Dietary Conjugated Linoleic Acid Reduces Rat Adipose Tissue Cell Size Rather than Cell Number

Abstract

We investigated the basis for the reduction in fat pad size in rats fed conjugated linoleic acid (CLA). In the first study, growing female Sprague-Dawley rats (initial weight150 g) were fed diets containing 0, 0.25 and 0.5 g/100 g diet of a purified (97% CLA) and 0.5% of a feed-grade (55% CLA) source of CLA for 5 wk to determine the effects on growth performance and fat mass. There was no effect of CLA on growth rate or food intake. Dietary CLA reduced retroperitoneal fat pad weight 13, 25 and 32% in rats fed 0.25 and 0. 5% of the pure CLA and 0.5% of the feed-grade CLA, respectively (P < 0.05). Similar effects were observed in the parametrial fat pad. The reduced pad size was due to smaller adipocyte size rather than a reduced cell number. Relative to the control group, mean cell volume was 15, 28 and 29% lower in tissue from rats fed 0.25 and 0.5% of the pure CLA and 0.5% of the feed-grade CLA, respectively (P < 0.01). In the second study, rats were fed CLA (0 vs. 0.5%) for 7 or 49 d. Reductions in fat pad weight were observed within 7 d. In addition, the effects of CLA on energy metabolism were studied in the chronically fed rats. There were no significant effects of CLA on oxygen consumption, CO(2) or heat production. During wk 4 of feeding, but not at other times, there was a 5% lower respiratory quotient in CLA-fed rats (P < 0.05). There was a time-dependent accumulation of CLA in adipose tissue and a decrease in monounsaturated fatty acids. These results suggest that the reduction in fat mass in rats fed CLA can be accounted for by a reduction in cell size rather than a change in cell number.

The effect of trans-10,cis-12 conjugated linoleic acid on lipogenesis is tissue dependent in hamsters

“…Kang et al [3] found an increase in FAS mRNA induced by 0.2% trans-10,cis-12 CLA feeding for 4 weeks in mice. In contrast, Azain et al [4] did not find changes in FAS activity induced by CLA feeding in rats. Other authors found reduced expression of FAS and ACC in mice [5,6] .…”

“…In some of these trials, hepatic triacylglycerol content was measured and it was concluded that hepatomegaly was due to lipid accumulation [5,[14][15][16]. In contrast, the studies performed on rats reported no effects on liver weight induced by CLA [4,10,[17][18][19][20].…”

Os efeitos do ácido linoléico conjugado no metabolismo animal: avanço das pesquisas e perspectivas para o futuro

“…A partir de então muitos foram os estudos com diversos animais [102][103][104] , com culturas de adipócito de roedores e humanos [105][106][107][108][109] e com humanos 8,65,[74][75][76][77][78][79][80]90,95,96,[110][111][112][113][114][115][116] , que surgiram com o objetivo de avaliar a propriedade de redução da gordura corporal, bem como elucidar os mecanismos de ação pelos quais o CLA desempenha esse papel.…”

“…Na verdade, os estudos apontam que a redução da gordura corporal induzida pelo CLA ocorre não somente pela diminuição do número de adipócitos, mas também, ou até mesmo somente, pela redução do seu tamanho. Considerando que o tamanho da célula adiposa está diretamente relacionado com o conteúdo de triacilgliceróis em seu interior, a redução desse lípide induzida pelo CLA resultaria, conseqüentemente, na diminuição do tamanho da célula 3,102,108 . É importante discutir que o mecanismo de ação responsável pela redução de triacilgliceróis induzida pelo CLA ainda necessita de maiores esclarecimentos.…”

Dietary conjugated linoleic acid has limited effects on tissue protein anabolism in sedentary and exercising adult rats

“…Mixtures of conjugated linoleic acid isomers (CLA) were initially shown to reduce the percentage of whole body fat and/or the mass of fat pads, in mice [1] and then in rats, hamsters, pigs and hu-CLA feeding had no effect on these parameters in mice [4], rats [5][6][7][8][9][10], hamsters [9,11] and humans [12]. In other studies, CLA increased body protein concentration or lean body percentage without modification of absolute amounts, in mice [13][14][15], rats [16] and humans [17,18].…”