Depletion of Δ9 desaturase (EC1.14.99.5) enzyme activity in growing rat during dietary protein restriction

Abstract

The effects of protein restriction on A9 desaturase (EC 1.14.99.5) activity were studied in growing rats. A control group was fed on a balanced diet (200 g caseinlkg; BD) for 28 d. The experimental group was fed on the low-protein diet (20 g caseinlkg; LP) for 26 d, then refed the balanced diet (BD-R) for 2 d. Rats were born to and suckled from normally fed dams. The enzyme activity was measured after 2 and 14 d of LP, and 26 d of L P plus 2 d of BD-R, by incubations in vitro of hepatic microsomal pellets with [ l-'4Cjstearic acid. The results indicated a decreased A9 desaturase activity after 2 and 14 d of LP of -33 and -43 YO respectively. Refeeding for 2 d was sufficient to super-repair this activity ( + 66 YO). The fatty acid composition of total liver lipids and microsomal phosphatidylethanolamines (PE) and phosphatidylcholines (PC) were also investigated; 18:O decreased in total liver lipids at 14 d of LP, when 18:ln-9 increased. Stearic acid (18:O) increased in PC at 2 d of L P and in P E a t 14 d of L P ; oleic acid (18:ln-9) did not change. Therefore, it is concluded that a defect occurred in the bioconversion of 18:O into 18:ln-9 by A9 desaturation during protein depletion. As oleic acid is accumulated in total liver lipids during LP, we speculate that this is due to a decreased oxidation or transport of this fatty acid. Microsomal desaturation: Protein restriction: Liver lipidsProtein restriction alters the metabolism of polyunsaturated fatty acids (Waterlow et al. 1960; Williams & Hurlebaus, 1965a, b, 1966 Truswell et al. 1969;Flores et al. 1970;Naismith, 1973;Anthony & Edozien, 1975; Brenner, 1981;Holman et al. 1981;Leat, 1983). Rogers (1971Rogers ( , 1972 has shown that liver mitochondria1 and microsomal polyunsaturated fatty acid compositions were altered by such a diet. All these findings suggested an impairment of the bioconversion of linoleic acid into arachidonic acid, via a decrease in desaturase activities. Mercuri et al. (1979) showed that A6 and A5 desaturase activities were diminished in pregnant rats fed on a low-protein diet (50 g casein/kg, LP). Then De Tomas et al. (1980Tomas et al. ( , 1983 reported decreased liver A6 and A5 desaturase activities in the early developing rat related to a maternal protein restriction. These authors also showed the negative effect of protein depletion on the supply of polyunsaturated fatty acids for normal development and metabolic adaptations. But Gerson & Wong (1978) indicated that, in the adult rat, if the liver fatty acid composition was affected by protein restriction, the A6 and A5 desaturase activities were not.We have demonstrated, by a time-course study using a low-protein diet (50 g gluten/kg), the impairment of A6 and A5 desaturase activities in growing rats (Narce et al.

Dietary Egg Yolk Supplementation Improves Low-Protein-Diet-Induced Fatty Liver in Rats

“…First, we chemically as well as histologically demonstrated the formation of fatty liver in rats fed the lowprotein diet (28)(29)(30). Impaired liver functions (31) in rats fed a protein-restricted diet were also confirmed in the present study, as shown by the decreased level of serum albumin and increased level of serum AST activity.…”

Distinct regulation of stearoyl-CoA desaturase 1 gene expression by cis and trans C18:1 fatty acids in human aortic smooth muscle cells

“…Cells were then collected, and total lipids were extracted according to Bligh and Dyer method for saponification and esterification. Radiolabelled fatty acid methyl esters were then separated by RP-HPLC and detected on line by a radioisotope detector (Packard Flow Scintillation Analyser, PerkinElmer Life Sciences Inc., Wellesley, MA) (Narce et al 1992 Western blotting Cells were washed with ice-cold PBS and lysed in ice-cold Ripa buffer containing protease inhibitor cocktail (Sigma) for 15 min on ice. We cleared protein lysate by centrifugation at 10,0009g for 10 min at 4°C.…”

Dietary docosahexaenoic acid affects stearic acid desaturation in spontaneously hypertensive rats

“…Before enzyme activity measurement, [1-14 C]stearic acid (1-14 C 18:0; 50 mCi/mmol, 98% pure; NEN Life ProductsFrance SA, Le Blanc Mesnil, France) was diluted in ethanol (Prolabo, Paris, France) to a specific activity of 5 mCi/mmol with the corresponding unlabeled fatty acid (Sigma Chemical Co, St. Louis, MO). Under such conditions the reaction was linear, proportional to the time of incubation and protein concentration (26). Before the incubation, the microsomes were preincubated at 37°C for 3 min.…”