Nope , sorry NUV is not insured. NIO & NVG are insured. You could switch to either. NIO & NVG have better yields than NUV. NIO & NVG are leveraged while NUV is not. That probably accounts for the higher yield. All these funds are run by Nuveen.
This type of information can be gotten on the website ETFCONNECT.COM
Thanks for recommending PTY. I sold half of my GIM holdings and shifted into PTY. The additional 4% in income was tempting. I trust PIMCO to do a good job, even though the fund is apparently too new to have yet disclosed its portfolio. In addition to individual munis and corporate bonds (e.g., Hasbro, D.R. Horton, Lyondell -- generally highest rating below investment grade, 5-8 years), I also own FAX and NLY for income. Both have done very well. FAX is a play on the Australian Dollar. NLY is a mortgage reit run by the best in the business which yields 12.5% even after a recent run-up.