Probiotic and high-fat diet: effects on pain assessment, body composition, and cytokines in male and female adolescent and adult rats

Abstract

Obesity in adolescence is increasing in frequency and is associated with elevated proinflammatory cytokines and chronic pain in a sex-dependent manner. Dietary probiotics may mitigate these detrimental effects of obesity. Using a Long-Evans adolescent and adult rat model of overweight (high fat diet - 45% kcal from fat from weaning; HFD), we determined the effect of a single strain dietary probiotic (L. plantarum 299v [Lp299v] from weaning) on the theoretically increased neuropathic injury-induced pain phenotype and inflammatory cytokines. We found that although HFD increased fat mass, it did not markedly affect pain phenotype, particularly in adolescence, but there were subtle differences in pain in adult male vs. female rats. The combination of HFD and Lp299v augmented the increase in leptin in adolescent females. There were many non-interacting, main effects of age, diet and probiotic on an array of cytokines and adipokines with adults being higher than adolescents, HFD higher than the control diet, and a decrease with probiotic compared to placebo. Of particular interest were the probiotic-induced increases in IL12p70 in female adolescents on a HFD. We conclude that a more striking pain phenotype could require a higher and longer duration caloric diet or different etiology of pain. A major strength of our study was that a single strain probiotic had a wide range of inhibiting effects on most pro-inflammatory cytokines. The positive effect of probiotic on leptin in female adolescent rats is intriguing and worthy of exploration.