Abstract
Obese animals and humans demonstrate higher sensitivity to pain stimuli. Among the endogenous factors prompting obesity, the intestinal microbiota has been proposed to influence responsiveness to pain. The beneficial effects of probiotics on obesity are well documented, whereas data on their analgesic efficacy is minimal. The protective effect of probiotics on nociception in diet-induced obese male mice has been previously demonstrated, but the sex differences in pain sensitivity and analgesic response do not allow for the generalization of these findings to the female gender. Hence, this study aimed at investigating the potential effects of oral probiotic supplementation on mechanical pain thresholds in female diet-induced obese mice compared with controls. Thirty-two adult female mice (N=32) were randomly divided into two groups receiving standard (normal-weight group; NW) or high-fat diet (diet-induced obesity; DIO). All rats received a single daily dose (1 × 109 CFU) of probiotics (Lactobacillus rhamnosus PB01, DSM14870) for four weeks by gavage. Mechanical pain thresholds were recorded by an electronic von Frey device at baseline, at the end of weeks 2, 4, 6, and 8 in both DIO and NW groups with and without consumption of probiotics. Blood samples were obtained for the measurement of lipid profile and reproductive hormone levels. Bodyweight was considerably lower (P < 0.001) in groups supplied with probiotics than groups without probiotics. Pressure pain threshold values showed a significant (P < 0.001) increase (reduced pain sensitivity) following probiotic supplementation, proposing a modulatory effect of probiotics on mechanical sensory circuits and mechanical sensitivity, which might be a direct consequence of weight loss or an indirect result of the probiotics' anti-inflammatory properties. Understanding the precise underlying mechanism for the effect of probiotics on weight loss and mechanical pain sensitivity seen in this study warrants further investigation.
Highlights
Pain is a complex, multidimensional perception that varies in quality, strength, duration, location, and unpleasantness. e strength and unpleasantness of pain are neither nor directly related to the nature and extent of tissue damage [1]
Obesity alters adipose tissue metabolic and endocrine functions, which have been previously reported to influence pain perception [6]. e adipose tissue generates proinflammatory cytokines such as interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), and leptin, in addition to C-reactive protein (CRP) which is released from the liver in response to IL-6 [7]
Erefore, this study aimed to assess the impact of oral administration of Lactobacillus rhamnosus PB01 (DSM 14870) on pressure pain thresholds in normal-weight and diet-induced obese female mouse models to address if probiotic supplements can potentially overcome the deleterious effects of obesity and reduce pain sensitivity. e results of this study would provide evidence on whether consumption of probiotics can modulate pain, obesity, or both and if hormonal changes would be present in response to the supplementation
Summary
Multidimensional perception that varies in quality, strength, duration, location, and unpleasantness. e strength and unpleasantness of pain are neither nor directly related to the nature and extent of tissue damage [1]. Multidimensional perception that varies in quality, strength, duration, location, and unpleasantness. E strength and unpleasantness of pain are neither nor directly related to the nature and extent of tissue damage [1]. Neurotransmitters, immune cells, and hormones have been demonstrated to contribute to the pathogenesis of chronic pain [3]. Biological factors, including gender and genetics, have been shown to alter pain perception both in humans and animals [4]. E influence of diet on pain perception is well known [5]. It has been suggested that adiposity is strongly associated with pain, which is more prevalent in obese than nonobese individuals [6]. Obesity alters adipose tissue metabolic and endocrine functions, which have been previously reported to influence pain perception [6]. Obesity alters adipose tissue metabolic and endocrine functions, which have been previously reported to influence pain perception [6]. e adipose tissue generates proinflammatory cytokines such as interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), and leptin, in addition to C-reactive protein (CRP) which is released from the liver in response to IL-6 [7]
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