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Effects of manganese on carbohydrate metabolism and mitochondrial enzymes in rats
Abstract:
The effect of daily intraperitoneal administration of Mn2+(4 mg/kg) was investigated on the metabolism of carbohydrates and certain enzymes involved in the oxidation of glucose in the rat liver and blood at the intervals of 30, 60 and 90 days after exposure. Mn2+ had no effect on the contents of blood reducing sugars and proteins, however the levels of pyruvic and lactic acids were reduced at 60 and 90 days after the metal treatment. The contents of liver glycogen and proteins remained unaffected while pyruvic acid content was decreased in Mn2+ treated rat liver throughout the experimental period. The activities of glycogen phosphorylase and lactate dehydrogenase decreased while that of phosphoglucoisomerase and glucose-6-phosphatase increased in the post mitochondrial supernatant at 60 and 90 days of Mn2+ exposure. The levels of hexokinase decreased and FDP-aldolase and fructose-1, 6-diphosphatase increased throughout the experimental period. The magnitude of alteration was found to be greater with the increase in the duration of Mn2+ treatment. Several of the mitochondrial enzymes in the liver were inhibited in the manganese exposed rats which may be responsible to inhibit the rate of dehydrogenation of Kreb cycle's intermediates along with the linked respiratory chain and eventually oxidation in the rat liver.
Insights
Manganese (Mn2+) exposure alters carbohydrate metabolism and glucose oxidation enzymes in rat liver and blood. Enzyme activity changes intensified with longer exposure, impacting energy production pathways.
Area of Science:
- Biochemistry
- Toxicology
- Metabolic Research
Background:
- Manganese (Mn2+) is an essential trace element but can be toxic at higher doses.
- Understanding Mn2+ effects on carbohydrate metabolism is crucial for assessing its toxicological impact.
Purpose of the Study:
- To investigate the impact of daily intraperitoneal Mn2+ administration on carbohydrate metabolism and glucose oxidation enzymes.
- To evaluate these effects in rat liver and blood at 30, 60, and 90 days post-exposure.
Main Methods:
- Rats were administered Mn2+ (4 mg/kg) daily via intraperitoneal injection.
- Carbohydrate levels (reducing sugars, glycogen, pyruvic acid, lactic acid) were measured.
- Enzyme activities (glycogen phosphorylase, lactate dehydrogenase, phosphoglucoisomerase, glucose-6-phosphatase, hexokinase, FDP-aldolase, fructose-1,6-diphosphatase) were assessed in liver homogenates.
Main Results:
- Mn2+ reduced pyruvic and lactic acids in blood and liver, and decreased hexokinase activity.
- Activities of glycogen phosphorylase and lactate dehydrogenase decreased, while phosphoglucoisomerase and glucose-6-phosphatase increased.
- Mitochondrial enzyme inhibition was observed, potentially affecting the Krebs cycle and cellular respiration.
Conclusions:
- Chronic Mn2+ exposure significantly alters carbohydrate metabolism and glucose oxidation pathways in rats.
- Enzyme activity modifications suggest impaired energy production and increased gluconeogenesis.
- Inhibition of mitochondrial enzymes points to a potential mechanism for Mn2+-induced hepatotoxicity.