Atrial fibrillation (AF) is prevalent in patients with obesity and diabetes, and such patients often exhibit cardiac steatosis. Since the role of cardiac steatosis per se in the induction of AF has not been elucidated, the present study was designed to explore the relation between cardiac steatosis and AF. Transgenic (Tg) mice with cardiac-specific overexpression of perilipin 2 (PLIN2) were housed in the laboratory for more than 12 mo before the study. Electron microscopy of the atria of PLIN2-Tg mice showed accumulation of small lipid droplets around mitochondrial chains, and five- to ninefold greater atrial triacylglycerol (TAG) content compared with wild-type (WT) mice. Electrocardiography showed significantly longer RR intervals in PLIN2-Tg mice than in WT mice. Transesophageal electrical burst pacing resulted in significantly higher prevalence of sustained (>5 min) AF (69%) in PLIN2-Tg mice than in WT mice (24%), although it was comparable in younger (4-mo-old) mice. Connexin 43 (Cx43), a gap junction protein, was localized at the intercalated disks in WT atria but was heterogeneously distributed on the lateral side of cardiomyocytes in PLIN2-Tg atria. Langendorff-perfused hearts using the optical mapping technique showed slower and heterogeneous impulse propagation in PLIN2-Tg atria compared with WT atria. Cardiac overexpression of hormone-sensitive lipase in PLIN2-Tg mice resulted in atrial TAG depletion and amelioration of AF susceptibility. The results suggest that PLIN2-induced steatosis is associated with Cx43 remodeling, impaired conduction propagation, and higher incidence of AF in aged mice. Therapies targeting cardiac steatosis could be potentially beneficial against AF in patients with obesity or diabetes.

Recent genome-wide association studies have identified multiple variants that confer risk of type 2 diabetes mellitus (DM). However, established associations explain only a part of the heritability. Thus, even at the genome-wide association studies era, candidate gene approach should be still useful. Recent interventional studies against the renin-angiotensin system (RAS) showed reduction in new onset of DM, implying the system is involved in the onset. We substantiated the hypothesis that genetic variants of RAS have significant association with prevalence of DM. We enrolled to the study consecutive 782 subjects who had consulted our hospitals for mainly lifestyle related diseases. They consisted of 282 (36.1 %) diabetes cases. Genotypes were assayed with genomic DNA for conventional four genes of the RAS, i.e., angiotensin converting enzyme (ACE) insertion/deletion variant, angiotensinogen (AGT) M235T variant, angiotensin II type I receptor (AT1) A1166C variant, and aldosterone synthase (CYP11B2) C-344T variant. Association between the genetic variants of the RAS and prevalence of type 2 DM was tested. A significant association of DM and CYP11B2 genotype was obtained. There was no significant association between DM and ACE, AGT and AT1 variants. A multivariate logistic regression showed that age, gender, and CYP11B2 genotype were independent factors for association to diabetes, the DM risk of CC/CT to TT being 1.40 (95 % CI 1.04–1.90, p = 0.029). Thus, it is concluded that a genetic variant of the RAS should have a modest but significant impact on the onset of type 2 diabetes mellitus.

Miglitol appears to have rapid action, which appears earlier than that of lispro. The combination of miglitol and Mix50 seems effective for the control of PPG and lipid profile in T2D.

The plasma renin activity (PRA) is affected by a number of environmental factors. However, significant heritability has been shown for the activity. A hypothesis that a candidate regulatory single-nucleotide polymorphism, C-5312T, of human renin gene should have a significant effect on PRA was elucidated and updating of independent determinants of PRA was attempted.Cross sectional study.Outpatient study.We enrolled consecutive 810 subjects who had consulted our hospitals for lifestyle-related diseases.Genotypes were assayed with genomic DNA for C-5312T. Among the genetic variants, the difference of PRA was evaluated. Monovariate linear regression analysis was performed to test the correlation between PRA and clinical variables. Finally, stepwise multiple regression analysis was performed to evaluate the independent determinants.On comparing 2 genotype groups, CC/CT and T allele homozygote, the geometric means of PRA were 0.778 and 0.941 ng/ml/h, respectively (F = 5.992, P = 0.015). Monovariate linear regression analysis revealed that a number of variables have a significant correlation with the activity, including urinary salt excretion. A stepwise multivariate regression analysis revealed that renin C-5312T variant (TT) is one of the independent determinants of PRA.Thus, for the first time, a human renin gene variant was associated with a significant increase in PRA as a genetic factor and the independent determinants for the activity were updated including genetic factor.

The renin-angiotensin system (RAS) is important in the onset and course of cardiovascular, kidney, and metabolic disorders. Previous reports showed that the RAS blockade protects organs and suppress the development of type 2 diabetes mellitus. A novel component of the RAS, namely, chromosome 9 open reading frame 3 (C9orf3), was recently identified, however, its effects are unclear. We evaluated whether the genetic variant of C9orf3 is associated with morbidity of hypertension among subjects with type 2 diabetes. We enrolled 382 subjects with type 2 diabetes, 222 of whom were diagnosed with hypertension. Human leukocyte genomic DNA was isolated and a genetic variant was analyzed for a C/T variant of C9orf3 (rs4385527) via PCR analysis. The relationship between the genotype and hypertension morbidity among subjects with diabetes was examined. The proportion of the respective C9orf3 genetic variants were as follows 247 CC, 119 CT, and 16 TT. The risk of hypertension was determined to be 1.58, with a 95% confidence interval of 1.11–2.27. Moreover, the p value was 0.012 for allelic comparison and for Armitage’s trend test, with the C allele identified as the risk factor. Consequently, hypertension was markedly associated with type 2 diabetes in subjects with the C9orf3 variant, exhibiting a nearly 1.6-fold increased risk. The C variant of a new component of the RAS, C9orf3 (rs4385527) might have a considerable impact on the pathogenesis of hypertension in diabetes.

BackgroundThe high heritability of plasma renin activity was confirmed in recent investigations. A variation located near the strong enhancer of the human renin gene (REN), C-5312T, has been shown to have different transcription activity levels depending on its allele: the 5312T allele shows transcription levels that are 45% greater than those of the 5312C allele. The purpose of this study was to confirm the hypothesis that variations in the enhancer region of the REN gene are involved in regulating renal expression of renin.MethodsSixty-four subjects with biopsy-proven renal diseases were included in this study (male/female: 35/29, age 41.9 ± 20.9 years, SBP/DBP 123.1 ± 23.7/73.4 ± 14.8 mmHg, s-Cr 0.93 ± 0.63 mg/dl). A genetic variant of REN, C-5312T, was assayed by PCR-RFLP and the TaqMan method. Total RNAs from a small part of the renal cortex were reverse-transcribed and amplified for REN and GAPDH with a real-time PCR system.ResultsLogarithmically transformed expression values of the relative ratio of REN to GAPDH (10−3) were as follows (mean ± SE): CC (26 cases), 0.016 ± 0.005; CT (33 cases), 0.047 ± 0.021 (p = 0.41 vs. CC); TT (5 cases), 0.198 ± 0.194 (p = 0.011 vs. CC, p < 0.031 vs. CT). Thus, significant differences in REN expression were observed among the genetic variants.ConclusionThe results suggest that variants in the enhancer region of the human renin gene have an effect on the expression levels of renin in renal tissue; this observation is in good accordance with the results of the transcriptional assay.

The liver is the central organ for ketone body production, and HMG-CoA synthase2 (HMGCS2) is a rate-limiting enzyme involved in this process. We reported that fasting markedly increased mRNA expression of HMGCS2 in mouse heart, whereas its protein expression was faint and increased only marginally with fasting. To clarify the pathophysiological role of HMGCS2 in the heart, we generated transgenic (Tg) mice with heart-specific HMGCS2 overexpression and analyzed the effects on metabolic status in the myocardium. Plasma concentrations of β-hydroxybutyrate (βOHB), glucose and free fatty acids were comparable between Tg and wild type (Wt) mice, whereas the cardiac βOHB content in Tg mice was increased 10-fold (fed state) or 2-fold (24h-fasted state) over that of Wt mice. Confocal microscopy demonstrated that the HMGCS2 protein co-localized with a mitochondrial protein, ATP5A, in cardiomyocytes of Tg mice. Transmission electron microscopy showed many swollen mitochondria, some of which contained vacuole-like vesicles and decreased cristae in Tg hearts, and ultrasonography showed impaired systolic function. Microarray gene expression analysis revealed that approximately 800 genes were altered &gt;2-fold in Tg hearts compared with Wt hearts. Among the altered genes, ATF4 and its target genes, including PHGDH, MTHFD2 and ASNS which promote glutathione production, were upregulated in Tg hearts. Consistent with this result, a metabolome analysis performed by capillary electrophoresis-mass spectrometry demonstrated that glutathione was increased in Tg hearts, suggesting an adaptation to mitochondrial stress. In addition, 3 branch-chain amino acids were increased in Tg hearts compared with Wt hearts. These results indicate that myocardial HMGCS2 can produce ketone bodies in mitochondria, leading to mitochondrial stress and cardiac dysfunction. The limited induction of HMGCS2 protein upon fasting might constitute a protective mechanism for cardiomyocytes. Disclosure Y. Zenimaru: None. J. Suzuki: None. T. Nakaya: None. M. Yamada: None. M. Ichikawa: None. S. Sato: None. M. Imagawa: None. F.B. Kraemer: None. T. Konoshita: None. T. Ishizuka: None.

Atrial fibrillation (AF) is prevalent among diabetic patients. Diabetes is also associated with myocardial lipid droplet accumulation (steatosis), which is thought to be a source of intracellular lipotoxicity. Since the relative contribution of cardiac steatosis per se to AF has not been elucidated, the current study was designed to clarify the causal effect of cardiac steatosis on AF using an aged mouse model of cardiac steatosis. Cardiac-specific perilipin (PLIN) 2-overexpressing mice (PLIN2-Tg) were created and maintained on a chow diet for &gt;12 months. Cardiac steatosis was assessed by electron microscopy and triacylglycerol (TAG) content. AF was induced by transesophageal electrical burst pacing, and the duration of AF was measured. Atrial impulse conduction patterns were analyzed in Langendorff-perfused hearts using optical mapping technique. Myocardial localization of a gap junction protein, connexin (Cx) 43, was analyzed by confocal microscopy. Electron microscopy of the atrium of PLIN2-Tg revealed accumulation of small lipid droplets around clusters of mitochondria, and the atrial TAG content in PLIN2-Tg was 4- to 8-fold higher than that in wild type (Wt) atrium. Electrocardiograms showed significantly longer RR intervals in PLIN2-Tg compared to Wt mice. The prevalence of sustained (&gt;5min) AF was significantly greater in PLIN2-Tg compared with Wt mice (69% vs. 24%). Confocal microscopy revealed that Cx43 was distributed at the intercalated discs in Wt atria, whereas it was heterogeneously redistributed to the lateral side of the cardiomyocytes in PLIN2-Tg atria. Isochrone mapping showed slow and heterogeneous impulse propagation in PLIN2-Tg atria compared with Wt atria. These results indicate that PLIN2-induced steatosis causes Cx43 remodeling, impaired conduction propagation, and a higher incidence of AF. Controlling cardiac steatosis might be an important target for inhibiting AF in patients with cardiac steatosis. Disclosure S. Sato: None. J. Suzuki: None. M. Hirose: None. T. Nakaya: None. M. Yamada: None. M. Ichikawa: None. M. Imagawa: None. Y. Zenimaru: None. S. Takahashi: None. F.B. Kraemer: None. T. Konoshita: None. T. Ishizuka: None.