Plasma 25‐hydroxyvitamin D to parathyroid hormone ratio is associated with glucose tolerance and insulin sensitivity in older adults

Abstract

Purpose To assess the relationships between plasma 25-hydroxyvitamin D (25OHD), plasma parathyroid hormone (PTH), and oral glucose tolerance (OGT) in older adults before and after a dietary protein and resistance training (RT) regimen. Methods 16 males (BMI 27.2 ± 4.2 kg/m2) and 19 females (BMI 25.5 ± 3.0 kg/m2) aged 50–80 y performed RT 3x/wk for 12 wk while consuming diets with either 0.9 or 1.2 g protein · kg BW−1· d−1. Results RT had no effect on body weight, plasma 25OHD or plasma PTH but reduced fat mass and increased lean body mass and strength independent of protein intake. OGT improved after RT (i.e. decreased area under the glucose curve (AUC) and 2-h plasma glucose) (all changes P<0.05). Using non-parametric statistics, at baseline, 25OHD to PTH ratio was correlated inversely with HOMA (Rho = −0.398, Prob > |Rho| = 0.03) and 2-h glucose (Rho = −0.463, Prob > |Rho| = 0.01) and positively with insulin sensitivity index (Rho = 0.406, Prob > |Rho| = 0.02). Similar results were found post intervention and AUC and 2-h glucose were lower in subjects with 25OHD ≥ 30 ng/mL versus subjects with 25OHD ≤ 20 ng/mL (P<0.05). Mean (average of pre & post) 25OHD, PTH, and 25OHD/PTH ratio were not correlated to the response of OGT-related parameters to RT. Conclusion Vitamin D status and the 25OHD to PTH ratio may impact glucose tolerance in older adults regardless of resistance training. Support: Amer. Egg Board; NIH UL 1 RR025761; Purdue Univ. Grant Funding Source: American Egg Board, NIH UL 1 RR025761, Purdue University