Changes in metabolic rate and brown adipose tissue composition during nutritional rehabilitation of postnatally undernourished rats
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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.