Long-term effects of diet on leptin, energy intake, and activity in a model of diet-induced obesity

Abstract

This study investigated the effect of long-term high-fat sucrose (HFS) or low-fat complex-carbohydrate (LFCC) diet consumption on leptin, insulin, fat cell size, energy intake, and markers of activity to ascertain the role that leptin plays in long-term energy balance in a model of diet-induced obesity. Female Fischer 344 rats were fed either a HFS or LFCC diet ad libitum for a period of 20 mo. Measurements of leptin concentration, insulin concentration, and adipocyte size were performed at 2 wk, 2 mo, 6 mo, and 20 mo. Body weight and energy intake were measured weekly for calculation of feed efficiency. Body temperature and activity levels were assessed over a 5-day period after 12 mo of the dietary intervention. Plasma leptin and insulin concentrations were significantly elevated within 2 wk of HFS diet consumption and remained elevated throughout the course of the study. After 2 mo, the adipocytes of the HFS group were significantly larger and continued to increase in size throughout the course of the study. A significant correlation was noted between leptin and adipocyte cell size (r = 0.96, P < 0.01). However, despite elevated leptin, energy intake was similar, and the HFS group weighed significantly more than the LFCC group, as a result of a higher feed efficiency. There were no significant differences in body temperature or activity levels between the groups. These results demonstrate that a HFS diet causes hyperleptinemia and hyperinsulinemia before adipocyte size is increased and suggests that leptin resistance may be present or, alternatively, that leptin does not to play a major role in the long-term regulation of energy intake or activity levels in this model.

Connective tissue growth factor/CCN-2 is upregulated in epididymal and subcutaneous fat depots in a dietary-induced obesity model

“…One characteristic feature of "insulin resistant" adipocytes is an increase in adipocyte cell size (29,47,48). Analysis of the adipocyte cell size showed that, as expected, the average size of the adipocytes in the HFD group was significantly larger than in the ND mice, a result reported previously by others in similar rodent models of dietary-induced obesity (22,29,35,44). Compared with the HFD-lean group, the relative distribution of adipocytes according to size was similar to that of the ND group, whereas the HFD-fat group showed a higher proportion of larger-sized adipocytes.…”

Effects of dietary fibers on weight gain, carbohydrate metabolism, and gastric ghrelin gene expression in mice fed a high-fat diet

“…However, it has been demonstrated that leptin is also synthesized by the gastric chief cells and release of gastric leptin occurs 15 min after refeeding in fasted rat (39). A high-fat sucrose (HFS) diet resulted in hyperleptinemia and hyperinsulinemia before adipocyte size was observed to increase (40). It was interesting to note in this study that high fat diets containing primarily sugar cane and psyllium resulted in lower plasma leptin concentrations when compared to the high-fat diet alone or high fat diet containing 10% cellulose.…”

High-fat diet-induced obesity in animal models

“…Energy from fat has a larger effect on body-weight gain than has energy from non-fat sources (12,14,22,49,106,150,151) . Diet-induced thermogenesis is the energy for digesting, absorbing and storing nutrients and produces a loss of energy for the body which is 2 -3 % for fats, 25 -30 % for proteins and 6 -8 % for carbohydrates.…”