Feline diabetes mellitus
As of feline diabetes mellitus (popularly "feline diabetes") diabetes (is diabetes mellitus ) of the domestic cat ( latin : felis , cat '), respectively. Both diagnostically and therapeutically, it is a difficult disease that differs in some essential features from diabetes in humans , dogs or other animals.
The form of diabetes mellitus arises when, due to various causes, the effect of the pancreatic hormone insulin on the body cells decreases. As a result, the cells are only inadequately able to take up sugar molecules and supply them to the cell's own metabolism . The lack of energy that occurs in this way causes the body's own regulatory mechanisms to increase blood sugar levels . If the concentration of sugar molecules in the blood exceeds the kidney threshold of about 250 mg / dl (corresponds to 13.8 mmol / l), they pass into the urine and cause water loss due to their osmotic activity . These mechanisms lead to the development of four main symptoms of diabetes: increased thirst ( polydipsia ), increased urination ( polyuria ), increased food intake ( polyphagia ) with progressive emaciation ( inanition ). The muscle tone can decrease and a nerve disease causes a patency of the hind limbs (plantigrades gait). In contrast to humans or dogs, lens opacities do not develop , the corresponding eye changes in diabetic cats are purely age-related. Often there is a bacterial urinary tract infection in diabetic cats , which can also be subclinical. Diabetes develops preferentially in middle-aged animals, with neutered males being most commonly affected.
There are two types of diabetes mellitus (DM) in domestic cats. By far the most common form is type 2 DM, in which there is reduced insulin production in the pancreas due to amyloidosis or glucotoxicity in the islet cells , but at the same time the body cells show increased insulin resistance. Glucotoxicity is understood to mean toxic damage to the beta cells from the high blood sugar . The proportion of type 2 DM in cats is 80–95%. Type 1 DM, in which the insulin-producing beta cells in the pancreas are destroyed, is less common. Clinically, the two types cannot be distinguished from one another.
Type 2 DM occurs in cats often only temporarily and as a side effect of glucocorticoid treatment or as a concomitant disease of another underlying disease. Urinary tract infections and also chronic inflammations of the oral cavity such as FORL or the gingivitis-stomatitis-pharyngitis complex can lead to the development of diabetes mellitus due to the constant secretion of stress hormones . In addition, as in humans, obesity and a high-carbohydrate diet, i.e. feed with added grain and sugar, are risk factors.
The correct assessment of the blood sugar of cats under practical conditions is generally difficult, as they easily react to manipulations with a stress-related increase in blood sugar. The same effect can occur in the presence of other diseases (stress-related hyperglycemia , hyperadrenocorticism ). The blood sugar level measured in the veterinary practice cannot be used as a diagnostic criterion.
The diagnosis of diabetes mellitus can only be made with a satisfactory degree of certainty on the basis of the fructosamine level, which in diabetic animals is above 340 µmol / l due to the permanently increased blood sugar level. The fructosamine value is problematic when the thyroid gland is overactive ( hyperthyroidism ), since this lowers the half-life of serum proteins and thus of fructosamine, and thus diabetes mellitus may be masked. Regular blood glucose testing at home ( home monitoring ) is more suitable for diagnosis and therapy control.
Treatment of any other underlying conditions is essential and can lead to remission . About 30 to 50% of cats show remission with treatment, especially if it is managed well in the first six months. About a quarter of these animals relapse and become diabetic again. Diets that are low in carbohydrates and high in protein reduce the need for insulin in cats.
The most common treatment is the injection of medium-acting insulin supplements twice a day . The control of the correct setting on the preparation proves to be problematic, since a blood sugar measurement at the vet does not produce any usable results due to the tendency to stress hyperglycaemia. One way out is the pet owner's blood sugar measurement at home, whereby a daily profile is created with a 2-hour measurement ( home monitoring ). A step-by-step dose adjustment can be made on the basis of these daily profiles. If the pet owner is not able to create a daily profile, the setting can only be made using the fructosamine determination.
There are currently two insulin preparations approved for cats in Germany . These are a so-called intermediate insulin from pigs (porcine Lente insulin, trade name Caninsulin from MSD Intervet ) and a recombinant human insulin (trade name Prozinc , Boehringer Ingelheim). Caninsulin lasts about 10 hours and the lowest blood sugar level ( nadir ) occurs after 4.7 hours. In some cats, however, the preparation only works for 4 to 8 hours, and therefore no setting can be achieved with two applications. The remission rate for Canisulin is 15 to 30%. The nadir of prozinc occurs after about 5 to 7 hours, so that a twice daily injection is advisable. One study with ProZinc was able to achieve an improvement in blood sugar levels in 84% of the cases.
According to the pharmaceutical regulations, other preparations may only be used in the sense of a therapeutic emergency ( off-label use ), i.e. if there is no or insufficient effect or intolerance. In these cases, human insulins can also be used. Insulin glargine (trade name Lantus ) works for about 22 hours in cats and, in contrast to the more even effect in humans, has a relatively clear nadir after 14 hours. In order to adjust it, cats usually have to use it twice a day; once a day, the risk of hypoglycaemia is greater. The remission rate of insulin glargine is between 50 and 80% if it is successfully discontinued within the first six months.
In the event of a derailment of glucose metabolism and / or ketoacidosis , very short-acting insulins or insulin lispro are used. Typical adverse effects are hypokalaemia , hypophosphataemia, and hypoglycaemia .
Cats with well-controlled diabetes without complications ( e.g. ketoacidosis ) can live well for years with a constant quality of life . The secondary diseases play a subordinate role due to the lower life expectancy compared to humans, but the recruitment phase, which sometimes lasts for months, often leads to kidney problems ( chronic kidney failure ). Complete remission is possible in type 2 DM, which can occur continuously or only briefly. By eliminating risk factors such as obesity and improper diet, after the side effects of cortisone administration have subsided and after successful treatment of an illness underlying diabetes, the pancreas usually recover.
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