Long-Term Intake of a High-Protein Diet Affects Body Phenotype, Metabolism, and Plasma Hormones in Mice

Abstract

Background: High-protein diets (HPDs) recently have been used to obtain body weight and fat mass loss and expand muscle mass. Several studies have documented that HPDs reduce appetite and food intake.Objective: Our goal was to determine the long-term effects of an HPD on body weight, energy intake and expenditure, and metabolic hormones.Methods: Male C57BL/6 mice (8 wk old) were fed either an HPD (60% of energy as protein) or a control diet (CD; 20% of energy as protein) for 12 wk. Body composition and food intakes were determined, and plasma hormone concentrations were measured in mice after being fed and after overnight feed deprivation at several time points.Results: HPD mice had significantly lower body weight (in means ± SEMs; 25.73 ± 1.49 compared with 32.5 ± 1.31 g; P = 0.003) and fat mass (9.55% ± 1.24% compared with 15.78% ± 2.07%; P = 0.05) during the first 6 wk compared with CD mice, and higher lean mass throughout the study starting at week 2 (85.45% ± 2.25% compared with 75.29% ± 1.90%; P = 0.0001). Energy intake, total energy expenditure, and respiratory quotient were significantly lower in HPD compared with CD mice as shown by cumulative energy intake and eating rate. Water vapor was significantly higher in HPD mice during both dark and light phases. In HPD mice, concentrations of leptin [feed-deprived: 41.31 ± 11.60 compared with 3041 ± 683 pg/mL (P = 0.0004); postprandial: 112.5 ± 102.0 compared with 8273 ± 1415 pg/mL (P < 0.0001)] and glucagon-like peptide 1 (GLP-1) [feed-deprived: 5.664 ± 1.44 compared with 21.31 ± 1.26 pg/mL (P = <0.0001); postprandial: 6.54 ± 2.13 compared with 50.62 ± 11.93 pg/mL (P = 0.0037)] were significantly lower, whereas postprandial glucagon concentrations were higher than in CD-fed mice.Conclusions: In male mice, the 12-wk HPD resulted in short-term body weight and fat mass loss, but throughout the study preserved body lean mass and significantly reduced energy intake and expenditure as well as leptin and GLP-1 concentrations while elevating postprandial glucagon concentrations. This study suggests that long-term use of HPDs may be an effective strategy to decrease energy intake and expenditure and to maintain body lean mass.

Keywords: appetite and energy intake; high-protein diet; metabolic hormones; metabolism and energy expenditure; respirometry and calorimetry.

Conflict of interest statement

Author disclosures: JPV, LL, WFP, SO, DS, AG, JRP, and PMG, no conflicts of interest. JRBL is the President and Chief Technology Officer of Sable Systems International, which produced the metabolic phenotyping system used in the study.

© 2017 American Society for Nutrition.

Figures

FIGURE 1

Body weight (A), body fat mass (B) and body lean mass (C) analysis of HPD- and CD-fed mice during the 12-wk period in 2-wk intervals. We used unpaired t tests to perform comparisons between HPD- and CD-fed mice. Values are means ± SEMs; HPD group, n = 8; CD group, n = 10. *P < 0.05, **P < 0.01, ***P < 0.001. CD, control diet; HPD, high-protein diet.

FIGURE 2

Food intake analysis between HPD- and CD-fed mice. (A) Food consumption data for HPD- and CD-fed mice expressed as 24-h average values over 48 h of uninterrupted recording; cumulative food intake was calculated by using 2-h intervals. (B) Bout duration, (C) bout frequency, (D) meal duration, (E) meal frequency, (F) meal size, and (G) eating rate analyzed between the dark and light cycles. We used unpaired t tests to perform comparisons of food consumption data. We used 2-factor ANOVA analysis to compare bout duration, bout frequency, meal duration, meal frequency, meal size, and eating rate values during the dark and light phases between HPD- and CD-fed mice. Values are means ± SEMs; HPD group, n = 8; CD group, n = 10. *P < 0.05, **P < 0.01, ***P < 0.001. CD, control diet; HPD, high-protein diet.

FIGURE 3

Water intake and drinking behavior variables between HPD- and CD-fed mice. Total water intake (A), mean water intake (B), drinking bouts (C), and time spent drinking (D) analyzed between the dark and light cycles. Values are means ± SEMs; HPD group, n = 8; CD group, n = 10. *P < 0.05, **P < 0.01. CD, control diet; HPD, high-protein diet.

FIGURE 4

Analysis of respirometry and calorimetry data between HPD- and CD-fed mice. TEE (A) and dark phase and light phase averages of TEE (B) between HPD- and CD-fed mice; TEE (C) and dark phase and light phase averages of TEE (D) between HPD- and CD-fed mice in feed-deprived conditions; RQ (E) and dark phase and light phase averages of RQ (F) between HPD- and CD-fed mice; RQ (G) and dark phase and light phase averages of RQ (H) between HPD- and CD-fed mice in 24-h feed-deprived conditions; VH2O (I) and dark phase and light phase averages of VH2O (J) between HPD- and CD-fed mice; VH2O (K) and dark phase and light phase averages of VH2O (L) between HPD- and CD-fed mice in 24-h feed-deprived conditions are shown. Values in panels B, D, F, H J, and L are means ± SEMs; HPD group, n = 8; CD group, n = 10. *P < 0.05, **P < 0.01. CD, control diet; HPD, high-protein diet; RQ, respiratory quotient; TEE, total energy expenditure; VH2O, water vapor.

FIGURE 5

Orexigenic and anorexigenic metabolic plasma hormone analyses of active ghrelin (A), leptin (B), insulin (C), GLP-1 (D), glucagon (E), and PYY (F) plasma concentrations measured in either feed-deprived or postprandial conditions between HPD- and CD-fed mice. Values are means ± SEMs; HPD group, n = 8; CD group, n = 10. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. CD, control diet; GLP-1, glucagon-like peptide 1; HPD, high-protein diet; PYY, peptide YY.