The effect of semaglutide 2.4 mg once weekly on energy intake, appetite, control of eating, and gastric emptying in adults with obesity

AIM

To investigate the effects of once-weekly subcutaneous (s.c.) semaglutide 2.4 mg on gastric emptying, appetite, and energy intake in adults with obesity.

MATERIALS AND METHODS

A double-blind, parallel-group trial was conducted in 72 adults with obesity, randomized to once-weekly s.c. semaglutide (dose-escalated to 2.4 mg) or placebo for 20 weeks. Gastric emptying was assessed using paracetamol absorption following a standardized breakfast. Participant-reported appetite ratings and Control of Eating Questionnaire (CoEQ) responses were assessed, and energy intake was measured during ad libitum lunch.

RESULTS

The area under the concentration-time curve (AUC) for paracetamol 0 to 5 hours after a standardized meal (AUC_0-5h,para ; primary endpoint) was increased by 8% (P = 0.005) with semaglutide 2.4 mg versus placebo at week 20 (non-significant when corrected for week 20 body weight; P = 0.12). No effect was seen on AUC_0-1h,para , maximum observed paracetamol concentration, or time to maximum observed paracetamol concentration. Ad libitum energy intake was 35% lower with semaglutide versus placebo (1736 versus 2676 kJ; estimated treatment difference -940 kJ; P <0.0001). Semaglutide reduced hunger and prospective food consumption, and increased fullness and satiety when compared with placebo (all P <0.02). The CoEQ indicated better control of eating and fewer/weaker food cravings with semaglutide versus placebo (P <0.05). Body weight was reduced by 9.9% with semaglutide and 0.4% with placebo. Safety was consistent with the known profile of semaglutide.

CONCLUSIONS

In adults with obesity, once-weekly s.c. semaglutide 2.4 mg suppressed appetite, improved control of eating, and reduced food cravings, ad libitum energy intake and body weight versus placebo. There was no evidence of delayed gastric emptying at week 20, assessed indirectly via paracetamol absorption.

Endocrine and metabolic diurnal rhythms in young adult men born small vs appropriate for gestational age

OBJECTIVE

Sleep disturbances and alterations of diurnal endocrine rhythms are associated with increased risk of type 2 diabetes (T2D). We previously showed that young men born small for gestational age (SGA) and with increased risk of T2D have elevated fat and decreased glucose oxidation rates during nighttime. In this study, we investigated whether SGA men have an altered diurnal profile of hormones, substrates and inflammatory markers implicated in T2D pathophysiology compared with matched individuals born appropriate for gestational age (AGA).

METHODS

We collected hourly blood samples for 24 h, to measure levels of glucose, free fatty acids (FFA), triglycerides (TG), insulin, C-peptide, leptin, resistin, ghrelin, plasminogen activator inhibitor-1 (PAI-1), incretins (GLP-1 and GIP), and inflammatory markers (TNF-α and IL-6) in 13 young men born SGA and 11 young men born AGA.

RESULTS

Repeated measurements analyses were used to analyze the diurnal variations and differences between groups. The SGA subjects had increased 24-h glucose (P=0.03), glucagon (P=0.03) and resistin (P=0.003) levels with no difference in diurnal rhythms compared with AGA controls. We found significant diurnal variations in levels of blood glucose, plasma TG, FFA, insulin, C-peptide, GLP-1, GIP, leptin, visfatin, TNF-α, IL-6 and PAI-1. The variation in FFA levels differed between the groups during the evening. Plasma ghrelin and glucagon levels did not display diurnal variations.

CONCLUSIONS

Young men born SGA exhibit elevated 24-h blood glucose, and plasma glucagon and resistin levels with no major differences in diurnal rhythms of these or other key metabolic hormones, substrates or inflammatory markers implicated in the origin of adiposity and T2D.

Metabolic and Transcriptional Changes in Cultured Muscle Stem Cells from Low Birth Weight Subjects

CONTEXT/OBJECTIVE

Developmental programming of human muscle stem cells could in part explain why individuals born with low birth weight (LBW) have an increased risk of developing type 2 diabetes (T2D) later in life. We hypothesized that immature muscle stem cell functions including abnormal differentiation potential and metabolic function could link LBW with the risk of developing T2D. Design/Settings/Participants: We recruited 23 young men with LBW and 16 age-matched control subjects with normal birth weight. Biopsies were obtained from vastus lateralis, and muscle stem cells were isolated and cultured into fully differentiated myotubes.

MAIN OUTCOME MEASURES

We studied glucose uptake, glucose transporters, insulin signaling, key transcriptional markers of myotube maturity, selected site-specific DNA methylation, and mitochondrial gene expression.

RESULTS

We found reduced glucose uptake as well as decreased levels of glucose transporter-1 and -4 mRNA and of the Akt substrate of 160-kDa mRNA and protein in myotubes from LBW individuals compared with normal birth weight individuals. The myogenic differentiation markers, myogenin and myosin heavy chain 1 and 2, were decreased during late differentiation in LBW myotubes. Additionally, mRNA levels of the peroxisome proliferator-activated receptor-γ coactivator-1α and cytochrome c oxidase polypeptide 7A were reduced in LBW myotubes. Decreased gene expression was not explained by changes in DNA methylation levels.

CONCLUSION

We demonstrate transcriptional and metabolic alterations in cultured primary satellite cells isolated from LBW individuals after several cell divisions, pointing toward a retained intrinsic defect conserved in these myotubes.

Dysregulation of muscle glycogen synthase in recovery from exercise in type 2 diabetes

AIMS/HYPOTHESIS

Insulin and exercise stimulate skeletal muscle glycogen synthase (GS) activity by dephosphorylation and changes in kinetic properties. The aim of this study was to investigate the effects of insulin, exercise and post-exercise insulin stimulation on GS phosphorylation, activity and substrate affinity in obesity and type 2 diabetes.

METHODS

Obese men with type 2 diabetes (n = 13) and weight-matched controls (n = 14) underwent euglycaemic-hyperinsulinaemic clamps in the rested state and 3 h after 60 min of cycling (70% maximal pulmonary oxygen uptake [VO2max]). Biopsies from vastus lateralis muscle were obtained before and after clamps, and before and immediately after exercise.

RESULTS

Insulin-stimulated glucose uptake was lower in diabetic patients vs obese controls with or without prior exercise. Post exercise, glucose partitioning shifted away from oxidation and towards storage in both groups. Insulin and, more potently, exercise increased GS activity (fractional velocity [FV]) and substrate affinity in both groups. Both stimuli caused dephosphorylation of GS at sites 3a + 3b, with exercise additionally decreasing phosphorylation at sites 2 + 2a. In both groups, changes in GS activity, substrate affinity and dephosphorylation at sites 3a + 3b by exercise were sustained 3 h post exercise and further enhanced by insulin. Post exercise, reduced GS activity and substrate affinity as well as increased phosphorylation at sites 2 + 2a were found in diabetic patients vs obese controls.

CONCLUSIONS/INTERPRETATION

Exercise-induced activation of muscle GS in obesity and type 2 diabetes involves dephosphorylation of GS at sites 3a + 3b and 2 + 2a and enhanced substrate affinity, which is likely to facilitate glucose partitioning towards storage. Lower GS activity and increased phosphorylation at sites 2 + 2a in type 2 diabetes in the recovery period imply an impaired response to exercise.

Glucose tolerance is associated with differential expression of microRNAs in skeletal muscle: results from studies of twins with and without type 2 diabetes

AIMS/HYPOTHESIS

We aimed to identify microRNAs (miRNAs) associated with type 2 diabetes and risk of developing the disease in skeletal muscle biopsies from phenotypically well-characterised twins.

METHODS

We measured muscle miRNA levels in monozygotic (MZ) twins discordant for type 2 diabetes using arrays. Further investigations of selected miRNAs included target prediction, pathway analysis, silencing in cells and association analyses in a separate cohort of 164 non-diabetic MZ and dizygotic twins. The effects of elevated glucose and insulin levels on miRNA expression were examined, and the effect of low birthweight (LBW) was studied in rats.

RESULTS

We identified 20 miRNAs that were downregulated in MZ twins with diabetes compared with their non-diabetic co-twins. Differences for members of the miR-15 family (miR-15b and miR-16) were the most statistically significant, and these miRNAs were predicted to influence insulin signalling. Indeed, miR-15b and miR-16 levels were associated with levels of key insulin signalling proteins, miR-15b was associated with the insulin receptor in non-diabetic twins and knockdown of miR-15b/miR-16 in myocytes changed the levels of insulin signalling proteins. LBW in twins and undernutrition during pregnancy in rats were, in contrast to overt type 2 diabetes, associated with increased expression of miR-15b and/or miR-16. Elevated glucose and insulin suppressed miR-16 expression in vitro.

CONCLUSIONS

Type 2 diabetes is associated with non-genetic downregulation of several miRNAs in skeletal muscle including miR-15b and miR-16, potentially targeting insulin signalling. The paradoxical findings in twins with overt diabetes and twins at increased risk of the disease underscore the complexity of the regulation of muscle insulin signalling in glucose homeostasis.

Metabolic response to 36 hours of fasting in young men born small vs appropriate for gestational age

AIMS/HYPOTHESIS

Being born small for gestational age (SGA) is associated with an increased risk of type 2 diabetes in an affluent society, but could confer an improved chance of survival during sparse living conditions. We studied whether insulin action and other metabolic responses to prolonged fasting differed between 21 young adults born SGA and 18 matched controls born appropriate for gestational age (AGA).

METHODS

A frequently sampled IVGTT and indirect calorimetry measurements were performed after a 36 h fast. Endogenous glucose production, insulin sensitivity (SI), first-phase insulin secretion and glucose effectiveness were estimated by stable isotope tracer techniques and minimal modelling. Muscle and fat biopsies were obtained after 35 h of fasting.

RESULTS

During fasting, SGA individuals experienced a more pronounced decrease in serum insulin and lower plasma triacylglycerol levels compared with AGA individuals. In addition, energy expenditure decreased in SGA but increased in AGA individuals. After fasting, SGA individuals displayed lower fat oxidation than AGA individuals. SG was reduced in SGA compared with AGA individuals, whereas hepatic or whole body insulin action (SI) did not differ between groups. SGA individuals had increased muscle PPARGC1A DNA methylation. We found no differences in adipose tissue PPARGC1A DNA methylation, muscle and adipose tissue PPARGC1A mRNA expression, or muscle glycogen levels between the groups.

CONCLUSION

Compared with AGA individuals, SGA individuals displayed a more energy-conserving and potentially beneficial [corrected] cardiometabolic response to 36 h fasting. The role of increased muscle PPARGC1A DNA methylation in mediating this response requires further study.

Physical inactivity affects skeletal muscle insulin signaling in a birth weight-dependent manner

AIMS

We investigated whether physical inactivity could unmask defects in insulin and AMPK signaling in low birth weight (LBW) subjects.

METHODS

Twenty LBW and 20 normal birth weight (NBW) subjects were investigated using the euglycemic-hyperinsulinemic clamp with excision of skeletal muscle biopsies pre and post 9days of bed rest. Employing Western blotting, we investigated skeletal muscle Akt, AS160, GLUT4, and AMPK signaling.

RESULTS

Peripheral insulin action was similar in the two groups and was decreased to the same extent post bed rest. Insulin and AMPK signaling was unaffected by bed rest in NBW individuals. LBW subjects showed decreased insulin-stimulated Akt phosphorylation and increased AMPK α1 and γ3 protein expression post bed rest. Insulin response of AS160 phosphorylation was lower in LBW subjects both pre and post bed rest.

CONCLUSIONS

Bed rest-induced insulin resistance is not explained by impaired muscle insulin or AMPK signaling in subjects with or without LBW. Lower muscle insulin signaling in LBW subjects post bed rest despite similar degree of insulin resistance as seen in controls may to some extent support the idea that LBW subjects are at higher risk of developing type 2 diabetes when being physically inactive.

Effect of birth weight and 12 weeks of exercise training on exercise-induced AMPK signaling in human skeletal muscle

Subjects with a low birth weight (LBW) display increased risk of developing type 2 diabetes (T2D). We hypothesized that this is associated with defects in muscle adaptations following acute and regular physical activity, evident by impairments in the exercise-induced activation of AMPK signaling. We investigated 21 LBW and 21 normal birth weight (NBW) subjects during 1 h of acute exercise performed at the same relative workload before and after 12 wk of exercise training. Multiple skeletal muscle biopsies were obtained before and after exercise. Protein levels and phosphorylation status were determined by Western blotting. AMPK activities were measured using activity assays. Protein levels of AMPKα1 and -γ1 were significantly increased, whereas AMPKγ3 levels decreased with training independently of group. The LBW group had higher exercise-induced AMPK Thr(172) phosphorylation before training and higher exercise-induced ACC2 Ser(221) phosphorylation both before and after training compared with NBW. Despite exercise being performed at the same relative intensity (65% of Vo2peak), the acute exercise response on AMPK Thr(172), ACC2 Ser(221), AMPKα2β2γ1, and AMPKα2β2γ3 activities, GS activity, and adenine nucleotides as well as hexokinase II mRNA levels were all reduced after exercise training. Increased exercise-induced muscle AMPK activation and ACC2 Ser(221) phosphorylation in LBW subjects may indicate a more sensitive AMPK system in this population. Long-term exercise training may reduce the need for AMPK to control energy turnover during exercise. Thus, the remaining γ3-associated AMPK activation by acute exercise after exercise training might be sufficient to maintain cellular energy balance.

Pre- and early-postnatal nutrition modify gene and protein expressions of muscle energy metabolism markers and phospholipid Fatty Acid composition in a muscle type specific manner in sheep

We previously reported that undernutrition in late fetal life reduced whole-body insulin sensitivity in adult sheep, irrespective of dietary exposure in early postnatal life. Skeletal muscle may play an important role in control of insulin action. We therefore studied a range of putative key muscle determinants of insulin signalling in two types of skeletal muscles (longissimus dorsi (LD) and biceps femoris (BF)) and in the cardiac muscle (ventriculus sinister cordis (VSC)) of sheep from the same experiment. Twin-bearing ewes were fed either 100% (NORM) or 50% (LOW) of their energy and protein requirements during the last trimester of gestation. From day-3 postpartum to 6-months of age (around puberty), twin offspring received a high-carbohydrate-high-fat (HCHF) or a moderate-conventional (CONV) diet, whereafter all males were slaughtered. Females were subsequently raised on a moderate diet and slaughtered at 2-years of age (young adults). The only long-term consequences of fetal undernutrition observed in adult offspring were lower expressions of the insulin responsive glucose transporter 4 (GLUT4) protein and peroxisome proliferator-activated receptor gamma, coactivator 1α (PGC1α) mRNA in BF, but increased PGC1α expression in VSC. Interestingly, the HCHF diet in early postnatal life was associated with somewhat paradoxically increased expressions in LD of a range of genes (but not proteins) related to glucose uptake, insulin signalling and fatty acid oxidation. Except for fatty acid oxidation genes, these changes persisted into adulthood. No persistent expression changes were observed in BF and VSC. The HCHF diet increased phospholipid ratios of n-6/n-3 polyunsaturated fatty acids in all muscles, even in adults fed identical diets for 1½ years. In conclusion, early postnatal, but not late gestation, nutrition had long-term consequences for a number of determinants of insulin action and metabolism in LD. Tissues other than muscle may account for reduced whole body insulin sensitivity in adult LOW sheep.

Akt2 influences glycogen synthase activity in human skeletal muscle through regulation of NH₂-terminal (sites 2 + 2a) phosphorylation

Type 2 diabetes is characterized by reduced muscle glycogen synthesis. The key enzyme in this process, glycogen synthase (GS), is activated via proximal insulin signaling, but the exact molecular events remain unknown. Previously, we demonstrated that phosphorylation of Thr³⁰⁸ on Akt (p-Akt-Thr³⁰⁸), Akt2 activity, and GS activity in muscle were positively associated with insulin sensitivity. Here, in the same study population, we determined the influence of several upstream elements in the canonical PI3K signaling on muscle GS activation. One-hundred eighty-one nondiabetic twins were examined with the euglycemic hyperinsulinemic clamp combined with excision of muscle biopsies. Insulin signaling was evaluated at the levels of the insulin receptor, IRS-1-associated PI3K (IRS-1-PI3K), Akt, and GS employing activity assays and phosphospecific Western blotting. The insulin-stimulated GS activity was positively associated with p-Akt-Thr³⁰⁸ (P = 0.01) and Akt2 activity (P = 0.04) but not p-Akt-Ser⁴⁷³ or IRS-1-PI3K activity. Furthermore, p-Akt-Thr³⁰⁸ and Akt2 activity were negatively associated with NH₂-terminal GS phosphorylation (P = 0.001 for both), which in turn was negatively associated with insulin-stimulated GS activity (P < 0.001). We found no association between COOH-terminal GS phosphorylation and Akt or GS activity. Employing whole body Akt2-knockout mice, we validated the necessity for Akt2 in insulin-mediated GS activation. However, since insulin did not affect NH₂-terminal phosphorylation in mice, we could not use this model to validate the observed association between GS NH₂-terminal phosphorylation and Akt activity in humans. In conclusion, our study suggests that although COOH-terminal dephosphorylation is likely necessary for GS activation, Akt2-dependent NH₂-terminal dephosphorylation may be the site for "fine-tuning" insulin-mediated GS activation in humans.

Carboxylesterase 1 gene duplication and mRNA expression in adipose tissue are linked to obesity and metabolic function

CONTEXT AND AIMS

Carboxylesterase 1 (CES1) appears to play an important role in the control of the metabolism of triglycerides and cholesterol in adipocytes and other cell types including hepatocytes. Therefore, it is relevant to gain insights into the genetic versus non-genetic mechanisms involved in the control of CES1 mRNA expression. Here, we investigated CES1 mRNA expression level in adipose tissue and its association with measures of adiposity and metabolic function in a population of elderly twins. Furthermore, the heritability of CES1 mRNA expression level in adipose tissue and the effect of CES1 gene duplication were assessed.

METHODOLOGY

A total of 295 monozygotic and dizygotic twin subjects (62-83 years) with (n = 48) or without (n = 247) type 2 diabetes mellitus were enrolled in the study. They were subjected to a standard oral glucose tolerance test and excision of abdominal subcutaneous fat biopsies during the fasting state. Levels of CES1 mRNA and copy number of the gene were assessed by quantitative PCR.

RESULTS

CES1 mRNA expression level in adipose tissue was positively associated with body-mass index (P<0.001), homeostasis model assessment-insulin resistance (P = 0.003) and level of fasting glucose (P = 0.002), insulin (P = 0.006), and triglycerides (P = 0.003). The heritability for the expression of CES1 mRNA in adipose tissue was high. CES1 gene duplication was positively associated with insulin sensitivity (P = 0.05) as well as glucose tolerance (P = 0.03) and negatively associated with homeostasis model assessment-insulin resistance (P = 0.02). Duplication of CES1 was not linked to mRNA level of this gene (P = 0.63).

CONCLUSION

CES1 mRNA in adipose tissue appears to be under strong genetic control and was associated with measures of metabolic function raising the possibility of a potential role of this enzyme in the development of type 2 diabetes mellitus. Further studies are needed to understand the potential effect of CES1 gene duplication on adipocyte and whole-body metabolic functions.

Exercise-induced AMPK activity in skeletal muscle: role in glucose uptake and insulin sensitivity

The energy/fuel sensor 5'-AMP-activated protein kinase (AMPK) is viewed as a master regulator of cellular energy balance due to its many roles in glucose, lipid, and protein metabolism. In this review we focus on the regulation of AMPK activity in skeletal muscle and its involvement in glucose metabolism, including glucose transport and glycogen synthesis. In addition, we discuss the plausible interplay between AMPK and insulin signaling regulating these processes.

Genome-wide analysis of DNA methylation differences in muscle and fat from monozygotic twins discordant for type 2 diabetes

BACKGROUND

Monozygotic twins discordant for type 2 diabetes constitute an ideal model to study environmental contributions to type 2 diabetic traits. We aimed to examine whether global DNA methylation differences exist in major glucose metabolic tissues from these twins.

METHODOLOGY/PRINCIPAL FINDINGS

Skeletal muscle (n = 11 pairs) and subcutaneous adipose tissue (n = 5 pairs) biopsies were collected from 53-80 year-old monozygotic twin pairs discordant for type 2 diabetes. DNA methylation was measured by microarrays at 26,850 cytosine-guanine dinucleotide (CpG) sites in the promoters of 14,279 genes. Bisulfite sequencing was applied to validate array data and to quantify methylation of intergenic repetitive DNA sequences. The overall intra-pair variation in DNA methylation was large in repetitive (LINE1, D4Z4 and NBL2) regions compared to gene promoters (standard deviation of intra-pair differences: 10% points vs. 4% points, P<0.001). Increased variation of LINE1 sequence methylation was associated with more phenotypic dissimilarity measured as body mass index (r = 0.77, P = 0.007) and 2-hour plasma glucose (r = 0.66, P = 0.03) whereas the variation in promoter methylation did not associate with phenotypic differences. Validated methylation changes were identified in the promoters of known type 2 diabetes-related genes, including PPARGC1A in muscle (13.9±6.2% vs. 9.0±4.5%, P = 0.03) and HNF4A in adipose tissue (75.2±3.8% vs. 70.5±3.7%, P<0.001) which had increased methylation in type 2 diabetic individuals. A hypothesis-free genome-wide exploration of differential methylation without correction for multiple testing identified 789 and 1,458 CpG sites in skeletal muscle and adipose tissue, respectively. These methylation changes only reached some percentage points, and few sites passed correction for multiple testing.

CONCLUSIONS/SIGNIFICANCE

Our study suggests that likely acquired DNA methylation changes in skeletal muscle or adipose tissue gene promoters are quantitatively small between type 2 diabetic and non-diabetic twins. The importance of methylation changes in candidate genes such as PPARGC1A and HNF4A should be examined further by replication in larger samples.

Muscle inflammatory signaling in response to 9 days of physical inactivity in young men with low compared with normal birth weight

OBJECTIVE

The molecular mechanisms linking physical inactivity and muscle insulin resistance in humans have been suggested to include increased muscle inflammation, possibly associated with impaired oxidative metabolism. We employed a human bed rest study including 20 young males with normal birth weight (NBW) and 20 with low birth weight (LBW) and increased risk of diabetes.

METHODOLOGY

The subjects were studied before and after 9 days of bed rest using the euglycemic-hyperinsulinemic clamp and muscle biopsy excision. Muscle inflammatory status was assessed as nuclear factor-κB (NF-κB) activity and mRNA expression of the pro-inflammatory MCP1 (CCL2) and IL6 and the macrophage marker CD68. Furthermore, mRNA expression of genes central to oxidative phosphorylation (OXPHOS) was measured including ATP5O, COX7A1, NDUFB6, and UQCRB.

RESULTS

At baseline, muscle inflammatory status was similar in NBW and LBW individuals. After bed rest, CD68 expression was increased in LBW (P=0.03) but not in NBW individuals. Furthermore, expression levels of all OXPHOS genes were reduced after bed rest in LBW (P ≤ 0.05) but not in NBW subjects and were negatively correlated with CD68 expression in LBW subjects (P ≤ 0.03 for all correlations). MCP1 expression and NF-κB activity were unaffected by bed rest, and IL6 expression was too low for accurate measurements. None of the inflammatory markers correlated with insulin sensitivity.

CONCLUSIONS

Although LBW subjects exhibit disproportionately elevated CD68 mRNA expression suggesting macrophage infiltration and reduced OXPHOS gene expression when exposed to bed rest, our data altogether do not support the notion that bed rest-induced (9 days) insulin resistance is caused by increased muscle inflammation.

The PNPLA3 rs738409 G-allele associates with reduced fasting serum triglyceride and serum cholesterol in Danes with impaired glucose regulation

BACKGROUND AND AIM

Non-alcoholic fatty liver disease (NAFLD) is a common condition, associated with hepatic insulin resistance and the metabolic syndrome including hyperglycaemia and dyslipidemia. We aimed at studying the potential impact of the NAFLD-associated PNPLA3 rs738409 G-allele on NAFLD-related metabolic traits in hyperglycaemic individuals.

METHODS

The rs738409 variant was genotyped in the population-based Inter99 cohort examined by an oral glucose-tolerance test, and a combined study-sample consisting of 192 twins (96 twin pairs) and a sub-set of the Inter99 population (n = 63) examined by a hyperinsulinemic euglycemic clamp (n(total) = 255). In Inter99, we analyzed associations of rs738409 with components of the WHO-defined metabolic syndrome (n = 5,847) and traits related to metabolic disease (n = 5,663). In the combined study sample we elucidated whether the rs738409 G-allele altered hepatic or peripheral insulin sensitivity. Study populations were divided into individuals with normal glucose-tolerance (NGT) and with impaired glucose regulation (IGR).

RESULTS

The case-control study showed no associations with components of the metabolic syndrome or the metabolic syndrome. Among 1,357 IGR individuals, the rs738409 G-allele associated with decreased fasting serum triglyceride levels (per allele effect(β) = -9.9% [-14.4%;-4.0% (95% CI)], p = 5.1×10(-5)) and fasting total cholesterol (β = -0.2 mmol/l [-0.3;-0.01 mmol/l(95% CI)], p = 1.5×10(-4)). Meta-analyses showed no impact on hepatic or peripheral insulin resistance in carriers of the rs738409 G-allele.

CONCLUSION

Our findings suggest that the G-allele of PNPLA3 rs738409 associates with reduced fasting levels of cholesterol and triglyceride in individuals with IGR.

Retinol-binding protein 4 in young men with low versus normal birth weight: physiological response to short-term overfeeding

Retinol-binding protein 4 (RBP4) is a plasma protein which is elevated in obesity and type 2 diabetes. We aimed to investigate whether RBP4 represents a mechanism underlying the associations between low birth weight (LBW), high-fat diet, and insulin resistance. Forty-six young, lean men with low (n = 20) or normal (n = 26) birth weight underwent a 5-day high-fat high-calorie (HFHC) dietary intervention. In vivo glucose metabolism was assessed by euglycemic-hyperinsulinemic clamp, glucose tracer and intravenous glucose tolerance test techniques. Body composition was measured by a dual-energy x-ray absorptiometry scan, and plasma RBP4 by an enzyme-linked immunosorbent assay. RBP4 was not associated with birth weight, but with BMI (β = 0.9 µg/ml (0.08; 1.8) (95% confidence interval), P = 0.03) and plasma levels of low-density lipoprotein cholesterol (β = 5.3 µg/ml (1.9; 8.7), P = 0.03) and triglycerides (β = 15.4 µg/ml (9.5; 21.3), P < 0.001). Under baseline diet conditions, RBP4 was associated with decreased disposition index (D(i)) (β = -2.4% (-4.5%; -0.2%), P = 0.04) and increased basal hepatic glucose production rate (HGP) (β = 0.02 mg kg(-1) min(-1) (0.002; 0.04), P = 0.03), but not associated with peripheral glucose disposal rate or hepatic insulin resistance index. RBP4 levels were not influenced by overfeeding or related to peripheral and hepatic insulin resistance provoked by the dietary intervention. In conclusion, plasma RBP4 in young men associates with components of the metabolic syndrome, but is not determined by birth weight and seems not to be involved in short-term high-fat diet-induced insulin resistance.

What is a 'secure base' when death is approaching? A study applying attachment theory to adult patients' and family members' experiences of palliative home care

OBJECTIVE

Attachment theory has received much interest lately in relation to how adults cope with stress and severe illness. The aim of this study was using the experiences of patients and family members to explore palliative home care as a 'secure base' (a central concept within the theory).

METHODS

Twelve patients and 14 family members were interviewed during ongoing palliative home care. The interviews were analysed with deductive qualitative content analysis.

RESULTS

Informants expressed the relevance of sensing security during palliative home care because death and dying were threats that contributed to vulnerability. Palliative home care could foster a feeling of security and provide a secure base. This was facilitated when informants had trust in staff (e.g. due to availability and competence in providing symptom relief), felt recognised as individuals and welcomed to contact the team in times of needs. Being comfortable, informed and having an everyday life also contributed to a perception of palliative home care as a secure base. Family members stressed the importance of being relieved from responsibilities that were too heavy. The underlying meanings of experiencing palliative home care as a secure base involved gaining a sense of control and of inner peace, perceiving that despite a demanding and changed life situation, one could continue partially being oneself and having something to hope for, even if this no longer concerned cure for the ill person.

CONCLUSIONS

Important aspects of palliative home care as providing a secure base were identified and these have implications for clinical practice.

Insulin resistance induced by physical inactivity is associated with multiple transcriptional changes in skeletal muscle in young men

Physical inactivity is a risk factor for insulin resistance. We examined the effect of 9 days of bed rest on basal and insulin-stimulated expression of genes potentially involved in insulin action by applying hypothesis-generating microarray in parallel with candidate gene real-time PCR approaches in 20 healthy young men. Furthermore, we investigated whether bed rest affected DNA methylation in the promoter region of the peroxisome proliferator-activated receptor-γ coactivator-1α (PPARGC1A) gene. Subjects were reexamined after 4 wk of retraining. We found that bed rest induced insulin resistance and altered the expression of more than 4,500 genes. These changes were only partly normalized after 4 wk of retraining. Pathway analyses revealed significant downregulation of 34 pathways, predominantly those of genes associated with mitochondrial function, including PPARGC1A. Despite induction of insulin resistance, bed rest resulted in a paradoxically increased response to acute insulin stimulation in the general expression of genes, particularly those involved in inflammation and endoplasmatic reticulum (ER) stress. Furthermore, bed rest changed gene expressions of several insulin resistance and diabetes candidate genes. We also observed a trend toward increased PPARGC1A DNA methylation after bed rest. We conclude that impaired expression of PPARGC1A and other genes involved in mitochondrial function as well as a paradoxically increased response to insulin of genes involved in inflammation and ER stress may contribute to the development of insulin resistance induced by bed rest. Lack of complete normalization of changes after 4 wk of retraining underscores the importance of maintaining a minimum of daily physical activity.

Differential aetiology and impact of phosphoinositide 3-kinase (PI3K) and Akt signalling in skeletal muscle on in vivo insulin action

AIMS/HYPOTHESIS

Insulin resistance in skeletal muscle is a key factor in the development of type 2 diabetes and although some studies indicate that this could be partly attributed to reduced content and activity of various proximal and distal insulin signalling molecules, consensus is lacking. We therefore aimed to investigate the regulation of proximal insulin signalling in skeletal muscle and its effect on glucose metabolism in a large non-diabetic population.

METHODS

We examined 184 non-diabetic twins with gold-standard techniques including the euglycaemic-hyperinsulinaemic clamp. Insulin signalling was evaluated at three key levels, i.e. the insulin receptor, IRS-1 and V-akt murine thymoma viral oncogene (Akt) levels, employing kinase assays and phospho-specific western blotting.

RESULTS

Proximal insulin signalling was not associated with obesity, age or sex. However, birthweight was positively associated with IRS-1-associated phosphoinositide 3-kinase (PI3K; IRS-1-PI3K) activity (p = 0.04); maximal aerobic capacity (VO2(max)), paradoxically, was negatively associated with IRS-1-PI3K (p = 0.02) and Akt2 activity (p = 0.01). Additionally, we found low heritability estimates for most measures of insulin signalling activity. Glucose disposal was positively associated with Akt-308 phosphorylation (p < 0.001) and Akt2 activity (p = 0.05), but not with insulin receptor tyrosine kinase or IRS-1-PI3K activity.

CONCLUSIONS/INTERPRETATION

With the exception of birthweight, 'classical' modifiers of insulin action, including genetics, age, sex, obesity and VO2(max) do not seem to mediate their most central effects on whole-body insulin sensitivity through modulation of proximal insulin signalling in skeletal muscle. We also demonstrated an association between Akt activity and in vivo insulin sensitivity, suggesting a role of Akt in control of in vivo insulin resistance and potentially in type 2 diabetes.

Impact of rs361072 in the phosphoinositide 3-kinase p110beta gene on whole-body glucose metabolism and subunit protein expression in skeletal muscle

OBJECTIVE

Phosphoinositide 3-kinase (PI3K) is a major effector in insulin signaling. rs361072, located in the promoter of the gene (PIK3CB) for the p110beta subunit, has previously been found to be associated with homeostasis model assessment for insulin resistance (HOMA-IR) in obese subjects. The aim was to investigate the influence of rs361072 on in vivo glucose metabolism, skeletal muscle PI3K subunit protein levels, and type 2 diabetes.

RESEARCH DESIGN AND METHODS

The functional role of rs361072 was studied in 196 Danish healthy adult twins. Peripheral and hepatic insulin sensitivity was assessed by a euglycemic-hyperinsulinemic clamp. Basal and insulin-stimulated biopsies were taken from the vastus lateralis muscle, and tissue p110beta and p85alpha proteins were measured by Western blotting. The genetic association with type 2 diabetes and quantitative metabolic traits was investigated in 9,316 Danes with glucose tolerance ranging from normal to overt type 2 diabetes.

RESULTS

While hepatic insulin resistance was similar in the fasting state, carriers of the minor G allele had lower hepatic glucose output (per-allele effect: -16%, P(add) = 0.004) during high physiological insulin infusion. rs361072 did not associate with insulin-stimulated peripheral glucose disposal despite a decreased muscle p85alpha:p110beta protein ratio (P(add) = 0.03) in G allele carriers. No association with HOMA-IR or type 2 diabetes (odds ratio 1.07, P = 0.5) was identified, and obesity did not interact with rs361072 on these traits.

CONCLUSIONS

Our study suggests that the minor G allele of PIK3CB rs361072 associates with decreased muscle p85alpha:p110beta ratio and lower hepatic glucose production at high plasma insulin levels. However, no impact on type 2 diabetes prevalence was found.

Dissociation between skeletal muscle inhibitor-kappaB kinase/nuclear factor-kappaB pathway activity and insulin sensitivity in nondiabetic twins

CONTEXT

Several studies suggest a link between increased activity of the inflammatory inhibitor-kappaB kinase/nuclear factor-kappaB (IKK/NF-kappaB) pathway in skeletal muscle and insulin resistance.

OBJECTIVE

We aimed to study the regulation of skeletal muscle IKK/NF-kappaB pathway activity as well as the association with glucose metabolism and skeletal muscle insulin signaling.

METHODS

The study population included a metabolically well-characterized cohort of young and elderly predominantly nondiabetic twins (n = 181). Inhibitor-kappaBbeta (IkappaBbeta) protein levels are negatively associated with IKK/NF-kappaB pathway activity and were used to evaluate pathway activity with p65 levels included as loading control. This indirect measure for IKK/NF-kappaB pathway activity was validated by a p65 binding assay.

RESULTS

Evaluating the effects of heritability, age, sex, obesity, aerobic capacity, and several hormonal factors (eg insulin and TNF-alpha), only sex and age were significant predictors of IkappaBbeta to p65 ratio (28% decreased ratio in the elderly, P < 0.01, and 49% increased in males P < 0.01). IkappaBbeta to p65 ratio was unrelated to peripheral insulin sensitivity (P = 0.51) and in accordance with this also unrelated to proximal insulin signaling (P = 0.81). Although no association was seen with plasma glucose after oral glucose challenge, there was a tendency for lower IkappaBbeta to p65 ratio (adjusted for age and sex) in subjects with impaired as opposed to normal glucose tolerance (P = 0.055).

CONCLUSIONS

Altogether the subtle elevated IKK/NF-kappaB pathway activity seen in glucose-intolerant subjects suggests that IKK/NF-kappaB pathway activation may be secondary to impaired glucose tolerance and that skeletal muscle IKK/NF-kappaB pathway activity is unlikely to play any major role in the control of skeletal muscle insulin action in nondiabetic subjects.

Genetic and metabolic effects on skeletal muscle AMPK in young and older twins

The protein complex AMP-activated protein kinase (AMPK) is believed to play an important role in the regulation of skeletal muscle glucose and lipid metabolism. Defects in the AMPK system might therefore be an important factor in the pathogenesis of type 2 diabetes. We aimed to identify genetic and environmental mechanisms involved in the regulation of AMPK expression and activity and to examine the association between AMPK protein levels and activity on the one hand, and glucose and fat metabolism on the other. We investigated skeletal muscle biopsies from 100 young and 82 older mono- and dizygotic nondiabetic twins excised during the basal and insulin-stimulated states of a physiological hyperinsulinemic-euglycemic clamp. AMPKalpha1, -alpha2, and -gamma3 mRNA expression was investigated using real-time PCR, and Western blotting was employed to measure protein levels. Multiple regression analyses indicated that skeletal muscle AMPK mRNA and protein expression as well as activity were regulated by sex, age, obesity, and aerobic capacity. Comparison of intraclass correlations on AMPK measurements from mono- and dizygotic twins suggested that skeletal muscle AMPK expression was under minor genetic influence. AMPKgamma3 protein expression and activity were negatively related to whole body glucose uptake through the nonoxidative metabolic pathway and positively related to phosphorylation of glycogen synthase. Our results suggest that skeletal muscle AMPK expression is under minor genetic control but regulated by age and sex and associated with obesity and aerobic capacity. Furthermore, our results indicate a role for gamma3-containing AMPK complexes in downregulation of insulin-stimulated nonoxidative glucose metabolism possibly through inhibition of glycogen synthase activity.

Gene expression in skeletal muscle biopsies from people with type 2 diabetes and relatives: differential regulation of insulin signaling pathways

BACKGROUND

Gene expression alterations have previously been associated with type 2 diabetes, however whether these changes are primary causes or secondary effects of type 2 diabetes is not known. As healthy first degree relatives of people with type 2 diabetes have an increased risk of developing type 2 diabetes, they provide a good model in the search for primary causes of the disease.

METHODS/PRINCIPAL FINDINGS

We determined gene expression profiles in skeletal muscle biopsies from Caucasian males with type 2 diabetes, healthy first degree relatives, and healthy controls. Gene expression was measured using Affymetrix Human Genome U133 Plus 2.0 Arrays covering the entire human genome. These arrays have not previously been used for this type of study. We show for the first time that genes involved in insulin signaling are significantly upregulated in first degree relatives and significantly downregulated in people with type 2 diabetes. On the individual gene level, 11 genes showed altered expression levels in first degree relatives compared to controls, among others KIF1B and GDF8 (myostatin). LDHB was found to have a decreased expression in both groups compared to controls.

CONCLUSIONS/SIGNIFICANCE

We hypothesize that increased expression of insulin signaling molecules in first degree relatives of people with type 2 diabetes, work in concert with increased levels of insulin as a compensatory mechanism, counter-acting otherwise reduced insulin signaling activity, protecting these individuals from severe insulin resistance. This compensation is lost in people with type 2 diabetes where expression of insulin signaling molecules is reduced.

The existential impact of starting corticosteroid treatment as symptom control in advanced metastatic cancer

Treatment with corticosteroids often results in increased appetite, reduced nausea and improved well-being in patients with advanced metastatic cancer. Therefore, we have studied the existential impact of starting corticosteroid treatment as symptom control in this patient group using qualitative content analysis with both a descriptive and an interpretative focus. Ten patients were interviewed before and after 1 week of treatment with 4 mg betamethasone. Prior to treatment, patients reported distressing symptoms, deterioration and diminished autonomy, symbolising threat and death. Corticosteroid treatment produced symptom relief in the majority of the patients. They reported enhanced physical abilities and experienced feelings of a more normalized life and strengthened autonomy, symbolising health and hope. This transfer from threat to hope has important existential consequences in end-of-life care and should be addressed when communicating goals of treatment and care with the patient and family.

Retinol-binding protein 4 in twins: regulatory mechanisms and impact of circulating and tissue expression levels on insulin secretion and action

OBJECTIVE

Retinol-binding protein (RBP) 4 is an adipokine of which plasma levels are elevated in obesity and type 2 diabetes. The aims of the study were to identify determinants of plasma RBP4 and RBP4 mRNA expression in subcutaneous adipose tissue (SAT) and skeletal muscle and to investigate the association between RBP4 and in vivo measures of glucose metabolism.

RESEARCH DESIGN AND METHODS

The study population included 298 elderly twins (aged 62-83 years), with glucose tolerance ranging from normal to overt type 2 diabetes, and 178 young (aged 25-32 years) and elderly (aged 58-66 years) nondiabetic twins. Peripheral and hepatic insulin sensitivity was assessed by a euglycemic-hyperinsulinemic clamp, and beta-cell function was estimated from an intravenous glucose tolerance test.

RESULTS

The influence of environmental versus genetic factors in the regulation of plasma RBP4 increased with age. Plasma RBP4 was elevated in type 2 diabetes and increased with duration of disease. Plasma RBP4 correlated inversely with peripheral, but not hepatic, insulin sensitivity. However, the association disappeared after correction for covariates, including plasma adiponectin. Plasma retinol, and not RBP4, was inversely associated with insulin secretion. SAT RBP4 expression correlated positively with GLUT4 expression and inversely with glucose tolerance. Skeletal muscle RBP4 expression reflected intramuscular fat, and although it was suppressed by insulin, no association with insulin sensitivity was evident. RBP4 expression was not associated with circulatory RBP4.

CONCLUSIONS

In conclusion, our data indicate that RBP4 levels in plasma, skeletal muscle, and fat may be linked to insulin resistance and type 2 diabetes in a secondary and noncausal manner.