Blood glucose, insulin and glycogen profiles in Sprague-Dawley rats co-infected with Plasmodium berghei ANKA and Trichinella zimbabwensis

Abstract

Background: Plasmodium falciparum and tissue dwelling helminth parasites are endemic in sub-Saharan Africa (SSA). The geographical overlap in co-infection is a common phenomenon. However, there is continued paucity of information on how the co-infection influence the blood glucose and insulin profiles in the infected host. Animal models are ideal to elucidate effects of co-infection on disease outcomes and hence, blood glucose, insulin and glycogen profiles were assessed in Sprague-Dawley rats co-infected with P. berghei ANKA (Pb) and Trichinella zimbabwensis (Tz), a tissue-dwelling nematode.

Methods: One-hundred-and-sixty-eight male Sprague-Dawley rats (weight range 90-150 g) were randomly divided into four separate experimental groups: Control (n = 42), Pb-infected (n = 42), Tz-infected (n = 42) and Pb- + Tz-infected group (n = 42). Measurement of Pb parasitaemia was done daily throughout the experimental study period for the Pb and the Pb + Tz group. Blood glucose was recorded every third day in all experimental groups throughout the experimental study period. Liver and skeletal muscle samples were harvested, snap frozen for determination of glycogen concentration.

Results: Results showed that Tz mono-infection and Tz + Pb co-infection did not have blood glucose lowering effect in the host as expected. This points to other possible mechanisms through which tissue-dwelling parasites up-regulate the glucose store without decreasing the blood glucose concentration as exhibited by the absence of hypoglycaemia in Tz + Pb co-infection group. Hypoinsulinemia and an increase in liver glycogen content was observed in Tz mono-infection and Tz + Pb co-infection groups of which the triggering mechanism remains unclear.

Conclusions: To get more insights into how glucose, insulin and glycogen profiles are affected during plasmodium-helminths co-infections, further studies are recommended where other tissue-dwelling helminths such as Taenia taeniformis which has strobilocercus as the metacestode in the liver to mimic infections such as hydatid disease in humans are used.

Keywords: Blood glucose; Co-infection; Insulin; Liver glycogen; Muscle glycogen; Plasmodium berghei; Trichinella zimbabwensis.

Figure 1. Percentage parasitaemia in male Sprague-Dawley rats infected with Plasmodium berghei (Pb) only and co-infected with Pb and Trichinella zimbabwensis (Pb + Tz) (Murambiwa et al., 2020; CC-BY-NC-ND).

Day 0 represents the day of Pb infection when Tz muscle larvae were in the rat muscle at day 28 post Tz infection. Values are presented as means and vertical bars indicate standard error of mean (SEM). N = 6 for each group. **P < 0.01, ***P < 0.001 (https://creativecommons.org/licenses/by-nc-nd/2.0/legalcode).

Figure 2. Mean number of intestinal adult worms (AW) and muscle larvae counts (ML)/gram of muscle (lpg) recovered from rats infected with Trichinella zimbabwensis (Tz) and the group co-infected at day 28 post-infection (Murambiwa et al., 2020; CC-BY-NC-ND).

Values are presented as means and vertical bars indicate standard error of mean (SEM). N = 6 for each group (https://creativecommons.org/licenses/by-nc-nd/2.0/legalcode).

Figure 3. Comparison of the effects of Plasmodium berghei (Pb) and Trichinella zimbabwensis (Tz) mono-infection and co-infection (Pb + Tz) on blood glucose concentration.

Day 0 represents the day of Pb infection when Tz muscle larvae were in the rat muscle at day 28 post Tz infection. Values are presented as means and vertical bars indicate standard error of mean (SEM). N = 6 for each group. **P < 0.01, ***P < 0.001.