Heat-Shock Protein 70-Mediated Heat Preconditioning Attenuates Hepatic Carbohydrate and Oxidative Disturbances in Rats With Type 1 Diabetes

Baihu Jia Renshen Decoction may improve skeletal muscle and adipose tissue functions of type I diabetic rats by affecting pancreatic β-cell function

BACKGROUND

Baihu Jia Renshen Decoction (BJRD) is used for diabetes mellitus (DM) management in clinics.

OBJECTIVE

To elucidate the potential mechanism of BJRD in treating type 1 DM (T1DM).

METHODS

T1DM models were established via intraperitoneal injection of streptozotocin (STZ). Rats were subsequently randomly divided into the normal control (NC), model (MOD), insulin (INS), INS + BJRD-medium dose (MID), and INS + BJRD-high dose (HIGH) groups. The rats' body weight was measured. Transcriptome sequencing was performed to detect differentially expressed genes (DEGs) in the muscle and adipose tissues. Quantitative real-time polymerase chain reaction was utilized to verify the DEG levels.

RESULTS

Body weights of MOD, INS, MID, and HIGH groups were significantly reduced as compared to those of NC group. Compared with NC group, MOD group showed significant Hspa1b and Notch3 downregulation and Camkk2 level elevation. Compared with MOD group, INS group showed further downregulation of the Hspa1b level, whereas MID group exhibited an increase. The Camkk2 levels in INS, MID, and HIGH groups were further reduced. The Notch3 levels did not significantly change in INS and MID groups, whereas that of HIGH group increased. Additionally, compared with NC group, MOD group demonstrated upregulation of the Myl1, Mylpf, Acacb, and Pygm levels and downregulation of Fasn level. Compared with MOD group, Myl1, Mylpf, and Pygm levels in INS, MID, and HIGH groups were down-regulated, whereas Fasn and Acacb levels were up-regulated.

CONCLUSION

BJRD may influence pancreatic β-cell function, thereby enhancing the function of the skeletal muscle and adipose tissues in a T1DM rat model.

The Role of Heat Shock Proteins in Type 1 Diabetes

Type 1 diabetes (T1D) is a T-cell mediated autoimmune disease characterized by recognition of pancreatic β-cell proteins as self-antigens, called autoantigens (AAgs), followed by loss of pancreatic β-cells. (Pre-)proinsulin ([P]PI), glutamic acid decarboxylase (GAD), tyrosine phosphatase IA-2, and the zinc transporter ZnT8 are key molecules in T1D pathogenesis and are recognized by autoantibodies detected in routine clinical laboratory assays. However, generation of new autoantigens (neoantigens) from β-cells has also been reported, against which the autoreactive T cells show activity. Heat shock proteins (HSPs) were originally described as “cellular stress responders” for their role as chaperones that regulate the conformation and function of a large number of cellular proteins to protect the body from stress. HSPs participate in key cellular functions under both physiological and stressful conditions, including suppression of protein aggregation, assisting folding and stability of nascent and damaged proteins, translocation of proteins into cellular compartments and targeting irreversibly damaged proteins for degradation. Low HSP expression impacts many pathological conditions associated with diabetes and could play a role in diabetic complications. HSPs have beneficial effects in preventing insulin resistance and hyperglycemia in type 2 diabetes (T2D). HSPs are, however, additionally involved in antigen presentation, presenting immunogenic peptides to class I and class II major histocompatibility molecules; thus, an opportunity exists for HSPs to be employed as modulators of immunologic responses in T1D and other autoimmune disorders. In this review, we discuss the multifaceted roles of HSPs in the pathogenesis of T1D and in autoantigen-specific immune protection against T1D development.

Nicotinamide and heat preconditioning - Effects on hepatic HSP70, carbohydrate and oxidative disturbances in STZ-induced diabetic rats

OBJECTIVE

Nicotinamide (NA) is known to have antioxidant potential and partially to protect insulin-secreting cells against diabetogenic agent STZ (streptozotocin). In a combination to heat stress (HS), NA is also known to induce heat-shock proteins (HSPs) production. Heat preconditioning (HP) and HSPs have cytoprotective effects against development of cellular injury caused by application of subsequent stressor. We aimed to determine if pretreatment with NA and HP (as HSP70 -inducers) can affect STZ-induced diabetic disturbances in rats.

METHODS

NA-pretreatment (250 mg/kg b.w., 7 days) and heat preconditioning (41 ± 1 °C, 45 min) of diabetic rats was performed. The changes in hepatic carbohydrate- and antioxidative-related enzymes and substrates were investigated.

RESULTS

NA-pretreatment, alone or in combination with HS, resulted in significant increase of HSP70 concentration in the liver of control and diabetic rats. Compared to diabetic controls, pretreatment with NA, in combination with HP, resulted in decrease of blood and liver glucose, increase of glycogen and glucose-6-phosphate level, increase of glycogenolytic/glycolytic enzymes, decrease of gluconeogenic enzymes, as well as an increase of glutathione content and glutathione peroxidase, decrease of glutathione reductase and catalase activities.

CONCLUSIONS

NA is a potent HSP70 coinducer, alone or in a combination with HS in the liver of both control and diabetic rats. Pretreatment with NA, accompanied by HP, has a pronounced corrective effect on STZ-induced diabetes disturbances in the key hepatic carbohydrate- and antioxidative-related parameters. It seems that this corrective effect is based on the increased production of hepatic HSP70.