Contribution of adipose tissue to plasma 25-hydroxyvitamin D concentrations during weight loss following gastric bypass surgery

Abstract

Roux-en-y gastric bypass (RYGB) surgery is associated with dramatic improvements in obesity-related comorbidity, but also with nutritional deficiencies. Vitamin D concentrations are depressed in the severely obese, but the impact of weight loss via RYGB is unknown. We determined associations between adiposity and systemic 25-hydroxyvitamin D (25(OH)D) during weight loss and the immediate and longer-term effects of RYGB. Plasma 25(OH)D concentrations and fat mass (FAT) were determined by immunoassay and air displacement plethysmography, respectively, at 0 (before RYGB surgery), and at 1, 6, and 24 months in severely obese white and African American (AA) women (n = 20). Decreases in adiposity were observed at 1, 6, and 24 months following RYGB (P < 0.05). Plasma 25(OH)D concentrations increased at 1 month (P = 0.004); a decreasing trend occurred over the remainder months after surgery (P = 0.02). Despite temporary improvement in vitamin D status, a high prevalence of vitamin D insufficiency was observed (76, 71, 67, and 82%, at baseline, 1, 6, and 24 months, respectively), and plasma 25(OH)D concentrations were lower in AA compared to white patients (P < 0.05). Strong positive baseline and 1 month cross-sectional correlations between FAT and plasma 25(OH)D were observed, which remained after adjustment for age and race subgroup (β = 0.76 and 0.61, respectively, P = 0.02). In conclusion, 25(OH)D concentrations increased temporarily and then decreased during the 24 months following RYGB. The acute increase and the positive associations observed between adipose tissue mass and systemic 25(OH)D concentrations suggest storage in adipose tissue and release during weight loss.

Conflict of interest statement

DISCLOSURE

The authors declared no conflict of interest.

Figures

Figure 1

Six months changes in plasma 25-hydroxyvitamin D concentrations following surgery. 25-Hydroxyvitamin D (25(OH)D)) was measured in plasma samples obtained at 0 (before surgery), and 1, and 6 months following Roux-en-y gastric bypass surgery as described in Methods and Procedures section. Open squares depicts non-Hispanic white women (n = 12) and open circles depicts non-Hispanic African-American women (n = 6), the thick line depicts the averages of total population (n = 20), the thin line depicts the cutoff for normal vitamin D status (≥75 nmol/l). *Depicts significant different from baseline value (P < 0.05).

Figure 2

Twenty-four months changes in plasma 25-hydroxyvitamin D concentrations following surgery. 25-Hydroxyvitamin D (25(OH)D) was measured in plasma samples obtained at 0 (before surgery), and 1, 6, and 24 months following Roux-en-y gastric bypass surgery as described in Methods and Procedures section. Open squares depicts non-Hispanic white women (n = 6) and open circles depicts non-Hispanic African-American women (n = 3), the thick line depicts the averages of total population (n = 10), the thin line depicts the cutoff for normal vitamin D status (≥75 nmol/l). *Significantly different from baseline value (P < 0.05); †significantly different from 1 month value (P < 0.05).

Figure 3

Relationship between plasma 25-hydroxyvitamin D and total adiposity before surgery. Cross-sectional Pearson correlations were determined between total fat mass (FAT) before surgery (baseline), and 25-hydroxyvitamin D (25(OH)D) at (a) baseline, (b) 1 and (c) 6 months following RYGB (n = 20). FAT, fat mass; RYGB, Roux-en-y gastric bypass.

Figure 4

Relationship between plasma 25-hydroxyvitamin D and adiposity at 1 month following surgery. Cross-sectional Pearson correlations were determined between total fat mass (FAT) at 1 month following surgery and 25-hydroxyvitamin D (25(OH)D) at (a) 1 and (b) 6 months following RYGB (n = 20). RYGB, Roux-en-y gastric bypass.

Figure 5

Changes in adiposity and 25-hydroxyvitamin D during 24 months following surgery. Absolute changes, compared to baseline measures, in total adipose tissue mass and 25-hydroxyvitamin D (25(OH)D) were determined at 1 (Δ1 month, n = 20), 6 (Δ6 months, n = 20) and 24 (Δ24 months, n = 10) months following Roux-en-y gastric bypass surgery. *Significantly different from baseline value (P < 0.05), †significantly different from 1 month value (P < 0.05).