Obesity in male volcano mice Neotomodon alstoni affects the daily rhythm of metabolism and thermoregulation.

The mouse N. alstoni spontaneously develops the condition of obesity in captivity when fed regular chow. We aim to study the differences in metabolic performance and thermoregulation between adult lean and obese male mice. The experimental approach included indirect calorimetry using metabolic cages for VO2 intake and VCO2 production. In contrast, the body temperature was measured and analyzed using intraperitoneal data loggers. It was correlated with the relative presence of UCP1 protein and its gene expression from interscapular adipose tissue (iBAT). We also explored in this tissue the relative presence of Tyrosine Hydroxylase (TH) protein, the rate-limiting enzyme for catecholamine biosynthesis present in iBAT. Results indicate that obese mice show a daily rhythm persists in estimated parameters but with differences in amplitude and profile. Obese mice presented lower body temperature, and a low caloric expenditure, together with lower VO2 intake and VCO2 than lean mice. Also, obese mice present a reduced thermoregulatory response after a cold pulse. Results are correlated with a low relative presence of TH and UCP1 protein. However, qPCR analysis of Ucp1 presents an increase in gene expression in iBAT. Histology showed a reduced amount of brown adipocytes in BAT. The aforementioned indicates that the daily rhythm in aerobic metabolism, thermoregulation, and body temperature control have reduced amplitude in obese mice Neotomodon alstoni.

Obese Neotomodon alstoni mice exhibit sexual dimorphism in the daily profile of circulating melatonin and clock proteins PER1 and BMAL1 in the hypothalamus and peripheral oscillators.

Obesity is a global health threat and a risk factor for several metabolic conditions. Though circadian dysfunction has been considered among the multiple causes of obesity, little work has been done to explore the relationship between obesity, circadian dysfunction, and sexual dimorphism. The Neotomodon alstoni mouse is a suitable model for such research. This study employed N. alstoni mice in a chronobiological analysis to determine whether there is circadian desynchronization of relative PER1 and BMAL1 protein levels in the hypothalamus, liver, visceral white adipose tissue, kidney, and heart. It also compared differences between sexes and lean and obese N. alstoni adult mice, by recording behavior and daily circulating serum melatonin as markers of circadian output. We found that obese mice display reduced locomotor activity. Additionally, Cosinor analyses of the relative expression of PER1 and BMAL1 show differences between lean and obese mice in a sex-linked manner. The PER1 24 h rhythm was absent in all tissues of obese males and significant in the tissues of obese females. The BMAL1 24 h rhythm also was significant in most of the tissues tested in lean males, whereas it was significant and shifted the acrophase (peak time of rhythm) in most of the tissues in obese females. Both lean male and female mice showed a rhythmic 24 h pattern of circulating serum melatonin. This daily profile was not only absent in obese mice of both sexes but showed sexual dimorphism. Obese male mice showed lower circulating levels of melatonin compared to lean male mice, but they were higher in obese females compared to lean females. Our results suggest that obesity in N. alstoni is associated with an internal circadian desynchronization in a sex-dependent manner. Overall, this study reinforces the need for further research on the neuroendocrinology of obesity and circadian rhythms using this biological model.

"Evening chronotype associates with increased triglyceride levels in young adults in two independent populations".

BACKGROUND & AIMS: Evening chronotype has been linked with obesity, diabetes and metabolic syndrome (MetS) in middle-aged and older adults. However, few studies have analyzed this association in young adults. The aim of this study was to assess potential associations between individual chronotype and cardiometabolic outcomes in young adults of two independent populations from Europe and America. METHODS: Total population comprised 2 223 young adults (18-29 years old), 525 from Spain (Europe) and 1 698 from Mexico (America). Anthropometric, body composition and biochemical analyses were performed. Circadian preference was determined using the Morningness-Eveningness Questionnaire (MEQ). RESULTS: In these two young adult populations, a higher metabolic risk was found in those individuals with evening chronotypes, whereas those with neither or morning chronotypes showed lower cardiometabolic risk. Evening chronotypes showed lipid alterations with increased levels of triglycerides in both populations, VLDL-c in Spaniards and total cholesterol and LDL-c in Mexicans. Among the Mexican population, evening chronotypes showed higher MetS risk and more obesity traits than the other two chronotypes; no significant differences for the same comparison were found among the equivalent Spanish chronotypes. Evening chronotypes showed lower carbohydrates and higher fat intake in Spaniards, while they had lower fiber intake in Mexicans. The associations between MEQ score and cardiometabolic risk were independent of the dietary characteristics. Lifestyle factors differed among chronotypes with more smokers and habitual drinkers among evening chronotypes than in neither or morning chronotypes (P < 0.05). CONCLUSIONS: This study performed in two American and European independent populations shows that even in apparently healthy young adults, evening chronotypes have increased cardiometabolic risk and lipid alterations as compared to neither or morning chronotypes.

Daily cycle in hepatic lipid metabolism in obese mice, Neotomodon alstoni: Sex differences.

Disruption of circadian rhythms influences the pathogenesis of obesity, particularly with the basic regulation of food intake and metabolism. A link between metabolism and the circadian clock is the peroxisome proliferator-activated receptors (PPARs). The Neotomodon alstoni mouse, known as the "Mexican volcano mouse," may develop obesity if fed a normo-caloric diet. This manuscript documents the changes in part of the hepatic lipid homeostasis in both sexes of lean and obese N. alstoni mice, comparing the daily changes in the BMAL1 clock protein, in regulators of lipid metabolism (PGC-1α, PPARα-γ, SREBP-1c, and CPT-1α) and in free fatty acid (FFA) and hepatic triacylglyceride (TAG) metabolites in light-dark cycles. Hepatic tissue and blood were collected at 5, 10, 15, 19, and 24 h. Samples were analyzed by western blotting to determine the relative presence of protein. The results indicate that obesity affects daily changes in lipid metabolism and the BMAL1 profile in females considerably more than in males. These results suggest that the impact of obesity on lipid metabolism has important differences according to sex.

Neotomodon alstoni mice present sex differences between lean and obese in daily hypothalamic leptin signaling.

This article compared the effects of spontaneous obesity on the daily profile in the relative amount of the leptin receptor (LepRb), and its output. That is the precursor Pro-opiomelanocortin (POMC) over a 24-hour period and compared with differences in locomotion and food intake in periods of artificial light. Differences between lean and obese mice were examined, as were sex differences. Body weight, food intake and locomotor activity were monitored in freely moving lean and obese mice. Hypothalamic tissue was collected at 5 h, 10 h, 15 h, 19 h and 24 h. Samples were analyzed by western blotting to determine the relative presence of protein for LepRb, STAT3 phosphorylation (by pSTAT3/STAT3 ratio) and POMC. Obese mice were 60% less active in locomotion than lean mice during the night. While both locomotor activity and food intake were noticeably greater during the day in obese mice than in lean mice, the hypothalamus in obese mice showed a lower relative abundance of POMC and reduced pSTAT3/STAT3 ratio and leptin receptors. Behavioral and biochemical differences were more evident in obese females than in obese males. These results indicate that obesity in N. alstoni affects hypothalamic leptin signaling according to sex.

Restricted feeding modulates the daily variations of liver glutamate dehydrogenase activity, expression, and histological location.

Glutamate dehydrogenase is an important enzyme in the hepatic regulation of nitrogen and energy metabolism. It catalyzes one of the most relevant anaplerotic reactions. Although its relevance in liver homeostasis has been widely described, its daily pattern and responsiveness to restricted feeding protocols has not been studied. We explored the daily variations of liver glutamate dehydrogenase transcription, protein, activity, and histochemical and subcellular location in a protocol of daytime food synchronization in rats. Restricted feeding involved food access for 2 h each day for three weeks. Control groups included food ad libitum as well as acute fasting (21 h fasting) and refeeding (22 h fasting followed by 2 h of food access). Glutamate dehydrogenase mRNA, protein, activity, and histological location were measured every 3 h by qPCR, Western blot, spectrophotometry, and immunohistochemistry, respectively, to generate 24-h profiles. Restricted feeding promoted higher levels of mitochondrial glutamate dehydrogenase protein and activity, as well as a loss of 24-h rhythmicity, in comparison to ad libitum conditions. The rhythmicity of glutamate dehydrogenase activity detected in serum was changed. The data demonstrated that daytime restricted feeding enhanced glutamate dehydrogenase protein and activity levels in liver mitochondria, changed the rhythmicity of its mRNA and serum activity, but without effect in its expression in hepatocytes surrounding central and portal veins. These results could be related to the adaptation in nitrogen and energy metabolism that occurs in the liver during restricted feeding and the concomitant expression of the food entrainable oscillator. Impact statement For the first time, we are reporting the changes in daily rhythmicity of glutamate dehydrogenase (GDH) mRNA, protein and activity that occur in the liver during the expression of the food entrained oscillator (FEO). These results are part of the metabolic adaptations that modulate the hepatic timing system when the protocol of daytime restricted feeding is applied. As highlight, it was demonstrated higher GDH protein and activity in the mitochondrial fraction. These results contribute to a better understanding of the influence of the FEO in the energy and nitrogen handling in the liver. They could also be significant in the pathophysiology of hepatic diseases related with circadian abnormalities.

Daytime restricted feeding modifies the daily variations of liver gluconeogenesis: adaptations in biochemical and endocrine regulators.

Daytime restricted feeding (DRF) promotes circadian adaptations in the metabolic processing of nutrients. We explored the hepatic gluconeogenic response in DRF rats by the temporal profiles of the following: (1) the activity of glucose 6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK), as well as the periportal and pericentral distribution of PEPCK; (2) conversion of alanine to glucose; (3) glycemia and liver glycogen content; (4) presence of glycogen synthase (GYS) and its phosphorylated form (at Ser641, pGYS); (5) circulating levels of corticosterone, glucagon and insulin; (6) glucose-tolerance test; and (7) sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor-coactivator 1α (PGC-1α). The results showed that DRF promoted: (1) a phase shift in G6Pase activity and an increase in PEPCK activity as well as a change of PEPCK from periportal to pericentral hepatocytes, (2) a net conversion of alanine to circulating glucose, (3) a decrease in glycemic values and a phase shift in the liver glycogen content, (4) a phase shift in GYS and an increase of pGYS, (5) an increase in the daily levels of corticosterone and glucagon, but a reduction in the levels of insulin, (6) normal glucose homeostasis in all groups and (7) an enhanced presence of SIRT1 and PGC-1α. It is proposed that the increased gluconeogenic in DRF group promotes synthesis of hepatic glycogen and the production of glucose. These results could be a modulation of the gluconeogenic process due to rheostatic adaptations in the endocrine, metabolic and timing regulation of liver and could be associated with the physiology of the food entrained oscillator.