The mean cell volume difference (dMCV) reflects serum hypertonicity in diabetic dogs

Serum hypertonicity may develop during diabetes mellitus due to hyperglycemia and other biochemical changes. Hypertonicity may produce detrimental cellular and systemic effects and has been identified as a serum marker for some clinical disorders. In non-diabetic dogs, the mean cell volume difference, a novel erythrocyte measure, is increased by serum hypertonicity. However, it is not known whether hyperglycemic hypertonicity produces a similar change. The hypothesis that the mean cell volume difference could detect serum hypertonicity in diabetes was investigated in a group of thirty-two dogs with naturally-occurring diabetes mellitus that were prospectively recruited over a 1-year period from the outpatient population of a veterinary teaching hospital. The effect of hyperglycemia on the mean cell volume difference and the ability of the mean cell volume difference to predict serum hypertonicity were examined. Serum hyperosmolality and hypertonicity due to hyperglycemia was present in 91% and 94% of dogs, respectively. Hyperglycemia was the principal cause identified for serum hypertonicity and hyperosmolality. Using a cut-off value of ≥ 3 μm3 for the mean cell volume difference, serum hypertonicity ≥ 320 mmol/kg was identified with 79% sensitivity and 61% specificity. The dMCV correlated with changes in serum glucose, tonicity, and measured osmolality. Dogs with a mean cell volume difference ≥ 3 μm3 were at risk for serum tonicity ≥ 320 mmol/kg (risk ratio = 2.2) and serum glucose ≥ 13.9 mmol/L (risk ratio = 2.3). In conclusion, the mean cell volume difference is a useful surrogate marker for detecting serum hypertonicity in diabetic dogs and elevated mean cell volume difference is associated with increased risks for clinically relevant serum hypertonicity and hyperglycemia.

Characterization of the hydroxycarboxylic acid receptor 2 in cats

The hydroxycarboxylic acid receptor 2 (HCA2) belongs to a family of nutrient-sensing receptors that bind β-hydroxybutyrate, an alternative fuel source produced during a negative energy balance. The HCA2 receptor has not been identified or characterized in cats. Therefore, the following were the objectives of this study: (1) identify the feline HCA2 receptor protein sequence and compare against known human and rodent sequences, (2) determine tissue distribution and relative expression in lean, healthy cats, and (3) demonstrate in vitro functionality in feline adipose tissue. Tissues (n = 6) and primary adipocytes (n = 4) were collected from lean, healthy, female cats. The published genomic sequence for cats was used to design primers for polymerase chain reaction isolation of HCA2. Relative tissue distribution was evaluated using reverse transcriptase-polymerase chain reaction with RNA isolated from 9 different tissues (spleen, pancreas, lymph node, jejunum, kidney, liver, heart, and subcutaneous and abdominal adipose tissue). Receptor function was evaluated in primary feline adipocyte culture, and changes were compared with basal lipolysis. The in silico predicted feline HCA2 protein sequence exhibited 83.1% and 86.5% amino acid similarity to human and mouse sequences, respectively. The feline HCA2 receptor is predominantly expressed in adipose tissue and spleen. Exposure of feline adipocytes to niacin, a pharmacologic ligand of HCA2, inhibited lipolysis to a similar degree as insulin, a potent lipolytic inhibitor. In conclusion, the feline HCA2 receptor is similar to human and murine receptors in sequence, distribution, and functionality. By gaining a better understanding of the HCA2 receptor in cats, we will be able to better manage feline patients.