Olavi Ukkola

Adiponectin: a link between excess adiposity and associated comorbidities?

Abstract. Adiponectin is a novel polypeptide that is highly specific to adipose tissue. In contrast to other adipocytokines, adiponectin levels are decreased in obesity and associated comorbidities, such as type 2 diabetes. Decreased expression of adiponectin is correlated with insulin resistance. It has been suggested that several agents, such as tumor necrosis factor α, could mediate their effects on insulin metabolism through modulating adiponectin secretion from adipocytes. The mechanisms for the development of atherosclerotic vascular disease in obese individuals are largely unknown. Several findings support the interesting hypothesis that adiponectin could be a link between obesity and related atherosclerosis. First, adiponectin levels are lower in patients with coronary artery disease. Second, adiponectin modulates endothelial function and has an inhibitory effect on vascular smooth muscle cell proliferation. Moreover, adiponectin is accumulated more preferably to the injured vascular wall than intact vessels and has been shown to suppress macrophage-to-foam cell transformation. Adiponectin may also be involved in the modulation of inflammation. Thiazolidinediones, antiatherogenic and other effects have been explained by their direct enhancing effect on adiponectin. In conclusion, adiponectin has anti-inflammatory and antiatherogeneic effects as well as multiple beneficial effects on metabolism. Therefore it is not a surprise that adiponectin therapy has been tested in animal models of obesity, and it has been shown to ameliorate hyperglycemia and hyperinsulinemia without inducing weight gain or even inducing weight loss in some studies. Unlike agents that exert their effects centrally, adiponectins effects seem to be peripherally mediated. The evidence of an association between adiponectin and the metabolic and cardiovascular complications of obesity is growing all the time.

Mutations in the adiponectin gene in lean and obese subjects from the Swedish obese subjects cohort.

Adiponectin (also called AdipoQ, gelatin-binding protein 28, Acrp30) DNA sequence variants were determined in 96 unrelated female subjects with severe obesity (mean body mass index [BMI], 42.3 kg/m2) and in 96 non-obese female controls (mean BMI, 23.0 kg/m2) from the Swedish Obese Subjects (SOS) cohort. A single base substitution (T45G) at codon 15 of exon 2 resulting in no change in amino acid (Gly15Gly) was found in equal frequencies among obese and control subjects. However, this polymorphism was associated with serum cholesterol and waist circumference (P=.023 and.043, respectively) in the obese group. A IVS2 + G62T sequence variation was also identified, but had similar prevalence rates in obese and control subjects. Blood glucose was highest in the obese female subjects who were homozygotes for the G allele (GG) of the IVS2 + G62T polymorphism (N=56; P=.033) and all the diabetics (n=6) in this sample were in this group. IVS2 + G62T polymorphism was also associated with BMI (P=.014), diastolic blood pressure (P=.009), and sagittal diameter (P=.032). A missense point mutation at codon 111 (Tyr111His) was not associated with any obesity-related phenotypes. In conclusion, adiponectin DNA sequence variations might play a role in the complications of morbid obesity and should be further investigated.

Ghrelin Arg51Gln mutation is a risk factor for Type 2 diabetes and hypertension in a random sample of middle-aged subjects

Aims/hypothesisExperimental studies have suggested that ghrelin, a novel gastrointestinal peptide hormone, could play a role in glucose homeostasis. In addition, ghrelin has been associated with beneficial haemodynamic effects in experimental settings. Since the Arg51Gln mutation changes the carboxyterminal amino acid of the mature hormone and is associated with low ghrelin concentrations, we assessed the hypothesis that Arg51Gln mutation is a risk factor for Type 2 diabetes, impaired glucose tolerance, and hypertension.MethodsBlood pressure recordings and oral glucose tolerance test were carried out in the hypertensive (n=519) and control cohorts (n=526) of our well-defined OPERA study. The genotypes and plasma IGF-I and IGFBP-1 concentrations of 1031 subjects were analysed.ResultsThe ghrelin 51Gln allele was a risk factor for Type 2 diabetes, and the effect remained significant after adjustment for age, BMI, and study group (OR=2.53, CI: 1.11–5.75, p=0.027). In addition, the 51Gln allele was a risk factor for hypertension (OR=2.63, CI: 1.37–5.08, p=0.003). 51Gln carriers had lower concentrations of IGF-I and higher concentrations of IGFBP-1 compared to non-carriers.Conclusion/interpretationThe ghrelin 51Gln allele could increase the risk for Type 2 diabetes and hypertension. The low IGF-I concentrations in 51Gln carriers suggest that the mechanism might be associated with low GH concentrations.

Lack of association between polymorphisms of catalase, copper-zinc superoxide dismutase (SOD), extracellular SOD and endothelial nitric oxide synthase genes and macroangiopathy in patients with type 2 diabetes mellitus.

Abstract. Ukkola O, Erkkilä PH, Savolainen MJ, Kesäniemi YA (University of Oulu, Oulu, Finland). Lack of association between polymorphisms of catalase, copper–zinc superoxide dismutase (SOD), extracellular SOD and endothelial nitric oxide synthase genes and macroangiopathy in patients with type 2 diabetes mellitus. J Intern Med 2001; 249: 451–459.

Apolipoprotein E phenotype is related to macro- and microangiopathy in patients with non-insulin-dependent diabetes mellitus.

The role of apoliprotein E (apo E) in modulating the susceptibility of individuals with non-insulin-dependent diabetes mellitus (NIDDM) to atherosclerotic vascular disease was studied in 143 male and 128 female patients with NIDDM. The data show that the apolipoprotein phenotype E2 somehow protects from macrovascular complications in NIDDM both in men and women. E2 also tends to protect from microvascular complications. In contrast, apo E phenotypes E4/4 and E4/3 tend to increase the risk for macroangiopathy in NIDDM patients. The lower prevalence of macroangiopathy in the subjects with E2 was associated with lower plasma total and LDL cholesterol concentrations and low plasma lipoprotein(a) levels. Overall, this study demonstrates the role of the apo E phenotype to modulate the risk for diabetic complications in patients with NIDDM. The confirmation of the association of apo E polymorphism with diabetic complications warrants, however, long-term follow-up studies.

Clustering of metabolic abnormalities in obese individuals: the role of genetic factors

The objective of this paper is to review the current evidence in support of genetic factors underlying the clustering of components of the metabolic syndrome in obese individuals. It has become clear that individual features of the metabolic syndrome are partially determined by familial factors some of which are unique to a given component and others that are shared among several features. A few candidate genes, encoding proteins of glucose, insulin and lipid metabolism, lipolytic cascade, fatty acid intestinal absorption, glucocorticoid metabolism, haemostasis and blood pressure, have been associated with a clustering of metabolic abnormalities, although the functional significance of these associations remains to be established. Furthermore, genetic polymorphisms, such as those detected at several lipoprotein metabolism loci, can modulate the relationships between different components of the metabolic syndrome. An overfeeding study conducted on identical twins has demonstrated that genetic factors play an important role in the responsiveness to changing energy balance conditions. Leptin receptor, β2 adrenergic receptor and glucocorticoid receptor gene polymorphisms have been associated with an augmented clustering of metabolic abnormalities in response to overfeeding. Gene-gene interaction effects between markers of the α2A, β2 and β3 adrenergic receptor genes on components of the metabolic syndrome have been described. Genetic factors also seem to modify the responsiveness of metabolic syndrome features to endurance training. A growing understanding of the genetic architecture of the metabolic syndrome may help in the prevention of this condition. The reduction of excess body fat, the most common clinical feature among the cluster of metabolic abnormalities, should be the focus of the prevention and treatment of the metabolic syndrome.

Cardiovascular and lifestyle risk factors in lumbar radicular pain or clinically defined sciatica: a systematic review.

Lumbar radicular pain is a fairly common health problem, yet its risk factors are far from clear. There are no published systematic reviews on associations between cardiovascular or lifestyle risk factors and lumbar radicular pain or sciatica. The aim of this systematic literature review was to assess associations between these risk factors and lumbar radicular pain or sciatica. We conducted a systematic search of the Medline database for all original articles on lumbar radicular pain or sciatica published until August 2006. Twenty-two papers from 19 studies were included in the review. Overweight or obesity was associated with sciatica in most of the case-control and cohort studies. Some studies showed an increased risk of lumbar radicular pain in smokers with a long smoking history or in those with high levels of physical activity. A few case-control studies showed an association between serum C-reactive protein and sciatica. No consistent associations were found for serum lipids levels or high blood pressure. In summary, the associations of overweight, long smoking history, high physical activity and a high serum C-reactive protein level with lumbar radicular pain or sciatica were substantiated by the present review. However, more prospective studies are needed in order to further clarify these associations and the mechanisms of action.

Glucocorticoid receptor Bcl I variant is associated with an increased atherogenic profile in response to long-term overfeeding.

The effect of the glucocorticoid receptor (GRL) gene Bcl I polymorphism on body composition and metabolic changes in response to overfeeding was studied. Twenty-four men (mean age 21+/-2 years) who constituted 12 pairs of identical twins ate a 4.2 MJ/day energy surplus, 6 days a week, during a period of 100 days. The GRL Bcl I marker was identified by Southern Blot technique. Total body fat was assessed by hydrodensitometry and abdominal fat areas were measured by computed tomography. Fasting plasma glucose and insulin during an oral glucose tolerance test (OGTT) were assayed. The insulin and glucose areas were computed using the trapezoidal method. Triglyceride and cholesterol concentrations in plasma and lipoprotein fractions were determined enzymatically. The results showed that overfeeding induced a greater increase in body weight (p=0.002) in the 2.3/2.3 kb (n=12) than in the 4.5/2.3 kb (n=12) subjects. In addition, plasma levels of total (p=0.007) and low-density lipoprotein (LDL) cholesterol (p=0.003), as well as systolic blood pressure (p=0.036) increased more in the 2.3/2.3 kb than in the 4.5/2.3 kb subjects. The 2.3/2.3 kb genotype was also associated with a greater increase in abdominal visceral fat (p=0.040) compared to the 4.5/2.3 kb genotype. In conclusion, 2.3/2.3 kb subjects of the GRL Bcl I polymorphism experience greater increases in body weight, blood pressure and cholesterol levels as well as visceral fat than 4.5/2.3 kb subjects in response to overfeeding. These data suggest that overfeeding induces an atherogenic profile in subjects who are homozygotes for the 2.3 kb allele.

Interactions among the glucocorticoid receptor, lipoprotein lipase and adrenergic receptor genes and abdominal fat in the Québec Family Study.

OBJECTIVE: To investigate whether interactions between glucocorticoid receptor (GRL), lipoprotein lipase (LPL) and adrenergic receptor (ADR) gene markers contribute to individual differences in indicators of adiposity and abdominal obesity, including visceral fat level.DESIGN AND SUBJECTS: Cross-sectional study; 742 individuals from the phase 2 of the Québec Family Study cohort.MEASUREMENTS: Total body fat assessed by hydrodensitometry and the sum of six skinfolds. Abdominal fat areas measured by computed tomography and adjusted for age, sex and total fat mass in all analyses. GRL Bcl I, α2A-ADR Dra I and β2-ADR Ban I markers were typed by Southern blot, and other markers by polymerase chain reaction technique.RESULTS: It is confirmed that the 4.5 kb allele of the GRL BclI polymorphism is associated with a higher amount of abdominal visceral fat (AVF) depot (P for trend<0.001) independent of the level of total body fat. Furthermore, the α2-ADR Dra I variant is associated with lower cross-sectional areas of abdominal total (P=0.003) and subcutaneous (P=0.012) adipose tissue. Gene–gene interactions between GRL and α2-ADR genes affecting overall adiposity (P=0.016) as well as between GRL and β2-ADR genes (P=0.049) having influence on total abdominal fat levels were observed. When the three genes were considered together in the same analysis, significant interactions having influence on overall adiposity (P=0.017), abdominal total (P=0.032) and visceral fat (P=0.002) were observed. About 1–2% of the total variation in total fatness and abdominal fat was explained by these gene–gene interactions.CONCLUSION: There is an association between the GRL BclI polymorphism and increased AVF levels independent of the level of total body fat. The α2-ADR DraI variant is associated with a lower cross-sectional area of abdominal total fat. Numerous interactions between GRL and ADR markers on overall adiposity and total abdominal fat as well as between GRL, LPL and ADR genes on overall adiposity, abdominal total and visceral fat suggest that the genetic architecture of body fat content and adipose tissue distribution is complex although some genes, like GRL, may have ubiquitous effects.

Low plasma ghrelin concentration is an indicator of the metabolic syndrome

BACKGROUND. Low ghrelin concentration has been associated with several features of metabolic syndrome (MS), but the relationship between ghrelin concentration and MS as a cluster of metabolic aberrations has not yet been studied. AIMS OF THE STUDY. To analyse whether ghrelin concentration is associated with MS. RESEARCH DESIGN AND METHODS. Fasting plasma ghrelin concentrations of the population‐based cohort of 1037 middle‐aged men and women were analysed using a commercial radioimmunoassay kit (Phoenix Peptide). MS was determined using the new International Diabetes Federation criteria. RESULTS. The prevalence of MS was 37.2%. The ghrelin concentrations were decreased in subjects with MS (635 pg/mL) compared to those without MS (687 pg/mL) (P = 0.001). Ghrelin levels decreased with an increase in the number of metabolic abnormalities. Low ghrelin was a statistically significant predictor of MS in logistic regression analysis (P = 0.005) so that the subjects in the 1st ghrelin quartile were at higher risk of having MS compared to the subjects in the 4th quartile (OR = 1.82, 95% CI: 1.27–2.60, P = 0.001). This association remained statistically significant after adjustment for age and sex (OR = 1.76, 95% CI: 1.24–2.55, P = 0.002). CONCLUSIONS. Metabolic syndrome is associated with low ghrelin levels suggesting a relationship of ghrelin in the metabolic disturbances of MS.