Food restriction decreases BMR, body and organ mass, and cellular energetics, in the Chinese Bulbul (Pycnonotus sinensis)

Peipei Yang,Weihong Zheng,Jinsong Liu,Yiying Zhang,Yingshi Su,Ke Yang

doi:10.1186/s40657-018-0131-8

Abstract

BackgroundFood is an important environmental factor that affects animals’ energy metabolism and food shortage has significant effects on animals’ behavior, physiology and biochemistry. However, to date few studies have focused on the thermogenesis and its effects on the body condition of birds. In this study, we examined the effects of food restriction on the body mass, basal metabolic rate (BMR) and body composition, and several physiological, biochemical and molecular markers potentially related to thermogenesis, in the Chinese Bulbul (Pycnonotus sinensis).MethodsBirds in the control group were provided with food ad libitum whereas those in the food restriction group were provided with one-half of the usual quantity of food for 12 days. Oxygen consumption was measured using an open-circuit respirometry system. Mitochondrial state 4 respiration and cytochrome c oxidase (COX) activity in the liver and pectoral muscle were measured with a Clark electrode. Avian uncoupling protein (avUCP) mRNA expression was determined in pectorals muscle with quantitative Real-time PCR.ResultsChinese Bulbuls in food restriction group decreased in body mass, BMR and internal organ (heart, kidneys, small intestine and total digestive tract) mass compared with the control group over the 12-day period of food restriction. Bulbuls in the food restriction group also had lower levels of state-4 respiration, COX activity in the liver and muscle, and mitochondrial avUCP gene expression in muscle compared to the control group. BMR was positively correlated with body mass, state 4 respiration in the liver and COX activity in the muscle.ConclusionsOur data indicate that Chinese Bulbuls not only sustain food shortage through simple passive mechanisms, such as reducing body and organ mass and energy expenditure, but also by reducing energetic metabolism in the liver and muscle.

Highlights

Food is an important environmental factor that affects animals’ energy metabolism and food shortage has significant effects on animals’ behavior, physiology and biochemistry
Birds in the food restriction group (FR) group underwent a significant decrease in body mass (t20 = 4.838, p < 0.0001; Fig. 1a) and basal metabolic rate (BMR) (t20 = 2.292, p = 0.033; Fig. 1b), relative to those in the control group
We found that 12 days of food restriction decreased the body mass, body fat, energy expenditure, internal organ mass, and BMR, of Chinese Bulbuls, and decreased state-4 respiration and c oxidase (COX) activity in their liver and muscle mitochondria

Summary

Introduction

Food is an important environmental factor that affects animals’ energy metabolism and food shortage has significant effects on animals’ behavior, physiology and biochemistry. It has been demonstrated that a bird’s body mass and composition (Kelly and Weathers 2002), energy balance (Liang et al 2015), basal metabolic rate (BMR) (AL-Mansour 2004; McKechnie and Wolf 2004; Gutiérrez et al 2011), and reproduction (Perrins 1965; Robb et al 2008) are all affected by food restriction. Such changes include changes in both physiology and metabolism (Marjoniemi 2000). Substantial efforts have been made to examine the effects of food restriction on animal survival, adaptation, and reproductive success (Prinzinger and Siedle 1988; Robb et al 2008)

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