Medical Chemistry: Lipids and Teeth Diseases

Introduction to Lipids

• Lipids are hydrophobic small molecules formed from alcohol and fatty acids combined together by an ester bond.
• Lipids include fats, waxes, sterols, fat-soluble vitamins, and phospholipids.
• Lipids are insoluble in water but soluble in organic solvents such as ether, benzene, acetone, and chloroform.

Biomedical Importance of Lipids

• Lipids are a source of energy due to their high energy value.
• Lipids are structural components of cell membranes (phospholipids and cholesterol).
• Lipids act as metabolic regulators (e.g., steroid hormones).
• Lipids help in the absorption of fat-soluble vitamins (A, D, E, and K).
• Lipids protect internal organs by providing a cushioning effect (pads of fat).
• Lipids provide insulation against changes in external temperature (subcutaneous fat).

Classification of Lipids

• Simple lipids are esters of fatty acids with various alcohols.
• Fatty acids may be saturated or unsaturated, and essential or nonessential.

Saturated and Unsaturated Fatty Acids

• Saturated fatty acids have no double bonds in their chain.
• Saturated fatty acids have a general formula of CH3-(CH2)n-COOH.
• Unsaturated fatty acids contain one or more double bonds.
• Unsaturated fatty acids are either monounsaturated or polyunsaturated.

Polyunsaturated Fatty Acids (PUFA)

• PUFA are classified according to the position of the first double bond in relation to ω carbon.
• PUFA are classified into ω3, ω6, ω7, and ω9 fatty acids.
• Functions of PUFA include:
  • Preventing atherosclerosis
  • Synthesizing prostaglandins and eicosanoids
  • Participating in the structure of all cellular and subcellular membranes
  • Maintaining skin integrity, normal growth, and reproduction
  • Playing an important role in blood clotting
  • Preventing and treating fatty liver
  • Maintaining the health of the retina and vision

Rancidity

• Rancidity is a physico-chemical change in the natural properties of fat leading to unpleasant odor, taste, or color.
• Types of rancidity include:
  • Hydrolytic rancidity
  • Oxidative rancidity
  • Ketonic rancidity
• Prevention of rancidity is achieved by:
  • Avoiding the causes of rancidity
  • Keeping fats or oils in well-closed containers in a cold, dark, and dry place
  • Adding antioxidants
• Hazards of rancid fats include:
  • Toxicity and food poisoning
  • Destruction of fat-soluble vitamins
  • Destruction of polyunsaturated essential fatty acids
  • Economical loss

Simple Lipids

• Simple lipids are formed from alcohols and fatty acids.
• There are two classes of simple lipids: acylglycerols and waxes.

Compound Lipids

• Compound lipids contain in addition to esters of fatty acids with alcohols, other groups.
• Compound lipids are classified into phospholipids, glycolipids, sulfolipids, and lipoproteins.

Derived Lipids

• Derived lipids are produced when simple and compound lipids combine and undergo hydrolysis.
• Derived lipids include cholesterol, carotenes, steroids, prostaglandins, ketone bodies, and fat-soluble vitamins.

The Role of Lipids in Teeth Diseases

• The total lipid fraction of saliva is predominantly neutral lipids.
• Lipids in saliva include free fatty acids, cholesterol, cholesterol esters, monoglycerides, diglycerides, and triglycerides.
• Salivary lipids have been linked to certain oral diseases caused by the oral environment and bacteria during dental caries or dental calculus.
• Lipids and dental calculus: the main ingredient of dental calculus is minerals, but it also contains organic components like proteins and lipids.