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Would an intravenous injection of insulin + glucose result in significantly quicker replenishment of exhausted glycogen stores than an injection of glucose alone?

This is a strictly theoretical question and I'm aware of serious dangers of intravenous insulin (Diabetes Spectrum). It is to help with writing a story in which a quick recovery from exhaustion is needed.

After heavy exercise, during which the glycogen stores are depleted, the glycogen can be replenished fully in about a day by consuming high-carbohydrate meals (PubMed).

According to one study, intravenous glucose stimulates glycogen synthesis, but there is no timing mentioned.

Would adding insulin into glucose injection further accelerate glycogen synthesis and for how much? Is there any minimal time needed for glycogen synthesis regardless of the amount of glucose and insulin available?

The added insulin would probably inhibit the natural secretion of insulin from the pancreas, so does intravenous insulin injection even make sense?

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Concluding from this 1991 PubMed article, intravenous (or subcutaneous) insulin may not stimulate glycogen synthesis more than naturally secreted insulin.

Experiments carried out in man have suggested that insulin may play only a permissive role in the determination of splanchnic glucose uptake. In a study by DeFronzo et al. (5), in which the plasma glucose and insulin levels were raised via peripheral intravenous infusion to 223 mg/dl and 55 μU/ml, respectively, net splanchnic glucose uptake was 1.0 mg/kg per min. The rate of glucose uptake did not change appreciably when the arterial insulin level was raised further to 191 μU/ml.

So, at insulin level 191 μU/ml, there was no greater hepatic glucose uptake than at 55 μU/ml and hence no further stimulation of glycogen synthesis.

According to Emedicine, insulin levels can increase to 276 μU/ml 1 hour after glucose administration.

Which means that even naturally secreted insulin can reach levels that no longer stimulate glycogen synthesis and there is no point to give insulin by injection to stimulate it.

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does intravenous insulin injection even make sense?

No, it does not make sense for two reasons:

  1. Half-life of insulin: Insulin has a half-life on the order of minutes. On the other hand, it takes much longer to remove the blood glucose and turn it into glycogen. This is why people with type 1 diabetes receive injections of microcrystalline insulin subcutaneously to form depots that are released into the blood stream at a slower pace.
  2. The body is able to make its own insulin in time: We are used to large increases in glucose levels, and the pancreas is quick in responding with secretion of insulin. So you are trying to find a solution for a problem that does not exist. Of course, injecting glucose instead of eating carbohydrates raises the blood sugar level more quickly. However, the processes downstream of insulin mobilization take some time too. So it the glucose concentration administered intravenously is too high in the absence of extra insulin, extra insulin will not fix the problem (and the problem could be death).
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  • $\begingroup$ Intravenous insulin injections exist and can be used to treat severe hyperglycemia emedicine.medscape.com/article/2049152-overview . They can be used in emergeny cases in hospitals and not by patients at home, because, yes, they can cause dangerous hypoglycemia. $\endgroup$ – Jan Jul 16 at 7:18

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