Disturbances in Carbohydrate Metabolism

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Disturbances in

Carbohydrate

MetabolismMohd.Toufeeq


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What are Carbohydrates?

Carbohydrates are composed of carbon,hydrogen andoxygen.

The name carbohydrates literally means hydrates ofcarbon.

They may be defined as polyhydroxyaldehydes orketones or compounds which produce them onhydrolysis.


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Functions of carbohydrates

Most abundant dietary source of energy.

Precursors for many organic compounds(fats,aminoacidS,etc.)

Structural components of many organisms like cellulosein plants, exoskeleton of some insects,etc.

Also serve as the storage form of energy(glycogen) to

meet the immediate source of energy demands of thebody.


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Classification ofCarbohydrates

Carbohydrates are broadly classified into three groups:

1. Monosaccharides-composed of a singlemonosaccharide unit. Eg:Glucose,Frutctose.

2. Oligosaccharides-compose of 2-10 monosaccharideunits. Eg:Maltose,Lactose,Surcose

3. Polysaccharides-polymers of several monosaccharide

units.


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Polysaccharides are of two types:

1. Homopolysaccharides-composed of only a single typeof monosaccharide.Eg:Starch,dextrins,inulin,glycogen,etc.

2. Heteropolysaccharides-composed of a mixture of afew monosccahrides.Eg:Mucopolysaccharides:Hyaluronic acid,heparansulfate,chondroitin sulfate and keratan sulfate.


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Normal CarbohydrateMetabolism


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Mucopolysaccharidoses

MPS result from abnormal degradation ofglycosaminoglycans like dermatan sulfate,keratan

sulfate,heparan sulfate and chondroitin sulfate. This results in organ accumulation and eventual

dysfunction.

The catabolic enzymes involved in the breakdown ofglycosaminoglycans are deficient.

Organs involved:brain,liver,heart,spleen and bloodvessels.


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Clinical Presentation

MPS type I includes Hurler,Hurler-Scheie,and Scheiesyndromes.

MPS type I H (Hurler syndrome)

MPS type I H/S. This form is intermediate betweenthe Hurler and Scheie syndrome.

MPS type I S (Scheie syndrome).Biochemical

findings are identical to type I Hurler syndrome, butclinical features are less severe.


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Hurlers Syndrome It is a disturbance of mucopolysaccharide metabolism

characterized by an elevated mucopolysaccharide excretionlevel in urine.

Clinical features

Large head Prominent forhead, broad saddle nose,wide

nostrils,hypertelorism,puffy eyelids,thick lips,largetongue,nasal congestion.

Short neck with spinal abnormalities.

Flexion contractures result in the claw hand.

Dwarfism with mental retardation.

Corneal clouding and hepatosplenomegaly are classicalmanifestations


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Oral manifestations

Shortening and broadening of mandible.

Greater than normal distance around the arch fromramus to ramus accounting for the spacing of the teeth.

Localized bone destruction in the jaws.

Small teeth which are widely spaced.

Gingival hyperplasia.


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Lipoid Proteinosis

It is a rare, autosomal recessive disorder exhibitinggeneralized thickening of skin,mucosae,and certainviscera.

Clincal features

Beaded eyelid papules

Laryngeal infiltration leading to hoarseness of voice.

Inability of infants to cry at birth due presence of wihteplaques in the epiglottis,aryepiglottic folds, and

interarytenoid region.


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Hereditary FructoseIntolerance

Over 25 years ago Chambers and Pratt reported anunusual case of a woman who became nauseated andcommitted after ingesting fruit or sugar. This was laterdiagnosed as hereditary fructose intolerance.

Clinical Features Transmitted as an autosomal recessive trait.

Hypoglycemia

Vomiting after ingestion of fructose-containing foods.

Results from a deficiency in fructose 1-phosphatealdolase.

Affected individuals rapidly acquire an intense aversionto all sweets and fruits.


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Oral Manifestatations

Subjects with hereditary fructose intolerance had a total

sucrose intake of less than 5% of that of controls.

Caries scores(DMFS) were less than 10% of those ofcontrols.

TreatmentTreatment is with a fructose free diet, which if adhered to,is concordant with a good prognosis.


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Glycogen storage disorders

The metabolic defects concerned with the glycogensynthesis and degradation are referred to as glycogenstorage disorders.

A few examples:

Fasting hypoglycemia: Due to defect in the enzymeglucose 6-phosphatase,enough free glucose is notreleased from the liver into blood.

Lactic acidemia: Glucose is not synthesized fromlactate produced in muscle and liver. Lactate level in theblood increases and the pH is lowered (acidosis)


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Treatment

The primary treatment goal is prevention of

hypoglycemia and the secondary metabolicderangements by frequent feedings of foods high inglucose or starch (which is readily digested to glucose).

To compensate for the inability of the liver to providesugar, the total amount of dietary carbohydrate should

approximate the 24-hour glucose production rate.


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Galactosemia

Galactosemia is a condition in which the body is unableto use (metabolize) the simple sugar galactose.

It occurs in approximately 1 out of every 60,000 birthsamong Caucasians. The rate is different for other

groups. Persons with galactosemia cannot tolerate any form of

milk (human or animal).

Galactose makes up half of lactose, the sugar found inmilk. The other sugar is glucose.

If an infant with galactosemia is given milk, substancesmade from galactose build up in the infant's system.These substances damage the liver, brain, kidneys, andeyes


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Clinical Features

Convulsions

Irritability

Poor feeding (baby refuses to eat formula containingmilk)

Yellow skin and whites of the eyes (jaundice)

Vomiting

Hepatomegaly

Lethargy

Poor weight gain


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References

Shafers Textbook of Oral Pathology-6th edition

U.Satyanarayana Textbook of Biochemistry-3rd edition

Disturbances in Carbohydrate Metabolism

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