Pseudomonas aeruginosa PAO1, a potential pathogen of plants and animals, produces the cyclodipeptides cyclo(l-Pro-l-Tyr), cyclo(l-Pro-l-Phe), and cyclo(l-Pro-l-Val) (PAO1-CDPs), whose effects have been implicated in inhibition of human tumor cell line proliferation. Our purpose was to investigate in depth in the mechanisms of HeLa cell proliferation inhibition by the PAO1-CDPs. The results indicate that PAO1-CDPs, both purified individually and in mixtures, inhibited HeLa cell proliferation by arresting the cell cycle at the G0–G1 transition. The crude PAO1-CDPs mixture promoted cell death in HeLa cells in a dose-dependent manner, showing efficacy similar to that of isolated PAO1-CDPs (LD₅₀ of 60–250 µM) and inducing apoptosis with EC₅₀ between 0.6 and 3.0 µM. Moreover, PAO1-CDPs showed a higher proapoptotic activity (~10³–10⁵ fold) than their synthetic analogs did. Subsequently, the PAO1-CDPs affected mitochondrial membrane potential and induced apoptosis by caspase-9-dependent pathway. The mechanism of inhibition of cells proliferation in HeLa cells involves inhibition of phosphorylation of both Akt-S473 and S6k-T389 protein kinases, showing a cyclic behavior of their expression and phosphorylation in a time and concentration-dependent fashion. Taken together our findings indicate that PI3K–Akt–mTOR–S6k signaling pathway blockage is involved in the antiproliferative effect of the PAO1-CDPs.

In response to diabetes mellitus, skeletal muscle is negatively affected, as is evident by reduced contractile force production, increased muscle fatigability, and increased levels of oxidative stress biomarkers. Apocynin is a widely used NADPH oxidase inhibitor, with antioxidant and anti-inflammatory potential. It has been effective for amelioration of a variety of disorders, including diabetic complications. Therefore, the present study was conducted to evaluate the effects and action mechanisms of apocynin in slow- and fast-twitch diabetic rat muscles. Male Wistar rats were rendered diabetic by applying intraperitoneally a single dose of streptozotocin (45 mg/kg). Apocynin treatment (3 mg/kg/day) was administered over 8 weeks. Fasting blood glucose (FBG), insulin tolerance and body weight gain were measured. Both slow (soleus) and fast (extensor digitorum longus, EDL) skeletal muscles were used for muscle function evaluation, oxidative stress markers, and evaluating gene expression using qRT-PCR. Treatment with apocynin significantly reduced FBG levels and enhanced insulin tolerance. Apocynin also prevented muscle contractile dysfunction in EDL muscle but had no significant effect on this parameter in soleus muscles. However, in both types of muscles, apocynin mitigated the oxidative stress by decreasing ROS levels and increasing total glutathione levels and redox state. Concomitantly, apocynin also statistically enhanced Nrf-2 and GLU4 mRNA expression and downregulated NOX2, NOX4, and NF-κB mRNA. Collectively, apocynin exhibits properties myoprotective in diabetic animals. These findings indicate that apocynin predominantly acts as an antioxidant in fast-twitch and slow-twitch muscles but has differential impact on contractile function.

Diabetic muscular atrophy is a complication of diabetes mellitus that can decrease quality of life. Its complex mechanisms include alterations in proteolytic pathways, oxidative stress, and intracellular lipid accumulation. NADPH oxidase enzymes (NOX) play a key role in the production of ROS, contributing to oxidative damage and insulin resistance. Apocynin, a NOX inhibitor, has antioxidant and anti-inflammatory effects, suggesting its therapeutic potential in various diabetic complications. This study evaluated the impact of apocynin on the mechanisms of muscle atrophy in slow- and fast-twitch muscles of diabetic rats. Diabetes was induced in male Wistar rats by intraperitoneal injection of a single dose of streptozotocin (60 mg/kg). Apocynin treatment (3 mg/kg/day) was administered for 8 weeks. Fasting blood glucose levels, lipid profile, and weight gain were measured. Both slow-twitch (soleus) and fast-twitch (extensor digitorum longus, EDL) skeletal muscles were weighed and used to assess triglycerides (TG) content, histological analysis, lipid peroxidation levels, and gene expression evaluated by qRT-PCR. Apocynin reduced blood glucose levels, improved body weight, and exhibited hypolipidemic effects. It significantly increased muscle weight in EDL and soleus, especially in EDL muscle, lowering triglycerides, lipid peroxidation, and increasing fiber size. Additionally, it decreased mRNA expression levels of MuRF-1, atrogin-1, myostatin and p47phox mRNA and upregulated PGC-1α and follistatin mRNA. Apocynin exerted a myoprotective effect by mitigating muscle atrophy in diabetic rats. Its effects were differentially mediated on TG accumulation and muscle fiber size, reducing oxidative stress, atrogene expression, and positively regulating PGC-1α.

Background: MASLD is a disorder linked to lipid metabolism and obesity, increasingly prevalent among sedentary people and leading to hepatic fibrosis. Cyclodipeptides (CDPs) have promising anti-obesogenic and liver-protective potential. Methods: CDP treatment was evaluated in a chronic MASLD model using female Wistar rats fed an obesogenic diet, with assessments of insulin resistance, glucose tolerance, liver damage, oxidative stress, and the expression of genes related to metabolic function. Results: MASLD CDP-treated rats showed low visceral adipose tissue (VAT) content, improved insulin responsiveness and glucose tolerance, reduced steatosis, and reversed oxidant stress and the NRF2, GPX1, and GCLC expression. Furthermore, MASLD-related dysregulation of genes involved in lipid metabolism was restored, including vLDL transport (MTTP, APOB, and RASAL2), β-oxidation (PPAR-α, ACOX1, and FOXO1), lipogenesis (ACC1 and SREBP 1C), and fatty acid transport (PSD3 and CD36). In accordance, genes of key signaling pathways were also restored, including mTOR, TSC1, and TSC2, along with fibrosis and inflammation TGF-β, Fas, NF-κB, and IL-6. In VAT of MASLD animals, crown-like structures and adiposity density were diminished by CDP treatment, with increased expression of genes associated with beige-like adipose tissue remodeling, including PGC-1α, UCP1, NRF1, ATP6v1, CEBP-α, COX4i1, PPARγ, and CS. Consistently, the UCP1 and PGC-1α protein expression was increased in the VAT of MASLD animals treated with CDPs. Conclusions: The anti-MASLD effects of CDPs were associated with reversal of key pathogenic markers in the liver and VAT, suggesting remodeling of white adipose tissue (WAT) toward a beige-like adipose tissue phenotype. The findings suggest that CDPs may modulate adipose tissue structure and adipogenesis, underscoring their therapeutic relevance for MASLD.

Background/Objectives: In all types of diabetes, elevated blood glucose levels cause pathological changes in skeletal muscle, primarily due to oxidative stress, mitochondrial dysfunction, and excessive production of reactive oxygen species (ROS). Regular exercise can help mitigate these effects; however, the underlying mechanisms, particularly those involving the mitochondrial permeability transition pore (mPTP), remain incompletely understood. This study aimed to explore the effects of aerobic exercise training (AET) on oxidative stress and the expression of mPTP components in the skeletal muscle of streptozotocin-induced diabetic rats. Methods: Male Wistar rats were randomly divided into three groups: Healthy Sedentary (H-SED), Diabetic Sedentary (D-SED), and Diabetic Exercise-trained (D-EXER); n = 6 per group. The D-EXER group performed AET (0° slope) 5 days/week for 8 weeks. After the intervention period, body weight and fasting blood glucose (FBG) levels were measured, and soleus muscles were collected and analyzed for oxidative stress biomarkers, Western blotting, and gene expression using qRT-PCR. Results: Following an 8-week intervention, AET reduced FBG concentrations. Accordingly, in the soleus muscles of the D-EXER group, ROS levels decreased, and redox balance was improved compared to the D-SED group. Exercise training reduced CypD and Casp9 mRNA expression and increased Bcl-2 mRNA expression, whereas Ant1 mRNA expression was only slightly altered. CypD protein expression was decreased in exercised diabetic rats, while VDAC1 protein and mRNA levels remained unchanged. In the D-EXER group, there were significant inverse correlations between CypD and Casp9 mRNA expression levels and glutathione redox state. Conclusions: The current study suggests that 8 weeks of AET, in addition to reducing hyperglycemia, may favorably influence oxidative balance and the expression of mPTP-related molecular components in diabetic skeletal muscle.