Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Acai Extract Increases the Red Blood Cell Population via Erythropoietin Upregulation in Mice

Version 1 : Received: 18 January 2020 / Approved: 19 January 2020 / Online: 19 January 2020 (05:16:11 CET)

A peer-reviewed article of this Preprint also exists.

Shibuya, S.; Toda, T.; Ozawa, Y.; Yata, M.J.V.; Shimizu, T. Acai Extract Transiently Upregulates Erythropoietin by Inducing a Renal Hypoxic Condition in Mice. Nutrients 2020, 12, 533. Shibuya, S.; Toda, T.; Ozawa, Y.; Yata, M.J.V.; Shimizu, T. Acai Extract Transiently Upregulates Erythropoietin by Inducing a Renal Hypoxic Condition in Mice. Nutrients 2020, 12, 533.


Acai (Euterpe oleracea Mart. Palmae, Arecaceae) is a palm plant native to the Brazilian Amazon. It contains many nutrients, such as polyphenols, iron, vitamin E, and unsaturated fatty acids, so in recent years, many of the antioxidant and anti-inflammatory effects of acai have been reported. However, the effects of acai on hematopoiesis have not been investigated yet. In the present study, we administered acai extract to mice and evaluated its hematopoietic effects. Acai treatment significantly increased the erythrocytes, hemoglobin, and hematocrit contents compared to controls for four days. We then examined the hematopoietic-related markers following a single injection. Acai administration significantly increased the levels of the hematopoietic-related hormone erythropoietin in blood compared to controls and also significantly upregulated the gene expression of Epo in the kidney. Furthermore, in the mice treated with acai extract, the kidneys were positively stained with the hypoxic probe pimonidazole in comparison to the controls. These results demonstrated that acai increases the number of blood cells through an increased erythropoietin expression via hypoxic action in the kidney. Acai can be expected to improve motility through hematopoiesis.


acai; erythropoiesis; erythropoietin


Biology and Life Sciences, Food Science and Technology

Comments (1)

Comment 1
Received: 15 March 2020
Commenter: Raquel Cruz, Laura Franco, Luis Mardomingo, Laura Martín, Lucas Morató, Begoña Parrondo, Sofía Pérez, Mireya Robles, Irene Rodríguez, Teresa Vázquez and Elena Verdún. 3ºB BIomedicine.
The commenter has declared there is no conflict of interests.
Comment: We are a group of biomedical students (3rd year) from Universidad Francisco de Vitoria (Madrid, Spain). As part of our assignments, we were asked to review this paper published as preprint. We would like to kindly share our thoughts and positive criticism in case that it would be of any help for the authors as well as the scientific community. Please see below our comments:

Shibuya et al. investigated the impact of açai administration on hematopoiesis using a mouse model. The study suggests that açai extract increases erythropoietin levels.

There are some issues that require careful consideration:
Major issues:
1. Abstract: The putative contribution of açai to motility via hematopoiesis is not well-defined. In this case, we assume that it refers to the passage of blood precursors to mature blood cells.
2. Introduction. Detailed information is missed:
● There is not a detailed description of the components of açai, especially on the amount of G3Glc.
● Information on how açai improves red blood cell maturation and why it does not affect the number of reticulocytes is not fully clear.
● Background information on how HIF activates EPO transcription (HIF-dimer formation under hypoxic conditions) is missing.
3. Methods and materials: The data show that açai extract increases erythropoiesis. However, in the Methods appears as if the mice were given açai together with an erythropoietic inducer.
● It is unclear how many experiments were conducted, the number of mice used in each as well as the experimental conditions.
● A larger sample would give more robust results.
● Line 5: It does not seem clear in which conditions ASP1517 is administrated.
● Line 5: It is not explained why an erythropoiesis stimulator (ASP1517) was used. Was it administrated together with açai?
● Given that the approximate duration of the complete process of erythropoiesis is 5-10 days (Hematopoyesis | Kierszenbaum, A. and Tres, L. (n.d.). Histología y biología celular + StudentConsult.), experiments longer that 4 days would be more appropriate to strengthen these data.
● The primers used for PCR, described mentioned in line 7 of point 2.5, are not optimal: by using the formula to calculate the melting temperature, 4(G+C)+2(A+T), we observe that the first forward of the actb is 70°C and the reverse is 64°C. On the other hand, the forward of EPO is 68ºC and the reverse is 72ºC. The maximum recommended difference between primers is 5°C but in the actb pair is 6. Therefore, while the technique used is appropriate, the primer design could improve (General concepts for PCR primer design. DOI: 10.1101/gr.3.3. s30).
● If we take into account the amount of açai administered to the mice and extrapolate the data to humans, the dose required to elicit a biological effect in humans would be relatively large
4. Results:
● The method used in each figure should be well-defined. The descriptions of the figures are not very detailed.
5. Discussion: Issues that are not the focus of the study predominate. Indeed, for the most part, the Discussion covers issues that are not related to the effect of açai on the maturation of erythrocytes.
In addition, we consider that there is not enough cohesiveness among the data presented. Besides that, additional information about the uses of açai is provided although is not relevant for this research. Indeed, this information is not lined up with the objectives.

Minor issues:
1. Abstract.
● The abstract does not include a clear hypothesis.
2. Methods and materials.
● The antibodies used for flow cytometry analysis are not described.
● The description of the control groups is unclear.
3. Results.
● More information about EPO should be added such as the time required for its synthesis or its half-life. This would allow the reader to better relate the results from experiment 1 and 2, since the time passed from the administration of açai to the measurement of EPO levels is quite different (4 days vs 2-3 hours).
● Figure 2: given that this experiment includes 4 groups, the statistical analysis should include ANOVA instead of t-test.
● Experiment 2: The time passed since the administration of açai to the measurement of the EPO should be narrower.
● Figure 3 B should include a scale to allow for size comparisons among panels.
4. Discussion.
● There is an unnecessary period after the Discussion section.
● “Discussion” should be written with the same style as “Results” (i.e., bold type instead of italics).
● The Discussion would benefit from discussing rather than just noting previous findings on açai. For example, the introduction talks about the role of açai with respect to haematopoiesis, whereas the discussion does not integrate the present results with previous findings.
We consider that including more information in the figure legends would be beneficial to the reader. Also, we would change the position of the figures to be more clearly connected with the results.
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