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G. Johansson, M. Uusitupa, M. Härkönen, O. Siitonen, A. Aro and T. Korhonen

Abstract. The effects of two different beta-receptor blocking agents, beta1-selective metoprolol (150 mg/day) and non-selective propranolol (120 mg/day), on hormonal responses to physical exercise (30 min bicycle ergometer test) were compared with placebo within a double-blind, cross-over design in 7 healthy male volunteers.

Plasma prolactin levels decreased from the initial values during and after exercise during treatments with placebo and beta-receptor blocking agents, but they were constantly higher with the two beta-blocking agents than with placebo. Exercise did not affect plasma testosterone levels, but during propranolol they remained higher than during placebo and metoprolol. The plasma LH and FSH levels were not affected by exercise, nor were they significantly modified by beta-blockade.

The results of this study as well as those of previous studies indicate that beta-receptor blocking agents interfere with physiological endocrine functions and that the non-selective agents may have more distinct effects in this respect.

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I Vauhkonen, L Niskanen, S Haffner, S Kainulainen, M Uusitupa and M Laakso

OBJECTIVE: To investigate whether there are differences in serum leptin levels between the offspring of non-insulin-dependent diabetes mellitus (NIDDM) patients representing different phenotypes of NIDDM, and furthermore to investigate the role of different fat tissue (subcutaneous fat area (SCFAT) and intra-abdominal fat area (IAFAT)) and insulin sensitivity on serum leptin levels. DESIGN: Twenty non-diabetic offspring of NIDDM patients with insulin secretion deficient phenotype (IS-group), 18 non-diabetic offspring of NIDDM patients with insulin resistant phenotype (IR-group) and 14 healthy control subjects without a family history of diabetes were studied. METHODS: Serum leptin levels were measured by RIA. SCFAT and IAFAT were measured by computed tomography. the total fat mass (TFM) by bioelectrical impedance and the whole body glucose uptake (WBGU) by the euglycemic hyperinsulinemic clamp technique. RESULTS: Subjects of the control group (P = 0.003) and the IS-group (P<0.001) had lower serum leptin levels than subjects of the IR-group even after adjustment for gender (P<0.001). TFM (P = 0.009), fasting plasma insulin (P = 0.003) and for IAFAT (P<0.001). The differences weakened after adjustments for SCFAT (P = 0.028) or WBGU (P = 0.040) and disappeared after adjustment for both SCFAT and WBGU (P = 0.058). In the stepwise multiple regression analyses SCFAT. WBGU and gender explained 58% of the variation of serum leptin levels whereas IAFAT failed to be a significant determinant of serum leptin levels. CONCLUSIONS: The higher serum leptin levels in the IR-group was markedly, but not solely, explained by lower rates of WBGU and higher SCFAT. SCFAT was shown to be a more important determinant of serum leptin levels than IAFAT among these study groups.

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IK Vauhkonen, LK Niskanen, L Mykkanen, SM Haffner, MI Uusitupa and M Laakso

OBJECTIVE: The purpose of this work was to study whether there are differences in plasma proinsulin levels and proinsulin-to-specific insulin ratio in the offspring of patients with different phenotypes of type II diabetes. DESIGN: Eleven glucose-tolerant offspring of type II diabetic patients with deficient insulin secretion phenotype (IS group), nine glucose-tolerant offspring of patients with insulin-resistant phenotype (IR group), and fourteen healthy control subjects without a family history of diabetes were studied. METHODS: Plasma specific insulin, plasma proinsulin, and plasma C-peptide levels were measured during a 2-h oral glucose tolerance test and during hyperglycemic clamp. RESULTS: Plasma proinsulin levels during the oral glucose tolerance test and the hyperglycemic clamp did not differ among the study groups. The IR group had a lower fasting plasma proinsulin-to-specific insulin ratio (10.3+/-1.7%) than the control group (15.4+/-1.4%; P<0.05) and the IS group (18.6+/-2.7%; P<0.05). Furthermore, the IR group had lower plasma proinsulin-to-specific insulin ratio at 30, 60 and 90 min after the oral glucose load than the IS group. However, there were no significant differences in proinsulin-to-C-peptide ratio during the oral glucose tolerance test among the study groups. In stepwise multiple regression analysis, hepatic specific insulin extraction in the fasting state (beta =0.65; P<0.001) and fasting blood glucose (beta =0.32; P<0.05) together explained 52% of the variation in fasting plasma proinsulin-to-specific insulin ratio. CONCLUSIONS: Hyperproinsulinemia is not a characteristic finding in glucose-tolerant offspring of type II diabetic probands with deficient insulin secretion or insulin-resistant phenotype. The differences in proinsulin-to-specific insulin ratios were most likely explained by different hepatic extraction among the study groups.

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T Lappalainen, M Kolehmainen, U Schwab, L Pulkkinen, D E Laaksonen, R Rauramaa, M Uusitupa and H Gylling

Objective

Serum amyloid A (SAA) is a novel link between increased adipose tissue mass and low-grade inflammation in obesity. Little is known about the factors regulating its serum concentration and mRNA levels. We investigated the association between SAA and leptin in obese and normal weight subjects and analyzed the effect of weight reduction on serum SAA concentration and gene expression in adipose tissue of the obese subjects.

Methods

Seventy-five obese subjects (60±7 years, body mass index (BMI) 32.9±2.8 kg/m2, mean±s.d.) with impaired fasting plasma glucose or impaired glucose tolerance and other features of metabolic syndrome, and 11 normal weight control subjects (48±9 years, BMI 23.7±1.9 kg/m2) were studied at the baseline. Twenty-eight obese subjects underwent a 12-week intensive weight reduction program followed by 5 months of weight maintenance. Blood samples and abdominal s.c. adipose tissue biopsies were taken at the baseline and after the follow-up. Gene expression was studied using real-time quantitative PCR.

Results

The gene expressions in women and serum concentrations of leptin and SAA were interrelated independently of body fat mass in the obese subjects (r=0.54, P=0.001; r=0.24, P=0.039 respectively). In multiple linear regression analyses, leptin mRNA explained 38% of the variance in SAA mRNA (P=0.002) in the obese women. Weight loss of at least 5% increased SAA mRNA expression by 48 and 36% in men and women, but serum SAA concentrations did not change.

Conclusions

The association between SAA and leptin suggests an interaction between these two adipokines, which may have implications in inflammatory processes related to obesity and the metabolic syndrome.