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  • GPR levels were not changed by any

    2021-11-29

    GPR40 levels were not changed by any treatment. GPR40 has the same agonists as GPR120 but only a 10% homology [35] despite using the same intracellular signaling cascades [7]. Previous data on the ability of exercise to modulate G protein coupled receptors in general are scarce. The long-chain fatty acids such as ω3 and ω9 are well-recognized GPR40 agonists [5]. Once activated, GPR40 could contribute against proinflammatory signaling in several tissues, increasing the insulin sensitivity and hence Guanethidine Sulfate uptake [4]. We also evaluated the effect of exercise training and FS oil on insulin action and glucose homeostasis, with both exercise alone and exercise with FS oil improving levels similar to those observed in lean controls. This is in line with previous studies that have shown that both acute physical exercise and chronic physical exercise are able to improve insulin action in obese mice [3], [24], [36]. We did not observe any effect of FS oil alone on insulin action. This is in line with a study where FS oil supplementation did not affect glucose control in individuals with well-controlled type 2 diabetes [37]. Surprisingly, physical training, FS oil or their combination did not have a significant effect on Akt or GSK3 activity, as some studies have shown [38], [39]. We attributed our negative findings here to high variance in the group given the observed improvements in insulin sensitivity and glucose levels. Overall, the role of FS oil in insulin signaling needs to be further investigated, with, notably, attention paid to the standardization of dose. For example, in the abovementioned where diabetic patients received FS oil, 13 g of the oil, totaling 7.4 g of alpha-linolenic fatty acid, was administered per day [37]. This is considered a very high dose, and this excess could be harmful, with our group previously showing that high levels FS oil in rodent diets (achievable only through supplementation) worsened several metabolic and molecular parameters, triggering a proinflammatory signaling [7]. Animal studies have also been inconsistent in FS oil dosage, with, for example, Bashir et al. [40] treating obese and diabetic mice with FS oil at 4 mg/kg, while Zhao et al. [41] used a diet containing 10% of FS oil to treat mice. This latter value corresponds to approximately 500 mg/day [41], and in our dosage studies, we determined the maximal safe dose to be at around 290 mg/day, which was easily achievable by diet alone. In our current study, we used 50 mg/day, which might not have been high enough to change the main pathophysiological parameters of obese mice despite the observed reduction of some proinflammatory proteins and the increase in GPR120 receptor levels in the liver of treated animals. Beyond dosing concerns, oil quality and the percentage of alpha-linolenic fatty acid in the oil can also cause difficulties to be reached. Generally, the percentage of ω3 in FS oil is around 58% [42], with a value of 52% obtained in this study, although levels as low as 33% have been used in other studies [43]. We therefore recommend that dose/response experiments to establish a minimal acceptable percentage of alpha-linolenic fatty acid in FS oil are necessary. In our current study, we also investigated a number of inflammatory markers after the exercise training and FS oil interventions. As expected from the literature, both treatments presented a consistent reduction in inflammatory markers. Exercise is well described as one of the most important nonpharmacological anti-inflammatory strategies, shown to reduce TNFα, IL1β, IL6, IκK and IκBα, among others [3], [44], [45], [46]. ω3 fatty acids induce the same pattern but through different mechanisms. As mentioned, an interesting research showed a coupling between GPR120 receptor and βarrestin2, an intracellular protein that disrupts the inflammatory signal transduced from TLR2/4 and TNF-α receptors [5]. Docosahexaenoic (DHA) and eicosapetaenoic (EPA) acid, and with a lower affinity alpha-linolenic (ALA) acid, activate this receptor and mediate the anti-inflammatory signaling [5], with the same molecular cascade observed across multiple body tissues [4], [7]. The association between exercise and FS oil reduced the proinflammatory markers, however without further improvement to the anti-inflammatory response, probably through the same pathways above described.