by Kohsuke Shirakawa, Wataru Yano, Keisuke Inoue, Yoshinori Katsumata, Jin Endo, Motoaki Sano
We previously found that senescence of cluster of differentiation 4 (CD4) T cells is accelerated in the visceral adipose tissue (VAT) of mice with diet-induced obesity (DIO) due to a high-fat diet (HFD), and that these senescent-associated T cells cause chronic inflammation of visceral adipose tissue through secretion of osteopontin, provoking systemic insulin resistance. In this study, we examined whether the development of chronic inflammation and senescence-associated T cells in VAT of DIO mice was improved by long-term weight loss after switching to normal chow (NC) or by administration of a sodium glucose cotransporter 2 inhibitor (tofogliflozin). Wild-type mice were fed an HFD for 26 weeks from 4 weeks old. At 30 weeks of age, half of these DIO mice were switched to NC with or without 0.005% tofogliflozin for 38 weeks. The other mice remained on the HFD with or without 0.005% tofogliflozin for 38 weeks. When DIO mice were switched to NC, their weight decreased to that of mice kept on NC since weaning. After 38 weeks (68 weeks of age), chronic inflammation of the VAT subsided with disappearance of senescence-associated T cells. In the HFD groups, the carbohydrate intake per mouse was half or less of that in the NC group, and urinary glucose excretion by the effect of tofogliflozin was lower in the HFD mice than in the NC mice. Mice that remained on the HFD showed no improvement in chronic inflammation in VAT, possibly because urinary glucose excretion was not sufficiently promoted by tofogliflozin due to the low carbohydrate intake. Thus, no improvement in glucose metabolism or weight loss was observed in these mice.