Pro-Opiomelanocortin Modulates the Thermogenic and Physical Activity Responses to High-Fat Feeding and Markedly Influences Dietary Fat Preference

Abstract

Complete proopiomelanocortin (POMC) deficiency causes a human syndrome of hypoadrenalism, altered skin and hair pigmentation, and severe hyperphagic obesity. Heterozygote carriers of nonsense mutations are strongly predisposed to obesity. Pomc(+/-) mice have normal body weight on a chow diet but increase food intake and become more obese than wild-type littermates when placed on a high-fat diet. To further explore the mechanisms whereby dietary fat interacts with Pomc genotype to produce obesity, we examined Pomc-null, Pomc(+/-), and wild-type mice for changes in the components of energy balance in response to provision of a high-fat diet and macronutrient preference when presented with a selection of dietary choices. In contrast to wild-type mice, Pomc null mice did not increase their resting energy expenditure or their spontaneous physical activity when given a high-fat diet. Pomc(+/-) mice increased resting energy expenditure similarly to wild types, but their increase in physical activity was significantly less than that seen in wild-type mice. In two independent experimental tests of macronutrient preference, Pomc genotype was a strong predictor of dietary fat preference with Pomc null animals choosing to eat approximately twice as much fat, but similar amounts of carbohydrate and protein, as wild-type animals. Pomc(+/-) mice showed an intermediate response. In summary, POMC-derived peptides have influences on multiple aspects of the organism's response to the presentation of high-fat diet. This includes a major influence, readily discernible even in heterozygote animals, on the dietary preference for fat.

Orexin activation counteracts decreases in nonexercise activity thermogenesis (NEAT) caused by high-fat diet

“…For example, Tung et al 2007 compared POMC −/− mice with wildtype mice of a 129/SvEv background provided HFD and observed increases in both SPA and EE [14]. The difference in SPA results between that investigation and the present study may be due to strain differences.…”

“…For example, several studies have shown a decrease in physical activity during exposure to high-fat diet (HFD), with others showing the opposite effect, suggesting this relationship may be complex [9–14]. Similarly, total EE may also be affected by the type of diet available, with studies showing both increases and decreases in energy expenditure in animals with access to HFD compared to chow and low-fat diets [9, 14, 15]. In addition, there have been no studies to date which have assessed the effect of chow-feeding vs. HFD specifically on NEAT, which is important for understanding the diet-based relative contribution of SPA to energy expenditure.…”

Induction of ketosis in rats fed low-carbohydrate, high-fat diets depends on the relative abundance of dietary fat and protein

“…In contrast, the opposite was the case, and EE and LA were even lower in rats fed the LC-HF diets. The observed reductions in LA during the dark phase could also be due to an altered eating behavior of the LC-HF groups, since it is known that the central mechanism associated with eating behavior can affect LA (40,47,48). Interestingly, investigations in humans have shown that study subjects consuming LC-HF diets often feel tired and exhausted (14), which potentially could lead to reduced LA.…”

<i>In vitro</i> antioxidant activity of extracts from the leaves of <i>Felicia muricata</i> Thunb. an underutilized medicinal plant in the Eastern Cape Province, South Africa

“…Flavonoids as one of the most diverse and widespread groups of natural compounds are probably the most important natural phenolics (Agrawal, 1989). These compounds possess a broad spectrum of chemical and biological activities including radical scavenging properties (Tung et al, 2007), such properties are especially distinct for flavonols (Miliauskas et al, 2004).…”