Dietary Caprylic Acid (C8:0) Does Not Increase Plasma Acylated Ghrelin but Decreases Plasma Unacylated Ghrelin in the Rat

Abstract

Focusing on the caprylic acid (C8:0), this study aimed at investigating the discrepancy between the formerly described beneficial effects of dietary medium chain fatty acids on body weight loss and the C8:0 newly reported effect on food intake via ghrelin octanoylation. During 6 weeks, Sprague-Dawley male rats were fed with three dietary C8:0 levels (0, 8 and 21% of fatty acids) in three experimental conditions (moderate fat, caloric restriction and high fat). A specific dose-response enrichment of the stomach tissue C8:0 was observed as a function of dietary C8:0, supporting the hypothesis of an early preduodenal hydrolysis of medium chain triglycerides and a direct absorption at the gastric level. However, the octanoylated ghrelin concentration in the plasma was unchanged in spite of the increased C8:0 availability. A reproducible decrease in the plasma concentration of unacylated ghrelin was observed, which was consistent with a decrease in the stomach preproghrelin mRNA and stomach ghrelin expression. The concomitant decrease of the plasma unacylated ghrelin and the stability of its acylated form resulted in a significant increase in the acylated/total ghrelin ratio which had no effect on body weight gain or total dietary consumption. This enhanced ratio measured in rats consuming C8:0 was however suspected to increase (i) growth hormone (GH) secretion as an increase in the GH-dependent mRNA expression of the insulin like growth Factor 1 (IGF-1) was measured (ii) adipocyte diameters in subcutaneous adipose tissue without an increase in the fat pad mass. Altogether, these results show that daily feeding with diets containing C8:0 increased the C8:0 level in the stomach more than all the other tissues, affecting the acylated/total ghrelin plasma ratio by decreasing the concentration of circulating unacylated ghrelin. However, these modifications were not associated with increased body weight or food consumption.

Gut Microbiota and Metabolic Health: The Potential Beneficial Effects of a Medium Chain Triglyceride Diet in Obese Individuals

“…Interestingly, MCT also lower caloric intake, compared to LCT, by improving satiety [ 129 , 130 ]. Octanoate, which constitutes most of the MCT used in dietary interventions, was suggested to be the main co-substrate of the Ghrelin O -acetyltransferase enzyme, involved in the activation of the powerful orexigenic peptide hormone Ghrelin [ 131 , 132 , 133 ]. However, an acute diminution of food intake induced by the consumption of MCT oil is associated with an elevation of Leptin, a hormone with a well-known anti-orexigenic effect [ 129 ].…”

Effects of diacylglycerol and triacylglycerol from peanut oil and coconut oil on lipid metabolism in mice

“…Lemarie et al. (2015) provided a dose–dependent caprylic acid (C8:0) in rats and was undetectable. Moreover, Shrestha et al.…”

Fatty acid acylation of proteins: specific roles for palmitic, myristic and caprylic acids

“…Additionally, we measured high levels of acylated ghrelin in the plasma of rats receiving no dietary C8:0. Thus, the low stomach C8:0 level observed in these rats could be enough to supply the octanoyl-CoA co-substrate used to acylate the proghrelin (Lemarié, Beauchamp, Dayot, et al, 2015).…”

“…To further understand the effect of dietary caprylic acid on the concentration of circulating plasma acylated and unacylated ghrelin, we recently designed a nutritional study (Lemarié, Beauchamp, Dayot, et al, 2015) including SpragueDawley male rats which were fed during 6 weeks with three dietary C8:0 levels (0, 8 and 21% of FAs). A specific doseresponse enrichment of the stomach tissue C8:0 was observed.…”