High Fat Mixed Meal Tolerance Test Leads to Suppression of Osteocalcin Decrease in Obese Insulin Resistant Subjects...

Area of Science:

• Endocrinology
• Bone Metabolism
• Nutritional Science

Background:

• Osteocalcin, a key bone protein, exists in carboxylated (Gla-OC) and undercarboxylated (Glu-OC) forms.
• Gla-OC is involved in bone formation, while Glu-OC influences glucose metabolism.
• Nutrient intake significantly impacts bone turnover processes.

Purpose of the Study:

• To investigate the postprandial changes in Gla-OC, Glu-OC, and total osteocalcin (total-OC) after a high-fat meal.
• To compare these responses between non-obese and obese individuals.
• To explore the relationship between osteocalcin levels, insulin resistance, and adiponectin.

Main Methods:

• A high-fat mixed meal tolerance test (HFMTT) was administered to 24 non-obese and 70 obese adults.
• Serum Gla-OC and Glu-OC were measured using ELISA at baseline, 2 hours, and 6 hours post-meal.
• Statistical analyses included comparisons between groups and correlation analyses with HOMA-IR and adiponectin.

Main Results:

• Obese subjects exhibited lower baseline levels of Gla-OC, Glu-OC, and total-OC compared to non-obese individuals.
• The typical postprandial decrease in Gla-OC and total-OC was attenuated in obese individuals.
• Higher insulin resistance (HOMA-IR) was associated with a less pronounced decrease in total-OC, and Gla-OC correlated inversely with adiponectin.

Conclusions:

• Obesity is characterized by altered osteocalcin metabolism and blunted bone turnover responses to meals.
• Insulin resistance may negatively impact bone turnover regulation in the postprandial state.
• Increased insulin sensitivity and adiponectin levels in obese individuals may offer a protective effect on postprandial bone turnover.