Increase in glycemic set point, alongside a decrease in waist circumference, in the non-diabetic population during the Japanese National Intervention Program for metabolic syndrome: A single-center, large-scale, matched-pair analysis.

Background: In 2008, the Japanese government implemented a National Intervention Program for metabolic syndrome. Low-risk individuals were not direct targets of this intervention. Nevertheless, they were indirectly enlightened by this massive campaign. Documentation of the metabolic shifts in low-risk individuals following the program launch may inform public health policy regarding approaches to metabolic risks in the general population.

Methods: We conducted a cross-sectional analysis of data from non-diabetic participants who underwent general health check-ups at the Physical Check-up Center of Sumitomo Hospital. Participants during 2007-2008 were pair-matched with those during 2015-2016 with respect to sex, age, smoking status, hemoglobin level, and red blood cell (RBC) count. Each participant was included only once in the study.

Results: Totals of 3,140 men and 2,048 women were pair-matched. The non-diabetic participants showed lower waist circumference, blood pressure, heart rate, and serum lipid concentrations during the second study period. In contrast, the entire distributions of fasting plasma glucose (FPG) concentration in both sexes and glycated hemoglobin (HbA1c) in women were shifted upwards. In men, Δ FPG was +1.6 mg/dL (P < 0.001) and Δ HbA1c was ±0% (P = 0.6). In women, Δ FPG was +3.0 mg/dL (P < 0.001), and Δ HbA1c was +0.1% (P < 0.001). Δ Homeostasis model assessment of β-cell function was -6.6 in men (P < 0.001) and -10.3 in women (P < 0.001). The homeostasis model assessment of insulin resistance did not change significantly.

Conclusions: The "glycemic set point" has increased in non-diabetic people in Japan during recent years. Lifestyle or environmental changes may have caused this metabolic shift through obesity-independent pathways, possibly through effects on pancreatic β-cell function. The underlying mechanism awaits further investigation.