In vivo functional investigations of lactic acid in patients with respiratory chain disorders

Touati, Guy; Rigal, Odile; Lombès, Anne; Frachon, Paule; Giraud, Marie-Noëlle; Baulny, Hélène Ogier de

doi:10.1136/adc.76.1.16

Cited by 37 publications

(18 citation statements)

References 14 publications

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“…Interestingly, a transplanted cystinotic patient had lactate/creatinine ratio comparable to nonFanconi renal controls. In patients with mitochondrial disorders urinary lactate was elevated in some, but not in all patients (19). This suggests that increased urinary lactate levels are not specific for identifying patients with mitochondrial disorders.…”

Section: Discussionmentioning

confidence: 83%

Mitochondrial Complex V Expression and Activity in Cystinotic Fibroblasts

et al. 2008

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Alterations in ATP metabolism have been proposed to be involved in the pathogenesis of cystinosis, the most common form of inherited Fanconi syndrome. A recent study showed normal activity of respiratory chain complexes I-IV with decreased ATP levels in cystinotic fibroblasts. Here, we show normal complex V expression and activity in mitochondria of cystinotic fibroblasts. This indicates that alterations in mitochondrial oxidative phosphorylation enzymes are not responsible for ATP decrease in cystinotic fibroblasts. T he autosomal recessive disorder cystinosis is caused by mutations in the CTNS gene (17p13.3), resulting in the defective lysosomal cystine transporter cystinosin (1). The consequential elevated cystine levels in the lysosomes lead to renal tubular dysfunction by mechanisms that are still elusive. Based on results of studies in cells loaded with cystine dimethyl ester, it was hypothesized that defects in mitochondrial ATP generating capacity are involved, resulting in decreased Na, K-ATPase activity (2,3). This ATP-driven proton pump generates a transmembrane Na ϩ gradient, required for tubular reabsorption of essential solutes such as amino acids, phosphate, and glucose in proximal tubules of the kidney. From this perspective, mitochondrial dysfunction is a possible cause of renal Fanconi syndrome in cystinosis (3). Recently our group extensively studied ATP metabolism in cystinotic fibroblasts and demonstrated slightly decreased intracellular ATP levels, but an intact Na, K-ATPase activity, hormone stimulated mitochondrial ATP production and normal activity of respiratory chain complexes I-IV (4). The activity of mitochondrial enzyme complex V, the ATP synthase complex of the oxidative phosphorylation system, could not be measured at the time of these studies, because lack of sensitivity of the assay. At present, we complete this study in cystinotic fibroblasts by measuring complex V activity using an enzymatic assay. In addition, we examined the expression and assembly status of complex V by Western blot analysis in a blue native gel. MATERIALS AND METHODSFibroblast culture. Patient (n ϭ 8) and control (n ϭ 9) fibroblasts were obtained after informed consent and subsequently cultured as described previously (4). The study was approved by the Institutional Review Board of Radboud University Medical Centre. All patients were diagnosed with cystinosis by measuring elevated cystine levels in isolated polymorphonuclear cells (Ͼ0.5 nmol cystine/mg protein) by high performance liquid chromatography (HPLC) and confirmed by molecular analysis. Previous data showed elevated levels of cystine in cystinotic fibroblasts compared with controls (4.3 Ϯ 1.1 versus 0.2 Ϯ 0.1 nmol/mg protein) and decreased ATP levels in cystinotic fibroblasts (mean 35.9 (Ϯ16.7) versus 51.7 (Ϯ4.5) nmol/mg protein) (4). Approximately 10 ϫ 10 6 cells were harvested using trypsin and divided in two samples for protein expression analysis and enzyme activity assay, respectively.Expression of complex V. A mitochondrial enriche...

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Section: Discussionmentioning

confidence: 83%

Mitochondrial Complex V Expression and Activity in Cystinotic Fibroblasts

et al. 2008

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“…The positive correlation between lactate and pyruvate concentrations and between lactate concentrations and the L/P ratio in both CSF and blood highlight their interdependency through the equilibrium constant KЈ eq and through the biological variability of the NADH/ NAD ϩ ratio. Blood lactate concentrations have been reported to decrease with age (13,15 ); they appear to show opposite trends in CSF and blood in childhood. However, this age dependency of lactate concentrations was not found by Hutchesson et al (9 ) in 39 healthy children 0.03-17.7 years of age (median, 1.39 years), although the upper limit of their CSF lactate values (1.97 mmol/L, mean ϩ 2 SD) was close to that observed here.…”

Section: Discussionmentioning

confidence: 99%

“…Both pyruvate and lactate concentrations are increased in PDH deficiency, but the L/P ratio remains normal or only slightly decreased (20 ) because the mitochondrial RC is not impaired. However, CSF appears to be more clinically relevant for pyruvate determinations because pyruvate concentrations in blood may be highly sensitive to sample preparation (13 ), giving rise to artificially low values (attributable to lactate dehydrogenase activity) and therefore to falsely high L/P ratios.…”

Section: Discussionmentioning

confidence: 99%

Cerebrospinal Fluid Lactate and Pyruvate Concentrations and Their Ratio in Children: Age-related Reference Intervals

Benoist

Alberti

Leclercq³

et al. 2003

Clinical Chemistry

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Background: Lactate (L) and pyruvate (P) concentrations in cerebrospinal fluid (CSF) and the L/P ratio have diagnostic value in numerous primary and acquired disorders affecting the central nervous system, but agerelated reference values are not available for children. Methods: We analyzed CSF and blood lactate and pyruvate concentrations and their ratio in a 4-year retrospective survey of a children's hospital laboratory database. Reference intervals (10th-90th percentiles) were established from data on 197 hospitalized children. A recent regression modeling method was used to normalize and smooth values against age. The model equation of best fit was calculated for each variable. Results: Slight age-related variations were shown by the model, with an increase in lactate, a decrease in pyruvate, and a resulting increase in the L/P ratio with increasing age. However, the SD did not vary with age. We defined the upper limit of the reference intervals as the 90th percentiles, which from birth to 186 months of age varied continuously from 1.78 to 1.88 mmol/L (6%), 148 to 139 mol/L (6%), and 16.9 to 19.2 (14%) for lactate, pyruvate, and the L/P ratio, respectively. At a threshold of 2 (in Z-score units), the sensitivity for a subgroup of inborn errors of metabolism (respiratory chain disorders) was 73%, 42%, and 31% for lactate, pyruvate, and the L/P ratio, respectively. Conclusions: In children, CSF lactate and pyruvate concentrations and their ratio appear to vary slightly with age. Average 90th percentile values of 1.8 mmol/L, 147 mol/L, and 17, respectively, could be used in

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“…We therefore assessed blood lactate and pyruvate in fed mice treated with the different NRTIs. We chose purposefully to measure the lactate and pyruvate levels in mice in the fed state because fasting can mask abnormalities of lactate metabolism induced by mitochondrial dysfunction (51). However, none of the eight different treatments with therapeutic doses of NRTI significantly increased blood lactate or blood pyruvate (data not shown).…”

Section: Vol 47 2003 Mitochondrial Effects Of Nucleoside Analogues mentioning

confidence: 99%

Mitochondrial and Metabolic Effects of Nucleoside Reverse Transcriptase Inhibitors (NRTIs) in Mice Receiving One of Five Single- and Three Dual-NRTI Treatments

Note

Maisonneuve

Lettéron

et al. 2003

Antimicrob Agents Chemother

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Although treatments with nucleoside reverse transcriptase inhibitors (NRTIs) can modify fat metabolism and fat distribution in humans, the mechanisms of these modifications and the roles of diverse NRTIs are unknown. We studied the mitochondrial and metabolic effects of stavudine (d4T), zidovudine (AZT), didanosine (ddI), lamivudine (3TC), zalcitabine (ddC), and three combinations (AZT-3TC, d4T-3TC, and d4T-ddI) in mice treated for 2 weeks with daily doses equivalent to the human dose per body area. Concentrations of AZT and d4T in plasma were lower when these drugs were administered with 3TC or ddI. Whatever the treatment, mitochondrial DNA was not significantly decreased in muscle, heart, brain, or white adipose tissue but was moderately decreased in liver tissue after the administration of AZT, 3TC, or d4T alone. Blood lactate was unchanged, even when NRTIs were administered at supratherapeutic doses. In contrast, the level of plasma ketone bodies increased with the administration of AZT or high doses of d4T but not with ddC, 3TC, or ddI, suggesting that the thymine moiety could be involved. Indeed, the levels of plasma ketone bodies increased in mice treated with ␤-aminoisobutyric acid, a thymine catabolite. Treatment with AZT, d4T, or ␤-aminoisobutyric acid increased hepatic carnitine palmitoyltransferase I (CPT-I) mRNA expression and the mitochondrial generation of ketone bodies from palmitate. In conclusion, therapeutic doses of NRTIs have no or moderate effects on mitochondrial DNA and no effects on plasma lactate in mice. However, AZT and high doses of d4T increase the levels of hepatic CPT-I, mitochondrial fatty acid ␤-oxidation, and ketone bodies, and these catabolic effects are reproduced by ␤-aminoisobutyric acid, a thymine metabolite.

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In vivo functional investigations of lactic acid in patients with respiratory chain disorders

Cited by 37 publications

References 14 publications

Mitochondrial Complex V Expression and Activity in Cystinotic Fibroblasts

Mitochondrial Complex V Expression and Activity in Cystinotic Fibroblasts

Cerebrospinal Fluid Lactate and Pyruvate Concentrations and Their Ratio in Children: Age-related Reference Intervals

Mitochondrial and Metabolic Effects of Nucleoside Reverse Transcriptase Inhibitors (NRTIs) in Mice Receiving One of Five Single- and Three Dual-NRTI Treatments

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