High glucose induces adipogenic differentiation

This is probably old news to some or most people. I myself have known for along time, just from intuitive observation of my own body, that there is something quite "fattening" about spiking your blood sugar.

High glucose induces adipogenic differentiation of muscle-derived stem cells

An In Vitro Model to Probe the Regulation of Adipocyte Differentiation under Hyperglycemia.

Again, just the title of these studies tells you what you need to know. In the first study, high glucose concentrations induced adipocyte differentiation of stem cells from adipose tissue. ( the glucose concentration used was very high, 25mM, so take it as you will. Also was done in vitro. )

Further down in the study results we also see how high glucose even makes muscle stem cells turn into adipocytes!

The mechanism by which this seems to be happening is ROS production signalling.....

The simplest interpretation of the data are that ROS produced in response to high glucose, by stimulating PKCβ (and possibly other effectors), act as a differentiation signal for adipogenic conversion of muscle derived stem cells.

And.....

In conclusion, we demonstrate that high glucose has an adipogenic potential on stem cells derived from both the adipose tissue and skeletal muscle, and we provide some insight into the signals and molecules that underlie this process. 

I think this is part of the puzzle as to why refined carbs in particular can be so fattening. It is well documented that the digestibility of carbohydrates determines the corresponding postprandial blood sugar spike ( glycemic index ). In addition, I suppose you could say that, being insulin resistant in muscle leads to exaggerated and prolonged elevated postprandial glucose levels, and these high glucose concentrations ( could potentially ) activate adipogenic pathways, in both muscle and fat tissue.

Granted, not everyone gets massively fat from spiking their blood sugar. We know that already. Another frustrating fact we all know, is that, stopping the blood sugar spikes and removing carbs from your diet doesnt magically return you to a state of complete health and lean-ness. Its as if the damage done by the historical blood sugar spikes is permanent.  ( like maybe, getting new fat cells ) .