Depression of lipogenesis in swine adipose tissue by specific dietary fatty acids.

Abstract

The objective of this study was to document the influence of specific dietary fatty acids on rates of lipid synthesis and sensitivity to insulin in porcine adipose tissue. Weanling pigs were assigned to one of six groups, and each group was fed diets containing 10 g/100 g of added cornstarch or 10 g/100 g of added fatty acid. The fatty acid-enriched diets contained either a combination of 14:1 plus 16:1 (14:1/16:1 diet), 16:0, 18:0, 18:1, or 18:2 (n-6). With the exception of the cornstarch diet, all diets contained approximately 35% 14:0. Subcutaneous adipose tissue samples were collected at slaughter from the area overlying the first cranial vertebra. Fresh samples were incubated for 2 h in 20 mM glucose and 0, 10, 100 or 1,000 microU/mL of porcine insulin. The smallest adipocytes were observed in adipose tissue from pigs fed the 16:0 or 18:2 diets. Glucose incorporation into lipids was greater (P < .05) in adipose tissue from cornstarch-fed pigs than in adipose tissue from the other treatment groups. Lipogenesis was 67, 53, 35, 32, and 20% lower (P < .05) in adipose tissue from 16:0-, 14:1/16:1-, 18:0-, 18:2-, and 18:1-fed pigs, respectively, than in adipose tissue from the cornstarch-fed pigs. Insulin increased lipogenesis by 19% (P < .05) in adipose tissue from the cornstarch-fed pigs and by 15 to 40% (P < .05) in adipose tissue from the 14:1/16:1-fed pigs. Insulin did not stimulate lipogenesis (P > .4) in adipose tissue from pigs fed the 16:0, 18:0, or 18:1 diets. The data suggest that fatty acid chain length and unsaturation are determinants in the effects of dietary fat and insulin on de novo lipogenesis.

Dietary fat source affects metabolism of fatty acids in pigs as evaluated by altered expression of lipogenic genes in liver and adipose tissues

“…In contrast to the liver, pigs fed with the no fat-added diet (NF diet) showed the highest mRNA abundance in adipose tissue of genes involved in the synthesis of palmitic acid (ACACA and FASN) and also a gene involved in FA desaturation (SCD). These results agree with the higher lipogenic rate observed by Smith et al (1996) in cultured adipocytes isolated from pigs fed a cornstarch diet as compared to pigs fed a 10% fat-added diet, and also agrees with the findings of Mersmann et al (1984) who measured adipose tissue lipogenesis comparing carbohydrate and fat as energy source. In the present study, the higher SCD mRNA abundance in adipose tissue with the NF diet showed a different response pattern to what was observed in the liver.…”

“…mRNA abundance in adipose tissue In previous reports, the effects of different FA types were tested to investigate their effects on lipogenesis; Allee et al (1971) demonstrated that 10% of corn oil or beef T added to diets had the same effects on suppressing lipogenesis in porcine adipose tissue. Smith et al (1996) tested in vitro lipogenesis in cultured adipocytes from piglets previously fed with different dietary treatments differing in their FA source. They observed that the C18:0-enriched diet resulted in lower lipogenesis compared to a C18:2-enriched diet and attributed this finding to the lower absorption of C18:0.…”

Fatty acid profile and meat quality of young bulls fed ground soybean or ground cottonseed and vitamin E

“…The potential of sterculic acid to inhibit Δ 9 -desaturase activity is well established in the literature (Smith et al, 1996;Yang et al, 1999) and, according to Gomez et al (2003), it directly inhibits Δ 9 -desaturase activity, possibly by a turnover-dependent reaction, without affecting the processes required for adipocyte differentiation, Δ 9 -desaturase gene expression or Δ 9 -desaturase protein translation. Furthermore, the subcutaneous fat from these animals had greater atherogenicity index.…”

GH and insulin affect fatty acid synthase activity in isolated porcine adipocytes in culture without any modifications of sterol regulatory element binding protein-1 expression

“…Moreover, one can assume that the half-life of FAS is about 40-50 h in porcine adipocytes as in rodents (Weiss et al 1980). In pigs, in vitro studies have concerned only short-term incubation of adipocytes (,24 h) (Etherton & Chung 1981, Smith et al 1996, Wang et al 1999 or of adipose tissue fragments (,48 h) ). In the current study, we have provided evidence that cultured adipocytes can be used as a model for studying hormonal control of lipogenesis in pigs.…”

“…An optimum response for FAS activity was reached for a concentration as low as 1·7 nM in s.c. adipocytes, whereas higher concentrations of insulin are often used in isolated adipocytes from other species, such as rat (Briquet-Laugier et al 1994) or human (Moustaïd et al 1996). In pigs, adipose tissue and/or adipocyte response to insulin has been often reported to be inconsistent (Mills 1999), with reports of absence of any responsiveness (Rule et al 1987, Benmansour et al 1991, little response (Liu et al 1989, Harris et al 1993 but not related to insulin concentrations (Mersmann & Hu 1987), or clear stimulation of glucose incorporation into fatty acids and lipogenesis in vitro , Smith et al 1996, Mills 1999. One possible explanation for these discrepancies is that an exaggerated basal rate of fatty acid synthesis could mask insulin responses in porcine adipocytes (Mills 1999).…”