Diabetes mellitus (DM) is one of the top two endocrinopathies in cats, with a prevalence estimated to be approximately 0.5% of cats seen in private practice. Unfortunately, data suggest feline DM has been increasing in prevalence in most countries since the mid-1980s. Our understanding of the risk factors, pathogenesis, and treatment options for feline diabetic patients has improved dramatically in the last 10–15 years. A recent study showed that cats with newly diagnosed DM have a fair to good prognosis, with 46% living longer than 2 years.¹

Goals of Therapy

Successful management of cats with DM includes four important goals of treatment:

1.  Minimizing clinical signs

2.  Improving quality of life

3.  Preventing complications

4.  Achieving a non-insulin dependent state when possible

One of the first questions owners of cats with DM ask is whether lifelong insulin treatment will be needed. Patients most likely to achieve remission share these common factors:²

1.  They are newly diagnosed

2.  They have no concurrent diseases causing insulin resistance

3.  The owner is able to achieve good glycemic control

4.  They are fed a diabetic management diet

Diabetic remission is typically defined as the ability to maintain normal blood glucose without insulin for at least 4 weeks without the reappearance of clinical signs. Diabetic remission is most likely to occur within the first 4–6 months of treatment in cats with good glycemic control. Trying to control DM with diet alone or with oral hypoglycemic medications and delaying the start of insulin therapy markedly reduces the chance of remission. Clinicians should acknowledge that not all cats will be able to achieve remission, whether due to concurrent diseases, or inability on the part of the owner to commit to early, intensive treatment and monitoring. The other goals of treatment - minimizing clinical signs, improving quality of life, preventing complications - are equally, if not more, important.

Choice of Insulin

While no true feline insulin is available commercially, there are products available that provide excellent therapeutic control. Studies evaluating remission rates for various insulin types in cats are difficult to interpret since many are not optimally designed and there is no standardization of protocols or diets. The type of insulin used for the best chance at achieving remission may be less important than factors such as instituting therapy as soon as possible, having a plan for close monitoring, achieving normal body weight, and whether concurrent diseases are present. Cats can go into remission with the use of any insulin. However, the duration of remission is highly variable and unfortunately, at least 25% of cats that achieve remission subsequently become overtly diabetic and must receive insulin again.

The choice of insulin should be based on what is available, as well as what is affordable and convenient for the owner. It is difficult to predict in advance which insulin is best for an individual patient, so clinicians should be familiar with at least two types of insulin appropriate for treating cats. The critical factor for insulin potency and duration of action is absorption. A common cause of inconsistent response to insulin in humans is poor absorption, even under ideal conditions. The same is likely true in cats.

Table 1. Comparison of insulin products for treatment of feline diabetes mellitus

*Based on lean body weight

What to Feed Diabetic Cats

There are two main strategies to feed cats with DM: low-carbohydrate diets (less than 15% of calories from carbohydrates) and high-fiber diets. The two are not necessarily mutually exclusive and both can provide variable levels of protein and fat (see Table 2).

Table 2. Calorie distribution (% of metabolizable energy from protein, fat and carbohydrates) and crude fiber content (g/1000 kcal) of U.S. feline diets for the management of diabetes mellitus (data from manufacturer's product guides)

There is one study³ evaluating the inclusion of insoluble fiber for glucose control in cats with DM for 24 weeks, and the study found that fiber inclusion (12% cellulose) resulted in lower blood glucose concentrations. However, the high-fiber diet was also lower in carbohydrates than the control diet; thus, it is not possible to distinguish the effects of each nutrient. Regarding the low-carbohydrate strategy, there are a variety of uncontrolled trials proposing a benefit. In most of the studies, the improvement was accompanied by weight loss in overweight patients and this might have confounded the results. One controlled study⁴ that compared two diets with different carbohydrate/fat/fiber content (but the same protein level) found the remission rate was higher in the low-carbohydrate group, but that a considerable percentage of cats from the high-fiber group also went into remission. One study⁵ found no effect on remission comparing one therapeutic low-carbohydrate diet to different over-the-counter diets (both dry and canned).

At this time, both low-carbohydrate and high-fiber approaches are reasonable as long as insulin dosing is adjusted to the diet and there is careful medical control. A thorough diet history is important to assess the current diet and feeding method to see which modifications are necessary. Overweight and obese-prone patients might benefit from the reduced energy density of high-fiber diets (and the use of any canned therapeutic diet for DM). On the other hand, thin cats with DM should not be fed a high-fiber/low-energy dense diet. Low-carbohydrate diets are usually high in fat; thus, they should be used with caution (or not at all) in hyperlipidemic patients. A trial-and-error process might be needed to see which strategy fits best each patient.

How Much and How to Feed

Obesity is common in DM cats. If present, it should be addressed with a therapeutic weight-loss diet and an energy-restriction plan. Some low-carb diets are formulated for weight loss but they are very energy dense; thus, only the canned versions are recommended for this purpose. Obesity predisposes cats to DM and care should be taken to prevent it. In DM cats prone to obesity, portion-controlled amounts to maintain a body condition score of 5/9 are recommended. In thin cats, free feeding is acceptable if the insulin dosage method permits it.

Monitoring

The goals of management are to provide good glycemic control and, if possible, to attain remission. A good body weight and body condition score is important and cats should be weighed and scored once a month by their owners (and at each veterinary visit). Food intake should be adjusted by 10% up/down to ensure these goals are met. A diet change might be necessary if the goals are not being met with the current diet.

References

1.  Callegari C, Mercuriali E, Hafner M, et al. Survival time and prognostic factors in cats with newly diagnosed diabetes mellitus: 114 cases (2000–2009). J Am Vet Med Assoc. 2013;243:91–95.

2.  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.

3.  Nelson RW, Scott-Moncrieff JC, Feldman EC, et al. Effect of dietary insoluble fiber on control of glycemia in cats with naturally acquired diabetes mellitus. J Am Vet Med Assoc. 2000;216:1082–1088.

4.  Bennett N, Greco DS, Peterson ME, et al. Comparison of a low carbohydrate-low fiber diet and a moderate carbohydrate-high fiber diet in the management of feline diabetes mellitus. J Feline Med Surg. 2006;8:73–84.

5.  Hall TD, Mahony O, Rozanski EA, et al. Effects of diet on glucose control in cats with diabetes mellitus treated with twice daily insulin glargine. J Feline Med Surg. 2009;11:125–130.