Ventilatory acclimatization to hypoxia (VAH) increases both (1) the hypoxic ventilatory response (HVR) to acute decreases in arterial PO₂, and (2) normoxic ventilatory drive when inspired O₂ is returned to normal. Previous studies have shown that N-methyl-D-aspartate (NMDA) receptors in the nucleus of the solitary tract (NTS) are involved in the acute HVR of awake rats. We hypothesized that non-NMDA receptors in the NTS are necessary for the complete manifestation of the VAH. To test this, male Sprague-Dawley rats were randomly divided into two groups: (1) normoxic sea level control (N, n = 13) and (2) chronically hypoxic rats (CH, n = 11) acclimatized in a hypobaric chamber (PIO₂ = 70 Torr) for 7 days. We microinjected artificial cerebrospinal fluid (aCSF) as a sham, and a non-NMDA receptor antagonist into the NTS (0.02 mmol NBQX in 50 nL, bilaterally) through a stereotaxically placed guide cannula. We used barometric pressure plethysmography to measure ventilation during acute hypoxia (10% O₂), normoxia (21% O₂) and acute hypercapnia (7% CO₂). We microinjected AMPA into the same location in the NTS of a subset of the same animals to confirm effectiveness of the NBQX. Microinjection sites were identified by colloidal gold or Evan's blue microinjections after the experiment. Non-NMDA receptor blockade with NBQX significantly (P<0.05) decreased the normoxic ventilatory drive after chronic hypoxia, but not in the normoxic control rats. In addition, non-NMDA receptor blockade depressed ventilation for both normoxic and chronically hypoxic rats acutely breathing hypoxic and hypercapnic gas. The ventilatory response to NBQX resulted primarily from significant effects on respiratory frequency, but not tidal volume. Hence, non-NMDA receptors in the NTS play a role in VAH, and are important for ventilatory drive during chronic and acute hypoxia

Ventilatory acclimatization to hypoxia (VAH) increases the hypoxic ventilatory response (HVR) and causes persistent hyperventilation when normoxia is restored, which is consistent with the occurrence of synaptic plasticity in acclimatized animals. Recently, we demonstrated that antagonism of individual glutamate receptor types (GluRs) within the nucleus tractus solitarii (NTS) modifies this plasticity and VAH (J. Physiol. 592(8):1839-1856); however, the effects of combined GluR antagonism remain unknown in awake rats. To evaluate this, we exposed rats to room air or chronic sustained hypobaric hypoxia (CSH, PiO2 = 70 Torr) for 7-9 days. On the experimental day, we microinjected artificial cerebrospinal fluid (ACSF: sham) and then a "cocktail" of the GluR antagonists MK-801 and DNQX into the NTS. The location of injection sites in the NTS was confirmed by glutamate injections on a day before the experiment and with histology following the experiment. Ventilation was measured in awake, unrestrained rats breathing normoxia or acute hypoxia (10% O2) in 15-min intervals using barometric pressure plethysmography. In control (CON) rats, acute hypoxia increased ventilation; NTS microinjections of GluR antagonists, but not ACSF, significantly decreased ventilation and breathing frequency in acute hypoxia but not normoxia (P < 0.05). CSH increased ventilation in hypoxia and acute normoxia. In CSH-conditioned rats, GluR antagonists in the NTS significantly decreased ventilation in normoxia and breathing frequency in hypoxia. A persistent HVR after combined GluR blockade in the NTS contrasts with the effect of individual GluR blockade and also with results in anesthetized rats. Our findings support the hypotheses that GluRs in the NTS contribute to, but cannot completely explain, VAH in awake rats.

Few studies have investigated the association between ectopic fat from different depots and cardiovascular risk scores and their components in the same population, and none have investigated these relations in South Asians. In a cross-sectional analysis of 796 participants in the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study who had measurements of visceral, subcutaneous, pericardial, hepatic, and intermuscular fat from abdominal and cardiac computed tomography scans, we used linear regression to determine the associations of 1 standard deviation difference in each ectopic fat depot with pooled cohort risk score and its components. Pericardial and visceral fat were more strongly associated with the pooled cohort risk score (3.1%, 95% confidence interval [CI] 2.5 to 3.7, and 2.7%, 95% CI 2.1 to 3.3, respectively) and components than intermuscular fat (2.3%, 95% CI 1.7 to 3.0); subcutaneous fat was inversely associated with the pooled cohort risk score (-2.6%, 95% CI -3.2 to 1.9) and hepatic fat attenuation was not linearly associated with the pooled cohort risk score when mutually adjusted (-0.3%, 95% CI -0.9 to 0.4). Associations for risk factor components differed by fat depot. In conclusion, subcutaneous and hepatic fat may have different functions than fat stored in other depots in South Asians. Determining whether these relations are heterogeneous by race may help elucidate the mechanisms underlying CVD disparities.

Objectives

Insulin resistance is central to the development of non-alcoholic fatty liver disease (NAFLD), and gestational diabetes mellitus (GDM) is an early marker of insulin resistance. We hypothesized that a history of GDM would identify women at higher risk of NAFLD in middle age.

Methods

Women from the multicenter Coronary Artery Risk Development in Young Adults (CARDIA) cohort study who delivered ≥1 birth, were free of diabetes prior to pregnancy(ies), and underwent CT quantification of hepatic steatosis 25 years following cohort entry (Y25: 2010-2011) were included (n=1,115). History of GDM by self-report, validated in a subsample by review of antenatal glucose testing, and metabolic risk factors were assessed prospectively. NAFLD was defined by liver attenuation (LA)≤40 Hounsfield Units on CT scan after exclusion of other causes of hepatic steatosis.

Results

Of 1,115 women meeting selection criteria (57% black, 43% white, median age 25 years at baseline), 124 (11%) reported a history of GDM and 75 (7%) met the CT definition for NAFLD at year 25. The crude risk of NAFLD at the 25-year visit was significantly higher in women with GDM compared to those without (14 vs. 5.8%, OR: 2.56, 95% CI: 1.44-4.55, P<0.01). History of GDM remained associated with NAFLD (OR: 2.29, 95% CI: 1.23-4.27, P=0.01) after adjustment for covariates in multivariable logistic regression. Addition of incident diabetes mellitus (DM) into the final model attenuated the association between GDM and NAFLD (OR: 1.48, 95% CI: 0.73-3.02, P=0.28).

Conclusion

GDM is a risk marker for NAFLD and represents an opportunity to identify women at risk for NAFLD at a young age and may be mediated by the development of incident DM.

Background & aims

Lactation lowers blood glucose and triglycerides, and increases insulin sensitivity. We hypothesized that a longer duration of lactation would be associated with lower prevalence of non-alcoholic fatty liver disease (NAFLD), which is the leading cause of chronic liver disease in the United States.

Methods

Participants from the Coronary Artery Risk Development in Young Adults cohort study who delivered ≥ 1 child post-baseline (Y0: 1985-1986), and underwent CT quantification of hepatic steatosis 25 years following cohort entry (Y25: 2010-2011) were included (n = 844). The duration of lactation was summed for all post-baseline births, and NAFLD at Y25 was assessed by central review of CT images and defined by liver attenuation ≤ 40 Hounsfield Units after exclusion of other causes of hepatic steatosis. Unadjusted and multivariable logistic regression analyses were performed using an a priori set of confounding variables; age, race, education, and baseline body mass index.

Results

Of 844 women who delivered after baseline (48% black, 52% white, mean age 49 years at Y25 exam), 32% reported lactation duration of 0 to 1 month, 25% reported >1 to 6 months, 43% reported more than 6 months, while 54 (6%) had NAFLD. Longer lactation duration was inversely associated with NAFLD in unadjusted logistic regression. For women who reported >6 months lactation compared to those reporting 0-1 month, the odds ratio for NAFLD was 0.48 (95% CI 0.25-0.94; p = 0.03) and the association remained after adjustment for confounders (adjusted odds ratio 0.46; 95% CI 0.22-0.97; p = 0.04).

Conclusions

A longer duration of lactation, particularly greater than 6 months, is associated with lower odds of NAFLD in mid-life and may represent a modifiable risk factor for NAFLD.

Lay summary

A longer duration of breastfeeding has been associated with multiple potential health benefits for the mother including reduction in heart disease, diabetes and certain cancers. In this study we found that breastfeeding for longer than 6 months was associated with a lower risk of non-alcoholic fatty liver disease in mid-life.

Background & aims

Cardiovascular disease (CVD) is the leading cause of death among patients with nonalcoholic fatty liver disease (NAFLD). Moderate drinking (vs abstinence) is associated with lower risk of CVD in the general population. We assessed whether alcohol use is associated with CVD risk in patients with NAFLD.

Methods

We analyzed data from participants in the Coronary Artery Risk Development in Young Adults longitudinal cohort study of 5115 black and white young adults, 18-30 years old, recruited from 4 cities in the United States from 1985 through 1986. Participants self-reported alcohol use at study entry and then again after 15, 20, and 25 years. At year 25 (2010-2011), participants underwent computed tomography examination of the thorax and abdomen and tissue Doppler echocardiography with myocardial strain measured by speckle tracking. Coronary artery calcification was defined as an Agatston score above 0. NAFLD was defined as liver attenuation <51 Hounsfield Units after exclusions. Drinkers reported 1-21 (men) or 1-14 (women) standard drinks/week at years 15, 20, or 25. Nondrinkers reported no alcohol use at years 15, 20, and 25.

Results

Of the 570 participants with NAFLD (mean age, 50 years; 54% black; 46% female), 332 (58%) were drinkers; significantly higher proportions of drinkers were white, male, and with higher levels of education compared with nondrinkers (P < .05 for all). Higher proportions of drinkers had obesity, diabetes, and metabolic syndrome compared with nondrinkers (P < .01). There was no difference in liver attenuation between groups (P = .12). After multivariable adjustment, there was no association between alcohol use and CVD risk factors (diabetes, hypertension, hyperlipidemia) or subclinical CVD measures (coronary artery calcification, early transmitral velocity/late (atrial) transmitral velocity (E/A) ratio, global longitudinal strain).

Conclusions

In a population-based sample of individuals with NAFLD in midlife, prospectively assessed alcohol use is not associated with significant differences in risk factors for CVD or markers of subclinical CVD. In contrast to general population findings, alcohol use may not reduce the risk of CVD in patients with NAFLD.

Whether kidney dysfunction is associated with coronary artery calcium (CAC) in young and middle-aged adults who have a cystatin C-derived estimated glomerular filtration rate (eGFRcys) greater than 60 mL/min/1.73 m(2) is unknown. In the Coronary Artery Risk Development in Young Adults (CARDIA) cohort (recruited in 1985 and 1986 in Birmingham, Alabama; Chicago, Illinois; Minneapolis, Minnesota; and Oakland, California), we examined 1) the association of eGFRcys at years 10 and 15 and detectable CAC over the subsequent 5 years and 2) the association of change in eGFRcys and subsequent CAC, comparing those with stable eGFRcys to those whose eGFRcys increased (>3% annually over 5 years), declined moderately (3%-5%), or declined rapidly (>5%). Generalized estimating equation Poisson models were used, with adjustment for age, sex, race, educational level, income, family history of coronary artery disease, diabetes, body mass index, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and tobacco use. Among 3,070 participants (mean age 35.6 (standard deviation, 4.1) years and mean eGFRcys 106.7 (standard deviation, 18.5) mL/min/1.73 m(2)), 529 had detectable CAC. Baseline eGFRcys was not associated with CAC. Moderate eGFRcys decline was associated with a 33% greater relative risk of subsequent CAC (95% confidence interval: 5, 68; P = 0.02), whereas rapid decline was associated with a 51% higher relative risk (95% confidence interval: 10, 208; P = 0.01) in adjusted models. In conclusion, among young and middle-aged adults with eGFRcys greater than 60 mL/min/1.73 m(2), annual decline in eGFRcys is an independent risk factor for subsequent CAC.

Background

Aphids, including the generalist herbivore Myzus persicae, transmit cucumber mosaic virus (CMV). CMV (strain Fny) infection affects M. persicae feeding behavior and performance on tobacco (Nicotiana tabacum), Arabidopsis thaliana and cucurbits in varying ways. In Arabidopsis and cucurbits, CMV decreases host quality and inhibits prolonged feeding by aphids, which may enhance virus transmission rates. CMV-infected cucurbits also emit deceptive, aphid-attracting volatiles, which may favor virus acquisition. In contrast, aphids on CMV-infected tobacco (cv. Xanthi) exhibit increased survival and reproduction. This may not increase transmission but might increase virus and vector persistence within plant communities. The CMV 2b counter-defense protein diminishes resistance to aphid infestation in CMV-infected tobacco plants. We hypothesised that in tobacco CMV and its 2b protein might also alter the emission of volatile organic compounds that would influence aphid behavior.

Results

Analysis of headspace volatiles emitted from tobacco plants showed that CMV infection both increased the total quantity and altered the blend produced. Furthermore, experiments with a CMV 2b gene deletion mutant (CMV∆2b) showed that the 2b counter-defense protein influences volatile emission. Free choice bioassays were conducted where wingless M. persicae could choose to settle on infected or mock-inoculated plants under a normal day/night regime or in continual darkness. Settling was recorded at 15 min, 1 h and 24 h post-release. Statistical analysis indicated that aphids showed no marked preference to settle on mock-inoculated versus infected plants, except for a marginally greater settlement of aphids on mock-inoculated over CMV-infected plants under normal illumination.

Conclusions

CMV infection of tobacco plants induced quantitative and qualitative changes in host volatile emission and these changes depended in part on the activity of the 2b counter-defense protein. However, CMV-induced alterations in tobacco plant volatile emission did not have marked effects on the settling of aphids on infected versus mock-inoculated plants even though CMV-infected plants are higher quality hosts for M. persicae.

Many aphid-vectored viruses are transmitted nonpersistently via transient attachment of virus particles to aphid mouthparts and are most effectively acquired or transmitted during brief stylet punctures of epidermal cells. In Arabidopsis thaliana, the aphid-transmitted virus cucumber mosaic virus (CMV) induces feeding deterrence against the polyphagous aphid Myzus persicae. This form of resistance inhibits prolonged phloem feeding but promotes virus acquisition by aphids because it encourages probing of plant epidermal cells. When aphids are confined on CMV-infected plants, feeding deterrence reduces their growth and reproduction. We found that CMV-induced inhibition of growth as well as CMV-induced inhibition of reproduction of M. persicae are dependent upon jasmonate-mediated signalling. BRASSINOSTEROID INSENSITIVE1-ASSOCIATED KINASE1 (BAK1) is a co-receptor enabling detection of microbe-associated molecular patterns and induction of pattern-triggered immunity (PTI). In plants carrying the mutant bak1-5 allele, CMV induced inhibition of M. persicae reproduction but not inhibition of aphid growth. We conclude that in wildtype plants CMV induces two mechanisms that diminish performance of M. persicae: a jasmonate-dependent and PTI-dependent mechanism that inhibits aphid growth, and a jasmonate-dependent, PTI-independent mechanism that inhibits reproduction. The growth of two crucifer specialist aphids, Lipaphis erysimi and Brevicoryne brassicae, was not affected when confined on CMV-infected A. thaliana. However, B. brassicae reproduction was inhibited on CMV-infected plants. This suggests that in A. thaliana CMV-induced resistance to aphids, which is thought to incentivize virus vectoring, has greater effects on polyphagous than on crucifer specialist aphids.

Background & aims

Insulin resistance is a risk marker for non-alcoholic fatty liver disease, and a risk factor for liver disease progression. We assessed temporal trajectories of insulin resistance and β-cell response to serum glucose concentration throughout adulthood and their association with diabetes risk in non-alcoholic fatty liver disease.

Methods

Three thousand and sixty participants from Coronary Artery Risk Development in Young Adults, a prospective bi-racial cohort of adults age 18-30 years at baseline (1985-1986; Y0) who completed up to 5 exams over 25 years and had fasting insulin and glucose measurement were included. At Y25 (2010-2011), non-alcoholic fatty liver disease was assessed by noncontrast computed tomography after exclusion of other liver fat causes. Latent mixture modelling identified 25-year trajectories in homeostatic model assessment insulin resistance and β-cell response homeostatic model assessment-β.

Results

Three distinct trajectories were identified, separately, for homeostatic model assessment insulin resistance (low-stable [47%]; moderate-increasing [42%]; and high-increasing [12%]) and homeostatic model assessment-β (low-decreasing [16%]; moderate-decreasing [63%]; and high-decreasing [21%]). Y25 non-alcoholic fatty liver disease prevalence was 24.5%. Among non-alcoholic fatty liver disease, high-increasing homeostatic model assessment insulin resistance (referent: low-stable) was associated with greater prevalent (OR 95% CI = 8.0, 2.0-31.9) and incident (OR = 10.5, 2.6-32.8) diabetes after multivariable adjustment including Y0 or Y25 homeostatic model assessment insulin resistance. In contrast, non-alcoholic fatty liver disease participants with low-decreasing homeostatic model assessment-β (referent: high-decreasing) had the highest odds of prevalent (OR = 14.1, 3.9-50.9) and incident (OR = 10.3, 2.7-39.3) diabetes.

Conclusion

Trajectories of insulin resistance and β-cell response during young and middle adulthood are robustly associated with diabetes risk in non-alcoholic fatty liver disease. Thus, how persons with non-alcoholic fatty liver disease develop resistance to insulin provides important information about risk of diabetes in midlife above and beyond degree of insulin resistance at the time of non-alcoholic fatty liver disease assessment.