Dual energy X-ray absorptiometry compared with anthropometry in relation to cardio-metabolic risk factors in a young adult population: Is the ‘Gold Standard’ tarnished?

Background and Aims: Assessment of adiposity using dual energy x-ray absorptiometry (DXA) has been considered more advantageous in comparison to anthropometryfor predicting cardio-metabolic risk in the older population, by virtue of its ability to distinguish total and regional fat. Nonetheless, there is increasing uncertainty regarding the relative superiority of DXA and little comparative data exist in young adults. This study aimed to identify which measure of adiposity determined by either DXA or anthropometry is optimal within a range of cardio-metabolic risk factors in young adults. Methods and Results: 1138 adults aged 20 years were assessed by DXA and standard anthropometry from the Western Australian Pregnancy Cohort (Raine) Study. Cross-sectional linear regression analyses were performed. Waist to height ratio was superior to any DXA measure with HDL-C. BMI was the superior model in relation to blood pressure than any DXA measure. Midriff fat mass (DXA) and waist circumference were comparable in relation to glucose. For all the other cardio-metabolic variables, anthropometricand DXA measures were comparable. DXA midriff fat mass compared with BMI or waist hip ratio was the superior measure for triglycerides, insulin and HOMA-IR. Conclusion: Although midriff fat mass (measured by DXA) was the superior measure with insulin sensitivity and triglycerides, the anthropometricmeasures were better or equal with various DXA measures for majority of the cardio-metabolic risk factors. Our findings suggest, clinical anthropometry is generally as useful as DXA in the evaluation of the individual cardio-metabolic risk factors in young adults

Effect of maternal steroid on developing diaphragm integrity.

Antenatal steroids reduce the severity of initial respiratory distress of premature newborn babies but may have an adverse impact on other body organs. The study aimed to examine the effect of maternal steroids on postnatal respiratory muscle function during development and elucidate the mechanisms underlying the potential myopathy in newborn rats. Pregnant rats were treated with intramuscular injections of 0.5 mg/kg betamethasone 7 d and 3 d before birth. Newborn diaphragms were dissected for assessment of contractile function at 2 d, 7 d or 21 d postnatal age (PNA), compared with age-matched controls. The expression of myosin heavy chain (MHC) isoforms and atrophy-related genes and activity of intracellular molecular signalling were measured using quantitative PCR and/or Western blot. With advancing PNA, neonatal MHC gene expression decreased progressively while MHC IIb and IIx isoforms increased. Protein metabolic signalling showed high baseline activity at 2 d PNA, and significantly declined at 7 d and 21 d. Antenatal administration of betamethasone significantly decreased diaphragm force production, fatigue resistance, total fast fibre content and anabolic signalling activity (Akt and 4E-BP1) in 21 d diaphragm. These responses were not observed in 2 d or 7 d postnatal diaphragm. Results demonstrate that maternal betamethasone treatment causes postnatal diaphragmatic dysfunction at 21 d PNA, which is attributed to MHC II protein loss and impairment of the anabolic signalling pathway. Developmental modifications in MHC fibre composition and protein signalling account for the age-specific diaphragm dysfunction

MHC Protein Expression.

<p>Western blots illustrate expression of MHC I and II proteins using representative samples above the graphs. Graphs show MHC I (A) and MHC II (B) protein content in the controls and maternal steroid treatment groups of 2 d (n = 4 for both control and steroid groups), 7 d (n = 4 for both control and steroid groups) and 21 d (n = 5 for both control and steroid groups) postnatal age. Values are Mean (SE). White and black bars refer to the control and steroid treatment groups respectively. ^{* ∧ #} indicates <i>p</i><0.05 compared with controls of 2 d, 7 d and 21 d respectively. MHC: myosin heavy chain.</p

Activity of Akt Signalling.

<p>Western blots illustrate expression of signalling molecules using representative samples above the graphs. Graphs show p-Akt (A), total Akt (B) and p-Akt/total Akt ratio (C) in the controls and maternal steroid treatment groups of 2 d (n = 4 for both control and steroid groups), 7 d (n = 4 for both control and steroid groups) and 21 d (n = 5 for both control and steroid groups) postnatal age. Values are Mean (SE). White and black bars refer to the control and steroid treatment groups respectively. ^# indicates <i>p</i><0.05 compared with 21 d controls. p: phosphorylated.</p

Activity of 4E-BP1 Signalling.

<p>Western blots illustrate expression of signalling molecules using representative samples above the graphs. Graphs show p-4E-BP1 (A), total 4E-BP1 (B) and p-4E-BP1/total 4E-BP1 ratio (C) in the controls and maternal steroid treatment groups of 2 d (n = 4 for both control and steroid groups), 7 d (n = 4 for both control and steroid groups) and 21 d (n = 5 for both control and steroid group) postnatal age. Values are Mean (SE). White and black bars refer to the control and steroid treatment groups respectively. ^{* #} indicates <i>p</i><0.05 compared with controls of 2 d and 21 d respectively. p: phosphorylated.</p

Fetal Diaphragm Contractile Properties.

<p>Twitch peak force (A), time to peak (B), half relaxation time (C) and maximum specific force (D) in the controls and maternal steroid treatment groups of 2 d, 7 d and 21 d postnatal age (n = 6 for each group). Values are Mean (SE). White and black bars refer to the control and steroid treatment groups respectively. ^{* ∧ #} indicates <i>p</i><0.05 compared with controls of 2 d, 7 d and 21 d respectively. TTP: time to peak; ½ Relax: half relaxation time.</p

MHC Gene Expression.

<p>Graphs show MHC neonatal (A), MHC I (B), MHC IIa (C), MHC IIb (D) and MHC IIx (E) mRNA level in the controls and maternal steroid treatment groups of 2 d (n = 4 for control, n = 8 for steroid group), 7 d (n = 7 for control, n = 4 for steroid group) and 21 d (n = 5 for both control and steroid groups) postnatal age. Values are Median (25^th, 75^th centile), expressed as fold change relative to 2 d control group. White and black box plots refer to the control and steroid treatment groups respectively. ^{* ∧ #} indicates <i>p</i><0.05 compared with controls of 2 d, 7 d and 21 d respectively. MHC: myosin heavy chain. C: control; S: steroid.</p

Force-Frequency Relationship and Post-Fatigue Force in 21 d Diaphragm.

<p>Force-stimulation frequency relationship (A) and post-fatigue force (B) in the 21 d betamethasone and control groups (n = 6 for each group). White and black box plots refer to the control and steroid treatment groups respectively. Values are Mean (SE). ^# indicates <i>p</i><0.05 compared with the control.</p

Atrophic Gene Expression.

<p>Graphs show MAFbx and MuRF1 mRNA level in the controls and maternal steroid treatment groups of 2(n = 4 for control, n = 8 for steroid group), 7 d (n = 7 for control, n = 4 for steroid group) and 21 d (n = 5 for both control and steroid groups) postnatal age. Values are Median (25^th, 75^th centile), expressed as fold change relative to 2 d control group. White and black box plots refer to the control and steroid treatment groups respectively. ^* indicates <i>p</i><0.05 compared with controls of 2 d. C: control; S: steroid.</p