CCDC3 is specifically upregulated in omental adipose tissue in subjects with abdominal obesity.

OBJECTIVE: The aim of this study was to search for novel markers of visceral adiposity. METHODS: Visceral (omental) and subcutaneous adipose tissues were obtained from 43 Japanese men. Microarray analysis using total RNA from visceral and subcutaneous adipose tissues obtained from five men with abdominal obesity and five nonobese men was first conducted. Then the expression pattern of candidate genes identified in the human study in mouse models of adiposity was examined. RESULTS: Among 30,500 genes evaluated, the mRNA expression of CCDC3 (encoding coiled-coil domain-containing protein 3) was upregulated in omental adipose tissues from abdominally obese subjects (3.07-fold) but not in subcutaneous adipose tissues (0.89-fold). Similar expression patterns were found in two distinct mouse models of obesity. In the analysis of all 43 men, CCDC3 mRNA levels in omental, but not in subcutaneous adipose tissue, were positively correlated with waist circumference and body mass index. CCDC3 was predicted to be a secretory protein, which was confirmed by western blotting, as overexpressed CCDC3 was secreted into the culture media. CONCLUSIONS: The expression of CCDC3 is specifically increased in visceral adipose tissues in abdominally obese subjects. These results suggest that CCDC3 is a potential biomarker for estimating visceral adiposity.

Overexpression of acetyl-coenzyme A carboxylase beta increases proinflammatory cytokines in cultured human renal proximal tubular epithelial cells.

BACKGROUND: We have identified the acetyl-coenzyme A carboxylase beta gene (ACACB) as a strong susceptibility gene to diabetic nephropathy in individuals with type 2 diabetes. To elucidate the mechanism by which ACACB contributes to conferring susceptibility to diabetic nephropathy, we examined the role of ACACB in human renal proximal tubular epithelial cells (RPTECs). METHODS: RPTECs were infected with adenovirus vectors encoding ACACB or LacZ (control), and messenger RNA (mRNA) expression profiles were evaluated with a microarray analysis. We determined the mRNA expressions of proinflammatory cytokines by real-time quantitative reverse transcription (RT) polymerase chain reaction (PCR) and secretion of these cytokines from cells by enzyme-linked immunosorbent assay (ELISA). RESULTS: Among 54,613 transcripts analyzed in the microarray analysis, genes encoding proinflammatory cytokines, including interleukin (IL)-6, chemokine (C-X-C motif) ligands (CXCL) 1, 2, 5, and 6, were remarkably up-regulated (>20-fold) in the ACACB-overexpressing cells. The increased expression of these inflammatory cytokines was reversed by the addition of a synthetic inhibitor of acetyl-coenzyme A carboxylase beta. Overexpression of ACACB could increase IL-6 mRNA expression and IL-6 protein secretion in a time-dependent manner. We further found that IL-6 mRNA stability and expression had significantly increased in ACACB-overexpressing RPTECs, and a treatment of the cells with p38 mitogen-activated protein kinase (MAPK) inhibitor partially but significantly reversed these effects. CONCLUSION: An excess of ACACB results in increased proinflammatory cytokine expression, such as IL-6, at least partly by increasing mRNA stability through a p38 MAPK-dependent pathway.

A single nucleotide polymorphism within the acetyl-coenzyme A carboxylase beta gene is associated with proteinuria in patients with type 2 diabetes.

It has been suggested that genetic susceptibility plays an important role in the pathogenesis of diabetic nephropathy. A large-scale genotyping analysis of gene-based single nucleotide polymorphisms (SNPs) in Japanese patients with type 2 diabetes identified the gene encoding acetyl-coenzyme A carboxylase beta (ACACB) as a candidate for a susceptibility to diabetic nephropathy; the landmark SNP was found in the intron 18 of ACACB (rs2268388: intron 18 +4139 C > T, p = 1.4x10(-6), odds ratio = 1.61, 95% confidence interval [CI]: 1.33-1.96). The association of this SNP with diabetic nephropathy was examined in 9 independent studies (4 from Japan including the original study, one Singaporean, one Korean, and two European) with type 2 diabetes. One case-control study involving European patients with type 1 diabetes was included. The frequency of the T allele for SNP rs2268388 was consistently higher among patients with type 2 diabetes and proteinuria. A meta-analysis revealed that rs2268388 was significantly associated with proteinuria in Japanese patients with type 2 diabetes (p = 5.35 x 10(-8), odds ratio = 1.61, 95% Cl: 1.35-1.91). Rs2268388 was also associated with type 2 diabetes-associated end-stage renal disease (ESRD) in European Americans (p = 6 x 10(-4), odds ratio = 1.61, 95% Cl: 1.22-2.13). Significant association was not detected between this SNP and nephropathy in those with type 1 diabetes. A subsequent in vitro functional analysis revealed that a 29-bp DNA fragment, including rs2268388, had significant enhancer activity in cultured human renal proximal tubular epithelial cells. Fragments corresponding to the disease susceptibility allele (T) had higher enhancer activity than those of the major allele. These results suggest that ACACB is a strong candidate for conferring susceptibility for proteinuria in patients with type 2 diabetes.

Transcription factor AP-2beta inhibits glucose-induced insulin secretion in cultured insulin-secreting cell-line.

AIM: We previously identified the transcription factor activating enhancer-binding protein-2beta (AP-2beta) gene as a new candidate for conferring susceptibility to type 2 diabetes. To ascertain the possible involvement of AP-2beta in the pathogenesis of type 2 diabetes we examined the effects of AP-2beta on glucose-induced insulin secretion. METHODS: We measured the insulin secretion stimulated by glucose, tolbutamide, or KCl in the HIT-T15 cells infected with adenovirus vectors encoding AP-2beta or LacZ (control). RESULTS: We identified clear expression of AP-2beta in isolated rat pancreatic islets and in HIT-T15 cells. Glucose-induced increase in insulin secretion was significantly inhibited in AP-2beta-overexpressing cells (LacZ, 5.0+/-0.8 ng h(-1)mg(-1) protein; AP-2beta, 1.7+/-0.2 ng h(-1)mg(-1) protein; P=0.0015), whereas insulin expression was the same in both types of cells. Tolbutamide-induced insulin secretion was also suppressed in the AP-2beta-overexpressing cells, but KCl-induced insulin secretion was not affected by AP-2beta overexpression. In addition, Kir6.2 and glucokinase expression was significantly decreased in the AP-2beta-overexpressing cells. CONCLUSION: We identified for the first time that AP-2beta expressed and functioned in insulin-secreting cell-line HIT-T15. These results suggest that AP-2beta contributes to susceptibility to type 2 diabetes by inhibiting glucose-induced insulin secretion in pancreatic beta cells.