Biology subjects

Altintas, A.

Publications and source records attributed to Altintas, A..

4 recordsLinked to original sources

bioRxiv2025

Muscle Cathepsin B treatment improves behavioral and neurogenic deficits in a mouse model of Alzheimer's Disease

Muscle secretes factors during exercise that enhance cognition. Myokine Cathepsin B (Ctsb) is linked to memory function, but its role in neurodegenerative disease is unclear. Here we show that AAV-vector-mediated Ctsb overexpression in skeletal muscle in an Alzheimers Disease (AD) mouse model (APP/PS1), improves motor coordination, memory function and adult hippocampal neurogenesis, while plaque pathology and neuroinflammation remain unchanged. Additionally, in AD mice, Ctsb treatment modifies hippocampal, muscle and plasma proteomic profiles to resemble that of wildtype controls. Conversely, in wildtype mice, Ctsb expression causes memory deficits and results in protein profiles across tissues that are comparable to AD control mice. In AD mice, Ctsb treatment increases the abundance of hippocampal proteins involved in mRNA metabolism and protein synthesis, including those relevant to adult hippocampal neurogenesis and memory function. Furthermore, Ctsb treatment enhances plasma metabolic and mitochondrial processes, and reduces inflammatory responses. In muscle, Ctsb expression elevates protein translation in AD mice, whereas in wildtype mice mitochondrial proteins decrease. Overall, the biological changes in the treatment groups are consistent with effects on memory function. Thus, skeletal muscle Ctsb application has potential as an AD therapeutic intervention.

neuroscience↗

bioRxiv2024

A multi-omics census reveals obesity-associated microRNA miR-let-7 as novel instigator of adipose mitochondrial dysfunction and of intergenerational metabolic decline.

We here describe that obesity and weight loss in male mice cause reversible abnormalities in glucose and lipid metabolism, serum metabolomes and lipidomes as well as expression of microRNAs, mRNAs and proteins controlling mitochondrial function in epididymal white adipose tissue. When mating obese male mice with lean females, we observed reductions in expression and translation of genes encoding mitochondrial respiratory components in (F1) offspring that closely resemble those observed in the paternal (F0) generation. When mapping miRNA regulation across somatic organs (i.e., liver, adipose) and sperm and F0/1 generations, we found that obesity and weight loss reversibly affected miRNA levels, and that let-7 isoforms were induced in obese F0 and F1 adipose tissue and sperm of obese F0 mice, eliciting qualitatively similar responses in two adjacent tissues. Overexpressing let-7 in adipocytes silenced DICER1, a miRNA processing enzyme crucial for adipose adaptation to obesity as evidenced by deficiencies in mitochondrial function following DICER1 loss in primary adipocytes. Also, microinjection of synthetic let-7 mimetics at physiological levels found in obese sperm into zygotes from lean mice elicited glucose intolerance and impediments in adipose mitochondrial gene expression in mice sired from let-7 microinjected zygotes, phenocopying hereditary aspects of paternal obesity. When performing single-cell RNA-Seq of miRNA-injected embryos, let-7 impaired mitochondrial gene expression, suggesting altered oxidative metabolism following zygotic let-7 delivery. When studying miRNA alterations in human semen, lifestyle-induced weight loss downregulated hsa-let-7, suggesting similar roles for human let-7 in gametic epigenomes and embryogenesis.

physiology↗

bioRxiv2021

Disrupted circadian core-clock oscillations in Type 2 Diabetes are linked to altered rhythmic mitochondrial metabolism

Circadian rhythms are generated by an auto-regulatory feedback loop composed of transcriptional activators and repressors. Disruption of circadian rhythms contributes to Type 2 diabetes (T2D) pathogenesis. We elucidated whether altered circadian rhythmicity of clock genes is associated with metabolic dysfunction in T2D. Transcriptional cycling of core clock genes ARNTL, CLOCK, CRY1 and NR1D1 was altered in skeletal muscle from individuals with T2D and this was coupled with reduced number and amplitude of cycling genes and disturbed circadian oxygen consumption. Mitochondrial associated genes were enriched for differential circadian amplitudes in T2D, and positively correlated with insulin sensitivity. ChIP- sequencing identified CLOCK and BMAL1 binding to circadian mitochondrial genes associated with insulin sensitivity, implicating regulation by the core clock. Mitochondria disruption altered core-clock gene expression and free-radical production, phenomena that were restored by resveratrol treatment. We identify bi-directional communication between mitochondrial function and rhythmic gene expression, processes which are disturbed in diabetes.

physiology↗

bioRxiv2021

Circadian Transcriptomic and Epigenomic Remodeling in Response to Lipid Overload and Human Obesity

Obesity and elevated circulating lipids may impair metabolism by disrupting the molecular circadian clock. We tested the hypothesis that lipid-overload may interact with the circadian clock and alter the rhythmicity of gene expression through epigenomic mechanisms in skeletal muscle. Palmitate reprogrammed the circadian transcriptome in myotubes without altering the rhythmic mRNA expression of core clock genes. Genes with enhanced cycling in response to palmitate were associated with post-translational modification of histones. Cycling of histone 3 lysine 27 acetylation (H3K27ac), a marker of active gene enhancers, was modified by palmitate treatment. Chromatin immunoprecipitation and sequencing confirmed that palmitate exposure altered the cycling of DNA regions associated with H3K27ac. Overlap of mRNA and DNA regions associated with H3K27ac and pharmacological inhibition of histone acetyl transferases revealed novel cycling genes associated with lipid exposure of primary human myotubes. Palmitate exposure disrupts transcriptomic rhythmicity and modifies enhancers through changes in histone H3K27 acetylation in a circadian manner. Thus, histone acetylation is responsive to lipid-overload and redirects the circadian chromatin landscape leading to reprogramming of circadian genes in skeletal muscle.

physiology↗