Some of the information around the issue of feeding cats with renal failure is either written in books that have copywrite, or the URL's keep changing. I will try to keep information on this site current.
First there is information written by Daniel P. Carey DVM and Leighann Daristotle DVM, PhD on the importance of protein for felines suffering CRF and demonstrating a concern about restriction of protein in the diet of a CRF patient. Unfortunately, Iams has removed their page from public access.
Then, Kenneth C. Bovée, DVM, MMedSc discusses the fact that there is no scientific basis for restricting good quality muscle meat protein in a cat facing renal failure, at least to the point of meeting the cat's nutritional needs.
Gregory Reinhart PhD's comments quoted from the Iam's Symposium papers in regard to dogs, who need less protein than cats. The same principles apply to cats. I should clarify, here, that Dr Reinhart has been financed by a variety of pet food companies, as are other researchers, and Iams only sponsored these specific symposiums, just as Purina did elsewhere, the same year, as you will see noted at the bottom of one or two of the above referenced papers.
There is also Finco et al who stated, "Results raise questions about the practice of restricting quantity of protein in the diet of cats with chronic renal failure, with the intention of ameliorating development of further renal damage," as part of their conclusion.
Another Note on Protein:
According to this information, written by David J. Polzin, DVM, PhD, Diplomate ACVIM, there are various reasons why your cat can have altered control, or lack of control, of glucose levels. You may note that reference is made to reduction of protein in the diet possibly causing the raised glucose levels.
And on Plant Based Oils:
Also, Scott A. Brown, VMD, PhD, Diplomate ACVIM, suggests trying to improve the Omega 3 fatty acid ratio with a cod liver oil capsule as the study suggests this may help. In a convoluted way the article points out, "However, cats have limited hepatic delta-6 desaturase activity and thus cannot effectively convert linoleic to arachidonic acid and both are considered essential dietary fatty acids in cats.18). In other words cats have "limited" ability to extract fatty acids from plant material, (not a feline appropriate source), so I would head for fish oils where you can, and find cat foods that are supplemented with Omega 3's. At the 28th Congress of WSAVA, Dr. Brown, echoes his theory in his speech. Information on this is echoed on our Petfood Pitfalls page under Flax Seed (Oils). Another study reflecting the absence of D6D activity in cats is here.