Purpose: Colorectal carcinogenesis is thought to be related to abdominal obesity and insulin resistance. To investigate whether visceral fat accumulation contributes to colorectal carcinogenesis, we examined its accumulation and the levels of the adipose tissue^derived hormone adiponectin in Japanese patients with colorectal adenoma. Experimental Design: Fifty-one consecutive Japanese patients ages z40 years and with colorectal adenoma were subjected to measurement of visceral fat area by computed tomography scanning and plasma adiponectin concentration. The patients also underwent the 75-g oral glucose tolerance test. Insulin resistance was calculated by the homeostasis metabolic assessment (HOMA-IR) method. The controls were 52 Japanese subjects ages z40 years and without colorectal polyp. Cigarette smokers and subjects who consumed alcohol (z30 g ethanol/d) were excluded. Results: The patients with colorectal adenoma showed significantly more visceral fat area and significantly less plasma adiponectin concentration in comparison with the controls [odds ratio (OR), 2.19; 95% confidence interval (95% CI), 1.47-3.28; P < 0.001 and OR, 0.24; 95% CI, 0.14-0.41; P < 0.001, respectively] by logistic regression analysis. HOMA-IR index was also associated with colorectal adenoma (OR 2.60; 95% CI, 1.20-5.64; P = 0.040). Visceral fat area and adiponectin were associated with adenoma number (1, 2, z 3), the size of the largest adenoma (<10 and z10 mm), and adenoma histology (tubular and tubulovillous/villous). Conclusions: These results suggest an association of visceral fat accumulation and decreased plasma adiponectin concentration with colorectal adenoma in Japanese patients. This study may offer a new insight to understanding the relationship of colorectal carcinogenesis with abdominal obesity and insulin resistance.
Genetic mutations in ryanodine receptors (RyRs), Ca-release channels in the sarcoplasmic reticulum essential for muscle contractions, cause various skeletal muscle and cardiac diseases. Because the main underlying mechanism of the pathogenesis is overactive Ca release by gain-of-function of the RyR channel, inhibition of RyRs is expected to be a promising treatment of these diseases. Here, to identify inhibitors specific to skeletal muscle type 1 RyR (RyR1), we developed a novel high-throughput screening (HTS) platform using time-lapse fluorescence measurement of Ca concentrations in the endoplasmic reticulum (ER) ([Ca]). Because expression of RyR1 carrying disease-associated mutation reduces [Ca] in HEK293 cells through Ca leakage from RyR1 channels, specific drugs that inhibit RyR1 will increase [Ca] by preventing such Ca leakage. RyR1 carrying the R2163C mutation and R-CEPIA1er, a genetically encoded ER Ca indicator, were stably expressed in HEK293 cells, and time-lapse fluorescence was measured using a fluorometer. False positives were effectively excluded by using cells expressing wild-type (WT) RyR1. By screening 1535 compounds in a library of well characterized drugs, we successfully identified four compounds that significantly increased [Ca] They include dantrolene, a known RyR1 inhibitor, and three structurally different compounds: oxolinic acid, 9-aminoacridine, and alexidine. All the hit compounds, except for oxolinic acid, inhibited [H]ryanodine binding of WT and mutant RyR1. Interestingly, they showed different dose dependencies and isoform specificities. The highly quantitative nature and good correlation with the channel activity validated this HTS platform by [Ca] measurement to explore drugs for RyR-related diseases.
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