OMB No. 0925-0001 (Rev. 03/2020 Approved Through 02/28/2023) Project Summary Obesity-induced inflammation contributes to the development of insulin resistance and Type 2 Diabetes (T2D). The gut plays an important yet poorly understood role in the development of T2D. Mounting evidence implicates impaired intestinal immune responses and dysbiosis of the gut microbiota in driving the onset of insulin resistance. Recently, a novel family of lipids called Palmitic Acid Hydroxy Stearic Acids (PAHSAs) was discovered that are anti-inflammatory and anti-diabetic. Preliminary data demonstrates that PAHSAs improve glucose homeostasis in insulin-resistant mice and this is associated with reduced intestinal inflammation and favorable shifts to gut microbial species that associate with leanness. Functional analyses of the cecal metabolome and metagenome from mice treated with PAHSA lipids has identified a probiotic that strongly associates with insulin sensitivity in these same mice. Daily oral supplementation with this probiotic has beneficial effects to reduce body weight gain and improve glucose homeostasis in conventional chow and high fat diet (HFD)-fed mice. Our central hypothesis is that the gut plays an important role in mediating the beneficial effects of PAHSAs on glucose homeostasis. The goals of this proposal are to 1) identify whether PAHSA effects on improved gut barrier function and glucose metabolism are mediated by gut T-cells, and 2) defining the cecal and serum metabolome from mice supplemented with the gut microbe that associates with insulin sensitivity in PAHSA-treated mice. This grant will define the mechanisms by which PAHSAs and beneficial gut microbes improve gut mucosal homeostasis and contribute to regulating glucose metabolism. These studies may reveal novel therapeutic strategies and targets that beneficially leverage gut immune responses and the gut microbiome to treat obesity and insulin resistance in humans.