The Intrauterine and Nursing Period Is a Window of Susceptibility for Development of Obesity and Intestinal Tumorigenesis by a High Fat Diet in Min/+ Mice as Adults

Figure 1

Experimental design. The mice were exposed to a 45% fat diet for combinations of three periods in life; (1) in utero, via the dams, (2) from birth to weaning, via milk during nursing, or (3) from weaning at 3 weeks to termination at 11 weeks of age (for Min/+ mice) or 23 weeks (for wild-type mice), to determine the most susceptible exposure period for development of obesity and intestinal tumorigenesis as adults. The effects of a 45% fat diet were studied on spontaneous tumorigenesis induced by the inherited mutation in the Apc gene and on tumors induced by the the food mutagen and carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). The mice in two experimental groups (marked with arrows) were given one s.c. injection of 25 mg/kg body weight of PhIP on days 3–6 after birth. In total, eight experimental groups were included in this experiment; a 10% fat diet throughout life as a negative control (10+10+10), a 45% fat diet in utero (45+10+10), a 45% fat diet during the nursing period (10+45+10), a 45% fat diet both in utero and during nursing (45+45+10), exposed to PhIP or not, a 45% fat diet as adults (10+10+45), or a 45% fat diet throughout life (45+45+45), exposed to PhIP or not.