Fig 2: Status of HSP60 in subcutaneous adipose tissue (SAT) of obese subjects with and without diabetes and its modulation by physical exercise. In adipose tissue of lean subjects, most resident macrophages are M2 phenotype that contribute to insulin sensitivity. Metabolic overload and lack of physical activity increase body weight, hypertrophy of adipocytes, and number of M1 macrophages, which increase the secretion of pro-inflammatory cytokines such as TNF-α, IL-6 leading to obese inflamed adipose tissue. This contribute to the chronic subclinical metaflammation causing insulin resistance locally and probably in liver that amplifies the inflammation by secreting other pro-inflammatory mediators including IFNγ (53). At this stage, the HSR, in particular HSP60, levels are increased to cope with this cellular stress. However, in diabetic obese this metaflammation process is amplified due to high oxidative stress, which decreases mitochondrial function and HSP60 levels and finally a failure to control such hyper-inflamed adipose tissue. Regular physical exercise intervention decreases stress levels and inflammation in the adipose tissue for both diabetic and non-diabetic obese. While HSR is consequently decreased in non-diabetic obese subjects, in diabetic subjects, HSR and thus HSP60 are increased which might reflect an increase in mitochondrial capacity to reduce excessive metabolic stress. Cell pictures were adapted from Servier Medical Art.

Fig 3: Decreased expression of HSP60 and modulation of its expression by exercise in the subcutaneous adipose tissue (SAT) of obese subjects with diabetes. (A) Immunohistochemical analysis of HSP60 expression in SAT sections from obese people without (ND) and with diabetes (D) before and after a 3-month physical exercise intervention (n = 10 for each group). (B) mRNA levels were measured by quantitative real-time PCR using SAT from obese subjects without (ND) and with diabetes (D) (n = 10 for each group) and normalized using GAPDH. Data are presented as fold changes in obese people with diabetes compared with the findings in the counterparts without diabetes. (C) Representative confocal immunofluorescence images illustrating HSP60 expression and localization in SAT from obese people without and with diabetes (n = 3 for each group). Densitometry quantification of the staining in SAT slides was performed as mentioned in Section “Materials and Methods.” The p-value was determined using the Mann–Whitney test for comparisons between the groups and using a paired t-test for intragroup comparisons before and after exercise. * denotes p < 0.05 between the diabetes and non-diabetes groups, and # denotes p < 0.05 between before and after exercise.

Fig 4: Secretion of HSP60 and HSP60 autoantibodies into blood. Circulating levels of (A) HSP60 protein and (B) HSP60 auto-Abs were measured by ELISA using plasma samples from obese people without (ND) and with diabetes (D) before and after a 3-month physical exercise intervention (n = 43 for each group). The p-value was determined using the Mann–Whitney test for comparisons between the diabetes and non-diabetes groups and using a paired t-test for intragroup comparisons before and after exercise. * denotes p < 0.05 between the diabetes and non-diabetes groups.

Fig 5: Expression profile of HSPs in 3T3-L1 adipocytes under PA treatment. mRNA expression levels of HSP60, HSP72, HSP90, and GRP78 were measured by quantitative real-time PCR in 3T3-L1 adipocytes in the absence and presence of PA (400 µM) overnight. GAPDH was used as an internal control for normalization and data are presented as fold changes under each condition compared with adipocytes transfected with PCMV from independent experiments (n = 4). *p < 0.05; **p < 0.01.