Dominant factors of the phosphorus regulatory network differ under various dietary phosphate loads in healthy individuals

Figures & data

Table 1. Baseline characteristics of six healthy participants.

Characteristics (Male, n = 6)	Mean ± SEM
Age (year)	28.5 ± 2.1
Weight (kg)	64.5 ± 2.4
Height (cm)	173.7 ± 2.2
Systolic pressure (mmHg)	111.8 ± 5.2
Diastolic pressure (mmHg)	75.3 ± 3.1
Body mass index (kg/m^2)	21.4 ± 0.5
eGFR (mL/min per 1.73m^2)	114.7 ± 2.9
Hemoglobin (g/L)	141.8 ± 4.5
Serum albumin (g/L)	47.0 ± 0.9
Blood biochemical indicators
Glucose (mmol/L)	4.8 ± 0.2
TG (mmol/L)	0.6 ± 0.1
TC (mmol/L)	4.0 ± 0.3
ALT (U/L)	17.3 ± 1.9
AST (U/L)	16.7 ± 0.7
BUN (mmol/L)	4.0 ± 0.3
Serum creatinine (umol/L)	78.3 ± 2.5
Uric acid (mmol/L)	0.3 ± 0.1
Serum phosphate (mmol/L)	1.1 ± 0.1
Serum calcium (mmol/L)	2.1 ± 0.1

Data are shown as mean ± SEM or median (interquartile range). Abbreviations: eGFR, estimated glomerular filtration rate calculated by the EPI equation; TG: triglyceride; TC: total cholesterol; ALT: glutamic-pyruvic transaminase; AST: glutamic-oxalacetic transaminase; BUN: urea nitrogen; Serum calcium, serum corrected calcium. Conversion factors for units: triglycerides in mmol/L to mg/dL, 88.6; serum creatinine in umol/L to mg/dL, 0.01131; eGFR in mL/min/1.73m² to mL/s/1.73m², 0.01667; serum calcium in mmol/L to mg/dL, 4; serum phosphate in mmol/L to mg/dL, 3.1.

Figure 1. Time courses of changes in the levels of mineral metabolism-related variables after each diet intervention.

Changes in serum phosphate (A), urinary Pi/Cr (B), serum calcium (C), FGF23 (D), PTH (E), α-Klotho (F), 1,25(OH)₂D₃ (G) and BALP (H) levels in six healthy participants at 9 times points during the last 24 hours of a regular phosphorus diet, low-phosphorus diet, and high-phosphorus diet intervention. Urinary Pi/Cr: urinary phosphorus/creatinine rate; FGF23: fibroblast growth factor 23; PTH: parathyroid hormone; 1,25(OH)₂D₃: 1,25-dihydroxyvitamin D3; BALP: bone alkaline phosphatase.

Table 2. Repeated measures correlation analysis of each mineral metabolic variable following different types of phosphorus diets.

Gray fill area: Repeated measures correlation coefficient between two metabolic variables; white fill area: p-value for the correlation of two metabolic variables. Abbreviations: Serum Ca, serum corrected calcium; Serum Pi: serum phosphate; FGF23: fibroblast growth factor 23; BALP: bone alkaline phosphatase; PTH: parathyroid hormone; Urinary Pi/Cr: urinary phosphorus/creatinine rate.

Figure 2. The network of phosphorus metabolism according to Granger causality analysis following regular, low-, and high-phosphorus diet interventions.

Causality graph with the betweenness centrality index (A1, B1 and C1), the weighted adjacency matrices (A2, B2 and C2) and the highest betweenness and degree effects (A3, B3 and C3) following regular, low- and high-phosphorus diet interventions. The shading, from light green for the lowest value to dark green for the highest value, represents the values of the variables (betweenness in the nodes of graphs A1 and A3, weighted adjacency in matrix A2). The shading scale is to the right of each panel. Graph A3 is the simplified version of graph A1, in which the phosphatonin with the highest betweenness value is placed in the middle, and the thin arrows show the regulatory relationships associated with this phosphatonin. In addition, the large orange and green arrows indicate the variables with the highest outdegree and indegree values. Abbreviations: U-Pi/Cr, urinary phosphorus/creatinine rate; PTH, parathyroid hormone; FGF23, fibroblast growth factor 23; BALP, bone alkaline phosphatase; 1,25D, 1,25-dihydroxyvitamin D3; S-Pi, serum phosphate; S-Ca, serum corrected calcium.

Table 3. Graph theory and network analysis of the interactions among variables in phosphorus regulatory network following different dietary interventions.

	1,25(OH)2D3	Serum Pi	FGF23	Serum Ca	Urinary Pi/Cr	α-Klotho	BALP	PTH
Regular-phosphorus diet
Betweenness	0.07	0.03	0.12	0.14	0.13	0.22	0.01	0.12
Out degree	0.57	0.29	0.43	0.71	0.29	0.71	0.14	0.57
In degree	0.43	0.43	0.57	0.29	0.71	0.57	0.29	0.43
Low-phosphorus diet
Betweenness	0.15	0.15	0.15	0.02	0.22	0.04	0.08	0.01
Out degree	0.43	0.71	0.57	0.57	0.57	0.29	0.43	0.29
In degree	0.86	0.43	0.29	0.14	0.71	0.57	0.57	0.29
High-phosphorus diet
Betweenness	0.36	0	0.36	0	0	0	0	0.14
Out degree	0.29	0.14	0.57	0	0.14	0.14	0.29	0.29
In degree	0.43	0.14	0.29	0.43	0	0.29	0	0.29

Serum Ca: serum corrected calcium; Serum Pi: serum phosphate; FGF23: fibroblast growth factor 23; BALP: bone alkaline phosphatase; PTH: parathyroid hormone; Urinary Pi/Cr: urinary phosphorus/creatinine rate.