Exercise and Metformin Intervention Prevents Lipotoxicity-Induced Hepatocyte Apoptosis by Alleviating Oxidative and ER Stress and Activating the AMPK/Nrf2/HO-1 Signaling Pathway in db/db Mice

Abstract

Objective. Nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes (T2DM) commonly coexist and act synergistically to drive adverse clinical outcomes. This study is aimed at investigating the effects of exercise intervention and oral hypoglycaemic drug of metformin (MET) alone or combined on hepatic lipid accumulation. To investigate if oxidative stress and endoplasmic reticulum stress (ERS) are involved in lipotoxicity-induced hepatocyte apoptosis in diabetic mice and whether exercise and/or MET alleviated oxidative stress or ERS-apoptosis by AMPK-Nrf2-HO-1 signaling pathway. Methods. Forty db/db mice with diabetes ( random blood glucose ≥ 250 mg / dL ) were randomly allocated into four groups: control (CON), exercise training alone (EX), metformin treatment alone (MET), and exercise combined with metformin (EM) groups. Hematoxylin-eosin and oil red O staining were carried out to observe hepatic lipid accumulation. Immunohistochemical and TUNEL methods were used to detect the protein expression of the binding immunoglobulin protein (BiP) and superoxide dismutase-1 (SOD1) and the apoptosis level of hepatocytes. ERS-related gene expression and the AMPK-Nrf2-HO-1 signaling pathway were tested by western blotting. Results. Our data showed that db/db mice exhibited increased liver lipid accumulation, which induced oxidative and ER stress of the PERK-eIF2α-ATF4 pathway, and hepatocyte apoptosis. MET combined with exercise training significantly alleviated hepatic lipid accumulation by suppressing BiP expression, the central regulator of ER homeostasis, and its downstream PERK-eIF2α-ATF4 pathway, as well as upregulated the AMPK-Nrf2-HO-1 signaling pathway. Moreover, the combination of exercise and MET displayed protective effects on hepatocyte apoptosis by downregulating Bax expression and TUNEL-positive staining, restoring the balance of cleaved-caspase-3 and caspase-3, and improving the antioxidant defense system to prevent oxidative damage in db/db mice. Conclusion. Compared to MET or exercise intervention alone, the combined exercise and metformin exhibited significant effect on ameliorating hepatic steatosis, inhibiting oxidative and ER stress-induced hepatocyte apoptosis via improving the capacity of the antioxidant defense system and suppression of the PERK-eIF2α-ATF4 pathway. Furthermore, upregulation of AMPK-Nrf2-HO-1 signaling pathway might be a key crosstalk between MET and exercise, which may have additive effects on alleviating hepatic lipid accumulation.

The Geroprotective Drug Candidate CMS121 Alleviates Diabetes, Liver Inflammation, and Renal Damage in db/db Leptin Receptor Deficient Mice

“…Given the increases in lipids in the livers of db/db mice, the reported pro-inflammatory role of lipids [ 49 ], and the fact that hepatic inflammation is a known characteristic of db/db mice [ 27 , 44 ], we next evaluated inflammatory markers in the liver using Western blotting ( Figure 4 A). The quantitative results are presented in Figure 4 B–G.…”

“…As an energy sensor, AMPK regulates energy balance, but has also been reported to protect against lipid-induced inflammation [ 84 ]. AMPK activation was proposed as the mechanism responsible for the decrease in hepatic lipotoxicity in db/db mice [ 49 ]. Thus, the reduced inflammatory state caused by the CMS121 diet may also be linked to AMPK activation, possibly in combination with the inhibition of FASN, which remains to be confirmed.…”

Theaflavin-3,3'-Digallate Protects Liver and Kidney Functions in Diabetic Rats by Up-Regulating Circ-ITCH and Nrf2 Signaling Pathway

“…Additionally, our trial showed that metformin combined with a low dose of TFDG was significantly more effective than a high dose of TFDG alone in reducing blood glucose and inhibiting oxidative stress. It has been reported that metformin combined with honey or exercise for the treatment of diabetes-related diseases is effective in reducing toxic side effects and results in better outcomes than interventions alone. , However, when the antioxidant pycnogenol is combined with metformin, it does not show a higher protective effect on diabetic heart complications than when it is used alone . It can be seen that the combination has different performances in different substances and different diabetic complications.…”

Plasma-derived extracellular vesicles released after endurance exercise exert cardioprotective activity through the activation of antioxidant pathways

“…However, we need to consider that circulating EVs total number can change in function of PE protocols and depends also on sex, age, and pathophysiological condition [ 72 ]. Moreover, it has been reported that oxidative stress can lead to MVBs (multi-vesicular bodies) degradation with consequent release of exosomes by stressed cells [ [73] , [74] , [75] ]. Since PE induces a general reduction in oxidative stress [ 76 , 77 ], we can hypothesize that our observed increase in size and decrease in the number of circulating particles could be due to a global decrease in the stress level of producing cells.…”