[Maternal vitamin D status in Martinique]. / Statut vitaminique D maternel à la Martinique Etude prospective de décembre 2004 à avril 2005 sur 63 femmes enceintes à terme.

OBJECTIVES: Evaluate vitamin D supplementation and vitamin D status during normal pregnancy in Martinique, a Caribbean region with sufficient sunshine for endogenous vitamin D production all year around; and "to validate" or not the necessity of supplementing pregnant women with vitamin D in Martinique. PATIENTS AND METHODS: A prospective evaluation of their vitamin D status was performed over a winter four-month period on 63 healthy women seen at term delivery. Maternal blood sampling for assays of serum 25 (OH)D, calcium, phosphates and alkaline phosphatase activity was realized in working room. All included women answered a questionnaire allowing to know various parameters known to influence vitamin D and calcium status, as their origin, their food habits, their exposure to sunshine, their supplementation or not with vitamin D during pregnancy. RESULTS: The sample represented 15% of the pregnant women seen in the department over the study period; 16% of the women had received vitamin D supplementation during pregnancy; at delivery, mean 25-(OH)D serum level in the total cohort was 32.6+/-10.7 ng/ml, with no value below 13 ng/ml; serum calcium and phosphates levels were in the normal range. CONCLUSION: These data suggest that, during normal pregnancy, and in the absence of any particular risk factor, systematic vitamin D supplementation is not required in the Martinique region.

Regular exercise (3x45 min/wk) decreases plasma viscosity in sedentary obese, insulin resistant patients parallel to an improvement in fitness and a shift in substrate oxidation balance.

UNLABELLED: Exercise training decreases blood viscosity in athletes parallel with metabolic improvements mostly characterized by an increase in insulin sensitivity. Patients with low insulin sensitivity exhibit a host of metabolic disorders that may also benefit from regular training. However, the hemorheologic aspects of training in such subjects are not known and we aimed at characterizing them. SUBJECTS: Thirty-two obese insulin resistant subjects were tested before and after 2 months. Twenty-one of them were trained (3x45 min/wk) at a level defined by exercise calorimetry and corresponding to the power at which lipid oxidation reaches a maximum (LIPOX(max )) and eleven served as controls. The two groups were matched for age and body mass index. There was no weight change in controls while the 2 months training period decreased weight by 2.5 kg (p<0.02). This change was totally explained by a loss in fat mass (-2.7 kg, p<0.02) while fat free mass remained unchanged. Blood rheology was unchanged in the control group while training improved plasma viscosity eta(pl) (before: 1.43+/-0.03 mPa.s; after: 1.35+/-0.03 mPa.s, p<0.02). There was no change in either hematocrit, red cell rigidity or red cell aggregation. The balance of substrates oxidation shifted towards a higher use of lipids (point of crossover where subjects oxidize 70% carbohydrates 30% lipids: before 39.3+/-6.9 watts; after 70.8+/-6 watts, p<0.001; point where lipid oxidation is maximal (LIPOX(max )) before: 16.5+/-1.4 watts; after: 21.4+/-1.3 watts, p<0.001) and V(O(2max )) increased by 74% (p<0.01). Consistent with observations in athletes, the metabolic and ergometric improvements induced by training reduces eta(pl) in sedentary, insulin resistant patients, but at those low levels training does not appear to induce "autohemodilution" (as reflected by hematocrit) neither it improves red cell deformability or aggregation. The reliability of eta(pl) as simple and unexpensive marker of efficiency of training in insulin resistant patients should be further evaluated.

Multivariate analysis of relationships between insulin sensitivity and blood rheology: is plasma viscosity a marker of insulin resistance?

We previously reported in populations exhibiting all the spectrum of insulin sensitivity (SI) values correlations between SI and blood viscosity eta suggesting that high eta is an additional symptom of the insulin resistance syndrome. However, due to the elevation of insulinemia (I) which is usually associated with insulin resistance it remained to determine whether this relationship was explained by SI or I. We analyzed SI with the minimal model procedure in 108 nondiabetic subjects and analyzed correlations of SI with blood rheology (eta, RBC aggregation and rigidity). Across quartiles of SI (defined after log transformation since distribution of SI was not normal), hematocrit and red cell rigidity remained stable, while aggregability and plasma viscosity (etap) increased in the lowest quartile. SI was correlated to only two rheological parameters: etap (r= -0.280, p=0.005) and Myrenne index M1 (r= -0.219, p=0.044). Among SI, I, age and BMI multivariate analysis selected only BMI as a determinant of either whole blood viscosity (etawb: r= -0.301, p=0.004) and RBC disaggregation threshold (gammaD: r= -0.331, p=0.013), only I as determinant of M1 (r=0.254, p=0.03), and a combination of BMI (p=0.009) and SI (p=0.007) for etap. Although age and obesity are factors of hyperviscosity, the hemorheological disturbances found in insulin resistance are not fully statistically "explained" by those two factors. While hyperaggregability (measured with M1) is rather related to hyperinsulinism, etap is influenced by SI and should be further investigated as a simple marker for the follow up of insulin-resistant states.