The Effect of DNAJB3 Deficiency on Metabolic Dysfunctions in Diet-induced Obese Mice

Objectives

Obesity and related metabolic dysfunctions are partly mediated by chronic low-grade inflammation and altered expression of numerous proteins including stress responsive heat shock proteins (HSPs). We are specifically interested in HSP40 (Heat Shock Protein-40), subfamily B, member 3 (DNAJB3), a chaperone protein that aids in restoring protein homeostasis. Patients with obesity and type 2 diabetes (T2D) expressed low levels of DNAJB3, which was partly restored by physical activity. Accordingly, we hypothesized that lack of DNAJB3 will increase body weight, inflammation, glucose intolerance and insulin resistance in diet-induced obese mice, compared to B6 wild type (WT) littermates fed the same diets.

Methods

DNAJB3 knockout (KO) mice were generated using the CRISPR/Cas 9 approach. Male and female KO and wild type (WT) mice were fed high fat (HF: 45 kcal% fat) or low fat (LF: 10 kcal% fat) diets for 12 weeks. Body weight and food intake were measured weekly; body composition measurements and glucose tolerance tests were also conducted during the intervention. Following euthanasia, blood, and tissues were harvested for further analyses. Serum adipokines and hormones were measured using a multiplex immunoassay.

Results

Compared to WT male and female, KO mice fed HF diets demonstrated higher body weight and fat mass. Similarly, both male and female KO HF groups demonstrated a slower glucose clearance rate as measured by GTT compared to the LF KO and WT groups as well as HF WT groups. Interestingly, these findings were more significant across the board in the female HF-KO group. Female HF group demonstrated a higher leptin, IL-6 and Insulin levels compared to the other groups (p < 0.0001). Additionally, Male Leptin and Resistin levels were higher in the HF-KO group compared to the other groups (p = 0.0001, p = 0.0253).

Conclusions

Lack of DNAJB3, increases adiposity and glucose intolerance in diet-induced obese male and female mice. Thus, DNAJB3 potentially plays an important role in metabolic functions and glucose homeostasis, warranting further research on DNAJB3 as a potential therapeutic target for obesity and T2D.

Funding Sources

Funded by Qatar National Research Funds, Hamad Bin Khalifa University & Qatar Biomedical Research Institute, Qatar.

Tart Cherry and Fish Oil Effects in Male and Female Diet-induced (C57B6/6J) and Genetically Obese (TALLYHO/Jng) Mice

Objectives

Obesity is a major public health concern that increases the risk of many other chronic diseases. Alteration and remodeling of adipose tissue due to obesity affect adipose functions, leading to chronic low-grade inflammation. Additionally, over accumulation of triglycerides in adipocytes can interfere with the endoplasmic reticulum (ER) functions. These functions include ER stress, as a mechanism to address protein misfolding and other cellular processes including autophagy. Previously, fish oil (FO) and tart cherry (TC) were shown to possess anti-inflammatory properties. We hypothesized that while TC and FO individually decrease inflammation, their combinatorial effects will be greater, either synergistic or additive on regulating inflammation and other adipose tissue functions.

Methods

Four-weeks old, male and female TALLYHO/Jng (TH) and C57BL/6J (B6) mice were fed five different diets including low fat (LF), high fat (HF), and HF supplemented with TC, FO, or TC + FO for 10 weeks. Mice were weighed and adipose tissue was collected and used for gene expression analyses by qRT-PCR.

Results

Both B6 and TH mice were significantly heavier on HF diets compared to LF with greater extent in TH for both sexes. In B6 males, HF group had higher expression levels of inflammatory markers including Mcp1, Il-6, NF-κB and Il-1b compared to LF group (p < 0.05). Supplementation with TC and TC + FO decreased mRNA levels of Mcp1 compared to HF in B6 male mice (p < 0.05). Furthermore, ER stress markers BIP, CHOP, and SXBP1 were significantly increased in TH males fed HF compared to LF diets (p < 0.01). Similarly, autophagy genes ATG12 and Beclin1 were upregulated in TH male HF group compared with LF group (p < 0.001). Additionally, supplementation with TC + FO reduced both ER stress (CHOP, sXBP1) and autophagy (ATG12) markers compared to HF in TH male mice (p < 0.01). Moreover, Beclin1 mRNA levels were significantly reduced in all supplemented groups compared to HF in B6 male mice (p < 0.05).

Conclusions

FO and TC individual and combined effects are in part mediated by changes in expression of genes involved in ER stress, autophagy, and inflammatory pathways in adipose tissue. Further experiments are ongoing to determine whether these changes will be translated at the protein level.

Funding Sources

USDA NIFA AFRI award # 2019-67,017-29,247.

Metabolic Effects of Dietary pH, Protein Source and Fat Content in Diet-induced Obese Mice

Objectives

Higher intake of saturated fats, salts, and fatty proteins has been linked to metabolic diseases (e.g., obesity), in part through low-grade metabolic acidosis and inflammation. Hence, our objective was to test the effects of protein sources and preparations in diet induced obese B6 male and female mice, compared to low fat-fed mice. We hypothesized that metabolic health will be improved by consuming a diet containing pH-enhanced beef or casein diets, compared to a non-pH-enhanced diets.

Methods

B6 male and female mice were randomized (n = 10) into 8 diets that differ in protein source, pH enhancement, and fat content: low fat casein (LFC), pH-enhanced (with ammonia) LFC (LFCN), LF lean beef (LFB), LFBN, high fat casein (HFC), HFCN, HF beef (HFB), HFBN. Body weight and food intake were measured weekly for 12 weeks. White adipose tissue (WAT) was collected at study termination and used for histology, RNA and protein isolation for analyses of fat cell size, and gene (qRT-PCR) and protein (Western blotting) expression. Three-way ANOVA was performed to identify main effects as well as interactions of dietary pH x protein source x fat content, separately in males, and females.

Results

We identified a significant main effect of diet (LF/HF) on fat pad weights in males (F (1,71) = 91.94, p < 0.0001) and females (F (1,72) = 5.111, p = 0.0268). No effect of protein source or change of dietary pH was observed on fat pad weights. However, WAT histology indicated a substantial change in adipose tissue quality, with reduced adipocyte area (p < 0.05) in LF, LFN, HFCN, HFB, HFBN groups compared to HFC in males. Additionally, in both males and females, protein levels of pAkt and pAMPK were upregulated in adipose tissue of mice fed HF diets with increased pH (HFCN, HFBN), compared to non-pH enhanced HF diets.

Conclusions

Our findings indicate potential metabolic benefits of increasing dietary pH, as shown by improved adipose tissue cellularity and improved insulin signaling and energy sensing/fat oxidation-related markers. Thus, additional research is warranted to determine mechanisms underlying the metabolic effects of pH enhancement. These findings also merit further mechanistic studies in animals, as well as future clinical research to translate our results into humans and dissect interactions between protein source, pH and fat content on metabolic diseases.

Funding Sources

Empirical Foods.

DNAJB3 Deficiency Exacerbates Diet-Induced Obesity and Insulin Resistance

Objectives

The prevalence of obesity and Type 2 Diabetes (T2D) continues to rise worldwide, leading to many other chronic diseases and imposing a large economic burden. DNAJ, also known as HSP40 (Heat Shock Protein-40), subfamily B, member 3 (DNAJB3), is a chaperone protein that can be induced under various stressors. Recent reports implicated DNAJB3 in protection against obesity and T2D. Specifically, DNAJB3 was downregulated in some patients with obesity and T2D; however, precise underlying mechanisms remained unclear. We hypothesized that lack of DNAJB3 will increase body weight and body fat, inflammation, glucose intolerance and insulin resistance in diet-induced obese mice, compared to B6 wild type (WT) littermates fed the same diets.

Methods

Three DNAJB3 knockout (KO) mutant lines were generated at the Pennington Biomedical Research Center (KO 30, 44 and 47). Male and female KO and wild type (WT) littermates were fed a high fat diet (45% kcal fat) for 12 weeks. Body weight and composition were measured weekly, and a glucose tolerance test (GTT) was conducted. Following euthanasia, blood, adipose and muscle tissues were harvested and used for serum analyses and tissue gene/protein expression, respectively.

Results

Compared to WT, only DNAJB3 KO male and female mice of line 47 demonstrated significantly higher body weight and fat mass (P < 0.05). Similarly, line 47 also showed a lower rate of glucose clearance as measured by GTT. Consistent with increased body weight and fat mass, male mice in line 47 also exhibited significantly higher mRNA levels of inflammatory markers including TNFα and IL-1β, in gonadal fat, compared to WT and lines 30 and 44. Moreover, similar trends towards increased TNF-α and MCP-1 expression was observed in muscle tissues of KO males of line 47, when compared to WT (P < 0.47), and line 30 (P < 0.15) respectively.

Conclusions

Absence of DNAJB3, increases adiposity, glucose intolerance and inflammation in diet-induced obese mice in both males and females. these findings suggest that DNAJB3 plays an important role in metabolic functions and glucose homeostasis, which warrants further research as a potential therapeutic target for obesity and T2D.

Funding Sources

Funded by Qatar National Research Funds, Hamad Bin Khalifa University & Qatar Biomedical Research Institute, Qatar.

Metabolic Effects of pH Enhanced Ground Beef in Diet-induced Obese Mice

Objectives

Western diets, characterized by higher amounts of saturated fats, fatty proteins, and lower consumption of fruits, vegetables and lean proteins (alkaline diet) has been suggested to contribute to metabolic diseases (e.g., obesity), through low-grade metabolic acidosis (low pH). Hence, our objective was to test the effects of diets rich in beef prepared at various pH levels, in diet induced obese B6 mice. We hypothesized that metabolic health will be improved by consuming a diet containing pH-enhanced cooked ground beef, compared to a non pH-enhanced beef diet.

Methods

B6 male and female mice were randomized (n = 5) into 6 groups; low fat (LF), pH-enhanced (ammonia) LF (LFN), high fat (HF), pH-enhanced HF (HFN), HF with beef (HFB), pH-enhanced HF beef (HFBN). Weight gain and food intake were measured weekly (for 12 weeks) and a glucose tolerance test (GTT) was performed at week 10. Tissues, including white adipose tissue (WAT) and liver were collected and used for histology, RNA and protein isolation, followed by analyses of gene (qRT-PCR) and proteins (Western blotting) related to fat and glucose metabolism.

Results

Final body weight was significantly higher in HF group compared to LF and LFN groups in males, but not in females. Moreover, glucose clearance was significantly better in LF groups compared to HF group for both male and females. Interestingly, pH enhanced groups (HFN and HFBN) demonstrated significantly improved glucose clearance at the end of GTT compared to HF group only in males. Male WAT had smaller fat cell size, and greater fat cell number (P < 0.05) in HFN and HFBN compared to HF and HFB respectively. HFBN showed less hepatic fat accumulation in male mice compared to HFB group. Corroborating these, mRNA level of fatty acid oxidation marker Cpt1α was upregulated in HFBN group compared to HFB (P value 0.07) in male liver.

Conclusions

Findings from this HF diet-induced obesity research suggest that there are potential metabolic benefits of increased dietary pH, through improved glucose clearance and fat metabolism. However, additional research is warranted to determine the underlying mechanisms and whether similar effects will be observed with LF pH-enhanced beef diets. These results can be further translated to human subjects to understand interactions between beef, pH and fat content on metabolic diseases.

Funding Sources

Empirical Foods, Inc.

The Metabolic Effects of Vitamin D and Fish Oil on Obesity

Objectives

Obesity is a widespread epidemic affecting approximately 93.3 million people in the United States. Common underlying causes of obesity include adipose tissue inflammation and insulin resistance. Vitamin D and fish oil both offer potential health benefits that include lowering inflammation and triglycerides. However, their combined effects have not been carefully evaluated in the context of obesity. Hence, we hypothesized that vitamin D and fish oil supplementation exert synergistic and/or additive effects to reduce obesity.

Methods

To test this hypothesis, male B6 mice were fed a high fat (HF) diet supplemented with a low dose (200 IU) or high dose (1000 IU) of vitamin D (HF + D), with or without fish oil (36 g/kg of diet) for 12 weeks. We measured body weight and food intake weekly and performed glucose tolerance test. At termination, liver and epididymal fat were harvested for gene and protein analyses.

Results

There were no differences in body weight or food intake across the 4 groups. Glucose clearance was higher in the fish oil supplemented groups with or without Vitamin D compared to mice fed HF. Only the group supplemented with fish oil along with Vitamin D had lower fatty acid synthesis and higher fatty acid oxidation in epididymal adipose tissue. However, in the liver, fatty acid synthesis was not altered, while fatty acid oxidation was increased by fish oil and Vitamin D combination compared to other groups (P < 0.05). Furthermore, in liver, the mRNA levels for the gluconeogenic marker, Pdk4, was higher in groups supplemented with fish oil with or without Vitamin D compared to HF (P < 0.05).

Conclusions

Additional molecular analyses are currently ongoing to determine the mechanistic basis for beneficial combined effects of vitamin D and fish oil in diet-induced obesity.

Funding Sources

Funded by a Come N Go grant from the College of Human Sciences, TTU.

Mechanisms linking the renin-angiotensin system, obesity, and breast cancer

Obesity is a complex disease and a global epidemic. It is a risk factor for other chronic diseases including breast cancer, especially in women after menopause. Diverse etiologies underlie the relationship between obesity and breast cancer. Adipose tissue is in part responsible for these interactions. In obesity, adipose tissue undergoes several metabolic dysregulations resulting in the secretion of many pro-inflammatory cytokines, growth factors, and hormones which in turn, can promote tumor microenvironment (TME) formation and cancer progression within the breast tissue. Angiotensin II (Ang II) is a well-known hypertensive hormone produced systemically and locally by the renin-angiotensin system (RAS). Activation of this system in obesity is a potential contributor to local and systemic inflammation in breast adipose tissue. Ang II actions are primarily mediated through binding to its two receptors, type 1 (AT1R) and type 2 (AT2R). RAS inhibitors include angiotensin-converting enzyme inhibitors (ACE-I) and angiotensin receptor blockers (ARBs) which are currently prescribed as safe antihypertensive therapies. Recent studies have explored the potential use of ACE-I and ARBs in breast cancer patients as anti-tumor agents. Therefore, it is vital to understand the role of RAS in breast cancer and identify mechanisms of Ang II and RAS inhibitors in the TME and in obesity and breast cancer crosstalk. In this review, we performed a detailed analysis and discussed mechanisms of Ang II-AT1R interactions in breast cancer with emphasis on obesity-associated breast cancer. We further summarized recent in vitro, in vivo and human studies that used ACE-I/ARB interventions to improve breast cancer outcomes.

Eicosapentaenoic Acid Regulates Brown Adipose Tissue Function, Independently of UCP1 (FS11-01-19)

Objectives

Brown adipose tissue (BAT) is a critical tissue in energy expenditure through its specific uncoupling protein 1 (UCP1). We previously reported that mice fed high fat (HF) diet supplemented with eicosapentaenoic acid (EPA) reduced body weight, adiposity, and insulin resistance, and increased UCP1 protein and mRNA levels of other thermogenic markers in BAT at ambient temperature. Hence, we hypothesized that these metabolic effects of EPA on BAT are in part mediated by UCP1.

Methods

To determine the role of UCP1 in obesity and BAT regulation by EPA, wild type (WT) and UCP1 knockout (KO) B6 male mice were housed at thermoneutral conditions (30°C), previously reported to induce obesity in the KO mice. Mice were fed a high-fat diet (HF, 45% kcal fat) or HF diet supplemented with 36 g/kg of AlaskOmega EPA-enriched fish oil (800 mg/g), kindly provided by Organic Technologies, for up to 14 weeks. We metabolically phenotyped these mice and investigated metabolic and molecular changes in their interscapular BAT. Specifically, we determined effects of UCP1 deficiency and EPA on BAT thermogenic and mitochondrial markers.

Results

The previously reported beneficial metabolic effects of EPA in WT mice at ambient, including increased UCP1 expression, were attenuated or lost at thermoneutral temperature. EPA reduced weight gain and adiposity, and improved glucose tolerance in KO mice. In both diets (HF and EPA), BAT triglyceride content was increased, while mitochondrial UCP1, COX I and COX IV protein levels were decreased in the KO compared to the WT genotype (P < 0.05). EPA also increased (P < 0.05) mitochondrial DNA/nuclear DNA ratio in the KO mice. Finally, BAT PGC1α at both gene and protein levels along with whole-body oxygen consumption were increased (P < 0.05) by EPA in KO mice. EPA did not alter the calcium cycling-related markers such as sarcoplasmic/endoplasmic reticulum calcium ATPase 2b (Serca2b) and transient receptor potential vanilloid 2 (Trpv2) in any of the genotypes.

Conclusions

EPA effects on BAT and mitochondrial function are independent of UCP1, and include increased mitochondrial DNA and oxygen consumption, which may be in part relate to increased PGC1α. Additional studies are required to determine fuel or mitochondrial mechanisms by which energy expenditure is increased independently of UCP1.

Funding Sources

NIH/NCCIH grant # R15AT008879-01A1.

Identification of miRNAs Mediating Effects of the Renin Angiotensin System in Adipose Tissue (P21-076-19)

Objectives

Renin angiotensin system (RAS) classically known to regulate blood pressure, is also involved in several metabolic disorders including obesity. Interestingly, RAS components are highly expressed in adipose tissue; however, mechanisms underlying RAS-obesity interactions are still ambiguous and limited information is available about RAS regulation in adipose tissue. We identified previously that RAS overactivation induces ER stress and inflammation, and our goal is to characterize additional mechanisms linking RAS to obesity. Hence, we hypothesized that overactivation of angiotensinogen (Agt, precursor protein in RAS), modulates processes linked to metabolic diseases such as oxidative stress, apoptosis and autophagy in adipocytes.

Methods

mRNA and small RNA profiling were performed in adipose tissues of male wild type B6 mice (Wt) and transgenic mice (Agt-Tg) overexpressing Agt which were either fed a low fat (LF) or a high fat (HF) diet with or without RAS inhibitor captopril, an angiotensin converting enzyme inhibitor.

Results

We identified 18 miRNAs and 5 miRNAs, which were significantly either up or downregulated respectively in Tg compared to Wt mice. Of these, we validated expression of mir195 and 690 which were significantly higher in Tg compared to Wt mice. Furthermore, these miRNAs were significantly reduced in high fat-fed Tg mice treated with captopril compared to non-treated high fat fed mice, indicating the role of angiotensin II in regulation of these miRNAs. Additionally, we identified and validated several genes involved in physiological processes such as oxidative stress and autophagy, some of which were direct targets of the above miRNAs. Mitogen-activated protein kinases including Mapk4, Map3k4, and Map3k7; Caspase 3, 8 and 9; autophagic genes such as autophagy 5 (Atg5), Atg14 and beclin1 were all significantly higher in Tg compared to Wt mice. Additional mechanistic studies are ongoing in cultured adipocytes to further dissect molecular mechanisms linking RAS to obesity.

Conclusions

Overexpression of RAS in adipose tissue alters various physiological processes such as oxidative stress, apoptosis and autophagy, which could be mediated, in part through regulatory miRNAs. These pathways and miRNAs could be potential therapeutic targets to reduce RAS-associated metabolic diseases.

Funding Sources

American Heart Association.

The renin angiotensin system, oxidative stress and mitochondrial function in obesity and insulin resistance

Obesity is a complex disease characterized by excessive expansion of adipose tissue and is an important risk factor for chronic diseases such as cardiovascular disorders, hypertension and type 2 diabetes. Moreover, obesity is a major contributor to inflammation and oxidative stress, all of which are key underlying causes for diabetes and insulin resistance. Specifically, adipose tissue secretes bioactives molecules such as inflammatory hormone angiotensin II, generated in the Renin Angiotensin System (RAS) from its precursor angiotensinogen. Accumulated evidence suggests that RAS may serve as a strong link between obesity and insulin resistance. Dysregulation of RAS also occurs in several other tissues including those involved in regulation of glucose and whole body homeostasis as well as insulin sensitivity such as muscle, liver and pancreas and heart. Here we review the scientific evidence for these interactions and potential roles for oxidative stress, inflammation and mitochondrial dysfunction in these target tissues which may mediate effects of RAS in metabolic diseases. This article is part of a Special Issue entitled: Oxidative Stress and Mitochondrial Quality in Diabetes/Obesity and Critical Illness Spectrum of Diseases - edited by P. Hemachandra Reddy.