Urinary and plasma catecholamines and metanephrines in dogs with pheochromocytoma, hypercortisolism, nonadrenal disease and in healthy dogs.

BACKGROUND: Diagnosis of pheochromocytoma (PC) is based on a combination of clinical suspicion, finding an adrenal mass, increased plasma, and urine concentrations of catecholamine metabolites and is finally confirmed with histopathology. In human medicine, it is controversial whether biochemically testing plasma is superior to testing urine. OBJECTIVES: To measure urinary and plasma catecholamines and metanephrines in healthy dogs, dogs with PC, hypercortisolism (HC), and nonadrenal diseases (NAD) and to determine the test with the best diagnostic performance for dogs with PC. ANIMALS: Seven PC dogs, 10 dogs with HC, 14 dogs with NAD, 10 healthy dogs. METHODS: Prospective diagnostic clinical study. Urine and heparin plasma samples were collected and stored at -80°C before analysis using high-pressure liquid chromatography (HPLC) coupled to electrochemical detection or tandem mass spectrometry were performed. Urinary variables were expressed as ratios to urinary creatinine concentration. RESULTS: Dogs with PC had significantly higher urinary normetanephrine and metanephrine : creatinine ratios and significantly higher plasma-total and free normetanephrine and plasma-free metanephrine concentrations compared to the 3 other groups. There were no overlapping results of urinary normetanephrine concentrations between PC and all other groups, and only one PC dog with a plasma normetanephrine concentration in the range of the dogs with HC and NAD disease. Performances of total and free plasma variables were similar. Overlap of epinephrine and norepinephrine results between the groups was large with both urine and plasma. CONCLUSION AND CLINICAL IMPORTANCE: Measurement of normetanephrine is the preferred biochemical test for PC and urine was superior to plasma

Serum insulin‐like growth factor‐1 concentrations in healthy cats before and after weight gain and weight loss

Background: Measurement of serum concentrations of insulin-like growth factor (IGF)-1 is used to diagnose acromegaly in cats. Hypothesis: Changes of body weight do not affect serum concentrations of IGF-1 in cats. Animals: Ten healthy purpose-bred cats. Methods: Prospective study. In lean cats, food availability was stepwise increased during the first week and given ad libitum for a total of 40 weeks to increase their body weight. From week 41 to week 60, food access was limited to reach a weight loss of 1% to 2% each week. Measurement of IGF-1 was performed at week 0, 16, 40, and 60. Insulin-like growth factor-1 was measured by radioimmunoassay. Body weight and IGF-1 were compared among the 4 time points. Results: Body weight increased by 44% from week 0 (4.5 ± 0.4 kg) to week 40 (6.5 ± 1.2 kg) (P < .001) and decreased by 25% from week 40 to week 60 (4.9 ± 0.7 kg) (P < .001). Serum IGF-1 concentrations did not differ during the study period (week 0, 16, 40, 60: 500 ± 188, 479 ± 247, 470 ± 184, 435 ± 154 ng/mL, respectively; P = .38). Correlations with body weight were not observed. Conclusions and clinical importance: Insulin-like growth factor-1 might not be influenced by changes of body weight in healthy cats, possibly suggesting that the latter is unimportant when interpreting IGF-1 results in this species

Glucose concentrations after insulin-induced hypoglycemia and glycemic variability in healthy and diabetic cats

BACKGROUND: Little information is available about posthypoglycemic hyperglycemia (PHH) in diabetic cats, and a causal link between hypoglycemia and subsequent hyperglycemia is not clear. Fluctuations in blood glucose concentrations might only represent high glycemic variability. HYPOTHESIS: Insulin induces PHH in healthy cats, and PHH is associated with poorly regulated diabetes and increased glycemic variability in diabetic cats. ANIMALS: Six healthy cats, 133 diabetic cats. METHODS: Insulin (protamine-zinc and degludec; 0.1-0.3 IU/kg) administered to healthy cats. Blood glucose curves were generated with portable glucose meter to determine the percentage of curves with PHH. Data from insulin-treated diabetic cats with blood glucose curves showing hypoglycemia included data of cats with and without PHH. Post-hypoglycemic hyperglycemia was defined as blood glucose concentrations 15 mmol/L within 12 hours. Glycemic variability was calculated as the standard deviation of the blood glucose concentrations. RESULTS: In healthy cats, all insulin doses caused hypoglycemia but PHH was not observed; glycemic variability did not differ between insulin preparations. Among diabetic cats with hypoglycemia, 33 (25%) had PHH. Compared with cats without PHH, their daily insulin dose was higher (1.09 ± 0.55 versus 0.65 ± 0.56 IU/kg; P < .001), serum fructosamine concentration was higher (565 ± 113 versus 430 ± 112 µmol/L; P < .001), remission was less frequent (10% versus 56%; P < .001), and glycemic variability was larger (8.1 ± 2.4 mmol/L versus 2.9 ± 2.2 mmol/L; P < .001). CONCLUSIONS AND CLINICAL IMPORTANCE: Insulin-induced hypoglycemia did not cause PHH in healthy cats but it occurred in 25% of diabetic cats with hypoglycemia, particularly when diabetes was poorly controlled. Glycemic variability was increased in cats with PHH

Oxidative status of erythrocytes, hyperglycemia, and hyperlipidemia in diabetic cats

Background: Erythrocytes of diabetic cats have decreased superoxide dismutaseactivity, possibly indicative of oxidative stress. Hypothesis: Erythrocytes of diabetic cats undergo oxidative stress, which is causedby hyperglycemia and hyperlipidemia, and improves with treatment. Animals: Twenty-seven client-owned cats with diabetes mellitus, 11 matched healthycats, and 21 purpose-bred healthy cats. Methods: Prospective study. Advanced oxidized protein products, carbonyls (proteinoxidation by-products), and thiols (antioxidants) were quantified in erythrocyte mem-brane, thiobarbituric acid reactive substances (TBAR, lipid peroxidation by-products),and thiols in erythrocyte cytoplasm of all cats. Comparison were performed betweendiabetic and matched healthy cats, between diabetic cats achieving remission or not,and among purpose-bred cats after 10 days of hyperglycemia (n = 5) or hyperlipid-emia (n = 6) versus controls treated with saline (n = 5) or untreated (n = 5). Results: Compared with controls, erythrocytes of diabetic cats initially had highermedian membrane carbonyls (4.6 nmol/mg total protein [range: 0.1-37.7] versus 0.7[0.1-4.7],P< .001) and lower cytoplasmic TBAR (1.9 nmol/mg [0.5-2.4] versus 2.4[1.4-3.5]P< .001), and thiols (419 nmol/mg [165-621] versus 633 [353-824],P< 0.001). After 12-16 weeks of treatment in diabetic cats, carbonyls decreased by13% (P< .001), but remained higher (P< .001) and TBAR and thiols lower (P= .02,P< .001) than those in controls. No differences were observed between diabetic catsachieving remission or not, and among purpose-bred cats. Conclusions and Clinical Importance:Diabetes mellitus is associated with increasedprotein oxidation and reduced antioxidant defenses, which persist during treatment and remission, although mild improvement in protein oxidation occurs. Short-termhyperglycemia or hyperlipidemia does not cause oxidative stress. The reason fordecreased TBAR remains unknown

Sample strategies for quantification of hepatic fat fraction mean MRI in healthy cats during body weight gain

Hepatic fat fraction (HFF) can be non-invasively estimated with magnetic resonance imaging (MRI) multiple echo gradient recalled echo (GRE) sequence. The aim of this study was to test different methods of sampling strategies to quantify the HFF in healthy cats during body weight gain. Twelve healthy adult male cats were examined in a 3 Tesla MRI unit. Sequences included morphological images, and multiple echo GRE sequence. Cats were scanned at the beginning of the study and twice, each 20 weeks apart during body weight gain. HFF was calculated with 5 different methods of sampling on the multiple echo GRE sequence with different number, size and position of regions of interest (ROIs) and by 2 operators. Results indicated that HFF increased with increasing body weight, and the increase was appreciated with all the 5 methods. There was overall excellent agreement (interclass correlation coefficient = 0.820 (95% confidence interval:0.775–0.856)) between the 2 operators. HFF in the left lateral hepatic lobe was lower than in the other analyzed lobes. HFF measured on large free-hand drawn ROIs was higher than HFF measured with smaller ROIs size. This study proves that different sampling methods for quantification of HFF on multiple echo GRE sequence have overall excellent repeatability and ability to appreciate increased HFF

Serum insulin-like growth factor-1 concentrations in healthy cats before and after weight gain and weight loss

Background: Measurement of serum concentrations of insulin-like growth factor (IGF)-1 is used to diagnose acromegaly in cats. Hypothesis: Changes of body weight do not affect serum concentrations of IGF-1 in cats. Animals: Ten healthy purpose-bred cats. Methods: Prospective study. In lean cats, food availability was stepwise increased during the first week and given ad libitum for a total of 40 weeks to increase their body weight. From week 41 to week 60, food access was limited to reach a weight loss of 1% to 2% each week. Measurement of IGF-1 was performed at week 0, 16, 40, and 60. Insulin-like growth factor-1 was measured by radioimmunoassay. Body weight and IGF-1 were compared among the 4 time points. Results: Body weight increased by 44% from week 0 (4.5 ± 0.4 kg) to week 40 (6.5 ± 1.2 kg) (P <.001) and decreased by 25% from week 40 to week 60 (4.9 ± 0.7 kg) (P <.001). Serum IGF-1 concentrations did not differ during the study period (week 0, 16, 40, 60: 500 ± 188, 479 ± 247, 470 ± 184, 435 ± 154 ng/mL, respectively; P =.38). Correlations with body weight were not observed. Conclusions and Clinical Importance: Insulin-like growth factor-1 might not be influenced by changes of body weight in healthy cats, possibly suggesting that the latter is unimportant when interpreting IGF-1 results in this species

Effects of trilostane on urinary catecholamines and their metabolites in dogs with hypercortisolism

BACKGROUND: Glucocorticoids influence the synthesis and metabolism of catecholamines (epinephrine and norepinephrine) and metanephrines (metanephrine and normetanephrine). The aim of this study was to measure urinary catecholamines and metanephrines in dogs with hypercortisolism before and during trilostane therapy. Urine samples were collected during initial work up and during therapy with trilostane in 14 dogs with hypercortisolism and in 25 healthy dogs. Epinephrine, norepinephrine, metanephrine and normetanephrine were measured using high-pressure liquid chromatography and expressed as ratios to urinary creatinine concentration. RESULTS: Untreated dogs with hypercortisolism had significantly higher epinephrine, norepinephrine, and normetanephrine:creatinine ratios compared to healthy dogs. During trilostane therapy, urinary catecholamines and their metabolites did not decrease significantly. However, dogs with low post-ACTH cortisol concentrations during trilostane therapy had less increased epinephrine, norepinephrine and normetanephrine:creatinine ratios compared to healthy dogs. There was no correlation of urinary catecholamines and their metabolites with baseline or post-ACTH cortisol or endogenous ACTH concentrations during trilostane therapy. CONCLUSION: Influences between steroid hormones and catecholamines seem to occur, as dogs with hypercortisolism have significantly higher urinary epinephrine, norepinephrine, and normetanephrine:creatinine ratios. Once-daily trilostane therapy does not lead to a significant decrease in catecholamines and their metabolites. Trilostane-treated dogs still have increased urinary epinephrine, norepinephrine and normetanephrine:creatinine ratios during trilostane therapy

Effect of tetra-hydroxylated bile acid on size and insulin sensitivity of subcutaneous adipocytes in healthy lean cats

Obesity leads to insulin resistance and is a major risk factor for the development of diabetes mellitus in cats. Prevention of obesity and obesity-induced insulin resistance is difficult, and reliable long-term strategies are currently lacking. Retinoid-related orphan receptor gamma (ROR gamma) was recently identified as an important transcription factor in the development of large insulin-resistant adipocytes in mice and humans. ROR gamma negatively affects adipocyte differentiation through expression of its target gene matrix metalloproteinase 3 (MMP3) and promotes the development of large insulin-resistant adipocytes. Preliminary studies in mice showed that ROR gamma can be inhibited by its ligand tetra-hydroxylated bile acid (THBA). In the present study, serum THBA levels were determined in healthy and diabetic cats. Moreover, potential side effects and the effects of THBA supplementation on adipocyte size, mRNA expression of ROR gamma, MMP3, interleukin 6, tumor necrosis factor alpha, adiponectin and leptin in feline subcutaneous adipocytes and insulin sensitivity were investigated in healthy normal weight cats. Thirteen healthy and 13 diabetic cats were used for determination of serum THBA level, and six healthy normal-weight cats were included in a feeding trial. Similar THBA levels were determined in serum of healthy and diabetic cats. Supplementation of 5 mg/kg THBA for 8 wk did not cause any negative effect on feeding behavior, general condition and blood parameters of tested cats. It significantly reduced adipocyte size and mRNA expression of MMP3, interleukin 6, and tumor necrosis factor alpha in adipocytes, while mRNA expression of adiponectin significantly increased and mRNA expression of ROR gamma and leptin remained unchanged. Administration of THBA did not influence fasting blood glucose levels or the response of cats to acute insulin administration. Based on these results, THBA is palatable and is considered safe for use in cats. It reduces expression of MMP3 and promotes the development of small adipocytes with increased expression of adiponectin and reduced expression of interleukin 6 and tumor necrosis factor alpha. Further studies are recommended to evaluate the effect of THBA on adipocyte size and insulin sensitivity in obese cats. (C) 2022 Elsevier Inc. All rights reserved

Comparison of the pharmacodynamics of protamine zinc insulin and insulin degludec and validation of the continuous glucose monitoring system iPro2 in healthy cats

With the aim to improve current therapeutic and monitoring options for diabetic cats, the present study compared pharmacodynamic parameters of protamine zinc insulin (PZI) and insulin degludec and validated the continuous glucose monitoring system (CGMS) iPro2 with Sof-sensor and Enlite-sensor focusing on the low glycemic range. Three doses (0.1, 0.2 and 0.3IU/kg) of the two insulin preparations and the CGMS iPro2 with two different sensors were tested in six healthy cats. After each insulin administration, onset of action, time to glucose nadir and duration of action were calculated by measuring glucose concentrations with a portable blood glucose meter (PBGM). After sensor placement, paired PBGM and sensor glucose measurements were done and analytical and clinical accuracy were calculated according to the ISO 15197:2013 criteria. Onset of action, time to glucose nadir and glucose nadir were similar for both insulin formulations. Duration of action of insulin degludec was significantly longer than those of PZI at 0.1IU/kg (P=0.043) and 0.2IU/kg (P=0.043). Overall, 166/191 (87%) Sof-sensor measurements and 106/121 (88%) Enlite-sensor measurements met ISO criteria for analytical accuracy, and all sensor measurements fulfilled ISO criteria for clinical accuracy. Insulin degludec was well tolerated in healthy cats and showed longer duration of action than PZI. Further studies on the use of insulin degludec in diabetic cats might be recommended. Both sensors had good clinical accuracy, when used with the CGMS iPro2, but the analytical accuracy was below the minimum set by ISO 15197:2013