Cortisol Response in Healthy and Diseased Dogs after Stimulation with a Depot Formulation of Synthetic ACTH

Differences in selected blood parameters between brachycephalic and non-brachycephalic dogs

Introduction

Cranial and upper-airway anatomy of short-nosed, flat-faced brachycephalic dogs predisposes them to brachycephalic obstructive airway syndrome (BOAS). Periodic apnoea increased inspiratory resistance, and an inability to thermoregulate effectively are characteristic of BOAS, but internationally accepted objective markers of BOAS severity are missing. The objective of this study was to compare the selected blood parameters between non-brachycephalic (NC) and brachycephalic (BC) dogs, exploring the possibility of developing a blood test for BOAS severity grading in the future.

Methods

We evaluated blood biochemistry, complete blood cell counts, red blood cell (RBC) indices, reticulocyte counts, a blood-born marker of intermittent hypoxia (glutathione, NO production), RBC hydration, deformability, and blood markers of metabolic changes and stress between BC (n = 18) and NC (meso- and dolichocephalic, n = 22) dogs.

Results

Reticulocyte counts and the abundance of middle-fluorescence immature reticulocytes were significantly (p < 0.05) higher in BC dogs compared to NC dogs. BC dogs had significantly more NO-derived NO2 - /NO3 - in plasma than NC dogs. RBCs of BC dogs were shedding significantly more membrane, as follows from the intensity of eosin maleimide staining, and had a significantly higher mean corpuscular hemoglobin concentration than NC dogs. Intracellular reduced glutathione content in RBCs of BC dogs was significantly lower, while plasma lactate was significantly higher in BC dogs compared to NC dogs. Plasma cholesterol and triglycerides were significantly lower, and cortisol was significantly higher in BC dogs compared to NC dogs. Eosinophil counts were significantly lower and the neutrophil-to-lymphocyte ratio was higher in BC dogs compared to NC dogs.

Discussion

Taken together, our findings suggest that the brachycephalic phenotype in dogs is associated with alterations at the level of blood cells and, systemically, with oxidation and metabolic changes. The parameters identified within this study should be further investigated for their potential as objective indicators for BOAS.

Effects of concurrent canine Cushing's syndrome and diabetes Mellitus on insulin requirements, trilostane dose, and survival time

Trilostane and insulin requirements and survival time of dogs with concurrent naturally-occurring Cushing's syndrome (CS) and diabetes mellitus (DM) has not been fully investigated. This retrospective study evaluated trilostane and insulin doses in dogs with concurrent CS and DM compared to dogs with only CS or DM. Additionally, a survival analysis was performed using a Kaplan-Meier survival curve. Survival time was compared through Log-rank test. Cox proportional regression method was used to screen predictor factors of death in dogs with CS, DM or concurrent CS and DM. A total of 95 dogs were included, 47 dogs had CS, 31 dogs had DM and 17 dogs had concurrent CS and DM. After long-term follow-up, dogs with concurrent CS and DM required higher final median doses of insulin than dogs with DM [0.90 (0.73-1.1) vs 0.67 (0.55-0.73) u/kg/12 h; P = 0,002]. Conversely, the median trilostane requirements in dogs with concurrent CS and DM did not differ from the median trilostane requirements of dogs with CS [1.52 (0.76-2.80) vs 1.64 (1.19-4.95) mg/kg/day; P = 0.283]. No statistical difference was found for the median survival time between dogs with CS and dogs with concurrent CS and DM (1245 vs 892 days; p = 0.152). Although, median survival time of dogs with DM was not reached, it was longer than median survival time of dogs with CS and DM (892 days; P = 0.002). In conclusion, diabetic dogs with concurrent CS need higher insulin doses and have a shorter survival time compared to diabetic dogs without CS.

Evaluation of the ACTH stimulation test using a low dose of a depot formulation in healthy dogs and in dogs with untreated Cushing's syndrome

The sensitivity of the adrenocorticotropic hormone (ACTH) stimulation test to detect Cushing's Syndrome (CS) using a depot formulation needs to be evaluated. The aims of this study were to propose a reference interval (RI) for cortisol values 1-hour after administration of a low-dose of depot ACTH in healthy dogs, and to evaluate the sensitivity of this test to detect CS, differentiating among types of CS based on ultrasound findings. Forty-one healthy dogs (20 males, 21 females) were prospectively included. Additionally, 90 dogs with CS (31 males, 59 females) were retrospectively included. Dogs with CS were ultrasonographically classified as follows: 44 dogs with symmetrical adrenomegaly consistent with pituitary-dependent hypercortisolism (PDH), 8 dogs with unilateral adrenomegaly and atrophy of the contralateral adrenal gland or unilateral or bilateral adrenomegaly with malignancy features consistent with adrenal-dependent hypercortisolism (ADH), 34 dogs with equivocal adrenal asymmetry (EAA) and 4 dogs with normal adrenal thickness. In healthy dogs, lower and upper limit of the 95% RI for 1-hour post-ACTH cortisol concentration and their 90% confidence intervals, were 4.4 (2.7-5.8) μg/dl and 18.4 (16.5-20.0) μg/dl, respectively. Post-ACTH cortisol concentration was above the RI in 90.0% (ci95%, 76.1-100) of dogs with CS. An elevated post-ACTH cortisol concentration was detected in 95.5% (ci95%, 76.1-100) of dogs with PDH, 62.5% (ci95%, 46.1-78.9) of dogs with ADH and 88.2% (ci95%, 69.1-100) of dogs with EAA. The sensitivity of the ACTH stimulation test using a low-dose of depot ACTH in high in dogs with CS.

Tertiary Oxidation of Deoxycholate Is Predictive of CYP3A Activity in Dogs

Deoxycholic acid (DCA, 3α, 12α-dihydroxy-5β-cholan-24-oic acid) is the major circulating secondary bile acid, which is synthesized by gut flora in the lower gut and selectively oxidized by CYP3A into tertiary metabolites, including 1β,3α,12α-trihydroxy-5β-cholan-24-oic acid (DCA-1β-ol) and 3α,5β,12α-trihydroxy-5β-cholan-24-oic acid (DCA-5β-ol) in humans. Since DCA has the similar exogenous nature and disposition mechanisms as xenobiotics, this work aimed to investigate whether the tertiary oxidations of DCA are predictive of in vivo CYP3A activities in beagle dogs. In vitro metabolism of midazolam (MDZ) and DCA in recombinant canine CYP1A1, 1A2, 2B11, 2C21, 2C41, 2D15, 3A12, and 3A26 enzymes clarified that CYP3A12 was primarily responsible for either the oxidation elimination of MDZ or the regioselective oxidation metabolism of DCA into DCA-1β-ol and DCA-5β-ol in dog liver microsomes. Six male dogs completed the CYP3A intervention studies including phases of baseline, inhibition (ketoconazole treatments), recovery, and induction (rifampicin treatments). The oral MDZ clearance after a single dose was determined on the last day of the baseline, inhibition, and induction phases, and subjected to correlation analysis with the tertiary oxidation ratios of DCA detected in serum and urine samples. The results confirmed that the predosing serum ratios of DCA oxidation, DCA-5β-ol/DCA, and DCA-1β-ol/DCA were significantly and positively correlated both intraindividually and interindividually with oral MDZ clearance. It was therefore concluded that the tertiary oxidation of DCA is predictive of CYP3A activity in beagle dogs. Clinical transitional studies following the preclinical evidence are promising to provide novel biomarkers of the enterohepatic CYP3A activities. SIGNIFICANCE STATEMENT: Drug development, clinical pharmacology, and therapeutics are under insistent demands of endogenous CYP3A biomarkers that avoid unnecessary drug exposure and invasive sampling. This work has provided the first proof-of-concept preclinical evidence that the CYP3A catalyzed tertiary oxidation of deoxycholate, the major circulating secondary bile acid synthesized in the lower gut by bacteria, may be developed as novel in vivo biomarkers of the enterohepatic CYP3A activities.

Ultrasound evaluation of adrenal gland size in clinically healthy dogs and in dogs with hyperadrenocorticism

BACKGROUND

Precise reference intervals of adrenal gland thickness are required for detection of adrenomegaly in dogs with hyperadrenocorticism (HAC).

METHODS

Eighty-six clinically healthy dogs were prospectively included, and 91 dogs with untreated HAC were retrospectively evaluated. Dorso-ventral adrenal gland thickness was ultrasonographically measured on the sagittal plane. Dogs were classified into four body weight categories, and those with HAC were also ultrasonographically classified as consistent with pituitary-dependent HAC (PDH), adrenal-dependent HAC (FAT), equivocal adrenal asymmetry (EAA), or normal adrenal thickness.

RESULTS

The upper limits for left adrenal gland in clinically healthy dogs were 5.1 mm (≥2.5-5 kg), 5.5 mm (>5-10 kg), 6.4 mm (>10-20 kg), and 7.3 mm (>20-40 kg), and for right adrenal gland the upper limits were 5.3 mm (≥2.5-5 kg), 6.8 mm (>5-10 kg), 7.5 mm (>10-20 kg), and 8.7 mm (>20-40 kg). The sensitivity of ultrasound to detect adrenomegaly in dogs with HAC was 95.6%. Most dogs with HAC (56.0%) had ultrasound findings consistent with either PDH or FAT; however, EAA was commonly occurring in 39.6% of dogs with HAC.

CONCLUSIONS

The sensitivity of ultrasonography to detect adrenomegaly in dogs with HAC is high when using four weight categories. EAA is common in dogs with HAC.

Presumptive iatrogenic hypoadrenocorticism induced by high-dose ketoconazole administration in a dog

A 11‐year‐old male neutered Shih Tzu was referred to a tertiary facility with a history of weight loss, decreased appetite, polydipsia, and lethargy. The dog had a 10‐year history of nonspecific allergic dermatitis and was being treated with 16 mg/kg of ketoconazole q12h for Malassezia dermatitis. Vague gastrointestinal signs, hypocholesterolemia, and lack of a stress leukogram increased suspicion for hypoadrenocorticism (HA). An adrenocorticotropic hormone (ACTH) stimulation test identified hypocortisolemia on pre‐ and post‐ACTH samples and ketoconazole was discontinued. After a short course of corticosteroid treatment, an ACTH stimulation test was repeated and pre‐ACTH cortisol concentration was within the reference range, and the post‐ACTH cortisol concentration was mildly increased. The temporal association between return of adequate adrenocortical cortisol production and discontinuation of ketoconazole led to the conclusion that the dog had developed iatrogenic HA secondary to ketoconazole treatment.

Diagnosis of spontaneous hyperadrenocorticism in dogs. Part 2: Adrenal function testing and differentiating tests

Hyperadrenocorticism is a relatively common endocrine disorder in dogs that has been extensively described. However, its diagnosis remains challenging because there is no true reference standard test, and a myriad factors can affect the diagnostic performance of the commonly used adrenal function tests. Ultimately, the diagnosis is based on a combination of signalment, history and clinical findings, and a variety of diagnostic test results. The second part of this review aims to appraise available data on diagnostic performance of adrenal function tests in naturally occurring canine hyperadrenocorticism.

Changes in the Canine Plasma Lipidome after Short- and Long-Term Excess Glucocorticoid Exposure

Glucocorticoids (GCs) are critical regulators of metabolic control in mammals and their aberrant function has been linked to several pathologies. GCs are widely used in human and veterinary clinical practice as potent anti-inflammatory and immune suppressive agents. Dyslipidaemia is a frequently observed consequence of GC treatment, typified by increased lipolysis, lipid mobilization, liponeogenesis, and adipogenesis. Dogs with excess GC show hyperlipidaemia, hypertension, and a higher risk of developing type 2 diabetes mellitus, but the risk of developing atherosclerotic lesions is low as compared to humans. This study aimed to examine alterations in the canine plasma lipidome in a model of experimentally induced short-term and long-term GC excess. Both treatments led to significant plasma lipidome alterations, which were more pronounced after long-term excess steroid exposure. In particular, monohexosylceramides, phosphatidylinositols, ether phosphatidylcholines, acyl phosphatidylcholines, triacylglycerols and sphingosine 1-phosphates showed significant changes. The present study highlights the hitherto unknown effects of GCs on lipid metabolism, which will be important in the further elucidation of the role and function of GCs as drugs and in metabolic and cardiovascular diseases.

Update on the use of trilostane in dogs

Many articles published in the past few years have contributed to a better understanding of the use of trilostane in dogs. Trilostane is a competitive inhibitor of 3β-hydroxysteroid dehydrogenase, the enzyme essential for synthesis of cortisol and all other steroids. Trilostane is reported to be safe and effective in the treatment of pituitary-dependent hyperadrenocorticism (HAC), adrenal-dependent HAC, and alopecia X. While trilostane controls most of the clinical signs associated with HAC, abnormalities such as hypertension, hypercoagulability, and proteinuria may persist despite therapy. Because the duration of cortisol suppression after a dose of trilostane is often less than 12 hours, many dogs with HAC could benefit from low dose trilostane treatment every 12 hours. Many controversies regarding trilostane still exist. This review provides a comprehensive commentary on trilostane's indications, mode of action, dose, monitoring, efficacy, and adverse effects.

Management of hypoadrenocorticism (Addison's disease) in dogs

Hypoadrenocorticism (HOAC; Addison’s disease) is an endocrine condition seen in small animal practice. Dogs with this disease can present in a variety of ways from acute hypovolemic collapse to vague, chronic, waxing, and waning clinical signs. In the most common form of this disease, animals have both mineralocorticoid and glucocorticoid deficiency, resulting in hyponatremia and hyperkalemia, and signs of cortisol deficiency. The etiology may be immune-mediated destruction of the adrenal cortex, drug-induced adrenocortical necrosis (mitotane), enzyme inhibition (trilostane), or infiltrative processes such as neoplastic or fungal disease. Much less commonly, dogs have signs of cortisol deficiency, but no electrolyte changes. This is referred to as atypical HOAC. The veterinarian needs to have a clinical suspicion for HOAC to make a diagnosis in a timely manner. Treatment of dogs with an acute presentation prioritizes correcting the hypovolemia, hyperkalemia, acidosis, and hypoglycemia. Fluid therapy addresses most of these issues, but other directed therapies may be required in the most severe cases. For chronic management, all patients with Addison’s disease will require replacement of glucocorticoids (usually prednisone), and most patients require replacement of mineralocorticoids with either desoxycorticosterone pivalate or fludrocortisone. Atypical Addisonians do not require mineralocorticoid supplementation, but electrolytes should be monitored in case the need arises in the future. The prognosis for dogs treated for HOAC promptly and appropriately is excellent; most patients die from other diseases. However, if the diagnosis is missed, patients may die as a consequence of HOAC. Thus, knowledge of the hallmarks of Addison’s disease is imperative.