I have been prompted to revist my comment prvious regarding MSG and it seems I may have been slightly misleading.
firstly, chinese cuisine dishes such as chow mein will probably contain MSG as umame flavour enhancer. MSG is generally considered safe as an additive (E621)
I cannot find any evidence that it raises glucose levels in blood. However ther is some evidence that it causes increased insulin secretion. this is without a corresponding drop in glucose levels, so is generally interpreted as incresing Insulin Resistance. It is not clear from the studies I read whether this is a temporary effect, or a longer term effect. The studies I read used healthy volunteers and did not look at effect on diabetic population.
There is a chinese study that found no change in insulin or glucose, but they used OGTT to measure glucose response and Area under Curve as an estimate for the insulin rather than measuring it in the blood. So not a valid study IMO.
If the insulin resistance is only temporary then it does not correspond to the OP question.
The other thing I found was that approx 1% of the general populace is affected by a reaction to MSG, but the reported effects are more aligned to an allergy than anything related to diabetes. (headaches, breathlessness, joint pain, swellings etc).