Jacques Belleville

Implication of acyl chain of diacylglycerols in activation of different isoforms of protein kinase C

We synthesized diacylglycerols (DAGs) containing ω‐6 or ω‐3 polyunsaturated fatty acids [i.e., 1‐stearoyl‐2‐arachidonoyl‐sn‐glycerol (SAG), 1‐stearoyl‐2‐docosahexaenoyL‐sn‐glycerol (SDG), and 1‐stearoyl‐2‐eicosapentaenoyl‐sn‐glycerol (SEG)] and assessed their efficiency on activation of conventional (α, βI, γ) and novel (ε, δ) protein kinase C (PKC). SAG exerted significantly higher stimulatory effects than SDG and SEG on activation of PKCα and PKCδ. Activation of PKCβI by SEG and SDG was higher than that by SAG. Activation of PKCγ did not differ significantly among DAG molecular species. Addition of SAG to assays containing SEG and SDG exerted additive effects on activation of α and ε, but not on βI and γ, isoforms of PKC. SDG‐ and SEG‐induced activation of PKCδ was significantly curtailed by the addition of SAG. Three DAG species significantly curtailed the PMA‐induced activation of βl, γ, and δ, but not of α and ε, isoforms of PKC. Our study demonstrates for the first time that in vitro activation of different PKC isoenzymes vary in response to different DAG species, and one can envisage that this differential regulation may be responsible for their in vivo effects on target organs.—Madani, S., Hichami, A., Legrand, A., Belleville, J., Khan, N. A. Implication of acyl chain of diacylglycerols in activation of different isoforms of protein kinase C. FASEB J. 15, 2595–2601 (2001)

Dietary protein level and origin (casein and highly purified soybean protein) affect hepatic storage, plasma lipid transport, and antioxidative defense status in the rat

The effects of different proportions (10, 20, and 30%) of dietary casein or highly purified soybean protein on lipid metabolism were studied in growing Wistar rats. Hepatic, plasma and lipoprotein lipid, and protein concentrations, plasma thiobarbituric acid-reactive substance (TBARS) levels, and resistance of red blood cells against free-radical attack were determined after a 4-wk dietary regimen. Compared with the 20% casein diet, the 20% soybean protein diet exhibited similar cholesterolemia but lower plasma triacylglycerol concentrations and very-low-density lipoprotein (VLDL) particle number, as measured by diminished contents of VLDL-triacylglycerol, VLDL-protein, and VLDL-apolipoprotein (Apo) B (B-100 and B-48). The soybean protein diet raised high-density lipoprotein (HDL)(2-3) particle number, as measured by enhanced concentrations of HDL(2-3) cholesterol, HDL-phospholipid, and HDL-ApoA-I. Increasing casein or soybean protein level (from 10 to 30%) in the diet involved higher VLDL-ApoB (B-100 and B-48), indicating an increase in the number of VLDL particles. Feeding the 30% casein or 30% soybean protein diet enhanced LDL-HDL(1) cholesterol contents. Despite similar HDL(2-3)-ApoA-I levels, the 30% casein diet enhanced the HDL(2-3) mass and its cholesterol concentrations. In contrast, feeding either the 10 or 30% soybean protein diet significantly lowered HDL(2-3) cholesterol and ApoA-I levels. These effects on cholesterol distribution in lipoprotein fractions occurred despite unchanged total cholesterol concentrations in plasma. Feeding 20% soybean protein versus 20% casein involved lower plasma TBARS concentrations. Decreasing casein or soybean protein levels in the diet were associated with higher plasma TBARS concentrations and had a lower resistance of red blood cells against free-radical attack. The present study shows that dietary protein level and origin play an important role in lipoprotein metabolism and the antioxidative defense status but do not affect total cholesterol concentrations in plasma.

Time-course effects of protein malnutrition on hepatic fatty acids delta 6 and delta 5 desaturation in the growing rat.

1. In growing rats, the time-course effects of giving a normal-protein diet (200 g casein/kg; NP) for 52 d, a low-protein diet (20 g casein/kg; LP) for 52 d and a LP diet for 26 d followed by balanced refeeding (200 g casein/kg; BR) for 26 d, on the fatty acid composition of liver total lipids and microsomal phospholipids were investigated together with delta 6- and delta 5-microsomal desaturase activities. 2. The oleic acid content (mg/g tissue) of liver total lipids increased progressively with the LP diet, while linoleic acid was increased only at days 7 and 52. 20:3 omega 6, 20:4 omega 6, 22:5 omega 6 and 22:6 omega 3 fatty acids decreased during the period on the LP diet. BR for 7 d was sufficient to restore the fatty acid composition of total lipids to control values. Changes in the fatty acid composition of liver microsomal L-alpha-phosphatidylcholines were observed only after 52 d on the LP diet; the proportions (% w/w total fatty acids) of 18:0, 20:3 omega 6 and 20:4 omega 6 fatty acids decreased while oleic acid increased. The fatty acid composition of L-alpha-phosphatidylethanolamines was less affected. 3. delta 6- and delta 5-desaturase activities decreased to 20-30% of their original values after 2 d on the LP diet; a smaller deficit prevailed after 14 d but disappeared after 25 d, to appear again after 52 d. As early as day 2 of BR, desaturase activities were greatly recovered and returned to control values at day 13. 4. The present work shows that modifications in microsomal delta 6- and delta 5-desaturase activities are not strictly paralleled by the changes in the composition of fatty acids of liver total lipids and microsomal phospholipids.

Impaired lipoprotein metabolism in obese offspring of streptozotocin-induced diabetic rats.

The time course of changes in lipoprotein metabolism of obese offspring of mildly diabetic rats was studied with respect to serum lipoprotein composition as well as LCAT and tissue lipoprotein lipase (LPL) activities. Mild hyperglycemia in pregnant rats was induced by intraperitoneal injection of streptozotocin on day 5 of gestation. Control pregnant rats were injected with citrate buffer. At birth, obese pups had higher serum glucose, insulin, and lipoprotein (VLDL, LDL-HDL1, HDL2–3) levels than control pups. After 1 mon of life, all of these parameters in obese rats became similar to those of controls. However, LCAT, adipose tissue LPL, and hepatic triacylglycerol lipase activities were high. At 2 mon of age, VLDL-TAG levels were higher in obese females than in controls. By the age of 3 mon, obese offspring had developed insulin resistance with hyperglycemia, hyperinsulinemia, and higher serum lipoprotein concentrations. Indeed, qualitative abnormalities of lipoproteins were seen and were typical of obese and diabetic human beings. Fetal hyperinsulinemia should be considered as a risk factor for later metabolic diseases, including dyslipoproteinemia.

Plasma lipoprotein lipase, hepatic lipase activities, VLDL, LDL compositions at different times of hemodialysis

The effects of hemodialysis duration (HD) on lipoprotein lipase (LPL) and hepatic lipase (HL) activities and very low density lipoprotein (VLDL), low density lipoproteins (LDL) amounts and compositions were investigated in 58 patients, divided according to HD: GI: under 1 year, GII: 1-5 years, GIII: 5-13 years. HL and LPL activities were reduced in GIII versus GI (P<0.01) and 47% of GIII patients had negligible HL activity. LPL and HL activities were correlated with HD (r=-0.80, P<0.001). Apo C-III concentrations were correlated with HD (r=0.58, P<0.05). Compared with controls, triacylglycerols (TG) were increased in GI, GII (P<0.01) and GIII (P<0.001), and were correlated with HD (r=0.75, P<0.05). VLDL amounts and VLDL-cholesteryl esters (CE) were enhanced in GIII versus GI and GII (P<0.05). VLDL-TG and VLDL-phospholipids (PL) were correlated with HD (r=0.60, P<0.05). LDL-apolipoproteins and unesterified cholesterol (UC) were increased in GII versus GI (P<0.05) and in GIII versus GII and GI (P<0.01). LDL-PLs were decreased in GIII versus GI (P<0.05). Compared with controls, LDL-TGs were higher in GI and GII (P<0.01) and in GIII (P<0.05). Long-term treatment with acetate hemodialysis using cuprophane membrane does not improve lipolytic activity decrease and lipoprotein alterations generated by chronic renal failure (CRF).

Depletion of Δ9 desaturase ( EC 1.14.99.5) enzyme activity in growing rat during dietary protein restriction

The effects of protein restriction on delta 9 desaturase (EC 1.14.99.5) activity were studied in growing rats. A control group was fed on a balanced diet (200 g casein/kg; BD) for 28 d. The experimental group was fed on the low-protein diet (20 g casein/kg; 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 LP plus 2 d of BD-R, by incubations in vitro of hepatic microsomal pellets with [1-14C]steric acid. The results indicated a decreased delta 9 desaturase activity after 2 and 14 d of LP of -33 and -43% respectively. Refeeding for 2 d was sufficient to super-repair this activity (+66%). The fatty acid composition of total liver lipids and microsomal phosphatidylethanolamines (PE) and phosphatidylcholines (PC) were also investigated; 18:0 decreased in total liver lipids at 14 d of LP, when 18:1n-9 increased. Stearic acid (18:0) increased in PC at 2 d of LP and in PE at 14 d of LP; oleic acid (18:1n-9) did not change. Therefore, it is concluded that a defect occurred in the bioconversion of 18:0 into 18:1n-9 by delta 9 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.

Metabolism of serum VLDL-, LDL-, and HDL-apoproteins in rats on two different low protein diets

Abstract Apoprotein (apo) metabolism of serum total lipoproteins (LP), very low, low and high density LP (VLDL, LDL and HDL) were evaluated using [ 3 H]-leucine pulse injected into rats fed 2% casein (C), 5% gluten (Gl) or 15% casein (T) diets, during 14 days. Apo contents were determined, after separation according to SDS gradient polyacrylamide gel electrophoresis. In the three groups, similar percent of [ 3 H]-leucine incorporation into the total LP was observed. In spite of a decrease in concentration and [ 3 H]-leucine incorporation of VLDL-apos with both depleted groups, the peak of VLDL specific radioactivity (SR) was reached between 30 and 60 min in the three groups. SR of each VLDL-apo differed (P apo B48 > apo E > apo A-I > apo C. The peak of LDL SR occured at 60 min in (Gl) and at 120 min in (T) and (C) groups and the SR of HDL rose to reach a plateau between 60 and 180 min after the [ 3 H]-pulse, and was significantly higher in both depleted groups. SR profiles of each HDL-apo were similar in the three groups. The percents of radioactivity found in the liver and kidneys were higher in both depleted groups. Therefore, our results provide evidence of changes in each apo metabolism with different diets, according to its synthesis location and its origin (VLDL or HDL).

Removal rates of rat serum [3H] labeled very low density lipoproteins after consumption of two different low protein diets

Abstract The fate of very low density lipoprotein (VLDL)-apoproteins, labeled with [ 3 H]-leucine was investigated in rats fed two different low protein diets, 2% casein (C group) or 5% gluten (Gl group) and a balanced diet, 15% casein (T group) for 14 days. The disappearance curve of radioactivity from serum was studied at various times during one hour after injection. The VLDL-apos were decreased by protein malnutrition (PM) and their removal time was accelerated. This study indicates that both protein depletions reduce the half life of VLDL-apos and increase their clearance from VLDL, probably on account of an increase in peripheral uptake of different organs but not because of a higher uptake by liver. The net trasnsfer of VLDL-apos to high density lipoprotein (HDL) occurs mostly in apo E and apo C. The clearance of VLDL-apos was more rapid for apo C than apo B, apo B48 and apo B100. It provides evidence that the metabolism of each VLDL-apo differs. The relative constancy of radioactivity percent of of HDL-apos confirms that their apo metabolism is significantly slower than that of VLDL and little modified by PM.

Étude chronologique des effets d'un régime hypoprotéique suivi d'un régime équilibré sur les DL6-et DL5-désaturations de l'acide linoléique des microsomes hépatiques de rat

AbstractA low protein diet affects amounts of linoleic and arachidonic acids in hepatic microsomal phospholipids of growing rats. Are the changes related to modifications in microsomal DL6-and DL5-linoleic acid desaturase activities?Two groups of Wistar rats weighing 80 5 g at the beginning of the experiment were used: Control group (T) was fed on a 16% gluten + 4% casein diet for 53 days; Experimental group (E) was fed on a 4% gluten + 1% casein diet for 26 days (MP) then Control diet for 27 days (RE). After 2, 14 and 26 days of MP and 2, 15 and 27 days of RE, rats of each group were sacrificed. Protein and water contents of liver, quantitative fatty acid, composition of total lipids in liver and hepatic microsomes were determined. DL6-and DL 5-linoleic acid desaturase activities were estimated from incubation of liver microsomes with [1-14C] C 18: 2 n-6 or [214C] C 20: 3 n-6 respectively.The low protein diet stops practically ponderal growth. The fatty-acid compositions of microsomal total lipids of E r...