How to Feed Cats with Diabetes: Part 2— Protein

Evolutionary events shaped the cat’s core metabolism such that their systems are uniquely set up to metabolize a diet which is high in moisture, high in protein, and very low in carbohydrates. Because this is the diet cats have relied upon for tens of thousands of years, they depend more on protein intake than omnivores (e.g., dogs and man) (1-3).

As I discussed in my last blog post (How to Feed Cats with Diabetes), cats do not have the ability to process carbohydrates very efficiently and show relative carbohydrate intolerance. This becomes extremely important when selecting a diet for cats with diabetes, and what is fed can play a key role in the successful management of the diabetic cat.

Weight Loss, Obesity, Muscle Wasting, and Sarcopenia— Common Features of Diabetes
At time of diagnosis of diabetes, weight loss is reported in about 70% of cats. However, cats are more often overweight or obese (40%) than of normal weight or underweight. In addition, muscle wasting and poor muscle condition scores are reported in about half of cats with diabetes.

One contributing factor for the muscle wasting seen in the diabetic cats is their age. The typical diabetic cat is a senior, with about 70% older than 10 years of age at time of diagnosis (4,5). Therefore, since most of these cats are older, they are also prone to develop sarcopenia (from the Greek meaning "poverty of flesh") which is commonly associated with aging. 

In human patients, Type 2 diabetes is associated with an increased risk of concurrent sarcopenia (8). In addition, because skeletal muscle is a primary site for insulin-mediated glucose uptake and deposition, sarcopenia (and especially sarcopenic obesity) (9) may promote insulin resistance, predisposing patients to development of type 2 diabetes and making existing diabetes more difficult to control (10,11).

We do not know if the loss of muscle mass alone (sarcopenia) or combined with weight gain (i.e., sarcopenic obesity) also contributes to the insulin resistance and hyperglycemia associated with the feline disorder. However, given that both obesity and some degree of muscle wasting are common in diabetic cats, it seems reasonable to assume that sarcopenia and sarcopenic obesity may indeed contribute to worsening of feline diabetes, as it does in man (8-11).

Management Goals of Feline Diabetes
In cats with diabetes, a primary goal of therapy is to feed a diet that will lessen postprandial hyperglycemia, reduce marked fluctuations of blood glucose concentrations, minimize the demand on beta cells to produce insulin, and improve insulin sensitivity (6,7,12). By doing this, we decrease the effect of “glucose toxicity” and hopefully allow the pancreatic islet cell to partially recover. In about half of newly diagnosed diabetic cats, this will lead to remission of the diabetic state (13-15). As I discussed last week, we can do this in our diabetic cats by feeding a diet low in carbohydrates.

A secondary goal of therapy is to provide a diet that will help normalize body weight and maintain and/or restore lost muscle mass (16,17), as discussed below.

Recommendations for Diabetic Cats: Higher Dietary Protein:
Because diabetes is a catabolic state, loss of muscle mass is common in cats with diabetes, even if their body condition score indicates overweight or obesity. In these cats, high-protein diets are essential to ensure replacement of any lost muscle mass. In addition, higher protein diets will help prevent the hepatic lipidosis from developing during induction of weight loss (needed in many diabetic cats), and are essential to increasing metabolism to help promote fat burning and normal insulin function (16-19).

Protein is the primary macronutrient responsible for maintenance of muscle mass (20,21). Restoring and preserving any remaining muscle tissue in diabetic cats, an obligate carnivore, depends upon the cat consuming a diet with sufficient amounts of high-quality protein (greater than 40% ME; greater than 10 g/100kcal). This higher than average protein level also helps restore and maintain lost muscle mass, since many diabetic cats will develop “sarcopenia” as they age.

Although it is important to implement a low-carbohydrate/high protein diet in the management of cats with diabetes as soon as possible, there are circumstances where this should be delayed or may be inappropriate (18). For example, in cats with advanced (IRIS stage 3-4) chronic kidney disease (CKD) requiring phosphorus restriction and a reduction in dietary protein, high-protein/low-carbohydrate diabetic diets may not be appropriate (19,22,23).

In cats with earlier stages of CKD, phosphorus should be restricted using other methods than changing to a protein-restricted/higher carb diet (if possible), because feeding higher amounts of carbohydrates would reduce the probability of remission. It is important to remember that over-the-counter low carbohydrate cat foods often contain predominantly fish or meat and tend to have substantially higher phosphate levels than some of the veterinary prescription diets designed for diabetes.

References:

1. MacDonald ML, Rogers QR, Morris JG. Nutrition of the domestic cat, a mammalian carnivore. Annu Rev Nutr 1984;4:521-562. 
2. Zoran DL. The carnivore connection to nutrition in cats. J Am Vet Med Assoc 2002;221:1559-1567. 
3. Eisert R. Hypercarnivory and the brain: protein requirements of cats reconsidered. J Comp Physiol B 2011;181:1-17. 
4. Farrow H, Rand JS, Morton JM, et al. Postprandial glycemia in cats fed a moderate carbohydrate meal persists for a median of 12 hours -- female cats have higher peak glucose concentrations. J Feline Med Surg 2012;14:706-715. 
5. Farrow HA, Rand JS, Morton JM, et al. Effect of dietary carbohydrate, fat, and protein on postprandial glycemia and energy intake in cats. J Vet Intern Med 2013;27:1121-1135. 
6. Rand JS. Feline diabetes mellitus In: Mooney CT, Peterson ME, eds. BSAVA Manual of Canine and Feline Endocrinology. Fourth ed. Quedgeley, Gloucester: British Small Animal Veterinary Association, 2012;133-147.
7. Baral RM, Little SE. Endocrine pancreatic disorders In: Little SE, ed. The Cat: Clinical Medicine and Management. St. Louis: Elsevier Saunders, 2012;547-571.
8. Kim TN, Park MS, Yang SJ, et al. Prevalence and determinant factors of sarcopenia in patients with type 2 diabetes: the Korean Sarcopenic Obesity Study (KSOS). Diabetes Care 2010;33:1497-1499. 
9. Stenholm S, Harris TB, Rantanen T, et al. Sarcopenic obesity: definition, cause and consequences. Curr Opin Clin Nutr Metab Care 2008;11:693-700. 
10. Srikanthan P, Hevener AL, Karlamangla AS. Sarcopenia exacerbates obesity-associated insulin resistance and dysglycemia: findings from the National Health and Nutrition Examination Survey III. PLoS One 2010;5:e10805. 
11. Moon SS. Low skeletal muscle mass is associated with insulin resistance, diabetes, and metabolic syndrome in the Korean population: The Korea National Health and Nutrition Examination Survey (KNHANES) 2009-2010. Endocr J 2013. 
12. Zini E, Osto M, Franchini M, et al. Hyperglycaemia but not hyperlipidaemia causes beta cell dysfunction and beta cell loss in the domestic cat. Diabetologia 2009;52:336-346. 
13. Zini E, Hafner M, Osto M, et al. Predictors of clinical remission in cats with diabetes mellitus. J Vet Intern Med 2010;24:1314-1321. 
14. Reusch CE, Hafner M, Tschuor F, et al. Diabetes remission in cats: a review. Schweiz Arch Tierheilkd 2011;153:495-500. 
15. Gottlieb S, Rand JS. Remission in cats: including predictors and risk factors. Vet Clin North Am Small Anim Pract 2013;43:245-249. 
16. Nguyen P, Leray V, Dumon H, et al. High protein intake affects lean body mass but not energy expenditure in nonobese neutered cats. J Nutr 2004;134:2084S-2086S. 
17. Keller U. Dietary proteins in obesity and in diabetes. Int J Vitam Nutr Res 2011;81:125-133. 
18. Zoran DL, Rand JS. The role of diet in the prevention and management of feline diabetes. Vet Clin North Am Small Anim Pract 2013;43:233-243. 
19. Frank G, Anderson W, Pazak H, et al. Use of a high-protein diet in the management of feline diabetes mellitus. Vet Ther 2001;2:238-246. 
20. Paddon-Jones D, Short KR, Campbell WW, et al. Role of dietary protein in the sarcopenia of aging. Am J Clin Nutr 2008;87:1562S-1566S. 
21. Wakshlag JJ. Dietary protein consumption in the healthy aging companion animal. Proceedings of the Nestlé Purina Companion Animal Nutrition Summit: Focus on Gerontology 2010;32-39.
22. Kidder AC, Chew D. Treatment options for hyperphosphatemia in feline CKD: what's out there? J Feline Med Surg 2009;11:913-924. 
23. Ross SJ, Osborne CA, Kirk CA, et al. Clinical evaluation of dietary modification for treatment of spontaneous chronic kidney disease in cats. J Am Vet Med Assoc 2006;229:949-957.