Protein, Insulin-like Growth Factor-1 (IGF-1) and Glucose Homeostasis

I've blogged previously on the LoBAG diets for treatment of diabetes.  These diets are higher in protein that standard recommendations - 30% vs. 15% - with varying carb content (20,30 & 40% have been studied).  With both of the lower carb diets, this group has achieved good improvements in HbA1c levels in relatively short time (5-10 weeks).  In comparing their diets  they observed:

Increasing the protein content of the diet from 15 to 30% resulted in an 35% increase in IGF-I regardless of whether the carbohydrate content was 40%, 20%, or 30% as in the present study. Thus the dietary protein-induced increase in IGF-I is independent of the amount of dietary carbohydrate and fat.

I believe the near-OCD obsession with insulin in the LC community overshadows the vast body of research on other hormones and peptides that's out there and their role in metabolism.

I've frequently heard that diabetics should limit protein, for example, because excess is turned to sugar.  This nugget of information is often traced to Dr. Bernstein - whether he states this or not, I do not know.  I've not read his books.  If anyone has a citation, I would appreciate it.   But clearly this is not the case demonstrated by the findings of these researchers.  

Anyway, I came across this article recently:  

Relationships between serum IGF1 levels, blood pressure, and glucose tolerance: an observational, exploratory study in 404 subjects

The Intro is chock full of interesting info so I'm C&P'ing it in its entirety.

Growth hormone (GH) is principally involved in the regulation of somatic growth, and exerts its effects either directly or indirectly, by stimulating the production of insulin-like growth factor-1 (IGF1) that mediates GH action on peripheral tissues (1, 2). IGF1 levels are strongly determined by changes in GH secretion; they are low in patients with GH deficiency (GHD) and high in those with acromegaly (1, 2). Age and sex also affect serum IGF1 concentrations; at the age of 65 years, daily spontaneous GH secretion is reduced by 50–70% and consequently IGF1 levels decline progressively (3), while male gender is associated with higher IGF1 levels than females (4).

Besides, GH and IGF1 are anabolic hormones, so that malnutrition and other catabolic states, such as severe trauma and sepsis, reduce serum IGF1 concentration. Patients with insulin-dependent diabetes have some hepatic resistance to GH, with elevated serum GH levels and reduced IGF1 levels (5). Moreover, subtle changes in IGF1 levels in the general population are associated with changes in blood pressure (BP) and insulin sensitivity: IGF1 levels in the upper normal range are associated with reduced BP (6) and vascular tone (7), increased insulin sensitivity (8, 9), and reduced prevalence of diabetes mellitus(10). Epidemiological studies have suggested that IGF1 levels in the lower normal range are associated with an increased risk of ischemic heart disease (11,12, 13) and stroke (14, 15, 16, 17). In this setting, a protective role in the development of atherosclerosis was suggested for free IGF1 levels (17). We also reported the existence of tight relationships between IGF1, IGF binding protein 3 (IGFBP3), and a surrogate marker of atherosclerosis such as the measurement of intima-media thickness (IMT) of common carotid arteries in a group of 174 healthy individuals (18). We found that IGF1 levels were the best predictors of total cholesterol levels and total/high density lipoprotein (HDL) cholesterol ratio; additionally, mean IMT was best predicted by subjects' age (as expected), but IGF1 and IGFBP3 were its second best predictors (18).

The study itself is not all that remarkable.  They looked at the relationship between IGF-1 levels and blood pressure and diabetes.  I think the plots of the results are more impressive than reading the numbers:

I was looking about the web on IGF-1 as it would seem to make a good treatment for diabetes.  Apparently it's been around the bodybuilding/athlete circuits as an anabolic agent for some time.   

I was also reminded of an article I read about increased protein needs as we age.  I'll try to dig that one out of the docs folder when I get a chance.  But given how IGF-1 levels drop as we age, it would seem reasonable that we should increase protein to help boost it.