Determination of human plasma xanthine oxidase activity by high-performance liquid chromatography

An assay for human plasma xanthine oxidase activity was developed with pterin as the substrate and the separation of product (isoxanthopterin) by high-performance liquid chromatography with a fluorescence detector. The reaction mixture consists of 60 microliters of plasma and 240 microliters of 0.2 M Tris-HCl buffer (pH 9.0) containing 113 microM pterin. With this assay, the activity of plasma xanthine oxidase could be easily determined despite its low activity. As a result, it could be demonstrated that the intravenous administration of heparin or the oral administration of ethanol did not increase plasma xanthine oxidase activity in normal subjects, and also that plasma xanthine oxidase activity was higher in patients with hepatitis C virus infection than in healthy subjects or patients with gout. In addition, a single patient with von Gierke's disease showed a marked increase in the plasma activity of this enzyme, relative to that apparent in normal subjects.

Difference of the plasma concentration and urinary excretion of allopurinol, oxypurinol, and purine bases between dietary intake and fasting

To investigate how much the metabolism of allopurinol, oxypurinol, and purine bases during dietary intake (total calorie 2,083 kcal, total protein 107.5 g, total lipid 74.1 g, total carbohydrate 228.3 g, total purine 180.5 mg) differs from that during fast, allopurinol (300 mg) was administered to 5 normal subjects after a 6-hour fast and then breakfast was taken. Four and 10 hours after the administration of allopurinol lunch and dinner were taken, respectively. Two weeks later the same protocol was performed, except for the intake of only water instead of diet. The fractional clearances and urinary excretions of oxypurinol, uric acid, and the clearance of creatinine were increased by dietary intake, compared with the respective ones resulting from fasting. At the same time the plasma concentrations of hypoxanthine, xanthine, and oxypurinol were decreased in dietary intake, compared with the respective ones in fasting, while the urinary excretion of neither allopurinol, hypoxanthine, nor xanthine was affected. These results suggest that the administration of allopurinol at bed time (during the nocturnal fast) may be more effective than that after breakfast in order to decrease the plasma concentration of uric acid.

[Alcohol-induced hypertriglyceridemia in subjects with decreased lipoprotein lipase--improvement after cessation of alcohol intake]

We systematically investigated the effect of lipoprotein lipase (LPL) and alcohol intake on the development of primary type IV hyperlipoproteinemia which is manifested as a moderate increase in serum triglycerides as a consequence of an elevated very low density lipoprotein concentration and a normal level of serum cholesterol. Twenty six type IV hyperlipoproteinemic and 28 normolipidemic males underwent measurement of the immunoreactive LPL mass in postheparin plasma (30 unit of heparin/kg of body weight) and were interviewed as to their alcohol consumption. They were divided into 4 groups, with a LPL mass of 150ng/ml (20 percentile of the normal range) and an alcohol intake of 33g/day as the borderlines. All subjects with LPL mass less than 150ng/ml and alcohol intake of more than 33g/day were prone to manifest type IV hyperlipoproteinemia. One of the subjects in this group showed a recovery to normolipidemic state after cessation of alcohol intake. Subject whose LPL mass value was more than 180ng/ml (50 percentile of the normal range) were not susceptible to type IV hyperlipoproteinemia even though they drank alcohol more than 33g/day.

Apolipoprotein E phenotypes in patients with gout: relation with hypertriglyceridaemia

OBJECTIVE

To elucidate the relationship, if any, between lipid abnormalities and apolipoprotein E (apo E) polymorphism, by investigating apo E phenotype and allele frequency.

METHODS

Fasting blood samples were taken for determination of apo E phenotype and serum lipids in 221 male patients with gout and 141 control male subjects. Apo E phenotype was determined by one dimensional flat gel isoelectric focusing.

RESULTS

Frequencies of apo E phenotypes in gout were apo E3/3 67.9%, E4/3 18.1%, E4/4 2.3%, E4/2 1.8%, E3/2 9.5%, and E2/2 0.5%; those in control male subjects were 74.5%, 15.6%, 0%, 1.4%, 7.1%, and 1.4%, respectively. Frequencies of the e2, e3, and e4 alleles in gout were 0.061, 0.817 and 0.122, compared with the corresponding control frequencies of 0.057, 0.858 and 0.085. These differences in apo E phenotype and allele frequencies between gout and control subjects were not significant. The frequency of apo e4 allele in hyperlipidaemic gout subjects was significantly greater than that in normolipidaemic gout subjects; in contrast, its frequency was not different between hyperlipidaemic and normolipidaemic control subjects. Serum triglyceride, total cholesterol, apo B and E concentrations were significantly greater in gouty patients with the apo E4/3 phenotype than in those with gout having the apo E3/3 phenotype.

CONCLUSIONS

These data suggest that gout subjects with hyperlipidaemia (hypertriglyceridaemia, hypercholesterolaemia or both) possess the apo e4 allele with higher frequency than those with normolipidaemia. They also suggest that apo e4 may induce some susceptibility to the development of hyperlipidaemia in gout in addition to that induced by obesity or excessive alcohol consumption, and may contribute to the high prevalence of atherosclerotic diseases in gout patients.

Increased concentrations of serum Lp(a) lipoprotein in patients with primary gout

OBJECTIVES

To investigate if serum Lp(a) lipoprotein (Lp(a)), a risk factor for atherosclerotic diseases, increases in patients with gout, who frequently also have atherosclerotic disease.

METHODS

Fasting blood samples were taken for measurement of Lp(a) and other variables in 175 male patients with primary gout. Serum concentrations of Lp(a) were measured by enzyme linked immunosorbent assay. The median value and frequency distribution of Lp(a) in gout patients were compared with those in 172 control male subjects. In addition, we examined the effect of niceritorol on serum Lp(a) values in gout patients in whom the Lp(a) concentration was greater than 20 mg/dl.

RESULTS

Serum Lp(a) was significantly higher in patients with gout than control subjects (median 15.5 mg/dl upsilon 8.6 mg/dl; p < 0.01). The frequency distribution of Lp(a) in gout was significantly shifted towards greater concentrations compared with control, although skewed distribution was noted in both groups. Serum Lp(a) concentration was not related to age, body mass index, alcohol intake, creatinine, fasting blood sugar or uric acid in patients with gout. Niceritorol decreased the serum concentrations of Lp(a) in gout.

CONCLUSIONS

These observations suggest that serum Lp(a) concentrations are increased in patients with gout and may play a role as one of the risk factors for atherosclerotic diseases in gout. Niceritorol seems effective in decreasing high levels of Lp(a) in patients with gout without detrimental influence on serum uric acid concentration.

A newly identified heterozygous lipoprotein lipase gene mutation (Cys239-->stop/TGC972-->TGA; LPLobama) in a patient with primary type IV hyperlipoproteinemia

We investigated measures for identification of heterozygous lipoprotein lipase (LPL) deficiency in unrelated subjects with primary type IV hyperlipoproteinemia in order to acquire a helpful clue for understanding the correlation between hypertriglyceridemia and the status of being a heterozygous carrier of an LPL gene variant. Identification of heterozygous LPL deficiency was performed by monitoring the immunoreactive LPL mass in postheparin plasma (PHP) using our developed sandwich-enzyme immunoassay technique for first screening. Then, in subjects found to have half or less than half of the control LPL mass value in PHP, the polymerase chain reaction-single strand conformation polymorphism method was used to detect LPL gene aberrations as a second screening. This approach was evaluated as being useful as it succeeded in identifying a subject (proband KD) with heterozygous LPL deficiency. The mutation in the LPL gene of proband KD was newly characterized as a nucleotide C972 to A transversion in exon 6, resulting in substitution of a premature termination codon (TGA) for Cys239 (TGC). This nonsense mutation, designated as LPLobama, creates an MboI restriction site and eliminates an HgiAI restriction site, and this allows rapid screening of subjects with type IV as well as type I hyperlipoproteinemia for the mutation. The homozygous state for the LPLobama allele resulted in neither detectable LPL activity nor immunoreactive LPL mass in PHP, and this was seen in two of proband KD's siblings.

Impaired lipoprotein metabolism in patients with primary gout--influence of alcohol intake and body weight

Using logistic regression analysis, we investigated whether or not excessive alcohol intake and increased BMI, both of which are known causes of lipid metabolism abnormality, are associated with increased serum triglyceride, apolipoprotein B concentrations and decreased high-density lipoprotein cholesterol (HDL-C), high-density lipoprotein 2 cholesterol (HDL2-C) levels in patients with gout. Serum triglyceride levels were significantly higher in patients with gout than in normal subjects. In contrast, serum levels of HDL-C and HDL2-C were significantly lower in patients with gout than in normal subjects. These results were further analysed using stepwise logistic regression. This analysis demonstrated that both serum triglyceride levels and alcohol consumption discriminated subjects with gout from controls but BMI, HDL-C and HDL2-C did not, suggesting that increased serum triglyceride levels exist intrinsically in gout, while decreased concentrations of HDL-C and HDL2-C may be attributed to hypertriglyceridaemia.

Molecular studies on primary lipoprotein lipase (LPL) deficiency. One base deletion (G916) in exon 5 of LPL gene causes no detectable LPL protein due to the absence of LPL mRNA transcript

We have systematically investigated a genetic defect resulting in a primary lipoprotein lipase (LPL) deficiency in a proband TN and his affected brother SN, both manifesting familial hyperchylomicronemia. Neither LPL activity nor immunoreactive LPL mass was detected in postheparin plasma from the two patients. Immunocytochemical and biosynthetic studies on the proband's monocyte-derived macrophages with rabbit anti-human LPL antiserum revealed that no immunochemically detectable LPL protein was found in either the cells or culture medium, whereas LPL having a molecular mass of 61 kD was detected in normal cells. No detectable LPL mRNA was identified from poly(A)+RNA of the proband's macrophages by Northern blot analysis, and grossly visible LPL gene rearrangement was not observed by Southern blot analysis. Sequence analysis of polymerase chain reaction-amplified LPL gene exons detected one base deletion of G (first position of Ala221) at base 916 in exon 5 which leads to a premature termination by a frameshift. This mutation, designated as LPLArita and resulting in the loss of an AluI restriction enzyme site, was newly identified. We further analyzed the LPL gene from the two patients and their family members by digestion with AluI. Both patients were homozygous for LPLArita allele, while their spouses did not have this mutation. As genetically expected, their children were all heterozygous for LPLArita. We conclude that primary LPL deficiency in the proband was caused by a lack of enzyme synthesis due to the absence of LPL mRNA resulting from one base deletion of G in exon 5, and that heterozygous LPLArita deficient subjects show almost half value of control LPL mass.

Recurrent Pneumocystis carinii pneumonia with long interval showing disparate radiographic findings

A case of recurrent Pneumocystis carinii pneumonia with a long interval between episodes and each episode showing a different radiographic appearance is reported. The radiographic finding in the initial infectious episode was bilateral, patchy, alveolar infiltrate predominantly in the upper and middle lung zones and that in the second infectious episode, six and a half years later, showed bilateral interstitial infiltrate predominantly in the middle and lower lung zones. T cell immunity expressed by mitogen-induced T cell proliferation was clearly different in the two infectious episodes. These differences in radiographic appearance could be due, at least in part, to altered immunological states between the first and second infectious episodes.