Context-dependent regulation of lipid accumulation in adipocytes by a HIF1α-PPARγ feedback network

Specific muscle targeted delivery of miR-130a loaded lipid nanoparticles: a novel approach to inhibit lipid accumulation in skeletal muscle and obesity

BACKGROUND

Skeletal muscle lipid deposition is a key manifestation of obesity, often accompanied by decreased exercise capacity and muscle atrophy. Skeletal muscle as the largest organ in the body, makes it challenges for designing targeted drug delivery systems. Lipid nanoparticles (LNPs) are widely used as a safe and efficient delivery carrier, there is limited research on LNPs that specifically target skeletal muscle.

RESULTS

A LNP designed with five specific receptor complements on its surface, which specifically targets skeletal muscle in vivo in mice, without off-target effects on other tissues and organs. MiR-130a, a regulator of PPARG, which is a key factor in skeletal muscle lipid deposition, was encapsulated with LNP (LNP@miR-130a). In high-fat diet (HFD) mice, LNP@miR-130a effectively reduced skeletal muscle lipid deposition, increased exercise activity and enhanced muscle mass. Interestingly, the myokines in skeletal muscle have also changed which may leading to reduce the adipose tissue weight and liver lipid deposition in HFD mice.

CONCLUSIONS

These results indicated LNP@miR-130a is a promising inhibitor of skeletal muscle lipid deposition and may help alleviate obesity. This study provides new insights for obesity treatment and lays foundation for the development of targeted skeletal muscle therapeutics.

Deciphering the anti-obesity mechanisms of pharmabiotic probiotics through advanced multiomics analysis

Probiotics with "pharmabiotic" properties are increasingly recognized as effective tools for combating obesity by altering gut microbiota and reducing body fat. However, the molecular mechanisms underlying their anti-obesity effects remain largely unexplored due to the absence of a universal methodology. Herein, we developed a multiomics-based strategy to elucidate how probiotics reduce lipid production in adipocytes. Our initial investigation assessed the impact of probiotics at defined adipocyte differentiation stages. Leveraging these insights, we performed comprehensive multiomics analyses at key intervals to identify the suppression mechanisms of lipid formation. Lactobacillus reuteri, specifically, targets early differentiation stages, inhibits branched-chain amino acid catabolism, and reduces lipid accumulation in adipocytes by suppressing Krüppel-like factor 5. Concurrently, enhanced hypoxia-inducible factor 1 expression impedes adipogenesis by downregulating lipin-1 expression. This study not only demonstrates the effectiveness of our approach in revealing complex host-microbe interactions but also significantly advances probiotic therapeutic development, offering promising avenues for obesity management.

Exploring cytochrome P450 under hypoxia: potential pharmacological significance in drug metabolism and protection against high-altitude diseases

High-altitude hypoxia affects the human respiratory, central nervous, cardiovascular, and endocrine systems. These outcomes affect the expression of cytochrome P450 (CYP), the most important family of metabolic enzymes in the body that is involved in the metabolism of both exogenous and endogenous substances (such as arachidonic acid, vitamins, and steroids). Hypoxia influences CYP expression and activity, mediating changes in drug and endogenous substance metabolism, with endogenous metabolites playing a significant role in controlling high-altitude diseases. However, the mechanisms regulating CYP changes under hypoxic conditions and the effects of CYP changes on drug and endogenous metabolism remain unclear. We explored how changes in CYP expression and activity during hypoxia affect the metabolism of drugs and endogenous substances, such as arachidonic acid, vitamins, and steroid hormones, and how CYPs are controlled by nuclear receptors, epigenetic modifications, cytokines, and gut microbiota during hypoxia. Special attention will also be given to the complex role of CYP and its metabolites in the pathophysiology of high-altitude diseases to provide valuable insights for plateau medicine research. SIGNIFICANCE STATEMENT: Cytochrome P450 is a class of monooxygenases that metabolize xenobiotics and endogenous substances. Hypoxia affects the expression and activity of cytochrome P450, and this in turn affects the metabolism of drugs and endogenous substances, leading to altered clinical efficacy and the development of hypoxia-associated diseases. A comprehensive understanding of the changes and regulatory mechanisms of cytochrome P450 under hypoxic conditions can improve therapeutic protocols in hypoxic environments and provide new ideas for the targeted treatment of hypoxic diseases.

Physiology-informed regularisation enables training of universal differential equation systems for biological applications

Systems biology tackles the challenge of understanding the high complexity in the internal regulation of homeostasis in the human body through mathematical modelling. These models can aid in the discovery of disease mechanisms and potential drug targets. However, on one hand the development and validation of knowledge-based mechanistic models is time-consuming and does not scale well with increasing features in medical data. On the other hand, data-driven approaches such as machine learning models require large volumes of data to produce generalisable models. The integration of neural networks and mechanistic models, forming universal differential equation (UDE) models, enables the automated learning of unknown model terms with less data than neural networks alone. Nevertheless, estimating parameters for these hybrid models remains difficult with sparse data and limited sampling durations that are common in biological applications. In this work, we propose the use of physiology-informed regularisation, penalising biologically implausible model behavior to guide the UDE towards more physiologically plausible regions of the solution space. In a simulation study we show that physiology-informed regularisation not only results in a more accurate forecasting of model behaviour, but also supports training with less data. We also applied this technique to learn a representation of the rate of glucose appearance in the glucose minimal model using meal response data measured in healthy people. In that case, the inclusion of regularisation reduces variability between UDE-embedded neural networks that were trained from different initial parameter guesses.

Contribution of glucose and glutamine to hypoxia-induced lipid synthesis decreases, while contribution of acetate increases, during 3T3-L1 differentiation

The molecular mechanisms linking obstructive sleep apnea syndrome (OSA) to obesity and the development of metabolic diseases are still poorly understood. The role of hypoxia (a characteristic feature of OSA) in excessive fat accumulation has been proposed. The present study investigated the possible effects of hypoxia (4% oxygen) on de novo lipogenesis by tracking the major carbon sources in differentiating 3T3-L1 adipocytes. Gas-permeable cultuware was employed to cultivate 3T3-L1 adipocytes in hypoxia (4%) for 7 or 14 days of differentiation. We investigated the contribution of glutamine, glucose or acetate using 13C or 14C labelled carbons to the newly synthesized lipid pool, changes in intracellular lipid content after inhibiting citrate- or acetate-dependent pathways and gene expression of involved key enzymes. The results demonstrate that, in differentiating adipocytes, hypoxia decreased the synthesis of lipids from glucose (44.1 ± 8.8 to 27.5 ± 3.0 pmol/mg of protein, p < 0.01) and partially decreased the contribution of glutamine metabolized through the reverse tricarboxylic acid cycle (4.6% ± 0.2-4.2% ± 0.1%, p < 0.01). Conversely, the contribution of acetate, a citrate- and mitochondria-independent source of carbons, increased upon hypoxia (356.5 ± 71.4 to 649.8 ± 117.5 pmol/mg of protein, p < 0.01). Further, inhibiting the citrate- or acetate-dependent pathways decreased the intracellular lipid content by 58% and 73%, respectively (p < 0.01) showing the importance of de novo lipogenesis in hypoxia-exposed adipocytes. Altogether, hypoxia modified the utilization of carbon sources, leading to alterations in de novo lipogenesis in differentiating adipocytes and increased intracellular lipid content.

Modeling elucidates context dependence in adipose regulation

Single-cell data and computational simulations reveal the dynamics of the transcription factors HIF1α and PPARγ during adipocyte differentiation and maturation. Modeling feedback within this network predicts a HIF1α-mediated choice between lipid accumulation and incomplete differentiation. In vitro experiments support this model, with implications for adipose dynamics in metabolic disorders involving hypoxia.