Journal of the Pancreas Open Access

Keywords

Carbachol; Data Interpretation, Statistical; Potassium Chloride; shogaol

Abbreviations

[Ca²⁺]_i: intracytoplasmic free calcium ion concentration

Dear Sir,

We read with a great deal of interest the study titled “[6]-shogaol induces Ca²⁺ signals by activating the TRPV1 channels in the rat insulinoma INS-1E cells” by Rebellato et al. [1] in the January 2014 issue of JOP. Journal of the Pancreas (Online). At the outset, we would like to congratulate the authors for having conducted an exhaustive research with insights on the mechanism of action of [6]-shogaol. The manuscript is intelligently written with ample graphical representation of data leaving little room for criticism. However, it would be of enormous help if the authors could clarify certain doubts we had while reading the article.

The abstract mentions in its results section “... [Ca²⁺]_i (i.e., intracytoplasmic free calcium ion concentration) increase obtained by 1 micro mole [6]-shogaol was greater than that obtained by 10 mM glucose ...”. However, this observation is left for the reader to compare in two different graphs (1a and 4b) [1]. Furthermore, we did not find any mention of this observation in the main-text-result section nor any elaboration of the same was found in the discussion [1]. We would like to understand if this observation is incidental or the authors think it is an important finding. In the latter case, we believe that its interpretation should be elaborated in the discussion as well.

Unpaired t-test is applied on experiments depicted in Figures 2, 3 and 4. However, there is no mention of test of significance for observation in Figure 1. Figure 1 elucidates increase in [Ca²⁺]_i from baseline after administration of [6]-shogaol (the drug) and return of [Ca²⁺]_i to baseline after the washout of the drug. We suggest that a paired test should have been applied in order to state that the increase was significant after [6]-shogaol administration. Moreover, pre-drug [Ca²⁺]_i level and post-drug [Ca²⁺]_i level also need to be statistically compared.

In our opinion, graphical representation of [Ca²⁺]_i in Figure 1a, 2, 3, and 4a,b,c does not follow a fixed interval on the y-axis [1]. Although the graphical representation between the values is depicted equidistant, the difference of intervals between them is not fixed (e.g., 460-255=205; 255-75=180; and so on). Which kind of scale was shown needs to be better described.

We would also like to mention that in the results about “... increase of [Ca²⁺]_i by [6]-shogaol was due to Ca²⁺ entry across the plasma membrane ...” , description of mechanism of action of both carbachol and KCl is without a reference [1]. We suggest that the authors should provide references for mechanisms of action of carbachol and KCl.

Diabetes mellitus is a major public health problem and the present study would help in new drug development for treatment of diabetes mellitus. We believe that the clarification of the above mentioned concerns would make the study more robust.

Financial supports

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Conflicts of interest

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References

1. Rebellato P, Islam MS. [6]-Shogaol induces Ca²⁺ signals by activating the TRPV1 channels in the rat insulinoma INS-1E cells.JOP.J Pancreas (Online) 2014; 15:33-7. [PMID: 24413781]