Ping H. Wang

Diabetic nephropathy (DN) is a leading cause of chronic kidney failure. We hypothesized that mitochondrial Akt1 dysfunction in renal proximal tubules plays a pathogenic role in DN development and that its activation may reverse DN progression. To study this signaling pathway, we generated a transgenic mouse model harboring a renal tubule-specific, tamoxifen-inducible, mitochondria-targeted constitutively active Akt1 (KMCAKT). Type 2 diabetes was induced by a high-fat, high-fructose diet (HFFD) for 40 weeks. Renal histology and function were evaluated, and glucose metabolism was assessed using dynamic glucose testing. We found that HFFD feeding resulted in the development of DN in control non-induced KMCAKT mice, whereas KMCAKT mice with constitutively active mitochondrial Akt1, induced by tamoxifen injection (TAM), exhibited a significant improvement in kidney dysfunction and histology. Urinary albumin, fasting plasma BUN levels, fibrosis, and Jablonski scores were all markedly improved in HFFD-TAM-KMCAKT mice compared with controls, while levels of α-smooth muscle actin (αSMA) and transforming growth factor-β1 (TGFβ1) were significantly reduced. HFFD-TAM-KMCAKT mice exhibited lower fasting blood glucose and improved oral glucose tolerance, while basal and stimulated insulin levels were higher, along with increased beta cell mass and insulin secretion (HOMA-β) compared with controls. Hyperglycemic clamp studies confirmed increased insulin secretion in HFFD-TAM-KMCAKT mice. We conclude that tubular mitochondrial Akt1 plays a key role in DN progression. Restoring tubular mitochondrial Akt1 signaling may represent a novel approach to reverse the development of chronic kidney disease. We also identified previously unrecognized metabolic cross talk between renal tubular mitochondrial Akt1 and pancreatic insulin secretion that may modulate systemic glucose homeostasis.

Background: Diabetes and obesity are associated with worse prognosis in women with breast cancer. However, the impact of glucagon-like peptide-1 receptor agonists (GLP-1RA) on survival following breast cancer diagnosis remains unclear. Methods: We conducted a single institution, propensity-score matched, retrospective, 2-year landmark study of women with type 2 diabetes (T2D) diagnosed with breast cancer at City of Hope (2009-2025). Patients were categorized based on post-diagnosis exposure to GLP-1RA. Patients were compared across exposure groups using t-tests for continuous variables, chi-square tests for categorical variables, multivariable Cox proportional hazards models for overall mortality risk, and Kaplan-Meier plots for survival time. Results: In 226 matched pairs, there were 47 deaths (30 in unexposed patients and 17 in exposed patients). GLP-1RA exposure was associated with a significantly lower risk of overall mortality (HR = 0.51, 95% CI 0.28-0.93, P = .03) on multivariable analysis. A sensitivity analysis in stage I-III patients yielded similar results (HR = 0.45, 95% CI 0.23-0.85, P = .01). Kaplan-Meier survival analysis also showed an association between increased overall survival and GLP-1RA exposure (log-rank P = .02). Conclusions: In this retrospective cohort of women with T2D and breast cancer, GLP-1RA use after diagnosis was associated with improved overall survival in T2D. These findings reflect all-cause mortality and do not distinguish between cancer-specific and non-cancer causes of death and should therefore be interpreted accordingly.

The migrating keratinocyte wound front is required for skin wound closure. Despite significant advances in wound healing research, we do not fully understand the molecular mechanisms that orchestrate collective keratinocyte migration. Here, we show that, in the wound front, the epidermal transcription factor Grainyhead like-3 (GRHL3) mediates decreased expression of the adherens junction protein E-cadherin; this results in relaxed adhesions between suprabasal keratinocytes, thus promoting collective cell migration and wound closure. Wound fronts from mice lacking GRHL3 in epithelial cells ( Grhl3 -cKO) have lower expression of Fascin-1 (FSCN1), a known negative regulator of E-cadherin. Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) on wounded keratinocytes shows decreased wound-induced chromatin accessibility near the Fscn1 gene in Grhl3 -cKO mice, a region enriched for GRHL3 motifs. These data reveal a wound-induced GRHL3/FSCN1/E-cadherin pathway that regulates keratinocyte-keratinocyte adhesion during wound-front migration; this pathway is activated in acute human wounds and is altered in diabetic wounds in mice, suggesting translational relevance.

Mitochondrial biogenesis and function are controlled by anterograde regulatory pathways involving more than 1000 nuclear-encoded proteins. Transcriptional networks controlling the nuclear-encoded mitochondrial genes remain to be fully elucidated. Here, we show that histone demethylase LSD1 KO from adult mouse liver (LSD1-LKO) reduces the expression of one-third of all nuclear-encoded mitochondrial genes and decreases mitochondrial biogenesis and function. LSD1-modulated histone methylation epigenetically regulates nuclear-encoded mitochondrial genes. Furthermore, LSD1 regulates gene expression and protein methylation of nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1), which controls the final step of NAD ⁺ synthesis and limits NAD ⁺ availability in the nucleus. Lsd1 KO reduces NAD ⁺ -dependent SIRT1 and SIRT7 deacetylase activity, leading to hyperacetylation and hypofunctioning of GABPβ and PGC-1α, the major transcriptional factor/cofactor for nuclear-encoded mitochondrial genes. Despite the reduced mitochondrial function in the liver, LSD1-LKO mice are protected from diet-induced hepatic steatosis and glucose intolerance, partially due to induction of hepatokine FGF21. Thus, LSD1 orchestrates a core regulatory network involving epigenetic modifications and NAD ⁺ synthesis to control mitochondrial function and hepatokine production.

Insulin resistance contributed to the development of type 2 diabetes (T2D) and is a major risk factor for diabetic cardiomyopathy (DCM). We have previously reported that insulin resistance led to impaired Akt1 translocation into myocardial mitochondria in DCM. To study the role of mitochondrial Akt1 in DCM, we have generated two cardiac-specific inducible Cre-lox transgenic mice models that expresses (1) a mitochondria-targeting dominant negative Akt (CAMDAKT) or (2) a mitochondria-targeting constitutively active Akt (CAMCAKT) upon Tamoxifen induction (T). T-CAMDAKT mice showed LV dysfunction with increased heart failure markers, while T-CAMCAKT mice restored LV dysfunction to normal in the T2D model. In a T2D model induced by high fat/high fructose diet with relative insulin deficiency, T-CAMCAKT mice showed lower body fat mass (16.6% vs. 26.5%, p<0.001) and higher body lean mass (77.1% vs. 68.1%, p<0.001). To study the mechanism underlying the changes of body composition, we performed transcriptomic profiling and analysis in gonadal white adipose tissues (WAT) by bulk RNA sequencing. When compared to the control T2D mice, 544 genes were upregulated and 1077 genes were downregulated in the WAT of T-CAMCAKT T2D mice. The result indicated enhanced lipid catabolism, triglyceride catabolism, HDL assembly, and downregulated critical nuclear transcription. Pathway analysis revealed the Liver X receptor/Retinoid X receptor signaling was activated in WAT of T-CAMCAKT mice as compared to the controls. This was accompanied by increased fatty acid oxidation and apolipoproteins expression. These findings suggest that impaired mitochondrial Akt signaling in DCM could remotely increase adiposity by reducing lipid catabolism in WAT through modulating LXR/RXR signaling. Disclosure: Y. Chen: None. A. Ta: None. E. Tom: None. Y. Chen: None. P.H. Wang: Board Member; Self; Dianavi. Funding: National Institutes of Health (R01HL096987)

The signaling mechanisms controlling somatic cell reprogramming are not fully understood. In this study, we report a novel role for mitochondrial Akt1 signaling that enhanced somatic cell reprogramming efficiency. The role of mitochondrial Akt1 in somatic cell reprogramming was investigated by transducing fibroblasts with the four reprogramming factors (Oct4, Sox2, Klf4, c-Myc) in conjunction with Mito-Akt1, Mito-dnAkt1, or control virus. Mito-Akt1 enhanced reprogramming efficiency whereas Mito-dnAkt1 inhibited reprogramming. The resulting iPSCs formed embryoid bodies in vitro and teratomas in vivo. Moreover, Oct4 and Nanog promoter methylation was reduced in the iPSCs generated in the presence of Mito-Akt1. Akt1 was activated and translocated into mitochondria after growth factor stimulation in embryonic stem cells (ESCs). To study the effect of mitochondrial Akt in ESCs, a mitochondria-targeting constitutively active Akt1 (Mito-Akt1) was expressed in ESCs. Gene expression profiling showed upregulation of genes that promote stem cell proliferation and survival and down-regulation of genes that promote differentiation. Analysis of cellular respiration indicated similar metabolic profile in the resulting iPSCs and ESCs, suggesting comparable bioenergetics. These findings showed that activation of mitochondrial Akt1 signaling was required during somatic cell reprogramming.

DNA damage signaling is critical for the maintenance of genome integrity and cell fate decision. Poly(ADP-ribose) polymerase 1 (PARP1) is a DNA damage sensor rapidly activated in a damage dose and complexity-dependent manner playing a critical role in the initial chromatin organization and DNA repair pathway choice at damage sites. However, the cell-wide consequence of its activation in damaged cells is not well delineated. Using the phasor approach to fluorescence lifetime imaging microscopy (FLIM) and fluorescence-based biosensors in combination with laser microirradiation, we found a rapid cell-wide increase of the bound/free NADH ratio in response to nuclear DNA damage, which is triggered by NAD+ depletion by PARP activation. This change is linked to the metabolic balance shift to oxidative phosphorylation (oxphos) over glycolysis. Inhibition of the respiratory chain resulted in rapid PARP-dependent ATP reduction and intracellular acidification, and eventually, PARP-dependent, AIF-independent, apoptosis indicating that oxphos becomes critical for damaged cell survival. The results reveal the novel pro-survival effect of PARP activation through a change in cellular metabolism, and demonstrate how unique applications of advanced fluorescence imaging technologies in combination with laser microirradiation can be a powerful tool to interrogate damage-induced metabolic changes at high spatiotemporal resolution in a live cell.

Diabetic nephropathy is a leading cause of chronic kidney disease (CKD) worldwide [1, 2] and occurs in 35–40% of both type 1 and type 2 patients within 10 years of onset of diabetes [2, 3]. Compared with patients who have diabetes mellitus without kidney involvement, presence of diabetic nephropathy significantly increases the risk of adverse cardiovascular events and mortality [1]. Approximately 40% of patients with diabetic nephropathy eventually progress to end-stage kidney disease [4, 5]. Unfortunately, studies examining urinary and pathologic biomarkers such as neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), proteinuria and extent of interstitial fibrosis on biopsy have been unsuccessful in identifying reliable predictors of disease progression in diabetic nephropathy [6–8].

Intra-tumoral heterogeneity is associated with therapeutic resistance of cancer and there exists a need to non-invasively identify functional tumor subpopulations responsible for tumor recurrence. Reduced nicotinamide adenine dinucleotide (NADH) is a metabolic coenzyme essential in cellular respiration. Fluorescence lifetime imaging microscopy (FLIM) of NADH has been demonstrated to be a powerful label-free indicator for inferring metabolic states of living cells. Using FLIM, we identified a significant shift towards longer NADH fluorescence lifetimes, suggesting an increase in the fraction of protein-bound NADH, in the invasive stem-like tumor-initiating cell (STIC) subpopulation relative to the tumor mass-forming cell (TMC) subpopulation of malignant gliomas. By applying our previously studied model to transition glioma from a majority of STIC to a majority of TMC in serum-adherent culture conditions following serial passages, we compared changes in NADH states, cellular respirations (oxidative phosphorylation and glycolysis), EGFR expression, and cell-growth speed over passages. We identified a significant positive correlation between free-NADH fraction and cell growth, which was related to an increase of TMC fraction. In comparison, the increase of EGFR and cellular respirations preceded all these changes. In conclusion, FLIM of NADH provides a non-invasive method to monitor the dynamics of tumor heterogeneity before and after treatment.

Objective The prevalence of diabetes mellitus (DM) is increasing rapidly, particularly in Asia. Asian immigrants in Western countries are a fast-growing population who carry both intrinsic risks due to their genetic background and extrinsic risks associated with Western lifestyles. However, recent trends in diabetes prevalence and associated risk factors among Asian immigrants in the USA are not well understood. Research design and methods We examined adults aged 18 and older from the recent California Health Interview Survey data sets from 2003 to 2013 to determine prevalence of known DM among first-generation Asian immigrants and whites. The impact of various DM risk factors in Asian immigrants relative to whites was analyzed and multivariable regression models were constructed to obtain adjusted DM risk in Asian immigrants versus in whites. Results Across the study span, we identified 2007 first-generation Asian immigrants and 14 668 whites as having known DM or prediabetes mellitus (pre-DM). From 2003 to 2013, the prevalence of DM and pre-DM combined rose from 6.8% to 12.4% in Asian immigrants and 5.5% to 6.9% in whites. Much of the increase could be attributed to pre-DM, which rose from 0.7% to 3.2% in Asian immigrants during the study period. The impacts of age and body mass index on DM risk were consistently greater in Asian immigrants than in whites. Non-DM Asian immigrants were found less likely to engage in physical activity than were non-DM whites. After adjustment of various associated factors, Asian immigrants were more likely than whites to have DM and this relative risk for DM gradually increased across the study period. Conclusions A rising prevalence of known DM and particularly pre-DM among Asian immigrants in California was observed during the previous decade. To reduce the burden of diabetes and its complications, future strategies should consider specific risk factors for this ethnic group, including encouraging physical activity.