Shares of Insulet Corp. /zigman2/quotes/205106258/composite PODD +3.91% gained 9.9% in premarket trading on Tuesday, the day after Bloomberg reported that the company is in talks to be acquired by Dexcom Inc. /zigman2/quotes/201324608/composite DXCM +4.16% , citing anonymous sources. Dexcom's stock was down 7.1% before the market opened on Tuesday. A tie-up between the companies would create a major player in the diabetes sector. Dexcom manufactures continuous glucose monitoring systems, while Insulet makes a disposable insulin delivery system. Insulet CEO Shacey Petrovic announced earlier this month that she's stepping down June 1 for family reasons. Insulet's stock is down 23.7% this year, while the broader S&P 500 /zigman2/quotes/210599714/realtime SPX +1.06% has slid 18.1%.