Diabetes Mellitus has been a recognised disease for thousands of years. Its name means 'sweet water', because the diagnosis was based on a taste test of the patient's urine, which was full of glucose and therefore quite sweet. Until insulin was discovered in 1921, the outcome for the sufferer was uniformly fatal, and even now control of human diabetes is rarely perfect, so there are long-term side effects which are difficult to control. In cats, diabetes is-- typically for many things feline!-- difficult to diagnose, frequently a problem to control, and often the cat just stops being diabetic for variable lengths of time! This all accumulates to make diagnosis and treatment of feline diabetes a bit of a clinical challenge. To me the summation is--the diagnosis of Diabetes Mellitus is not a death sentence, but it can be a lifetime gaol term. Not everyone has the lifestyle to accommodate a diabetic cat, but for those who embark on treatment, the outcome can be very rewarding. We are lucky in Australia to have a couple of world authorities on feline diabetes doing research here, and much fascinating information is now coming to light. These specialists are also accessible for the 'fine tuning' and individual regimes that most feline diabetics seem to need! The following is a small section of the vast amount of new information which is being accumulated daily on this interesting topic.
The simplest picture of diabetes goes like this--Insulin is a hormone produced in the pancreas (part of the digestive system) which allows most of the body's tissues to extract glucose from the blood travelling through them, and absorb it into the cell where it is used as an energy source for the cell to survive, grow, and do whatever its job is. The insulin also affects other major organs of metabolism such as the liver, and assists in its producing the right kind of energy (fat for storage or glucose to burn now). Diabetics have no (or low levels of) insulin, so their energy metabolism becomes deranged. The clinical entity of diabetes is of a cat (or person) who drinks large amounts of water, eats more food and still loses weight, and who passes large volumes of urine. Interestingly, it is the urine which is the driving mechanism for the clinical signs, not the drinking as one might assume. Diabetics must drink large volumes of water because the excess glucose in the blood (no insulin to remove it for use in the tissues) gets filtered into urine by the kidneys, and because glucose draws water with it (think of clumpy sugar in hot weather!), water from the body is also dragged into the urine, so the body dehydrates. Therefore, the cat has to drink more to counteract that effect. The weight loss is because the glucose is the main source of calories for the body's metabolism, and they are being eliminated uselessly in the urine. The initial digestive processes are unaffected, so food which goes into the cat is still digested, but most of it comes out again as glucose in the urine. Basically the cat cannot eat enough to maintain itself.
This is the billion dollar research question, of course. So far, only risk factors and classifications of types of diabetes have been identified, but the hunt continues. The statistics are quite interesting, however, and our feline friends seem eerily close to humans again. One in 400 cats will get diabetes, but 15% will stop being diabetic (although they remain prone to it). There are two types of human diabetes - type I which requires insulin because the pancreatic tissue has been destroyed (this is the type commonly found in dogs), and type II where there are still some cells in the pancreas producing insufficient insulin, but not enough (less than 20 - 25% of normal). Alternatively, there is enough insulin being produced but the tissues that need to use the insulin are resistant (the insulin cannot help the cell take the glucose from the blood). This means that diabetic cats can sometimes be helped with tablets which stimulate the remaining pancreatic tissue. About 50% of diabetic cats respond for at least some of the time to oral hypoglycaemics which are also used in humans or to dietary modification (if you can convince the cat to change!). This is also the reason some cats stop being diabetic or at least stop needing insulin or any treatment. There is another hormone that has recently been put under the microscope as being involved in the process of causing diabetes, but its role is not clear. The hormone is called amylin, and it is produced in the same pancreatic cells as insulin (the beta cells), and is even stored in the same granules to be released at the same time as insulin. Amylin seems to directly oppose the actions of insulin, and also to destroy some of the beta cells themselves. The amylin in humans, cats and primates is similar in its ability to disrupt beta cell function and thus causing the type II diabetes, whereas this effect is not seen in dogs and rats.
weighing more than 6.8 kg (although diabetics are frequently thin by the time they are seen by the vet) being more than 10 years old being desexed (bear in mind there are lots of bigger risks involved in not being desexed, but it seems proportionally fewer intact cats get diabetes)
gender - it is a bit unclear whether there are more male than female diabetic cats in Australia, being a brown Burmese is a big risk, but this is not seen elsewhere.
There are other features or diseases associated with diabetes in cats, which means that there are often combinations of problems going on in the same cat and these obviously cloud the picture. Renal failure, post-progesterone administration (once used regularly for oestrous control, behavioural modification and skin allergy treatments), Hyperthyroidism, Cushings disease (hyperadrenocorticism - very rare in cats) and acromegaly (excess Growth Hormone, also rare) can all present as diabetics initially.
'Stress' is also increasingly being labelled as destabilising some cats who are diabetes-prone.
There is no typical diabetic cat, and the diagnosis usually comes as a surprise to owners (and sometimes to vets as well). The most common symptoms in cats are actually lethargy (which is seen in nearly every feline problem!), a poor hair coat and jaundice. Owners do not always know whether a cat is drinking more (unless it is exclusively indoors) and the same goes for urinating more. And an increase in appetite? Well cats are always asking for food, so it takes a while to register that Kitty is actually eating all the food he's demanded! Weight loss is another insidious entity, because often the cat appears only to change shape, with a bigger abdomen (due to liver enlargement and changed fat deposition) and thinning of muscle along the spine. (Three of the cats I've seen have presented for cystitis - urinating outside the litter tray with blood in the urine. Maybe it was the only way they could draw attention to their problem... Now I make sure I test the urine of all cats who change their litter tray habits!).
The Clinical Picture as described above, can mean that early symptoms are overlooked. Many cats just are not good at giving the signals that they are in trouble, so they just do less. Combined with advancing age, and 'old cats get kidney problems so we should expect them to drink more' traditions, many cats are in deep trouble and actually vomiting or close to comatose by the time they get to the vet's (in one study, 18% of diabetics were presented to the vet for being paralysed, when really they were in a diabetic coma). One of the tricky things about diabetics is that they can go into comas both from a lack of insulin (the deranged metabolism of the liver finally makes the blood too acidic with ketones for the brain to function--this is the ketoacidotic crisis) and from an excess of insulin (because then there is no glucose in the blood for the brain to work with, so it shuts off--this is the 'hypo' that diabetics talk about). One in 400 cats represents quite a large number of cats who are diabetic, but as an average cat owner, you may well not experience nor know of a cat with the condition. Many owners think that diabetes is a human-only condition so none of the symptoms triggers recognition of the potential problem of diabetes, nor of the possibility of treating it. The other difficulty is that some cats (up to 15% 'transient' diabetics) are not full-time card-carry members of the diabetic club. These cats tend to be fine until they strike a problem (infection, social stress, metabolic upset) and then their insulin production becomes inadequate so they become diabetic. Interestingly, at this point the diabetes becomes self-perpetuating because the raised blood glucose (no insulin to take it out of the blood) leads to a reduced insulin output and so the diabetes accelerates. When these cats have been sorted out, they go back to the knife edge of producing just enough insulin to get by till the next problem. Frustrating? Tricky? Unnerving? You bet.
The Diagnostic Picture is not much easier to get a grip on. You have to know that a visit to the vet is not a cat's idea of a pleasure cruise. And when a cat gets wound up, it releases cortisol (the hormone of 'stress' or 'flight/fright' reactions, along with the adrenaline which makes super feline strength possible when a cat gets really scared!). This raises the blood glucose up to the same level as a diabetic (all that glucose is ready for a huge increase in demand for the muscles so the cat can run or fight), so that a 'fasting blood glucose' taken at the vet's has little diagnostic value. To get around this, cats can be kept in hospital for a couple of hours to cool off, but even then the results can be equivocal. However there is now a very promising pair of blood tests which detect whether glucose has been raised in the blood for a long period (tests for serum fructoseamine and glycosylated haemoglobin) which are proving reliable in identifying diabetics from just plain scared cats.
Urine is also of great value, although we no longer do the taste test. Urine sticks will pick up glucose and ketones in the urine and indicate roughly how much glucose is in the urine. If there are ketones, then the cat is pretty definitely diabetic, if there is only glucose, then once again it may only be a cat which has been scared, has another problem which raises the serum glucose, or has been stressed for a longish period resulting in regular excess glucose peaks in the blood and hence tipping over into the urine. Frustrating? Tricky? You bet. The term is clinical judgement and the "plan is to stay with the problem till you can tell exactly what's going on!
This is the final hurdle, and while the theory is simple, the practise is time consuming and regimented. If yours is one of the diabetic cats who can be managed by a change of diet (which is basically the Atkins diet for cats, though it was developed by a lady called Deb Greco for cats!), a loss of excess poundage and the resolution of a problem which precipitated the diabetes, then treatment only requires a lifestyle change (tell that to a dieting cat!) and a temporary hiccough in the usual routine.
If your cat is one of the 50% - 85% who need insulin to be administered, then a whole new world of clinical finesse and intimacy with your cat will arise. You will have to accept that your cat's food and water requirements will need monitoring, that occasional access to unadulterated (i.e. litter-free) urine is invaluable, and that you or someone else will have to give the cat a tiny amount of insulin using a very fine needle and syringe twice a day (a rare few cats are OK with once a day), at the same times,12 hours apart, every day.
This can be a truly bonding experience or it can create great social torment, hence my comment that diabetes is not a death sentence but it can be a gaol term. About 60% of my clients are prepared to embark on the commitment of a diabetic maintenance program (remember to include holiday plans and irregular work vs. weekend hours in your calculations). I think it is better to assess the cost and commitment realistically at the start rather than put the cat through a stabilisation program only to find the maintenance needs are impossible. I make no judgement on a person's willingness or not to attempt treatment, as I have a sneaky feeling that I, myself, wouldn't have the time to make good metabolic control possible.
The stabilisation process depends on the state in which the cat is first presented. There is the 'happy' diabetic who is only drinking a lot and losing weight, the 'unhappy' diabetic whose metabolism is in real trouble with ketoacidosis or the 'really critical' diabetic in a coma or with pancreatitis or other major complication. The clinical needs and variations that you and your vet will live through to find the appropriate amount, type and frequency of insulin needed, whether to control with tablets (Glipizide / oral hypoglycaemics),and attempting a dietary adjustment can be a real bonding experience with your vet! Sometimes it is straightforward, frequently not. However, assuming the cat is on the 'standard' (i.e. most common) programme of twice daily injections of insulin followed by a measured food intake, what else needs to be done? Although daily urine glucose measurements are no longer de rigeur, regular urine monitoring is helpful, so that if the diabetes starts to accelerate again (more glucose in the urine), blood tests can be started early to define where the problem is ( wrong dose, wrong type of insulin, wrong food, poor injection technique, the list goes on) and restabilise. At the other end of the scale, if there is no glucose in the urine, it may indicate that the cat is restoring its own insulin production and the treatment is no longer required. The danger of having insulin administered by an owner when the cat no longer needs it is that the cat can be pushed into a 'hypo' coma which can be fatal, especially if the early symptoms go unnoticed (basically the brain slows down from lack of glucose so the cat gets sleepier until it goes into a coma or fit). Giving the cat liquid glucose will counteract the problem, and most cats don't go as deeply into a coma as to have their life threatened, but it can be a bit of a fright for all concerned. I had a cat killed by having too many people administering the insulin, without communicating, and one morning the cat got 3 doses within an hour. Another succumbed to being given a human dose of insulin by a well-meaning nurse friend who minded the cat while the owner was away and reverted to a routine human dose instead of reading the instructions. These are rare problems of course, but the possibilities must be borne in mind.
In its simplest concept, Diabetes Mellitus is a lack of insulin in an animal. Although we now know that there is a great deal more to the underlying problem, diabetes revolves around the inability of the body to either produce or use insulin. Insulin is a powerful hormone, with deep seated and wide ranging effects, and it is wonderful to contemplate that its power can be harnessed to improve the lives of so many animals as well as humans. Refinements are always being made, especially to the monitoring procedures so that better metabolic control is achieved for more patients. Maybe soon the 'switch' will be identified and then the animal's own insulin regulation can be turned back on!