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Improvement of Glucose Metabolism with High-Protein Diets

Insulin sensitivity found only in the animal-protein diet group

Previous data has both positive and negative associations on the impact of high-protein diet in type 2 diabetes (T2DM). In the study presented during the 51st European Association for the Study of Diabetes Annual Meeting in Stockholm, Mariya Markova, PhD, of the German Institute of Human Nutrition at Charité University Medicine in Berlin, Germany, and colleagues compared effects of two isocaloric high-protein diets of animal (AP) and plant (PP) origin on metabolic markers, liver fat content and signaling pathways in white blood cells and adipose tissue.

This was a 6-week parallel randomized prospective dietary intervention study with type 2 diabetes that was completed earlier this year in March 2015. The goal was to investigate the nutritional influence of animal protein compared to plant protein on glucose metabolism.

These researchers analyzed 30 individuals with T2DM, mean age 65 ± 6 years, with BMI of 30.5 ± 3.6 kg/m2, and HbA1C of 7.0 ± 0.6%. These participants were randomized into either high-animal (meat and dairy foods) or high-plant (dietary pulses) protein diet (30% protein, 40% carbohydrates, 30% fat) for 6 weeks. Prior to and after the diet intervention, magnetic resonance imaging, hyperinsulinemic euglycemic clamps, and meal tolerance tests were performed, and blood and subcutaneous adipose tissue samples were collected. They analyzed key proteins of the Akt/mTOR signaling pathway in isolated white blood cells and adipose tissue.

Results showed that levels of liver parameters, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyl transferase (GGT) improved in both study groups. In addition, liver fat contents and HbA1C were reduced in both the AP group (p < 0.001 and p < 0.05, respectively) and the PP group (p < 0.001 for both factors).

The clamp-derived insulin sensitivity were found to improve significantly only the AP group (p < 0.05). However, only in the PP group was there a significant reduction of plasma creatinine (p < 0.01) and also an improvement of the glomerular filtration rate (p < 0.001), and this was not seen in the AP group. The researchers noted no alterations of the Akt/mTOR pathway; however, in the adipose tissue, the phosphorylation of AMPK, Erk1/2 and 4E-BP1 was around twofold higher in the AP group, whereas in the PP group, they found significantly increased phosphorylation of BAD and PDK1.

The researchers concluded that in diabetic subjects, regardless of the protein origin, the 6-week high-protein leads to an improvement of glucose metabolism and decrease of liver fat content. No adverse effects on kidney parameters were observed in these high-protein diet and kidney function has also shown to improve in the plant-protein group.

Practice Pearls:

  • Improvement in insulin sensitivity was only found in the animal-protein diet group.
  • A high-protein diet led to improvement of glucose metabolism and the decrease of liver fat content.
  • Kidney function improved in the plant-protein group.

Markova M, Pfeiffer AFH, Hornemann S, Pivovarova O, Sucher S. Abstract #701: Metabolic and molecular effects of a high-protein diet in subjects with type 2 diabetes. Presented at: 51st EASD Annual Meeting; Sep 14-18, 2015; Stockholm.

Pfeiffer AFH, German Institute of Human Nutrition. Comparison of a Plant Protein Diet to a Animal Protein Diet Emphasized in Type 2 Diabetes (LeguAN). In: ClinicalTrials.gov [Internet]. Bethesda (MD): National Library of Medicine (US). 2000- [cited 2015 Sep 29]. Available from: https://clinicaltrials.gov/ct2/show/NCT02402985?term=NCT02402985&rank=1 Identifier: NCT02402985.