Transient clinical diabetes mellitus in cats: 10 cases (1989-1991)

Medical records of 10 cats with transient clinical diabetes mellitus were reviewed. At the time diabetes was diagnosed, clinical signs included polyuria and polydipsia (10 cats), weight loss (8 cats), polyphagia (3 cats), lethargy (2 cats), and inappetence (1 cat). Mean (+/- SD) fasting blood glucose concentration was 454 +/- 121 mg/dL, mean blood glucose concentration during an 8-hour period (MBG/8 hours) was 378 +/- 72 mg/dL, and glycosuria and trace ketonuria were identified in 10 and 5 cats, respectively. Baseline serum insulin concentration was undetectable (6 cats) or within the reference range (4 cats) and serum insulin concentration did not increase after i.v. glucagon administration in any cat. Insulin-antagonistic drugs were being administered to 5 cats and concurrent disorders were identified in all cats. Management of diabetes included administration of glipizide (6 cats), insulin (3 cats), or both (1 cat), discontinuation of insulin-antagonistic drugs, and treatment of concurrent disorders. Insulin and glipizide treatment was discontinued 4-16 weeks (mean, 7 weeks) after the initial diagnosis of diabetes was confirmed. At the time treatment for diabetes was discontinued, clinical signs had resolved, mean fasting blood glucose concentration was 102 +/- 48 mg/dL, MBG/ 8 hours was 96 +/- 32 mg/dL, glycosuria and ketonuria were not identified in any cat, and concurrent disorders (except mild renal insufficiency in 1 cat) had resolved. Significant (P < .05) increases occurred in postglucagon serum insulin concentrations, insulin peak response, and total insulin secretion, compared with values obtained when clinical diabetes was diagnosed. Histologic abnormalities were identified in pancreatic islets of 5 cats in which pancreatic biopsies were obtained and included decreased number of islets (4 cats), islet amyloidosis (3 cats), and vacuolar degeneration of islet cells (3 cats). Mean beta cell density was significantly (P < .001) decreased in diabetic cats compared with control cats (1.4 +/- 0.7 versus 2.6 +/- 0.5%, respectively). Cells within islets stained positive for insulin, however, the number of insulin-staining cells per islet and the intensity of insulin staining were decreased in 5 and 2 cats, respectively. Clinical diabetes had not recurred in 1 cat after 6 years, in 4 cats lost to follow-up after 1.5, 1.5, 2.0, and 2.5 years, and in 2 cats that died 6 months and 5.5 years after clinical diabetes resolved. Clinical diabetes recurred in 3 cats after 6 months, 14 months, and 3.4 years, respectively. These findings suggest that cats with transient clinical diabetes have pancreatic islet pathology, including decreased beta cell density, and that treatment of diabetes and concurrent disorders results in improved beta cell function, reestablishment of euglycemia, and a transition from a clinical to subclinical diabetic state.

Change in serum thyroid-stimulating hormone concentration in response to administration of thyrotropin-releasing hormone to healthy dogs, hypothyroid dogs, and euthyroid dogs with concurrent disease

OBJECTIVE

To determine whether measuring change in serum thyroid-stimulating hormone (TSH) concentration in response to thyrotropin-releasing hormone (TRH) administration can be used as a test of thyroid function in dogs suspected of having hypothyroidism.

DESIGN

Case-cohort study.

ANIMALS

13 healthy dogs, 20 hypothyroid dogs, and 18 euthyroid dogs with concurrent diseases.

PROCEDURE

Blood samples were collected before and 30 minutes after TRH administration, and serum TSH concentration was measured. The 13 healthy dogs were used to establish a reference range for change in TSH concentration after TRH administration. The remaining 38 dogs were categorized as hypothyroid or euthyroid on the basis of baseline total thyroxine (T4) and TSH concentrations, T4 concentration 4 hours after TRH administration, and clinical response to administration of sodium levothyroxine.

RESULTS

Median baseline TSH concentration was 0.25 ng/ml (range, 0.03 to 0.44 ng/ml) in healthy dogs, 0.93 ng/ml (0.21 to 3.5 ng/ml) in hypothyroid dogs, and 0.21 ng/ml (0.03 to 0.63 ng/ml) in euthyroid dogs with concurrent diseases. Median percentage change in TSH concentration after TRH administration was 207% (range, 25 to 2,200%) in healthy dogs, 24% (-21 to 134%) in hypothyroid dogs, and 167% (69 to 1,800%) in euthyroid dogs with concurrent diseases. Overall accuracy of using the TRH-induced change in TSH concentration to identify hypothyroid dogs was 90%.

CLINICAL IMPLICATIONS

Although percentage change in TSH concentration in response to TRH administration can be used to differentiate euthyroid from hypothyroid dogs, the test has little advantage over measurement of baseline TSH and total or free T4 concentration.

Beta-catenin directly induces expression of the Siamois gene, and can initiate signaling indirectly via a membrane-tethered form

Beta-catenin is shown to directly induce the expression of siamois (a homeobox-containing gene involved in axial patterning) in a cell-autonomous, protein synthesis independent manner. Siamois can thus be considered a direct target of beta-catenin signaling in Xenopus. Expression of a portion of the armadillo repeat region of beta-catenin via a membrane-tethered fusion protein is shown to give similar levels of siamois induction and axis duplication as a free, untethered form. Reduction of endogenous free beta-catenin levels by overexpression of C-cadherin leads to complete inhibition of signaling by the membrane-tethered repeat region. Since the membrane-tethered repeat region is unlikely to be bound up by C-cadherin, these results show that the membrane-tethered beta-catenin relies on endogenous beta-catenin for signaling. We propose that the membrane-tethered construct acts by titrating a cytoplasmic inhibitor of beta-catenin signaling.

Systemic hypertension and proteinuria in dogs with diabetes mellitus

OBJECTIVE

To determine prevalence and severity of systemic arterial hypertension and proteinuria in dogs with naturally developing diabetes mellitus (DM) and to determine whether these abnormalities were related to age, sex, duration of DM, or degree of control of glycemia.

DESIGN

Case series and cohort study.

ANIMALS

Fifty dogs with naturally developing DM.

PROCEDURES

Blood pressure was measured in all 50 dogs. Thirty-eight dogs were evaluated once, and 12 were evaluated sequentially. Thirty-five were evaluated for proteinuria by determining protein-to-creatinine ratio in urine (n = 35) or by electrophoresis of urine (33).

RESULTS

Hypertension was detected in 23 on the basis of a systolic pressure > 160 mm HG (12 dogs), a diastolic pressure > 100 mm HG (21), or a mean pressure > 120 mm HG (23). All dogs with systolic hypertension had concurrent diastolic and mean hypertension, and 19 of 21 dogs with diastolic hypertension had concurrent high mean pressure. Ten of 12 dogs reevaluated at subsequent visits had no change in blood pressure. Blood pressure remained consistent in 3 dogs tested at different times during the day on a single visit. Duration of DM and presence of proteinuria were significant predictors of hypertension. Seven of 35 (20%) dogs had an increased protein-to-creatinine ratio in their urine. Albumin concentration and albumin-to-creatinine ratio were significantly higher in urine from diabetic dogs, compared with healthy, nondiabetic dogs. Hypertension was associated with an increased albumin-to-creatinine ratio.

CLINICAL IMPLICATIONS

Systemic hypertension and proteinuria may be common in diabetic dogs, but the clinical importance of these findings are, as yet, unknown.

Cobalt 60 irradiation of pituitary gland tumors in three cats with acromegaly

Acromegaly was diagnosed in 3 cats with insulin-resistant diabetes mellitus (DM) on the basis of history and physical examination findings, which ruled out other causes of insulin-resistant DM, and by documenting high plasma concentrations of growth hormone. Computed tomography revealed a mass in the area of the pituitary gland in each cat. Pituitary gland tumors were irradiated with cobalt 60, and none of the cats developed complications to radiotherapy. Each cat received a total dose of 48 Gy of cobalt 60 during 12 treatments. After completion of radiotherapy, insulin requirements were less for all cats, although in 1 cat, this improvement was transient. Diabetes mellitus resolved in 2 of 3 cats. After treatment, decreases in insulin requirements correlated with decreases in plasma growth hormone concentrations in 2 of 3 cats in which DM resolved. On the basis of these findings, irradiation of pituitary gland tumors appears to be a treatment option for cats with acromegaly.

Effect of dietary insoluble fiber on control of glycemia in dogs with naturally acquired diabetes mellitus

OBJECTIVE

To evaluate the effect of a high insoluble-fiber (HF) diet containing 12% cellulose in dry matter and a low insoluble-fiber (LF) diet on control of glycemia in dogs with naturally acquired insulin-dependent diabetes mellitus.

DESIGN

Prospective randomized crossover controlled trial.

ANIMALS

11 dogs with naturally acquired diabetes mellitus.

PROCEDURE

Dogs were fed HF and LF diets for 8 months each in 1 of 2 randomly assigned diet sequences. Caloric intake and insulin treatment were adjusted as needed to maintain stable body weight and control of glycemia, respectively. After a 2-month adaptation period, control of glycemia was evaluated every 6 weeks for 6 months. Variables assessed included serum glucose concentration measured during the preprandial state, blood glycosylated hemoglobin concentration, serum glucose concentration measured every 2 hours for 24 hours beginning at the time of the morning insulin injection, 24-hour mean serum glucose concentration, mean serum glucose concentration fluctuation from the 24-hour mean serum glucose concentration, and 24-hour urinary excretion of glucose.

RESULTS

Significant differences in mean daily caloric intake, body weight, or daily insulin dosage among dogs fed HF and LF diets were not found. Mean preprandial serum glucose concentration, most postprandial serum glucose concentrations, 24-hour mean serum glucose concentration, and 24-hour urinary excretion of glucose were significantly lower in dogs fed the HF diet, compared with the LF diet.

CLINICAL IMPLICATIONS

Results of this study support feeding of commercially available insoluble fiber diets to dogs with naturally acquired diabetes mellitus.

Comparison of serum concentrations of thyroid-stimulating hormone in healthy dogs, hypothyroid dogs, and euthyroid dogs with concurrent disease

OBJECTIVE

To evaluate use of an assay for measuring serum concentration of canine thyroid-stimulating hormone (cTSH) as an aid for diagnosing thyroid disease in a population of dogs suspected of having hypothyroidism.

DESIGN

Case-cohort study.

ANIMALS

62 healthy dogs and 49 dogs with clinical signs consistent with hypothyroidism (16 were hypothyroid and 33 were euthyroid with concurrent disease).

PROCEDURE

Samples from healthy dogs were used to establish a reference range for serum cTSH concentration. The 49 dogs were categorized as hypothyroid or euthyroid with concurrent disease on the basis of clinical signs, results of additional diagnostic and thyroid-stimulating hormone (TSH) response tests, and response to administration of levothyroxine sodium. Function of the thyroid gland was considered normal when serum total thyroxine (T4) concentration 6 hours after TSH administration was > 2.5 micrograms/dl. Hypothyroidism was diagnosed when serum T4 concentration after TSH administration was < or = 1.5 microgram/dl.

RESULTS

Serum cTSH concentration differed significantly among all 3 groups. Four of 33 (12%) euthyroid dogs had cTSH concentrations that were greater than the reference range, whereas 6 of 16 (38%) hypothyroid dogs had cTSH concentrations within the reference range. Specificity for serum cTSH concentration was 0.88 and sensitivity was 0.63. When interpreted in combination with serum T4 concentration, specificity increased to 1.0.

CLINICAL IMPLICATIONS

cTSH assay had good specificity for use in the diagnosis of hypothyroidism in dogs. Because this assay had low sensitivity, a diagnosis of hypothyroidism could not be excluded on the basis of a serum cTSH concentration that was within the reference range.

Mass spectrometric methods for evaluating point mutations

Two methods for internally calibrating spectra resulting from the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry analysis of partially digested proteins are described. Partial digestion of proteins results in a large number of ion signals present in the MALDI-TOF mass spectrum, which in turn represent a significant over-sampling of each amino acid present in the analyte. This over-sampling allows ion signals of undisputed origin to be used as internal calibrants for the evaluation of fragments suspected to contain point mutations. Correlated with the correct amino acid sequence, the mass values of all ion signals (calibrants and analytes) are observed to fall into a single low-error data set. Conversely, empirically derived data applied to an incorrect sequence split the data into subsets of different errors. The methods take advantage of the self-consistent nature of data generated during the enzymatic mass mapping of proteins using MALDI-TOF, and they aid in the rapid, sensitive and accurate evaluation of point mutations present in proteins.

Response to insulin treatment and survival in 104 cats with diabetes mellitus (1985-1995)

Medical records of 104 cats with diabetes mellitus were reviewed. Information from 54 cats that had multiple blood glucose concentrations evaluated at least 5 times over a minimum of 3 months, beginning at the time insulin treatment was initiated, was used to evaluate the efficacy of insulin in treating diabetes mellitus. Fourteen of 54 cats were treated with protamine zinc insulin (PZI), 26 with ultralente insulin, and 14 with lente insulin. Six, 29, and 19 cats had good, mediocre, and poor glycemic control, respectively, based on mean blood glucose concentrations, whereas 31, 21, and 2 owners thought clinical response was good, mediocre, and poor, respectively. No significant difference was found in glycemic control among cats treated with PZI, ultralente, or lente insulin. Glycemic control was significantly (P < .05) better in 33 cats without than in 21 cats with concurrent disease. All 104 cats were used to calculate survival data. Fifty-one of 104 cats were alive at the time of the study. Mean (+/- standard deviation [SD]) and median survival times were 24 (+/- 16) and 20 months, respectively, in the 51 cats still alive at the end of the evaluation, and 25 (+/- 4) and 17 months, respectively, in the 53 cats that had died during the period of evaluation. Pancreatic abnormalities identified in 37 cats that underwent necropsy included chronic pancreatitis (n = 17), acute to subacute pancreatitis (n = 2), exocrine pancreatic adenocarcinoma (n = 7) and adenoma (n = 1), islet cell atrophy and vacuolar degeneration (n = 27), and islet amyloidosis (n = 8). No association was found between glycemic control and islet amyloidosis or exocrine pancreatic neoplasia, or between survival time and chronic pancreatitis, islet amyloidosis, or exocrine pancreatic neoplasia. In conclusion, diabetic cats evaluated in this study showed a variable response to exogenously administered insulin, ranging from excellent to poor. By maintaining mean blood glucose concentrations under 300 mg/dL, clinical signs were improved, and owners were satisfied with insulin treatment. Concurrent potentially insulin-antagonistic diseases were common and deleteriously affected glycemic control and survival time.

Surface plasmon resonance biomolecular interaction analysis mass spectrometry. 2. Fiber optic-based analysis

Fiber optic probe-based surface plasmon resonance (SPR) detection has been used in combination with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry for the rapid, sensitive, and selective detection of biomolecules. SPR was used to monitor the covalent immobilization of a polyclonal antibody to the surface of a fiber optic probe. The derivatized probe was then used for the selective detection (from solution) of the corresponding antigen and a secondary antibody directed toward the antigen. Species retained during the SPR detection process were next analyzed by direct MALDI-TOF analysis of the probe surface (after exposed to the MALDI matrix and introduction into the mass spectrometer). The combined approach allowed for the two-dimensional detection of biomolecules, with SPR analysis yielding quantitative information pertinent to the binding events and MALDI-TOF providing details on the qualitative nature of the binding partners.

Surface plasmon resonance biomolecular interaction analysis mass spectrometry. 1. Chip-based analysis

The use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) in concert with surface plasmon resonance-based biomolecular interaction analysis (SPR-BIA) is reported. A chip-based biosensor unit was used to simultaneously monitor biomolecular interactions taking place on four different regions of the sensor chip (flow cells). Species retained during SPR-BIA were then identified by performing MALDI-TOF directly from within the area of the flow cells. Analyses were performed on an antibody/antigen/antibody system with detection limits in the low-femtomole range. The combined assay demonstrates the use of SPR-BIA to evaluate the relative stability of sequential solution-phase interactions, as well as, upon MALDI-TOF analysis, the ability to unambiguously confirm the presence of species retained during the interaction analysis.

The use of bioreactive probes in protein characterization

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) has in the past decade found routine use in the biological sciences. With this use has evolved several mass spectrometric-based methods directed at the intricate investigation of biomolecular structure and function. One such methodology involves the enzymatic modification of a protein prior to the mass spectrometric readout of the resulting products. The enzyme-modification/mass spectrometric approach has a definite use in a number of applications, including: the verification/identification of protein sequence, elucidation of post-translational modifications, the investigation of protein higher-order structure, and even the characterization of the modifying enzyme. To avoid the potentials of sample loss and autolytic interferences in the mass spectrum, mass spectrometer targets can be covalently derivatized with enzymes for use in the characterization procedures. The enzymatically active, or bioreactive, probes are used by application of the analyte to the activated surface, followed by application of a suitable MALDI matrix and mass analysis from the surface of the probe. Limited transfer and handling steps eliminate sample losses, and surface-tethered enzymes (and autolytic fragments) are prohibited from interfering with analytical signals in the mass spectra. In addition, the probes are rapid and easy to use. Reviewed here are issues of concern during the manufacture and use of the bioreactive probes, and application of the probes to investigate protein structure and function.

Use of urine cortisol:creatinine ratio versus adrenocorticotropic hormone stimulation testing for monitoring mitotane treatment of pituitary-dependent hyperadrenocorticism in dogs

OBJECTIVE

To evaluate use of urine cortisol-to-creatinine ratio (UC:C) as a means of monitoring response to long-term mitotane treatment in dogs with pituitary-dependent hyperadrenocorticism.

DESIGN

Prospective uncontrolled study.

ANIMALS

101 dogs with pituitary-dependent hyperadrenocorticism.

PROCEDURE

Urine samples were obtained from dogs on the morning an ACTH stimulation test was performed, and owners were asked their opinion on the health of their dog to monitor response to mitotane treatment. Urine was assayed for cortisol and creatinine concentrations, and UC:C was calculated. The UC:C was compared with post-ACTH plasma cortisol concentration.

RESULTS

Post-ACTH plasma cortisol concentration was used to categorize each dog's response to mitotane treatment. The UC:C did not correlate satisfactorily with results of ACTH stimulation testing. Twenty-seven of 85 (32%) dogs would have been incorrectly considered as having received appropriate doses using UC:C. In addition, 16 dogs that received overdoses could not be distinguished from 29 dogs that received appropriate doses.

CLINICAL IMPLICATIONS

UC:C does not provide a consistent, correct assessment of mitotane-induced adrenocortical destruction. The ACTH stimulation test, although more time-consuming and expensive, is recommended for monitoring response to mitotane treatment.

Glycosylated hemoglobin concentrations in the blood of healthy dogs and dogs with naturally developing diabetes mellitus, pancreatic beta-cell neoplasia, hyperadrenocorticism, and anemia

OBJECTIVE

To characterize glycosylated hemoglobin (GHb) concentrations in the blood of dogs with disorders that may affect serum glucose or blood GHb concentrations, and to determine whether changes in GHb concentration correlate with changes in control of diabetes in dogs.

DESIGN

Prospective study.

ANIMALS

63 healthy dogs, 9 dogs with anemia, 24 dogs with untreated hyperadrenocorticism, 12 dogs with pancreatic beta-cell neoplasia, 23 dogs with newly diagnosed diabetes mellitus, and 77 diabetic dogs treated with insulin.

PROCEDURE

Control of diabetes in dogs treated with insulin was classified as good or poor on the basis of history, physical examination findings, changes in body weight, and measurement of serum glucose concentrations Sequential evaluations of control were performed and GHb concentration in blood was measured, by means of affinity chromatography, for 5 untreated diabetic dogs before and after initiating insulin treatment, for 10 poorly controlled diabetic dogs before and after increasing insulin dosage, and for 5 diabetic dogs before and after pancreatic islet cell transplantation.

RESULTS

Mean (+/-SD) GHb concentration was 3.3 +/- 0.8% in the blood of healthy dogs. Compared with results from healthy dogs, mean GHb concentration was significantly lower in the blood of dogs with anemia and pancreatic beta-cell neoplasia and significantly higher in the blood of untreated diabetic dogs. Mean GHb concentration was significantly higher in the blood of 46 poorly controlled diabetic dogs, compared with 31 well-controlled diabetic dogs (7.3 +/- 1.8 vs 5.7 +/- 1.7%, respectively). Mean GHb concentration in blood decreased significantly in 5 untreated diabetic dogs after treatment (8.7 +/- 1.9 vs 5.3 +/- 1.9%). Mean GHb concentration in blood also decreased significantly in 10 poorly controlled diabetic dogs after control was improved and in 5 diabetic dogs after they had received a pancreatic islet cell transplant.

CLINICAL IMPLICATIONS

Measurement of GHb concentration in blood may assist in monitoring control of diabetes in dogs.

Diabetic ketosis and ketoacidosis in cats: 42 cases (1980-1995)

OBJECTIVE

To determine clinical signs, clinicopathologic abnormalities, prevalence of concurrent disease, treatment, complications of treatment, and outcome in cats with diabetic ketosis (DK) or diabetic ketoacidosis (DKA).

DESIGN

Retrospective study.

ANIMALS

42 cats with DK or DKA.

PROCEDURE

Medical records of diabetic cats with ketonuria were reviewed.

RESULTS

In 26 cats, diabetes was newly diagnosed; in 16, diabetes had been diagnosed previously and cats had been treated with insulin (n = 14) or sulfonylurea drugs (2). Common clinical findings were lethargy, anorexia, polyuria, polydipsia, and weight loss. Common laboratory findings were hyperglycemia, hyponatremia, hypochloremia, hypokalemia, hypocalcemia, hypophosphatemia, low total CO2 content, hyperosmolality, high serum alanine transaminase activity, azotemia, glycosuria, and ketonuria. Concurrent disorders were identified in 39 cats and included hepatic lipidosis, cholangiohepatitis, pancreatitis, chronic renal failure, urinary tract infection, and neoplasia. Treatment of DK and DKA included administration of regular crystalline (34 cats), NPH (6), or ultralente (2) insulin, intravenous (38) or subcutaneous (4) administration of fluids, and enterall parenteral or administration of antibiotics (42). Complications during treatment included abnormalities in serum electrolyte concentrations (27 cats), hemolytic anemia (4), hypoglycemia (3), and neurologic abnormalities unrelated to hypoglycemia (2). Eleven cats died or were euthanatized during the initial hospitalization period for treatment of DK or DKA. Azotemia, metabolic acidosis, and hyperosmolality were more severe in cats that died than in cats that survived. Differences in regard to treatment or complications were not apparent between cats that died and cats that survived. The 31 cats that survived were discharged 1 to 16 days (median, 5 days) after initiation of insulin treatment. Diabetic ketosis or ketoacidosis recurred in 13 (42%) of these cats.

CLINICAL IMPLICATIONS

A thorough diagnostic evaluation should be performed on cats with DK or DKA to identify concurrent disorders, formulate an appropriate treatment plan, and provide prognostic information to the owner.

Comparison of results of hormonal analysis of samples obtained from selected venous sites versus cervical ultrasonography for localizing parathyroid masses in dogs

OBJECTIVE

To compare a technique in which samples obtained from selected venous sites are analyzed for parathyroid hormone (PTH) concentration versus usefulness of cervical ultrasonography for localizing primary hyperparathyroidism (PHP) in dogs.

DESIGN

Prospective study.

ANIMALS

12 dogs with PHP.

PROCEDURE

For each dog, blood samples were collected from the left and right jugular veins and 1 cephalic vein for determination of serum PTH concentration. Ultrasonography of the neck was performed in each dog. Each dog underwent exploratory surgery of the neck. Abnormal appearing parathyroid tissue was removed. Dogs were included in the study if serum calcium concentration decreased within 12 hours after surgery, hypercalcemia completely resolved within 96 hours after surgery, and serum calcium concentration was maintained within the reference range for at least 6 months after surgery.

RESULTS

Serum PTH concentrations from the 3 veins were similar in 11 of 12 dogs with PHP. In 1 dog, the serum PTH concentration from the jugular vein ipsilateral to a parathyroid adenoma was greater than that from the contralateral jugular or cephalic vein. Ultrasonography correctly identified a parathyroid mass and its location in 10 of 11 dogs with a solitary abnormal parathyroid gland and in 1 dog in which both parathyroid glands were enlarged.

CLINICAL IMPLICATIONS

Surgeons may benefit from knowing the location of abnormal parathyroid tissue in dogs with PHP before surgical exploration. Ultrasonography has potential value for identifying and localizing abnormal parathyroid tissue, whereas sample collection from selected sites for PTH analysis is not likely to be helpful.

Glycosylated hemoglobin concentration for assessment of glycemic control in diabetic cats

Blood glycosylated hemoglobin (GHb) concentration was quantified in 84 healthy cats, 9 cats with stress-induced hyperglycemia, 37 cats with newly diagnosed diabetes mellitus, and 122 diabetic cats treated with insulin or glipizide. Diabetic control was classified as good or poor in insulin-treated or glipizide-treated cats based on review of history, physical examination findings, changes in body weight, and measurement of blood glucose concentrations. Blood GHb concentration was determined using an affinity chromatography assay. Mean blood GHb concentration was similar for healthy normoglycemic cats and cats with transient, stress-induced hyperglycemia, but was significantly (P < .001) higher in untreated diabetic cats when compared with healthy normoglycemic cats. Mean blood GHb concentration was significantly (P < .001) higher in 84 cats with poorly controlled diabetes mellitus when compared with 38 cats in which the disease was well controlled. Mean blood GHb concentration decreased significantly (P < .01) in 6 cats with untreated diabetes mellitus after insulin and dietary treatment. A similar significant (P < .01) decrease in mean blood GHb concentration occurred in 7 cats with poorly controlled diabetes mellitus after diabetic control was improved by an increase in insulin dosage from 1.1 +/- 0.9 to 1.4 +/- 0.6 U/kg/ 24 h and by feeding a diet containing increased fiber content and in 6 cats with transient diabetes mellitus 8.2 +/- 0.6 weeks after discontinuing insulin treatment. There was a significant (P < .01) stress-induced increase in mean fasting blood glucose concentration and mean blood glucose concentration for 12 hours after administration of insulin or glipizide but no change in mean blood GHb concentration in 5 docile diabetic cats 12.2 +/- 0.4 weeks after the cats became fractious as a result of frequent hospitalizations and blood samplings. Results of this study suggest that evaluation of blood GHb concentration may be a clinically useful tool for monitoring glycemic control of diabetes in cats.

Intensive 50-week evaluation of glipizide administration in 50 cats with previously untreated diabetes mellitus

OBJECTIVE

To evaluate use of the oral hypoglycemic drug glipizide in diabetic cats.

DESIGN

Prospective study.

ANIMALS

50 cats with recently diagnosed but untreated diabetes mellitus.

PROCEDURE

Each cat received glipizide (5 mg, q 12 h) for 16 weeks. Medication was not given during the subsequent 16 weeks; then glipizide treatment was repeated. Each cat was evaluated prior to treatment and at 2, 4, 8, 12, and 16 weeks during each of the 3 phases: blood samples for serum glucose and insulin determinations were obtained every 2 hours, from 8 AM to 6 PM. A preprandial blood glycosylated hemoglobin percentage was determined for the first sample obtained at each visit.

RESULTS

During the first 22 weeks of the study, diabetes worsened in 28 of the 50 cats, which then were disqualified from the study and treated with insulin. Of the remaining 22 cats that improved clinically, 7 had corresponding metabolic improvement in each diabetes-related parameter assessed and did not become hypoglycemic. Six of the 22 cats became hypoglycemic. Glipizide was discontinued, and diabetes did not recur. Serum glucose concentration did not improve in 6. Three cats had metabolic and clinical improvement during initial glipizide treatment, but had recurrence of the disease during repeated treatment; glipizide was discontinued and insulin was administered. None of the 50 treated cats died, and observed morbidity was mild and transient. Transient anorexia and vomiting were observed in 8 cats, and 4 became transiently icteric with abnormal liver enzyme activities.

CLINICAL IMPLICATIONS

Trial use of glipizide is feasible in diabetic cats of owners who are unable or unwilling to administer insulin.

Effect of weight gain and subsequent weight loss on glucose tolerance and insulin response in healthy cats

The effects of weight gain and subsequent weight loss on glucose tolerance and insulin response were evaluated in 12 healthy cats. Intravenous glucose tolerance tests (IVGTT) were performed at entry into the study, after a significant gain of body weight induced by feeding palatable commercial cat food ad libitum, after a significant loss of body weight induced by feeding a poorly palatable purified diet to discourage eating and promote fasting, and after recovery from fasting when body weight had returned to pre-study values and cats were eating commercial foods. A complete physical examination with measurement of body weight was performed weekly, a CBC and serum biochemistry panel were evaluated at the time of each IVGTT, and a liver biopsy specimen obtained 2 to 4 days after each IVGTT was evaluated histologically for each cat. Mean serum glucose and insulin concentrations after glucose infusion and total amount of insulin secreted during the second 60 minutes and entire 120 minutes after glucose infusion were significantly (P < .05) increased after weight gain, as compared with baseline. At the end of weight loss, cats had hepatic lipidosis and serum biochemical abnormalities consistent with feline hepatic lipidosis. There was a significant (P < .05) increase in mean serum glucose concentration and t1/2, and a significant (P < .05) decrease in mean serum insulin concentration and the glucose disappearance coefficient (K) after glucose infusion for measurements obtained after weight loss, compared with those obtained after weight gain and at baseline. Insulin peak response, insulinogenic index, and total amount of insulin secreted during the initial 10 minutes, 20 minutes, and 60 minutes after glucose infusion were decreased markedly (P < .05), compared with measurements obtained after weight gain and at baseline. In addition, the total amount of insulin secreted for 120 minutes after glucose infusion was decreased markedly (P < .05) in measurements obtained after weight loss, compared with those obtained after weight gain. At the end of recovery, all cats were voluntarily consuming food, serum biochemical abnormalities identified after weight loss had resolved, the number and size of lipid vacuoles in hepatocytes had decreased, and results of IVGTT were similar to those obtained at baseline. These findings confirmed the reversibility of obesity-induced insulin resistance in cats, and documented initial deterioration in glucose tolerance and insulin response to glucose infusion when weight loss was caused by severe restriction of caloric intake.

BIA/MS: interfacing biomolecular interaction analysis with mass spectrometry

Biomolecular interaction analysis (BIA) which utilizes surface plasmon resonance (SPR) detection of affinity-captured analytes has been interfaced with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI). Femtomole quantities of a peptide, myotoxin a, were detected by direct MALDI analysis of sensor chips used during BIA of a polyclonal anti-myotoxin a IgG/myotoxin a system. Further, different interactive surfaces (flow cells) present on a single biosensor were targeted individually for mass spectrometric analysis. System compatibility of the combined approach was demonstrated with sensitivities, detection limits, and analytical performances comparable to those intrinsic to the individual analyses. The combined approach unites the real-time capabilities of SPR-based BIA with the qualitative specificity of mass spectrometry.

Central diabetes insipidus in dogs: 20 cases (1986-1995)

OBJECTIVE

To assess clinical signs, biochemical findings, results of modified water deprivation and other diagnostic tests, response to treatment, and survival time in dogs with central diabetes insipidus (CDI).

DESIGN

Retrospective study.

ANIMALS

20 dogs with CDI.

PROCEDURE

Signalment, history, physical examination, results of diagnostic tests, response to treatment, and survival time were extracted from the medical record of each dog and supplemented with information obtained from owners via telephone.

RESULTS

Isosthenuria or hyposthenuria was a consistent finding. Seven dogs with complete CDI and 13 dogs with partial CDI were identified on the basis of results of a modified water deprivation test. Dogs treated with desmopressin acetate responded well to treatment. Seven dogs were alive 18 to 72 months (median, 36 months) after diagnosis, and 10 dogs died or were euthanatized 1 week to 2 years (median, 2 months) after diagnosis. Seven of 10 dogs that died developed neurologic signs after diagnosis of CDI. Computed tomography revealed a mass in the region of the pituitary gland in 5 of 7 dogs. Necropsy of 6 dogs, including 2 dogs on which computed tomography had been performed, revealed neoplasia in the pituitary gland.

CLINICAL IMPLICATIONS

Onset of neurologic signs after diagnosis of CDI in middle- to old-aged dogs indicates that CDI may not be a benign disease that is treated easily. Brain imaging is recommended after diagnosis of CDI in middle- to old-aged dogs. Also, because many dogs are isosthenuric on initial examination, CDI cannot be ruled out as a cause of polyuria and polydipsia on the basis of lack of hyposthenuria.

Systemic arterial blood pressure and urine protein/creatinine ratio in dogs with hyperadrenocorticism

OBJECTIVE

To determine prevalence and severity of systemic arterial hypertension and proteinuria in dogs with naturally developing hyperadrenocorticism and to determine whether these abnormalities resolve with adequate management of the disease.

DESIGN

Case series and cohort study.

ANIMALS

77 dogs with naturally developing hyper-adrenocorticism examined once; 15 dogs examined before and after treatment.

RESULTS

Among dogs examined only once, hypertension was diagnosed in 21 of 26 dogs with untreated pituitary-dependent hyperadrenocorticism (PDH), 17 of 21 with inadequately controlled PDH, 8 of 16 with well-controlled PDH, 10 of 10 with an untreated adrenocortical tumor, and 0 of 4 that had undergone adrenalectomy because of an adrenocortical tumor. Untreated dogs and dogs with inadequately controlled PDH had significantly higher blood pressures than did other dogs. Proteinuria was documented in 12 of 26 dogs with untreated PDH, 5 of 16 with inadequately controlled PDH, 3 of 14 with well-controlled PDH, 5 of 8 with an untreated adrenocortical tumor, and 1 of 3 that had undergone adrenalectomy. Dogs with untreated PDH and dogs with an untreated adrenocortical tumor had higher urine protein/creatinine ratios than did dogs with well-controlled PDH. Among dogs evaluated before and after treatment, blood pressure and urine protein/creatinine ratio did not change in 8 dogs with inadequately controlled hyperadrenocorticism, but decreased in 7 dogs with well-controlled disease.

CLINICAL IMPLICATIONS

Results suggest that systemic hypertension and proteinuria are common in dogs with untreated hyperadrenocorticism and that successful treatment of hyperadrenocorticism will result in resolution of these abnormalities in many, but not all, dogs.

Evaluation of continuous intraspinal narcotic analgesia for chronic pain from benign causes

Intraspinal narcotic analgesia (INA) has been used for chronic pain from nonmalignant causes with moderate success. To ascertain the efficacy of the morphine pump, we reviewed the 2-year results of continuous INA in 18 patients with failed back syndrome or arachnoiditis and intractable, debilitating pain that was unrelieved by conventional means. All patients underwent a trial screening of single-dose intrathecal narcotics with good pain relief. After 2 years, 8 pumps were still functioning, 8 patients had the pump removed or turned off, and 2 patients were lost to follow-up. Our patients averaged 1.4 additional procedures or hospitalizations after initial pump insertion. Overall, only 4 patients had objective evidence of benefit from INA, for a success rate of 25%. Results of this review suggest INA should not be used for the long-term management of chronic pain from nonmalignant causes.

Use of low- and high-dose dexamethasone tests for distinguishing pituitary-dependent from adrenal tumor hyperadrenocorticism in dogs

OBJECTIVE

To evaluate low- and high-dose dexamethasone suppression tests for differentiating pituitary dependent hyperadrenocorticism (PDH) from adrenal tumor hyperadrenocorticism (ATH) in dogs.

DESIGN

Prospective study.

ANIMALS

181 dogs with PDH and 35 dogs with ATH.

PROCEDURE

Plasma cortisol concentrations from dogs with naturally developing hyperadrenocorticism were evaluated before, and 4 and 8 hours after administration of standard low- and high-doses of dexamethasone (0.01 mg/kg of body weight, i.v., and 0.1 mg/kg, i.v.; respectively).

RESULTS

In response to the low-dose test, all but 3 dogs had an 8-hours post-dexamethasone plasma cortisol concentration that was consistent with a diagnosis of hyperadrenocorticism, that is, > or = 1.4 micrograms/dl. Criteria used to distinguish PDH from ATH in response to low-dose dexamethasone included a 4-hour post-dexamethasone plasma cortisol concentration < 50% of the basal value or < 1.4 micrograms/dl, or an 8-hours post-dexamethasone plasma cortisol concentration < 50% of the basal concentration. Criteria used to distinguish PDH from ATH in response to high-dose dexamethasone included 4- or 8-hour post-dexamethasone plasma cortisol concentrations < 50% of the basal concentration or < 1.4 micrograms/dl. In response to the low-dose test, 111 dogs met criteria for suppression (each had PDH). In response to the high-dose test, 137 dogs met criteria for suppression (2 had ATH, 135 had PDH). Twenty-six dogs with PDH (12%) had indications of adrenal suppression in response to high-dose but not low-dose testing.

CLINICAL IMPLICATIONS

Low-dose dexamethasone test has value as a discrimination test to distinguish dogs with PDH from those with ATH. The high-dose test need only be considered in dogs with hyperadrenocorticism that do not have adrenal suppression in response to the low-dose test.