National Australia Bank is slowly building up the portfolio of investment management businesses that it owns, or part-owns, through nabInvest.One of those acquisitions received some publicity yesterday via the Financial Standard: a stake in Altrinsic Global Advisors, based in Connecticut. Altrinsic manages around US$12 billion for global clients, including US$3 billion for Australian institutional investors.Altrinsic is the eleventh investment by nabInvest.NAB describes nabInvest as a "boutique funds management incubator". The group formed the business in 2007.Recent additions to the portfolio include equity positions in UK-based Wiltshire Capital Limited, a specialist international credit opportunities fund manager and  New York-based AREA Property Partners, a global real estate fund manager managing. The group also bought outright Montreal-based Presima Inc, a manager of listed real estate investment trusts. nabInvest made the last three investments over the last year or so.