CONCERNS about Macquarie Bank's profit levels as a result of its exposure to volatile markets has seen the bank suffer its second credit rating downgrade this week. Moody's today cut Macquarie's ratings by one notch from A2 to A3 after a lengthy review of banks and firms operating on global markets. By noon, Macquarie shares were four cents lower at $27.34. Macquarie was trading at around $40 just over 12 months ago. Moody's senior vice-president Patrick Winsbury said the downgrade was a reflection of "ongoing earnings challenges for Macquarie and the evolution of its business model against the backdrop of protracted weakness in financial markets''. The report warns it is hard to predict Macquarie's "sustainability and profitability'' as moves to change its business model while maintaining its traditional "strong capital cover'' and moderate risk appetite and meeting investors' expectations for equity returns.