Metformin attenuates hepatic insulin resistance in type-2 diabetic rats through PI3K/Akt/GLUT-4 signalling independent to bicuculline-sensitive GABA_A receptor stimulation

Figures & data

Table 1. Effect of metformin in presence/absence of bicuculline or wortmannin on T2DM-induced changes in plasma glucose level of T2DM rats in OGTT.

Groups	Plasma glucose level (mmol/L)
	0 min	30 min	60 min	120 min
	Control	3.7 ± 0.13	6.6 ± 0.05	7.3 ± 0.08	5.3 ± 0.13
T2DM	25.1 ± 1.22^a	26.7 ± 1.27^a	26.5 ± 1.23^a	26.4 ± 1.43^a
T2DM + MET	12.5 ± 1.07^a^,^b	14.4 ± 1.13^a^,^b	15.2 ± 1.33^a^,^b	15.4 ± 1.28^a^,^b
T2DM + MET + BIC	12.7 ± 1.15^a^,^b	13.9 ± 1.31^a^,^b	15.9 ± 1.12^a^,^b	16.1 ± 1.13^a^,^b
T2DM + MET + WAT	25.3 ± 1.07^a^,^c^,^d	25.5 ± 1.24^a^,^c^,^d	26.1 ± 1.23^a^,^c^,^d	26.3 ± 1.23^a^,^c^,^d
T2DM + BIC	24.9 ± 1.13^a^,^c^,^d	24.8 ± 1.28^a^,^c^,^d	25.2 ± 1.25^a^,^c^,^d	25.9 ± 1.31^a^,^c^,^d
T2DM + WAT	24.7 ± 1.32^a^,^c^,^d	25.1 ± 1.31^a^,^c^,^d	25.4 ± 1.25^a^,^c^,^d	26.3 ± 1.33^a^,^c^,^d

All values are mean ± SEM (n = 6).

^a p < 0.05 compared to control,

^b p < 0.05 compared to T2DM,

^c p < 0.05 compared to T2DM + MET and

^d p < 0.05 compared to T2DM + MET + BIC (repeated measures of two-way ANOVA followed by Bonferroni post hoc test).

Table 2. Effect of metformin in presence/absence of bicuculline or wortmannin on T2DM-induced changes in the plasma glucose level of T2DM rats in ITT.

Groups	Plasma glucose level (mmol/L)
	0 min	30 min	60 min	90 min
	Control	4.5 ± 0.13	2.6 ± 0.23	2.7 ± 0.24	2.8 ± 0.25
T2DM	26.1 ± 1.25^a	19.9 ± 1.14^a	21.3 ± 1.02^a	22.5 ± 1.25^a
T2DM + MET	14.1 ± 1.11^a^,^b	10.7 ± 1.27^a^,^b	11.1 ± 1.13^a^,^b	11.1 ± 1.16^a^,^b
T2DM + MET + BIC	14.7 ± 1.03^a^,^b	11.1 ± 1.21^a^,^b	10.9 ± 1.12^a^,^b	11.1 ± 1.24^a^,^b
T2DM + MET + WAT	26.4 ± 1.44^a^,^c^,^d	21.4 ± 1.13^a^,^c^,^d	21.8 ± 1.21^a^,^c^,^d	21.5 ± 1.25^a^,^c^,^d
T2DM + BIC	25.2 ± 0.78^a^,^c^,^d	19.9 ± 1.15^a^,^c^,^d	20.4 ± 1.05^a^,^c^,^d	20.6 ± 1.06^a^,^c^,^d
T2DM + WAT	25.5 ± 1.13^a^,^c^,^d	19.8 ± 1.21^a^,^c^,^d	20.3 ± 0.78^a^,^c^,^d	20.4 ± 1.73^a^,^c^,^d

All values are mean ± SEM (n = 6).

^a p < 0.05 compared to control,

^b p < 0.05 compared to T2DM,

^c p < 0.05 compared to T2DM + MET and

^d p < 0.05 compared to T2DM + MET + BIC (repeated measures of two-way ANOVA followed by Bonferroni post hoc test).

Table 3. Effect of metformin in presence/absence of bicuculline or wortmannin on T2DM-induced changes in the fasting blood glucose and insulin level, HOMA-IR and HOMA-B indices of T2DM rats.

Groups	Fasting blood Glucose (mmol/L)	Fasting blood Insulin (pmol/L)	HOMA-IR	HOMA-B
Control	4.8 ± 0.19	75.2 ± 3.22	2.7 ± 0.32	175.4 ± 13.41
T2DM	25.7 ± 1.23^a	122.4 ± 10.21^a	21.2 ± 1.29^a	15.5 ± 4.85^a
T2DM + MET	15.3 ± 1.17^a^,^b	81.4 ± 8.71^a^,^b	10.3 ± 0.33^a^,^b	45.2 ± 3.22^a^,^b
T2DM + MET + BIC	15.5 ± 1.14^a^,^b	80.8 ± 9.15^a^,^b	10.5 ± 1.53^a^,^b	44.8 ± 4.41^a^,^b
T2DM + MET + WAT	26.4 ± 1.43^a^,^c^,^d	121.8 ± 8.29^a^,^c^,^d	21.4 ± 1.44^a^,^c^,^d	13.2 ± 5.23^a^,^c^,^d
T2DM + BIC	25.9 ± 1.21^a^,^c^,^d	122.2 ± 7.74^a^,^c^,^d	19.2 ± 1.52^a^,^c^,^d	13.2 ± 3.42^a^,^c^,^d
T2DM + WAT	25.8 ± 1.21^a^,^c^,^d	121.6 ± 8.73^a^,^c^,^d	19.1 ± 1.41^a^,^c^,^d	13.6 ± 4.29^a^,^c^,^d

All values are mean ± SEM (n = 6).

^a p < 0.05 compared to control,

^b p < 0.05 compared to T2DM,

^c p < 0.05 compared to T2DM + MET and

^d p < 0.05 compared to T2DM + MET + BIC (one-way ANOVA followed by Student–Newman–Keuls test).

Figure 1. The effect of metformin in presence/absence of bicuculline or wortmannin on T2DM-induced changes in the level of hepatic intracellular calcium. All values are mean ± SEM (n = 6). ^ap < 0.05 compared to control, ^bp < 0.05 compared to T2DM, ^cp < 0.05 compared to T2DM + MET ^dp < 0.05 compared to T2DM + MET + BIC and ^ep < 0.05 compared to T2DM + MET + WAT (one-way ANOVA followed by Student–Newman–Keuls test).

Figure 2. The effect of metformin in presence/absence of bicuculline or wortmannin on the level of expression of Akt (B) and p-Akt (C), and ratio of p-Akt to Akt (D) in liver of T2DM rats. The blots are representative of Akt and p-Akt in liver (A). The results in the histogram are expressed as the ratio of relative intensity of levels of expression of Akt or p-Akt to β-actin. All values are mean ± SEM of three separate sets of independent experiments. ^ap < 0.05 compared to control, ^bp < 0.05 compared to T2DM and ^cp < 0.05 compared to T2DM + MET [One-way ANOVA followed by Student–Newmann–Keuls post-hoc test].

Figure 3. The effect of metformin in presence/absence of bicuculline or wortmannin on the level of expression of cytoplasmic (B) and membranous (C), and ratio of p-membranous to cytoplasmic (D) GLUT-4 in liver of T2DM rats. The blots are representative of cytoplasmic and membranous (A) GLUT-4 in liver. The results in the histogram are expressed as the ratio of relative intensity of levels of expression of cytoplasmic or membranous GLUT-4 to β-actin. All values are mean ± SEM of three separate sets of independent experiments. ^ap < 0.05 compared to control, ^bp < 0.05 compared to T2DM and ^cp < 0.05 compared to T2DM + MET [One-way ANOVA followed by Student–Newmann–Keuls post hoc test].