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Biomedical subjects

P H Groot

Publications and source records attributed to P H Groot.

68 records · Page 4Linked to original sources
PubMed1980

The effect of oral calcium carbonate administration on serum lipoproteins of children with familial hypercholesterolaemia (type II-A).

The effect of oral calcium carbonate on serum lipoprotein concentrations was tested in 50 children with familial hypercholesterolemia (type II-A) consuming a low cholesterol high polyunsaturated fat diet, using a cross-over design versus a placebo. Cholesterol was measured in serum and in the individual lipoprotein density classes. Serum apolipoprotein B (the protein moiety of low density lipoprotein) and apolipoprotein A-I (the main protein of high density lipoprotein) were measured by specific immunoassays. Calcium carbonate treatment induced only a slight increase in serum apolipoprotein A-I (+ 4%) and a slight decrease in low density lipoprotein cholesterol (-4%), both changes being significant at the P = 0.05 level.

Administration, Oral↗
PubMed1980

Effects of amount and type of dietary fat on serum lipids, lipoproteins and apolipoproteins in man. A controlled 8-week trial.

We have studied whether a low-fat diet is as effective in lowering some risk factors for atherosclerosis as a diet rich in polyunsaturated fat (PUFA). During a 2.5 week control period, 60 volunteers were given a moderate-fat diet (MOD) providing 30% of the daily energy intake (energy %) in the form of fat, one-third of which was PUFA. For the next 5 weeks subjects were divided into 4 groups and received diets providing varying amounts of total fat and of PUFA: for group LO, 20 energy % PUFA; group HIPUF, 40 energy % fat and 19 energy % PUFA; and group HISAT, 40 energy % fat and 3 energy % PUFA. The diets contained the same amounts of cholesterol, phytosterols, oligosaccharides and other nutrients, known to affect serum lipid levels. All food was prepared daily and weighed out for each individual appropriate to his energy needs. Nutrient intakes were checked by 7-day records and by chemical analysis of double portions. On diet LO, total serum cholesterol concentration increased by 0.25 mmol/l while HDL cholesterol concentration did not change significantly. The HDL cholesterol/apoprotein-A1 ratio fell, and VLDL and LDL triglyceride centrations were elevated. On the HIPUF diet, total serum cholesterol concentration was not significantly lower, but HDL cholesterol concentration increased by 0.10 mmol/l. On the HISAT diet, total serum cholesterol concentration went up by 0.38 mmol/l; 0.12 mmol/l of this was due to HDL. LDL cholesterol/serum apoprotein-B ratios were unaffected by any of the diets. It was concluded that after 5 weeks, the influence of a low-fat, high-carbohydrate diet on the concentrations of serum lipoproteins was less favourable than that of moderate- or high-fat diets rich in polyunsaturated fatty acids.

Adolescent↗
PubMed1978

Triglyceridase and phospholipase A1 activities of rat-heart lipoprotein lipase. Influence of apolipoproteins C-II and C-III.

The influence of purified human apolipoprotein C-II on phospholipase A1 and triglyceridase activities of lipoprotein lipase were compared. Lipoprotein lipase was obtained from rat hearts by perfusion with a medium containing heparin and purified on a heparin Sepharose 4-B column. Using phosphatidyl-ethanolamine-coated triglyceride particles as substrate it was found that the phospholipase A1 and triglyceridase activities of lipoprotein lipase similarly depend on the presence of apolipoprotein C-II. Apolipoprotein C-III cannot replace apolipoprotein C-II. However, addition of apolipoprotein C-III in the presence of C-II affects both lipase activities. While strong inhibition of triglyceridase activity was observed under these conditions, phospholipase A1 activity was slightly stimulated. On the basis of these findings a model was constructed for the role of apolipoprotein C-II in lipoprotein lipase action.

Animals↗
PubMed1976

Acyl-CoA synthetases in guinea-pig liver mitochondria. Purification and characterization of a distinct propionyl-CoA synthetase.

Guinea-pig liver mitochondria contain three soluble ATP-dependent acyl-CoA synthetases: (a) a medium-chain acyl-CoA synthetase, (b) a salicylate activating enzyme, and (c) a propionyl-CoA synthetase. A complete separation of these enzymes has been accomplished and the resulting preparation of propionyl-CoA synthetase (Spec. act. 4 units/mg protein) accepts acetate, propionate and butyrate as substrates with a high preference for propionate.

Acetates↗
PubMed1975

Organ and intracellular localization of short-chain acyl-CoA synthetases in rat and guinea-pig.

1. Homogenates of rat epididymal fat pad, heart, kidney, lactating mammary gland, liver, skeletal muscle and small intestinal mucosa have been partitioned into a particulate and supernatant fraction. With reliable marker enzymes for the mitochondrial matrix and the cytosol: propionyl-CoA carboxylase and pyruvate kinase, the distributions of the acyl-CoA synthetase activities measured at 1 and 10 mM C2, C3 and C4 over mitochondria and cytosol have been calculated. From these values an estimate was made of the K0.5 of the fatty acids. 2. A distinct fatty acid-activating enzyme was assumed to be present in one of the compartments when that fatty acid was activated with a K0.5 less than or equal to 1.5 mM in an amount of greater than 13% of the total cellular activity. Adipose tissue, gut, liver and mammary gland, all organs of a high lipogenetic capacity, contained a cytosolic acetyl-CoA synthetase. At 1 mM acetate 60, 31, 77 and 83% of the total cellular activities in these organs were cytosolic in nature, with activities of 0.021, 0.32, 0.37 and 1.16 mumol C2 activated per min per g wet weight, respectively. 3. Mitochondrial acetyl-CoA and butyryl-CoA synthetases were found in adipose tissue, gut, heart, kidney, mammary gland and muscle. They were absent in liver. Adipose tissue and liver contained a mitochondrial propionyl-CoA synthetase with activities at 1 mM C3 of 0.014 and 1.50 mumol C3 activated per min per g wet weight, respectively. 4. At 1 mM, C2 was activated with decreasing rates by kidney, heart, mammary gland and gut (7.6-1.0 mumol C2 activated per min per g wet weight). C3 (1 mM) activation was about equal (1.6-1.9 mumol C3 activated per min per g wet weight) in liver, kidney and heart. C4 (1 mM) was activated with decreasing rates by heart, liver, kidney and gut (4.0-0.5 mumol C4 activated per min per g wet weight) in the order given. 5. The influence of the isolation method and the diet on fatty acid activation in small intestinal mucosal scrapings have been studied. To demonstrate the existence of cytosolic acetyl-CoA synthetase in fed animals a pre-treatment of everted intestine by low amplitude vibration has been found essential. Also C16 activation was highly (95%) decreased in a non-pre-vibrated preparation. 24 h starvation lowered cytosolic C2 and total C16 activation by 90 and 80%, respectively. Refeeding of starved rats with a balanced fat-free diet, and not with sucrose only, gave the same cytosolic C2 and total C16 activation as normally fed rats. 6. In guienea-pig heart, kidney, liver and muscle about the same partitions have been found as in the respective rat organs. The acetate activation in liver was factor 6 lower. Acetate and butyrate activation in guinea-pig muscle was much higher (6 and 37 times, respectively).

Adipose Tissue↗
PubMed1975

The activation of short-chain fatty acids by the soluble fraction of guinea-pig heart and liver mitochondria. The search for a distinct propionyl-CoA synthetase.

1. The ATP dependent acetyl-, propionyl- and butyryl-CoA synthetase activities were measured in the soluble fraction of both guinea-pig heart and liver mitochondria. 2. When measured in 300 mM Tris-HC1, the V of propionate activation in heart (equals 892 munits/mg protein) is much higher than the V of acetate (equals 637 munits/mg protein) and butyrate activation (equals 143 munits/mg protein. Fatty acid competition experiments, however, clearly show that most of the propionate activation (Km equals 7.94 mM) is caused by the acetyl-CoA synthetase (EC 6.2.1.1) (Km for acetate equals 0.8 mM), while the remaining activity is probably caused by a butyryl-CoA synthetase (Km for butyrate equals 0.83 mM). This indicates that in guinea-pig heart the presence of a distinct propionyl-CoA synthetase is very unlikely. 3. In liver a completely different pattern of short-chain fatty acid activation is found: low acetate activation and moderate propionate and butyrate activation. Substrate competition experiments and kinetics of fatty acid activation indicate that in this tissue a distinct propionyl-CoA synthetase is present with high affinity for propionate (Km equals 0.6 mM) and some affinity towards acetate and butyrate (Km values respectively 11 mM and 5.4 mM).

Acetates↗
PubMedDate not supplied

Localisation of mRNA for JE/MCP-1 and its receptor CCR2 in atherosclerotic lesions of the ApoE knockout mouse.

MCP-1 has potent chemotactic activity for monocytes and is strongly implicated in the pathogenesis of atherosclerosis. In the present study, we have used in situ hybridisation to examine the gene expression of JE, the murine homologue of MCP-1, and its receptor, CCR2, during the development of atherosclerotic lesions in the ApoE knockout mouse. Interestingly, the earliest expression of JE detected during lesion development was found to be localised in mesenchymal cells in the adventitia and not in the intima. Macrophages were subsequently found to accumulate in these affected regions of the adventitia and these cells were found to express high levels of JE. At this stage, early macrophage-rich lesions with high expression of JE were also seen in the intima, but expression of mRNA for the receptor for JE (CCR2) was only found on adventitial macrophages and not in the intima. This sequence of events suggests that adventitial inflammation may be an important early event in lesion development and responsible for the subsequent accumulation of macrophages in the intima possibly by recruitment from the adventitia as well as via the vessel lumen.

Animals↗
PubMedDate not supplied

Postprandial lipoprotein metabolism in normolipidemic men with and without coronary artery disease.

A delayed clearance of postprandial lipoproteins from the plasma may play a role in the etiology of premature coronary atherosclerosis. To address this hypothesis, we studied chylomicron (remnant) metabolism in two groups of 20 selected normolipidemic men aged 35-65 years, a group of coronary artery disease (CAD) patients, and a matched control group with documented minimal coronary atherosclerosis. Subjects received an oral fat load supplemented with cholesterol and retinyl palmitate. Plasma samples obtained during the next 24-hour period were analyzed for total as well as d less than 1.019 g/ml and d greater than 1.019 g/ml triacylglycerol, cholesterol, and retinyl ester concentrations. Although both groups of patients responded identically in terms of the appearance of gut-derived lipids in the plasma, CAD patients showed a marked delay in the clearance of retinyl esters as well as in the normalization of plasma triacylglycerol concentrations. Postheparin plasma hepatic lipase activity was significantly lower in the CAD group. Apolipoprotein E phenotype measurements did not reveal marked differences in frequency between both groups. The frequency distribution was not unusual in comparison with the normal Dutch population. The magnitude of the postprandial responses of triacylglycerol and retinyl esters was correlated positively with the fasting levels of plasma triacylglycerol and negatively with high density lipoprotein subfraction 2 cholesterol concentrations. These data indicate that the clearance of postprandial lipoproteins in normolipidemic CAD patients as selected in the present study is delayed as compared with that of controls without coronary atherosclerosis and suggest that postprandial lipoproteins may play a role in the etiology of their disease.

Adult↗