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Changes in metabolic rate and brown adipose tissue composition during nutritional rehabilitation of postnatally
Insights
Undernourished rats exhibited reduced weight gain and increased metabolic rate, linked to sympathetic activation of brown adipose tissue (BAT). This suggests early nutrition impacts long-term energy expenditure and growth.
Area of Science:
- Physiology
- Nutrition Science
- Metabolic Research
Background:
- Early life undernutrition can have lasting effects on growth and metabolism.
- Brown adipose tissue (BAT) plays a key role in thermogenesis and energy expenditure.
Purpose of the Study:
- To investigate the metabolic consequences of early undernutrition in rats.
- To explore the role of sympathetic activation and BAT in the altered growth of previously undernourished rats.
Main Methods:
- Comparative study of previously undernourished (PU) rats and control rats during a rehabilitation period.
- Measurement of weight gain, food intake, resting oxygen consumption, and thermogenic response to noradrenaline.
- Assessment of brown adipose tissue (BAT) mass and the effect of beta-adrenergic blockade (propranolol).
Main Results:
- PU rats showed reduced weight gain despite similar food intake per body weight.
- Resting oxygen consumption was elevated in PU rats, an effect largely reversed by propranolol.
- Thermogenic activity after noradrenaline was greater in PU rats.
- BAT mass was initially reduced by undernutrition but increased beyond control levels during rehabilitation.
Conclusions:
- The reduced weight gain in previously undernourished rats is partly attributed to an elevated metabolic rate.
- Sympathetic nervous system activation, particularly involving brown adipose tissue (BAT), contributes to this increased metabolic rate.
- Early nutritional status significantly influences long-term metabolic regulation and growth trajectory.
Abstract:
Rats previously undernourished (PU) during the first 3 postnatal weeks gained less weight than controls during the subsequent rehabilitation period, in spite of similar levels of food intake per body weight 0.75. Resting oxygen consumption (ml/min/kg0.75) was significantly elevated (15-22%) in the PU group after 36 days of age but this difference was almost completely abolished by beta-adrenergic blockade with propranolol. PU rats also showed a greater thermogenic activity after noradrenaline (25 micrograms/100 g b.wt.) than controls. The mass of brown adipose tissue (BAT, mg/100 g b.wt.) was reduced by undernutrition but during rehabilitation BAT increased in PU rats to a value greater than that of controls. These results indicate that the low weight gain of PU rats may result partly from a high metabolic rate due to sympathetic activation of BAT.