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Background: The association between myocardial parasitic load (MPL) and cardiac biomarkers in Canine Leishmaniasis (CanL) has not been studied. Methods: Dogs with advanced CanL were prospectively recruited and were included if they were euthanised. Prior to euthanasia these variables were assessed: hematocrit, globulin, creatinine, N‐terminal‐pro brain natriuretic peptide (NT‐proBNP), cardiac troponin I (cTnI), blood pressure, urine protein/creatinine ratio and echocardiographic parameters. A left ventricular (LV) sample was taken for histopathology and MPL evaluation by quantitative PCR. Correlation of MPL with all variables was analysed. Dogs with lower and higher histopathology scores were compared. Results: Ten dogs were included. NT‐proBNP was 6946 pmol/ (interquartile range [IQR] 3751–9268 pmol/L) and cTnI 4.56 ng/mL (IQR 0.46–13.1 ng/mL). In all dogs, echocardiography showed an increase in LV thickening, and histopathology revealed moderate to severe lympho‐plasmocytic myocarditis and/or myocardial cell degeneration. MPL was 215.53 parasites/gram (IQR 21.2–1372.63 parasites/gram). A strong correlation (p < 0.001; R = 0.90; R20.81) with cTnI was observed but correlation with any of the other variables or differences between the two histopathological scores, were not detected. Conclusions: MPL in dogs with advanced CanL shows variable but generally high levels. A strong association between MPL and cTnI was observed, which encourages the exploration of cTnI as a marker in CanL.

Stanniocalcins are expressed in the pancreas tissue, and it was suggested a direct correlation between circulating insulin and STC2 concentrations in human. Here, we show a significant correlation between STC1 and both glycaemia and glycosylated haemoglobin among DM2 patients, while DM2 patients who present the greatest glycosylated haemoglobin values exhibited the lowest STC2 expression. However, treatment of patients with antiglycaemic drugs does not significantly modify the expression of both STCs. On the other hand, STC2‐/‐ mice that exhibited neonatal and adult overweight further presented deregulated glycaemia when they were feed with a hypercaloric diet (breeding pellet, BP). This alteration is more evident at the early stages of the animal life. Deregulated glycaemia in these mice was confirmed using glucose oral test. In addition, STC2‐/‐ mice present enhanced pancreas size; thus, the histological analysis reveals that WT mice respond to BP diet by increasing the size of the pancreatic islets through inducing cell division, and STC2‐/‐ mice lack this compensatory mechanism. Contrary, BP fed STC2‐/‐ mice show enhanced number of islets but of similar size than those fed with regular pellet. Histopathological analysis demonstrates tissue structure disruption and erythrocytes infiltrations in STC2‐/‐ mice, possibly due to the stress evoked by the BP diet. Finally, enhanced glucagon immunostaining was observed in the islet of STC2‐/‐ mice, and the glucagon ELISA assay confirmed the increase in the circulating glucagon. Summarizing, we present evidence of the role of STCs, mainly STC2, as a possible early marker during development of diabetes mellitus.

Stanniocalcin 2 (STC2) is a fish protein that controls body Ca2+ and phosphate metabolism. STC2 has also been described in mammals, and as platelet function highly depends on both extracellular and intracellular Ca2+, we have explored its expression and function in these cells. STC2−/− mice exhibit shorter tail bleeding time than WT mice. Platelets from STC2-deficient mice showed enhanced aggregation, as well as enhanced Ca2+ mobilization in response to the physiological agonist thrombin (Thr) and the diacylglycerol analog, OAG, a selective activator of the non-capacitative Ca2+ entry channels. Interestingly, platelets from STC2−/− mice exhibit attenuated interaction between STIM1 and Orai1 in response to Thr, thus suggesting that STC2 is required for Thr-evoked STIM1-Orai1 interaction and the subsequent store-operated Ca2+ entry (SOCE). We have further assessed possible changes in the expression of the most relevant channels involved in non-capacitative Ca2+ entry in platelets. Then, protein expression of Orai3, TRPC3 and TRPC6 were evaluated by Western blotting, and the results revealed that while the expression of Orai3 was enhanced in the STC2-deficient mice, others like TRPC3 and TRPC6 remains almost unaltered. Summarizing, our results provide for the first time evidence for a role of STC2 in platelet physiology through the regulation of agonist-induced Ca2+ entry, which might be mediated by the regulation of Orai3 channel expression.