Epigallocatechin-3-gallate (EGCG) possesses anti-fibrotic potential in diverse tissues; however, the molecular mechanisms underlying the impacts of EGCG on diabetes-induced myocardial fibrosis remain unclear. This present study aimed to unravel the anti-fibrotic effects of EGCG on the heart in type 2 diabetic rats and investigate its molecular mechanisms. Rats were randomly assigned to the following four groups: Normal (NOR), diabetic cardiomyopathy (DCM), DCM + 40 mg/kg EGCG, and DCM + 80 mg/kg EGCG groups. After 8 weeks of EGCG treatment, fasting blood glucose, left ventricular hemodynamic indices, heart index, and myocardial injury-related parameters were measured. Hematoxylin and eosin staining and Sirius Red staining were used to evaluate myocardial pathological alterations and collagen accumulation. The contents of myocardial hydroxyproline, collagen-I, collagen-III, transforming growth factor (TGF)-β1, matrix metalloprotease (MMP)-2, and MMP-9 were measured. The gene expression levels of myocardial TGF-β1, MMP-2, and MMP-9 were detected. Autophagic regulators, including adenosine 5’-monophosphate-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR), and autophagic markers, including microtubule-associated protein-1 light chain 3 and Beclin1 were estimated. The results indicated that diabetes significantly decreased cardiac contractile function and aggravated myocardial hypertrophy and injury. Furthermore, diabetes repressed the activation of autophagy in myocardial tissue and promoted cardiac fibrosis. Following ingestion with different doses of EGCG, myocardial contractile dysfunction, hypertrophy and injury were ameliorated; myocardial autophagy was activated, and myocardial fibrosis was alleviated in the EGCG treatment groups. In conclusion, these findings suggested that EGCG could attenuate cardiac fibrosis in type 2 diabetic rats, and its underlying mechanisms associated with activation of autophagy via modulation of the AMPK/mTOR pathway and then repression of the TGF-β/MMPs pathway.

Inflammation plays a crucial part in hyperglycemia-induced myocardial damage. Hydrogen sulfide has been found to possess multiple biological activities in previous studies. This study investigated whether hydrogen sulfide conferred cardiac protection against damage in a diabetic rat model by inhibiting nucleotide-binding oligomerization domain-like receptor protein (NLRP) 3 inflammasome activation. Male animals were assigned to control, streptozotocin, streptozotocin + sodium hydrosulfide, and streptozotocin + DL-propargylglycine groups. Animals in the three streptozotocin groups were administrated 55 mg/kg streptozotocin by intraperitoneal injection. Streptozotocin + sodium hydrosulfide and streptozotocin + propargylglycine groups were treated with sodium hydrosulfide (56 μmol/kg) and propargylglycine (40 mg/kg), respectively, for four weeks. Estimation of fasting blood glucose, heart-weight/body-weight, cardiac function, and histopathological analysis, and measurement of myocardial enzymes were done to evaluate the degree of cardiac injury. In order to investigate the redox changes, the levels of total antioxidant capacity, malondialdehyde and lipid peroxidation, and the activities of superoxide dismutase, catalase, and glutathione peroxidase were assessed; the protein expression levels of Thioredoxin and Thioredoxin-interacting protein were measured in myocardial tissue. In addition, inflammatory reactions were assessed by measuring the concentration levels of interleukin-6, tumor necrosis factor-α, interleukin-1β, and interleukin-18 in serum and the expression levels of NLRP3 inflammasome complex-associated proteins in cardiac tissue. In the heart, hyperglycemia significantly induced cardiac dysfunction and injury, redox perturbation, and aggravation of inflammatory reactions. However, except for fasting blood glucose, treatment with sodium hydrosulfide significantly ameliorated these alterations, whereas treatment with propargylglycine further aggravated these alterations. This study highlights the protective properties of hydrogen sulfide against hyperglycemia-induced cardiac injury, and its possible mechanism was shown to involve negative regulation of Thioredoxin-interacting protein-mediated NLRP3 inflammasome activation. Impact statement: Diabetic cardiomyopathy is a serious complication of diabetic patients, accompanied by chronic inflammation. The nucleotide-binding oligomerization domain-like receptor protein (NLRP) 3 inflammasome complex is involved in the progression of the inflammatory response of diabetes, including diabetic cardiomyopathy. Hydrogen sulfide (H₂S) is a novel endogenous gas messenger. Several pieces of evidence have exhibited that H₂S exerts anti-oxidant and anti-inflammatory activities against hyperglycemia-induced myocardial injury, but the mechanism remains unclear. The current study indicated that H₂S protected the myocardium against hyperglycemia-induced injury by preventing Thioredoxin-interacting protein (TXNIP)-mediated NLRP3 inflammasome complex activation. The inhibition of TXNIP-mediated NLRP3 inflammasome complex would be an efficient therapy for H₂S treatment in diabetic cardiomyocytes.

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by hyperglycemia mainly due to insulin resistance. The objective of this study was to investigate the effects of polysaccharides from Armillariella tabescens mycelia (AT) on insulin resistance in mice fed a high-fat diet in combination with streptozotocin to induce T2DM. Following treatment with different doses of AT, hyperglycemia and lipid metabolism dysfunction, insulin resistance, and hepatic function-related indices were markedly ameliorated; the histopathological alterations, oxidative stress, and inflammatory reaction in hepatic tissue were also alleviated; most importantly, AT inhibited the expression of hepatic thioredoxin-interacting protein (TXNIP) to repress the nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome activation and activated the 5′AMP-activated protein kinase (AMPK) pathway in a dose-dependent manner in T2DM mice. In conclusion, these findings revealed that the hypoglycemic and hypolipidemic activities of AT were associated with the alleviation of insulin resistance through repression of the TXNIP/NLRP3 inflammasome pathway and activation of the AMPK pathway.

The present study aimed to investigate the antifibrogenic effects of genistein (GEN) on the kidney in streptozotocin (STZ)‑induced diabetic rats and to determine the associated mechanisms. Rats were randomized into four groups: Normal control (N), STZ (S), L (STZ + low‑dose GEN) and H (STZ + high‑dose GEN). After 8 weeks, the fasting blood glucose (FBG) level, the ratio of kidney weight to body weight (renal index), 24‑h urine protein, blood urea nitrogen (BUN), serum creatinine (SCr), renal total antioxidant capacity (T‑AOC), superoxide dismutase (SOD), lipid peroxidation (LPO), malondialdehyde (MDA) and hydroxyproline (Hyp) contents were measured. The histomorphology and ultrastructure of the kidney were also assessed. In addition, mRNA expression levels of transforming growth factor‑β1 (TGF‑β1) and protein expression levels of nuclear factor erythroid 2‑related factor 2 (Nrf2), heme oxygenase‑1 (HO‑1), NAD(P)H:quinone oxidoreductase 1 (NQO1), TGF‑β1, mothers against decapentaplegic homolog 3 (Smad3), phosphorylated (p)‑Smad3 and collagen IV were estimated. Compared with group N, the levels of FBG, renal index, 24‑h urine protein, BUN, SCr, LPO, MDA and Hyp were increased, whereas the levels of T‑AOC and SOD were decreased in group S. The structure of renal tissue was damaged, and the expression of Nrf2, HO‑1 and NQO1 were reduced, whereas the expression of TGF‑β1, Smad3, p‑Smad3 and collagen IV were increased in group S. Compared with group S, the aforementioned indices were improved in groups L and H. In conclusion, GEN exhibited reno‑protective effects in diabetic rats and its mechanisms may be associated with the inhibition of oxidative stress by activating the Nrf2‑HO‑1/NQO1 pathway, and the alleviation of renal fibrosis by suppressing the TGF‑β1/Smad3 pathway.

Epigallocatechin-3-gallate (EGCG), an essential polyphenolic constituent found in tea leaves, possesses various potent biological activities. This research was undertaken to investigate the impact of EGCG against endoplasmic reticulum (ER) stress-mediated inflammation and to clarify the underlying molecular mechanism in type 2 diabetic kidneys. The male rats were randomized into four groups: normal, diabetic, low-dose EGCG, and high-dose EGCG. In type 2 diabetic rats, hyperglycemia and hyperlipidemia noticeably caused renal structural damage and dysfunction and aggravated ER stress. Meanwhile, sustained ER stress activated the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome and then upregulated the contents of inflammatory cytokines in the diabetic kidney. Following supplementation with 40 mg/kg and 80 mg/kg EGCG, hyperglycemia, hyperlipidemia, and renal histopathological alterations and dysfunction were noticeably ameliorated; renal ER stress, NLRP3 inflammasome, and inflammatory response were markedly repressed in the EGCG treatment groups. In summary, the current study highlighted the renoprotective effects of EGCG in type 2 diabetes and its mechanisms are mainly associated with the repression of ER stress-mediated NLRP3 inflammasome overactivation.