Hypothalamic steroid receptor coactivator-2 regulates adaptations to fasting and overnutrition.

The neuroendocrine system coordinates metabolic and behavioral adaptations to fasting, including reducing energy expenditure, promoting counterregulation, and suppressing satiation and anxiety to engage refeeding. Here, we show that steroid receptor coactivator-2 (SRC-2) in pro-opiomelanocortin (POMC) neurons is a key regulator of all these responses to fasting. POMC-specific deletion of SRC-2 enhances the basal excitability of POMC neurons; mutant mice fail to efficiently suppress energy expenditure during food deprivation. SRC-2 deficiency blunts electric responses of POMC neurons to glucose fluctuations, causing impaired counterregulation. When food becomes available, these mutant mice show insufficient refeeding associated with enhanced satiation and discoordination of anxiety and food-seeking behavior. SRC-2 coactivates Forkhead box protein O1 (FoxO1) to suppress POMC gene expression. POMC-specific deletion of SRC-2 protects mice from weight gain induced by an obesogenic diet feeding and/or FoxO1 overexpression. Collectively, we identify SRC-2 as a key molecule that coordinates multifaceted adaptive responses to food shortage.

Sex-specific epigenetic alterations of the hypothalamic Agrp-Pomc system do not explain 'diabesity' in the offspring of high-fat diet (HFD) overfed maternal rats.

Maternal high-fat diet (HFD) overfeeding pre- and during pregnancy and lactation may 'program' a 'diabesity' predisposition in the offspring, for inconclusive reasons. Acquired alterations of the hypothalamic promoter methylation and mRNA expression of the satiety neurohormone Pomc are possibly of critical importance here. We investigated within one developmental approach, including male and female rats, the sex-specific DNA methylation pattern and corresponding mRNA expression of both Pomc and its endogenous functional antagonist Agrp in the hypothalamus of adult HFD offspring. Obesity and diabetic disturbances occurred in both male and female HFD offspring, accompanied by altered Pomc promoter methylation pattern. However, this was not related to significant Pomc mRNA expression alterations. In contrast, male-specific alterations of Agrp promoter methylation were found, even associated with reduced mRNA expression of this orexigenic/anabolic Pomc antagonist. In conclusion, acquired epigenetic alterations of the hypothalamic Agrp-Pomc system hardly explain the 'diabesity' phenotype in HFD offspring, while distinct vulnerability and functionality of Agrp promoter and related genomic regions methylation should be further investigated.

Genetically high plasma vitamin C and urate: a Mendelian randomization study in 106 147 individuals from the general population.

Objective: Gout is the most common form of inflammatory arthritis and is caused by hyperuricaemia. Some studies have found a reduction in plasma urate with vitamin C supplementation. We tested the hypothesis that high plasma vitamin C is causally associated with low plasma urate and low risk of hyperuricaemia, using a Mendelian randomization approach. Methods: We measured plasma urate and genotyped for the SLC23A1 rs33972313 vitamin C variant in 106 147 individuals from the Copenhagen General Population Study, of which 24 099 had hyperuricaemia. We measured plasma vitamin C in 9234 individuals and genotyped for the SLC2A9 rs7442295 urate variant in 102 345 individuals. Results: Each 10 µmol/l higher plasma vitamin C was associated with a -2.3(95%CI: -0.69 to -3.9) µmol/l lower plasma urate after multivariable adjustments. The SLC23A1 rs33972313 GG genotype was associated with a 9% (5.6%, 11.9%) higher plasma vitamin C compared with AA and AG combined but was not associated with plasma urate (P = 0.31). Likewise, for each 10 µmol/l higher plasma vitamin C the odds ratios for hyperuricaemia were 0.92 (0.86, 0.98) observationally after multivariable adjustments, but 1.01 (0.84, 1.23) genetically. Conclusion: High plasma vitamin C was associated with low plasma urate and with low risk of hyperuricaemia. However, the SLC23A1 genetic variant causing lifelong high plasma vitamin C was not associated with plasma urate levels or with risk of hyperuricaemia. Thus, our data do not support a causal relationship between high plasma vitamin C and low plasma urate.

Maternal overnutrition programs epigenetic changes in the regulatory regions of hypothalamic Pomc in the offspring of rats.

BACKGROUND AND OBJECTIVE: Maternal overnutrition has been implicated in affecting the offspring by programming metabolic disorders such as obesity and diabetes, by mechanisms that are not clearly understood. This study aimed to determine the long-term impact of maternal high-fat (HF) diet feeding on epigenetic changes in the offspring's hypothalamic Pomc gene, coding a key factor in the control of energy balance. Further, it aimed to study the additional effects of postnatal overnutrition on epigenetic programming by maternal nutrition. METHODS: Eight-week-old female Sprague-Dawley rats were fed HF diet or low-fat (LF) diet for 6 weeks before mating, and throughout gestation and lactation. At postnatal day 21, samples were collected from a third offspring and the remainder were weaned onto LF diet for 5 weeks, after which they were either fed LF or HF diet for 12 weeks, resulting in four groups of offspring differing by their maternal and postweaning diet. RESULTS: With maternal HF diet, offspring at weaning had rapid early weight gain, increased adiposity, and hyperleptinemia. The programmed adult offspring, subsequently fed LF diet, retained the increased body weight. Maternal HF diet combined with offspring HF diet caused more pronounced hyperphagia, fat mass, and insulin resistance. The ARC Pomc gene from programmed offspring at weaning showed hypermethylation in the enhancer (nPE1 and nPE2) regions and in the promoter sequence mediating leptin effects. Interestingly, hypermethylation at the Pomc promoter but not at the enhancer region persisted long term into adulthood in the programmed offspring. However, there were no additive effects on methylation levels in the regulatory regions of Pomc in programmed offspring fed a HF diet. CONCLUSION: Maternal overnutrition programs long-term epigenetic alterations in the offspring's hypothalamic Pomc promoter. This predisposes the offspring to metabolic disorders later in life.

Developmental programming of somatic growth, behavior and endocannabinoid metabolism by variation of early postnatal nutrition in a cross-fostering mouse model.

BACKGROUND: Nutrient deprivation during early development has been associated with the predisposition to metabolic disorders in adulthood. Considering its interaction with metabolism, appetite and behavior, the endocannabinoid (eCB) system represents a promising target of developmental programming. METHODS: By cross-fostering and variation of litter size, early postnatal nutrition of CB6F1-hybrid mice was controlled during the lactation period (3, 6, or 10 pups/mother). After weaning and redistribution at P21, all pups received standard chow ad libitum. Gene expression analyses (liver, visceral fat, hypothalamus) were performed at P50, eCB concentrations were determined in liver and visceral fat. Locomotor activity and social behavior were analyzed by means of computer-assisted videotracking. RESULTS: Body growth was permanently altered, with differences for length, weight, body mass index and fat mass persisting beyond P100 (all 3>6>10,p<0.01). This was paralleled by differences in hepatic IGF-I expression (p<0.01). Distinct gene expression patterns for key enzymes of the eCB system were observed in fat (eCB-synthesis: 3>6>10 (DAGLα p<0.05; NAPE-PLD p = 0.05)) and liver (eCB-degradation: 3>6>10 (FAAH p<0.05; MGL p<0.01)). Concentrations of endocannabinoids AEA and 2-AG in liver and visceral fat were largely comparable, except for a borderline significance for higher AEA (liver, p = 0.049) in formerly overfed mice and, vice versa, tendencies (p<0.1) towards lower AEA (fat) and 2-AG (liver) in formerly underfed animals. In the arcuate nucleus, formerly underfed mice tended to express more eCB-receptor transcripts (CB1R p<0.05; CB2R p = 0.08) than their overfed fellows. Open-field social behavior testing revealed significant group differences, with formerly underfed mice turning out to be the most sociable animals (p<0.01). Locomotor activity did not differ. CONCLUSION: Our data indicate a developmental plasticity of somatic growth, behavior and parameters of the eCB system, with long-lasting impact of early postnatal nutrition. Developmental programming of the eCB system in metabolically active tissues, as shown here for liver and fat, may play a role in the formation of the adult cardiometabolic risk profile following perinatal malnutrition in humans.

Early postnatal nutrition determines adult physical activity and energy expenditure in female mice.

Decades of research in rodent models has shown that early postnatal overnutrition induces excess adiposity and other components of metabolic syndrome that persist into adulthood. The specific biologic mechanisms explaining the persistence of these effects, however, remain unknown. On postnatal day 1 (P1), mice were fostered in control (C) or small litters (SL). SL mice had increased body weight and adiposity at weaning (P21), which persisted to adulthood (P180). Detailed metabolic studies indicated that female adult SL mice have decreased physical activity and energy expenditure but not increased food intake. Genome-scale DNA methylation profiling identified extensive changes in hypothalamic DNA methylation during the suckling period, suggesting that it is a critical period for developmental epigenetics in the mouse hypothalamus. Indeed, SL mice exhibited subtle and sex-specific changes in hypothalamic DNA methylation that persisted from early life to adulthood, providing a potential mechanistic basis for the sustained physiological effects. Expression profiling in adult hypothalamus likewise provided evidence of widespread sex-specific alterations in gene expression. Together, our data indicate that early postnatal overnutrition leads to a reduction in spontaneous physical activity and energy expenditure in females and suggest that early postnatal life is a critical period during which nutrition can affect hypothalamic developmental epigenetics.

Developmental overfeeding alters hypothalamic neuropeptide mRNA levels and response to a high-fat diet in adult mice.

It has been suggested that nutritional manipulations during the first weeks of life can alter the development of the hypothalamic circuits involved in energy homeostasis. We studied the expression of a large number of the hypothalamic neuropeptide mRNAs that control body weight in mice that were overfed during breastfeeding (mice grown in a small litter, SL) and/or during adolescence (adolescent mice fed a high-fat diet, AHF). We also investigated possible alterations in mRNA levels after 50 days of a high-fat diet (high-fat challenge, CHF) at 19 weeks of age. Both SL and AHF conditions caused overweight during the period of developmental overfeeding. During adulthood, all of the mouse groups fed a CHF significantly gained weight in comparison with mice fed a low-fat diet, but the mice that had undergone both breast and adolescent overfeeding (SL-AHF-CHF mice) gained significantly more weight than the control CHF mice. Of the ten neuropeptide mRNAs studied, only neuropeptide Y (NPY) expression was decreased in all of the groups of developmentally overfed adult mice, but CHF during adulthood by itself induced a decrease in NPY, agouti-related protein (AgRP) and orexin (Orx) mRNA levels. Moreover, in the developmentally overfed CHF mice NPY, AgRP, galanin (GAL) and galanin-like peptide (GalP) mRNA levels significantly decreased in comparison with the control CHF mice. These results show that, during adulthood, hypothalamic neuropeptide systems are altered (NPY) and/or abnormally respond to a high-fat diet (NPY, AgRP, GAL and GalP) in mice overfed during critical developmental periods.

Maternal and postnatal overnutrition differentially impact appetite regulators and fuel metabolism.

Maternal obesity is increasing, and it is known that the intrauterine experience programs fetal and newborn metabolism. However, the relative contributions of pre- or postnatal factors are unknown. We hypothesized that maternal overnutrition caused by long-term maternal obesity would exert a stronger detrimental impact than postnatal overnutrition on offspring metabolic homeostasis, with additional postnatal overnutrition exaggerating these alterations. Female Sprague Dawley rats were exposed to chow or high-fat cafeteria diet for 5 wk before mating and throughout gestation and lactation. On postnatal d 1, litters were adjusted to three per litter to induce postnatal overnutrition (vs. 12 in control). Hypothalamic appetite regulators neuropeptide Y and proopiomelanocortin, glucose transporter 4, and lipid metabolic markers were measured. At postnatal d 20, male pups born of obese dams, or those overnourished postnatally, were 42% heavier than controls; combining both interventions led to 80% greater body weight. Maternal obesity increased pup adiposity and led to glucose intolerance in offspring; these were exaggerated by additional postnatal overnutrition during lactation. Maternal obesity was also linked to hyperlipidemia in offspring and reduced hypothalamic neuropeptide Y and increased proopiomelanocortin mRNA expression. Postnatal overnutrition of offspring from obese dams amplified these hypothalamic changes. Both maternal and postnatal overnutrition reduced muscle glucose transporter 4. Adipose carnitine palmitoyl-transferase-1 and adipose triglyceride lipase mRNA was up-regulated only by postnatal overnutrition. Maternal overnutrition appears to alter central appetite circuits and promotes early-onset obesity; postnatal overnutrition interacted to cause peripheral lipid and glucose metabolic disorders, supporting the critical message to reduce early-life adverse nutritional impact.

A new model for nonalcoholic steatohepatitis in the rat utilizing total enteral nutrition to overfeed a high-polyunsaturated fat diet.

We have used total enteral nutrition (TEN) to moderately overfeed rats high-polyunsaturated fat diets to develop a model for nonalcoholic steatohepatitis (NASH). Male Sprague-Dawley rats were fed by TEN a 187 kcal.kg(-3/4).day(-1) diet containing 5% (total calories) corn oil or a 220 kcal.kg(-3/4).day(-1) diet in which corn oil constituted 5, 10, 25, 35, 40, or 70% of total calories for 21 or 65 days. Rats fed the 5% corn oil, 220 kcal.kg(-3/4).day(-1)diet had greater body weight gain (P < or = 0.05), fat mass (P < or = 0.05), and serum leptin and glucose levels (P < or = 0.05), but no liver pathology. A dose-dependent increase in hepatic triglyceride deposition occurred with increase in percent corn oil in the 220 kcal.kg(-3/4).day(-1) groups (P < or = 0.05). Steatosis, macrophage infiltration, apoptosis, and focal necrosis were present in the 70% corn oil group, accompanied by elevated serum alanine aminotransferase (ALT) levels (P < or = 0.05). An increase in oxidative stress (thiobarbituric acid-reactive substances) and TNF-alpha expression (P < or = 0.05) was observed in the 70% corn oil group, as well as an increase in hepatic CYP2E1 and CYP4A1 expression (P < or = 0.05). Significant positive correlations were observed between the level of dietary corn oil and the degree of pathology, ALTs, oxidative stress, and inflammation. Liver pathology was progressive with increased necrosis, accompanied by fibrosis, observed after 65 days of TEN. Increased expression of CD36 and l-fabp mRNA suggested development of steatosis was associated with increased fatty acid transport. These data suggest that intragastric infusion of a high-polyunsaturated fat diet at a caloric level of 17% excess total calories results in pathology similar to clinical NASH.