Changes in insulin-like growth factor-I and -II associated with fat but not lean mass in early old age

Increased insulin-like growth factor 1 concentrations in a population of non-diabetic cats with overweight/obesity

Feline hypersomatotropism (HST) is typically associated with diabetes mellitus (DM), whereas HST without concurrent DM has only been reported in a few cases. Weight gain may be observed in cats with HST. The aims of this study were to evaluate circulating insulin-like growth factor-1 (IGF-1) in non-diabetic cats with overweight/obesity, to screen this population for the presence of HST, and to assess whether there is a correlation between body weight/body condition score (BCS) and serum IGF-1 concentration in overweight/obese cats. In this prospective study, 80 overweight/obese cats from referral centers in Buenos Aires (Argentina) were evaluated. Serum IGF-1 was measured as part of the routine tests for overweight/obesity. Non-diabetic cats were included in the study if they had a BCS>6/9. Twenty-nine cats were classified as overweight (BCS 7/9), whereas 51 were classified as obese (BCS 8-9/9). Median serum IGF-1 concentrations of cats with BCS 7/9, 8/9, and 9/9 were 570 ng/ml (range 123-1456 ng/ml), 634 ng/ml (range 151-1500 ng/ml), and 598 ng/ml (range 284-2450 ng/ml), respectively. There was a positive linear correlation between serum IGF-1 concentrations and body weight (r= 0.24, 95% CI 0.01-0.44 P=0.03), and between IGF-1 and BCS (r= 0.27, 95% CI 0.08-0.44 P=0.004). In total, 8.75% (95% confidence interval 3.6-17.2%) of the cats with overweight/obesity had IGF-1 concentrations >1000 ng/ml. Pituitary enlargement was detected on computed tomography in 4/7 cases. These seven cats showed varying degrees of phenotypic changes consistent with acromegaly. A proportion of 8.75 % of overweight/obese non-diabetic cats from referral centers in Buenos Aires had serum IGF-1 concentration in a range consistent with HST in diabetic cats. Likewise, 5% of overweight/obese cats were likely to be diagnosed with HST, supported by evidence of pituitary enlargement. Serum IGF-1 concentrations were positively correlated with body weight and BCS in this population of cats. This study highlights the relevance of screening different populations of non-diabetic cats to increase the detection of HST/acromegaly.

Declining Levels and Bioavailability of IGF-I in Cardiovascular Aging Associate With QT Prolongation-Results From the 1946 British Birth Cohort

Background

As people age, circulating levels of insulin-like growth factors (IGFs) and IGF binding protein 3 (IGFBP-3) decline. In rat cardiomyocytes, IGF-I has been shown to regulate sarcolemmal potassium channel activity and late sodium current thus impacting cardiac repolarization and the heart rate-corrected QT (QTc). However, the relationship between IGFs and IGFBP-3 with the QTc interval in humans, is unknown.

Objectives

To examine the association of IGFs and IGFBP-3 with QTc interval in an older age population-based cohort.

Methods

Participants were from the 1946 Medical Research Council (MRC) National Survey of Health and Development (NSHD) British birth cohort. Biomarkers from blood samples at age 53 and 60-64 years (y, exposures) included IGF-I/II, IGFBP-3, IGF-I/IGFBP-3 ratio and the change (Δ) in marker levels between the 60-64 and 53y sampled timepoints. QTc (outcome) was recorded from electrocardiograms at the 60-64y timepoint. Generalized linear multivariable models with adjustments for relevant demographic and clinical factors, were used for complete-cases and repeated after multiple imputation.

Results

One thousand four hundred forty-eight participants were included (48.3% men; QTc mean 414 ms interquartile range 26 ms). Univariate analysis revealed an association between low IGF-I and IGF-I/IGFBP-3 ratio at 60-64y with QTc prolongation [respectively: β -0.30 ms/nmol/L, (95% confidence intervals -0.44, -0.17), p < 0.001; β-28.9 ms/unit (-41.93, -15.50), p < 0.001], but not with IGF-II or IGFBP-3. No association with QTc was found for IGF biomarkers sampled at 53y, however both ΔIGF-I and ΔIGF-I/IGFBP-3 ratio were negatively associated with QTc [β -0.04 ms/nmol/L (-0.08, -0.008), p = 0.019; β -2.44 ms/unit (-4.17, -0.67), p = 0.007] while ΔIGF-II and ΔIGFBP-3 showed no association. In fully adjusted complete case and imputed models (reporting latter) low IGF-I and IGF-I/IGFBP-3 ratio at 60-64y [β -0.21 ms/nmol/L (-0.39, -0.04), p = 0.017; β -20.14 ms/unit (-36.28, -3.99), p = 0.015], steeper decline in ΔIGF-I [β -0.05 ms/nmol/L/10 years (-0.10, -0.002), p = 0.042] and shallower rise in ΔIGF-I/IGFBP-3 ratio over a decade [β -2.16 ms/unit/10 years (-4.23, -0.09), p = 0.041], were all independently associated with QTc prolongation. Independent associations with QTc were also confirmed for other previously known covariates: female sex [β 9.65 ms (6.65, 12.65), p < 0.001], increased left ventricular mass [β 0.04 ms/g (0.02, 0.06), p < 0.001] and blood potassium levels [β -5.70 ms/mmol/L (-10.23, -1.18) p = 0.014].

Conclusion

Over a decade, in an older age population-based cohort, declining levels and bioavailability of IGF-I associate with prolongation of the QTc interval. As QTc prolongation associates with increased risk for sudden death even in apparently healthy people, further research into the antiarrhythmic effects of IGF-I on cardiomyocytes is warranted.

Old blood from heterochronic parabionts accelerates vascular aging in young mice: transcriptomic signature of pathologic smooth muscle remodeling

Vascular aging has a central role in the pathogenesis of cardiovascular diseases contributing to increased mortality of older adults. There is increasing evidence that, in addition to the documented role of cell-autonomous mechanisms of aging, cell-nonautonomous mechanisms also play a critical role in the regulation of vascular aging processes. Our recent transcriptomic studies (Kiss T. et al. Geroscience. 2020;42(2):727-748) demonstrated that circulating anti-geronic factors from young blood promote vascular rejuvenation in aged mice. The present study was designed to expand upon the results of this study by testing the hypothesis that circulating pro-geronic factors also contribute to the genesis of vascular aging phenotypes. To test this hypothesis, through heterochronic parabiosis, we determined the extent to which shifts in the vascular transcriptome (RNA-seq) are modulated by the old systemic environment. We reanalyzed existing RNA-seq data, comparing the transcriptome in the aorta arch samples isolated from isochronic parabiont aged (20-month-old) C57BL/6 mice [A-(A); parabiosis for 8 weeks] and young isochronic parabiont (6-month-old) mice [Y-(Y)] and also assessing transcriptomic changes in the aortic arch in young (6-month-old) parabiont mice [Y-(A); heterochronic parabiosis for 8 weeks] induced by the presence of old blood derived from aged (20-month-old) parabionts. We identified 528 concordant genes whose expression levels differed in the aged phenotype and were shifted towards the aged phenotype by the presence of old blood in young Y-(A) animals. Among them, the expression of 221 concordant genes was unaffected by the presence of young blood in A-(Y) mice. GO enrichment analysis suggests that old blood-regulated genes may contribute to pathologic vascular remodeling. IPA Upstream Regulator analysis (performed to identify upstream transcriptional regulators that may contribute to the observed transcriptomic changes) suggests that the mechanism of action of pro-geronic factors present in old blood may include inhibition of pathways mediated by SRF (serum response factor), insulin-like growth factor-1 (IGF-1) and VEGF-A. In conclusion, relatively short-term exposure to old blood can accelerate vascular aging processes. Our findings provide additional evidence supporting the significant plasticity of vascular aging and the existence of circulating pro-geronic factors mediating pathological remodeling of the vascular smooth muscle cells and the extracellular matrix.

Genetically predicted insulin-like growth factor-I in relation to muscle mass and strength

OBJECTIVE

Insulin-like growth factor I (IGF-I) has been associated with muscle status in animal- and population-based studies. We conducted a Mendelian randomisation study to assess the causality of the associations of IGF-I with muscle strength and mass.

DESIGN AND PATIENTS

Genetic variants associated with serum IGF-I at genome-wide significance in the UK Biobank study (358,072 individuals of European descent) were selected as instrumental variables. Summary-level data on the associations of those variants with muscle weakness (low-grip strength) and muscle mass (fat-free body mass) were available from a meta-analysis of 22 genome-wide association studies including 46,596 cases and 209,927 noncases and genome-wide association analysis in 155,961 individuals from the UK Biobank study, respectively. The univariable and multivariable inverse-variance weighted methods were used.

RESULTS

Higher genetically predicted IGF-I levels were associated with a reduced risk of muscle weakness and increased muscle mass. For one standard deviation increase in genetically predicted IGF-I levels, the odds ratio was 0.92 (95% confidence interval [CI], 0.88, 0.97; p = .001) for muscle weakness and the change was 0.53 (95% CI: 0.28, 0.79; p < .001) kg for muscle mass. In the multivariable model with adjustment for genetically predicted height, the associations were attenuated but persisted for both muscle weakness (odds ratio: 0.95, 95% CI: 0.91, 0.99; p = .015) and muscle mass (change: 0.25, 95% CI: 0.10, 0.40; p = .001).

CONCLUSION

This study suggests that high IGF-I levels may decrease the risk of muscle weakness and loss.

Investigating the Relationship Between IGF-I, IGF-II, and IGFBP-3 Concentrations and Later-Life Cognition and Brain Volume

BACKGROUND

The insulin/insulin-like signaling (IIS) pathways, including insulin-like growth factors (IGFs), vary with age. However, their association with late-life cognition and neuroimaging parameters is not well characterized.

METHODS

Using data from the British 1946 birth cohort, we investigated associations of IGF-I, IGF-II and IGF binding protein 3 (IGFBP-3; measured at 53 and 60-64 years of age) with cognitive performance [word-learning test (WLT) and visual letter search (VLS) at 60-64 years and 69 years of age] and cognitive state [Addenbrooke's Cognitive Exam III (ACE-III) at 69-71 years of age], and in a proportion, quantified neuroimaging measures [whole brain volume (WBV), white matter hyperintensity volume (WMHV), hippocampal volume (HV)]. Regression models included adjustments for demographic, lifestyle, and health factors.

RESULTS

Higher IGF-I and IGF-II at 53 years of age was associated with higher ACE-III scores [ß 0.07 95% confidence interval (CI) (0.02, 0.12); scoreACE-III 89.48 (88.86, 90.1), respectively). IGF-II at 53 years of age was additionally associated with higher WLT scores [scoreWLT 20 (19.35, 20.65)]. IGFBP-3 at 60 to 64 years of age was associated with favorable VLS score at 60 to 64 and 69 years of age [ß 0.07 (0.01, 0.12); ß 0.07 (0.02, 0.12), respectively], higher memory and cognitive state at 69 years of age [ß 0.07 (0.01, 0.12); ß 0.07 (0.01, 0.13), respectively], and reduced WMHV [ß -0.1 (-0.21, -0.00)]. IGF-I/IGFBP-3 at 60 to 64 years of was associated with lower VLS scores at 69 years of age [ß -0.08 (-0.15, -0.02)].

CONCLUSIONS

Increased measure in IIS parameters (IGF-I, IGF-II, and IGFBP-3) relate to better cognitive state in later life. There were apparent associations with specific cognitive domains (IGF-II relating to memory; IGFBP-3 relating to memory, processing speed, and WMHV; and IGF-I/IGFBP-3 molar ratio related to slower processing speed). IGFs and IGFBP-3 are associated with favorable cognitive function outcomes.

Serum insulin-like growth factor-1 concentrations in healthy cats before and after weight gain and weight loss

Background

Measurement of serum concentrations of insulin‐like growth factor (IGF)‐1 is used to diagnose acromegaly in cats.

Hypothesis

Changes of body weight do not affect serum concentrations of IGF‐1 in cats.

Animals

Ten healthy purpose‐bred cats.

Methods

Prospective study. In lean cats, food availability was stepwise increased during the first week and given ad libitum for a total of 40 weeks to increase their body weight. From week 41 to week 60, food access was limited to reach a weight loss of 1% to 2% each week. Measurement of IGF‐1 was performed at week 0, 16, 40, and 60. Insulin‐like growth factor‐1 was measured by radioimmunoassay. Body weight and IGF‐1 were compared among the 4 time points.

Results

Body weight increased by 44% from week 0 (4.5 ± 0.4 kg) to week 40 (6.5 ± 1.2 kg) (P < .001) and decreased by 25% from week 40 to week 60 (4.9 ± 0.7 kg) (P < .001). Serum IGF‐1 concentrations did not differ during the study period (week 0, 16, 40, 60: 500 ± 188, 479 ± 247, 470 ± 184, 435 ± 154 ng/mL, respectively; P = .38). Correlations with body weight were not observed.

Conclusions and Clinical Importance

Insulin‐like growth factor‐1 might not be influenced by changes of body weight in healthy cats, possibly suggesting that the latter is unimportant when interpreting IGF‐1 results in this species.

A novel oral nutritional supplement improves gait speed and mitochondrial functioning compared to standard care in older adults with (or at risk of) undernutrition: results from a randomized controlled trial

Undernutrition in older adults is mainly addressed by oral nutritional supplements, which do not affect physical functioning. In this study, we tested a novel oral nutritional supplement that included whey and casein protein, ursolic acid, free branch-chained amino acids and vitamin D against a standard supplement. We included older adults (>65y) with (or at risk of) undernutrition (n=82) and randomized them to 12 weeks of novel or standard supplement.

Both groups showed significant increases in body mass. No within or between-group differences in lean body mass were observed. Fat mass increased significantly more in the standard than the novel supplement group (time*treatment effect P=0.045). The novel supplement group showed a larger improvement in walking performance on distances of 4m (treatment x time interaction P=0.048) and 400m (treatment x time interaction P=0.038) than the standard treatment group. Gene sets related to mitochondrial functioning and oxidative phosphorylation were upregulated in the novel supplement group and downregulated in the standard supplement group.

We conclude that a 12-week intervention with the novel supplement improved walking performance both during short and long distance as compared to a standard supplement, which can largely be explained by increased mitochondrial functioning in the group receiving the novel supplement.

Impact of Long-Term HFD Intake on the Peripheral and Central IGF System in Male and Female Mice

The insulin-like growth factor (IGF) system is responsible for growth, but also affects metabolism and brain function throughout life. New IGF family members (i.e., pappalysins and stanniocalcins) control the availability/activity of IGFs and are implicated in growth. However, how diet and obesity modify this system has been poorly studied. We explored how intake of a high-fat diet (HFD) or commercial control diet (CCD) affects the IGF system in the circulation, visceral adipose tissue (VAT) and hypothalamus. Male and female C57/BL6J mice received HFD (60% fat, 5.1 kcal/g), CCD (10% fat, 3.7 kcal/g) or chow (3.1 % fat, 3.4 kcal/g) for 8 weeks. After 7 weeks of HFD intake, males had decreased glucose tolerance (p < 0.01) and at sacrifice increased plasma insulin (p < 0.05) and leptin (p < 0.01). Circulating free IGF1 (p < 0.001), total IGF1 (p < 0.001), IGF2 (p < 0.05) and IGFBP3 (p < 0.01) were higher after HFD in both sexes, with CCD increasing IGFBP2 in males (p < 0.001). In VAT, HFD reduced mRNA levels of IGF2 (p < 0.05), PAPP-A (p < 0.001) and stanniocalcin (STC)-1 (p < 0.001) in males. HFD increased hypothalamic IGF1 (p < 0.01), IGF2 (p < 0.05) and IGFBP5 (p < 0.01) mRNA levels, with these changes more apparent in females. Our results show that diet-induced changes in the IGF system are tissue-, sex- and diet-dependent.

The Neglected Insulin: IGF-II, a Metabolic Regulator with Implications for Diabetes, Obesity, and Cancer

When originally discovered, one of the initial observations was that, when all of the insulin peptide was depleted from serum, the vast majority of the insulin activity remained and this was due to a single additional peptide, IGF-II. The IGF-II gene is adjacent to the insulin gene, which is a result of gene duplication, but has evolved to be considerably more complicated. It was one of the first genes recognised to be imprinted and expressed in a parent-of-origin specific manner. The gene codes for IGF-II mRNA, but, in addition, also codes for antisense RNA, long non-coding RNA, and several micro RNA. Recent evidence suggests that each of these have important independent roles in metabolic regulation. It has also become clear that an alternatively spliced form of the insulin receptor may be the principle IGF-II receptor. These recent discoveries have important implications for metabolic disorders and also for cancer, for which there is renewed acknowledgement of the importance of metabolic reprogramming.

Aging and the Male Reproductive System

This narrative review presents an overview of current knowledge on fertility and reproductive hormone changes in aging men, the factors driving and modulating these changes, their clinical consequences, and the benefits and risks of testosterone (T) therapy. Aging is accompanied by moderate decline of gamete quality and fertility. Population mean levels show a mild total T decline, an SHBG increase, a steeper free T decline, and a moderate LH increase with important contribution of comorbidities (e.g., obesity) to these changes. Sexual symptoms and lower hematocrit are associated with low T and are partly responsive to T therapy. The relationship of serum T with body composition and metabolic health is bidirectional; limited beneficial effects of T therapy on body composition have only marginal effects on metabolic health and physical function. Skeletal changes are associated primarily with estradiol and SHBG. Cognitive decline is not consistently linked to low T and is not improved by T therapy. Although limited evidence links moderate androgen decline with depressive symptoms, T therapy has small beneficial effects on mood, depressive symptoms, and vitality in elderly patients with low T. Suboptimal T (and/or DHT) has been associated with increased risk of stroke, but not of ischemic heart disease, whereas an association with mortality probably reflects that low T is a marker of poor health. Globally, neither severity of clinical consequences attributable to low T nor the nature and magnitude of beneficial treatment effects justify the concept of some broadly applied "T replacement therapy" in older men with low T. Moreover, long-term safety of T therapy is not established.

IGFBP-2 and aging: a 20-year longitudinal study on IGFBP-2, IGF-I, BMI, insulin sensitivity and mortality in an aging population

Objective Insulin-like growth factor-binding protein-2 (IGFBP-2) concentrations are low in subjects with metabolic syndrome and type 2 diabetes. Intriguingly, recent studies have demonstrated an association between high IGFBP-2 concentrations and increased mortality not only in populations with certain types of cancer, but also in relatively healthy populations. We evaluated the role of IGFBP-2 in relation to BMI and mortality. Design and Participants BMI, insulin sensitivity, insulin-like growth factor 1 (IGF-I) and IGFBP-2 were assessed repeatedly in 539 participants of the Baltimore Longitudinal Study of Aging around the ages of 55, 65 and 75 years. Results IGFBP-2 concentrations positively correlated with insulin sensitivity and inversely with BMI, both at baseline and follow-up. Independent of IGF-I, sex, BMI and insulin sensitivity, circulating IGFBP-2 levels positively correlated with age (P < 0.001). Changes over time in BMI were associated with an inverse correlation in IGFBP-2 concentrations. Furthermore, we found indications of a relationship between low baseline IGFBP-2 levels and mortality. Remarkably, after adjustment for insulin sensitivity, the opposite association was found, as a unit increase of log(IGFBP2) was associated with an increase in the log hazard by 1.43 (95% CI: 0.3-2.6). This accounted for both baseline (P = 0.02) as well as serial (P < 0.001) measurements of IGFBP2. Finally, in this longitudinal study, we found that IGF-I concentrations increased with age (0.82 ± 0.2 (µg/L)/year, P < 0.001). Conclusion This is the first study investigating the relationship between IGFBP-2 levels and age in a longitudinal setting. Serum IGFBP-2 levels increase with age after the age of 50 years and evolve in parallel with insulin sensitivity. IGFBP-2 may therefore be a potential marker for insulin sensitivity. We further show that IGFBP-2 levels can predict mortality in this aging population. However, its predictive value for mortality can only be interpreted in relation to insulin sensitivity. After adjustment for insulin sensitivity, high IGFBP-2 levels are predictive of increased mortality.

Trajectories of body fatness from age 5 to 60 y and plasma biomarker concentrations of the insulin-insulin-like growth factor system

Background

A major pathway through which obesity increases the risk of cardiometabolic diseases and cancer is by inducing hormonal and metabolic abnormalities, including hyperinsulinemia and altered insulin-like growth factor (IGF) signaling. However, little is known about the influence of lifetime adiposity on the relevant biomarkers.

Objective

The aim of this study was to examine associations of trajectories of body fatness with plasma biomarker concentrations of the insulin-IGF system in 2 large prospective cohorts of US men and women.

Design

Associations between trajectories of body fatness and concentrations of plasma C-peptide, IGF-I, IGF-binding protein (IGFBP) 1, IGFBP-3, and the IGF-I-to-IGFBP-3 molar ratio was examined in 9386 women of the Nurses' Health Study and 3941 men of the Health Professionals Follow-Up Study. Group-based trajectory modeling was used to create trajectory groups on the basis of self-reported somatotype data at ages 5, 10, 20, 30, and 40 y and body mass index (BMI) at ages 45, 50, 55, and 60 y. We used multivariate linear regression models to examine the associations of trajectories with biomarker concentrations.

Results

Five trajectories of body fatness were identified: "lean-stable," "lean-moderate increase," "lean-marked increase," "medium-stable/increase," and "medium-marked increase." Compared with the lean-stable group, the lean-marked increase and medium-marked increase groups had significantly higher concentrations of C-peptide (percentage difference-women: 44% and 73%; men: 27% and 51%) and lower concentrations of IGFBP-1 (women: -61% and -78%; men: -47% and -65%). Adjustment for current BMI attenuated the association to null for the medium-marked increase group, but the lean-marked increase group still had modestly higher concentrations of C-peptide (women: 10%; men: 6%) and lower concentrations of IGFBP-1 (women: -18%; men: -21%) than the lean-stable group.

Conclusions

Adiposity across the life span was associated with higher C-peptide and lower IGFBP-1 concentrations in adulthood. The associations were largely driven by attained adiposity and, to a lesser extent, weight gain in early-middle adulthood. This trial was registered at www.clinicaltrials.gov as NCT03419455.

Deficiency of myeloid-related proteins 8 and 14 (Mrp8/Mrp14) does not block inflammaging but prevents steatosis

The Mrp8 and Mrp14 proteins (calprotectin) accumulate within tissues during aging and may contribute to chronic inflammation. To address this possibility, we evaluated female calprotectin-deficient Mrp14-KO and wild-type (WT) mice at 5 and 24 months of age. However, there was no evidence that age-related inflammation is blunted in KO mice. Inflammation markers were in fact elevated in livers from old KO mice, and microarray analysis revealed more consistent elevation of genes specifically expressed by B-cells and T-cells. Adipose-specific genes, however, were less consistently elevated in aged KO mice, suggesting an anti-steatosis effect of Mrp8/14 deficiency. Consistent with this, genes decreased by the anti-steatosis agent SRT1720 were decreased in old KO compared to old WT mice. Expression of lipid metabolism genes was altered in KO mice at 5 months of age, along with genes associated with development, biosynthesis and immunity. These early-age effects of Mrp8/14 deficiency, in the absence of any external stressor, were unexpected. Taken together, our findings demonstrate a pro-steatosis rather than pro-inflammatory role of calprotectin within the aging liver. This appears to reflect a developmental-metabolic phenotype of Mrp14-KO mice that is manifest at a young age in the absence of pro-inflammatory stimuli.

Cortical Bone Size Deficit in Adult Patients With Type 1 Diabetes Mellitus

CONTEXT

The increased fracture risk associated with type 1 diabetes mellitus (T1DM) remains unexplained by traditional risk factors such as low areal bone mineral density (aBMD). Nonetheless, few data exist on other determinants of bone strength in T1DM, including volumetric bone mineral density (vBMD) and bone geometry.

OBJECTIVE

We compared areal and volumetric bone parameters and cortical bone geometry in adult T1DM patients and sex- and age-matched controls.

DESIGN

Cross-sectional study including 64 adult T1DM patients (38 men; mean age, 41.1 ± 8.1 years) and 63 sex- and age-matched controls.

MAIN OUTCOME MEASURES

Areal bone parameters using dual-energy X-ray absorptiometry; volumetric bone parameters and cortical bone geometry using peripheral quantitative computed tomography.

RESULTS

T1DM was associated with lower aBMD at the total body, femoral neck, and total hip; lower trabecular vBMD at the distal radius; and higher cortical but lower total vBMD at the radial shaft. In addition, subjects with T1DM had a similar periosteal but larger endosteal circumference, smaller cortical thickness, and lower cortical over total bone area ratio. Differences in bone parameters could not be explained by differences in bone turnover markers or body composition, but cortical area was inversely associated with glycemic variability and long-term glycemic control.

CONCLUSIONS

Besides decreased aBMD and trabecular vBMD, adult T1DM patients present with a cortical bone size deficit, which may contribute to their increased fracture risk. This deficit is mainly situated at the endosteal envelope, suggesting imbalanced remodeling rather than compromised modeling processes as the underlying mechanism.

Racial/Ethnic Differences in the Associations of Overall and Central Body Fatness with Circulating Hormones and Metabolic Factors in US Men

BACKGROUND

Racial/ethnic disparities in the associations of body fatness with hormones and metabolic factors remain poorly understood. Therefore, we evaluated whether the associations of overall and central body fatness with circulating sex steroid hormones and metabolic factors differ by race/ethnicity.

METHODS

Data from 1,243 non-Hispanic white (NHW), non-Hispanic black (NHB) and Mexican-American (MA) adult men in the third national health and nutrition examination survey (NHANES III) were analyzed. Waist circumference (central body fatness) was measured during the physical examination. Percent body fat (overall body fatness) was calculated from bioelectrical impedance. Associations were estimated by using weighted linear regression models to adjust the two measures of body fatness for each other.

RESULTS

Waist circumference, but not percent body fat was inversely associated with total testosterone and SHBG in all three racial/ethnic groups after their mutual adjustment (all P < 0.0001). Percent body fat (P = 0.02), but not waist circumference was positively associated with total estradiol in NHB men; no association was present in NHW and MA men (P-interaction = 0.04). Waist circumference, but not body fat was strongly positively associated with fasting insulin (all P < 0.0001) and inversely associated with HDL cholesterol (all P ≤ 0.003) in all three racial/ethnic groups. Both percent body fat and waist circumference were positively associated with leptin (all P < 0.0001) in all three racial/ethnic groups.

CONCLUSIONS

There was no strong evidence in the associations of sex hormones and metabolic factors with body fatness in different racial/ethnic groups. These findings should be further explored in prospective studies to determine their relevance in racial/ethnic disparities of chronic diseases.

Protein intake and risk of hip fractures in postmenopausal women and men age 50 and older

In this study, we followed postmenopausal women and men aged 50 and above for up to 32 years and found no evidence that higher protein intake increased the risk of hip fracture. Protein intake from specific sources was inversely associated with risk, but these associations appeared to differ by gender.

INTRODUCTION

We examined the association between intakes of total and specific sources of protein and hip fracture risk in postmenopausal women and men over 50 years of age. Our hypothesis was that a higher protein intake would not be associated with a higher risk of hip fractures.

METHODS

In this analysis, we followed 74,443 women in the Nurses' Health Study between 1980 and 2012 and 35,439 men from the Health Professionals Follow-up Study between 1986 and 2012. Health and lifestyle information and hip fractures were self-reported on biennial questionnaires. Protein was assessed approximately every 4 years with a food frequency questionnaire. Relative risks (RR) were computed for hip fracture by quintiles of total, animal, dairy, and plant protein intakes using Cox proportional hazard models, adjusting for potential confounders.

RESULTS

During follow-up, we ascertained 2156 incident hip fractures in women and 595 fractures in men. Among men, we observed significant inverse associations for each 10 g increase of total protein (RR = 0.92, 95% CI = 0.85-0.99) and animal protein (RR = 0.91, 95% CI = 0.85-0.98) intakes. Total and animal proteins were not significantly associated with hip fractures in women. Both plant (RR = 0.88, 95% CI 0.79-0.99 per 10 g) and dairy protein (RR = 0.92, 95% CI 0.86-0.97) were associated with significantly lower risks of hip fracture when results for men and women were combined. None of these associations were modified by BMI, smoking, physical activity, age, or calcium intake.

CONCLUSION

We found no evidence that higher protein intake increases risk of hip fracture in these Caucasian men and women. Protein intake from specific sources was inversely associated with risk, but these associations appeared to differ by gender.

Circulating insulin-like growth factor 1 and insulin-like growth factor binding protein-3 level in Alzheimer's disease: a meta-analysis

It has been reported that the associations between circulating insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) and Alzheimer's disease (AD) are controversial. Thus, present meta-analysis was carried out to confirm the probable associations. We searched "PubMed", "Springer" and "Medline" databases using the term ("insulin-like growth factor-1" or "IGF-1" or "insulin-like growth factor binding protein-3" or "IGFBP-3") and ("Alzheimer's disease") until April 2016. Furthermore, standard mean differences (SMDs) were calculated. A total of seven reports involving 1342 percipients were pooled. SMDs were -0.25 (P = 0.22) and -0.33 (P = 0.08) for IGF-1 and IGFBP-3, respectively. Furthermore, the circulating IGF-1 levels in AD patients were lower than controls when studies with the difference of mean age ≤1 year (SMD -0.57, P = 0.007) or 2 years (SMD -0.58, P = 0.02) or difference of mean MMSE scores ≤10 scores (SMD -0.94, P < 0.00001), or studies from Europe (SMD -0.89, P < 0.00001) were excluded. In addition, the circulating IGFBP-3 levels in AD patients were lower than controls when studies with the difference of mean age ≤2 years (SMD -0.62, P = 0.006) or difference of mean MMSE scores ≤6 scores (SMD -0.48, P = 0.0004), 7 scores (SMD -0.58, P = 0.02), or 8 scores (SMD -0.80, P = 0.03) were excluded. Even though no significant difference of circulating IGF-1 and IGFBP-3 levels in AD patients comparing with controls was found in present meta-analysis, the current study provided the evidence that the circulating IGF-1 and IGFBP-3 level in AD patients were influenced by the difference of mean age as well as MMSE scores. Furthermore, circulating IGFBP-3 levels in AD patients may be decreased earlier than IGF-1.

Klotho and the Growth Hormone/Insulin-Like Growth Factor 1 Axis: Novel Insights into Complex Interactions

The growth hormone (GH)/insulin-like growth factor (IGF)-1 axis is pivotal for many metabolic functions, including proper development and growth of bones, skeletal muscles, and adipose tissue. Defects in the axis' activity during childhood result in growth abnormalities, while increased secretion of GH from the pituitary results in acromegaly. In order to keep narrow physiologic concentration, GH and IGF-1 secretion and activity are tightly regulated by hypothalamic, pituitary, endocrine, paracrine, and autocrine factors. Klotho was first discovered as an aging-suppressor gene. Mice that do not express klotho die prematurely with multiple symptoms of aging, several of them are also characteristic of decreased GH/IGF-1 axis activity. Klotho is highly expressed in the brain, the kidney, and parathyroid and pituitary glands, but can also serve as a circulating hormone by its shedding, forming soluble klotho that can be detected in blood, cerebrospinal fluid, and urine. Several lines of evidence suggest an association between klotho levels and activity of the GH/IGF-1 axis: the GH-secreting cells in the anterior pituitary of klotho-deficient mice are hypotrophic; klotho levels are altered in subjects with pathologies of the GH/IGF-1 axis; and accumulating data indicate that klotho is a direct regulator of GH secretion. Thus, klotho seems to be a new player in the intricate regulation of the GH/IGF-1 axis.

Socioeconomic conditions across life related to multiple measures of the endocrine system in older adults: Longitudinal findings from a British birth cohort study

Background

Little is known about how socioeconomic position (SEP) across life impacts on different axes of the endocrine system which are thought to underlie the ageing process and its adverse consequences. We examined how indicators of SEP across life related to multiple markers of the endocrine system in late midlife, and hypothesized that lower SEP across life would be associated with an adverse hormone profile across multiple axes.

Methods

Data were from a British cohort study of 875 men and 905 women followed since their birth in March 1946 with circulating free testosterone and insulin-like growth factor-I (IGF-I) measured at both 53 and 60–64 years, and evening cortisol at 60–64 years. Indicators of SEP were ascertained prospectively across life—paternal occupational class at 4, highest educational attainment at 26, household occupational class at 53, and household income at 60–64 years. Associations between SEP and hormones were investigated using multiple regression and logistic regression models.

Results

Lower SEP was associated with lower free testosterone among men, higher free testosterone among women, and lower IGF-I and higher evening cortisol in both sexes. For example, the mean standardised difference in IGF-I comparing the lowest with the highest educational attainment at 26 years (slope index of inequality) was −0.4 in men (95% CI -0.7 to −0.2) and −0.4 in women (−0.6 to −0.2). Associations with each hormone differed by SEP indicator used and sex, and were particularly pronounced when using a composite adverse hormone score. For example, the odds of having 1 additional adverse hormone concentration in the lowest compared with highest education level were 3.7 (95% CI: 2.1, 6.3) among men, and 1.6 (1.0, 2.7) among women (P (sex interaction) = 0.02). We found no evidence that SEP was related to apparent age-related declines in free testosterone or IGF-I.

Conclusions

Lower SEP was associated with an adverse hormone profile across multiple endocrine axes. SEP differences in endocrine function may partly underlie inequalities in health and function in later life, and may reflect variations in biological rates of ageing. Further studies are required to assess the likely functional relevance of these associations.

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Socioeconomic position (SEP) across life was related to multiple hormone measures.

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Lower SEP was related to lower testosterone in men, higher testosterone in women.

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Lower SEP was related to lower IGF-I and higher evening cortisol in both sexes.

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SEP differences in multiple hormone axes may underlie later life health inequality.