Adverse Metabolic Phenotypes in Parenterally Fed Neonatal Pigs Do Not Persist into Adolescence

Abstract

Background: Nutrition during fetal and neonatal life is an important determinant for the risk of adult-onset diseases, especially type 2 diabetes and obesity.

Objectives: We aimed to determine whether total parenteral nutrition (TPN) compared with enteral formula feeding [enteral nutrition (EN)] in term piglets during the first 2 wk after birth would increase the long-term (5-mo) development of metabolic syndrome phenotypes with adverse glucose homeostasis, fatty liver disease, and obesity.

Methods: Neonatal female pigs were administered TPN (n = 12) or fed enterally with a liquid enteral milk-replacer formula (EN, n = 12) for 14 d. After transitioning TPN pigs to enteral feeding of liquid formula (days 15-26), both groups were adapted to a solid high-fat diet (30% of the total diet) and sucrose (20% of the total diet) diet (days 27-33), which was fed until the end of the study (140 d). Body composition was measured by dual-energy X-ray absorptiometry at 14, 45, and 140 d. Serum biochemistry and glucose-insulin values (after a fasting intravenous glucose tolerance test) were obtained at 140 d. Liver and muscle were analyzed for insulin receptor signaling and triglycerides.

Results: Body weight was similar, but percent fat was higher, whereas percent lean and bone mineral density were lower in TPN than in EN pigs (P < 0.01) at 45 d of age but not at 140 d. At 140 d, there were no differences in serum markers of liver injury or lipidemia. Intravenous glucose tolerance test at 140 d showed a lower (P < 0.05) AUC for both glucose and insulin in TPN than in EN pigs, but the ratio of AUCs of insulin and glucose was not different between groups.

Conclusions: Administration of TPN during the neonatal period increased adipose deposition that transiently persisted in early adolescence when challenged with a high-fat diet but was not sustained or manifested as glucose intolerance.

Keywords: insulin resistance; neonatal programming; obesity; pig; total parenteral nutrition.

FIGURE 1

Study design (Reproduced from BioRender.com with permission). DXA, dual-emission X-ray absorptiometry; EN, enteral nutrition; IVGTT, intravenous glucose tolerance test; TPN, total parenteral nutrition.

FIGURE 2

Body weight and weight gain. (A) Body weight over time for pigs fed either total parenteral nutrition (TPN) or enteral nutrition (EN) for the first 2 wk of life (TPN, n = 8; EN, n = 10; time, P < 0.01, feeding treatment, P = 0.16; time × feeding treatment, P < 0.01). (B) Body weight gain as g/(kg/d) between dual-energy X-ray absorptiometry scans for pigs fed either TPN or EN for the first 2 wk of life (TPN, n = 8; EN, n = 10; time, P < 0.01, feeding treatment, P = 0.71; time × feeding treatment, P < 0.05). Data are shown as means ± SE; ∗P < 0.05.

FIGURE 3

(A) Percent fat, (B) total fat, (C) percent lean, (D) total lean, (E) bone mineral content, and (F) bone mineral density by dual-energy X-ray absorptiometry at days 16, 45, and 140 of pigs fed either total parenteral nutrition (TPN) or enteral nutrition (EN) for the first 2 wk of life (TPN, n = 8; EN, n = 10). Data were analyzed by 2-way analysis of variance; percent fat, time, P < 0.01, feeding treatment, P = 0.79, time × feeding treatment, P < 0.05; total fat, time, P < 0.01, feeding treatment, P < 0.05, time × feeding treatment, P < 0.05; percent lean, time, P < 0.01, feeding treatment, P = 0.87, time × feeding treatment, P < 0.05; total lean, time, P < 0.01, feeding treatment, P = 0.07, time × feeding treatment, P < 0.05; bone mineral content, time, P < 0.01, feeding treatment, P = 0.08, time × feeding treatment, P < 0.06; and bone mineral density, time, P < 0.01, feeding treatment, P = 0.08, time × feeding treatment, P < 0.56. Data are shown as means ± SE; ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, ∗∗∗∗P < 0.0001.

FIGURE 4

Triglyceride concentrations in the (A) liver and (B) muscle at day 140 after pigs were fed total parenteral nutrition (TPN) or enteral nutrition (EN) for the first 2 wk of life (TPN, n = 8; EN, n = 10; feeding treatment, P > 0.05). Representative Oil Red O staining of liver from pigs that were fed TPN for the first 2 wk or life at magnifications of (C) 20× and (D) 40×. Dots with red pigmentation are indicative of lipids. Representative Oil Red O staining of liver from pigs that were fed EN for the first 2 wk or life at magnifications of (E) 20× and (F) 40×. Dots with red pigmentation are indicative of lipids. Data are shown as means ± SE.

FIGURE 5

(A) Plasma glucose and (B) insulin concentrations during intravenous glucose tolerance test on day 140 after pigs were fed total parenteral nutrition (TPN) or enteral nutrition (EN) for the first 2 wk of life (TPN, n = 8; EN, n =10; glucose and insulin: time, P < 0.01; glucose and insulin: feeding treatment, P < 0.05; glucose: time × feeding treatment, P < 0.05; insulin: time × feeding treatment, P > 0.05). AUC for (C) glucose, (D) insulin, and insulin-to-glucose ratio on day 140 after pigs were fed TPN or EN for the first 2 wk of life (TPN, n = 8; EN, n = 10; glucose and insulin: feeding treatment, P < 0.05; insulin-to-glucose ratio: feeding treatment, P > 0.05). Data are shown as means ± SE; ∗P < 0.05.

FIGURE 6

Relative abundance of phospho-IR (pIR) and phospho-IRS-1 (pIRS-1) in the (A) liver and (B) muscle of pigs fed total parenteral nutrition (TPN) or enteral nutrition (EN) for the first 2 wk of life (n = 7 each) after 90 min IVGTT on day 140. Phosphorylated proteins are expressed relative to total protein (tIR and tIRS-1, respectively). Results are expressed in arbitrary units as mean ± SEM. Data are shown as means ± SE. IR, insulin receptor; IRS-1, insulin receptor substrate 1; IVGTT, intravenous glucose tolerance test.

FIGURE 7

Insulin staining in the pancreas on day 140 pigs fed total parenteral nutrition (TPN) or enteral nutrition (EN) for the first 2 wk of life. (A) Total cells counted and included in the analysis (TPN, n = 8; EN n = 10, P < 0.05). (B) Number of insulin-positive cells (TPN, n = 8; EN n = 10, P > 0.05). (C) The ratio of insulin-positive (+) cells to the total number of cells analyzed (TPN, n = 8; EN, n = 10, P > 0.05). Data are shown as means ± SE; ∗P < 0.05.