Background: Diabetic dyslipidemia is characterized by elevated levels of triglyceride-rich lipoproteins and reduced levels of HDL-cholesterol (HDL-C) . Low levels of HDL-C are associated with an increased risk of atherosclerotic cardiovascular disease, because HDL protects against atherosclerosis through multiple mechanisms include removal of excess cholesterol from macrophages. HDL can also influence cholesterol homeostasis in pancreatic β-cell. It is noteworthy that absence of ATP-binding cassette transporter A1 (ABCA1) , which is a cellular cholesterol transporter and regulates islet cholesterol efflux, results in islet cholesterol overload and impaired insulin release in mice. We examined the associations of cholesterol efflux and insulin secretion in MIN6 cells with polyphenols that is reported to increase cholesterol efflux. Methods: Murine MIN6 cells were labeled with 3H-cholesterol and incubated with ApoA1 (μg/ml) or HDL (25 μg/ml) for 24 hours. The percentage cholesterol efflux was calculated by dividing the media-derived radioactivity by the sum of the radioactivity in the media and the cells. The effect of polyphenols on the cholesterol efflux was studied, adding that into the medium before the analysis of the cholesterol efflux. Insulin secretion was assessed by ELISA as the concentration of insulin in the culture medium. The mRNA expression of ABCA1 and ABCG1 were determined by real-time Quantitative RT-PCR. Results: Under the existence of polyphenols (isorhamnetin) , the ApoA1 or HDL-mediated cholesterol efflux had significantly increased by 1.4% or 1.8%, respectively (n=4, p<0.01) . Isorhamnetin had increased insulin secretion by 882 ng/mg protein/h (n=3, p<0.05) and significantly decreased ABCA1 and ABCG1 expressions. Conclusion: These data suggest that isorhamnetin increases cholesterol efflux and insulin secretion in MIN6 cells. Isorhamnetin could be the interesting candidate to investigate the new treatment for patients with diabetes mellitus. Disclosure K.Matsuki: None. Y.Kimura: None. K.Matsumura: None. J.Tanabe: None. H.Murakami: None. M.Daimon: None. Funding JSPS KAKENHI Grant Number 20K11549
Objective: Equol (Eq) , a metabolite produced from soy isoflavone daidzein by intestinal bacteria, exhibits estrogen activity and may exert effects on glucose metabolism. Eq levels vary extensively depending on the capability for Eq production and amounts of daidzein consumed. We examined the relationship between Eq levels and type 2 diabetes mellitus. Research Design and Methods: Among 1,395 outpatients with diabetes at our hospital, 147 subjects (age: 70-89 years) were recruited (DM group) . Also, 147 age-/sex-matched non-DM subjects were recruited from 1,113 individuals who underwent routine health examinations (non-DM group) . As the estrogenic effect of Eq becomes apparent after menopause, the subjects were age restricted. Eq producers (EqPr) were determined based on the logarithm of the ratio of urinary Eq to the concentration of daidzein with a cut-off value of −1.75. Results: Urinary daidzein (p=0.03) and Eq concentrations (p=0.01) were significantly lower in the DM group versus the non-DM group. The proportion of EqPr differed significantly between the groups (38.8% and 53.1%, respectively; p=0.01) . However, analyses with sex-based stratification showed such difference only in women; the proportion of EqPr was 31.4% and 52.8%, respectively (p<0.01) . Reversely, there were significantly fewer DM subjects among EqPr versus non-EqPr (p=0.01) . Among women, EqPr had significantly less DM than non-EqPr (p<0.01) . However, such differences were not observed in men. Correlation analyses showed a significant positive correlation between urinary Eq and daidzein concentrations only in EqPr (r=0.55, p<0.01) . Conclusion: In postmenopausal women, EqPr were less diabetic; this status appears to be protective against DM. Eq levels increased in parallel with the amount of daidzein consumed in EqPr, but not in non-EqPr. Therefore, Eq supplements and/or enteric bacteria transplantation, rather than dietary intervention, may be effective in preventing DM in non-EqPr. Disclosure K.Hamaura: None. H.Murakami: None. A.Tamura: None. Y.Nishiya: None. S.Mizushiri: None. M.Daimon: None.
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