Differential expression of HSP60 and exercise effects on its levels in Obese Diabetic and non-Diabetic humans
Sina Kavalakatt, Abdelkrim Khadir and Ali Tiss
Research Division, Dasman Diabetes Institute, Kuwait 

Background: 
Obesity is a growing epidemic worldwide and is characterized by low grade inflammation and impaired heat shock response (HSR). Sedentary lifestyle and high caloric intake are major contributors to obesity, diabetes and its complications. Physical activity is known to improve overall health in many chronic diseases by modulating metabolic stress pathways including HSR. However, limited data exist on these mechanisms in adipose tissue. HSP60, a member of HSR, interestingly can induce both pro-inflammatory and anti-inflammatory markers suggesting its role in modulating inflammation in metabolic diseases. We recently reported that, HSP60 acting as a chaperonin for proteins in the mitochondrion, was increased in human obese. However, the expression levels of HSP60 in obese diabetic are yet to be investigated.

Aim: 
Assess the expression levels of HSP60 in diabetic obese as non-diabetic humans and its correlation with inflammatory and metabolic markers as well as its modulation by physical exercise. 

Methods:
Adult male and female subjects consisting of non-diabetic (138) and diabetic (92) obese were recruited for the study. Subjects were enrolled for a 3-month supervised exercise program. Subcutaneous adipose tissue (SAT) biopsies and venous peripheral blood were collected before and after exercise. Anthropometric measurements and blood biochemistry were done at baseline and after exercise. Plasma levels of inflammatory and metabolic markers were measured using Bioplex-200 system. The expression levels of Hsp60 was studied using immunohistochemistry and confocal microscopy and then validated using Real Time-PCR. Circulating levels of Hsp60 and its auto-antibodies were estimated using ELISA. All statistical analyses were done using SAS version 9.2.

Results: 
In this study, the expression levels of HSP60 were significantly decreased in SAT of diabetic obese patients when compared to non-diabetic obese. This downregulation was concomitant with increased levels of IL6 and TNFα inflammatory markers in SAT of diabetic obese. HSP60 is known to be released under inflammatory stress conditions. In our study, there was no difference in the levels of circulating HSP60 and its auto-antibody between these two groups. Our 3-months exercise protocol increased significantly HSP60 expression levels in SAT of diabetic obese along with a decreased inflammation. In non-diabetic obese the same exercise protocol decreased both HSP60 and inflammatory markers TNF and IL6, suggesting a differential exercise effect in the two groups.

Discussion:
The role of the HSP's in the progression of obesity and diabetes is not yet fully elucidated. Our earlier data has demonstrated increased expression of major HSPs including Hsp60 in obese non-diabetic subjects suggesting that metabolic stress of obesity triggers upregulation of HSR. In contrast, our current study shows reduction in HSP60 expression in diabesity whereas exercise increase its expression along with reduced inflammation. Interestingly, the effects of physical exercise on HSP60 levels in diabetic and non-diabetic obese were opposite. This might reflect a specific adaptive response to exercise according to the metabolic stress status. Therefore, enhancing HSR defense system through exercise might have a beneficial impact on future approaches to diabetes prevention and treatment.

Differential expression of HSP60 and exercise effects on its levels in obese diabetic and non-diabetic humans