Conjugated linoleic acid and betaine affect lipolysis in pig adipose tissue explants

Authors: FERNÁNDEZ-FÍGARES,, IGNACIO - Ihsm-Uma-csic, Estación Experimental “la Mayora”; LACHICA, MANUEL - Ihsm-Uma-csic, Estación Experimental “la Mayora”; MARTÍNEZ-PÉREZ, MAYULY - Instituto De Ciencia Animal (ICA); Ramsay, Timothy

Submitted to: Animal-The International Journal of Animal Biosciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2019
Publication Date: 5/31/2019
Citation: Ramsay, T.G., Fernández-Fígares, I., Lachica, M., Martínez-Pérez, M. 2019. Conjugated linoleic acid and betaine affect lipolysis in pig adipose tissue explants. Animal-The International Journal of Animal Biosciences. https://doi.org/10.1017/S1751731119001186.
DOI: https://doi.org/10.1017/S1751731119001186

Interpretive Summary: This project was performed at the Spanish Research Council Facilities in Granada, Spain with the collaboration of a scientist at ARS Beltsville. The ARS affiliated scientist trained the lead author in the techniques used within the study. The study examined the impact of feeding two metabolic modifiers betaine and conjugated linoleic acid (CLA) to a special breed of pig in Spain whose meat is highly valued world-wide, valued at ten-fold the price of traditional hams in the US. The metabolic modifiers betaine and CLA are dietary ingredients, not drugs, and have been reported to decrease carcass fat and promote growth in different animal models, but the mechanisms are not clearly elucidated. This study was focused on determining how these metabolic modifiers affect adipose tissue metabolism in fat samples treated with CLA and betaine within a tissue culture environment in the laboratory. This study showed that treatment with CLA or the combination of CLA and betaine increased the breakdown of the fat in adipose tissue from this highly valued breed of Spanish pigs. These data also demonstrated that these two metabolic modifiers function to partition energy away from lipid accumulation within swine adipose tissue in part by reducing insulin-mediated inhibition of fat breakdown. These effects have favorable consequences for consumers interested in healthier, lower fat pork.

Technical Abstract: The current study was performed to determine the lipolytic effect of betaine and conjugated linoleic acid (CLA) in the adipose tissue of Iberian pigs. Adipose tissue samples from five pigs (38 kg BW) were used per experiment. Adipose tissue explants were prepared from dorsal subcutaneous adipose tissue samples and cultivated for 2 h (acute experiments) or 72 h (chronic experiments). Treatments included 100 µM linoleic acid (control), 100 µM trans-10, cis-12 CLA (CLA), 100 µM linoleic acid + 1mM betaine (BET) and 100 µM trans-10, cis-12 CLA + 1mM betaine (CLABET). To examine the ability of betaine or CLA to inhibit insulin's suppression of isoproterenol-stimulated lipolysis, the test medium was amended with 1 µM isoproterenol ±10 nM insulin. Media glycerol was measured at the end of the incubations. Acute lipolysis (2 h) was increased by CLA and CLABET (85-121%; P<0.05) under basal conditions. When lipolysis was stimulated with isoproterenol (1090% compared to basal), acute exposure to BET tended to increase (13%; P=0.071) while CLA and CLABET increased (14-18%; P<0.05) isoproterenol stimulated lipolysis compared to control. When insulin was added to isoproterenol-stimulated explants, lipolytic rate was decreased by 50% (P<0.001). However, supplementation of betaine to the insulin + isoproterenol containing medium tended to increase (P=0.07) while CLA and CLABET increased (45% on average; P<0.05) lipolysis, partly counteracting insulin inhibition. When culture was extended for 72h, CLA decreased lipolysis under basal conditions (18%; P<0.05) with no effect of BET and CLABET (P>0.10). When lipolysis was stimulated by isoproterenol (125% increase in rate compared to basal), CLA and CLABET decreased glycerol release (27%; P<0.001) compared to control (isoproterenol alone). When insulin was added to isoproterenol-stimulated explants, isoproterenol stimulation of lipolysis was completely blunted and neither betaine or CLA altered the inhibitory effect of insulin on lipolysis. Isoproterenol and especially isoproterenol + insulin stimulated leptin secretion compared to basal conditions (68 and 464%, respectively; P<0.001), with no effect of CLA or betaine exposure (P>0.10). CLA decreased leptin release (25%; P<0.001) when insulin was present in the media, partially inhibiting insulin stimulation of leptin release. In conclusion, betaine and CLA produced a biphasic response regarding lipolysis so that glycerol release was increased in acute conditions while CLA decreased glycerol release and betaine had no effect in chronic conditions. Furthermore, CLA and CLABET indirectly increased lipolysis by reducing insulin-mediated inhibition of lipolysis during acute conditions.