The increasing prevalence of aging has led to a rising incidence of comorbidity of sarcopenia and obesity, posing significant burdens on socioeconomic and public health. Current research has systematically explored the pathogenesis of each condition; however, the mechanisms underlying their comorbidity remain unclear. This study reviews the current literature on sarcopenia and obesity in the aging population, focusing on their shared biological mechanisms, which include loss of autophagy, abnormal macrophage function, mitochondrial dysfunction, and reduced sex hormone secretion. It also identifies metabolic mechanisms such as insulin resistance, vitamin D metabolism abnormalities, dysregulation of iron metabolism, decreased levels of nicotinamide adenine dinucleotide, and gut microbiota imbalances. Additionally, this study also explores the important role of genetic factors, such as alleles and microRNAs, in the co-occurrence of sarcopenia and obesity. A better understanding of these mechanisms is vital for developing clinical interventions and preventive strategies.
Humans ; Sarcopenia/physiopathology* ; Obesity/physiopathology* ; Aging/physiology* ; Autophagy/physiology* ; Insulin Resistance ; Comorbidity ; Vitamin D/metabolism* ; Gonadal Steroid Hormones/metabolism* ; Gastrointestinal Microbiome ; Mitochondria ; MicroRNAs

Parkinson's disease (PD), a chronic and common neurodegenerative disease, is characterized by the progressive loss of dopaminergic neurons in the dense part of the substantia nigra and abnormal aggregation of alpha-synuclein. Type 2 diabetes mellitus (T2DM) is a metabolic disease characterized by chronic insulin resistance and deficiency in insulin secretion. Extensive evidence has confirmed shared pathogenic mechanisms underlying PD and T2DM, such as oxidative stress caused by insulin resistance, mitochondrial dysfunction, inflammation, and disorders of energy metabolism. Conventional drugs for treating T2DM, such as metformin and glucagon-like peptide-1 receptor agonists, affect nerve repair. Even drugs for treating PD, such as levodopa, can affect insulin secretion. This review summarizes the relationship between PD and T2DM and related therapeutic drugs from the perspective of insulin signaling pathways in the brain.
Humans ; Parkinson Disease/drug therapy* ; Diabetes Mellitus, Type 2/pathology* ; Signal Transduction/physiology* ; Receptor, Insulin/metabolism* ; Animals ; Insulin Resistance/physiology* ; Insulin/metabolism*

The maintenance of skeletal muscle quality involves various signal pathways that interact with each other. Under normal physiological conditions, these intersecting signal pathways regulate and coordinate the hypertrophy and atrophy of skeletal muscles, balancing the protein synthesis and degradation of muscle. When the total rate of protein synthesis exceeds that of protein degradation, the muscle gradually becomes enlarged, while when the total rate of protein synthesis is lower than that of protein degradation, the muscle shrinks. Myocyte atrophy mainly involves two protein degradation pathways, namely ubiquitin-proteasome and autophagy-lysosome. Protein degradation pathway is activated during muscle atrophy, resulting in the loss of muscle mass. Muscle atrophy can occur under various conditions such as malnutrition, aging and cachexia. Skeletal muscle atrophy caused by orthopedic diseases mainly includes disuse muscular atrophy caused by fracture and denervation muscular atrophy. The signal pathways that control and coordinate protein synthesis and degradation in skeletal muscle include insulin-like growth factor 1 (IGF1)-Akt-mammalian target of rapamycin (mTOR), myostatin-activin A-Smad, G protein α inhibitory peptide 2 (Gαi2)-PKC, nuclear factor κB (NF-κB), ectodysplasin A2 receptor (EDA2R)-NF-κB inducing kinase (NIK) and mitogen-activated protein kinase (MAPK) pathways. This paper provides a comprehensive review of the protein degradation pathways in skeletal muscle atrophy and the associated signal pathways regulating protein degradation in muscular atrophy.
Humans ; Muscular Atrophy/etiology* ; Muscle, Skeletal/pathology* ; Signal Transduction ; Animals ; Insulin-Like Growth Factor I/metabolism* ; Myostatin/physiology* ; TOR Serine-Threonine Kinases/metabolism* ; Autophagy/physiology* ; NF-kappa B/metabolism* ; Proteolysis ; Proteasome Endopeptidase Complex/physiology*

To explore the effect and mechanism of Zuogui Pills in promoting neural tissue recovery and functional recovery in mice with ischemic stroke. Male C57BL/6J mice were randomly divided into a sham group, a model group, and low-, medium, and high-dose Zuogui Pills groups(3.5, 7, and 14 g·kg~(-1)), with 15 mice in each group. The ischemic stroke model was established using photochemical embolization. Stiker remove and irregular ladder walking behavioral tests were conducted before modeling and on days 7, 14, 21, and 28 after medication. Triphenyl tetrazolium chloride(TTC) staining was performed on day 3 after modeling, and T2-weighted imaging(T2WI) and diffusion-weighted imaging(DWI) were performed on day 28 after medication to evaluate the extent of brain injury. Hematoxylin-eosin(HE) staining was performed to observe the histology of the cerebral cortex. Axonal marker proteins myelin basic protein(MBP), growth-associated protein 43(GAP43), mammalian target of rapamycin(mTOR), and its downstream phosphorylated s6 ribosomal protein(p-S6), as well as mechanism-related proteins osteopontin(OPN) and insulin-like growth factor 1(IGF-1), were detected using immunofluorescence and Western blot. Zuogui Pills had a certain restorative effect on the neural function impairment caused by ischemic stroke in mice. TTC staining showed white infarct foci in the sensory-motor cortex area, and T2WI imaging revealed cystic necrosis in the sensory-motor cortex area. The Zuogui Pills groups showed less brain tissue damage, fewer scars, and more capillaries. The number of neuronal axons in those groups was higher than that in the model group, and neuronal activity was stronger. The expression of GAP43, OPN, IGF-1, and mTOR proteins in the Zuogui Pills groups was higher than that in the model group. In summary, Zuogui Pills can promote the recovery of neural function and axonal growth in mice with ischemic stroke, and its mechanism may be related to the activation of the OPN/IGF-1/mTOR signaling pathway.
Mice ; Animals ; Male ; Ischemic Stroke ; Recovery of Function/physiology* ; Insulin-Like Growth Factor I/pharmacology* ; Mice, Inbred C57BL ; TOR Serine-Threonine Kinases/metabolism* ; Stroke/drug therapy* ; Brain Ischemia/drug therapy* ; Mammals/metabolism*

Branched chain amino acids, as essential amino acids, can be used to synthesize nitrogen-containing compounds and also act as signal molecules to regulate substance metabolism. Studies have shown that the elevated level of branched chain amino acids is closely related to insulin resistance and type 2 diabetes. It can affect insulin signal transduction by activating mammalian target of rapamycin (mTOR) signal pathway, and regulate insulin resistance by damaging lipid metabolism and affecting mitochondrial function. In addition, abnormal catabolism of branched amino acids can lead to the accumulation of metabolic intermediates, such as branched chain α-keto acids, 3-hydroxyisobutyrate and β-aminoisobutyric acid. Branched chain α-keto acids and 3-hydroxyisobutyrate can induce insulin resistance by affecting insulin signaling pathway and damaging lipid metabolism. β-aminoisobutyric acid can improve insulin resistance by reducing lipid accumulation and inflammatory reaction and enhancing fatty acid oxidation. This paper systematically reviewed the regulatory effects and mechanisms of branched chain amino acids and their metabolic intermediates on insulin resistance, which will provide a new direction for the prevention and treatment of insulin resistance and type 2 diabetes.
Humans ; Amino Acids, Branched-Chain/metabolism* ; Insulin Resistance/physiology* ; Diabetes Mellitus, Type 2 ; Insulin/pharmacology* ; Keto Acids/metabolism*

Simiao Wan (SMW) is a traditional Chinese formula, including Atractylodis Rhizoma, Achyranthis Bidentatae Radix, Phellodendri Chinensis Cortex and Coicis Semen at the ratio of 1:1:2:2. It can be used to the treatment of diabetes. However, its bioactive compounds and underlying mechanism are unclear. This study aimed to screen the antilipolytic fraction from SMW and investigate its therapeutic mechanisms on hepatic insulin resistance. Different fractions of SMW were prepared by membrane separation combined with macroporous resin and their antilipolytic activities were screened in fasted mice. The effects of 60% ethanol elution (ESMW) on lipolysis were investigated in 3T3-L1 adipocytes stimulated by palmitic acid (PA) and high fat diet (HFD)-fed mice. In our study, ESMW is the bioactive fraction responsible for the antilipolytic activity of SMW and 13 compounds were characterized from ESMW by UHPLC-QTOF-MS/MS. ESMW suppressed protein kinase A (PKA)-hormone-sensitive lipase (HSL) related lipolysis and increased AMP-activated protein kinase (AMPK) phosphorylation in PA challenged 3T3-L1 adipocytes. AMPKα knockdown abolished the inhibitory effects of ESMW on IL-6 and HSL pSer-660, revealing that the antilipolytic and anti-inflammatory activities of ESMW are AMPK dependent. Furthermore, ESMW ameliorated insulin resistance and suppressed lipolysis in HFD-fed mice. It inhibited diacylglycerol accumulation in the liver and inhibited hepatic gluconeogenesis. Conditional medium collected from ESMW-treated 3T3-L1 cells ameliorated insulin action on hepatic gluconeogenesis in liver cells, demonstrating the antilipolytic activity contributed to ESMW beneficial effects on hepatic glucose production. In conclusion, ESMW, as the antilipolytic fraction of SMW, inhibited PKA-HSL related lipolysis by activating AMPK, thus inhibiting diacylglycerol (DAG) accumulation in the liver and thereby improving insulin resistance and hepatic gluconeogenesis.
AMP-Activated Protein Kinases/metabolism* ; Animals ; Insulin/metabolism* ; Lipolysis/physiology* ; Liver/metabolism* ; Mice ; Tandem Mass Spectrometry

Skeletal muscle is the largest organ of human body, which completes 80%-90% of glucose intake stimulated by insulin, and is closely related to the occurrence and development of insulin resistance (IR). Skeletal muscle is one of the main places of lipid metabolism, and lipid metabolites participate in skeletal muscle metabolism as signal molecules. Fatty acids regulate skeletal muscle insulin sensitivity through insulin signaling pathway, inflammatory response and mitochondrial function. Saturated fatty acids (SFAs) induce insulin resistance by impairing insulin signal transduction, inducing mitochondrial dysfunction and inflammatory response, while unsaturated fatty acids reverse the adverse effects of SFAs and ameliorate IR by enhancing insulin signal transduction and anti-inflammatory effect. In addition, disorders of lipid metabolism in skeletal muscle cause accumulation of harmful metabolic intermediates, such as diacylglycerol, ceramide and long-chain acyl-coenzyme A, and induce IR by directly or indirectly damaging insulin signaling pathway. This article reviews the research progress of lipid metabolic intermediates regulating insulin sensitivity in skeletal muscle, which will help to better understand the pathogenesis of diabetes.
Humans ; Insulin Resistance/physiology* ; Muscle, Skeletal/metabolism* ; Insulin/metabolism* ; Lipid Metabolism ; Fatty Acids/metabolism*

The influence of β-cell function on cardiovascular autonomic neuropathy (CAN), an important diabetes-related complication, is still unclear. In this study, we aimed to investigate the association between residual β-cell function and CAN in patients newly diagnosed with type 2 diabetes. We enrolled 90 newly-diagnosed type 2 diabetic patients and 37 participants with normal glucose tolerance as controls. The patients were divided into a CAN+ group (diabetic patients with CAN, n = 20) and a CAN- group (diabetic patients without CAN, n = 70) according to the standard Ewing battery of tests. Fasting and postprandial plasma glucose, insulin, and C-peptide were measured. Homeostasis model assessment-beta cells (HOMA-B) and HOMA-insulin resistance (IR) were calculated. The prevalence of CAN in this population was 22.2%. Compared with the CAN- group, the CAN+ group had significantly lower fasting plasma insulin (6.60 ± 4.39 vs 10.45 ± 7.82 μ/L, P = 0.029), fasting C-peptide (0.51 ± 0.20 vs 0.82 ± 0.51 nmol/L, P = 0.004), and HOMA-B (21.44 ± 17.06 vs 44.17 ± 38.49, P = 0.002). Fasting C-peptide was correlated with the Valsalva ratio (r = 0.24, P = 0.043) and the 30:15 test (r = 0.26, P = 0.023). Further analysis showed that fasting C-peptide (OR: 0.041, 95% CI 0.003-0.501, P = 0.012) and HOMA-B (OR: 0.965, 95% CI 0.934-0.996, P = 0.028) were independently associated with cardiovascular autonomic nerve function in this population. The patients with fasting C-peptide values < 0.67 nmol/L were more likely to have CAN than those with C-peptide levels ≥0.67 nmol/L (OR: 6.00, 95% CI 1.815-19.830, P = 0.003). A high prevalence of CAN was found in patients with newly-diagnosed type 2 diabetes. Decreased β-cell function was closely associated with CAN in this population.
Adult ; Asian Continental Ancestry Group ; Blood Glucose ; analysis ; Diabetes Mellitus, Type 2 ; complications ; metabolism ; Diabetic Neuropathies ; etiology ; Fasting ; physiology ; Female ; Glucose ; metabolism ; Humans ; Insulin ; metabolism ; Insulin Resistance ; physiology ; Insulin-Secreting Cells ; metabolism ; Male ; Middle Aged

Exosome is a kind of nanoscale-size extracellular vesicles secreted by the means of cell active stimulation with outer membrane structure of vacuoles corpuscle. It can carry and transfer a lot of biological molecules, such as DNA fragments, circular RNA (circRNA), messenger RNA (mRNA), microRNA (miRNA), functional proteins, transcription factors, etc., so as to achieve the goal of information transmission between cells. The relationship between exosomes and diabetes has received extensive attention in recent years. The exosomes play an important role in insulin sensitivity, glucose homeostasis and vascular endothelial function. This paper reviews the role of exosomes in the occurrence and development of diabetes and its complications, and discusses the role and prospect of exosomes as a target for diabetes treatment and its role in the diagnosis and treatment of diabetes.
Diabetes Mellitus ; diagnosis ; physiopathology ; therapy ; Exosomes ; metabolism ; Humans ; Insulin Resistance ; physiology ; MicroRNAs ; metabolism ; RNA, Messenger ; metabolism

This prospective study was designed to examine the combined influence of insulin resistance (IR) and inflammatory biomarker levels on type 2 diabetes mellitus (T2DM) among 1,903 Inner Mongolians. During follow-up, 205 (10.77%) participants developed T2DM, and the incidence of T2DM was higher among subjects with IR, elevated C-reactive protein (CRP), elevated sICAM-1, elevated sE-selectin, or the coexistences of IR with elevated CRP, elevated sICAM-1, elevated sE-selectin, and elevated angiotensin II (all P < 0.05) compared with patients without IR or any elevated biomarkers. In multivariate analysis, the odd ratios [OR, (95% confidence intervals)] for these conditions were 1.944 (1.405-2.691), 2.003 (1.449-2.767), 1.706 (1.232-2.362), 1.560 (1.123-2.165), 2.708 (1.809-4.054), 1.885 (1.155-3.078), 2.101 (1.340-3.295), and 2.260 (1.426-3.582), respectively. Our findings demonstrated that IR and elevated inflammatory biomarkers were associated with T2DM, and that the coexistence of IR and elevated inflammatory biomarkers increased the risk of T2DM.
Asian Continental Ancestry Group ; Biomarkers ; China ; epidemiology ; Cohort Studies ; Diabetes Mellitus, Type 2 ; blood ; epidemiology ; genetics ; Humans ; Inflammation ; metabolism ; Insulin Resistance ; genetics ; physiology ; Multivariate Analysis ; Odds Ratio ; Prospective Studies