The effects of heat-killed Lactobacillus plantarum L-137 (HK L-137) on chronic inflammation associated with metabolic disorders have remained unknown. We examined the effects of HK L-137 on cardiac and adipose tissue pathophysiology in DahlS.Z-Lepr fa /Lepr fa (DS/obese) rats as a model of metabolic syndrome. DS/obese rats were treated orally with HK L-137 (2 or 75 mg kg-1 day-1) from 9 to 13 weeks of age. HK L-137 attenuated left ventricular (LV) inflammation and fibrosis as well as adipocyte hypertrophy, inflammation, and up-regulation of sterol regulatory element-binding protein-1c (SREBP-1c) gene expression in visceral and subcutaneous adipose tissue, without affecting body weight gain or hypertension. The low dose of HK L-137 also ameliorated LV diastolic dysfunction, the increase in subcutaneous fat mass, and insulin resistance as well as attenuated the down-regulation of Akt phosphorylation in visceral and subcutaneous adipose tissue, and the elevation of the circulating interleukin-6 concentration. Furthermore, the proportion of regulatory T (Treg) cells among CD4+ T cells in the spleen was increased by HK L-137. These results suggest that the anti-inflammatory effects of HK L-137 on the heart and adipose tissue are related, at least partly, to suppression of systemic inflammation associated with an increase in splenic Treg cell.