|This is part I of a multipart series, you will be able to navigate by clicking on the pictures in the box below.|
In the coming weeks I will use their review as a starting point for my own overview of the effects of non-carbohydrate and "almost cabohydrate" nutrients on glucose metabolism. And for today, I decided, to conclude this week that was full of exciting protein news on Monday ("Protein Power" | read more) and Saturday ("Dieting, High Protein, Testosterone & IGF-1" | read more) with - what else could it be - a summary of a the anti-diabetic effects of peptides, proteins and amino acids.
Protein, the glucose repartitioner?! Due to its insulinogenic effects protein increases the non-oxidative glucose disposal. In contrast to whey proteins, turkey, beef, eggs and co., i.e. "slow digesting proteins", will induce a significantly reduced insulin surge and have a correspondingly less pronounced effect on blood glucose.
|It does not even take whole proteins. Single amino acids and dipeptides (=2-amino acids) can have glucose repoartitioning trick, too | learn more|
In its effects on GLP-1 whey is pretty unique. Even similarly fast absorbing protein sources, such as soy, or other dairy proteins such as casein, do not cause such a pronounced effect on GLP-1 and insulin secretion. A recent study from the Iran University of Medical Sciences and Health Services, for example, compared the effects of the pre-ingestion of additional 65/60g of whey protein concentrate (WPC) and soy protein isolate (ISP) before a meal on a hole host of metabolic markers in 45 healthy overweight and obese men.
Hypoglycemia warning: If experience fatigue, agitation, sweating, shivering, feeling cold, a having really bad temper and/or other symptoms of low blood sugar, after having a bolus of whey protein, it may be a good idea to (a) check your blood glucose levels and (b) consume your whey with a source of readily available carbohydrates in the future.The first improvements in a hole host of parameters were observed after only two weeks and at the end of the 12-week study period, the consumption of additional 65 gr WPC or 60 gr ISP in 500 ml water 30 min before lunch in a non-restricted diet scenario had brought about significant improvements in
|Figure 1: Effects of 12 week of WPC vs. ISP supplementation on fasting blood glucose (Tahavorgar. 2014)|
- systolic and diastolic blood pressure
⤷ improved heart health,
lipoprotein A-I and apo B
⤷ improved cholesterol metabolism,
⤷ reduced lipid oxidation,
- HDL, LDL and triglycerides
⤷ improved lipid metabolism,
- high sensitive C- reactive protein
⤷ reduced inflammation
|Figure 2: Glucose and insulin release levels after 50g glucose load w/ 30g whey or 30g canola oil (Lan-Pidhainy. 2010)|
How does protein work?
The ameliorative, yet not significant effect of soy protein isolate on the blood sugar levels of the subjects in Tahavorgar study, as well as the observations the researchers from University of Bonn made when they studied the effect of bed-rest, confirm that it does not always have to be whey protein to benefit from the anti-diabetic effects of the chains of amino acid residues we know as "proteins".
Ok, the GLP-1 inducing effects of whey protein appears to be particularly pronounced, and partly related to the presence of certain functional dairy peptides, which may, as the data from a 2009 study by Chen et al. suggests, be even more pronounced for casein than whey (see Figure 3).
|Figure 3: Relative GLP-1 production in intestinal cell culture exposed to BCAAs, skim milk or casein (Chen. 2009)|
"Although the mechanism is not well understood, some in vitro studies show how the insulinotropic effect might be induced (Dunne, 1990; Brennan. 2005; Cunningham. 2005). In cell experiments with the application of L-alanine, the increase in insulin secretion might be caused by an increased intracellular oxidation of amino acids, which raises the ATP content of the cell. Increase in intracellular ATP content leads to closure of the ATP-sensitive potassium channels, and this channel closure leads to depolarization of the cell membrane and activation of the calcium channels. Activation of the calcium channels then causes an exocytosis of insulin from the cells (Brennan. 2005; Cunningham. 2005)." (Heer. 2014)Another possibility could be that amino acids are co-transported into the cell together with
sodium, as shown in further cell experiments . This could also lead to a depolarization of
the plasma membrane in the pancreas and finally to an exocytosis (=pumping process) of insulin.
- Astrup, Arne, et al. "Safety, tolerability and sustained weight loss over 2 years with the once-daily human GLP-1 analog, liraglutide." International journal of obesity 36.6 (2012): 843-854.
- Bendtsen, Line Q., et al. "Effect of dairy proteins on appetite, energy expenditure, body weight, and composition: A review of the evidence from controlled clinical trials." Advances in Nutrition: An International Review Journal 4.4 (2013): 418-438.
- Brennan, Lorraine, et al. "A nuclear magnetic resonance-based demonstration of substantial oxidative L-alanine metabolism and L-alanine-enhanced glucose metabolism in a clonal pancreatic β-cell line metabolism of L-alanine is important to the regulation of insulin secretion." Diabetes 51.6 (2002): 1714-1721.
- Chen, Qixuan, and Raylene A. Reimer. "Dairy protein and leucine alter GLP-1 release and mRNA of genes involved in intestinal lipid metabolism in vitro." Nutrition 25.3 (2009): 340-349.
- Cunningham, GA, et al. "L-Alanine induces changes in metabolic and signal transduction gene expression in a clonal rat pancreatic β-cell line and protects from pro-inflammatory cytokine-induced apoptosis." Clinical science 109 (2005): 447-455.
- Dunne, M. J., et al. "Effects of alanine on insulin-secreting cells: Patch-clamp and single cell intracellular Ca 2+ measurements." Biochimica et Biophysica Acta (BBA)-Molecular Cell Research 1055.2 (1990): 157-164.
- Heer, Martina, et al. "High Protein Intake Improves Insulin Sensitivity but Exacerbates Bone Resorption in Immobility (WISE Study)." (2012).
- Lan-Pidhainy, Xiaomiao, and Thomas MS Wolever. "The hypoglycemic effect of fat and protein is not attenuated by insulin resistance." The American journal of clinical nutrition 91.1 (2010): 98-105.
- Meier, Juris J. "GLP-1 receptor agonists for individualized treatment of type 2 diabetes mellitus." Nature Reviews Endocrinology 8.12 (2012): 728-742.
- Tahavorgar, Atefeh, et al. "Effects of whey protein concentrate consumption compared with isolated soy protein on metabolic indices, inflammatory and oxidative stress factors in healthy overweight and obese men." Razi Journal of Medical Sciences 20.115 (2014): 17-30.