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Effects of chronic renal failure on the regulation of pyruvate kinase
Abstract:
The effects of chronic renal failure on the enzyme activity of pyruvate kinase and the mRNA level of this enzyme were studied in 7 out of 8 nephrectomized rats. The mRNA level was measured by RNA-DNA dot blot hybridization, using cloned pyruvate kinase cDNA as hybridized probe. Neither the activity of M1-type pyruvate kinase nor the level of this enzyme in rat gastrocnemius muscle was affected by chronic renal failure, whereas L-type pyruvate kinase enzyme activity in uremic rat liver was lower than that in control at both fasted and refed states. The levels of L-type pyruvate kinase mRNA were not different between two groups at the fasted state. Induction of L-type pyruvate kinase mRNA after high carbohydrate diet refeeding was suppressed proportionally to the severity of chronic renal failure, which was expressed by the serum creatinine concentrations (r = -.876, P less than .005). These results indicate that the suppression of L-type pyruvate kinase activity in uremia was partly reflected by the decreased accumulation of this enzyme mRNA. There was a significantly negative correlation between L-type pyruvate kinase mRNA levels and plasma glucagon/insulin ratios (r = -.719, P less than .05). Hyperglucagonemia in uremia might play a major role in this suppression.
Insights
Chronic renal failure reduces L-type pyruvate kinase activity in rat liver, linked to decreased enzyme mRNA accumulation. Hyperglucagonemia in uremia may drive this suppression, impacting pyruvate kinase regulation.
Area of Science:
- Biochemistry
- Renal Physiology
- Molecular Biology
Background:
- Chronic renal failure (CRF) alters metabolic pathways.
- Pyruvate kinase (PK) is a key glycolytic enzyme with different isoforms (L-type and M1-type).
- The impact of CRF on PK enzyme activity and mRNA levels is not fully understood.
Purpose of the Study:
- To investigate the effects of CRF on pyruvate kinase (PK) enzyme activity and mRNA levels in different rat tissues.
- To explore the relationship between CRF severity, PK mRNA levels, and hormonal factors.
Main Methods:
- Induction of chronic renal failure in rats via subtotal nephrectomy.
- Measurement of PK enzyme activity in liver and gastrocnemius muscle.
- Quantification of PK mRNA levels using RNA-DNA dot blot hybridization.
- Correlation analysis with serum creatinine, glucagon, and insulin levels.
Main Results:
- CRF did not affect M1-type PK activity or mRNA in muscle.
- L-type PK enzyme activity was significantly reduced in the liver of uremic rats.
- Induction of L-type PK mRNA by refeeding was suppressed in CRF rats, correlating with serum creatinine levels.
- L-type PK mRNA levels showed a negative correlation with plasma glucagon/insulin ratios.
Conclusions:
- CRF partially suppresses L-type PK activity in the liver through decreased mRNA accumulation.
- Hyperglucagonemia in uremia may be a key factor in suppressing L-type PK mRNA levels.
- These findings highlight metabolic dysregulation in CRF affecting key glycolytic enzymes.