Effects of a Small Protein and Lipid Preload on Glucose Tolerance in Subjects With Impaired Glucose Homeostasis

Mechanisms Through Which a Small Protein and Lipid Preload Improves Glucose Tolerance in Subjects With Impaired Glucose Homeostasis

The purpose of this study is:

• to measure the size of the effect on glucose tolerance of a small mixed protein and lipid meal given as a pre-load in individuals with different glucose tolerance status
• to investigate the underlying mechanisms by accurately evaluating beta cell function, insulin sensitivity, insulin clearance and glucose kinetics (oral absorption, endogenous production, rate of utilization) together with gut hormones plasma concentration.

As supported by experimental and clinical data, oral carbohydrate tolerance is influenced by the coingestion of nutrients through multiple mechanisms. The ingestion itself, the contact with the gastric mucosa, the arrival into the intestine and the subsequent digestion are known to produce neural reflexes, hormonal responses and plasma substrates gradients which, by modulating gastric emptying, insulin secretion and insulin clearance participate in the regulation of postprandial glycaemia. The size of this effect is influenced by a number of factors: the specific nutrient chemical characteristics (fat vs protein and composition) and their physical properties (solid vs liquid), the timing (pre-load vs coingestion) and finally the individual glucose tolerance status. To our knowledge, the effect on glucose excursions of a combination of protein and fat given before carbohydrate is still unknown and also unknown is the contribution of different mechanisms involved in the control of glucose homeostasis in subjects with different degrees of glucose tolerance.

Inclusion Criteria:

• healthy, prediabetic or diet-controlled type 2 diabetic patients
• Subjects ≥ 18 and ≤65 years of age
• Lean, Overweight or Obese (BMI: 18 to 35 kg/m2)
• Normal liver and kidney function
• Normal thyroid function
• Read and understood the informed consent form and signed it voluntarily

Exclusion Criteria:

• Liver, heart, kidney, lung, infectious, neurological, psychiatric, immunological or neoplastic diseases.
• Type 1 or insulin treated diabetes.
• Pregnancy or lactation
• Illicit drug abuse or alcoholism
• Subject treated with insulin or treatment
• Subjects taking anoretic drugs
• Subjects on steroid treatment
• Subjects after bariatric surgery.