The alarming increase in the prevalence of obesity and its strong association with insulin resistance (IR) and type 2 diabetes (T2D) represent major medical, social and economic challenges of the 21st century. More importantly, the micro- and macro-vascular complications associated with these metabolic disorders such as cardiovascular diseases, retinopathy, kidney failure and stroke/dementia are extremely costly to manage and as a direct consequence, they represent a major burden for the health care system. Originally taught to be restricted to western nations favoring sedentary lifestyles, these diseases have become among the top chronic diseases occurring over a wide geographic area and affecting virtually all ages, genders and socioeconomic groups. Qatar is among the top 10 countries in the world with the highest prevalence of obesity and T2D as >35% and ~20% of the population is obese and diabetic, respectively. Increased IR in peripheral organs and progressive failure of the pancreatic β-cells to produce insulin in sufficient amount are the two early core metabolic defects leading to chronic hyperglycemia and overt T2D. The etiology of the disease involves a complex interplay between genetic/epigenetic susceptibility, aging, ethnicity, behavioral and environmental factors but overweight and obesity are the major contributors to T2D through the development of IR. Metabolic stress is a prominent hallmark underlying both obesity and T2D and it consists of an array of stress response forms including metaflammation, glucolipotoxicity, increased oxidative stress, mitochondrial dysfunction and persistent ER stress in metabolically relevant organs. This metabolically toxic environment leads to the activation of JNK stress kinase and IKK inflammatory kinase that abrogate the insulin action in key insulin-responsive tissues. Failure of the heat shock response to cope with metabolic stress and to restore cellular homeostasis was documented in obese and T2D in a manner that correlates with the degree of IR. Conversely, interventions that activate the HSR prevent metabolic stress; improve IR and glucose homeostasis in rodents and humans. Recently, we showed that obese and diabetic patients among the Kuwaiti population have reduced expression of DNAJB3/HSP-40 co-chaperone, which was associated with increased metabolic stress and poor clinical outcomes. We also showed that regular physical exercise restored the normal expression of DNAJB3 in obese/diabetic subjects with a concomitant improvement of the metabolic, physical and clinical outcomes, suggesting a protective role of DNAJB3 against metabolic stress-induced IR. In support of this, we demonstrated that DNAJB3 interacts with both JNK and IKK. To gain further insights about the relevance of such interactions, we carried out a series of functional assays in skeletal muscle and adipocytes. Our preliminary data indicate clearly that DNAJB3 prevents the activation of both JNK and IKK under the conditions of metabolic stress while it promotes the PI3K/AKT pathway (see below). Our preliminary data further demonstrate an important role of DNAJB3 in enhancing glucose uptake in skeletal muscle and this is in large part mediated by Glut4 transporter. Taken together, these data are suggestive of a fundamental physiological role of DNAJB3 in mitigating metabolic stress and improving glucose homeostasis and insulin signaling. A deep understanding of its pathophysiological role in obesity-induced IR and T2D in experimental animal models will provide new insights into a critical signaling pathway that is perturbed in obese and diabetic conditions. The overall objective of this proposal is to validate our human findings in an experimental animal model of diet-induced obesity (DIO), IR and T2D. We propose first to extend our previous studies on Kuwaiti population to determine the expression levels of DNAJB3 in Qatari subjects and relate the findings to their phenotype, clinical, metabolic and biochemical profiles. We propose also to validate these findings in an experimental DIO mouse model of IR and T2D and to dissect the in vivo role of DNAJB3 in DIO, IR and T2D using a DNAJB3 knockout (KO) mouse model. Finally, we will elucidate the cellular/molecular mechanisms by which DNAJB3 mediates its beneficial effects. More specifically, our aims are: • Replicate the findings on the expression levels of DNAJB3 mRNA obtained from Kuwaiti cohort on Qatari cohort across different BMI (i.e., 20 to 40 kg/m2) in non-diabetic, pre-diabetic and diabetic Qatari people and relate the findings to their metabolic and anthropometric phenotypes, clinical and biochemical profiles of those subjects. • Validate the human findings in an experimental animal model of DIO, IR and T2D. We will first effect of DIO on the expression of DNAJB3 mRNA and protein in different metabolically relevant organs including muscle, adipose tissue, liver and pancreas. Subsequently, we propose to determine whether DNAJB3 KO mice are more susceptible to DIO and IR as well as their vulnerability to progress to T2D, as compared to the wild types (wt) animals. For this purpose, five-week-old male mice (C57BL/6 mouse strain) and DNAJB3 KO mice will be subjected to high fat diet (60% Kcal fat) or standard low fat diet (control group) for 8-weeks. The expression of DNAJB3 will be monitored by RT-PCR, western blot and immunohistochemistry. The levels of DNAJB3 will be related to the BMI, glycemic index and metabolic profiles of these animals. IR and β-cell function will be measured at the end of the diet intervention using the clamp techniques. The degree of metabolic stress in KO and control animals will be determined and related to the expression levels of DNAJB3. • Identify the interacting partners of DNAJB3 using whole tissue lysates and evaluate their possible role in IR and T2D. DNAJB3 partners may provide additional novel therapeutic targets for metabolic diseases.