Table 3. Mean serum concentrations (μM) of amino acids, amino acid derivatives, and ammonium compounds determined by DI-MS in overweight cats (n = 14) receiving control (no additional choline supplementation, 1.2 x NRC RA, 77 mg/kg BW^0.67), choline at 2 x NRC RA (126 mg/kg BW^0.67), 4 x NRC RA (252 mg/kg BW^0.67), 6 x NRC RA (378 mg/kg BW^0.67), and 8 x NRC RA (504 mg/kg BW^0.67), in a 5 x 5 Latin square design for 3-week periods.

	Choline Dose
	Control	2 x NRC RA	4 x NRC RA	6 X NRC RA	8 X NRC RA	PDose
Amino Acids
Alanine	443.89 ± 48.10	459.87 ± 48.54	477.19 ± 49.19	543.70 ± 56.04	512.11 ± 52.79	0.350
Arginine	162.25 ± 8.03b	177.01 ± 7.84ab	179.34 ± 7.68ab	180.43 ± 7.68ab	187.43 ± 7.68a	0.039
Asparagine	47.15 ± 3.85ab	45.30 ± 3.81b	52.66 ± 3.77a	53.55 ± 3.77a	53.81 ± 3.77a	0.003
Aspartic acid	62.61 ± 8.52	65.30 ± 8.34	69.08 ± 8.19	75.92 ± 8.19	75.56 ± 8.19	0.308
Citrulline	22.73 ± 1.59	23.61 ± 1.56	25.18 ± 1.53	25.51 ± 1.53	24.33 ± 1.53	0.266
Glutamic acid	93.92 ± 14.73	111.36 ± 14.64	105.75 ± 14.55	104.25 ± 14.55	95.86 ± 14.55	0.311
Glutamine	740.68 ± 37.34	694.80 ± 36.52	755.70 ± 35.80	696.03 ± 35.80	727.72 ± 35.80	0.295
Glycine	336.20 ± 14.64	348.06 ± 14.27	360.79 ± 13.94	368.74 ± 13.94	360.14 ± 13.94	0.222
Histidine	106.29 ± 3.33	107.62 ± 3.22	115.98 ± 3.11	117.20 ± 3.11	117.01 ± 3.11	0.014
Homocysteine	8.28 ± 0.31ab	7.81 ± 0.29ab	8.07 ± 0.28ab	8.75 ± 0.28a	7.52 ± 0.28b	0.019
Isoleucine	55.18 ± 3.08	55.69 ± 3.02	56.22 ± 2.97	56.22 ± 2.97	57.13 ± 2.97	0.965
Leucine	113.00 ± 6.43	112.00 ± 6.29	114.90 ± 6.18	114.82 ± 6.18	116.98 ± 6.18	0.922
Lysine	152.50 ± 8.19b	164.75 ± 8.01ab	175.50 ± 7.85a	170.68 ± 7.84ab	181.56 ± 7.85a	0.006
Methionine	43.45 ± 2.24b	45.10 ± 2.20bc	49.68 ± 2.17ac	50.37 ± 2.17a	49.75 ± 2.17ac	0.001
Ornithine	36.34 ± 5.34	33.07 ± 5.19	38.41 ± 5.05	44.29 ± 5.05	39.70 ± 5.05	0.378
Phenylalanine	79.04 ± 4.17	83.00 ± 4.11	82.01 ± 4.06	84.37 ± 4.06	82.67 ± 4.06	0.527
Proline	138.03 ± 5.90b	139.61 ± 5.75b	157.52 ± 5.62a	166.10 ± 5.62a	157.69 ± 5.62a	< 0.0001
Serine	137.41 ± 6.13b	136.99 ± 5.94b	159.11 ± 5.79a	165.13 ± 5.78a	157.41 ± 5.79a	0.0001
Taurine	4.45 ± 0.19	4.61 ± 0.18	4.47 ± 0.17	4.65 ± 0.17	4.63 ± 0.17	0.864
Threonine	112.54 ± 5.32	114.61 ± 5.18	120.02 ± 5.06	120.32 ± 5.06	124.46 ± 5.06	0.203
Tyrosine	51.66 ± 3.23	49.95 ± 3.16	50.52 ± 3.09	51.80 ± 3.09	53.19 ± 3.09	0.837
Tryptophan	72.56 ± 2.72	73.75 ± 2.64	70.69 ± 2.57	71.31 ± 2.57	70.35 ± 2.57	0.759
Valine	152.13 ± 7.04	150.12 ± 6.92	157.83 ± 6.81	154.35 ± 6.81	153.76 ± 6.81	0.743
Total amino acids	3283.34 ± 133.91	3390.69 ± 130.02	3499.44 ± 126.55	3604.20 ± 126.55	3574.06 ± 126.55	0.179
Amino Acid Derivatives
Betaine	252.53 ± 58.92c	358.69 ± 56.95c	609.81 ± 55.23b	851.65 ± 55.23a	816.46 ± 55.23a	< 0.0001
Creatine	9.55 ± 1.23	9.92 ± 1.19	9.81 ± 1.15	11.09 ± 1.15	11.93 ± 1.15	0.477
Methylhistidine	24.09 ± 1.33	23.24 ± 1.31	24.67 ± 1.29	23.82 ± 1.29	24.27 ± 1.29	0.754
Ammonium Compounds
Choline	18.98 ± 3.73	19.11 ± 3.66	22.56 ± 3.59	21.89 ± 3.59	20.77 ± 3.59	0.835

Values expressed as LSM ± SEM; Values in a row with superscripts without a common letter differ; P < 0.05, Repeated measures ANOVA with Tukey post-hoc test. DI-MS = direct infusion mass spectrometry; BW = body weight; NRC = National Research Council; RA = Recommended Allowance.