Intermittent glucocorticoid treatment improves muscle metabolism via the PGC1α/Lipin1 axis in an aging-related sarcopenia model.

Sarcopenia burdens the older population through loss of muscle energy and mass, yet treatments to functionally rescue both parameters are lacking. The glucocorticoid prednisone remodels muscle metabolism on the basis of frequency of intake, but its mechanisms in sarcopenia are unknown. We found that once-weekly intermittent prednisone administration rescued muscle quality in aged 24-month-old mice to a level comparable to that seen in young 4-month-old mice. We discovered an age- and sex-independent glucocorticoid receptor transactivation program in muscle encompassing peroxisome proliferator-activated receptor γ coactivator 1 α (PGC1α) and its cofactor Lipin1. Treatment coordinately improved mitochondrial abundance through isoform 1 and muscle mass through isoform 4 of the myocyte-specific PGC1α, which was required for the treatment-driven increase in carbon shuttling from glucose oxidation to amino acid biogenesis. We also probed myocyte-specific Lipin1 as a nonredundant factor coaxing PGC1α upregulation to the stimulation of both oxidative and anabolic effects. Our study unveils an aging-resistant druggable program in myocytes for the coordinated rescue of energy and mass in sarcopenia.

Impact of circadian time of dosing on cardiomyocyte-autonomous effects of glucocorticoids.

OBJECTIVE: Mitochondrial capacity is critical to adapt the high energy demand of the heart to circadian oscillations and diseased states. Glucocorticoids regulate the circadian cycle of energy metabolism, but little is known about how circadian timing of exogenous glucocorticoid dosing directly regulates heart metabolism through cardiomyocyte-autonomous mechanisms. While chronic once-daily intake of glucocorticoids promotes metabolic stress and heart failure, we recently discovered that intermittent once-weekly dosing of exogenous glucocorticoids promoted muscle metabolism in normal and obese skeletal muscle. However, the effects of glucocorticoid intermittence on heart metabolism and heart failure remain unknown. Here we investigated the extent to which circadian time of dosing regulates the effects of the glucocorticoid prednisone in heart metabolism and function in conditions of single pulse or chronic intermittent dosing. METHODS AND RESULTS: In WT mice, we found that prednisone improved cardiac content of NAD+ and ATP with light-phase dosing (ZT0), while the effects were blocked by dark-phase dosing (ZT12). The drug effects on mitochondrial function were cardiomyocyte-autonomous, as shown by inducible cardiomyocyte-restricted glucocorticoid receptor (GR) ablation, and depended on an intact cardiomyocyte clock, as shown by inducible cardiomyocyte-restricted ablation of Brain and Muscle ARNT-like 1 (BMAL1). Conjugating time-of-dosing with chronic intermittence, we found that once-weekly prednisone improved metabolism and function in heart after myocardial injury dependent on circadian time of intake, i.e. with light-phase but not dark-phase dosing. CONCLUSIONS: Our study identifies cardiac-autonomous mechanisms through which circadian-specific intermittent dosing reconverts glucocorticoid drugs to metabolic boosters for the heart.

Nutrient sensitive protein O-GlcNAcylation modulates the transcriptome through epigenetic mechanisms during embryonic neurogenesis.

Protein O-GlcNAcylation is a dynamic, nutrient-sensitive mono-glycosylation deposited on numerous nucleo-cytoplasmic and mitochondrial proteins, including transcription factors, epigenetic regulators, and histones. However, the role of protein O-GlcNAcylation on epigenome regulation in response to nutrient perturbations during development is not well understood. Herein we recapitulated early human embryonic neurogenesis in cell culture and found that pharmacological up-regulation of O-GlcNAc levels during human embryonic stem cells' neuronal differentiation leads to up-regulation of key neurogenic transcription factor genes. This transcriptional de-repression is associated with reduced H3K27me3 and increased H3K4me3 levels on the promoters of these genes, perturbing promoter bivalency possibly through increased EZH2-Thr311 phosphorylation. Elevated O-GlcNAc levels also lead to increased Pol II-Ser5 phosphorylation and affect H2BS112O-GlcNAc and H2BK120Ub1 on promoters. Using an in vivo rat model of maternal hyperglycemia, we show similarly elevated O-GlcNAc levels and epigenetic dysregulations in the developing embryo brains because of hyperglycemia, whereas pharmacological inhibition of O-GlcNAc transferase (OGT) restored these molecular changes. Together, our results demonstrate O-GlcNAc mediated sensitivity of chromatin to nutrient status, and indicate how metabolic perturbations could affect gene expression during neurodevelopment.

Intermittent prednisone treatment in mice promotes exercise tolerance in obesity through adiponectin.

The fat-muscle communication regulates metabolism and involves circulating signals like adiponectin. Modulation of this cross-talk could benefit muscle bioenergetics and exercise tolerance in conditions like obesity. Chronic daily intake of exogenous glucocorticoids produces or exacerbates metabolic stress, often leading to obesity. In stark contrast to the daily intake, we discovered that intermittent pulses of glucocorticoids improve dystrophic muscle metabolism. However, the underlying mechanisms, particularly in the context of obesity, are still largely unknown. Here we report that in mice with diet-induced obesity, intermittent once-weekly prednisone increased total and high-molecular weight adiponectin levels and improved exercise tolerance and energy expenditure. These effects were dependent upon adiponectin, as shown by genetic ablation of the adipokine. Upregulation of Adipoq occurred through the glucocorticoid receptor (GR), as this effect was blocked by inducible GR ablation in adipocytes. The treatment increased the muscle metabolic response of adiponectin through the CAMKK2-AMPK cascade. Our study demonstrates that intermittent glucocorticoids produce healthful metabolic remodeling in diet-induced obesity.

Higher O-GlcNAc Levels Are Associated with Defects in Progenitor Proliferation and Premature Neuronal Differentiation during in-Vitro Human Embryonic Cortical Neurogenesis.

The nutrient responsive O-GlcNAcylation is a dynamic post-translational protein modification found on several nucleocytoplasmic proteins. Previous studies have suggested that hyperglycemia induces the levels of total O-GlcNAcylation inside the cells. Hyperglycemia mediated increase in protein O-GlcNAcylation has been shown to be responsible for various pathologies including insulin resistance and Alzheimer's disease. Since maternal hyperglycemia during pregnancy is associated with adverse neurodevelopmental outcomes in the offspring, it is intriguing to identify the effect of increased protein O-GlcNAcylation on embryonic neurogenesis. Herein using human embryonic stem cells (hESCs) as model, we show that increased levels of total O-GlcNAc is associated with decreased neural progenitor proliferation and premature differentiation of cortical neurons, reduced AKT phosphorylation, increased apoptosis and defects in the expression of various regulators of embryonic corticogenesis. As defects in proliferation and differentiation during neurodevelopment are common features of various neurodevelopmental disorders, increased O-GlcNAcylation could be one mechanism responsible for defective neurodevelopmental outcomes in metabolically compromised pregnancies such as diabetes.

Serum Anti-Cryptosporidial gp15 Antibodies in Mothers and Children Less than 2 Years of Age in India.

Little is known about the type and longevity of the humoral response to cryptosporidial infections in developing countries. We evaluated serum antibody response to Cryptosporidium gp15 in 150 sets of maternal, preweaning and postinfection/end-of-follow-up sera from children followed up to 2 years of age to determine the influence of maternal and preweaning serological status on childhood cryptosporidiosis. Fifty two percent (N = 78) of mothers and 20% (N = 30) of children were seropositive preweaning. However, most positive preweaning samples from children were collected early in life indicating transplacental transfer and subsequent rapid waning of antibodies. Although 62% (N = 94) of children had a parasitologically confirmed cryptosporidial infection (detected by stool polymerase chain reaction) during the follow-up, only 54% (N = 51) of children were seropositive postinfection. Given there were striking differences in seropositivity depending on when the sample was collected, even though Cryptosporidium was detected in the stool of the majority of the children, this study indicates that antibodies wane rapidly. During follow-up, the acquisition or severity of cryptosporidial infections was not influenced by maternal (P = 0.331 and 0.720, respectively) as well as the preweaning serological status of the child (P = 0.076 and 0.196, respectively).

Risk factors for cryptosporidiosis among children in a semi urban slum in southern India: a nested case-control study.

The risk factors for acquisition of cryptosporidial infection in resource-poor settings are poorly understood. A nested case-control study was conducted to assess factors associated with childhood cryptosporidiosis (detected by stool polymerase chain reaction) in an endemic, Indian slum community using data from two community-based studies with 580 children followed prospectively until their second birthday. Factors were assessed for overall cryptosporidiosis (N = 406), and for multiple (N = 208), asymptomatic (N = 243), and symptomatic (N = 163) infections, respectively. Presence of older siblings (odds ratio [OR] = 1.88, P = 0.002) and stunting at 6 months of age (OR = 1.74, P = 0.019) were important risk factors for childhood cryptosporidiosis. Always boiling drinking water before consumption, the use of a toilet by all members of the family, and maternal age ≥ 23 years were protective. These results provide insights into acquisition of childhood cryptosporidiosis in settings with poor environmental sanitation, contaminated public water supply systems, and close human-animal contact. Disease control strategies will require a multifaceted approach.

Cryptosporidiosis among children in an endemic semiurban community in southern India: does a protected drinking water source decrease infection?

BACKGROUND: A quasi-experimental study was conducted to determine whether or not a protected water supply (bottled drinking water) could prevent or delay cryptosporidial infections among children residing in an endemic community. METHODS: A total of 176 children residing in a semiurban slum area in southern India were enrolled preweaning and received either bottled (n = 90) or municipal (n = 86) drinking water based on residence in specific streets. Weekly surveillance visits were conducted until children reached their second birthday. Stool samples were collected every month and during diarrheal episodes, and were tested for the presence of Cryptosporidium species by polymerase chain reaction. Differences in the incidence of cryptosporidiosis between bottled and municipal water groups were compared using Poisson survival models, and a propensity score model was developed to adjust for the effect of potential confounders. RESULTS: A total of 186 episodes of cryptosporidiosis, mostly asymptomatic, were observed in 118 (67%) children during the follow-up period at a rate of 0.59 episodes per child-year. Diarrhea associated with Cryptosporidium species tended to be longer in duration and more severe. Stunting at 6 months was associated with a higher risk of cryptosporidiosis (rate ratio [RR] = 1.40; 95% confidence interval [CI], 1.03-1.91). A higher gastrointestinal disease burden was also seen in children with cryptosporidiosis. Drinking bottled water was not associated with a reduced risk of cryptosporidiosis (adjusted RR = 0.86; 95% CI, .60-1.23). CONCLUSIONS: This study documented a high burden of cryptosporidiosis among children in an endemic Indian slum community. The lack of association between drinking bottled water and cryptosporidiosis suggests possible spread from asymptomatically infected individuals involving multiple transmission pathways.