Automatic deep learning-based assessment of spinopelvic coronal and sagittal alignment.

PURPOSE: The purpose of this study was to evaluate an artificial intelligence (AI) solution for estimating coronal and sagittal spinopelvic alignment on conventional uniplanar two-dimensional whole-spine radiograph. MATERIAL AND METHODS: This retrospective observational study included 100 patients (35 men, 65 women) with a median age of 14 years (IQR: 13, 15.25; age range: 3-64 years) who underwent conventional uniplanar two-dimensional whole-spine radiograph in standing position between January and July 2022. Ten most commonly used spinopelvic coronal and sagittal parameters were retrospectively measured without AI by a junior radiologist and approved or adjusted by a senior musculoskeletal radiologist to reach final measurements. Final measurements were used as the ground truth to assess AI performance for each parameter. AI performances were estimated using mean absolute errors (MAE), intraclass correlation coefficient (ICCs), and accuracy for selected clinically relevant thresholds. Readers visually classified AI outputs to assess reliability at a patient-level. RESULTS: AI solution showed excellent consistency without bias in coronal (ICCs ≥ 0.95; MAE ≤ 2.9° or 1.97 mm) and sagittal (ICCs ≥ 0.85; MAE ≤ 4.4° or 2.7 mm) spinopelvic evaluation, except for kyphosis (ICC = 0.58; MAE = 8.7°). AI accuracy to classify low Cobb angle, severe scoliosis or frontal pelvic asymmetry was 91% (95% CI: 85-96), 99% (95% CI: 97-100) and 94% (95% CI: 89-98), respectively. Overall, AI provided reliable measurements in 72/100 patients (72%). CONCLUSION: The AI solution used in this study for combined coronal and sagittal spinopelvic balance assessment provides results consistent with those of a senior musculoskeletal radiologist, and shows potential benefit for reducing workload in future routine implementation.

Lack of Hypothalamus Polysialylation Inducibility Correlates With Maladaptive Eating Behaviors and Predisposition to Obesity.

High variability exists in individual susceptibility to develop overweight in an obesogenic environment and the biological underpinnings of this heterogeneity are poorly understood. In this brief report, we show in mice that the vulnerability to diet-induced obesity is associated with low level of polysialic acid-neural cell adhesion molecule (PSA-NCAM), a factor of neural plasticity, in the hypothalamus. As we previously shown that reduction of hypothalamic PSA-NCAM is sufficient to alter energy homeostasis and promote fat storage under hypercaloric pressure, inter-individual variability in hypothalamic PSA-NCAM might account for the vulnerability to diet-induced obesity. These data support the concept that reduced plasticity in brain circuits that control appetite, metabolism and body weight confers risk for eating disorders and obesity.

Brain Control of Plasma Cholesterol Involves Polysialic Acid Molecules in the Hypothalamus.

The polysialic acid (PSA) is a large glycan that is added to cell-surface proteins during their post-translational maturation. In the brain, PSA modulates distances between cells and controls the plasticity of the nervous system. In the hypothalamus, PSA is involved in many aspects of energy balance including food intake, osmoregulation, circadian rhythm, and sleep. In this work, we investigated the role of hypothalamic PSA in the regulation of plasma cholesterol levels and distribution. We report that HFD consumption in mice rapidly increased plasma cholesterol, including VLDL, LDL, and HDL-cholesterol. Although plasma VLDL-cholesterol was normalized within the first week, LDL and HDL were still elevated after 2 weeks upon HFD. Importantly, we found that hypothalamic PSA removal aggravated LDL elevation and reduced HDL levels upon HFD. These results indicate that hypothalamic PSA controls plasma lipoprotein profile by circumventing the rise of LDL-to-HDL cholesterol ratio in plasma during overfeeding. Although mechanisms by which hypothalamic PSA controls plasma cholesterol homeostasis remains to be elucidated, these findings also suggest that low level of hypothalamic PSA might be a risk factor for dyslipidemia and cardiovascular diseases.

Plasticity of the Melanocortin System: Determinants and Possible Consequences on Food Intake.

The melanocortin system is one of the most important neuronal pathways involved in the regulation of food intake and is probably the best characterized. Agouti-related peptide (AgRP) and proopiomelanocortin (POMC) expressing neurons located in the arcuate nucleus of the hypothalamus are the key elements of this system. These two neuronal populations are sensitive to circulating molecules and receive many excitatory and inhibitory inputs from various brain areas. According to sensory and metabolic information they integrate, these neurons control different aspects of feeding behavior and orchestrate autonomic responses aimed at maintaining energy homeostasis. Interestingly, composition and abundance of pre-synaptic inputs onto arcuate AgRP and POMC neurons vary in the adult hypothalamus in response to changes in the metabolic state, a phenomenon that can be recapitulated by treatment with hormones, such as leptin or ghrelin. As described in other neuroendrocrine systems, glia might be determinant to shift the synaptic configuration of AgRP and POMC neurons. Here, we discuss the physiological outcome of the synaptic plasticity of the melanocortin system, and more particularly its contribution to the control of energy balance. The discovery of this attribute has changed how we view obesity and related disorders, and opens new perspectives for their management.

The histone acetyltransferase MOF activates hypothalamic polysialylation to prevent diet-induced obesity in mice.

Overfeeding causes rapid synaptic remodeling in hypothalamus feeding circuits. Polysialylation of cell surface molecules is a key step in this neuronal rewiring and allows normalization of food intake. Here we examined the role of hypothalamic polysialylation in the long-term maintenance of body weight, and deciphered the molecular sequence underlying its nutritional regulation. We found that upon high fat diet (HFD), reduced hypothalamic polysialylation exacerbated the diet-induced obese phenotype in mice. Upon HFD, the histone acetyltransferase MOF was rapidly recruited on the St8sia4 polysialyltransferase-encoding gene. Mof silencing in the mediobasal hypothalamus of adult mice prevented activation of the St8sia4 gene transcription, reduced polysialylation, altered the acute homeostatic feeding response to HFD and increased the body weight gain. These findings indicate that impaired hypothalamic polysialylation contribute to the development of obesity, and establish a role for MOF in the brain control of energy balance.

Cerebral cell renewal in adult mice controls the onset of obesity.

The hypothalamus plays a crucial role in the control of the energy balance and also retains neurogenic potential into adulthood. Recent studies have reported the severe alteration of the cell turn-over in the hypothalamus of obese animals and it has been proposed that a neurogenic deficiency in the hypothalamus could be involved in the development of obesity. To explore this possibility, we examined hypothalamic cell renewal during the homeostatic response to dietary fat in mice, i.e., at the onset of diet-induced obesity. We found that switching to high-fat diet (HFD) accelerated cell renewal in the hypothalamus through a local, rapid and transient increase in cell proliferation, peaking three days after introducing the HFD. Blocking HFD-induced cell proliferation by central delivery of an antimitotic drug prevented the food intake normalization observed after HFD introduction and accelerated the onset of obesity. This result showed that HFD-induced dividing brain cells supported an adaptive anorectic function. In addition, we found that the percentage of newly generated neurons adopting a POMC-phenotype in the arcuate nucleus was increased by HFD. This observation suggested that the maturation of neurons in feeding circuits was nutritionally regulated to adjust future energy intake. Taken together, these results showed that adult cerebral cell renewal was remarkably responsive to nutritional conditions. This constituted a physiological trait required to prevent severe weight gain under HFD. Hence this report highlighted the amazing plasticity of feeding circuits and brought new insights into our understanding of the nutritional regulation of the energy balance.

A high-fat diet increases L-carnitine synthesis through a differential maturation of the Bbox1 mRNAs.

l-carnitine is a key molecule in both mitochondrial and peroxisomal lipid metabolisms. l-carnitine is biosynthesized from gamma-butyrobetaine by a reaction catalyzed by the gamma-butyrobetaine hydroxylase (Bbox1). The aim of this work was to identify molecular mechanisms involved in the regulation of l-carnitine biosynthesis and availability. Using 3' RACE, we identified four alternatively polyadenylated Bbox1 mRNAs in rat liver. We utilized a combination of in vitro experiments using hybrid constructs containing the Bbox1 3' UTR and in vivo experiments on rat liver mRNAs to reveal specificities in the different Bbox1 mRNA isoforms, especially in terms of polyadenylation efficiency, mRNA stability and translation efficiency. This complex maturation process of the Bbox1 mRNAs in the liver was studied on rats fed a high-fat diet. High-fat diet selectively increased the level of three Bbox1 mRNA isoforms in rat liver and the alternative use of polyadenylation sites contributed to the global increase in Bbox1 enzymatic activity and l-carnitine levels. Our results show that the maturation of Bbox1 mRNAs is nutritionally regulated in the liver through a selective polyadenylation process to adjust l-carnitine biosynthesis to the energy supply.

Hypothalamus-olfactory system crosstalk: orexin a immunostaining in mice.

It is well known that olfaction influences food intake, and conversely, that an individual's nutritional status modulates olfactory sensitivity. However, what is still poorly understood is the neuronal correlate of this relationship, as well as the connections between the olfactory bulb and the hypothalamus. The goal of this report is to analyze the relationship between the olfactory bulb and hypothalamus, focusing on orexin A immunostaining, a hypothalamic neuropeptide that is thought to play a role in states of sleep/wakefulness. Interestingly, orexin A has also been described as a food intake stimulator. Such an effect may be due in part to the stimulation of the olfactory bulbar pathway. In rats, orexin positive cells are concentrated strictly in the lateral hypothalamus, while their projections invade nearly the entire brain including the olfactory system. Therefore, orexin appears to be a good candidate to play a pivotal role in connecting olfactory and hypothalamic pathways. So far, orexin has been described in rats, however, there is still a lack of information concerning its expression in the brains of adult and developing mice. In this context, we revisited the orexin A pattern in adult and developing mice using immunohistological methods and confocal microscopy. Besides minor differences, orexin A immunostaining in mice shares many features with those observed in rats. In the olfactory bulb, even though there are few orexin projections, they reach all the different layers of the olfactory bulb. In contrast to the presence of orexin projections in the main olfactory bulb, almost none have been found in the accessory olfactory bulb. The developmental expression of orexin A supports the hypothesis that orexin expression only appears post-natally.

Food intake adaptation to dietary fat involves PSA-dependent rewiring of the arcuate melanocortin system in mice.

Hormones such as leptin and ghrelin can rapidly rewire hypothalamic feeding circuits when injected into rodent brains. These experimental manipulations suggest that the hypothalamus might reorganize continually in adulthood to integrate the metabolic status of the whole body. In this study, we examined whether hypothalamic plasticity occurs in naive animals according to their nutritional conditions. For this purpose, we fed mice with a short-term high-fat diet (HFD) and assessed brain remodeling through its molecular and functional signature. We found that HFD for 3 d rewired the hypothalamic arcuate nucleus, increasing the anorexigenic tone due to activated pro-opiomelanocortin (POMC) neurons. We identified the polysialic acid molecule (PSA) as a mediator of the diet-induced rewiring of arcuate POMC. Moreover, local pharmacological inhibition and genetic disruption of the PSA signaling limits the behavioral and metabolic adaptation to HFD, as treated mice failed to normalize energy intake and showed increased body weight gain after the HFD challenge. Altogether, these findings reveal the existence of physiological hypothalamic rewiring involved in the homeostatic response to dietary fat. Furthermore, defects in the hypothalamic plasticity-driven adaptive response to HFD are obesogenic and could be involved in the development of metabolic diseases.

RNA polymerase II C-terminal heptarepeat domain Ser-7 phosphorylation is established in a mediator-dependent fashion.

The largest subunit of RNA polymerase II (RNAPII) C-terminal heptarepeat domain (CTD) is subject to phosphorylation during initiation and elongation of transcription by RNA polymerase II. Here we study the molecular mechanisms leading to phosphorylation of Ser-7 in the human enzyme. Ser-7 becomes phosphorylated before initiation of transcription at promoter regions. We identify cyclin-dependent kinase 7 (CDK7) as one responsible kinase. Phosphorylation of both Ser-5 and Ser-7 is fully dependent on the cofactor complex Mediator. A subform of Mediator associated with an active RNAPII is critical for preinitiation complex formation and CTD phosphorylation. The Mediator-RNAPII complex independently recruits TFIIB and CDK7 to core promoter regions. CDK7 phosphorylates Ser-7 selectively in the context of an intact preinitiation complex. CDK7 is not the only kinase that can modify Ser-7 of the CTD. ChIP experiments with chemical inhibitors provide evidence that other yet to be identified kinases further phosphorylate Ser-7 in coding regions.

L-carnitine supplementation and physical exercise restore age-associated decline in some mitochondrial functions in the rat.

In mammals, during the aging process, an atrophy of the muscle fibers, an increase in body fat mass, and a decrease in skeletal muscle oxidative capacities occur. Compounds and activities that interact with lipid oxidative metabolism may be useful in limiting damages that occur in aging muscle. In this study, we evaluated the effect of L-carnitine and physical exercise on several parameters related to muscle physiology. We described that supplementing old rats with L-carnitine at 30 mg/kg body weight for 12 weeks (a) allowed the restoration of L-carnitine level in muscle cells, (b) restored muscle oxidative activity in the soleus, and (c) induced positive changes in body composition: a decrease in abdominal fat mass and an increase in muscle capabilities without any change in food intake. Moderate physical exercise was also effective in (a) limiting fat mass gain and (b) inducing an increase in the capacities of the soleus to oxidize fatty acids.

Hormonal and nutritional control of L-carnitine uptake in myoblastic C2C12 cells.

L-Carnitine plays an important role in skeletal muscle bioenergetics, and its bioavailability and thus its import may be crucial for muscle function. We studied the effect of thyroid hormone, insulin, and iron overload, hormones and nutrients known to alter muscle metabolism, on L-carnitine import into C2C12 cells. We report here L-carnitine uptake is increased by thyroid hormones and decreased by iron. Insulin was found to be ineffective in altering the L-carnitine uptake.

Extracellular ATP increases L-carnitine transport and content in C2C12 cells.

Extracellular ATP regulates cell proliferation, muscle contraction and myoblast differentiation. ATP present in the muscle interstitium can be released from contracting skeletal muscle cells. L-Carnitine is a key element in muscle cell metabolism, as it serves as a carrier for fatty acid through mitochondrial membranes, controlling oxidation and energy production. Treatment of C2C12 cells with 1 mmol/l of ATP induced a marked increase in L-carnitine uptake that was associated with an increase in L-carnitine content in these cells. These effects were found to be dependent on the density of the cultured cells and on the dose of ATP. The use of specific inhibitors of P2X and P2Y receptors abolished the effect of ATP on L-carnitine metabolism. As ATP can be released from stressed or exercising cells, it can be hypothesized that ATP acts as a messenger in the muscle. ATP will be released to recruit the next cells and increase their metabolism.

Changes in l-carnitine content of fish and meat during domestic cooking.

Human adults store around 20g of l-carnitine. In the human body, l-carnitine is not metabolized but excreted through the kidney. Lost l-carnitine has to be replenished either by a biosynthetic mechanism or by the consumption of foods containing l-carnitine. Today, there is no "official" recommended daily allowance for l-carnitine but the daily need for l-carnitine intake has been estimated in the wide range of 2-12µmol/day/kg body weight for an adult human. In this study we evaluated the effect of freezing and of different cooking methods on the l-carnitine content of red meat and fish. l-carnitine was abundantly present in all beef products analyzed. The amounts in the various cuts were similar and our data showed that freezing or cooking did not modify l-carnitine content. Salmon contained about 12 times less l-carnitine than beef but except in smoked salmon, cooking or freezing did not alter l-carnitine content. This study confirms the important role that meet products play for providing adequate amount of l-carnitine to the human body.

Characteristics of L-carnitine import into heart cells.

L-carnitine is an essential cofactor for the transport of fatty acids across the mitochondrial membranes. L-carnitine can be provided by food products or biosynthesized in the liver. After intestinal absorption or hepatic biosynthesis, L-carnitine is transferred to organs whose metabolism is dependent upon fatty acid oxidation, such as the skeletal muscle and the heart. The intracellular transport of L-carnitine into the cell requires specific transporters and today, several of these have been characterized. Most of them belong to the solute carrier family. Heart is one of the major target for carnitine transport and use, however basic properties of carnitine uptake by heart cells have never been studied. In this paper, the transport of L-carnitine by rat heart explants has been examined and the kinetic properties of this transport determined and compared to data obtained in skeletal muscle explants. As in muscle, L-carnitine uptake by heart cells was shown to be dependent on sodium and was inhibited by L-carnitine analogues. Molecules known to interact with the skeletal muscle L-carnitine transport were studied in the heart. While trimethyl hydrazinium propionate (THP) was shown to fully inhibit the L-carnitine uptake by muscle cells, it remained inefficient in inhibiting the L-carnitine uptake by heart cells. On the other hand, compounds such as verapamil and AZT were both able to inhibit both the skeletal muscle and the cardiac uptake of L-carnitine. These data suggested that the muscle and heart systems for L-carnitine uptake exhibited different systems of regulation and these results have to be taken in consideration while administrating those compounds that can alter l-carnitine uptake in the muscle and the heart and can lead to damage to these tissues.

Genomic structure, alternative maturation and tissue expression of the human BBOX1 gene.

Gamma-butyrobetaine hydroxylase (BBOX1) is the enzyme responsible for the biosynthesis of l-carnitine, a key molecule of fatty acid metabolism. This cytosolic dimeric protein belongs to the dioxygenase family. In human, enzyme activity has been detected in kidney, liver and brain. The human gene encoding gamma-butyrobetaine hydroxylase is located on chromosome 11. Although the protein structure and activity have been extensively described, little information is available concerning BBOX1 structure and expression. In this study, the organization of the human gene was determined. The structure and functions of the 5'- and 3'-untranslated regions of the human BBOX1 mRNA were characterized in kidney, liver and brain. Our experiments revealed that the transcription initiation of the human BBOX1 gene might occur at 3 different exons, and that the expression level of each type of transcript is organ-specific. We showed that the use of 3 different promoters is responsible for the 5'-end heterogeneity. Investigations on BBOX1 mRNA maturation highlighted an alternative polyadenylation mechanism that generates two 3'-untranslated regions differing by their length. This alternative polyadenylation exhibited a tissue specificity.

Beneficial effects of L-carnitine in myoblastic C2C12 cells. Interaction with zidovudine.

L-Carnitine is a key molecule in the transfer of fatty acid across mitochondrial membranes. Bioavailable L-carnitine is either provided by an endogeneous biosynthesis or after intestinal absorption of dietary items containing L-carnitine. After intestinal absorption or hepatic biosynthesis, L-carnitine is transferred to organs whose metabolism is dependent upon fatty acid oxidation, such as skeletal muscle. To cross the muscle plasma membrane, there are several transporters involved. Among those transporters, OCTN2 is actually the only one to have been clearly characterized. Zidovudine is a commonly used inhibitor of human immunodeficiency virus (HIV) replication. Zidovudine has many side effects, including induction of myopathy characterized by a metabolic mitochondria dysfunction and a diminution of the muscle L-carnitine content. In this study, we described the characteristics of L-carnitine transport in C2C12 cells. We also demonstrated that zidovudine inhibited the L-carnitine transporter. This inhibition led to a significant reduction of the muscle cell growth. In C2C12 cells, the supplementation of L-carnitine prevented the effects of zidovudine and restored the normal cell growth.