Expression and Mechanism of TXNIP/NLRP3 Inflammasome in Sciatic Nerve of Type 2 Diabetic Rats.

Objective: To determine the expression profiling and mechanism of thioredoxin-interacting protein (TXNIP)/nucleotide-binding domain-like receptor protein 3 (NLRP3) inflammasome pathway in sciatic nerve (SN) of type 2 diabetes mellitus (T2DM) rats. Methods: Ten out of the 35 healthy SD rats (specific pathogen free) purchased were randomized into the control group, while the others were established a T2DM model by feeding a high-fat and high-sugar diet plus laparoscopic injection of 1% streptozotocin (STZ). The successfully modeled rats were subgrouped into two arms: a DM group with 10 rats and a resveratrol- (RES-) treated DM intervention group with 11 rats. Normal saline to control and DM groups. Alterations in fasting blood glucose (FBG) and body weight (BW) at different time points after administration were observed. Sciatic nerve conduction velocity (SNCV) and mechanical pain threshold (MPT) were measured. TXNIP, NLRP3, caspase-1, and interleukin- (IL-) 1ß levels in rat SN tissue were determined. Results: DM group rats showed higher FBG and lower BW than control rats at different time points (P < 0.05). The FBG of DM intervention group at 2, 4, and 6 weeks after administration was lower, and the BW at 4 and 6 weeks after dosing was higher than DM group. Higher MPT and SNCV were determined in DM intervention group versus DM group (P < 0.05). DM group rats had disordered, swollen, and dissolved SN myelin sheath structure; TXNIP inhibition led to a small amount of nerve myelin fragments and mild pathological changes. Lower TXNIP, NLRP3, caspase-1, and IL-1ß protein levels were found in DM intervention group versus DM group (P < 0.05). Conclusion: The pathogenesis of peripheral neuropathy in T2DM rats may be linked to TXNIP/NLRP3 inflammasome pathway activation, indicating the potential of this pathway as a therapeutic target for diabetic peripheral neuropathy (DPN).

Berberine Reduces Lipid Accumulation by Promoting Fatty Acid Oxidation in Renal Tubular Epithelial Cells of the Diabetic Kidney.

Abnormal lipid metabolism in renal tubular epithelial cells contributes to renal lipid accumulation and disturbed mitochondrial bioenergetics which are important in diabetic kidney disease. Berberine, the major active constituent of Rhizoma coptidis and Cortex phellodendri, is involved in regulating glucose and lipid metabolism. The present study aimed to investigate the protective effects of berberine on lipid accumulation in tubular epithelial cells of diabetic kidney disease. We treated type 2 diabetic db/db mice with berberine (300 mg/kg) for 12 weeks. Berberine treatment improved the physical and biochemical parameters of the db/db mice compared with db/m mice. In addition, berberine decreased intracellular lipid accumulation and increased the expression of fatty acid oxidation enzymes CPT1, ACOX1 and PPAR-α in tubular epithelial cells of db/db mice. The mitochondrial morphology, mitochondrial membrane potential, cytochrome c oxidase activity, mitochondrial reactive oxygen species, and mitochondrial ATP production in db/db mice kidneys were significantly improved by berberine. Berberine intervention activated the AMPK pathway and increased the level of PGC-1α. In vitro berberine suppressed high glucose-induced lipid accumulation and reversed high glucose-induced reduction of fatty acid oxidation enzymes in HK-2 cells. Importantly, in HK-2 cells, berberine treatment blocked the change in metabolism from fatty acid oxidation to glycolysis under high glucose condition. Moreover, berberine restored high glucose-induced dysfunctional mitochondria. These data suggested that berberine alleviates diabetic renal tubulointerstitial injury through improving high glucose-induced reduction of fatty acid oxidation, alleviates lipid deposition, and protect mitochondria in tubular epithelial cells.

[Palmitate enhances toll-like receptor 4 expression and signaling in porcine vascular endothelial cells].

OBJECTIVE: To study the effect of palmitate on toll-like receptor 4 (TLR4) expression and signaling in vascular endothelial cells. METHODS: Pig iliac endothelial cells (PIECs) were incubated with palmitate. TLR4 gene expression levels were measured by quantitative real-time PCR, and TLR4 and IκBα protein expressions by Western blotting. The expression levels of TLR4 protein on the surface of PIECs were quantified using flow cytometry. ELISA was employed to detect tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) concentrations in the cell medium. RESULTS: Palmitate treatment significantly increased TLR4 mRNA and protein expression levels in PIECs compared with those in the control cells (4.73∓0.61 vs 1.25∓0.90, P<0.05; 5.79∓0.05 vs 4.07∓0.31, P<0.05). The expression levels of TLR4 on the cell surface significantly increased (38.070∓3.907 vs 29.390∓1.072, P<0.05), while IκBα protein level was significantly lowered in PIECs after palmitate treatment as compared with those in the control cells (2.04∓0.22 vs 3.98∓0.18, P<0.05). Palmitate treatment significantly elevated TNF-α (2.52∓0.30 vs 1.38∓0.26, P<0.05) and IL-6 (IL-6: 3.28∓0.32 vs 1.44∓0.28, P<0.05) concentrations in the cell culture medium. CONCLUSION: Palmitate can enhance TLR4 expression and signaling in porcine vascular endothelial cells.

[Alpha-linolenic acid improves insulin sensitivity in obese patients].

OBJECTIVE: To explore the effects of α-linolenic acid on insulin sensitivity in obese patients. METHODS: From October 2011 to April 2012, 16 patients received an oral dose of α-linolenic acid for 8 weeks.Oral glucose tolerance test (OGTT) and insulin releasing test were performed before and after treatment. Homeostasis model assessment insulin resistance (HOMA-IR) index and area under curve of insulin (AUCI) were calculated to evaluate the insulin sensitivity. The levels of serum triglyceride, free fatty acids (FFA), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) were measured after an overnight fast. RESULTS: Obese patients had significantly elevated serum insulin, triglyceride, FFA, IL-6 and TNF-α versus the subjects in normal control group (all P < 0.05). Obese patients were also more insulin-resistant than normal subjects based on a higher HOMA-IR (P < 0.05). Decreased serum insulin, triglyceride, FFA, IL-6 and TNF-α were observed after treatment. With the administration of α-linolenic acid, HOMA-IR and AUCI significantly decreased in obese patients (HOMA-IR: 1.8 ± 0.2 vs 1.2 ± 0.3, P < 0.05; AUCI: 1151 ± 505 vs 768 ± 347, P < 0.05). CONCLUSION: α-linolenic acid increases peripheral insulin sensitivity in obese patients and it may aid the prevention and treatment of type 2 diabetes mellitus and atherosclerotic vascular diseases.