Whole blood was collected from Lgr5+-GFP mice on LFD or HFD following a 3–4 hr fast into K2-EDTA collection tubes (Sarstedt AG & Co; Numbrect, Germany), and immediately centrifuged (1500 × g; 4°C, 15 min) to separate plasma from red blood cells. Plasma Insulin levels were measured by a rat/mouse ELISA (EMD Millipore, Inc) with rat insulin standards using a spectrophotometer (Biorad iMark platereader) following the manufacturer’s instructions. Plasma glucose was determined via the glucose oxidase method with an Analox GM7 analyzer (Analox Inst., USA Inc, Lunenberg, MA), as described (Einstein, et al. 2010 (link); Huffman, et al. 2016 (link); Muzumdar, et al. 2009 (link)).