Canine diabetes mellitus
Canine diabetes mellitus is the medical term for diabetes mellitus in domestic dogs ( Latin canis , 'dog'). In colloquial language, the terms " dog diabetes " are also used for the disease and " sugar dog" for a sick dog. The initial symptoms are increased thirst with increased urination and emaciation despite increased food intake. In dogs, diabetes almost always requires a lifelong dose of insulin , but it is easy to control.
As with humans, the number of people with diabetes increases in dogs. It is unclear, however, whether the incidence of the disease is actually increasing or whether the disease is only being detected more frequently thanks to improved diagnostics in the veterinary practice. It is estimated that around 0.3 to 1% of the total domestic dog population has diabetes mellitus. Diabetes is now the second most common hormonal disorder in dogs . In eight out of ten cases, the sick animals are adult, uncastrated bitches.
The classification of canine diabetes mellitus is handled differently in the specialist literature. In principle, the disease can be divided into insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM). In principle, all forms of diabetes can also occur in dogs. In practice, however, insulin-dependent diabetes mellitus ( type I diabetes according to the DDG classification ) is observed almost exclusively , while non-insulin-dependent ( type II diabetes ) - i.e. insulin resistance of the peripheral insulin target cells - in contrast to humans and cat almost never.
In primary diabetes mellitus with absolute insulin deficiency ( type I diabetes ), the insulin-producing β cells in the islets of Langerhans in the pancreas no longer work or no longer work adequately. The causes are not fully understood, it is probably a combination of genetic disposition and external factors such as infectious , toxic or inflammatory damage. They lead to the formation of antibodies against various parts of the islets of Langerhans and ultimately to a destruction of the β cells. It accounts for about half of the cases in dogs, but, in contrast to humans, develops predominantly in adult animals.
The so-called secondary diabetes mellitus ( type III diabetes in humans) occurs as a secondary disease. This can be inflammation of the pancreas ( pancreatitis ), a pancreatic tumor , an overactive adrenal gland ( Cushing's syndrome ), an underactive thyroid ( hypothyroidism ) or an excessive release of growth hormone ( hypersomatotropism ). In addition, secondary diabetes mellitus can be triggered by the administration of diabetogenic drugs ( glucocorticoids , growth hormone, gestagens ). This type of diabetes occurs most frequently in the diestrus in uncastrated bitches. Here, the stimulation of the ovaries distributed progesterone formation of growth hormone, which acts as opponent acts of insulin.
Both primary and secondary diabetes mellitus in dogs, in contrast to cats, are usually irreversible.
There are various genetic and environmental factors that can promote the occurrence of diabetes in dogs. Obesity seems to have little effect on the risk of illness. The frequency and duration of walks do not influence the risk, but it can be reduced through regular physical activity. When it comes to feeding, self-prepared diets increase the risk compared to dry food, and the same applies to frequent giving of treats . In addition, dogs weighing less than 22.7 kg have an increased risk compared to larger dogs, older dogs are more often affected than young ones and bitches more often than males. Most new cases occur between the ages of five and twelve years.
Breeds with a high risk of diabetes ( relative risk > 5) are Samoyed and Cairn Terriers . A moderately increased risk (RR 2–5) exists in poodles , border terriers , English setters , dachshunds , long-haired collies , border collies , schnauzers , Yorkshire terriers and bichons frize . Breeds with below average risk (RR <0.7) are German Boxer , Weimaraner , German Shepherd , Staffordshire Bull Terrier , Golden Retriever and English Springer Spaniel .
In contrast to human diabetes, canine diabetes is mainly caused by a lack of insulin (type I), diabetes caused by insulin resistance (type II) is very rare in dogs. With the insulin deficiency, grape sugar ( glucose ) can no longer be used in the cells. In addition, disturbances in fat and amino acid metabolism occur. As a result of the impaired usability of glucose, which occurs in the body through food intake and synthesis in the liver , it first accumulates in the blood ( hyperglycemia ). Above a certain limit value - the kidney threshold of around 180 mg / dl or 10 mmol / l - the recovery capacity in the tubules of the kidney is exceeded and sugar is excreted in the urine ( glucosuria ). As a result of the osmotic effect of glucose, more water is excreted in the urine, so the amount of urine increases ( polyuria ). The increased water loss is compensated for by increased water absorption ( polydipsia ). The glucose deficiency in the brain , especially in the satiety center in the hypothalamus , leads to hunger and increased food intake ( polyphagia ). As a result of the impaired utilization of glucose, the body tries to compensate for the lack of energy by breaking down proteins (especially from the muscles ) and fat . This leads to emaciation ( inanition , cachexia ).
Long-term insulin deficiency can lead to a further metabolic imbalance known as ketoacidosis . As a result of the increased fat breakdown, more fatty acids are released, which can no longer be used by the body in the citric acid cycle , but are converted into keto bodies in the β-oxidation . Since keto bodies have an acidic pH value , acidosis ( acidosis ) occurs. The excess keto bodies can also be excreted in the urine ( ketonuria ) and, due to their osmotic effect, increase the polyuria. Pronounced ketoacidosis is a life-threatening condition.
Another important pathogenetic factor is glucose and lipotoxicity. This is understood to mean a programmed cell death of the β cells of the pancreas as a result of high blood sugar and blood lipid levels. This leads to a progressive loss of insulin-producing cells and thus to a decrease in insulin secretion even in type II and type III diabetes.
Diabetes often goes unnoticed at first unless an elevated blood sugar level is discovered during routine examinations. Clinical symptoms only occur when glucose is excreted in the urine (glucosuria) or ketoacidosis occurs. Typical symptoms of clinically manifest diabetes are excessive fluid intake ( polydipsia ), increased urination ( polyuria ), greatly increased food intake (polyphagia) and weight loss.
If these initial symptoms are overlooked, secondary symptoms can predominate. Often the first symptom noticed by the owner is deteriorating eyesight, which can be traced back to diabetes-induced lens opacity . The glucose , which also occurs in increased amounts in the aqueous humor , is converted in the lens by the enzyme aldose reductase into sorbitol , which accumulates there and leads to cataracts due to the osmotic influx of water. It is not uncommon for diabetes mellitus to be noticed only with manifest ketoacidosis. Here the general condition is severely disturbed, the animals can be beaten or even comatose .
The diagnosis by the veterinarian is made with the help of a measurement of the blood sugar level. A persistent blood sugar level of more than 150 mg / dl (8.3 mmol / l) in fasting animals, i.e. without prior food consumption, is proof of the disease of diabetes mellitus. Physiologically (ie considered healthy) fasting values in the blood plasma are 70 to 120 mg / dl (3.9 to 6.7 mmol / l). The determination of the fructosamine content plays only a minor role in dogs, in contrast to diabetes mellitus in cats . Values above 340 µmol / l indicate diabetes mellitus.
Evidence of glucose in the urine is not conclusive as it can also occur in dogs with kidney disease. However, evidence of diabetes mellitus is indicated by the presence of glucose in the urine if the specific gravity of the urine is high (> 1.035 kg / l) or if ketone bodies occur in the urine at the same time.
Replacing the insulin-producing islets of Langerhans with islet cell transplantation is out of the question in dogs, although this procedure was first performed in a dog by Oskar Minkowski in 1891 . This method is still in the experimental stage in human medicine and is unlikely to establish itself in veterinary medicine because of the high costs. Canine diabetes mellitus is always treated by taking insulin . The oral administration of antidiabetic agents is not indicated in dogs.
In uncastrated bitches, castration ( ovariohysterectomy ) is recommended as the first measure, since the formation of progesterone during metestrus or diestrus leads to the destabilization of the disease and, due to the induced insulin counterpart somatotropin, a correct adjustment to insulin is not possible. Ideally, although this rarely occurs, the symptoms of the disease disappear with the removal of the ovaries and there is no need for further treatment.
In the setting phase, the required insulin dose is first determined by gradually increasing the amount of insulin. This requires a blood sugar measurement at least once a day, namely around the time of the lowest blood sugar value ( nadir ). However, several measurements per day are better (“day profile”). The insulin dose can be increased gradually after five to seven days until blood sugar levels, thirst, appetite and urine volume stabilize. The goal is a nadir of 80–120 mg / dl (4.4–6.6 mmol / l) and glucose values within 12 hours that are always below 200 mg / dl (11.1 mmol / l). Lower values are not aimed for in order to keep the risk of hypoglycaemia as low as possible. The discontinuous measurement, however, harbors the risk that the nadir is not reliably detected and that animals can therefore briefly experience hypoglycaemia. The measurement with measuring devices from human medicine, which enable a continuous recording of the sugar level, has so far only been tested in a few studies. The values of these systems deviate from the measurement data collected with classic blood sugar devices, but it is still possible to set the insulin dose on the basis of such continuous measurements. The extent to which temporary hypoglycaemia or a Somogyi effect can be reliably detected with this must be validated by further studies.
The optimal insulin dose is maintained after the adjustment phase has been completed and the success of the therapy is checked on the basis of regular monitoring of blood sugar levels; in very well-adjusted patients, one urine glucose measurement per week is sufficient.
Cataracts, a typical consequence of diabetes in dogs, cannot be influenced by medication, but only remedied by removing the lens.
The only insulin preparation currently approved for dogs in Germany is a so-called intermediate insulin from pigs (porcine lente insulin, trade name Caninsulin from MSD Intervet ). The insulin of the pig is structurally identical to that of the dog. Since Caninsulin contains 35% amorphous and 65% crystalline zinc insulin , it has two activity maxima, namely after 3 and after 6-8 hours, the nadir occurs around 8 hours. The effects last about 14 hours, so Caninsulin is administered twice a day. The majority of dogs can be adjusted well with Caninsulin . A pen (trade name Vetpen ) is also available for caninsulin for easier administration . If intermediate insulin is too short to work in an individual, the blood sugar level will be too high for longer periods of the day and the dog will continue to drink and urinate more often. If intermediate insulin works too long for an individual, hypoglycaemia and possibly a Somogyi effect will occur in the overlapping area . Both conditions can only be recognized via a daily profile or continuous blood sugar measurement and require a change to another insulin.
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 12 hours in dogs and must therefore also be administered twice a day. The nadir occurs after two hours. Previous studies show that the quality of the settings is slightly worse than with Caninsulin . Insulin detemir (trade name Levemir ) is mainly used in dogs where Caninsulin has poor effects. It lasts 14 hours in dogs, so it has to be administered twice a day. However, there is a risk of hypoglycaemia in the overlapping area of the two injections .
In the case of a complicated course of the disease, individually tailored combinations of long-acting and short-acting insulins can be used.
Feeding a high-fiber food with complex carbohydrates ensures that the intestines absorb glucose more slowly and evenly. For underweight patients, however, a low-fiber diet can make sense. If high blood lipid levels, fatty liver disease or pancreatitis occur, the ration should be low in fat. The type of feed, the amount of feed and the feeding time should be as constant as possible. The feeding time should be chosen so that the insulin is already in the bloodstream when glucose is absorbed into the blood. When using Caninsulin , feeding 30 minutes before the insulin administration is optimal. If you use insulin twice a day, two meals are also useful. If insulin is administered once a day, which, however, rarely leads to a good setting, a second feeding should take place at the time of the nadir.
- Minimizing physical and psychological stress (e.g. no unusual physical strain)
In addition, any other underlying diseases must be excluded or treated. Comorbidities also need to be diagnosed and treated as they can reduce the effectiveness of the insulin administered. 21% of dogs suffering from diabetes mellitus develop a mostly subclinical urinary bladder inflammation .
Insulin resistance is the term used to describe the condition when insulin therapy does not lower blood sugar, or lower it sufficiently. If a twice daily dose of 1.5 IU / kg body mass does not lower the blood sugar level below 300 mg / dl, this indicates insulin resistance. First of all, application errors (incorrect injection technique, incorrect dosage, ineffective insulin, feeding) must be ruled out and any diabetes-inducing drugs such as glucocorticoids or megestrol administered due to other diseases must be clarified. The most common causes of insulin resistance are other diseases such as Cushing's syndrome , bacterial infections, hypothyroidism , heart, liver and kidney diseases, and pancreatitis . Antibodies against the administered insulin are only formed in about 5% of cases, in which case another insulin should be used.
As in human medicine, home monitoring , i. H. the control of the sugar levels at home with a blood sugar measuring device . The procedure is not as essential in dogs as it is in cats, but it is definitely recommended during the insulin adjustment phase.
Here, the blood sugar value is determined from a drop of blood with a blood sugar measuring device. This home monitoring has the great advantage that an impending hypoglycemia is recognized at an early stage. In addition, the insulin treatment can be better tailored to the individual's everyday life. Home monitoring is easy and can be learned by every dog owner. It should be done once every two weeks for well-adjusted dogs. A veterinary check-up is recommended every three months.
Long-term monitoring can also be carried out by the dog owner himself. Here, the amount of water consumed, the amount of urine produced and the sugar content in the urine at least once a week should be checked with a urine test strip or with a blood glucose meter.
Even with a well- adjusted dog there may be a hypo ( hypoglycaemic shock ) d. H. your blood sugar level is too low. The signs for this are severe hunger, restlessness, tremors, movement disorders ( twitching ) and even coma . Hypoglycaemia is always an emergency and must be corrected immediately.
The recommended countermeasures are:
- Offering feed
- Pouring a sugar solution (grape sugar, honey or glucose syrup) into the mouth,
- Giving a lump of sugar or glucose under the tongue,
If these measures do not lead to success, an immediate presentation to the veterinarian is essential.
- Swiss Association for Small Animal Medicine Brief summary of diabetes mellitus in dogs
- www.caninsulin.de Pharmaceutical information from a manufacturer of dog insulin , partly easy to understand even for laypeople.
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