Familial partial lipodystrophy linked to a novel peroxisome proliferator activator receptor -γ (PPARG) mutation, H449L: a comparison of people with this mutation and those with classic codon 482 Lamin A/C (LMNA) mutations.

AIMS: To describe the phenotype associated with a novel heterozygous missense PPARG mutation discovered in a Turkish family and to compare the fat distribution and metabolic characteristics of subjects with the peroxisome proliferator activator receptor -γ (PPARG) mutation with those of a cluster of patients with familial partial lipodystrophy with classic codon 482 Lamin A/C (LMNA) mutations. METHODS: The study involved four subjects with familial partial lipodystrophy who had a novel PPARG mutation (H449L) and six subjects with classic codon 482 LMNA mutations (R482W). RESULTS: Compared with subjects with LMNA R482W mutation, fat loss was generally less prominent in subjects with the PPARG H449L mutation. Partial fat loss was limited to the extremities, whilst truncal fat mass was preserved. The PPARG H449L mutation was associated with insulin resistance, hypertriglyceridaemia and non-alcoholic fatty liver disease in all affected subjects, but the severity was variable. Three out of four mutation carriers had overt diabetes or impaired glucose tolerance. Pioglitazone therapy in these three individuals resulted in a modest improvement in their metabolic control, and regular menstrual cycles in the two female subjects. CONCLUSIONS: We suggest that relatively modest fat loss in patients with PPARG mutations may render the recognition of the syndrome more difficult in routine clinical practice. The PPARG H449L mutation is associated with insulin resistance and metabolic complications, but their severity is variable among the affected subjects.

Mechanistic insights into insulin resistance in the genetic era.

Sir Harold Himsworth first observed and articulated the phenomenon of insulin resistance in the late 1930s. Although a long delay followed before his observations were acknowledged and enshrined in formal diagnostic classifications of diabetes mellitus, insulin resistance-related pathology in the early 21st century poses one of the major global healthcare challenges for contemporary physicians. Whilst insulin resistance is closely related to obesity and decreased physical fitness, despite intensive investigation it has proved extremely challenging to discriminate key events in its causation from epiphenomena, many related to compensation for the primary defect. Thus, a complete account of the molecular pathogenesis of insulin resistance-related diseases remains elusive. One approach circumventing such problems is the study of patients with single gene defects causing severe insulin resistance. In such patients the primary defect is known, and thus lessons may be learned about human physiology from detailed physiological study allied to knowledge of the function of the mutated protein. This review discusses developments in understanding of monogenic severe insulin resistance since discovery of the first insulin receptor mutations in 1988 and reviews the physiological lessons learnt, including the critical role of adipose tissue in human metabolic health and the meaning and importance of 'partial' insulin resistance for major human disease.

The effects of aerobic exercise on metabolic risk, insulin sensitivity and intrahepatic lipid in healthy older people from the Hertfordshire Cohort Study: a randomised controlled trial.

AIMS/HYPOTHESIS: We sought to determine the effect of an aerobic exercise intervention on clustered metabolic risk and related outcomes in healthy older adults in a single-centre, explanatory randomised controlled trial. METHODS: Participants from the Hertfordshire Cohort Study (born 1931-1939) were randomly assigned to 36 supervised 1 h sessions on a cycle ergometer over 12 weeks or to a non-intervention control group. Randomisation and group allocation were conducted by the study co-ordinator, using a software programme. Those with prevalent diabetes, unstable ischaemic heart disease or poor mobility were excluded. All data were collected at our clinical research facility in Cambridge. Components of the metabolic syndrome were used to derive a standardised composite metabolic risk score (zMS) as the primary outcome. Trial status: closed to follow-up. RESULTS: We randomised 100 participants (50 to the intervention, 50 to the control group). Mean age was 71.4 (range 67.4-76.3) years. Overall, 96% of participants attended for follow-up measures. There were no serious adverse events. Using an intention-to-treat analysis, we saw a non-significant reduction in zMS in the exercise group compared with controls (0.07 [95% CI -0.03, 0.17], p = 0.19). However, the exercise group had significantly decreased weight, waist circumference and intrahepatic lipid, with increased aerobic fitness and a 68% reduction in prevalence of abnormal glucose metabolism (OR 0.32 [95% CI 0.11-0.92], p = 0.035) compared with controls. Results were similar in per-protocol analyses. CONCLUSIONS/INTERPRETATION: Enrolment in a supervised aerobic exercise intervention led to weight loss, increased fitness and improvements in some but not all metabolic outcomes. In appropriately screened older individuals, such interventions appear to be safe. TRIAL REGISTRATION: Controlled-trials.com ISRCTN60986572 FUNDING: Medical Research Council.

Morbid obesity exposes the association between PNPLA3 I148M (rs738409) and indices of hepatic injury in individuals of European descent.

CONTEXT: The PNPLA3 I148M variant (rs738409) is robustly associated with hepatic steatosis. Intriguingly, initial findings in cohorts with a mean body mass index (BMI) of 30 kg m(-2) also suggested that it is associated with elevated liver enzymes but not with insulin resistance and dyslipidaemia. OBJECTIVE: To determine whether the PNPLA3 variant alters the susceptibility of morbidly obese subjects to develop liver injury and metabolic sequelae. PARTICIPANTS AND METHODS: The study was carried out in 678 obese Italians (mean BMI = 41 kg m(-2)) who were genotyped for the I148M variant. All participants provided fasting blood samples and then underwent oral glucose tolerance tests. MAIN OUTCOME MEASURES: Indices of liver injury (alanine transaminase (ALT), aspartate transaminase (AST)), glucose tolerance and insulin resistance were measured. RESULTS: Markers of hepatic injury such as ALT and AST were significantly higher in carriers of the 148M allele (P = 2.2 x 10(-5) and 0.001, respectively). In all, 50% of 148M risk allele homozygotes had pathological levels of ALT (>40 U l(-1)) compared with 25% of 148I allele homozygotes (P = 0.005). Glucose tolerance and insulin sensitivity were similar in all three genotypes. CONCLUSION: Obese Southern Europeans carrying the 148M allele have increased indices of liver damage uncoupled from proxy measures of insulin resistance.

Correlation of the leptin:adiponectin ratio with measures of insulin resistance in non-diabetic individuals.

AIMS/HYPOTHESIS: Obesity is the dominant cause of insulin resistance. In adult humans it is characterised by a combination of adipocyte hypertrophy and, to a lesser extent, adipocyte hyperplasia. As hypertrophic adipocytes secrete more leptin and less adiponectin, the plasma leptin:adiponectin ratio (LAR) has been proposed as a potentially useful measure of insulin resistance and vascular risk. We sought to assess the usefulness of the LAR as a measure of insulin resistance in non-diabetic white adults. METHODS: Leptin and adiponectin levels were measured in 2,097 non-diabetic individuals from the Ely and European Group for the Study of Insulin Resistance (EGIR) Relationship between Insulin Sensitivity and Cardiovascular Risk (RISC) study cohorts. LAR was compared with fasting insulin and HOMA-derived insulin sensitivity (HOMA-S) in all individuals and with the insulin sensitivity index (M/I) from hyperinsulinaemic-euglycaemic clamp studies in 1,226 EGIR RISC participants. RESULTS: The LAR was highly correlated with HOMA-S in men (r = -0.58, p = 4.5 x 10(-33) and r = -0.65, p = 1.1 x 10(-66) within the Ely and EGIR RISC study cohorts, respectively) and in women (r = -0.51, p = 2.8 x 10(-36) and r = -0.61, p = 2.5 x 10(-73)). The LAR was also strongly correlated with the clamp M/I value (r = -0.52, p = 4.5 x 10(-38) and r = -0.47, p = 6.6 x 10(-40) in men and women, respectively), similar to correlations between HOMA-S and the M/I value. CONCLUSIONS/INTERPRETATION: The leptin:adiponectin ratio is a useful measure of insulin resistance in non-diabetic white adults. These data highlight the central role of adipocyte dysfunction in the pathogenesis of insulin resistance. Given that variations between fasting and postprandial leptin and adiponectin levels tend to be small, the leptin to adiponectin ratio might also have potential value in assessing insulin sensitivity in the non-fasted state.

Gene-gene and gene-environment interactions in lipodystrophy: Lessons learned from natural PPARγ mutants.

Monogenic lipodystrophies are a heterogeneous group of rare disorders characterized by a lack of adipose tissue (AT), all of which predispose patients to the development of insulin resistance and its related metabolic sequelae. The extent of AT loss ranges from partial, as in familial partial lipodystrophy (FPLD), to a total absence of metabolically active AT in congenital generalized lipodystrophy (CGL) and is generally associated with the severity of metabolic complications. Significant genetic, allelic, phenotypic, and clinical heterogeneity exists among the lipodystrophies. Patients with FPLD3 due to mutations in the PPARG gene, which encodes a key transcriptional regulator of adipocyte development and function, provide a particularly striking example of this heterogeneity. We will present several gene-gene and gene-environment factors and mechanisms that are critical for adequate PPARγ expression and activity in AT and discuss how these interactions potentially contribute to the observed spectrum of FPLD3 phenotypes. Comparable mechanisms may play a role in other types of lipodystrophies too, and their elucidation may further improve our molecular understanding of AT dysfunction.

Farmers' Perceptions of Dairy Cattle Breeds, Breeding and Feeding Strategies: A Case of Smallholder Dairy Farmers in Western Kenya.

To understand farmers' preference and perceptions of breed attributes, breeding and feeding practices, 419 households in western Kenya were interviewed in a cross-sectional survey. Respondents scored their preference for cattle breeds, traits and breeding methods on a scale of 1 (most preferred) to 5 (least preferred). Preferences were compared using multinomial logistic regression models on weighted scores. The Ayrshire breed was most preferred followed by the Friesian. Using hardship tolerance as a reference trait, the Friesian was preferred 4.86 times more for high milk production and Ayrshire, Jersey and Guernsey breeds 4.61, 4.60 and 4.18 times (p < 0.01) more, respectively, for milk fat content. The Ayrshire was preferred 4.16 times more for its perceived low feed requirement and 1.22 times more (p < 0.01) for resistance to diseases. Friesian was the only breed preferred (3.18 times more) (p < 0.01) for high growth rate of calves. Artificial insemination (AI) was the breeding method of choice, but majority (>68%) of respondents used natural mating, because it was readily available and cheaper. The current study highlights the importance of taking into account farmers' objectives and the production environment when designing breed improvement programmes and recommends packaging of breeding together with feeding interventions.

Genetic syndromes of severe insulin resistance.

Insulin resistance underpins the link between obesity and most of its associated metabolic disorders including type 2 diabetes, fatty liver disease, dyslipidaemia and cardiovascular disease. Despite its importance and extensive scientific endeavour, its precise molecular pathogenesis remains unclear. Monogenic syndromes of extreme insulin resistance, whilst rare in themselves, can provide unique insights into the pathogenesis of human insulin resistance. Severe insulin resistance syndromes are broadly classified into three categories: lipodystrophies, primary insulin signalling defects or complex syndromes including severe insulin resistance. Genetically confirmed classification has facilitated the identification of robust diagnostic biochemical features accelerating accurate clinical diagnosis. Interestingly the biochemical features of lipodystrophies are far more closely aligned to what is seen in prevalent forms of insulin resistance than those of primary insulin signalling defects, suggesting that lipodystrophy could be a relevant model for common disease. This assertion is supported by genome-wide association data indicating that SNPs associated with fasting hyperinsulinemia and metabolic dyslipidaemia, are strongly associated with a subtle reduction in hip fat, suggesting that subtle forms of lipodystrophy are likely to be a significant contributor to prevalent insulin resistance.

Use of body linear measurements to estimate liveweight of crossbred dairy cattle in smallholder farms in Kenya.

Body linear measurements, and specifically heart girth (HG), have been shown to be useful predictors of cattle liveweight. To test the accuracy of body linear measurements for predicting liveweight, crossbred dairy cattle of different genotypes were measured and weighed. A total of 352 mature cows and 100 heifers were weighed using an electronic weighing scale and measurements of HG, body length, height at withers were taken using an ordinary measuring tape and body condition scored (BCS) using a five-point scale. The animals were grouped according to genotype and age. Genotype classification was undertaken from farmer recall and by visual appraisal as 40-60, 61-80 or 81-100 % exotic (non-indigenous). Age classification was simply as mature cows or heifers. Liveweight of the animals ranged from 102 to 433 kg. Liveweight was strongly correlated with HG (r = 0.84) and body condition scores (r = 0.70) and moderately correlated with body length (r = 0.64) and height at withers (0.61). Regressing LW on HG measurements gave statistically significant (P < 0.01) equations with R(2) ranging from of 0.53 to 0.78 and residual standard deviation ranging from 18.11 to 40.50 kg. The overall model developed (adjusted R(2) = 0.71) had a prediction error of 26 kg (or 11 % of the mean) and predicted LW of over 95 % of crossbred dairy cattle in the range of 100-450 kg, regardless of age and breed group. Including BCS in the model slightly improved the model fit but not the prediction error. It was concluded that the model can be useful in making general management decisions in smallholder farms.

Resistin / Fizz3 expression in relation to obesity and peroxisome proliferator-activated receptor-gamma action in humans.

Recent studies in murine models suggest that resistin (also called Fizz3 [1]), a novel cysteine-rich protein secreted by adipocytes, may represent the long-sought link between obesity and insulin resistance (2). Furthermore, peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists appear to inhibit resistin expression in murine adipocytes, providing a possible explanation for the mode of action of this class of insulin sensitizers (2). Using a fluorescent real-time reverse transcriptase-polymerase chain reaction-based assay, we found that resistin mRNA levels in whole adipose tissue samples were increased in morbidly obese humans compared with lean control subjects. However, in freshly isolated human adipocytes, resistin mRNA levels were very low and showed no correlation with BMI. Resistin mRNA was undetectable in preadipocytes, endothelial cells, and vascular smooth muscle cells, but it was readily detectable in circulating mononuclear cells. Although exposure of human mononuclear cells to PPAR-gamma agonists markedly upregulated fatty acid-binding protein-4 expression, these agents had no effect on mononuclear cell resistin expression. Finally, resistin mRNA was undetectable in adipocytes from a severely insulin-resistant subject with a dominant-negative mutation in PPAR-gamma (3). We conclude that the recently described relationships of murine resistin/Fizz3 expression with obesity, insulin resistance, and PPAR-gamma action may not readily translate to humans. Further studies of this novel class of proteins are needed to clarify their roles in human metabolism.

Clinical and molecular characterization of a novel PLIN1 frameshift mutation identified in patients with familial partial lipodystrophy.

Perilipin 1 is a lipid droplet coat protein predominantly expressed in adipocytes, where it inhibits basal and facilitates stimulated lipolysis. Loss-of-function mutations in the PLIN1 gene were recently reported in patients with a novel subtype of familial partial lipodystrophy, designated as FPLD4. We now report the identification and characterization of a novel heterozygous frameshift mutation affecting the carboxy-terminus (439fs) of perilipin 1 in two unrelated families. The mutation cosegregated with a similar phenotype including partial lipodystrophy, severe insulin resistance and type 2 diabetes, extreme hypertriglyceridemia, and nonalcoholic fatty liver disease in both families. Poor metabolic control despite maximal medical therapy prompted two patients to undergo bariatric surgery, with remarkably beneficial consequences. Functional studies indicated that expression levels of the mutant protein were lower than wild-type protein, and in stably transfected preadipocytes the mutant protein was associated with smaller lipid droplets. Interestingly, unlike the previously reported 398 and 404 frameshift mutants, this variant binds and stabilizes ABHD5 expression but still fails to inhibit basal lipolysis as effectively as wild-type perilipin 1. Collectively, these findings highlight the physiological need for exquisite regulation of neutral lipid storage within adipocyte lipid droplets, as well as the possible metabolic benefits of bariatric surgery in this serious disease.

An approach to quantifying abnormalities in energy expenditure and lean mass in metabolic disease.

BACKGROUND/OBJECTIVES: The objective of this study was to develop approaches to expressing resting energy expenditure (REE) and lean body mass (LM) phenotypes of metabolic disorders in terms of Z-scores relative to their predicted healthy values. SUBJECTS/METHODS: Body composition and REE were measured in 135 healthy participants. Prediction equations for LM and REE were obtained from linear regression and the range of normality by the standard deviation of residuals. Application is demonstrated in patients from three metabolic disorder groups (lipodystrophy, n=7; thyrotoxicosis, n=16; and resistance to thyroid hormone (RTH), n=46) in which altered REE and/or LM were characterised by departure from the predicted healthy values, expressed as a Z-score. RESULTS: REE (kJ/min) = -0.010 × age (years)+0.016 × FM (kg)+0.054 × fat-free mass (kg)+1.736 (R2 = 0.732, RSD = 0.36 kJ/min). LM (kg)=5.30 × bone mineral content (kg)+10.66 × height2 (m)+6.40 (male). LM (kg)=0.20 × fat (kg)+14.08 × height2 (m)-2.93 (female).(male R2=0.55, RSD = 3.90 kg; female R2 = 0.59, RSD=3.85 kg).We found average Z-scores for REE and LM of 1.77 kJ/min and -0.17 kg in the RTH group, 5.82 kJ/min and -1.23 kg in the thyrotoxic group and 2.97 kJ/min and 4.20 kg in the LD group. CONCLUSION: This approach enables comparison of data from individuals with metabolic disorders with those of healthy individuals, describing their departure from the healthy mean by a Z-score.

Anionic salts and dietary 25-hydroxyvitamin D stimulate calcium availability in steers.

The influence of feeds containing varying dietary cation-anion differences (DCADs) with and without supplements of 25-hydroxyvitamin D (25(OH)D) on urine pH and excretion of macro minerals was determined in fistulated crossbred steers (mean live weight 315 ± 45 kg). A basal forage diet comprising lucerne hay and wheat chaff was used, to which varying quantities of MgCl(2) or K(2)CO(3) were added to achieve four levels of DCAD: -300, 50, 150 or 250 mEq/kg dry matter (DM). Steers were allocated to one of six treatments, one treatment for each diet and a further treatment for both the 50 and 150 mEq/kg DCAD diets, which were supplemented with 25(OH)D at a rate of 3 mg/steer per day. Urine pH from steers offered the diets comprising DCADs of 50, 150 and 250 mEq/kg ranging from 8.3 to 8.8. In treatments not containing 25(OH)D with DCADs of 50 to 250 mEq/kg, there were no significant differences in urine pH or Ca excretion. However, steers offered the diet with a DCAD of -300 mEq/kg DM produced urine with a significantly lower pH (6.5 to 7.5). Daily output of Ca in urine was also significantly higher from steers given this diet. Supplementation with 25(OH)D significantly increased urinary Ca excretion from steers offered diets of DCADs 50 and 150 mEq/kg DM. Estimates of daily urinary Ca excretion, calculated using the ratio of creatinine to Ca in 'spot' urine samples, were less variable than those based on total collection (residual mean square of 0.54 and 0.63, respectively).

An activating mutation of AKT2 and human hypoglycemia.

Pathological fasting hypoglycemia in humans is usually explained by excessive circulating insulin or insulin-like molecules or by inborn errors of metabolism impairing liver glucose production. We studied three unrelated children with unexplained, recurrent, and severe fasting hypoglycemia and asymmetrical growth. All were found to carry the same de novo mutation, p.Glu17Lys, in the serine/threonine kinase AKT2, in two cases as heterozygotes and in one case in mosaic form. In heterologous cells, the mutant AKT2 was constitutively recruited to the plasma membrane, leading to insulin-independent activation of downstream signaling. Thus, systemic metabolic disease can result from constitutive, cell-autonomous activation of signaling pathways normally controlled by insulin.