Antimetabolites

Certain compounds similar in structure to the vitamin molecule (or to the portion of the molecule containing the active site) can replace the vitamin by attaching themselves to the enzyme. These substances are called ‘antimetabolites’ or ‘metabolic antagonists’. They block the normal action of the co-enzyme and in effect, result in cellular deficiency of the vitamin.

The antimetabolite is a chemical substance which is shaped like the substrate. In other words, it is a structural relative or analogue of the substrates. Probably for this reason it also is able to combine with the active center of the enzyme.

Certain other antimetabolites exhibit anti-vitamins activity because they are capable of blocking biosynthesis of the coenzyme molecule; such compounds may or may not resemble the vitamin in structure.

In either case, a condition similar to true vitamins deficiency is produced. Antimetabolites are useful in producing experimental vitamin deficiencies, especially those deficiency that developed slowly from dietary restriction alone.

Antimetabolites also useful adjuncts in delineating the biochemical pathways in which the vitamin is involved, and in relating metabolic disturbances to symptoms of deficiency.

The use of vitamin metabolites created new opportunities for inducing a studying many aspects of s wide range and variety of malformations and fortuitously led to an avenue of human studies.

A variety of antagonists of vitamins, hormones and cell metabolites had been synthesized after Donald Woods of Oxford University discovered in 1940 that sulfonamides exerted their antibacterial action by antagonizing the role of 4-aminobenzoic acid, a growth factor for  bacteria. Such antagonists were described as antimetabolites.
Antimetabolites

Vitamin C and diabetes

Vitamin C seems to be important in the immune system and in the manufacture and metabolism of neurotransmitters and hormones.

Numerous studies have shown that vitamin C plasma levels are about 30 percent lower in people with diabetes, as compared with people who do not have diabetes.

Insulin facilitates the transport of vitamin C into the cells. People with type 2 diabetes, however, are resistance to their own insulin and not enough insulin enters their cells.

So when there is an insulin deficiency, there will be a deficiency in intracellular vitamin C – thus the relative deficiency in vitamin C in many diabetics, even if they consume an adequate amount of vitamin in their diet.

This lead to a subclinical scurvy problem, which creates an increased tendency to bleed, poor wound healing, microvascular disease, heart disease, elevation of cholesterol and a depressed immune system.

In one study, researchers found that high doses of vitamin C markedly improved blood sugar regulation in people with non-insulin-dependent diabetes mellitus. In another study, it was observed that vitamin C enhanced glucose disposal by enhancing insulin sensitivity without affecting insulin secretion.

Vitamin C has also been shown to improve blood vessel dilation, which is often impaired in people with diabetes.

A large population-based study in England, published in 2000, showed that the people with the lowest long-term blood sugar levels had the highest levels of vitamin C and vice versa.
Vitamin C and diabetes