normalized by the potent aldose reductase inhibitor fidarestat (SNK-860).
The accumulation of sorbitol by the activated polyol pathway is considered to be a major cause of diabetic neuropathy. Because the erythrocytic sorbitol contents reportedly reflects that in nerves, erythrocytic sorbitol measurement would be useful for confirming the effect of an aldose reductase inhibitor (ARI). In this study, we examined erythrocytic sorbitol contents in healthy subjects and diabetic patients under fasting and postprandial conditions. Then, the contributions of blood aldose reductase (AR) contents and plasma glucose levels to the accumulated erythrocytic sorbitol contents were also analyzed. Erythrocytic sorbitol contents in the healthy subjects were 11.7 and 12.5-12.6 nmol/g Hb in fasting and postprandial status, respectively. In contrast, the erythrocytic sorbitol contents in diabetic patients were apparently higher (approximately 2.5-fold), but fidarestat treatment restored the elevated erythrocytic sorbitol contents to normal. In the diabetic patients, erythrocytic sorbitol contents were highly correlated with blood AR contents multiplied by the plasma glucose levels, whereas in the normal and fidarestat-treated diabetic patients no such correlation was observed. Taken together, these results suggest both the blood AR contents and the plasma glucose levels are factors determining erythrocytic sorbitol contents in diabetic patients. Notably, the potent ARI fidarestat was shown to normalize elevated erythrocytic sorbitol contents.
Aldehyde Reductase↗
Fidarestat (SNK-860), a potent aldose reductase inhibitor, normalizes the elevated sorbitol accumulation in erythrocytes of diabetic patients.
Sorbitol accumulation in nerves has been regarded as one of the major causes of diabetic neuropathy. In this study, fidarestat (SNK-860; 1 mg daily), a potent new aldose reductase inhibitor (ARI), or the commercially available ARI epalrestat (150 mg daily), was administered for 4 weeks to 58 Type 2 diabetic patients. Treatment with these drugs had no effect on glycemic control, judging from plasma glucose and HbA(1c) levels. However, fidarestat treatment normalized the elevated sorbitol content of erythrocytes under fasting as well as postprandial conditions. In contrast, the effect of epalrestat was minimal. There were no major side effects with fidarestat. Thus, fidarestat is considered to be a potent and promising ARI, possibly useful for both preventing and treating diabetic neuropathy. Further studies are needed to clarify how much the occurrence and progression of diabetic neuropathy are inhibited by normalizing sorbitol elevation with fidarestat treatment.
Aldehyde Reductase↗