Urinary lactate excretion in type 1 glycogenosis--a marker of metabolic control or renal tubular dysfunction?

Clinical evaluation of a portable lactate meter in type I glycogen storage disease

High lactate concentrations occur in type I glycogen storage disease (GSD) whenever glycogenolysis occurs. Not only does hyperlactataemia cause acute clinical deterioration, but chronic lactate elevations have also been associated with many of the long-term complications in GSD. A portable finger-stick blood lactate meter has recently been marketed as a training tool for high-performance athletes, but it has not been tested as a clinical diagnostic tool. This study was performed to assess the accuracy of the portable lactate meter in subjects with GSD I who are predisposed to high lactate concentrations. A total of 166 intravenous and 39 capillary samples from 13 subjects were tested concomitantly on three different lactate meters. The meter readings were compared with the lactate concentration determined by the laboratory gold-standard enzymatic colorimetric assay. Almost no inter-meter variability was found. The lactate meter values had outstanding correlation with the laboratory lactate determination, although the meters were found to run 0.5 mmol/L higher than the laboratory assay. The meter deviation was independent of lactate concentration. More variability was noted with finger-stick capillary lactate determinations, but monitoring of trends with capillary samples should prove valuable as a method for determining long-term control or acute deterioration. The portable lactate meter is a highly accurate tool for monitoring lactate concentrations, and should prove valuable for monitoring metabolic control in patients with GSD type I and other disorders associated with hyperlactataemia.

Guidelines for management of glycogen storage disease type I - European Study on Glycogen Storage Disease Type I (ESGSD I)

Life-expectancy in glycogen storage disease type I (GSD I) has improved considerably. Its relative rarity implies that no metabolic centre has experience of large series of patients and experience with long-term management and follow-up at each centre is limited. There is wide variation in methods of dietary and pharmacological treatment. Based on the data of the European Study on Glycogen Storage Disease Type I, discussions within this study group, discussions with the participants of the international SHS-symposium 'Glycogen Storage Disease Type I and II: Recent Developments, Management and Outcome' (Fulda, Germany; 22-25th November 2000) and on data from the literature, guidelines are presented concerning: (1). diagnosis, prenatal diagnosis and carrier detection; (2). (biomedical) targets; (3). recommendations for dietary treatment; (4). recommendations for pharmacological treatment; (5). metabolic derangement/intercurrent infections/emergency treatment/preparation elective surgery; and (6). management of complications (directly) related to metabolic disturbances and complications which may develop with ageing and their follow-up.

CONCLUSION

In this paper guidelines for the management of GSD I are presented.

Decreased urinary citrate excretion in type 1a glycogen storage disease

OBJECTIVES

To quantify urinary citrate and calcium excretion and systemic acid-base status in patients with type 1a glycogen storage disease (GSD1a) and to investigate their relationship to renal complications.

STUDY DESIGN

Fifteen patients (7 male and 8 female; age range, 3--28 years) were studied during annual evaluations of metabolic control. All were treated with intermittent doses of uncooked cornstarch. Hourly blood sampling and a 24-hour urine collection were obtained while subjects followed their usual home dietary regimen.

RESULTS

All but the youngest subject had low levels of citrate excretion (mean 2.4 +/- 1.8 mg/kg/d; 129 +/- 21 mg citrate/g creatinine). Normally, urinary citrate excretion increases with age; however, in patients with GSD1a, a strong inverse exponential relationship was found between age and citrate excretion (r = -0.84, P <.0001). Urinary citrate excretion was unrelated to markers of metabolic control. Hypercalciuria occurred in 9 of 15 patients (mean urinary calcium/creatinine ratio, 0.27 +/- 0.15) and was also inversely correlated with age (r = -0.62, P =.001).

CONCLUSIONS

Hypocitraturia that worsens with age occurs in metabolically compensated patients with GSD1a. The combination of low citrate excretion and hypercalciuria appears to be important in the pathogenesis of nephrocalcinosis and nephrolithiasis. Citrate supplementation may be beneficial in preventing or ameliorating nephrocalcinosis and the development of urinary calculi in GSD1a.

Urinary lactate excretion to monitor the efficacy of treatment of type I glycogen storage disease

The purpose of this study was to investigate the usefulness of urinary lactate measurements to assess the adequacy of dietary treatment in patients with type I glycogen storage disease (GSD-I). We determined the correlation of urine and blood lactate concentrations in 21 GSD-I patients during 24-h admissions to the General Clinical Research Center (GCRC) during which hourly blood samples and aliquots of every void were obtained. In all but 1 patient, we found a good correlation between blood lactate concentrations and urinary lactate excretion. One patient did not excrete lactate in significant amounts despite elevated blood lactate concentrations. In 17 patients, the highest blood lactate concentrations occurred during the night. Markedly elevated nighttime average blood lactate concentrations above 3.5 mmol/l resulted in a urinary lactate concentration above the normal limit of 0.067 mmol/mmol creatinine in the first morning urine specimen. Mildly elevated nighttime blood lactate concentrations (between 2.2 and 3.5 mmol/l) led to urinary lactate concentrations that were either normal or moderately elevated. All patients with normal blood lactate concentrations during the night also had normal first morning urinary lactate concentrations. The degree of urinary lactate excretion in relation to blood lactate concentrations varied by individual. Urinary filter paper specimens, collected at home during the night and in the morning and mailed to the laboratory, were used to monitor the dietary compliance of 5 GSD-I patients at home over a period of 6 to 9 weeks prior to their GCRC admissions. These data suggested variable degrees of dietary control. In conclusion, the urinary lactate concentration is a useful parameter to monitor therapy of GSD-I patients at home. To be interpretable, the baseline urinary lactate concentration in relation to the blood lactate concentration has to be determined.