normalization data transformation protocol
Raw gene expression data were first analyzed using ArrayTrack bioinformatics tool with robust multichip average algorithm and quantile normalization. Differentially expressed genes were defined by p < 0.05 and fold change > 1.3 in Welch t-test comparing treatment and control groups. Expression data were then imported to Ingenuity Pathway Analysis (IPA) tool for further analyses of pathway, biofunction, and toxicity using general and pancreas-specific knowledge bases. ID_REF = VALUE = RMA quantile signal intensity
array scanning protocol
GeneChips were scanned using the GeneArray Scanner M10
Target preparation was performed using 4 ug of amplified cDNA and the NuGEN FL-Ovation cDNA Biotin Module V2. Fragmented and biotin-labeled target was hybridized to Affymetrix GeneChip Mouse Genome 430 2.0 microarrays.
The isolated RNA was labeled and gene expression analysis performed by Expression Analysis, Inc. (Durham, NC). The 3 samples with the highest RIN from each treatment group were used to probe treatment effect on gene expression. Total RNA samples (100 ng) were converted into cDNA using Ovation WGA FFPE System (NuGEN, Part No. 6200). The second strand cDNA is then purified with Agencourt RNAClean beads and followed by SPIA amplification. Amplified SPIA cDNA product is purified using Agencourt RNAClean beads and quantitated using a NanoDrop ND-8000 spectrophotometer.
sample treatment protocol
Thorough out the experiment all mice were weighed weekly and dosing adjusted accordingly for each mouse. A cohort of eighty 6 to 8 week-old male C57BL6 mice were received from Harlan Laboratories. The cohort represented a 12 week experimental time point. Cohort was further divided into 4 exenatide (EXE) treatment groups (0, 3, 10, or 30 ug/kg) of 20 mice each. Initially, all mice were placed on HFD for six weeks without additional treatment and were then maintained on HFD for an additional 12 weeks while receiving daily subcutaneous injections of saline or EXE (Creative Peptides, Shirley, NY; 3, 10, or 30 ug/kg). At 12 week timepoint, twenty-four hours following their final dose, the mice from the treatment cohort were anesthetized with isoflurane and euthanized by exsanguination with collection of blood for serum harvest. The pancreas from 12 mice in each cohort was preserved in 10% formalin for histology processing. The pancreas from 5 mice in each cohort was placed in RNAlater (Life Technologies, Grand Island, NY) for subsequent RNA extraction and the pancreas from 3 mice in each cohort was immediately frozen in liquid nitrogen and then stored at -80 degreeC.
nucleic acid extraction protocol
Pancreas tissue was resected, preserved in RNALater, and stored at -80 C. After thawing, 2.5 mg of each sample were processed using miRNeasy Mini Kits (Cat # 217004) (Qiagen, Valencia, CA). Samples were homogenized in 700 uL of Qiazol Lysis Reagent (Qiagen), for 5 minutes at 50 hz in a TissueLyser LT (Qiagen), and processed using the automated purification of total RNA on a Qiacube (Qiagen), using the 'Purification of total RNA, including small RNAs, from animal tissues & cells (aqueous phase), version 2 (April 2010)' standard protocol, as described in the miRNeasy Mini Handbook (1073008 07/2012) & http://www.qiagen.com/QIAcube/Standard/ProtocolView.aspx?StandardProtocolID=847.Mean yield per 2.5 mg of pancreas tissue was approximately 35 ug, determined by NanoDrop spectrophotometer (Thermo Scientific, Wilmington, DE). Average RIN values were approximately 5.4 +/- 1.4, as assayed by a 2100 Bioanalyzer Instrument (Agilent Technologies, Santa Clara, CA), using an Agilent RNA 6000 Nano Kit (cat # 5067-1511). This RIN mean was consistent with our previous experiences in RNA extraction from murine pancreatic tissue.
Male C57BL/6 mice 6 to 8 weeks of age were purchased from Harlan Laboratories (Frederick, MD). Mice were housed individually in an environmentally controlled room (18C-21C, 40%-70% relative humidity) with a twelve-hour light/dark cycle. Mice were initially fed Certified Purina Rodent Chow #5002 (Ralston Purina Co., St. Louis, MO) providing 63% of calories through carbohydrates, 24% from protein, and 13% from fat. Per the experimental design, mice were subsequently placed on a Teklad Custom Research Diet, TD.06415 (Harlan, Frederick, MD), providing 45% of calories through fats (36% saturated, 47% monounsaturated, 17% polyunsaturated), 36% from carbohydrates, and 19% from protein. Water and food were available ad libitum.