Sex related diurnal variations in venous blood glucose and plasma insulin levels effects of estrogens in men

Abstract

Summary. Significant sex differences were observed in 24 young lean men and women submitted to two mixed isocMorie meals (880 KcM; protein 40 g; carbohydrate 90 g; fat 40 g;) at 8.15 AM and 12.45 PM. After an overnight fast venous blood glucose levels were lower in women than in men. Plasma insulin responses were lower after the afternoon meal than after the morning one in men bu~ not in women. Thus women did not present the well known cycle of insulin secretion described in men. Estradiol benzoate, 10 mg per day given intra-muscularly for eight days in six men who served as their own control, lowered fasting venous blood glucose levels and enhanced post prandial plasma insulin levels after the morning and the afternoon meal as well. It is suggested that the sex related differences in venous blood glucose and plasma insulin patterns may be due in part to estrogens.Key words: Blood glucose, plasma insulin, meals, diurnal patterns, estrogens.Diurnal and circadian changes in blood glucose and plasma insulin levels have been described in man by several authors [1--13]. The insulin secretion induced by oral glucose [1,6,7, 11,13], tolbutamide [2,13] or isoealorie meals [3,5] was more pronounced in the morning than in the afternoon. Blood glucose levels were lower in the morning than in the afternoon in response to various stimuli [1, 2, 6, 7, 9--13], but not after meals [3].After 3 and 4 days of total fast, plasma insulin levels were higher in the morning than in the afternoon in normal young men [1r These studies were done mainly or only in men.In male rats a daily rhythm of plasma glucose and insulin levels [15] and a diurnal cycle in the pancreatic beta and alpha 2 cells nuclear size [16] were described.The possibility that the circadian variations observed in blood glucose and plasma insulin levels might be sex-related has not been studied until now. However sex-related differences have been observed in substrate and hormone studies. Women responded more than men to several stimuli of Growth Hormone (GH) secretion [17]. Merimee and Fineberg have recently shown [18] that in fasting women venous blood glucose levels decrease more than in fasting men, without significant differences in plasma insulin levels. In rats blood glucose levels were higher fasting in females than in males [19]. Estrogen administration enhanced GI-I secretion in men [17,20], insulin secretion in the rat [21--23] and lowered the post absorptive blood glucose levels in men [17].The aim of this study was to compare the diurnal changes of venous glucose and plasma insulin values in men and women submitted, after an overnight fast, to two identical meals at 8.15 A?r and 12.45 PM. Some men were reinvestigated after parenterM estradiol benzoate administration.

Plasma glucose, insulin and catecholamine responses to a Wingate test in physically active women and men

“…Many authors reported that, in fasting conditions, there is a smaller resting glucose concentration in women compared to men (Hautecouverture et al 1974;Selmi et al 1976;Tchobroutsky 1991). In the present study, the carbohydrate ingestion during breakfast was the same in both sexes, since all subjects ate a standardized breakfast.…”

Blood glucose levels in diabetic and non-diabetic subjects

“…Fasting glycaemia is lower in pre-menopausal women than in men [13,16] (Table 2). We have also shown that natural oestrogen administration decreases fasting blood glucose levels in young healthy men [17].…”

What is the lower limit for postprandial venous plasma glucose in healthy young adults?

“…Results were subanalysed by gender, because of known gender differences in carbohydrate intake, 2 and glucose. 1,4,5 Mean fasting glucose was lower in women (5.1 mmol/L) than men (5.3 mmol/L), P ¼ 0.03. There were no significant gender differences for age (t ¼ À1.20, P ¼ 0.23), postprandial glucose (t ¼ À1.98, P ¼ 0.051) or prandial change in glucose (t ¼ À1.23, P ¼ 0.22).…”

“…2 Although the exact timing of the postprandial venous plasma glucose nadir is unknown, other studies would suggest that it is around 90 min with the maximal capillary-venous glucose difference occurring at one hour. 4,5,8 Alternative methods of glucose measurement such as continuous glucose monitoring of interstitial glucose (CGM) are unfortunately unlikely to define the exact timing of the nadir, due to the complex relationship between glucose concentrations within the capillary, venous and interstitial compartments. 9 In addition, although CGM results are thought to reflect venous glucose concentration, especially under stable conditions, 9 CGM calibration is usually undertaken using a capillary sample measured with a glucose meter, thus introducing an element of incorporation bias into the CGM results.…”

“…1 The postprandial drop in mean venous plasma glucose (see Figure 1) was unexpected, however at least three other studies showed a similar phenomenon. [4][5][6] Study participants chose their breakfast size and composition, thus the measured glucose reflected a 'real-world' setting…”