Diabetes in dogs


Diabetes mellitus is a disease in which the beta cells of the endocrine pancreas either stop producing insulin or can no longer produce it in enough quantity for the body's needs. The disease can affect humans as well as animals such as dogs.
The condition is treatable and need not shorten the animal's life span or interfere with the quality of life. If left untreated, the condition can lead to cataracts, increasing weakness in the legs, malnutrition, ketoacidosis, dehydration, and death. Diabetes mainly affects middle-aged and older dogs, but there are juvenile cases. The typical canine diabetes patient is middle-aged, female, and overweight at diagnosis.
The number of dogs diagnosed with diabetes mellitus has increased three-fold in thirty years. In survival rates from around the same time, only 50% survived the first 60 days after diagnosis and went on to be successfully treated at home. Currently, diabetic dogs receiving treatment have the same expected lifespan as non-diabetic dogs of the same age and gender.
The condition is commonly divided into two types, depending on the origin of the condition: type 1 and type 2.
  • Type 1 diabetes, sometimes called "juvenile diabetes", is caused by destruction of the beta cells of the pancreas. The condition is also referred to as insulin-dependent diabetes, meaning exogenous insulin injections must replace the insulin the pancreas is no longer capable of producing for the body's needs. Type 1 is the most common form of diabetes in dogs and affects approximately 0.34% of dogs.
  • Type 2 diabetes can develop in dogs, although it is not as prevalent as type 1. Because of this, there is no possibility the permanently damaged pancreatic beta cells could re-activate to engender a remission as may be possible with some feline diabetes cases, where the primary type of diabetes is type 2.
Gestational diabetes can develop in dogs as well. It can be prevented by behavioral and dietary management. Diabetes insipidus, which has nothing to do with blood sugar, but is a condition of insufficient antidiuretic hormone or resistance to it, also exists in dogs.

Classification and causes

At present, there is no international standard classification of diabetes in dogs. Commonly used terms are:
  • Insulin deficiency diabetes or primary diabetes, which refers to the destruction of the beta cells of the pancreas and their inability to produce insulin.
  • Insulin resistance diabetes or secondary diabetes, which describes the resistance to insulin caused by other medical conditions or by hormonal drugs.
While the occurrence of beta cell destruction is known, all of the processes behind it are not. Canine primary diabetes mirrors type 1 human diabetes in the inability to produce insulin and the need for exogenous replacement of it, but the target of canine diabetes autoantibodies has yet to be identified. Breed and treatment studies have been able to provide some evidence of a genetic connection. Studies have furnished evidence that canine diabetes has a seasonal connection not unlike its human Type 1 diabetes counterpart, and a "lifestyle" factor, with pancreatitis being a clear cause. This evidence suggests that the disease in dogs has some environmental and dietary factors involved. Canine obesity causes the corresponding diabetes in dogs also known as canine diabetes.
Secondary diabetes may be caused by use of steroid medications, the hormones of estrus, acromegaly,, pregnancy, or other medical conditions such as Cushing's disease. In such cases, it may be possible to treat the primary medical problem and revert the animal to non-diabetic status. Returning to non-diabetic status depends on the amount of damage the pancreatic insulin-producing beta cells have sustained.
It happens rarely, but it is possible for a pancreatitis attack to activate the endocrine portion of the organ back into being capable of producing insulin once again in dogs. It is possible for acute pancreatitis to cause a temporary, or transient diabetes, most likely due to damage to the endocrine portion's beta cells. Insulin resistance that can follow a pancreatitis attack may last for some time thereafter. Pancreatitis can damage the endocrine pancreas to the point where the diabetes is permanent.

Genetic susceptibility of certain breeds

This list of risk factors for canine diabetes is taken from the genetic breed study that was published in 2007. Their "neutral risk" category should be interpreted as insufficient evidence that the dog breed genetically shows a high, moderate, or a low risk for the disease. All risk information is based only on discovered genetic factors.
High risk
  • Cairn Terrier
  • Samoyed
Moderate risk
  • Bichon Frisé
  • Border Collie
  • Border Terrier
  • Collie
  • Dachshund
  • English Setter
  • Poodle
  • Schnauzer
  • Yorkshire Terrier
Neutral risk
Low risk
  • Boxer
  • English Springer Spaniel
  • German Shepherd
  • Golden Retriever
  • Staffordshire Bull Terrier
  • Weimaraner
  • Welsh Springer Spaniel

    Gene therapy

In February 2013 scientists successfully cured type 1 diabetes in dogs using a pioneering gene therapy.

Pathogenesis

The body uses glucose for energy. Without insulin, glucose is unable to enter the cells where it will be used for this and other anabolic purposes, such as the synthesis of glycogen, proteins, and fatty acids. Insulin is also an active preventor of the breakdown or catabolism of glycogen and fat. The absence of sufficient insulin causes this breaking-down process to be accelerated; it is the mechanism behind metabolizing fat instead of glucose and the appearance of ketones.
Since the glucose that normally enters the cells is unable to do so without insulin, it begins to build up in the blood where it can be seen as hyperglycemia or high blood glucose levels. The tubules of the kidneys are normally able to re-absorb glucose, but they are unable to handle and process the amount of glucose they are being presented with. At this point, which is called the renal threshold, the excess glucose spills into the urine, where it can be seen in urine glucose testing. It is the polyuria, or over-frequent urination, which causes polydipsia, or excessive water consumption, through an osmotic process. Even though there is an overabundance of glucose, the lack of insulin does not allow it to enter the cells. As a result, they are not able to receive nourishment from their normal glucose source. The body begins using fat for this purpose, causing weight loss; the process is similar to that of starvation.

Symptoms

The main symptoms which occur in nearly all dogs with diabetes mellitus are:
  • excessive water consumption; this condition is often called polydipsia.
  • frequent and/or excessive urination, known as polyuria, often requiring the dog to be let outside to urinate during the night,
  • abnormal increase in appetite, a condition known as polyphagia.,
  • weight loss; dogs with diabetes may also suffer from severe weight loss, weakness, anorexia and blindness.
Sometimes, the first sign of diabetes noticed by the owner may be that their dog either has become blind, or has vomiting, anorexia, lethargy and weakness.

Checkups

Although the symptoms of diabetes mellitus such as frequent urination, thirstiness, greater appetites and inactiveness are easily visible, frequent checking of the dog for the disease is required. The dog's body weight should be determined and calculated once every two weeks using weight scale. The daily caloric requirement by the dog's body and BCS should also be determined using a scale as part of dietary management in maintaining average body weight. The protein intake by the dog should also be considered and checked twice a month.
Blood pressure of the dog should also be constantly and daily checked in order to predict any future occurrence. The blood sugar level may also be checked using glucometer to check the glucose level in the body of the dog.

Management

Early diagnosis and treatment can reduce the incidence of complications such as cataracts and neuropathy. Since dogs are insulin dependent, oral diabetes drugs, which require a functional endocrine pancreas with beta cells capable of producing insulin, are ineffective. Diabetic dogs require insulin therapy, which must be continued for life.
The goal of treatment is to regulate blood glucose using insulin and some probable diet and daily routine changes. The process may take a few weeks or many months and is similar as in type 1 diabetic humans. The aim is to keep the blood glucose values in an acceptable range. The commonly recommended dosing method is by "starting low and going slow" as indicated for people with diabetes.
During the initial process of regulation and periodically thereafter, the effectiveness of the insulin dose at controlling blood glucose is evaluated. This is done by a series of blood glucose tests called a curve. Blood samples are taken and tested at intervals of one to two hours over a 12- or 24-hour period. The results are generally transferred into graph form for easier interpretation. They are compared against the feeding and insulin injection times for judgment. The curve provides information regarding the action of the insulin in the animal. It is used to determine insulin dose adjustments, determine lowest and highest blood glucose levels, discover insulin duration and, in the case of continued hyperglycemia, whether the cause is insufficient insulin dose or Somogyi rebound, where blood glucose levels initially reach hypoglycemic levels and are brought to hyperglycemic ones by the body's counterregulatory hormones. Curves also provide evidence of insulin resistance which may be caused by medications other than insulin or by disorders other than diabetes which further testing can help identify.
Other diagnostic tests to determine the level of diabetic control are fructosamine and glycated hemoglobin blood tests which can be useful especially if stress may be a factor. While anxiety or stress may influence the results of blood or urine glucose tests, both of these tests measure glycated proteins, which are not affected by them. Fructosamine testing provides information about blood glucose control for an approximate 2- to 4-week period, while GHb tests measure a 2- to 4-month period. Each of these tests has its own limitations and drawbacks and neither are intended to be replacements for blood glucose testing and curves, but are to be used to supplement the information gained from them. While HbA1c tests are a common diagnostic for diabetes in humans, only recently has an A1C test become available for cats and dogs. The product is called A1CARE and is available from Baycom Diagnostics.
The diabetic pet is considered regulated when its blood glucose levels remain within an acceptable range on a regular basis. Acceptable levels for dogs are between 5 and 10 mmol/L or 90 to 180 mg/dL. The range is wider for diabetic animals than non-diabetics, because insulin injections cannot replicate the accuracy of a working pancreas.