Discovering The Developmental Origins of Obesity

The Polish Academy of Sciences in Olsztyn, Poland

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Inherent Plasticity of Brown Adipogenesis in White Fat of Mice Allows for Recovery from Effects of Post-Natal Malnutrition

Leslie P. Kozak1, Robert A. Koza2, Rea Anunciado-Koza2, Tamra Mendoza2, Susan Newman2

1 Institute of Animal Reproduction and Food Research of the Polish Academy of Sciences, Olsztyn, Poland,
2 Pennington Biomedical Research Center, Baton Rouge, Louisiana, United States of America

ABSTRACT
Interscapular brown adipose tissue (iBAT) is formed during fetal development and stable for the life span of the mouse. In addition, brown adipocytes also appear in white fat depots (wBAT) between 10 and 21 days of age in mice maintained at a room temperature of 23uC. However, this expression is transient. By 60 days of age the brown adipocytes have disappeared, but they can re-emerge if the adult mouse is exposed to the cold (5uC) or treated with b3-adrenergic agonists. Since the number of brown adipocytes that can be induced in white fat influences the capacity of the mouse to resist the obese state, we determined the effects of the nutritional conditions on post-natal development (birth to 21 days) of wBAT and its longterm effects on diet-induced obesity (DIO).

Under-nutrition caused essentially complete suppression of wBAT in inguinal fat at 21 days of age, as indicated by expression of Ucp1 and genes of mitochondrial structure and function based upon microarray and qRT-PCR analysis, whereas over-nutrition had no discernible effects on wBAT induction. Surprisingly, the suppression of wBAT at 21 days of age did not affect DIO in adult mice maintained at 23uC, nor did it affect the reduction in obesity or cold tolerance when DIO mice were exposed to the cold at 5uC for one week. Gene expression analysis indicated that mice raised under conditions that suppressed wBAT at 21 days of age were able to normally induce wBAT as adults. Therefore, neither severe hypoleptinemia nor hypoinsulinemia during suckling permanently impaired brown adipogenesis in white fat. In addition, energy balance studies of DIO mice exposed to cold indicates that mice with reduced adipose stores preferentially increased food intake, whereas those with larger adipose tissue depots preferred to utilize energy from their adipose stores.

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