208
phosphoglucomutase [27]. The experimental study reveals that the storage ability of
glycogen in animals is decreased due to the exposure of heavy metals such as cadmium [28]. The phenomenon of glycogenolysis occurs due to a higher level of glycogen phosphorylase and its activity. The glycogen level may be reduced due to
decreased activity of glycogen transferase. The decrease in the production of
glucose- 6-phosphate which is a very essential substance for glycogen synthesis may
occur due to reducing the glucokinase activity [29].
If cadmium is exposed to placenta, then increased glycogen phosphorylase
activity is observed [30]. Exposure of cadmium may increase the level of cortisol
in plasma which may contribute to the activation of glycogenolysis [31]. Cadmium
has the ability to accumulate in the pancreas and increases oxidative stress [32].
Cadmium is divalent which has the ability to interact with thiol group and zincbinding site, which is generally present in proteins [33]. It has been revealed that
chronic exposure of cadmium has a positive effect on the activity of serum amylase [34].
Effect of Cadmium Gluconeogenesis
In gluconeogenesis, pyruvate is formed from amino acids and lactate then transported into mitochondria from the cytosol. In mitochondria, pyruvate is converted
into oxaloacetate with the help of an enzyme pyruvate carboxylase.
Phosphoenolpyruvate carboxykinase acts on oxaloacetate and converts it into phosphoenolpyruvate. Then phosphoenolpyruvate is passed through a series of reactions
and converted into fructose-6-phosphate. Then it is converted into glucose-6phosphate by an enzyme phosphohexose isomerase that acts on fructose-6phosphate. Finally, glucose-6-phosphate is converted into glucose after releasing the
phosphate group [35].
Only a high dose of cadmium has an effect on enzymes that are involved in gluconeogenesis such as glucose-6-phosphatase, phosphoenolpyruvate carboxykinase,
and fructose 1, 6-bisphosphatase [36]. It has been proposed that phosphoenolpyruvate carboxykinase is very important to target to treat diabetes mellitus associated
with hyperglycemia [12].
Effect of Cadmium on Lipid Metabolism
The exposure of cadmium has a great potential on acetyl CoA carboxylase and
fatty acid synthase that is involved in the synthesis of fatty acids [37]. Cadmium
induces the lipid peroxidation of polyunsaturated fatty acids [38]. Chronic exposure to cadmium causes impairment in the storage and metabolism of lipids. Higher
mobilization of lipids to mitochondria cause lower lipid content and decrease the
level of triglycerides and ATP [39]. Further exposure to cadmium decreases the
K. Irshad et al.
phosphoglucomutase [27]. The experimental study reveals that the storage ability of
glycogen in animals is decreased due to the exposure of heavy metals such as cadmium [28]. The phenomenon of glycogenolysis occurs due to a higher level of glycogen phosphorylase and its activity. The glycogen level may be reduced due to
decreased activity of glycogen transferase. The decrease in the production of
glucose- 6-phosphate which is a very essential substance for glycogen synthesis may
occur due to reducing the glucokinase activity [29].
If cadmium is exposed to placenta, then increased glycogen phosphorylase
activity is observed [30]. Exposure of cadmium may increase the level of cortisol
in plasma which may contribute to the activation of glycogenolysis [31]. Cadmium
has the ability to accumulate in the pancreas and increases oxidative stress [32].
Cadmium is divalent which has the ability to interact with thiol group and zincbinding site, which is generally present in proteins [33]. It has been revealed that
chronic exposure of cadmium has a positive effect on the activity of serum amylase [34].
Effect of Cadmium Gluconeogenesis
In gluconeogenesis, pyruvate is formed from amino acids and lactate then transported into mitochondria from the cytosol. In mitochondria, pyruvate is converted
into oxaloacetate with the help of an enzyme pyruvate carboxylase.
Phosphoenolpyruvate carboxykinase acts on oxaloacetate and converts it into phosphoenolpyruvate. Then phosphoenolpyruvate is passed through a series of reactions
and converted into fructose-6-phosphate. Then it is converted into glucose-6phosphate by an enzyme phosphohexose isomerase that acts on fructose-6phosphate. Finally, glucose-6-phosphate is converted into glucose after releasing the
phosphate group [35].
Only a high dose of cadmium has an effect on enzymes that are involved in gluconeogenesis such as glucose-6-phosphatase, phosphoenolpyruvate carboxykinase,
and fructose 1, 6-bisphosphatase [36]. It has been proposed that phosphoenolpyruvate carboxykinase is very important to target to treat diabetes mellitus associated
with hyperglycemia [12].
Effect of Cadmium on Lipid Metabolism
The exposure of cadmium has a great potential on acetyl CoA carboxylase and
fatty acid synthase that is involved in the synthesis of fatty acids [37]. Cadmium
induces the lipid peroxidation of polyunsaturated fatty acids [38]. Chronic exposure to cadmium causes impairment in the storage and metabolism of lipids. Higher
mobilization of lipids to mitochondria cause lower lipid content and decrease the
level of triglycerides and ATP [39]. Further exposure to cadmium decreases the
K. Irshad et al.