Conjugated linoleic acid supplementation in humans: Effects on circulating leptin concentrations and appetite

Abstract

Conjugated linoleic acid (CLA) has been demonstrated to reduce body fat in animals. However, the mechanism by which this reduction occurs is unknown. Leptin may mediate the effect of CLA to decrease body fat. We assessed the effects of 64 d of CLA supplementation (3 g/d) on circulating leptin, insulin, glucose, and lactate concentrations in healthy women. Appetite was assessed as a physiological correlate of changes in circulating leptin levels. Analysis of plasma leptin concentrations adjusted for adiposity by using fat mass as a covariate showed that CLA supplementation significantly decreased circulating leptin concentrations in the absence of any changes of fat mass. Mean leptin levels decreased over the first 7 wk and then returned to baseline levels over the last 2 wk of the study in the CLA-treated group. Appetite parameters measured at around the time when the greatest decreases in leptin levels were observed showed no significant differences between supplementation and baseline determinations in the CLA-supplemented group or between the CLA and placebo-supplemented groups. There was a nonsignificant trend for mean insulin levels to increase toward the end of the supplementation period in CLA-treated subjects. CLA did not affect plasma glucose and lactate over the treatment period. Thus, 64 d of CLA supplementation in women produced a transient decrease in leptin levels but did not alter appetite. CLA did not affect these parameters in a manner that promoted decreases of adiposity.

Impact of dietary betaine and conjugated linoleic acid on insulin sensitivity, protein and fat metabolism of obese pigs

“…In our experiment, there was no effect of any treatment on serum leptin concentration. Dietary CLA reduced serum leptin levels in rats, mice and humans (Delany et al, 1999;Medina et al, 2000;Yamasaki et al, 2000b), whereas it was increased in lactating sows (Bontempo et al, 2004).…”

Conjugated linoleic acid and obesity control: efficacy and mechanisms

“…31,102,[107][108][109][110][111] The effect of CLA on insulin sensitivity and glucose control are also inconsistent. 28,29,93,114,116,126 In conclusion, most existing evidence of CLA efficacy on adiposity stems from animal studies, particularly those conducted in mice. The majority of these animal studies have examined CLA mixtures but not individual isomers for weight and fat-lowering properties.…”

“…Insulin and glucose levels remained unaffected. 126 In type II diabetes subjects, CLA supplementation was associated with increases of fasting plasma glucose concentration; correlation analyses showed that plasma levels of the t10c12, but not the c9t11, CLA isomer was inversely associated with serum leptin. 121 Supplementation with t10c12 CLA caused isomer-specific insulin resistance in obese men with the metabolic syndrome.…”

Hyperinsulinaemia triggered by dietary conjugated linoleic acid is associated with a decrease in leptin and adiponectin plasma levels and pancreatic beta cell hyperplasia in the mouse

“…However, it also constitutes a limitation in that it prevents the direct extrapolation of these results to other species. Given that CLAmediated increases in plasma insulin levels and insulin resistance have been reported in humans [7,30], the effect of CLA on insulin homeostasis may not be restricted to the mouse. Furthermore, if the early and profound decreases in leptin and adiponectin levels documented here in CLA-fed mice also occur in humans, this could have deleterious consequences for whole body insulin sensitivity and favour the development of fatty liver.…”