Journal of Pain & Relief
Open Access

Abstract

Background and Aims: Pain thresholds or responsiveness to painful stimuli has been demonstrated to be affected by body conditions such as obesity. Generally, a lower pain threshold has been demonstrated in obesity both in animals and humans. Among the endogenous factors influencing the obesity, intestinal microbiota has also been suggested to influence the pain sensitivity. However, the effect of oral probiotics on pain has not been studied systematically. This study examined the effect of oral probiotic (Lactobacillus Rhamnusus) on mechanical sensitivity in behaving diet-induced obese (DIO) mice. Methods: Six-week old male C57BL/6NTac mice were fed with a high fat diet (week 1-4) to produce DIO mice. The DIO mice were then randomly assigned to 2 groups treated with a single daily dose (1x109CFU) of L. Rhamnusus (test group) or physiological saline (control group) for 4weeks (weeks 5-8). Sensitivity to mechanical stimulation (hind-paw withdrawal), was assessed by the electronic Von Frey every two weeks throughout the study period. Results: The DIO mice in the test group did not significantly gain weight after the start ofprobiotic administration while the control group maintained the weight rising trend leading to a significant weight difference on week 5 which remained up to week 6. The test group showed a trend of lower pain sensitivity (i.e. higher pain threshold) to mechanical stimulation compared to the control group after two weeks of receiving the probiotic treatment (12.96±0.822 g and 9.57±0.822 g, respectively, P>0.05). After 4 weeks of probiotic administration, a significant difference was observed between the two groups (16.05±0.88 g intest group and 7.97±0.88 g in control group; P<0.01). Conclusions: The results of this study demonstrated lower mechanical pain sensitivity inprobiotic-treated obese mice. The protective effect of probiotics on nociception circuits could beassociated with the weight reduction or anti-inflammatory properties of the probiotics. Translation of this result in humans can potentially suggest a novel therapeutic strategy in pain management of obese individuals.

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