👤 Byron H Hartman

The APOE genotype influences metabolic and neurodegenerative outcomes, with APOE4 carriers at higher risk for Alzheimer's disease (AD) and metabolic dysfunction. This study examines how long-term dietary interventions affect systemic metabolism, retinal structure/ function in APOE3-knock-in (KI, neutral for AD) and APOE4-KI mice. Humanized APOE3 and APOE4-KI mice received either a control diet (CD) or a Western diet (WD) for 2, 6, or 12 months. Body weight, glucose metabolism, lipid profiles, retinal structure, function, vasculature, visual performance, and inflammatory markers were analyzed. WD induced early glucose intolerance in APOE4 mice (2 months); APOE3 mice showed impairment only after prolonged exposure (6-12 months). Notably, WD-fed APOE3 mice exhibited more pronounced hyperlipidemia than APOE4 mice. APOE4 CD mice displayed early retinal thinning (6 months), while APOE4 WD mice initially exhibited retinal swelling, followed by degeneration (12 months). WD exacerbated retinal vascular dysfunction in APOE4 mice, with increased tortuosity and reduced vascular area. Elevated Il1b expression in WD-fed APOE4 mice confirmed inflammation-associated retinal dysfunction. APOE4 mice showed heightened dietary vulnerability, with WD worsening metabolic, retinal, and vascular impairments. While CD showed better glucose tolerance, it did not prevent retinal dysfunction. These findings underscore the need for genotype-specific dietary strategies to mitigate APOE4-associated risks. Show less

The aim of this study was to determine if retatrutide, a triple agonist of glucose-dependent insulinotropic polypeptide (GIP) receptor, glucagon-like peptide 1 (GLP-1) receptor and glucagon (GCG) receptor, may lower serum triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C) levels in part by decreasing circulating concentrations of the angiopoietin-like protein 3/8 complex (ANGPTL3/8). In post-hoc analyses of two phase 2 retatrutide trials, concentrations of ANGPTL3/8, ANGPTL4/8 complex (ANGPTL4/8), ANGPTL3 and ANGPTL4 were measured using dedicated immunoassays to determine percent changes from baseline. Correlations of ANGPTL protein and complex levels with lipid and metabolic parameters at baseline were analysed. Correlations of the changes in ANGPTL protein and complex levels versus the changes in lipid and metabolic parameters at study endpoints were also analysed. Direct effects of retatrutide itself, GIP, GLP-1, GCG and a GCG receptor (GCGR) antagonist antibody on ANGPTL3/8 secretion were studied in vitro using primary human hepatocytes. ANGPTL3/8 reductions were observed with 8 and 12 mg retatrutide doses in participants with type 2 diabetes, and with 1, 4, 8 and 12 mg retatrutide doses in participants with obesity or overweight but without diabetes. In both cases, ANGPTL3/8 decreases paralleled retatrutide-induced reductions in TG and LDL-C. In primary human hepatocytes, both glucagon and retatrutide decreased ANGPTL3/8 secretion, and these reductions were blocked with the GCGR antagonist antibody. Together, these results suggest that the GCGR agonism of retatrutide could lead to reduced circulating ANGPTL3/8 concentrations, which may then contribute to decreases in TG and LDL-C levels. Show less

Alzheimer's disease (AD) is a common neurodegenerative condition involving a complex blend of disturbances in synaptic development and maintenance, neurovascular cross-talk, ionic and nutrient transport, and mitochondrial metabolism. The precise molecular profile of AD onset with insight for major pathological contributors remains unclear with corresponding impedances in therapeutic development. The current study sought two objectives, as (i) to resolve the molecular pathogenesis from cognitive impairment to the onset of AD-like neuropathology and (ii) whether the novel agent cannabidiol (CBD), noted for its neuroprotective effects, influences the molecular transition associated with AD onset. Dietary CBD was administered daily (80-100 mg/kg/day) in male There were >1,000 differentially expressed markers of AD onset, whereby >75% were either eliminated or reversed in the direction of expression in response to CBD. Signaling pathways encompassed synaptic development and plasticity (e.g., Foxp2), neurovascular interactions (Smad9, Angptl6), receptors and ion channels (Gria4, Chrna2, Rgs7/Rgs7bp), mitochondrial genes (Ndufa7, Cox7a2), immunity (Ncr1), oxidation-reduction (Esr1), lipid synthesis (Fasn, ApoE), and carbohydrate metabolism (Mafa, Mlxipl). As potentially addressable with CBD treatment, AD onset represents molecular integration of neurovascular interactions, channelopathies, metabolic disturbances, and aberrations in developmental genes with involvement of major pathological contributors such as inflammation, oxidative signaling, dyslipidemia, and insulin resistance. Show less

Modulation of sarcomere contractility represents a new therapeutic opportunity for the treatment of heart failure by directly targeting the thick and thin filament proteins of the sarcomere to increase cardiac muscle contraction. This study compared the effect of 2 small molecules (M and T) that selectively alter myosin thick filament (M) or troponin thin filament (T) activity on overall cardiac muscle mechanics. This study revealed key differences related to the mechanism utilized by M and T to increase contractile force generation and suggests that targeting different proteins within the sarcomere may result in differentiating therapeutic profiles. Show less

CHF1/Hey2 is a Notch-responsive basic helix-loop-helix transcription factor involved in cardiac development. Common variants in Hey2 are associated with Brugada syndrome. We hypothesized that absence of CHF1/Hey2 would result in abnormal cellular electrical activity, altered cardiac conduction system (CCS) development, and increased arrhythmogenesis. We isolated neonatal CHF/Hey2-knockout (KO) cardiac myocytes and measured action potentials and ion channel subunit gene expression. We also crossed myocardial-specific CHF1/Hey2-KO mice with cardiac conduction system LacZ reporter mice and stained for conduction system tissue. We also performed ambulatory ECG monitoring for arrhythmias and heart rate variability. Neonatal cardiomyocytes from CHF1/Hey2-KO mice demonstrate a 50% reduction in action potential dV/dT, a 50-75% reduction in SCN5A, KCNJ2, and CACNA1C ion channel subunit gene expression, and an increase in delayed afterdepolarizations from 0/min to 12/min. CHF1/Hey2 cKO CCS-lacZ mice have a ∼3-fold increase in amount of CCS tissue. Ambulatory ECG monitoring showed no difference in cardiac conduction, arrhythmias, or heart rate variability. Wild-type cells or animals were used in all experiments. CHF1/Hey2 may contribute to Brugada syndrome by influencing the expression of SCN5A and formation of the cardiac conduction system, but its absence does not cause baseline conduction defects or arrhythmias in the adult mouse.-Hartman, M. E., Liu, Y., Zhu, W.-Z., Chien, W.-M., Weldy, C. S., Fishman, G. I., Laflamme, M. A., Chin, M. T. Myocardial deletion of transcription factor CHF1/Hey2 results in altered myocyte action potential and mild conduction system expansion but does not alter conduction system function or promote spontaneous arrhythmias. Show less

Generating cardiomyocytes from embryonic stem cells is an important technique for understanding cardiovascular development, the origins of cardiovascular diseases and also for providing potential reagents for cardiac repair. Numerous methods have been published but often are technically challenging, complex, and are not easily adapted to assessment of specific gene contributions to cardiac myocyte differentiation. Here we report the development of an optimized protocol to induce the differentiation of mouse embryonic stem cells to cardiac myocytes that is simplified and easily adapted for genetic studies. Specifically, we made four critical findings that distinguish our protocol: 1) mouse embryonic stem cells cultured in media containing CHIR99021 and PD0325901 to maintain pluripotency will efficiently form embryoid bodies containing precardiac mesoderm when cultured in these factors at a reduced dosage, 2) low serum conditions promote cardiomyocyte differentiation and can be used in place of commercially prepared StemPro nutrient supplement, 3) the Wnt inhibitor Dkk-1 is dispensable for efficient cardiac differentiation and 4) tracking differentiation efficiency may be done with surface expression of PDGFRα alone. In addition, cardiac mesodermal precursors generated by this system can undergo lentiviral infection to manipulate the expression of specific target molecules to assess effects on cardiac myocyte differentiation and maturation. Using this approach, we assessed the effects of CHF1/Hey2 on cardiac myocyte differentiation, using both gain and loss of function. Overexpression of CHF1/Hey2 at the cardiac mesoderm stage had no apparent effect on cardiac differentiation, while knockdown of CHF1/Hey2 resulted in increased expression of atrial natriuretic factor and connexin 43, suggesting an alteration in the phenotype of the cardiomyocytes. In summary we have generated a detailed and simplified protocol for generating cardiomyocytes from mES cells that is optimized for investigating factors that affect cardiac differentiation. Show less

The cardiovascular restricted bHLH transcription factor CHF1/Hey2 has been reported to play an important role in regulation of vascular smooth muscle phenotype and gene expression, but the downstream target genes that mediate these effects have not been completely elucidated. We have previously found that loss of CHF1/Hey2 in vascular smooth muscle cells leads to dysregulated expression of the matrix metalloproteinase gene MMP10 after treatment with PDGF. Here we report that loss or knockdown of CHF1/Hey2 in vascular smooth muscle cells leads to increased expression and activity of MMP10 at baseline, suggesting a direct effect of CHF1/Hey2 on MMP10 promoter regulation. To test this hypothesis, we assessed the effects of CHF1/Hey2 on a 2.5 kb MMP10 promoter region upstream of the transcriptional start site. We found that this region contains multiple elements including 12 E-boxes that mediate constitutive activity and repression by CHF1/Hey2 in 293T cells and A7r5 smooth muscle cells. Surprisingly, mutation of these E-boxes not only abolished CHF1/Hey2 repression, but also diminished constitutive expression. In addition, we observed that some of these mutations unmasked an activator function for CHF1/Hey2, which has not been previously described. These findings support the hypothesis that CHF1/Hey2 is an important regulator of MMP10 expression. Show less

A series of tetrahydro-cyclopenta[b]indoles modulating the activity of the liver-X-receptor (LXR) were derived from a high throughput screening hit. The potency and selectivity for LXRbeta versus LXRalpha was improved. One compound, administered to wild-type mice modestly increased plasma HDL-cholesterol with no change in plasma triglycerides (TG) and reduced effects on liver TG content compared to T0901317. This novel series of LXR agonists shows promise to improve therapeutic efficacy with reduced potential to increase TG. Show less

In cochlear development, the Notch signaling pathway is required for both the early prosensory phase and a later lateral inhibition phase. While it is known that Hes genes are important downstream mediators of Notch function in lateral inhibition, it is not known what genes function as mediators of the early prosensory function of Notch. We report that two members of the Hes-related gene family, Hesr1 and Hesr2, are expressed in the developing cochlea at a time and place that makes them excellent candidates as downstream mediators of Notch during prosensory specification. We also show that treatment of cochlear explant cultures at the time of prosensory specification with a small-molecule inhibitor of the Notch pathway mimics the results of conditional Jag1 deletion. This treatment also reduces Hesr1 and Hesr2 expression by as much as 80%. These results support the hypothesis that Hesr1 and Hesr2 are the downstream mediators of the prosensory function of Notch in early cochlear development. Show less