miRNAs Caught Up in Metabolic Organ Crosstalk to Combat Obesity

A Conversation with James Ntambi

An interview with James M. Ntambi, professor of biochemistry and the Katherine Berns Van Donk Steenbock Professor in Nutrition, College of Agricultural and Life Sciences, at the University of Wisconsin-Madison, took place via Zoom in April 2022. He was interviewed by Patrick J. Stover, director of the Institute for Advancing Health through Agriculture and professor of nutrition and biochemistry and biophysics at Texas A&M University. Dr. James Ntambi is a true pioneer in the field of nutritional biochemistry. He was among the very first to discover and elucidate the role that diet and nutrients play in regulating metabolism through changes in the expression of metabolic genes, focusing on the de novo lipogenesis pathways. As an African immigrant from Uganda, his love of science and his life experiences in African communities suffering from severe malnutrition molded his scientific interests at the interface of biochemistry and nutrition. Throughout his career, he has been an academic role model, a groundbreaking nutrition scientist, and an educator. His commitment to experiential learning through the many study-abroad classes he has hosted in Uganda has provided invaluable context for American students in nutrition. Dr. Ntambi's passion for education and scientific discovery is his legacy, and the field of nutrition has benefited enormously from his unique perspectives and contributions to science that are defined by his scientific curiosity, his generosity to his students and colleagues, and his life experiences. The following is an edited transcript.

MiR-27a promotes insulin resistance and mediates glucose metabolism by targeting PPAR-γ-mediated PI3K/AKT signaling

This study aimed to establish a high-fat diet (HFD)-fed obese mouse model and a cell culture model of insulin resistance (IR) in mature 3T3-L1 adipocytes. A dual-luciferase reporter assay (DLRA) was confirmed interaction between miR-27a and the 3'-untranslated region (UTR) of Peroxisome proliferator-activated receptor (PPAR)-γ. The inhibition of PPAR-γ expression by microRNA (miR)-27a in IR cells at both the protein and mRNA levels was confirmed by a mechanistic investigation. Moreover, the 3'-UTR of PPAR-γ was found to be a direct target of miR-27a, based on the DLRA. Furthermore, antagomiR-27a upregulated the activation of PI3K/Akt signaling and glucose transporter type 4 (GLUT4) expression at the protein and mRNA levels. Additionally, the PPAR inhibitor T0070907 repressed the insulin sensitivity upregulated by antagomiR-27a, which was accompanied by the inhibition of PPAR-γ expression and increased levels of AKT phosphorylation and GLUT4. The PI3K inhibitor wortmannin reduced miR-27a-induced increases in AKT phosphorylation, glucose uptake, and GLUT4. miR-27a is considered to be involved in the PPAR-γ-PI3K/AKT-GLUT4 signaling axis, thus leading to increased glucose uptake and decreased IR in HFD-fed mice and 3T3-L1 adipocytes. Therefore, miR-27a is a novel target for the treatment of IR in obesity and diabetes.