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Exercise exerts a wide range of beneficial effects for healthy physiology1. However, the mechanisms regulating an individual’s motivation to engage in physical activity remain incompletely understood. An important factor stimulating the engagement in both competitive and recreational exercise is the motivating pleasure derived from prolonged physical activity, which is triggered by exercise-induced neurochemical changes in the brain. Here, we report on the discovery of a gut–brain connection in mice that enhances exercise performance by augmenting dopamine signalling during physical activity. We find that microbiome-dependent production of endocannabinoid metabolites in the gut stimulates the activity of TRPV1-expressing sensory neurons and thereby elevates dopamine levels in the ventral striatum during exercise. Stimulation of this pathway improves running performance, whereas microbiome depletion, peripheral endocannabinoid receptor inhibition, ablation of spinal afferent neurons or dopamine blockade abrogate exercise capacity. These findings indicate that the rewarding properties of exercise are influenced by gut-derived interoceptive circuits and provide a microbiome-dependent explanation for interindividual variability in exercise performance. Our study also suggests that interoceptomimetic molecules that stimulate the transmission of gut-derived signals to the brain may enhance the motivation for exercise.It is demonstrated that the brain circuitry involved in regulating the motivation for physical activity is not strictly central nervous system autonomous but is shaped by peripheral influences that originate in the intestinal microbial community. [ABSTRACT FROM AUTHOR]

The prevalence of obesity increases with age in humans and in rodents. Age‐related obesity is characterized by leptin resistance and associated with heightened risk of metabolic disorders. However, the effect of leptin resistance per se has been difficult to disentangle from other effects of aging. Here we demonstrate that celastrol, a natural phytochemical that was previously shown to act as a leptin sensitizer, induces weight loss in aged animals, but not in young controls. Celastrol reduces food intake and lowers fasting glucose without affecting energy expenditure. Unexpectedly, administration of celastrol just before the dark period disrupted circadian rhythms of sleep and activity. This regimen was also associated with loss of lean mass an outcome that would not be desirable in elderly patients. Adjusting the timing of celastrol administration by 12 hr, to the beginning of the light period, avoided interference with circadian rhythms while retaining the reductions in body weight and adiposity. Thus, targeting leptin signaling is an effective strategy to ameliorate age‐associated weight gain, and can profoundly impact circadian rhythms. [ABSTRACT FROM AUTHOR]

Purpose: Optical redox imaging (ORI) technique images cellular autofluorescence of nicotinamide adenine dinucleotide (NADH) and oxidized flavoproteins (Fp containing FAD, i.e., flavin adenine dinucleotide). ORI has found wide applications in the study of cellular energetics and metabolism and may potentially assist in disease diagnosis and prognosis. Fixed tissues have been reported to exhibit autofluorescence with similar spectral characteristics to those of NADH and Fp. However, few studies report on quantitative ORI of formalin-fixed paraffin-embedded (FFPE) unstained tissue slides for disease biomarkers. We investigate whether ORI of FFPE unstained skeletal muscle slides may provide relevant quantitative biological information.Procedures: Living mouse muscle fibers and frozen and FFPE mouse muscle slides were subjected to ORI. Living mouse muscle fibers were imaged ex vivo before and after paraformaldehyde fixation. FFPE muscle slides of three mouse groups (young, mid-age, and muscle-specific overexpression of nicotinamide phosphoribosyltransferase (Nampt) transgenic mid-age) were imaged and compared to detect age-related redox differences.Results: We observed that living muscle fiber and frozen and FFPE slides all had strong autofluorescence signals in the NADH and Fp channels. Paraformaldehyde fixation resulted in a significant increase in the redox ratio Fp/(NADH + Fp) of muscle fibers. Quantitative image analysis on FFPE unstained slides showed that mid-age gastrocnemius muscles had stronger NADH and Fp signals than young muscles. Gastrocnemius muscles from mid-age Nampt mice had lower NADH compared to age-matched controls, but had higher Fp than young controls. Soleus muscles had the same trend of change and appeared to be more oxidative than gastrocnemius muscles. Differential NADH and Fp signals were found between gastrocnemius and soleus muscles within both mid-aged control and Nampt groups.Conclusion: Aging effect on redox status quantified by ORI of FFPE unstained muscle slides was reported for the first time. Quantitative information from ORI of FFPE unstained slides may be useful for biomedical applications. [ABSTRACT FROM AUTHOR]

Background and aims: Associated with numerous metabolic and behavioral abnormalities, obesity is classified by metrics reliant on body weight (such as body mass index). However, overnutrition is the common cause of obesity, and may independently contribute to these obesity-related abnormalities. Here, we use dietary challenges to parse apart the relative influence of diet and/or energy balance from body weight on various metabolic and behavioral outcomes. Materials and methods: Seventy male mice (mus musculus) were subjected to the diet switch feeding paradigm, generating groups with various body weights and energetic imbalances. Spontaneous activity patterns, blood metabolite levels, and unbiased gene expression of the nutrient-sensing ventral hypothalamus (using RNA-sequencing) were measured, and these metrics were compared using standardized multivariate linear regression models. Results: Spontaneous activity patterns were negatively related to body weight (p<0.0001) but not diet/energy balance (p = 0.63). Both body weight and diet/energy balance predicted circulating glucose and insulin levels, while body weight alone predicted plasma leptin levels. Regarding gene expression within the ventral hypothalamus, only two genes responded to diet/energy balance (neuropeptide y [npy] and agouti-related peptide [agrp]), while others were related only to body weight. Conclusions: Collectively, these results demonstrate that individual components of obesity—specifically obesogenic diets/energy imbalance and elevated body mass—can have independent effects on metabolic and behavioral outcomes. This work highlights the shortcomings of using body mass-based indices to assess metabolic health, and identifies novel associations between blood biomarkers, neural gene expression, and animal behavior following dietary challenges. [ABSTRACT FROM AUTHOR]

The nuclear receptor hepatocyte nuclear factor 4α (HNF4α) is tumor suppressive in the liver but amplified in colon cancer, suggesting that it also might be oncogenic. To investigate whether this discrepancy is due to different HNF4α isoforms derived from its two promoters (P1 and P2), we generated Tet-On-inducible human colon cancer (HCT116) cell lines that express either the P1-driven (HNF4α2) or P2-driven (HNF4α8) isoform and analyzed them for tumor growth and global changes in gene expression (transcriptome sequencing [RNA-seq] and chromatin immunoprecipitation sequencing [ChIP-seq]). The results show that while HNF4α2 acts as a tumor suppressor in the HCT116 tumor xenograft model, HNF4α8 does not. Each isoform regulates the expression of distinct sets of genes and recruits, colocalizes, and competes in a distinct fashion with the Wnt/β-catenin mediator T-cell factor 4 (TCF4) at CTTTG motifs as well as at AP-1 motifs (TGAXTCA). Protein binding microarrays (PBMs) show that HNF4α and TCF4 share some but not all binding motifs and that single nucleotide polymorphisms (SNPs) in sites bound by both HNF4α and TCF4 can alter binding affinity in vitro, suggesting that they could play a role in cancer susceptibility in vivo. Thus, the HNF4α isoforms play distinct roles in colon cancer, which could be due to differential interactions with the Wnt/β-catenin/TCF4 and AP-1 pathways. [ABSTRACT FROM AUTHOR]

The nuclear receptor hepatocyte nuclear factor 4α (HNF4α) is tumor suppressive in the liver but amplified in colon cancer, suggesting that it also might be oncogenic. To investigate whether this discrepancy is due to different HNF4α isoforms derived from its two promoters (P1 and P2), we generated Tet-On-inducible human colon cancer (HCT116) cell lines that express either the P1-driven (HNF4α2) or P2-driven (HNF4α8) isoform and analyzed them for tumor growth and global changes in gene expression (transcriptome sequencing [RNA-seq] and chromatin immunoprecipitation sequencing [ChIP-seq]). The results show that while HNF4α2 acts as a tumor suppressor in the HCT116 tumor xenograft model, HNF4α8 does not. Each isoform regulates the expression of distinct sets of genes and recruits, colocalizes, and competes in a distinct fashion with the Wnt/β-catenin mediator T-cell factor 4 (TCF4) at CTTTG motifs as well as at AP-1 motifs (TGAXTCA). Protein binding microarrays (PBMs) show that HNF4α and TCF4 share some but not all binding motifs and that single nucleotide polymorphisms (SNPs) in sites bound by both HNF4α and TCF4 can alter binding affinity in vitro, suggesting that they could play a role in cancer susceptibility in vivo. Thus, the HNF4α isoforms play distinct roles in colon cancer, which could be due to differential interactions with the Wnt/β-catenin/TCF4 and AP-1 pathways. [ABSTRACT FROM AUTHOR]

The obesity epidemic in the U.S. has led to extensive research into potential contributing dietary factors, especially fat and fructose. Recently, increased consumption of soybean oil, which is rich in polyunsaturated fatty acids (PUFAs), has been proposed to play a causal role in the epidemic. Here, we designed a series of four isocaloric diets (HFD, SO-HFD, F-HFD, F-SO-HFD) to investigate the effects of saturated versus unsaturated fat, as well as fructose, on obesity and diabetes. C57/BL6 male mice fed a diet moderately high in fat from coconut oil and soybean oil (SO-HFD, 40% kcal total fat) showed statistically significant increases in weight gain, adiposity, diabetes, glucose intolerance and insulin resistance compared to mice on a diet consisting primarily of coconut oil (HFD). They also had fatty livers with hepatocyte ballooning and very large lipid droplets as well as shorter colonic crypt length. While the high fructose diet (F-HFD) did not cause as much obesity or diabetes as SO-HFD, it did cause rectal prolapse and a very fatty liver, but no balloon injury. The coconut oil diet (with or without fructose) increased spleen weight while fructose in the presence of soybean oil increased kidney weight. Metabolomics analysis of the liver showed an increased accumulation of PUFAs and their metabolites as well as γ-tocopherol, but a decrease in cholesterol in SO-HFD. Liver transcriptomics analysis revealed a global dysregulation of cytochrome P450 (Cyp) genes in SO-HFD versus HFD livers, most notably in the Cyp3a and Cyp2c families. Other genes involved in obesity (e.g., Cidec, Cd36), diabetes (Igfbp1), inflammation (Cd63), mitochondrial function (Pdk4) and cancer (H19) were also upregulated by the soybean oil diet. Taken together, our results indicate that in mice a diet high in soybean oil is more detrimental to metabolic health than a diet high in fructose or coconut oil. [ABSTRACT FROM AUTHOR]

Src tyrosine kinase has long been implicated in colon cancer but much remains to be learned about its substrates. The nuclear receptor hepatocyte nuclear factor 4α (HNF4α) has just recently been implicated in colon cancer but its role is poorly defined. Here we show that c-Src phosphorylates human HNF4α on three tyrosines in an interdependent and isoform-specific fashion. The initial phosphorylation site is a Tyr residue (Y14) present in the N-terminal A/B domain of P1but not P2-driven HNF4α. Phospho-Y14 interacts with the Src 5H2 domain, leading to the phosphorylation of two additional tyrosines in the ligand binding domain (LBD) in P1-HNF4α. Phosphomimetic mutants in the LBD decrease P1-HNF4α protein stability, nuclear localization and transactivation function. Immunohistochemical analysis of approximately 450 human colon cancer specimens (Stage III) reveals that P1-HNF4α is either lost or localized in the cytoplasm in approximately 80% of tumors, and that staining for active Src correlates with those events in a subset of samples. Finally, three SNPs in the human HNF4α protein, two of which are in the HNFαa F domain that interacts with the Src SH3 domain, increase phosphorylation by Src and decrease HNF4α protein stability and function, suggesting that individuals with those variants may be more susceptible to Src-mediated effects. This newly identified interaction between Src kinase and HNF4α has important implications for colon and other cancers. [ABSTRACT FROM AUTHOR]

The mechanistic target of rapamycin (mTOR) is an evolutionarily conserved protein kinase that regulates growth and metabolism. mTOR is found in two protein complexes, mTORC1 and mTORC2, that have distinct components and substrates and are both inhibited by rapamycin, a macrolide drug that robustly extends lifespan in multiple species including worms and mice. Although the beneficial effect of rapamycin on longevity is generally attributed to reduced mTORC1 signaling, disruption of mTORC2 signaling can also influence the longevity of worms, either positively or negatively depending on the temperature and food source. Here, we show that loss of hypothalamic mTORC2 signaling in mice decreases activity level, increases the set point for adiposity, and renders the animals susceptible to diet‐induced obesity. Hypothalamic mTORC2 signaling normally increases with age, and mice lacking this pathway display higher fat mass and impaired glucose homeostasis throughout life, become more frail with age, and have decreased overall survival. We conclude that hypothalamic mTORC2 is essential for the normal metabolic health, fitness, and lifespan of mice. Our results have implications for the use of mTORC2‐inhibiting pharmaceuticals in the treatment of brain cancer and diseases of aging. [ABSTRACT FROM AUTHOR]