Associations between neck circumference and markers of dysglycemia, non-alcoholic fatty liver disease, and dysmetabolism independent of Body Mass Index in an Emirati population

AIM

Neck circumference (NC) is quick and easy to measure and may be a useful surrogate marker for body composition. We investigated NC as a potential marker of dysglycemia, MetS, and NAFLD.

METHODS

674 individuals were recruited at the Imperial College London Diabetes Centre in a study of sleep apnea prevalence. Of these, 547 (Age 46 ± 11.4 years, Body Mass Index (BMI) 31 ± 6 kg/m², 279 (51%) female, 113 normal glucose tolerance (NGT), 108 Prediabetes, 326 Type 2 diabetes (T2DM)) met all inclusion criteria for analysis. NC was measured at the thyroid cartilage, and collar size was recorded. Analysis was performed using univariate and multivariate linear regression.

RESULTS

Adjusted for BMI, sex, and age, NC was 0.65 ± 0.3 cm greater in prediabetes (p = 0.0331), and 1.07 ± 0.28 cm greater in T2DM, compared with NGT (p = 0.0002). Adjusting for BMI, sex, and glycemic status, 1-cm increase in NC was associated with a 1.04 ± 1.01 U/L (p <0.0001) increase in ALT and, additionally, correcting for statin use, a 0.03 ± 0.01 mmol/L reduction in HDL (p <0.0001) and a 0.1 ± 0.02 increase in TC : HDL. A 1 cm increase in NC was associated with a 1.15 ± 1.02% (p <0.0001) increase in 10-year AHA cardiovascular risk in individuals over 40 years old and a 0.16 ± 0.02 (p <0.0001) increase in NAFLD fibrosis score. The neck circumference was associated with the hazard of new onset of deranged ALT adjusted for age, sex, glycemic status, and BMI (hazard ratio 1.076 (95% CI 1.015-1.14, p = 0.0131) and with the incidence of Fatty Liver Index associated with high probability of NAFLD (hazard ratio 1.153 (95% CI 1.019-1.304), p = 0.0239).

CONCLUSION

NC is associated with dysglycemia, components of the MetS, and factors predictive of NAFLD, but does not appear to independently predict subsequent progression to high risk of liver fibrosis in this predominantly diabetic population.

The Importance of Interpreting Urine Calcium:Creatinine Ratio in PHPT Within Ethnic Context

A 56-year-old Afro-Caribbean lady was found to have incidental hypercalcaemia on routine GP investigations. Tiredness was the only elicitable hypercalcaemic symptom and aside from early menopause at age 40, she had no significant past medical or family history. Examination was unremarkable. Blood results showed a raised adjusted calcium 2.68mmol/L (2.2–2.6), normal phosphate 1.06mmol/L (0.80–1.50), raised parathyroid hormone (PTH) 14.1pmol/L (1.6–7.2) and low 25-hydroxyvitamin D 28.1nmol/L (70–150).

She had osteopaenia of the femora and left radius on DEXA scan but no nephrocalcinosis on renal ultrasound. On initial investigation, her urinary calcium output was low at 1.55mmol/day resulting in a 24h calcium:creatinine ratio (UCCR) of 0.0065. Although suggestive of Familial Hypocalciuric Hypercalcaemia (FHH), her notable Vitamin D deficiency was considered to contribute to the observed hypocalciuria. After Vitamin D repletion, a repeat UCCR improved to 0.012, however, remained in the indeterminate range. No known pathogenic variant was identified on genetic analysis for FHH.

Her PTH and Calcium levels remained persistently high within 9.7–17.1pmol/L and 2.65-2.82mmol/L respectively, suggestive of Primary Hyperparathyroidism (PHPT) given the end organ damage and negative genetic studies. Based on her symptom of fatigue, osteopaenia at a young age and hypercalcaemia, localisation studies were arranged which showed no definitive evidence of a parathyroid adenoma and explorative surgery was planned.

The negative genetic testing, PTH level 17.1pmol/L, osteopaenia, low-normal magnesium and phosphate level collectively support a diagnosis of PHPT in this case, despite a low UCCR which however is observed in some PHPT patients. Indeed, a lower UCCR ratio has been reported in the healthy Afro-Carribean population across all age groups, as well as in Afro-Carribean patients with PHPT [1]. The underlying mechanism for this is yet to be determined but may be due to increased renal sensitivity to PTH or altered activity of the tubular calcium reabsorptive pathways. One can further speculate regarding an evolutionary reason behind a protective homeostatic system favouring renal calcium reabsorption over excretion in this frequently vitamin D deficient population.

Clinical practice relies heavily on the use of UCCR in aiding the biochemical differentiation of PHPT and FHH. However, as this case highlights, its use can be misleading in Afro-Carribean patients and therefore should be interpreted within an ethnic context.

References: Taha W., Singh N., Flack J. M., Abou-Samra A. B. Low urine calcium excretion in African American patients with Primary Hyperparathyroidism. Endocr Pract. 2011; 17: 867–872

Impairments to the GH-IGF-I axis in hSOD1G93A mice give insight into possible mechanisms of GH dysregulation in patients with amyotrophic lateral sclerosis

GH deficiency has been found in subjects with amyotrophic lateral sclerosis (ALS). Disrupted endocrine function could contribute to the progressive muscle loss and hypermetabolism seen in ALS. It is not possible to study all the elements of the GH-IGF-I axis in ALS patients. Consequently, it remains unclear whether dysfunctional GH secretion contributes to disease pathogenesis and why GH and IGF-I directed treatment strategies are ineffective in human ALS. The hSOD1(G93A) transgenic mouse model is useful for the detailed investigation of the pathogenesis of ALS. We report that symptomatic male hSOD1(G93A) transgenic mice exhibit a deficiency in GH secretion similar to that seen in human ALS. Further characterization of the GH-IGF-I axis in hSOD1(G93A) mice reveals central and peripheral abnormalities that are not found in wild-type age-matched controls. Specifically, we observe aberrant endogenous pulsatile GH secretion, reduced pituitary GH content, and decreased circulating levels of IGF-I, indicating global GH deficiency in hSOD1(G93A) mice. Furthermore, a reduction in the expression of the IGF-I receptor α-subunit in skeletal muscle and lumbar spinal cords of hSOD1(G93A) mice suggests impaired IGF-I signaling within these tissues. This is the first account of disrupted GH secretion in a transgenic mouse model of ALS. These observations are essential for the development of effective GH and IGF-I targeted therapies in ALS.

Early growth restriction leads to down regulation of protein kinase C zeta and insulin resistance in skeletal muscle

Epidemiological studies have revealed a relationship between early growth restriction and the subsequent development of type 2 diabetes. A rat model of maternal protein restriction has been used to investigate the mechanistic basis of this relationship. This model causes insulin resistance and diabetes in adult male offspring. The aim of the present study was to determine the effect of early growth restriction on muscle insulin action in late adult life. Rats were fed either a 20% or an isocaloric 8% protein diet during pregnancy and lactation. Offspring were weaned onto a 20% protein diet and studied at 15 Months of age. Soleus muscle from growth restricted offspring (LP) (of dams fed 8% protein diet) had similar basal glucose uptakes compared with the control group (mothers fed 20% protein diet). Insulin stimulated glucose uptake into control muscle but had no effect on LP muscle. This impaired insulin action was not related to changes in expression of either the insulin receptor or glucose transporter 4 (GLUT 4). However, LP muscle expressed significantly less (P<0.001) of the zeta isoform of protein kinase C (PKC zeta) compared with controls. This PKC isoform has been shown to be positively involved in GLUT 4-mediated glucose transport. Expression levels of other isoforms (betaI, betaII, epsilon, theta) of PKC were similar in both groups. These results suggest that maternal protein restriction leads to muscle insulin resistance. Reduced expression of PKC zeta may contribute to the mechanistic basis of this resistance.