Abstract
Here, we aim to investigate the independent and combined associations of serum 25-hydroxyvitamin D (25(OH)D) and cardiorespiratory fitness (CRF) with glucose metabolism. Fasting blood samples of 107 men aged 40–79 years were analyzed for 25(OH)D, glucose, insulin, glycated hemoglobin, and lipid profile. Homeostasis model assessment of insulin resistance index (HOMA-IR) was calculated from the fasting concentrations of glucose and insulin. Visceral fat area (VFA) was determined by magnetic resonance imaging and CRF by measuring maximal oxygen uptake. Median 25(OH)D concentration was 36.3 nmol/L, while the prevalence of 25(OH)D deficiency was 74.8%. Participants with high CRF had significantly lower HOMA-IR, glycated hemoglobin, and insulin values than participants with low CRF (p < 0.05). Higher 25(OH)D concentration was strongly correlated with lower HOMA-IR and insulin values independent of VFA (p < 0.01) but significantly affected by CRF. In the high CRF group, participants with higher 25(OH)D concentration had lower HOMA-IR values than participants with low 25(OH)D concentration (p < 0.05). Higher 25(OH)D and CRF are crucial for reducing insulin resistance regardless of abdominal fat. In addition, higher 25(OH)D concentration may strengthen the effect of CRF on reducing insulin resistance in middle-aged and elderly Japanese men with high CRF.
Highlights
Obesity and overweight are the most important risk factors for insulin resistance and type 2 diabetes mellitus (T2DM) [1,2]
Recent evidence showed that high circulating 25-hydroxyvitamin D (25(OH)D) was associated with low prevalence of increased homeostasis model assessment of insulin resistance (HOMA-IR) and T2DM in individuals with impaired glucose tolerance or T2DM [9,10], and in healthy individuals [11,12,13,14]; these associations were independent of body mass indices (BMI)
Data from the Tokyo Gas Company in Japan showed that high cardiorespiratory fitness (CRF) groups have significantly lower risk of developing T2DM compared with other fitness groups, even after controlling for BMI in healthy Japanese men [21,24]
Summary
Obesity and overweight are the most important risk factors for insulin resistance and type 2 diabetes mellitus (T2DM) [1,2]. Besides obesity, other lifestyle factors, such as regular physical activity or ensuring sufficient micronutrient intake, may play an important role in the prevention of insulin resistance or T2DM in Japan. Recent evidence showed that high circulating 25-hydroxyvitamin D (25(OH)D) was associated with low prevalence of increased homeostasis model assessment of insulin resistance (HOMA-IR) and T2DM in individuals with impaired glucose tolerance or T2DM [9,10], and in healthy individuals [11,12,13,14]; these associations were independent of BMI.
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